A nanozyme that can go beyond an enzyme: the selective detection of two species in the same whole blood sample

The specificity of enzymes for their substrate typically means there is one enzyme for one molecule. Nanozyme research has focussed on mimicking reactions that enzymes can perform, with far less emphasis on selectively reacting with species in complex biological fluids. Herein we ask the question, can a nanozyme be engineered to do what enzymes cannot do, detect and react selectively with two different substrates in the same blood sample? This is achieved using a nanoparticle that mimics the three-dimensional geometry of an enzyme with isolated substrate channels leading to an active site. The nanoparticle was composed of an active gold core and an inert carbon shell that has nanochannels and was immobilised onto an electrode. With careful choices of electrochemical potential, the solution environment inside the carbon nanochannels can be controlled to create the conditions ideal for selectively reacting with each species in sequence. In this way it was shown that glucose and dopamine could be selectively detected in the same unadulterated whole blood, by using two different electrochemical potential pulse profiles. The concept of using nanoconfinement as enzymes do, altering the solution environment inside channels, and using electrochemical potentials to choose which reactions take place, which enzymes cannot do, is a general principle and can be extended to other active sites and substrates.