Dual-modality Imaging Of Pancreatic Cancer Based On CTSE Enzyme-responsive Molecular Probe

Pancreatic cancer is prone to early metastasis,and most of diagnosed patients with a poor prognosis are at the middle or advanced stage,which determines the significance of early diagnosis of the malignancy.As an emerging discipline,molecular imaging which is based on molecular biology can make the early diagnosis of diseases come true.The research of magnetic resonance and fluorescent dual-modality molecular probes in molecular imaging can realize the complementary advantages of different imaging methods,which will be beneficial to the early diagnosis of pancreatic cancer.In this research,an enzyme-responsive bimodal molecular probe was constructed to study the early diagnosis of pancreatic cancer at the cellular level.Objective:This research was studied based on the high expression of cathepsin E（CTSE）in the early stage of pancreatic cancer and superparamagnetic iron oxide nanoparticles with the characteristic of fluorescence quenching,and an enzyme-responsive molecular probe named Fe₃O₄-HSP-QM for magnetic resonance and fluorescence dual-modality imaging of pancreatic cancer cells PANC1-CTSE was constructed by conjugating the aggregation induced emission（AIE）fluorescence entitled QM-COOH to the surface of magnetic nanoparticles using the substrate peptide of CTSE.Methods:Western Blot was used to detect the expression level of cathepsin E in pancreatic cancer cells.The aggregation induced emission of QM-COOH and the fluorescence quenching property of Fe₃O₄ were tested.The particle size of the nanoprobes Fe₃O₄-HSP-QM and Fe₃O₄ were measured by transmission electron microscopy（TEM）and dynamic light scattering（DLS）.The cytotoxicity of the two were tested by MTT assay,and their relaxation rates were measured.And in vitro magnetic resonance imaging and cell fluorescence imaging were performed.Results:Western Blot showed that pancreatic cancer cells expressed higher level of cathepsin E compared with the controlled group cells.QM-COOH had aggregation induced emission property,and Fe₃O₄ was capable of quenching fluorescence.TEM and DLS results showed that both Fe₃O₄-HSP-QM and Fe₃O₄ had good dispersibility,and there was no significant difference in particle size between the two.MTT assay showed that Fe₃O₄-HSP-QM and Fe₃O₄ had neglected cytotoxicity（p>0.05）.Compared with Fe₃O₄,Fe₃O₄-HSP-QM had higher transverse relaxation rate r₂.In vitro magnetic resonance imaging showed that Fe₃O₄-HSP-QM exhibited a more obvious T₂ signal change trend.Fluorescence imaging proved that Fe₃O₄-HSP-QM showed obvious fluorescence in pancreatic cancer cells,while the fluorescence signals of the controlled group cells were always quenched.Conclusion:the synthesized Fe₃O₄-HSP-QM which can be used for magnetic resonance and fluorescence imaging had neglected toxicity,good dispersibility and biocompatibility.And the research proves the feasibility of its dual-modality imaging preliminarily.It also solves the problem of interference caused by autofluorescence,and greatly improves the diagnostic efficiency that lays the foundation for further animal-level research,and has broad application value and prospect.