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PubMed1993

Synthesis and application of new microcarriers for animal cell culture. Part I: Design of polystyrene based microcarriers.

In this work (Part I), surface modified styrene polymers as new microcarrier material for animal cell culture were extensively investigated. The first synthesis steps--carried out by chloromethylation, sulphonation and nitration of the polystyrene matrix--resulted in precursors with a defined surface layer thickness. The obtained hydrophobic bulk phase showed a limited absorption of hydrophilic media components compared to polysaccharides matrices like dextran. By varying reaction conditions for microcarrier synthesis and/or by using similar styrene type polymer matrices like polyvinyltoluene, the specific density (1.028-1.05 g/cm3) of the microcarrier matrix was adjusted without problems. Chemical varying of the microcarrier surface by reaction of the precursors with different amines, saccharides or proteins led to new microcarriers with optimal conditions for cell adhesion and cell growth. All biological investigations were carried out with a BHK 21 (c-13) cell line. Detailed results will be discussed and summarized in Part II of this work.

Amines↗

PubMed1995

Coadsorption of IgG and BSA onto sulfonated polystyrene latex: I. Sequential and competitive coadsorption isotherms.

In this work the sequential and competitive coadsorption of IgG and BSA proteins on a sulfonate polystyrene latex with high surface charge density have been studied. For sequential coadsorption the IgG/a-CRP was first adsorbed and then the free surface of the particle was saturated by redispersion of the pellet in a solution with a high concentration of monomeric BSA (m-BSA). The competitive coadsorption experiments were carried out in two separate experiments by changing the initial concentration of one protein when the concentration of other protein was high and constant. During the incubation the pH was 5 or 6, and the ionic strength 2 mM, as in previous studies the adsorption of BSA was very low at neutral or basic pH regardless of the amount of adsorbed IgG. From these coadsorption experiments it was possible to obtain latex-protein complexes with a similar degree of coverage by each protein, high adsorption of IgG and different amounts of BSA, or high adsorption of BSA and a low, but significant, amount of IgG. The latex-protein complexes were electrokinetically characterized by measuring the electrophoretic mobility of each complex vs the pH of redispersion. In that way we can detect the i.e.p. of the complexes and the pH range in which the electrostatic repulsion can make them colloidally stable.

Adsorption↗

PubMed1995

Coadsorption of IgG and BSA onto sulfonated polystyrene latex: II. Colloidal stability and immunoreactivity.

The present work deals with the study of the colloidal stability and immunoreactivity of sulfonated polystyrene latex particles covered by different amounts of m-BSA and IgG/a-CRP. These proteins have been previously adsorbed onto a sulfonated latex by sequential and competitive coadsorption experiments and it was possible to obtain latex-protein particles with different degrees of coverage by each protein. The latex particles, fully or partially covered by each protein (termed latex-protein complexes), were resuspended under several conditions (different pH and ionic strength values) and their colloidal stability, vs the addition of the electrolyte was studied using turbidity measurements. This stability appeared at a high degree of coverage by BSA and at a pH in which the BSA was negatively charged. At a high degree of coverage by IgG, the latex particles were unstable at all pHs. As a final part of this work, the immunoreactivity of several complexes was studied following the changes in the turbidity after the addition of CRP antigen. Only the complexes which were colloidally stable gave detectable reactivity. However, the complexes with a relatively low degree of coverage by IgG/a-CRP gave good immunoreactivity. Therefore, the latex-protein complex properties depended on the percentage of BSA or IgG adsorbed and on the electric state of the proteins at the redispersion pH. Under specific incubation conditions, sulfonated latex covered by significant IgG/BSA percentages was obtained, which showed a high colloidal stability and good immunoreactivity.

Adsorption↗

PubMed1995

Phagocytosis of monosize polystyrene-based microspheres having different size and surface properties.

In this study, nondegradable monosize polystyrene (PS) based polymeric microspheres with different size and surface chemistries were prepared by different polymerization techniques. Surfaces of the plain microspheres were further modified biologically by albumin (BSA) or fibronectin (Fn) preadsorption. Phagocytosis of these polymeric microspheres by leukocytes and macrophages were investigated. The phagocytic response of both leukocytes and macrophages decreased by increasing size of the particles. More hydrophilic particles phagocytosed less. Positive charges increased the uptake while negative charges oppositely reduced the uptake. BSA on the surface almost prevented the uptake, while Fn caused opsonization.

Animals↗

PubMed1996

A new plasma-based method to promote cell adhesion on micrometric tracks on polystyrene substrates.

A new procedure has been developed in order to obtain heterogeneous polymer surfaces for the promotion of cell adhesion. For this purpose, a microelectronic photosensitive resin was spin coated on polystyrene (PS) substrates. The resin was then submitted to UV light irradiation through a mask and partially developed. The sample was further submitted to a plasma oxygen discharge prior to dissolution of the remaining resin. The characterization by time of flight secondary ion mass spectrometry (ToF SIMS), X-ray photoelectron spectroscopy (XPS), and dynamic contact angle (DCA) allowed us to conclude that hydrophilic paths were created on the more hydrophobic PS substrate together with the complete removal of the resin. In order to optimize cell adhesion contrast, the modified surfaces were then conditioned with a solution containing both a surfactant (pluronic F68) and a protein. Two different proteins were tested (collagen I and fibronectin). PC12 cell cultures on those conditioned surfaces showed that cell adhesion occurs only on the hydrophilic tracks. ToF SIMS spectra and images recorded on those substrates revealed the presence of the proteins only in the hydrophilic tracks. In the same time, the surfactant is suspected to adsorb mainly on the hydrophobic areas of the samples.

Adsorption↗

PubMed1996

Detection of specific plasma proteins on surfaces by immunospecific adhesion of dyed polystyrene beads.

This paper describes and evaluates a method for quantifying the amounts of specific plasma proteins adsorbed to biomaterial surfaces. In particular, it demonstrates that macroscopic images ('stains'), that assess the spatial distribution of albumin, IgG, fibrinogen, and HMK (high molecular weight kininogen), can be obtained over areas of at least 12 cm2 using immunospecific adhesion of dyed polystyrene beads. Stain intensities, measured with a scanner and an image analysis system, were found to quantify the amount of specific protein in the solution used to coat the surfaces. Results obtained with the proposed method produced single protein isotherms for albumin, immunoglobulin G (IgG) and fibrinogen that followed Langmuir-like adsorption behavior and were similar to previously published isotherms. The HMK isotherm also exhibited Langmuir-like adsorption behavior. The proposed method also detected the presence of an expected maximum in the adsorption of fibrinogen onto glass as a function of plasma dilution. Adsorption of fibrinogen out of 6.4% plasma onto glass from a separated flow produced results indicating the quantity as well as the location of fibrinogen at the boundary of the separated region. This result confirmed the utility of the proposed method for detecting spatial distributions of specific proteins adsorbed from plasma in practical devices.

Adsorption↗

PubMed1998

Tissue factor expression by rat osteosarcoma cells adherent to tissue culture polystyrene and selected orthopedic biomaterials.

Tissue factor (TF), a transmembrane glycoprotein expressed by numerous cell types, plays a critical role in the initiation of blood coagulation at sites of vascular injury. Activated products of the coagulation cascade may then enhance the inflammatory responses associated with wound healing. In the present investigation the ability of rat osteosarcoma (ROS) cells to express TF activity was examined following their growth on tissue-culture polystyrene (TCPS) and selected orthopedic biomaterials (titanium and zirconium alloys, and stainless steel). ROS cells exhibited significant TF activity as evidenced by the conversion of Factor X to Factor Xa in the presence of TF, Factor VIIa, and Ca2+. Factor Xa concentrations ranged from 1.0 fM per cell at 10 min to 6.0 fM per cell after 60 min. Additionally, ROS cells stimulated with calcium ionophore (A23187) exhibited approximately twice the activity of non-stimulated cells when grown on TCPS but not on the metallic substrates. ROS cells (stimulated or unstimulated) adherent to the zirconium alloy generated lower amounts of Factor Xa compared to those bound to the other alloys and unstimulated cells grown on TCPS. These results indicate that ROS cells cultured on these synthetic surfaces differentially express procoagulant activity and that cells grown on TCPS, but not the metallic alloys, exhibit increased TF activity in response to stimulation by calcium ionophore. This procoagulant activity may potentiate subsequent inflammatory responses associated with the use of orthopedic biomaterials and thereby influence the tissue compatibility of the implant.

Alloys↗

PubMed1999

The role of fibronectin in platelet adhesion to plasma preadsorbed polystyrene.

Platelet adhesion to synthetic surfaces that come in contact with blood is mediated by the adsorption of adhesive plasma proteins, especially fibrinogen. However, the roles of other adhesive proteins, such as fibronectin, vitronectin, and von Willebrand factor in platelet adhesion are not yet clear. In this study, the role of fibronectin in platelet adhesion to surfaces was assessed using three approaches. First, platelet adhesion was measured on Immulon I preadsorbed with fibronectin-depleted plasma or fibronectin-depleted plasma replenished with increasing amount of fibronectin. Under these conditions, fibronectin adsorbed from plasma did not have any effect on platelet adhesion, while fibrinogen played a major role in mediating platelet adhesion. Since fibronectin might play a role in platelet adhesion to surfaces which adsorb little or no fibrinogen, we also used two other strategies to assess the potential role of fibronectin. One was to use platelets treated with a platelet activation inhibitor, prostaglandin E1, which prevents the activation of platelet fibrinogen receptor GP IIb/IIIa. The adhesion of prostaglandin E1-treated platelets to Immulon I preadsorbed with plasma was greatly decreased compared to that of untreated platelets, but was increased by the addition of supernormal concentrations of fibronectin to the plasma. This suggests that GP Ic/IIa, rather than GP IIb/IIIa, might be the platelet receptor which is responsible for platelet adhesion to surface-bound fibronectin. Finally, we studied the effect of fibronectin on platelet adhesion to surfaces preadsorbed with fibronectin-depleted afibrinogenemic plasma. We found that fibronectin re-addition to fibronectin-depleted afibrinogenemic plasma increased platelet adhesion. However, our most important finding was that fibronectin seems to play little or no role in mediating platelet adhesion to polystyrene surfaces preadsorbed with normal plasma.

Alprostadil↗

PubMed1999

Synthesis of polystyrene nanospheres having lactose-conjugated hydrophilic polymers on their surfaces and carbohydrate recognition by proteins.

We prepared a poly(vinylamine)-grafted polystyrene nanosphere by the free radical polymerization of poly(N-vinylacetamide) macromonomer and styrene with AIBN in ethanol and subsequent acid hydrolysis. We conjugated lactose on the nanosphere by an amide linkage and found that the lactose was recognized by a galactose-specific lectin RCA120, which was analyzed by enzyme-linked lectin assay (ELLA). The binding ability of the lectin to lactose on the nanosphere was at least 10(2) times larger than that to a monomeric lactose. Binding ability was clearly affected by the lactose density on the nanosphere and showed a maximum value at the suitable surface density of lactose. We found that the carbohydrate-conjugated nanosphere would be a useful biomaterial for a site specific drug carrier.

Carbohydrate Metabolism↗

PubMed2002

Nanoparticles of latexes from commercial polystyrene.

Nanoparticles of polystyrene (PS) (Mw = 1.0-3.0 x 10(6) g/mol) latexes have been successfully prepared from their respective dilute PS (commercial) solutions in cyclohexane, toluene/methanol, or cyclohexane/toluene at each theta temperature. The cationic surfactant cetyltrimethylammonium bromide (CTAB) was used to stabilize the formed PS latex particles. By varying different concentrations of CTAB and PS solution of various Mw, we have successfully produced, for the first time, stable bluish-transparent latex particles ranging from about 10 to 30 nm in diameter (Dw). The number of polymer chains per latex particle (np) is directly proportional to the volume occupied by each latex particle and hence associated to its Dw. The characteristics of these preformed PS latex particles are quite similar to those obtained from the microemulsion polymerization of styrene as reported in literature. These PS latex particles could be further grown by seeding polymerization of styrene to about 50 nm (Dw) with a monodisperse size distribution of Dw/Dn = 1.08.

Cetrimonium↗

PubMed2003

Nanoparticles of polystyrene latexes by semicontinuous microemulsion polymerization using mixed surfactants.

Nanosized polystyrene (PS) latexes stabilized by the mixture of cationic/cationic, anionic/anionic, or anionic/cationic surfactants of various types with high weight ratios of PS to surfactant (ca. 10:1) have been successfully synthesized by a semicontinuous microemulsion polymerization process. For cationic or anionic systems, spherical latex particles with a weight-averaged diameter (Dw) ranging from about 22 to 53 nm were nearly linearly dependent on the weight ratio of the mixed surfactants with similar charges. Their particle size distributions were rather uniform (Dw/Dn < 1.20). For a system with oppositely charged surfactants at nonequimolar ratios, it could produce stable PS particles up to 94 nm in diameter. High molar masses (Mw) of PS ranging from 1.1 to 1.9 x 10(6) g/mol could easily be obtained for all three systems investigated. For both cationic/cationic and anionic/anionic surfactant systems, the number of PS particles per milliliter of latex (Np) generated in the very early stage of O/W' microemulsion remained rather constant throughout the polymerization. This was controlled by using only 1 wt% of mixed surfactants and the continuous addition of a small amount of styrene. The present polymerization method allows one to synthesize nanoparticles of PS or other polymers of high polymer/surfactant weight ratios at some particle sizes that are unable to achieve them with a single type of surfactant.

Emulsions↗

PubMed2005

Electrophilic modification of polystyrene nanospheres.

Monodisperse polystyrene nanospheres synthesized via emulsifier-free emulsion polymerization were modified at their surfaces with amino and hydroxy groups using trimethylsilyl azide and bis(trimethylsilyl) peroxide, respectively, in the presence of trifluoromethanesulfonic acid. The acid chloride functionality was also introduced onto the surface using AlCl3-oxalyl chloride. The size, integrity, nature and functionality of the nanospheres were investigated by Scanning Electron Microscopy, diffuse reflectance IR and UV-Vis spectroscopy. The surface amino, hydroxyl and carboxylate groups were easily transformed into other useful functionalities by known methodologies.

Electrochemistry↗

PubMedDate not supplied

Concentration dependent structural ordering of poloxamine 908 on polystyrene nanoparticles and their modulatory role on complement consumption.

Adsorption of poloxamine 908, a tetrafunctional polyethylene oxide (PEO)-polypropylene oxide ethylenediamine block copolymer, onto the surface of monodispersed polystyrene nanoparticles (232 +/- 0.33 nm) follows a bimodal pattern. Initially, the isotherm follows a Langmuir profile with a plateau observable over a very narrow equilibrium poloxamine concentration (0.0018-0.0031 mM). The isotherm then begins to rise again, reaching a final plateau at equilibrium poloxamine concentrations above 0.0089 mM. Similarly, the profile of the adsorbed layer thickness of poloxamine on the surface of nanoparticles is bimodal. The first plateau corresponds to a thickness of 4.6 +/- 0.07 nm, which occurs over the same range of poloxamine concentrations as in the initial plateau of the adsorption isotherm. The second plateau corresponds to a thickness of 9.53 +/- 0.32 nm, observable at a minimum poloxamine concentration of 0.0067 mM. By using a calculated radius of gyration of a PEO chain in poloxamine as 3.1 nm, these observations reflect dynamic changes in the arrangement of surface projected PEO chains; a mushroom-like conformation at the first plateau region of the adsorption isotherm, followed by a transition into a brush-like conformation. These conformational changes are also reflected in rheological studies; the apparent viscosity of nanoparticles in which the PEO chains are in mushroom conformation is considerably higher than particles displaying the brush conformation. Further, atomic force microscopy studies (height profile and phase lag measurements) corroborated that the proposed poloxamine concentration dependent transition of surface associated PEO chains from mushroom to brush appearance is conserved when nanoparticles are dried under ambient conditions. Finally, we compared the influence of the surface PEO characteristics on complement consumption in human serum. Our results show complement-activating nature of all poloxamine-coated nanoparticles. However, complement consumption is reduced substantially with particles bearing a minimum of 11448 poloxamine molecules on their surface, thus demonstrating the importance of PEO surface density as well as brush conformation in suppressing complement consumption. This relationship between surface characteristics of poloxamine nanoparticles and their in vivo performance is discussed.

Adsorption↗

PubMed2005

Compound transfer efficiency from polystyrene surfaces: application to microarrayed compound screening.

In microarrayed compound screening (microARCS), compounds are spotted and dried onto a polystyrene sheet (ChemCard)ata high density and introduced into the assay by contacting with agarose gels that contain reagents for the assay. The authors have conducted studies to characterize the compound transfer process using 59 compounds of diverse properties. The amount of compounds remaining on the ChemCard was determined by liquid chromatography/mass spectrometry after incubation with agarose gels for predetermined time periods. The results showed good correlation with kinetics of compound transfer to phosphate-buffered saline (PBS) buffer, but only moderate correlation with equilibrium solubility of compounds in PBS buffer. These observations indicate that the major factor determining compound transfer efficiency is the kinetics of dissolution of compounds, rather than equilibrium solubility and diffusion of compounds in the gel. Compounds of lower ClogP showed a higher rate of transfer to agarose gels and vice versa. Other compound properties such as molecular weight, size, acid-base, and H-bonding properties did not significantly affect compound transfer. Importantly, the majority of the compounds studied show greater than 20% transfer after a 10-min incubation with agarose gels, providing sufficient amounts of compounds for screening purposes.

Chromatography, High Pressure Liquid↗

PubMed2006

Porous polystyrene beads as carriers for self-emulsifying system containing loratadine.

The aim of this study was to formulate a self-emulsifying system (SES) containing a lipophilic drug, loratadine, and to explore the potential of preformed porous polystyrene beads (PPB) to act as carriers for such SES. Isotropic SES was formulated, which comprised Captex 200 (63% wt/wt), Cremophore EL (16% wt/wt), Capmul MCM (16% wt/wt), and loratadine (5% wt/wt). SES was evaluated for droplet size, drug content, and in vitro drug release. SES was loaded into preformed and characterized PPB using solvent evaporation method. SES-loaded PPB were evaluated using scanning electron microscopy (SEM) for density, specific surface area (S(BET)), loading efficiency, drug content, and in vitro drug release. After SES loading, specific surface area reduced drastically, indicating filling of PPB micropores with SES. Loading efficiency was least for small size (SS) and comparable for medium size (MS) and large size (LS) PPB fractions. In vitro drug release was rapid in case of SS beads due to the presence of SES near to surface. LS fraction showed inadequate drug release owing to presence of deeper micropores that resisted outward diffusion of entrapped SES. Leaching of SES from micropores was the rate-limiting step for drug release. Geometrical features such as bead size and pore architecture of PPB were found to govern the loading efficiency and in vitro drug release from SES-loaded PPB.

Chemistry, Pharmaceutical↗

PubMed2006

Preparation and in vitro evaluation of polystyrene-coated diltiazem-resin complex by oil-in-water emulsion solvent evaporation method.

The purpose of this study was to examine the suitability of polystyrene-coated (PS-coated) microcapsules of drug-resin complex for achieving prolonged release of diltiazem-HCl, a highly water-soluble drug, in simulated gastric and intestinal fluid. The drug was bound to Indion 254, a cation-exchange resin, and the resulting resinate was microencapsulated with PS using an oil-in-water emulsion-solvent evaporation method. The effect of various formulation parameters on the characteristics of the microcapsules was studied. Mean diameter and encapsulation efficiency of the microcapsules rose with an increase in the concentration of emulsion stabilizer and the coat/core ratio, while the same characteristics tended to decrease with an increase in the volume of the organic disperse phase. The desorption of drug from the uncoated resinate was quite rapid and independent of the pH of the dissolution media. On the other hand, the drug release from the microcapsules was prolonged for different periods of time depending on the formulation parameters and was also found to be independent of the pH of the dissolution media. Both the encapsulation efficiency and the retardation of drug release were found to be dependent on the uniformity of coating, which in turn was influenced by the formulation parameters. Kinetic studies revealed that the desorption of drug from the resinate obeyed the typical particle diffusion process, whereas the drug release from the microencapsulated resinate followed the diffusion-controlled model in accordance with the Higuchi equation. PS appeared to be a suitable polymer to provide prolonged release of diltiazem independent of the pH of the dissolution media.

Absorption↗

PubMed1984

Polystyrene latex particles as indicators of abnormal plasma properties in multiple sclerosis.

Polystyrene latex particles were incubated in plasma from multiple sclerosis (MS) patients or normal subjects. Compared with plasma from healthy controls, MS plasma produced a significantly lower mean electrophoretic mobility of the latex particles after the addition of linoleic acid. The effect was similar to that found when erythrocytes were used as the indicator particle. However, the result with latex particles demonstrates that the phenomenon originates from a plasma component of MS patients rather than from an intrinsic difference in membranes of the red blood cell.

Culture Media↗

PubMed1992

Induction of acetylcholine receptor clustering by native polystyrene beads. Implication of an endogenous muscle-derived signalling system.

Aneural muscle cells in culture often form acetylcholine receptor (AChR) clusters, termed hot spots, which are similar to those found at the postsynaptic membrane both in structure and in molecular composition. Although hot spots form on both dorsal and ventral surfaces of the cell, the ventral ones are better characterized because of their association with sites of cell-substratum contact. To understand the stimuli and mechanisms involved in ventral hot spot formation, native, uncoated polystyrene beads were applied to cultured Xenopus myotomal muscle cells to create local membrane-substratum contacts. These beads were able to induce a postsynaptic-type development as evidenced by the clustering of AChRs and the development of a set of ultrastructural specializations, including membrane infoldings and a basement membrane. Whereas these native beads were effective in inducing clustering, beads coated with bovine serum albumin or treated with serum-containing medium were ineffective. Native beads were also capable of inducing clusters in serum-free medium, indicating that their effect was mediated by endogenous molecules that were locally presented by the beads, rather than by bead adsorption of components in the medium. Heparan sulfate proteoglycan (HSPG) is a major component of the muscle extracellular matrix and our previous study has shown that basic fibroblast growth factor (bFGF), a member of the heparin-binding growth factor (HBGF) family, and its receptor are present in Xenopus myotomal muscle during the period of synaptogenesis. Therefore, we tested the involvement of HBGF in bead induction. The results of this study show the following: (1) preincubation of cultures in heparin, which solubilizes matrix-bound HBGFs, suppressed the bead-induced AChR clustering. (2) Suramin, which interferes with the interaction between several growth factors and their receptors, also inhibited bead-induced clustering. (3) Tyrphostin, which blocks tyrosine kinase activity associated with a number of growth factor receptors, was also inhibitory to the bead effect. (4) The percentage of bead-induced AChR clusters was significantly enhanced by pretreating the cultures with bFGF prior to bead application. This exogenously applied bFGF could be largely removed by treatment of cultures with heparin, suggesting its association with HSPG at the cell surface. (5) An anti-bFGF neutralizing antiserum significantly reduced the efficacy of the bead stimulation. These data suggest that uncoated beads, which adhere to the cell surface and can mimic the cell-substratum interaction, effect a local presentation of HBGFs, such as bFGF, residing with the HSPG to their membrane receptors, thereby locally activating receptor-associated tyrosine kinases.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗