Advances in quantum dots as diagnostic tools.

Quantum dots (QDs) are crystalline inorganic semiconductor nanoparticles a few nanometers in size that possess unique optical electronic properties vs those of larger materials. For example, QDs usually exhibit a strong and long-lived photoluminescence emission, a feature dependent on size, shape and composition. These special optoelectronic properties make them a promising alternative to conventional luminescent dyes as optical labels in biomedical applications including biomarker quantification, biomolecule targeting and molecular imaging. A key parameter for use of QDs is to functionalize their surface with suitable (bio)molecules to provide stability in aqueous solutions and efficient and selective tagging biomolecules of interest. Researchers have successfully developed biocompatible QDs and have linked them to various biomolecule recognition elements, i.e., antibodies, proteins, DNA, etc. In this chapter, QD synthesis and characterization strategies are reviewed as well as the development of nanoplatforms for luminescent biosensing and imaging-guided targeting. Relevant biomedical applications are highlighted with a particular focus on recent progress in ultrasensitive detection of clinical biomarkers. Finally, key future research goals to functionalize QDs as diagnostic tools are explored.

Absolute quantification of proteins using element mass spectrometry and generic standards.

Elemental mass spectrometry is a powerful analytical technique widely established in inorganic analysis. However, despite its quantitative capabilities, it is not yet fully integrated or considered in Life Sciences fields like proteomics. Whereas it is true that ICP-MS has suffered from several instrumental and analytical limitations that have hindered its applicability in protein analysis, significant developments during the last decades have turned ICP-MS into an interesting and, in our opinion, a powerful tool to consider for accurate protein quantification without recourse to specific protein standards. Herein we will try to discuss how these traditional limitations in ICP-MS have been overcome, what further improvements are yet necessary (some of which are shared with MS-based proteomics platforms) and enlighten some of the already existing and potential applications of ICP-MS in absolute quantitative proteomics. SIGNIFICANCE: ICP-MS has the potential to become a complementary tool to help molecular mass spectrometry cope with existing limitations, especially those related to standardization and accuracy, in the absolute proteomics field. It can provide absolute quantification of diverse proteoforms using a single generic compound containing sulfur and/or another target element (e.g., phosphorous). Moreover, its applications in quantitative proteomics are no longer limited to protein standards certification or quantification of simple or purified mixtures. Interestingly, absolute quantification of proteins using ICP-MS is favored when carried out at the intact level, making it very compatible with top-down proteomics approaches. Recent instrumental and methodological advances enable synergic combination of ICP-MS with stablished LC-MS proteomics methodologies, setting the basis for its implementation in quantitative proteomics workflows.