Until
next week,Bioengineering: Parts of android evolution.
Dateline: November 9, 1997
Artificial hearts, lungs, and kidneys, prosthetic hands, arms, and legs, artificial hips . . . these wonders have become commonplace in modern surgery. In previous articles, we’ve seen that artificial neural chips (e.g., Professor Berger’s work at the University of Southern California), artificial brains (e.g., Dr. de Garis’ work at Japan’s ATRI), artificial eyes (the recent announcement of an eye-on-a-chip from France), artificial noses (various chemical-sniffing devices), factory-produced skin (being used for skin grafts), and artificial muscle (e.g., work at MIT) are not far behind. This article looks at two other developments: artificial bone and artificial blood.
Artificial Bone
In a project at Arizona State University’s Center for Solid State Science, biomedical engineers are working on ion beam modification of hydroxy apatite, an artificial bone-like material, to make it adhere better to metal. (Ions are atoms or groups of atoms that carry a positive or negative electrical charge.) An immediate benefit from such research is to improve artificial joint surgery, such as hip and knee replacements, in which metal parts need to be attached to bone and inserted into joint sockets. But the uses of artificial bone for cyborg purposes is obvious. If it can be made to withstand greater stress than human bone, then it would enable a cyborg with powerful artificial muscle to lift very heavy objects and leap great distances. It would also circumvent the problem of bone loss that occurs in prolonged exposure to the zero gravity of space. A cyborg astronaut (with perhaps a pacemaker-assisted heart or a heart made from artificial muscle) would have none of the weakness endemic to current astronauts upon returning from a prolonged space mission.
Bioengineers and associates of Rice University are also working on tissue-engineered bone, looking for methods to fabricate bone using a combination of biocompatible polymers, growth factors, and cell transplantation. They have demonstrated the fabrication of vascularized bone flaps for reconstructive surgery using formed plastic chambers packed with an osteoinductive scaffold and implanted adjacent to the rib periosteum in sheep. The ability to "prefabricate" bone segments by inducing autogenous tissue to grow into useful shapes that are vascularized from a single anatomic source, suitable for microvascular transfer, would represent a significant advance for the reconstruction of complex osseous defects.
Another method being pursued is to inject a degradable, polymeric composite biomaterial able to "guide" bone regeneration into people with skeletal defects. The biomaterial is moldable so it can fill irregularly shaped defects, hardens within ten to fifteen minutes, is as strong as the bone it replaces, degrades over time (thus avoiding problems encountered with non-degradable implants), can be replaced by new bone, and can maintain a specified minimum mechanical strength during the period of degradation and new bone growth.
Biodegradable polymers and bioactive scaffolds are also being investigated for treating nerve defects. Illnesses, injuries, and sometimes resulting medical or surgical treatment can often damage or destroy critical nerves. To restore neural functionality in a damaged area, surgeons may cut nerve or muscle from an uninjured location and attach it to the injured site.
Artificial Blood
Though still at an early stage, a mathematical model has been developed and a combination of experimental and theoretical methods is being applied to generate information that will facilitate the design of blood substitutes. The applications for a substitute for blood are fairly obvious.
Artificial Blood Vessels
Inserting genes into smooth muscle cells will transform them into a "pseudo-endothelial" cell that can be used to line artificial blood vessels and surfaces of heart pump devices. Naturally-occurring endothelial cells are few and difficult to use for this purpose without inducing thrombosis.
So What?
If all this leaves you thinking that within a few decades we’ll have all the pieces to make an artificial human—an android—you’re right. Whether we would want to make an artificial human is another matter. But it is very clear that we do want to improve the performance of existing human bodies. Initially, and properly, we want to remove the handicaps of handicappers, but I believe it is only a matter of time before we extend the technology of bioengineering to make bionic men and women of all of us. Another word for bionic human is cyborg.
Science fiction? I don’t think so.
Until
next week,
NEXT WEEK: Notes from Steve Pinker's latest book, How the Mind Works.