Synthesis And Bioimaging Application Of Near-Infrared ? Fluorescence Nanoprobes

Compared with the fluorescence imaging in the first near-infrared region(NIR-I,650-900 nm)fluorescent probe,the fluorescence imaging in the second near-infrared region(NIR-II,900-1700 nm)has many advantages,such as the small light scattering,the weak spontaneous fluorescence and the strong tissue penetration.And the research of NIR-II fluorescent probe has become the focus of attention.At present,the NIR-II fluorescent probes have some problems which have been reported,such as easy elimination,high toxicity,lack of active targeting ability and weak clinical conversion potential.It has become an urgent problem for the new generation of fluorescent probe to improve its imaging time,biocompatibility and targeting performance by designing the molecular structure of the near-infrared fluorescent probe.In this paper,a conjugated polymer probe with the second near-infrared region fluorescence is designed based on the donor-acceptor structure.The amphiphilic compound is introduced to improve biocompatibility.By the covalent coupling method to combine the FDA approved drug molecules,the active targeting fluorescent probe ICG-Tra was prepared.And the developed probe has the potential application prospect of clinical transformation.The specific research content of this article is as follows:(1)Synthesis of NIR-II conjugated polymer fluorescent probe.In this paper,A low energy band gap conjugated polymer(pTB)was prepared based on the electron donor benzodithiophene and the electron acceptor thienothiadiazole.We encapsulated it in DSPE-mPEG aqueous solution to form water-soluble nanoparticles(pTB-PEG)with a particle size of about 130 nm.The pTBPEG has a good absorption peak at 831 nm and a large stokes displacement of 206 nm,which allows the tissue penetration depth of the probe to reach 6 mm.And the fluorescence imaging in the second near-infrared region(NIR-II)of healthy mouse's blood vascular system and tumor bearing mice was effectively realized.The nanoparticles have excellent photostability and good biocompatibility.At the same time,it has excellent photothermal treatment performance,which photothermal conversion efficiency is up to 54 %.It has potential applications in photothermal therapy under the guidance of NIR-II fluorescence imaging.(2)Synthesis of NIR-II targeting probes.A fluorescent probe ICG-Tra was prepared by by covalent coupling method,which combining the FDA approved fluorescent dye indocyanine green(ICG)and the diagnostic antibody trastuzumab.It was found that the optimal ratio of trastuzumab labeled ICG was 10 times the molar equivalent.The emission peak of the ICG-Tra probe in the NIR-II region is 920 nm,and there is a significant fluorescence signal in the range of 920 nm-1150 nm.At the same time,we incubated the probes with different concentration gradients with 4T1 cells to verify the efficient targeting specificity and internalization of the probes on 4T1 cells in vitro.Even when the probe concentration is 100 nM,the fluorescence signal of the cell can be observed.Further plasma half-life evaluation indicated that the optimal imaging time of the probe in vivo was 5 to 15 min after injection.And it has a high target retention level within 1 hour.NIR-II imaging of the blood vascular system of healthy mice and tumors of tumor-bearing mice confirmed the specific targeting of breast cancer by ICG-Tra fluorescent probe.In this paper,two kinds of NIR-II fluorescent probes with good biocompatibility were prepared,which increased the retention time of the probe at the imaging target,improved the active targeting ability of NIR-II fluorescence imaging,and realized the imaging of NIR-II fluorescent probes in deep tissue in vivo.It provides a new design idea for the development of clinical application of NIR-II fluorescent probe.