SERS Monitoring The Dynamics Of Metabolites In Lysosome Of Living Cells

Surface-enhanced Raman scattering (SERS) is an ultra-sensitive vibrational spectroscopy technique for detecting the molecular structure changes on the surface of SERS substrate. Depending on the long-range electromagnetic enhancement and short-range chemical enhancement, it can make the signal of Raman tag on the surface of SERS substrate enhanced by several orders of magnitude. Due to its advantages such as ultra-sensitivity, multi-path detection, photo-bleaching resistance, SERS technique has emerged as a powerful tool for cellular imaging and bioanalysis. The system which flexibly combines the ultra-sensitivity of SERS with the high selectivity, high specificity and configuration transformation of functional nucleic acid probe has been widely used in the fields such as biosensing, analytical chemistry, biomedicine, disease diagnosis and drug development.The paper, with gold nanorod particles as SERS substrate, builds system for real-time monitoring of metabolite changes in cell. It carries out the research work from the following two aspects:(1)Dynamics of pH in cell during SERS monitoring-based photo-thermal therapyIn this chapter, with the gold nanorod as SERS substrate, pH-sensitive Raman reporter molecule(4-MBA) modified on its surface and peptide fragment which can enhance its biocompatibility. Because gold nanorod has strong light absorption coefficientin the visible light and near-infrared (NIR) region, it can be employed for photo-thermal therapy(PTT) while achieving pH SERS detection during PTT. The system enters into lysosome by endocytosis and the heat generated from PTT will damage lysosomal membrane, thereby the acid proton is released from the lysosome and then pH in lysosome increases.The carboxyl in 4-MBA has deprotonation which will cause the Raman peak to change, thereby achieving dynamic monitoring of lysosome pH during photo-thermal therapy.(2)SERS-based dual control imaging lysosome ATPIn this chapter, gold particle surface is modified with avidin and Raman reporter 4-aminothiophenol(4-ABT). Through the interaction of avidin and biotin, C-rich chain(i-motif) with one end modified by bition and the other end modified by thiol is attached to the gold particle. And then adds aptamer chain complementary which specifically recognizing ATP to form double-chain structure, and uses Au-S to connect the other end of i-motif to the surface of gold nanorod to construct an acidity and ATP dual control system. When the system intakes cell, only when ATP combines with aptamer chain and in acidic environment (typically in lysosome), i-motif conformation folds to form tetramer structure, thereby narrowing the distance between gold particle and gold nanorod, forming hot spot of Raman, and then generating SERS signal. It will not generate SERS if lacking either condition, so this system achieves the purpose of ATP imaging in cell lysosome.