Enzyme Activity Triggered Blocking of Plasmon Resonance Energy Transfer for Highly Selective Detection of Acid Phosphatase

Plasmon resonance energy transfer (PRET), as a new form of energy transfer first discovered in 2007, has been widely applied for the biomolecular recognition, detection of ions, cellular physiological status monitoring, and energy conversion. It occurs between noble metal nanoparticles (donor) and conjugated molecules or nanoparticles (acceptor). In this study, we used urchin-like gold nanoplasmonics (UGPs) and oxTMB as a new donor–acceptor pair to establish a novel PRET coupling system, avoiding trivial modification. PRET from UGPs to conjugated redox-active oxTMB leads to resonant quenching in the localized surface plasmon resonance (LSPR) spectra. However, when the acid phosphatase (ACP) was introduced, the hydrolyzate ascorbic acid (AA) converted from 2-phospho-l-ascorbic acid trisodium salt (AAP) could be capable of reducing oxTMB into TMB, thereby preventing the occurrence of PRET. The recovery of the scattering spectral intensity of UGPs was linearly related to the concentration of ACP in the range of 0.1 to 5.0 U/L, and the ACP with a detection limit of 0.076 U/L could be measured. In addition, this method also showed good selectivity attributed to the substrate specificity of enzyme.