Nickel-assisted selective detection of histidine and histidine-rich proteins via an ON-OFF-ON fluorescent probe and its imaging in live cells

Abstract

Amino acids and proteins are ubiquitous in all biological processes. Therefore, fluctuations in their levels profoundly impact the general well-being of any human being. Structural similarities between amino acids hamper their direct detection by fluorophores. Thus, it becomes crucial to employ an ancillary approach to accomplish this goal. In this work, the selective fluorescence response of Ni2+ towards a probe PyPP was used as a precursor for selective histidine sensing. The probe showed selectivity towards Ni2+ by fluorescence quenching, and it could be revived only in the presence of histidine. The limit of detection (LOD) for Ni2+ was 4 x10-6 M, whereas LOD for histidine was 1.08 × 10−6 M. The Ni2+ mediated selectivity could also be extended to histidine-rich proteins bovine serum albumin (BSA) and human serum albumin (HSA). The devised system was also applied to a macrophage cell line (RAW 264.7) to indicate the presence of Ni2+/histidine/HSA-BSA via confocal fluorescence microscopy, and quantitative response could be studied with flow cytometry.