BioChemPen for a Rapid Analysis of Compounds Supported on Solid Surfaces

We present BioChemPen, a portable wireless biosensor device for rapid analysis of substances adsorbed on solid surfaces. The device takes advantage of (bio)luminescent reactions taking place in a hydrogel matrix. In a typical embodiment, the active element of this device is a hydrogel disk (chemotransducer) containing enzyme(s), electrolyte solution, and all of the necessary substrates. When the hydrogel is exposed to a solid sample surface containing the target analyte, light is produced. A photoresistor (phototransducer), placed in close proximity to the hydrogel disk, detects the light. The operation of the BioChemPen is enabled by a MicroPython PyBoard microcontroller board and other low-cost electronic modules. The obtained results are immediately uploaded to the Internet cloud. In one application, we demonstrate an analysis of hypochlorite-containing cleaning agents present on the surfaces of daily use objects by an assay based on hydrogel embedded with luminol and hydrogen peroxide. In another application, we use hydrogel embedded with luciferin, luciferase, and pyruvate kinase to detect adenosine triphosphate (ATP), and adenosine diphosphate (ADP), and link the ATP content with meat freshness. Lastly, we demonstrate the detection of organophosphate pesticides present on vegetables with the hydrogel containing acetylcholinesterase, choline oxidase, and horseradish peroxidase. The limits of detection for sodium hypochlorite, ATP, ADP, and chlorpyrifos-methyl (a pesticide) were 7.95 × 10^-11, 2.73 × 10^-13, 2.35 × 10^-12, and 2.59 × 10^-10 mol mm^-2, respectively.