NanoVelcro rare-cell assays for detection and characterization of circulating tumor cells

Abstract

Circulating tumor cells (CTCs) are cancer cells shredded from either a primary tumor or a metastatic site and circulate in the blood as the potential cellular origin of metastasis. By detecting and analyzing CTCs, we will be able to noninvasively monitor disease progression in individual cancer patients and obtain insightful information for assessing disease status, thus realizing the concept of "tumor liquid biopsy". However, it is technically challenging to identify CTCs in patient blood samples because of the extremely low abundance of CTCs among a large number of hematologic cells. In order to address this challenge, our research team at UCLA pioneered a unique concept of "NanoVelcro" cell-affinity substrates, in which CTC capture agent-coated nanostructured substrates were utilized to immobilize CTCs with remarkable efficiency. Four generations of NanoVelcro CTC assays have been developed over the past decade for a variety of clinical utilities. The 1st-gen NanoVelcro Chips, composed of a silicon nanowire substrate (SiNS) and an overlaid microfluidic chaotic mixer, were created for CTC enumeration. The 2nd-gen NanoVelcro Chips (i.e., NanoVelcro-LMD), based on polymer nanosubstrates, were developed for single-CTC isolation in conjunction with the use of the laser microdissection (LMD) technique. By grafting thermoresponsive polymer brushes onto SiNS, the 3rd-gen Thermoresponsive NanoVelcro Chips have demonstrated the capture and release of CTCs at 37 and 4 °C respectively, thereby allowing for rapid CTC purification while maintaining cell viability and molecular integrity. Fabricated with boronic acid-grafted conducting polymer-based nanomaterial on chip surface, the 4th-gen NanoVelcro Chips (Sweet chip) were able to purify CTCs with well-preserved RNA transcripts, which could be used for downstream analysis of several cancer specific RNA biomarkers. In this review article, we will summarize the development of the four generations of NanoVelcro CTC assays, and the clinical applications of each generation of devices.

Liquid Biopsies in Cancer Diagnosis, Monitoring, and Prognosis

“…Alternative approaches, preferable because they include EpCAM low and EpCAMpopulations, leaving CTCs unstained, involve the immunomagnetic depletion of CD45 + leukocytes [114]. Other EpCAM-based strategies include microfluidic platforms such as the CTC-Chip [115] and the NanoVelcro system [116], and devices for the in vivo capture of CTCs directly into patients' veins, such as the GmbH CellCollector device [117].…”

Aqueous Palladium‐Catalyzed Direct Arylation Polymerization of 2‐Bromothiophene Derivatives

“…Conjugated polyelectrolytes have been utilized in applications including chemical/biosensing, [ 30–32 ] cell imaging, [ 33–35 ] and disease diagnosis/therapy. [ 36,37 ] Their synthesis comprises the preparation of organic‐soluble conjugated polymers followed by post‐functionalization. A typical post‐functionalization reaction is the nucleophilic substitution of an alkyl‐bromide with amines to afford ammonium salts, which render the resultant conjugated polyelectrolytes aqueous soluble.…”

The Use of Microfluidic Technology for Cancer Applications and Liquid Biopsy

“…This chip consists of two parts, the bottom substrate is a brush-like silicon nanowire coated with an anti-EpCAM antibody, and a PDMS herringbone structure on the top layer that generates the chaotic flow, which increases the contact chance between CTCs and the antibody substrate at the bottom. After the capture of CTCs, Cytokeratin/CD45/DAPI staining is performed to identify putative CTCs on the chip ( Figure 2 a) [ 63 ].…”

“…( a ) The graphic illustration of the NanoVelcro CTC chip of four generations. Reprinted with permission from the authors of [ 63 ]; ( b ) Schematic of the CTC-iChip. The schematic of the workflow begins from the red blood cell filtration, inertial focusing of CTCs, and white blood cells, followed by the removal of white blood cells under a magnetic field.…”