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Fleshing out the state of the art
3D printing is driving innovation in many areas, from engineering and manufacturing to art and education. The technology is also being broadly applied in medicine-from printing prosthetic limbs to making patient-specific models of body parts that surgeons use as guides during reconstructive surgery. 3D printers have been used to make implants used in a small number of patients, including a titanium jawbone and a tailor-made, bioresorbable tracheal splint that saved a baby's life. The next frontier in medical printing is bioprinting-using living ceils to print replacement tissues and organs.
The idea of lab-built organs is not new and scientists have demonstrated the function of engineered airways, bladders, blood vessels and urine tubes in patients. These engineered structures have three key components: scaffolds, made of materials compatible with the body and fashioned in the shape of a tissue or organ; cells, ideally from the patient; and biomolecules, such as growth factors, to induce tissue formation.
This same "recipe" that was used to engineer human organs and tissue by hand is now used with 3D printers to produce structures such as bone, cartilage, blood vessels, cardiac tissue and heart valves that show promise for clinical use. The ultimate goal is to print complex organs such as livers and kidneys for transplant and to create composite tissues made up of skin, muscle, tendon, nerves, bone and blood vessels for reconstructive surgery.
The advantages of printing tissues, rather than engi- neering them by hand, are many. Printers allow the proper placement of multiple cell types, biomaterials and bioactive molecules in defined locations. They also offer the ability to control the size, microarchitecture and interconnectivity of pores in the scaffolds-essential to transporting oxygen and nutrients for cell survival. The technology also offers the option of using a patient's medical images, such as MRI or CT scans, to tailor-make organs.
Of course, there are many challenges to overcome before printing organs for patients is a reality. The technologies that were designed to print molten plastics and metals must be adapted to print sensitive, living biological materials. And, the more central challenge is to reproduce the complex microarchitecture of living tissue to ensure that printed tissues have biological function.
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