reported a specially designed three-dimensional microfilter consisting of two layers of parylene membrane with pores and gaps to filter out small cells, the relatively larger tumor cells are left behind. liquid biopsy, circulating tumor cells, microfluidic, graphene oxide, surface modification 1. Introduction Cancer is usually a complex FB23-2 disease which involves abnormal growth of cells through a multi-step evolutionary process. It has been characterized as a heterogeneous disease consisting of many different subtypes with the potential to invade or spread to FB23-2 distant parts of the body. Almost all cancers can metastasize, and it has been estimated that 80% of cancer-related deaths are due to metastases [1]. The metastatic ability make malignancy a leading cause of death worldwide. Globally, in 2012, there were 14.1 million new cancer cases and 8.2 million cancer-related deaths. The World Health Business estimated that, by 2035, the world could observe 24 million new malignancy cases and 14. 5 million FB23-2 cancer-related deaths a 12 months [2,3]. The early detection of patients with breast, colorectal, gastric, and liver cancer, has a better prognosis and increased life expectancy [4]. Recently, liquid biopsy, including CTCs, cell-free DNA (cfDNA) and extracellular vehicles (EVs), has drawn more attention due to its minimal-invasiveness and bio-informatics affluence [5]. Compared with traditional solid biopsy, which cannot always be performed to determine tumor dynamics, liquid biopsy has notable advantages in its noninvasive modality [6,7,8]. Moreover, studies have found the changes in CTC figures before and after chemotherapy and during follow-up might predict malignancy relapse [9,10]. Ried et al. reported that CTCs were detected in patients with high risk of developing cancer. In this case, different type of malignancy patients with a useful screening tool for the early detection of malignancy in patients with a higher risk profile [11]. These suggest that CTCs are one of the important indicators for early detection, monitoring malignancy progression and evaluating treatment effectiveness. Despite CTCs encouraging clinical application, their rarity makes the detection extremely challenging. In 7.5 mL of blood from cancer patient, probably only 1 1 to 10 CTCs exisits [12], along with billions of red blood cells (RBCs) and millions of white blood cells (WBCs). Since the discovery of CTCs in 1869 [13], a large number of techniques have been developed to analysis them. Most of the strategies include the isolation of targets from body fluids and followed by characterization and analysis of the isolated targeted cells. Here, we elucidate the physical and biological properties of CTCs. We evaluate different microfluidic-based technologies for CTCs isolation and detection. Besides, we put emphasis on how integrating nanobiological interface to microfluidic systems could improve specificity and sensitivity in CTCs enumeration and analysis. We also discuss the importance of a standardized approach in promoting the transition of basic bench-side technologies into clinical applications. 2. Circulating Tumor Cells (CTCs) 2.1. Formation of CTCs Malignancy metastasis is usually a multi-step, stochastic process through which invasive tumor cells detach from the primary tumor and enter the blood circulation to invade distant tissue sites. Two biological mechanisms are involved in releasing CTCs from tumor site into blood stream, they are epithelial-mesenchymal transition (EMT) and non-EMT mediated invasion. The metastatic potential of tumor cells may be entirely shaped at the primary tumor site, or also by signaling events occurring during the intravascular transit of tumor cells. Tumor cells process local invasion, followed by intravasation to enter the circulatory system [14]. When cancerous cells migrate in the blood circulation, they may interact with platelets, lymphocytes, and other blood components, and eventually reach their distant organs and begin proliferation. Though the process of metastasis has been more familiarized, the mechanism governing organ-specific metastasis is still poorly comprehended [15,16]. 2.2. Biological Properties of CTCs-Heterogeneity of CTCs CTCs are rare cell species present in peripheral blood and appear in circulatory system during malignancy metastasis. CTCs are malignancy cells discovered in malignancy patients peripheral blood that successfully escape from the primary tumor site and lead to metastases, these CTCs struggle to survive Tal1 in the bloodstream, and have potential for seeding metastases [17,18]. They must survive a variety of, epithelial cell normally adhere to the extracellular matrix via integrin and this is essential for cell survival. In the absence of such an anchor,.