High Sensitivity Detection Of Lymph Node Metastasis With Nearinfrared Upconversion Luminescent Nanoprobes

The high incidence of breast cancer has become one of the significant killers of female health,however,the occurrence of lymphatic metastasis is even worse for patients.Nevertheless,the existing diagnostic methods,including palpation,biopsy.ultrasound,X-ray molybdenum target,CT,MRI and PET,can still not timely,effectively or non-invasive detect lymphatic metastasis of breast cancer.Benefiting from the development and integration of nanotechnology and imaging technology,imaging nanoprobes such as magnetic nanoprobes,radioactive nanoprobes and fluorescent nanoprobes have been widely used in cancer diagnosis,treatment and therapeutic effect monitoring.Although the development of these probes has enriched the application of single imaging,and also have been used in detection and treatment of metastatic lymph nodes,there are still some limitations in sensitivity,resolution and specificity.Therefore,the nanoprobes for lymphatic metastasis detection need to be further developed.Rare earth up-conversion nanomaterials have attracted much attention because of their ability to absorb low-energy photons and emit high-energy photons,especially,they can convert near-infrared light into short-wavelength light.Compared with traditional down-conversion nanomaterials,rare earth up-conversion nanomaterials with narrow emission band,adjustable emission peak position,high optical stability,less tissue damage,high penetration ability,low background and high imaging sensitivity have become one of the most potential nanomaterials in biomedical imaging,and also opened up a new direction for the specific diagnosis of metastatic lymph nodes.Based on the current status of lymphatic metastasis detection and the excellent characteristics of rare earth upconversion nanomaterials,the upconversion nanoparticles NaGdF4:Yb,Tm,Ca@NaLuF4 with distinctive nearinfrared emission were prepared by thermal decomposition.The following studies revealed that the characteristic Tm dopant emission at 804 nm showed a penetration depth up to 7.7 mm through multi-layered mice skin tissues.To render the hydrophobic nanoparticles biocompatible and introduce functional groups,asymmetric polyethylene glycol(PEG)bearing a maleimide group at one end was used to replace the oleate ligand since the diphosphate group possesses a much higher binding affinity to Lu3+.And then the Herceptin antibody was conjugated to upconversion nanoparticles through a "click"reaction between the maleimide moiety of the PEG ligand on the particle surface and thiol residues from the partly reduced Herceptin antibody.Cell binding assays showed that the obtained nanoprobes had good specific targeting properties.The upconversion imaging results showed that the upconversion nanoprobes could specifically image the metastatic lymph nodes in mice using a lymphatic metastasis mice model.Moreover,the pharmacokinetics of the resulting nanoprobes were intensively studied through both upconversion luminescence imaging and SPECT imaging,and the results revealed that the surface conjugation of antibodies largely altered the pharmacokinetic behaviors and substantially prolonged the blood circulation time.In order to further investigate the behavior of nanoprobes in vivo,NP-IgG and NP-BSA nanoprobes were designed for exploring the effect of protein-modified nanoprobes on biodistribution,and thereby lay the foundation for the application of rare earth upconversion nanoprobes.