International Journal of Pharmaceutics (v.318, #1-2)
Editorial Board (iii).
Gels as vaginal drug delivery systems by J. das Neves; M.F. Bahia (1-14).
The vagina has been used as a mucosal drug delivery route for a long time. Its single characteristics can be either limitative or advantageous when drug delivery is considered. Gels are semi-solid, three-dimensional, polymeric matrices comprising small amounts of solid, dispersed in relatively large amounts of liquid, yet possessing more solid-like character. These systems have been used and are receiving a great deal of interest as vaginal drug delivery systems. Gels are versatile and have been used as delivery systems for microbicides, contraceptives, labour inducers, and other substances. Although somewhat neglected in clinical studies, pharmaceutical characterization of vaginal gels is an important step in order to optimize safety, efficacy and acceptability. Indeed, the simple formulation of a gel can lead to different performances of systems containing the same amount of active substances. Therefore, this paper discusses and summarizes current use and research of vaginal drug delivery systems based in gels.
Keywords: Vagina; Gels; Microbicides; Contraceptives; Labour inducers;
Zero-order release of aspirin, theophylline and atenolol in water from novel methylcellulose glutarate matrix tablets by A. Khairuzzaman; S.U. Ahmed; M. Savva; N.K. Patel (15-21).
A novel hydrocolloidal polymer, methylcellulose glutarate (MC-GA), was prepared by esterifying methylcellulose with glutaric anhydride. The formation of ester was confirmed by FTIR and NMR spectroscopy, DSC and elemental analysis. The physicochemical properties such as, rate of swelling in water, viscosity and hygroscopicity of MC-GA were determined and compared with those of methycellulose A (MC). Aspirin, theophylline and atenolol tablets were compacted on a Carver press using the wet granulation method. Each tablet contained: 200 mg active, 80 mg anhydrous lactose, 8 mg povidone, 4 mg magnesium stearate, 4 mg talc, 50 mg MC or MC-GA (drug-to-polymer ratio, 4:1). Contrary to the first-order release profile of all the drugs from the MC matrix tablets, a zero-order release was obtained from the MC-GA matrix tablets in water.
Keywords: Methylcellulose; Methylcellulose glutarate; Hydrocolloid; Matrix bases; Matrix tablets; Zero-order release;
Investigation to find a suitable reference material for use as an inverse gas chromatography system suitability test by J. Stapley; G. Buckton; D. Merrifield (22-27).
The purpose of this study was to find a suitable material for use as a system suitability test material for inverse gas chromatography (IGC). The purpose of a system check is to measure the variability of the instrument being used rather than the material being analysed. Having such a system check for IGC enables a basic GMP requirement to be met. IGC results can then be used in regulatory submissions to support other already established techniques for characterising pharmaceutical materials. α-Alumina was chosen because it is inorganic, stable at high temperatures, resistant to hydration and is already established as a system check material for surface area determination by nitrogen adsorption. Two columns (1 and 2) packed from the same reference sample jar of α-alumina and analysed under the same conditions yielded dispersive surface energies of 34.8 ± 0.8 and 35.3 ± 0.8 mJ/m2, respectively, at 15% RH. Column 1 was analysed on a second IGC system, and gave a dispersive surface energy of 34.7 ± 0.2 mJ/m2. No significant change was evident after 7 months storage under laboratory ambient conditions. Analysis of material from a second reference sample jar of α-alumina produced results not noticeably different to those of the first, yielding a dispersive surface energy of 35.3 ± 0.1 mJ/m2. A change was seen to occur in the surface properties α-alumina when the humidity was varied, but the change appeared to be consistent across the two columns reported. Based upon the data in this experimental, α-alumina appears to be a suitable material for use as a system suitability test material for IGC.
Keywords: Inverse gas chromatography; System suitability; α-Alumina; Dispersive surface energy;
Effects of the anti-neoplastic agent ET-18-OCH3 and some analogs on the biophysical properties of model membranes by Alejandro Torrecillas; J. Daniel Aroca-Aguilar; Francisco J. Aranda; Consuelo Gajate; Faustino Mollinedo; Senena Corbalán-García; Ana de Godos; Juan C. Gómez-Fernández (28-40).
The effect of 1-O-octadecyl-2-O-methyl-sn-glycero-3-phosphocholine (ET-18-OCH3, edelfosine), and six other analog asymmetric phosholipids on the physical properties of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) model membranes was studied using differential scanning calorimetry (DSC), 31P-nuclear magnetic resonance (31P NMR) and X-ray diffraction. DSC data revealed that, at concentrations of 40 mol% and higher, a new type of mixtures with higher T c and narrower transitions appeared with all the asymmetric lipids studied. At very high concentrations of these lipids (50–80 mol%), destabilization was observed in the systems probably because of the formation of micelles or small vesicles. In all cases, the asymmetric lipids at concentrations of 40 mol% induced the formation of interdigitated structures in the lamellar gel phase, as deduced from X-ray diffraction. The asymmetric phospholipids were also added to 1,2-dielaidoyl-sn-glycero-3-phosphoethanolamine (DEPE) model membranes and DSC data revealed that the lipids primarily affected transition from the lamellar gel (Lβ) to the lamellar liquid crystalline (Lα) phase in two aspects: the transition temperature was reduced, and the transition itself became broader and smaller. The lamellar liquid crystalline (Lα) to inverted hexagonal phase (HII) transition was also affected, as detected by DSC and 31P NMR data. Increasing concentrations of the asymmetric lipids reduced the formation of inverted hexagonal phases, which were completely inhibited in the case of ET-18-OCH3. Since these compounds have been shown to have important biological actions through the plasma membrane, these results may help to understand the mechanism of action of these compounds. In addition these asymmetric lipids were tested for their capacity to induce cell apoptosis, and only ET-18-OCH3 was found to have a clear effect, thus suggesting that the apoptotic effect is not exerted through changes in the biophysical properties of model membranes.
Keywords: ET-18-OCH3; ET-18-OH; ET-18-H; ET-16-OCH3-Ser; PAPC; LPC; PAF; Model membranes; 31P-NMR;
In vitro evaluation of the effect of cyclodextrin complexation on pulmonary deposition of a peptide, cyclosporin A by L. Matilainen; K. Järvinen; T. Toropainen; E. Näsi; S. Auriola; T. Järvinen; P. Jarho (41-48).
The effect of hydroxypropyl-α-cyclodextrin (HP-α-CD) complexation on in vitro pulmonary deposition of a cyclic peptide cyclosporin A (CsA) was studied. In addition, the effect of storage (32 days, 40 °C, 75% RH) on CsA/HP-α-CD complexes was studied. The complexation of CsA with CDs was evaluated by a phase-solubility method. Solid CsA/HP-α-CD complexes were prepared by freeze drying. Three inhalation formulations were prepared: CsA/lactose reference formulation (LF) (drug:carrier 1:364, w/w), CsA/HP-α-CD complex formulation (CDF) (drug:CD 1:269, w/w) and CsA/HP-α-CD complex/lactose formulation (CDLF) (complex:carrier 100:114, w/w). The inhalation studies were performed in vitro using Andersen Sampler (Ph. Eur.) and Taifun® multi-dose dry powder inhalers (DPIs). Before the storage, the respirable fraction value (RF%) of CsA was 19.8 ± 0.7%, 33.0 ± 7.0% and 34.6 ± 1.1% (mean ± S.D., n = 4 × 20) with LF, CDF and CDLF, respectively. When exposed to moisture (storage in a permeable polystyrene tube), the RF% values of CsA from formulations containing CsA/HP-α-CD complexes were lower than before the storage. However, when stored in the Taifun® DPI, the RF% value of CsA from any of the formulations did not decrease. In conclusion, an acceptable RF% value of a peptide CsA from freeze-dried, simply micronized CsA/HP-α-CD complex powder was achieved before and after storage in the DPI.
Keywords: Peptide; Cyclodextrin; Inhalation powder; Deposition;
Use of a molecular form technique for the penetration of supersaturated solutions of salicylic acid across silicone membranes and human skin in vitro by N. Leveque; S.L. Raghavan; M.E. Lane; J. Hadgraft (49-54).
Permeation enhancement of salicylic acid (SA) from supersaturated solutions formed using a ‘molecular form’ technique was investigated. In a conventional cosolvent technique, two solvents are used, one in which the drug is considerably more soluble than the other. Propylene glycol and water have been predominantly used as cosolvents to create supersaturation in skin permeation enhancement. In this paper, we report the use of buffer solutions with different pHs as media for producing different molecular forms.Supersaturated solutions were prepared using pH 8:pH 2 (80:20 v/v), which gave a nominal pH when mixed of around 5. Model silicone membranes and human skin were used. Hydroxypropyl methyl cellulose (HPMC) was employed to stabilise the supersaturated states. Stability data showed that while the SA supersaturated solutions without HPMC crystallised between 15 min and 46 h depending on the degree of supersaturation, the solutions with HPMC were stable for more than 2 months. The flux of SA increased with the degree of saturation for solutions prepared in a 80:20 buffer pH 8/buffer pH 2 mixture. Although the fluxes of SA with and without HPMC were similar both through silicone membrane and human skin, HPMC was found to be effective in increasing the stability of supersaturated solutions of SA.
Keywords: Supersaturation; pH; Silicone membrane; Skin; Salicylic acid; Permeation enhancement;
Preparation and properties of poly(vinyl alcohol)-stabilized liposomes by Xiaomei Mu; Zhensheng Zhong (55-61).
The purpose of this work is to evaluate the improvement in physical stability of poly(vinyl alcohol) (PVA) modified liposomes. Liposomes composed of soya phosphatidylcholile (SPC) and cholesterol (1:1 molar ratio) were prepared by reverse phase evaporation method. Two types of interaction between liposome and PVA were investigated: PVA addition into lipid bilayer during liposome preparation and coating of already formed liposomes with PVA. The microparticles system was morphologically characterized by transmission electron microscopy (TEM) and particles analysis. Changes in particles size and zeta potential confirmed the existence of a thick polymer layer on the surface of liposomes. The amount of PVA adsorbing to liposomes and the encapsulation efficiency increased with increasing polymer concentration. The physical stability was evaluated by measuring the release rate of contents at 20 and 37 °C, the PVA modified liposomes were more stable than the conventional liposomes. Comparing with PVA-coated liposomes, the liposomes with PVA addition to the bilayer were more stable, and had higher entrapment efficiency.
Keywords: Liposome; Poly(vinyl alcohol); Polymer modifying; Stability; Zeta potential;
Preparation of roxithromycin-polymeric microspheres by the emulsion solvent diffusion method for taste masking by Yan Gao; Fu-de Cui; Ying Guan; Lei Yang; Yong-sheng Wang; Li-na Zhang (62-69).
Microspheres of roxithromycin with Eudragit S100 and silica were prepared by the emulsion solvent diffusion method to mask the bitter taste of the antibiotic. The effect of different polymers and drug–polymer ratios on the taste masking and the characteristics of the microspheres were investigated. It was found that Eudragit S100 was the best for masking the unpleasant taste of roxithromycin among the six kinds of polymers investigated. The results of DSC, X-ray diffraction and IR showed that there were several combinations of roxithromycin and Eudragit S100. The influence of other formulation factors, i.e. dichloromethane–acetone ratios and silica–polymer ratios on the properties of the microspheres were also examined. In conclusion, the results of the present study will be helpful for the preparation of oral forms of roxithromycin with an acceptable taste.
Keywords: Roxithromycin; Eudragit S100; Microspheres; Emulsion solvent diffusion method; Taste masking;
A bilogarithmic method for the spectrophotometric evaluation of stability constants of 1:1 weak complexes from mole ratio data by Maravillas Boccio; Ana Sayago; Agustín G. Asuero (70-77).
The absorbance changes that occur when the mole ratio of the components of ligand complex equilibria is varied while the concentration of one component is kept constant (mole ratio method) allow evaluating stability constants in favourable conditions. Values of the corresponding stability (association) constants are normally assigned on the basis of spectrophotometric analysis. Determination of stability constants can be performed by a number of linear procedures, but most of these, suffer from theoretical and practical drawbacks, e.g., linear transformation of the rectangular hyperbola type of binding constants, is valid only when one of the two species is present in a large excess. A rigorous treatment of the experimental mole ratio data for 1:1 weak complexes is carried out in this paper with the aim of eliminating some of the assumptions involved in the other methods usually applied for evaluating stability constants. Orthogonal regression is required in order to take into account the error in both axes. The method has been applied to literature data for the iron(III)-thiocyanate and nickel(II)-selenocyanate systems, as well as to a number of host–guest cyclodextrin complexes.
Keywords: Mole ratio method; Bilogarithmic method; Orthogonal regression; Spectrophotometry; Iron(III)-thiocyanate; Nickel(II)-selenocyanate; Host–guest cyclodextrin complexes;
The use of Stokes deformation number as a predictive tool for material exchange behaviour of granules in the ‘equilibrium phase’ in high shear granulation by A.M. Bouwman; M.R. Visser; G.M.H. Meesters; H.W. Frijlink (78-85).
The objective of this study was three-fold; to investigate the different mechanisms of material exchange during the equilibrium phase of the granulation process and whether these mechanisms are consistent with the mechanisms described in the growth regime map, to study how material properties and process conditions affect these exchange mechanisms, and to correlate Stokes deformation number to the exchange mechanisms.Microcrystalline cellulose (MCC), α-lactose, microfine cellulose (MFC), and dextrin were granulated using water as a binding agent. Once in the equilibrium phase, 5% (w/w) of the granular mass was replaced with wet tracer granules, after which the granulation process was continued. Granules were typically of a size of approximately 1 mm in diameter. Therefore, these granules can also be called pellets.Tracer experiments show indeed solid material exchange can take place in the equilibrium phase of the high shear granulation process. Tracer material was equally dispersed throughout the whole batch for all materials tested. However, the granulation time needed to reach this homogeneous distribution varied with material and granulation conditions. Three different mechanisms of material exchange were identified: exchange by disintegration, where granules are rapidly crushed and formed to granules again; exchange by deformation, where abraded granule fragments immediately fuse with other granules; and exchange by distribution, where there is a prolonged period over which both tracer and standard granules stay intact, followed by uncontrolled growth and exchange of material. It was found that it is possible to shift between the mechanisms by changing the process conditions, e.g., changing viscosity or amount of binder liquid. These observations indicate that by choosing the appropriate process conditions improved distribution of small amounts of insoluble materials in the granules can be obtained.A relation exists between the exchange mechanisms and the growth regime map: the disintegration mechanism resembles ‘crumb behaviour’, the deformation mechanism resembles ‘steady growth’, and the distribution mechanism resembles ‘nucleation’ and ‘induction growth’. Unfortunately, Stokes deformation number cannot be used as a predictive tool when low viscosity binders like water are used, due to the importance of viscosity in the equation. However, this number is one of the variables of the growth regime map. Since the exchange mechanisms correspond to the granule growth mechanisms in the regime map, alternatively colour experiments might be used to reveal the granulation regime.
Keywords: Stokes’ deformation number; High shear granulation; Material exchange; Equilibrium phase; Growth regime map;
Thermodynamic and kinetic characterization of polymorphic transformation of famotidine during grinding by Shan-Yang Lin; Wen-Ting Cheng; Shun-Li Wang (86-91).
Two polymorphs of famotidine were prepared by recrystallization from acetonitrile for form A and methanol for form B, respectively. The effect of grinding process on the polymorphic transformation of famotidine was investigated. Each famotidine sample ground for various grinding times in a ceramic mortar was determined by differential scanning calorimetry (DSC), conventional and thermal Fourier transform infrared (FT-IR) microspectroscopy. The results indicate that the raw material of famotidine was proved to be a form B. A unique IR absorption band at 3505 cm−1 for famotidine form B gradually decreased its intensity with the grinding time, while two newer IR absorption bands at 3451 and 1671 cm−1 for famotidine form A slowly appeared. The peak intensity ratio of 3451/3505 cm−1 was linearly (r = 0.9901) increased with the grinding time, suggesting that the grinding process could induce the polymorphic transformation of famotidine from form B to form A by a zero-order process. The DSC endothermic peaks also confirmed this polymorphic transformation from famotidine form B (167 °C, ΔH: 165 J/g) to famotidine form A (174 °C, ΔH: 148 J/g) in which the values of enthalpy were linearly reduced with the increase of grinding time (r = 0.9943). The phase transition temperature of the different ground famotidine samples could be easily and only evidenced by using thermal FT-IR microspectroscopy, rather than by DSC analysis. These phase transition temperatures of the famotidine form B ground for 5–20 min quickly reduced from 144 to 134 °C and maintained a constant at 134 °C even after 20–30 min grinding. The grinding process not only decreased the crystallinity of famotidine form B but also reduced the particle size of famotidine form B, resulting in easy induction of the polymorphic transformation of famotidine from form B to form A in ground famotidine sample.
Keywords: Famotidine; Grinding; Polymorphic transformation; DSC; Thermal FT-IR;
Evaluation of melt granulation and ultrasonic spray congealing as techniques to enhance the dissolution of praziquantel by Nadia Passerini; Beatrice Albertini; Beatrice Perissutti; Lorenzo Rodriguez (92-102).
Praziquantel (PZQ), an anthelminthic drug widely used in developing countries, is classified in Class II in the Biopharmaceutics Classification Systems; this means that PZQ has very low water solubility and high permeability, thus the dissolution is the absorption rate-limiting factor. The aim of this work was to evaluate the suitability of melt granulation and ultrasonic spray congealing as techniques for enhancing the dissolution rate of PZQ. Granules in high shear mixer were prepared by melt granulation, using polyethylene glycol 4000 or poloxamer 188 as meltable binders and α-lactose monohydrate as a filler. Quite regularly shaped granules having main size fraction in the range 200–500 μm were obtained using both formulations; however, only poloxamer 188 granules demonstrated a significant (P = 0.05) increase of the PZQ dissolution rate compared to pure drug. To evaluate the potential of ultrasonic spray congealing, Gelucire 50/13 microparticles having different drug to carrier ratios (5, 10, 20 and 30%, w/w) were then prepared. The results showed that all the microparticles had a significant higher dissolution rate (P = 0.05) respect to pure PZQ. The increase of the PZQ content considerably decreased the dissolution rate of the drug: 5 and 10% PZQ loaded systems evidenced dissolution significantly enhanced compared to 20 and 30% PZQ microparticles. The microparticle's characterisation, performed by Differential Scanning Calorimetry, Hot Stage Microscopy, X-ray powder diffraction and FT-Infrared analysis, evidenced the absence of both modifications of the solid state of PZQ and of significant interactions between the drug and the carrier. In conclusion, melt granulation and ultrasonic spray congealing could be proposed as solvent free, rapid and low expensive manufacturing methods to increase the in vitro dissolution rate of PZQ.
Keywords: Praziquantel; Dissolution; Melt granulation; Spray congealing;
Design and evaluation of colon specific drug delivery system containing flurbiprofen microsponges by Mine Orlu; Erdal Cevher; Ahmet Araman (103-117).
The purpose of this study was to design novel colon specific drug delivery system containing flurbiprofen (FLB) microsponges. Microsponges containing FLB and Eudragit RS 100 were prepared by quasi-emulsion solvent diffusion method. Additionally, FLB was entrapped into a commercial Microsponge® 5640 system using entrapment method. Afterwards, the effects of drug:polymer ratio, inner phase solvent amount, stirring time and speed and stirrer type on the physical characteristics of microsponges were investigated. The thermal behaviour, surface morphology, particle size and pore structure of microsponges were examined. The colon specific formulations were prepared by compression coating and also pore plugging of microsponges with pectin:hydroxypropylmethyl cellulose (HPMC) mixture followed by tabletting. In vitro dissolution studies were done on all formulations and the results were kinetically and statistically evaluated. The microsponges were spherical in shape, between 30.7 and 94.5 μm in diameter and showed high porosity values (61–72%). The pore shapes of microsponges prepared by quasi-emulsion solvent diffusion method and entrapment method were found as spherical and cylindrical holes, respectively. Mechanically strong tablets prepared for colon specific drug delivery were obtained owing to the plastic deformation of sponge-like structure of microsponges. In vitro studies exhibited that compression coated colon specific tablet formulations started to release the drug at the 8th hour corresponding to the proximal colon arrival time due to the addition of enzyme, following a modified release pattern while the drug release from the colon specific formulations prepared by pore plugging the microsponges showed an increase at the 8th hour which was the time point that the enzyme addition made. This study presents a new approach based on microsponges for colon specific drug delivery.
Keywords: Microsponge; Flurbiprofen; Pore structure; Quasi-emulsion solvent diffusion method; Colon specific drug delivery;
A DSC and Raman spectroscopy study on the effect of PAMAM dendrimer on DPPC model lipid membranes by Konstantinos Gardikis; Sophia Hatziantoniou; Kyriakos Viras; Matthias Wagner; Costas Demetzos (118-123).
The interaction between PAMAM (polyamidoamine) dendrimer generation 4 (G4) and 3,5 (G3,5) with model lipid membranes composed of dipalmytoylphosphatidylcholine (DPPC) has been investigated. Differential scanning calorimetry (DSC) and Raman spectroscopy were applied to assess the thermodynamic changes caused by PAMAM G4 and G3,5 and to specify the exact location of these dendrimers into the DPPC lipid bilayer. DSC thermograms indicated that the maximum percentages of PAMAM G4 and of G3,5 that can be incorporated in the DPPC membrane without deranging its integrity were 5% and 3%, respectively. The Raman intensity ratios I 2935/2880, I 2844/2880 and I 1090/1130 cm−1 showed the degree of the fluidity of the lipid bilayer, while the absorption at 715 cm−1 showed a strong interaction of PAMAM G4 and G3,5 with the polar head group of phospholipid. The results showed that the incorporation of the PAMAM G4 and G3,5 dendrimers in DPPC bilayers causes a concentration dependent increase of the membrane fluidity and that the bilayers interact strongly with both the lipophilic part and the polar head group of the phospholipids. Due to the current weak knowledge relating to the mechanism(s) under which dendrimers interact with lipidic membranes and transport through cells, these results may justify the tendency of dendrimers to disrupt biological membranes. The findings from this study could also prove helpful to rationally design new liposomal drug carriers for bioactive molecules by combining dendrimeric and liposomal technologies.
Keywords: Lipid membrane; Dendrimer; PAMAM; DSC; Raman spectroscopy;
Development of pulsatile multiparticulate drug delivery system coated with aqueous dispersion Aquacoat® ECD by Andrei Dashevsky; Ahmad Mohamad (124-131).
The objective of this study was to develop and evaluate a pulsatile multiparticulate drug delivery system (DDS), coated with aqueous dispersion Aquacoat® ECD. A rupturable pulsatile drug delivery system consists of (i) a drug core; (ii) a swelling layer, comprising a superdisintegrant and a binder; and (iii) an insoluble, water-permeable polymeric coating. Upon water ingress, the swellable layer expands, resulting in the rupturing of outer membrane with subsequent rapid drug release.Regarding the cores, the lag time was shorter, when 10% (w/w) theophylline was layered on sugar cores compared with cores consisting of 100% theophylline. Regarding swelling layer, the release after lag time was fast and complete, when cross-linked carboxymethyl cellulose (AcDiSol®) was used as a swelling agent.In contrast, a sustained release was achieved after the lag time, when low-substituted hydroxypropyl cellulose (L-HPC) and sodium starch glycolate (Explotab®) were used as swelling agents. The optimal level of AcDiSol® to achieve a fast and complete release after the lag time was 26% (w/w) (based on the weight of the coated pellets) for poorly soluble theophylline and 48% (w/w) for highly soluble propranolol HCl. The lag time can be controlled by the coating level of an outer membrane and increased with increasing coating level of the outer membrane. Outer membrane, formed using aqueous dispersion Aquacoat® ECD was brittle and ruptured sufficiently to ensure fast drug release, compared to ethylcellulose membrane formed using organic solution. The addition of talc led to increase brittleness of membrane and was very advantageous because of (i) reduced sensitivity of lag time on variations in the coating level and (ii) fast and complete drug release. Drug release starts only after rupturing of outer membrane, which was illustrated by microscopical observation of pellet during release.
Keywords: Pulsatile release; Rupturing system; Superdisintegrant; AcDiSol®; Aqueous coating; Aquacoat® ECD;
Sigmoidal release of indomethacin from pectin matrix tablets: Effect of in situ crosslinking by calcium cations by Xiuli Wei; Ningyun Sun; Baojian Wu; Chunhua Yin; Wei Wu (132-138).
Sigmoidal release pattern is therapeutically beneficial for timed release and colonic drug delivery, and is always observed in coated systems. In this study, sigmoidal release from pectin matrix tablets with indomethacin as a model drug was investigated. The underlying mechanisms are calcium cation-induced in situ crosslinking that retard the initial drug release to a limited percentage. Power law equation n values were estimated for sigmoidal release profiles. Results indicated that calcium chloride incorporated in pectin matrix functioned as retarding mechanisms on drug release. Larger amount of calcium chloride led to slower drug release and matrix erosion. Even at extremely high levels, retarding on drug release and matrix erosion rate was obvious, which highlighted the effect of calcium-induced in situ crosslinking as calcium chloride was a freely water-soluble salt. The sigmoidal release profiles were characterized by power law equation with high correlation coefficients of about 0.99 or over. Power law n values increased up to as high as 1.20 when calcium chloride content kept increasing. Erosion correlated well with release in almost all pectin matrix tablets indicating erosion-controlled mechanisms. It is concluded that large amount of calcium induces in situ crosslinking of pectin matrix and leads to sigmoidal release of indomethacin, and power law n values, sometimes larger than 1.0, are suitable to be used to describe sigmoidal release profiles.
Keywords: Pectin; Calcium chloride; Indomethacin; Matrix tablets; In situ crosslinking; Power law;
Influence of disease stage on polyethylenimine-mediated plasmid DNA delivery in murine hepatitis by Hitoshi Sasaki; Shohei Yoshida; Takashi Kitahara; Takashi Yoshioka; Hiroo Nakagawa; Tadahiro Nakamura; Nobuhiro Ichikawa; Koyo Nishida; Junzo Nakamura; Mikiro Nakashima (139-145).
In order to determine the influence of hepatic disease-stage on polyethylenimine-mediated gene delivery, we investigated branched and linear polyethylenimine (B-PEI, L-PEI)-mediated plasmid DNA delivery with time in murine hepatitis induced by a subcutaneous injection of tetrachloro carbon (CCl4). Plasmid DNA (pDNA) encoding firefly luciferase was used as the model reporter gene. We determined luciferase activity in various organs of CCl4-treated mice and control mice after an intravenous administration of B-PEI and L-PEI/pDNA complexes. Both B-PEI and L-PEI/pDNA complexes showed significantly lower gene expression in the liver, spleen, and lung at the stage of severe hepatitis (18 h after CCl4 injection), whereas the complexes induced gene expression in the liver at the liver regeneration stage (48 h after CCl4 injection). Significant differences in gene expressions between CCl4-treated mice and control mice vanished in most organs at the hepatitis subsidence stage (168 h after CCl4 injection), indicating that the influence of hepatitis induced by CCl4 was reversible with PEI-mediated gene delivery. Our findings demonstrated that murine hepatitis induced by CCl4 could influence polyethylenimine-mediated plasmid DNA delivery according to the disease stage. These results indicate the necessity of considering the timing and dose of gene therapy according to the disease stage.
Keywords: Gene delivery; Polyethylenimine; Murine hepatitis; Non-viral vector; Disease stage;
Solid-state 13C NMR study of indomethacin polymorphism by Katsuhiko Masuda; Sachio Tabata; Hiroyuki Kono; Yasuyuki Sakata; Tetsuo Hayase; Etsuo Yonemochi; Katsuhide Terada (146-153).
The purpose of this study was to analyze the difference in the molecular conformation packed in the crystal lattice between the meta-stable α-form and stable γ-form of indomethacin on the basis of solid-state 13C NMR spectral patterns. The chemical shifts of each resonance of the α-form were distinctly different from the γ-form. Each carbon nucleus of the γ-form showed a single signal with no splitting. In contrast, carbon nuclei of the α-form showed a complicated set of resonances for each carbon. For some carbons of the α-form, four signals assigned to one carbon were observed at 203 K. Two of these four signals were merged between the temperature range from 203 to 343 K without a transformation in the crystal structure. It was found that solid-state 13C NMR can be a powerful tool to estimate the number of molecular conformations as well as configurational differences in the packing of molecules in a unit cell.
Keywords: Solid-state 13C NMR; Indomethacin; Polymorphism;
Hexosomes formed from glycerate surfactants—Formulation as a colloidal carrier for irinotecan by Ben J. Boyd; Darryl V. Whittaker; Shui-Mei Khoo; Greg Davey (154-162).
A new class of amphiphiles with a glycerate headgroup, recently shown to form reverse hexagonal phase in excess water, have been dispersed to form Hexosome dispersions comprising sub-200 nm particles retaining the internal nanostructure of the parent HII phase. The application of these novel materials to the development of a new injectable formulation of irinotecan was investigated. The formulation of irinotecan with a small percentage of oleic acid in oleyl glycerate permitted a clinically relevant dose of irinotecan to be dissolved in the glycerate surfactant and dispersed in aqueous medium to form an injectable particle-based dose form of irinotecan. Importantly, incorporation of irinotecan into Hexosomes at neutral pH did not result in conversion from the active lactone to the inactive carboxylate form on storage, and is hence a promising alternative to the current low pH formulation of irinotecan required to inhibit this conversion. Although release of irinotecan from the Hexosomes was shown to be virtually instantaneous from the Hexosomes on substantial dilution, the retention of the drug in lactone form at neutral pH demonstrates a potential application of these novel nanostructured particles in injectable drug delivery.
Keywords: Nanostructured lipid carriers; Liquid crystalline phases; Irinotecan; Formulation; In vitro release;
Lectin anchored stabilized biodegradable nanoparticles for oral immunization by Prem N. Gupta; Sunil Mahor; Amit Rawat; Kapil Khatri; Amit Goyal; Suresh P. Vyas (163-173).
The investigation comprises development of a stable and targeted formulation of HBsAg for the oral immunization against Hepatitis B. PLGA nanoparticles bearing HBsAg was prepared by double emulsion method. The antigen was protected from organic/aqueous interface by using protein stabilizer, trehalose. The acidic environment generated within PLGA nanoparticles was neutralized by co-encapsulation of a basic additive, Mg(OH)2 which provides an additional stabilization to the antigen especially against acid induced antigen inactivation. Furthermore, lectin from Arachis hypogaea (PNA) was anchored on to the surface of the HBsAg loaded nanoparticles in order to enhance their affinity towards the antigen presenting cells of the Peyer's patches. The developed system was characterized for shape, size and loading efficiency. The antigen integrity was assessed by using SDS-PAGE followed by isoelectric focusing analysis. Bovine submaxillary mucin (BSM) was used as a biological model for in vitro ligand affinity determination and activity studies. The lectin anchored nanoparticles exhibited 52.18 ± 4.73% loading while ligand density was estimated to be of 17.90 ± 1.14 μg/mg. The results suggest that HBsAg can be successfully stabilized by co-encapsulation of an appropriate protein stabilizer, i.e. trehalose and a basic additive, Mg(OH)2. The ligand-coupled nanoparticles demonstrated approximately four folds increase in degree interaction with the BSM as compared to plain nanoparticles. Additionally, the nanoparticles maintained their intrinsic sugar specificity as associated due to lectin (PNA).
Keywords: Oral immunization; HBsAg; Protein stability; Vaccine targeting; Nanoparticles; Arachis hypogaea;