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Discovering new 3D bioprinting applications: Analyzing the case of optical tissue phantoms
Table 5. Global trends for optical tissue phantoms development using 3D printing
Category Trend
Methods Spin coating process predominates because this technique allows thin layers to be generated (30–60 µm in thickness), which better mimic
the layer structure of biological tissues
Materials Polydopamine, polydimethylsiloxane, and the hydrogel, PVA, are present to elaborate matrix tissue phantoms. To mimic scattering properties, TiO 2
powders, intralipids, and PVA (involving a freeze-thaw treatment) are used. Finally, those applied to mimic absorption properties include India ink,
dyes, graphite powder, hemoglobin solutions, and coffee
Uses Applications are divided into the following:
Diagnosis techniques, specifically: (1) Medical imaging procedures: confocal microscopy, optical coherence tomography, optical diffusion tomography,
hyperspectral reflectance imaging, fluorescence imaging and photoacoustic; and (2) spectroscopy (diffuse reflectance and near-infrared spectroscopy); and
Phototherapy techniques, especially in tests for tattoo removal using laser
PVA: Polyvinyl alcohol, 3D: Three-dimensional
the predominant materials for the matrix of 3D printed both scientific papers and patents in the field - Purdue
optical tissue phantoms include both polymers and University and Georgia Institute of Technology, both in
hydrogels since they facilitate the addition of other the United States and Pukyong National University in
substances to improve the optical properties of the South Korea. Specifically, a quarter of the total scientific
phantom [31] and can be used easily for 3D printing [16,51] . papers identified was published in the proceedings of the
Materials of non-biological origin (TiO , India ink, dyes, SPIE.
2
graphite powder, and PVA) are preferred over biological Regarding limitations, this research was restricted by
materials (such as intralipid and hemoglobin solutions). a lack of information, due to the novelty of applying 3D
Finally, two categories of phantom applications were printing in the development of optical tissue phantoms.
identified, namely diagnosis and phototherapy, with the This issue led to obtaining few scientific papers and
first predominating; the dearth of research on optical especially patents, and it was not possible to identify a
tissue phantoms for phototherapy may be because clear trend of the behavior of patents published in this
phantoms do not yet possess thermal properties and field. In terms of 3D bioprinting, no documents using
dynamics like blood flow in tissue, which is crucial for this technique to produce optical tissue phantoms were
phototherapies [64] . However, efforts are being made to detected, which limited the study to analyzing publications
develop phantoms that include vascular tissue filled on 3D-printed phantoms.
with blood or hemoglobin solutions to mimic the tissue Since the applications of both 3D printing and 3D
oxygenation and blood perfusion [31,54,65] . bioprinting are growing, future analysis will be based on
a higher number of publications, especially for the latter.
4 Conclusions Indeed, 3D bioprinting is already utilized to produce
In this study, scientometric and patentometric analyses were phantoms, but in other areas, such as ultrasound imaging,
[63]
carried out to identify trends in the use of 3D printing or 3D where they are known as “biophantoms” . Ultimately,
bioprinting to develop optical tissue phantoms, focusing 3D printing technology has a disruptive potential for the
on the following key elements: Methods, materials, and development of optical tissue phantoms; this technology
uses, as well as predominant countries, institutions, and has distinct advantages over traditional methods, such
journals. The results revealed that 3D printing is already as the development of complex multilayered structures,
used for the development of optical tissue phantoms, where easy production, and low cost. Unique biophotonic
the spin coating is the most frequently employed method. prototypes can be built using 3D bioprinting, thereby
Materials such as polymers and hydrogels prevail as the facilitating diagnosis tests, equipment validation, and so
[66]
phantom matrix; meanwhile, to mimic optical properties, on . The 3D bioprinting domain is still in development,
the use of synthetic materials such as TiO , India ink, or and its uses and applications in many areas have not
2
dyes outweighs that of biological materials (intralipids, been completely studied, so this research reveals a new
hemoglobin, etc.). Finally, it was identified that 3D printed window of opportunity to explore.
optical tissue phantoms are mainly focused on diagnostic Conflicts of Interest
purposes rather than phototherapy.
The insights obtained in this study illustrate that the No conflicts of interest are reported by the authors.
more active countries in R&D on optical tissue phantoms
using 3D printing are the United States and China. The References
main institutions that publish scientific papers in this area
are located in the United States; meanwhile, in terms of 1. ASTM F2792-10, 2010, Standard Terminology for Additive
patents, the leading institutions come from South Korea. Manufacturing Technologies. West Conshohocken, PA:
Only three institutions were detected that published ASTM International. https://www.astm.org.

8 International Journal of Bioprinting (2019)–Volume 5, Issue 1