Page 77 - IJB-9-6

International Journal of Bioprinting 3D Aerosol Jet® printing for microstructuring

Table 3. Results for the 3D AJ®P of microstructures for each ink and print strategy investigated, along with the geometrical
characterization, the process reproducibility, and the printing time
3D AJ P Results
®
Ink Print strategy Height, h (μm) Width base-tip, Aspect ratio, Internal Process Printing time, t (s)
w (μm) AR (#) structure reproducibility
Nondiluted CJD ~ 230 ~ 30 7.6 Dendritic-like Low 60
AgNPs-based LBL 955.8 ± 15.2 110.4 ± 9.8 8 < AR < 50 High 60 < t < 300
18.9 ± 2.2
Diluted CJD 590 ± 42 (pillar) 92.9 ± 11.9 1< AR <12 Dense Low 3
AgNPs-based 54.6 ± 5.1
LBL 960.4 ± 37.7 47.7 ± 5.6 20 Hollow High 300 (for array 6 × 4)
PEDOT: PSS-std CJD ~ 240 ~ 35 6.8 (bended) Dense Low 30
PEDOT: PSS- CJD ~ 300 ~ 70 4.3 (bended) Low 15
own formula
LBL 256.3 ± 5.3 56.8 ± 4.8 4.5 Medium 70
Col-HAp CJD ~ 220 ~ 76, ~ 11 ~2.5 Dense High 30
LBL 213.4 ± 7.4 90.5 ± 8.6 ~2.4 Hollow High 60
Col-HAp-1 M PW ±400 µm (22.0 ± 97.3 ± 3.9 ~4 Dense Low 300
glycerol 0.5 layer height)
LBL 223.3 ± 46.5 159.4 ± 2.9 ~1.4 Hollow High 300 (for array 6 × 4)

their use in life science applications must be wisely by the rATP cytotoxicity assays. Therefore, this type of ink
considered. AgNPs are known to induce cytotoxicity, has potential to be used for 3D AJ®P microstructures for
mainly in a dose-, size-, shape-, and time-dependent way, bioelectronic sensing or lab-on-a-chip devices.
due to the surface oxidation of AgNPs, which activates Alternatively, collagen exhibits excellent
the release of Ag ions in the medium culture, eventually biocompatibility with MC3T3 cells (Live-Dead TM assay
+
leading to oxidative stress and cellular death [50-52] . As till day 7), being the most abundant protein in mammals,
denoted by the rATP and immunofluorescence assays especially in the bone tissue. Due to the presence of
in the present study, the release of such Ag ions from specific cellular recognition amino acid sequences,
+
exposed AgNPs printed patterns indeed induced high collagen indeed plays a crucial role in cellular processes,
levels of cytotoxicity on h-iPSC-derived NSCs and HFs. such as cell attachment and proliferation. For instance,
Hence, the use of 2D/3D AgNPs-based printed constructs collagen type I and II inks have recently been AJ®-printed
is recommended only if they are properly coated at an to produce dense collagen films for applications in corneal
adequate thickness with biocompatible, saline water- tissue engineering . However, printing of 3D structures
[36]
resistant, dielectric encapsulator. For example, the is new to this respect. In order to mimic the composition
authors demonstrated the biocompatibility of electrical of human bone tissue, HAp nanoparticles (<200 nm) were
patches composed of AJ®-printed AgNPs-based circuits incorporated into the ink in a biomimetic ratio (1:2 Col:HAp
encapsulated in polydimethylsiloxane (PDMS) on both ratio). As mentioned previously, the solid loading of the
HFs and B-Lymphoblastoid cell lines till day 21 .
[53]
inks plays a crucial role in 3D printing using AJ®P. Hence,
In order to avoid this issue, in the context of life it was hypothesized that the addition of HAp nanoparticles
science, the use of biocompatible inks is preferable, such could improve the 3D printing behavior of the collagen
as PEDOT:PSS- and collagen-based inks. PEDOT:PSS composite inks. The collagen-HAp ink allowed for the
shows good potential as bioconductive 3D AJ®P ink for printing of hollowed pillars, but more complex structures
multifunctional applications in the field of bioelectronics. could not be fabricated using this ink composition.
Particularly, the addition of polyethylene glycol (PEG) Hence, the effect of adding glycerol was assessed, as it is
and carboxymethyl cellulose (CMC) to the standard believed that adding a solvent with low volatility could
PEDOT:PSS formulation supported the build-up of well- aid in the build-up of 3D structures. Indeed, the addition
defined 3D micropillars, due to their action as binders and of glycerol allowed for the fabrication of more complex
loading contents. The own-formulated PEDOT:PSS-based structures, such as the pyramid shown in Figure 5e.
ink also shows good levels of biocompatibility at 72 h These pyramids could be used as unit-cells for more
when in contact with h-iPSC-derived NSCs, as reported complex lattice structures. It should be noted, however,

Volume 9 Issue 6 (2023) 69 https://doi.org/10.36922/ijb.0257