Fabrication of cross-linked alginate beads using electrospraying for adenovirus delivery

Cross-linked alginate beads containing adenovirus (Ad) were successfully fabricated using an electrospraying method to achieve the protection and release of Ad in a controlled manner. An aqueous alginate solution containing Ad was electrosprayed into an aqueous phase containing a cross-linking agent (calcium chloride) at different process variables (voltages, alginate concentrations, and flow rates). Alginate beads containing Ad were used for transduction of U343 glioma cells and the transduction efficiency of the alginate beads was measured by quantification of gene expression using a fluorescence-activated cell sorter at different time points. In vitro results of gene expression revealed that the Ad encapsulated in the alginate beads with 0.5 wt% of alginate concentration exhibited a high activity for a long period (over 7 days) and was released in a sustained manner from the alginate beads. The Ad-encapsulating alginate beads could be promising materials for local delivery of Ad at a high concentration into target sites.     

Sustained release of antineoplastic drugs from chitosan-reinforced alginate microparticle drug delivery systems

Alginate based microparticle drug delivery systems were prepared for the sustained release of antineoplastic drugs. Two drugs, 5-fluorouracil (5-FU) and tegafur, were encapsulated into the microparticles. The drug loaded microparticles were fabricated using a very convenient method under very mild conditions, i.e., directly shredding the drug loaded beads into microparticles in a commercial food processor. The mean sizes of the obtained microparticles were between 100 and 200 μm. To effectively sustain the drug release, alginate microparticles were reinforced by chitosan during gelation. The drug release from the chitosan-reinforced alginate microparticles was obviously slower than that from the unreinforced microparticles. The effect of the reinforcement conditions on the drug release property of the microparticles was studied, and the optimized concentration of chitosan solution for reinforcement was identified. The effects of drug feeding concentration and pH value of the release medium on the drug release were investigated.     

Bioefficacy of budesonide loaded crosslinked polyeletrolyte microparticles in rat model of induced colitis

A targeted delivery system for inflammatory bowel diseases, chitosan-Ca-alginate microparticles efficiently loaded with budesonide (BDS), were designed using one-step spray-drying process. They were eudragit-coated and examined for in vivo efficacy. Experimental colitis was induced by rectal instillation of 2,4,6-trinitrobenzene sulphonic acid (TNBS) into male Wistar rats. Drugs were administered by oral gavage daily for 5 days. Colon/body weight ratio, gross morphological and histological evaluation, and clinical activity score were determined as inflammatory indices. Individual clinical and histological evaluation showed that colitis severity was suppressed the most greatly in order BDS < BDS/C-Ca-A < E-BDS/C-Ca-A. Clinical activity score decreased in the same order. Statistical analyses of total score points indicate that the incorporation of BDS in microparticles had significant differences in favor of efficacy of designed delivery system with mucoadhesive and controlled release properties (one-way ANOVA, P?<?0.05). The results established the prediction by previous in vitro studies.     

Liquid phase coating to produce controlled-release alginate microspheres

This study explored a liquid phase coating technique to produce polymethyl methacrylate (PMMA)-coated alginate microspheres. Alginate microspheres with a mean diameter of 85.6?µm were prepared using an emulsification method. The alginate microspheres, as cores, were then coated with different types of PMMA by a liquid phase coating technique. The release characteristics of these coated microspheres in simulated gastric (SGF) and intestinal (SIF) fluids and the influence of drug load on encapsulation efficiency were studied. The release of paracetamol, as a model hydrophilic drug, from the coated microspheres in SGF and SIF was greatly retarded. Release rates of Eudragit RS100-coated microspheres in SGF and SIF were similar as the rate-controlling polymer coat was insoluble in both media. Drug release from Eudragit S100-coated microspheres was more sustained in SGF than in SIF, due to the greater solubility of the coating polymer in media with pH greater than 7.0. The drug release rate was affected by the core:coat ratio. Drug release from the coated microspheres was best described by the Higuchi's square root model. The liquid phase coating technique developed offers an efficient method of coating small microspheres with markedly reduced drug loss and possible controlled drug release.     

pH-dependent release property of alginate beads containing calcium carbonate particles

Alginate bead containing calcium carbonate particle were prepared by dropping the suspension of alginate/calcium carbonate (4/1, w/w) into aqueous solution of CaCl₂ (0.1?M). The pH-dependent release property of the bead was observed for 12?h using blue dextran as a model drug. The release increased up to 4?h in a saturation manner. When no calcium carbonate was contained, the release exhibited no marked variation with pH and the values were 27–39%. On the other hand, in case calcium carbonate was included in the matrix of alginate beads, intensive release(40–50%) was achieved in acidic and neutral conditions and the degrees of release were suppressed in alkali conditions and the values were ～20%. The pH-sensitive release property is possibly because the particles of calcium carbonate embedded in the matrix of beads were leached out in acidic and neutral conditions, leaving cavities in the matrix. The cavities are likely to be main pathways for the release of blue dextran.     

Diffusion loading and drug delivery characteristics of alginate gel microparticles produced by a novel impinging aerosols method

Microencapsulation of a hydrophilic active (gentamicin sulphate (GS)) and a hydrophobic non-steroidal anti-inflammatory drug (ibuprofen) in alginate gel microparticles was accomplished by molecular diffusion of the drug species into microparticles produced by impinging aerosols of alginate solution and CaCl₂ cross-linking solution. A mean particle size in the range of 30–50 µm was measured using laser light scattering and high drug loadings of around 35 and 29% weight/dry microparticle weight were obtained for GS and ibuprofen respectively. GS release was similar in simulated intestinal fluid (phosphate buffer saline (PBS), pH 7.4, 37°C) and simulated gastric fluid (SGF) (HCl, pH 1.2, 37°C) but was accelerated in PBS following incubation of microparticles in HCl. Ibuprofen release was restricted in SGF but occurred freely on transfer of microparticles into PBS with almost 100% efficiency. GS released in PBS over 7?h, following incubation of microparticles in HCl for 2?h was found to retain at least 80% activity against Staphylococcus epidermidis while Ibuprofen retained around 50% activity against Candida albicans. The impinging aerosols technique shows potential for producing alginate gel microparticles of utility for protection and controlled delivery of a range of therapeutic molecules.     

Microencapsulation of a recombinant aminopeptidase (PepN) from Lactobacillus rhamnosus S93 in chitosan-coated alginate beads

A recombinant aminopeptidase (90 kDa) of Lactobacillus rhamnosus S93 produced by E. coli was encapsulated in alginate or chitosan-treated alginate beads prepared by an extrusion method. This study investigated the effects of alginate, CaCl₂, chitosan concentrations, hardening time, pH and alginate/enzyme ratios on the encapsulation efficiency (EE) and the enzyme release (ER). Chitosan in the gelling solution significantly increased the EE from 30.2% (control) to 88.6% (coated). This polycationic polymer retarded the ER from beads during their dissolution in release buffer. An increase in alginate and chitosan concentrations led to greater EE and lesser ER from the beads. The greatest EE was observed in a pH 5.4 solution (chitosan-CaCl₂) during bead formation. Increasing the CaCl₂ concentration over 0.1 M neither affected the EE nor the ER. Increasing hardening time beyond 10 min led to a decrease in EE and the alginate:enzyme ratio (3 : 1) was optimal to prevent the ER.     

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.     

ZnS-壳聚糖海藻酸钠包裹布洛芬纳米微球的制备和性能研究

目的以壳聚糖-海藻酸钠为基质材料,掺杂入纳米ZnS包裹非甾体抗炎药物布洛芬,制备缓、控释性能优异的载药纳米微球;为研发四代新剂型打下基础。方法利用复凝聚法,通过调整添加基质材料速度、反应温度、搅拌速度等,制备含ZnS的壳聚糖海藻酸钠布洛芬纳米微球,透射电镜观察纳米微球的形态,测试纳米微球的载药量与包封率,拟肠液条件下测试所致纳米微球的释放特性。结果含ZnS壳聚糖海藻酸钠布洛芬纳米载药微球的粒径约为80~100nm,载药量为40.2%药物包封率78.2%,ZnS粒径3nm。在水溶液、0.9%NaCl和磷酸盐缓冲液中的吸水膨胀程度小于不含ZnS的载药纳米微球;体外拟肠条件溶出表明含ZnS的载药纳米微球具有良好的缓控释性能,药代动力学特征为被动扩散。结论掺入了ZnS的壳聚糖海藻酸钠布洛芬纳米微球,形状圆整,包封率理想,具有良好的缓控释性能。     

Nanotechnologies and controlled release systems for the delivery of antisense oligonucleotides and small interfering RNA

Antisense oligonucleotides and small interfering RNA have enormous potential for the treatment of a number of diseases, including cancer. However, several impediments to their widespread use as drugs still have to be overcome: in particular their lack of stability in physiological fluids and their poor penetration into cells. Association with or encapsulation within nano-and microsized drug delivery systems could help to solve these problems. In this review, we describe the progress that has been made using delivery systems composed of natural or synthetic polymers in the form of complexes, nanoparticles or microparticles.This article is part of a themed section on Vector Design and Drug Delivery. For a list of all articles in this section see the end of this paper, or visit: http://www3.interscience.wiley.com/journal/121548564/issueyear?year=200     

Design and development of gliclazide-loaded chitosan microparticles for oral sustained drug delivery: in-vitro/in-vivo evaluation

Objectives The objective of this study was to prepare gliclazide–chitosan microparticles with tripolyphosphate by ionic crosslinking. Methods Chitosan microparticles were produced by emulsification and ionotropic gelation. The effects of process variables including chitosan concentration, pH of tripolyphosphate solution, glutaraldehyde volume and release modifier agent such as pectin added to the tripolyphosphate crosslinking solution were evaluated. The microparticles were examined with scanning electron microscopy, infrared spectroscopy and differential scanning colorimetry. The serum glucose lowering effect of gliclazide microparticles was studied in streptozotocin‐diabetic rabbits compared with the effect of pure gliclazide powder and gliclazide commercial tablets. Key findings The particle sizes of tripolyphosphate–chitosan microparticles were over the range 675–887 µm and the loading efficiency of drug was greater than 94.0%. In‐vivo testing of the gliclazide–chitosan microparticles in diabetic rabbits demonstrated a significant antidiabetic effect of gliclazide–chitosan microparticles after 8 h that lasted for 18 h compared with gliclazide powder, which produced a maximum hypoglycaemic effect after 4 h. Conclusions The results suggests that gliclazide–chitosan microparticles are a valuable system for the sustained delivery of gliclazide.     

Preparation and characterization of chitosan microparticles for oral sustained delivery of gliclazide: in vitro/in vivo evaluation

Chitosan microparticles were prepared with tripolyphosphate (TPP) by ionic cross‐linking with gliclazide (GLZ) as a model drug. The particle sizes of TPP‐chitosan microparticles ranged from 675–887 µm with loading efficiencies of greater than 94%. Chitosan concentration, TPP solution pH, and glutaraldehyde volume solution added to the TPP cross‐linking solution affected drug release characteristics. Pectin interactions with cationic chitosan on the surface of TPP/chitosan microparticles led to the formation of polyelectrolyte complex films that improved drug sustained release performance. In vivo testing of the GLZ‐chitosan microparticles in diabetic albino rabbits demonstrated a significant antidiabetic effect of GLZ/chitosan microparticles after 8 h that lasts for 18 h compared with GLZ powder that produced a maximal hypoglycemic effect at 4 h, suggesting that GLZ/chitosan microparticles represent an improved system for the long‐term delivery of GLZ. Drug Dev Res 72: 235–246, 2011. © 2010 Wiley‐Liss, Inc.     

Biodegradable alginate microparticles developed by electrohydrodynamic spraying techniques for oral delivery of protein

In this study, alginate microparticles were prepared by cross-linking alginate with calcium chloride solution using an electrohydrodynamic spraying technique. The effects of alginate and calcium chloride concentration as well as electrical potential on particle size and shape were investigated. The results showed that 1 mg ml^?1 alginate medium viscosity (AMV), 2.5 mg ml^?1 CaCl₂, electrical potential 18 kV (F1) and 0.5 mg ml^?1 alginate low viscosity (ALV), 2.5 mg ml^?1 CaCl₂, electrical potential 20 kV (F2) yielded the spherical shape and small particles of 937 ± 158 nm and 1556 ± 51 nm, respectively. In bovine serum albumin (BSA) entrapment efficiency study, initial BSA of 5, 10, 20, 40 and 60% w/w to polymer was incorporated into these alginate microparticles. The results revealed that F2 with initial BSA 10% w/w showed the highest entrapment efficiency of 49.70 ± 0.01%. The result of BSA content revealed that F2'with the initial BSA of 20% w/w showed the highest amount of BSA content of 3.92 ± 0.02 mg g^?1 of particles. F1 and F2 with the initial BSA of 5%, 20% and 40% w/w were chosen to evaluate for the release in PBS pH 7.4. It was found that F1 with the initial BSA of 40% w/w showed the slowest release rate and sustained release. The release of F1 in 0.1 N HCl solution (pH 1.2) was slower than that in pH 7.4. This electrohydrodynamic spray technique (EHDA) can be applied to prepare alginate in micro size and can encapsulate BSA. Alginate microparticles can further be optimized for oral delivery of several pharmaceutical peptides and proteins.     

Gastroretentive drug delivery systems

A controlled drug delivery system with prolonged residence time in the stomach is of particular interest for drugs that i) are locally active in the stomach, ii) have an absorption window in the stomach or in the upper small intestine, iii) are unstable in the intestinal or colonic environment, or iv) exhibit low solubility at high pH values. This article gives an overview of the parameters affecting gastric emptying in humans as well as on the main concepts used to design pharmaceutical dosage forms with prolonged gastric residence times. In particular, bioadhesive, size-increasing and floating drug delivery systems are presented and their major advantages and shortcomings are discussed. Both single- and multiple-unit dosage forms are reviewed and, if available, results from in vivo trials are reported.     

Carboxymethyl xanthan microparticles as a carrier for protein delivery

Xanthan gum (XG) was derivatized to sodium carboxymethyl xanthan gum (SCMXG) and then cross-linked with aluminium ions (Al⁺³) to prepare BSA-loaded microparticles (MPs) from a completely aqueous environment. The derivatized gum was characterized by various physical methods. Discrete and spherical BSA-loaded MPs were obtained from SCMXG solution, the pH of which was adjusted to 6 and 7 and the BSA entrapment efficiency was found to reach as high as 82%. The protein release in acidic dissolution medium was faster than that in alkaline dissolution medium and was accounted for the higher swelling ratio of the MPs in acidic environment. Moreover, the pH of the gum solution used to prepare the MPs also influenced the swelling and consequently protein release considerably.     

Coacervate delivery systems for proteins and small molecule drugs

Coacervates represent an exciting new class of drug delivery vehicles, developed in the past decade as carriers of small molecule drugs and proteins. This review summarizes several well-described coacervate systems, including: i) elastin-like peptides for delivery of anticancer therapeutics; ii) heparin-based coacervates with synthetic polycations for controlled growth factor delivery; iii) carboxymethyl chitosan aggregates for oral drug delivery; iv) Mussel adhesive protein and hyaluronic acid coacervates. Coacervates present advantages in their simple assembly and easy incorporation into tissue engineering scaffolds or as adjuncts to cell therapies. They are also amenable to functionalization such as for targeting or for enhancing the bioactivity of their cargo. These new drug carriers are anticipated to have broad applications and noteworthy impact in the near future.     

Wheat germ agglutinin-conjugated chitosan–Ca–alginate microparticles for local colon delivery of 5-FU: Development and in vitro characterization

The aim of this work was to prepare lectin-conjugated chitosan–Ca–alginate microparticles (MPs) loaded with acid-resistant particles of 5-fluorouracil (5-FU) for efficient local treatment of colon cancer. MPs were prepared by a novel one-step spray-drying technique and after wheat germ agglutinin (WGA) conjugation, they were characterized for size, swelling behavior, surface charge, entrapment efficiency and in vitro drug release. Prepared particles were spherical, with 6.73 μg/mg of WGA conjugated onto their surface. The size and zeta potential increased after conjugation, from 6.6 to 14.7 μm and from 9.6 to 15.3 mV, while drug encapsulation was 75.6 and 72.8%, respectively after conjugation. The swelling behavior of beads was mainly determined by properties of the cross-linked chitosan–alginate network. In vitro drug release studies carried out in simulated in vivo conditions with respect to pH, confirmed the potential of the particles to release the drug in a controlled manner. Also, the drug release was not significantly affected by WGA conjugation. The retention of biorecognitive activity of WGA after covalent coupling to MPs was confirmed by haemagglutination test. Functionalized MPs showed excessive mucoadhesiveness in vitro, due to the positive surface charge, pH-dependent swelling of the matrix and lectin–sugar recognition.     

Prolonged retention of cross-linked trypsin in calcium alginate microspheres

Abstract

Trypsin microencapsulated in a calcium alginate matrix was lost quickly through diffusion when the microspheres were placed in an aqueous medium. This problem was overcome by first reacting trypsin with glutaraldehyde to form cross-linkages and then incorporating the enzyme in the alginate micro-spheres. The performance of the cross-linked trypsin remained optimal at pH 8 while it was found to be more heat-stable and remained highly active even at 80°C. Esters and amides of L-arginine were preferentially hydrolysed by the enzyme indicating that cross-linking did not adversely affect the conformation of the active site. There was a suppression in enzymatic activity when the microspheres were placed in reaction media with an increasing concentration of organic solvent such as ethanol, acetonitrile or isopropanol. However, when returned to a totally aqueous environment, the enzyme resumed its initial tryptic capability. Such a microencapsulated form of cross-linked enzyme may find application in enzyme replacement therapy, optical resolution of racemic compounds as well as organic synthesis in an aqueous-organic environment.     

Polyelectrolyte-coated alginate microspheres as drug delivery carriers for dexamethasone release

Alginate microspheres loaded with dexamethasone were prepared by the droplet generator technique. Important parameters affecting drug release, including initial drug content, the type of polyelectrolyte coating, and a combination of different ratios of coated and uncoated microspheres were investigated to achieve in vitro dexamethasone delivery with approximately zero order release kinetics, releasing up to 100% of entrapped drug within 1 month, wherein dexamethasone released at a steady rate of 4.83 μg/day after an initial burst release period. These findings imply that these polyelectrolyte-coated alginate microspheres show promise as release systems to improve biocompatibility and prolong lifetime of implantable glucose sensors.     

A new hydrogel drug delivery system based on Hydroxyethylstarch derivatives

A new method has been developed to produce a drug delivery system (DDS) for proteins and peptides. Employing a water-in-water emulsion technique with polyethylenglycol and hydroxyethylstarch substituted by hydroxyethylmethacrylate and a subsequent photopolymerization, microspheres can be produced. This process can be carried out with proteins present in the cross-linkable phase and without the need of any organic solvents. The hydrogel microparticles are promising to fulfil the requirements for a DDS regarding biocompatibility and biodegradability.