Highly-branched Cu2O as well-ordered co-reaction accelerator for amplifying electrochemiluminescence response of gold nanoclusters and procalcitonin analysis based on protein bioactivity maintenance.

The point of fabricating ultrasensitive electrochemiluminescence (ECL)-based biosensors should be focused on how to maintain high immune recognition of antigens by antibodies in whole process. That is not effortless due to the structure of the protein can be destroyed root in toxic nanocarriers, excessive cyclic potential and superoxide radicals in coreactant, all of which can lead to reduce the bioactivity of antigen and antibody. In this work, the effect of negative voltage and divers coreactant on protein bioactivity were verified. Based on that, a motivated ECL biosensor with good biocompatibility was fabricated for procalcitonin (PCT) detection using Au nanoclusters (Au NCs) as low-potential cathodic luminophor and K2S2O8 as non-toxic coreactant, respectively. Besides, highly-branched Cu2O was utilized to catalyze K2S2O8 and produce more radical anion SO4•-, which can oxidize Au NCs•- to generate more high-energy-state Au NCs*, thus doubling the ECL intensity to meet the requirements of trace analysis. In addition, protein A (PA) as specific antibody capturer was employed to bind the Fc region of anti-PCT in an orientated way, further maintaining the physiological activity of antibody. As expected, all strategies undoubtedly practically improved the immune recognition of the biosensor and reduced the detection limit to 2.90 fg/mL.