International Journal of Pharmaceutics (v.349, #1-2)
Editorial Board (iii).
Surface crosslinking for delayed release of proxyphylline from PHEMA hydrogels by Linfeng Wu; Christopher S. Brazel (1-10).
Delayed release systems find applications in chronotherapeutics and colon-specific delivery. They have also been considered suitable carriers for the oral delivery of peptides and proteins. In prior work, our research group has reported surface crosslinking as an effective technique to modify drug release profiles for poly(vinyl alcohol) (PVA) hydrogels, reducing the early burst effect in particular. Here, we demonstrate the feasibility of delayed release of proxyphylline from poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogels via surface crosslinking. Studies on in vitro drug release and the morphology changes of PHEMA hydrogels during swelling and drug release showed that the highly surface crosslinked layers and the ruptures occurring in these layers during swelling were likely responsible for the delayed release. In addition, the initial burst was significantly reduced or even eliminated from the drug release profile for PHEMA to achieve near zero-order release by judicious selection of two surface crosslinking parameters: crosslinking reagent concentration and exposure time used for the surface crosslinking treatment.
Keywords: PHEMA hydrogels; Delayed release; Initial burst; Rupture; Surface crosslinking; Lag time;
Konjac glucomannan and konjac glucomannan/xanthan gum mixtures as excipients for controlled drug delivery systems. Diffusion of small drugs by Felipe Alvarez-Manceñido; Mariana Landin; Igor Lacik; Ramón Martínez-Pacheco (11-18).
Konjac glucomannan (KGM), alone or in combination with xanthan gum (XG), was evaluated as main component of systems capable of controlling the diffusion of small molecules with a view of their use in drug delivery. To provide the study with enough general character, KGM batches were obtained from the three main areas of excipient harmonization (Europe, USA and Japan). The rheological evaluation at physiological temperature of KGM (0.5%, w/v) aqueous dispersions, with or without XG at different ratios, showed significant variability among the three KGMs owing to differences in the acetylation degree. The Japanese and European varieties of KGM synergically interact with XG giving rise to gel formation; the synergism being maximum at a 1:1 ratio. By contrast, the American KGM does not show such effect forming only viscous solutions. Drug diffusion coefficients of theophylline and diltiazem HCl, with different molecular size and net charge, were evaluated in systems containing KGM/XG ratio 1:1. KGM/XG systems were more efficient than the XG alone dispersion for controlling drug diffusion of small molecules because of the gel formation. These results point out the potential of mixtures of some KGM types with XG to develop delivery systems capable of maintaining physical integrity and drug release control for up to 8-h period.
Keywords: Konjac glucomannan; Xanthan gum; Synergistic interaction; Diffusion coefficient; Microviscosity; Rheology;
Granule fraction inhomogeneity of calcium carbonate/sorbitol in roller compacted granules by C. Bacher; P.M. Olsen; P. Bertelsen; J.M. Sonnergaard (19-23).
The granule fraction inhomogeneity of roller compacted granules was examined on mixtures of three different morphologic forms of calcium carbonate and three particle sizes of sorbitol. The granule fraction inhomogeneity was determined by the distribution of the calcium carbonate in each of the 10 size fractions between 0 and 2000 μm and by calculating the demixing potential. Significant inhomogeneous occurrence of calcium carbonate in the size fractions was demonstrated, depending mostly on the particles sizes of sorbitol but also on the morphological forms of calcium carbonate. The heterogeneous distribution of calcium carbonate was related to the decrease in compactibility of roller compacted granules in comparison to the ungranulated materials. This phenomenon was explained by a mechanism where fracturing of the ribbon during granulation occurred at the weakest interparticulate bonds (the calcium carbonate: calcium carbonate bonds) and consequently exposed the weakest areas of bond formation on the surface of the granules. Accordingly, the non-uniform allocation of the interparticulate attractive forces in a tablet would cause a lowering of the compactibility. Furthermore, the ability of the powder to agglomerate in the roller compactor was demonstrated to be related to the ability of the powder to be compacted into a tablet, thus the most compactable calcium carbonate and the smallest sized sorbitol improved the homogeneity by decreasing the demixing potential.
Keywords: Granule inhomogeneity; Roller compaction; Dry granulation; Compactibility; Morphology; Particle size;
Neutron activation based gamma scintigraphic evaluation of enteric-coated capsules for local treatment in colon by Tuuli Marvola; Janne Marvola; Hanna Kanerva; Aapo Ahonen; Kai Lindevall; Martti Marvola (24-29).
The fate of two colon-specific formulations developed in our previous study was investigated using a gamma scintigraphic imaging method. The formulations contained paracetamol and samarium oxide (Sm2O3) and either microcrystalline cellulose (MCC) or hypromellose (HPMC K4M) as diluent and were coated with Eudragit® S polymer. The gamma scintigraphic evaluation proved that the products remained intact in the stomach and the upper gastrointestinal tract. The gastric residence time was less that 1 h. Three to four hours after administration the formulations had reached the ileo-caecal junction, i.e. the small intestine transit time was approximately 3 h. The capsules disintegrated in the ileo-caecal junction or in the ascending colon. The capsules containing MCC released the marker momentarily, the capsules containing HPMC K4M gradually spreading it to the whole colon. The gamma images also verified that the HPMC gel disintegrates completely in 12–14 h. While comparing the results to those previously obtained from the bioavailability studies it could be concluded that it is possible to develop colon specific drug products that begin releasing the drug in the ileo-caecal junction or at the beginning of the ascending colon and spread the drug dose to a larger surface area by using enteric coats and hydrophilic polymers.
Keywords: Colon-specific delivery; Modified release; Gamma scintigraphy; Enteric polymers; Hydrophilic polymers;
Imprinted polymers as drug delivery vehicles for metal-based anti-inflammatory drug by Vijayakumari Sasidharan Sumi; Ramakrishnan Kala; Ramachandran Sarojam Praveen; Talasila Prasada Rao (30-37).
A drug delivery system based on metal-chelate imprinting is described for the first time for a metal-based drug, copper salicylate. Metal-chelate embedded polymer (MCEP) material was prepared by adding 2 equiv. of 4-vinyl pyridine, 8 equiv. of 2-hydroxyethyl methacrylate, 32 equiv. of ethyleneglycoldimethacrylate to 1 equiv. of copper salicylate in 10 ml of 2-methoxyethanol and then polymerizing thermally in the presence of 2,2′-azobisisobutyronitrile as initiator. The removal of the embedded copper salicylate from MCEP to prepare metal-chelate imprinted polymer (MCIP) was assessed by X-ray photoelectron spectroscopy (XPS), flame atomic absorption spectroscopy (FAAS) and high performance liquid chromatography (HPLC) techniques. Conventional or non-imprinted polymer material was prepared in a similar manner to MCEP, but without the addition of copper salicylate to the synthesis recipe. The drug release behaviour was examined in vitro with polymer materials having different template to monomer ratio, different crosslinker density and with polymer material loaded with copper salicylate to different extent. Detailed drug release studies with the drug loaded to MCIP and NIP materials unequivocally establish the higher and sustained release of the therapeutic agent over several days in addition to higher drug loading capacity with the former material.
Keywords: Controlled release; Copper salicylate; Drug delivery system; Metal-based drug; Molecular imprinting;
Use of a passive equilibration methodology to encapsulate cisplatin into preformed thermosensitive liposomes by Janet Woo; Gigi N.C. Chiu; Göran Karlsson; Ellen Wasan; Ludger Ickenstein; Katarina Edwards; Marcel B. Bally (38-46).
A conventional, cholesterol-containing liposome formulation of cisplatin has demonstrated insignificant activity in clinical trials, due in part, to insufficient release of encapsulated content following localization within solid tumors. For this reason, the development of a triggered release liposome formulation is desirable. In this report, cisplatin was encapsulated into lysolipid-containing thermosensitive liposomes (LTSL) using a novel technique, which relies on the equilibration of cisplatin across the liposomal membrane at temperatures above the gel-to-liquid crystalline phase transition temperature (T C) of the bulk phospholipid. Mild heating and drug loading into LTSL did not induce morphological changes of the liposomes. In vitro data demonstrated that >95% of encapsulated cisplatin was released from LTSL within 5 min following mild heating at 42 °C, while <5% was released at 37 °C. Under similar conditions, lysolipid-free thermosensitive liposomes exhibited 70% release of cisplatin at 42 °C, and cholesterol-containing liposomes exhibited negligible drug release at 42 °C. The pharmacokinetic profiles of LTSL- and TSL-cisplatin indicated that these formulations were rapidly eliminated from circulation (terminal t 1/2 of 1.09 and 2.83 h, respectively). The therapeutic utility of LTSL-cisplatin formulation will be based on strategies where hyperthermia is applied prior to the administration of the liposomal drug—a strategy similar to that used in the clinical assessment of LTSL-doxorubicin formulation.
Keywords: Thermosensitive liposomes; Cisplatin; Passive equilibration; Drug release;
Development of photocrosslinked polyacrylic acid hydrogel as an adhesive for dermatological patches: Involvement of formulation factors in physical properties and pharmacological effects by Yoshinori Onuki; Masato Nishikawa; Mariko Morishita; Kozo Takayama (47-52).
Photocrosslinked polyacrylic acid hydrogel is a promising candidate adhesive for dermatological patches. In this study, we investigated the effects of the composition and molecular weight of the polymer on the characteristics of the hydrogel. Several photocrosslinkable polymers with different photocrosslinkable moieties or molecular weights were prepared, and various physical properties were measured. Differences in photocrosslinkable modifications markedly affected the swelling behavior of the hydrogel. The molecular weight of the polymer had a significant effect on various physical properties, such as the viscosity of the polymer solution, gel formation, and the swelling behavior of the prepared hydrogels. The pharmacological effects of the hydrogel were also evaluated using carrageenan-induced edema in rats. Application of the hydrogels maintained the skin surface at a reduced temperature throughout the experimental period, and the cooling effect was accompanied by an anti-inflammatory response. Because we can freely control the physical properties of the hydrogel and anticipate the significant pharmacological effects, photocrosslinked polyacrylic acid hydrogel is an attractive candidate adhesive for dermatological patches.
Keywords: Photopolymerization; Polyacrylic acid; Hydrogel; Dermatological patch adhesive;
Analysis of hepatic metabolism affecting pharmacokinetics of propranolol in humans by A. Kiriyama; A. Honbo; K. Iga (53-60).
We examined the metabolic kinetics of propranolol, constructed from saturable and non-saturable components, using liver microsomes. The metabolic activity in rat microsomes was much higher than that in human microsomes within the clinically observed plasma range. Using the physiologically based pharmacokinetic (PBPK) model incorporating the obtained metabolic parameters, the plasma kinetics of propranolol was well correlated with reported values, and then used to analyze the effect of hepatic first-pass metabolism on propranolol plasma pharmacokinetics in clinical doses.The simulated plasma concentrations and AUC values of propranolol increased proportionally to its dose; these levels were almost equivalent to intrinsic clearance (CLint1), presumed to be non-saturable. When Michaelis–Menten parameters were decreased to one twentieth, plasma concentrations slightly increased after 160 mg dosing. A similar result was obtained with steady-state plasma levels after repeated administration. On the other hand, the first-order absorption rate constant of propranolol did not affect AUC values. The dose-normalized AUC value started to increase about 103 mg dosing. When the dose exceed 106 mg dose, the CLint1 component hardly contributed to propranolol pharmacokinetics. Accordingly, under the conditions of the PBPK model, propranolol pharmacokinetics was considered to be dose-independent within the clinical dose range.
Keywords: Propranolol; Pharmacokinetics; Hepatic metabolism; Physiologically based pharmacokinetic model; Human;
The impact of low-level inorganic impurities on key physicochemical properties of paracetamol by Wendy L. Hulse; Ian M. Grimsey; Marcel De Matas (61-65).
Trace inorganic impurities in active pharmaceutical ingredients (APIs) while having limited toxicological significance might affect the down stream processing properties of those substances. The level of impurities in paracetamol batches was quantified and mapped using inductively coupled polarization mass spectrometry (ICP-MS) and scanning electron microscopy coupled with energy dispersive X-ray microanalysis (SEM–EDX). The physical form of samples was assessed using X-ray powder diffraction (XRPD) and characterised thermally using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Surface properties were evaluated using inverse gas chromatography (IGC) and moisture sorption. Size distribution was measured using an aerosizer with dry powder dispersion. Physical analysis confirmed that the batches were of the same physical form and particle size distribution was shown to be similar. The SEM–EDX analysis however revealed the presence of aluminium on the surface of particles. This was supported by ICP-MS analysis, which showed different levels of aluminium between batches ranging from 0.1 to 5.6 ppm. IGC indicated that the batches with the highest aluminium content had the highest dispersive free energy. Differences in levels of inorganic impurities typically not considered significant in drug substance specifications correspond with differences in physical properties of APIs, with potential downstream consequences for processing and finished product performance.
Keywords: PAT; Inorganic impurities; Processing; Surface free energy; Physicochemical properties; Paracetamol;
Unexpected differences in dissolution behavior of tablets prepared from solid dispersions with a surfactant physically mixed or incorporated by H. de Waard; W.L.J. Hinrichs; M.R. Visser; C. Bologna; H.W. Frijlink (66-73).
In a previous study, it was shown that the incorporation of poorly soluble drugs (BCS class II) in sugar glasses could largely increase the drug's dissolution rate [van Drooge, D.J., Hinrichs, W.L.J., Frijlink, H.W., 2004b. Anomalous dissolution behaviour of tablets prepared from sugar glass-based solid dispersions. J. Control. Release 97, 441–452]. However, the application of this technology had little effect when high drug loads or fast dissolving sugars were applied due to uncontrolled crystallization of the drug in the near vicinity of the dissolving tablet. To solve this problem a surfactant, sodium lauryl sulphate (SLS), was incorporated in the sugar glass or physically mixed with it. Diazepam and fenofibrate were used as model drugs in this study. The dissolution behavior of tablets prepared from solid dispersions in which SLS was incorporated was strongly improved. Surprisingly, the dissolution rate of tablets prepared from physical mixtures of SLS and the solid dispersion was initially fast, but slowed down after about 10 min. The solid dispersions were characterized by DSC to explain this unexpected difference. These measurements revealed the existence of interaction of SLS with both the drug and the sugar in the solid dispersion when SLS was incorporated. It is hypothesized that due to this interaction, the dissolution of SLS was slowed down by which a high solubility of the drug in the near vicinity of the dissolving tablet is maintained during the whole dissolution process. Therefore, uncontrolled crystallization is effectively prevented.
Keywords: Sugar glass; Poorly soluble drug; High drug load; Crystallization; Sodium lauryl sulphate;
Radiosterilization of drugs in aqueous solutions may be achieved by the use of radioprotective excipients by Aubert Maquille; Jean-Louis Habib Jiwan; Bernard Tilquin (74-82).
The aim of this study was to assess the feasibility of radiosterilization of drugs aqueous solutions and to evaluate the effects of some additives, such as mannitol, nicotinamide and pyridoxine, which might protect the drug from degradation. Metoclopramide was selected as a model drug. The structures of the degradation products were determined to gain insight on the radiolysis mechanisms in aqueous solution in order to design strategies to lower the drug degradation.Metoclopramide hydrochloride aqueous solutions with and without excipients were irradiated either with gamma rays or high-energy electrons. HPLC-DAD was used to measure the loss of chemical potency and to quantify the degradation products which were also characterized by LC–APCI–MS-MS. Metoclopramide recovery for gamma and electron beam-irradiated solutions containing either mannitol, pyridoxine or nicotinamide meets the pharmacopoeial specifications for metoclopramide content up to a 15 kGy irradiation so that metoclopramide solutions containing these excipients might be radiosterilized at 15 kGy either with gamma rays or high-energy electrons. Structures are proposed for the majority of radiolysis products. Similar radiolysis products were detected for gamma and electron beam irradiations but the chromatographic profiles were different (differences in the distribution of radiolysis products).
Keywords: Metoclopramide hydrochloride; Radiolysis; HPLC-DAD; LC–MS; Radioprotective excipients;
Stabilization and encapsulation of photosensitive resveratrol within yeast cell by Guorong Shi; Liqun Rao; Huazhong Yu; Hua Xiang; Hua Yang; Runa Ji (83-93).
The photosensitive resveratrol was successfully encapsulated in yeast cells for the first time, as characterized by FT-IR spectra, fluorescence and confocal micrographs of the yeast cells, resveratrol and microcapsules. The release characteristic of the obtained yeast-encapsulated resveratrol in simulated gastric fluid was evaluated, and its storage stability as a powder was investigated at 25 °C/75% relative humidity (RH), 25 °C/90% RH and 60 °C under the laboratory fluorescent lighting conditions (ca. 300 lx) or in the dark. Also, the scavenging capacity of yeast-encapsulated resveratrol on DPPH radical was compared with that of non-encapsulated resveratrol. It could be demonstrated clearly that no chemical changes occurred during the encapsulation. Besides, the DPPH radical-scavenging activity increased after the encapsulation. In addition, the yeast-encapsulated resveratrol exhibited good stability, and its bioavailability was enhanced as a result of increased solubility of resveratrol and sustained releasing.
Keywords: Microencapsulation; Resveratrol; Yeast cells; Stability; Bioavailability;
Influence of various combinations of mucolytic agent and non-ionic surfactant on intestinal absorption of poorly absorbed hydrophilic compounds by Shinya Takatsuka; Takahiro Morita; Yuji Horikiri; Hiroshi Yamahara; Hideo Saji (94-100).
The absorption enhancing effects of various combinations of a mucolytic agent and a non-ionic surfactant on the intestinal absorption of poorly absorbed hydrophilic compounds were examined. Fluorescein isothiocyanate-labeled dextran with an average molecular weight of ca. 4.4 kDa (FD-4) was used as a model compound. Cysteine derivatives such as N-acetylcysteine (NAC), S-carboxymethylcysteine (SCMC), S-ethylcysteine (SEC), and S-methylcysteine (SMC) were selected as mucolytic agents. A homogeneous series of single chain polyoxyethylene alkyl ethers were employed as non-ionic surfactants. Various dosing solutions were administered into rat jejunum, and the bioavailability of FD-4 was determined. Unlike NAC, the agents such as SCMC, SEC, and SMC, which do not possess a free thiol group, did not show any apparent enhancement of intestinal FD-4 absorption, when they were co-administered with p-t-octyl phenol polyoxyethylene-9.5 (Triton® X-100, TX-100). In addition, the absorption enhancement was dependent on the kinds of polyoxyethylene alkyl ethers used, when used in combination with NAC. For a constant alkyl chain of 12 with a varying polyoxyethylene (POE) chain length, the surfactant with a short to medium POE chain length such as lauryl poly (4.2) oxyethylene ether (BL-4.2) and lauryl poly (9) oxyethylene ether (BL-9) were effective. In addition, for a constant alkyl chain of 18 with a varying POE chain length, the surfactants with a longer POE chain length such as oleyl poly (15) oxyethylene ether (BO-15) and stearyl poly (20) oxyethylene ether (BS-20) showed the effective enhancement.All these results suggest that a mucolytic agent not possessing a free thiol group is not effective for enhancing the intestinal absorption of poorly absorbed hydrophilic compounds. Also, they indicate that the combination of a mucolytic agent possessing a free thiol group and a non-ionic surfactant either with a short to medium POE chain length and a medium alkyl chain length, or with a longer POE chain length and a longer alkyl chain length shows the effective enhancement. This fundamental information might be useful for finding the optimal combination.
Keywords: Intestinal absorption; Combination; Mucolytic agent; Polyoxyethylene alkyl ethers; Poorly absorbed hydrophilic compounds;
Formulation and evaluation of ondansetron nasal delivery systems by Eunsook Cho; Hyesun Gwak; Inkoo Chun (101-107).
This study aimed to formulate and evaluate nasal delivery systems containing ondansetron hydrochloride. In the in vitro study, the permeation rate with the addition of 10% polyethylene glycol 300 (PEG 300) to aqueous solution containing 0.01% benzalkonium chloride (BC) and 10% sulfobutylether ß-cyclodextrin sodium salt (SBCD) was somewhat more rapid up to 1.5 h compared to the addition of 10% PG. The permeation flux increased as the drug concentration increased regardless of the vehicles used. The addition of nicotinamide or chitosan to aqueous drug solution (40 mg/ml) with 10% PEG 300 and 0.01% BC rather decreased permeation rate and delayed lag time. Even though cyclodextrins including SBCD or dimethyl-ß-cyclodextrin failed to show permeation enhancing effects of ondansetron hydrochloride, the addition of 10% SBCD to aqueous solution containing 10% PEG 300 and 0.01% BC could be a good candidate for ondansetron nasal delivery systems because of its safety profile, stable storage in refrigerator and solubilizing effect. With the above formulation, the nasal delivery system increased AUC0–2 h and C max by 2.1 and 1.7 times compared to those of oral delivery, respectively while there was no difference found in AUC0–2 h with intravenous administration. Therefore, the nasal delivery system of ondansetron hydrochloride formulated in this study was feasible for nasal administration.
Keywords: Ondansetron hydrochloride; Vehicles; Permeation rate; Lag time; Pharmacokinetic parameters;
Cremophor-free intravenous microemulsions for paclitaxel by Adwoa O. Nornoo; David W. Osborne; Diana S.-L. Chow (108-116).
Two cremophor-free microemulsions, lecithin:butanol:myvacet oil:water (LBMW) and capmul:myvacet oil:water (CMW) for paclitaxel (PAC) were developed for intravenous (i.v.) administration. Six surfactants and four oils were screened with various combinations for maximal water incorporation and PAC solubility. Microemulsion regions were subsequently determined in ternary phase diagrams. Cytotoxicity in an MDA-M231 human breast cancer cell line and hemolytic potential were assessed in these systems compared to Taxol® (cremophor EL:ethanol, 1:1, 6 mg PAC/ml). The maximal water incorporation into the lecithin:butanol surfactant blend was greater than that incorporated into capmul when combined with the oils screened. PAC solubility in myvacet oil was increased 1389-fold over its aqueous solubility. LBMW had a larger microemulsion region (46.5% of total ternary phase diagram) than that seen with CMW (18.6%). The droplet size of the dispersed phase was 111.5 (4.18) nm for LBMW and 110.3 (8.09) nm for CMW. Cytotoxicity of PAC was in decreasing order of: Taxol® > LBMW > CMW. The IC50 values for LBMW and CMW ranged from 4.5 to 5.7 and >10 μM, respectively, as compared to that of Taxol® (1.3 to 1.8 μM). Eighty-three percent, 68%, and 63% of red blood cells remain unlysed at a formulation volume to blood ratio of 0.035 in LBMW, CMW and Taxol®. Promising microemulsions, LBMW and CMW were developed that can incorporate approximately 12 mg/g of PAC, substantially higher than its aqueous solubility (10.8 μg/ml) and that in the Taxol® vehicle (6 mg/ml). PAC retained its cytotoxicity in the LBMW and CMW and was less likely to cause hemolysis compared to Taxol®. This higher drug loading results in a smaller vehicle volume in required doses of these formulations and potentially less vehicle-related side effects are anticipated.
Keywords: Paclitaxel; Microemulsion; Intravenous; Hemolysis; Cytotoxicity;
Cremophor-free intravenous microemulsions for paclitaxel by Adwoa O. Nornoo; Diana S.-L. Chow (117-123).
Two cremophor-free microemulsion systems LBMW (lecithin:butanol:myvacet:water) and CMW (capmul:myvacet:water), for intravenous (IV) administration of paclitaxel (PAC) were previously developed and characterized. Their chemical stability, in vitro release and pharmacokinetics of PAC were assessed using Taxol® (cremophor:ethanol 1:1, 6 mg/ml) as a reference. The shelf-lives of PAC at 25 °C in Taxol®, LBMW and CMW, in an accelerated stability study, were 71, 57 and 31 days, respectively. The activation energy (E a) for PAC in Taxol®, LBMW and CMW was 23, 16 and 14 kcal/mol, respectively. PAC released from LBMW and CMW using a dialysis technique was significantly slower than that from Taxol®. The extents of release of PAC from LBMW and CMW were 25 and 50% of that from Taxol®. In vivo pharmacokinetic studies in male Sprague–Dawley rats after IV administration revealed that PAC in LBMW and CMW remained in the systemic circulation five and two times longer and was eight and three times more widely distributed than PAC from Taxol®. LBMW and CMW offer a significant clinical advantage in terms of the prolonged half-life and wide tissue distribution, indicating that PAC delivered by these systems intravenously may result in prolonged exposure of PAC to the tumor and subsequently an improved clinical efficacy.
Keywords: Paclitaxel; Microemulsion; Intravenous; In vitro release; Stability; Pharmacokinetics;
Evaluation of self-dissolving needles containing low molecular weight heparin (LMWH) in rats by Yukako Ito; Aiko Murakami; Tomohiro Maeda; Nobuyuki Sugioka; Kanji Takada (124-129).
Feasibility study of self-dissolving needles containing polysaccharide was performed. Low molecular weight heparin (LMWH) was used as a representative polysaccharide. Using chondroitin, dextran and dextrin as the base, self-dissolving needles (SDN) were prepared. The obtained SDNs were evaluated in rat absorption experiment, where pharmacological availability (PA) was calculated by comparing the plasma anti-Xa activity vs. time curves between SDNs and i.v. solution. After the insertion of SDNs to rats skin where the doses of LMWH were 25, 50 and 100 IU/kg, plasma samples were collected for 6 h and anti-Xa activity was measured as the pharmacological index of LMWH. The anti-Xa level was maintained above 0.2 IU/ml, the therapeutic level, for about 2 h at a dose of 100 IU/kg. Almost the same PAs of LMWH were obtained with dextran and dextrin SDNs, 97.7% and 102.3%, though lower PA was obtained with chondroitin SDN, 81.5%. In vitro dissolution experiment showed that LMWH was released from dextran, dextrin and chondroitin SDNs within 10 min. The T 50%s were 0.84 ± 0.06 min for dextran SDN, 1.07 ± 0.12 min for chondroitin SDN and 2.11 ± 0.31 min for dextrin SDN, respectively. Plasma anti-Xa activity vs. time profiles showed good dose-dependency in the 25–100 IU/kg range and high PAs were obtained, 90.0% for 25 IU/kg, 95.4% for 50 IU/kg and 97.7% for 100 IU/kg from dextran SDNs. Stability experiment was performed with dextran SDNs for 3 months. Above 97% of LMWH were remained in SDNs under three different conditions, −80, 4 and 40 °C. These results suggest the usefulness of SDN to polysaccharide drug.
Keywords: Low molecular weight heparin; Self-dissolving needles; Percutaneous administration; Pharmacological availability; Anticoagulant; Rats;
Linker-based lecithin microemulsions for transdermal delivery of lidocaine by Jessica S. Yuan; Maham Ansari; Micheline Samaan; Edgar J. Acosta (130-143).
In this work, we introduce alcohol-free lecithin microemulsions formulated with linkers to produce transdermal delivery vehicles. The food-grade linker system consists of a combination of sodium caprylate and caprylic acid (hydrophilic linkers), and sorbitan monooleate (lipophilic linker). A “carrier” oil (isopropyl myristate) was used to predissolve a model lipophilic drug, lidocaine. The first part of the article describes the phase behavior and physical properties of these linker-based lecithin microemulsions. In the second part of the article, we evaluate the transdermal permeation and cytotoxicity of lidocaine formulated in oil-in-water (Type I), water-in-oil (Type II), and bicontinuous (Type IV) linker microemulsions. The transdermal permeation studies show that compared to a conventional Type II alcohol-based lecithin microemulsion, Type II linker-based microemulsions provide twice the absorption and penetration of lidocaine through skin. The larger flux obtained with linker systems is due to the presence of sodium caprylate and caprylic acid. These hydrophilic linkers accelerate the microemulsion-skin mass transfer by reducing the interfacial rigidity of the systems. Furthermore, the cytotoxicity studies show that these linker microemulsions are significantly less toxic than the alcohol-based system. The Type II linker microemulsion (containing approximately 4% lidocaine) has a comparable cytotoxicity to water saturated with lidocaine (0.4% lidocaine).
Keywords: Microemulsions; Transdermal drug delivery; Lecithin; Linker molecules; Skin permeation; Cytotoxicity; Lidocaine;
Modifying the release of proxyphylline from PVA hydrogels using surface crosslinking by Linfeng Wu; Christopher S. Brazel (144-151).
Drug release profiles were altered to prevent the initial burst effect or introduce a lag phase by creating surface crosslinked layers in poly(vinyl alcohol) (PVA) hydrogels. Confocal laser scanning microscopy (CLSM) confirmed the successful introduction of these surface crosslinked layers. The thickness and crosslinking density of the surface crosslinked layer were highly dependent on the surface crosslinking conditions (i.e., exposure time and glutaraldehyde (GTA) concentration used). By judicious selection of these parameters, the initial burst release could be eliminated and a reproducible delayed release could be achieved. Highly surface crosslinked layers had a tendency to rupture during the swelling process of PVA hydrogels; these raptures were found to coincide with delayed release of proxyphylline from surface crosslinked PVA hydrogels.
Keywords: Initial burst effect; PVA hydrogel; Surface crosslinking; Drug delivery;
Release profiles and morphological characterization by atomic force microscopy and photon correlation spectroscopy of 99mTechnetium-fluconazole nanocapsules by Danielle Nogueira de Assis; Vanessa Carla Furtado Mosqueira; José Mário Carneiro Vilela; Margareth Spangler Andrade; Valbert Nascimento Cardoso (152-160).
Several classes of antifungal have been employed in candidiasis treatment, but patients with advanced immunodeficiency can present unsatisfactory results after therapy. In these cases, high doses of drugs or the use of multiple agents are sometimes used, and hence increasing the risk of serious side effects. Considering theses difficulties, the encapsulation of antifungal agents in nanoparticulate carriers has been used with the objective of modifying the pharmacokinetic of drugs resulting in more efficient treatments with less side effects. The purpose of this work was the preparation, characterization and the investigation of the release profiles of radiolabeled fluconazole nanocapsules. The size, homogeneity and zeta potential of NC preparations were determined with a Zetasizer 3000HS. The morphology and the structural organization were evaluated by atomic force microscopy (AFM). The release study in vitro of NC was evaluated in physiologic solution with or without 70% mouse plasma. The labeling yield of fluconazole with 99mTc was 94% and the radiolabeled drug was stable within 24 h period. The encapsulation percentage of 99mTc-fluconazole in PLA-POLOX NC and PLA-PEG NC was approximately of 30%. The average diameter calculated by photon correlation spectroscopy (PCS) varied from 236 to 356 nm, while the average diameter determined by AFM varied from 238 to 411 nm. The diameter/height relation decreased significantly when 25% glutaraldehyde was used for NC fixation on mica. The zeta potential varied from −55 to −69 nm and surface-modified NC showed lower absolute values than conventional NC. The in vitro release of 99mTc-fluconazole in plasma medium of the conventional and surface-modified NC was greater than in saline. The drug release in plasma medium from conventional NC was faster than for surface-modified NC. The results obtained in this work suggest that the nanocapsules containing fluconazole could be used to identify infectious foci, due to the properties, such as size, zeta potential and controlled release of 99mTc-fluconazole. The surface-modified nanocapsules could constitute a long-circulating intravenous formulation of fluconazole for treating sepsis caused by disseminated form of candidiasis. However, in vivo studies should be considered and are under investigation.
Keywords: Nanocapsules; Atomic force microscopy; 99mTechnetium-fluconazole; Photon correlation spectroscopy; Morphological characterization; Radioactive labeling;
In vitro permeation of levothyroxine across the skin by Cristina Padula; Alice Pappani; Patrizia Santi (161-165).
The aim of this work was to investigate the in vitro transdermal permeation characteristics of sodium levothyroxine, in view of its topical application. Permeation experiments were performed in vitro, using rabbit ear skin as barrier. At the end of the experiments levothyroxine retained in the skin was extracted and quantified by HPLC. The formulations tested were solutions and a commercial cream. The use of dimethyl β-cyclodextrin as solubilizing agent increased to a significant extent levothyroxine solubility, but reduced its skin accumulation. Skin stripping before drug application produced a considerable increase in the amount retained and levothyroxine was found also in the receptor compartment. The application of the commercial cream in occlusive conditions increased to a significant extent drug retention in the skin. In conclusion, levothyroxine skin administration is promising in view of a localized effect, because it was retained in the skin. On the contrary, transdermal administration in view of systemic effect does not represent a concrete possibility.
Keywords: Levothyroxine; Skin absorption; Skin retention;
Possibility of enterohepatic recycling of ketoprofen in dogs by Gladys E. Granero; Gordon L. Amidon (166-171).
Ketoprofen is mainly cleared by glucuronidation. The rate of glucuronidation of this compound has been demonstrated to be greater in dog than in human liver microsomes. Dog is the most common secondary nonprimate species used in drug metabolism studies in the pharmaceutical industry. Therefore, this study was undertaken to provide valuable information to pharmaceutical companies using dog as a model species for pharmacokinetic analyses when differences in glucuronidation occur across species for therapeutic drugs known to be extensively glucuronidated. The pharmacokinetics of ketoprofen was investigated after intravenous (0.27, 0.57 and 1.10 mg/kg) and oral administration of ketoprofen (∼10 mg/100 ml) of the racemate in dogs. Serial blood samples were collected at timed intervals for 7 and 24 h following intravenous and oral administration of the dose, respectively, and concentrations in plasma were determined by a sensitive and specific HPLC method. By comparing the AUC0−∞ following oral and intravenous administrations, ketoprofen bioavailability was ∼100%. A possibility of enterohepatic cycling of ketoprofen in dogs was proposed because of multiple peak phenomenon in the concentration–time profiles after intravenous and oral dosing was observed.
Keywords: Ketoprofen; Enterohepatic circulation; Pharmacokinetics; Absorption;
Axial tensile fracture of microcrystalline cellulose compacts by S.J. Inman; B.J. Briscoe; K.G. Pitt; C. Shiu (172-179).
An adapted tensile stress methodology for the fracture of microcrystalline cellulose (MCC) tablets has been investigated and implemented. The application of the generally applied linear elastic fracture mechanic (LEFM) parameters used to describe the fracture behaviour of these porous systems has been discussed. The application of an effective crack length concept, comprising of the notch depth and a process zone length designated Δc, has enabled the localised non-linear response of the MCC tablets to be characterised in a quantified manner. The requirement of the composite value Δc is postulated to be a direct result of the internal properties of the tablet formed during the compaction process due to its strong dependence on porosity. The high compact relative density creates a greater possibility for both local small-scale plastic yielding at the crack tip, commonly found in polymer materials and microcracking ahead of the crack tip, typically observed in the fracture of ceramics. The extrapolated value of K IC0 of 0.72 MPa m0.5 found in this work lies within the range found in literature for this material indicating that the adopted procedure is acceptable for the determination of the resistance to fracture of MCC compacts.
Keywords: Microcrystalline cellulose; Fracture mechanics; Effective crack length; Tensile strength;
Preparation of ionic-crosslinked chitosan-based gel beads and effect of reaction conditions on drug release behaviors by Shilan Chen; Mingzhu Liu; Shuping Jin; Bin Wang (180-187).
Drug-loaded chitosan (CS) beads were prepared under simple and mild condition using trisodium citrate as ionic crosslinker. The beads were further coated with poly(methacrylic acid) (PMAA) by dipping the beads in PMAA aqueous solution. The surface and cross-section morphology of these beads were observed by scanning electron microscopy and the observation showed that the coating beads had core–shell structure. In vitro release of model drug from these beads obtained under different reaction conditions was investigated in buffer medium (pH 1.8). The results showed that the rapid drug release was restrained by PMAA coating and the optimum conditions for preparing CS-based drug-loaded beads were decided through the effect of reaction conditions on the drug release behaviors. In addition, the drug release mechanism of CS-based drug-loaded beads was analyzed by Peppa's potential equation. According to this study, the ionic-crosslinked CS beads coated by PMAA could serve as suitable candidate for drug site-specific carrier in stomach.
Keywords: Chitosan; Trisodium citrate; Ionic-crosslink; Poly(methacrylic acid); Polyelectrolyte complex; Drug release;
Effect of chitosan on the release of protein from thermosensitive poly(organophosphazene) hydrogels by Gyung Don Kang; Soo-Chang Song (188-195).
Poly(organophosphazenes) have been suggested as a potential thermosensitive hydrogel for use in the development of an injectable gel-depot system. Under biological conditions, hydrophilic model protein drugs, including bovine serum albumin (BSA), gelatin type B (MW 20,000) (GB20), and fluorescein isothiocyanate albumin (FITC-albumin) loaded in the hydrogels were released for 1–2 weeks, showing an initial burst release. However, this initial burst release could be suppressed when the proteins were couched in a complex with chitosan, and under these conditions evidenced a prolonged release period. BSA, GB20, and FITC-albumin, all of which are negatively charged at a pH of 7.4, interacted with chitosan harboring positive amine groups. The formation of these protein/chitosan complexes were confirmed via measurements of changes in zeta-potential and high-performance liquid chromatography. We determined the appropriate ratio of proteins to chitosan for suppression of the initial burst to be 1:5 to 1:10. From these findings, we were able to conclude that both the release rate and release period could be controlled via the formation of protein/chitosan complex.
Keywords: Poly(organophosphazenes); Thermosensitive hydrogel; Drug delivery system; Protein/chitosan complex; Ionic interaction;
Modulation of brain delivery and copulation by intranasal apomorphine hydrochloride by Wei Lu; Wenming Jiang; Jun Chen; Ming Yin; Zejian Wang; Xinguo Jiang (196-205).
Clinical studies showed apomorphine (APO) nasal spray was well tolerated, with lower dose and less side effect in treatment of erectile dysfunction compared with its sublingual formulation. The aim of this paper was to find out whether there exists any direct drug transport from nasal cavity to brain following intranasal administration to rats. Pharmacokinetic results illustrated there were no significant differences of AUC0→120 values in most brain regions and cerebrospinal fluid (CSF) through intranasal delivery route compared with subcutaneous injection, while its plasma AUC0→120 was only one-half. APO brain and CSF profiles after intranasal administration displayed faster onset compared with subcutaneous delivery. About 35–50% of APO content at 2 h, by calculating brain drug direct transport percentage, were transported to different brain regions via the olfactory pathway. In addition, the similar brain drug concentration–time profiles through intranasal delivery compared with subcutaneous route had good correlation with its equivalent sexual stimulant activity on copulatory behaviour in rats. Therefore, we could conclude a nose-to-brain pathway for APO intranasal delivery, which significantly increased brain accumulation of APO. Current experiments also explained the reason why the intranasal application of APO could be an effective alternative to subcutaneous and oral formulations.
Keywords: Apomorphine; Intranasal delivery; Brain distribution; Copulatory behaviour;
Transdermal delivery of capsaicin derivative-sodium nonivamide acetate using microemulsions as vehicles by Yaw Bin Huang; Yong Hao Lin; Tzy Ming Lu; Ren Jiunn Wang; Yi Hung Tsai; Pao Chu Wu (206-211).
The objective of this study was to prepare sodium nonivamide acetate (SNA) microemulsion for topical administration. Microemulsions consisted of a mixed surfactant of Tween 80 and Span 20 as surfactant, ethanol as cosurfactant, isopropyl myristate (IPM) as an oil phase and water as an external phase. The effect of composition of microemulsion including the ratio of oil phase/surfactant/aqueous phase, various cosurfactant and polymer on the character and permeability of microemulsion were evaluated. The mean droplet size of SNA microemulsions ranged from 64 to 208 nm. Microemulsions showed potent enhancement effect for SNA transdermal delivery by a 3.7–7.1-fold increase when compared with the control group. Microemulsion containing ethanol as cosurfactant had the highest enhancement effect. With incorporated polymer, the viscosity of microemulsions increased resulting in the decrease in penetration rate of SNA. However, the permeability of SNA delivered from microemulsion was higher than SNA from volatile vehicles (pH 4.2 buffer containing 25% ethanol) reported in an earlier study, therefore microemulsions could be an effective vehicle for topical delivery of SNA.
Keywords: Sodium nonivamide acetate; Microemulsion; Transdermal delivery; Isopropyl myristate; Viscosity;
S-Propranolol imprinted polymer nanoparticle-on-microsphere composite porous cellulose membrane for the enantioselectively controlled delivery of racemic propranolol by Chutima Jantarat; Naruedom Tangthong; Sarunyoo Songkro; Gary P. Martin; Roongnapa Suedee (212-225).
Molecularly imprinted polymer (MIP) nanoparticle-on-microspheres (NOM) selective for S-propranolol were successfully prepared using suspension polymerization involving agitation of the reaction mixture at high speed. The integration of the MIP-NOM into a self-assembled porous cellulose membrane allowed a controlled distribution and availability of the molecule recognition sites within a porous structure. The nature of the membrane-included microparticles determined the degree of porosity whilst the adherent nanoparticles provided an increased surface area enabling the composite membrane to be employed efficiently for the trans-membrane transport of the imprinted molecule. The MIP-NOM within the membrane were easily accessible for binding of the imprinted molecule and appeared to maintain high selectivity, indicating that the composite membranes may potentially provide valuable affinity matrices. In this study, the application for MIP-NOM composite cellulose membranes were investigated for their potential to act as transdermal drug delivery systems for the S-enantiomers from racemic propranolol, its ester prodrugs (cyclopropanoyl- and valeryl-propranolol) or other β-blockers (pindolol and oxprenolol). The enantioselective release of the fluorescently active 1-pyrene-butyryl ester prodrug of S-propranolol from MIP-NOM composite membranes and its diffusion and transit across excised rat skin was monitored by confocal laser scanning microscopy. The mechanism underlying the release of S-propranolol from the MIP-NOM composite membrane was found to involve specific adsorption and mobility of this enantiomer at the binding site in the MIP-NOM as the latter undergo a transition from the dry to wet state. The proposed MIP-NOM composite membrane controlled release system may be applicable for fabrication of novel membranes with self-controllable permeability responding to the presence of target solutes.
Keywords: Molecularly imprinted polymer; Nanoparticle; Composite membrane; Propranolol; Transdermal delivery;
In vitro and in vivo study of N-trimethyl chitosan nanoparticles for oral protein delivery by Fu Chen; Zhi-Rong Zhang; Fang Yuan; Xuan Qin; Minting Wang; Yuan Huang (226-233).
In this study, the effects of alginate modification on absorption properties of FITC-BSA loaded TMC nanoparticles were investigated on an in vitro model of GI epithelium (Caco-2 cells). The feasibility of applying TMC nanoparticles loaded with a model vaccine urease in oral vaccination was also studied. Alginate modified TMC nanoparticles showed higher FITC-BSA permeate efficiency than non-modified TMC nanoparticles. However, alginate modification barely had any effect on TMC nanoparticles’ property of decreasing TEER or enhancing drug paracellular transport. Mice s.c. immunized with urease loaded TMC nanoparticles showed highest systematic immune response (IgG levels) but the lowest mucosal response (secretory IgA levels). In the contrast, mice i.g. immunized with urease loaded TMC nanoparticles showed much higher antibody titers of both IgG and secretory IgA than those with urease solution or urease co-administrated with TMC solution. These results indicated that TMC nanoparticles are potential carriers for oral protein and vaccine delivery.
Keywords: N-Trimethyl chitosan; Nanoparticles; Protein carriers; Oral vaccination;
Adhesion of PLGA or Eudragit®/PLGA nanoparticles to Staphylococcus and Pseudomonas by Kathleen Dillen; Chris Bridts; Pieter Van der Veken; Paul Cos; Jo Vandervoort; Koen Augustyns; Wim Stevens; Annick Ludwig (234-240).
The aim of present study was to examine whether cationic Eudragit® containing poly(lactide-co-glycolide) (PLGA) nanoparticles can adhere to Pseudomonas aeruginosa and Staphylococcus aureus. In order to prepare fluorescent nanoparticles, fluorescein was covalently coupled to PLGA. Fluorescent PLGA and Eudragit®/PLGA nanoparticles were prepared by w/o/w emulsification solvent evaporation. Particle size and zeta potential of the nanoparticles were measured. Nanoparticles were incubated for a short time with P. aeruginosa and S. aureus followed by measurement of the size of nanoparticles and of P. aeruginosa and S. aureus with and without adherent nanoparticles. Flow cytometric measurements were performed to detect the attachment of particles to microorganisms. Eudragit® containing nanoparticles possessed a positive zeta potential, while PLGA nanoparticles were negatively charged. Following adsorption of Eudragit® containing nanoparticles, a size increase for P. aeruginosa was observed. Flow cytometric analyses confirmed that Eudragit® containing particles showed stronger interactions with the test organisms than PLGA nanoparticles. Adhesion of particles was more pronounced for P. aeruginosa than for S. aureus. Cationic Eudragit® containing nanoparticles showed better adhesion to microorganisms than anionic PLGA nanoparticles, which is probably due to enhanced electrostatic interactions.
Keywords: Nanoparticles; PLGA; Eudragit®; Pseudomonas aeruginosa; Staphylococcus aureus; Flow cytometry;
Preparation of rapamycin-loaded chitosan/PLA nanoparticles for immunosuppression in corneal transplantation by Xu-Bo Yuan; Yan-Bo Yuan; Wei Jiang; Jie Liu; En-Jiang Tian; Hui-Ming Shun; Ding-Hai Huang; Xiao-Yan Yuan; Hong Li; Jing Sheng (241-248).
Rapamycin-loaded chitosan/polylactic acid nanoparticles with size of about 300 nm in diameter were prepared through nanoprecipitation method using cholesterol-modified chitosan as a stabilizer. The surface coating of chitosan, which was demonstrated by zeta potential measurement, endowed the nanoparticles good retention ability at the procorneal area, facilitating the sustained release of rapamycin on the corneal. The immunosuppression in corneal transplantation of the nanoparticles was investigated using rabbit as animal model, the median survival time of the corneal allografts treated with nanoparticles was 27.2 ± 1.03 days and 50% grafts still remained surviving by the end of the observation, while the group treated with 0.5% rapamycin suspension was 23.7 ± 3.20 days. The median survival time of drug-free nanoparticles group and untreated groups were 10.9 ± 1.45 and 10.6 ± 1.26 days, respectively. The results demonstrated the excellent immunosuppression of rapamycin-loaded chitosan/polylactic acid nanoparticles in corneal transplantation.
Keywords: Chitosan; Polylactic acid; Nanoparticles; Corneal transplantation; Immunosuppression;
PLGA nanoparticles of different surface properties: Preparation and evaluation of their body distribution by Farnaz Esmaeili; Mohammad Hossein Ghahremani; Behnaz Esmaeili; Mohammad Reza Khoshayand; Fatemeh Atyabi; Rassoul Dinarvand (249-255).
The opsonization or removal of nanoparticulate drug carriers from the body by the reticuloendothelial system (RES) is a major obstacle that hinders the efficiency of the nanoparticulate drug delivery systems. Therefore, several methods of camouflaging or masking nanoparticles (NPs) have been developed to increase their blood circulation half-life. In this study, rhodamine B isothiocyanate (RBITC) loaded NPs were fabricated by an emulsification/solvent diffusion method.The surface of NPs was then modified using either poly ethylene glycol (PEG) or block copolymer of ethylene oxide and propylene oxide, Poloxamer 407 (POL). The surface treatment was carried out using two different methods: (a) co-incorporation of the surface modifying agents (SMAs) into NPs and (b) the external surface adsorptions method and both of these methods were done only by physical incorporation of the SMAs into the NPs, without the need of special chemical reagents. The biodistribution properties of the NPs were then measured.The results confirmed that the surface treatment of the NPs using co-incorporation of the SMAs into NPs is more efficient in increasing the blood circulation half-life of the NPs when compared with the external surface adsorptions method.
Keywords: PLGA nanoparticles; Biodistribution; Surface treatment; Poly ethylene glycol; Poloxamer 407;
Selectivity of folate conjugated polymer micelles against different tumor cells by Haizheng Zhao; Lin Yue Lanry Yung (256-268).
Folate or folic acid has been employed as a targeting moiety of various anticancer agents to increase their cellular uptake within target cells since folate receptors are vastly overexpressed in several human tumors. In this study, a biodegradable polymer poly(d,l-lactide-co-glycolide)–poly(ethylene glycol)–folate (PLGA–PEG–FOL) was used to form micelles for encapsulating anticancer drug doxorubicin (DOX). The drug loading content, encapsulation efficiency and in vitro release were characterized. To evaluate the targeting ability of the folate conjugated micelles, the cytotoxicity and cellular uptake of DOX-loaded micelles on three cancer cell lines with different amount of folate receptors (KB, MATB III, C6) and normal fibroblast cells (CCL-110) were compared. The cytotoxicity of PLGA–PEG–FOL micelles to cancer cells was found to be much higher than that of normal fibroblast cells, demonstrating that the folate conjugated micelles has the ability to selectively target to cancer cells. For normal cells, the cellular uptake of PLGA–PEG–FOL micelles was similar to PLGA–PEG micelles without folate conjugation, and was substantially lower than that of cancer cells. In addition, the cell cycle analysis showed that the apoptotic percentage of normal fibroblasts was substantially lower compared with the cancer cells after exposing to DOX-loaded PLGA–PEG–FOL micelles. An optimal folate amount of approximately 40–65% on the micelles was found to be able to kill cancer cells but, at the same time, to have very low effect to normal cells.
Keywords: Folate; Polymer micelle; Selectivity; Drug targeting; Doxorubicin;
The advantage of polymer addition to a non-ionic oil in water microemulsion for the dermal delivery of progesterone by Babette Biruss; Claudia Valenta (269-273).
The influence of progesterone on the physicochemical behaviour of the o/w microemulsion consisting of the non-ionic surfactant polyoxyethylene-10-dodecyl ether, tributyrin and water was investigated. Thereby no significant influence could be detected in terms of droplet size, zeta potential, conductivity and pH by progesterone. However the chemical stability of progesterone was insufficient during the storage of 6 months. Therefore, two different polymeric agents, named silicon dioxide and polymeric emulsifier, were added to the progesterone containing microemulsions. These polymers increased the chemical stability of progesterone significantly. Moreover the polymeric additives improved the skin permeation 1.24- and 1.63-fold and decreased the skin retention in relation to the pure microemulsion. The polymer-stabilized progesterone microemulsions are interesting vehicles for skin application of progesterone.
Keywords: Progesterone; Polymeric additives; Microemulsion; Stability; Skin permeation;
Preparation and characterization of sodium ferulate entrapped bovine serum albumin nanoparticles for liver targeting by Feng-Qian Li; Hua Su; Jing Wang; Ji-Yong Liu; Quan-Gang Zhu; Yi-Bo Fei; Yong-Hua Pan; Jin-Hong Hu (274-282).
Sodium ferulate (SF) loaded nanoparticles were prepared by desolvation procedure and subsequent cross-linking of the wall material of bovine serum albumin (BSA). Several factors in the nanoencapsulation process, such as the addition rate of the desolvation agent, composition of BSA and SF solution, amount of the cross-linker glutaraldehyde, were investigated to elucidate their influences on the particle size, zeta potential, drug loading and encapsulation efficiency of the resulted nanoparticles. The obtained spherical nanoparticles were negative charged with zeta potential from −20 to −40 mV, and characterized between 100 and 200 nm with a narrow size distribution. In the condition of introducing 1.0 mL 8% glutareldehyde per mg of BSA, the drug entrapment efficiency (EE) of 80% (w/w) and loading capacity of about 16% (w/w) could be achieved for the cross-linked BSA nanoparticles with SF encapsulated (SF-BSA-NP). And the drug EE was decreased along with the increasing amount of glutareldehyde used for cross-linking. The in vitro drug release properties of SF-BSA-NP behaved with an initial burst effect and then sustained-release stage. To some extent, the drug release rate could be adjusted by cross-linking with different amount of glutaraldehyde. Compared with SF solution, SF-BSA-NP showed a much higher drug distribution into liver and a lower drug concentration in other tissues, after intravenously injected to mice. So, BSA based nanoparticles might be a suitable controlled released carrier for the freely water-soluble drug SF and further hepatic targeted drug delivery.
Keywords: Sodium ferulate; Bovine serum albumin; Nanoparticles; Desolvation; Liver-targeted delivery;
LAPONITE®-based nanohybrid for enhanced solubility and controlled release of itraconazole by Hyun Jung; Hyun-Mi Kim; Young Bin Choy; Seong-Ju Hwang; Jin-Ho Choy (283-290).
LAPONITE®, a form of layered aluminosilicates, and itraconazole, a water insoluble drug, were hybridized through an interfacial reaction at the boundary between water and a water-immiscible liquid. The reaction was carried out under a controlled pH to maintain both physical and chemical stability of the drug. The X-ray diffraction patterns and spectroscopic analyses indicated that itraconazole was intercalated into the interlayer space of clay with a lateral monolayer structure. No significant chemical structural change of itraconazole was seen through the formation of the hybrid. The hybrid system exhibited enhanced solubility and controlled release of itraconazole. The released amount of itraconazole could be controlled in the range from 18 to 75%, depending on the kinds of cations in the release media.
Keywords: Itraconazole; Clay; Nanohybrid; Solubility; Controlled release;
The properties of bufadienolides-loaded nano-emulsion and submicro-emulsion during lyophilization by Fang Li; Tao Wang; Hai Bing He; Xing Tang (291-299).
The aim of this study was to prepare two types of emulsions, bufadienolides-loaded nano-emulsion (BU-NE) and submicro-emulsion (BU-SE) which were separately prepared by ultrasonic-high-pressure homogenization (UHPH) and high-pressure homogenization (HPH) methods, and to try to stabilize the colloid systems by lyophilization. The lyoprotective effects of cryoprotectant carbohydrates during the freeze-thawing and freeze-drying cycles on the emulsions were investigated in detail. The lyophilized products were characterized with regard to their appearance and particle size by transmission electron microscopy (TEM), scanning electron microscopy (SEM), photon correlation spectroscopy (PCS) and zeta potential. The median diameter, polydispersity index (PI) and zeta potential of BU-NE and BU-SE were 43.5 nm versus 161.4 nm, 0.100 versus 0.143 and −19.7 to −26.2 mV versus −29.4 to −35.3 mV, respectively. With the same drug content (0.28 mg mL−1) BU-SE exhibited a higher entrapment efficiency than BU-NE. The optimum cryoprotectant for BU-NE and BU-SE was maltose (20%) and trehalose (20%), respectively. The median diameters (95.7 and 168.5 nm) of the rehydrated BU-NE and BU-SE were slightly increased. For both of them, the bufadienolides entrapment efficiency was reduced whereas the drug content was not. The lyophilized BU-NE and BU-SE powders were stable over a period up to 3 months with no change in visual appearance, reconstitution ability, particle size distribution and drug concentration. This shows that freeze-drying could be a promising method to stabilize the emulsions.
Keywords: Bufadienolides; Nano-emulsion; Submicro-emulsion; Cryoprotectant; Lyophilization;
Sulfonamides as a subject to study molecular interactions in crystals and solutions: Sublimation, solubility, solvation, distribution and crystal structure by German L. Perlovich; Nadezda N. Strakhova; Vladimir P. Kazachenko; Tatyana V. Volkova; Valery V. Tkachev; Klaus-Jurgen Schaper; Oleg A. Raevsky (300-313).
Crystal structures of 4-amino-N-(4-chlorophenyl)-benzene-sulfonamide (IV), 4-amino-N-(2,3-dichlorophenyl)-benzene-sulfonamide (V), 4-amino-N-(3,4-dichlorophenyl)-benzene-sulfonamide (VI) and 4-amino-N-(2,5-dichlorophenyl)-benzene-sulfonamide (VII) were solved by X-ray diffraction method. Temperature dependencies of saturated vapour pressure and thermodynamic functions of sublimation process were calculated (IV: Δ G sub 298 = 74.0 kJ mo l − 1 , Δ H sub 298 = 134.1 ± 1.2 kJ mo l − 1 , Δ S sub 298 = 202 ± 3 J mo l − 1 K − 1 ; V: Δ G sub 298 = 61.7 kJ mo l − 1 , Δ H sub 298 = 141.1 ± 0.7 kJ mo l − 1 , Δ S sub 298 = 266 ± 2 J mo l − 1 K − 1 ; VI: Δ G sub 298 = 85.8 kJ mo l − 1 , Δ H sub 298 = 167.5 ± 3.6 kJ mo l − 1 , Δ S sub 298 = 274 ± 8 J mo l − 1 K − 1 ; VII: Δ G sub 298 = 75.7 kJ mo l − 1 , Δ H sub 298 = 155.4 ± 1.6 kJ mo l − 1 , Δ S sub 298 = 268 ± 4 J mo l − 1 K − 1 ). Thermochemical parameters of fusion and evaporation processes for the compounds were obtained. Temperature dependencies of the solubility in water, n-octanol were measured. The thermodynamic functions of solubility and solvation processes were deduced. The transfer processes of the molecules from water to n-octanol were analysed by diagram method and main driven forces were established.
Keywords: 4-Amino-N-(4-chlorophenyl)-benzene-sulfonamide; 4-Amino-N-(2,3-dichlorophenyl)-benzene-sulfonamide; 4-Amino-N-(3,4-dichlorophenyl)-benzene-sulfonamide; 4-Amino-N-(2,5-dichlorophenyl)-benzene-sulfonamide; Sublimation thermodynamics; Solubility; Solvation; Crystal structure; Transfer process;
Effect of particle size of dry powder mannitol on the lung deposition in healthy volunteers by William Glover; Hak-Kim Chan; Stefan Eberl; Evangelia Daviskas; Jordan Verschuer (314-322).
There is a lack of in vivo studies focusing on the effect of particle size of dry powder aerosols on lung deposition and distribution. We investigated the dose and distribution of radiolabelled powder aerosols of mannitol in the lungs using single photon emission tomography (SPECT). Three different sized radiolabelled powders were produced by co-spray drying mannitol with 99mTc-DTPA. The primary particle size distribution of the powders measured by laser diffraction showed a volume median diameter of 2, 3 and 4 μm with span 2.3, 2.0 and 2.1, respectively, which corresponded to an aerodynamic diameter of 2.7, 3.6, 5.4 μm and geometric standard deviation of 2.6, 2.4 and 2.7 when the powders were dispersed using an Aeroliser® dry powder inhaler. Three capsules each containing approximately 20 mg (i.e. a total of 60 mg containing 60–90 MBq) of each of the radiolabelled powders were inhaled by eight healthy volunteers using the Aeroliser® inhaler. Images of aerosol deposition in the lungs were acquired using fast, multi-bed position SPECT. The lung dose markedly decreased with increasing aerosol particle size (mean ± S.E.M.: 44.8 ± 2.4, 38.9 ± 0.9, 20.6 ± 1.6% for 2.7, 3.6, 5.4 μm, respectively, p < 0.0001). The sites of deposition of the 2.7 and 3.6 μm aerosols were similar (penetration index, PI = 0.63 ± 0.05, 0.60 ± 0.03, respectively, p > 0.3), but different to the 5.4 μm aerosols (PI = 0.52 ± 0.04, p < 0.02). The lung dose followed the in vitro powder dispersion performance, with the % lung dose being related to fine particle fraction by a slope of 0.8 for a regression with intercepts forced through the origin. The SPECT results provide direct evidence that the lung deposition of dry powder aerosols depends on the particle size. The lung dose of the 2.7 and 3.6 μm aerosols using the Aeroliser® was double compared to that of the 5.4 μm aerosols and the deposition of the smaller particles was more peripheral.
Keywords: Aerosol deposition; Particle size; Dry powder inhaler; SPECT imaging; Mannitol;
Probing the permeation enhancement of mefenamic acid by ethanol across full-thickness skin, heat-separated epidermal membrane and heat-separated dermal membrane by Charles M. Heard; Cerian Screen (323-325).
The permeation enhancement of mefenamic acid by ethanol across full-thickness porcine skin, heat-separated epidermal membrane and heat-separated dermal membrane has been probed. Three donor phases saturated with mefenamic acid were used: (1) PEG400; (2) PEG400 with 10% ethanol; (3) mefenamic acid in PEG 400 with 30 mg ml−1 cetrimide; these were applied to membranes mounted in Franz diffusion-type cells with 30 mg ml−1 cetrimide as receptor phase (n ≥ 5). Across full-thickness skin, the flux was below the limit of detection from PEG400, but with the inclusion of 10% ethanol was 0.83 μg cm−2 h−1. When cetrimide was present in the donor (and receptor) phase the flux was very low 0.1 μg cm−2 h−1. Across heat-separated epidermal membrane the flux from PEG was 11.9 ± 2.4 μg cm−2 h−1 with a 2.42× increase in flux observed when 10% ethanol was present (p = 0.0095). Across heat-separated dermal membrane the flux from PEG400 was 0.62 ± 0.13 μg cm−2 h−1, with a 2.34× increase in flux observed when 10% ethanol was present (p = 0.0027). To conclude, complexation and co-permeation with ethanol via a pull effect was confirmed as the mechanism of enhanced skin permeation of mefenamic acid. Full thickness skin provides a more effective barrier than either isolated dermis or epidermis, casting doubt over the use of heat-separated epidermal membranes to model skin permeation and penetration. There was evidence that cetrimide does not cause skin barrier modulation, supporting its use as an effective receptor phase.
Keywords: Mefenamic acid; Skin; Penetration enhancer; Ethanol; Mechanism; Complexation; Pull effect; Barrier; Stratum corneum; Epidermal membrane; Dermal membrane; Full-thickness skin;