Water-in-Silicone Oil Emulsion Stabilizing Surfactants Formed From Native Albumin and α,ω-Triethoxysilylpropyl-Polydimethylsiloxane

Functional silicone oils and elastomers: new routes lead to new properties

Silicones are mostly utilized for their stability to a range of vigorous environmental conditions, which arises, in part, from the lack of functionality in finished products. The commonly used functional groups in silicones, e.g., SiH, SiCHCH2, are mostly consumed during final product synthesis. Organic functional groups may also be found in silicone products, including organic alcohols, amines, polyethers, etc., that deliver functionality not achieved by traditional organic polymers (e.g., aminosilicones, softening of fabrics; silicone polyethers, superwetting agricultural adjuvants). However, relatively little organic chemistry is practiced in commercial silicones, limiting the types of desirable functionality that can be attained. We report the utilization of a series of simple-to-practice organic reactions that take place efficiently on silicone oils to allow the preparation of a wide variety of functional silicones. The silicone oil starting materials typically act as both solvent and educt to allow many of the newer reactions, such as Click processes, to be used to tune the properties of both silicone oil and elastomer products. The review considers the concept of 'functionality' to include: the reactive groups used to enable synthesis of more complicated structures; and separately, the functional properties of the product silicones. One such property that is considered throughout is degradability at end-of-life, which is related to the sustainability of silicones.

Synergistics of Carboxymethyl Chitosan and Mangosteen Extract as Enhancing Moisturizing, Antioxidant, Antibacterial, and Deodorizing Properties in Emulsion Cream

Carboxymethyl chitosan (CMCH) from native chitosan of high molecular weight (H, 310–375 kDa) was synthesized for improving water solubility. The water solubility of high-molecular-weight carboxymethyl chitosan (H-CMCH) was higher than that of native chitosan by 89%. The application of H-CMCH as enhancing the moisturizer in mangosteen extract deodorant cream was evaluated. Different concentrations of H-CMCH (0.5–2.5%) were investigated in physicochemical characteristics of creams, including appearance, phase separation, pH, and viscosity, by an accelerated stability test. The different degrees of skin moisturizing (DM) on pig skin after applying H-CMCH solution, compared with untreated skin, water, and propylene glycol for 15 and 30 min using a Corneometer^®, were investigated. The results showed that the 0.5% H-CMCH provided the best DM after applying the solution on pig skin for 30 min. Trans-2-nonenal, as an unsatisfied odor component, was also evaluated against components of the mangosteen extract deodorant cream, which were compared to the standard, epigallocatechin gallate (EGCG). In addition, DPPH and ABTS radical scavenging activity, ferric reducing antioxidant power (FRAP), and antibacterial activities were examined for the mangosteen extract deodorant cream using 0.5% H-CMCH. Results indicated that the mangosteen extract synergized with H-CMCH, which had a good potential as an effective skin moisturizing agent enhancer, deodorizing activity on trans-2-nonenal odor, antioxidant properties, and antibacterial properties.

A calorimetric, volumetric and combined SANS and SAXS study of hybrid siloxane phosphocholine bilayers

Siloxanes are molecules used extensively in commercial, industrial, and biomedical applications. The inclusion of short siloxane chains into phospholipids results in interesting physical properties, including the ability to form low polydispersity unilamellar vesicles. As such, hybrid siloxane phosphocholines (SiPCs) have been examined as a potential platform for the delivery of therapeutic agents. Using small angle X-ray and neutron scattering, vibrating tube densitometry, and differential scanning calorimetry, we studied four hybrid SiPCs bilayers. Lipid volume measurements for the different SiPCs compared well with those previously determined for polyunsaturated PCs. Furthermore, the different SiPC's membrane thicknesses increased monotonically with temperature and, for the most part, consistent with the behavior observed in unsaturated lipids such as, 1-palmitoyl-2-docosahexaenoyl-sn-glycero-3-phosphocholine and 1-stearoyl-2-docosahexaenoyl-sn-glycero-3-phosphocholine, and the branched lipid 1,2-diphytanoyl-sn-glyerco-3-phosphocholine (DPhyPC).

Naturally Derived Silicone Surfactants Based on Saccharides and Cysteamine

Silicone surfactants are widely used in many industries and mostly rely on poly(ethylene glycol) (PEG) as the hydrophile. This can be disadvantageous because commercial PEG examples vary significantly in polydispersity—constraining control over surface activity of the surfactant—and there are environmental concerns associated with PEG. Herein, we report a three-step synthetic method for the preparation of saccharide-silicone surfactants using the natural linker, cysteamine, and saccharide lactones. The Piers–Rubinsztajn plus thiol-ene plus amidation process is attractive for several reasons: if employed in the correct synthetic order, it allows for precise tailoring of both hydrophobe and hydrophile; it permits the ready utilization of natural hydrophiles cysteamine and saccharides in combination with silicones, which have significantly better environmental profiles than PEG; and the products exhibit interesting surface activities.

Exploring the utility of hybrid siloxane-phosphocholine (SiPC) liposomes as drug delivery vehicles

Hybrid siloxane-phosphocholines (SiPCs) are a unique class of lipids that spontaneously form unilamellar vesicles (ULVs) that are ∼100 nm in diameter upon exposure to aqueous media without the need for extrusion and can be used as delivery vehicles.

Highly stable, electrostatically attractive silicone nanoemulsions produced by interfacial assembly of amphiphilic triblock copolymers

This article presents a useful and promising approach for fabricating extremely stable silicone oil nanoemulsions, whose liquid-liquid interface is structured with a thin film of amphiphilic triblock copolymers. For this, two types of amphiphilic triblock polymer, poly(2-methacryloyloxy ethyl phosphorylcholine)-block-poly(ε-caprolactone)-block-poly(2-methacryloyloxy ethyl phosphorylcholine) (PMPC-PCL-PMPC) and poly(2-aminoethyl methacrylate)-block-poly(ε-caprolactone)-block-poly(2-aminoethyl methacrylate) (PAMA-PCL-PAMA), were synthesized by atom transfer radical polymerization. Employing the phase separation technique was critical for the formation of thin polymer interfaces, of less than 10 nm, thus eventually producing structurally stable silicone oil nanoemulsions. The co-assembly of PAMA-PCL-PAMA with PMPC-PCL-PMPC enabled the patching of positive charges on the surface of the emulsion drops. We show that these charged silicone oil nanoemulsions could be used to form a multilayer emulsion thin film by layer-by-layer deposition. Finally, we experimentally demonstrate that the silicone oil nanoemulsions fabricated in this way were highly stable and had the ability to electrostatically interact with hair, which enabled complete coating of the hair surface with a layer of silicone oil.

High internal phase water/oil and oil/water gel emulsions formed using a glucose-based low-molecular-weight gelator

High internal phase silicone-oil-containing water/oil and oil/water emulsions were prepared using low loadings of a glucose-based low-molecular-weight gelator.

The stability of insulin solutions in syringes is improved by ensuring lower molecular weight silicone lubricants are absent

Protein drugs such as insulin are almost universally delivered via glass syringes lubricated with silicone oil. It is not uncommon for prefilled syringes (PFS) to become cloudy, which may affect bioavailability or total drug dose. To examine the role, if any, of the silicone oil lubricant in this process, a systematic evaluation of the degree of insulin denaturation and aggregation as a function of silicone oils of different molecular weights was undertaken. The former was measured using fluorescence changes of aqueous insulin/silicone dispersions, while the latter examined changes in turbidity as a function of mixing and silicone oil type; the results were confirmed at two different insulin concentrations and agitation speeds. Lower molecular weight silicones led to the most rapid denaturation and aggregation, and when examined in blends of silicones at a fixed viscosity of 1000 cSt, commonly used for syringe lubrication, more rapid denaturation/aggregation was noted in blends of silicones containing the largest fractions of low molecular weight materials. As a consequence, the molecular weight profile of silicone lubricants should be established prior to the preparation of prefilled syringes.

Silicone oil emulsions: strategies to improve their stability and applications in hair care products

Silicone oils have wide range of applications in personal care products due to their unique properties of high lubricity, non-toxicity, excessive spreading and film formation. They are usually employed in the form of emulsions due to their inert nature. Until now, different conventional emulsification techniques have been developed and applied to prepare silicone oil emulsions. The size and uniformity of emulsions showed important influence on stability of droplets, which further affect the application performance. Therefore, various strategies were developed to improve the stability as well as application performance of silicone oil emulsions. In this review, we highlight different factors influencing the stability of silicone oil emulsions and explain various strategies to overcome the stability problems. In addition, the silicone deposition on the surface of hair substrates and different approaches to increase their deposition are also discussed in detail.

Measuring interactions between polydimethylsiloxane and serum proteins at the air-water interface

The interaction between synthetic polymers and proteins at interfaces is relevant to basic science as well as a wide range of applications in biotechnology and medicine. One particularly common and important interface is the air-water interface (AWI). Due to the special energetics and dynamics of molecules at the AWI, the interplay between synthetic polymer and protein can be very different from that in bulk solution. In this paper, we applied the Langmuir-Blodgett technique and fluorescence microscopy to investigate how the compression state of polydimethylsiloxane (PDMS) film at the AWI affects the subsequent adsorption of serum protein [e.g., human serum albumin (HSA) or immunoglobulin G (IgG)] and the interaction between PDMS and protein. Of particular note is our observation of circular PDMS domains with micrometer diameters that form at the AWI in the highly compressed state of the surface film: proteins were shown to adsorb preferentially to the surface of these circular PDMS domains, accompanied by a greater than 4-fold increase in protein found in the interfacial film. The PDMS-only film and the PDMS-IgG composite film were transferred to cover glass, and platinum-carbon replicas of the transferred films were further characterized by scanning electron microscopy and atomic force microscopy. We conclude that the structure of the PDMS film greatly affects the amount and distribution of protein at the interface.

Proteins, polysaccharides, and their complexes used as stabilizers for emulsions: alternatives to synthetic surfactants in the pharmaceutical field?

Emulsions are widely used in pharmaceutics for the encapsulation, solubilization, entrapment, and controlled delivery of active ingredients. In order to answer the increasing demand for clean label excipients, natural polymers can replace the potentially irritative synthetic surfactants used in emulsion formulation. Indeed, biopolymers are currently used in the food industry to stabilize emulsions, and they appear as promising candidates in the pharmaceutical field too. All proteins and some polysaccharides are able to adsorb at a globule surface, thus decreasing the interfacial tension and enhancing the interfacial elasticity. However, most polysaccharides stabilize emulsions simply by increasing the viscosity of the continuous phase. Proteins and polysaccharides may also be associated either through covalent bonding or electrostatic interactions. The combination of the properties of these biopolymers under appropriate conditions leads to increased emulsion stability. Alternative layers of oppositely charged biopolymers can also be formed around the globules to obtain multi-layered "membranes". These layers can provide electrostatic and steric stabilization thus improving thermal stability and resistance to external treatment. The novel biopolymer-stabilized emulsions have a great potential in the pharmaceutical field for encapsulation, controlled digestion, and targeted release although several challenging issues such as storage and bacteriological concerns still need to be addressed.

Biocatalytic synthesis of silicone polyesters

The immobilized lipase B from Candida antarctica (CALB) was used to synthesize silicone polyesters. CALB routinely generated between 74-95% polytransesterification depending on the monomers that were used. Low molecular weight diols resulted in the highest rates of esterification. Rate constants were determined for the CALB catalyzed polytransesterifications at various reaction temperatures. The temperature dependence of the CALB-mediated polytransesterifications was examined. A lipase from C. rugosa was only successful in performing esterifications using carboxy-modified silicones that possessed alkyl chains greater than three methylene units between the carbonyl and the dimethylsiloxy groups. The proteases alpha-chymotrypsin and papain were not suitable enzymes for catalyzing any polytransesterification reactions.