Boosting the sensitivity of paper-based biosensors with polymeric water-soluble reservoirs

Abstract

Storing highly concentrated reagents and releasing them with high efficiency is crucial for developing highly sensitive biosensors. However, the performance of reservoirs in biosensors made of filter paper is limited by the intrinsic physicochemical properties of untreated cellulose. In this article, the impact of 9 different polymer modifications on the storage and release of enzymes and nanoparticles in paper-based biosensors is studied for the first time. Carboxymethylcellulose, polyvinyl alcohol, carrageenan, and chitosan, which contain hydroxyl groups, yielded paper-based reservoirs with the highest concentration of reagents in them. Polymer reservoirs made of carboxymethylcellulose release enzymes rapidly and at high concentration, which results in colorimetric glucose biosensors with an ultralow limit of detection of 0.005 mM. Reservoirs made with a blend of polymers concentrate antibody-decorated nanoparticles and decrease 10 times the limit of detection of a model immunosensor. An adaption of this design was used for detecting the pathogen Klebsiella pneumoniae in urine samples from hospital patients at the infectious dose threshold rapidly and with high specificity. The fabrication of the reservoirs only requires drop-casting a polymer solution on the paper and drying. This procedure is compatible with the fabrication of origami biosensors, which are made from a single piece of filter paper.