Release of Propolis phenolic acids and vanillin from cellulose-based hydrogels in vitro

Abstract

Introduction. Hydrogels are hydrophilic polymer networks which may absorb up to thousands of times their dry weight in water [1]. Cellulose-based hydrogels have a lot of suitable properties such as hydrophilicity, biocompatibility, transparency, low cost, non-toxicity and can be used as controllable delivery system [2]. The aim of the study: to investigate the propolis phenolic acids and vanillin release from cellulose-based hydrogels in vitro. Materials and methods. Four formulations of cellulose-based hydrogels with aqueous extract of propolis were developed. Each hydrogel was made with one type of cellulose: hydroxyethyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose and sodium carboxymethyl cellulose (medium viscosity). The pH value and the dynamic viscosity of developed hydrogels were estimated. In vitro release experiments were performed using the modified Franz type diffusion cells. The samples from the receptor solution were removed at 0.25, 0.5, 1, 2, 4 hour and 37°C temperature was maintained. All samples were analyzed by HPLC. Mean values and standard deviations of the results were calculated using Microsoft Office Excel 2007 software. Results. All developed formulations were homogenous, transparent, light yellow in colour. The dynamic viscosity of prepared hydrogels ranged from 2.34±0.01 to more than 11 Pa·s. The pH values were estimated from 4.70±0.01 to 6.00±0.02. Release data demonstrated that after 4 hours hydroxyethyl cellulose-based hydrogel showed the highest stream value of propolis phenolic acids and vanillin – 56.43±1.84 μg/cm2 . Sodium carboxymethyl cellulose-based hydrogel showed 48.81±3.09 μg/cm2 of phenolic acids and vanillin, hydroxypropylmethyl cellulose-based hydrogel – 44.59±6.94 μg/cm2 , methyl cellulose-based hydrogel – 39.27±2.72 μg/cm2 . Conclusions. All developed formulations were suitable appearance, the estimated pH values were close to the skin pH. The obtai