Page 84 - IJB-9-4

International Journal of Bioprinting Laser transfer for CTC isolation

in coincidence with the deployment of several different approaches for enrichment , with CELLSEARCH® being
[28]
techniques for CTCs analysis . Directly linked with cancer the only FDA-approved test for enumeration of CTCs of
[2]
metastasis, CTCs detection and characterization alone or epithelial origin . However, immunomagnetic α-EpCAM
[29]
with other cancer biomarkers is considered a valuable tool positive selection approaches need to seed the sample with
in disease prognosis and progression monitoring [3-5] . ferromagnetic particles, thus implying the direct tagging of
It has been extensively reported that metastatic CTCs, which is not compatible with the idea of maintaining
dynamics of solid tumors is linked to the circulation of the CTCs as unaltered as possible. In addition, some works
tumor cells, leaving the primary tumor and traveling defend the clinical utility of non-EpCAM assays due to the
through the peripheral blood to colonize other tissues [6-8] . limitations of the immunomagnetic techniques to detect
[30]
In addition, these cells appear to be responsible for more nonepithelial CTCs of clinical relevance in many tumors .
complex tumor dissemination processes like those based On the other hand, biophysical methods for enrichment
on tumor self-seeding . Therefore, an accurate monitoring have the advantage of avoiding labeling, addressing the
[9]
of CTCs and specially a full liquid biopsy in cancer patients separation of CTCs through their distinctive physical
is of great importance for clinical oncology . properties (morphological, electrical, and mechanical).
[10]
Among them, size-based isolation methodologies (due
Isolation of CTCs from body fluids is a liquid biopsy
method that can be used both for early diagnosis, which to the larger size of CTCs, 12–25 μm, compared with
surrounding cells) have a huge potential in maintaining the
may lead to a selection of more suitable treatments, as well CTCs unmodified [2,31] . Microfluidic devices, microfiltration,
as for real-time monitoring of the disease progression . dielectrophoresis, and other related techniques including
[11]
Molecular analysis at the single-cell level by single-cell approaches based on advanced lab-on-a-chip concepts
sequencing (SCS) allows the complete characterization of or even advanced programmable materials [32–37] appear as
the amplified genetic material, offering a huge advantage well suited as enrichment methods. However, in many of
for the characterization of both cell populations with these approaches, the subsequent CTCs isolation from the
limited number or singular cell populations [12-14] . Moreover, enriched liquid remains a challenge. There is an unmet
a comprehensive phenotypic profiling of heterogeneous need to increase the purity and concentration of CTCs
CTCs at single-cell resolution would have an important fraction, as well as to maintain cellular viability in order
impact on cancer management [15-17] . Therefore, the to facilitate both the molecular characterization and the
appropriate combination of liquid biopsy with SCS would possibility of performing in vitro studies.
be useful to monitor the patient’s response to a particular
treatment or the disease evolution. Once the prognostic or For the detection and selection of the appropriate
predictive role of these biomarkers is confirmed, they could cells for isolation, the technologies are intimately linked
be used in developing targeted therapies [18-20] . However, to the enrichment process. Moreover, standard optical
the effective capture of CTCs with different phenotypic technologies (especially those related to fluorescence
characteristics and with the potential of subpopulation detection for negative or positive selection) are relevant for
sorting is still a goal that is not completely fulfilled. accurate selection of appropriate targets for final isolation
[38]
Although several technologies have been developed and sequencing .
or adapted for CTCs isolation in the last few years, cell
isolation remains a challenge, in particular when good cell 2. Lasers in CTCs research
viability is required. The main problem is related to the very Laser technology is currently a widely used tool in
low concentration of CTCs in cancer early stages (1 CTC CTCs studies. Used as a coherent light source for
per 10 –10 blood cells), making it challenging in terms of illumination in microscopy and fluorescence set-ups,
6
9
sensitivity and specificity of the detection technologies [5,21] . especially for detection, laser technology is employed
Due to the low concentration of CTCs, enrichment-based as well for subpopulation separation in approaches for
methods for isolation are currently preferred for CTCs CTCs isolation and sorting using flow cytometry [21,39] .
detection and analysis.
However, lasers could play a fundamental role in the most
Different enrichment methods based on physical and/ challenging step in CTCs analysis: isolation of viable cells.
or biological properties have been proposed, and in the In fact, laser capture microdissection (LCM), a widely
last years, a number of reviews [3,18,19,22-25] have summarized used technique for cell isolation of complex tissue [40,41] has
the pros and cons of the available technologies and the been proposed for CTCs isolation, both in combination
challenges of implementation in clinical practice [26,27] . with microfluidic devices for previous enrichment and as
Immunomagnetic techniques for positive and negative a part of sophisticated techniques that requires previous
selection of CTCs are probably the most common CTCs encapsulation in hydrogels [42,43] . However, these

Volume 9 Issue 4 (2023) 76 https://doi.org/10.18063/ijb.720