Self-powered sensor for Hg2+ detection based on hollow-channel paper analytical devices

Abstract

In this work, a novel and effective self-powered device was introduced in a microfluidic paper-based analytical device (μ-PAD) with hollow channels to transport fluids for mercury ion (Hg²⁺) detection. In this device, a mediator-less and compartment-less glucose/O₂ biofuel cell (BFC) device served as the core component, using gold nanoparticle (AuNP) and platinum nanoparticle functionalized carbon nanotube (Pt/CNT) modified paper electrodes as the anodic and cathodic substrates, respectively. To construct the self-powered Hg²⁺ sensor, an Hg²⁺-specific oligonucleotide capture aptamer was first immobilized on an AuNP modified anode. In the presence of Hg²⁺, a AuNP@glucose dehydrogenase (GDH) labeled signal aptamer was hybridized with the immobilized capture probe through a thymine (T)–Hg²⁺–T interaction. Nicotinamide adenine dinucleotide (NAD⁺/NADH) was used as a cofactor in the proposed BFC device, and GDH in the anode could catalyze the oxidation of glucose used as fuel to generate gluconolactone, protons and electrons. Meanwhile the Pt/CNT in the cathode showed direct bioelectrocatalytic activity towards the oxygen reduction reaction (ORR). At the optimal conditions, this self-powered sensor could detect Hg²⁺ at the picomolar level, providing a simple approach to fabricate low-cost and portable powered devices on small-size paper for point-of-care testing. In addition, this self-powered sensor could be also used as a powerful tool for a wide range of potential applications in biotechnology and medicine.