In vivo and in vitro biodegradation of oxychitin–chitosan and oxypullulan–chitosan complexes

Synthesis and characterization of chitosan-polyvinyl alcohol-bioactive glass hybrid membranes

The tissue engineering strategy is a new approach for the regeneration of cementum, which is essential for the regeneration of the periodontal tissue. This strategy involves the cell cultures present in this tissue, called cementoblasts, and located on an appropriate substrate for posterior implantation in the regeneration site. Prior studies from our research group have shown that the proliferation and viability of cementoblasts increase in the presence of the ionic dissolution products of bioactive glass particles. Therefore, one possible approach to obtaining adequate substrates for cementoblast cultures is the development of composite membranes containing bioactive glass. In the present study, composite films of chitosan-polyvinyl alcohol-bioactive glass containing different glass contents were developed. Glutaraldehyde was also added to allow for the formation of cross-links and changes in the degradation rate. The glass phase was introduced in the material by a sol-gel route, leading to an organic-inorganic hybrid. The films were characterized by Fourier-transformed infrared spectroscopy (FTIR), scanning electron microscopy (SEM) with electron dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analysis. Bioactivity tests were also conducted by immersion of the films in simulated body fluid (SBF). Films containing up to 30% glass phase could be obtained. The formation of calcium phosphate was observed after the immersion of the films. A calcium phosphate layer formed more quickly on materials containing higher bioactive glass contents. In the hybrid containing 23% bioactive glass, a complete layer was formed after 24 h immersion, showing the high bioactivity of this material. However, despite the higher in vitro bioactivity, the film with 23% glass showed lower mechanical properties compared with films containing up to 17% glass.

In vitro degradation and drug release of a biodegradable tissue adhesive based on functionalized 1,2-ethylene glycol bis(dilactic acid) and chitosan

Biodegradability and adhesive-associated local drug release are important aspects of research in tissue adhesive development. Therefore, this study focuses on investigating the in vitro degradation and drug release of a tissue adhesive consisting of hexamethylene diisocyanate functionalized 1,2-ethylene glycol bis(dilactic acid) and chitosan chloride. To prevent infections, ciprofloxacin hydrochloride (CPX·HCl) was incorporated into the adhesive. The influence of CPX·HCl on the adhesive reaction and adhesive strength was analyzed by FTIR-ATR-spectroscopy and tensile tests. The CPX·HCl release was investigated by HPLC. The degradation-induced changes at 37 °C were evaluated by gravimetric/morphological analyzes and micro-computer tomography. The antibiotic potential of the CPX·HCl loaded adhesive was determined by agar diffusion tests. The degradation tests revealed a mass loss of about 78 % after 52 weeks. The adhesive reaction velocity and tensile strength were not influenced by CPX·HCl. Using a 2 mg/g CPX·HCl loaded adhesive an inhibition of all tested bacteria was observed.

Hybrid polymeric hydrogels for ocular drug delivery: nanoparticulate systems from copolymers of acrylic acid-functionalized chitosan and N-isopropylacrylamide or 2-hydroxyethyl methacrylate

Nanoparticulate hybrid polymeric hydrogels (10-70 nm) have been obtained via the radical-induced co-polymerization of acrylic acid-functionalized chitosan with either N-isopropylacrylamide or 2-hydroxyethyl methacrylate, and the materials have been investigated for their ability to act as controlled release vehicles in ophthalmic drug delivery. Studies on the effects of network structure upon swelling properties, adhesiveness to substrates that mimic mucosal surfaces and biodegradability, coupled with in vitro drug release investigations employing ophthalmic drugs with differing aqueous solubilities, have identified nanoparticle compositions for each of the candidate drug molecules. The hybrid nanoparticles combine the temperature sensitivity of N-isopropylacrylamide or the good swelling characteristics of 2-hydroxyethyl methacrylate with the susceptibility of chitosan to lysozyme-induced biodegradation.

Natural origin scaffolds with in situ pore forming capability for bone tissue engineering applications

This work describes the development of a biodegradable matrix, based on chitosan and starch, with the ability to form a porous structure in situ due to the attack by specific enzymes present in the human body (alpha-amylase and lysozyme). Scaffolds with three different compositions were developed: chitosan (C100) and chitosan/starch (CS80-20, CS60-40). Compressive test results showed that these materials exhibit very promising mechanical properties, namely a high modulus in both the dry and wet states. The compressive modulus in the dry state for C100 was 580+/-33MPa, CS80-20 (402+/-62MPa) and CS60-40 (337+/-78MPa). Degradation studies were performed using alpha-amylase and/or lysozyme at concentrations similar to those found in human serum, at 37 degrees C for up to 90 days. Scanning electron micrographs showed that enzymatic degradation caused a porous structure to be formed, indicating the potential of this methodology to obtain in situ forming scaffolds. In order to evaluate the biocompatibility of the scaffolds, extracts and direct contact tests were performed. Results with the MTT test showed that the extracts of the materials were clearly non-toxic to L929 fibroblast cells. Analysis of cell adhesion and morphology of seeded osteoblastic-like cells in direct contact tests showed that at day 7 the number of cells on CS80-20 and CS60-40 was noticeably higher than that on C100, which suggests that starch containing materials may promote cell adhesion and proliferation. This combination of properties seems to be a very promising approach to obtain scaffolds with gradual in vivo pore forming capability for bone tissue engineering applications.

In vitro and in vivo degradation behavior of acetylated chitosan porous beads

Chitosans with different degree of acetylation (DA, 10-50%) were synthesized by the acetylation reaction of deacetylated chitosan and acetic anhydride with different ratios. The porous beads (approx. 500 mum) fabricated from the acetylated chitosans were used to investigate the degradation behaviors of chitosans with different DA in vitro and in vivo. The in vitro degradation behavior of the acetylated chitosan beads was investigated in solutions of lysozyme and/or N-acetyl-beta-D-glucosaminidase (NAGase), which are enzymes for chitosan present in the human body. It was observed that the degradation rate of acetylated chitosans can be controlled by adjusting the DA value: the degradation increased with increasing DA value of the acetylated chitosans. It seemed that NAGase plays an important role for the full degradation of chitosans in the body, even though NAGase itself can not initiate the degradation of chitosans. The in vitro degradation behavior of the chitosans in the mixture solution of lysozyme and NAGase was more similar to the in vivo degradation behavior than in the single lysozyme or NAGase solution. It may be owing to the sequential degradation reaction of chitosans in the mixture solution of lysozyme and NAGase (initial degradation by lysozyme to low-molecular-weight species or oligomers and the following degradation by NAGase to monomer forms). The in vivo degradation rate of acetylated chitosan beads was faster than the in vitro degradation rate. The acetylated chitosan porous beads with different DA value (and thus different degradation time) can be widely applicable as cell carriers for tissue-engineering applications.

Porous-conductive chitosan scaffolds for tissue engineering II. in vitro and in vivo degradation

Porous-conductive chitosan scaffolds were fabricated by blending conductive polypyrrole (PPy) particles with chitosan solution and employing an improved phase separation method. In vitro and in vivo degradation behaviors of these scaffolds were investigated. In the case of in vitro degradation, an enzymatic degradation system was employed and lysozyme was used as a working enzyme. Meanwhile, the degradation products of scaffolds, glucosamine and N-acetyl-glucosamine, were also analyzed with a HPLC method. In vivo degradation of scaffolds was performed by subcutaneously implanting these scaffolds in rat for pre-scheduled time intervals. In the both cases, the weight-loss of scaffolds was monitored during the whole degradation process for evaluating the degradation of scaffolds. The changes in conductivity of scaffolds afterin vitro or in vivo degradation were also measured using a four-point technique. It was observed that the pore parameters of scaffolds themselves could significantly influence the degradation behaviors of scaffolds but the PPy content in the scaffolds seemed not to impart its effect to the degradation of scaffolds. Degradation dynamics of scaffolds and conductivity measurements indicated that these scaffolds shown fairly different behaviors in their in vitro and in vivo degradation process. According to the results obtained from in vitro and in vivo degradation of scaffolds and based on some requirements of practical tissue engineering application, it was suggested that the PPy content in the scaffold should be slightly higher than 3 wt.% but lower than 6 wt.%.

Biodegradable plastics from renewable sources

Plastic waste disposal is a huge ecotechnological problem and one of the approaches to solving this problem is the development of biodegradable plastics. This review summarizes data on their use, biodegradability, commercial reliability and production from renewable resources. Some commercially successful biodegradable plastics are based on chemical synthesis (i.e. polyglycolic acid, polylactic acid, polycaprolactone, and polyvinyl alcohol). Others are products of microbial fermentations (i.e. polyesters and neutral polysaccharides) or are prepared from chemically modified natural products (e.g., starch, cellulose, chitin or soy protein).