Biomedical applications

Biomedical applications in the area of spaceflight aim at the reduction of medical risks for astronauts. As critical risks, the following should be mentioned among other things (Stilwell 2001):

• heart and blood circulation problems

• performance loss

• distortion of the sense of balance

• distortion of the immune system

• radiation damages

• insufficient methods for on-board medical therapy and diagnostics

Within the biomedical range, NASA aims at the development of the following applications with possible contributions from nanotechnology (Hines 2001):

• minimal invasive, efficient and mobile detection systems for mal-functionings in the entire organism (e.g. biomolecular sensors for measurements of the bone density/condition, blood chemistry or the radiation load)

• methods of early diagnosis of cancer (in particular important for longer manned missions)

• biomolecular imaging (sensor technology and visualization)

health monitoring of astronauts

• miniaturized diagnostics (e.g. lab-on-a-chip systems) whereby both the measuring and the analysis unit should be miniaturized

• autonomous therapy forms for a multiplicity of possible diseases and health damage

At present numerous research programs of NASA are accomplished in the area of Life Sciences also in co-operation with other federal institutions (e.g. NIH) or industrial partners. To be mentioned here among other things are the following research sectors of priority:

• fundamental technologies for the development of biomolecular sen-Lab-on-a-chip systems sors (NASA/ NIH)

for an autonomous • advanced human support technology programme (NASA)

• human operations in space (NASA, Johnson Space Center, Small Business Technology Transfer Program)

Application potentials for nanotechnology can be identified for example in the range of miniaturized analytical devices for medical diagnostics, e.g. lab-on-a-chip-systems. Although biochips or lab-on-a-chip-systems are microfluidic devices, they are often discussed in context with nano-technology. One of the underlying reasons is the fact that frequently na-noparticles are used for the detection of the analyte molecules. For example gold nanoparticles, semiconductor nano-crystals (so-called quantum dots)36 or also magnetic nanoparticles37 are used as markers for the substances to be determined (proteins, DNA etc.). The detection methods are based on different methods such as fluorescence spectroscopy, magnetic field measurings, electron microscopy or optical color change. The latter procedure offers the advantage that the test result is indicated without further reading instruments and therefore is in principle suitable for self diagnosis of patients.

The manufacturing of high-density oligonucleotide biochips (e.g. for gene analysis) is performed frequently by means of optical lithography, serving to produce binding positions for the individual nucleotide molecules. The advantages of biochips are the simultaneous detection of different analytes, the high speed of analyses, as well as small and compact test kits. In development are lab-on-a-chip systems, which allow complex analysis sequences by individual controllable micro valves and channels. Particularly in human space flight biochips and lab-on-a-chip systems will improve an autonomous self diagnostics of astronauts.

Rather visionary at present are nanotechnological approaches which aim at the development of biomolecular and biomimetic sensors for the online monitoring of cellular processes, for example by utilization of carbon Nanoscale drug-delivery , , , , ,TT , , . . , , ,,

. nanotubes as molecular probes (Hoenk et al. 2001). Major obstacles for systems such kind of applications are the connection of such molecular probes to

36 Rosenthal 2001

37 Colton 2001

macroscopic measuring devices as well as the amplification of the measuring signals, for which at present no technological solutions exist.

In medical therapy a substantial application field for nanotechnology is the controlled and targeted transport of drugs ("drug delivery"). The use of nanoscale transportation vehicles should make it possible to achieve, that the active drugs affect selectively the targeted regions of the human body only, minimizing unwanted side effects. Such transportation systems could be realized in principle from nanoscale cage molecules (e.g. liposomes, fullerenes or other cage molecules such as dendrimers) or by coupling with nanoparticles. The goal here is to carry the active drugs selectively to the targeted cells by means of nanoparticles with specific surface functionalization. Nanoparticles are small enough to penetrate cell membranes and overcome physiological barriers (e.g. blood-brain barrier) in the organism. Furthermore nanoparticles and nanoscale suspensions improve the solubility and bio-availability of drugs and allow the application of drugs, which are so far not applicable.

By the coupling of drugs with nanoparticles less burdening application procedures can be realized like inhalation instead of infusions for example. By functionalised nanostructured coating of the drug particles the deposition speed can be controlled and smaller doses can be applied reducing unwanted side effects.

With the help of nanotechnological therapy procedures a distinct progress in the autonomous self medication of astronauts is expected in the future including counter measures for acute intoxication (Partch 2001). An autonomous medical supply of astronauts is an important prerequisite for the realization of long manned space missions outside of the earth orbit. During a manned Mars mission, which is considered as a long term objective both of NASA and ESA, there would be no possibility of external medical supply of the astronauts for a period of up to three years, apart from capabilities of tele medicine which will be developed until then.

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