Integrating multifunctionality such as adhesiveness, stretchability, and self-healing ability on a single hydrogel has been a challenge and is a highly desired development for various applications including electronic skin, wound dressings, and wearable devices. In this study, a novel hydrogel was synthesized by incorporating polydopamine-coated talc (PDA-talc) nanoflakes into a polyacrylamide (PAM) hydrogel inspired by the natural mussel adhesive mechanism. Dopamine molecules were intercalated into talc and oxidized, which enhanced the dispersion of talc and preserved catechol groups in the hydrogel. The resulting dopamine-talc-PAM (DTPAM) hydrogel showed a remarkable stretchability, with over 1000% extension and a recovery rate over 99%. It also displayed strong adhesiveness to various substrates, including human skin, and the adhesion strength surpassed that of commercial double-sided tape and glue sticks, even as the hydrogel dehydrated over time. Moreover, the DTPAM hydrogel could rapidly self-heal and regain its mechanical properties without needing any external stimuli. It showed excellent biocompatibility and improved cell affinity to human fibroblasts compared to the PAM hydrogel. When used as a strain sensor, the DTPAM hydrogel showed high sensitivity, with a gauge factor of 0.693 at 1000% strain, and was capable of monitoring various human motions such as the bending of a finger, knee, or elbow and taking a deep breath. Therefore, this hydrogel displays favorable attributes and is highly suitable for use in human-friendly biological devices.

Polylactic acid (PLA) and thermoplastic polyurethane (TPU) are two kinds of biocompatible and biodegradable polymers that can be used in biomedical applications. PLA has rigid mechanical properties while TPU possesses flexible mechanical properties. Blended TPU/PLA tissue engineering scaffolds at different ratios for tunable properties were fabricated via twin screw extrusion and microcellular injection molding techniques for the first time. Multiple test methods were used to characterize these materials. Fourier transform infrared spectroscopy (FTIR) confirmed the existence of the two components in the blends; differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) confirmed the immiscibility between the TPU and PLA. Scanning electron microscopy (SEM) images verified that, at the composition ratios studied, PLA was dispersed as spheres or islands inside the TPU matrix and that this phase morphology further influenced the scaffold’s microstructure and surface roughness. The blends exhibited a large range of mechanical properties that covered several human tissue requirements. 3T3 fibroblast cell culture showed that the scaffolds supported cell proliferation and migration properly. Most importantly, this study demonstrated the feasibility of mass producing biocompatible PLA/TPU scaffolds with tunable microstructures, surface roughnesses, and mechanical properties that have the potential to be used as artificial scaffolds in multiple tissue engineering applications.

This review summarized the recent progress in the synthesis, characterization, properties, photoluminescence mechanism and biological applications of carbon dots.

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