A Next Generation Label-Free PoC Sensing Platform

Abstract

Current Point-of-Care Testing (PoCTs) or biomarkers are affinity based and require immobilisation on the substrate for sensitive detection. This not only increases the production and overall costs but also introduce measurement error leading to false interpretations. The PoCT devices are well established for protein and cell based assays but challenges remain for label-free, inexpensive and multiplex protein screening tools. Nanopore sensing allows detection of biomolecular interactions and intramolecular structural alterations. It monitors ionic currents changes when a charged molecule translocates through the pore with external electric potential. The ultimate advantage is removing the clouding of ensemble averaging. There are two types of nanopores, biological and solid-state which both efficiently probe analytes at the single molecule level but they either have limitation on pore diameter or required very expensive equipment to fabricate the pore. Here we employ a conical solid-state nanopore - nanopipettes (sub-nanometer size) to screen through different targets. They are quicker and cheaper to fabricate and can select the optimum pore diameter. The material of nanopipette (quartz) have low electrical noise which would be ideal to differentiate the binding signal with the complex. Traditional assays use antibodies because of high specificity and selectivity however they are difficult to implement onto the nanopipette due to relatively large size and hydrodynamic complexity in the nanochannels. Distinguishing between binding and transient blockade remains unresolved. Aptamers are single-stranded oligonucleotides which bind to relevant target molecules with high affinities similar to antibodies but are more robust, smaller in size and cost effective. Due to the specificity of the aptamers, integrating with nanopipette will allow single protein molecules to be detected to in a low cost, label-free manner and able to screen targets in a high-throughput format leading to next generation PoC electrochemical sensing platforms for screening proteins.