Biodegradable poly(lactic acid)/chitosan-modified montmorillonite nanocomposites: Preparation and characterization

Poly(vinyl chloride) film filled with microcrystalline cellulose prepared from cotton fabric waste: properties and biodegradability study

Hydrolysis of cotton fabric waste to produce microcrystalline cellulose (MCC) was carried out using 2.5 N hydrochloric acid at 100 degrees C for 30 min. Characterization of the structure, morphology, particle size as well as the thermal decomposition of the obtained MCC were studied using X-ray diffractometer, scanning electron microscope and laser light scattering particle size analyzer and thermogravimetric analyzer, respectively. These results indicated that the obtained MCC had a fibrous structure of a 40 microm average particle size and possessed a form of highly native crystalline cellulose I. In addition, its maximum degradation temperature was observed at 350 degrees C. The poly(vinyl chloride) (PVC) films in this work were produced by first blending the produced MCC with PVC resin in amounts of 5-30 parts per hundred of resin. The blends were then made into film using a two-roll mill. The tensile properties of the film were measured using a Universal Testing Machine. The biodegradation tests were carried out in soil and in a moisture-controlled chamber. The biodegradability was estimated by the loss of mass, moisture absorption capacity and electron microscope studies. It was found that the tensile strength and Young's modulus of the blends increased with increasing amounts of MCC. Similarly, moisture absorption and biodegradability of the films were also increased as the amount of MCC increased. The results implied that MCC behaved not only as a reinforcing filler but also as a biodegradability promoter of PVC films.

Preparation, Cytotoxicity and Degradability of Chitosan-Based Thermosensitive Hydrogels as Drug Delivery System

A new thermosensitive hydrogel had been prepared that could be transformed into gel at 37 °C from chitosan and a mixture of α- and β-glycerophosphate (αβ-GP). The appearance of hydrogel was compact and corrugated. There was little granule in the appearance of gel loaded with adriamycin and the granules might be crystals of the added model drug. In vitro cytotoxicity of the hydrogel was tested by the MTT method using mouse embryonic fibroblasts (MEF). MEF cultured with leachates of CS-αβ-GP were investigated and the relative growth rate (RGR) was calculated and the cytotoxicity was graded by generally accepted standard. The study of in vitro degradation of CS-αβ-GP hydrogels included hydrolysis and degradation by lysozyme. The CS-αβ-GP thermosensitive hydrogel was degradable in vitro and the degradation rate was faster in lysozyme solution than that in the medium of PBS. So the CS-αβ-GP system had good cell biocompatibility and biodegradability which provided possibilities and foundations for the further research.

Preparation, characterization, and antimicrobial activity of quaternized chitosan/organic montmorillonite nanocomposites

Quaternized chitosan/layered silicate nanocomposite was prepared by simple solution-mixing in aqueous media. Montmorillonite (MMT) modified with cetyltrimethyl ammonium bromide was used as an organically modified layered silicate. XRD and TEM analyses respectively confirmed that silicate layers of MMT were intercalated and nicely distributed in quaternized chitosan matrix in despite of the high content of MMT (25-50 wt %). The interactions between the quaternized chitosan macromolecules and MMT in aqueous media were analyzed using FTIR, XRD, and zeta-potential measurements. Antimicrobial studies showed that the nanocomposites could strongly inhibit the growth of a wide variety of microorganisms, including Gram-positive bacteria, Gram-negative bacteria, and fungi; more importantly, they exhibited good antimicrobial capacity in whichever medium, in weak acid, water, or weak base. As the amount of MMT increased, the nanocomposites had better inhibitory effect on microorganisms, especially Gram-positive bacteria. The lowest minimum inhibition concentration (MIC) value of the nanocomposites against Staphylococcus aureus and Bacillus subtilis were less than 0.00313% (w/v) under all the conditions. The adsorption action of MMT on bacteria was simply discussed via SEM images. The results revealed that the strong antimicrobial of the nanocomposites may be attributed to the fine dispersion and the interaction between quaternized chitosan and MMT.