Determination of Intracellular Esterase Activity Using Ratiometric Raman Sensing and Spectral Phasor Analysis.

Carboxylesterases (CEs) are a class of enzymes that catalyze the hydrolysis of esters in a variety of endogenous and exogenous molecules. CEs play an important role in drug metabolism, in the onset and progression of disease, and can be harnessed for prodrug activation strategies. As such, the regulation of CEs is an important clinical and pharmaceutical consideration. Here, we report the first ratiometric sensor for CE activity using Raman spectroscopy based on a bisarylbutadiyne scaffold. The sensor was shown to be highly sensitive and specific for CE detection and had low cellular cytotoxicity. In hepatocyte cells, the ratiometric detection of esterase activity was possible, and the result was validated by multimodal imaging with standard viability stains used for fluorescence microscopy within the same cell population. In addition, we show that the detection of localized ultraviolet damage in a mixed cell population was possible using stimulated Raman scattering microscopy coupled with spectral phasor analysis. This sensor demonstrates the practical advantages of low molecular weight sensors that are detected using ratiometric Raman imaging and will have applications in drug discovery and biomedical research.

Expanding the Range of Bioorthogonal Tags for Multiplex Stimulated Raman Scattering Microscopy.

Multiplex optical detection in live cells is challenging due to overlapping signals and poor signal-to-noise associated with some chemical reporters. To address this, the application of spectral phasor analysis to stimulated Raman scattering (SRS) microscopy for unmixing three bioorthogonal Raman probes within cells is reported. Triplex detection of a metallacarborane using the B-H stretch at 2480-2650 cm-1 , together with a bis-alkyne and deuterated fatty acid can be achieved within the cell-silent region of the Raman spectrum. When coupled to imaging in the high-wavenumber region of the cellular Raman spectrum, nine discrete regions of interest can be spectrally unmixed from the hyperspectral SRS dataset, demonstrating a new capability in the toolkit of multiplexed Raman imaging of live cells.

Synthesis, characterisation and multi-modal intracellular mapping of cisplatin nano-conjugates.

The synthesis of nanocarriers for the delivery of the antitumor drug cisplatin is reported. Multimodal-imaging consisting of surface enhanced Raman scattering and laser ablation inductively coupled plasma time of flight mass spectrometry was used to visualise the intracellular uptake of both the nanocarrier and drug.