Positively Charged Silver Nanoparticles as Labels for Paper-Based Colorimetric Detection of Heparin

A novel paper-based colorimetric sensor has been developed for ultrasensitive detection of heparin based on aggregation of positively charged silver nanoparticles. The electrostatic interaction between negatively charged heparin and positively charged silver nanoparticles (AgNPs) resulted in a shift in the surface plasmon resonance (SPR) wavelength leading to a color change from yellow to colorless. The proposed assay can selectively detect heparin with an ultra-low detection limit of 1.898 ng mL(-1) in solution and 8.68 mu g mL(-1) on paper. In future, the assay can be further employed for detection of heparin in human blood serum samples.