Nanotechnology has begun to find potential applications in the area of functional food by engineering biological molecules toward functions very different from those they have in nature, opening up a whole new area of research and development. Of course, there seems to be no limit to what food technologists are prepared to do to our food (read this delightful romp through the food processing industry to get the idea: "Twinkie, Deconstructed". For the non-U.S. reader: a Twinkie is a processed foodlike substance that has reached iconic status in this country) and nanotechnology will give them a whole new set of tools to go to new extremes. We have taken a critical view of food nanotechnology before in this column and in our news coverage, just take a look at "Nanotechnology food coming to a fridge near you" or "Are you ready for your nano-engineered wine?". Today, though, we look at the potentially beneficial effects nanotechnology-enabled innovations could have on our foods and, subsequently, on our health.
Engineered nanoparticles are at the forefront of the rapidly developing field of nanomedicine. Their unique size-dependent properties, of which optical and magnetic effects are the most used for biological applications, makes them suitable for a wide range of biomedical applications such as cell labeling and targeting, tissue engineering, drug delivery and drug targeting, magnetic resonance imaging, probing of DNA structure, tumor destruction via heating (hyperthermia), and detection and analysis of biomolecules such as proteins or pathogens. Many of these applications can also be tailored to target skin to help in the early diagnosis of a skin disease, which then could also be treated via nanocarriers. In addition, a tissue engineering approach could be useful for skin wound healing therapies and the magnetic properties of these particles might help in directing and localizing these agents in a particular layer of the skin where their action is desired. Unfortunately, if nanoparticles are able to penetrate layers of skin for therapeutic purposes, they might equally be able to penetrate skin unintentionally. This raises the question if people, who are exposed to such nanomaterials, could accidentally be contaminated and thus exposed to a potential local and/or systemic health risk. Researchers in Italy now have begun to systematically evaluate both risks and applications of nanoparticle skin absorption.
Biosensors, which incorporate biological probes coupled to a transducer, have been developed during the last two decades for environmental, industrial, and biomedical diagnostics. The application of nanotechnology to biosensor design and fabrication promises to revolutionize diagnostics and therapy at the molecular and cellular level. The convergence of nanotechnology, biology, and photonics opens the possibility of detecting and manipulating atoms and molecules using a new class of fiberoptic biosensing and imaging nanodevices. These nanoprobes and nanosensors have the potential for a wide variety of medical uses at the cellular level. The potential for monitoring in vivo biological processes within single living cells, e.g. the capacity to sense individual chemical species in specific locations within a cell, will greatly improve our understanding of cellular function, thereby revolutionizing cell biology. Existing nanoprobes have already demonstrated the capability of performing biologically relevant measurements inside single living cells.
The market for medical implant devices in the U.S. alone is estimated to be $23 billion per year and it is expected to grow by about 10% annually for the next few years. Implantable cardioverter defibrillators, cardiac resynchronization therapy devices, pacemakers, tissue and spinal orthopedic implants, hip replacements, phakic intraocular lenses and cosmetic implants will be among the top sellers. Current medical implants, such as orthopaedic implants and heart valves, are made of titanium and stainless steel alloys, primarily because they are biocompatible. Unfortunately, in many cases these metal alloys with a life time of 10-15 years may wear out within the lifetime of the patient. They also might not achieve the same fit and stability as the original tissue, and in a worst case, the host organism might reject the implant altogether. While available implants can alleviate excruciating pain and allow patients to live more active lives, there often are problems getting bone to attach to the metal devices. Small gaps between natural bone and the implant can increase over time, requiring the need for additional surgery to replace the implant. In the quest to make bone, joint and tooth implants almost as good as nature's own version, scientists are turning to nanotechnology. Researchers have found that the response of host organisms (including at the protein and cellular level) to nanomaterials is different than that observed to conventional materials. While this new field of nanomedical implants is in its very early stage, it holds the promise of novel and improved implant materials.
The assembly of nanoparticles along the external or internal surface of carbon nanotubes (CNTs) is of both fundamental and technological interest. Combining unique properties of CNTs and nanoparticles, the nanoparticle/nanotube composite structure attracts a broad range of advanced applications, including nanoelectronics, chemical and biosensors, catalysis and fuel cells. This so-called 'decoration' of CNTs has been used to increase the hydrogen storage capacity, to make nanotubes magnetic, or to grow secondary structures inside the nanotubes to increase the available surface for catalysis. In the case of interior wall decoration of CNTs, the internal cavity of the nanotube often is obstructed and no flow can be achieved or there could be release of the particles in the environment. In the case of exterior wall decorations, the particles enter in direct contact with the environment and may be lost during the nanotube handling. A novel technique of multifunctional nanotubes with controllable amounts of nanoparticles embedded in their walls during the synthesis process solves both problems leaving the CNT bore accessible and keeping the nanoparticles shielded from the environment by the CNT walls. This paves the way to using carbon nanotubes as nanoscale biological probes for sub-cellular investigation.
Can a major component of a catalytic converter or a fullerene derivative lead to an eventual treatment for Parkinson's disease or arthritis? Research to date certainly hints at this possibility. In chemistry, radicals (often referred to as free radicals) are atomic or molecular species with unpaired electrons on an otherwise open shell configuration. These unpaired electrons are usually highly reactive, so radicals are likely to take part in chemical reactions. Radicals play an important role in human physiology but, because of their reactivity, they also can can participate in unwanted side reactions resulting in cell damage. Free radicals damage components of the cells' membranes, proteins or genetic material by "oxidizing" them - the same chemical reaction that causes iron to rust. This is called "oxidative stress". Many forms of cancer are thought to be the result of reactions between free radicals and DNA, resulting in mutations that can adversely affect the cell cycle and potentially lead to malignancy. Oxidative stress is believed to play a role in neurodegenerative diseases such as Alzheimer's and Parkinson's.Some of the symptoms of aging such as arteriosclerosis are also attributed to free-radical induced oxidation of many of the chemicals making up the body. Despite the broad role that oxidative stress plays in human disease, medicine has been limited in its development of treatments that counteract free radical damage and the ensuing burden of oxidative stress. In contrast, in the field of engineering, considerable effort has been developed to counter the effects of oxidative stress at the materials science level. Nanotechnology has provided numerous constructs that reduce oxidative damage in engineering applications with great efficiency. A recent review looks at how these nanoengineering concepts could be applied to biomedical problems, ultimately leading to nanotechnology-based therapeutical treatments for oxidative stress-induced diseases.
One of the key avenues to understanding how biological systems function at the molecular level is to probe biomolecules individually and observe how they interact with each other directly in vivo. Laser-induced fluorescence is a technique widely adopted for this purpose owing to its ultrahigh sensitivity and capabilities of performing multiple-probe detection. However, in applying this technique to imaging and tracking a single molecule or particle in a biological cell, progress is often hampered by the presence of ubiquitous endogenous components such as flavins and collagens that produce high fluorescence background signals. These biomolecules typically absorb light at wavelengths in the range of 300-500 nm and fluoresce at 400-550 nm. To avoid such interference, a good biological fluorescent probe should absorb light at a wavelength longer than 500 nm and emit light at a wavelength longer than 600 nm, at which the emission has a long penetration depth through cells and tissues. Organic dyes and fluorescent proteins are two types of molecules often used to meet such a requirement; however, the detrimental photophysical properties of these molecules, such as photobleaching and blinking, inevitably restrict their applications for long-term in vitro or in vivo observations. Fluorescent semiconductor nanocrystals (or quantum dots), on the other hand, hold a number of advantageous features including high photobleaching thresholds and broad excitation but narrow emission spectra well suited for multicolor labeling and detection. Unfortunately, most quantum dots are toxic, and hence reduction of cytotoxicity and human toxicity through surface modification plays a pivotal role in their successful application to in vivo labeling, imaging, and diagnosis. Researchers in Taiwan have demonstrated that nanodiamond particles possess several unique features, including facile surface modification, long-term photostability, and no fluorescence blinking, that makes their detection and long-term tracking in living cells not only possible but practical.
Current medical and biological fluorescent imaging is limited by the use of dye markers, which are not photostable. The dyes can break down under photoexcitation, room light or higher temperatures. The observation of strong visible emission in porous silicon therefore has triggered substantial interest in exploring the synthesis and characterization of silicon nanoparticles. Due to their biocompatibility, high photoluminescence quantum efficiency and stability against photobleaching, silicon nanoparticles are expected to be an ideal candidate for replacing fluorescent dyes in many biological assays and fluorescence imaging techniques. For instance, they have been proposed as better quantum dots for in vivo applications, potentially replacing quantum dots of highly toxic cadmium. Different synthetic and physical methods have been used to prepare silicon nanoparticles. However, the yields of nanoparticles from these methods are very low and an HF (hydrofluoric acid) etching process is often necessary to obtain photoluminescent, hydrogen-terminated silicon nanoparticles. Now, researchers have developed a new solution route for the production of macroscopic amounts of hydrogen terminated silicon nanoparticles without hazardous material handling. This synthesis route is simple and thus offers great opportunity for scaled-up preparation of semiconductor materials.