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a b s t r a c tThis work describes the freeze-drying technique preparation and characterization of porous scaffolds (sponges) of blends between chitosan and anionic collagen. Chitosan (CHI) was obtained from the partial deacetylation of squid pen chitin and the anionic collagen was prepared by alkaline hydrolysis of porcine serosa at different times (COL24, COL48, COL72 and COL96 h). Separate materials and sponges (1:1) were characterized by thermal analysis (DSC, TG/DTG), FT-IR and SEM. The time course of alkaline hydrolysis in a collagen structure has a remarked influence on sponge properties. In DSC curves, negative net charge increased in the collagen molecules reducing the denaturation temperature in the sponges, 58.4°C (CHI:-COL24) to 49.2°C (CHI:COL72). In TG/DTG curves the collagen presence influenced the thermal stability, whose tendency for degradation temperature reduced (155, 148.8°C at CHI:COL24 and CHI:COL96, respectively). Different mean pore sizes were observed for the sponges, where a great reduction of the pore size with alkaline hydrolysis time occurred, which varies from 88.5 ± 7.4 (CHI:COL24) to 59.1 ± 8.6 (CHI:COL96).

Nanomaterials have emerged as antimicrobial agents due to their unique physical and chemical properties. The development of nanoparticles (NPs) composed of natural biopolymers and biosurfactants have sparked interest, as they can be obtained without the use of complex chemical synthesis and toxic materials. In this study, we develop antimicrobial nanoparticles combining the biopolymer chitosan with the biosurfactant rhamnolipid. Addition of rhamnolipid reduced the size and polydispersity index of chitosan nanoparticles showing a more positive surface charge with improved stability, suggesting that chitosan-free amino groups are predominantly present on the surface of nanoparticles. Antimicrobial activity of chitosan/ rhamnolipid nanoparticles (C/RL-NPs) against Staphylococcus strains surpassed that of either single rhamnolipid or chitosan, both in planktonic bacteria and biofilms. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of C/RL-NPs were determined considering the concentration of each individual molecule in NPs. MIC values of 14/19 μg mL −1 and MBC of 29/37 μg mL −1 were observed for S. aureus DSM 1104 and MIC and MBC of 29/37 and 58/75 μg mL −1 were observed against S. aureus ATCC 29213, respectively. For S. epidermidis, MIC and MBC of 7/9 and 14/19 μg mL −1 were noticed. Chitosan and chitosan nanoparticles eliminate the bacteria present in the upper parts of biofilms, while C/RL-NPs were more effective, eradicating most sessile bacteria and reducing the number of viable cells below the detection limit, when NPs concentration of 58/75 μg mL −1 was applied for both S. aureus DSM 1104 and S. epidermidis biofilms. The improved antibacterial efficacy of C/RL-NPs was linked to the increased local delivery of chitosan and rhamnolipid at the cell surface and, consequently, to their targets in Gram-positive bacteria. The combination of chitosan and rhamnolipid offers a promising strategy to the design of novel nanoparticles with low cytotoxicity, which can be exploited in pharmaceutical and food industries.

This study compares a wound dressing based on bacterial cellulose/collagen (BC/COL) hydrogel in rat dorsum with commercial collagenase ointment and untreated wound. The hydrogel was characterized by Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA), Fourier transformed -Infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). According to the In vivo test and macroscopic evaluation, BC/COL hydrogel showed a better repair of wounds and promoted statistically significant differences of tissue repair between treatments on the 7th day after surgery. Better quality, quantity and orientation evaluation of collagen fibers (p=0.0001) were observed in the BC/COL hydrogel and collagenase ointment groups in relation to the control group. The BC/COL hydrogel promoted better wound healing than collagenase and the control group, therefore, it can be considered a potential wound dressing for skin regeneration.

Biomaterials are used as a promising alternative to bone grafts, including bioceramics whose composition resembles that of bone and fibrin sealants due to their hemostatic properties. The objective was to evaluate the repair of cranial defects in 40 rats, grafted with hydroxyapatite and a new fibrin sealant derived from snake venom. The animals were divided into four groups: C (control, no graft); Ha (hydroxyapatite); FS (fibrin sealant), and HaFS (hydroxyapatite and fibrin sealant). The animals were euthanized 2 and 6 weeks after surgery and wound area were submitted to analysis. After 2 weeks, immature bone was formed from the borders of the defect and in groups Ha and HaFS, few hydroxyapatite particles were surrounded by new bone. After 6 weeks, the new bone was mature and surrounded several hydroxyapatite particles, without connective tissue interposition and the volume of new bone was higher in HaFS group. The hydroxyapatite in combination with the new fibrin sealant accelerates bone repair.

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This work describes the preparation and characterization of anionic collagen composites with rhamsan and vinylidene fluoride-trifluorethylene with improved rheological and dielectric properties without loss of collagen secondary structure with an interaction occurring between both macromolecules of the composites. On a comparative basis, the force needed for the extrusion of anionic collagen:rhamsan composites was in the range from 0.088 to 0.080 J compared to that for collagen of 0.189 J. Anionic collagen:vinylidene fluoride-trifluorethylene composites were characterized, in the case of the 1:1 composite, by a pyroelectric coefficient of 1.89 x 10(-4) cm(-2) K(-1), which was significantly higher than those determined under the same conditions for native anionic collagen and vinylidene fluoride-trifluorethylene.

BIOMATERIAL APPLICATIONS. This work describes the selective hydrolysis of carboxyamide groups of asparagine and glutamine of collagen matrices for the preparation of negatively charged collagen biomaterials. The reaction was performed in the presence of chloride and sulfate salts of alkaline and alkaline earth metals in aqueous dimethylsulfoxide solution and, selectively hydrolysis of carboxyamide groups of collagen matrices was promoted without cleavage of the peptide bond. The result is a new collagen material with controlled increase in negative charge content. Although triple helix secondary structure of tropocollagen was preserved, significative changes in thermal stabilities were observed in association with a new pattern of tropocollagen macromolecular association, particularly in respect microfibril assembly, thus providing at physiological pH a new type of collagen structure for biomaterial preparation, characterized by different charge and structural contents .