Poly(Vinyl Alcohol) Cryogel Membranes Loaded with Resveratrol as Potential Active Wound Dressings

Abstract

Hydrogel wound dressings are highly effective in the therapy of wounds. Yet, most of them do not contain any active ingredient that could accelerate healing. The aim of this study was to prepare hydrophilic active dressings loaded with an anti-inflammatory compound - trans-resveratrol (RSV) of hydrophobic properties. A special attention was paid to select such a technological strategy that could both reduce the risk of irritation at the application site and ensure the homogeneity of the final hydrogel. RSV dissolved in Labrasol was combined with an aqueous sol of poly(vinyl) alcohol (PVA), containing propylene glycol (PG) as a plasticizer. This sol was transformed into a gel under six consecutive cycles of freezing (-80 °C) and thawing (RT). White, uniform and elastic membranes were successfully produced. Their critical features, namely microstructure, mechanical properties, water uptake and RSV release were studied using SEM, DSC, MRI, texture analyser and Franz-diffusion cells. The cryogels made of 8 % of PVA showed optimal tensile strength (0.22 MPa) and elasticity (0.082 MPa). The application of MRI enabled to elucidate mass transport related phenomena in this complex system at the molecular (detection of PG, confinement effects related to pore size) as well as at the macro level (swelling). The controlled release of RSV from membranes was observed for 48 h with mean dissolution time of 18 h and dissolution efficiency of 35 %. All in all, these cryogels could be considered as a promising new active wound dressings.

Keywords: cryogels; polyvinyl alcohol; resveratrol; wound dressings; wound healing.

Fig. 1

Images of cryogel membranes (M) captured using an optical microscope. First row shows placebo cryogels. Second row shows cryogels loaded with trans-resveratrol (RSV). Numbers correspond to percentage of PVA. L—Labrasol

Fig. 2

SEM pictures of freeze-dried cryogel membranes (M). First row shows placebo xerogels. Second row shows xerogels loaded with trans-resveratrol (RSV). Numbers correspond to percentage of PVA. L—Labrasol

Fig. 3

DSC curves recorded for RSV raw material (in black) and M8_L_RSV before freezing (in red), after freezing at −80°C for 24 h followed by 6 FT cycles (in green) in three temperature segments: a from −30 to 30°C, b from 50 to 70°C, and c from 100 to 300°C (10°C min⁻¹)

Fig. 4

Impact of matrix composition on mechanical properties of cryogel membranes determined using a texture analyzer: a tensile strength; b Young modulus

Fig. 5

Impact of matrix composition on water uptake capacity (%) of cryogel membranes (n = 6, ± SD)

Fig. 6

Selected MR images of cryogel membranes at various hydration times (TE = 10.5 ms)

Fig. 7

Swelling of cryogels: M8 (in green), M8_L (in red) and M8_L_RSV (in blue) on the basis of MRI data analysis

Fig. 8

Impact of PVA content on release of resveratrol (RSV) from cryogel membranes (n = 3, ± SD)