In recent years, biodegradable polymeric systems have gained importance for design of surgical devices, artificial organs, drug delivery systems with different routes of administration, carriers of immobilized enzymes and cells, biosensors, ocular inserts, and materials for orthopedic applications. Polysaccharide-based polymers represent a major class of biomaterials, which includes agarose, alginate, dextran, and chitosan. Chitosan has found many biomedical applications, including tissue engineering, owing to its biocompatibility, low toxicity, and degradation in the body, which has opened up avenues for modulating drug release in vivo in the treatment of various diseases. These chitosan-based delivery systems range from microparticles to nanoparticles and from gels to films. In this study, chitosan (CH) and chitosan-polyethylene glycol (CH-PEG) microspheres with different compositions were prepared by oil/water emulsion method and crosslinked with gluteraldehyde. Some microspheres were loaded with a model chemotherapeutic drug, methotrexate (MTX). SEM, particle size and in vitro release analysis were performed. In vitro drug release studies showed that the release of MTX from CH-PEG microspheres was faster compared to CH microspheres. In the second part, CH-PEG microspheres were conjugated with a monoclonal antibody which is immunoglobulin G (IgG). The cytotoxicity efficiencies of entrapped drug were determined by using MCF-7 and MCF-7/MDA-MB breast cancer cell lines. In the third part, CHF-PEG films with the same compositions as in microspheres were prepared by solvent casting method. IR, DSC, mechanical and surface analysis were performed. The mechanical properties of films were improved by the presence of proper amount of PEG but higher amounts of PEG caused the deteriotion in the properties.

Three experiments were conducted to evaluate the effects of dietary chitin and chitosan on growth, immune responses and resistance of grass prawn Penaeus monodon against white spot syndrome virus (WSSV) and Vibrio infections. In the first experiment, two levels (0.5¡B1 g/100g diet) of chitin and three levels (0.5¡B1¡B5 g/100g diet) of chitosan were evaluated. The results show that weight gain of the shrimp fed on diet containing no chitosan or the lowest level of chitosan (0.5 %) was higher than other groups. In the second experiment, four levels of chitosan (0¡B0.5¡B1¡B5 g/100g diet) were tested. Weight gains of the control (0 %) and 0.5 % chitosan groups were significantly (P<0.05) higher than the 0.1 and 1 % chitosan groups. Shrimp survival rate was not influenced by chitosan inclusion. The test shrimp of the first experiment were evaluated for their immune responses after dietary exposures. The results show that phenoloxidase activity and superoxide dismutase were not significantly different (P>0.05) among treatments. The production of superoxide anion in the 0.5 % chitin group was significantly (P<0.05) lower than the other groups at day 3 and 12. The last experiment evaluated the effectiveness of dietary chitosan against infection of WSSV and Vibrio damsela. Shrimp were fed for 20 days on test diets containing four levels of chitosan (0¡B0.5¡B1¡B5 g/100g diet) and then challenged by injection of WSSV or Vibrio solution. In the WSSV challenge, except at day 7, shrimp survivals were not different among treatments. At day 7, however, the survival rates of the shrimp fed the diet containing 0.1 or 1 % chitosan were significantly (P<0.05) higher than those of the other groups. When challenged with Vibrio damsela, there was no difference in shrimp survival among dietary treatments. The present study shows that dietary chitin and chitosan do not significantly enhance immune responses and disease resistance of juvenile P. monodon. Dietary incorporation of chitin or chitosan negatively affects shrimp growth.

No description available.

Chitosan films are an excellent media for binding metal ions due to the electrostatic nature of the chitosan molecules. Addition of cross-linking or plasticizing agents alters texture of the films, but their effect on metal-binding capacity has not been fully characterized. The objective of this research was to determine effects of plasticizers and cross-linkers on physical and metal-binding properties of chitosan films and coatings prepared by casting and by spincoating. Chitosan films were prepared using 1% w/w chitosan in 1% acetic acid with or without (control) additives. Plasticizing agents were tetraethylene glycol (TEG) and glycerol while citric acid, ethylenediamine tetraacetic acid (EDTA), and tetraethylene glycol diacrylate (TEGDA) were used as cross-linkers. The additives were applied in concentrations of 0.10%, 0.25%, and 0.50% w/w of film-forming solution. The films were prepared by casting and by spincoating. Films were cast at ambient conditions for tests within one week (fresh films) and eight weeks (aged) after casting. The cast films were evaluated for thickness, residual moisture (by the Karl Fischer method), Cr(VI) binding capacity, puncture strength, and puncture deformation while the chitosan coatings were tested for thickness, Cr(VI) binding capacity, solubility in aqueous solution, and surface morphology (using atomic force microscopy). Cast films with cross-linkers showed an increase in resistance to puncture while plasticized films become more elastomeric. Control films bound 97.2% Cr(VI) ions from solution (0.56 mg Cr(VI)/g film), and addition of plasticizers did not affect chromium binding, tying up to 96.7% Cr(VI) ions from solution (0.56 mg Cr(VI)/g film). Films containing cross-linkers yielded binding capabilities ranging from 42.3% to 94.3% bound Cr(VI) ions (0.26-0.52 mg Cr(VI)/g film). Ultrathin coatings also possess the ability to bind Cr(VI) from solution, though only a maximum of 7.4% of Cr(VI) ions could be bound from solution, the thin films had the ability to bind up to 224 mg Cr(VI)/g ultrathin film. These coatings use less chitosan, but they display greater binding per mass. Overall, plasticizers do not alter, while cross-linkers may reduce, the binding capacity of chitosan films, but physical properties of the films can be controlled by inclusion of additives.

Thesis (M.S.)--Mississippi State University. Department of Agricultural and Biological Engineering. / Title from title screen. Includes bibliographical references.

Thesis (doctoral)--Christian-Albrechts-Universität zu Kiel, 2003.

The U.S. Environmental Protection Agency is in the process of developing a nationwide standard for turbidity in construction site runoff. It is widely expected that this standard cannot be met with conventional erosion and sediment control measures; consequently, innovative practices for managing sediment on construction sites must be developed. The objective of this research was to develop an understanding of how soil characteristics and polymer properties affect the amount of turbidity reduction that can be achieved through flocculation. The polymers used were PAMs, a proprietary product, and chitosan. The charge density of the PAMs ranged from 0% to 50% and the molecular weights ranged from 0.2 to 14 Mg/mol. A protocol for creating modified synthetic stormwater runoff for soil samples was developed and used on soils from seven construction sites. Particle size distributions were used to compare the modified synthetic stormwater runoff with grab samples of stormwater from one site and showed the synthetic runoff was representative of the actual runoff. Flocculation tests were performed on the synthetic runoffs with PAM and chitosan doses from 0.03 to 10 mg/L. The non-ionic PAM, proprietary product, and chitosan were found to be the most effective at reducing the turbidity of all the synthetic runoff below 200 NTU. The high molecular weight anionic PAMs were effective on only two of the seven synthetic runoff samples. Hardness tests were performed indicating interparticle bridging to be the bonding mechanism of the PAM. Electrophoretic mobility tests were performed on two of the soil suspensions and indicated the bonding mechanism of PAM to be interparticle bridging, and the bonding mechanism of chitosan to be a combination of charge neutralization and interparticle bridging. Tests showed as the charge density of the PAM increased, their effectiveness decreased. / text

In recent years, tissue engineering has shown great potential in treatment of injured tissues which aims to create artificial structures for cells to regenerate new tissues for replacing the damaged and diseased ones. The selection of scaffold materials is one of the critical factors affecting tissue healing process. Among a wide range of scaffold materials, chitosan (CS) has been demonstrated as an ideal material due to its biocompatibility, nontoxicity, biodegradability, antibacterial activity and favorable strength and stiffness. However, its insufficient mechanical properties limits its feasibility and scope for clinical application, especially for bone scaffolds. The main purpose of the study is to explore the potential of incorporation of nanofillers into CS to enhance the mechanical properties for tissue engineering. In this work, nanodiamond (ND) is applied and studied due to its high surface to volume ratio, rich surface chemistry, high mechanical strength, and excellent biocompatibility. ND/CS nanocomposites with different diamond concentration from 1wt. % to 5wt. % were synthetized through a solution casting method. The microstructure and mechanical properties of the composites were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Differential scanning calorimetry (DSC), and nanoindentation. Compared with pristine CS, the addition of ND resulted in a dramatic improvement of mechanical properties, including a 239%, 276%, 321%, 333%, and 343% increase in Young’s modulus and 68%, 96%, 114%, 118%, and 127% increase in hardness when ND amount is 1wt. %, 2wt. %, 3wt. %, 4wt. %, and 5wt. %, respectively. The strong interaction between ND surface groups and chitosan matrix is of great importance in changing polymer structure and improving mechanical properties. The cell viability and cytotoxicity of the nanocomposite were also studied using MTT (3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide) assay. The results show that the addition of ND has no negative effect on cell viability and the nanocomposites have no cytotoxicity.

Bacteria have been confirmed as the main etiological factor for root canal infection as well as for root canal treatment failure. Thus the success of endodontic treatment depends on the complete elimination of bacteria and prevention of bacterial recolonization in the root canal system. The major challenge for conventional root canal disinfection strategies is the ability of bacteria to persist as biofilms within the anatomical complexities of the root canal system. In addition, the alterations in the ultrastructure of dentin tissue results in compromised structural integrity of root dentin leading to higher risk of fracture in root-filled teeth. The objectives of this study are twofold: 1) develop and test functionalized nanoparticles to eliminate biofilm bacteria and, 2) to stabilize and strengthen the dentin organic matrix by crosslinking collagen fibrils in the presence of biopolymeric nanoparticles. A bioactive polymeric nanoparticle functionalized with a photosensitizer may present as a single step treatment to achieve both the objectives. Chitosan a bioactive polymer was used owing to their inherent antibacterial and biocompatible characteristics. Chitosan micro-/nanoparticles were synthesized as well as functionalized with photosensitizer (rose bengal) for photodynamic activation. Bioactive chitosan nanoparticle functionalized with a rose bengal is expected to combine the properties of chitosan i.e., polycationic with higher affinity to bacterial cell wall and alter membrane integrity; that of a photosensitizer i.e., to generate singlet oxygen when photoactivated; and the nano-form further potentiate these specific properties. These photodynamically activable chitosan nanoparticles showed the distinct characteristics of chitosan and rose bengal. The synergistic effect of the chitosan conjugated nanoparticles was able to eliminate monospecies and multi-species bacterial biofilms with complete disruption of the biofilm structure. The singlet oxygen generated during photoactivation produced photochemical crosslinking of dentin collagen and infiltration of chitosan nanoparticles. Following crosslinking the dentin collagen showed significantly improved mechanical properties (ultimate tensile strength and toughness) and improved resistance to degradation by bacterial collagenase. In conclusion, this study presents a potential photosensitizer functionalized chitosan nanoparticles based treatment strategy to improve the success of endodontic treatment to achieve complete disinfection of the root canal system and enhanced the mechanical/ structural integrity of the root-filled teeth.

Simple technologies are required for reducing the post harvest losses of horticultural produce. Edible films are being studied extensively for application on fresh and cut fruits and vegetables. Tomato, being a very nutritious and important food and a highly perishable climacteric fruit, this study was planned to investigate the application of chitosan films. Chitosan is a biodegradable waste product from sea food and is safe for consumption. With a view to broaden its antimicrobial activity it was combined with lysozyme, a lytic enzyme. Since the edible films are sensitive to changes in temperature and humidity, they were studied under ambient and optimal conditions of storage. / This study showed that 1% chitosan was more suitable for tomatoes for storage at both conditions of ambient and low temperature. Respiration study showed that 1% chitosan treatments resulted in more favorable levels of CO 2 production and internal O2. This was reflected in the quality of tomatoes held under these conditions. Two per cent chitosan films were unsuitable due to their high CO2 production and low internal O 2 levels. Spoilage was more apparent in this treatment. Lysozyme addition did not show any additional benefit. / The research in this study has demonstrated that the selection of edible films for horticultural produce needs to be integrated with the requirement of storage conditions of the produce.