Catalytic Nanoparticle-based Microfluidic Biosensors For Quantitative Point-of-care Detection

Immunoachemical biosensors or immunosensors have increased attention to diverse analytical platforms for quantification of biomolecules with high selectivity and sensitivity.Immunosensors have been developed with Point-of-care testing(POCT)requirements,including easy sample preparation,simple device,and satisfactory sensitivity.Lateral flow immunoassays(LFAs)are one of the POCT platforms,owing to the fast result outcome,low-cost materials,convenience and comfort.However,it has the limitation for quantitative assay as well as sensitivity.For signal transducers,nanoparticles are used in immunosensors,including metallic,magnetic,and carbon-based nanoparticles.Nanoparticles have optical properties,catalytic activity as a nanozyme,and converts the absorbed light into thermal energy.They have been applied in chemistry,clinical fields and biotechnology.Among various nanoparticles,gold nanoparticles(AuNPs)have incredible attention in bioanalytical areas due to their distinct physical and chemical properties.AuNPs are easy to synthesis,have a long storage time,tunable optical properties and excellent biocompatibility.With these properties,LFAs commonly used AuNPs as optical readers.However,LFAs provide only simple yes/no test results,and to overcome this drawback,catalytic properties of nanoparticles are applied to amplify the signal for quantitative readouts.Plantinum(Pt)nanoparticle has excellent catalytic ability to oxidize H2O2 into oxygen.Pt is prepared as foaming bimetallic layers on Au@Ag@Pt.It can amplify the signal of AuNPs but also generate the oxygen gas as catalytic ability.Pressure based assay with a handy portable device produces quantitative results by detecting oxygen gas produced from catalytic decomposition of H2O2.Herein,Pt nanoshell method for gas generation in LFAs was developed to quantitatively detect procalcitonin(PCT)with high correlation for clinical tests.The photothermal effect is another significant property of nanoparticles,a phenomenon of proton energy transformed into heat energy by nanoparticles.While many researchers use a thermometer for quantitative assay because of the conversion of light to heat thermal energy under photothermal effects,a special designed PMMA chip was developed to show quantitative assay on commercial LFA products without other signal transducers due to silver nanoparticle(Ag)mediated photothermal performance at 450 nm laser irradiation.Ag is easily prepared on colloidal gold as Au@Ag,and the photothermal effect of Au@Ag makes the temperature elevation of the chip environment and the pressure elevations in a limited chamber place.With this pressure elevation in a chamber,it explores the ink movements toward the outlet hole on the chip,corresponding to the concentrations of Au@Ag proportional to the target analytes.This integrated ink distance-based PMMA chip overcomes the limitation of the necessity of additional transducers for LFA quantitative assay.Polypyrrole nanoparticle is an excellent photothermal agent.It can be used as an efficient thermal source to control heat when exposed to specific excitation wavelengths such as 808 nm.Polypyrrole can be generated by pyrrole polymerization with Fe3+.Magnetic beads contain Fe2O3 that can release Fe3+ for pyrrole polymerization to produce polypyrrole.Using antibody modified magnetic beads,qualitative and quantitative assay can be confirmed by polypyrrole concentration,which would be shown in temperature and pressure variations in a sealing well with a digital thermometer and a pressure meter.Once polypyrrole is under laser irradiation,the conversion of light to heat energy occurs,and during this process,temperature elevation is monitored.Since temperature elevation leads the liquid evaporation in a sealing well,the pressure elevation is also observed.With these principles,polypyrrole-mediated photothermal immunoassay is conducted for the quantitative assay using a digital thermometer and a pressure meter.This method can offer dual readouts with the enhancement of accuracy.Moreover,polypyrrole has strong photothermal stability and repeatability.This protocol could reduce the background of undesirable reactions with a false negative result.For POCT,nanoparticle properties’ catalytic and photothermal performance have been applied in a suited detection platform.These developed methods can be widely used for quantitative assay in clinical fields.