which are commonly not dialyzable can be removed. the purification process is based on functionalized iron oxide or carbon coated metal nanoparticles with ferromagnetic or superparamagnetic properties. binding agents such as proteins, antibiotics, or synthetic ligands are covalently linked to the particle surface. these binding agents are able to interact with target species forming an agglomerate. applying an external magnetic field gradient allows exerting a force on the nanoparticles. hence the particles can be separated from the bulk fluid, thereby cleaning it from the contaminants. the small size (< 100 nm) and large surface area of functionalized nanomagnets leads to advantageous properties compared to hemoperfusion, which is a clinically used technique for the purification of blood and is based on surface adsorption. these advantages are high loading and accessible for binding agents, high selectivity towards the target compound, fast diffusion, small hydrodynamic resistance, and low dosage. tissue engineering nanotechnology may be used as part of tissue engineering to help reproduce or repair or reshape damaged tissue using suitable nanomaterial-based scaffolds and growth factors. tissue engineering if successful may replace conventional treatments like organ transplants or artificial implants. nanoparticles such as graphene, carbon nanotubes, molybdenum disulfide and tungsten disulfide are being used as reinforcing agents to fabricate mechanically strong biodegradable polymeric nanocomposites for bone tissue engineering applications. the addition of these nanoparticles in the polymer matrix at low concentrations (~0.2 weight %) leads to significant improvements in the compressive and flexural mechanical properties of polymeric nanocomposites. potentially, these nanocomposites may be used as a novel, mechanically strong, light weight composite as bone implants. for example, a flesh welder was demonstrated to fuse two pieces of chicken meat into a single piece using a suspension of gold-coated nanoshells activated by an infrared laser. this could be used to weld arteries during surgery. another example is nanonephrology, the use of nanomedicine on the kidney. medical devices neuro-electronic interfacing is a visionary goal dealing with the construction of nanodevices that will permit computers to be joined and linked to the nervous system. this idea requires the building of a molecular structure that will permit control and detection of nerve impulses by an external computer. a refuelable strategy implies energy is refilled continuously or periodically with external sonic, chemical, tethered, magnetic, or biological electrical sources, while a non-refuelable strategy implies that all power is drawn from internal energy storage which would stop when all energy is drained. a nanoscale enzymatic biofuel cell for self-powered nanodevices have been developed that uses glucose from biofluids including human blood and watermelons. one limitation to this innovation is the fact that electrical interference or leakage or overheating from power consumption is possible. the wiring of the structure is extremely difficult because they must be positioned precisely in the nervous system. the structures that will provide the interface must also be compatible with the body's immune system. cell repair machines molecular nanotechnology is a speculative subfield of nanotechnology regarding the possibility of engineering molecular assemblers, machines which could re-order matter at a molecular or atomic scale. nanomedicine would make use of these nanorobots, introduced into the body, to repair or detect damages and infections. molecular nanotechnology is highly theoretical, seeking to anticipate what inventions nanotechnology might yield and to propose an agenda for future inquiry. the proposed elements of molecular nanotechnology, such as molecular assemblers and nanorobots are far beyond current capabilities. future advances in nanomedicine could give rise to life extension through the repair of many processes thought to be responsible for aging. k. eric drexler, one of the founders of nanotechnology, postulated cell repair machines, including ones operating within cells and utilizing as yet hypothetical molecular machines, in his 1986 book engines of creation, with the first technical discussion of medical nanorobots by robert freitas appearing in 1999. raymond kurzweil, a futurist and transhumanist, stated in his book the singularity is near that he believes that advanced medical nanorobotics could completely remedy the effects of aging by 2030. according to richard feynman, it was his former graduate student and collaborator albert hibbs who originally suggested to him (c. 1959) the idea of a medical use for feynman's theoretical micromachines (see nanotechnology). hibbs suggested that certain repair machines might one day be reduced in size to the point that it would, in theory, be possible to (as feynman put it) "swallow the doctor". the idea was incorporated into feynman's 1959 essay there's plenty of room at the bottom.