A bi-functionalized molecularly imprinted silica (MIS) was prepared for solid phase extraction of quercetin. To ensure the specificity of molecular recognition, aluminum ions were inserted in the silica matrix to form Lewis and Brønsted acid sites and allow the interaction with quercetin, as well as with 3-aminopropyltriethoxysilane as a functional monomer. A sol–gel process was used to prepare MIS–Al with tetraethoxysilane as the crosslinker reagent. The efficiency of imprinted silica was evaluated by comparing the amount of quercetin adsorbed by MIS–Al with those by non-imprinted silica (NIS–Al) and control polymers without Al. The adsorption capacity and extraction efficiency were studied using different solvents and a mixture of ethanol–water (60 : 40, v/v) was found to be most effective for the binding of quercetin with MIS–Al while pure ethanol was most effective for extraction. The selectivity was evaluated by HPLC using a mixture of quercetin and rutin, a molecule which was considered to have an analogous structure. Characterization of the imprinted silica and adsorption capacity tests suggested that the MIS–Al had a higher adsorption capacity and reproducibility than MIS without Al (248.5 ± 3.5 against 159.7 ± 35.0), proving that the presence of aluminum ions improved the selectivity and efficiency for quercetin extraction. Herbal medicine samples of Ginkgo biloba L. capsules (40 and 80 mg) were analysed by passing the extract through an SPE–MIS–Al cartridge and the fractions collected were analysed by HPLC-PDA. The MIS–Al was shown to be selective and resulted in cleaner chromatograms with better resolution of the quercetin peak, proving this to be an effective clean-up step before chromatographic analysis. By the proposed method, it was found that 40 and 80 mg capsules contained 0.25 ± 0.01 mg and 0.24 ± 0.01 mg quercetin per capsule of Ginkgo biloba L., corresponding to 2.6% and 1.3% (w/w), respectively. These results are in agreement with scientific studies in the literature that reports a range of 0.5 to 4.7% mg of quercetin per capsule.

As interações biomoleculares (antígeno-anticorpo, enzima-substrato e fármaco-receptor) há muito tempo têm despertado o interesse de diversos pesquisadores quanto à sua natureza seletiva. Nesse contexto, principalmente a partir de 1940, observa-se uma crescente busca por materiais sintéticos dotados de sítios seletivos de reconhecimento. Hoje, esses materiais encontram-se bem estabelecidos em diversas áreas da ciência como farmácia, química analítica, bioquímica, dentre outras, e são rotineiramente intitulados como polímeros impressos molecularmente (molecularly imprinted polymers-MIP). Embora sua maior aplicação esteja voltada às técnicas de extração/separação, alguns trabalhos têm empregado os MIP como matrizes em sistemas de liberação controlada de fármacos (drug delivery system-DDS), devido ao caráter promissor de tal aplicação e pela facilidade de obtenção desses materiais. Entretanto, o emprego clínico de MIP como DDS ainda é inexistente em decorrência de sua recente aplicação e também pelos extensivos testes que precedem a aprovação de um novo sistema de liberação controlada de fármaco. O objetivo deste trabalho é apresentar os mais recentes avanços no emprego de MIP como DDS reforçando os aspectos mais significativos dessa aplicação, bem como classificando e detalhando esses sistemas quanto aos mecanismos pelos quais o fármaco é liberado. Biomolecular interactions (antigen-antibody, enzyme-substrate and drug-receptor) have been investigated due to their selective nature. Thus, since 1940, the search for synthetic materials presenting specific binding sites has been increasing. Nowadays, they are well established in different science areas such as pharmacy, analytical chemistry, biochemistry, among others, being the referred materials called molecularly imprinted polymers-MIP. Although the largest applications of MIP are found in the separations science field, few applications of these polymers have been reported as drug delivery systems-DDS. Such applications have been promising due to the feasibility of the MIP synthesis. However, the clinical use of the MIP as DDS is still not observed, probably due to its recent application, as well as extensive tests necessary for its approval as a new pharmaceutical form. In this way, this work aims to present the most recent progresses in the use of MIP as DDS, reinforcing the most significant aspects of this application (potentialities and limitations), as well as classifying and detailing such systems