Page 85 - IJB-9-4

International Journal of Bioprinting Laser transfer for CTC isolation

Figure 1. Liquid laser transfer for CTC isolation.

approaches, besides comprising an important number of Most LIFT approaches use a pulsed laser beam to
complex processes in sample preparation, in some cases transfer material from a donor substrate to an acceptor
imply a final laser pressure catapulting process (LCP) of surface or any other receptacle. In its simplest configuration,
the sample in which direct irradiation, normally in the LIFT is performed irradiating the interface between a
ultraviolet (UV) range, is unavoidable . More recently transparent substrate and the material to be transferred,
[44]
sophisticated processes using laser induced isolation of previously deposited forming a thin layer onto the substrate
microstructures with CTCs, and using IR laser light to surface. Conversion of laser energy into kinetic energy of
transfer the functional structure have been proposed as part of the material allows the transfer of small volumes
well . with high spatial accuracy, providing a printing method
[45]
with spatial resolution in the order of 1 µm. The process
In this work, we propose a completely new approach
for CTC isolation in the classical flow sequence for CTCs dynamics is strongly dependent on the physical properties
sample treatment of enrichment-identification-isolation and thickness of the material to be transferred, the gap
but using a liquid laser transfer (LLT) process for the last between acceptor and donor substrate, the configuration
step. This transfer approach is based on an adaptation of of the donor substrate, and the parameters used in the laser
[52]
the blister-actuated laser-induced forward transfer (BA- irradiation process . The main advantage of the technique,
LIFT) direct write technique that completely avoids the if compared with other mature printing technologies like
interaction between the laser photonic field and the cells inkjet or extrusion, is the capacity to transfer material in
to be isolated (Figure 1). This work demonstrates the an enormous range of viscosities and rheological behavior,
feasibility of this approach with a first proof of concept, from solid-state to low-density inks. In addition, the
isolating cells of a breast cancer line (MDA-MB-231) in the capability of the technique to transfer small volumes of
negative selection and later SCS of the isolated cells. material (as low as picoliters) and the high lateral spatial
resolution (down to a few micrometers) to produce printed
In our approach, we adapted the BA-LIFT technique, patterns are remarkable.
using a thick adhesive polyimide layer conveniently treated LIFT has attracted huge attention as bioprinting
to improve hydrophilicity, to produce a droplet containing technique as well, and in the last 20 years, several works
the previously identified and selected CTCs using a single have demonstrated applications of 2D and 3D printing of
laser pulse. The CTCs were recovered in a tube or culture biomolecules and living cells both for in vitro and in vivo
well for further SCS and/or viability studies. The process is approaches [52-61] , including single cell isolation [46,47] and
conceptually presented in Figure 1 and discussed in next using different laser pulse duration regimes . In addition,
[62]
sections.
it has been extensively shown that LIFT is one of the
2.1. Cell isolation using laser direct write bioprinting techniques with the highest cell viability, even
Laser direct write techniques have been considered for better than the widely applied extrusion or inkjet printing
cell isolation in different fields , with those based in methods. It guarantees in general the DNA integrity after
[46]
laser-induced forward transfer (LIFT) approaches being the transfer process, despite the fact that the cells could
the most currently envisaged . LIFT refers to a group of suffer some mechanical stresses due to the dynamics of the
[47]
laser-based direct write techniques developed originally liquid transfer process, has it has been published in a very
[63]
for art graphics and semiconductor industry and now recent work even for cancer cell lines . However, the fact
applied in different technological and scientific fields. that direct laser irradiation and/or heating of the media
Due to the interest in many different technological and containing the cells could affect cell functionality in any
industrial sectors, an increasing number of reviews about extent beyond DNA integrity has been a constant concern
the technology are available [48–53] . in this field, and a number of approaches envisaged the

Volume 9 Issue 4 (2023) 77 https://doi.org/10.18063/ijb.720