Chemical complexity of the retina addressed by novel phasor analysis of unstained multimodal microscopy

UVR and RPE - The Good, the Bad and the degenerate Macula

Ultraviolet Radiation (UVR) has a well-established causative influence within the aetiology of conditions of the skin and the anterior segment of the eye. However, a grounded assessment of the role of UVR within conditions of the retina has been hampered by a historical lack of quantitative, and spectrally resolved, assessment of how UVR impacts upon the retina in terms congruent with contemporary theories of ageing. In this review, we sought to summarise the key findings of research investigating the connection between UVR exposure in retinal cytopathology while identifying necessary avenues for future research which can deliver a deeper understanding of UVR's place within the retinal risk landscape.

Ultrahigh-Throughput Single-Particle Hyperspectral Imaging of Gold Nanoparticles

Gold nanoparticles (AuNPs) have become increasingly useful in recent years for their roles in nanomedicine, cellular biology, energy storage and conversion, photocatalysis, and more. At the single-particle level, AuNPs have heterogeneous physical and chemical properties which are not resolvable in ensemble measurements. In the present study, we developed an ultrahigh-throughput spectroscopy and microscopy imaging system for characterization of AuNPs at the single-particle level using phasor analysis. The developed method enables quantification of spectra and spatial information on large numbers of AuNPs with a single snapshot of an image (1024 × 1024 pixels) at high temporal resolution (26 fps) and localization precision (sub-5 nm). We characterized the localized surface plasmonic resonance (SPR) scattering spectra of gold nanospheres (AuNSs) of four different sizes (40-100 nm). Comparing to the conventional optical grating method which suffers low efficiency in characterization due to spectral interference caused by nearby nanoparticles, the phasor approach enables high-throughput analysis of single-particle SPR properties in high particle density. Up to 10-fold greater efficiency of single-particle spectro-microscopy analysis using the spectra phasor approach when compared to a conventional optical grating method was demonstrated.

Introducing the multi-dimensional spectral phasors: a tool for the analysis of fluorescence excitation-emission matrices

The use of phasors to analyze fluorescence data was first introduced for time-resolved studies for a simpler mathematical analysis of the fluorescence-decay curves. Recently, this approach was extended to steady-state experiments with the introduction of the spectral phasors (SP), derived from the Fourier transform of the fluorescence emission spectrum. In this work, we revise key mathematical aspects that lead to an interpretation of SP as the characteristic function of a probability distribution. This formalism allows us to introduce a new tool, called multi-dimensional spectral phasor (MdSP) that seize, not only the information from the emission spectrum, but from the full excitation-emission matrix (EEM). In addition, we developed a homemade open-source Java software to facilitate the MdSP data processing. Due to this mathematical conceptualization, we settled a mechanism for the use of MdSP as a tool to tackle spectral signal unmixing problems in a more accurate way than SP. As a proof of principle, with the use of MdSP we approach two important biophysical questions: protein conformational changes and protein-ligand interactions. Specifically, we experimentally measure the EEM changes upon denaturation of human serum albumin (HSA) or during its association with the fluorescence dye 1,8-anilinonaphtalene sulphate (ANS) detected via tryptophan-ANS Förster Resonance Energy Transfer (FRET). In this sense, MdSP allows us to obtain information of the system in a simpler and finer way than the traditional SP. Specifically, understanding a protein's EEM as a molecular fingerprint opens new doors for the use of MdSP as a tool to analyze and comprehend protein conformational changes and interactions.