Uma nova plataforma para imobilização de oligonucleotídeos baseado em eletrodos modificados com ácido 4-mercaptobenzóico

4-mercaptobenzoic acid (MBA) is a common structure to sensor development through surface-enhanced Raman spectroscopy due to its high RAMAN signal [1] but with no reports of polymer formation. In this work, electrochemical modification of MBA over a pencil carbon graphite electrode (PCGE) was carried out with the application to an oligonucleotide immobilization. After formation and characterization of the polymer over PCGE, the stability of the modified electrode was evaluated with stored time. After 30 days the polymer maintains its initial activity and, therefore, it can be used for sensor development. Oligonucleotide immobilization (a sequence containing 18 base pair of guanine) was performed through a chemical reaction between the carboxylic acid present in the polymer and the amino group in the oligonucleotide using EDC/NHS. The hybridization with the complementary and non-complementary target was performed followed by the the addition of methylene blue (MB) for indirect electrochemical detection through Differential Pulse Voltammetry (DPV) as it is electroactive and presents excellent interaction with free guanine bases [2]. There is a decrease in MB reduction current upon hybridization. This is attributed to lesser MB accumulation on the double-strand as the guanine bases are interacting with cytosine bases. Thus, linearity was determined and the calibration curve obtained through DPV was constructed. Working linear range for target detection was from 56.3 nmol L−1 to 225.2 nmol L−1 . The DPV results provided a good linear correlation coefficient (r2 =0.9915). The equation obtained from the linear regression was: I(μA) =−364.90+52.24×log[target](nmol L−1 ). The limit of detection (LOD =3σ/S) calculated was 1.17 nmol L−1 . The reproducibility was also evaluated. After a set of analyses (10 measurements), the standard deviation was 2.75%, proving the reproducibility of the system. The polymeric material formed on the low-cost pencil carbon graphite electrodes functionalized with carboxyl groups is quite promising for further studies involving the development of new non-conductive biosensor systems.