Circular dichroism imaging has proved a powerful and simple method for extracting information on chiral molecules without specific fluorescent labels. Numerous mathematical models show that outside the absorption band, the circular dichroism signal comes from the scattering interaction and brings additional information about the organization of biopolymers. With this article, we propose a fast method to control the polarization states without moving parts, by means of a photoelastic modulator. We implemented the technique on a modified commercial confocal microscope realizing a multimodal configuration. We demonstrate its imaging capabilities by studying the organization of chromatin DNA inside isolated cell nuclei.
The application of
ultrafast pulsed laser sources and spectroscopic
techniques enables label-free, deep-tissue optical microscopy. However,
circumvention of the diffraction limit in this field is still an open
challenge. Among such approaches, pump–probe microscopy is
of increasing interest thanks to its highly specific nonfluorescent-based
contrast mechanisms for the imaging of material and life science samples.
In this paper, a custom femtosecond-pulsed near-infrared pump–probe
microscope, which exploits transient absorption and stimulated Raman
scattering interactions, is presented. The conventional pump–probe
configuration is combined with a spatially shaped saturation pump
beam, which allows for the reduction of the effective focal volume
exploiting transient absorption saturation. By optimizing the acquisition
parameters, such as power and temporal overlap of the saturation beam,
we can image single-layer graphene deposited on a glass surface at
the nanoscale and with increased layer sensitivity. These results
suggest that saturation pump–probe nanoscopy is a promising
tool for label-free high-resolution imaging.
High-density lipoprotein (HDL) is involved in the transport and metabolism of phospholipids, triglycerides, and cholesterol. Mimics of HDL are being explored as potential therapeutic agents for removing excess cholesterol from arterial plaques. Gold nanoparticles (AuNPs) functionalized
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