Microfluidic nanopaper based analytical device for colorimetric and naked eye determination of cholesterol using color changing of triangular silver nanoprisms

A microfluidic nanopaper-based analytical device (µNPAD) has been prepared for the determination of cholesterol by using triangular silver nanoprisms (T-AgNPrs). We have developed a simple enzyme-based biosensor that can detect cholesterol by a colorimetric reaction based on the etching of T-AgNPrs. In the presence of cholesterol and cholesterol oxidase (ChOx), H2O2 was produced which etched the T-AgNPrs. As a result, after the etching process, a blue shift occurred and a color change from blue to light orange was observed. Based on this phenomenon, the amount of cholesterol was obtained by UV-Vis spectroscopy and µNPAD. A linear calibration curve in the range of 0.10-4.0 mM was obtained with a detection limit of 0.065 mM and a correlation coefficient (R2) of 0.993 using UV–Visible spectrophotometer. In the case of µNPAD, cholesterol concentration from 0.20-3.0 mM can be used with a detection limit of 0.14 mM and correlation coefficient (R2) of 0.985. T-AgNPrs detection system showed high selectivity to cholesterol and no color change was observed in the presence of other interferences. The proposed µNPAD based on T-AgNPrs can be used in the applications of point-of-care diagnostics