Layer-by-layer functionalized nanotube arrays: A versatile microfluidic platform for biodetection

We demonstrate the layer-by-layer (LbL) assembly of polyelectrolyte multilayers (PEM) on three-dimensional nanofiber scaffolds. High porosity (99%) aligned carbon nanotube (CNT) arrays are photolithographically patterned into elements that act as textured scaffolds for the creation of functionally coated (nano)porous materials. Nanometer-scale bilayers of poly(allylamine hydrochloride)/poly(styrene sulfonate) (PAH/SPS) are formed conformally on the individual nanotubes by repeated deposition from aqueous solution in microfluidic channels. Computational and experimental results show that the LbL deposition is dominated by the diffusive transport of the polymeric constituents, and we use this understanding to demonstrate spatial tailoring on the patterned nanoporous elements. A proof-of-principle application, microfluidic bioparticle capture using N-hydroxysuccinimide-biotin binding for the isolation of prostate-specific antigen (PSA), is demonstrated.National Science Foundation (U.S.) (Award DMR-0819762

RNA Sequencing of Pancreatic Circulating Tumour Cells Implicates WNT Signaling in Metastasis

Circulating tumour cells (CTCs) shed into blood from primary cancers include putative precursors that initiate distal metastases. While these cells are extraordinarily rare, they may identify cellular pathways contributing to the blood-borne dissemination of cancer. Here, we adapted a microfluidic device for efficient capture of CTCs from an endogenous mouse pancreatic cancer model and subjected CTCs to single molecule RNA sequencing, identifying Wnt2 as a candidate gene enriched in CTCs. Expression of Wnt2 in pancreatic cancer cells suppresses anoikis, enhances anchorage-independent sphere formation, and increases metastatic propensity in vivo. This effect is correlated with fibronectin upregulation and suppressed by inhibition of Map3k7 (Tak1) kinase. In humans, formation of non-adherent tumour spheres by pancreatic cancer cells is associated with upregulation of multiple Wnt genes, and pancreatic CTCs revealed enrichment for Wnt signaling in 5 of 11 cases. Thus, molecular analysis of CTCs may identify candidate therapeutic targets to prevent the distal spread of cancer

Preservation of Mouse Sperm by Convective Drying and Storing in 3-O-Methyl-D-Glucose

With the fast advancement in the genetics and bio-medical fields, the vast number of valuable transgenic and rare genetic mouse models need to be preserved. Preservation of mouse sperm by convective drying and subsequent storing at above freezing temperatures could dramatically reduce the cost and facilitate shipping. Mouse sperm were convectively dried under nitrogen gas in the Na-EGTA solution containing 100 mmol/L 3-O-methyl-D-glucose and stored in LiCl sorption jars (Relative Humidity, RH, 12%) at 4°C and 22°C for up to one year. The functionality of these sperm samples after storage was tested by intracytoplasmic injection into mouse oocytes. The percentages of blastocysts produced from sperm stored at 4°C for 1, 2, 3, 6, and 12 months were 62.6%, 53.4%, 39.6%, 33.3%, and 30.4%, respectively, while those stored at 22°C for 1, 2, and 3 months were 28.8%, 26.6%, and 12.2%, respectively. Transfer of 38 two- to four-cell embryos from sperm stored at 4°C for 1 year produced two live pups while 59 two- to four-cell embryos from sperm stored at 22°C for 3 months also produced two live pups. Although all the pups looked healthy at 3 weeks of age, normality of offspring produced using convectively dried sperm needs further investigation. The percentages of blastocyst from sperm stored in the higher relative humidity conditions of NaBr and MgCl2 jars and driest condition of P2O5 jars at 4°C and 22°C were all lower. A simple method of mouse sperm preservation is demonstrated. Three-O-methyl-D-glucose, a metabolically inactive derivative of glucose, offers significant protection for dried mouse sperm at above freezing temperatures without the need for poration of cell membrane

Brain Tumor Cells in Circulation Are Enriched for Mesenchymal Gene Expression

Glioblastoma (GBM) is a highly aggressive brain cancer characterized by local invasion and angiogenic recruitment, yet metastatic dissemination is extremely rare. Here, we adapted a microfluidic device to deplete hematopoietic cells from blood specimens of patients with GBM, uncovering evidence of circulating brain tumor cells (CTCs). Staining and scoring criteria for GBM CTCs were first established using orthotopic patient-derived xenografts (PDX), and then applied clinically: CTCs were identified in at least one blood specimen from 13/33 patients (39%; 26/87 samples). Single GBM CTCs isolated from both patients and mouse PDX models demonstrated enrichment for mesenchymal over neural differentiation markers, compared with primary GBMs. Within primary GBMs, RNA-in-situ hybridization identifies a subpopulation of highly migratory mesenchymal tumor cells, and in a rare patient with disseminated GBM, systemic lesions were exclusively mesenchymal. Thus, a mesenchymal subset of GBM cells invades into the vasculature, and may proliferate outside the brain

HER2 expression identifies dynamic functional states within circulating breast cancer cells

Circulating tumor cells (CTCs) in women with advanced estrogen receptor-positive/HER2-negative breast cancer acquire a HER2-positive subpopulation following multiple courses of therapy1,2. In contrast to HER2-amplified primary breast cancer, which is highly sensitive to HER2-targeted therapy, the clinical significance of acquired HER2 heterogeneity during the evolution of metastatic breast cancer is unknown. Here, we analyzed CTCs from 19 ER+/HER2− patients, 84% of whom had acquired CTCs expressing HER2. Cultured CTCs maintain discrete HER2+ and HER2− subpopulations: HER2+ CTCs are more proliferative but not addicted to HER2, consistent with activation of multiple signaling pathways. HER2− CTCs show activation of Notch and DNA damage pathways, exhibiting resistance to cytotoxic chemotherapy, but sensitivity to Notch inhibition. HER2+ and HER2− CTCs interconvert spontaneously, with cells of one phenotype producing daughters of the opposite within four cell doublings. While HER2+ and HER2− CTCs have comparable tumor initiating potential, differential proliferation favors the HER2+ state, while oxidative stress or cytotoxic chemotherapy enhances transition to the HER2− phenotype. Simultaneous treatment with paclitaxel and Notch inhibitors achieves sustained suppression of tumorigenesis in orthotopic CTC-derived tumor models. Together, these results point to distinct yet interconverting phenotypes within patient-derived CTCs, contributing to progression of breast cancer and acquisition of drug resistance

Antibody-Functionalized Fluid-Permeable Surfaces for Rolling Cell Capture at High Flow Rates

AbstractAdhesion-based cell capture on surfaces in microfluidic devices forms the basis of numerous biomedical diagnostics and in vitro assays. However, the performance of these platforms is partly limited by interfacial phenomena that occur at low Reynolds numbers. In contrast, cell homing to porous vasculature is highly effective in vivo during inflammation, stem cell trafficking, and cancer metastasis. Here, we show that a porous, fluid-permeable surface functionalized with cell-specific antibodies promotes efficient and selective cell capture in vitro. This architecture is advantageous due to enhanced transport as streamlines are diverted toward the surface. Moreover, specific cell-surface interactions are promoted due to reduced shear, allowing gentle cell rolling and arrest. Together, these synergistic effects enable highly effective cell capture at flow rates more than an order of magnitude larger than those provided by existing devices with solid surfaces