Tricalcium phosphate sheets with chitosan obtained via aqueous tape casting

Tricalcium phosphate (TCP) is a biomaterial produced in several biomedical applications, in addition to having biocompatibility and osteoconductive capacity. Biodegradable polymers of natural or synthetic origin such as chitosan and polyvinyl alcohol (PVA) have been used for tissue engineering applications because they have the properties of the native organic phase of bone tissue. Thus, the objective of this study was to obtain ceramic tapes based on TCP, chitosan, and PVA through the tape casting method. The viscosity data for all suspensions were ideal for the chosen processing. The thermogravimetric curves showed similar profiles, and it was possible to observe that a greater total mass loss occurred with the increase in the chitosan content. XRD reflections related to the β-TCP phase of the orthorhombic structure were found, showing no phase transformation. SEM analysis showed degrees of roughness on the film surfaces with little influence from the increase in chitosan content.

EFFECTS OF CHITOSAN COATING ON THE PHYSICAL, MECHANICAL AND ANTIMICROBIAL PROPERTIES OF FOOD PACKAGING PAPER

EFFECTS OF CHITOSAN COATING ON THE PHYSICAL, MECHANICAL AND ANTIMICROBIAL PROPERTIES OF FOOD PACKAGING PAPER. The coating process on food packaging paper is carried out to improve the food safety and health aspect from dangerous substance migration from food packaging into food. Chitosan has attracted interest in packaging, especially in food packaging as edible films and coatings. A paper from oil palm empty fruit bunches (OPEFB) pulp was coated with chitosan using different pulp weight (1, 1.5, 2 g) and chitosan content (0.25, 0.50, 0.75, 1 g) as parameters. The effect of chitosan as coating material on physical, mechanical, and antimicrobial properties was studied. The results showed that the density and grammage values of the paper increased after coating due to the increasing of chitosan content. The mechanical properties of the coated paper, such as tensile strength, tensile modulus and elongation, improved in line with the increase of chitosan content and pulp weight. The addition of chitosan on paper imparts antimicrobial properties against Gram-positive bacteria (Staphylococcus aureus) and Gram- negative bacteria (Escherichia coli).

Melanin deposition in two Cryptococcus species depends on cell-wall composition and flexibility

Cryptococcus neoformans and Cryptococcus gattii are two species complexes in the large fungal genus Cryptococcus and are responsible for potentially lethal disseminated infections. These two complexes share several phenotypic traits, such as production of the protective compound melanin. In C. neoformans, the pigment associates with key cellular constituents that are essential for melanin deposition within the cell wall. Consequently, melanization is modulated by changes in cell-wall composition or ultrastructure. However, whether similar factors influence melanization in C. gattii is unknown. Herein, we used transmission EM, biochemical assays, and solid-state NMR spectroscopy of representative isolates and “leaky melanin” mutant strains from each species complex to examine the compositional and structural factors governing cell-wall pigment deposition in C. neoformans and C. gattii. The principal findings were the following. 1) C. gattii R265 had an exceptionally high chitosan content compared with C. neoformans H99; a rich chitosan composition promoted homogeneous melanin distribution throughout the cell wall but did not increase the propensity of pigment deposition. 2) Strains from both species manifesting the leaky melanin phenotype had reduced chitosan content, which was compensated for by the production of lipids and other nonpolysaccharide constituents that depended on the species or mutation. 3) Changes in the relative rigidity of cell-wall chitin were associated with aberrant pigment retention, implicating cell-wall flexibility as an independent variable in cryptococcal melanin assembly. Overall, our results indicate that cell-wall composition and molecular architecture are critical factors for the anchoring and arrangement of melanin pigments in both C. neoformans and C. gattii species complexes.

Tuning the strength and swelling of an injectable polysaccharide hydrogel and the subsequent release of a broad spectrum bacteriocin, nisin A

Balance of glycol chitosan content and crosslink density modulates injectable gel swelling, strength and the release of an antimicrobial peptide.

Synthesis and performance evaluation of PES/chitosan membranes coated with polyamide for acid mine drainage treatment

In this article, performance evaluation of PES membrane infused with chitosan and coated with polyamide layer for treatment of acid mine drainage (AMD) is reported. PES/chitosan membranes were fabricated by varying chitosan concentration (0, 0.5, 0.75 and 1 wt%) using phase inversion method. PES/chitosan membranes were coated with polyamide (PA) via co-solvent assisted interfacial polymerization technique (CAIP). Scanning electron microscopy (SEM) and contact angle analysis show that chitosan and polyamide could enhance permeability without affecting rejection of the membrane. The permeability was improved with increasing chitosan content. Atomic absorption spectroscopy (AAS) was used to quantitatively determine cations in the permeate and the sulphate ions were analysed using ultraviolet and visible (UV-VIS) spectrophotometer. Pure water flux of PES/PA membrane was significantly improved from 56 to 93 l/m2.hr with 1 wt% chitosan addition. Cation rejection (90.4, 88.3, 89.3 and 75.7% for Mn2+,Fe2+, Mg2+ and Ca2+, respectively) was observed to be higher than anion rejection (56.33% for SO42−), when chitosan content was 0.75 wt%. These results indicate that the positively charged membranes under acidic condition had strong repulsive forces with the cations than attractions forces with anions. Polyethersulphone membrane modified with chitosan and coated with polyamide layer displayed potential for application in treatment of AMD.

Synthesis of Self-Healing Waterborne Polyurethane Systems Chain Extended with Chitosan

In this study, the self-healing properties of waterborne polyurethane (WPU) were implemented by chitosan as a chain extender of polyurethane prepolymers. The physical properties and self-healing efficiency of WPU were studied by changing the molar fractions of chitosan from 0.1 to 0.3. After thermal treatment for 24 h at 110 °C, the self-healing efficiency for the tensile strength of the highest chitosan content (WPU-C3) was found to be 47%. The surface scratch was also completely restored. The efficiency of the sample with the lowest chitosan content (WPU-C1) was found to be 35%, while that of the control sample without chitosan (WPU-C0) was 4%. The self-healing properties of the as-prepared films were attributed to the exchange reactions between the hydroxyl groups of chitosan and the urethane groups in the films at elevated temperature. It is inferred that self-healing WPU can be synthesized by chain extension with chitosan.