Laser printing: trends and perspectives

In this paper, I present my personal view on the possible development and applications of laser printing technologies based on laser-induced forward transfer of inorganic and biological materials. Laser printing of micro- and nanoparticles, living cells, and microorganisms are discussed

On the origin of photon mass, momentum, and energy in a dielectric medium [Invited]

The debate and controversy concerning the momentum of light in a dielectric medium (Abraham vs Minkowski) is well-known and still not fully resolved. In this paper, we investigate the origin of both momenta in the frame of special relativity by considering photons in media as relativistic quasiparticles. We demonstrate for the first time to the best of our knowledge that the Minkowski form of the photon mass, momentum, and energy follows directly from the relativistic energy conservation law. We introduce a new expression for the momentum of light in a dispersive medium, consistent with the experimentally observed propagation of photons at the group velocity. Finally, the effect of light-induced optical stretching is discussed, which can be used for experimental verification of the existing expressions for the photon momentum

Laser bioprinting of human iPSC-derived neural stem cells and neurons: Effect on cell survival, multipotency, differentiation, and neuronal activity

Generation of human neuronal networks by three-dimensional (3D) bioprinting is promising for drug testing and hopefully will allow for the understanding of cellular mechanisms in brain tissue. The application of neural cells derived from human induced-pluripotent stem cells (hiPSCs) is an obvious choice, since hiPSCs provide access to cells unlimited in number and cell types that could be generated by differentiation. The questions in this regard include which neuronal differentiation stage is optimal for printing of such networks, and to what extent the addition of other cell types, especially astrocytes, supports network formation. These aspects are the focus of the present study, in which we applied a laser-based bioprinting technique and compared hiPSC-derived neural stem cells (NSCs) with neuronal differentiated NSCs, with and without the inclusion of co-printed astrocytes. In this study, we investigated in detail the effects of cell types, printed droplet size, and duration of differentiation before and after printing on viability, as well as proliferation, stemness, differentiation potential, formation of dendritic extensions and synapses, and functionality of the generated neuronal networks. We found a significant dependence of cell viability after dissociation on differentiation stage, but no impact of the printing process. Moreover, we observed a dependence of the abundance of neuronal dendrites on droplet size, a marked difference between printed cells and normal cell culture in terms of further differentiation of the cells, especially differentiation into astrocytes, as well as neuronal network formation and activity. Notably, there was a clear effect of admixed astrocytes on NSCs but not on neurons

Metal Nanoparticles in Laser Bioprinting

Laser bioprinting is a promising method for applications in biotechnology, tissue engineering, and regenerative medicine. It is based on a microdroplet transfer from a donor slide induced by laser pulse heating of a thin metal absorption film covered with a layer of hydrogel containing living cells (bioink). Due to the presence of the metal absorption layer, some debris in the form of metal nanoparticles is printed together with bioink microdroplets. In this article, experimental investigations of the amount of metal nanoparticles formed during the laser bioprinting process and transported in bioink microdroplets are performed. As metal absorption layers, Ti films with the thickness in the range of 25–400 nm, produced by magnetron spattering, were applied. Dependences of the volume of bioink microdroplets and the amount of Ti nanoparticles within them on the laser pulse fluence were obtained. It has been experimentally found that practically all nanoparticles remain in the hydrogel layer on the donor slide during bioprinting, with only a small fraction of them transferred within the microdroplet (0.5% to 2.5%). These results are very important for applications of laser bioprinting since the transferred metal nanoparticles can potentially affect living systems. The good news is that the amount of such nanoparticles is very low to produce any negative effect on the printed cells

Massive surface-plasmon polaritons

It is well-known that a quantum of light (photon) has a zero mass in vacuum. Entering into a medium the photon creates a quasiparticle (polariton, plasmon, surface-phonon, surface-plasmon polariton, etc.) whose rest mass is generally not zero. In this letter, devoted to the memory of Mark Stockman, we evaluate the rest mass of light-induced surface-plasmon polaritons (SPPs) and discuss an idea that collisions of two massive SPP quasiparticles can result in changes of their frequencies according to the energy and momentum conservation laws

Laser bioprinting of human iPSC-derived neural stem cells and neurons: Effect on cell survival, multipotency, differentiation, and neuronal activity

Generation of human neuronal networks by three-dimensional (3D) bioprinting is promising for drug testing and hopefully will allow for the understanding of cellular mechanisms in brain tissue. The application of neural cells derived from human induced-pluripotent stem cells (hiPSCs) is an obvious choice, since hiPSCs provide access to cells unlimited in number and cell types that could be generated by differentiation. The questions in this regard include which neuronal differentiation stage is optimal for printing of such networks, and to what extent the addition of other cell types, especially astrocytes, supports network formation. These aspects are the focus of the present study, in which we applied a laser-based bioprinting technique and compared hiPSC-derived neural stem cells (NSCs) with neuronal differentiated NSCs, with and without the inclusion of co-printed astrocytes. In this study, we investigated in detail the effects of cell types, printed droplet size, and duration of differentiation before and after printing on viability, as well as proliferation, stemness, differentiation potential, formation of dendritic extensions and synapses, and functionality of the generated neuronal networks. We found a significant dependence of cell viability after dissociation on differentiation stage, but no impact of the printing process. Moreover, we observed a dependence of the abundance of neuronal dendrites on droplet size, a marked difference between printed cells and normal cell culture in terms of further differentiation of the cells, especially differentiation into astrocytes, as well as neuronal network formation and activity. Notably, there was a clear effect of admixed astrocytes on NSCs but not on neurons

Editorial: Innovative 3D technologies in cancer immunity research and therapy

[No abstract available

Dispensing pico to nanolitre of a natural hydrogel by laser-assisted bioprinting

<p>Abstract</p> <p>Background</p> <p>Laser-assisted bioprinting of multi-cellular replicates in accordance with CAD blueprint may substantially improve our understandings of fundamental aspects of 3 D cell-cell and cell-matrix interactions <it>in vitro</it>. For predictable printing results, a profound knowledge about effects of different processing parameters is essential for realisation of 3 D cell models with well-defined cell densities.</p> <p>Methods</p> <p>Time-resolved imaging of the hydrogel jet dynamics and quantitative assessment of the dependence of printed droplet diameter on the process characteristics were conducted.</p> <p>Results</p> <p>The existence of a counterjet was visualised, proving the bubble collapsing theory for the jet formation. Furthermore, by adjusting the viscosity and height of the applied hydrogel layer in combination with different laser pulse energies, the printing of volumes in the range of 10 to 7000 picolitres was demonstrated. Additionally, the relationship between the viscosity and the layer thickness at different laser pulse energies on the printed droplet volume was identified.</p> <p>Conclusions</p> <p>These findings are essential for the advancement of laser-assisted bioprinting by enabling predictable printing results and the integration of computational methods in the generation of 3 D multi-cellular constructs.</p