Chitosan microspheres in PLG films as devices for cytarabine release

Perspectives on: Chitosan Drug Delivery Systems Based on their Geometries

Chitosan is a natural polymer that has many physicochemical (polycationic, reactive OH and NH2 groups) and biological (bioactive, biocompatible, biodegradable) properties. These unique properties make chitosan an excellent material for the development of new biomedical applications. One of the most well known biomedical chitosan applications is in drug delivery systems. Chitosans have been used in the design of many different types of drug carriers for various administration routes such as oral, bucal, nasal, transdermal, parenteral, vaginal, cervical, intrauterine and rectal. Chitosan can be engineered into different shapes and geometries such as nanoparticles, microspheres, membranes, sponges and rods. This paper is a perspective on the preparation of the chitosan drug delivery systems based on different structural geometries. In this respect, special preparation techniques are used to prepare chitosan drug carriers by altering such parameters as crosslinker concentration, chitosan molecular weight, drug/polymer ratio and processing conditions all of which affect the morphology of chitosan drug carriers and release rate of the loaded drug.

Impact of chitosan composites and chitosan nanoparticle composites on various drug delivery systems: A review

Chitosan is a promising biopolymer for drug delivery systems. Because of its beneficial properties, chitosan is widely used in biomedical and pharmaceutical fields. In this review, we summarize the physicochemical and drug delivery properties of chitosan, selected studies on utilization of chitosan and chitosan-based nanoparticle composites in various drug delivery systems, and selected studies on the application of chitosan films in both drug delivery and wound healing. Chitosan is considered the most important polysaccharide for various drug delivery purposes because of its cationic character and primary amino groups, which are responsible for its many properties such as mucoadhesion, controlled drug release, transfection, in situ gelation, and efflux pump inhibitory properties and permeation enhancement. This review can enhance our understanding of drug delivery systems particularly in cases where chitosan drug-loaded nanoparticles are applied.

Formulation of Vanillin Cross-Linked Chitosan Nanoparticles and its Characterization

Chitosan nanoparticles were successfully prepared by chemical cross-linking with vanillin. The nanoparticles were spherical in shape with smooth surface, and the average particle size of chitosan nanoparticles was 141 nm. The formulation of chitosan nanoparticles is based on Shiff reaction between aldehyde group of vanillin and amino group of chitosan. Chitosan nanoparticles prepared by crosslinking with vanillin are promising vehicle for the drug delivery of various anticancer drugs in the chemotherapy of cancers.

Chitosan/polyethylene glycol beads crosslinked with tripolyphosphate and glutaraldehyde for gastrointestinal drug delivery

This study reports on the preparation of chitosan (CS)/polyethylene glycol (PEG) hydrogel beads using sodium diclofenac (DFNa) as a model drug. Following the optimization of the polymer to drug ratio, the chitosan beads were modified by ionic crosslinking with sodium tripolyphosphate (TPP). The CS/PEG/DFNa beads obtained from a (w/w/w) ratio of 1/0.5/0.5 with crosslinking in 10% (w/v) TPP at pH 6.0 for 30 min yielded excellent DFNa encapsulation levels with over 90% loading efficiency. The dissolution profile of DFNa from CS/PEG/DFNa beads demonstrated that this formulation was able to maintain a prolonged drug release for approximately 8 h. Among the formulations tested, the CS/PEG/DFNa (1/0.5/1 (w/w/w)) beads crosslinked with a combination of TPP (10% (w/v) for 30 min) and glutaraldehyde (GD) (5% (w/v)) were able to provide minimal DFNa release in the gastric and duodenal simulated fluids (pH 1.2 and 6.8, respectively) allowing for a principally gradual drug release over 24 h in the intestinal (jejunum and ileum) simulated fluid (pH 7.4). Thus, overall the CS/PEG beads crosslinked with TPP and GD look to be a promising and novel alternative gastrointestinal drug release system.

Mucoadhesive chitosan microspheres of carvedilol for nasal administration

The aim of the present study was to develop and characterize chitosan mucoadhesive microspheres of carvedilol (CRV) for nasal delivery to improve bioavailability for treatment of hypertension and angina pectoris. The microspheres were prepared by emulsification-cross-linking method and evaluated for size, shape, entrapment efficiency (EE), in vitro mucoadhesion, in vitro drug release, differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The mucoadhesive properties were also evaluated by Freundlich and Langmuir adsorption isotherms. In vivo tests were carried out in rabbits. The microspheres were spherical with size of 20-50 microm, which is favorable for intranasal absorption. The EE was observed from 42% to 68% while percentage mucoadhesion was from 74% to 88%. A strong interaction between mucin and chitosan microspheres was detected explaining adsorption with electrostatic interaction. The microspheres released around 75% of drug in 8 h. DSC and XRD studies revealed that CRV was molecularly dispersed. The absorption rate was rapid and the absolute bioavailability was high, 72.29%. The gamma scintigraphy indicated that the microspheres cleared slowly from the nasal cavity. It was concluded that chitosan microspheres could be used to deliver CRV following nasal administration for improving the bioavailability.

Improved properties of incorporated chitosan film with ethyl cellulose microspheres for controlled release

In this article, to discover an innovative drug release system, ciprofloxacin hydrochloride-loaded blending films of chitosan (CS)/ethyl cellulose (EC) microspheres were prepared. Two steps were adopted in the film forming process. The first was formation of the drug-loaded EC microspheres in CS solution by solvent remove/solvent evaporation methods; then, the composite films were made by casting and solvent evaporation. The results were that the drug-loaded round EC microspheres dispersed asymmetrically in the CS films and largely improved the release time. Moreover, the drug-loaded blending film containing 0.5 g EC microspheres prepared at 90 degrees C showed highlighted extended release property. The drug was stable in the blending films, which expressed good cytocompatibility proved by MTT test. The film should be a promising carrier for controlled and extended drug release system in pharmaceutical applications.

Cellulose Acetate/Chitosan Multimicrospheres Preparation and Ranitidine Hydrochloride Release In Vitro

A noval cellulose acetate/chitosan multimicrospheres (CACM) was prepared by the method of w/o/w emulsion. The concentration of cellulose acetate (CA) and the ratio of CA/chitosan (CS) had influence on the CACM size, and appearance. Ranitidine hydrochloride loading, and releasing efficiency in vitro were investigated. The optimal condition for preparation of the microspheres was CA concentration at 2% and the ratio of CA/CS at 3/1. The microspheres size was 200-350 microm. The appearance of microspheres was spherical, porous, and nonaggregated. The highest loading efficiency was 21%. The ranitidine release from the CACM was 40% during 48 hr in buffers.

Chitosan/Cellulose Acetate Microspheres Preparation and Ranitidine Release In Vitro

New microspheres containing hydrophilic core and hydrophobic coating as a controlled-release system with no toxic reagents were proposed. Water in oil in water (W/O/W) emulsion and solvent evaporation methods were used to make chitosan/ cellulose acetate (CCA) microspheres sized 200 - 400 microm. Ranitidine hydrochloride, as a model drug, was investigated for its release properties in vitro. The loading efficiency and release rate of ranitidine were affected by chitosan concentration and molecular weight. Higher loadings were obtained at lower concentrations in the interval of 1% to 2%. With chitosan at a 2% concentration microspheres could be obtained with more spherical appearance, smaller size, and higher ranitidine loading efficiency microspheres than at other concentrations. Among the different molecular weight chitosan (47, 145, 308, 499, and 1130 KD) microspheres, the high molecular weight chitosan (1130 KD) microspheres had relatively high loading efficiency (10%). Molecular weight and concentration of chitosan as well as the size of microspheres affected the release of ranitidine. Microspheres smaller than 280 microm released the drug faster than did the bigger by about 10%. The optimal condition for the preparation of the microspheres was chitosan concentration 2%, molecular weight 1130 KD. The ranitidine release from the microspheres was 30% during 48 h in phosphate-buffer saline medium.

Nucleoside analogue delivery systems in cancer therapy

Nucleoside analogues (NAs) are important agents in the treatment of hematological malignancies. They are prodrugs that require activation by phosphorylation. Their rapid catabolism, cell resistance and overdistribution in the body jeopardize nucleoside analogue chemotherapy. Accordingly, therapeutic doses of NAs are particularly high and regularly have to be increased, resulting in severe toxicity and narrow therapeutic index. The major challenge is to concentrate the drug at the tumour site, avoiding its distribution to normal tissues. New drug carriers and biomaterials are being developed to overcome some of these obstacles. This review highlights novel NA delivery systems and discusses new technologies that could improve NA cancer therapy.

Drug incorporation and release of water soluble drugs from novel functionalized poly(glycerol adipate) nanoparticles

We have previously demonstrated the ability of poly(glycerol adipate) backbone (PGA) and PGA polymer backbone substituted with varying amounts of pendant C(18) chain length acyl groups to yield Dexamethasone phosphate DXMP loaded nanoparticles. The aim of this study was to obtain a deeper understanding of the underlying principles responsible for good drug incorporation and controlled release of drugs from poly (glycerol adipate) (PGA) nanoparticles. We compared the incorporation of the water soluble drugs DXMP and Cytosine arabinoside (CYT-ARA) in both unmodified and substituted PGA polymers. We investigated the effect of change in acyl group chain length and the degree of substitution on the physicochemical properties, drug loading and release of DXMP and CYT-ARA. Nanoparticles were prepared by the interfacial deposition technique and the simultaneous emulsification method. Amongst the nanoparticles prepared using acylated polymers with varying chain lengths (C(2) to C(10)) for DXMP incorporation, polymers with acyl group chain lengths containing 8 carbon atoms (C(8)) showed maximum drug incorporation. Amongst the C(8) series, polymers with 100% acylation provided both good drug incorporation and a controlled release for DXMP while for CYT-ARA it was the unsubstituted polymer backbone that had maximum drug loading and slower release. A number of inter-related factors are responsible for producing particles with particular size, zeta potential, drug loading and release characteristics. Drug loading and release from nanoparticles are primarily influenced by the nature of interactions between the drug and polymers which in turn depend upon the type of drug used and the physical chemistry of the polymer.

The promise of chitosan microspheres in drug delivery systems

Chitosan is a partially deacetylated polymer obtained from the alkaline deacetylation of chitin, which is a glucose-based, unbranched polysaccharide that occurs widely in nature as the principal component of exoskeletons of crustaceans and insects, as well as of the cell walls of some bacteria and fungi. Chitosan exhibits a variety of physicochemical and biological properties resulting in numerous applications in fields such as waste water treatment, agriculture, fabric and textiles, cosmetics, nutritional enhancement and food processing. In addition to its lack of toxicity and allergenicity, its biocompatibility, biodegradability and bioactivity make it a very attractive substance for diverse applications as a biomaterial in the pharmaceutical and medical fields. This review takes a closer look at the biomedical applications of chitosan microspheres. Based on recent research and existing products, some new and potential future approaches in this fascinating area are discussed.

Preparation and preliminary characterization of concentric multi-walled chitosan microspheres

Chitosan was first converted into micro-droplets by using a high voltage electrostatic field system. The droplets were then dropped into a series of Na(5)P(3)O(10)/NaOH solution mixtures with volume ratio of 17:3, 19:1, 1:0 (pure aqueous Na(5)P(3)O(10)) or 0:1 (pure aqueous NaOH) in order to fabricate chitosan microspheres with different membrane structures. The microspheres exhibit distinct chemical and physical properties, including release behaviors of encapsulated drugs. These chitosan microspheres prepared by this method exhibited good sphericity within the range of (286.6 +/- 15.9) to (356 +/- 9.5) microm in diameters. SEM observations have indicated that the chitosan microspheres exhibited distinct surface structures depending on the post-treatment solutions. The mechanical strength of the chitosan microspheres significantly improved upon treatment with Na(5)P(3)O(10)/NaOH solution at ratio of 17:3 (v/v), as compared with the same but at ratio of 19:1, 1:0 (pure Na(5)P(3)O(10)) and 0:1 (pure NaOH) solutions. In addition, chitosan microspheres with unique multi-walled concentric shell membrane structures were prepared by treating with Na(5)P(3)O(10)/NaOH solution at ratio of 19:1. Release studies were carried out to evaluate the kinetic profiles of two model drugs (5-fluorouracil and cytochrome C) from these prepared chitosan microspheres. When chitosan microspheres treated with Na(5)P(3)O(10)/NaOH ratio at 17:3, the release of cytochrome C was found to be the slowest as compared to those treated by the same Na(5)P(3)O(10)/NaOH solution of other mixing ratios, after a period of 35-day "endurance" test. However, in one case, 5-fluorouracil released quite quickly in a period of 30 min (about 80% completion). The wide range of drug release results might be attributed to the unique and wide range of surface characteristics, porosities, and various structures of chitosan microspheres upon treatment with Na(5)P(3)O(10)/NaOH solutions. These results indicate that, by adjusting the Na(5)P(3)O(10)/NaOH ratios, without extra manipulation on polymer material formulation, one could obtain an additional degree of freedom in drug release profile that permits the simultaneous regulation of morphologies of surface texture and internal structure, mechanical properties, and molecular permeability of the microspheres.

Development and characterization of biodegradable chitosan films for local delivery of Paclitaxel

Intratumoral and local drug delivery strategies have gained momentum recently as a promising modality in cancer therapy. In order to deliver paclitaxel at the tumor site in therapeutically relevant concentrations, chitosan films were fabricated. Paclitaxel could be loaded at 31% wt/wt in films, which were translucent and flexible. Physicochemical characterization of paclitaxel via thermal, spectroscopic, x-ray diffraction, and electron microscopy techniques revealed information on solid-state properties of paclitaxel as well as chitosan in films. While chitosan was in amorphous form, paclitaxel seemed to be present in both amorphous and crystalline forms in film. The polymeric dispersion of paclitaxel in poloxamer formed fibrous structures generating discontinuities in the film matrix, thereby leading to the introduction of perturbations in the packing arrangement of polymer chains. These films released only 10% to 15% of loaded paclitaxel by a burst effect under in vitro testing conditions, with lysozyme having no effect on the release. However, films softened after implantation in mice and lost integrity over time. The implantable delivery system is not only biodegradable but also well tolerated in vivo and hence, biocompatible as revealed by histological studies. The lack of formulation-induced local inflammatory responses of paclitaxel chitosan films suggests a new paradigm for localized chemotherapy based on implantable systems.

Sustained release of bupivacaine from devices based on chitosan

Chitosan beads loaded with bupivacaine (16+/-3 microg of drug per milligram of beads) were prepared by cross-linking with glutaraldehyde. In vitro drug release at pH and temperature conditions similar to those of the biological systems were studied. Maximum release of bupivacaine was obtained between 100 and 120 h, depending on the presence of lysozyme in the release medium, since the enzyme facilitates the release process. A constant release rate of the drug, between 11 and 15 microg/h, was observed for 30 h. In order to prolong bupivacaine release, the drug-loaded chitosan beads were coated with a poly(DL-lactide-co-glycolide) film. The resulting device allows the drug to be released in a sustained form; a constant release rate between 28.5 and 29.5 microg/h was obtained for 3 days, and the maximum release of bupivacaine took place at day 9. The in vitro results indicate a possible application of these bupivacaine loaded chitosan systems as drug release devices with an analgesic action. Thus, they could be used in the treatment of dental pain in the buccal cavity, where drug release would be made easier by lysozyme of the saliva.

Chitosan microspheres as a potential carrier for drugs

Chitosan is a biodegradable natural polymer with great potential for pharmaceutical applications due to its biocompatibility, high charge density, non-toxicity and mucoadhesion. It has been shown that it not only improves the dissolution of poorly soluble drugs but also exerts a significant effect on fat metabolism in the body. Gel formation can be obtained by interactions of chitosans with low molecular counterions such as polyphosphates, sulphates and crosslinking with glutaraldehyde. This gelling property of chitosan allows a wide range of applications such as coating of pharmaceuticals and food products, gel entrapment of biochemicals, plant embryo, whole cells, microorganism and algae. This review is an insight into the exploitation of the various properties of chitosan to microencapsulate drugs. Various techniques used for preparing chitosan microspheres and evaluation of these microspheres have also been reviewed. This review also includes the factors that affect the entrapment efficiency and release kinetics of drugs from chitosan microspheres.

Cytarabine release from comatrices of albumin microspheres in a poly(lactide–co-glycolide) film: in vitro and in vivo studies

Cytarabine (ara-C) was included in albumin microspheres and these microspheres were immersed in a poly(lactide-co-glycolide) (PLGA) film to constitute a comatrix system to develop a prolonged form of release. Cytarabine-loaded albumin microspheres were synthesized by emulsion, and 25 or 50 mg of drug were included in the disperse phase. Thus, microspheres with 46+/-4 microg drug/mg microspheres and 50+/-5 microg drug/mg microspheres were obtained, which means a percentage of incorporation efficiency of 42+/-4% and 25+/-2%, respectively. These cytarabine-loaded microspheres were used to prepare PLGA-comatrices. Kinetic release studies indicated that total cytarabine release only takes place in the presence of protease, probably due to the fact that glutaraldehyde establishes covalent links with the amine side group of the drug and cross-links it with the protein matrix. A slower kinetic release of the drug was obtained from PLGA-comatrices, although only 80% of the included cytarabine was released on day 7. The comatrices were subcutaneously implanted in the back of rats and in both cases the ara-C administered dose was 36 mg of ara-C per kg of body weight. The drug was detected in plasma 10 days. The mean residence time (MRT) of the drug administered by these comatrices was 87-91 times larger when compared to the value obtained when the drug was administered in solution by intraperitoneal injection. The histological studies show that a degradative process of the comatrices takes place. The comatrices do not damage surrounding tissue; a normal regeneration of the implanted zone was observed.

Release phenomena of insulin from an implantable device composed of a polyion complex of chitosan and sodium hyaluronate

An implant controlled-release system for protein drug delivery based on a polyion complex device composed of chitosan (CS) and sodium hyaluronate (HA) was investigated. The conditions which generated the greatest amount of the polyion solid complex were studied to ascertain the formation of polyion complex between CS and HA. The greatest amount of the polyion complex was formed at the weight ratio of 3 to 7 (CS:HA) at pH 3.5. Furthermore, the CS-HA pellets were prepared and then drug release from CS-HA pellets was evaluated using insulin as a model drug. The results demonstrated that the insulin release from CS-HA pellets was markedly influenced by both the change in the polymer mixing ratio and the total pellet weight, whereas the compression pressure did not affect the release significantly. An artificial neural network (ANN) and biharmonic spline interpolation (HSI) were employed to predict the actual relation between causal factors and the release rate constant of insulin. Although both the ANN and HSI successfully represented a non-linear relationship between the formulation factors and the release rate constant, HSI methodology gave a better estimation than that of the ANN.

Preparation and characterization of chitosan microparticles intended for controlled drug delivery

Chitosan microparticles were prepared with tripolyphosphate (TPP) by ionic crosslinking. The particle sizes of TPP-chitosan microparticles were in range from 500 to 710 microm and encapsulation efficiencies of drug were more than 90%. The morphologies of TPP-chitosan microparticles were examined with scanning electron microscopy. As pH of TPP solution decreased and molecular weight (MW) of chitosan increased, microparticles had more spherical shape and smooth surface. Release behaviors of felodipine as a model drug were affected by various preparation processes. Chitosan microparticles prepared with lower pH or higher concentration of TPP solution resulted in slower felodipine release from microparticles. With decreasing MW and concentration of chitosan solution, release behavior was increased. The release of drug from TPP-chitosan microparticles decreased when cross-linking time increased. These results indicate that TPP-chitosan microparticles may become a potential delivery system to control the release of drug.