Separation Of The Bound And Unbound Forms Of The Radioactivity
Erwin Regoeczi in Iodine-Labeled Plasma Proteins, 2019
By polymerizing just the vinylbenzene monomers, that can be done by a free-radical process, a chain is obtained which we have already encountered in Figure 10, with the difference that the group attached to every second carbon is a benzene, instead of pyrrolidone. This is polystyrene. However, if DVB is present, the cross-linked structure shown in Figure 39 is obtained. This cross-linked polystyrene is the matrix of ion-exchange resins. By keeping the polymerizing solution in a droplet distribution, the product consists of nearly perfect spheres which are subsequently sorted according to size. The size is conventionally indicated by the mesh number. For ordinary chromatographic work with gravity flow, including the removal of nonprotein radioactivity from iodination mixtures, mesh 100 to 200 (150 to 80 μ diameter) is used; smaller beads (200 to 400 mesh, 80 to 40 μ) are useful for highresolution chromatography.8
Bio-Implants Derived from Biocompatible and Biodegradable Biopolymeric Materials
P. Mereena Luke, K. R. Dhanya, Didier Rouxel, Nandakumar Kalarikkal, Sabu Thomas in Advanced Studies in Experimental and Clinical Medicine, 2021
PBS is biodegradable aliphatic polyesters which is one of the members of biodegradable polymers family. In order to improve the properties number of copolymerization stages are made according to Darwin et al. [37]; Jin et al. (2000, 2001). Phenyl units are introduced into the side chain of PBS, which leads to the better biodegradability of the copolyesters. Jung et al. (1999) successfully synthesized new PBS copolyesters containing alicyclic 1; 4-cyclohexanedimethanol. The applications for PLA are mainly as thermoformed products such as drink cups, take-away food trays, containers, and planter boxes. Polystyrene and PET are partially replaced with PLA material due to the rigidity. Applications include mulch film, packaging film, bags, and ‘flushable’ hygiene products [38].
Nanomaterials for Theranostics: Recent Advances and Future Challenges *
Valerio Voliani in Nanomaterials and Neoplasms, 2021
Hyeon et al. used PLGA-modified polymer to encapsulate ZnS QD, SPIONs, and anticancer drug DOX [798]. The drugs were released at pH 5.0 due to reprotonation of the amine group of DOX and faster degradation of PLGA matrix at a lower pH. Accordingly, DOX were released faster in tumor sites, which are acidic, than in normal tissues. Nanoparticles without DOX exhibited almost no toxicity in KB cells, whereas DOX-loaded and FA-conjugated nanoparticles were more cytotoxic than the free DOX. In addition, cell growth was significantly inhibited in the presence of an external magnetic field. Simultaneous use of the FA-based active targeting and the magnetic field synergistically increased the cell growth inhibition effect on the KB cells. Shi et al. synthesized superparamagnetic, QD-based nanosphere for targeted imaging and drug delivery [160]. They encapsulated Fe3O4 nanoparticles inside a spherical polystyrene matrix upon which QDs were conjugated. The resulting nanocomposite was capable of both MR and optical imaging. The chemotherapeutic agent PTX was loaded on the surface of polystyrene using a layer of biodegradable poly(lactic-co-glycolic acid) (PLGA). The PGLA could be further conjugated with antiprostate-specific membrane antigen (anti-PSMA) for active cancer cell targeting. The cellular uptake of antigen-modified PTX-loaded nanoparticles by human PC3-MM2 prostate cancer cells and LNCaP was assessed by fluorescence microscopy. LNCaP cells, which express PSMA, were targeted successfully by the antigen-modified and PTX-loaded nanoparticles. In contrast, PC3-MM2 human prostate cells, which are known as PSMA negative, showed no fluorescent signals with and without anti-PSMA conjugation.
In vitro assessment of inter-kingdom biofilm formation by bacteria and filamentous fungi isolated from a drinking water distribution system
Published in Biofouling, 2019
Tiago Barros Afonso, Lúcia Chaves Simões, Nelson Lima
Since DWDS are very complex systems, of difficult accessibility, biofilm studies in situ are not common (Douterelo et al. 2014, 2018). In order to study DW biofilms separately from DWDS several devices and methodologies have been developed (Gomes et al. 2014). Microtitre plates are the most frequently used in vitro model for studying biofilm formation under strict laboratory conditions, including with DW microorganisms (Gomes et al. 2014). Despite the disadvantages they have in the reproducing conditions found in DWDS (i.e. hydrodynamic forces), polystyrene microtitre plates are commonly used as the standard bioreactor system to study adhesion and biofilm formation by bacteria and fungi isolated from these systems (Simões et al. 2010, 2015; Gomes et al. 2014). They can be used as a rapid and simple method for analysing the effects of a variety of parameters on biofilm formation as equivalent biofilms can be produced simultaneously (Simões et al. 2007a, 2010, 2015). Polystyrene also has physico-chemical surface properties similar to those of other materials used in DWDS, such as polyvinylchloride and stainless steel (Simões et al. 2007b). Regions of low shear stress easily reproduced by microtitre plates are common in DWDS, particularly in reservoirs, households pipes, corners and valves. These areas are associated with zones of abundant biofilm formation due to the high accumulation of organic material (Simões and Simões 2013). For the reasons depicted, microtitre plates were selected to study biofilm formation and behaviour of inter-kingdom biofilms containing fungi and bacteria isolated from DW.
Oligomers of styrene are not endocrine disruptors
Published in Critical Reviews in Toxicology, 2018
Heinz-Peter Gelbke, Marcy Banton, Christian Block, Gordon Dawkins, Edgar Leibold, Mark Pemberton, Atsunobu Sakoda, Atsushi Yasukawa
Oligomers of styrene are known to be present in polystyrene (PS) polymers that are used for food packaging. These are formed as by-products of incomplete polymerization during production of PS and/or by degradation after irradiation or thermal treatment of PS during downstream applications (Hoppe et al. 2016). Oligomers, and in this context especially dimers (Di) and trimers of styrene (Tri), are quantitatively an important part of nonintentionally added substances (NIAS) that may potentially migrate into food. According to EU (2011) (Article 19), the potential risk to health of NIAS has to be assessed in addition to the basic monomers. A general “cutoff” criterion was established by the European Union (EU 2011) that migration of a substance should not be detectable at a limit of detection of 10 µg/kg food (or food simulant). This limit was introduced based upon the current state of analytical technology as opposed to toxicological considerations. As the concentrations of Di and Tri and the sum of both (SDT) may sometimes exceed this limit, especially when certain aggressive food simulants are employed, a toxicological assessment was undertaken.
Polystyrene nanoparticles: the mechanism of their genotoxicity in human peripheral blood mononuclear cells
Published in Nanotoxicology, 2022
Kinga Malinowska, Bożena Bukowska, Ireneusz Piwoński, Marek Foksiński, Aneta Kisielewska, Ewelina Zarakowska, Daniel Gackowski, Paulina Sicińska
Nanoplastics (NPs) and microplastics (MPs) resulting from decomposition of large pieces of plastic are pollutants of global concern. Until recently, it has been considered that the diameter of plastic NPs should not exceed 100 nm, although in the latest reports the diameter of 1000 nm has been assumed as the upper limit (Gigault et al. 2018; Rakowski and Grzelak 2020; Mitrano, Wick, and Nowack 2021). MPs are plastic particles up to 5 mm in diameter (Hartmann et al. 2019). In this work, we have adopted a traditional size of particles referring to NPs, which should not exceed a diameter of above 100 nm. Among the above-mentioned particles, polypropylene (PP) and polyethylene (PE) NPs are commonly found in the environment, while polystyrene nanoparticles (PS-NPs) are determined in smaller amounts. Polystyrene is produced by polymerization of styrene monomers and it is the fifth leading thermoplastic material on the global market. This polymer is widely used in the production of food packaging, automotive industry, electronics, household appliances, and more (ChemicalSafetyFacts.org 2020). The key to understanding the potential toxicity of NPs is their physico-chemical properties, that is, size, shape, and surface charge. We used PS-NPs because they are commercially available in different size and well-characterized by their size, shape, and lack of functionalization to understand the principles of polymer chemistry. Additionally, using scanning electron microscopy (SEM), atomic force microscopy (AFM), and dynamic light scattering (DLS), we confirmed the size and shape of the tested particles. Additionally, we performed zeta potential measurements.
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