Hydrogels dressings based on guar gum and chitosan: Inherent action against resistant bacteria and fast wound closure.

Hydrogels made with depolymerized guar gum, oxidized with theoretical oxidation degrees of 20, 35 and 50 %, were obtained via Schiff's base reaction with N-succinyl chitosan. The materials obtained were subjected to characterization by FT-IR, rheology, swelling, degradation, and morphology. Additionally, their gelation time categorized all three hydrogels as injectable. The materials' swelling degrees in Phosphate-Buffered Saline (PBS) were in the range of 26-35 g of fluid/g gel and their pore size distribution was heterogeneous, with pores varying from 67 to 93 µm. All hydrogels degraded in PBS solution, but maintained around 40 % of their initial mass after 28 days, which was more than enough time for wound healing. The biomaterials were also flexible, self-repairing, adhesive and cytocompatible and presented intrinsic actions, regardless of the presence of additives or antibiotics, against gram-positive (Staphylococcus aureus, Staphylococcus epidermidis) and gram-negative bacteria (Escherichia coli). However, the most pronounced bactericidal effect was against resistant Staphylococcus aureus - MRSA. In vivo assays, performed with 50 % oxidized gum gel, demonstrated that this material exerted anti-inflammatory effects, accelerating the healing process and restoring tissues by approximately 99 % within 14 days. In conclusion, these hydrogels have unique characteristics, making them excellent candidates for wound-healing dressings.

Synthesis and characterization of scaffolds produced under mild conditions based on oxidized cashew gums and carboxyethyl chitosan.

This study describes the development of scaffolds based on carboxyethyl chitosan (CEC) and different oxidized cashew gums (CGOx) for tissue engineering (TE) applications. After the physico-chemical characterizations of CEC and CGOx (oxidation degree of 20, 35 and 50%), these macromolecules were used for producing the CGOx-CEC hydrogels through a Schiff base reaction, in the absence of any crosslinking agent. The CGOx-CEC scaffolds obtained after a freeze-drying process were characterized for their morphology, mechanical properties, swelling ability, degradation, and porosity. Those revealed to be highly porous (25-65%), and showed a stable swelling behavior, as well as degradation properties in the absence of enzymes. The use of the cashew gum with higher degree of oxidation led to scaffolds with higher crosslinking densities and increased compressive modulus. None of the hydrogels show cytotoxicity during the 14 days of incubation. Considering all the properties mentioned, these scaffolds are excellent candidates for soft tissue regeneration, owing to the use of eco-friendly starting materials and the easy tuning of their properties.