Apr 11, 2014
Quantum dot-anthraquinone conjugates as intracellular pH nanosensors
A whole family of quantum dot (QD)-anthraquinone conjugates could be used as nanosensors for the determination of pH in physiological samples. Exhibiting high selectivity and pKa (acid disassociation constant) values ranging from ~5 to 8, makes them ideal for applications in samples like blood or serum, for intracellular pH determination, and for more acidic cellular compartments such as endosomes and lysosomes. Now, this new group of conjugates have been reported in Nanotechnology and their sensing applications explored.
The structure of the anthraquinone derivatives and emission spectra of a QD-anthraquinone nanocomposite
Quantum dot nanoparticles are highly sensitive to charge and energy transfer processes, which can be used to develop sensing platforms. The researchers from the University of Granada in Spain and the University of Cambridge in the UK, take advantage of the high pH sensitivity of anthraquinones to examine the photoluminescence pH dependency of the new nanocomposites.
The new family
The attachment of six different anthraquinone dyes on the surface of QDs results in an electron transfer-based quenching of the photoluminescence (PL) intensity. The efficiency of this quenching was found to vary at different pH values; consistent with the pH-sensitive anthraquinone redox chemistry. The PL of the resultant conjugates exhibits pH sensitivity in a broad response range, making them very interesting for the determination of pH in samples of different natures.
The usefulness of the proposed nanosensors is successfully demonstrated with the determination of pH in samples mimicking the intracellular environment. Currently, the researchers are working on the incorporation of these and other QD-based nanosensors into the cellular cytoplasm to measure in cellulo and in real time the changes of pH related to different metabolic processes.
More information can be found in the journal Nanotechnology 25 195501.
About the author
Maria J Ruedas-Rama is an assistant professor at the University of Granada (Spain) in the Department of Physical Chemistry (Faculty of Pharmacy). With a background in analytical biotechnology, her current research interests focus on the development of QD-based nanosensors for the intracellular determination of target molecules by using fluorescence microscopy techniques.