Search results for "Polystyrene"

Interfacial tension and interaction parameters

1994

In view of various contradictory theoretical equations relating the interfacial tension σ between phase-separated polymer solutions to the Flory-Huggins interaction parameter of the system, the idea that σ should depend on the extent of the ‘hump’ in the concentration dependence of the Gibbs energy of mixing was studied. This investigation is based on 12 series of σ( T ) measurements reported in the literature and on additional experiments for the system cyclohexane/polystyrene. To quantify the extent of the ‘hump’, a reduced ‘hump energy’ ɛ was introduced and its value calculated for different temperatures from the measured critical data of the systems. The analysis of the entire experimen…

Timing of Heparin Addition to the Biomolecular Corona Influences the Cellular Uptake of Nanocarriers.

2019

Few studies have considered the interaction of nanocarriers with drugs and the implications for their individual efficiency. Here, we demonstrate that heparin, a common anticoagulant, interacts with nanocarriers. Hence, nanocarriers, precoated with heparin and plasma in different conditions, were incubated with cancer cells, as well as primary cells from human blood. The relation between the timing of the heparin's addition to the nanocarrier and the cellular uptake extent was assessed by flow cytometry. Through proteomics the effect of heparin on the biomolecular corona composition was determined. We found that HeLa cells, monocytes and macrophages reacted differently to the presence of he…

Polymeric nanoparticles of different sizes overcome the cell membrane barrier.

2012

Abstract Polymeric nanoparticles have tremendous potential either as carriers or markers in treatment for diseases or as diagnostics in biomedical applications. Finding the optimal conditions for effective intracellular delivery of the payload to the location of interest is still a big challenge. The particles have to overcome the barrier of the cell membrane. Here, we investigated the uptake in HeLa cells of fluorescent polystyrene particles with different size and surface charge. Particles stabilized with the nonionic surfactant Lutensol AT50® (132 nm, 180 nm, 242 nm, 816 nm, 846 nm diameter) were synthesized via dispersion polymerization. Cationic particles (120 nm, 208 nm, 267 nm, 603 n…

Uptake of polymeric nanoparticles in a human induced pluripotent stem cell-based blood-brain barrier model: Impact of size, material, and protein cor…

2021

The blood–brain barrier (BBB) maintains the homeostasis of the central nervous system, which is one of the reasons for the treatments of brain disorders being challenging in nature. Nanoparticles (NPs) have been seen as potential drug delivery systems to the brain overcoming the tight barrier of endothelial cells. Using a BBB model system based on human induced pluripotent stem cells (iPSCs), the impact of polymeric nanoparticles has been studied in relation to nanoparticle size, material, and protein corona. PLGA [poly(lactic-co-glycolic acid)] and PLLA [poly(d,l-lactide)] nanoparticles stabilized with Tween® 80 were synthesized (50 and 100 nm). iPSCs were differentiated into human brain m…

α-Chymotrypsin-Catalyzed Reaction Confined in Block-Copolymer Vesicles

2010

Herein the reactivity of the enzyme α-chymotrypsin in the confinement of polystyrene-block-poly(acrylic acid) (PS-b-PAA) vesicles was investigated. Enzyme and substrate molecules were encapsulated in PS-b-PAA vesicles with internal diameters ranging from 26 nm to 165 nm during the formation of the vesicles. While the loading efficiencies of enzyme and substrate molecules were practically identical for vesicles of identical size, they were found to increase with decreasing vesicle size. The kinetics of the α-chymotrypsin catalyzed hydrolysis of N-succinyl-Ala-Ala-Phe-7-amido-4-methylcoumarin (AMC) was evaluated following the increase of the absorption of the product 7-amino-4-methylcoumarin …

Hydrophobically directed aldol reactions: polystyrene-supported L-proline as a recyclable catalyst for direct asymmetric aldol reactions in the prese…

2007

A simple synthetic methodology for the preparation of a polystyrene- supported L-proline material is reported, and this material has been used as catalyst in direct asymmetric aldol reactions between several ketones and arylaldehydes to furnish aldol products in high yields and stereoselectivities. Screening of solvents showed that these reactions take place only in the presence of water or methanol, at lower levels of conversion in the latter case. This solvent effect, coupled with the observed high stereoselectivities, has been ex- Introduction In the last decade organocatalysis has became a field of great interest.[1] Organocatalysts are metal-free small organic molecules that are able t…

An immunoassay for terbutryn using direct hapten linkage to a glutaraldehyde network on the polystyrene surface of standard microtiter plates.

2001

2-Aminobutylamino-4-ethylamino-6-isopropylamino-1,3,5-triazine (ABA-atrazine) has been synthesized and used as a coating hapten in an immunoassay with a monoclonal antibody against terbutryn. Coating was achieved by covalently linking ABA-atrazine to a glutaraldehyde polymer network directly bound to the polystyrene surface of a standard 96-well microtiter plate. The assay was carefully optimized. In particular, the coating hapten concentration had a strong effect on the ELISA sensitivity. By including a pre-incubation step a low test midpoint (IC50-value) of 0.130 microg L(-1) was achieved. As far as we are aware this is the most sensitive ELISA for terbutryn yet reported. The coating-hapt…

Straightforward Approach for Preparing Durable Antibacterial ZnO Nanoparticle Coatings on Flexible Substrates

2022

Flexible antibacterial materials have gained utmost importance in protection from the distribution of bacteria and viruses due to the exceptional variety of applications. Herein, we demonstrate a readily scalable and rapid single-step approach for producing durable ZnO nanoparticle antibacterial coating on flexible polymer substrates at room temperature. Substrates used are polystyrene, poly(ethylene-co-vinyl acetate) copolymer, poly(methyl methacrylate), polypropylene, high density polyethylene and a commercial acrylate type adhesive tape. The deposition was achieved by a spin-coating process using a slurry of ZnO nanoparticles in toluene. A stable modification layer was obtained when tolu…

2021

The abundance of microplastics (MPs) in the atmosphere, on land, and especially in water bodies is well acknowledged. In this study, we establish an optical method based on three different techniques, namely, specular reflection to probe the medium, transmission spectroscopy measurements for the detection and identification, and a speckle pattern for monitoring the sedimentation of MPs filtrated from wastewater sludge and suspended in ethanol. We used first Raman measurements to estimate the presence and types of different MPs in wastewater sludge samples. We also used microscopy to identify the shapes of the main MPs. This allowed us to create a teaching set of samples to be characterized …

Statistical Characterization of Self-Assembled Colloidal Crystals by Single-Step Vertical Deposition

2014

Abstract We have statistically characterized the self-assembly of multi-layer polystyrene colloidal crystals, using the technique of vertical deposition, with parameters chosen to produce thick layers of self-assembled crystals in one deposition step. The size distribution of domains produced with this technique was seen to follow a log-normal distribution, hinting that aggregation or fragmentation phenomena play a role. In addition, using a lithographically directed self-assembly method, we have shown that the size of multi-layer, continuous crack-free domains in lithographically defined areas can be many times larger than in the surrounding areas. In a single deposition step, we have prod…