Rapid Equilibrated Colorimetric Detection of Protamine and Heparin: Recognition at The Nanoscale Liquid-Liquid Interface.

Abstract

Demands for the rapid quantitation of polyions including heparin and protamine are ever-growing. Previous paper-based and polymeric optical and electrochemical sensing devices required more than several hours for the signal stabilization. Therefore, signals were acquired with fixed sample exposure time mode, which was time-consuming and technically demanding. We present here for the first time the optical detection of protamine and heparin in equilibrium mode with emulsified nanospheres. The method significantly shortened the response time from hours to typically less than 10 s, and offered tunable, sensitive, and colorimetric detection within the clinical relevant range (10 to 100 mg/L) for heparin. The improved characteristics were attributed to the small size of the nanospheres (ca. 50 nm in diameter) as well as the reversible recognition at the nanoscale liquid-liquid interface. Detection of the anticoagulant heparin was also successfully demonstrated in human blood serum background.