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International Journal of Bioprinting Medical regenerative in situ bioprinting

and easy to disassemble, clean, and disinfect to meet the be used to mediate in situ curing of sound-sensitive inks.
operational requirements of surgical procedures. Handheld In this regard, other sound-sensitive materials with good
in situ bioprinters are typically used in emergency trauma biocompatibility may be developed to enhance tissue
scenarios (e.g., car accidents, battlefields), where users are regeneration on printed scaffolds. In situ-bioprinted
generally non-professionals. A smartphone can be combined tissue scaffolds require uniform pore structure and
with a handheld in situ bioprinter, and the smartphone’s mechanical strength, both of which share an inverse
high-definition camera and computing power can be used correlation. Therefore, alternative pore-forming methods
to scan the damaged area and plan the print path. Deep need to be developed, such as optimizing microgels to
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learning can also be combined with cloud computing to serve as porous scaffolds. 113
monitor and calibrate printhead movements in real time,
improving print accuracy. In the future, the handheld in 5. Conclusion
situ bioprinter may become an essential tool for astronauts
during space emergencies, such as the extraction and storage In this review, we introduced 3D in situ bioprinting to
of biological products containing blood or stem cells before fabricate complex structures for tissue regeneration.
astronauts embark on missions. 130 Conventional 3D bioprinting strategies require a long
incubation period for pre-printed structures in a large
At present, a few studies are focusing on real-time working space, potentially leading to a mismatch in the
monitoring of in situ printing processes, utilizing large shape of the wound. In situ bioprinting can compensate for
imaging devices and complex equipment. In the future, it these deficiencies by using the recipient body as a bioreactor
is necessary to miniaturize imaging detection systems to where living biomaterials and cells of scaffolds can be
integrate them with minimally invasive printing platforms further cultured. The in situ bioprinting approach can be
to enhance the fidelity of printed structures. The use of divided into three types: RASBS, HISBS, and minimally
external magnetic fields to control the precise positioning invasive in situ bioprinting. RASBS has higher printing
of magnetic bioinks in the body is a promising technology, accuracy with less human intervention and can adjust
and this strategy does not require complex minimally printing models and paths according to the actual printing
invasive printing robotic arms. Technical validation and conditions. Furthermore, combined with minimally
optimization for more complex geometric defect printing invasive tools, RASBS can achieve in situ deposition of
is also required in the future. To further reduce the volume bioinks without open wounds. Driven by human hand
of the minimally invasive printing platform, the injection movement, handheld bioprinters are easier to operate
device can also be placed outside the body and connected but are limited in their application to internal trauma
to the pipe through the dispensing nozzle to achieve in situ and complex structures. Bioinks normally contain living
printing. However, the effect of the material temperature at biomaterials and cells as a matrix to rearrange regenerative
the dispensing nozzle and the ambient temperature on the factors. Bioinks should have optimal rheological properties
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printing performance of the material will be a challenge. for in situ bioprinting, ensuring sufficient mechanical
For in vivo bioprinting, the selection of suitable bioink strength and printing resolution. Overall, in situ bioprinting
depends on the specific tissue repair area. For example, in holds great promise as an emerging technology for tissue
the acidic environment of the stomach, polyelectrolytes repair. This technology is expected to make significant
with opposite charges can be added to the bioink to progress in the coming years with technological advances
achieve instant curing, without the need for external in AI, medical robotics, and biomaterials.
conditions, such as near-infrared light or ultrasound, to
mediate polymerization. Acknowledgments
Hydrogels, including collagen, gelatin, and alginate, None.
have been widely used for in situ bioprinting. Most of these
materials have excellent biocompatibility and low toxicity, Funding
but a single biomaterial cannot meet the requirements
of tissue repair. Therefore, developing a multi-material This work was supported by the National Key Research
in situ bioprinting system could expand its applications and Development Program of China (2018YFA0703100),
significantly. For photocured hydrogels, near-infrared Guangdong Basic and Applied Basic Research Foundation
light is required to induce bioink polymerization for (2021A1515110902, 2021A1515110794), Shenzhen Science
minimally invasive bioprinting in vivo. Hence, it may and Technology Funding (JCYJ20220530142206014),
be crucial to optimize the type and concentration of and the Shanghai Municipal Health Commission
photoinitiator, light wavelength, and irradiation time. Health Industry Clinical Research Program for
For minimally invasive printing in vivo, ultrasound can Youth (20224Y0184).

Volume 10 Issue 5 (2024) 61 doi: 10.36922/ijb.3366