Maturation effects in fish gelatin and HPMC composite gels

Bioinspired Injectable Self-Healing Hydrogel Sealant with Fault-Tolerant and Repeated Thermo-Responsive Adhesion for Sutureless Post-Wound-Closure and Wound Healing

Hydrogels with multifunctionalities, including sufficient bonding strength, injectability and self-healing capacity, responsive-adhesive ability, fault-tolerant and repeated tissue adhesion, are urgently demanded for invasive wound closure and wound healing. Motivated by the adhesive mechanism of mussel and brown algae, bioinspired dynamic bonds cross-linked multifunctional hydrogel adhesive is designed based on sodium alginate (SA), gelatin (GT) and protocatechualdehyde, with ferric ions added, for sutureless post-wound-closure. The dynamic hydrogel cross-linked through Schiff base bond, catechol-Fe coordinate bond and the strong interaction between GT with temperature-dependent phase transition and SA, endows the resulting hydrogel with sufficient mechanical and adhesive strength for efficient wound closure, injectability and self-healing capacity, and repeated closure of reopened wounds. Moreover, the temperature-dependent adhesive properties endowed mispositioning hydrogel to be removed/repositioned, which is conducive for the fault-tolerant adhesion of the hydrogel adhesives during surgery. Besides, the hydrogels present good biocompatibility, near-infrared-assisted photothermal antibacterial activity, antioxidation and repeated thermo-responsive reversible adhesion and good hemostatic effect. The in vivo incision closure evaluation demonstrated their capability to promote the post-wound-closure and wound healing of the incisions, indicating that the developed reversible adhesive hydrogel dressing could serve as versatile tissue sealant.

Morphology and Rheology of a Cool-Gel (Protein) Blended with a Thermo-Gel (Hydroxypropyl Methylcellulose)

This study investigates the morphological and rheological properties of blended gelatin (GA; a cooling-induced gel (cool-gel)) and hydroxypropyl methylcellulose (HPMC; a heating-induced gel (thermo-gel)) systems using a fluorescence microscope, small angle X-ray scattering (SAXS), and a rheometer. The results clearly indicate that the two biopolymers are immiscible and have low compatibility. Moreover, the rheological behavior and morphology of the GA/HPMC blends significantly depend on the blending ratio and concentration. Higher polysaccharide contents decrease the gelling temperature and improve the gel viscoelasticity character of GA/HPMC blended gels. The SAXS results reveal that the correlation length (ξ) of the blended gels decreases from 5.16 to 1.89 nm as the HPMC concentration increases from 1 to 6%, which suggests that much denser networks are formed in blended gels with higher HPMC concentrations. Overall, the data reported herein indicate that the gel properties of gelatin can be enhanced by blending with a heating-induced gel.

Effect of Curdlan on the Rheological Properties of Hydroxypropyl Methylcellulose

This work focuses on the effect of curdlan (CL) on dynamic viscoelastic property, thermal reversible property, viscosity, and the fluid types of hydroxypropyl methylcellulose (HPMC) at different temperatures. Compared to the blends at 25 °C, the blends had a smaller linear viscoelastic region (LVR), a higher gel strength, and larger storage modulus (G') and loss modulus (G") values at 82 °C. G', G", gel strength, and viscosity increased with the increase of CL. Repeated temperature sweep led to increased G' and G" of HPMC/CL blends. For HC6 and HC8, the gel formation temperature of the repeated temperature sweep was significantly lower than that of the first sweep. The samples at 82 °C, except for the sample with 8% CL, were all yield-shear thinning fluids, and the samples at 40 °C were shear thinning fluids. The creation of HPMC/CL and its rheological research might provide some methodological references for the study of other thermal-thermal gel blends.

Thermal gelation of aqueous hydroxypropylmethylcellulose solutions with SDS and hydrophobic drug particles

The thermal gelation of hydroxypropylmethylcellulose (HPMC) solutions has been studied as a function of sodium dodecyl sulfate (SDS) concentration with and without griseofulvin, a model particulate BCS Class II drug by rheological measurements of gelation temperature (Tgel), steady-state viscosity (η) at 25 °C, and ζ-potential. Polymer adsorption on the drug was demonstrated by a decrease in η and potential in the absence of SDS. Griseofulvin had a synergistic effect on gelation which was attributed to an effective spanning of associated hydrophobic polymeric regions through interactions with the adsorbed polymer. Adding SDS offsets this effect on Tgel shielding hydrophobic interactions. Higher SDS concentrations had no effect on the particles surface as evidenced by constant ζ-potential and Tgel. Yet, polymeric chains are saturated and larger surfactant aggregates account for the increase in viscosity. Understanding the gelation mechanism and complex interactions of HPMC with surfactants and drugs is necessary for the design of pharmaceutical products and optimization of their performance properties.