Glutaraldehyde cross-linked chitosan microspheres as a long acting biodegradable drug delivery vehicle: studies on the in vitro release of mitoxantrone and in vivo degradation of microspheres in rat muscle

Hollow quaternized chitosan microspheres increase the therapeutic effect of orally administered insulin

The delivery of insulin by non-parenteral routes has gained significant attention over the last two decades. In the present study, we prepared hollow quaternized chitosan microspheres by the SPG membrane emulsification technique and glutaraldehyde cross-linking method. The structural properties, as well as the uniform size and autofluorescence, enabled us to develop oral delivery of insulin which conserved the bioactivity of the encapsulated insulin, achieving bioadhesion of microspheres, increasing the loading ability and optimizing the release profile. In vivo evaluation also saw an optimal reduction in blood glucose level and powerful therapeutic effects after treatment with the designed microspheres, which further confirmed the feasibility of using hollow quaternized chitosan microspheres as insulin carriers for oral administration.

Biodegradation of Chitosan-Tripolyphosphate Beads:In VitroandIn VivoStudies

In this study, chitosan [(1 --> 4) linked 2-amino-2-deoxy-beta-D-glucopyranose] beads were prepared by interacting this polycation (> 90% deacetylated) with the tripolyphosphate (TPP) polyanion. The resulting chitosan-TPP beads (C) were modified either by coating with sodium alginate (CA) or by cross-linking with glutaraldehyde (CGA). The in vitro degradation of C beads was found to be faster than its CA and CGA counterparts. C beads degraded faster at pH 6.5, compared to pH 7.4 conditions. At pH 7.4, about 41%, 37% and 10% of dry mass loss after 12 months was determined for C, CA and CGA, respectively. At pH 6.5, the dry mass loss of CA and CGA after the same period of time was found to be 73% and 37%, respectively. However, C beads completely degraded at pH 6.5 after 8 months of in vitro incubation. The in vivo biodegradation experiments were performed on Wistar rats (n = 24) for a duration of 6 months. No sign of fibrotic capsule formation was observed around any of the implanted beads at 2 and 6 months post-transplantation. At 2 months, the in vivo-degradation was slow-going and the beads in all groups were intact; CGA beads had more tissue reaction than C and CA beads at this time point. While the C beads had almost completely degraded after 6 months, the biodegradation process in CA and CGA beads was progressing. Histomorphometric analysis revealed that the in vivo biodegradation was in the order of C (approximately 85%) > CA (approximately 50%) > CGA (approximately 25%) after 6 months. Neovascularization was observed at the vicinity of the bead implants close to major blood vessels, both at 2 and 6 months time-points.

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.

Preparation of doxorubicin-containing chitosan microspheres for transcatheter arterial chemoembolization of hepatocellular carcinoma

A new form of doxorubicin hydrochloride (DRH)-containing chitosan microspheres (CMs) was prepared by employing an expanding-loading-shrinking (E-L-S) process. One hundred mg of pre-formed CMs were soaked in absolute ethanol and then placed in reduced pressure (the expanding process). Ten mg of DRH (2 mg ml(-1)) were added into the expanded CMs (the loading process). Next the microspheres were freeze-dried (the shrinking process). As a result of this E-L-S process, 10% (w/w) DRH-containing CMs (DRH-CM) were made. During 7 days, 22.6% of the DRH was observed to be released on the in vitro drug release study. In addition, these new DRH-CMs could be used for transcatheter arterial chemoembolization (TACE) procedure in VX2 hepatic tumour models of rabbit and the anti-tumour effects of DRH-CMs were investigated. On the post-CT scan 7 days after the TACE, total infarctions of the VX2 tumour were observed in 5 rabbits among the 6 total rabbits.

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.

Formation of composites comprised of calcium deficient HAp and cross-linked gelatin

Cross-linked gelatin/calcium deficient hydroxyapatite (CDHAp) composites were prepared at or near physiologic temperature. alpha-tricalcium phosphate (alpha-TCP) or a mixture of tetracalcium phosphate and dicalcium phosphate were used as CDHAp precursors. Glutaraldehyde was used to cross-link the gelatin fibers. CDHAp formation reached completion in the presence of cross-linked gelatin fibers. Effects of cross-linking concentrations, proportions of gelatin fiber, molecular weight of gelatin and the temperature of the hydration reaction on the formation of CDHAp were studied. Cross-linked gelatin acts as a nucleating agent for CDHAp formation. The pH variations during CDHAp formation are lower at the onset of the reactions in the presence of cross-linked gelatin fibers. Although cross-linked gelatin fibers enhance CDHAp formation their composites have low mechanical strengths. Swelling of gelatin appears to be a major factor that limits the strengths of the CDHAp/cross-linked gelatin composites.

Chitosan-based aerogels with high adsorption performance

New natural polymer-based aerogels, cross-linked chitosan aerogels, were prepared by the sol-gel route with glutaradehyde, glyoxal, and formaldehyde as cross-linkers. The alcogels were dried by supercritical carbon dioxide (CO2) fluid extraction. The resulting materials were characterized using scanning electron microscopy (SEM), nitrogen adsorption/desorption analysis, and Fourier transform infrared (FT-IR) spectroscopy. Furthermore, the adsorption of the anionic surfactant sodium dodecylbenzene-sulfonate (SDBS) from aqueous solution by the materials was investigated. The aerogels exhibit high adsorption capability, can remove SDBS from acidic aqueous solutions, and have potential applications in controlling SDBS pollution.

In vitro and in vivo evaluation of mucoadhensiveness of chitosan/cellulose acetate multimicrospheres

Chitosan/cellulose acetate multimicrospheres (CCAM) with or without ranitidine (RT) were prepared by the method of W/O/W emulsion with no toxic reagents and had the size interval of 200-280 microm. The angles of repose were only a little more than 30 degrees and the maximum angles of one-plane-critical-stability (OPCS phi) were about 20 degrees . The CCAM had good suspension ability for the tapped density of CCAM was less than 0.127g/mL. The pH value affected the swelling ability of CCAM and the relative humidity had little effect on the characteristics of CCAM when it was not more than 75%. The CCAM system had good effect on the controlled release of RT in vitro and the release rate was almost 60% during 48 h. Furthermore the release of RT was not affected by pH value of release medium. The mucoadhesive tests showed that CCAM could retain in gastrointestinal tract for an extended period of time. There were 53.7% of CCAM remained in stomach after administered for 2(1/2) h and 98.9% of CCAM remained in stomach and small intestine after administered for 3(1/2) h. These results suggest that CCAM is a useful dosage form targeting the gastric mucosa or prolonging gastric residence time as a multiple-unit mucoadhesive system.

Low-swelling chitosan derivatives as biosorbents for basic dyes

In this study, three different chitosan microsphere derivatives were prepared as sorbents for basic dyes. Preparation was succeeded by a novel cross-linking method based on ionic gelation with tripolyphosphate and subsequent covalent cross-linking with glutaraldheyde in order to address the large amount of swelling of the powdered form of the respective derivatives. Basic blue 3G (dye) was selected as the sorbate, and chitosan microsheres grafted with acrylamide and acrylic acid were used as biosorbents. Techniques such as FTIR spectroscopy, SEM, and swelling measurements facilitated the evaluation of the materials. Sorption-desorption experiments over the whole pH range were carried out to reveal the optimum value of sorption-desorption. The Langmuir isotherm model was used to fit the equilibrium experimental data, giving a maximum sorption capacity of 0.808 mmol/g at 338 K. An intraparticle diffusion model was employed to fit the kinetic data, and the resulting diffusion coefficients were in the range of (1-10) x 10(-11) m(2)/s. Thermodynamic analysis showed that the sorption process was spontaneous and endothermic with an increased randomness. In addition, sorption experiments were realized with a mixture of three basic dyes at various concentrations of sorbents.

A novel method to obtain chitosan/DNA nanospheres and a study of their release properties

Polysaccharides and other cationic polymers have recently been used in pharmaceutical research and industry for their properties to control the release of antibiotics, DNA, proteins, peptide drugs or vaccines, and they have also been extensively studied as non-viral DNA carriers for gene delivery and therapy. Among them, chitosan is the most used since it can promote long-term release of incorporated drugs. This work is focused on the preparation of chitosan and chitosan/DNA nanospheres by using a novel and simple osmosis-based method, recently patented. The morphology of chitosan/DNA particles is spherical (as observed by scanning electron microscopy, SEM) and the nanospheres' average diameter is 38 ± 4 nm (obtained by dynamic light scattering, DLS). With this method, DNA is incorporated with high yield (up to 30%) and the release process is gradual and prolonged in time. The novelty of the reported method resides in the general applicability to various synthetic or natural biopolymers. Solvent, temperature and membrane cut-off are the physicochemical parameters that one is able to use to control the overall osmotic process, leading to several nanostructured systems with different size and shape that may be used in several biotechnological applications.

Chitosan microspheres for intrapulmonary administration of moxifloxacin: Interaction with biomembrane models and in vitro permeation studies

Chitosan microspheres loaded moxifloxacin were prepared to obtain sustained release of the drug after intrapulmonary administration. The microspheres were produced by the spray-drying method using glutaraldehyde as the crosslinking agent. The particles were spherical with a smooth but distorted surface morphology and were of small size, ranging from 2.5 to 6.0microm, thus suitable for inhalation. In vitro release studies showed a significant burst effect for all crosslinked systems, followed by a prolonged moxifloxacin release, particularly in the presence of the highest glutaraldehyde concentration. Lipid vesicles made of dipalmitoylphosphatidylcholine (DPPC) were used as an in vitro biomembrane model to evaluate the influence of chitosan microspheres on the interaction of moxifloxacin with biological membranes. Differential scanning calorimetry was used as a simple and non-invasive technique of analysis. Moxifloxacin freely permeates through DPPC liposomes, interacting with the hydrophobic zone of the bilayers (lowering of the DeltaH value and loss of the cooperativity of the main transition peak). Uncrosslinked microspheres rapidly swelled and dissolved releasing free chitosan that was able to interact with liposomes (increase of DeltaH value), probably altering the biomembrane permeability to the drug. Crosslinked microspheres did not show this property. Pulmonary absorption of moxifloxacin-loaded chitosan microspheres was evaluated compared to the free drug. A monolayer of Calu-3 human bronchial epithelial cells mounted on Franz diffusion cells was used as an in vitro bronchial epithelium model. Microspheres retard the absorption of moxifloxacin and within 6h the cumulative amount of permeated drug was about 18%, 11% and 7% (w/w) for free moxifloxacin, moxifloxacin-loaded crosslinked and moxifloxacin-loaded uncrosslinked microspheres, respectively.

Dextran and hyaluronan methacrylate based hydrogels as matrices for soft tissue reconstruction

Polysaccharide hydrogels have become increasingly studied as matrices in soft tissue engineering because of their known cytocompatibility. In this work cross-linkable dextran methacrylates and hyaluronan methacrylate were synthesized and their transformation into stable hydrogels was studied. The in vitro degradation behaviour of the formed hydrogels could be controlled by the polysaccharide structure and the cross-linking density. Under in vitro conditions, the formed gels had no cytotoxic effects against fibroblasts, but cells could adhere only inefficiently in long term experiments. The use of composite gels improved the adherence of cells. Different scaffold architectures were studied including porous structures and perforated gel layers. Selected hydrogels were examined in an in vivo pilot study using a rabbit model to evaluate their biocompatibility, stability and degradation. No signs of inflammation were seen and with prolonged duration the material was degraded and lacunas were formed by immigrating or ingrowing cells. Optimizing their mechanical properties, the formed hydrogels represent promising candidates as matrices for soft tissue reconstruction.

Nanoparticles based on the complex of chitosan and polyaspartic acid sodium salt: Preparation, characterization and the use for 5-fluorouracil delivery

New nonstoichiometric polyelectrolyte complex nanoparticles were prepared based on chitosan (CS) and polyaspartic acid sodium salt (PAsp). The physicochemical properties of the complexes were investigated by means of turbidity, dynamic light scattering, transmission electron microscopy and zeta potential. The results indicated that the slow dropwise addition of chitosan into PAsp allowed to elaborate either anionic or cationic particles in the size range of 85-300 nm with proper CS and PAsp unit molar ratios. Investigation of structural changes during the addition of CS revealed that the microstructure of the nanoparticles depended strongly on the unit molar ratio of CS to PAsp. Nanoparticles containing a hydrophilic drug, 5-fluorouracil (5FU), were prepared by mixing and absorption method. In vitro and in vivo experiment indicated that the drug-loaded CS-PAsp nanoparticles presented a sustained release of 5FU compared to the 5FU solution and the areas under curve (AUC) were increased by about four times.

Direct force measurements between siRNA and chitosan molecules using force spectroscopy

Information on the interaction strength between small interfering RNA (siRNA) and chitosan can contribute to the understanding of the formation and stability of chitosan/siRNA nanoparticles used as siRNA delivery systems for gene silencing. In this study, we utilize atomic force microscopy to obtain force spectroscopy results of the interaction strengths between siRNA and chitosan measured in physiological phosphate buffered saline buffer at different pH. The force measurements revealed that the adhesive interactions decreased in force strength and force frequency as the pH was increased from 4.1 to 6.1, 7.4, and 9.5, exhibiting distinct multimodal distributions of the interaction forces between siRNA and chitosan molecules at acidic pH and only negligible adhesive forces were observed at neutral or high pH. The strong pH dependence of siRNA-chitosan interactions can provide a convincing rationale for siRNA/chitosan complex formation and nanoparticle stability under low acidic conditions. These findings demonstrate that the use of force spectroscopy for the adhesive force measurements allows an evaluation of the complexing ability between siRNA and chitosan that can be utilized to predict nanoparticle stability.

Effect of oppositely charged polymer and dissolution medium on swelling, erosion, and drug release from chitosan matrices

The reasons for retarded release of naproxen sodium from the chitosan matrices at different pH include poor aqueous solubility of drug, the formation of a rate-limiting polymer gel barrier along the periphery of matrices, the interaction of naproxen sodium with protonated amino groups of chitosan, and the interaction of ionized amino groups of chitosan with ionized sulfate groups of kappa-carrageenan.

Cross-Linking Chitosan Nanofibers

In the present study, we have electrospun various grades of chitosan and cross-linked them using a novel method involving glutaraldehyde (GA) vapor, utilizing a Schiff base imine functionality. Chemical, structural, and mechanical analyses have been conducted by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and Kawabata microtensile testing, respectively. Additionally, the solubilities of the as-spun and cross-linked chitosan mats have been evaluated;solubility was greatly improved after cross-linking. SEM images displayed evidence that unfiltered low, medium, and high molecular weight chitosans, as well as practical-grade chitosan, can be electrospun into nanofibrous mats. The as-spun medium molecular weight chitosan nanofibers have a Young's modulus of 154.9 +/- 40.0 MPa and display a pseudo-yield point that arose due to the transition from the pulling of a fibrous mat with high cohesive strength to the sliding and elongation of fibers. As-spun mats were highly soluble in acidic and aqueous solutions. After cross-linking, the medium molecular weight fibers increased in diameter by an average of 161 nm, have a decreased Young's modulus of 150.8 +/- 43.6 MPa, and were insoluble in basic, acidic, and aqueous solutions. Though the extent to which GA penetrates into the chitosan fibers is currently unknown, it is evident that the cross-linking resulted in increased brittleness, a color change, and the restriction of fiber sliding that resulted in the loss of a pseudo-yield point.

Polysaccharide-based polymer blends: Methods of their production

The existing methods of preparing polymer blends of cellulose, chitin and chitosan with natural and synthetic polymers and their applications are reviewed. The methods of solid-phase blending of these polymers under conditions of joint action of high pressure and shear deformation are discussed. Normally, under these conditions the processes of dispersion of polymer particles, amorphization, mixing at different levels, depolymerization as well as a chemical interaction resulting in formation of branched and crosslinked structures can take place. The probability and intensity of these processes depend in many respects on the type and magnitude of the external force, but the properties of the polymers are of higher importance. The advantages of the method of joint action of high pressure and shear deformation compared to the conventional techniques of polysaccharides mixtures production are shown.

Ionotropic cross-linked chitosan microspheres for controlled release of ampicillin

The solubility of non cross-linked chitosan in weak acid solutions restricts its utility in microspheres for drug delivery. The primary aim of this study was to produce pentasodium tripolyphosphate cross-linked chitosan microspheres with higher acid resistance for controlled release of ampicillin. The microspheres were prepared by two different microencapsulation procedures (by emulsification and by spray-drying) and characterized by their particle size, surface morphology, stability, drug entrapment efficiency and drug release. The size of the microspheres was <10 microm with a narrow size distribution. The entrapment of ampicillin in the microspheres was more than 80%. Stability of uncross-linked and cross-linked microspheres was affected by the pH of simulated gastric fluid (SGF, pH 1.2) and simulated intestinal fluid (SIF, pH 7.5). The inclusion of the enzymes pepsin and pancreatin did not affect the stability of the microspheres. The inclusion of lysozyme in phosphate buffer saline resulted in increased solubilization. The release of the drug was affected by cross-linking of microspheres with tripolyphosphate (TPP). The cross-linked microspheres were more stable in simulated gastric fluid and showed slower but sustained release of ampicillin. The antimicrobial activity of the released ampicillin was confirmed by Staphylococcus aureus bioassay.

Effect of molecular weight heterogeneity on drug encapsulation efficiency of gelatin nano-particles

Influence of molecular weight heterogeneity and drug solubility, drug loading and hydrodynamic conditions on drug release kinetics from gelatin nanoparticles were investigated. Also to assess the ability of gelatin nanoparticles as a potential intravascular probe for diagnostic purposes and in improving the biodelivery of cycloheximide (CHX), which is being used as a representative drug. Comparative characterization of 75 Bloom (type B, bovine), 175 and 300 Bloom (type A, porcine) gelatin nanoparticles was done to understand the phase behavior and hydrodynamic properties of gelatin chains and its nanoparticles. Gelatin nanoparticles were prepared by two-step desolvation method. Dynamic light scattering studies were performed to estimate hydrodynamic radii as well as intermolecular interaction. Effects of parameters like pH, temperature and molecular weight on the size and stability of the nanoparticles were studied. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) measurements were done for size and stability analysis. Enhanced visco-elastic properties of nanoparticles were observed as compared to normal solutions of gelatin.

Colloid stability of sodium dihexadecyl phosphate/poly(diallyldimethylammonium chloride) decorated latex

The colloid stability of supramolecular assemblies composed of the synthetic anionic lipid sodium dihexadecyl phosphate (DHP) on cationic poly(diallyldimethylammonium chloride) (PDDA) supported on polystyrene sulfate (PSS) microspheres was evaluated via turbidimetry kinetics, dynamic light scattering for particle sizing, zeta-potential analysis, and determination of DHP adsorption on PDDA-covered particles. At 0.05 g/L PDDA and 5 x 10(9) PSS particles/mL, PDDA did not induce significant particle flocculation and a vast majority of PDDA covered single particles were present in the dispersion so that this was the condition chosen for determining DHP concentration (C) effects on particle size and zeta-potentials. At 0.8 mM DHP, charge neutralization, maximal size, and visible precipitation indicated extensive flocculation and minimal colloid stability for the DHP/PDDA/PSS assembly. At 0.05 g L(-1) PDDA, isotherms of high affinity for DHP adsorption on PDDA-covered particles presented a plateau at a limiting adsorption of 135 x 10(19) DHP molecules adsorbed per square meter PSS which was well above bilayer deposition on a smooth particle surface. The polyelectrolyte layer on hydrophobic particles was swelled and fluffy yielding ca. 6 +/- 1.5 nm hydrodynamic thickness. Maximal and massive adsorption of DHP lipid onto this layer produced polydisperse DHP/PDDA/PSS colloidal particles with low colloid stability and which, at best, remained aggregated as doublets over a range of large lipid concentrations so that it was not possible to evaluate the mean total thickness for the deposited film. The assembly anionic lipid/cationic PDDA layer/polymeric particle was relatively stable as particle doublets only well above charge neutralization of the polyelectrolyte by the anionic lipid, at relatively large lipid concentrations (above 1 mM DHP) with charge neutralization leading to extensive particle aggregation.

Sustained insulin release with biodegradation of chitosan gel beads prepared by copper ions

Chitosan (CS) gel beads were prepared with chelated copper (II) ions as a vehicle for the delivery of peptide and protein drugs. Insulin, which is a model of peptide and protein drugs, was scarcely released from the CS gel beads in vitro, presumably due to the nature of interactions occurring between insulin, CS and the copper (II) ions. The efficacy of insulin released from the CS gel beads was confirmed by implantation into diabetic mice. A consistent reduction in blood glucose level was observed in vivo due to insulin release as the CS gel beads were degraded. Control over insulin release was achieved by altering the properties of the CS. Thus, CS gel beads are promising as a biocompatible and biodegradable vehicle by which peptide and protein drugs can be delivered.

Entrapment of some compounds into biocompatible nano-sized particles and their releasing properties

Two types of biocompatible nanoparticles with an average diameter of around 200 nm were formed only by mixing hydrolysates of chitosan and carboxymethyl cellulose (CMC). Nanoparticle A was produced from chitosanase hydrolysate of chitosan and cellulase hydrolysate of carboxymethyl cellulose, and nanoparticle B was produced from lysozyme hydrolysate of chitosan and the carboxymethyl cellulose hydrolysate. Negatively charged or amphoteric compounds were first mixed with chitosan hydrolysate and then added to carboxymethyl cellulose hydrolysate to effectively entrap them in the particles. Positively charged compounds could also be effectively entrapped by mixing the hydrolysates and the compound in the reverse order. Negatively charged compounds with high molecular weights were maintained in the particles even at the higher pH levels than the pK(a) of the amino groups of chitosan. Entrapped compounds were gradually released from nanoparticle A by lysozyme treatment. In contrast, there was no release from nanoparticle B. These results indicate that nanoparticle A can be applied to controlled-release drug delivery systems, and that nanoparticle B is stably retained in the body without releasing the entrapped compounds.