Multifunctional Up-conversion Nanoprobes Are Used For The Fluorescence Imaging Of Tumor Markers And The Integrated Research Of Diagnosis And Treatment

Rare earth doped upconversion nanoparticles?UCNPs?are a class of new luminescent materials that emit ultraviolet-visible region fluorescence under near-infrared light excitation.Compared with traditional organic dyes,quantum dots and other luminescent materials,Currently,researchers are involved in the synthesis,surface modification,bio-functionalization,biosafety of UCNPs and their application in the cell labeling,in vivo imaging,multi-modal imaging,photodynamic therapy,and imaging-guided cancer therapy.UCNPs have been successfully applied to cell tracing,lymph and angiography imaging,small animal imaging,and tumor targeted imaging.For the treatment of tumors,UCNPs are modified with mesoporous silica and polymer to load anti-tumor drugs,photosensitizers and interfering RNA to achieve the chemotherapy,photodynamic therapy,photothermal therapy,immunotherapy and gene therapy of tumor.In this experiment,multi-color sandwich-upconversion nanoparticles were synthesized by co-doping multi-activators via the seed growth method to confine the luminescent layer in an intermediate layer with a thickness of about 2 nm to shorten the luminescence resonance energy transfer distance between UCNPs and the surface ligand.Thus,with the merits of the improved energy transfer efficiency,the prepared UCNPs nanoprobes have been successfully realized the fluorescence imaging of hydroxyl radicals,hydrogen ions and calcium ions in cancer cells and tumor tissues.Moreover,coated with the ultra-thin silica layer,UCNPs-involved photodynamic nanoprobes have been developed and successfully induced cancer apoptosis and the growth inhibition of tumor tissue.The detailed research were as follows:?1?Detection and fluorescence imaging of hydroxyl radicals in cancer cells and tumor tissues:Hydroxyl radicals is an important reactive oxygen species in the human body.It is recognized to be an important tumor marker in cancer cells and tumor tissues.In this paper,a dual-activator codoped multi-color UCNPs have been prepared.Based on the energy transfer and sensitization between luminescent rare earth ions,the fluorescence intensity and lifetime were enhanced by 46 and 2.6 times,respectively,which is quite importance to the fluorescence imaging of deep tissue in animals.The prepared multi-shells UCNPs was competent in monitoring the subtle fluctuation of hydroxyl radical and achieved its fluorescence bioimaging in small animals with inflammation and tumor.?2?Simultaneous detection and fluorescence imaging of[Ca²⁺]_i and[H⁺]_i in cancer cells and tumor tissues:[Ca²⁺]_i and[H⁺]_i in cancer cells are closely related,and their abnormal levels can cause cell dysfunction and are easily accompanied by disease.Therefore,simultaneous tracking of changes in[Ca²⁺]_i and[H⁺]_i in cells allows for more accurate study of complex biological processes.The prepared dual-activators codoped multi-color UCNPs obtained three different fluorescence?peaking at 480 nm,545 nm,and 650 nm?.Based on the luminescence resonance energy transfer,the fluorescent probes,Fluo-4 and SNARF-4Ffor specifically recognizing[Ca²⁺]_i and[H⁺]_i respectively,quenched the blue and green fluorescence,and developed an UCNPs nanoprobes.The experimental results showed that the decrease of intracellular pH would induce the release of calcium ions from the intracellular stores and weaken its binding ability to the binding protein,resulting in an increase in[Ca²⁺]_i concentration.An increase in intracellular[Ca²⁺]_i concentration induces the release of HCO₃^-,altering the activity of the Na⁺/H⁺exchange channel and the anion exchange channel,resulting in a decrease in intracellular pH.Therefore,the construction of mulit-color UCNPs can simultaneously track the changes of various markers in cells,and has important guiding significance for the prevention and detection of related diseases.?3?Upconversion nano-fluorescence probes for photodynamic therapy of cancer cells and tumor tissues:As an energy donor,the UCNPs can effectively excite the photosensitizer,generate active oxygen,exert photodynamic effects,improve the tissue penetrating ability of the photosensitizer,and reduce autofluorescence.In order to effectively shorten the energy transfer distance between the UCNPs and the photosensitizer and improve the energy transfer efficiency,ultrathin silicon layer?thickness 7.5-9.0 nm?was coated on the surface of the UCNPs.At the same time,PEG-FA is modified on the surface of the probe to increase the biocompatibility of the probe and the targeting of tumor tissues,thereby achieving efficient photodynamic therapy of cancer cells and tumors.The experimental results show that the constructed up-conversion-photodynamic therapy nanoprobe can be distributed in the cytoplasm of cancer cells through receptor-mediated endocytosis.Under the excitation of near-infrared light,the UCNPs could activate photosensitizer molecules to produce reactive oxygen species,induce tumor cell apoptosis,and effectively inhibit tumor growth.