Back in March Nanowerk Spotlight reported on work by Sandia researchers who developed a range of novel platinum nanostructures with potential applications in fuel and solar cells (see: Novel platinum nanostructures). Through the use of liposomal templating and a photocatalytic seeding strategy the Sandia team produced a variety of novel dendritic platinum nanostructures such as flat dendritic nanosheets and various foam nanostructures (nanospheres and monoliths). In an intriguing follow-up report on the growth of hollow platinum nanocages, they now show for the first time a one-to-one correspondence between the porphyrin photocatalyst molecules and the seed particles that go on to grow the dendrites. This indicates that the whole process might be used for nanotagging biological molecules and other structures that have been labeled with a photocatalytic porphyrin.
Conventional diagnostic imaging is mainly based on morphological contrast that is a result of different general tissue characteristics. Molecular imaging is a new approach for detecting diseases much earlier, visualizing biological processes at the cellular and molecular level in living organisms, and detecting changes in biochemistry. Corresponding molecular markers appear in quite low concentrations. Hence, the imaging technique must be very sensitive. Magnetic resonance imaging (MRI) has some significant advantages in terms of using non-ionizing radiation (in contrast to x-rays) and giving high resolution tomographies for any arbitrary position and orientation. However, conventional MRI suffers from inherent low sensitivity. A new method, using xenon as the signal source, was developed by researchers in California and will make MRI an important technique in molecular imaging, offering a huge potential for specific detection of disease markers. The new technique allows detection of signals from molecules present at 10,000 times lower concentrations than conventional MRI techniques. Called HYPER-CEST, for hyperpolarized xenon chemical exchange saturation transfer, this new technique could become a valuable tool for medical diagnosis, including the early detection of cancer.
Antibodies are large Y-shaped proteins used by the immune system to identify and neutralize foreign objects like bacteria and viruses. Each antibody recognizes a specific antigen unique to its target. That makes them valuable tools for the analysis of biomolecules in research, diagnostics and therapy. However, antibodies are huge (150 kDa) biomolecules and are not functional within a living cell due to the reductive environment of the cytoplasm. Normally, antibodies are used to detect antigens on fixed an permeabilized cells (in other words: dead cells). But neither does that provide any information about the dynamic changes of the antigen within different stages of the cell cycle, nor about its overall mobility. A research group at the University of Munich has now succeeded in developing much smaller molecules for antigen detection in living cells.
Nucleoside analogues, which are a class of therapeutic agents, display significant anticancer or antiviral activity by interfering with DNA synthesis. They work by incorporating into the elongating DNA strands and terminating the extension process. However, they also affect normal cell growth, such as bone marrow cells, so there can be significant toxic effects. Further limitations to their use are relatively poor intracellular diffusion, rapid metabolism, poor absorption after oral use, and the induction of resistance. French and Italian researchers have now come up with a completely new approach to render anticancer and antiviral nucleoside analogues significantly more potent. By linking the nucleoside analogues to squalene, a biochemical precursor to the whole family of steroids, the researchers observed the self-organization of amphiphilic molecules in water. These nanoassemblies exhibited superior anticancer activity in vitro in human cancer cells.
The potential use of antimicrobial surface coatings ranges from medicine, where medical device infection is associated with significant healthcare costs, to the construction industry and the food packaging industry. Thin films which contain silver have been seen as promising candidate coatings. Silver is known as one of the oldest antimicrobial agents. Silver ions are thought to inhibit bacterial enzymes and bind to DNA. Silver has been used effectively against different bacteria, fungi and viruses. Researchers in Germany developed a new method for producing antibacterial metal/polymer nanocomposite coatings, where silver and gold nanoparticles are only incorporated in a thin surface layer. The new material shows a greatly enhanced antibacterial efficiency of the thin films.
Phagocytosis is a cellular phenomena that describes the process in which phagocytes (specialized cells such as macrophages) destroy viruses and foreign particles in blood. Phagocytes are an important part of the immune system. Unfortunately, phagocytes are also a major limitation for the intravenous delivery of polymeric nanoparticles. The use of such nanoparticles to deliver therapeutic agents is currently being studied as a promising method by which drugs can be effectively targeted to specific cells in the body, such as cancerous cells. Researchers at Penn State are trying to trick the body's immune system, and increase the circulation time of nano drug carriers in the blood, with stealth drug nanoparticles that could be fabricated by self-assembling a shell on the surface of a solid drug core. This research could lead to the possibility of long term drug treatment in vivo.
Particulate nanocarriers have been praised for their advantageous drug delivery properties in the lung, such as avoidance of macrophage clearance mechanisms and long residence times. However, instilled non-biodegradable polystyrene nanospheres with small diameters and thus large surface areas have been shown to induce pulmonary inflammation. New evidence suggests that biodegradable polymeric nanoparticles designed for pulmonary drug delivery may not induce the same inflammatory response as non-biodegradable polystyrene particles of comparable size.
For the treatment of eye conditions, conventional eye drops have three major disadvantages: they must be applied frequently; their ocular bioavailability is low (i.e. less than 5% of the administered active is absorbed or becomes available at the site of physiological activity); and, their use is often associated with high systemic exposure to actives. The common alternative option, ophthalmic inserts, achieve sustained drug delivery but suffer from other limitations: they are difficult to insert (especially for the elderly and others with visual impairment) and easy to misapply; they are easily expulsed from the eye; patient compliance is low (discomfort and blurring of vision, difficulty of insertion, need for removal at the end of their useful life); and, they are costly to manufacture. Researchers in the UK believe that biodegradable polymer nanoparticles show great promise as drug delivery devices for the eye. They have developed well-tolerated systems that combine the sustained release characteristics of inserts with the patient acceptability of conventional eye drops.