Influence of PVA Molecular Weight and Concentration on Electrospinnability of Birch Bark Extract-Loaded Nanofibrous Scaffolds Intended for Enhanced Wound Healing.

Francis Kamau Mwiiri,Rolf Daniels

doi:10.3390/molecules25204799

Abstract

Triterpenes from the outer bark of birch (TE) are known for various pharmacological effects including enhanced wound healing. Apart from an already authorized oleogel, electrospun nanofiber mats containing these triterpenes in a polyvinyl alcohol (PVA) matrix appear to be an advantageous application form. The effects of PVA molecular weight and concentration on the fiber morphology have been investigated. Three different molecular weights of PVA ranging from 67 to 186 kDa were used. The concentration of PVA was varied from 5 to 20 wt%. Polymer solutions were blended with colloidal dispersions of birch bark extract at a weight ratio of 60:40 (wt.%). The estimated viscosity of polymer solutions was directly linked to their concentration and molecular weight. In addition, both pure and blended solutions showed viscoelastic properties with a dominant viscous response in the bulk. Fiber morphology was confirmed using scanning electron microscopy (SEM). Both polymer concentration and molecular weight were found to be significant factors affecting the diameter of the fibers. Fiber diameter increased with a higher molecular weight and polymer concentration as more uniform fibers were obtained using PVA of higher molecular weight (146–186 kDa). In vitro drug release and ex vivo permeation studies indicated a faster drug release of betulin from electrospun scaffolds with lower PVA molecular weight. Our research suggests that the fabricated TE-loaded PVA electrospun dressings represent potential delivery systems of TE for wound care applications.

Highlights

Once the skin is damaged, very important skin functions such as physical protection and thermoregulation are lost which can result in either acute or chronic wounds
Affected further the properties of an active is added as a colloidal dispersion consisting of and sunflower oil compound which is added to the matrix forming polymer
The properties of solutions and blended dispersions as a colloidal dispersion consisting of triterpene dry extract (TE), Phospholipon 90H (PL90H) and sunflower oil (SO) dispersed were assessed and relatedthe to properties their abilityoftoPVA

Summary

Introduction

Once the skin is damaged, very important skin functions such as physical protection and thermoregulation are lost which can result in either acute or chronic wounds. Most of the wound dressings in the market have their basic functions to provide a protective barrier against bacterial contamination and absorb exudate [1]. Developing wound dressings for covering wounds but with loaded active ingredients to improve the wound healing process would be greatly beneficial. The pentacyclic triterpenes from outer birch bark extract are known for their pharmacological effects such as anti-inflammatory, antimicrobial, anti-viral, anti-cancer activity and wound healing effects [2,3,4,5,6,7,8,9]. A suitable triterpene dry extract (TE) from the outer bark of birch contains >80% (w/w) betulin as the main component and is obtained by accelerated solvent extraction with n-heptane [10].

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