Medical dressing fights infection

Scientists at the University of Bath in the UK are exploiting nanotechnology to create an advanced wound dressing that can detect and treat infection. When triggered by the presence of pathogenic bacteria in the wound, the dressing releases antibiotics from nanocapsules. It also changes colour when the antibiotic is released, indicating the presence of infection (J. Am. Chem. Soc. 132 6566).

"The dressing is only triggered by disease-causing bacteria, which produce toxins that break open capsules containing the antibiotics and dye," explained University of Bath project leader Toby Jenkins. "This means that antibiotics are only released when needed, which reduces the risk of the evolution of new antibiotic-resistant super-bugs such as MRSA."

The researchers have already tested fabric coated with the nanocapsules, which have been shown to react specifically to harmful bacteria. Over the next four years the project team – a collaboration of 11 partners across Europe and Australia – will work to integrate the colour-change technology into a suitable dressing and examine cost-effective routes for industrial production.

Shaken up: multifunctional biological imaging

A novel nanoparticle-based imaging technique from the University of Washington (Seattle, WA) claims to provide a first step towards detecting single cancerous cells travelling through the bloodstream. While nanoparticles are promising contrast agents for ultrasensitive medical imaging, in all techniques that do not use radioactive tracers, their weak signals tend to be overwhelmed by signal from surrounding tissues, preventing detection of single cells. To combat this, the researchers have developed a multifunctional nanoparticle that eliminates this background noise (Nature Comms. 1 41).

The 30-nm particle comprises an iron-oxide magnetic core with a thin gold shell that surrounds but does not touch the centre. The gold shell absorbs infrared light, enabling its use in photoacoustic imaging (as well as optical imaging, delivering heat therapy, or attaching biomolecules that target specific cells). The researchers applied a pulsing magnetic field at a specific frequency, which shakes the nanoparticles by their magnetic cores. They then recorded a photoacoustic image and used image processing techniques to remove everything except the vibrating pixels.

Experiments with synthetic tissue showed that this technique can almost completely suppress a strong background signal. Future work will try to duplicate the results in lab animals. "Today, we can use biomarkers to see where there's a large collection of diseased cells," said co-author Matthew O'Donnell. "This new technique could get you down to a very precise level, potentially of a single cell."

Nanoparticles plus stem cells demolish plaque

A combination of laser-activated nanoparticles and adult stem cells appears to destroy atherosclerotic plaque and rejuvenate the arteries, according to a study reported at last month's American Heart Association conference: Basic Cardiovascular Sciences 2010 Scientific Sessions. The study treated 19 pigs with silica-gold nanoshells, while 18 control animals received saline solution. Nanoparticles were delivered in one of three ways: intracellularly with adult stem cells infused into the heart; via an infusion of gas-filled, protein-coated microbubbles with no stem cells; or delivered through a bioengineered patch attached to the artery that also contained adult stem cells.

After the nanoparticles were heated by exposure to laser light, they burned away arterial plaque. Plaque volume decreased by 28.9% (average across the three groups) immediately after the procedure and by 56.8% six months later. In the control group, plaque volume increased by an average of 4.3%. The greatest reductions occurred in the two treatment groups that received stem cells along with the nanoparticles. These groups also showed signs of new blood vessel growth and restoration of artery function.

"This unique approach holds promise for use in humans for acute care and urgent restoration of blood flow," said lead author Alexandr Kharlamov, research manager at the Department of Internal Medicine and Research Center of Regenerative Medicine, Ural State Medical Academy in Russia. "Nanoburning in combination with stem cell treatment promises demolition of plaque and functional restoration of the vessel wall."

Iron oxide particles tackle brain tumours

Particles of iron oxide could provide simultaneous imaging and treatment of the brain tumour glioblastoma multiforme, report researchers at Emory University School of Medicine (Atlanta, GA). The Emory team conjugated 10-nm-diameter iron oxide particles to antibodies that selectively bind to a molecule on the surface of glioblastoma cells. After treatment with these nanoparticles, a significant decrease in glioblastoma cell survival was observed, while no toxicity was observed upon treatment of normal human astrocytes (Cancer Res. 70 6303).

The researchers used convection-enhanced delivery – continuous infusion of fluid under positive pressure – to introduce the antibody-linked nanoparticles into mice implanted with human glioblastoma cells. The particles lengthened the median survival of the mice to 19 days, compared with 16 days for bare particles and 11 days for no particles. The particles also made the tumour visible via MRI, darkening the area of the brain where the tumour was located.

To heighten the anti-cancer effects, Emory's Brain Tumor Nanotechnology Laboratory is investigating the use of magnetic fields to generate local hyperthermia against malignant brain tumours. The team now plan to translate the use of bioconjugated iron-oxide nanoparticles for use in canine brain tumour models and into a human clinical trial for patients suffering from brain cancer.