Design e Fabricação de Dispositivos Flexíveis Nanoestruturados para Detecção de Lactato em Saliva

Diagnostics with saliva for detecting specific biomarkers has drawn significant attention since extraction is simple, cost-effective, and precise. Saliva contains a similar variety of DNA, RNA, proteins, metabolites and microbiota as in blood, which can be compiled into a multiplex detection of biomarkers1 . In this study, we developed a nanostructured flexible device made with an interdigitated microelectrode array (IMA) of platinum/gold (Pt/Au) for detecting biomarkers. The array was fabricated with a photolithographic and lift-off process on transparent acetate sheets coated with a 5nm layer of chromium (Cr) and a 100 nm layer of platinum (Pt), onto which a layer of positive photoresist AZ4210 was spin-coated with rotation speed of 3000 rpm for 30 s. The structure was treated at 90 °C for 5 min, exposed to UV light for 40 s and immersed in a developing solution (K400) for 15 s. The interdigitated pattern was coated with 100 nm gold, whereas the excess photoresist and gold was removed by immersing the substrate in acetone (lift-off). A self-assembled monolayer (SAM) was immobilized by immersion of the flexible device in a solution containing 5 mM of 11-mercaptoundecanoic acid (11-MUA) during 20 h, followed by deposition of a layer of lactate oxidase with N-(3-Dimethylaminopropyl)-N′-ethylcarbodiimide and NHydroxysuccinimide (EDC/NHS). The electrochemical oxidation of the biomarkers was monitored in cyclic voltammetry in a phosphate-buffer solution (PBS) solution by measuring the increase in oxidation current (lactate) to the flexible surface. Optimized electrocatalytic activity was reached for the architecture Pt/Au-SAM/LOx, where synergy between Pt and Au allowed for detection of hydrogen peroxide (H2O2) at a low applied potential (0 V vs. Ag/AgCl). Detection was performed for H2O2 in the range between 0 and 6.0 pmol L–1 , with detection limit of 1.05 × 10−14 mol L−1 (0.01 pmol L−1) and an apparent Michaelis-Menten rate constant of 2.8 × 10-10 mol L−1. The methodology was applied to measure lactate in artificial saliva, including in the presence of interferents. The flexible device is promising for wearable devices and noninvasive detection.