Laser-Assisted Cell Printing: Principle, Physical Parameters Versus Cell Fate and Perspectives in Tissue Engineering

Abstract

We describe the physical parameters involved in laser-assisted cell printing and present evidence that this technology is coming of age. Finally we discuss how this high-throughput, high-resolution technique may help in reproducing local cell microenvironments, and thereby create functional tissue-engineered 3D constructs.

Advances in bioprinted cell-laden hydrogels for skin tissue engineering

“…For tissue engineering applications, traditional LIFT apparatus has been modified mostly regarding the print ribbon and receiving substrate in order to improve the compatibility with biological materials. The bioink is coated onto the bottom side of the laser transparent substrate and consists in cells suspended in a liquid medium or in a viscous polymer solution [57,58,134]. A high-powered laser pulse (usually a near infra-red laser) is focused onto a thin metal layer (1-100 nm), placed above the laser transparent substrate, generating a high-pressure bubble that propels the material towards a parallel substrate [14,57,128].…”

“…The bioink is coated onto the bottom side of the laser transparent substrate and consists in cells suspended in a liquid medium or in a viscous polymer solution [57,58,134]. A high-powered laser pulse (usually a near infra-red laser) is focused onto a thin metal layer (1-100 nm), placed above the laser transparent substrate, generating a high-pressure bubble that propels the material towards a parallel substrate [14,57,128]. The most widely used modified-LITF processes in biofabrication comprise matrix-assisted pulsed laser evaporation direct writing (MAPLE DW) and absorbing film-assisted laser-induced forward transfer with its variants such as the biological laser processing (BioLP).…”

“…The distinctive feature between such processes is the inclusion of either an optical absorbing material (MAPLE DW) or a sacrificial absorbing layer (BioLP) at the interface between the laser-transparent ribbon and the material to be transferred [128,163]. In BioLP, the laser absorption interlayer, usually a thin metal coating (Au, Ag, Ti, TiO 2 *100 nm), displays several functions, such as: (1) eliminate the interaction between the laser and the biological material, (2) protect cells from light exposure, (3) minimize the bioink heating, (4) promote a quick thermal expansion with a more efficient droplet ejection, and (5) increase the printing reproducibility [14,57,128,165].…”

“…In contrast to inkjet, laser-assisted bioprinting enables the processing of bioinks with a broad range of viscosities (1-300 mPa s -1 ) and higher cell concentrations (10 8 cells mL -1 ) [59,89,125,165], which is a prime requisite to mimic the native organization of human tissues. Although the absence of an orifice reduces the stresses to which cells are subjected, cell injury and dysfunctionality may occur due to thermal heating, optical irradiation and mechanical impact with the receiving substrate [57,128,165]. Previous research has shown that these effects can be significantly reduced, or even eliminated, by controlling the laser pulse characteristics, the bioink viscosity, the thickness of absorbing layer and the substrate properties [27,53,101].…”

“…These parameters can also be optimized in order to better control the printing process and improve the reproducibility and resolution [54]. Laser-assisted bioprinting also enables a great control over the droplet size and number of printed cells per droplet via manipulation of the laser pulse energy, the laser spot size, the distance between the ribbon and the substrate, and the thickness of both energy absorbing layer and cell support layer [53,57,59,89]. Several works have also shown the ability of laser-assisted bioprinting to print mammalian cells without affecting their viability or function, or inducing DNA damage [14,53,55,58,60,89,90,200,203].…”