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Microparticles
Terms modified by Microparticles Selected AbstractsMonodisperse Poly(3,4-ethylenedioxythiophene),Silica Microspheres: Synthesis and Assembly into Crystalline Colloidal Arrays,ADVANCED MATERIALS, Issue 13 2008Timothy L. Kelly Monodisperse poly(3,4(ethylenediox( ythiophene),silica microparticles (PEDOT,silica) are prepared (see figure). The composite materials are ordered by the vertical deposition technique, yielding well(formed opal films of 15 µm thickness. The silica hosts can be selectively removed by etching with HF, leaving behind an intact PEDOT microparticle. [source] Application of poly(acrylic acid) superporous hydrogel microparticles as a super-disintegrant in fast-disintegrating tabletsJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 4 2004Shicheng Yang ABSTRACT Poly(acrylic acid) superporous hydrogel (SPH) microparticles possessing a unique porous structure were used as a wicking agent to decrease disintegration time of fast-disintegrating tablets (FDTs). The compression behaviour of poly(acrylic acid) SPH microparticles was evaluated using the Kawakita equation. Effects of various SPH microparticle sizes and a 19-run fractional factorial design were evaluated. The factorial design was based on four factors consisting of ketoprofen, SPH microparticle, filler, and tableting pressure, and each factor contained three levels on the disintegration time and tensile strength of the prepared FDTs. The poly(acrylic acid) SPH microparticles existed in an amorphous state and swelled approximately 80-times in distilled water and 50-times in pH 6.8 0.2 m phosphate buffer. The compressibility of SPH microparticles increased significantly as the microparticle size increased. The FDTs made of SPH microparticles in the range of 75,106 ,m showed the fastest disintegration time and higher tensile strength. SPH microparticle, tableting pressure and ketoprofen had significant effects on disintegration time and tensile strength of ketoprofen FDTs. The FDTs that were prepared with 2.5% w/w SPH microparticles of 75,106 ,m at 63 MPa pressure possessed a tensile strength of 84.4+4.1 N cm,2 and disintegrated in 15.0+2.0 s. It was concluded that the poly(acrylic acid) SPH microparticles could serve as a good super-disintegrant decreasing the disintegration time of FDTs. [source] Platelet hyperprocoagulant activity in Type 2 diabetes mellitus: attenuation by glycoprotein IIb/IIIa inhibitionJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 12 2008M. RAZMARA Summary.,Background:,Platelets are hyperactive in Type 2 diabetes mellitus (T2DM), and antiplatelet treatment with glycoprotein (GP) IIb/IIIa inhibitors provides better thrombotic protection in DM than in non-diabetic subjects. Objective:,We hypothesized that diabetic platelets are hyperprocoagulant, and that this hyperactivity can be inhibited by GPIIb/IIIa blockade. Methods:,Patients with T2DM and gender/age/body mass index-matched non-diabetic controls were recruited (n = 12 for both) to study the effect of GPIIb/IIIa blockade on platelet procoagulant activity. Platelet phosphotidylserine (PS), factor (F) Va expression, and platelet-derived microparticle (PDMP) generation were measured by whole blood flow cytometry. Platelet-dependent thrombin generation and plasma clotting time were monitored in recalcified platelet-rich plasma. Results:,Compared to controls, basal platelet activation was similar, while thrombin receptor activating peptide stimulated activation was enhanced in patients with T2DM. Diabetic platelets also displayed more profound elevations of platelet PS exposure, FVa binding, and PDMP generation upon stimulation. These alterations resulted in a hyperprocoagulant state, as evidenced by a marked increase in the platelet procoagulant index, enhanced thrombin generation, and a shortened plasma clotting time. GPIIb/IIIa blockade by c7E3 or SR121566 decreased platelet PS exposure and FVa binding, and diminished platelet procoagulant activity in patients with T2DM. Conclusions:,Platelets have increased procoagulant activity in patients with T2DM. The hyperprocoagulant activity is counteracted by GPIIb/IIIa blockade. [source] Heparin-induced thrombocytopenia: a prospective study on the incidence, platelet-activating capacity and clinical significance of antiplatelet factor 4/heparin antibodies of the IgG, IgM, and IgA classesJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 8 2007A. GREINACHER Summary.,Introduction:,Platelet-activating antiplatelet factor 4/heparin (anti-PF4/heparin) antibodies are the major cause of heparin-induced thrombocytopenia (HIT). However, the relative utility of functional (platelet activation) vs. antigen [enzyme-immunoassay (EIA)] assays, and the significance of assay discrepancies remain unresolved.Methods:,Consecutive patient sera (n = 1650) referred for diagnostic HIT testing were screened prospectively by both the heparin-induced platelet activation (HIPA) test and anti-PF4/heparin EIA , including individual classes (IgG, IgA, IgM) , with clinical correlations studied. Platelet microparticle and annexin-V-binding properties of the sera were also investigated.Results:,Only 205 (12.4%) sera tested positive in either the HIPA and/or EIA: 95 (46.3%) were positive in both, 109 (53.1%) were only EIA-positive, and, notably, only one serum was HIPA-positive/EIA-negative. Of 185 EIA-positive sera, only 17.6% had detectable IgM and/or IgA without detectable IgG. Among sera positive for EIA IgG, optical density values were higher when the sera were HIPA-positive (1.117 vs. 0.768; P < 0.0001), with widely overlapping values. Two HIPA-positive but EIA-IgG-negative sera became HIPA-negative following IgG depletion, suggesting platelet-activating antibodies against non-PF4-dependent antigens. Clinical correlations showed that HIPA-negative/EIA-positive patients did not develop thrombosis and had reasons other than HIT to explain thrombocytopenia. IgM/A antibodies did not increase microparticle penetration, but increased annexin-V binding.Conclusions:,The anti-PF4/heparin EIA has high (,99%) sensitivity for HIT. However, only about half of EIA-positive patients are likely to have HIT. Anti-PF4/heparin antibodies of IgM/A class and non-PF4-dependent antigens have only a minor role in HIT. [source] Fibronectin-adherent monocytes express tissue factor and tissue factor pathway inhibitor whereas endotoxin-stimulated monocytes primarily express tissue factor: physiologic and pathologic implicationsJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 7 2007M. S. BAJAJ Summary Background:,Monocytes are critical cells in initiating physiologic and/or pathologic tissue factor (TF)-induced intravascular and extravascular coagulation. Monocytes constitutively express small amounts of TF and tissue factor pathway inhibitor (TFPI). Non-adherent lipopolysaccharide (LPS)-stimulated monocytes express significant amounts of TF; however, increased expression of TFPI by these cells is controversial. Further, whether fibronectin-adherent monocytes (mimicking conditions in the extravascular space) express sufficient TFPI to inhibit TF-procoagulant activity (PCA) is unknown.Objective:,To compare TF and TFPI expression by fibronectin-adherent and LPS-stimulated non-adherent monocytes.Methods:,Monocytes were isolated from normal peripheral blood, adhered to fibronectin or stimulated with lipopolysaccharide (LPS) under non-adherent conditions and examined for expression of TF and TFPI using quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR), ELISA and factor X (FX) activation.Results:,Under LPS-free conditions, the fibronectin-adherent monocyte TF mRNA, antigen and activity were markedly upregulated. Notably, cell and microparticle (MP)-associated TF and alternatively spliced TF (asTF) were all upregulated. TFPI mRNA and antigen were also upregulated in the fibronectin-adherent monocytes, which significantly inhibited TF-PCA. TFPI mRNAs for both alpha and beta forms were detected. The peak in TFPI activity occurred in tandem with the peak in TF-PCA. In contrast, LPS-stimulated monocytes, which expressed cell and MP-associated TF and asTF, demonstrated only minimal expression of TFPI as determined by mRNA, antigen or inhibition of TF activity.Conclusion:,Both LPS-stimulated and fibronectin-adherent monocytes demonstrate a procoagulant phenotype by expressing TF but only fibronectin-adherent monocytes express significant amounts of TFPI to control thrombin generation and fibrin formation in the context of extravascular space. [source] Sorption and Diffusion of Propylene and Ethylene in Heterophasic Polypropylene CopolymersMACROMOLECULAR SYMPOSIA, Issue 1 2007Michael Bartke Abstract Summary: Sorption experiments of ethylene and propylene in different polypropylene powder samples, both homopolymer and heterophasic copolymers with different rubber content, have been carried out in a high-pressure magnetic suspension balance at 10 bars pressure and 70,°C. The gross solubilities measured can be well correlated with the rubber content of the polymer samples. Solubility of ethylene and propylene in the rubber phase differ from solubility in the amorphous fraction of the homopolymer, especially the concentration ratio of propylene to ethylene differs significantly between rubber phase and amorphous fraction of the homopolymer. From the slope of monomer uptake, information on kinetics of mass-transfer can be gained. No significant differences were observed in terms of mass-transfer for ethylene and propylene. With increasing rubber content, effective diffusion coefficients increased slightly. By combined sorption studies with powder samples and compressed films, information about both effective diffusion coefficients and the effective length scale of diffusion could be gained. It could be shown, that the particle radius is not the characteristic length of diffusion in the studied powder samples. Mass transfer of nearly all samples could be described by a constant diffusion length of 120 to 130 µm, independently on particle size. This indicates that the effective scale of diffusion in polymer particles is in between microparticle and macroparticle scale used in classical particle modeling. [source] Phosphatidylserine exposure and other apoptotic-like events in Bernard-Soulier syndrome platelets,AMERICAN JOURNAL OF HEMATOLOGY, Issue 8 2010Margaret L. Rand In the Bernard-Soulier syndrome (BSS), the giant platelets are said to have increased phosphatidylserine (PS) surface exposure in the resting state and shortened survival in the circulation. When normal platelets are activated, they undergo many biochemical and morphological changes, some of which are apoptotic. Herein, we investigated apoptotic-like events in BSS platelets upon activation, specifically, PS exposure, microparticle (MP) formation, cell shrinkage, and loss of mitochondrial inner membrane potential (,,m). Platelets from two unrelated BSS patients were examined in whole blood; agonists used were collagen, thrombin, PAR1- or PAR4-activating peptides (APs), or combinations of collagen with thrombin, and the PAR-APs. Flow cytometry was used to measure PS exposure (annexin A5 binding), platelet-derived MPs (forward scatter; events <0.75 ,m size), and ,,m (TMRM fluorescence). PS exposure was increased on resting and activated BSS platelets, and this was independent of the platelet size. MP formation by BSS platelets was generally enhanced. Cell shrinkage occurred on activation to form smaller, PS-exposing platelets in BSS and controls. A proportion of PS-exposing BSS and control platelets exhibited ,,m loss, but unlike controls, there was also loss of ,,m in the BSS platelets not exposing PS. Thus, BSS platelets undergo apoptotic-like events upon activation, with PS exposure and MP formation being enhanced. These events may play a role in the shortened survival in BSS, as well as affecting thrombin generation. Am. J. Hematol. 85:584,592, 2010. © 2010 Wiley-Liss, Inc. [source] Micronization of the officinal component baicalin by SEDS-PA processCRYSTAL RESEARCH AND TECHNOLOGY, Issue 6 2007Wen Zhi He Abstract Application of micronizing technologies in processing Chinese herbal medicines is very important to improve the forms of prepared Chinese herbal medicines and promote their therapeutic efficacy. Baicalin, a major active component of the typical Chinese herb medicine Scullateria baicallensis Georgi, was micronized using the Solution Enhanced Dispersion by Supercritical fluids though Prefilming Atomization (SEDS-PA) process with the aim of evaluating the efficiency of applying supercritical fluid precipitation technologies in Chinese herb medicine. This study has shown that acicula or rod-like baicalin crystals with Particle Size (PS) of about 20×100 ,m were successfully micronized by the SEDS-PA process to long rod-like, twisted fiber-like or fibrous net-like microparticles with PS of 0.1-2.2 ,m in width within the range of experiments performed. It was found that a substantial reduction of baicalin microparticles' sizes could lead to a marked increase of adhesions among them and subsequent microparticles agglomeration. With the increase of supercritical CO2 flow rate and the decrease of solution concentration and solution flow rate, smaller and much more agglomerated microparticles were obtained. Increasing pressure led to formation of smaller microparticles. A larger tendency of particles agglomeration was produced at a higher temperature. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Radioevaluation of PAMs, CMs, and PS-Lip as an oral carrier for vaccine delivery into intestinal Peyer's patchesDRUG DEVELOPMENT RESEARCH, Issue 12 2006Chang-Moon Lee Abstract The aim of the present study was to evaluate the utility of pullulan acetate microparticles (PAMs), chitosan micropaticles (CMs), and dipalmitoylphosphatidyl-serine-liposomes (PS-Lip) as oral carriers for delivery to the intestinal Peyer's patches (PPs). To monitor PP delivery after oral administration, PAMs, CMs, and PS-Lip were radiolabeled with 99mTc. Radiolabeling efficiencies of the particles were 95±2.5% (PAMs), 87±4.3% (CMs), and 77.2±5.8% (PS-Lip). In delivery studies to the PPs, the percentage of PS-Lip taken up to the PPs was 3.8 × 10,3±0.3% of the administered dose with PS-Lip group showed significantly high uptake compared to the PAM and CM groups. These results suggest that PS-Lip may be used as a potential system for developing an oral delivery carrier. Drug Dev. Res. 67:884,889, 2006. © 2007 Wiley-Liss, Inc. [source] A Peroxidase-Based Biosensor Supported by Nanoporous Magnetic Silica Microparticles for Acetaminophen Biotransformation and Inhibition StudiesELECTROANALYSIS, Issue 17 2006Donghui Yu Abstract Magnetized nanoporous silica based microparticles (MMPs) were used for horseradish peroxidase (HRP) immobilization and applied for amperometric peroxidase-based biosensor development. A magnetized carbon paste electrode permitted the MMPs attraction. The biosensor was applied to the investigation of the enzymatic oxidation of acetaminophen (paracetamol). The biosensor operated at low applied potential and the signal corresponded to the electroreduction of N -acetylbenzoquinoneimine (NAPQI) generated by the enzyme HRP in the presence of hydrogen peroxide. The biosensor allowed performing the quantitation of acetaminophen in the micromolar concentration range and the comparative study of thiols which inhibited the biosensor response. Distinct inhibition results were observed for HRP entrapped in the silica microparticles compared to the soluble HRP. [source] Accumulation and filtering of nanoparticles in microchannels using electrohydrodynamically induced vortical flowsELECTROPHORESIS, Issue 14 2008Maika Felten Abstract We present an approach for the accumulation and filtering of nano- and microparticles in microfluidic devices that is based on the generation of electric traveling waves in the radio-frequency range. Upon application of the electric field via a microelectrode array, complex particle trajectories and particle accumulation are observed in well-defined regions in a microchannel. Through the quantitative mapping of the 3-D flow pattern using two-focus fluorescence cross-correlation spectroscopy, two vortices could be identified as one of the sources of the force field that induces the formation of particle clouds. Dielectrophoretic forces that directly act on the particles are the second source of the force field. A thorough 2-D finite element analysis identifies the electric traveling wave mechanism as the cause for the unexpected flow behavior observed. Based on these findings, strategies are discussed, first, for avoiding the vortices to optimize electrohydrodynamic micropumps and, secondly, for utilizing the vortices in the development of microdevices for efficient particle accumulation, separation, and filtering. Such devices may find numerous biomedical applications when highly diluted nano- and microsuspensions have to be processed. [source] Separation of cationic polymer particles and characterization of avidin-immobilized particles by capillary electrophoresisELECTROPHORESIS, Issue 5-6 2006Yukihiro Okamoto Abstract Cationic polymer microparticles have received much attention especially in the field of biotechnology, such that their analysis and separation have become important. So far, the separation of cationic polymer particles with different size using CE has not been achieved and the cationic particles migrated as if they are negatively charged, probably due to electrostatic interaction between capillary wall and cationic polymer particles. In this paper, the separation of cationic polymer microparticles by CE was investigated in detail. The separation of cationic particles with different size was achieved in CE by taking into account the interaction between sample particles and the inner surface of capillaries. By employing a poly(vinyl alcohol)-coated capillary, a better size separation of amine-modified latex particles was obtained compared to a Polybrene-coated capillary. It was elucidated that the composition, concentration, and pH of the background solution were also important factors in the separation of colloidal particles to avoid the surface adsorption and the characteristic aggregation of polymer particles. Furthermore, the CE analysis was applied to the characterization of cationic protein-immobilized particles. [source] CD31+/Annexin V+ microparticles in healthy offsprings of patients with coronary artery diseaseEUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 1 2009D. Bulut ABSTRACT Background, First-degree relatives of patients with premature coronary artery disease (CAD) develop endothelial dysfunction even in the case they are apparently healthy. In this study we wanted to clarify whether reduced blood levels of circulating endothelial progenitor cells (EPCs), an endogenous repair mechanism to replace dysfunctional endothelium, or elevated endothelial-derived microparticles (EMPs), an indicator and a mediator of increased endothelial cell damage/apoptosis, are an initial step in the pathogenesis of endothelial dysfunction in genetically predisposed subjects. Materials and methods, Fifty-six healthy young men (aged 23 to 31 years) from a fire brigade were enrolled, of which 20 subjects had a positive family history (FH) for premature CAD. Subjects with or without a positive FH did not differ with respect to age, body mass index, risk factors and C-reactive protein. Endothelial function was assessed by hyperaemia-mediated relaxation of the brachial artery, blood levels of EPCs (VEGFR2+CD34+ cells) and number of EMPs (CD31+(bright)/Annexin V+ particles) were analysed by flow cytometry. Results, Hyperaemia-mediated relaxation of the brachial artery was similar in both groups, and the blood levels of EPCs were comparable. However, the number of EMPs were significantly increased in subjects with a positive FH compared to those with a negative FH (neg. FH: 55·31 ± 4·88 vs. pos. FH: 70·37 ± 6·32 particles µL,1 platelet poor plasma; P < 0·05). Number of EMPs correlate inversely with the FMD response. Conclusions, These results suggest that increased plasma levels of EMPs may be an initial step in the development of endothelial dysfunction in genetically predisposed subjects. [source] Cellular microparticles: new players in the field of vascular disease?EUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 6 2004M. Diamant Abstract Microparticles are small membrane vesicles that are released from cells upon activation or during apoptosis. Cellular microparticles in body fluids constitute a heterogeneous population, differing in cellular origin, numbers, size, antigenic composition and functional properties. Microparticles support coagulation by exposure of negatively charged phospholipids and sometimes tissue factor, the initiator of coagulation in vivo. Microparticles may transfer bioactive molecules to other cells or microparticles, thereby stimulating cells to produce cytokines, cell-adhesion molecules, growth factors and tissue factor, and modulate endothelial functions. Microparticles derived from various cells, most notably platelets but also leucocytes, lymphocytes, erythrocytes and endothelial cells, are present in the circulation of healthy subjects. Rare hereditary syndromes with disturbances in membrane vesiculation leading to a decreased numbers of microparticles clinically present with a bleeding tendency. In contrast, elevated numbers of microparticles are encountered in patients with a great variety of diseases with vascular involvement and hypercoagulability, including disseminated intravascular coagulation, acute coronary syndromes, peripheral arterial disease, diabetes mellitus and systemic inflammatory disease. Finally, microparticles are a major component of human atherosclerotic plaques. In view of their functional properties, cell-derived microparticles may be an important intermediate in the cascade of cellular and plasmatic dysfunctions underlying the process of atherogenesis. [source] Magnetic Control of Tubular Catalytic Microbots for the Transport, Assembly, and Delivery of Micro-objectsADVANCED FUNCTIONAL MATERIALS, Issue 15 2010Alexander A. Solovev Abstract Recently a significant amount of attention has been paid towards the development of man-made synthetic catalytic micro- and nanomotors that can mimic biological counterparts in terms of propulsion power, motion control, and speed. However, only a few applications of such self-propelled vehicles have been described. Here the magnetic control of self-propelled catalytic Ti/Fe/Pt rolled-up microtubes (microbots) that can be used to perform various tasks such as the selective loading, transportation, and delivery of microscale objects in a fluid is shown; for instance, it is demonstrated for polystyrene particles and thin metallic films ("nanoplates"). Microbots self-propel by ejecting microbubbles via a platinum catalytic decomposition of hydrogen peroxide into oxygen and water. The fuel and surfactant concentrations are optimized obtaining a maximum speed of 275,µm,s,1 (5.5 body lengths per second) at 15% of peroxide fuel. The microbots exert a force of around 3.77,pN when transporting a single 5,µm diameter particle; evidencing a high propulsion power that allows for the transport of up to 60 microparticles. By the introduction of an Fe thin film into the rolled-up microtubes, their motion can be fully controlled by an external magnetic field. [source] Fabrication of Density Gradients of Biodegradable Polymer Microparticles and Their Use in Guiding Neurite OutgrowthADVANCED FUNCTIONAL MATERIALS, Issue 10 2010Xiaoran Li Abstract A new method for generating both continuous and discrete density gradients in microparticles of biodegradable polymers via an electrospray technique is reported. The gradients are generated by spatially varying the deposition time of electrosprayed microparticles. The substrate coated with a density gradient of microparticles has varying surface roughness, offering a unique system for studying the effect of physical cues on neurite outgrowth from dorsal root ganglia. An optimal surface roughness for promoting neuron adhesion and neurite extension in vitro is obtained. Furthermore, this capability of approach is extended to generate a gradient of fluorescein isothiocyanate labeled bovine serum albumin by encapsulating it in the polymer microparticles in situ during electrospray. Taken together, this new class of substrates with gradients of microparticle density can potentially be used in various biomedical applications such as neural tissue engineering. [source] Encapsulation and release of a fluorescent probe, khusimyl dansylate, obtained from vetiver oil by complex coacervationFLAVOUR AND FRAGRANCE JOURNAL, Issue 1 2008A. S. Prata Abstract The essential oil of vetiver [Vetiveria zizanoides (L.) Nash ex. Small] is widely used in the perfume industry, owing to its pleasant, long-lasting, woody aroma. If this substance can be encapsulated in microparticles so that its release can be controlled, the effective duration of its properties should be extended for a much longer period of time. The present study was thus designed to investigate the encapsulation of this vetiver essential oil in microparticles. Since the detection of the effective release of such a complex mixture from these microparticles into the receiving medium can be problematic, an identifiable probe can be released with it to facilitate evaluation of the progression of the release process. Zizanoic acid is one of the compounds found in vetiver oil which depreciates its sensorial quality. This acid was thus extracted and reduced to the corresponding alcohol, khusimol, which was combined with dansyl chloride to form a fluorescent ester, khusimyl dansylate (KD). The vetiver oil and the fluorescent probe were then encapsulated (100:1) in microparticles produced by the complex coacervation of gum Arabic and gelatin. The microparticles showed spherical shape, multinuclear distribution of the core material and high encapsulation efficiency (95%). Two versions of these microparticles, moist and freeze-dried ones, were tested for the release of the KD into an ethanol medium. The moist particles released the whole KD after 5 h, although only 80% of the fluorescent probe was released with the freeze-dried microparticles at that time, probably due to the constriction caused by freeze-drying. The release of the components of vetiver oil, under the same experimental conditions, was followed, in parallel, by gas chromatography and the results obtained were compared and discussed. Copyright © 2007 John Wiley & Sons, Ltd. [source] Preparation of phosphorus and carbohydrate microcapsules for manipulating dietary C : P ratio for aquatic suspension-feedersFRESHWATER BIOLOGY, Issue 2 2003Daniel A. Kreeger SUMMARY 1.,Dietary phosphorus can be limiting for aquatic animals such as suspension-feeders. However, our understanding has been limited by the difficulty of manipulating dietary P without altering other aspects of food quality. We microencapsulated various forms of bioavailable P with carbohydrate to manipulate dietary C : P ratio for suspension-feeders. 2.,Calcium phosphate, sodium hexametaphosphate, sodium tripolyphosphate and tetrasodium pyrophosphate were each mixed with a concentrated solution of a carbohydrate base (either maltodextrin or potato starch) and microencapsulated using an interfacial polymerisation technique. Each of the 10 types of capsules produced had a particle size ideal for suspension-feeders (3,10 ,m). 3.,Leakage rates were low (<12% of capsule weight per day). Relative enzymatic breakdown in vitro by carbohydrases (amylase or cellulase) was similar among the 10 capsule types and was always at least 15 times the comparable leakage rate. 4.,Release of dissolved P from enzyme-treated capsules varied depending on capsule P content. Liberation of P from capsules prepared from 20% w/w sodium hexametaphosphate in maltodextrin (molar C : P = 1.8) was three times greater than all other types, and this combination appears most suitable as a dietary supplement for zooplankton. 5.,Although P content and capsule integrity were greatly influenced by choice of carbohydrate, choice of P compound, and the mixing ratio of the two, P-rich artificial microparticles can be produced that have low leakiness, high digestibility, and a physical size suitable for aquatic suspension-feeders. Therefore, microcapsules represent promising tools for manipulating dietary C : P for suspension feeders. [source] Preparation of Protamine,Titania Microcapsules Through Synergy Between Layer-by-Layer Assembly and Biomimetic MineralizationADVANCED FUNCTIONAL MATERIALS, Issue 1 2009Yanjun Jiang Abstract A novel approach combining layer-by-layer (LbL) assembly with biomimetic mineralization is proposed to prepare protamine,titiania hybrid microcapsules. More specifically, these microcapsules are fabricated by alternative deposition of positively charged protamine layers and negatively charged titania layers on the surface of CaCO3 microparticles, followed by dissolution of the CaCO3 microparticles using EDTA. During the deposition process, the protamine layer induces the hydrolysis and condensation of a titania precursor, to form the titania layer. Thereafter, the negatively charged titania layer allows a new cycle of deposition step of the protamine layer, which ensures a continuous LbL process. The morphology, structure, and chemical composition of the microcapsules are characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared, and X-ray photoelectron spectroscopy. Moreover, these protamine,titania hybrid microcapsules are first employed as the carrier for the immobilization of yeast alcohol dehydrogenase (YADH), and the encapsulated YADH displays enhanced recycling stability. This approach may open a facile, general, and efficient way to prepare organic,inorganic hybrid materials with different compositions and shapes. [source] The Influence of , -Tricalcium Phosphate Nanoparticles and Microparticles on the Degradation of Poly(D,L -lactide-co-glycolide)ADVANCED MATERIALS, Issue 38-39 2009Zhijie Yang The in vitro degradation behavior of a series of resorbable, bioactive nano- and microcomposites designed for orthopaedic application is explored. Nanoparticles of , -tricalcium phosphate are significantly more effective than the equivalent microparticles in reducing heterogeneity of the poly(D,L -lactide-co-glycolide) degradation. More uniform degradation, reduced acid release, and less swelling of polymer were observed. [source] Microparticles for the delivery of DNA vaccinesIMMUNOLOGICAL REVIEWS, Issue 1 2004Derek T. O'Hagan Summary:, DNA vaccines have demonstrated a lack of adequate potency in humans, which has necessitated the exploration of various adjunct technologies. Inefficient delivery of DNA vaccines, particularly to antigen-presenting cells, may be contributing to this lack of potency. One effective means of facilitating delivery of DNA vaccines to APCs is through the use of microparticles. In this article, we review the background and rationale for microparticles as a vaccine delivery system, data demonstrating their utility and mode of action for DNA delivery, and the prospects for their development. [source] Biodegradable Thermoresponsive Microparticle Dispersions for Injectable Cell Delivery Prepared Using a Single-Step ProcessADVANCED MATERIALS, Issue 18 2009Wenxin Wang Surface-engineered microparticles with a biodegradable polymer core and a programmable thermoresponsive biocompatible copolymer corona are produced. The particles form free-flowing dispersions below 37,°C, but form porous space-filling gels above this temperature, as a result of chain collapse of the copolymer corona. When particles are mixed with biological materials, they form encapsulating gels that can support cell growth. [source] Fabrication of Micropatterned Stimulus-Responsive Polymer-Brush ,Anemone'ADVANCED MATERIALS, Issue 18 2009Tao Chen A simple strategy to fabricate stimulus-responsive patterned PNIPAAM-brush microstructures (,anemones') is presented. The size of the microstructures can be adjusted by setting the composition of thiol and the contact pressure. We demonstrate that the patterned PNIPAAM-brush microstructures have a triggerable and reversible conformation transition, and can potentially be used as microcontainers to reversibly dock and release microparticles. [source] Monodisperse Poly(3,4-ethylenedioxythiophene),Silica Microspheres: Synthesis and Assembly into Crystalline Colloidal Arrays,ADVANCED MATERIALS, Issue 13 2008Timothy L. Kelly Monodisperse poly(3,4(ethylenediox( ythiophene),silica microparticles (PEDOT,silica) are prepared (see figure). The composite materials are ordered by the vertical deposition technique, yielding well(formed opal films of 15 µm thickness. The silica hosts can be selectively removed by etching with HF, leaving behind an intact PEDOT microparticle. [source] Influence of the surface on thrombin generationINTERNATIONAL JOURNAL OF LABORATORY HEMATOLOGY, Issue 4 2008T. W. STIEF Summary Thrombin generation depends on the surface of the blood vessel or container. With a new ultra-sensitive and -specific thrombin assay the surface-dependent thrombin generation was quantified. Citrated blood or plasma was preincubated for 1 h (37 °C). Citrated blood, plasma, or plasma with 0,10 g/l hemoglobin,erythrocyte microparticles (Hb,MP) were preincubated at 23 °C or at 37 °C. Plasma samples (50 ,l) were recalcified in polystyrol (PS) wells and incubated for different coagulation reaction times (CRT). Final supramolar arginine concentrations, 0.1% Triton X 100, and chromogenic thrombin substrate concentrations in the onefold km,range were added and the linear ,A/t was measured in the recalcified coagulation activity assay (RECA). Aprotinin or corn trypsin inhibitor were added. (i) Recalcification of plasma (in different monovettes) pre-incubated for 1 h (37 °C) generated the following thrombin activities after 7 min (37 °C): 0.74 IU/ml (polypropylene (PP)-citrate), 0.39 IU/ml (PP-EDTA), 0.06 IU/ml (PP-heparin), 1.38 IU/ml (PS), 0.63 IU/ml (1 ml volume PP), 0.13 IU/ml (15 ml volume PP), and 3.62 IU/ml (glass). (ii) Recalcification of preincubated whole blood generated up to about fivefold more thrombin. (iii) Thrombin generation is proportional to the plasmatic concentration of Hb,MP, 10 g/l Hb,MP generating about 4 IU/ml thrombin within 20 min CRT. (iv) The IC50 of aprotinin and corn typsin inhibitor on thrombin generation in RECA are about 2 KIU/ml and about 1 U/ml, respectively. The reaction wall, the preincubation temperature, and hemolysis influences thrombin generation. The RECA allows to diagnose the prothrombotic capacity of any material. [source] Food plaquette digestion in the ciliated protozoan Hyalophysa chattoniINVERTEBRATE BIOLOGY, Issue 2 2001Stephen C. Landers Abstract. The digestion of food plaquettes in the ciliated protozoan Hyalophysa chattoni was analyzed by light and electron microscopy. Through the use of nigrosin as a tracer for light microscopy and polystyrene microparticles for electron microscopy, we have demonstrated that food plaquettes transform to late-stage digestive vesicles. Eventually, in the phoront, some of the late-stage vesicles merge to form larger fusion vesicles, which are retained in the peripheral cytoplasm of the ensuing feeding stage. After the feeding stage settles and encysts, these vesicles are either retained by the daughter cells or are left in the divisional cyst as residual bodies. Food plaquettes, digestive vesicles, and fusion vesicles stain positively with neutral red and acridine orange, indicating an acidic pH. These results portray a unique digestive pathway in which stored, undigested material is reorganized into larger fusion vesicles as the cell prepares for additional feeding. [source] Oxycellulose: Significant characteristics in relation to its pharmaceutical and medical applicationsADVANCES IN POLYMER TECHNOLOGY, Issue 3 2009Bajerová Martina Abstract As a biomaterial, cellulose can be converted into a wide range of derivatives with desired properties for a variety of medical, biomedical, and pharmaceutical applications. The oxidation of cellulose yields oxidized cellulose (OC, oxycellulose, 6-carboxycellulose). OC represents an important class of biocompatible and bioresorbable polymers. In vivo bioabsorption of OC occurs via chemical depolymerization and enzymatic hydrolysis. Despite the fact OC is well established as a hemostatic agent and is widely used in a clinical practice, it still attracts a great interest and its new applications, especially pharmaceutical, are investigated. The present review is focused on characterization of OC's physical and chemical properties. Its synthesis and mechanisms involved in its in vivo and in vitro biodegradation are discussed. Medical and biomedical applications of OC are summarized, and especially its hemostatic, enterosorbent, and wound-healing properties are described. In addition to these applications, OC could be used as a pharmaceutical excipient in solid (e.g., tablets, microparticles), semisolid (e.g., gels), as well as liquid (e.g., suspensions) dosage forms. © 2009 Wiley Periodicals, Inc. Adv Polym Techn 28:199,208, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20161 [source] Microencapsulation of doxycycline into poly(lactide- co -glycolide) by spray drying technique: Effect of polymer molecular weight on process parametersJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Pradip Patel Abstract Poly(lactide- co -glycolide) (PLGA) polymers with three different molecular weights were prepared, and microparticles were produced by spray drying and water-in-oil-water (w/o/w) double emulsion techniques to encapsulate 86% of doxycycline (DXY), an antibiotic drug, for the use of periodontitis. Placebo and drug-loaded microspheres and pristine DXY were analyzed by Fourier transform infrared spectroscopy, which indicated no chemical interactions between DXY and PLGA. X-ray diffraction of drug-loaded microspheres confirmed the molecular level dispersion of DXY in PLGA. Scanning electron microscopy confirmed spherical nature and smooth surfaces of the microspheres. Mean particle size as measured by laser light scattering technique ranged between 10 and 25 ,m. In vitro release of DXY performed in 7.4 pH media continued up to 72 h and depended on molecular weight of PLGA and extent of DXY loading. Antimicrobial studies performed on one formulation and placebo microspheres suggested that drug concentrations during in vitro release are above the minimum inhibitory concentration (MIC) for Staphylococcus aureus growth. Overall, the release studies depended on the molecular weight of PLGA, extent of drug loading, and the method used to prepare microspheres. Statistical analyses of release data performed using the analysis of variance (ANOVA) method agreed well with experimental observations. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Preparation and optimization of 2,4-D loaded cellulose derivatives microspheres by solvent evaporation techniqueJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2007Z. El Bahri Abstract Controlled release herbicide formulations were prepared by microencapsulation using solvent evaporation technique. 2,4-D was chosen as core material, which was microencapsulated in two cellulose derivatives as matrices: cellulose acetate butyrate butyryl (CAB) and ethylcellulose (EC). The work is intended to produce systems containing the herbicide to reduce its risks by dermal contact, evaporation, or degradation and to control the release of the active agent. The microspheres loaded by 2,4-D were characterized by scanning electron microscopy and infrared spectroscopy. We have obtained microparticles in the range of D32 of 42,277 ,m with CAB and 88,744 ,m with EC by varying the process parameters. The drug entrapment was improved by controlling certain factors such as polymer/solvent ratio, pH of continuous phase, and organic phase solvent. The drug release was established in deionized water at pH = 5.5 and 25°C and the 2,4-D concentrations were estimated by UV analysis. The release data were analyzed according to Fick's law and the results demonstrate that the release rate can be controlled by modifying the process parameters. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2742,2751, 2007 [source] Comparison of cytotoxic and inflammatory responses of photoluminescent silicon nanoparticles with silicon micron-sized particles in RAW 264.7 macrophagesJOURNAL OF APPLIED TOXICOLOGY, Issue 1 2009Jonghoon Choi Abstract Photoluminescent silicon nanoparticles have a bright and stable fluorescence and are promising candidates for bio-imaging, cell staining and drug delivery. With increasing development of nanotechnology applications for biomedicine, an understanding of the potential toxicity of nanoparticles is needed to assess safety concerns for clinical applications. The objective of this study was to compare biological responses of silicon nanoparticles (SNs, 3 nm diameter) with silicon microparticles (SMs, ,100,3000 nm diameter) in cultured murine macrophages (RAW 264.7) using standard protocols for assessing cytotoxicity/cell viability and inflammatory responses developed for micron-sized particles. SNs and SMs were exposed to macrophages with and without addition of endotoxin lipopolysaccharide (LPS), a positive inducer of tumor necrosis factor-alpha (TNF- ,), interleukin 6 (IL-6), and nitric oxide (NO). Cytotoxicity was assayed using the dye exclusion and MTT assays. Cell supernatants were assayed for production TNF- ,, IL-6 and NO. SNs at concentrations ,20 µg ml,1 exhibited no cytotoxicity or inflammatory responses; however, SNs and SMs >20 and 200 µg ml,1, respectively, increased cytotoxicity compared with controls. SMs induced concentration-related increases in TNF- , and IL-6 production; in contrast, the production of these cytokines was shown to decrease with increasing concentrations of SNs. NO production was not induced by SNs or SMs alone. Fluorescence microscopy demonstrated that SNs were associated with the macrophages, either internalized or attached to cell membranes. In conclusion, evaluating differences in biological responses for nanoparticles compared with microparticles of the same material may help improve tests to assess biological responses of nanoparticles that may be used in biomedical applications. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||