PS Particles Research Articles

A Novel Approach of Daunorubicin Application on Formation of Proliferative Retinopathy Using a Porous Silicon Controlled Delivery System: Pharmacodynamics.

Proliferative vitreoretinopathy (PVR) is the most common cause of poor visual outcomes in association with retinal detachment surgeries and ocular trauma. Daunorubicin (DNR) has shown the strongest efficacy in proliferation inhibition in vitro. However, clinical studies have shown only mild effect owing to limitations of narrow therapeutic window and short vitreous half-life. Three milligrams of DNR-loaded particles were intravitreally injected into 18 pigmented rabbits, and vitreous samples were collected up to 84 days for analysis. Thirty-seven rabbits were used for a dose-escalation (1, 3, 6 mg) safety and efficacy study in a rabbit PVR model using a pretreatment design. Loading efficiency of DNR was 108.55 ± 12 μg per 1 mg particles. Eighty-four days of follow-up did not reveal any adverse reaction. Pharmacokinetic analysis demonstrated a vitreous half-life of 29 days with a maximum DNR concentration of 178 ng/mL and a minimum concentration of 29 ng/mL at day 84. Daunorubicin-loaded porous silicon (pSi) particles were dosed 8 to 9 weeks before PVR induction, and PVR severity score was dose dependent (Spearman ρ = -0.25, P = 0.0005). Proliferative vitreoretinopathy with tractional retinal detachment was 88% in the control group, 63% in the low-dose group, 14% in the medium-dose group, and 0% in the high-dose group (Cochran-Armitage Trend Test, Z = 8.99, ρ = -0.67, P < 0.0001). Daunorubicin-loaded pSi particles can safely reside in the vitreous for at least 3 months. The pSi-based delivery expanded the therapeutic window of DNR by a factor of 862 and drove down the minimum effective concentration by a factor of 175.

Systematic in vitro and in vivo study on porous silicon to improve the oral bioavailability of celecoxib

Mesoporous materials are promising candidates for improving dissolution rate of poorly water-soluble drugs in vitro and their bioavailability in vivo. In the present study, sixteen batches of celecoxib-loaded PSi particles with pore sizes ranging from 17 to 58 nm and celecoxib content from 5 to 36 w-% were prepared and a detailed physicochemical characterization of the drug was performed by several methods. Interaction between co-culture of Caco-2/HT29-MTX cells and unloaded PSi particles was tested in toxicity assays, and increased toxicity for particles with large pore size was observed. Dissolution rate of celecoxib was improved in vitro by lowering the drug loading degree which hindered the recrystallization of celecoxib on the external surface of the particles. The fastest permeation of loaded celecoxib through the co-culture monolayer as well as the highest bioavailability in rats was observed with the particles with small pore size and low loading degree. New insights were obtained on how various parameters of the mesoporous delivery system affect the state of the drug inside the pores and its release in vitro and in vivo.

Surface-tunable colloidal particles stabilized by mono-tethered single-chain nanoparticles

In these years synthesis and applications of single-chain nanoparticles (SCNPs) have aroused great interests. In this article, the surfactant behaviors of amphiphilic mono-tethered SCNPs are reported. Amphiphilic mono-tethered SCNPs were prepared by intramolecular cross-linking reaction. In the mono-tethered SCNPs, there are disulfide bonds at the junction points between coil chains and the SCNPs. 1H NMR, size exclusion chromatography and transmission electron microscopy results demonstrated successful synthesis of the SCNPs. The amphiphilic mono-tethered SCNPs are able to lower the surface tension of water. Critical micelle concentration of the SCNPs in aqueous solution was determined. The mono-tethered SCNPs were used as surfactants in the suspension polymerization of styrene, and polystyrene colloidal particles with SCNPs on the surfaces were prepared. SCNPs on the colloidal particles were cleaved from the surfaces of the colloidal particles, leaving thiol groups on the surfaces. Pyridyl disulfide-modified PS colloidal particles were synthesized by a reaction between 2,2′-dipyridyl disulfide and the thiol groups on the PS particles. The pyridyl disulfide-modified colloidal particles were used as a platform for the preparation of functional colloidal particles. Herein, fluorescence-labeled colloidal particles were prepared by a reaction of thiol-modified fluorescein isothiocyanate and pyridyl disulfide groups on the particles.

Conelike Janus Composite Particles

Conelike cross-linked PS particles are polymerized at a patchy emulsion interface. The PS particles synthesized in the dispersed paraffin phase immigrate toward the interface due to the Pickering effect. At the triple phase contact line, the particles are squeezed into cone shape under an outward convex interfacial tension mismatch. The conelike PS particles are adhered to paraffin sphere surface and synchronously protected, which allows selective modifications of the two sides. The Janus particles can self-organize into superstructures in dispersions. Robust coatings are easily fabricated from the Janus particles, whose wettability is tunable from highly adhesive for water to superhydrophobic by simply changing the size distribution of the Janus particles.

Surface engineering of porous silicon microparticles for intravitreal sustained delivery of rapamycin.

To understand the relationship between rapamycin loading/release and surface chemistries of porous silicon (pSi) to optimize pSi-based intravitreal delivery system. Three types of surface chemical modifications were studied: (1) pSi-COOH, containing 10-carbon aliphatic chains with terminal carboxyl groups grafted via hydrosilylation of undecylenic acid; (2) pSi-C12, containing 12-carbon aliphatic chains grafted via hydrosilylation of 1-dodecene; and (3) pSiO2-C8, prepared by mild oxidation of the pSi particles followed by grafting of 8-hydrocarbon chains to the resulting porous silica surface via a silanization. The efficiency of rapamycin loading follows the order (micrograms of drug/milligrams of carrier): pSiO2-C8 (105 ± 18) > pSi-COOH (68 ± 8) > pSi-C12 (36 ± 6). Powder X-ray diffraction data showed that loaded rapamycin was amorphous and dynamic drug-release study showed that the availability of the free drug was increased by 6-fold (compared with crystalline rapamycin) by using pSiO2-C8 formulation (P = 0.0039). Of the three formulations in this study, pSiO2-C8-RAP showed optimal performance in terms of simultaneous release of the active drug and carrier degradation, and drug-loading capacity. Released rapamycin was confirmed with the fingerprints of the mass spectrometry and biologically functional as the control of commercial crystalline rapamycin. Single intravitreal injections of 2.9 ± 0.37 mg pSiO2-C8-RAP into rabbit eyes resulted in more than 8 weeks of residence in the vitreous while maintaining clear optical media and normal histology of the retina in comparison to the controls. Porous silicon-based rapamycin delivery system using the pSiO2-C8 formulation demonstrated good ocular compatibility and may provide sustained drug release for retina.

Time-resolved visible and infrared difference spectroscopy for the study of photosystem I with different quinones incorporated into the A1 binding site

Room (298K) and low (77K) temperature time-resolved visible and infrared difference spectroscopy has been used to study photosystem I particles with phylloquinone (2-methyl-3-phytyl-1,4-naphthoquinone), menadione (2-methyl-1,4-naphthoquinone) and plastoquinone 9 (2,3-dimethyl-5-prenyl-l,4-benzoquinone), incorporated into the A1 binding site. Concentrated samples in short path-length (~5μm) sample cells are typically used in FTIR experiments. Measurements were undertaken using standard “dilute” samples at 298K, and concentrated (~5×) samples at both 298 and 77K. No concentration induced alterations in the flash-induced absorption changes were observed. Concentrated samples in short path-length cells form a transparent film at 77K, and could therefore be studied spectroscopically at 77K without addition of a cryoprotectant. At 298K, for photosystem I with plastoquinone 9/menadione/phylloquinone incorporated, P700+FA/B− radical pair recombination is characterized by a time constant of 3/14/80ms, and forward electron transfer from A1A− to Fx by a time constant of 211/3.1/0.309μs, respectively. At 77K, for concentrated photosystem I with menadione/phylloquinone incorporated, P700+A1− radical pair recombination is characterized by a time constant of 240/340μs, with this process occurring in 58/39% of the PSI particles, respectively. The origin of these differences is discussed. Marcus electron transfer theory in combination with kinetic modeling is used to simulate the observed electron transfer time constants at 298K. This simulation allows an estimate of the redox potential for the different quinones in the A1 binding site.

The partition behavior of perfluorooctanesulfonate (PFOS) and perfluorooctanesulfonamide (FOSA) on microplastics

Microplastics have been recognized as transport vectors for heavy metals and organic pollutants to marine animals. Thus, the sorption behavior of contaminant on microplastic is crucial to their transport in marine system. In this study, the sorption behavior of PFOS and FOSA (two perfluorochemicals) on three kinds of microplastics (PE, PS, and PVC) are reported. The isotherm study showed that the sorption of PFOS and FOSA on microplastics is highly linear, and it indicated that partition by hydrophobic interaction is the predominant sorption mechanism. The Kd values of FOSA on three kinds of microplastics are all higher than those of PFOS, and the reason is attributed to their different functional groups. The Kd value of FOSA on three types of microplastics followed the order as: PE>PVC>PS. Such finding may indicate that the molecule composition and structure of microplastics play important roles in their sorption processes of organic pollutants. The PFOS sorption levels on PE and PS particles were increased with the increase of NaCl and CaCl2 concentrations, while the ion concentrations have no effect on FOSA sorption. The study on the pH effects on PFOS and FOSA sorption indicated FOSA could partition under various pH conditions on three types of microplastics while PFOS sorption on PE and PS were favored with lower pH.

Effect of surfactants on apparent oxygen consumption of photosystem I isolated from Arthrospira platensis.

Surfactants play a significant role in solubilization of photosystem I (PSI) in vitro. Triton X-100 (TX), n-Dodecyl-β-D-maltoside (DDM), and sodium dodecyl sulfate (SDS) were employed to solubilize PSI particles in MES buffer to compare the effect of surfactant and its dosage on the apparent oxygen consumption rate of PSI. Through a combined assessment of sucrose density gradient centrifugation, Native PAGE and 77K fluorescence with the apparent oxygen consumption, the nature of the enhancement of the apparent oxygen consumption activity of PSI by surfactants has been analyzed. Aggregated PSI particles can be dispersed by surfactant molecules into micelles, and the apparent oxygen consumption rate is higher for surfactant-solubilized PSI than for integral PSI particles. For DDM, PSI particles are solubilized mostly as the integral trimeric form. For TX, PSI particles are solubilized as incomplete trimeric and some monomeric forms. For the much harsher surfactant, SDS, PSI particles are completely solubilized as monomeric and its subunit forms. The enhancement of the oxygen consumption rate cannot be explained only by the effects of surfactant on the equilibrium between monomeric and trimeric forms of solubililized PSI. Care must be taken when the electron transfer activity of PSI is evaluated by methods based on oxygen consumption because the apparent oxygen consumption rate is influenced by uncoupled chlorophyll (Chl) from PSI, i.e., the larger the amount of uncoupled Chl, the higher the rate of apparent oxygen consumption. 77K fluorescence spectra can be used to ensure that there is no uncoupled Chl present in the system. In order to eliminate the effect of trace uncoupled Chl, an efficient physical quencher of (1)O2, such as 1mM NaN3, may be added into the mixture.

Polystyrene/Ag nanoparticles as dynamic surface-enhanced Raman spectroscopy substrates for sensitive detection of organophosphorus pesticides

We report the use of Polystyrene/Ag (PS/Ag) nanoparticles as dynamic surface-enhanced Raman spectroscopy (dynamic-SERS) substrates for sensitive detection of low levels of organophosphorus pesticides. The PS particles clearly observed using Raman microscopy provide the masterplate for in situ growth of Ag NPs, leading to multiple active sites for SERS measurements. Besides obtaining the fingerprints of target molecules and recording time-resolved Raman spectra, this dynamic-SERS method can be used as an ultra-sensitive analytical technique which can enhance 1–2 orders of magnitude the signals of analytes in comparison to that of the traditional methods. On the other hand, importantly, it shows much better correlations between concentration and intensity than does the conventional SERS technique so that it can build the foundation for quantitative analysis of analytes. The as-prepared individual PS/Ag nanoparticle has been demonstrated for the sensitive detection of organophosphorus paraoxon and sumithion. SERS spectra are acquired at different concentrations of each pesticide and linear calibration curves are obtained by monitoring the strongest intensity value of bands arising from stronger stretching mode as a function of analyte concentration. The limits of detection and limits of quantitation are reported for two pesticides. The limit of detection for paraoxon is 96nM (0.026ppm) and for sumithion is 34nM (0.011ppm). The limits of quantitation are 152nM (0.042ppm) and 57nM (0.016ppm) for paraoxon and sumithion, respectively. It can be seen that these two organophosphorus pesticides can be detected in the low nM range based on this dynamic-SERS analytical method. Also, in the real sample experiments of paraoxon and sumithion, the results confirm that this dynamic-SERS technique would have potential applicability for quantitative analysis with slight interference.

Oxidation-Induced Trapping of Drugs in Porous Silicon Microparticles.

An approach for the preparation of an oxidized porous silicon microparticle drug delivery system that can provide efficient trapping and sustained release of various drugs is reported. The method uses the contraction of porous silicon’s mesopores, which occurs during oxidation of the silicon matrix, to increase the loading and retention of drugs within the particles. First, a porous Si (pSi) film is prepared by electrochemical etching of p-type silicon with a resistivity of >0.65 Ω cm in a 1:1 (v/v) HF/ethanol electrolyte solution. Under these conditions, the pore walls are sufficiently thin to allow for complete oxidation of the silicon skeleton under mild conditions. The pSi film is then soaked in an aqueous solution containing the drug (cobinamide or rhodamine B test molecules were used in this study) and sodium nitrite. Oxidation of the porous host by nitrite results in a shrinking of the pore openings, which physically traps the drug in the porous matrix. The film is subsequently fractured by ultrasonication into microparticles. Upon comparison with commonly used oxidizing agents for pSi such as water, peroxide, and dimethyl sulfoxide, nitrite is kinetically and thermodynamically sufficient to oxidize the pore walls of the pSi matrix, precluding reductive (by Si) or oxidative (by nitrite) degradation of the drug payload. The drug loading efficiency is significantly increased (by up to 10-fold), and the release rate is significantly prolonged (by 20-fold) relative to control samples in which the drug is loaded by infiltration of pSi particles postoxidation. We find that it is important that the silicon skeleton be completely oxidized to ensure the drug is not reduced or degraded by contact with elemental silicon during the particle dissolution–drug release phase.

A Novel Method for the Fabrication of Monodispersed Carbon Nanospheres and Their Crosslinked Forms

shell, PS particles were effectively separated during pyrolysis process which resulted to CNSs with anaverage diameter of 40 nm. Moreover, CNSs could be crosslinked with each other through the bondingsbetween the functional groups on their surfaces. Morphology of the fabricated carbon spheres and theircrosslinked form were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy(FESEM), transmission electron microscopy (TEM), and fourier transform infrared spectroscopy (FT-IR). Key Words : Carbon nanosphere, Polystyrene, Silica, Core-shell, Crosslinked formIntroductionSpherical carbon particles have attracted many attentionsbecause of their applications as electronic devices, supporterof catalysts, adsorbents, and anode materials in lithium-ionbatteries, etc.

Synthesis, characterization, and properties of polystyrene/SiO2 hybrid materials via sol–gel process

Isocyanate‐functionalized polystyrene (P(St‐co‐TMI)) was successfully synthesized by solution free radical polymerization, which was then used to react with (3‐aminopropyl) triethoxysilane (APTES) to prepare a precursor of polystyrene/inorganic composites (PS/SiO2). To obtain PS/SiO2 composites with chemical bond, the precursor was mixed with triethoxysilane (TEOS) under the sol–gel reaction condition. The chemical bond between the PS and SiO2 particles made the crosslink network more stable and avoided aggregation compared with the physical connection and barely mechanical mixing. The Fourier transform infrared (FT‐IR) results indicate that the isocyanate group (NCO) was completely reacted with APTES. The field‐emission scanning electron microscopy results show that the morphology of composites and the distribution of the particles, which exhibit good compatibility between organic and inorganic phases, and the inorganic particles show good spatial uniformity. The differential scanning calorimetry shows that the glass transition temperature (Tg) of the PS/SiO2 composites was shifted to high temperature when the amount of APTES increased. The thermal degradation temperature of the PS/SiO2 composites increases with the increasing of APTES content. Master curves at 200°C are constructed for the storage and loss modulus as well as complex viscosity. POLYM. COMPOS. 36:482–488, 2015. © 2014 Society of Plastics Engineers

Synthesis and properties of amphiphilic nonspherical SPS/PS composite particles by multi-step seeded swelling polymerization

Amphiphilic nonspherical particles have asymmetric surface physical and chemical properties. Such a unique structure makes them suitable for applications in many areas, such as chemical and biological sensors, colloidal surfactants, self-assembly, building blocks of complex superstructures, and materials engineering. In this study, amphiphilic sulfonated polystyrene/polystyrene (SPS/PS) composite particles with controllable morphologies are synthesized by combining modified treatment and multistage seeded swelling polymerization. Core-shell SPS particles were first obtained by modifying cross-linked PS particles with concentrated sulfuric acid, and the surface of SPS particles was a hydrophilic sulfonated polystyrene layer. With further twice seeded swelling polymerization, new hydrophobic PS oil phase sprouted on the strong hydrophilic surface even without any surfactant assistance in aqueous media. The morphologies of these SPS/PS composite particles could be adjusted by changing the crosslinking density of the seed microspheres, the sulfonation temperature and the swelling ratio of monomer/seed. These polymer composite particles can be used as solid surfactants.

Synthesis of Different Mesoporous SiO2 Structures by Using PNIPAM‐co‐PS Particles as Templates

SummaryDifferent mesoporous SiO2 structures were synthesized by a novel process in which poly(N‐isopropyl acrylamide)‐co‐polystyrene (PNIPAM‐co‐PS) copolymer particles with 10 and 35 wt% styrene, respectively, acted as templates. The copolymer particles were prepared by direct miniemulsion polymerization and subsequently assembled by sedimentation‐aggregation with the silica precursor tetraethyl orthosilicate (TEOS). After a sol‐gel process the polymeric cores were removed by calcination at 650 °C. The influence of temperature of the sol‐gel process on the morphology of the mesoporous silica was investigated. Choosing the temperature below or above the lower critical solution temperature (LCST) of the copolymer allows fine‐tuning of the pore size and pore distribution.

Saponins: A Renewable and Biodegradable Surfactant From Its Microwave-Assisted Extraction to the Synthesis of Monodisperse Lattices

Synthetic surfactants are widely used in emulsion polymerization, but it is increasingly desirable to replace them with naturally derived molecules with a reduced environmental burden. This study demonstrates the use of saponins as biodegradable and renewable surfactants for emulsion polymerization. This chemical has been extracted from soapnuts by microwave assisted extraction and characterized in terms of surfactant properties prior to emulsion polymerization. The results in terms of particle size distribution and morphology control have been compared to those obtained with classical nonionic (NP40) or anionic (SDS) industrial surfactants. Microwave-extracted saponins were able to lead to latexes as stable as standard PS latex, as shown by the CMC and CCC measurements. The saponin-stabilized PS particles have been characterized in terms of particle size and distribution by Dynamic Light Scattering and Asymmetrical Flow Field Flow Fractionation. Monomodal and monodispersed particles ranging from 250 to 480 nm in terms of diameter with a particle size distribution below 1.03 have been synthesized.

Popcorn-like morphology of asymmetric nanoparticles co-adjusted by hydrophilicity and crosslinking degree of the seeds

This paper presents a facile synthesis method for poly(methyl methacrylate-co-acetoacetoxyethyl methacrylate)–polystyrene popcorn-like particles by soap-free seeded emulsion polymerization. In this study, popcorn-like, raspberry-like and reverse core–shell structures of the P(MMA-co-AAEM)–PS particles could be obtained in a reliable manner. And it was found that the hydrophilicity and crosslinking degree of the seed particles, which were respectively controlled by the addition amount of comonomer AAEM and crosslinker ethyleneglycol dimethacrylate in the P(MMA-co-AAEM) seed particles, co-adjusted the popcorn-like morphology of P(MMA-co-AAEM)–PS particles. In order to make sense of the formation mechanism of the morphology, a thermodynamic model utilizing an equilibrium among the elastic-retractile force of the cross-linked polymer network, the mixing force of monomer and polymer and the interfacial tension force between the particle and water, was used to explain the formation of anisotropic particles.

Introduction of two-dimensional defects in inverse opal films by means of planar lithography and sol-gel co-assembly methods

By applying planar lithography and sol-gel co-assembly methods, the designed two-dimensional defects were introduced in inverse opal films. Composite colloidal crystal films which can turn into inverse opal films after calcination were fabricated by sol-gel co-assembly method. Photoresist patterns produced by planer lithograph either on silicon or composite colloidal film/silicon substrate were used as the sacrificial structure to form the designed defects. To form the embedded defects in inverse opal films, a layer of composite colloidal crystal film was assembled on the photoresist patterns. After calcination, both PS spheres and photoresist were removed, and the designed defects were introduced in the inverse opal films. Influence of the photoresist patterns on self-assembled PS particles was also characterized.

Relationship between branch length and the compatibilizing effect of polypropylene‐g‐polystyrene graft copolymer on polypropylene/polystyrene blends

ABSTRACTThree polypropylene‐g‐polystyrene (PP‐g‐PS) graft copolymers with the same branch density but different branch lengths were evaluated as compatibilizing agents for PP/PS blends. The morphological and rheological results revealed that the addition of PP‐g‐PS graft copolymers significantly reduced the PS particle size and enhanced the interfacial adhesion between PP and PS phases. Furthermore, it is verified that the branch length of PP‐g‐PS graft copolymer had opposite effects on its compatibilizing effect: on one hand, increasing the branch length could improve the compatibilizing effect of graft copolymer on PP/PS blends, demonstrated by the reduction of PS particle size and the enhancement of interfacial adhesion; on the other hand, increasing the branch length would increase the melt viscosity of PP‐g‐PS graft copolymer, which prevented it from migrating effectively to the interface of blend components. Additionally, the crystallization and melting behaviors of PP and PP/PS blends were compared. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40126.

InclusiveJ/ψandψ(2S)production fromb-hadron decay inpp¯andppcollisions

We study the inclusive production of J/psi and psi(2S) mesons originating from the decays of bottom-flavored hadrons produced in p anti-p collisions at the Fermilab Tevatron and in pp collisions at the CERN LHC. We work at next-to-leading order in the general-mass variable-flavor-number scheme (GM-VFNS) implemented with nonperturbative fragmentation functions fitted to e^+e^- data of inclusive b-hadron production exploiting their universality. The three-momentum distributions of the charmonia used were extracted from B-decay data in the framework of nonrelativistic-QCD factorization. Comparing the theoretical predictions thus obtained with transverse-momentum distributions measured by the CDF II, ALICE, ATLAS, CMS, and LHCb Collaborations, we find excellent overall agreement as for both absolute normalization and lineshape, which provides a nontrivial test of the GM-VFNS over wide ranges of center-of-mass energy, transverse momentum, and rapidity.

Morphing Metal–Polymer Janus Particles

The direct deformation and shape recovery of micron-sized polystyrene particles via nanoimprint lithography is reported. The recovery of the programmed PS particles can be utilized to create a range of smart Janus particles with contrasting properties in conductivity and topography, by use of metal-layer constrained recovery.