Home | University of Pittsburgh



Disclaimer—This paper partially fulfills a writing requirement for first year (freshman) engineering students at the University of Pittsburgh Swanson School of Engineering. This paper is a student, not a professional, paper. This paper is based on publicly available information and may not provide complete analyses of all relevant data. If this paper is used for any purpose other than these authors’ partial fulfillment of a writing requirement for first year (freshman) engineering students at the University of Pittsburgh Swanson School of Engineering, the user does so at his or her own risk. 3D BIO-PRINTING AND ENINGEERING Daniel Funari (daf107@pitt.edu) INTRODUCTIONHumans have always had a fascination with enhancement. This is constantly shown in popular culture, such as our obsession with superheroes. While we may not ever be as fantastical as superheroes, we are still constantly trying to make our bodies better, whether through exercise, surgery, or drugs. However, this often proves to be futile. Despite our efforts, we remain very delicate creatures. Our lives can be abruptly changed by disease, limb loss, and organ loss. Enormous amounts of people each day die from organ failure. 119,000+ people are currently on the organ transplant waiting list, 22 of whom die each day while waiting for a transplant [1]. Often we are unable to appreciate something until it is gone. Approximately 185,000 amputations occur in the United States each year, and even more in the rest of the world [2] While not life threatening, many times our conditions are life changing, whether by loss of non-vital organs, sight, hearing, skin, or limbs, countless humans are left with their bodies incomplete.3D-PRINTINGThe advent of 3d printing has taken the technological world by storm, and given light to enormous amounts of potential. For a while, 3D printing was only used for quick prototype fabrication, with materials usually limited to plastic resins and the like. Now, 3D printing is being used on both an industrial level and a consumer level. Printing materials are no longer limited to plastics anymore either. Now different types of 3d printers are able to print parts using multiple types of plastics, metals, (such as stainless steel, gold, titanium, silver, etc.) and even ceramics. On the industrial level, such as in the aero space and automotive industry, 3D printing allows many companies to fabricate complex custom metal parts, often with complex hollowed out cavities that wouldn’t be possible with CNC or machining. 3D printing is often referred to as “additive manufacturing”, where material is added to make parts, opposed to conventional methods such as CNC, where material is taken away, much of which is not recyclable. On a consumer level, affordable desktop 3D printers are now widely available, inspiring shared innovation and creativity amongst individuals on an even larger scale [3]. 3D PRINTING AND MEDICINE3D printing also has many medical applications. Because 3D printed objects are designed and built on CAD programs, they can be custom made with great ease to fit any system, whether that be a machine or a human being. For example, we can now print inexpensive plastic prosthetics for amputees, or artificial hip, knee, and facial replacements, which previously would’ve cost thousands of dollars if they were not 3D printed. 3D printing can also be applied to smaller scales, such as an airway splint to fit the trachea of an infants, made by researchers at the university of Michigan Ann Arbor [4]. A team at Harvard also found a way to print hollow tube like structures that could be used for artificial blood vessels, and another team at the Henry Ford innovation Institute is printing artificial heart valves [4]. Advances such as these could prove to be an invaluable asset to surgeons and doctors alike. BIO-PRINTINGNow, with 120,000 people on the organ transplant waiting list and only 30,000 donors (and that gap is only getting bigger), and 185,000 people receiving amputations annually, wouldn’t it be nice if we could supply organs on the same scale that we can now supply 3D printed parts? The newest and most exciting advance in the world of 3D printing may be the answer: bioprinting. Bioprinting is the construction of organic constructs, usually organs or parts of organs, by 3D printing with organic tissue. The fundamental process is essentially the same as typical 3D printing, where material is placed in the x and y axis to form a single layer, and subsequent layers are stacked up in the z direction. However, because the material used are living cells, certain steps must be taken to ensure that the cells are able to retain the shape they are placed in, and do not die. The first example of bio printing was done at the Wake Forest Institute for Regenerative medicine, using a biofriendly scaffold structure to support the printed cells, so that they may later grow and interconnect with each other in an incubator. The Printer prints layers of the scaffold material and cells over each other until the structure is complete. The cells are suspended or printed with microgel, a gelatin enriched with vitamins and proteins, in order to sustain the cells and space them properly. The printed cells are usually referred to as “bio ink”. The scaffold material is usually made up of microgel, hydrogel (water based gelatin), collagens (main structural protein found in connective tissue), bio-compatible plastic, or other biofriendly materials [5]. THE CHALLENGESBecause there are so many different types of human tissues, and each organ can be made up of multiple types of tissues, and have different structures, bioprinting becomes much more complicated. For each organ and tissue, intensive research has to be done to be able to successfully print that particular living tissue or organ. For example, skin cells change depending on depth, bladders are made up of different inner and outer cell linings, and kidneys and livers are even more complex. If these organs are successfully printed, then there is the challenge of transplanting it into patients [5]. In order for the organ to not be rejected, it has to be made from cells or stem cells from the patient. Even then, there is still a risk of rejection, because tissue from one part of the body isn’t always accepted in other parts of the body, as common surgical practice has shown [6].The biggest problem with printing working human organs is the issue of vasculature. Bone, skin, nerve tissue [7], and even ovaries [8] have been functionally printed and successfully transplanted into rats, but doing the same for humans is a little different. Cells need nutrients and oxygen to live, which in normal organs is supplied by blood running through our complex vasculature. In order to survive, cells must be within 150 to 200 microns (the width of a few human hairs) of the nearest capillary, otherwise, the amount of oxygen and nutrients will not be sufficient. Pre-existing vasculature has the tendency to penetrate and spontaneously grow into the newly added tissue, to an extent. In the cases of 3D printed organs and tissues in rats, the level of spontaneous vascularization is sufficient due to the small size of rat organs and tissues. However, in the case of humans, the size of the organs is too great for such undirected vascularization to supply enough blood to all the cells [9]. BIO-PRINTING AT WAKEFORESTA pioneer in the bioprinting world is the Wake Forest Institute for Regenerative Medicine, led by its director, Dr. Anthony Alata (and funded by the Armed Forces Institute for Regenerative Medicine). Dr. Alata and his team have been developing bioprinting and printed tissues for decades [10]. So far they have printed skin, muscle, bone, cartilage, bladders, vaginas, heart valves, ear scaffolds, and kidney prototypes. Many of the previously mentioned printed parts have been successfully placed into rats and mice. The way the parts are made is by printing both bio friendly scaffolding and cell enriched hydrogel simultaneously, and then placing the part in tissue growth encouraging liquid for an extended period of time, until cell growth has begun all throughout the scaffolding. The part is then placed into the host, where the cells continue to grow and vascularize until the part is a functioning part of the body. Simpler tests included transplanting an ear scaffold under the skin of a rat (in order to receive vascularization), where cartilage eventually fully developed and the ear appeared as normal [11].While many of the successes have been through experimenting on mice, there are cases of successes on humans other than simple tissue grafts. The bladders printed at The Wake Forest Lab were successfully transplanted into 7 patients with myelomeningocele, ages 4-19 in 2006 [9]. In another endeavor, 3D printed vaginas were successfully implanted into 4 women with vaginal aplasia, using cells from the existing vulva tissue [12].Eventually, Atlata and his team hope to print and successfully implement more complicated organs, such as kidneys. Development for printing a functional kidney is already underway, as the wake forest team has previously printed a kidney shaped prototype, made up of living kidney tissue. However, the prototype was without the intricate inner structures, such as the fine networks of vessels called glomeruli that allow the organ to filter waste materials from the blood [9]. Kidneys are made up of 3 different kinds of cells, and the inner structures need proper vascularization in order to survive. To solve the issue of blood, Wake forest scientists made a newer 3D printer called ITOP (Integrated Tissue-Organ Printer) that prints biodegradable polymers (PCL) at regular intervals, which creates very small channels in the printed tissue, allowing for even and thorough vascularization throughout the tissue. The bio-ink used in ITOP is delivered within a strong gel that helps the printed material retain its shape during printing. After, the scaffolding is washed away, leaving just the bio printed tissue [11]. Using ITOP, the Wake Forest team has printed muscle, bone (in the form of a jaw bone), and cartilage (in the form of the previously discussed ear).Atlata and his team have also looked into 3D printing skin directly onto burn sites. The have developed a skin printer that sprays the skin tissue on the wounds, and depending on the depth of the wound (gauged by a depth sensing laser) different types of skin cells are sprayed [13]. So far the printer has been used on pigs [14] successfully, but it is still pre-clinical. CONCLUSIONImagine a world where 3D printing organs became its own industry, with organs being produced on enormous scales. Bio-printing could very well be approaching that situation. While Bio printing may seem like science fiction, it is a very real technology that is being developed right now. With a steady supply of livers and kidneys being pumped out, the need for donors would become nonexistent. The 22 people who die each day waiting for a transplant would be saved, and the donor-transplant gap would close rapidly. Perhaps one day skin printers could be used to heal soldiers and burn victims, or provide cosmetic applications with a new way to approach facial reconstructive surgery. Maybe one day we could even be able to print entire limbs. Bio-printing is a technology worth advancing in, and the prospects are getting ever closer.ELECTRONIC/DIGITAL/ONLINE SOURCES[1] "Organ Donation Statistics." : Why Be an Organ Donor? HRSA, n.d. Web. 31 Oct. 2016. [2] "Amputee Coalition." Amputee Coalition. N.p., n.d. Web. 31 Oct. 2016. [3] "3D Printing Industry Examples and Case Studies." 3D Printer. N.p., n.d. Web. 31 Oct. 2016. [4] Ledford, Heidi. “The printed organs coming to a body near you”. . Nature Publishing Group, April 15, 2015. Web. 31 Oct. 2016. [5] Harris, Willaims. "How 3-D Bioprinting Works." HowStuffWorks. N.p., 17 Dec. 2013. Web. 31 Oct. 2016. [6] Gilpin, Lyndsey. "3D 'bioprinting': 10 Things You Should Know about How It Works - TechRepublic." TechRepublic. N.p., 15 Apr. 2015. Web. 31 Oct. 2016. [7] Boggs, Will. "3D 'bioprinter' Produces Bone, Muscle, and Cartilage." Reuters. Thomson Reuters, 16 Feb. 2016. Web. 31 Oct. 2016. [8] Fan, Shelly. "New 3D Printed Ovaries Allow Infertile Mice to Give Birth." Singularity HUB. N.p., 03 June 2016. Web. 31 Oct. 2016. [9] Yandell, Kate. "Organs on Demand | The Scientist Magazine?." N.p., Sep 1 2013. Web. 31 Oct. 2016. [10] Scott, Clare. "Wake Forest Researchers Successfully Implant Living, Functional 3D Printed Human Tissue Into Animals." 3DPrintcom. N.p., 2016. Web. 31 Oct. 2016. [11] Dubnicoff, Todd. "Meet ITOP: A One Stop Shop for 3D Printing Body Parts." The Stem Cellar. N.p., 2016. Web. 31 Oct. 2016. [12] Lytton, Charlotte. "Lab-Created Vaginas, Successfully Implanted in Four Women, Function Normally." The Daily Beast. Newsweek/Daily Beast, April 11 2016. Web. 31 Oct. 2016. [13] "Printing Skin Cells on Burn Wounds." - Wake Forest School of Medicine. January 4 2014, 2016. Web. 31 Oct. 2016. [14] Shaer, Matthew. Smithsonian Magazine. Smithsonian, May 2015. Web. 31 Oct. 2016. ACKNOWLEDGMENTSI would like to acknowledge my Mom, my floormate Jack, my floormate Daniel Zunino, and Dr. Natasa Vidic ................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download