Antimicrobial Activities of Propolis in Poloxamer Based Topical Gels

Propolis contains a group of compounds with various activities. However, their low solubility is a drawback for the development of pharmaceutical formulations. In this study, poloxamers as a solubilizer and gelling agent were evaluated to develop a topical antimicrobial formulation of propolis. The effects of poloxamer type and concentration on the propolis solubility, release rate, and antimicrobial activities were investigated. Staphylococcus aureus (S. aureus) and Candida albicans (C. albicans) were the representative bacteria and fungi, respectively. At 5%, poloxamer 407 (P407) and poloxamer 188 (P188) enhanced the propolis solubility by 2.86 and 2.06 folds, respectively; at 10%, they were 2.81 and 2.59 folds, respectively. The micelle size in the P188 formulation increased in the presence of propolis, whereas there was no change in the P407 formulation. Release rates of propolis decreased with the P188 concentration increase, which was attributed to viscosity increase. Both P188 and P407 formulations showed antimicrobial activity against S. aureus in a time-kill kinetics assay. However, only the P188 formulation reduced the cell’s numbers significantly against C. albicans, compared to the control. We speculate that P188 mixed micelles were more effective in releasing free active compounds to exhibit anti-microbial activity compared to the P407 micelles encapsulating the hydrophobic compounds in their cores. Propolis in P188 formulation is proposed as a potential topical antimicrobial agent based on its activity against both S. aureus and C. albicans.

Improvement of monodispersity and shape symmetry of silica shell for PbS quantum dots by introducing surface silanization and adjusting reverse micelle size

Increasing the thickness of the quantum dot silica coating layer reduces monodispersity and shape symmetry. This paper reports three effective ways to solve this problem and achieve a large silica-coated QDs, i.e., proper silanization on the QD surface, control of reverse micelle size by adjusting the amount of QD solvent, and two-step formation of silica shell. Proper substitution of ligands on the QD surface in the early stages of silica shell formation was important for uniform coating reaction. An amount of toluene as QD solvent determined the size of reverse micelles during the silica shell formation. There was an optimum combination of inverse micelle size and silica shell size to obtain silica-coated QDs with good monodispersity and high shape symmetry. We succeeded in growing the thick silica shell with expanding reverse micelle size by additionally supplying toluene with the raw material using the optimum silica-coated QDs as growth nucleus

Variation in Dairy Milk Composition and Properties Has Little Impact on Cheese Ripening: Insights from a Traditional Swedish Long-Ripening Cheese

The monthly variation in raw dairy silo milk was investigated and related to the ripening time of the resulting cheese during an industrial cheese-making trial. Milk composition varied with month, fat and protein content being lowest in August (4.19 and 3.44 g/100 g, respectively). Casein micelle size was largest (192–200 nm) in December–February and smallest (80 nm) in August. In addition, SCC, total bacteria count, proteolytic activities, gel strength, and milk fatty acid composition were significantly varied with month. Overall sensory and texture scores of resulting cheese were mainly influenced by plasmin and plasminogen activity, indicating the importance of native proteolytic systems. Recently, concepts based on the differentiated use of milk in dairy products have been suggested. For the investigated cheese type, there might be little to gain from such an approach. The variation in the investigated quality characteristics of the dairy milk used for cheese making had little effect on cheese ripening in our study. In contrast to our hypothesis, we conclude that as long as the quality of the milk meets certain minimum criteria, there are only weak associations between cheese milk characteristics and the time required for the development of aroma and texture in the cheese. To find answers behind the observed variation in cheese ripening time, studies on the effects of process parameters are needed.

Foam film stratification studies probe intermicellar interactions

Ultrathin foam films containing supramolecular structures like micelles in bulk and adsorbed surfactant at the liquid–air interface undergo drainage via stratification. At a fixed surfactant concentration, the stepwise decrease in the average film thickness of a stratifying micellar film yields a characteristic step size that also describes the quantized thickness difference between coexisting thick–thin flat regions. Even though many published studies claim that step size equals intermicellar distance obtained using scattering from bulk solutions, we found no reports of a direct comparison between the two length scales. It is well established that step size is inversely proportional to the cubic root of surfactant concentration but cannot be estimated by adding micelle size to Debye length, as the latter is inversely proportional to the square root of surfactant concentration. In this contribution, we contrast the step size obtained from analysis of nanoscopic thickness variations and transitions in stratifying foam films using Interferometry Digital Imaging Optical Microscopy (IDIOM) protocols, that we developed, with the intermicellar distance obtained using small-angle X-ray scattering. We find that stratification driven by the confinement-induced layering of micelles within the liquid–air interfaces of a foam film provides a sensitive probe of non-DLVO (Derjaguin–Landau–Verwey–Overbeek) supramolecular oscillatory structural forces and micellar interactions.

Do equilibrium and rate constants of intramicellar reactions depend on micelle size ?

We have studied the combined static and dynamic quenching of pyrene by methyl viologen in sodium alkyl sulfate micelles varying in volume by a factor of more than 4. Size...

Accessing the Frank-Kasper Phase of Block Copolymer in the Fuzzy Colloid Regime

The discovery of Frank-Kasper (FK) phase in block copolymer (bcp) has prompted the progress of the field of soft quasicrystals. In principle, the formation of FK phase from the supercooled liquid phase of the bcp micelles should involve the mass transport of constituent molecules to transform the unimodal distribution of micelle size into the multimodal distribution prescribed by the volume asymmetry of the Voronoi cells in the FK phase. Here we present a new regime in which the Laves C14 phase of bcp developed below the glass transition temperature of the micelle core, where the mass transport was inhibited by the immobile block chains forming the core. The bcp micelle comprising a glassy core and a soft corona resembles the fuzzy colloid and the strong van der Waals attraction between the cores directs their organization into C14 phase to minimize the interparticle interaction energy under the metastable condition.