Chitosan hydrogels enriched with bioactive phloroglucinol for controlled drug diffusion and potential wound healing.

We report a facile strategy to prepare chitosan (CS) hydrogels that eliminates the need for chemical crosslinking for advanced biomedical therapies. This approach gives controlled properties to the hydrogels by incorporating a natural bioactive phenolic compound, phloroglucinol (PG), into their microstructure. The adsorption of PG onto CS chains enhanced the hydrogels' antioxidant activity by up to 25 % and resulted in a denser, more entangled structure, reducing the pore size by 59 µm while maintaining porosity above 94 %. This allowed us to finely adjust pore size and swelling capacity. These structural properties make these hydrogels well-suited for wound healing dressings, promoting fibroblast proliferation and exhibiting excellent hemocompatibility. Furthermore, to ensure the versatility of these hydrogels, herein, we demonstrate their potential as drug delivery systems, particularly for dermal infections. The drug release can be controlled by a combination of drug diffusion through the swollen hydrogel and relaxation of the CS chains. In summary, our hydrogels leverage the synergistic effects of CS's antibacterial and antifungal properties with PG's antimicrobial and anti-inflammatory attributes, positioning them as promising candidates for biomedical and pharmaceutical applications, more specifically in advanced wound healing therapies with local drug delivery.

Influence of Chitosan and Grape Seed Extract on Thermal and Mechanical Properties of PLA Blends.

Blends based on polylactic acid (PLA), chitosan, and grape seed extract (GE) were prepared by extrusion and injection molding. The effect of chitosan (5% and 15% on PLA basis) and natural extract (1% on PLA basis) incorporated into the PLA host matrix was explored regarding the thermal and mechanical properties. GE showed antioxidant activity, as determined by the DPPH assay method. Chitosan and GE affect the degree of crystallinity up to 30% as the polysaccharide acts as a nucleating agent, while the extract reduces the mobility of PLA chains. The decomposition temperature was mainly affected by adding chitosan, with a reduction of up to 25 °C. The color of the blends was specially modified after the incorporation of both components, obtaining high values of b* and L* after the addition of chitosan, while GE switched to high values of a*. The elongation at break (EB) exhibited that the polysaccharide is mainly responsible for its reduction of around 50%. Slight differences were accessed in tensile strength and Young's modulus, which were not statistically significant. Blends showed increased irregularities in their surface appearance, as observed by SEM analysis, corresponding to the partial miscibility of both polymers.

Effects of Mangosteen Peel Phenolic Compounds on Tilapia Skin Collagen-Based Mineralized Scaffold Properties.

A proper valorization of biological waste sources for an effective conversion into composites for tissue engineering is discussed in this study. Hence, the collagen and the phenolic compound applied in this investigation were extracted from waste sources, respectively, fish industry rejects and the peels of the mangosteen fruit. Porous scaffolds were prepared by combining both components at different compositions and mineralized at different temperatures to evaluate the modifications in the biomimetic formation of apatite. The inclusion of mangosteen extract showed the advantage of increasing the collagen denaturation temperature, improving the stability of its triple helix. Moreover, the extract provided antioxidant activity due to its phenolic composition, as confirmed by 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) antioxidant assays. Mineralization was successfully achieved as indicated by thermogravimetry and scanning electron microscopy. A higher temperature and a lower extract concentration reduced the calcium phosphate deposits. The extract also affected the pore size, particularly at a lower concentration. The X-ray diffraction pattern identified a low degree of crystallization. A high mineralization temperature induced the formation of smaller crystallites ranging from 18.9 to 25.4 nm. Although the deposited hydroxyapatite showed low crystallinity, the scaffolds are suitable for bone tissue applications and may be effective in controlling the resorbability rate in tissue regeneration.

Influence of blend ratio and mangosteen extract in chitosan/collagen gels and scaffolds: Rheological and release studies.

This study proposes the incorporation of mangosteen peel extract in chitosan and collagen gels and scaffolds, at different ratios, for fabricating materials with potential wound dressing applications. The extract addition increases the thermal stability of the collagen while decreasing to about one-fifth the swelling capability of its scaffolds. Oppositely, it enables chitosan and its blends to withstand high swelling percentages. Release studies showed an extract delivery of 30%, indicating that the formulation does not affect this property. Additionally, the models of Weibull and the Korsmeyer-Peppas adequately fitted the release curves, in which the last one suggested a faster release regarding extract concentration. In contrast, rheology profiling demonstrated distinct behavior associated with the formulations. Even though all the samples exhibit a shear-thinning characteristic, changes in the blend ratio increased the extension of the Newtonian plateau range. The applied Cross mathematical model showed an increase in interactions between the components.

Mineralization of Phosphorylated Fish Skin Collagen/Mangosteen Scaffolds as Potential Materials for Bone Tissue Regeneration.

In this study, a potential hard tissue substitute was mimicked using collagen/mangosteen porous scaffolds. Collagen was extracted from Tilapia fish skin and mangosteen from the waste peel of the respective fruit. Sodium trimetaphosphate was used for the phosphorylation of these scaffolds to improve the nucleation sites for the mineralization process. Phosphate groups were incorporated in the collagen structure as confirmed by their attenuated total reflection Fourier transform infrared (ATR-FTIR) bands. The phosphorylation and mangosteen addition increased the thermal stability of the collagen triple helix structure, as demonstrated by differential scanning calorimetry (DSC) and thermogravimetry (TGA) characterizations. Mineralization was successfully achieved, and the presence of calcium phosphate was visualized by scanning electron microscopy (SEM). Nevertheless, the porous structure was maintained, which is an essential characteristic for the desired application. The deposited mineral was amorphous calcium phosphate, as confirmed by energy dispersive X-ray spectroscopy (EDX) results.

Rheological and antioxidant properties of chitosan/gelatin-based materials functionalized by pomegranate peel extract.

Biopolymer-based materials are potential candidates for food coatings application. In this study, pomegranate (Punica granatum L.) peel extract (PPE) at different concentrations was incorporated to chitosan/gelatin gels and the rheological, antioxidant and structural properties were evaluated. Due to its high phenolic content, PPE enhanced the antioxidant capacity of chitosan/gelatin mixtures. PPE addition extended linear viscoelastic range and enabled the samples to easily flow under the applied shear rate. Rheological properties indicated that both viscosity and activation energy of materials containing natural compounds are highly dependent on temperature. Scanning electron microscopy (SEM) images revealed the influence of PPE concentration in the scaffolds pores size. Findings of this study proved that PPE was capable to improve the functional characteristics of chitosan/gelatin-based materials enhancing the desired properties for their potential application as food coatings.

Influence of collagen addition on the thermal and morphological properties of chitosan/xanthan hydrogels.

This study investigates the collagen influence on thermal and morphological characteristics of chitosan/xanthan hydrogels for potential tissue engineering applications. Anionic collagen was prepared by selective hydrolysis of type I collagen found in bovine tendons. Chitosan was obtained from the partial deacetylation of squid pen ß-chitin and xanthan was acquired from Fluka. The hydrogels were obtained in different ratios and were characterized by thermal and morphological analysis. FT-IR suggested only electrostatic interactions between NH3(+) groups of chitosan and COO(-) groups of xanthan and collagen. Thermogravimetric curves showed that hydrogels contain a great amount of water (above 98%) and the presence of collagen does not change this characteristic. Freezing-bound water transition in DSC curves was shifted to higher values due to the increase of water/polymer interaction, mainly when different ratios of chitosan and xanthan were used. SEM images showed sheet-form structures with the presence of collagen promoting an increase in pore size.