# Simultaneous Cross-Linking and Nanoparticle Anchoring by Dialdehyde Cellulose in Injectable Composite Chitosan/Polypyrrole Hydrogels

## TL;DR

A new injectable hydrogel combines chitosan and polypyrrole for wound healing, showing self-healing and anti-inflammatory properties.

## Contribution

First injectable hydrogel system using dynamic imine bonds and covalent PPy anchoring for self-healing and anti-inflammatory effects.

## Key findings

- Hydrogels showed shear-thinning behavior and rapid self-healing with moduli of 25–47 Pa.
- SCN_DAC_20_PPy reduced wound area to 39% after 10 hours compared to 83% in controls.
- PPy-containing hydrogels reduced IL-6 and nitric oxide in macrophages.

## Abstract

The injectable composite hydrogel with covalently bound
polypyrrole
(PPy) has been prepared using dialdehyde cellulose (DAC) as a bifunctional
cross-linker, forming dynamic imine bonds with water-soluble half
acetylated chitosan (SCN) and simultaneously tethering the PPy nanoparticles
by aldol condensation. The novelty lies in translating this dual chemistry
into an injectable, self-healing hydrogel system, for the first time
fully utilizing dynamic Schiff base cross-linking in combination with
covalent PPy anchoring. PPy is also involved both in hydrogel cross-linking,
altering its rheological behavior, but also providing antioxidative
and anti-inflammatory effects. The resulting hydrogels exhibited shear-thinning
behavior, rapid self-healing, and storage moduli ranging from 25 to
47 Pa, allowing for injection through 21 G needles. All formulations
were noncytotoxic toward NIH/3T3 fibroblasts and RAW 264.7 macrophages.
In scratch assays, SCN_DAC_20_PPy significantly accelerated wound
closure, with the residual wound area to 39 ± 2% after 10 h versus
83 ± 7% for controls and 65 ± 3% for the corresponding PPy-free
hydrogel. In LPS-stimulated macrophages, all hydrogels decreased nitric
oxide production, and PPy-containing hydrogels additionally reduced
IL-6 secretion. The SCN/DAC/PPy injectable hydrogels thus exhibit
cytocompatibility, self-healing properties, and anti-inflammatory
activity, representing a promising platform for the future development
of advanced wound dressings.