A sensitive immunosensor for the detection of alkaline phosphatase as a biomarker for fracture healing

Fractures occur at all ages and are highly prevalent. At the same time, there is a problem of delayed healing after fracture, and drugs are often taken to promote healing. Alkaline phosphatase (ALP) is an important indicator for assessing fracture healing, and achieving its quantification would be helpful in evaluating fracture recovery in patients on medication. Here, we present an ultrasensitive immunosensor based on NH2-MIL-101(Cr)@AuNPs/ rGO nanocomposites. The poor conductivity of metal-organic frameworks (MOF) limits their electrochemical applications. In this study, NH2-MIL-101(Cr) was used as a carrier for the in situ reductive growth of gold nanoparticles (AuNPs) on its surface. Then NH2-MIL-101(Cr)@AuNPs were synergized with reduced graphene oxide (rGO) to amplify the electrochemical signals. The obtained NH2-MIL-101(Cr)@AuNPs/rGO nano -composites exhibited electrical conductivity and stability. Mercaptosuccinic acid introduces a sufficiently large number of carboxyl groups by binding to AuNPs, providing abundant binding sites for ALP antibodies. The immunosensor used differential pulse voltammetry (DPV) for electrochemical analysis, and could capture the concentration response in the range of 10-12 -10-5 g mL-1 with a relatively low detection limit of 1.64 pg mL-1. In addition, the sensor has been successfully applied to the detection of ALP in massively diluted serum of fracture patients before and after drug administration.