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A Smart Surface-Enhanced Resonance Raman Scattering Nanoprobe for Monitoring Cellular Alkaline Phosphatase Activity during Osteogenic Differentiation

Sun DXu WLiang CShi WXu S.

ACS Sens. 2020 May 10. doi: 10.1021/acssensors.0c00428. [Epub ahead of print]

High-efficiency induction of bone marrow mesenchymal stem cells (BMSCs) to osteogenic differentiation in vitro can help to solve a series of bone diseases such as bone injury, fracture repair, and osteoporosis. In order to explore the optimal conditions for different chemical inducers to promote BMSCs differentiation and the possible differentiation mechanisms, we developed a smart nanoprobe that can achieve in situ alkaline phosphatase (ALP) activity detection during osteogenic differentiation in cells. The smart nanoprobe (Au@BCIP) was designed as the surface decoration of gold nanoparticles (AuNPs) with 5-bromo-4-chloro-3-indolyl phosphate (BCIP). The nanoprobe was co-cultured with differentiated BMSCs at different stages to monitor the ALP activity based on an ALP-catalyzed hydrolysis reaction with the BCIP as a substrate. The product can be quickly oxidized by dissolved oxygen to achieve a Raman-active species (5,5′-dibromo-4,4′-dichloro-1H,1H-[2,2′] biindolylidene-3,3′-dione; BCI). The SERS sensitivity has been greatly improved by resonating the excitation wavelength of 632.8 nm. It is a new strategy for tracing bone disease related ALP activity in vivo model with high sensitivity, selectivity, and non-invasion. By using this nanoprobe, osteogenic differentiation of cells under osteogenic supplements was assessed and the p38 MAPK signaling pathway for osteogenic differentiation was experimentally evidenced, which are of significance for understanding BMSCs and regulating their osteogenic differentiation process.