When I posted my article on Gold Nanoparticles, my thoughts were that all the ‘major’ biosensing applications have been covered but it took less than 10 days for a cool new application to pop up. Prof Rotello at University of Massachusetts Amherst has developed a gold nanoparticle based chemical nose/sensor to “sniff out” not only cancerous cell from healthy cells but also differentiate between metastatic and non-metastatic cancer cells. At the core of this sensor are gold nanoparticle-fluorescent polymer dyads. Each of these dyads consists of gold nanoparticles that are designed to have a cationic surface charge conjugated with a fluorescent polymer. In these dyads, Gold nanoparticles quench the fluorescence of the polymers. In presence of cells, the cationic gold nanoparticles interact with cell surface (phospholipids, membrane proteins and carbohydrates) freeing up the polymer and dramatically increasing the fluorescence signal. After careful optimization, the researchers selected three gold nanoparticles with different surface groups that interact with polymer differently. When set of these three sensors are added to cells each gold nanoparticle interact with cells in different manner and there is net increase or decrease in fluorescence based on cell types. The array of three sensors was able to distinguish cancer cells from healthy normal cells and also the cancer cells that have metastasized or not.
The sensors obviously are working nicely in simulated laboratory condition but as many biosensor scientists already know the challenge is moving the system to real life situation. How the array sensor will work when injected into blood stream or a drop of blood is still need to be investigated. In complex biological systems cationic gold nanoparticles can potentially interact not only with any number of cells but also proteins hence contributing to large background signal. The quencher—polymer dyad idea has been around for at least a decade now. David Whitten in 1999 proposed a biosensor using similar approach. In addition, Alan J. Heeger (Winner of 2000 Nobel Prize in Chemistry) has developed biosensors using quenched fluorescent polymers. The lessons learned from previous work will hopefully make dealing with challenge little easier.
But idea of a simple method for detecting cancer cells in Doctor’s clinic is just too attractive that despite my serious reservations about the technology I will be rooting for it.