Study On Chemical Preparation And Properties Of Near Infrared Photoresponsive Nano-drugs

The preparation and application of nano drugs with near infrared light response are the research hotspots in the fields of chemistry,biology,materials and medicine.By combining the upconversion materials with the materials of different properties,the nano drugs prepared by using the synergistic effect between the drugs can monitor,analyze and treat the tumors in the nanometer scale.However,the existing synthetic upconversion luminescent materials require multiple series of complex operations such as centrifugal precipitation,water washing,redispersed seed crystals.Aiming at this problem,this paper developed a convenient and low toxicity continuous hot injection method.The synthesis method was the addition of quantitative NH₄F and NaOH in the mixed solution of octadecene and oleic acid.After the reaction solution was raised to high temperature,The oleic acid complex of lanthanide ions was injected at a certain time interval to grow nuclei at high temperature,and the upconversion nanocrystals were generated rapidly when the specific surface energy of the reaction system was minimum.We prepared near-infrared photoresponsive nano drugs by the method.The results are summarized as follows:（1）Monodispersed ultrasmall lanthanide doped CaF₂ upconversion fluorescent reagents（<10 nm）have been prepared via the successive hot-injection method based on NaOH mediated process.The as-prepared product was investigated by X-ray diffraction（XRD）,transmission electron microscopy（TEM）,X-ray photoelectron spectroscopy（XPS）,Fluorescence spectra,respectively.The results suggest that the Na+ plays a critical role in the formation of the as-prepared ultrasmall lanthanide doped CaF₂.Upconversion luminescent and size of the resultant nanoparticles could be improved by the successive injection of precursors at elevated temperature,the results provide an efficient way to increase upconversion of nanoparticles fluorescent intensity and tune size of upconversion nanoparticles.It is proved that the continuous hot injection method is a simple,efficient and versatile method for the synthesis of upconversion nanoparticles.（2）We demonstrate a layer by layer process to synthesize upconversion nanoparticles（UCNPs）NaYF₄:Yb,Tm@NaYF₄@mesoporous SiO₂（mSiO₂）core-shell nanoparticles decorated with CdS nanoparticles.The size and morphology of the as-prepared products have been investigated carefully,which show that the UCNPs and CdS nanoparticles with ca.50 and 5 nm in diameter,respectively,and the mesoporous silica layer with 10 nm in thickness.XRD and nitrogen adsorption desorption（BET）found that UCNPs@mSiO₂/CdS had good crystallinity and huge specific surface area（760 m2g-1）.UV-Vis absorption spectra and fluorescence spectra of the as-prepared UCNPs@mSiO₂/CdS nanoparticles show that the fluorescence emissions（380,451 and 470 nm）have been greatly quenched via fluorescence resonance energy transfer process from the UCNPs nanoparticles（donors）to the CdS nanoparticles（acceptors）.CdS nanoparticles were activated by the UCNPs to produce photo-generated ·OH radicals under irradiation of infrared（IR）light.Photodegradation towards RhB dyes was studied to demonstrate the active free radical generation efficiency for the as-prepared UCNPs@mSiO₂/CdS nanoparticles under irradiation of near infrared light.The as-designed nanostructures of UCNPs@mSiO₂/CdS nanoparticles show excellent photodegradation performance on photodegradation towards RhB under irradiation of infrared light.At the same time,we evaluated the photodynamic therapy effect of UCNPs@mSiO₂/CdS with Hela cancer cells at 980 nm near infrared light.The experimental results showed that the prepared photodynamic therapy system had good photodynamic therapy effect.