Laser-induced micro- and nanostructures at polymer surfaces for applications in cell biology

We describe the formation of laser-induced photonic micro- and nanostructures at polyethylene terephthalate (PET) surfaces, which can be used for applications in cell biology. Two types of laser-induced periodic structures are investigated in detail: (1) structures with dimensions of a few m originating from relaxation of stress fields in laser-irradiated polymer surfaces and (2) sub-wavelength ripple-type structures formed by interference of the incident laser-beam with scattered light at the surface. We demonstrate that both types of structures are able to induce an alignment of living biological cells cultured thereon. In order to study mammalian cell cultures there is a need to perform biological assays, e.g., for introduction of genetically active material into cells. This process is known as cell transfection, which can be performed by electroporation exposing the cells to an electrical field gradient. In the current paper, we demonstrate that laser-induced micro-or nano-structures on a polymer surface between 100 m wide gold lead to biological cells oriented either parallel or perpendicular to the electrodes. Finally, we discuss the potential of these laser-patterned polymer electroporation chips for enhanced sorting selectivity and better transfection efficiency.