Bioactive paper dipstick sensors for acetylcholinesterase inhibitors based on sol–gel/enzyme/gold nanoparticle composites

Abstract

A bioactive paper-based colorimetric "dipstick" bioassay is reported that is based on acetylcholinesterase (AChE) catalyzed enlargement of gold nanoparticles that are co-entrapped with the enzyme in a sol-gel based silica material that is coated on a functionalized paper substrate. Test solutions containing acetylthiocholine (ATCh) and a Au(III) salt are spotted over the sensing area of the bioactive test strips containing small (3 nm diameter) primary gold nanoparticles (AuNP). Biocatalyzed hydrolysis of ATCh via AChE leads to formation of thiocholine, which in turn reduces the Au(III) onto the entrapped nanoparticles, producing particle growth and a concomitant increase in color intensity that can be correlated to the amount of substrate or inhibitor present in test solutions. The entrapped AuNP cannot leach from the silica material, leading to a bioactive paper assay that can utilize visual detection of a color change as a simple readout. Our results show that the dipstick based bioassay is sufficiently sensitive to allow for detection of Paraoxon over the concentration range of 500 nM to approximately 1 mM. Detection can be made by eye or using a digital camera and image analysis, making the assay suitable for remote analysis.

Evolution and Expectations of Enzymatic Biosensors for Pesticides

“…In search of alternative technological solutions, bioactive paper-based materials are being developed with the aim of detecting toxins in food packaging (Luckman & Brennan, 2010). The operating principle of this material consists in producing rapid colorimetric detection of one or more analytes simultaneously.…”

A perspective on paper-based microfluidics: Current status and future trends

“…One proposal is combining assay reagents with sol-gel materials to immobilize reagents on paper. [64][65][66] In this way, Hossain et al developed a paper-based sensor which can detect organophosphate pesticides of nanomolar quantities in milk or lettuce by color changing. 65 Another proposal is using gold nanoparticle (AuNP) based colorimetric detection which can dramatically improve both the sensitivity and the specificity of detection.…”

Nanomaterial-functionalized Cellulose: Design, Characterization and Analytical Applications

“…82 In other examples, pH changing polyaniline-poly(sodium 4-styrenesulfonate) (PANI:PSS) NPs have been used to detect concentrations of amine vapors by monitoring the change in color to blue for basic pH environments. 83 Chaiyo et al detected Cu 2+ by measuring the change in color of Ag nanoplates in the presence of thiosulfate from pink to colorless on paper due to catalytic etching.…”

“…105 Luckham et al deposited enzyme/NP composites on paper to detect the acetylcholinesterase inhibitor paraoxon which is found in insecticides and nerve gases. 82 Ying et al reported an immunosensor for the detection of Escherichia coli (E. coli). Graphene paper was decorated by AuNPs through one-step electrodeposition and E. coli was immobilized on the surface using biotin-streptavidin chemistry.…”