Optofluidic cell manipulation for a biological microbeam

Combined ion beam irradiation platform and 3D fluorescence microscope for cellular cancer research

To improve particle radiotherapy, we need a better understanding of the biology of radiation effects, particularly in heavy ion radiation therapy, where global responses are observed despite energy deposition in only a subset of cells. Here, we integrated a high-speed swept confocally-aligned planar excitation (SCAPE) microscope into a focused ion beam irradiation platform to allow real-time 3D structural and functional imaging of living biological samples during and after irradiation. We demonstrate dynamic imaging of the acute effects of irradiation on 3D cultures of U87 human glioblastoma cells, revealing characteristic changes in cellular movement and intracellular calcium signaling following ionizing irradiation.

Trapping and viability of swimming bacteria in an optoelectric trap

Non-contact manipulation methods capable of trapping and transporting swimming bacteria can significantly aid in chemotaxis studies. However, high swimming speed makes the trapping of these organisms an inherently challenging task. We demonstrate that an optoelectric technique, rapid electrokinetic patterning (REP), can effectively trap and manipulate Enterobacter aerogenes bacteria swimming at velocities greater than 20 μm s(-1). REP uses electro-orientation, laser-induced AC electrothermal flow, and particle-electrode interactions for capturing these cells. In contrast to trapping non-swimming bacteria and inert microspheres, we observe that electro-orientation is critical to the trapping of the swimming cells, since unaligned bacteria can swim faster than the radially inward electrothermal flow and escape the trap. By assessing the cell membrane integrity, we study the effect of REP trapping conditions, including optical radiation, laser-induced heating, and the electric field on cell viability. When applied individually, the optical radiation and laser-induced heating have negligible effect on cells. At the standard REP trapping conditions fewer than 2% of cells have a compromised membrane after four minutes. To our knowledge this is the first study detailing the effect of REP trapping on cell viability. The presented results provide a clear guideline on selecting suitable REP parameters for trapping living bacteria.

Optofluidic cell manipulation for a biological microbeam

This paper describes the fabrication and integration of light-induced dielectrophoresis for cellular manipulation in biological microbeams. An optoelectronic tweezers (OET) cellular manipulation platform was designed, fabricated, and tested at Columbia University's Radiological Research Accelerator Facility (RARAF). The platform involves a light induced dielectrophoretic surface and a microfluidic chamber with channels for easy input and output of cells. The electrical conductivity of the particle-laden medium was optimized to maximize the dielectrophoretic force. To experimentally validate the operation of the OET device, we demonstrate UV-microspot irradiation of cells containing green fluorescent protein (GFP) tagged DNA single-strand break repair protein, targeted in suspension. We demonstrate the optofluidic control of single cells and groups of cells before, during, and after irradiation. The integration of optofluidic cellular manipulation into a biological microbeam enhances the facility's ability to handle non-adherent cells such as lymphocytes. To the best of our knowledge, this is the first time that OET cell handling is successfully implemented in a biological microbeam.