International Journal of Pharmaceutics (v.348, #1-2)
Editorial Board (iii).
Rejection by Alexander T Florence (1-2).
One-solvent polymorph screen of carbamazepine by A. Getsoian; R.M. Lodaya; A.C. Blackburn (3-9).
To emphasize the fact that solvents can be either critical or immaterial in crystallizing specific polymorphs, a method for obtaining multiple polymorphs of a compound using only one solvent is demonstrated. By varying the crystallization temperature and level of supersaturation, three of the four polymorphs of carbamazepine (CBZ; 5H-dibenz [b,f]azepine-5-carboxamide) were crystallized from cumene (isopropyl benzene). Form III, also referred to as the primitive monoclinic form, was produced at temperatures below 60 °C from supersaturated solutions concentrated at less than twice the solubility of that form. When the supersaturation was increased to twice the solubility of form III at temperatures below 60 °C, form II, also referred to as the trigonal form, was produced. Form I, also referred to as the triclinic form, was produced regardless of the level of supersaturation at temperatures above 80 °C. Between 60 °C and 80 °C, mixtures of forms were produced. Competition slurries were employed to establish the transition temperature to be between 79 °C and 82 °C for the enantiotropically related forms III and I. These results indicate that crystallization of CBZ from cumene can either be under thermodynamic control or affected by the kinetics of crystallization of metastable forms. This raises the question about the importance of solvent diversity when looking for polymorphs, suggesting that a rational experimental design can be used to greatly reduce the number of solvents and crystallization conditions. The results of this one-solvent polymorph screen correlate somewhat with a phase–solubility diagram for CBZ.
Keywords: Carbamazepine; Polymorphism; Polymorph screen; Supersaturation; Crystallization; Cumene; Enantiotropic transition temperature;
Influence of fine lactose and magnesium stearate on low dose dry powder inhaler formulations by R. Guchardi; M. Frei; E. John; J.S. Kaerger (10-17).
The behaviour of dry powder blends for inhalation, depending on the amount of fine lactose particles smaller than 10 μm and the presence of magnesium stearate (MgSt), was studied in this work. A laser light diffraction method was developed to determine accurately size and volume fraction of these fine lactose particles in coarse carrier lactose (x 50 ∼ 220 μm). A linear relationship between measured volume fraction undersize at 10 μm Q 3(10 μm) and added fine lactose could be established. Aerodynamic particle size distribution analysis of lactose showed that the fine lactose was attached to the coarse particles. In the presence of MgSt this interaction was increased. Consequently, the number of free active sites on the carrier surface was reduced and the investigated drug (formoterol fumarate dihydrate) was more effectively delivered. Addition of fine lactose and MgSt improved the aerodynamic performance the drug, as determined by resulting fine particle fraction, by 3% (for each 1% of added fine lactose) and 10%, respectively. Stability tests indicated that added MgSt was the most relevant of the studied parameter to achieve a stable aerodynamic performance. Its ability to protect the moisture uptake into the system was considered as rational for this effect.
Keywords: Formoterol; DPI; Inhalation; Lactose; Magnesium stearate;
Impact milling of pharmaceutical agglomerates in the wet and dry states by Luke R. Schenck; Russell V. Plank (18-26).
This study focused on the milling of wet granulated agglomerates at points before and after drying in a typical high-shear pharmaceutical process train. These steps, referred to here as wet and dry milling, utilized a conical screen mill. Milling of granulation in the wet state eliminated 1–10 mm size agglomerates without affecting granule porosity or inducing further agglomeration. These millimeter-size agglomerates broke down during wet milling into moderately sized fragments larger than 125 μm. In contrast, when milled after drying, these same 1–10 mm-size agglomerates broke down predominantly into fine particles less than 125 μm. Data from screen-less milling trials suggest that the mill screen served only as a classifier and did not significantly contribute to the route of breakage for either wet or dry milling. However, in the case of dry milling, mill screens with grated surface textures did result in fewer fines than non-grated screens. This may be a result of reduced residence time in the mill. Experiments varying the size fraction of feed material and the rotational speed of the mill's impeller identified impact attrition as the primary mechanism governing dry granule breakage. The findings in this study shed light into the fundamental breakdown behavior of pharmaceutical agglomerates and demonstrate how breakdown of wet agglomerates via a de-lumping step prior to drying can lead to a reduced level of fine particle generation during dry milling.
Keywords: Impact milling; Agglomerates; Wet granulation; Impact attrition;
Zero-order delivery of a highly soluble, low dose drug alfuzosin hydrochloride via gastro-retentive system by Quan Liu; Reza Fassihi (27-34).
A composite gastro-retentive matrix for zero-order delivery of highly soluble drug alfuzosin hydrochloride (10 mg) has been designed and characterized. Two systems containing polyethylene oxide (PEO), hydroxypropylmethylcellulose (HPMC), sodium bicarbonate, citric acid and polyvinyl pyrrolidone were dry blended and compressed into triple layer and bi-layer composite matrices. Dissolution studies using the USP 27 paddle method at 100 and 50 rpm in pH 2.0 and 6.8 were performed using UV spectroscopy at 244 nm, with automatic sampling over a 24 h period using a marketed product as a reference to calculate the “f 2” factor. Textural characteristics of each layer, the composite matrix as a whole, and floatation potential were determined under conditions similar to dissolution. Percent matrix swelling and erosion along with digital images were also obtained. Both systems proved to be effective in providing prolonged floatation, zero-order release, and complete disentanglement and erosion based on the analysis of data with “f 2” of 68 and 71 for PEO and HPMC based systems, respectively. The kinetics of drug release, swelling and erosion, and dynamics of textural changes during dissolution for the designed composite systems offer a novel approach for developing gastro-retentive drug delivery system that has potential to enhance bioavailability and site-specific delivery to the proximal small intestine.
Keywords: Gastro-retentive system; Controlled release alfuzosin; Zero-order drug delivery; Composite matrix; Texture analysis;
Study on colon-specific pectin/ethylcellulose film-coated 5-fluorouracil pellets in rats by Wei He; Qing Du; De-Ying Cao; Bai Xiang; Li-Fang Fan (35-45).
The purpose of the present study is to assess the biodistribution and pharmacokinetics of pectin/ethylcellulose film-coated and uncoated pellets containing 5-fluorouracil (5-FU) in rats. Both coated and uncoated pellets were orally administered to the rats at a dosage equivalent to 15 mg/kg. 5-FU concentrations in different parts of the gastrointestinal (GI) tract and plasma were quantitatively analyzed using a high-performance liquid chromatography (HPLC) assay. 5-FU released from uncoated pellets mainly distributes in the upper GI tract, however, 5-FU released from coated pellets mainly distributes in the cecum and colon. In plasma, the observed mean C max from the coated pellets group (3.65 ± 2.3 μg/mL) was lower than that of the uncoated pellets group (23.54 ± 2.9 μg/mL). The AUC values obtained from the uncoated pellets and the coated pellets were 49.08 ± 3.1 and 9.06 ± 1.2 μg h/mL, respectively. The relatively high local drug concentration with prolonged exposure time provides a potential to enhance anti-tumor efficacy with low systemic toxicity for the treatment of colon cancer.
Keywords: Colon-specific drug delivery; 5-Fluorouracil; Film-coated; Biodistribution; Pharmacokinetics; Colon cancer;
Evaluation of the deformation behavior of binary systems of methacrylic acid copolymers and hydroxypropyl methylcellulose using a compaction simulator by Aditya S. Tatavarti; Francis X. Muller; Stephen W. Hoag (46-53).
Methacrylic acid copolymers have been shown to enhance release of weakly basic drugs from rate controlling polymer matrices through the mechanism of microenvironmental pH modulation. Since these matrices are typically formed through a compaction process, an understanding of the deformation behavior of these polymers in there neat form and in combination with rate controlling polymers such as HPMC is critical to their successful formulation. Binary mixes of two methacrylic acid copolymers, Eudragit® L100 and L100-55 in combination with HPMC K4M were subjected to compaction studies on a compaction simulator. The deformation behavior of the powder mixes was analyzed based on pressure–porosity relationships, strain rate sensitivity (SRS), residual die wall force data and work of compaction. Methacrylic acid copolymers, L100-55 and L-100 and the hydrophilic polymer, HPMC K4M exhibited Heckel plots representative of plastic deformation although L-100 exhibited significantly greater resistance to densification as evident from the high yield pressure values (∼120 MPa). The yield pressures for the binary mixes were linearly related to the weight fractions of the components. All powder mixes exhibited significant speed sensitivity with SRS values ranging from 21.7% to 42.4%. The residual die-wall pressures indicated that at slow speeds (1 mm/s) and at lower pressures (<150 MPa), HPMC possesses significant elastic behavior. However, the good compacts formed at this punch speed indicate significant plastic deformation and bond formation which is able to predominate over the elastic recovery component. The apparent mean yield pressure values, the residual die-wall forces and the net work of compaction exhibited a linear relationship with mixture composition, thereby indicating predictability of these parameters based on the behavior of the neat materials.
Keywords: Compaction; Tablets; Eudragit®; pH modulating; Methacrylic acid; HPMC;
Thiolated chitosan: Development and in vitro evaluation of an oral delivery system for acyclovir by Thomas F. Palmberger; Juliane Hombach; Andreas Bernkop-Schnürch (54-60).
The aim of the study was to develop a novel oral delivery system for the efflux pump substrate acyclovir (ACY) utilizing thiolated chitosan as excipient which is capable of inhibiting P-glycoprotein (P-gp). Three chitosan–4-thiobutylamidine (Chito–TBA) conjugates with increasing molecular mass (Chito-9.4 kDa–TBA, Chito-150 kDa–TBA and Chito-600 kDa–TBA) were synthesized and permeation studies on rat intestinal mucosa and Caco-2 monolayers were performed. Additionally, tablets comprising the conjugates and ACY were tested towards their drug release behaviour. The efflux ratio (secretory P app/absorptive P app) of ACY across Caco-2 monolayers was determined to be 2.5 and in presence of 100 μM verapamil 1.1 which indicates ACY as P-gp substrate. In comparison to buffer only, the transport of ACY in presence of 0.5% (m/v) unmodified chitosan, 0.5% (m/v) Chito-150 kDa–TBA and 0.5% (m/v) Chito-150 kDa–TBA with 0.5% (m/v) reduced glutathione (GSH), was 1.3-, 1.6- and 2.1-fold improved, respectively. Transport studies across Caco-2 monolayers showed that P-gp inhibition is dependent on the average molecular mass of thiolated chitosan showing following rank order: 0.5% (m/v) Chito-150 kDa–TBA/GSH > 0.5% (m/v) Chito-9.4 kDa–TBA/GSH > 0.5% (m/v) Chito-600 kDa–TBA/GSH. The higher the molecular mass of Chito–TBA was, the more sustained was the release of ACY.Chito-150 kDa–TBA/GSH might be an appropriate sustained release drug delivery system for ACY, which is able to enhance ACY transport due to efflux pump inhibition.
Keywords: Acyclovir; Chitosan; Thiolated polymer; P-glycoprotein; Drug release;
Spherical crystallization of benzoic acid by Jyothi Katta; Åke C. Rasmuson (61-69).
This paper deals with the development of a method for spherical crystallization of benzoic acid. Benzoic acid is dissolved in ethanol, water is used as anti-solvent and chloroform is used as bridging liquid. After an introductory screening of different methods, the influence of the amount of the bridging liquid, the solute concentration and the stirring rate is investigated. The product particle characterization includes the particle size distribution, morphology and strength. The mechanical strength of single agglomerates has been determined by compression in a materials testing machine, using a 10 N load cell. It is found that favourable properties are obtained if the bridging liquid is added during the crystallization. Larger and stronger well-shaped agglomerates are formed. The stress–strain curves are J-shaped with no clear fracturing of the particles, and are well correlated by an exponential–polynomial equation.
Keywords: Crystallization; Spherical agglomeration; Benzoic acid; Physico-mechanical properties (size distribution, particle morphology, compression strength);
A lipid microsphere vehicle for vinorelbine: Stability, safety and pharmacokinetics by Hong Yao Zhang; Xing Tang; Hong Ying Li; Xiao Liang Liu (70-79).
A lipid microsphere vehicle for vinorelbine (VRL) was designed to reduce the severe venous irritation caused by the aqueous intravenous formulation of VRL. Lipid microspheres (LMs) were prepared by high pressure homogenization. The physical stability was monitored by the appearance, particle size and zeta potential changes while the chemical stability was achieved by using effective antioxidants and monitored by long-term investigations. Safety tests were performed by testing rabbit ear vein irritation and a guinea pig hypersensitivity reaction. A pharmacokinetic study was performed by determining the drug levels in plasma up to 24 h after intravenous administration of VRL-loaded LMs and conventional VRL aqueous injection separately. The VRL-loaded LMs had a particle size of 180.5 ± 35.2 nm with a 90% cumulative distribution less than 244.1 nm, while the drug entrapment efficiency was 96.8%, and it remained stable for 12 months at 6 ± 2 °C. The VRL-loaded LMs were less irritating and toxic than the conventional VRL aqueous injection. The pharmacokinetic profiles were similar and the values of AUC0−t were very close for the two formulations. A stable and easily mass-produced VRL-loaded LM preparation has been developed. It produces less venous irritation and is less toxic but has similar pharmacokinetics in vivo to the VRL aqueous injection currently commercially available.
Keywords: Vinorelbine; Lipid microspheres; Stability; Safety; Pharmacokinetics; Drug delivery;
Gastrointestinal distribution and absorption behavior of Eudragit-coated chitosan–prednisolone conjugate microspheres in rats with TNBS-induced colitis by Tomoko Oosegi; Hiraku Onishi; Yoshiharu Machida (80-88).
Conjugate of chitosan and succinyl-prednisolone, termed Ch–SP, was synthesized, and Ch–SP microspheres (Ch–SP-MS) and Eudragit L100-coated Ch–SP-MS (Ch–SP-MS/EuL) were prepared using Ch–SP. Ch–SP-MS and Ch–SP-MS/EuL had a mean size of 1.5 and 26.6 μm, respectively, and a drug content of 4.6 and 3% (w/w), respectively. Prednisolone (PD) was released very slow in JP 14 first fluid (pH 1.2), and gradually in JP 14 second fluid (pH 6.8). The addition of cecal or colonic content did not accelerate the release. Rats with 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced colitis were used in animal studies. Gastrointestinal distribution and plasma concentration were investigated by oral administration of PD alone and Ch–SP-MS/EuL. For PD alone, PD was distributed at the stomach and small intestine, and disappeared from the gastrointestinal tracts within 8 h. When administering Ch–SP-MS/EuL, the drug was distributed mainly in the lower intestine between 3 and 24 h. Plasma concentration was much lower in Ch–SP-MS/EuL than in PD alone, suggesting lower toxic side effects of Ch–SP-MS/EuL. Thus, Ch–SP-MS/EuL delivered PD specifically near the diseased site and PD was released gradually, with much less plasma concentration of PD. Ch–SP-MS/EuL are suggested as a useful delivery system to the site of inflammatory bowel disease.
Keywords: Eudragit L100-coated chitosan–prednisolone conjugate microspheres; TNBS-induced colitis; Gastrointestinal distribution; Plasma concentration; Drug release;
Assessment of oil polarity: Comparison of evaluation methods by M. El-Mahrab-Robert; V. Rosilio; M.-A. Bolzinger; P. Chaminade; J.-L. Grossiord (89-94).
In multiple emulsion systems, oily or aqueous transfers may occur between the dispersed droplets through the continuous phase. These transfers are controlled by both the surfactant system (micellar transport), and the partial solubility of one phase in another (molecular transport). The latter could be anticipated from the knowledge of oil polarity, if this information could easily be obtained. In this work, the relative polarity of eight oils used for various purposes has been evaluated from the comparison of their dielectric requirement for solubilization, their interfacial tension and chromatographic analysis. The results showed the complementarities of HPLC analysis and interfacial tension measurements and their superiority over the solubilization method for classifying oils as a function of their polarity.
Keywords: Multiple emulsions; Molecular transport; Oil polarity; Interfacial tension; HPLC;
Injectable block copolymer hydrogels for sustained release of a PEGylated drug by Lin Yu; Guang Tao Chang; Huan Zhang; Jian Dong Ding (95-106).
The paper employs the spontaneous physical gelling property of a biodegradable polymer in water to prepare an injectable sustained release carrier for a PEGylated drug. A series of thermogelling PLGA–PEG–PLGA triblock copolymers were synthesized. The PEGylated camptothecin (CPT) was also prepared and employed as the model of a PEGylated drug, and the solubility of this hydrophobic drug was significantly enhanced to over 150 mg/mL. The model drug was completely entrapped into the polymeric hydrogel, and the sustained release lasted for 1 month. The mechanism of the sustained release was diffusion-controlled at the first stage and then was the combination of diffusion and degradation at the late stage. In vivo anti-tumor tests in mice further confirmed the efficacy of the model PEGylated drug released from the hydrogel. This work also revealed the specificity of the PEGylated drug in such a kind of carrier systems by decreasing the critical gelling temperature and increasing the viscosity of the sol. Due to the very convenient drug formulation and highly tunable release rate, an injectable carrier platform for PEGylated drugs is thus set up.
Keywords: Injectable hydrogel; Block copolymer; PEGylation; Camptothecin (CPT); Sustained release;
Purified and surfactant-free coenzyme Q10-loaded biodegradable nanoparticles by Barrett J. Nehilla; Magnus Bergkvist; Ketul C. Popat; Tejal A. Desai (107-114).
The intent of this work was to synthesize and comprehensively characterize ubiquinone-loaded, surfactant-free biodegradable poly(lactic-co-glycolic acid) (PLGA) nanoparticles in vitro. Surfactant-free, empty and ubiquinone (CoQ10)-loaded biodegradable nanoparticles were synthesized by nanoprecipitation, and the physicochemical properties of these nanoparticles were analyzed with a variety of techniques. Nanoprecipitation consistently yielded individual, sub-200 nm, surfactant-free empty and CoQ10-loaded nanoparticles, where the physical and drug encapsulation characteristics were controlled by varying the formulation parameters. CoQ10 release was sustained for 2 weeks but then plateaued before 100% CoQ10 release. A novel, nondestructive purification protocol involving transient sodium dodecyl sulfate (SDS) adsorption to nanoparticles followed by centrifugation and dialysis was developed to yield purified, surfactant-free, CoQ10-loaded nanoparticles. This protocol permitted removal of unencapsulated CoQ10, prevented centrifugation-induced nanoparticle aggregation and preserved the surfactant-free and drug encapsulation properties of the nanoparticles. These CoQ10-loaded nanoparticles are promising as sustained drug delivery devices due to their extended CoQ10 release. Importantly, a surfactant-free nanoprecipitation procedure is presented that in combination with a novel purification step enables the synthesis of individual and purified CoQ10-loaded nanoparticles.
Keywords: Nanoprecipitation; PLGA nanoparticles; Coenzyme Q10; Drug delivery; Surfactant-free;
Incorporation of novel 1-alkylcarbonyloxymethyl prodrugs of 5-fluorouracil into poly(lactide-co-glycolide) nanoparticles by P.A. McCarron; M. Hall (115-124).
Incorporation of 1-alkylcarbonyloxymethyl prodrugs of 5FU into poly(lactide-co-glycolide) nanoparticles using nanoprecipitation methods gave increased loading efficiencies over that obtained using the parent drug substance. SEM studies revealed spherical nanoparticles of around 200 nm in diameter, corresponding well with measurements made using photon correlation spectroscopy. The C7 prodrug gave the best mean loading of 47.23%, which compared favourably to 3.68% loading achieved with 5FU. Loading efficiency was seen to follow the hydrophilic–lipophilic balance in the homologue series, where increases in lipophilicities alone were not good predictors of loading. Drug release, in terms of resultant 5FU concentration, was monitored using a flow-through dissolution apparatus. Cumulative drug release from nanoparticles loaded with the C5 prodrug was linear over 6 h, with approximately 14% of the total available 5FU dose released and with no evidence of a burst effect. The flux profile of the C5-loaded nanoparticles showed an initial peak in flux in the first sampling interval, but became linear for the remainder of the release phase. C7-loaded nanoparticles released considerably less (4% in 6 h) with a similar flux pattern to that seen with the C5 prodrug. The C9-loaded nanoparticles released less than 1% of the available 5FU over 6 h, with a similar zero-order profile. The C7 prodrug was deemed to be the prodrug of choice, achieving the highest loadings and releasing 5FU, following hydrolysis, in a zero-order fashion over a period of at least 6 h. Given the lack of burst effect and steady-state flux conditions, this nanoparticulate formulation offers a better dosing strategy for sustained intravenous use when compared to that arising from nanoparticles made by direct incorporation of 5FU.
Keywords: Nanoparticle; Fluorouracil; Prodrug; Alkylcarbonyloxymethyl; Poly(lactide-co-glycolide);
Dirhenium decacarbonyl-loaded PLLA nanoparticles: Influence of neutron irradiation and preliminary in vivo administration by the TMT technique by Misara Hamoudeh; Hatem Fessi; Henri Mehier; Achraf Al Faraj; Emmanuelle Canet-Soulas (125-136).
In a previous study, we have described the elaboration of PLLA-based nanoparticles loaded with non radioactive dirhenium decacarbonyl [Re2(CO)10], a novel neutron-activatable radiopharmaceutical dosage form for intra-tumoral radiotherapy. These nanoparticles are designed for a neutron irradiation which can be carried out in a nuclear reactor facility. This new paper describes the neutron irradiation influence on these Re2(CO)10-loaded PLLA nanoparticles. The loaded nanoparticles with 23% (w/w) of metallic rhenium have shown to remain stable and separated and to keep out their sphericity at the lower neutron flux (1 × 1011 n/cm2/s for 0.5 h) which was used for rhenium content determination (neutron activation analysis, NAA). However, when loaded nanoparticles were irradiated at the higher neutron flux (1.45 × 1013 n/cm2/s, 1 h), they have shown to be partially coagglomerated and some pores appeared at their surface. Furthermore, DSC results showed a decrease in the PLLA melting point and melting enthalpy in both blank and loaded nanoparticles indicating a decrease in polymer crystallinity. In addition, the polymer molecular weights (M n, M w) decreased after irradiation but without largely affecting the polymer polydispersity index (P.I.) which indicated that an irradiation-induced PLLA chain scission had occurred in a random way. The XRD patterns of irradiated PLLA provided another proof of polymer loss of crystallinity. FTIR spectra results have shown that irradiated nanoparticles retained the chemical identity of the used Re2(CO)10 and PLLA despite the reduction in polymer crystallinity and molecular weight. Nanoparticles suspending after irradiation became also more difficult, but it was properly achievable by adding PVA (1%) and ethanol (10%) into the dispersing medium. Moreover, after 24 h incubation of different irradiated nanoparticles in two different culture mediums, visual examination did not show bacterial growth indicating that applied neutron irradiation, yielding an absorbed dose of 450 kGy, can be a terminal method for nanoparticles sterilisation. Thereafter, in a preliminary in vivo experiment, superparamagnetic non radioactive nanoparticles loaded with Re2(CO)10 and oleic-acid coated magnetite have been successfully injected into a mice animal model via targeted multi therapy (TMT) technique which would be our selected administration method for future in vivo studies. In conclusion, although some induced neutron irradiation damage to nanoparticles occurs, dirhenium decacarbonyl-loaded PLLA nanoparticles retain their chemical identity and remain almost as re-dispersible and injectable nanoparticles by the TMT technique. These nanoparticles represent a novel interesting candidate for local intra-tumoral radiotherapy.
Keywords: Rhenium; PLLA; Nanoparticles; Neutron irradiation; Polymer; Crystallinity; TMT; Cancer;
Cellular uptake of solid lipid nanoparticles and cytotoxicity of encapsulated paclitaxel in A549 cancer cells by Hong Yuan; Jing Miao; Yong-Zhong Du; Jian You; Fu-Qiang Hu; Su Zeng (137-145).
The aim of this study was to investigate the cellular uptake of solid lipid nanoparticles (SLN) and cytotoxicity of its paclitaxel delivery system. The conjugate of octadecylamine–fluorescein isothiocyanate (ODA–FITC) was synthesized, and used as a marker to prepare fluorescent SLN. The cellular uptakes of fluorescent SLN with different lipid material were evaluated by fluorescence microscopy and the measurement of fluorescence intensity. The order of cellular uptake ability was glycerol tristearate SLN > monostearin SLN > stearic acid SLN > Compritol 888 ATO SLN (ATO888 SLN). The cellular cytotoxicities of paclitaxel were highly enhanced by the encapsulation of lipid matrix. Due to the lower drug entrapment efficiency of glycerol tristearate SLN, monostearin SLN was considered as the best lipid material to improve the cytotoxicity of drug. The polyethylene glycol monostearate (PEG–SA) and the synthesized conjugate of folic acid–stearic acid (FA–SA) were further introduced into monostearin SLN, respectively. The PEG and folate modified SLN could enhance the cellular uptake of SLN and the cellular cytotoxicity of drug by the membrane disturb ability of PEG chains on the SLN surface and the improved endocytosis mediated by folate receptor.
Keywords: Solid lipid nanoparticles; Cellular uptake; Cytotoxicity; Fluorescein isothiocyanate; Polyethylene glycol monostearate; Folic acid;
Nimodipine loaded lipid nanospheres prepared by solvent diffusion method in a drug saturated aqueous system by Fu-Qiang Hu; Yu Zhang; Yong-Zhong Du; Hong Yuan (146-152).
To overcome the disadvantages such as lower drug entrapment efficiency (EE) of lipid nanospheres prepared by conventional solvent diffusion method, a solvent diffusion method in drug saturated aqueous system was developed. Nimodipine was used as a model drug to incorporate into lipid nanospheres. The monostearin (MS) solid lipid nanoparticles (SLN) produced by conventional method under different production temperature only showed 24.40–30.21 wt% EE, and relatively higher EE was achieved when the production temperature was 0 °C. The EE could be enhanced by the incorporation of liquid lipid (caprylic/capric triglycerides, CT) into SLN and the employing of drug saturated dispersion medium. The nanostructured lipid carrier (NLC) with higher CT content indicated the highest EE as the drug saturated aqueous solution was used as dispersion medium. The differential scanning calorimetry (DSC) results demonstrated the present method could improve the drug encapsulation into lipid nanospheres. In vitro drug release experiments indicated the present preparation method could delay the drug release rate from lipid nanospheres, and the drug release rate could adjust by the CT content in lipid nanospheres. The highest drug loading (DL) was reached up to 4.22 wt% when 8 wt% drug was charged in the preparation of lipid nanospheres.
Keywords: Nimodipine; Lipid nanospheres; Solvent diffusion method; Monostearin; Caprylic/capric triglycerides; Drug entrapment efficiency;
Surface pressure measurements in particle interaction and stability studies of poly(lactic acid) nanoparticles by S. Hirsjärvi; L. Peltonen; J. Hirvonen (153-160).
Stability of nanoparticle dispersion in different environments is one key issue in determining the performance and safety of the drug delivery system in question. In this study, aggregation tendency and particle–particle interactions of poly(lactic acid) nanoparticles were evaluated by their interfacial behavior upon compression. Surface pressure versus trough area (π vs. A) isotherms of the nanoparticles were registered on different subphases (pH, electrolyte concentration). The compressed particle populations were transferred to silica plates by Langmuir–Schaefer deposition and analyzed with scanning electron microscope. Aggregation of the electrostatically stabilized surfactant-free nanoparticles due to subphase alterations was clearly detected from the isotherms even though zeta potential value of the nanoparticles (−35 mV) suggested a stable system. When steric stabilization, provided by a surfactant (Poloxamer 188) in this study, was involved besides the electrostatic stabilization, the nanoparticles remained non-aggregated over a wider range of conditions. Steric stabilization together with electrostatic stabilization extended the repulsion to a longer distance.
Keywords: Poly(lactic acid); Nanoparticle; Stability; Aggregation; Surface pressure; Langmuir–Schaefer deposition;
Evaluation of chitosan salts as non-viral gene vectors in CHO-K1 cells by Wanlop Weecharangsan; Praneet Opanasopit; Tanasait Ngawhirunpat; Auayporn Apirakaramwong; Theerasak Rojanarata; Uracha Ruktanonchai; Robert J. Lee (161-168).
The aim of this study was to investigate chitosan/DNA complexes formulated with various chitosan salts (CS) including chitosan hydrochloride (CHy), chitosan lactate (CLa), chitosan acetate (CAc), chitosan aspartate (CAs) and chitosan glutamate (CGl). They were assesed for their DNA complexing ability, transfection efficiency in CHO-K1 (Chinese hamster ovary) cells and their effect on cell viability. CHy, CLa, CAc, CAs and CGl, MW 45 kDa formed a complex with pcDNA3-CMV-Luc at various N/P ratios. CGl/DNA complexes were formulated with various chitosan molecular weights (20, 45, 200 and 460 kDa). The CS/DNA complexes were characterized by agarose gel electrophoresis and investigated for their transfection efficiency in CHO-K1 cells. The cytotoxicity of the complexes was determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay in CHO-K1 cells. Gel electrophoresis illustrated that complete complexes formed at N/P ratios above 2 in all CS of MW 45 kDa. The transfection efficiency of CS/DNA complexes was dependent on the salt form and MW of chitosan, and the N/P ratio of CS/DNA complexes. Of different CS, the maximum transfection efficiency was found in different N/P ratios. CHy/DNA, CLa/DNA, CAc/DNA, CAs/DNA and CGl/DNA complexes showed maximum transfection efficiencies at N/P ratios of 12, 12, 8, 6 and 6, respectively. Cytotoxicity results showed that all CS/DNA complexes had low cytotoxicity. This study suggests CS have the potential to be used as safe gene delivery vectors.
Keywords: Chitosan salt; Transfection efficiency; Gene delivery; CHO-K1 cells;
Design and in vivo evaluation of a patch delivery system for insulin based on thiolated polymers by Vjera Grabovac; Florian Föger; Andreas Bernkop-Schnürch (169-174).
The aim of this study was to develop and evaluate a novel three-layered oral delivery system for insulin in vivo.The patch system consisted of a mucoadhesive layer, a water insoluble backing layer made of ethylcellulose and an enteric coating made of Eudragit®. Drug release studies were performed in media mimicking stomach and intestinal fluids. For in vivo studies patch systems were administered orally to conscious non-diabetic rats. Orally administered insulin in aqueous solution was used as control. After the oral administration of the patch systems a decrease of glucose and increase of insulin blood levels were measured.The mucoadhesive layer, exhibiting a diameter of 2.5 mm and a weight of 5 mg, comprised polycarbophil-cysteine conjugate (49%), bovine insulin (26%), gluthatione (5%) and mannitol (20%). 74.8 ± 4.8% of insulin was released from the delivery system over 6 h. Six hours after administration of the patch system mean maximum decrease of blood glucose level of 31.6% of the initial value could be observed. Maximum insulin concentration in blood was 11.3 ± 6.2 ng/ml and was reached 6 h after administration. The relative bioavailability of orally administered patch system versus subcutaneous injection was 2.2%.The results indicate that the patch system provides enhancement of intestinal absorption and thereby offers a promising strategy for peroral peptide delivery.
Keywords: Oral insulin; Oral delivery; Oral peptide delivery; Polymer; Intestinal absorption;
Effect of chitosan, benzalkonium chloride and ethylenediaminetetraacetic acid on permeation of acyclovir across isolated rabbit cornea by Soumyajit Majumdar; Ketan Hippalgaonkar; Michael A. Repka (175-178).
The overall objective of this study was to evaluate the effect of chitosan, benzalkonium chloride (BAK) and disodium ethylendiaminetetraacetic acid (EDTA), alone and in combination, on permeation of acyclovir (ACV) across excised rabbit cornea. Corneas of male New Zealand White rabbits were used in these studies. Transcorneal permeation studies were conducted at 34 °C using a side-bi-side diffusion apparatus. In the presence of 0.01% BAK, transcorneal permeability of ACV was observed to increase almost 10.5-fold, from 3.5 × 10−6 to 37.4 × 10−6 cm/s. At 0.005% BAK, permeability of ACV was almost 3-fold higher than control. Combination of BAK 0.005% and EDTA 0.01% increased transcorneal penetration of ACV by 2.5-fold. Chitosan 0.2 and 0.1% increased corneal permeability of ACV by 5.8- and 3.1-fold, respectively, whereas, at 0.02%, chitosan did not exhibit a statistically significant effect. BAK at 0.005%, in combination with 0.01% EDTA and 0.1% chitosan, increased transcorneal ACV permeation by 5.5-fold. This study suggests that a judicious combination of chitosan, BAK and EDTA can lead to a significant increase in ACV's transcorneal permeability and that chitosan can enhance diffusion of hydrophilic agents across the corneal membrane. Further in vivo evaluation is warranted.
Keywords: Chitosan; Cornea; Permeability; BAK; EDTA; Acyclovir; Hydrophilic;