Progress in developing polymerized crystalline colloidal array sensors for point-of-care detection of myocardial ischemia

The difficulty of rapid, definitive diagnosis of myocardial ischemia leads to unnecessary hospital admissions and treatment delays. Previously, decreased metal binding affinity in human serum was investigated as a marker for myocardial ischemia. Polymerized Crystalline Colloidal Array (PCCA) sensors for Ni2+ may be useful in developing a point-of-care test to determine metal binding affinity in plasma and to help rule out myocardial ischemia. PCCA sensors for Ni2+, with 5-amino-8-hydroxyquinoline as a chelating agent, were tested in aqueous solutions and diluted human plasma. The peak wavelength diffracted by the sensors was monitored by reflectance spectrometry and correlated with Ni2+ concentration. The PCCA sensors show a linear response to aqueous Ni2+ concentrations between 0.2 and 1.0 mmol L−1, and can detect changes in free Ni2+ concentration of <60 µmol L−1. The sensors respond at physiologic pH and can be reversibly dehydrated. The PCCA sensors developed here can report on free Ni2+ concentration in the presence of human plasma. These sensors can be used to detect a decrease in the Ni2+ affinity of plasma proteins, which may indicate recent myocardial ischemia. PCCA sensors offer a practical approach to rapid, point-of-care detection of a proposed biochemical signature of myocardial ischemia.