Partículas de polímeros de impressão molecular como sistemas para liberação controlada de fármacos

Abstract

Molecularly imprinted polymers (MIPs) are synthetic polymers that have the property to establish selective interactions with a compound called template e.g. a drug. The template is added in the synthesis step. After the synthesis, the template is removed. However, the property to establish selective interactions remain among MIPs and template. MIPs have been applied in the analytical field due to their selective interactions. The application of these materials as sustained release drug delivery systems has also been evaluated. Sustained release drug delivery systems may offer advantages, avoiding the high plasmatic peak concentrations of drugs related to their side effects. These drug delivery systems may also contribute to develop better clinical strategies to administration of drugs in the clinical practice. In this study, we select basic compounds with tertiary amine moieties to propose sustained release drug delivery systems based on MIPs. The selected drugs were nicotine (hydrophilic drug administered as an aid to smoking cessation therapy) and donepezil (lipophilic drug administered in the treatment of the Alzheimer’s disease). Polymer particles of MIPs were synthetized by precipitation polymerization and characterized by different techniques as infrared spectroscopy, scanning electron microscopy, and atomic force microscopy. Adsorption isotherms studies indicated the heterogeneity of the binding sites with the better adjust to Langmuir-Freundlich model. The formulations were designed to administration by different pathways (transdermal or oral), and they were prepared from the dispersion of polymer particles in an oil vehicle as oleic acid and mineral oil. The drug was previously incorporated in the oil vehicle. Nicotine was administered by transdermal formulations based on MIPs using mineral oil as vehicle, and the results indicated that drug release was controlled according to Higuchi kinetic model, characterising the drug diffusion from the polymer matrix. Permeation studies were carried out using porcine ear skin, and the results demonstrated that the permeation of nicotine was prolonged up to 48 h according to zero order kinetic. The nicotine transdermal formulations based on MIPs showed a better effect in the control of drug permeation across the skin in relationship to the non-imprinted ones (NIPs) only when the amount of nicotine in the formulations was increased, with a drug/polymer ratio of 1:3. The donepezil release from the formulations based on MIPs using oleic acid as vehicle was better adjusted to Higuchi kinetic model, and the release rate of MIPs was smaller than NIPs, independent of the drug/polymer ratio. In this way, novel sustained release drug delivery systems based on MIPs were successfully developed and characterised for drug administration by different pathways.