Ultrasensitive Double-Channel Microfluidic Biosensor-Based Cathodic Photo-electrochemical Analysis via Signal Amplification of SOD-Au@PANI for Cardiac Troponin I Detection

Interesting double-channel microfluidic chip integration with a sandwich-type cathodic photo-electrochemical (PEC) biosensor is utilized for ultrasensitive and efficient detection of cardiac troponin I (cTnI) based on a signal amplification strategy. The Pd nanoparticles loading on the I-doped bismuth oxybromide with oxygen vacancies (Pd/I:BiOBr-OVs) as a sensing platform can effectively enhance cathodic photocurrent response by improving the visible light absorption ability with I doping, facilitating the efficiency separation of photogenerated electron–hole pairs with OVs, and increasing the electron-transfer rate with Pd loading, where the photogenerated electron could be captured by dissolved O 2 to boost generation of a superoxide anion radical ( • O 2 – ). To further enhance the PEC response, a novel superoxide dismutase loaded on [email protected] ( [email protected] ) as a signal amplification label is developed for incubating the detection antibody (dAb). It is particularly noteworthy that SOD can effectively catalyze dismutation of the • O 2 – to produce H 2 O 2 and O 2, and [email protected] with a good reduction and catalytic property can catalyze the produced H 2 O 2 into H 2 O and O 2 . Then, the produced O 2 that has been dissolved or adsorbed can capture more photogenerated electrons, resulting in more electron–hole pairs to separate, so as to the cathodic photocurrent signal of this system which can be amplified more significantly. Therefore, a signal amplification cathodic PEC biosensor is prepared for sensitively detecting cTnI, in which a good linearity ranging from 0.1 pg/mL to 100 ng/mL with a low detection limit of 0.042 pg/mL is obtained. Furthermore, the proposed biosensor exhibits excellent sensitivity and high selectivity, which could be extended to detect other disease markers in biological analysis and early disease diagnosis.