Antenna effect of pyridoxal phosphate on the fluorescence of mitoxantrone-silicon nanoparticles and its application in alkaline phosphatase assay

As a kind of sensing and imaging fluorescent probe with the merit of low toxicity, good stability, and environment-friendly, silicon nanoparticles (SiNPs) are currently attracting extensive research. In this work, we obtained mitoxantrone-SiNPs (MXT-SiNPs) with green emission by one-pot synthesis under mild temperature condition. The antenna based on pyridoxal phosphate (PLP) was designed for light-harvesting to enhance the luminescence of MXT-SiNPs and to establish a novel sensing strategy for alkaline phosphatase (ALP). PLP transfers the absorbed photon energy to MXT-SiNPs by forming Schiff base. When PLP is dephosphorized by ALP, the released free hydroxyl group reacts with aldehyde group to form internal hemiacetal, which leads to the failure of Schiff base formation. Based on the relationship between antenna formation ability and PLP hydrolysis degree, the activity of ALP can be measured. A good linear relationship was obtained from 0.2 to 3.0 U/L, with a limit of detection of 0.06 U/L. Furthermore, the sensing platform was successfully used to detect ALP in human serum with recovery of 97.6-106.2%. The rational design of antenna elements for fluorescent nanomaterials can not only provide a new pathway to manipulate the luminescence, but also provide a new direction for fluorescence sensing strategy.