## 4 Bioprinting as a Solution to Organ Failure
### Opportunities Presented by Bioprinting  
According to Grand View Research, is expected to reach $4.1 billion USD by 2026 registering a compound annual growth rate (CAGR) of 19.5% [55]. More specifically, this growth will be keyed by the need for donor kidneys due to diseases such as chronic kidney disease (CKD). Dental segments, prosthetics, and 3D-printed medical devices (syringes, catheters) are seeing the greatest growth [55]. Given a rapidly aging world population with a rapidly growing global middle class that can afford and will demand cutting-edge healthcare, it is highly likely that the market for bioprinted organs--and bioprinting in general--will see steady growth throughout the first half of the 21 st century [52; 53]. Venture capitalists poured $10.6 billion USD into healthcare startups in the first half of 2018 [56]. This sustained market growth provides an ample opportunity for institutional investors with the patience to invest in healthcare and biotechnology startups [56]. \"The risks may be high and returns may take longer, but as Swiss philosopher [PERSON] said: although patience is bitter, its fruit is sweet\" [56]. Additionally, of course, such investment will also pay dividends on the humanitarian side of the equation. The first bioinks were used in drop-on-demand cell printing were simple salt solutions [57; 58]. Bioinks are usually a biopolymer gel used as a carrier for embedded cells and also provide a protective environment [58]. Bioinks, as a carrier, are then used in a variety of bioprinting technologies including robocasting, ink jet, direct ink writing, and stereolithography [59]. Examples of bioinks include agarose, alginate and chitosan-based bioinks, cellulose, collagen, fibrin, hyaluronic acid, and silk. Synthetic biomaterial that are often used include gellan gum, gelatin methacrylate pluronic, and polyethylene glycol [60]. Figure 4: Bioprinting uses computer-aided design, bioinks, and a bioprinter to produce tissues and organs (**top left**). Three-dimensional printed prosthetics using thermoplastics will remain an essential clinical tool (**top right**). Examples of bioprinted tissues and organs include ducts (**top middle**), blood vessels (**lower left**), an external ear (**lower middle**), and bone implants (**lower right**). The future of bioprinting resides in integrated bioprinters. Dr. [PERSON] recently introduced a tissue-organ printer (ITOP), a device that prints cells within a hydrogel supported by a temporary scaffold [61]. This printer can produce human-sized tissues containing microchannels that aid in oxygen and nutrient transport throughout the construct. [PERSON] et al. (2020) recently developed a handheld 3D printer that applied a stem-cell-loaded bioink directly onto a wound, such as burns, to promote tissue healing [62]. Three-dimensional bioprinting has the capacity to produce transformative results for patients suffering from numerous health conditions not just organ failure [64]. In addition to lives saved and lives improved, 3D bioprinting also has the capacity to drive significant medical cost savings in the United States and worldwide. Additionally, the prices of medical procedures and biomedicines could see a drastic cut in cost if competition accelerates due to 3D printing. In addition to reducing costs, 3D printers may also simplify treatment reduce inherent inefficiencies. Due to 3D bioprinting's humanitarian and financial benefits for human society, it will likely be one of the most important medical innovations of this generation. Short-term applications that have seen the greatest impact relate to drug testing (thereby reducing the need for animal testing), as drug testing can take place on \"organ-on-a-chip\" technologies [62]. A patients' own stem cells can be used to generate bioprinted organoids that test the potency and efficacy of pharmaceutical drugs [64]. This will eliminate the use of animals for drug testing, and more efficient and reliable results will ensue, as the testing can be done on human tissues [64].