We combine several single and multi-cell laser-based manipulation techniques to achieve cell surgery, ablation or stimulation in cells, tissue, or in in vivo model systems.

Single and Multi-Cell Manipulation
We have established several techniques to achieve laser manipulation with simultaneous and continuous imaging of single or multiple cells in cooperation with REBIRTH Unit 7.6 “LASER MANIPULATION AND CELLULAR ENGINEERING” by Prof. Heisterkamp and with the Laser Zentrum Hannover e.V. by Dr. Heiko Meyer. Single cells can be targeted by ultrashort laser pulses during simultaneous multiphoton microscopy. This enables penetration depths down to 300 µm in most tissues. Due to thermal and thermo-elastic confinement and a precise deposition of the laser energy, it is possible to manipulate on scales down to the size of small cell organelles, like cytoskeletal elements. To achieve multi-cell targeting, we can combine these approaches with gold nanoparticles, which can exemplarily adhere to the cell membrane. These are irradiated by weakly focused laser pulses thereby enabling multi-cell targeting. Localized effects at the nanoparticle (heating and bubble formation) lead, for instance, to a permeabilization of the cell membrane such that molecules from the surrounding can flow into the cell.

Cell Surgery and Ablation
We address regeneration in single cells by femtosecond laser based surgery and ablation. As an example, we aim to study the cytoskeleton in muscle cells like cardiomyocytes after laser based surgery in stress fibers or in the sarcomere (see Figure 1). We employ different microscopy techniques to follow cell reaction. On a larger scale, in more complex tissue or 3D cultures, we are interested in cell rearrangement and regeneration after ablation of single cells. How are surrounding cells affected, how is the tissue affected, and how does it regenerate? We are planning to extend this microregeneration approach to in vivo settings with simultaneous multiphoton microscopy.

Cell Transfection
Laser targeting of the membrane with a focused laser beam or gold nanoparticle mediated laser transfection enable a transient cell permeabilization and molecules from the surrounding space can flow into the cells. We are applying these techniques for targeted genetic modification of cells, either on a single cell or multi cell stage. The methods have been in particular proven successful for delivery of dyes, proteins or small antisense molecules.

Cell Stimulation
The laser irradiation can induce different responses of the cell, for instance, if membrane permeabilization occurs, this also results in ion exchange with the surrounding. We have used this exchange and direct triggering for a stimulation of cardiomyocytes. Alternatively, it might be possible to indirectly stimulate cells via laser irradiation by heat, membrane permeabilization, or stress responses via appropriate promoter systems.