Boronate ester bond-based potentiometric aptasensor for screening carcinoembryonic antigen-glycoprotein using nanometer-sized CaCO3 with ion-selective electrode.

Phenylboronic acid-functionalized nanometer-sized CaCO3 particles (PBA-CaCO3) were designed to determine the carcinoembryonic antigen (CEA) glycoprotein with a portable Ca2+ ion-selective electrode (Ca-ISE) through a typical boronate ester bond. CaCO3 nanospheres were conjugated to 3-aminophenylboronic acid by amine-epoxy reaction, whereas target CEA was captured into the aptasensing interface by the immobilized thiolated aptamer on gold substrate. Upon PBA-CaCO3 introduction, 3-aminophenylboronic acid labeled to CaCO3 microsphere specifically recognized with CEA glycoprotein based on sugar-boronic acid interaction to form a sandwiched complex. The carried CaCO3 was dissolved under acidic conditions to release Ca2+ ion with a portable Ca-ISE readout. Thanks to the specific boronate ester bond between PBA and 1,2-diols, the synthesized PBA-CaCO3 exhibited good conjugation properties for CEA glycoprotein. Under optimum conditions, Ca-ISE-based aptasensing platform exhibited good electrode potential response for evaluation of target CEA, and allowed detection of CEA at a concentration as low as 7.3 pg mL-1. Importantly, Ca-ISE-based aptasensing system is readily extended to detect other disease-related glycoproteins by controlling the corresponding aptamer.

Biocompatible and flexible paper-based metal electrode for potentiometric wearable wireless biosensing.

A paper-based electrode is a very attractive component for a disposable, nontoxic, and flexible biosensor. In particular, wearable biosensors, which have recently been attracting interest, not only require these characteristics of paper-based electrodes but must also be able to detect various ions and biomolecules in biological fluids. In this paper, we demonstrate the detection ability of paper-based metal electrodes for wearable biosensors as part of a wireless potentiometric measurement system, focusing on the detection of pH and sodium ions. The paper-based metal electrodes were obtained by simply coating a silicone-rubber-coated paper sheet with a Au (/Cr) thin film by sputtering then modifying it with different functional membranes such as an oxide membrane (Ta2O5) and a fluoropolysilicone (FPS)-based Na+-sensitive membrane, corresponding to the targeted ions. Satisfactory and stable detection sensitivities of the modified paper-based Au electrodes were obtained over several weeks even when they were bent to a radius of curvature in the range of 6.5 to 25 mm, assuming use in a flexible body patch biosensor. Moreover, the Na+ concentration in a sweat sample was evaluated using the paper-based Au electrode with the FPS-based Na+-sensitive membrane in a wireless and real-time manner while the electrode was bent. Thus, owing to their complex mesh structure, flexible paper sheets should be suitable for use as potentiometric electrodes for wearable wireless biosensors.