Preparation of genipin cross-linked chitosan-gelatin microcapsules for encapsulation of Zanthoxylum limonella oil (ZLO) using salting-out method

Zanthoxylum limonella oil (ZLO) containing chitosan-gelatin complex microcapsules cross-linked with genipin, a cross-linker of natural origin, have been prepared by a complex coacervation process using the salting-out method. The effects of various parameters such as oil loading, degree of cross-linking, ratio of chitosan to gelatin, etc. on oil content, encapsulation efficiency and the release rate of ZLO have been studied. FT-IR spectroscopy has been used to understand the interaction between the polymers and oil. Scanning electron microscopy (SEM) has been employed to study the morphology of the prepared microcapsules.     

Formulation and evaluation of flurbiprofen-loaded genipin cross-linked gelatin microspheres for intra-articular delivery

Oral and parenteral formulations are challenging to produce therapeutic concentration of flurbiprofen in the joints. This encourages for the development of formulation for long term drug retention in the joint through intra-articular (i. a.) administration. In this study, genipin cross-linked gelatin microspheres of flurbiprofen were prepared for i. a. delivery. The microspheres were prepared using emulsification-homogenization-cross-linking method by changing the experimental variables such as concentration of cross-linker, cross-linking time and cross-linking temperature. The microspheres showed drug entrapment up to 76.19% with a mean particle size range of 5.91–8.19 µm. The degree of cross-linking and water-soluble fraction were 8.27–59.33% and 12.29–81.23%, respectively. SEM confirmed smooth surface and spherical shape of the microspheres. FTIR and ¹³C-NMR confirmed cross-linking of gelatin by genipin. No chemical change in encapsulated drug was observed by FTIR and TGA. DSC and XRD indicated the molecular dispersion of drug within microspheres. Optimized microspheres could prolong the drug release for more than 108?h with anomalous transport. Histopathology confirmed the biocompatibility of microspheres in the rat (Wistar) knee joint. After 96?h of i. a. injection, significant higher amount (42.56%) of administered drug in cross-linked microspheres was recovered than uncross-linked microspheres (8.27%) confirming better drug retention efficiency (p < 0.01).     

Synthesis and characterization of cross-linked chitosan microspheres for drug delivery applications

The present study deals with the synthesis and characterization of cross-linked chitosan microspheres containing an hydrophilic drug, hydroquinone. The microspheres were prepared by the suspension cross-linking method using glutaraldehyde as the cross-linking agent of the polymer matrix. Perfectly spherical cross-linked hydrogel microspheres loaded with hydroquinone were obtained in the size range of 20–100 μm. The effect of the degree of polymer cross-linking, chitosan molecular weight, chitosan concentration and amount of the encapsulated drug on the hydroquinone release kinetics was extensively investigated. It was found that slower drug release rates were obtained from microspheres prepared by using a higher initial concentration of chitosan, a higher molecular weight of chitosan or/and a lower drug concentration. Most importantly, it was shown that the release rate of hydroquinone was mainly controlled by the polymer cross-linking density and, thus, by the degree of swelling of the hydrogel matrix.     

Nerve conduits based on immobilization of nerve growth factor onto modified chitosan by using genipin as a crosslinking agent

Incorporation of nerve growth factor (NGF) into a nerve conduit can improve peripheral nerve regeneration. Here, genipin, a natural and low toxic agent, was used to crosslink chitosan, a natural polysaccharide, and concurrently to immobilize NGF onto modified chitosan, followed by fabrication of chitosan (CS)-genipin (GP)-NGF nerve conduits. MTT test showed that the cell viability of Schwann cells cultured in the conduit extract was not significantly different from that in plain medium. The neurite outgrowth measurement and immunocytochemistry with anti-growth-associated protein-43 and anti-neurofilament indicated that NGF released from CS-GP-NGF nerve conduits retained the bioactivity of stimulating neuronal differentiation of PC12 cells. Fracture strength measurements and vitamin B12 release analysis confirmed that CS-GP-NGF nerve conduits possessed good mechanical properties and adequate permeability. We also investigated the in vitro release kinetics of NGF from CS-GP-NGF nerve conduits by ELISA. The continuous release profile of NGF, within a 60-day time span, consisted of an initial burst that was controlled by a concentration gradient-driven diffusion, followed by a zero-order release that was controlled by a degradation of chitosan matrix. Collectively, CS-GP-NGF nerve conduits had an integrated system for continuous release of NGF, thus holding promise for peripheral nerve repair applications.     

壳聚糖/海藻酸钠自组装微球的制备及释药性能

目的利用壳聚糖(CS)聚阳离子及海藻酸钠(ALG)聚阴离子电解质的性质,在药物微球表面自组装形成多层包覆结构的壳聚糖载药微球,并研究组装层数、温度及盐离子浓度对自组装微球释药性能的影响。方法采用乳化交联法制备CS载四环素(TC)的药物微球,并在其表面交替自组装ALG及CS。利用IR测试技术及电极电位法进行表征。结果CS交联微球未破坏CS及TC的结构,CS与ALG以静电作用相结合。CS交联微球的载药量为40.2%,自组装六层的微球载药量为32%。组装后,药物释放时间延长,初期暴释现象得到极大改善,释药速率随组装层数的增加而下降,温度较高时组装完整,盐离子浓度存在较佳点。结论温度为60℃、盐离子浓度为0.5 mol.L-1、组装层数为四层的微球释药性能较佳。     

New poly(ester-amide) copolymers modified with polyether (PEAE) for anticancer drug encapsulation

New poly(ester–amide) copolymers modified with polyethers were developed for carboplatin encapsulation. These new copolymers contain hydrophobic blocks made of tyrosine derivative and dimer fatty acid, and poly(ethylene glycol) (PEG) as hydrophilic blocks. Short-term hydrolytic degradation revealed high water absorption, slight increase of pH of simulated body fluid and change of sample shape, which indicated the erosive mechanism of polymers degradation. Poly(ester-amide)-PEG copolymers were used for microspheres preparation and carboplatin encapsulation. A double emulsification process was used to produce microspheres with an average diameter of 20–30?μm. It was found that the amount of drug released was controlled by the molecular mass of PEG used for microspheres preparation. Mathematical models were used to elucidate the release mechanism of the carboplatin from the microspheres. The results demonstrate that poly(ester-amide)-PEG copolymers may be used for targeted carboplatin encapsulation and release.     

Preparation of cross-linked chitosan microspheres by spray drying: Effect of cross-linking agent on the properties of spray dried microspheres

Chitosan microspheres cross-linked with three different cross-linking agents viz, tripolyphosphate (TPP), formaldehyde (FA) and gluteraldehyde (GA) have been prepared by spray drying technique. The influence of these cross-linking agents on the properties of spray dried chitosan microspheres was extensively investigated. The particle size and encapsulation efficiencies of thus prepared chitosan microspheres ranged mainly between 4.1–4.7?µm and 95.12–99.17%, respectively. Surface morphology, % erosion, % water uptake and drug release properties of the spray dried chitosan microspheres was remarkably influenced by the type (chemical or ionic) and extent (1 or 2%?w/w) of cross-linking agents. Spray dried chitosan microspheres cross-linked with TPP exhibited higher swelling capacity, % water uptake, % erosion and drug release rate at both the cross-linking extent (1 and 2%?w/w) when compared to those cross-linked with FA and GA. The sphericity and surface smoothness of the spray dried chitosan microspheres was lost when the cross-linking extent was increased from 1 to 2%?w/w. Release rate of the drug from spray dried chitosan microspheres decreased when the cross-linking extent was increased from 1 to 2%?w/w. The physical state of the drug in chitosan-TPP, chitosan-FA and chitosan-GA matrices was confirmed by the X-ray diffraction (XRD) study and found that the drug remains in a crystalline state even after its encapsulation. Release of the drug from chitosan-TPP, chitosan-FA and chitosan-GA matrices followed Fick's law of diffusion.     

Preparation and characterisation of multilayer films and microcapsules containing poly(N-isopropylacrylamide-co-sodium vinylsulphonate) and applicability on controlled release

The copolymers of N-isopropylacrylamide and sodium vinylsulphonate were synthesised by free radical polymerisation. The layer-by-layer self-assembly of the copolymers with poly(allylamine) hydrochloride was performed through assembling onto silicon wafer to form multilayer films and onto CaCO₃ microparticles doped with poly(styrene sulphonate) as well as deltamethrin microcrystals to form microcapsules. The multilayer films and microcapsules were characterised by atomic force microscopy, transmission electron microscopy and scanning electron microscopy. The release behaviour of deltamethrin in the microcapsules under different conditions was also investigated by high performance liquid chromatography. Results show that these deltamethrin microcapsules have good thermo-sensitive properties and deltamethrin release can be controlled via changing temperature or self-assembly layers.     

Genipin crosslinked curcumin loaded chitosan/montmorillonite K-10 (MMT) nanoparticles for controlled drug delivery applications

Abstract

Here, we have reported the influence of MMT and genipin in releasing curcumin from the Genipin crosslinked Chitosan/MMT nanoparticles, prepared by ionic gelation method. The nanoparticles were characterised using Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffractometry (XRD), Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM). Zeta potential and average diameter of the nanoparticles were found in the range 32–47?mV and 430–560?nm. Swelling and release of curcumin from the nanoparticles increased with the decrease in pH of the medium, MMT, and genipin content. Curcumin released from the nanoparticles reduced the viability of MCF-7 and Hep G2 cells as compared to untreated cells. The nanoparticles increased the level of reduced glutathione (GSH), superoxide dismutase (SOD), and catalase level in human PBMCs and decreased the level of Lipid peroxidation suggesting an enhanced protection against cellular damage. Lower pH and higher MMT concentration in the nanoparticles improved the mucoadhesive properties.     

A novel cell encapsulation method using photosensitive poly(allylamine alpha-cyanocinnamylideneacetate)

A photosensitive alpha-cyanocinnamylideneacetyl group was coupled to poly(allylamine) to obtain a photosensitive polymer. This photosensitive poly(allylamine) can cross-link upon light exposure. Microcapalpha-cyanocinnamylideneacetate sules were fabricated from alginate in contact with Ca+2 ion, followed by coating with the photosensitive poly(allylamine alpha-cyanocinnamylideneacetate). The microcapsules, thus formed, can be strengthened significantly by the lightinduced cross-linking of poly(allylamine alpha-cyanocinnamylideneacetate). Only 16 capsules (out of 50) prepared from the photosensitive poly(allylamine alphacyanocinnamylideneacetate) fractured after 48 h of agitation. For microcapsules prepared from the unmodified poly(allylamine), 32 capsules fractured. The photo cross-linked capsular membrane was permeable to cytochrome C, moderately permeable to myoglobin, and least permeable to serum albumin. IW32 (a mouse leukaemia cell line) cells were entrapped and cultured within these microcapsules. The cells proliferated to a density of about 9 x 106 cells/ml in the capsules after 7 days of cultivation.     

Modulation of buspirone HCl release from hypromellose matrices using chitosan succinate: Implications for pH-independent release

Chitosan succinate (CS) was synthesized through the acylation of chitosan with succinic anhydride. The interaction of CS with buspirone HCl (BUSP) was evaluated using dialysis experiments and shown to result in complex with a stability constant of 2.26 mM and a capacity of 0.0362 μmol BUSP/mg CS.The extent of complexation upon dry and wet mixing of CS and BUSP was determined quantitatively using differential scanning calorimetry. The extent of the interaction was highest in wet mixtures and was found to be dependent on the pH of the granulation liquid.CS was incorporated in BUSP-containing hypromellose (HPMC) tablets using dry mixing and wet granulation with BUSP. Tablet dissolution was tested in 0.1 N HCl and phosphate buffer, pH 6.8. According to f₂ and mean dissolution time results, the similarity of profiles increased as CS content increased with the highest f₂ value observed when CS was wet granulated with BUSP.Dissolution was also tested in deionized water and 5% NaCl; where increased ionic strength resulted in faster dissolution suggesting an ion exchange involvement in drug release.CS was proved effective in modulating BUSP release from HPMC matrices for pH-independent release through ionic complex formation.     

Adsorption and recovery of Cu (II) with polysulphone microcapsules containing chitosan gel

Polysulphone (PSF) microcapsules (PSF-CTS) containing chitosan gel with higher mechanical stability and anti-biodegradability were prepared using a novel surface coating method. The thickness and microstructures of the polysulphone coating layer were analysed by SEM. The experiments to examine the mechanical improvement of the encapsulated gel beads were carried out. The adsorption for Cu²⁺ and regeneration properties of unencapsulated and encapsulated gel beads were also tested. The results showed that the mechanical strength of the encapsulated gel beads was significantly enhanced. However, this improvement led to a decrease of the adsorption kinetics due to the increase of the mass transfer resistance. The potentially available methods are suggested to reduce mass transport resistance through the PSF coating layer.     

Preparation of mucoadhesive chitosan-poly(acrylic acid) microspheres by interpolymer complexation and solvent evaporation method II

A mucoadhesive microsphere was prepared by an interpolymer complexation and solvent evaporation method, using chitosan and poly(acrylic acid) (PAA), to prolong the gastric residence time of the delivery system. The Fourier transform infrared results showed that microspheres were formed by an electrostatic interaction between the carboxyl groups of the PAA and the amine groups of the chitosan. X-ray diffraction and differential scanning calorimetry analysis showed that the enrofloxacin in the chitosan-PAA microsphere was molecularly dispersed in an amorphous state. Scanning electron microscopy of the surface and the quantity of mucin attached to the microspheres indicated that chitosan-PAA microspheres had a higher affinity for mucin than those of chitosan alone. The swelling and dissolution of the chitosan-PAA microspheres were found to be dependent on the pH of the medium. The rate of enrofloxacin released from the chitosan-PAA microspheres was slower at higher pH; therefore, based on their mucoadhesive properties and morphology, the chitosan-PAA microspheres can be used as a mucoadhesive oral drug delivery system.     

Preparation and characterization of chitosan microspheres for controlled release of synthetic oligopeptide derived from BMP-2

The localized and temporally controlled release of growth factors is key to achieving optimal clinical efficacy. To achieve sustained delivery of a novel bone-induced growth factor, chitosan microspheres loaded with synthetic oligopeptide (S^[PO4]KIPKASSVPTELSAISTLYLDDD, P24) were prepared by an emulsion-ionic cross-linking method in the presence of tripolyphosphate, with bovine serum albumin (BSA) as a control. Both microspheres containing oligopeptide or BSA were of spherical shape with size ranging from 10–60 µm. The encapsulation efficiency was usually higher than 80% and the loading capacity was affected by initial protein dosage. From the release experiments, it was found that both proteins were slowly released from the microspheres over 7 days in a PBS solution (pH 7.4), in which the release rate of oligopeptide was much lower than that of BSA. Released oligopeptide was demonstrated to possess biological activity as evidenced by stimulation of rabbit marrow mesenchymal stem cells (MSCs) alkaline phosphatase (ALP) activity in vitro. These results indicate that the TPP-chitosan microspheres loaded with synthetic oligopeptide may possess potential application in bone tissue engineering.     

去甲斑蝥素肝动脉栓塞缓释微球的制备及其体外释放性评价

目的:制备去甲斑蝥素肝动脉栓塞缓释微球(NCTD-MS),并考察其体外释放特性。方法:以NCTD为主药,海藻酸钠ALG)/壳聚糖(CS)为复合载体,采用内部凝胶化法制备NCTD-MS;选取ALG浓度、凝胶化反应剂冰醋酸的用量、药物-载体重量比(简称药载比)为因素,以粒径偏差、载药量及包封率为指标进行正交设计优化最佳处方并进行验证;动态透析法考察微球在不同介质(磷酸盐缓冲液和生理盐水)中的体外释放特性,并与NCTD原料药的释放性进行比较。结果:最佳处方为ALG浓度2.0%、冰醋酸1.0mL、药-载重量比0.8∶1,以该处方制备的微球平均粒径为(309.75±2.19)μm、载药量为(12.65±0.87)%、包封率为(68.66±0.38)%;NCTD-MS在2种介质中24h释放可达80%,释放行为均遵循Weibull方程,而NCTD原料药在3h内即释放完毕。结论:NCTD-MS制备工艺简单,缓释效果明显。     

Stimulation of human macrophages (THP-1) using Toll-like receptor-2 (TLR-2) agonist decorated nanocarriers

The purpose of this study was to prepare and characterize nanocarrier systems, which allow the application of pDNA vaccines and adjuvants to mucosal vaccination. Chitosan from a vegetal source (Agaricus bisporus) and of GMP quality was used to synthesize the derivative 6-O-carboxymethyl-N,N,N-trimethylchitosan (CM-TMC). Toll-like receptor-2 (TLR-2) agonist, Pam₃Cys, was synthesized and coupled to CM-TMC through a polyethylene glycol (PEG) spacer. Successively, Pam₃Cys decorated nanocarriers were prepared by complexation with plasmid DNA (pDNA) expressing green fluorescence protein (GFP), and characterized with respect to their physicochemical properties and protection of the included plasmid against DNase I enzymatic degradation. In vitro studies using phorbol 12-myristyl 13-acetate (PMA) stimulated macrophage-like THP-1 (mTHP-1) cells were focused on cytotoxicity of both polymers and particles, and their potential to stimulate IL-8 release via the TLR-2 pathway. Our results showed that the TLR-2 functionalized pDNA nanocarriers have the ability to complex and to protect pDNA against enzymatic degradation. pDNA nanocarriers were of around 400?nm in size, and displayed a positive zeta potential of 27.9?±?1.6 mV. Chitosan, CM-TMC, and Pam₃Cys-functionalized CM-TMC polymers displayed cytotoxicity on mTHP1 cells in a concentration-dependent manner, which decreased by 50-fold on complexation with pDNA. In addition, decorated pDNA nanocarriers induced IL-8 secretion by mTHP-1 macrophages, which was increased by 10-fold as compared to nondecorated carriers.     

Block copolymer design for stable encapsulation of N-(4-hydroxyphenyl)retinamide into polymeric micelles in mice

For stable encapsulation of N-(4-hydroxyphenyl)retinamide (4-HPR) into polymeric micelles, four types of block copolymers were synthesized with different esterified functional groups: heptyl (C7), nonyl (C9), benzyl (Bz), and phenylpropyl (C3Ph). The stability of 4-HPR encapsulated polymeric micelles was evaluated by measuring the blood concentration of 4-HPR in mice. After intravenous administration of 4-HPR and 4-HPR encapsulated PEG liposomes, the blood concentration of 4-HPR was about 2.8% and 2.2% of the dose/mL, suggesting the rapid release of 4-HPR from PEG liposomes. In contrast, the blood concentration of 4-HPR after intravenous administration of all 4-HPR encapsulated polymeric micelles studied was much higher (about 22–34% of the dose/mL). Among them, the polymeric micelles prepared by block copolymers (Bz) showed the highest blood concentration of 4-HPR. As far as the effects of the level of Bz groups in the block copolymers are concerned, the blood concentration of 4-HPR was enhanced by Bz groups at a level of 72% and 77%, but not by Bz groups at a level of 43% and 51%. These results suggest that 4-HPR is stably encapsulated in polymeric micelles prepared by block copolymers (Bz) but a level of over 72% of Bz groups is needed. These findings will be of value in the future use, design, and development of polymeric micelles for in vivo application of 4-HPR.     

羧甲基壳聚糖的制备与质量分析

用氯乙酸对壳聚糖进行了化学改性,其产物羧甲基壳聚糖有良好的水溶性。还对此产物进行了质量分析。     

Preparation and characterization of tri-block poly(lactide)-poly(ethylene glycol)-poly(lactide) nanogels for controlled release of naltrexone

Tri-block poly(lactide)-poly(ethylene glycol)-poly(lactide) (PLA-PEG-PLA) copolymers and related acrylated derivative were synthesized and used to prepare micelles and nanogels for controlled release of naltrexone. The resulting copolymers, micelles and nanogels were characterized by various techniques such as proton nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, gel permeation chromatography, fluorescence spectrometry, differential scanning calorimetry, photon correlation spectroscopy and scanning electron microscopy. The nanogels exhibited high encapsulation efficiency around 60% and excellent stability for long periods of time. The drug release profiles of micelles and nanogels were compared and it was found that the naltrexone loaded nanogels offered a steady and long-term release pattern for different periods of time up to 35 days, depending on the crosslinker concentration, compared to the micelles. The size of nanogels could be manipulated easily in the range of 128-200 nm by variations in polymer concentration used in the nanogels preparation step. From the results obtained it can be concluded that PLA-PEG-PLA nanogels can be considered as a promising carrier for drug delivery purpose.     

Release of peptides from sustained delivery systems (microcapsules and microparticles) in vivo

Sustained delivery systems (microcapsules, microparticles, or implants) developed for once a month administration of peptides are efficacious and convenient. Long acting formulations of several bioactive peptides are based on microcapsules of a biodegradable polymer poly(dl -lactide-co-glycolide) (PLG), but a better understanding is required of the mechanism of the peptide release from the microcapsules, which is assumed to be primarily by diffusion through pores. In order to clarify this mechanism, microcapsules and microparticles of the agonist [d -Trp⁶]-LHRH and microcapsules of the LHRH antagonist SB-75 were given i.m. to rats 2 h and 1, 2, 4, 7, 14 and 21 days before histological and immunohistochemical investigation. Signs of biodegradation of the PLG matrix could be seen the first day after the injection, in a form of vacuole development in the interior of the particles and connected with the presence of macrophages within the matrix. The microcapsules showed excellent tissue-compatibility, and no significant foreign body reaction was detected. Immunohistochemical study on the microcapsules revealed no visible decrease in peptide concentration in the remnants of the matrix even 2 weeks after the injection. Evaluation of serum [d -TrP⁶]-LHRH showed that after an initial burst, both microcapsules and microparticles maintained elevated serum [d -Trp⁶]-LHRH levels for more than 3 weeks. Our results suggest that the previously proposed mechanisms do not reflect the experimental findings, particularly for the insoluble peptides. The peptide release from the PLG microcapsules or microparticles appears to be controlled mostly by the speed of the biodegradation of the polymer matrix and the diffusion of the peptides from the PGL is negligible.