Optically-Guided Nanoparticles and Cell Scalextrics

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Steering nanoparticle transport in human cells - why is this important?Viruses seem to travel effortlessly into tissues and cells, being transported selectively in the body to reach the sites where they can cause most harm. They do this by breaching cellular barriers such as the outer or plasma membrane of cells and use human cellular machinery to make copies of themselves. Drug molecules on the other hand spread non-selectively throughout the body thus reducing effects where they are most needed, and causing adverse side-effects where they are not wanted. One reason for this is that current synthetic carriers for drugs and diagnostic agents, unlike viruses, are unable to effectively cross biological barriers and then reach specific sites inside cells. An artificial particle that could transport through tissue, in a manner analogous to a virus and then into defined cell locations but without causing disease, would therefore revolutionise healthcare applications. This would be particularly important for the early stage diagnostics and therapeutics needed in developing nations and for ageing populations.What do novel polymer-coated gold nanoparticles have to offer?These materials are an optimal test platform for proof-of-concept studies described in this application. Firstly, gold particles can be tracked in cells using a number of microscopic approaches including the newly developed highly sensitive four-wave mixing imaging system available to this team. They can be coated with a variety of polymeric materials that will help to guide them into cells and into specific cell locations. We have previously shown that polymers which are capped with functional 'keys' to enter natural cell portals can have their entry switched on and off by small increases in temperature which cause them to change their conformations. We also have shown that we can generate these temperature increases at gold nanoparticles inside cells through laser pulses but without damaging the cells. By attaching the temperature-responsive polymers to gold, it should be possible to use laser pulses to switch the functional keys on and off, and in this way guide particles to reach defined cellular locations. This will help to unravel the mechanisms by which materials travel in cells, thus enabling us to guide diagnostics and therapeutics to where they are required.Impact.A major hurdle to effective therapy against major disease burdens such as cancer, coronary heart disease and neurodegeneration is our inability to direct therapeutic molecules such as genes and proteins to specific tissue and defined compartments inside cells. This is a major objective of this application and progress here could have widespread implications for academia, industry and the society that they serve. One could envisage a commercial application in which a combined imaging and guiding instrument (e,g, ultrasonic probes and imaging) is used with a set of nanoparticles with functionality for specific disease markers, with a potential for truly selective personalised therapies.Better diagnostics are also needed that allow earlier detection of disease and thus better healthcare outcomes. Successful completion of this work could allow development of an imaging/detection platform where specific markers of disease could be detected through their interaction with selective receptors on gold nanoparticles guided to intracellular sites by the local laser-heating method. When it is considered that 1 in 3 individuals in the EU will be affected directly or indirectly by cancer by 2010, it is clear that earlier detection and intervention will bring marked benefits to patients, carers and society as a whole.Longer-term development could generate impact through a new biomedical technology i.e. laser-guided therapeutics wherein local heating by focused ultrasound guides biodegradable responsive nanoparticles in humans.