Nanotextured polymer substrates show enhanced cancer cell isolation and cell culture.

Detection of circulating tumor cells (CTCs) in the early stages of cancer is a great challenge because of their exceedingly small concentration. There are only a few approaches sensitive enough to differentiate tumor cells from the plethora of other cells in a sample like blood. In order to detect CTCs, several antibodies and aptamers have already shown high affinity. Nanotexture can be used to mimic basement membrane to further enhance this affinity. This article reports an approach to fabricate nanotextured polydimethylsiloxane (PDMS) substrates using micro reactive ion etching (micro-RIE). Three recipes were used to prepare nanotextured PDMS using oxygen and carbon tetrafluoride. Micro-RIE provided better control on surface properties. Nanotexturing improved the affinity of PDMS surfaces to capture cancer cells using surface immobilized aptamers against cell membrane overexpressed with epidermal growth factor receptors. In all cases, nanotexture of PDMS increased the effective surface area by creating nanoscale roughness on the surface. Nanotexture also enhanced the growth rate of cultured cells compared to plain surfaces. A comparison among the three nanotextured surfaces demonstrated an almost linear relationship between the surface roughness and density of captured tumor cells. The nanotextured PDMS mimicked biophysical environments for cells to grow faster. This can have many implications in microfluidic platforms used for cell handling.

Nucleic acid aptamers in cancer research, diagnosis and therapy.

Aptamers are single-stranded DNA or RNA oligomers, identified from a random sequence pool, with the ability to form unique and versatile tertiary structures that bind to cognate molecules with superior specificity. Their small size, excellent chemical stability and low immunogenicity enable them to rival antibodies in cancer imaging and therapy applications. Their facile chemical synthesis, versatility in structural design and engineering, and the ability for site-specific modifications with functional moieties make aptamers excellent recognition motifs for cancer biomarker discovery and detection. Moreover, aptamers can be selected or engineered to regulate cancer protein functions, as well as to guide anti-cancer drug design or screening. This review summarizes their applications in cancer, including cancer biomarker discovery and detection, cancer imaging, cancer therapy, and anti-cancer drug discovery. Although relevant applications are relatively new, the significant progress achieved has demonstrated that aptamers can be promising players in cancer research.

Capture, isolation and release of cancer cells with aptamer-functionalized glass bead array.

Early detection and isolation of circulating tumor cells (CTC) can enable better prognosis for cancer patients. A Hele-Shaw device with aptamer functionalized glass beads is designed, modeled, and fabricated to efficiently isolate cancer cells from a cellular mixture. The glass beads are functionalized with anti-epidermal growth factor receptor (EGFR) aptamer and sit in ordered array of pits in polydimethylsiloxane (PDMS) channel. A PDMS encapsulation is then used to cover the channel and to flow through cell solution. The beads capture cancer cells from flowing solution depicting high selectivity. The cell-bound glass beads are then re-suspended from the device surface followed by the release of 92% cells from glass beads using combination of soft shaking and anti-sense RNA. This approach ensures that the cells remain in native state and undisturbed during capture, isolation and elution for post-analysis. The use of highly selective anti-EGFR aptamer with the glass beads in an array and subsequent release of cells with antisense molecules provide multiple levels of binding and release opportunities that can help in defining new classes of CTC enumeration devices.

Nanotextured substrates with immobilized aptamers for cancer cell isolation and cytology.

BACKGROUND: The detection of a small number of circulating tumor cells (CTCs) is important, especially in the early stages of cancer. Small numbers of CTCs are hard to detect, because very few approaches are sensitive enough to differentiate these from the pool of other cells. Improving the affinity of a selective, surface-functionalized molecule is important given the scarcity of CTCs in vivo. There are several proteins and aptamers that provide such high affinity; however, using surface nanotexturing increases this affinity even further. METHODS: The authors report an approach to improve the affinity of tumor cell capture by using novel aptamers against cell membrane overexpressed epidermal growth factor receptors (EGFRs) on a nanotextured polydimethylsiloxane (PDMS) substrate. Surface-immobilized aptamers were used to specifically capture tumor cells from physiologic samples. RESULTS: The nanotexturing of PDMS increased surface roughness at the nanoscale. This increased the effective surface area and resulted in a significantly higher degree of surface functionalization. The phenomenon resulted in increased density of immobilized EGFR-specific RNA aptamer molecules and provided significantly higher efficiency to capture cancer cells from a mixture. The data indicated that CTCs could be captured and enriched, leading to higher yield yet higher background. CONCLUSIONS: A comparison between glass slides, plain PDMS, and nanotextured PDMS functionalized with aptamers demonstrated that a 2-fold approach of using aptamers on nanotextured PDMS can be important for cancer cytology devices, and especially for the idea of a "lab-on-chip," toward higher yield in capture efficiency.