# A Multifunctional Double-Network Hydrogel Based on Bullfrog Skin Collagen: High-Value Utilization of Aquaculture By-Products

## TL;DR

This study creates a strong, self-healing hydrogel from bullfrog skin collagen, offering a way to turn aquaculture waste into valuable biomedical materials.

## Contribution

A novel double-network hydrogel is developed using bullfrog skin collagen with enhanced mechanical and antibacterial properties.

## Key findings

- The Gel–CO@Zn hydrogel showed strong tissue adhesion and rapid self-healing.
- It exhibited good antibacterial activity against Staphylococcus aureus and Escherichia coli.
- The hydrogel significantly reduced blood loss in a liver injury model in mice.

## Abstract

Bullfrog skin, as a by-product of bullfrog processing, is an ideal source of high-quality collagen due to its high protein content and low-fat characteristics. However, its comprehensive utilization is relatively low, and the discarded skins cause resource waste and environmental pollution. In this study, a citric acid extraction process for frog skin collagen was established through single-factor optimization. A multifunctional double-network hydrogel was developed by combining the prepared high-purity type I collagen with oxidized hyaluronic acid (OHA). Due to the network structure design of Schiff base bonds and Zn2+ coordination bonds, the mechanical strength of the hydrogel based on collagen and OHA compositing Zn2+ (Gel–CO@Zn) enhanced significantly. It was found that the Gel–CO@Zn hydrogel had strong tissue adhesion (16.58 kPa shear strength), rapid self-healing (<6 h), and low hemolysis (<5%). Furthermore, the Gel–CO@Zn hydrogel could reduce the survival rate of Staphylococcus aureus and Escherichia coli to 1.06% and 6.73%, respectively, showing good antibacterial properties. Through the treatment of Gel–CO@Zn, the clotting time was shortened from 433 s to 160 s and greatly reduced the blood loss (>60%) in the liver injury model of male Kunming mice. This research not only presents a novel approach for the high-value utilization of aquaculture by-products but also establishes a new paradigm for developing cost-effective, multifunctional biomedical materials, demonstrating the transformation of waste into high-value resources.