Entropy‐driven binding of octyl gallate in albumin: Failure in the application of temperature effect to distinguish dynamic and static fluorescence quenching

Circular dichroism spectrum of (R)-(+)-3,3'-dibromo-1,1'-bi-2-naphthol in albumin: Alterations caused by complexation-Experimental and in silico investigation

This study describes the interaction of human serum albumin (HSA) with the binol derivative (R)-(+)-3,3'-dibromo-1,1'-bi-2-naphthol (R-BrB), which has its optical activity based on the prohibitive energetic barrier for conversion into the enantiomer (S)-(+)-3,3'-dibromo-1,1'-bi-2-naphthol (S-BrB). The objective was to assess the ability of HSA to differentiate axial enantiomers based on their binding efficiency and their impact on the CD spectra. We discovered that both enantiomers were effective ligands, and the CD signal disappeared when equimolar amounts of R-BrB and S-BrB were simultaneously added, indicating no preference for either enantiomer. The complexation resulted in a significant signal increase at 250 nm and a bathochromic effect at 370 nm. Molecular docking simulations were performed, and the lower energy pose of R-BrB was selected for DFT calculations. The theoretical CD spectra of free and complexed R-BrB were obtained and showed alterations corroborating the experimental results. By comparing the difference spectrum (HSA:R-BrB minus HSA) with the spectrum of free RBrB in water or ethyl alcohol, we concluded that the CD signal intensification was due to the increased solubilization of R-BrB upon binding to HSA.

Plant-inspired Pluronic-gallol micelles with low critical micelle concentration, high colloidal stability, and protein affinity

Polymeric micelles are the most common carriers used for hydrophobic drug delivery. However, they are vulnerable to physiological barriers, such as temperature changes and enzymatic degradation, and can be easily disassembled upon dilution below the critical micelle concentration (CMC) by body fluids after an intravenous injection. Here, we report that Pluronic® micelles with octyl gallate, which is a surfactant containing gallol moieties widely found in antioxidative plant polyphenols, have a low CMC, which improves their colloidal stability without the need for covalent crosslinking. Furthermore, the incorporated gallol moieties provide enzymatic degradation resistance to the micelles owing to their protein affinity, maintaining the hydrophobic cavity of unmodified Pluronic®. Thus, plant-inspired polymeric micelles with low CMC and bioavailability are promising multifunctional vehicles for drug delivery.

Interactions of 3-deoxyanthocyanins with gum arabic and sodium alginate contributing to improved pigment aqueous stability

3-Deoxyanthocyanins (3DXA) are of interest as food colorants but readily precipitated in aqueous solutions, limiting their potential applications. This work investigated ability of gum arabic vs alginate to stabilize 3DXA in aqueous systems and mechanisms involved. Apigeninidin and luteolinidin, and sorghum extracts dominant in these compounds, API-EX and LUT-EX, respectively, were prepared in pH 3 and 5 polysaccharide solutions (0.5-1.0 g/L), and colloidal properties and 10-week stability measured. Alginate equally stabilized both pigments at pH 5 (75% retention), but only LUT-EX at pH 3 (65%); viscosity and H-bonding contributed to the effects. By contrast, gum arabic highly stabilized API-EX (100%, pH 5), but not LUT-EX. Gum arabic formed a stable complex with apigeninidin via hydrophobic encapsulation, but much weaker complex with luteolinidin due to its more hydroxylated B-ring. Structure of 3DXA is critical to its interaction with hydrocolloids, thus pigment profile must be considered when selecting stabilizing polysaccharides.

Caffeine as a Viscosity Reducer for Highly Concentrated Monoclonal Antibody Solutions

Many monoclonal antibody (mAb) solutions exhibit high viscosity at elevated concentrations, which prevents manufacturing and injecting of concentrated mAb drug products at the small volumes needed for subcutaneous (SC) administration. Addition of excipients that interrupt intermolecular interactions is a common approach to reduce viscosity of high concentration mAb formulations. However, in some cases widely used excipients can fail to lower viscosity. Here, using infliximab and ipilimumab as model proteins, we show that caffeine effectively lowers the viscosity of both mAb formulations, whereas other common viscosity-reducing excipients, sodium chloride and arginine, do not. Furthermore, stability studies under accelerated conditions show that caffeine has no impact on stability of lyophilized infliximab or liquid ipilimumab formulations. In addition, presence of caffeine in the formulations does not affect in vitro bioactivities of infliximab or ipilimumab. Results from this study suggest that caffeine could be a useful viscosity reducing agent that complements other traditional excipients and provides viscosity reduction to a wider range of mAb drug products.