The last few years saw tremendous progress in the use of nanoparticles to enhance the in vivo efficiency of many drugs. Currently used pharmaceutical nanocarriers, such as liposomes, micelles, nanoemulsions, polymeric nanoparticles and many others demonstrate a broad variety of useful properties, such as for instance increased longevity in the blood, specific targeting to certain disease sites, or enhanced intracellular penetration. Some of these pharmaceutical carriers have already made their way into clinics, while others are still under preclinical development. In the next phase of developing nanocarriers, researchers are intrigued by the possibility to synthesize pharmaceutical nanocarriers that possess not only one but several properties. Such particles can significantly enhance the efficacy of many therapeutic and diagnostic protocols. A brandnew review paper considers current status and possible future directions in the emerging area of multifunctional nanocarriers with primary attention on the combination of such properties as longevity, targetability, intracellular penetration and contrast loading.
Wound healing is a complex process and has been the subject of intense research for a long time. Wound healing proceeds through an overlapping pattern of events including coagulation, inflammation, proliferation, and matrix and tissue remodeling. The holy grail for wound healing is accelerated healing without scars. Silver has been used for centuries to prevent and treat a variety of diseases. Its antibacterial effect may be due to blockage of the respiratory enzyme pathways and alteration of microbial DNA and the cell wall. In addition to its recognized antibacterial properties, some authors have reported on the possible pro-healing properties of silver. The use of silver in the past has been restrained by the need to produce silver as a compound, thereby increasing the potential side effects. Nanotechnology has provided a way of producing pure silver nanoparticles and this has provided a new therapeutic modality for use in burn wounds. Nonetheless, the beneficial effects of silver nanoparticles on wound healing remain unknown. A new study reports that silver nanoparticles can promote wound healing and reduce scar appearance.
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.