Silicone-protein surfactants; stability of water-in-silicone oil emulsions

Small scale water-in-silicone oil emulsions were readily prepared using high speed mixers. Two surfactant systems were studied: a comb-type silicone-polyether surfactant, and a surfactant system employing a mixture of the surface active protein human serum albumin (HSA, in the internal phase) and an alkoxysilane-modified silicone TES-PDMS in the silicone oil (continuous phase). Little difference in particle sizes was noted between the two surfactant types for a given mixing protocol, but dual-blade turbulent mixing led to relatively monodisperse particles of approximately 2–5 m in diameter while high speed Dremel mixers led to bimodal particle distributions. Prior to spontaneous demulsification of the latter emulsions stabilized by HSA/TES-PDMS (the 3225C emulsions remain stable), they proved very difficult to break. The addition of dibutyltin dilaurate to the HSA/TES-PDMS-stabilized emulsions led to catastrophic collapse of the emulsion and formation of a silicone elastomer at the bulk water/oil interface. This makes unlikely the possibility that silicone elastomers, formed by protein-catalyzed crosslinking of the alkoxysilane in albumin/TES-PDMS-stabilized emulsions, are involved in stabilizing the emulsion. The nature of the stabilization of the interface is discussed.     

A new particle mounting method for surface analysis

The chemical analysis of microparticles is challenging due to the need to mount the particles on a substrate for analysis; double-sided adhesive tape is often used (sometimes conductive), however that is usually coated with poly (dimethyl siloxane) (PDMS) that is often used as a release agent. PDMS is a common surface contamination that can mask surface chemistries and hinder material performance where it is dependent on this contaminated interface. It is known that PDMS contains a very mobile oligomeric fraction that readily diffuses across surfaces resulting in the contamination of mounted particulate samples before and during surface chemistry analysis. This makes it impossible to determine whether the PDMS has arisen from the analysis procedure or from the sample itself. A new sample preparation method is proposed where polymer microparticles are mounted on a poly (hydroxyethyl methacrylate) (pHEMA) polymer solution, which we compare with particles that have been mounted on adhesive discs using time-of-flight secondary ion mass spectrometry (ToF-SIMS) and 3D OrbiSIMS analysis. Particles mounted on the pHEMA substrate results in a reduction of PDMS signal by 99.8% compared with microparticles mounted on adhesive discs. This illustrates how a simple, quick and inexpensive polymer solution can be used to adhere particles for analysis by ToF-SIMS, or other surface chemical analysis techniques such as X-ray photoelectron spectroscopy (XPS), without introduction of large amounts of silicone contaminant.     

Synthesis of nonspherical superparamagnetic particles: in situ coprecipitation of magnetic nanoparticles in microgels prepared by stop-flow lithography

We present the synthesis of nonspherical magnetic microparticles with multiple functionalities, shapes, and chemistries. Particle synthesis was performed in two steps: polymeric microparticles functionalized homogenously with carboxyl groups were generated using stop-flow lithography, and then in situ coprecipitation was used to grow magnetic nanoparticles at these carboxyl sites. With successive growth of magnetic nanoparticles, we obtained polymeric particles with saturation magnetizations of up to 42 emu/g microparticle. The growth in the magnetic nanoparticle mean size and polydispersity was determined from the magnetization curves obtained following each growth cycle; nanoparticle sizes were limited by the physical constraint of the effective mesh within the hosting gel microparticle. Particles with spatially segregated domains of varying magnetic properties (e.g., Janus particles, particles with step changes in magnetite concentration, etc.) can be synthesized readily using this approach.     

Preparation and properties of inhalable nanocomposite particles: effects of the temperature at a spray-dryer inlet upon the properties of particles

To overcome the disadvantages both of microparticles and nanoparticles for inhalation, we have prepared nanocomposite particles as drug carriers targeting lungs. The nanocomposite particles having sizes about 2.5 μm composed of sugar and drug-loaded PLGA nanoparticles can reach deep in the lungs, and they are decomposed into drug-loaded PLGA nanoparticles in the alveoli. Sugar was used as a binder of PLGA nanoparticles to be nanocomposite particles and is soluble in alveolar lining fluid. The primary nanoparticles containing bioactive materials were prepared by using a probe sonicator. And then they were spray dried with carrier materials, such as trehalose and lactose. The effects of inlet temperature of spray dryer were studied between 60 and 120 °C and the kind of sugars upon properties of nanocomposite particles. When the inlet temperatures were 80 and 90 °C, nanocomposite particles with average diameters of about 2.5 μm are obtained and they are decomposed into primary nanoparticles in water, in both sugars are used as a binder. But, those prepared above 100 °C are not decomposed into nanoparticles in water, while the average diameter was almost 2.5 μm. On the other hand, nanocomposite particles prepared at lower inlet temperatures have larger sizes but better redispersion efficiency in water. By the measurements of aerodynamic diameters of the nanocomposite particles prepared with trehalose at 70, 80, and 90 °C, it was shown that the particles prepared at 80 °C have the highest fine particle fraction (FPF) value and the particles are suitable for pulmonary delivery of bioactive materials deep in the lungs. Meanwhile the case with lactose, the particles prepared at 90 °C have near the best FPF value but they have many particles larger than 11 μm.     

Properties of polystyrene/poly(butyl acrylate) core/shell polymers modified with N‐methylol acrylamide

Polystyrene/poly(butyl acrylate) PS/PBA polymer dispersions with core/shell particles functionalized by N‐methylol acrylamide (N‐MA) were prepared through two‐step emulsion polymerization. The influence of N‐MA situated in shell and/or in core/shell of particles on the crosslinking reaction was studied to relate its mechanical properties and organic solvent resistance of films cast from basic and modified PS/PBA latexes. The changes in the phase arrangement of functionalized and unfunctionalized films after treatment with solvent and annealing were monitored. It was found that at the presence of N‐MA the crosslinking reaction occured already during the polymerization. Films from functionalized dispersions exhibit improved tensile strength and higher resistance against organic solvent.     

Composites of poly (dimethylsiloxane) and spherically shaped poly (2‐hydroxyethylmethacrylate) particles for biomedical use

Silicone rubbers have shown considerable promise in the biomedical field, but their hydrophobicity leads to serious problems in long‐term implants. In our study, composites of poly (dimethylsiloxane) (PDMS) and spherically shaped poly (2‐hydroxyethylmethacrylate) (PHEMA) microparticles were prepared. Unlike previous silicone hydrogel composites, suspension polymerization was carried out in an aqueous medium to prepare PHEMA particles directly, which avoided the removal of organic phase and give hydrogel particles with high purity. Very fine PHEMA particles with uniform geometry and small size were obtained through various influencing factors during their formation. Through the introduction of PHEMA particles, PDMS matrix was endowed with hydrophilicity to a certain extent. With an increase in hydrogel content, higher swelling ability and surface wettability of the composites were observed. We have also demonstrated that smaller sized particles are more favorable for hydrophilicity improvement. The results of improved swelling ability, surface wettability, and low affinity to lipid show that this composite material is suitable for biomedical use. Copyright © 2009 John Wiley & Sons, Ltd.     

A Novel Potentiometric Detection Strategy for the Determination of Amlodipine Besylate Based on Functionalized Particles

A novel potentiometric strategy based on functionalized magnetite nanoparticles and microparticles were compared with the classical potentiometric strategy. This strategy provided nano‐ and microsized particles that were highly dispersed and coated with ionophore and plasticizer to promote an in situ cooperative ion‐pairing interaction between the ionophore and the analyte present in inner solution of sensor membrane, compared to the classical technique. Three amlodipine (AML) sensors were constructed using functionalized nanoparticles in sensor 1; microparticles in sensor 2, as ionophores, and the polymeric membrane ionophoric property in sensor 3.     

Synthesis and characterization of paramagnetic microparticles through emulsion-templated free radical polymerization

A novel method is described for the preparation of high-magnetization paramagnetic microparticles functionalized with a controlled density of poly(ethylene glycol) (PEG) and carboxyl groups. These microparticles were synthesized using four steps: (1) creation of an oil-in-water emulsion in which hydrophobic iron oxide nanoparticles and a UV-activated initiator were distributed in hexane; (2) formation of uniform microparticles through emulsion homogenization and evaporation of hexane; (3) functionalization of the microparticle with a PEG-functionalized surfactant and acrylic acid; and (4) polymerization of the microparticles. Characterization of the microparticles with electron microscopy and light scattering revealed that they were composed of densely packed iron oxide nanoparticles and that the size of the microparticles may be controlled through the pore size of the membrane used to homogenize the emulsion. The concentration of surfactant and acrylic acid used in the third processing step was found to determine the surface chemistry, iron content, and magnetization of the microparticles. Increasing the PEG surfactant to acrylic acid ratio resulted in higher PEG surface densities, lower iron content, and lower magnetization. The resulting microparticles were readily functionalized with antibodies and showed a low propensity for nonspecific protein adsorption. We believe that these microparticles will be useful for magnetic tweezers measurements and bioanalytical devices that require microparticles with a high magnetization.     

Properties of oxygen permeation and partial oxidation of methane in La0.6Sr0.4CoO3−δ (LSC)–La0.7Sr0.3Ga0.6Fe0.4O3−δ (LSGF) membrane

The oxygen separation membrane having perovskite structure for the partial oxidation of methane to synthesis gas was prepared. La_0.7Sr_0.3Ga_0.6Fe_0.4O_3−δ (LSGF) perovskite membrane coated with La_0.6Sr_0.4CoO_3−δ (LSC) (M1), and the one side of M1 membrane coated with NiO (M2) was prepared to examine the partial oxidation of methane. The single oxygen permeations of the LSC + LSGF (M1) membrane and NiO coated membrane (M2) were measured. The oxygen permeation flux in M1 membrane was higher than that of M1 membrane at 850 °C.

The partial oxidation experiment of methane using the prepared membranes was examined at 850 °C. The value of CH₄ conversion and CO selectivity of M2 membrane was higher than that of M1 membrane.

NiO/NiAl₂O₄ catalyst was used to improve the methane conversion, and the partial oxidation experiment of methane with M1 membrane was examined at 850 °C. The CH₄ conversion was 88%, and CO selectivity was 100%.     

Monomodal polyelectrolyte complex nanoparticles of PDADMAC/Poly(styrenesulfonate): preparation and protein interaction

The binding of the model proteins HSA, LYZ and MYO to PEC nanoparticles is reported. PEC particles were prepared by mixing solutions of PDADMAC either with PSS or PMA-MS, followed by consecutive centrifugation. Monomodal anionic (PEC-1.50) and cationic (PEC-0.66) PEC particles were obtained using non-stoichiometric mixing ratios. PEC/protein conjugates were prepared by adding charged protein solutions to dispersions of respective like charged PEC particles, followed by one centrifugation step. Mixing proteins and PEC particles under attractive conditions led to flocculation of the dispersion. From CD, DLS and AFM the following trend for protein binding at PEC particles under repulsive conditions was obtained: HSA/PEC-1.50 > MYO/PEC-1.50 > LYZ/PEC-0.66. Protein uptakes up to 0.33 g x g(-1) (protein/PEC) (CD) and particle diameter enlargements up to 13 nm (AFM) were obtained at c(PROT) = 0.091 mg . mL(-1). Furthermore, novel spin coated films of PEC particles were interacted with proteins under both repulsive and attractive conditions. In-situ ATR FT-IR spectroscopy revealed that the adsorbed amount of HSA and LYZ under attractive conditions was significantly higher than under repulsive ones, which is analogous to protein adsorption at polyelectrolyte multilayers terminated either by polycation or polyanion. Similarly to the dispersed PEC/protein conjugates, under repulsive conditions the uptake of HSA was higher compared to LYZ. The shown protein uptake under repulsive conditions is related to concepts of mild enzyme or protein binding at nonbiogenic substrates.     

Design of silica microparticles with oligopeptide brushes and their interaction with proteins

Synthesis of small oligopeptide brushes (oligo(S-benzyl-l-cysteine)) onto polyelectrolyte functionalized silica microparticles was developed. Poly(vinyl amine) (PVAm) adsorbed from salt-free and KCl 10⁻¹ mol L⁻¹ aqueous solution onto silica microparticles was chemically and naturally cross-linked by epichlorohydrin and CO₂, respectively. After the adsorption of PVAm onto microporous silica particles and stabilization by cross-linking, five repeated coupling reactions of Boc-S-benzyl-l-cysteine were performed. To test the protein interactions with the newly designed surface, human serum albumin (HSA) has been selected as a model protein. X-ray photoelectron spectroscopy, total organic carbon, potentiometric and polyelectrolyte titrations, and electrokinetic analysis were employed to obtain information about the polyelectrolyte adsorption and the amount of the amino acid S-benzyl-l-cysteine that was covalently bound to the solid surface and for determination of the protein amount adsorbed onto functionalized surface. The amount of HSA adsorbed onto modified silica microparticles decreased in order: silica/PVAm-cross-linked (silica/PVAm-C) (8.00 mg g⁻¹) > silica/PVAm-C/S-benzyl-l-cysteine (6.34 mg g⁻¹) > silica (4.86 mg g⁻¹) > silica/PVAm-C/(S-benzyl-l-cysteine)₅ (1.86 mg g⁻¹).     

ABC copolymer silicone surfactant templating for biomimetic silicification

Using the ABC copolymer silicone surfactant polydimethylsiloxane (PDMS)-graft-(polyethylene oxide (PEO)-block-propylene oxide (PPO)) (PSEP, Scheme 1a) as a template and tetraethoxysilane (TEOS) as a silica source, silica particles with various structures and morphologies (i.e., disordered spherical micellar aggregation, two-dimensional p6mm mesostructure, asymmetric multi-layer non-equilibrium vesicles and symmetric monolayer vesicles) were synthesized by changing the synthesis temperature from 30 to 80 °C. Increasing the hydrophobicity of the surfactant by increasing the temperature resulted in an increase in the surfactant packing parameter g, which led to the mesophase transformation from micellar to cylinder and later to a lamellar structure. The good compatibility between the PDMS and the TEOS, the different natures of the hydrophobic PDMS and PPO segments, and the hydrolysis and condensation rates of TEOS enabled the variation of silicification structures. This novel silicone surfactant templating route and a new type of materials with highly ordered mesostructures and asymmetric morphologies provide a new insight into the molecular factors governing inorganic-organic mesophase and biosilicification for fabricating functionalized materials.     

Evaluation of solid-phase micro-extraction coupled to gas chromatography-mass spectrometry for the headspace analysis of volatile compounds in cocoa products

The aroma profile of cocoa products was investigated by headspace solid-phase micro-extraction (HS-SPME) combined with gas chromatography–mass spectrometry (GC–MS). SPME fibers coated with 100 μm polydimethylsiloxane coating (PDMS), 65 μm polydimethylsiloxane/divinylbenzene coating (PDMS-DVB), 75 μm carboxen/polydimethylsiloxane coating (CAR-PDMS) and 50/30 μm divinylbenzene/carboxen on polydimethylsiloxane on a StableFlex fiber (DVB/CAR-PDMS) were evaluated. Several extraction times and temperature conditions were also tested to achieve optimum recovery. Suspensions of the samples in distilled water or in brine (25% NaCl in distilled water) were investigated to examine their effect on the composition of the headspace. The SPME fiber coated with 50/30 μm DVB/CAR-PDMS afforded the highest extraction efficiency, particularly when the samples were extracted at 60 °C for 15 min under dry conditions with toluene as an internal standard. Forty-five compounds were extracted and tentatively identified, most of which have previously been reported as odor-active compounds. The method developed allows sensitive and representative analysis of cocoa products with high reproducibility. Further research is ongoing to study chocolate making processes using this method for the quantitative analysis of volatile compounds contributing to the flavor/odor profile.     

How citrate ligands affect nanoparticle adsorption to microparticle supports

Residual ligands from colloidal synthesis of nanoparticles influence adsorption of nanoparticles to supports and may complicate fabrication of nanoparticle-decorated microparticles. In this work, we studied the adsorption of completely ligand-free metal nanoparticles and controlled ligand-functionalized nanoparticles to chemically inert microparticle supports. Adsorption of ligand-free silver nanoparticles to barium sulfate microparticle supports is a quantitative, nonreversible process following Freundlich adsorption isotherm. However, adsorption efficiency is very sensitive to ligand concentration applied during laser-based synthesis of silver nanoparticles: exceeding a specific threshold concentration of 50 μmol/L citrate equal to a nanoparticle ligand surface coverage of about 50%, results in an almost complete prevention of nanoparticle adsorption because of electrosteric repulsion by ligand shell. Laser-based synthesis of nanoparticle-decorated microparticles is demonstrated with a variety of metal nanoparticles (Ag, Au, Pt, Fe) and supporting microparticles (calcium phosphate, titanium dioxide, barium sulfate) with application potential in heterogeneous catalysis or biomedicine where ligand control offers extra value, like enhanced catalytic activity or biocompatibility.     

New Approach to Enhance the Yield Stress of Electro‐Rheological Fluids by Polyaniline‐Coated Layered Silicate Nanocomposites

We synthesized new polyaniline (PANI)/organoclay (aminosilane surface‐treated) nanocomposite particles and prepared electro‐rheological (ER) fluids by dispersing the particles in silicone oil. A distinct enhancement in yield stress was observed due to the presence of PANI‐coated clay particles. The effects of delaminated clay on the ER yield stress were investigated and compared with other ER fluid systems, which use PANI particles only or a simply intercalated PANI/clay nanocomposite.     

Functionalization/passivation of porous graphitic carbon with di-tert-amylperoxide

Porous graphitic carbon (PGC) particles were functionalized/passivated in situ in packed beds at elevated temperature with neat di-tert-amylperoxide (DTAP) in a column oven. The performance of these particles for high performance liquid chromatography (HPLC) was assayed before and after this chemistry with the following analytes: benzene, toluene, ethyl benzene, n-propyl benzene, n-butyl benzene, p-xylene, phenol, 4-methylphenol, phenetole, 3,5-xylenol, and anisole. After the first functionalization/passivation, the retention factors, k, of these compounds decreased by about 5% and the number of theoretical plates (N) increased by ca. 15%. These values of k then remained roughly constant after a second functionalization/passivation but a further increase in N was noticed. In addition, after each of the reactions, the peak asymmetries decreased by ca. 15%, for a total of ca. 30%. The columns were then subjected twice to methanol at 100°C for 5h at 1 mL/min. After these stability tests, the values of k remained roughly constant, the number of plates increased, which is favorable, and the asymmetries rose and then declined, where they remained below the initial values for the unfunctionalized columns. Functionalized and unfunctionalized particles were characterized by scanning electron microscopy and BET measurements, which showed no difference between the functionalized and unfunctionalized materials, and X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry (ToF-SIMS), where ToF-SIMS suggested some chemical differences between the functionalized and unfunctionalized materials. In particular ToF-SIMS suggested that the expected five-carbon fragments from DTAP exist at higher concentrations on DTAP-functionalized PGC. First principle calculations on model graphitic surfaces suggest that the first addition of a DTAP radical to the surface proceeds in an approximately isothermal or slightly favorable fashion, but that subsequent DTAP additions are then increasingly thermodynamically favorable. Thus, this analysis suggests that the direct functionalization/passivation of PGC with DTAP is plausible. Chemometric analyses of the chromatographic and ToF-SIMS data are also presented.     

Ultrathin polydimethylsiloxane-coated carbonyl iron particles and their magnetorheological characteristics

An ultrathin polydimethylsiloxane (PDMS) layer with a mean thickness of 1 nm was coated on soft magnetic carbonyl iron (CI) particles by using a simple thermal evaporation process, and then their physical characteristics were examined using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), thermal gravimetry analysis (TGA), and vibrating sample magnetometry (VSM). Magnetorheological (MR) fluid was prepared by using PDMS-coated CI powder, and its rheological behavior was investigated under different external magnetic field strengths using a rotational rheometer. The CI particles coated by a thin PDMS layer showed higher oxidation temperature than pristine CI particles and MR fluid consisting of PDMS-coated CI particles demonstrated better dispersion stability in a nonmagnetic carrier fluid.     

Detection of polydimethylsiloxanes transferred from silicone‐coated parchment paper to baked goods using direct analysis in real time mass spectrometry

The non‐stick properties of parchment papers are achieved by polydimethylsiloxane (PDMS) coatings. During baking, PDMS can thus be extracted from the silicone‐coated parchment into the baked goods. Positive‐ion direct analysis in real time (DART) mass spectrometry (MS) is highly efficient for the analysis of PDMS. A DART‐SVP source was coupled to a quadrupole‐time‐of‐flight mass spectrometer to detect PDMS on the contact surface of baked goods after use of silicone‐coated parchment papers. DART spectra from the bottom surface of baked cookies and pizzas exhibited signals because of PDMS ions of the general formula [(C₂H₆SiO)_n + NH₄]⁺ in the m/z 800–1900 range. Copyright © 2016 John Wiley & Sons, Ltd.     

Composite microparticle drug delivery systems based on chitosan, alginate and pectin with improved pH-sensitive drug release property

Composite microparticle drug delivery systems based on chitosan, alginate and pectin with improved pH sensitivity were developed for oral delivery of protein drugs, using bovine serum albumin (BSA) as a model drug. The composite drug-loaded microparticles with a mean particle size less than 200 μm were prepared by a convenient shredding method. Since the microparticles were formed by tripolyphosphate cross-linking, electrostatic complexation by alginate and/or pectin, as well as ionotropic gelation with calcium ions, the microparticles exhibited an improved pH-sensitive drug release property. The in vitro drug release behaviors of the microparticles were studied in simulated gastric (pH 1.2 and pH 5.0), intestinal (pH 7.4) and colonic (pH 6.0 and pH 6.8 with enzyme) media. For the composite microparticles with suitable compositions, the releases of BSA at pH 1.2 and pH 5.0 could be effectively sustained, while the releases at pH 7.4, pH 6.8 and pH 6.0 increased significantly, especially in the presence of pectinase. These results clearly suggested that the microparticles had potential for site-specific protein drug delivery through oral administration.     

Cellular uptake behavior of unfunctionalized and functionalized PBCA particles prepared in a miniemulsion

Fluorescent dye labeled unfunctionalized and functionalized poly(n-butylcyanoacrylate) nanoparticles were prepared using a miniemulsion technique. Amino acid and methoxyPEG functionalization could be introduced by using aqueous solutions as an initiator for the anionic polymerization in the heterophase. All the particles prepared had sizes smaller than 250 nm and negative zeta-potentials. The molar mass distribution of the polymer was dependent on the acid used as the continuous phase and the initiator solution applied. Cells of three lines (HeLa, Jurkat and mesenchymal stem cells) were incubated with the particles. The molar mass of the polymer determined the onset and extent of apoptosis, and the total uptake was determined by the size and functionalization of the particles. Different uptake kinetics were obtained with HeLa and Jurkat cells after incubation with the same particle batch. The intracellular particle distribution, visualized by confocal laser scanning microscopy, did not show significant differences for either of the cell lines or particle batches.