Develop Ment Of ALP-Activable Bimodality Imaging Probes For In Vivo Imaging

Strategies enabling the development of molecular imaging probes with prominent detection performance have provided promising tools for precise diagnosis of diseases.Stimuli-triggered in situ self-assembly of small molecules into nanostructures,which leverages the strong tumor permeability of small-molecule probes and high accumulation of nanomaterials in tumor tissues,have been successfully applied to build molecular imaging probes with different modalities for in vivo imaging.However,the applications of this strategy in simultaneous activation of multimodality imaging signals are remaining challenging.To our knowledge,there is still lack of near-infrared(NIR)fluoresence/magnetic resonance imaging(MRI)bimodal probes allowing for high sensitivity and high spatial resolution in early diagnosis of malignant tumors and surgical guidance.Alkaline phosphatase(ALP)is an important indicator of liver dysfunction in clinic and is upregulated in some malignant tumors.Precise detection of ALP activity in vivo will facilitate to the early diagnosis of liver dysfunction and some malignant tumors.In the past few years,several imaging probes have been reported to detect ALP activity in tumors in living subjects.However,these probes were usually designed to be single-modal probe incapable of imaging of ALP activity simultaneously with high resolution and sensitivity in vivo.To solve this limitation,we rationally integrate a fluorogenic reaction into an ALP-mediated in situ self-assembly to design small-molecule-based activatable NIR fluorescence and MRI bimodal probes for in vivo imaging.This thesis is divided into two chapters.The first chapter is an introduction,in which we introduce the basic knowledge of molecular imaging technology,activatable molecular image probes and in situ self-assembly.The first part is about the introduction of molecular imaging,categories and methods to build different molecular imaging probes.The second part focuses on the mechanism,and the application of in situ self-assembly in building activatable molecular imaging probes.The third section outlines the recent advances of in-situ self-assembly to build imaging probe with different imaging modalities and their applications in in vivo analysis.In the second chapter,an activatable NIR fluorescence/MRI bimodal probes(P-CyFF-Gd)was designed and synthesized for imaging of ALP activity in tumors of living mice through an enzyme-triggered fluorogenic reaction and in situ self-assembly strategy.P-CyFF-Gd consisting of(1)a pre-quenched NIR fluorophore(Cy-Cl)capped with an ALP recognition phosphate group(-PO3H);(2)a paramagnetic DOTA-Gd chelate for MRI;and(3)a hydrophobic dipeptide Phe-Phe(FF)linker to promote self-assembly.We demonstrate that P-CyFF-Gd can be activated by ALP in vitro and then self-assmeble into nanoparticles,resulting in remarkable enhancements in NIR fluorescence(>70-fold at 710 nm)and r1 relaxivity(?2.3-fold).Cell study results show that P-CyFF-Gd can be activated by endogenous ALP overexpressed on cell membranes,producing membrane-localized assembled nanoparticles(NPs)that can be directly visualized by cryo-SEM.Take advantage of simultaneously enhanced NIR fluorescence and MRI contrast,P-CyFF-Gd is successfully applied for the real-time detection and of GGT activity and location in xenograft HeLa tumors following systemic administration.Moreover,P-CyFF-Gd can also effectively delineate orthotopic liver tumor foci,facilitating efficient real-time,image-guided surgical resection of tumor tissues in intraoperative mice.This study reveals that using a combination of an enzyme-mediated fluorogenic reaction and in-situ self-assembly to design an ALP activatable NIR fluorescence/MRI bimodal probe can effectively facilitate the real-time,non-invasive detection and precise localization analysis of ALP activity in vivo.