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Green Metal-Based Nanoparticles Synthesized Using Medicinal Plants and Plant Phytochemicals against Multidrug-Resistant Staphylococcus aureus
Published in Richard L. K. Glover, Daniel Nyanganyura, Rofhiwa Bridget Mulaudzi, Maluta Steven Mufamadi, Green Synthesis in Nanomedicine and Human Health, 2021
Abeer Ahmed Qaed Ahmed, Lin Xiao, Tracey Jill Morton McKay, Guang Yang
FTIR results of Sargassum muticum showed soluble elements present in the aqueous extract (such as the C–O from C–O–SO3 group, C─C groups from aromatic rings and carbonyl [–C═O] group) acted as a capping agent preventing NPs aggregation in the solution. This played a major role in the extracellular synthesis as well (Mahdavi et al., 2013). Likewise, FTIR results of Calotropis procera aqueous leaf extract showed that carboxylic acids, ketones, amines, aldehydes and hydroxyl groups were responsible for the biochemical reaction (Gawade et al., 2017). Polyphenols from plants lose electrons easily, resulting in zinc–ellagate complex formation. Zinc ions ligated with aromatic hydroxyl groups found in Nephelium lappaceum peel extracts formed zinc–ellagate complex at pH 5–7 to synthesize ZnO-NPs (Yuvakkumar et al., 2014). In summary, various plant phytochemicals such as phenolic acids, alkaloids terpenoids and polyphenols can bioreduce metal ions to form NPs (Table 10.4). They are both capping and stabilizing agents. Additionally, they have desirable properties such as antimicrobial, antioxidant and anticancer activities. These characteristics make them highly suitable for pharmaceutical applications.
Environmental and Cytotoxicity Risks of Graphene Family Nanomaterials
Published in Suresh C. Pillai, Yvonne Lang, Toxicity of Nanomaterials, 2019
Due to electrostatic charges and nonspecific protein binding many of the graphene family members tend to aggregate in biological fluids (Guo and Mei, 2014; Pan et al., 2012). To address the issue of poor dispersity and provide adequate suspension in physiological solutions, stabilizing agents or surfactants have previously been employed. The problematic toxicity of the latter, however, has been uncovered by previous experience with CNTs (Sanchez et al., 2011). On the other hand, the development of functionalized GFNs has provided improved solubility and biocompatibility and reduced environmental and cytotoxic impacts (Guo and Mei, 2014). Surface chemical functionalization alters the surface chemistry and charge of GFNs, modulating nanotoxicity (Rafiee et al., 2010). Surface functionalization or modification also commonly affects the blood retention and organ translocation of NMs, either placating or provoking toxicity (Bettinger et al., 2009). For example, hydrophilic carboxyl-functionalized graphene, with an increased degree of oxidation, exhibited intracellular internalization in comparison to the ill consequences of hydrophobic, non-functionalized graphene (Sasidharan et al., 2011).
Industrial Uses Of Phosphonates
Published in Richard L. Hilderbrand, The Role of Phosphonates in Living Systems, 2018
George L. Drake, Timothy A. Calamari
Heat stabilizers are chemical additives used to protect certain polymers especially those that contain regular, repeating units against degradation resulting from heat or exposure to UV radiation. By virtue of their chemical composition and modes of function, many heat stabilizers also function as light stabilizing agents.
The effect of capping agents on the toxicity of silver nanoparticles to Danio rerio embryos
Published in Nanotoxicology, 2019
N. Abramenko, T. B. Demidova, Yu. A. Krutyakov, P. M. Zherebin, E. Y. Krysanov, L. M. Kustov, W. Peijnenburg
In spite of growing attention to the safety of nanomaterials (Wang et al. 2012; Ivask et al. 2014; Wijnhoven et al. 2009), there is no agreement among authors about the mechanisms of possible toxicity of silver NPs and to what extent silver NPs affect the environment and human beings. The data on toxicity of Ag NPs are contradictory and require additional verification. Unfortunately, in most studies the attention paid to the toxic effects of stabilizers on the test objects is insufficient. It is, therefore, difficult to draw firm conclusions about the mechanism of toxicity and the role of a capping agent in process of interaction of NPs with test organisms. The choice of a stabilizing agent significantly influences the results of toxicity tests. Therefore, biological effects of these substances must be evaluated in sufficient detail during experiments.
Is it clinically defensible to treat children longer term with second generation antipsychotics?
Published in Expert Opinion on Drug Safety, 2018
Controlled trial evidence of longer term benefit is most likely to come from randomized discontinuation studies, while uncontrolled evidence may come from observational studies or the interrogation of large prescribing databases. There is skepticism that discontinuation studies truly reflect protection from relapse, as it is possible that symptoms attributed to syndrome recurrence are actually drug withdrawal symptoms. Evidence supporting the longer term use of SGA drugs for schizophrenia in children is limited [3] but there are observational studies showing that clozapine reduces the rate of hospitalization[4], leads to better functioning out to 9 years from treatment initiation [5], and is superior in effectiveness to other first and SGAs [3]. A 72-week randomized discontinuation study found aripiprazole was superior to placebo in preventing relapse of bipolar disorder [6]. Mood stabilizing agents are a plausible alternative to antipsychotic drugs for the maintenance treatment of bipolar disorder, and arguably have fewer side effects. However, Guidance on the matter is contradictory [7] and as such antipsychotic drugs must be considered a viable first line treatment in this context. The hazards of untreated illness, and the absence of safer effective alternative treatments, make the longer term use of SGAs for schizophrenia and bipolar disorder defensible.
Injectable sustained release PLA microparticles prepared by solvent evaporation-media milling technology
Published in Drug Development and Industrial Pharmacy, 2018
Yan Zhang, Siyang Fei, Meiling Yu, Yuting Guo, Haibing He, Yu Zhang, Tian Yin, Hui Xu, Xing Tang
Six common stabilizing agents such as Carboxymethyl Cellulose Sodium (CMC-Na), Polyvinyl pyrrolidon (PVP k30), Tween 80, Vitamin E polyethylene glycol succinate (TPGS), Poloxamer 188 (F68) and Polyvinyl alcohol(PVA) were tested at a concentration of 1% (m/v). An additional sample without any added stabilizer was used as a blank control. The average particle size and span were selected as indicators during the milling process. Figure 2 shows the effect of the different stabilizers on the particle size and distribution of the suspension. It was observed that significant aggregation occurred when using the semi-synthetic polymers CMC-Na and HPMC as the stabilizers, with a resultant relatively large D50 (over 50 µm), which is similar to the formulation without any added stabilizer, and may be due to their viscosity limits. There was no significant difference of D50 when using F68, Tween 80 or TPGS, however a relatively large size with a large span was found when using PVP K30 as the stabilizer, but was overall in the acceptable range. Tween 80 produced a large amount of foam during the grinding process, which unfortunately limits its applicability and maneuverability. TPGS is expensive and unsuitable for industrial production, and therefore in this study, a mixture of 1% F68 and 0.05% PVA was selected to be the stabilizer. The nonionic surfactant F68 is amphipathic, with a unique structure of hydrophobic core and hydrophilic shell, and thus the hydrophobic group could cover the surface of the drug and the hydrophilic group could improve the wettability of the particles [28]. The addition of a small amount of the polymeric material PVA played a three-dimensional stabilizing effect to prevent particle aggregation [29]. The stabilization mechanism of the stabilizer mixture is shown in Figure 3(A).