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International Journal of Bioprinting Applications of 3D printing in aging

physiological pressure of normal blood vessel. Lee et al. [147] diseases. Cardiovascular structure restoration is made
3D-printed biodegradable PLA stents using polymer possible by the careful sorting and placement of cells or
electrolyte membrane (PEM), and used polydopamine tissue blocks in a complex 3D microenvironment with
(PDA), polyethyleneimine (PEI), and heparin (Hep) bioprinting technology. Although bioprinting techniques,
to prevent restenosis and thrombosis by improving bioink materials, and post-bioprinting processing are still
anticoagulation and hemocompatibility. Alonzo et al. [148] in their infancy in this area, reproducing heart structures
3D-printed annular hydrogel (gelatin-alginate) scaffolds including the myocardium, blood arteries, and heart valves
with microvascular endothelial cells using DIW. These via 3D bioprinting has shown great promises. New bioinks
3D heart-like scaffolds supported long-term cell survival, and printers with the ability to manufacture objects with
function, and maintenance of cell phenotype throughout high resolution will advance the science and eventually
the entire culture period because they were structurally accomplish the ultimate goal of total organ engineering.
and mechanically stable with highly interconnected pores.
The model supported paracrine signaling in addition to 3.4. Digestive system
heterogeneous cellular contact between endothelial cells 3.4.1. Application of 3D printing in oral cavity
and cardiac fibroblasts, cardiomyocytes, and both [148] . Jia diseases
et al. used a multilayer coaxial extrusion technique to The tooth loss among the elderly people is mostly caused
[19]
3D-print a cell-responsive bioink made of GelMA, sodium by periodontal and dental caries. While the gums are aging
alginate, and 4-arm poly(ethylene glycol)-tetraacrylate and shrinking, the exposed area of the cervical root is
(PEGTA) to enable direct 3D bioprinting for one-step increased, thereby elevating the risk for caries [150] . Aging also
production of perfusable vascular systems with highly causes severe resorption of alveolar bone, in which case, the
organized structures. This hybrid bioink encapsulated supporting structure of teeth is destroyed, causing instability
stem cell and endothelium in bioprinted structures and in teeth. Long-term caries and periodontal diseases activate
supported their growth, producing biologically relevant, the oxidative damage by free radicals and weaken the
highly structured, and perfusable vasculature. Lee et al. [149] repairing ability of the oral cavity, causing tooth loss in the
proposed free-form reversible encapsulation with elderly. In summary, tooth loss in the elderly is a systemic
suspended hydrogels (FRESH) to directly write collagen process caused by many factors associated with aging [151-154] .
into bioconstructs of various scales, ranging from
capillaries to whole organs. At 20-µm filament resolution, Tooth loss adversely affects the life quality and brings
porous microstructures were capable of cellular infiltration great harm to the elderly both physically and mentally.
and microvascularization. The mechanical strength Dental regeneration faces a significant difficulty in
adequate for the production and perfusion of multi-scale replicating the structural complexity and multicellular
vascular systems and trilobular valves were enabled via interactions that resemble their natural 3D counterpart.
pH-driven gelation control. The results showed that the Due to improvements in 3D printing technology, which
3D-bioprinted heart accurately reproduced the patient- enables the creation of structures with patient-specific
specific anatomy determined by micro-CT (Figure 4D). characteristics, efforts to construct teeth and dental support
Human cardiomyocyte imprinting resulted in coordinated devices, such as periodontal ligament, alveolar bone, and
contraction, directed action potential propagation, and dental ossicles, have made some progress [155,156] . Although
wall thickening of up to 14% at peak contraction in the some dental applications of 3D printing are not targeted at
ventricular tissues. the aging population, we focus on the potential applications
of these cases in the elderly population, such as 3D-printed
The application of 3D printing in cardiovascular diseases crowns and dental implant scaffolds for dental implants in the
mainly involves cardiovascular phantoms fabricated by elderly. It is becoming more apparent that a single material
material jetting, cardiovascular stents fabricated by material is difficult to meet all the requirements; therefore, the search
extrusion, and heart patches for treatment fabricated by for more suitable hybrid materials has also become one of the
material extrusion. Materials for bioink mainly include focuses of tissue engineering development [157] . Jeong et al. [158]
biopolymers such as GelMA and ECM. Live and functional used PEM to 3D-print PCL mixed with HA/β-tricalcium
cells are frequently encapsulated and printed together phosphate (β-TCP) into novel scaffolds. It combined bone
with the biopolymers to simulate certain functions of the grafting and implant fixation devices to simplify alveolar
cardiovascular system in vitro. However, 3D printing of the bone regeneration and dental implant procedures. The
entire organ remains difficult. Cardiovascular system is a new scaffold had high porosity and good microstructural
complex anatomical structure. Therefore, to replicate its interoperability. Cell proliferation and alkaline phosphatase
internal structure and reproduce its function is the greatest assay results were significantly better than those of control
challenge in the research and treatment of cardiovascular scaffolds. The emergence of new hybrid materials is often

Volume 9 Issue 4 (2023) 246 https://doi.org/10.18063/ijb.732