Bioprinting with 3-µm laser pulses

Abstract

Laser-Induced Forward Transfer (LIFT) technology has now found its wide application in the field of bioprinting. Laser bioprinting allows the spatial transfer of living micro-objects (cells, microorganisms) in a gel medium using the energy of a laser pulse. Typically, to effectively absorb laser pulse energy, a thin metal layer is deposited on the donor substrate. The disadvantages of this approach are the appearance of cytotoxic metal nanoparticles during laser bioprinting and the need for continuous movement of the donor substrate. The article proposes a method that allows moving to absorption film-free bioprinting using Q-switched Er:YAG nanosecond laser operating at a wavelength of 2.94 µm. This wavelength is effectively absorbed in a top ten-micron hydrogel layer, allowing for a cleaner (without nanoparticles from absorbing layer) and simpler (without the need to constantly move the donor substrate from pulse to pulse) laser bioprinting process. Using strain Escherichia coli as an example, the suitability of the proposed method for successful laser bioprinting is demonstrated. A model describing in detail the processes occurring in the hydrogel layer is presented.