An infinite coordination polymer nanoparticles-based near-infrared fluorescent probe with high photostability for endogenous alkaline phosphatase in vivo

Alkaline phosphatase (ALP) is an essential enzyme in phosphate metabolism and widely distributes in mammalian body fluids and tissues. So far, various fluorescent probes for ALP have been well developed, but some disadvantages such as short emission wavelength and low photostability restrict their biological application. Herein, a near-infrared (NIR) fluorescent nanoprobe based on infinite coordination polymer nanoparticles (CyOH@Tb-GMP) is constructed for endogenous ALP activity assay. The characteristics of the nanoprobe are as following: (1) The fluorescence emission of the nanoprobe is at 718   nm belonging to NIR region, which is suitable for bioimaging. (2) The nanoprobe displays better photostability than common NIR dyes such as ICG as well as CyOH. (3) The nanoprobe exhibits high sensitivity for ALP activity with a 7.5-fold fluorescence enhancement when 2.5   U/mL ALP is added. (4) The NIR nanoprobe is employed for monitoring endogenous ALP activity in various biological samples such as cell, tissue and mice with satisfactory results.