Synthesis Of Composite Nanoparticles Based On Ag₂S Quantum Dots For Fluorescent Imaging And Photothermal Therapy

In recent two decades, with the development of science and technology, nanotechnology had been rapidly developed, and the combination of materialogy and biomedical is more and more. What is more, nanomaterials have made great achievements in biological applications and shown a good development prospects. Fluorescent quantum dots(QDs)have been widely used in various fields due to its unique optical properties, and near-infrared quantum dot has been widely used in the fields of biomarkers and biological imaging because of its advantages in near infrared region, such as good tissue penetrability, strong capacity of light absorption,and weak scattering. As a new near-infrared quantum dot, Ag2 S QDs is a potential near-infrared fluorescent molecules because of its broad and continuous excitation spectum, adjustable emission spectrum, the fluorescence emission peak located within the second infrared region, anti-photobleaching, long fluorescence lifetime, and free of toxic heavy metals. This paper studies the synthesis of protein nanogels, the synthetic method of near-infrared quantum dots Ag2 S and water-soluble probe Ag2 S QDs@PC10ARGD. Besides, we also study the characterization of the Ag2 S QDs@PC10ARGD probe, the photothermic therapy, and fluorescence characteristics. The main contents are as follows:(1) By genetic engineering method, we obtained the PC10 RGD polypeptide. Because PC10 ARGD can form a nanogel under neutral conditions by selef-assembly, an oil-soluble Ag2 S QDs were encapsulated successfully in the protein nanogel under the function of ultrasonic condition. Thereby it can form a multifunctional nano probe Ag2 S QDs@PC10ARGD containing the targeted function. it shows that the probe has good dispersibility and the size of it is about 160 nm by the TEM analysis. Besides, the results of fluorescence imaging show that the fluorescence intensity of the probe is stronger with the increasing concentration. In addition, the Ag2 S QDs @ PC10 ARGD probe has a good photothermal effect, its concentration and the intensity of the laser light is directly proportional to the thermal effect of the probe.(2) We can detect the probe's cytotoxicity by MTT assay. And the experimental results show that it has no obvious cytotoxicity when the probe concentration is 2.4 mg/m L. The cell photothermal experiment results shows that the cell incubated with the probe can be killed after laser illuminates in five minutes under the situation of the intensity of the laser being 4W/cm2. These results indicate that multifunctional nano probes Ag2 S QDs@PC10ARGD can be swallowed and have excellent thermal effects in the cell.In summary, this research is mainly to make a nano probes Ag2 S QDs@PC10ARGD with specifically targeted tumor cells based on the near-infrared quantum dots by using Ag2 S QDs and PC10 ARGD polypeptides. And the probe not only have the ability of the near-infrared fluorescence imaging, it also has the effect of photothermal treatment of tumors.This research has a positive implications for the modification method of developing quantum dots and tumor detection.