Opt. Lett. 36, 2877–2879 (2011)

A focused laser beam can perforate the membrane of a single cell, but the same spatial localization that permits such precise ablation prohibits application of the technique to multiple cells. Mitsuhiro Terakawa and Yuto Tanaka offer a solution to this problem, demonstrating the enhanced optical field generated when polystyrene microspheres bound to cells are excited by a femtosecond laser pulse.

The spheres, it turns out, act as microlenses, localizing laser power and extending focused intensity more than 2 μm beneath them — well within range of the underlying cells. Simulation results accompanying the experimental study suggest that the intensity under each sphere exceeds the ablation threshold of the cell membrane, increasing the probability of transfection. And that's exactly what Terakawa and Tanaka saw in their experiments: fluorescent molecules taken up by the cells indicated a clear boost in membrane permeability on irradiation.

Although the underlying physics is not yet clear, the approach presents a high-throughput analogue to single-cell perforation, with implications for drug delivery.