Uso de técnicas eletroquímicas para monitorar a liberação controlada de fármacos em membranas de acetato de celulose produzidas a partir de resíduos agroindustriais

Abstract

In the present study we evaluated the use of voltammetric techniques to monitor in real time the release of the drugs paracetamol and ciprofloxacin incorporated on cellulose triacetate membranes. The voltammetric method was based on the electrochemical oxidation of the drugs on disposable screen-printed electrodes (SPEs) and was compared with the spectrophotometric method in the UV region (243 and 272 nm for paracetamol and ciprofloxacin, respectively) and with the amperometic method (only in the case of ciprofloxacin release). Cellulose triacetate \"TAC\" was produced by the acetylation of cellulose corn straw, to obtain membranes used as matrices for controlled release of drugs. The following formulations were used for the production of symmetric and asymmetric membranes for subsequent evaluation of the release of drugs: TAC / dichloromethane / TAC drug and / dichloromethane / water / drug, respectively. The SPEs used in voltammetric measurements presented as working electrode a carbon ink modified with multiwalled carbon nanotubes, the auxiliary ink composed of carbon, and a reference silver ink. The release of drug from the TAC membranes was performed in phosphate buffer pH 7.4 at a temperature of 36 °C. The results showed release of paracetamol of 40% and 46% for symmetric and asymmetric membranes, respectively, with good agreement between voltammetric and UV spectrophotometric techniques. For the release of ciprofloxacin, the percentage values ranged from 30% to 44% and 40% to 67% for symmetric and asymmetric membranes, respectively. However, there was no correlation between the same techniques as seen in the release of paracetamol, even with the inclusion of a second comparative method (amperometry). Probably, the difference between the values of ciprofloxacin release monitored by different techniques was due to the lack of homogeneity in the drug incorporation in these membranes. In both studies there was a higher percentage of drug release in asymmetric membranes, as these presented a more porous structure, as confirmed by scanning electron microscopy, which allowed greater access of drugs to the release solution. The voltammetric technique presented advantages in relation to spectrophotometry such as in situ monitoring, high degree of automation, analysis in a short time, no dilutions required, easy to use, low cost of operation and high sensitivity, and therefore, presents potential in the evaluation of drug release from membranes used as matrices for controlled release of drugs.