Degradable Nanomaterials Applied For Microfluidic Circulating Tumor Cell Isolation And Release

Circulating tumor cells(CTCs)are cancer cells isolated from the peripheral blood of cancer patients.They shed from the primary tumors,extravasate the tissue base membrane and vascular wall,enter into the bloodstream,and finally invade the distant tissues or organs to form metastatic lesions.As so-called "liquid biopsy" for tumors,CTCs have great significance in the investigation and clinical applications of cancer metastasis:1.Liquid biopsy based on CTCs detection in the blood is much safer,more convenient and more sensitive.2.Detection of CTCs can help to predict the occurrence of cancer.Moreover,the enumeration variation of CTCs can prognose the state of cancer as well as the treatment.3.The analysis of DNA and RNA of CTCs can help to understand the phenotype as well as the heterogeneity of metastatic tumors,and also reveal the signaling pathways in the process of tumor metastasis.4.The molecular mechanisms of CTCs invasion,intravasation,circulation,extravasion,colonization and proliferation can be investigated by analyzing the protein secretion of CTCs.The study of CTCs will help to reveal the mechanism of cancer metastasis and achieve early diagnosis and monitoring of cancer.However,blood is a very complicated system,which contains huge numbers of normal blood cells(e.g.billions of red blood cells and milliions of white blood cells per mL blood)and various kinds of proteins,nucleic acids and saccharides.Meanwhile,CTCs are very rare,whose number is as low as tens or hundreds of CTCs in 1 mL cancer patient blood.Therefore,the isolation,enrichment and downstream analysis of CTCs are very challenging.As an emerging technique to manipulate a trace of liquid,Microfluidics can detect,analyze and manipulate specific biochemical processes at the micro/nano scale.The feature of Microfluidics lies on the network of microchannels and microstructures which are fabricated by MEMS(micro electro mechanical system)techniques.These fluid networks enable the integration,automation and miniaturization of all kinds of sample detection/analysis inside a microchip to fuction as a conventional biochemical laboratory.Moreover,Microfluidics can provide new insights for chemical and biological researches due to the different phenomenons/rules at the micro/nano scale compared to macro scale.Based on the above advantages,Microtluidics has been gradually applied in isolating CTCs.Although it is able to capture CTCs efficiently nowadays,Microfluidics still has lots of limits in CTC enrichment:1.CTCs are difficult to be released from the devices after isolation.2.It is difficult to ensure the fine cellular state on microchips.3.The purity of the isolated CTCs is very low.All these limits hinder the downstream biomedical analysis greatly.In this thesis,degradable nanomaterials are utilized to address the aforementioned drawbacks of Microfluidic CTC isolation due to their various funtions.Nanomaterials with good biocompatibility and degradable ability are employed in the microfluidic chips to realize the capture as well as release of CTCs with high efficiency,purity and viability for biochemical analysis.The main work of this thesis is briefly summarized here:1.We fabricated a new cancer cell capture/release microchip based on the self-sacrificed MnO2 nanofibers.Through electrospinning,lift-off and soft-lithography procedures,MnO2 nanofibers were successfully fabricated in microchannels to implement enrichment and detection of cancer cells in liquid samples.The microchip achieved effective capure performance because the Mn02 nanofiber net which mimiced the extra cellular matrix could lead to high capture ability with the help of a cancer cell-specific antibody bio-conjugation.Then,a friendly substrate-sacrificed method was worked out by chemically digesting MnO2-based substrate using low concentration of oxalic acid to effectively release cells with high cell viability.These released cells were renewable and could reach the final viability of about 93%after reculture of 2 days.2.We presented an acoustofluidic platform assisted by removable SiO2@gel size-amplifiers to retrieve CTCs with high purity and negligibly influence on cellular proliferation.Gelatin-coated 40-μm-size SiO2 microbeads with anti-EpCAM decoration were fabricated as so-called "removable size-amplifiers",which could specifically bond to EpCAM-positive CTCs to amplify physical difference between CTCs and normal blood cells,and could also be removed by enzymatic degradation to further improve the purity of the retrieved CTCs.With the help of this amplification-remove strategy,travelling surface acoustic wave(TSAW)generated in a laminar flow microchip was able to sort CTCs with high purity and viability.This removable size-amplifier aided acoustofluidic CTC purification strategy provided a high-purity and biocompatible platform that will benefit rigorous CTC biomedical researches greatly.