Synergistic Effect of Thermoresponsive and Photocuring Methacrylated Chitosan-Based Hybrid Hydrogels for Medical Applications.

The thermoresponsive drug-loaded hydrogels have attracted widespread interest in the field of medical applications due to their ease of delivery to structurally complex tissue defects. However, drug-resistant infections remain a challenge, which has prompted the development of new non-antibiotic hydrogels. To this end, we prepared chitosan-methacrylate (CTSMA)/gelatin (GEL) thermoresponsive hydrogels and added natural phenolic compounds, including tannic acid, gallic acid, and pyrogallol, to improve the efficacy of hydrogels. This hybrid hydrogel imparted initial crosslinking at physiological temperature, followed by photocuring to further provide a mechanically robust structure. Rheological analysis, tensile strength, antibacterial activity against E. coli, S. aureus, P. gingivalis, and S. mutans, and L929 cytotoxicity were evaluated. The experimental results showed that the hybrid hydrogel with CTSMA/GEL ratio of 5/1 and tannic acid additive had a promising gelation temperature of about 37 °C. The presence of phenolic compounds not only significantly (p < 0.05) enhanced cell viability, but also increased the tensile strength of CTSMA/GEL hybrid hydrogels. Moreover, the hydrogel containing tannic acid revealed potent antibacterial efficacy against four microorganisms. It was concluded that the hybrid hydrogel containing tannic acid could be a potential composite material for medical applications.

Role of Organically-Modified Zn-Ti Layered Double Hydroxides in Poly(Butylene Succinate-Co-Adipate) Composites: Enhanced Material Properties and Photodegradation Protection.

In this research, the effects of Zn-Ti layered double hydroxide (Zn-Ti LDH) as a UV-protection additive, which was added to the poly(butylene succinate-co-adipate) (PBSA) matrix, were investigated. Stearic acid was used to increase the hydrophobicity of Zn-Ti LDH via ion-exchange method. Transmission electron microscopy images of PBSA composites showed that modified Zn-Ti LDH (m-LDH) well-dispersed in the polymer matrix. Due to the effect of heterogeneous nucleation, the crystallization temperature of the composite increased to 52.9 °C, and the accompanying crystallinity increased to 31.0% with the addition of 1 wt% m-LDH. The additional m-LDH into PBSA copolymer matrix significantly enhanced the storage modulus, as compared to pure PBSA. Gel permeation chromatography and Fourier transform infrared spectroscopy analysis confirmed that the addition of m-LDH can reduce the photodegradation of PBSA.

Enhanced Photodegradation Stability in Poly(butylene adipate-co-terephthalate) Composites Using Organically Modified Layered Zinc Phenylphosphonate.

The enhancement of the ultraviolet (UV) photodegradation resistance of biodegradable polymers can improve their application efficacy in a natural environment. In this study, the hexadecylamine modified layered zinc phenylphosphonate (m-PPZn) was used as a UV protection additive for poly(butylene adipate-co-terephthalate) (PBAT) via solution mixing. The results from the Fourier transform infrared spectroscopy (FTIR) and wide-angle X-ray diffraction analysis of the m-PPZn indicated the occurrence of hexadecylamine intercalation. FTIR and gel permeation chromatography were used to characterize the evolution of the PBAT/m-PPZn composites after being artificially irradiated via a light source. The various functional groups produced via photodegradation were analyzed to illustrate the enhanced UV protection ability of m-PPZn in the composite materials. From the appearance, the yellowness index of the PBAT/m-PPZn composite materials was significantly lower than that of the pure PBAT matrix due to photodegradation. These results were confirmed by the molecular weight reduction in PBAT with increasing m-PPZn content, possibly due to the UV photon energy reflection by the m-PPZn. This study presents a novel approach of improving the UV photodegradation of a biodegradable polymer using an organically modified layered zinc phenylphosphonate composite.

Synthesis, Physical Properties and Enzymatic Degradation of Biodegradable Nanocomposites Fabricated Using Poly(Butylene Carbonate-Co-Terephthalate) and Organically Modified Layered Zinc Phenylphosphonate.

A new biodegradable aliphatic-aromatic poly (butylene carbonate-co-terephthalate) (PBCT-85) with the molar ratio [BC]/[BT] = 85/15, successfully synthesized through transesterification and polycondensation processes, was identified using 1H-NMR spectra. Various weight ratios of PBCT/organically modified layered zinc phenylphosphonate (m-PPZn) nanocomposites were manufactured using the solution mixing process. Wide-angle X-ray diffraction and transmission electron microscopy were used to examine the morphology of PBCT-85/m-PPZn nanocomposites. Both results exhibited that the stacking layers of m-PPZn were intercalated into the PBCT-85 polymer matrix. The additional m-PPZn into PBCT-85 copolymer matrix significantly enhanced the storage modulus at -70 °C, as compared to that of neat PBCT-85. The lipase from Pseudomonas sp. was used to investigate the enzymatic degradation of PBCT-85/m-PPZn nanocomposites. The weight loss decreased as the loading of m-PPZn increased, indicating that the existence of m-PPZn inhibits the degradation of the PBCT-85 copolymers. This result might be attributed to the higher degree of contact angle for PBCT-85/m-PPZn nanocomposites. The PBCT-85/m-PPZn composites approved by MTT assay are appropriate for cell growth and might have potential in the application of biomedical materials.

Enzymatic Degradation of Acrylic Acid-Grafted Poly(butylene succinate-co-terephthalate) Nanocomposites Fabricated Using Heat Pressing and Freeze-Drying Techniques.

Biodegradable acrylic acid-grafted poly(butylene succinate-co-terephthalate) (g-PBST)/organically modified layered zinc phenylphosphonate (m-PPZn) nanocomposites were effectively fabricated containing covalent bonds between the g-PBST and m-PPZn. The results of wide-angle X-ray diffraction and transmission electron microscopy revealed that the morphology of the g-PBST/m-PPZn nanocomposites contained a mixture of partially exfoliated or intercalated conformations. The isothermal crystallization behavior of the nanocomposites showed that the half-time for crystallization of 5 wt % g-PBST/m-PPZn nanocomposites was less than 1 wt % g-PBST/m-PPZn nanocomposites. This finding reveals that increasing the loading of m-PPZn can increase the crystallization rate of nanocomposites. Degradation tests of g-PBST/m-PPZn nanocomposites fabricated using the heat pressing and the freeze-drying process were performed by lipase from Pseudomonas sp. The degradation rates of g-PBST-50/m-PPZn nanocomposites were significantly lower than those of g-PBST-70/m-PPZn nanocomposites. The g-PBST-50 degraded more slowly due to the higher quantity of aromatic group and increased stiffness of the polymer backbone. The degradation rate of the freeze-drying specimens contained a more extremely porous conformation compared to those fabricated using the heat pressing process.