1.2 Antimicrobial Properties. Efforts are focused on investigating nanomaterials with strong antimicrobial properties. Nanocrystalline silver, for example, is already being used for wound treatment.

Biopharmaceutics. Efforts are focused on drug delivery applications using Nanomaterial coatings to encapsulate drugs and to serve as functional carriers. Nanomaterial encapsulation could improve the diffusion, degradation, and targeting of a drug. Furthermore, nanomaterials could serve as camouflage to avoid immune responses, or as agents which could catalyze or respond to certain molecules or chemical events⁴.

Implantable Materials. Efforts are centered on using nanomaterials to repair and replace damaged or diseased tissues. Nanomaterial implant coatings could increase the adhesion, durability, and lifespan of implants, and nanostructure scaffolds could provide a framework for improved tissue regeneration. Moreover, Nanomaterial implants could be engineered for biocompatibility with the host environment to minimize side effects and the risk of rejection. Furthermore, smart nanomaterials could detect and respond to environmental conditions and chemical reactions.

Implantable Devices. Efforts are concentrated on implanting small devices to serve as sensors, fluid injection systems, drug dispensers, pumps and reservoirs and aid to restore vision and hearing functions. Devices with Nanoscale components could monitor environmental conditions, detect specific properties, and deliver appropriate physical, chemical, or pharmaceutical responses. In the longer term, the development of nanoelectronic systems that can detect and process information could lead to nanodevices that serve as retina implants by acting as photoreceptors, and cochlear implants by improving nerve stimulation.

Diagnostic Tools. Efforts are directed at utilizing lab-on-a-chip devices to perform DNA analysis and drug discovery research by reducing the required sample sizes and accelerating the chemical reaction process⁵. Moreover, imaging technologies such as nanoparticle probes and miniature imaging devices could promote early detection and diagnosis of disease.

Figure 2: Current Areas of Nanomedicine Development3

1.3 Imaging:

Techniques such as tomography, nuclear magnetic resonance or ultrasound scanning have enormously expanded the classical use of X-rays in producing images of increasing quality of the human body that are already widely used in multiple types of diagnosis, including analysis of functions of the human brain. Imaging includes also analysis of microscopic images of tissues used in pathology. Nanotechnologies may allow a more precise diagnosis. As an example, ultra small, super-paramagnetic iron oxides, with a diameter of less than 50 nm, allow the imaging of organs and have been successfully evaluated for improved lymph node metastases detection in various clinical trials.

There are many other techniques in use or at the design stage that use nanoparticles to assist in the imaging process or that use nano-techniques to provide images of living systems⁶. These techniques can be both in-vivo, for example contrast agents introduced in the body, and ex-vivo, such as specific markers used in histology. In the more distant future a combination of improved in vivo agents, scanners and software could offer diagnostic support to the practitioner (e.g. displaying real-time statistics about similar symptoms).

1.4 Stem cell therapy:

Stem cell therapy combined with nanotechnology, based on magnetic cell sorting, also offers promising possibilities for the regeneration of diseased tissue. Stem cells may be identified, activated and guided to the place of damage within the body with the use of cell–signaling molecules as a source of molecular regeneration messengers.

1.5 Implants:

With regard to the use of electronic nanodevices, it has also been advocated that nano- and related micro-technologies might be used to develop a new generation of smaller and potentially more powerful devices to restore loss of vision. Another future approach may be the use of a miniature video camera attached to a blind person’s glasses to capture visual signals processed by a microcomputer worn on the belt and transmitted to an array of electrodes placed in the eye. Another uses a sub-retinal implant designed to replace Photoreceptors in the retina. For hearing, an implanted transducer may be pressure-fitted onto a bone in the inner ear, causing the bones to vibrate and move the fluid in the inner ear, which stimulates the auditory nerve.

Figure 3: Retinal Implant4

1.6 Cosmetic applications

One major area of health related non-medical nanotechnological applications is in the field of cosmetics. A number of cosmetics products using nanotechnology are already on the market⁷. The market is growing at about 10% a year and companies believe that nanotechnology will help to create a new generation of products. Toxic effects connected with the use of nanocosmetics have not been reported so far, but both US Food and Drug Administration and the Royal Society in Britain have stressed a lack of knowledge in this area.

Drug Encapsulation:

One major class of drug delivery systems is materials that encapsulate drugs to protect them during transit in the body. Drug encapsulation materials include liposomes and polymers (i.e. Polylactide (PLA) and Lactide-co-Glycolide (PLGA)) which are used as micro scale particles. The materials form capsules around the drugs and permit timed drug release to occur as the drug diffuses through the encapsulation material. The drugs can also be released as the encapsulation material degrades or erodes in the body.

Figure 4: Nanospores⁶

When encapsulation materials are produced from Nanoparticles in the 1 to 100nm size range instead of bigger micro particles, they have a larger surface area for the same volume, smaller pore size, improved solubility, and different structural properties. This can improve both the diffusion and degradation characteristics of the encapsulation Material. In addition to liposomes and polymers, other types of Nanoparticles are available for encapsulation. Materials such as silica and calcium phosphate (hydroxyapatite) have demonstrated superior properties at the nanoscale than the micro scale, and can potentially be better suited for certain drug delivery challenges mentioned above.

1.7 Implantable Materials:

Tissue Repair and Replacement:

Nanotechnology provides a new generation of biocompatible nanomaterials for repairing and replacing human tissues.

Human tissue that is diseased or traumatically compromised may require synthetic materials for its repair or replacement. While most types of tissues repair the interaction of stem cells with chemical modulators, there are differences in the ways that various tissues heal.

“Hard” tissues such as bone and teeth heal by reproducing tissues indistinguishable from the original. However in cases where a dental or artificial bone implant is required, the structural material used in the implant may trigger immune rejection, corrode in the body fluids, or no longer bond to the host bone. This can require additional surgery or result in the loss of the implant’s function. In many cases, the failure occurs at the tissue-implant interface, which may be due to the implant material weakening its bond with the natural material. To overcome this, implants are often coated with a biocompatible material to increase their adherence properties and produce a greater surface area to volume ratio for the highest possible contact area between the implant and natural tissue.

Implant Coatings:

Nanotechnology brings a variety of new high surface area biocompatible nanomaterials and coatings to increase the adhesion, durability and lifespan of implants. Ceramic materials such as calcium phosphate (hydroxyapatite or HAP) are made into implant coatings using nano-sized particles instead of micro-sized particles.

Tissue Regeneration Scaffolds:

Nanostructures are being researched for the preparation and improvement of tissue regeneration scaffolds. Research areas include the ability to develop molecularly sensitive polymers using the optical properties of nanoparticles as control systems, manipulating the stiffness and strength of scaffolds using hybrid nanostructures, and the use of nanotechnology to prepare molecular imprints to maximize long-term viability and function of cells on scaffold surfaces.

Structural Implant Materials:

Nanotechnology provides a new generation of biocompatible materials that can be used as implants or temporary biosorbable structures. Bone is a high strength material that is used as both weight bearing and non-weight bearing structures. Bones are more than just structural materials as they also contain interconnected pores that allow body fluids to carry nutrients and permit interfacial reactions between hard and soft tissues. In the case of bone fractures, grafts, disorders, dental applications and other types of surgery, bones may require repair or replacement.

Bone Repair:

Nanotechnology brings a variety of new high surface area biocompatible nanomaterials that can be used for bone repair and cavity fillers. High strength nanoceramic materials, such as calcium phosphate apatite (CPA) and hydroxyapatite (HAP), can be made into a flowable, moldable Nanoparticles paste that can conform to and interdigitate with bone. As natural bone is approximately 70% by weight CPA including hydroxyapatite (HAP), biocompatibility is thought to be extremely high with minimal side effects.

Bioresorbable Materials:

Nanotechnology also brings advances in bioresorbable materials. Bioresorbable polymers are currently being used in degradable medical applications such as sutures and orthopaedic fixation devices. With new production methods, nanostructures are being fabricated which could be used as temporary implants.

Smart Materials:

Smart materials are a class of nanomaterials that respond to changes in the environment such as a drop in temperature or pH. An environmental change could trigger a physical or chemical effect that mimics a natural mechanism in the body. For example, applications could include a smart polymer that flexes with mechanical strength as an artificial muscle, or a hydrogel that dissolves according to body chemistry to more efficiently deliver drugs.

Assessment and Treatment Devices:

Nanotechnology offers sensing technologies that provide more accurate and timely medical information for diagnosing disease, and miniature devices that can administer treatment automatically if required. Health assessment can require medical professionals, invasive procedures and extensive laboratory testing to collect data and diagnose disease. This process can take hours, days or weeks for scheduling and obtaining results.

Sensory Aids:

Nano and related micro technologies are being used to develop a new generation of smaller and potentially more powerful devices to restore lost vision and hearing functions. The devices collect and transform data into precise electrical signals that are delivered directly to the human nervous system.

Retina Implants:

Retinal implants are in development to restore vision by electrically stimulating functional neurons in the retina. One approach being developed by various groups including a project at Argonne National Laboratory is an artificial retina implanted in the back of the retina. The artificial retina uses a miniature video camera attached to a blind person’s eyeglasses to capture visual signals. The signals are processed by a microcomputer worn on the belt and transmitted to an array of electrodes placed in the eye. The array stimulates optical nerves, which then carry a signal to the brain⁸.

Imaging:

Nano and micro technologies offer new imaging technologies that provide high quality images not possible with current devices, along with new methods of treatment. Malignant tumors are highly localized during the early stage of their development. If detected early, the tumors can often be surgically removed with high success. The longer a patient has a malignant tumor the more likely the cancer will spread to neighboring lymph nodes and other anatomic structures. Aggressive surgery or chemotherapy, or very high doses of radiation may kill the cancer but at the same time severely injure normal tissue. In many patients, particularly those with breast cancer, the cancer can spread to other parts of the body even after the original cancer tumor has been removed⁹.

2 MEDICAL NANOMATERIALS AND NANODEVICES:

2.1 Nanopores:

Perhaps one of the simplest medical nanomaterials is a surface perforated with holes, or nanopores¹⁰. In 1997 Desai and Ferrari created what could be considered one of the earliest therapeutically useful nanomedical devices, employing bulk micromachining to fabricate tiny cell-containing chambers within single crystalline silicon wafers. The chambers interface with the surrounding biological environment through polycrystalline silicon filter membranes which are micromachined to present a high density of uniform Nanopores as small as 20 nanometers in diameter^11,12. These pores are large enough to allow small molecules such as oxygen, glucose, and insulin to pass, but are small enough to impede the passage of much larger immune system molecules such as immunoglobulin and graft-borne virus particles¹³.

2.2 Fullerenes and Nanotubes:

Soluble derivatives of fullerenes such as C60 have shown great utility as pharmaceutical agents. These derivatives, many already in clinical trials (www.csixty.com), have good biocompatibility and low toxicity even at relatively high dosages. Fullerene compounds may serve as antiviral agents (most notably against HIV, where they have also been investigated computationally), antibacterial agents (E. coli, Streptococcus, Mycobacterium tuberculosis, etc.), photodynamic antitumorand anticancer therapies, antioxidants and anti-apoptosis agents which may include treatments for amyotrophic lateral sclerosis (ALS or Lou Gehrig’s disease) and Parkin-.disease.Single-walled and multi-walled carbon nanotubes are being investigated as biosensors, for example to detect glucose, ethanol hydrogen peroxide selected proteins such as immuno globulins, and as an electrochemical DNA hybridization biosensor¹⁴.

Figure 5: Fullerene - based HIV protease inhibitor9

CONCLUSION:

Nanomedicine is a global business enterprise impacting universities, startsup and boardrooms of Multinationals Corporation alike. Industry and government are clearly beginning to envision nanomedicine’s enormous potential. As long as government expenditure encourages facile technology transfer to the private sector, nanotechnology will eventually blossom as a source for corporate investment and revenue.However, for nanomedicine to truly become a global mega trend, the hype must be separated from reality. In addition, societal, environmental, and ethical concerns will also need to be addressed as scientific advances occur. A numerous novel nanomedicine-related application are under development or nearing commercialization, the process of converting basic research in nanomedicine into commercially viable products will be long and difficult. Although realization of the full potential of nanomedicine may be years or decades away, recent advances in nanotechnology-related drug delivery, diagnosis, and drug development are beginning to change the landscape medicine. New nanotechnologies may offer the only hope for systematic, affordable, and long term improvements to the health status of our population. This is because nano therapies (combined with related advances in surgery, therapeutics, diagnostics and computerization) could, in the long run, be much more economical, effective and safe and could greatly reduce the cost or substantially eliminate current medical procedures (compare stents with bypassoperations or antibody therapy for Crohn’s disease versus surgery).

REFERENCES:

1. The Royal Society. (July, 2004) “Nanoscience and Nanotechnologies: Opportunities and Uncertainties.” Accessed online at: www.royalsoc.ac.uk Roco, M.C. “Government Nanotechnology Funding: An International Outlook.” National Science Foundation. Accessed online at: www.nano.gov

2. Roco, M.C. “Government Nanotechnology Funding: An International Outlook” National Science Foundation. Accessed online at: www.nano.gov

3. Kanellos, Michael. “Nanotech funding to grow to $8.6 billion,” TechRepublic.com. Accessed online at: http://techrepublic.com

4. “Applications/Products” National Nanotechnology Initiative. Accessed online at http://www.nano.gov “Nanotechnology – Product News.” Country Doctor. Accessed http://www.countrydoctor.co.uk

5. http://www.systemsbiology.org/extra/PressRelease_102204.html and also http://cmliris.harvard.edu

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7. Tegart, Greg. “Nanotechnology: The Technology for the 21st Century.” The APEC Center for Technology Foresight. Bangkok, Thailand. Presented at the First International Conference on Technology Foresight, Tokyo, and Feb. 27-28, 2003.

8. Tegart, Greg. “Nanotechnology: The Technology for the 21st Century.” The APEC Center for Technology Foresight. Bangkok, Thailand. Presented at The Second International Conference on Technology Foresight, Tokyo, and Feb. 27-28, 2003.

9. “Applications/Products” National Nanotechnology Initiative. Accessed online at http://www.nano.gov

10. “Emerging nanomedicine technologies could dramatically transform medical science” News Medical.net. July 23, 2004. Accessed online at ://www.newsmedical.net

11. Richard Feynman (1918-1988), Nobel Prize winner in Physics 1965, lecture given on 29 December 1959 at the annual meeting of the American Physical Society.

12. Drexler, K.E. (1981) “Molecular engineering: An approach to the development of general capabilities for molecular manipulation”, Proceedings of the Nation Academy of Science USA 78:5275-5278.

13. Drexler, K.E. (1986) Engines of Creation: The Coming Era of Nanotechnology. New York, Anchor Press/Doubleday.

14. The Royal Society & The Royal Academy of Engineering (July 2004) Nanoscience and nanotechnologies: Opportunities and uncertainties. London, ISBN 0 85403 604

Received on 13.03.2010

Accepted on 11.07.2010

Research J. Science and Tech. 2(3): May –June. 2010: 41-46