Establishing Structure Property Relationship in Drug Partitioning into and Release from Niosomes: Physical Chemistry Insights with Anti-Inflammatory Drugs

The effect of water in THF/water mixtures on CMC, aggregation sizes, and fluorescence quenching of a new calix[4]resorcinarene macrocycle

This study explores how water content modulates the self-assembly and fluorescence behavior of a novel calixarene, C1. C1 forms large, flattened structures in pure THF, but water addition triggers a transition to smaller, unimodal clusters. A critical micellar concentration (CMC) is identified, decreasing with increasing water content. Fluorescence quenching is observed upon water addition, attributed to nonradiative deactivation. These findings highlight water as a key regulator of C1's assembly and fluorescence, paving the way for further development of water-responsive calixarene systems.

Micro-Raman spectroscopic analysis of liquid-liquid phase separation

Liquid-liquid phase separation (LLPS) plays a significant role in various biological processes, including the formation of membraneless organelles and pathological protein aggregation. Although many studies have found various factors that modulate the LLPS process or the liquid-to-solid phase transition (LSPT) using microscopy or fluorescence-based methods, the molecular mechanistic details underlying LLPS and protein aggregation within liquid droplets remain uncharacterized. Therefore, structural information on proteins inside liquid droplets is required to understand the mechanistic link to amyloid formation. In the present study, we monitored droplet formation related to protein fibrillation using micro-Raman spectroscopy in combination with differential interference contrast (DIC) microscopy to study the conformational change in proteins and the hydrogen-bonding (H-bonding) structure of water during LLPS. Interestingly, we found that the O-D stretching band for water (HOD in H₂O) inside the droplets exhibited a distinct Raman spectrum from that of the bulk water, suggesting that the time-dependent change in the hydration environment in the protein droplets during the process of LLPS can be studied. These results demonstrate that the superior spatial resolution of micro-Raman spectroscopy offers significant advantages in investigating the molecular mechanisms of LLPS and following LSPT processes.

Red-Emitting Carbon Dots as a Dual Sensor for In3+ and Pd2+ in Water

We have demonstrated the synthesis, characterization, and application of nitrogen-doped red-emitting carbon dots (NRCDs) for dual sensing of indium (In3+) and palladium (Pd2+) in water. The detection of In3+ was associated with "turn-on" fluorescence response with a red shift, while in the presence of Pd2+, the fluorescence intensity of NRCDs was quenched to show a "turn-off" response. The interaction of NRCDs with the metal ions was investigated using 1H nuclear magnetic resonance and Fourier-transform infrared spectroscopy studies. The synthesized nanoprobes possessed good biocompatibility and photostability and were found to be suitable candidates for bioimaging due to their emission profiles in the near-infrared (NIR) window. Applicability of the as-prepared NRCDs was demonstrated in the NIR region when they were loaded in vesicle membranes with and without cations and subjected to confocal imaging successfully.

Metal-Enhanced Fluorescence Study in Aqueous Medium by Coupling Gold Nanoparticles and Fluorophores Using a Bilayer Vesicle Platform

Gold nanoparticles (AuNPs) display excellent plasmonic properties, which are expected to assist fluorescence enhancement for dyes, and the phenomenon is known as "metal-enhanced fluorescence" (MEF). In this study, we demonstrate AuNP-induced MEF for a modified bipyridine-based construct 4-(pyridine-2-yl)-3H-pyrrolo[2,3-c]quinoline (PPQ) when it binds with biologically important Zn2+. Importantly, this phenomenon is observed under aqueous conditions in a biocompatible bilayer vesicle platform. When PPQ binds with Zn2+ to form the complex in the presence of appropriate AuNPs, MEF is evident once compared with the fluorescence intensity in the absence of AuNPs. Among the three different sizes of AuNPs used, the enhancement is observed with an average diameter of 33 nm, whereas 18 and 160 nm do not show any enhancement. A possible mechanism is ascribed to the radiating plasmons of the AuNPs, which can couple with the emission frequencies of the fluorophore under a critical distance-dependent arrangement. We witness that the enhancement in fluorescence is accompanied with a reduction in lifetime components. It is proposed that the mechanism may be predominantly derived from the enhancement of an intrinsic radiative decay rate and partly from the localized electric field effect. Overall, this work shows a rational approach to design fluorophore-metal configurations with the desired emissive properties and a basis for a useful nanophotonic technology under biological conditions.