# Release of natural extracts from PVA and PVA-CMC hydrogel wound dressings: a power law swelling/delivery

## TL;DR

This study explores how adding sage extract and dragon's blood to PVA hydrogels affects their properties and ability to release natural compounds for wound healing.

## Contribution

The paper introduces a power-law model to describe swelling and delivery kinetics of natural extracts in PVA-CMC hydrogels.

## Key findings

- PVA-CMC gels with 15% dragon's blood show optimal swelling and flavonoid delivery.
- Dragon's blood and sodium CMC reduce mechanical strength but increase swelling capacity.
- Sage extract shows low interaction with PVA-CMC matrix compared to dragon's blood.

## Abstract

PVA hydrogels present many characteristics of the ideal dressing, although without antimicrobial properties. The present work aims to study the physical, mechanical and release characteristics of hydrogel wound dressings loaded with either of two natural herbal products, sage extract and dragon's blood.

Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC) and tensile mechanical testing were used to investigate the structure and properties of the gels. Swelling and degradation tests were conducted according to ISO 10993-9. Release characteristics were studied using UV Spectrophotometry.

PVA matrices incorporating sage extract or dragon's blood (DB) present hydrogen bonding between these components. PVA-CMC hydrogels containing sage present similar spectra to PVA-CMC alone, probably indicating low miscibility or interaction between the matrix and sage. The opposite is found for DB, which exhibits more pronounced interference with crystallinity than sage. DB and NaCMC negatively affect Young's modulus and failure strength. All samples appear to reach equilibrium swelling degree (ESD) in 24 h. The addition of DB and sage to PVA increases the gels' swelling capacity, indicating that the substances likely separate PVA chains. The inclusion of CMC contributes to high media uptake. The kinetics profile of media uptake for 4 days is described by a power-law model, which is correlated to the drug delivery mechanism.

A PVA-CMC gel incorporating 15% DB, the highest amount tested, shows the most favorable characteristics for flavonoid delivery, as well as flexibility and swelling capacity.