Paperfluidic devices with a selective molecularly imprinted polymer surface for instrumentation-free distance-based detection of protein biomarkers

Microfluidic paper-based analytical devices (mu PADs) offer the advantages of simplicity, extremely low costs, robustness, and miniaturisation, synergistically supporting portability and point-of-care (POC) analysis. When mu PADs are combined with distance-based detection in D mu PADs, they uniquely enable a quantitative analytical platform that is truly instrumentation-free (naked-eye readout), or at least, does not require any specialised scientific instrumentation (only mobile phone camera). However, a significant drawback of D mu PADs is their limited selectivity. In this work, we present for the first time molecularly imprinted polymer (MIP) as a selectivity-enhancing element in MIP-modified D mu PADs (MIP-D mu PADs). Herein, a layer of polydopamine MIP was coated onto the paper substrate of a D mu PAD, in a simple process using dopamine as the monomer deposited onto the paper matrix in the migration-detection zone of the D mu PAD, and polymerised in a rapid low cost procedure in the presence of oxygen under alkaline conditions. The polydopamine MIP-D mu PAD was then systematically investigated for the selective determination of chymotrypsinogen (chymo) as a model protein biomarker in urine, within the linear concentration range 2.4-29.2 mu M (R2 = 0,9903) with corresponding relative standard deviations ranging from 2% to 11 % and LOD =3.5 mu M and LOQ =11.8 mu M. The here presented analytical concept based on MIP-D mu PADs has a potential in POC diagnostics, because of the combination of low cost automated fabrication, the rapid quantitative near to instrumentation-free analysis, and selectivity through the use of MIPs as a synthetic, more stable, cheaper and easily prepared alternative to bio-macromolecules.