Water-Dispersible Carboxymethyl Dextran-Coated Melamine Nanoparticles for Biosensing Applications

In this study, we developed a simple method for preparing highly dispersed, stable, and streptavidin (SA)-functionalized carboxymethyl dextran (CMD)-coated melamine nanoparticles (MNPs) in an aqueous buffer at neutral pH. Dynamic light scattering (DLS) revealed the agglomeration of MNPs in an aqueous buffer at neutral pH. When CMD, N-hydroxysuccinimide (NHS), and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) were simultaneously mixed with the MNPs, CMD was bound to the MNPs, promoting their dispersibility. Preparation of SA-CMD-MNPs was accomplished simply by adding SA solution to the CMD-MNPs. The amount of SA bound to the CMD-MNPs was quantified by the bicinchoninic assay, and the amount of SA molecules bound to each CMD-MNP was 417 ± 4. SA-CMD-MNPs exhibited high dispersity (polydispersity index = 0.058) in a neutral phosphate buffer and maintained it for 182 days with dispersion using a probe sonicator (5 s) before DLS characterization. The performance of the SA-CMD-MNPs in biosensing was evaluated by immunohistochemistry, which revealed that the nanoparticles could specifically stain MCF-7 cells derived from breast cancer cells with low HER2 expression. This study provides an effective method for synthesizing highly dispersible nanoparticles for biosensing.

Silane-Based SAMs Deposited by Spin Coating as a Versatile Alternative Process to Solution Immersion

Functionalization of silica surfaces with silane-based self-assembled monolayers (SAMs) is widely used in material sciences to tune surface properties and introduce terminal functional groups enabling subsequent chemical surface reactions and immobilization of (bio)molecules. Here, we report on the synthesis of four organotrimethoxysilanes with various molecular structures and we compare their grafting by spin coating with the one performed by the conventional solution immersion method. Strikingly, this study clearly demonstrates that the spin coating technique is a versatile, fast, and more convenient alternative process to prepare robust, smooth, and homogeneous SAMs with similar properties and quality as those deposited via immersion. SAMs were characterized by PM-IRRAS, AFM, and wettability measurements. SAMs can undergo several chemical surface modifications, and the reactivity of amine-terminated SAM was confirmed by PM-IRRAS and fluorescence measurements.

Synthesis and UV-irradiation of photocaged nitrobenzyl-BODIPY derivatives

Two different photocaged 2-nitrobenzyl-BODIPY derivatives were designed and synthesized, where the 2-nitrobenzyl phototrigger is either directly attached to the meso position of BODIPY or through a phenoxy linker. The photochemical and photophysical properties of the two constructs were studied and their fluorescence quantum yields were determined. The ultraviolet irradiation of the two photocaged BODIPYs demonstrated a twofold fluorescence enhancement accompanying the uncaging of the BODIPY with the directly attached phototrigger, while the second switchable dyad with the phenoxy linker retains its essentially unaltered emissive behavior.

Photophysics of crystal violet lactone in reverse micelles and its dual behaviour

The photophysics of Crystal Violet Lactone (CVL) in aqueous and non aqueous reverse micelles (RMs) have been studied. It was observed that in RMs, the CT_A → CT_B transformation is retarded.