Photoelectrochemical biosensor constructed using TiO2 mesocrystals based multipurpose matrix for trypsin detection.

Herein, a delicate photoelectrochemical biosensor for quantitative detection of trypsin was successfully established by virtue of polyethylenimine-sensitized TiO2 mesocrystal as the photoactive matrix integrated with Boron-doped carbon quantum dots labeled peptide as the signal amplification tags. Specifically, polyethylenimine with fine photo-stability was introduced here as the electron transporting layer to reduce the energy barrier of TiO2 mesocrystal, thereby facilitating the carriers transfer and improving the photocurrent response. Moreover, the Boron-doped carbon dots-peptide bioconjugates could noticeably decrease the photocurrent due to the competitively light harvesting by Boron-doped carbon dots and the steric hindrance of peptide chains, leading to less light energy arriving at the TiO2 mesocrystal and hindering the electrons transfer between the electrolyte and electrode. The anchored conjugates synergistically promoted the decline of photocurrent signal, evidently enhancing the sensitivity of this detection protocol. When trypsin was incubated, the photoelectric signal was obviously re-promoting because arginine-containing peptide chains could be specifically cleaved by trypsin and the Boron-doped carbon quantum dots was affranchised from the electrode, making the most of the previous suppression effects released. Therefore, the intensity of photocurrent signal was proportional to the trypsin concentration in a wide linger range from 1×10-7mg/mL to 1.0mg/mL. This practical and elegant "on-off-on" biosensor with high sensitivity offered a promising scheme to monitor various proteases and the inhibitors screening for early diagnoses of different diseases.