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Posted: Mar 01, 2006
Bionanotechnology progress and advances
(Nanowerk News) Chemists, physicists and biologists each view nanotechnology as a branch of their own subject, and collaborations in which they each contribute equally are common. One result is the hybrid field of bionanotechnology (also used are the terms biomedical nanotechnology or nanomedicine) that uses biological starting materials, biological design principles or has biological or medical applications.
In describing recent developments, Chan focuses on three areas where he provides state-of-the-art examples of advances in nanotechnology research that have provided a new set of research tools, materials, structures, and systems for biological and medical research and applications.
He makes it clear, though, that although the integration of nanomaterials with biology has led to the development of diagnostic devices, contrast agents, analytical tools, therapy, and drug-delivery vehicles, bionanotechnology research is still in its infancy; few nanotechnology-based products are in clinical use.
Quantum dots for bio-imaging
Quantum dots, the name given to semiconductor crystals with diameters of just a few nanometers, are at the forefront of a new class of inorganic probes. Quantum dots are particularly significant for optical applications due to their theoretically high quantum yield.
As biological probes, they are extremely bright and have fluorescence properties. (In general, the larger the dot, the more towards the red end of the spectrum the fluorescence is; the smaller the dot, the more towards the blue end it is. The coloration is directly related to the energy levels of the quantum dot.) When quantum dots are used in biological research and applications, these optical properties will lead to improved detection sensitivity for analysis and to simplification in experimental and instrumental design.
Fluorescence induced by exposure to ultraviolet light in vials containing various sized quantum dots (Source: Philips)
For instance, in in vitro applications, quantum dots are used for labeling receptors on live cells and tissues. For in vivo applications, successful demonstration of quantum dots as contrast agents for cancer imaging has already been achieved.
Four major areas of research will advance the study and application of quantum dots: improvement as optical probes with better optical qualities; understanding the relationship with biological systems; understanding the influence of biological environments and conditions on their optical and electronic properties; and applying quantum dots toward clinical applications.
As examples Chan describes biological sensors where metallic nanoparticles are used as contrast agents in electron microscopy; as a platform for surface-enhanced Raman spectroscopy (SERS) where a single molecule could be detected if that molecule was adsorbed onto a metallic nanostructure; and therapeutical applications where photothermal properties can be engineered into the metallic nanostructures for laser ablation therapy.
Without going into details, Chan also mentions that other nanostructures such as carbon nanotubes, fullerenes, dendrimers, and magnetic nanostructures are used in biomedical research and already found their way into applications such as drug delivery.
Integration of nanostructures with biological molecules and structures
Moving towards the futuristic side of nanobiotechnology, Chan finally addresses the area of multifunctional nanodevices. Researchers are now starting to figure out how to build such devices, and mimicking of biological systems for designing nanodevices looks like a powerful strategy.
Theoretically, if one could find the answers to two major questions – how can one organize nanostructures into a functional device? and how can one control the function of these nanostructures? – devices would become feasible that offer a new type of advanced therapy for the treatment of cancer, Alzheimer disease, or infections. With these multifunctional nanodevices, molecules and motors will guide nanomaterial movements, sensors for diagnosis, actuators (which are connected to the sensor) to release therapy, and a secondary sensor to monitor the disease as it is being treated.
That goal, according to Chan, is 50-100 years away.