Polímeros impressos molecularmente como sistemas para liberação transdérmica de nicotina

Abstract

Polymers have been investigated in pharmaceutical technology as safe and efficient drug delivery systems (DDS). Molecular imprinted polymers (MIPs) are well established tool in analytical field; however, the feasibility of these materials has been discussed as DDS. Drug-polymer interactions can be established when these materials are incorporated in pharmaceutical dosages and, consequently, can be expected the modification of drug release profile. The aim of this work was to evaluate nicotine imprinted polymers and its application in transdermal drug delivery. Nicotine imprinted polymers were synthesized using methylene chloride as porogenic solvent, methacrylic acid as functional monomer and ethylenoglycol dymethacrylate as cross-linker. Free radical polymerization reaction was initiated using 2,2- azobisisobutyronitryle (initiator) and heating at 60°C. Non-imprinted polymers (NIPs) were synthesized in the same way without nicotine. The polymeric material was grounded in a mortar and washed with a mixture of methanol: acetic acid (4:1) to remove nicotine. Polymer particles were passed through appropriate meshes and fractions of 75-106 μm were separated for formulations preparation and characterization tests. Transdermal formulations were prepared by mixing polymer particles (MIPs and NIPs) with nicotine dispersions in mineral oil (nonpolar vehicle) or in propylene glycol (polar vehicle) in order to investigate the molecular recognition properties in different media. In vitro release and skin permeation studies were performed in vertical diffusion cell. Release studies were carried out using dialysis membrane and permeation studies were carried out with excised porcine ear skin. Receptor phase was isotonic phosphate buffer (pH 7.4) and the quantification was performed by high performance liquid chromatography. Additional studies using infrared spectroscopy (IR), thermogravimetry (TG) and differential scanning calorimetry (DSC) were performed to characterize interactions between drug and polymer particles. According IR, TG and DSC studies, nicotine can be physically adsorbed in polymer particles, suggesting a potential application as DDS. Nicotine release rate in MIPs formulations including nonpolar vehicle was slower than that observed when polar vehicle was employed in the formulations. The drug-polymer interactions can be larger in media with similar polarity to the porogenic solvent. This fact is due to MIPs molecular recognition mechanism. The polymer particle concentration was investigated in the MIPs formulations including nonpolar vehicle. It was demonstrated that the increase of polymer concentration reduces nicotine release rate in the formulations. Permeation profiles were studied for 48 h indicating that significant amounts of nicotine can cross the skin structure according Higuchi kinetic model. Important advantages were demonstrated using MIPs for nicotine transdermal delivery. The release rate using MIPs in transdermal formulations was slower than that using NIPs. Moreover, the standard relative deviations observed in MIPs formulations were lower than that observed in NIPs formulations. In this work it was possible to demonstrate that MIPs can offer controlled release matrices for nicotine transdermal delivery.