Efficacy of Mucoadhesive Hydrogel Microparticles of Whey Protein and Alginate for Oral Insulin Delivery

Purpose

To evaluate the efficacy of mucoadhesive insulin-loaded whey protein (WP) /alginate (ALG) microparticles (MP) for oral insulin administration.

Methods

Insulin-loaded microparticles (ins-MP) made of whey protein and alginate were prepared by a cold gelation technique and an adsorption method, without adjunction of organic solvent in order to develop a biocompatible vehicle for oral administration of insulin. In vitro characterization, evaluations of ins-MP in excised intestinal tissues and hypoglycaemic effects after intestinal administration in healthy rats were performed

Results

The release properties and swelling behaviors, investigated in different pH buffers, demonstrated a release based on diffusion mechanism following matrix swelling. Mucoadhesion studies in rabbits and insulin transport experiments with excised intestinal rat tissues revealed that encapsulation in microparticles with mucoadhesive properties promotes insulin absorption across duodenal membranes and bioactivity protection. In vivo experiments reinforced the interest of encapsulation in whey protein/alginate combination. Confocal microscopic observations associated with blood glucose levels bring to light duodenal absorption of insulin biologically active following in vivo administration.

Conclusions

Insulin-loaded WP/ALG MP with high quantities of drug entrapped, in vitro matrix swelling and protective effect as well as excellent mucohadesive properties was developped. Improvement of intestinal delivery of insulin and increased in bioavailability were recorded.     

Coated whey protein/alginate microparticles as oral controlled delivery systems for probiotic yeast

Viable Saccharomyces boulardii, used as a biotherapeutic agent, was encapsulated in food-grade whey protein isolate (WP) and alginate (ALG) microparticles, in order to protect and vehicle them in gastrointestinal environment. Yeast-loaded microparticles with a WP/ALG ratio of 62/38 were produced with high encapsulation efficiency (95%) using an extrusion/cold gelation method and coated with ALG or WP by a simple immersion method. Swelling, yeast survival, WP loss and yeast release in simulated gastric and intestinal fluids (SGF and SIF, pH 1.2 and 7.5) with and without their respective digestive enzymes (pepsin and pancreatin) were investigated. In SGF, ALG network shrinkage limited enzyme diffusion into the WP/ALG matrix. Coated and uncoated WP/ALG microparticles were resistant in SGF even with pepsin. Survival of yeast cells in microparticles was 40% compared to 10% for free yeast cells and was improved to 60% by coating. In SIF, yeast cell release followed coated microparticle swelling with a desirable delay. Coated WP/ALG microparticles appear to have potential as oral delivery systems for Saccharomyces boulardii or as encapsulation means for probiotic cells in pharmaceutical or food processing applications.     

Therapeutic deep eutectic solvents assisted the encapsulation of curcumin in alginate-chitosan hydrogel beads

Alginate (ALG)-Chitosan (CHI) hydrogel beads have been broadly studied as vehicles for controlled drug delivery applications. However, encapsulation of poorly-water soluble compounds is somehow limited by the need to use emulsifying agents and/or organic solvents. This study aimed to encapsulate curcumin in ALG-CHI beads using as drug solubilizing vehicles deep eutectic solvents (DES). Using this approach hydrogel beads were successfully produced using extrusion-dripping method. The beads were vacuum-dried and freeze-dried which impairs their morphology, shape and dimensions features, as well as physicochemical properties. Vacuum-dried beads showed superior performance and were further evaluated as curcumin carriers for drug release control. The results indicated that swelling, degradation and in vitro release studies were influenced by the pH, highlighting the suitability of these systems for intestinal drug delivery. These outcomes indicate that the encapsulation of curcumin in pH-responsive ALG-CHI hydrogel beads using DES can be successfully accomplished, holding a great promise as encapsulation strategy of poorly water-soluble compounds for intestinal-targeted delivery of curcumin.     

Mucoadhesive and floating chitosan-coated alginate beads for the controlled gastric release of amoxicillin

This work focused on the development of mucoadhesive and floating chitosan-coated alginate beads as a gastroretensive delivery vehicle for amoxicillin, towards the effective eradication of Helicobacter pylori, a major causative agent of peptic ulcers. Alginate was used as the core bead core polymer and chitosan as the mucoadhesive polymer coating. Amoxicillin-loaded alginate beads coated with 0.5% (w/v) chitosan (ALG/0.5%CHI) exhibited excellent floating ability, high encapsulation efficiency, high drug loading capacity, and a strong in vitro mucoadhesion to the gastric mucosal layer. In vitro, amoxicillin was released faster in simulated gastric fluid (pH 1.2, HCl) than in simulated intestinal fluid (phosphate buffer, pH 7.4). ALG/0.5%CHI could be prepared with a > 90% drug encapsulation efficiency and exhibited more than 90% muco-adhesiveness, 100% floating ability, and achieved sustained release of amoxicillin for over six hours in SGF.     

Bioadhesive Chitosan-Coated Cationic Nanoliposomes With Improved Insulin Encapsulation and Prolonged Oral Hypoglycemic Effect in Diabetic Mice

Oral administration of insulin is hampered by the lack of carriers that can efficiently achieve high encapsulation, avoid gastric degradation, overcome mucosal barriers, and prolong the hypoglycemic effect. Chitosan (CS)-coated insulin-loaded cationic liposomes have been developed and optimized for improved oral delivery. Liposomes were prepared cationic to improve insulin encapsulation. CS was selected as a mucoadhesive coat to prolong the system's residence and absorption. The performance of CS-coated liposomes compared with uncoated liposomes was examined in vitro, ex vivo, and in vivo in streptozotocin-induced diabetic mice. Free uncoated liposomes showed high positive zeta potential of +58.8 ± 2.2 mV that reduced (+29.9 ± 1.4 mV) after insulin encapsulation, confirming the obtained high entrapment efficiency of 87.5 ± 0.6%. CS-coated liposomes showed nanosize of 439.0 ± 12.3 nm and zeta potential of +60.5 ± 1.9 mV. In vitro insulin release was limited to 18.9 ± 0.35% in simulated gastric fluid, whereas in simulated intestinal fluid, 73.33 ± 0.68% was released after 48 h from CS-coated liposomes. Ex vivo intestinal mucoadhesion showed increased tissue residence of CS-coated liposomes compared with uncoated liposomes. A striking reduction in the glucose level was observed 1 h after oral administration of CS-coated liposomes and maintained up to 8 h (p <0.01 vs. insulin solution or uncoated liposomes) within the normal value 129.29 ± 3.15 mg/dL. In conclusion, CS-coated insulin-loaded cationic liposomes improved loading efficiency with promising prolonged pharmacological effect.     

Effect of matrix composition,sphere size and hormone concentration on diffusion coefficient of insulin for controlled gastrointestinal delivery for diabetes treatment

Oral insulin administration is limited due to its degradation by proteases. The hormone was encapsulated in spheres made of either pure calcium alginate (ALG) or its association with whey protein isolate (WPI-ALG) in order to minimise loss in the stomach region while allowing liberation in the maximum absorption area, located in the intestine. Diffusion coefficients for both matrix compositions were determined in vitro for gastric pH (5.88 and 10.26?×?10^?12?m²?s^?1) and intestinal pH (21.11 and 79.29?×?10^?12?m²?s^?1). Higher initial insulin concentrations and lower diameters accelerated its release, confirming Fickian behaviour. The analytic model exhibited a good fit in most cases. Computer simulations revealed that ALG spheres are more convenient for oral administration because they release more insulin in the intestine than the WPI-ALG ones, thus supporting its therapeutic viability for the purpose of reducing stress in those who depend on insulin.     

Evaluation of Monooleine Aqueous Dispersions as Tools for Topical Administration of Curcumin: Characterization,In Vitro and Ex-Vivo Studies

Curcumin (CUR) is a well-known natural compound showing antioxidant, anti-inflammatory, and antitumor abilities but characterized by poor bioavailability and chemical instability, which drastically reduce its application in the treatment of chronic diseases such as osteoarthritis. The aim of the present study is the design and evaluation of monooleine aqueous dispersion (MAD) as novel carriers for the topical administration of CUR. CUR-loaded MAD was formulated using two different emulsifier systems, namely poloxamer 407 (MAD-A) and sodium cholate-sodium caseinate (MAD-B). These vehicles were characterized, and their influence on in vitro percutaneous absorption of CUR was also evaluated. Furthermore, an oxygen radical absorbance capacity assay was used to determine their antioxidant activity, and a Western blot analysis was performed to evaluate the inhibitory effect of the formulations on inducible nitric oxide synthase and cyclooxygenase 2 expressions. From the obtained results, CUR encapsulation efficiency was higher than 98% for MAD-A and 82% for MAD-B. Shelf-life studies showed that MAD-A maintains CUR stability better than MAD-B, and both vehicles demonstrated, in vitro, control of drug diffusion through the skin. Finally, MAD-A and MAD-B were able to extend the antioxidant/anti-inflammatory effects of CUR, also confirming the protective effect toward CUR chemical stability. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 102:2349–2361, 2013     

Squalene-Containing Nanostructured Lipid Carriers Promote Percutaneous Absorption and Hair Follicle Targeting of Diphencyprone for Treating Alopecia Areata

Purpose

Diphencyprone (DPCP) is a therapeutic agent for treating alopecia areata. To improve skin absorption and follicular targeting nanostructured lipid carriers (NLCs) were developed.

Methods

Nanoparticles were characterized by size, zeta potential, molecular environment, differential scanning calorimetry (DSC), and nuclear magnetic resonance (NMR). In vitro and in vivo skin absorption experiments were performed. Fluorescence and confocal microscopes for imaging skin distribution were used.

Results

NLCs with different designs were 208?~?265 nm with ?>?77% DPCP encapsulation. NLCs incorporating a cationic surfactant or more soybean phosphatidylcholine (SPC) showed higher lipophilicity compared to typical NLCs by Nile red emission. All NLCs tested revealed controlled DPCP release; burst release was observed for control. The formulation with more SPC provided 275 μg/g DPCP skin retention, which was greater than control and other NLCs. Intersubject deviation was reduced after DPCP loading into NLCs. Cyanoacrylate skin biopsy demonstrated greater follicular deposition for NLCs with more SPC compared to control. Cationic NLCs but not typical or SPC-containing carriers were largely internalized into keratinocytes. In vivo skin retention of NLCs with more SPC was higher than free control. Confocal imaging confirmed localization of NLCs in follicles and intercellular lipids of stratum corneum.

Conclusions

This work encourages further investigation of DPCP absorption using NLCs with a specific formulation design.     

Gastrointestinal Responsive Polymeric Nanoparticles for Oral Delivery of Insulin: Optimized Preparation,Characterization, and In Vivo Evaluation

Gastrointestinal responsive polymeric nanospheres (NPs) based on hydroxypropyl methylcellulose phthalate were prepared using spontaneous emulsification solvent diffusion method for improved oral administration of insulin. The NPs prepared under optimized conditions have an encapsulation efficiency of 90% and a particle size of about 200 nm. In vitro drug release experiments demonstrated that the NPs exhibited a gradient release profile of loaded drug when the pH value gradually increased from 3.0 to 7.4. Enzyme resistance experiments showed that under simulated gastrointestinal conditions, the NPs protected more than 60% of the drug from being degraded by trypsin. The oral hypoglycemic experiments revealed that insulin-loaded NPs could significantly reduce blood glucose levels in diabetic rats with a relative bioavailability of 8.6%. Ex vivo imaging investigation of rat tissues showed that the drug-loaded NPs could promote the absorption of insulin in the ileum and colon. The work described here suggests that the gastrointestinal responsive polymeric NPs may be promising candidates for improving gastrointestinal tract delivery of hydrophilic biomacromolecules. Accordingly, the results indicated that hydroxypropyl methylcellulose phthalate NPs with gastrointestinal stimuli responsiveness could be a promising candidate for oral insulin delivery.     

rhEGF microsphere formulation and in vitro skin evaluation

An optimized process for protein encapsulation was applied to formulate epidermal growth factor (rhEGF)-poly-ε-caprolactone microspheres. Microparticles mean size was 3.8 µm ± 0.2 and the encapsulation efficiency was 41.9% ± 2.6. rhEGF recovery after the encapsulation process was ～70% (41.9% inside the microspheres and 30% still active in the external phase). In vitro release experiments in McIlvaine buffered solution showed a rhEGF sustained release over 4 days. Skin absorption studies conducted on full-thickness human skin using the Franz cell method showed that 20% rhEGF was released from the microspheres after 24 h exposure. Microspheres accumulated in the stratum corneum where they may act as a rhEGF reservoir. Therefore, rhEGF-PCL microparticles seemed to be promising systems due to their ability to provide locally a sustained release of rhEGF in skin layers.     

Evaluation of polyanhydride microspheres for basal insulin delivery: Effect of copolymer composition and zinc salt on encapsulation,in vitro release,stability, in vivo absorption and bioactivity in diabetic rats

The potential of poly 1,3-bis-(p-carboxyphenoxy) propane-co-sebacic acid (p(CPP:SA)) microspheres was investigated for controlled delivery of basal insulin. CPP:SA copolymers with molar compositions of 20:80, 40:60, and 50:50 were synthesized, characterized, and used in the fabrication of microspheres by water-in-oil-in-water double emulsion solvent evaporation technique. Insulin stability was assessed using various analytical methods and in vivo insulin absorption and bioactivity were studied in diabetic rats. Microspheres exhibited smooth surfaces and mean particle size ranged from 41.5 to 49.8 µm. Insulin encapsulation efficiency (EE) and in vitro release kinetics were influenced by the molar ratios of CPP:SA copolymer. Increasing CPP content and addition of zinc oxide increased EE, reduced burst release, and prolonged insulin in vitro release over a month. Dimer aggregates were observed for insulin encapsulated in CPP:SA 50:50 microspheres and addition of zinc oxide prevented dimer formation. Subcutaneous administration of CPP:SA 50:50 microspheres in diabetic rats controlled insulin release over a month, and the released insulin was bioactive as determined by lowering blood glucose levels. The results indicate that CPP:SA microspheres controlled insulin release in vitro and in vivo over a month and the released insulin was conformationally and chemically stable, and bioactive. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:4237–4250, 2009     

Co-Delivery of Ciprofloxacin and Colistin in Liposomal Formulations with Enhanced <Emphasis Type="BoldItalic">In Vitro</Emphasis> Antimicrobial Activities against Multidrug Resistant <Emphasis Type="BoldItalic">Pseudomonas aeruginosa</Emphasis>

Purpose

This study aims to develop liposomal formulations containing synergistic antibiotics of colistin and ciprofloxacin for the treatment of infections caused by multidrug-resistant Pseudomonas aeruginosa.

Methods

Colistin (Col) and ciprofloxacin (Cip) were co-encapsulated in anionic liposomes by ammonium sulfate gradient. Particle size, encapsulation efficiency, in vitro drug release and in vitro antibiotic activities were evaluated.

Results

The optimized liposomal formulation has uniform sizes of approximately 100 nm, with encapsulation efficiency of 67.0% (for colistin) and 85.2% (for ciprofloxacin). Incorporation of anionic lipid (DMPG) markedly increased encapsulation efficiency of colistin (from 5.4 to 67.0%); however, the encapsulation efficiency of ciprofloxacin was independent of DMPG ratio. Incorporation of colistin significantly accelerated the release of ciprofloxacin from the DMPG anionic liposomes. In vitro release of ciprofloxacin and colistin in the bovine serum for 2 h were above 70 and 50%. The cytotoxicity study using A549 cells showed the liposomal formulation is as non-toxic as the drug solutions. Liposomal formulations of combinations had enhanced in vitro antimicrobial activities against multidrug resistant P. aeruginosa than the monotherapies.

Conclusions

Liposomal formulations of two synergistic antibiotics was promising against multidrug resistant P. aeruginosa infections.

     

Direct in vitro effects of bis (tri-n-butyltin)oxide on hepatic cytochrome P-450

Bis(tri-n-butyltin)oxide, an agriculturally important biocidal agent, when added in vitro to liver microsomes containing the phenobarbital-induced form of cytochrome P-450, produced a typical type I binding spectrum (an absorption maximum at 390 nm; an absorption minimum at 420 nm). Studies with microsomal preparations containing cytochrome P-448, induced by 3-methylcholanthrene or β-naphthoflavone, revealed that this hemeprotein was more susceptible to direct degradation by bis (tri-n-butyltin)oxide than was the uninduced or phenobarbital-induced forms of cytochrome P-450. The disappearance of spectrally detectable cytochrome P-450 was accompanied by an increase in cytochrome P-420. The formation of cytochrome P-420 was both time and temperature dependent, and it also occurred to a greater extent in microsomal preparations containing cytochrome P-448 than in microsomes containing the phenobarbital-induced form of cytochrome P-450. In all cases, the decreases in spectrally detectable cytochrome P-450 produced by the organotin were not accompanied by decreases in microsomal heme or cytochrome b₅ content. The findings provide evidence for the direct interaction followed by conversion of cytochrome P-450 to cytochrome P-420 produced by a trialkyltin compound in vitro, and indicate that different susceptibilities to degradation exist within the various subspecies of this hemeprotein.     

Preparation of pH-sensitive beads for NSAID using three-component gel systems

The aim of this study is to prepare novel pH-sensitive beads to obtain a gastric mucosa protective formulation and to ensure drug delivery into the intestine. Diclofenac sodium was used as a model drug. Bead formation was achieved by ionotropic gelation method using three-component gel system containing sodium alginate (Na-Alg), hydroxyethylcellulose (HEC) and hydroxypropylmethylcellulose (HPMC). Factors influencing the characteristics of beads (exposure time, cross-linking agent concentration, polymer ratio) were investigated by swelling and erosion tests based on gravimetric method. Drug release was tested in distilled water and/or artificial digestive fluids and evaluated with Korsmeyer–Peppas equation and Baker–Lonsdale model. The encapsulation behaviour was qualitatively indicated by differential scanning calorimetry (DSC) method. In vivo experiments were conducted to test ulcerogenicity and intestinal absorption in rats. HPMC increased the encapsulation efficiency (EE) and HEC improved the drug release in the intestinal fluids. The equilibrium water uptake (EWU) was correlated with exposure time, calcium chloride concentration and HEC amounts. Bead erosion increased proportionately to exposure time, while it reduced when calcium chloride concentrations were increased. Higher amounts of HEC increased, while higher pH values reduced the encapsulation efficacy. The in vivo experiments demonstrated that the studied encapsulation technology markedly reduced the ulcerogenic effect of diclofenac. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:4285–4295, 2009     

High payload nanostructured lipid carriers fabricated with alendronate/polyethyleneimine ion complexes

Oral bioavailability of the anti-osteoporotic drug alendronate (AL) is limited to ≤ 1% due to unfavorable physicochemical properties. To augment absorption across the gastrointestinal mucosa, an ion pair complex between AL and polyethyleneimine (PEI) was formed and incorporated into nanostructured lipid carriers (NLCs) using a modified solvent injection method. When compared to free AL, ion pairing with PEI increased drug encapsulation efficiency in NLCs from 10% to 87%. Drug release from NLCs measured in vitro using fasted state simulated intestinal fluid, pH 6.5 (FaSSIF-V2) was significantly delayed after PEI complexation. Stability of AL/PEI was pH-dependent resulting in 10-fold faster dissociation of AL in FaSSIF-V2 than measured at pH 7.4. Intestinal permeation properties estimated in vitro across Caco-2 cell monolayers revealed a 3-fold greater flux of AL encapsulated as hydrophobic ion complex in NLCs when compared to AL solution (P_app?=?8.43?±?0.14?×?10^?6 cm/s and vs. 2.76?±?0.42?×?10^?6 cm/s). Cellular safety of AL/PEI-containing NLCs was demonstrated up to an equivalent AL concentration of 2.5 mM. These results suggest that encapsulation of AL/PEI in NLCs appears a viable drug delivery strategy for augmenting oral bioavailability of this clinically relevant bisphosphonate drug and, simultaneously, increase gastrointestinal safety.     

PHARMACEUTICAL NANOTECHNOLOGY: A Novel Composite Hydrogel Based on Chitosan and Inorganic Phosphate for Local Drug Delivery of Camptothecin Nanocolloids

In attempt to overcome the problem of low water solubility and severe toxicity of camptothecin (CPT) after intravenous administration, a novel drug carrier system based on chitosan (CS) and dibasic sodium phosphate (DSP) has been developed in this paper to encapsulate CPT intending for local administration. Nanocolloids of CPT with size about 500 nm were first prepared, followed by encapsulation in the chitosan/dibasic sodium phosphate (CS/DSP) formulation. The formulation was sol state below 37°C and transformed to nonflowing gel state at 37°C. Encapsulation of CPT nanocolloids had greatly effect on the gelling time as well as the micro-structure of hydrogel. In vitro and in vivo degradation studies revealed that the developed CS/DSP hydrogel was biodegradable and biocompatible. In vitro release study revealed that CPT released from CS/DSP hydrogel in an extended period with about 70% of total CPT released from hydrogel after 18 days. Furthermore, nearly 90% of CPT in the chitosan hydrogels could be preserved in the lactone form (active form) even after 7 days's storage at 37°C. Furthermore, in vitro cytotoxicity of CPT nanocolloids on SKOV3 human ovarian cancer cells suggested the well anti-tumor cell efficiency could be gained at a lower concentration.     

Cardiac-specific overexpression of metallothionein rescues nicotine-induced cardiac contractile dysfunction and interstitial fibrosis

Predictive toxicology aims at developing methodologies to relate the results obtained from in vitro experiments to in vivo exposure. In the case of polycyclic aromatic hydrocarbons (PAHs), a substantial amount of knowledge on effects and modes of action has been recently obtained from in vitro studies of gene expression. In the current study, we built a physiologically based toxicokinetic (PBTK) model to relate in vivo and in vitro gene expression in case of exposure to benzo(a)pyrene (BaP), a referent PAH. This model was calibrated with two toxicokinetic datasets obtained on rats exposed either through intratracheal instillation or through intravenous administration and on an in vitro degradation study. A good agreement was obtained between the model's predictions and the concentrations measured in target organs, such as liver and lungs. Our model was able to relate correctly the gene expression for two genes targeted by PAHs, measured in vitro on primary human macrophages and in vivo in rat macrophages after exposure to BaP. Combining in vitro studies and PBTK modeling is promising for PAH risk assessment, especially for mixtures which are more efficiently studied in vitro than in vivo.     

Development of a topical ointment of betamethasone dipropionate loaded nanostructured lipid carrier

The purpose of this study was to design an innovative topical ointment containing betamethasone dipropionate loaded nanostructured lipid carrier (BD-NLC) for the treatment of atopic dermatitis (AD). BD-loaded NLC was produced with precirol ATO 5 and oleic oil (OA) by melt emulsification method. Effects of surfactant concentration, amount of solid lipid and liquid lipid on skin retention and skin penetration were investigated by in vitro percutaneous permeation experiment. The optimized BD-NLC showed a homogeneous particle size of 169.1 nm (with PI = 0.195), negatively charged surface (−23.4 mV) and high encapsulation efficiency (85%). Particle morphology assessed by TEM revealed a spherical shape. In vitro skin permeation study was carried out to investigate the percutaneous behaviors of W/O ointment with BD-NLC and Carbopol emulgel ointment with BD-NLC. W/O ointment with BD-NLC showed high skin retention (35.43 µg/g) and low penetration (0.87 µg/ml). In vitro drug release studies were carried out to demonstrate the drug releasing properties of the two ointments. W/O ointment with BD-NLC showed an advantage for skin retention as it was better for drug release. The tissue distribution test suggested that BD distribution was skin > muscle > blood. Self-made topical ointment in mice showed no skin irritation. The animal experiments indicated that BD-loaded NLC ointment was effective and safe for topical use.     

Fabrication via a nonaqueous nanoprecipitation method,characterization and in vitro biological behavior of N6-cyclopentyladenosine-loaded nanoparticles

A novel nonaqueous nanoprecipitation method was proposed to achieve the encapsulation of a small weight hydrophilic drug (N⁶-cyclopentyladenosine, CPA) in PLGA nanoparticles using a mixture of cottonseed oil and Tween-80 as nonsolvent phase. The nanoparticles were characterized in vitro as concerns size, morphology, drug loading, drug release, and drug stability in human blood. Human retinal pigment epithelium (HRPE) cells were employed to study intracellular accumulation of encapsulated or free CPA with and without unloaded particles, in the presence or absence of an equilibrative nucleoside transporter inhibitor. The particles displayed a mean size lower than 300 nm and a drug loading considerably higher than that found by conventional encapsulation methods. The suitable in vitro release properties permitted to obtain good drug stabilization in the blood. Studies on HRPE cells suggested that CPA can permeate their membrane by both diffusive- and transport-mediated mechanisms. The loaded and unloaded nanoparticles appeared able to increase the permeation rate of the diffusive mechanism, without interfering with the transporter. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:4272–4284, 2009     

依托泊苷壳聚糖胶束的制备及壳聚糖促进依托泊苷肠吸收作用的研究

目的 制备依托泊苷壳聚糖胶束,并研究壳聚糖对依托泊苷肠吸收的促进作用。方法 用透析法制备依托泊苷壳聚糖胶束,建立依托泊苷HPLC含量测定方法,测定了其包封率与载药量;采用大鼠在体肠循环实验,研究不同剂量壳聚糖对依托泊苷全肠段和各个肠段吸收的影响。结果 壳聚糖胶束平均粒径为139.5 nm,多分散系数为0.569;依托泊苷标准曲线为A=8 436.8C-4 963.8,r=1.000 0,日内、日间精密度符合要求;包封率为（47.3±2.84）%,载药量为（1.10±1.27）%;随着壳聚糖浓度的增加,依托泊苷在全肠段的单位面积吸收量有不同程度的增加;壳聚糖对依托泊苷的吸收促进作用存在着肠道特异性,作用大小顺序：回肠 >空肠 >十二指肠。结论 在十二指肠、空肠和回肠,壳聚糖都不同程度促进了药物的吸收,且在空肠和回肠有显著性的影响。