Reflectance Confocal Microscopy: A Powerful Tool for Large Scale Characterization of Ordered/Disordered Morphology in Colloidal Photonic Structures

Advancements in Neurosurgical Intraoperative Histology

Despite their relatively low incidence globally, central nervous system (CNS) tumors remain amongst the most lethal cancers, with only a few other malignancies surpassing them in 5-year mortality rates. Treatment decisions for brain tumors heavily rely on histopathological analysis, particularly intraoperatively, to guide surgical interventions and optimize patient outcomes. Frozen sectioning has emerged as a vital intraoperative technique, allowing for highly accurate, rapid analysis of tissue samples, although it poses challenges regarding interpretive errors and tissue distortion. Raman histology, based on Raman spectroscopy, has shown great promise in providing label-free, molecular information for accurate intraoperative diagnosis, aiding in tumor resection and the identification of neurodegenerative disease. Techniques including Stimulated Raman Scattering (SRS), Coherent Anti-Stokes Raman Scattering (CARS), Surface-Enhanced Raman Scattering (SERS), and Tip-Enhanced Raman Scattering (TERS) have profoundly enhanced the speed and resolution of Raman imaging. Similarly, Confocal Laser Endomicroscopy (CLE) allows for real-time imaging and the rapid intraoperative histologic evaluation of specimens. While CLE is primarily utilized in gastrointestinal procedures, its application in neurosurgery is promising, particularly in the context of gliomas and meningiomas. This review focuses on discussing the immense progress in intraoperative histology within neurosurgery and provides insight into the impact of these advancements on enhancing patient outcomes.

Waterborne Polymer Coatings with Bright Noniridescent Structural Colors

Structural color pigments offer an efficient, sustainable, and environmentally friendly approach to obtain waterborne polymer coatings. We developed polymer-based spherical photonic pigments to incorporate in aqueous dispersions of polymer nanoparticles used to obtain waterborne polymer films. Our spherical photonic pigments are assembled from polymer nanoparticles and are highly stable in water dispersion, maintaining their optical properties in the final polymer films. Unlike conventional dyes and pigments, which are prone to photobleaching because they are based on the absorption of light, photonic pigments rely on the selective reflection of light by their nanostructure and therefore are not photodegraded. Furthermore, different colors can be obtained from the same materials, changing only their nanostructure, in this case, the size of the polymer nanoparticles. Our novel spherical photonic pigments are noniridescent and can be incorporated in aqueous polymer nanoparticle dispersions without deteriorating their structure to produce waterborne polymer coatings with structural color. This approach for structural colored waterborne polymer coatings is efficient, simple, and environmentally friendly, offering excellent prospects for application in paints and coatings.

Integrated FRET Polymers Spatially Reveal Micro- to Nanostructure and Irregularities in Electrospun Microfibers

A spatial view of macroscopic polymer material properties, in terms of nanostructure and irregularities, can help to better understand engineering processes such as when materials may fail. However, bridging the gap between the molecular-scale arrangement of polymer chains and the spatially resolved macroscopic properties of a material poses numerous difficulties. Herein, an integrated messenger material that can report on the material micro- to nanostructure and its processes is introduced. It is based on polymer chains labeled with fluorescent dyes that feature Förster resonance energy transfer (FRET) dependent on chain conformation and concentration within a host polymer material. These FRET materials are integrated within electrospun polystyrene microfibers, and the FRET is analyzed by confocal laser scanning microscopy (CLSM). Importantly, the use of CLSM allows a spatial view of material nanostructure and irregularities within the microfibers, where changes in FRET are significant when differences in fiber geometries and regularities exist. Furthermore, changes in FRET observed in damaged regions of the fibers indicate changes in polymer conformation and/or concentration as the material changes during compression. The system promises high utility for applications where nano-to-macro communication is needed for a better understanding of material processes.

A Continuous Gradient Colloidal Glass

Colloidal crystals and glasses manipulate light propagation depending on their chemical composition, particle morphology, and mesoscopic structure. This light-matter interaction has been intensely investigated, but a knowledge gap remains for mesostructures comprising a continuous property gradient of the constituting particles. Here, a general synthetic approach to bottom-up fabrication of continuous size gradient colloidal ensembles is introduced. First, the technique synthesizes a dispersion with a specifically designed gradual particle size distribution. Second, self-assembly of this dispersion yields a photonic colloidal glass with a continuous size gradient from top to bottom. Local and bulk characterization methods are used to highlight the significant potential of this mesostructure, resulting in vivid structural colors along, and in superior light scattering across the gradient. The process describes a general pathway to mesoscopic gradients. It can expectedly be transferred to a variety of other particle-based systems where continuous gradients will provide novel physical insights and functionalities.