# Peptide-reinforced, photocrosslinkable PEG-based hydrogels

## TL;DR

This paper introduces a new method to strengthen PEG-based hydrogels by adding peptide blocks, improving their mechanical properties while keeping their swelling ability.

## Contribution

A bio-inspired approach using PBLA blocks to reinforce PEG hydrogels, enhancing their strength and toughness.

## Key findings

- PEG-based hydrogels reinforced with PBLA blocks show improved mechanical strength and toughness.
- The co-networks retain the swelling ability of PEG hydrogels while being photocrosslinkable.
- This method offers a promising avenue for practical applications in biomaterials and drug delivery.

## Abstract

Hydrogels are polymer networks that swell in aqueous solvents. These materials have applications in many fields, including drug delivery, tissue engineering, and soft robotics. For example, polyethylene glycol (PEG) diacrylate is often used as a light-curable crosslinker for the synthesis of PEG-based hydrogels, e.g., in bioinks for 3D printing. However, a common limitation of PEG hydrogels is their typically poor mechanical properties, particularly when in a swollen state. The mechanical strength of natural polymeric materials, such as spider silk and collagen, arises from the formation of hierarchical secondary protein structures that unfold under mechanical load. Here, we present a bio-inspired approach to reinforcing PEG-based hydrogels that mimics these hierarchical structures by incorporating poly(β-benzyl-l-aspartate) (PBLA) blocks between cross-linking end groups and PEG chain segments. We used this peptide-containing crosslinker in combination with a small hydrophilic comonomer, 2-hydroxyethyl acrylate, to synthesise PHEA-linked by-(PBLA-b-PEG-b-PBLA) co-networks with tailored compositions, yielding improved and tailorable mechanical properties. This approach affords hydrogels with increased strength and toughness while retaining the networks’ swelling ability. This research presents a promising avenue for developing robust photocrosslinkable hydrogels with broad practical applications.

Peptide blocks close to the crosslinking points mechanically reinforce photocurable PEG-based hydrogels. These polymer conetworks could be applied as biomaterials or for controlled drug delivery systems.