Multiamine-induced self-healing poly (Acrylic Acid) hydrogels with shape memory behavior

Application of Shape Memory and Self-Healable Polymers/Composites in the Biomedical Field: A Review

Shape memory-assisted self-healing polymers have drawn attention over the past few years owing to their interdisciplinary and wide range of applications. Self-healing and shape memory are two approaches used to improve the applicability of polymers in the biomedical field. Combining both these approaches in a polymer composite opens new possibilities for its use in biomedical applications, such as the "close then heal" concept, which uses the shape memory capabilities of polymers to bring injured sections together to promote autonomous healing. This review focuses on using shape memory-assisted self-healing approaches along with their respective affecting factors for biomedical applications such as tissue engineering, drug delivery, biomaterial-inks, and 4D printed scaffolds, soft actuators, wearable electronics, etc. In addition, quantification of self-healing and shape memory efficiency is also discussed. The challenges and prospects of these polymers for biomedical applications have been summarized.

A pH controlled temperature response reprogramming hydrogel for monitoring human electrophysiological signals

This study proposes a simple method to prepare a pH-responsive and shape memory hydrogel based on cooperative hydrophobic interaction and hydrogen bonding. Acryloyl 11-aminoundecanoic acid (A11AUA) and acrylamide were selected as hydrophobic monomers and hydrophilic monomers, respectively. The mechanical properties of the prepared hydrogel strongly depend on the pH. Under acidic conditions, the maximum tensile strength of the hydrogel can reach 7.8 MPa, and the tensile modulus of the hydrogel can be increased by more than 10 000 times. The mechanical properties of acidic gels are affected by temperature and exhibit a temperature-controlled shape memory function. The acidic gel is immersed in NaOH and HCl solutions in sequence to achieve the function of reprogramming. Hydrogels under alkaline and neutral conditions exhibit conductivity and adhesion properties controlled by pH. Using the hydrogel as an adhesive electrode, the performance of the hydrogel in monitoring human electrophysiological signals was discussed.

Preparation and characterization of semi-IPNs of polycaprolactone/poly (acrylic acid)/cellulosic nanowhisker as artificial articular cartilage

Cartilage is a semi-solid resilient and smooth elastic connective tissue and upon damage, its repair is almost impossible or occurs with a very slow recovery process. Polycaprolactone (PCL), used as a biocompatible polymer, withholds all required mechanical properties, except suitable cell adhesion due to its hydrophobicity. In order to resolve this issue, we sought to introduce appropriate semi-IPNs into the system to regain its hydrophilicity base on increasing of the hydrophilic polymer. PCL and Cellulose nanowhiskers (CNWs) were entrapped in a network of poly (acrylic acid) that had been crosslinked via a novel acrylic-urethane crosslinker. The influential synthetic parameters on the preparation of artificial articular cartilages were investigated based on the Taguchi test design. The prepared CNW, acrylic-urethane crosslinker and semi-IPNs were studied via ¹H NMR, FTIR, SEM, TEM, TGA, water swelling, water contact angle, tensile, and MTT analyses. According to the results, the optimal amount of monomer was about 46%. Incorporation of an optimized amount of CNW, which was 0.5%, improved the mechanical properties of artificial cartilage. After a 30 h time period, semi-IPNs showed the water absorption of about 30%. MTT on days 1, 3 and 5, as well as cell attachment, confirmed the biocompatibility of the semi-IPNs.