Sasha Ebrahimi, Principal Investigator and Associate Fellow at GSK began by posing the question how do we create probes, sensors, or diagnostics that can enable us to study the biology that's happening inside of living cells in a new and better way? Over the years, many scientists have devised techniques to study behaviours inside cells, including GFP, FISH and PCR. While these tools are powerful, Ebrahimi noted that they are not perfect.
Ebrahimi’s research aims to study proteins, nucleic acids, glycans, lipids, and inorganic ions. There are many challenges when it comes to looking at things inside living cells. DNA is negatively charged, and the cell membrane is also negatively charged. To deliver substances into the cell that do not degrade the DNA, Ebrahimi and his team have been developing a new class of structures called spherical nucleic acids or SNAs.
Ebrahimi described the structure of SNAs: they are DNA structures that are densely functionalized around a central nanoparticle core in a spherical nucleic structure. Unlike their linear cousins, SNAs are more resistant to nucleus degradation. Furthermore, they display improved specificity and sensitivity.
Upon discovering these properties, Ebrahimi created NanoFlares for detecting intracellular mRNA and other targets. Ebrahimi added: “NanoFlares have been used as the first platform capable of isolating circulating tumour cells from blood based on genetic signatures.”
The limitation of NanoFlares is that it creates a false positive signal due to degradation. To overcome this Ebrahimi introduced Forced Intercalation Aptamers (FIT), where fluorescence is activated upon structural changes induced by target binding, this promotes a faster response, higher specificity, and fewer false positives. Furthermore, Ebrahimi replaced gold nanoparticle cores with biodegradable and biocompatible protein cores to create versatile platforms.
Ebrahimi used glucose oxidase as a protein core: “If we take a mixture of our glucose oxidase, SNAs, and hydrogen peroxide sensitive dye and titrate in more and more glucose, we see we get fluorescent enhancement up to 120-fold physiologically relevant concentrations of glucose.” The glucose oxidase enabled the detection of intracellular glucose and other analytes with potential applications in monitoring conditions like cancer and neurological disorders. These platforms demonstrated significant improvements in specificity, fluorescence enhancement, and practical use within live cells.
Looking ahead, Ebrahimi aims to expand the capabilities of his technology. He highlighted that multiplexing for spatial-temporal analysis, amplification for low-abundance targets, and achieving absolute quantification of analytes are avenues for further research.