If you were to go to the hospital today for an illness, you would likely receive the same medical treatment as another individual with a similar ailment even though that individual may vary in age, gender or ethnicity from you. Despite these differences, the field of medicine often utilizes a “one-size-fits-all” approach to serve its patients. However, the unique genetic makeup of an individual has a significant impact on that person’s health and how these “universal” treatments will be tolerated by the body. As a result, the field of personalized medicine has gained much attention in recent years. This method tailors a medical treatment plan to the characteristics, needs and preferences of each individual patient .
In the case of organ transplants, few patients today know that instead of waiting for an organ donor with the perfect compatibility, they can potentially participate in personalized medicine by procuring an artificial organ derived from their very own cells. Currently, in the United States, more than 120,000 people are on the waitlist for a life-saving organ transplant, with the addition of another individual every ten minutes . However, a large shortage of donors is insufficient to fulfill this demand, with only about 11,700 organ donations made annually . One novel solution to this shortage is the development of engineered tissues through a derivative of personalized medicine: 3D bioprinted organs.
Since its birth in 1986, 3D printing has been utilized in many, if not all, aspects of STEM applications, spanning form aeronautics to tissue engineering. 3D printing employs the concept of additive printing to allow the formation of a three-dimensional object in a highly accurate and consistent manner. Similar to how your traditional printer creates a two dimensional image through a series of one-dimensional lines, 3D printing fabricates a three-dimensional object from layers of two dimensional “images”. If one can mold plastic, glass, metal and even food into any shape and form, why not cells?
The very first inkjet printers used for 3D bioprinting were simply modified versions of commercially available 2D office printers. Instead of providing ink within the printer cartridges, biological materials, such as living cells, proteins and interstitial structures are substituted and printed upon an adjustable stage . Once one layer of material is successfully printed, the stage lowers, allowing for another layer to be deposited upon the first. Through this repetitive process of administration and solidification, a three-dimensional product is obtained. Since 2D inkjet printers are widely available, a fully customizable setup can be achieved for a relatively low price. This method also provides high resolution and speed, which are critical for tissue organization and cell survival.
Large strides have been made in laboratories across the world in growing the many different cell types that comprise the human body in a dish: Heart muscle cells capable of contracting on their own in a synchronized fashion, neurons that develop complex communication networks and epithelial cells that organize themselves into vascular tubes. Countless researchers have demonstrated the resilience and potential of tissue growth in vitro, or outside of the body . The next step of this pipeline is to mediate the transition between cultured cells and full-scale organ regeneration — a feat possible through 3D organ bioprinting.
Three-dimensional tissue generation has begun to gain momentum for less complex applications. Tissue samples can be collected from a localized area of a patient, grown outside the body, and then be transplanted without manipulation back into that same individual to aid in regeneration. Likewise, a simple cheek swab from a patient can be used to recover cells that can be manipulated via reprogramming into any type of cell in the patient’s body through a stem cell intermediate. Using cells obtained from oneself decreases the probability of triggering negative immune responses that are often associated with rejection of transplanted organs from foreign sources, such as another person or animal . These techniques have been successfully utilized to grow functional heart valves and bladders with the aid of biomaterial scaffolds and have been successfully transplanted into patients [4, 6]. Until fairly recently, backbone structures like these have been primarily made by careful mechanical manipulation in a machine-independent fashion, introducing susceptibility to human error in crafting such structures. Today, there are biomaterial 3D printers with smaller margins of error capable of accurately generating the scaffold of transplanted organs .
Although the concept itself is promising, it is important to note that 3D bioprinting adds another layer of complexity to the equation: Living tissue. Due to the highly selective nature of cells, choice of material, growth and differentiation factors and biomechanical patterns become crucial when it comes to crafting 3D printed organs. In order to fully recapitulate native functional tissues, 3D bioprinters need to be further adapted to a wider range of biological components of the microenvironment before reaching their full potential. In order for these organs to be successfully translated from the lab bench into common clinical applications, these methods will require further optimization of printing speed and biocompatibility. In addition, quality standards and regulations will also need to be addressed by the FDA.
The field of personalized medicine is advancing the health care system toward a more predictable, powerful and individualized patient experience. Continued research will hopefully mitigate the effects of genetic makeup on health, disease and drug response in order to provide the ideal care to each unique individual, creating a medical community in which each individual treatment can be tailored to match the extensive diversity of the population.
 “Paving the way for personalized medicine: FDA’s role in a new era of medical product development,” in U.S. Food and Drug Administration, 2013. [Online]. Available: http://www.fda.gov/downloads/ScienceResearch/SpecialTopics/PersonalizedMedicine/UCM372421.pdf. Accessed: Nov. 27, 2016.
 “OPTN: Organ procurement and transplantation network,” 2016. [Online]. Available: https://optn.transplant.hrsa.gov/. Accessed: Nov. 5, 2016.
 L. Gilpin, “3D ‘bioprinting’: 10 things you should know about how it works,” TechRepublic, 23-Apr-2014. [Online]. Available: http://www.techrepublic.com/article/3d-bioprinting-10-things-you-should-know-about-how-it-works/. [Accessed: 17-Nov-2016].
 F. J. O’Brien, “Biomaterials & scaffolds for tissue engineering,” ScienceDirect. Marc-2011. [Online]. Available: http://www.sciencedirect.com/science/article/pii/S136970211170058X. Accessed: 17-Nov-2016.
 “Advanced Immunology: Transplantation,” Immunopaedia. [Online]. Available: http://www.immunopaedia.org.za/immunology/advanced/1-transplantation/. Accessed: 15-Nov-2016.
 R. Weiss, “First Bladders Grown in Lab Transplanted,” Washington Post, 04-Apr-2006. [Online]. Available: http://www.washingtonpost.com/wp-dyn/content/article/2006/04/03 /AR2006040301387.html. Accessed: 15-Nov-2016.