(627c) Microengineered, Photodegradable Hydrogels for the Selective Capture and Release of Mammalian Cells

The capture and characterization of rare circulating tumor cells (CTCs) presents a unique opportunity in the development of personalized medicine and cancer treatment. Recently, microfluidic devices have been presented that sense and capture CTCs from complex biologic fluids, such as whole blood. Initially, high surface area post arrays were introduced,¹ followed by the design and implementation of a microvortex-generating herringbone channel with improved capture efficiency.² Currently, these devices are being applied clinically to diagnose and monitor cancer progression.³ However, a significant limitation of CTC capture technologies is the inability to recover selectively captured cells in a viable state for downstream analysis. A few approaches have been proposed to mitigate this limitation, such as reversible alginate capture coatings⁴ or thermally responsive capture surfaces.⁵ These approaches, however, cannot be applied to the complex geometries needed for efficient cell capture and do not enable selective, individual cell release for on-chip purification and downstream analysis. Here, we present a photopolymerized, poly(ethylene glycol) (PEG) based hydrogel that can be photodegraded post-fabrication for the selective capture and release of cells from complex microfluidic geometries. To fabricate the microfluidic capture surfaces, a ~25 µm tall polydimethylsiloxane (PDMS) channel (straight or herringbone) was filled with a gel-forming monomer solution containing photodegradable PEG diacrylate (PEGdiPDA),⁶ which was then photopolymerized using visible light. After the gel was formed, the initial PDMS mold was removed and the gel was capped with a ~75 µm tall PDMS straight channel. Then, the PEG gel was functionalized with capture antibodies. A suspension of A549 human lung carcinoma cells were flowed through the microfluidic channel and captured on the surface. Herringbone channels captured cells from media with a higher efficiency than straight channels. In each case, cells were released after capture by irradiated the gel with UV light under flow. The UV light degraded the gel completely and liberated the cells from the capture device so that they could be recovered downstream. In this manner, the PEG capture devices are employed for improved capture and purity of mammalian cells and may provide an avenue for earlier cancer detection as well as better diagnostics and prognostics.

References

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