Reaction of Silver Ions with Gelatin

A simple one-pot fabrication of silver loaded semi-interpenetrating polymer network (IPN) hydrogels with self-healing and bactericidal abilities

In the last decade, there has been a significant increase in the development of self-healing hydrogels. However, in most cases, the synthesized self-healing hydrogels possess no antibacterial properties. Further, the preparation of self-healing hydrogels usually requires sophisticated processes and also involves multiple steps. Herein, we proposed a simple one-pot synthesis of silver loaded semi-IPN hydrogels with self-healing and antibacterial properties. The hydrogels were prepared by physical cross-linking between polyacrylic acid (PAA) and ferric ions (Fe³⁺) and further modified by the interpenetration of gelatin-silver in the networks. In addition, the effect by varying the gelatin concentration was also studied. The mechanical properties of the as-prepared hydrogels reached 0.79 MPa in stress and 920% in strain with the self-healing efficiency of 87.5% (healed at 70 °C for 2 h). As displayed by the SEM images, the incorporated silver chloride nanoparticles (AgCl NPs) in gelatin-free hydrogels were agglomerated. Meanwhile, well-distributed AgCl NPs in the hydrogels were obtained in the presence of gelatin which acts as a stabilizer. Moreover, due to Fe³⁺ and AgCl NPs, the hydrogels were able to inhibit the growth of bacteria indicated by an inhibition zone (9–9.6 mm) which was examined toward Escherichia coli via the disk-diffusion method.

The semi-interpenetrating polymer network hydrogel possesses self-healing ability due to the dynamic ionic interactions between polyacrylic acid and Fe³⁺. The antibacterial properties are due to embedded silver chloride nanoparticles well-distributed in the hydrogel.