DNA-programmed Nanoparticles Polymerization For Ultrasensitive Capture And Detection Of Cancer Cells

So far,cancer has become the major disease that threat to human life.The early treatment is very helpful to cure cacer desease,thus the early detection of caner cells in cancer patients is very meaningful.However,because of the small volume of tumour in the early stage,the metastasis ability of cancer cells and the limited detection thechnology,the early diagnosis and treatment of cancer is still a big challenge.Recently,the emergence of nanomaterials based nanotechnology offers opportunities for the diagnosis and treatment of cancers in human body.Because of the unique physical and chemical properties,a variety of nanomaterials can be used for effective diagnosis and treatment of cancer.Inorganic nanocrystals,such as quantum dots(QDs),hold great promise as molecular imaging contrast agents because of their superior optical properties.However,the molecular imaging sensitivity of these probes is far from optimization due to the lack of efficient and general methods for molecularly engineering nanocrystal into effective bioprobes for signal-amplified imaging.Herein,we develop a strategy to boost the molecular imaging sensitivity of QDs over the limit by copolymerizing QDs and cell specific binding DNA aptamers into linear QD-aptamer polymers(QAPs)through DNA-programmed hybridization chain reaction.We show that the cancer cells treated with QAPs exhibit 10.5-fold enhancement of mean photoluminescence(PL)signal than those treated with QD-aptamer monomers(QAMs)at very low QD concentration(5 nM)because of multivalent binding and multi-QD-based signal amplification.In addition,the enhanced cell binding and imaging capacity of QAPs significantly improves imaging-based discrimination between different cancer cell types.We show that the discrimination factors of QAPs between CCRF-CEM and Ramos cells are 32.5,which is 6.1-fold higher than QAMs when the QDs'concentration is 20 nM.Finally,the QAPs were further applied for analysis of clinical samples and the mean PL intensity of cancer cells stained with QAPs is 4.3-fold higher than that of QAMs,indicating significant improvement in molecular imaging sensitivity.Circulating tumor cells(CTCs)are tumor cells circulatingin in the peripheral blood of patients with metastatic cancer.Circulating tumor cell enumeration and analysis has emerged as an important platform for cancer diagnosis and prognosis.A great challenge,however,is to efficiently capture 1-3000 CTCs per milliliter with high efficiency and purity from more than 10~9 per milliliter normal haemocytes in a rapid and high-throughput manner for accurate and sensitive CTC detection.Herein,a new class of DNA-templated magnetic nanoparticle-QDs-aptamer copolymers(MQAPs)is developed for rapid magnetic isolation of CTCs from human blood.These MQAPs are constructed through hybridization chain reaction to achieve amplified magnetic response,extraordinary specific binding selectivity for target cells over background cells,and ultra bright ensemble QDs PL for single cell detection.We show that compared magnetic nanoparticle-QDs-aptamer monmers(MQAMs),the magnetic particles'concentration in CEM cells treated with MQAPs is 2.75-fold higher,the mean PL intensity is 2.65-fold stronger and the cell binding affinity is 6.62-fold better.Also,MQAPs are free from nonspecific binding that would otherwise compromise the capture purity of target cells.As a result,facile isolation and enumeration of rare CTCs in blood samples could be achieved in 20 min with high capture efficiency approaching 80%.The capture purity is 84%,which is much higher than the U.S.Food and Drug Administration(FDA)-approved Cell Search system,whose capture purity is less than 1%.It opens up a new way to detect CTCs with high sensitivity and high accuracy.