Patterned Photothermal Cavitation for Cell Surgeries

Ting-Hsiang Wu
Advisors: Oscar Stafsudd (EE) & Pei-Yu Eric Chiou (MAE)

Tuesday, June 1, 2010 at 2:00pm
Engr. IV Maxwell Room 57-124

Abstract:
Opening large transient pores in the membranes of living cells is highly desirable in many fields of biology for transferring cargo over a wide range of sizes, including proteins, DNA, RNA, organelles and inanimate particles, such as quantum dots, surface-enhanced Raman scattering (SERS) particles, and microbeads. However, it is difficult to achieve controlled cutting on elastic, mechanically fragile, and rapidly resealing mammalian cell membranes. Here we report a method that utilizes metallic nanostructures to absorb nanosecond laser pulse energies and convert them into highly localized and specifically shaped cavitation bubbles. The explosive bubble expansion and collapse rapidly punctures a lightly-contacting cell membrane via high-speed fluidic flows and induced transient shear stress. Two device configurations are demonstrated: a gold nanoparticles coated substrate that can spatially select and target cells for molecular delivery by light image patterning, and a photothermal micropipette for micron-sized cargo transfer into single cells.

Surface plasmon enhanced optical absorption distribution in the metallic nanostructures were calculated using finite-difference time-domain (FDTD) method. The corresponding cavitation bubble dynamics were characterized using a time-resolved imaging system. By controlling the metallic structure configuration, laser pulse polarization, and energy, various membrane cutting patterns can be obtained. For micron-sized cargo delivery into live mammalian cells, a self-resealing, "cat door"-like membrane access port was used which achieved delivering highly concentrated cargo (5×108 live bacteria/ml) with high efficiency (46%) and cell viability (>90%). Additional biologic and inanimate cargo over 3-orders of magnitude in size including DNA, RNA, 200 nm polystyrene beads to 2 ?m bacteria have also been delivered into multiple mammalian cell types.

Biography:
Ting-Hsiang Wu received her B.S. degree in Electrical Engineering from Columbia University, summa cum laude and B.A. degree in Physics from Wesleyan University in 2004. She received her M.S. degree in Electrical Engineering from the University of California, Los Angeles in 2006 and is currently a Ph.D. candidate in the same department with professor Oscar Stafsudd and professor Pei-Yu Chiou in the Mechanical and Aerospace Engineering department. Her research interests include metallic nanostructure guided photothermal cell surgery and applications of pulsed laser beams in microfluidics and biotechnology.