The sol-gel technique has drawn considerable attention in the area of biomolecules immobilization by virtue of its intrinsic properties including chemical inertness, thermal stability, and good biocompatibility. The present work reports the development of a bio-sensing methodology which involves the immobilization of horseradish peroxidase enzyme (HRP) on pencil graphite electrode (PGE) using TiO2 sol-gel and its application for 5-aminosalicylic acid (5-ASA) determination in pharmaceutical formulations. TiO2 sol-gel film was deposited on the PGE surface by dip coating, and the HRP enzyme was immobilized on the film by adsorption and cross-linked binding using glutaraldehyde. The analytical performance of the methodology was investigated through amperometric measurements at -0.08 V in the presence of 5-ASA (electron mediator) and hydrogen peroxide (substrate). The biosensor was successfully applied for 5-ASA determination, where limits of detection and quantification of 3.3 and 10.0 µmol L -1, respectively, were obtained. The application of the methodology for 5-ASA determination in pharmaceutical formulations led to satisfactory recovery rates ranging from 80 to 98%. The biosensor developed in this work is simple, inexpensive and has the potential to be applied for the determination of other pharmaceutical compounds, which also act as electron mediators in the catalytic cycle of HRP.

A detecção individual e em mistura equimolar dos nucleotídeos de DNA guanosina (GMP), adenosina (AMP), timidina (TMP) e citidina (CMP) 5'-monofosfato, utilizando a voltametria de onda quadrada, foi realizada sobre o eletrodo de diamante dopado com boro (DDB) prétratado catodicamente (Red-DDB) e anodicamente (Oxi-DDB). A oxidação dos nucleotídeos individuais de DNA foi mais sensível sobre o Oxi-DDB. Na detecção simultânea de nucleotídeos, as respostas de GMP, AMP, TMP e CMP foram muito adequadas sobre ambos os eletrodos tratados. Particularmente, picos mais sensíveis e mais separados para TMP e CMP sobre o Oxi-DDB e Red-DDB, respectivamente, foram observados após procedimento de deconvolução. A detecção dos nucleotídeos em soluções aquosas certamente contribuirá para avaliação genotóxica de substâncias e em reações de hibridização por meio da imobilização de ss ou ds-DNA sobre a superfície do DDB.

The individual detection and equimolar mixture of DNA nucleotides guanosine monophosphate (GMP), adenosine monophosphate (AMP), thymidine (TMP) and cytidine (CMP) 5'-monophosphate using square wave voltammetry was performed on boron doped diamond (BDD) electrodes cathodically (Red-DDB) and anodically (Oxi-DDB) pretreated. The oxidation of individual DNA nucleotides was more sensitive on Oxi-BDD electrode. In a simultaneous detection of nucleotides, the responses of GMP, AMP, TMP and CMP were very adequate on both treated electrodes. Particularly, more sensitive and separate peaks for TMP and CMP on Oxi-BDD and Red-BDD electrodes, respectively, were observed after deconvolution procedure. The detection of nucleotides in aqueous solutions will certainly contribute for genotoxic evaluation of substances and hybridization reactions by immobilizing ss or ds-DNA on BDD surface.