Submitted by birger on Mon, 03/01/2010 - 22:39

The treatment of disease includes several key stages: diagnosis, treatment and, finally, confirmation of success (also called «guidance»). Unfortunately, these steps usually involve different methods, which can lengthen and complicate the treatment process.

Combining diagnosis, treatment and guidance represents a challenge, especially when the disease is at an early stage and is expressed only through a few specific cells. Detecting these cells, being able to kill them immediately and selectively without harming healthy cells, and then identifying that the diseased cells have been destroyed will be a basis for future medicine. Such three-in-one medicine (recently referred to as theranostics) requires an agent or probe that can find, signal, kill and report on the target cells. Scientists are busy searching for such a tunable probe that can switch from diagnosis to treatment and then to treatment guidance in a fast and reliable way, and without toxicity to the host organism.

A team from Belarus and the US has proposed a system involving light and heat (but no chemicals) – the two most natural factors of life – together with gold nanoparticles that can find target cells with the help of diagnosis-specific molecules (antibodies). When excited by a short laser pulse, the gold nanoparticles convert light into heat thanks to the mechanism of plasmon resonance. Fast and local heating evaporates the nano-environment around the tiny particles to create a vapour nanobubble referred to as a plasmonic nanobubble (PNB). The size and lifetime of these bubbles can be controlled at the nanoscale by varying the energy of the laser (see plots in top image). Unlike the nanoparticles themselves, PNBs do not exist until activated by a laser and can be thought of as a stealth probe.

Researchers have discovered several features of PNBs that can be applied to theranostics. The bubbles scatter light more strongly than gold nanoparticles, which means that a PNB is a very bright optical probe that may help to discover a single cell. Next, a PNB can provide treatment through mechanical disruption of the target cells without thermal impact to surrounding tissues. At the same time, the cell-killing PNB can be easily distinguished optically from the non-invasive diagnostic PNB to give guidance of the treatment. All three stages of PNB theranostics take less than a microsecond and can be performed in individual diseased cells. By tuning the diameter of the PNB with a laser pulse, the concept can be adapted to support several biomedical applications including drug delivery, gene transfection, imaging, micro-surgery and, ultimately, theranostics. See full results «here»: http://www.iop.org/…21/8/085102/ can be found in the journal Nanotechnology.

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This work is a team effort performed at the joint US-Belarussian lab for fundamental and biomedical nanophotonics at Rice University, in collaboration with researchers at the A. V. Lykov Heat and Mass Transfer Institute of the Academy of Science of Belarus and the M. D. Anderson Cancer Center (Houston, TX). Co-authors of the study include Jason Hafner at Rice University, Ehab Hanna of the University of Texas M. D. Anderson Cancer Center and Ekaterina Lukianova-Hleb of the Lykov Institute. Dr. Dmitri Lapotko is the director of the Joint US-Belarussian lab for fundamental and biomedical nanophotonics and the founding director of the Laser Cytotechnology Lab at Lykov Insitute. The research was supported by the National Institutes of Health and the Institute of International Education's Scholar Rescue Fund.