Sensing
All bio-chemical reactions, responsible for cellular functions occur either exothermically or endothermically at particular locations within a cell’s organelles exposed on different oxygen conditions, and are fundamentally co-regulated by intracellular temperature distribution. In a living object the intracellular oxygen concentration as well the local temperature are tightly regulated and maintained within narrow physiological limits. In an ideal case, non-invasive intracellular thermometry and oximetry could be used to probe many functional characteristics of biological specimens, their physiological behavior under various conditions, metabolic parameters and responses to drug treatment or other external stimuli, such as chemical and environmental stress.
Besides the scaling-down problematic of the sensing techniques in the life-science field, the necessity of minimally-invasive measurement tools becomes imperative. A powerful and elegant solution of these sensing problems demonstrates the process of triplet-triplet annihilation photon energy upconversion (TTA – UC): instead of a single material response on the acting parameter (sample temperature, local viscosity change or variation of the oxygen concentration) a ratiometric material response is delivered. The TTA–UC relays of optically created densely populated organic triplet ensembles, in which the inter-molecular energy transfer depends strongly on a variety of environment parameters, such as temperature, viscosity, presence of heavy metal atoms or oxidizing agents, as well on the contamination with molecular oxygen. Using the mutual dependence of the residual sensitizer phosphorescence and emitter delayed fluorescence on the acting parameter ensures inherent / instantaneous compensation regarding other unwanted local changes of the sample parameters.
Our research focuses on the development of a sensing technology, based on real-time, all-optical and minimally invasive testing of the local temperature and oxygen concentration in human sentinel lymph nodes, in order to distinguish between healthy / malignant cells. Special attention was paid to the ability to excite and to observe the response of the T&O2-sensing nanoconfined system at wavelengths, matching optimally with the transparency window of the main organic substances creating the human breast skin. These objectives were reached by merging the techniques of annihilation upconversion and miniemulsion polymerization. The initial target of our research is metastatic breast cancer, with potential later involvement in other cancer diseases (e.g. vulval, renal, colorectal, gastric, etc.).
