Wu et al. J Nanobiotechnol (2018) 16:65 https://doi.org/10.1186/s12951-018-0390-x Journal of Nanobiotechnology RESEARCH Open Access A micro‑/nano‑chip and quantum dots‑based 3D cytosensor for quantitative analysis of circulating tumor cells Xuan Wu1, Tingyu Xiao1, Zhang Luo1, Rongxiang He1, Yiping Cao1*, Zhenzhong Guo2*, Weiying Zhang1* and Yong Chen1,3 Abstract Background: Due to the high transfer ability of cancer cell, cancer has been regarded as a world-wide high mortality disease. Quantitative analysis of circulating tumor cells (CTCs) can provide some valuable clinical information that is particularly critical for cancer diagnosis and treatment. Along with the rapid development of micro-/nano-fabrication technique, the three-dimensional (3D) bionic interface-based analysis method has become a hot research topic in the area of nanotechnology and life science. Micro-/nano-structure-based devices have been identifed as being one of the easiest and most efective techniques for CTCs capture applications. Methods: We demonstrated an electrospun nanofbers-deposited nickel (Ni) micropillars-based cytosensor for electrochemical detection of CTCs. Breast cancer cell line with rich EpCAM expression (MCF7) were selected as model CTCs. The ultra-long poly (lactic-co-glycolic acid) (PLGA) nanofbers were frstly-crosswise stacked onto the surface of Ni micropillars by electrospinning to construct a 3D bionic interface for capturing EpCAM-expressing CTCs, following immuno-recognition with quantum dots functionalized anti-EpCAM antibody (QDs-Ab) and forming immunocom- plexes on the micro-/nano-chip. Results: The Ni micropillars in the longitudinal direction not only play a certain electrical conductivity in the electro- chemical detection, but also its special structure improves the efciency of cell capture. The cross-aligned nanofbers could simulate the extracellular matrix to provide a good microenvironment which is better for cell adhesion and 2 physiological functions. Bioprobe containing quantum dots will release ­Cd + in the process of acid dissolution, result- ing in a change in current. Beneath favourable conditions, the suggested 3D cytosensor demonstrated high sensitivity 1 5 1 1 with a broad range of ­10 –10 cells mL− and a detection limit of 8 cells mL− . Conclusions: We constructed a novel 3D electrochemical cytosensor based on Ni micropillars, PLGA electrospun nanofbers and quantum dots bioprobe, which could be used to highly sensitive and selective analysis of CTCs. More signifcantly, the 3D cytosensor can efciently identify CTCs from whole blood, which suggested the potential appli- cations of our technique for the clinical diagnosis and therapeutic monitoring of cancers. Keywords: Micropillar, Nanofber, Quantum dots, Three-dimensional cytosensor, Circulating tumor cells *Correspondence: [email protected]; [email protected]; [email protected] 1 Institute for Interdisciplinary Research, Key Laboratory of Optoelectronic Chemical Materials and Devices of Ministry of Education, Jianghan University, Wuhan 430056, People’s Republic of China 2 Hubei Province Key Laboratory of Occupational Hazard Identifcation and Control, Medical College, Wuhan University of Science and Technology, Wuhan 430065, People’s Republic of China Full list of author information is available at the end of the article © The Author(s) 2018. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creat​iveco​mmons​.org/licen​ses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creat​iveco​mmons​.org/ publi​cdoma​in/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Wu et al. J Nanobiotechnol (2018) 16:65 Page 2 of 9 Background benefcial for cellular flopodia climbing, helping cell Due to the high transfer ability of cancer cell, cancer adhesion and growth. has been regarded as a world-wide high mortality dis- Herein, we demonstrated an electrospun nanofbers- ease. It is reported that the increase amount of circulat- deposited nickel (Ni) micropillars-based cytosensor for ing tumor cells (CTCs) emerged in the peripheral blood electrochemical detection of CTCs. Breast cancer cell will result in the cancer metastasis and relapse [1–3]. line with rich EpCAM expression (MCF7) were selected Quantitative analysis of CTCs can provide some valu- as model CTCs. Te ultra-long poly (lactic-co-glycolic able clinical information that is particularly critical for acid) (PLGA) nanofbers were frstly-crosswise stacked cancer diagnosis and treatment. However, the number onto the surface of Ni micropillars by electrospin- of CTCs in the whole bloodstream is usually very low (a ning to construct a 3D bionic interface for capturing few to hundreds per milliliter), quantifcation of CTCs EpCAM-expressing CTCs, following immuno-recog- to assess cancer metastasis faces a huge challenge [4, 5]. nition with quantum dots functionalized anti-EpCAM In the past few years, various approaches have already antibody (QDs-Ab) and forming immunocomplexes on been presented to enrich/count CTCs, including fow the micro-/nano-chip. Te signal current response was cytometry [6], immunemagnetic beads [7], microfu- achieved by electrochemical assay of the released cad- idic devices [8–10] and so on. Tough those developed mium ion (Cd2+) after acid-dissolving QDs from immu- methods have been greatly accepted, their sensitivity is nocomplexes. Using this 3D substrate, we dependably still a major faw. Terefore, developing a highly sensi- gathered cancer cells from synthetic CTC blood samples. tive CTCs assay method is urgent for predicting cancer Te integration of crossed PLGA nanofbers and conduc- metastasis and relapse. tive Ni micropillars not only provide an excellent micro- Along with the rapid development of micro-/nano- environment for CTCs capture, preventing CTCs from fabrication technique, the three-dimensional (3D) fowing away in the process of rinse and increasing the bionic interface-based analysis method has become a capture efciency of target cell, but also greatly amplify hot research topic in the area of nanotechnology and the current signal, improving detection sensitivity. Cou- life science. 3D bionic interface, usually displayed in pling with 3D micro-/nano-structure, the proposed bio- the form of micro-/nano-structure (e.g., micropillars sensing platform exhibited great potential for on-site [11], nanofbers [12], nanotubes [13, 14] and nanopil- monitoring cancer progress. We expect that this platform lars [15]), are endowed with good biocompatibility and could be applied in isolating rare populations of cells that large specifc surface area [16–19]. Simultaneously, cannot be easily realized using existing technologies, as combined with the nanoscale characters implanted in well as in early diagnosis and longitudinal monitoring of cellular surface elements (e.g., microvilli and flopodia) cancer in the clinic. and extracellular matrix (ECM) scafolds, 3D bionic interface provides a comfortable microenvironment Methods where cell capture and rare cell detection could be Chemicals achieved. Furthermore, functional nanomaterials have Indium tin oxide (ITO) glasses with a resistance of 10 Ω been introduced into 3D bionic interface, signifcantly were purchased from South of China Xiangcheng Tech- diversifying the detection methods and enhancing the nology. AZ9260 photoresists and the developer AZ- detection sensitivity. Wang’s group has ever reported 300MIF were purchased from AZ Electronic Materials a novel silicon nanopillar coated with anti-EpCAM- Corp. (Philadelphia, PA). Bovine serum albumin (BSA), based biosensing platform for CTCs capture and subse- fuorescein diacetate (FDA) and streptavidin (SA) were quent sensitive assay [20]. Our group also developed a purchased from Sigma (St. Louis, MO). A quantum dots graphene-modifed 3D microchip-based supersandwich (Qdot) 585 CdSe@ZnS antibody labeling kit was pur- cytosensor for quantitative immunoassay of CTCs [21]. chased from Life Technologies. DMEM medium for cell Nanostructure-based devices have been identifed culture was obtained from GIBCO. Biotinylated goat as being one of the easiest and most efective tech- IgG polyclonal anti-EpCAM antibody was obtained from niques for CTC capture applications. Electrospinning R&D Systems (Minneapolis, MN). Pan-Cytokeratin anti- is an easy and universal nanofabrication technique, by body (C11) Alexa Fluor ® 488 and CD45 Antibody (2D-1) which a variety of soluble and fusible polymers could PE were purchased from Santa Cruz Biotechnology. Can- be transferred to form the desired nanofbers with cer patient serum was provided by Zhongnan Hospital of steerable diameters from a few nanometers to several Wuhan University (Wuhan, China). All other chemicals micrometers [20, 22–24]. Te prepared nanofbers used in this study were analytical-grade. All solutions are coated onto the 3D bionic interface to simulate an were prepared with ultrapure water obtained from a Mil- excellent porous microenvironment, which is especially lipore water-purifcation system (Millipore, USA). Wu et al. J Nanobiotechnol (2018) 16:65 Page 3 of 9 Cell culture electroplating with the current density of 0.05 A/cm2 for Te MCF7 cells were cultured in DMEM, which was 5 min at 50 °C,