Technologies for Separation and Drying of Algal Biomass for Varied Applications
Gokare A. Ravishankar, Ranga Rao Ambati in Handbook of Algal Technologies and Phytochemicals, 2019
In microalgae flocculation, metallic cations (as salts) and polymeric agents are often used. For metallic cations, the most important are Fe3+, Al3+ and to a lesser extent Ca2+ or magnesium Mg2+. Usually the efficiency increases with the cation valence. Common flocculants are sulfates and chlorides of these cations. For polymeric agents, the most important are cationic polymers, water soluble macromolecules with positive charge. Natural polymeric flocculants such as chitosan, tannins, polysaccharides and proteins have the advantage of being non-toxic and biodegradable (Schwarz et al. 2007; Vandamme et al. 2010; Bakpai et al. 2014; Gorin et al. 2015; Mikulec et al. 2015; Roselet et al. 2015; Bratby 2016). Synthetic flocculating agents are the most widespread because they can be custom synthesized and thus very efficient. The most common are derived from acrylamide and polyacrylic acid (Bolto and Gregory 2007; Harun et al. 2010; Borges et al. 2011).
Current Status and Role of Dental Polymeric Restorative Materials
Mary Anne S. Melo in Designing Bioactive Polymeric Materials for Restorative Dentistry, 2020
Even though MMGICs are of improved physical properties and have been commercialized, their strength still does not match other posterior restorative materials (Naasan and Watson 1998; Yap et al. 2002). Their clinical performance in posterior teeth is not very well (Holst, 1996). RMGICs are developed by incorporating methacrylate components into the polyacrylic acid, supplementing the fundamental acid-base reaction by polymerization reaction as illustrated in Figure 2.5. Most of them were found to have the potential to release fluoride equivalent to that of conventional GICs (Wiegand et al. 2007). The introduction of polymerization reaction improved the mechanical strength of RMGICs to some extent, and they are mostly used as liners and bases and restorative materials in the clinic (Sidhu 2011).
Glycerine in Creams, Lotions, and Hair Care Products
Eric Jungermann, Norman O.V. Sonntag in Glycerine, 2018
Finally, getting back to the standard glycerine mucilages (often referred to as glycerine/rosewater), Hiuga et al. teach a concentrated gel thickened with polyacrylic acid [12]. For example, a conditioner was prepared consisting of crosslinking type polyacrylic acid 2.0, glycerine 68.0, propylene glycol 1.0, sodium hydroxide 1.4, and water to 100% by weight. The patent teaches that this concentrate is diluted with other products, such as an emulsion lotion, prior to use. Consequently, one would end up with a fairly standard glycerine lotion of the type discussed above. Nevertheless, this does help to emphasize that workers continue to recognize the benefits of the material and find different ways of utilizing it.
Overview of intranasally delivered peptides: key considerations for pharmaceutical development
Published in Expert Opinion on Drug Delivery, 2018
Wisam Al Bakri, Maureen D. Donovan, Maria Cueto, Yunhui Wu, Chinedu Orekie, Zhen Yang
Polyacrylic acid derivatives have also been studied to evaluate their influence on nasal absorption. Carbopol® 934 (0.5%) has been used as a model mucoadhesive to study the nasal delivery of levonorgestrel in rats. A liposomal formulation of levonorgestrel combined with Carbopol® 934 resulted in a bioavailability of 99% compared with 26% from the liposomal preparation alone [111]. Besides the gel-forming mucoadhesive properties of Carbopol® 934, the increase in the extent of absorption of levonorgestrel was attributed to the ability of Carbopol 934 to bind with extracellular calcium ions, which resulted in a significant opening of tight junctions to facilitate transcellular transport. This mechanism was suggested based on the measured decrease in TEER across Caco-2 cell monolayers in the presence of Carbopol® 934 [112].
In situ gelling and mucoadhesive polymers: why do they need each other?
Published in Expert Opinion on Drug Delivery, 2018
Forouhe Zahir-Jouzdani, Julian Dominik Wolf, Fatemeh Atyabi, Andreas Bernkop-Schnürch
Polyacrylic acid (PAA) and its crosslinked derivatives such as carbopols (CP) and polycarbophils (PCP) exhibit a comparatively high molecular mass and a high density of carboxylic acid groups. Therefore, at acidic pH these polymers show only minor swelling due to a low percentage of dissociated acidic moieties. Upon an increase in pH, additional charges result in electrostatic repulsion as well as osmotic forces within the polymeric backbone and uncoiling and expansion of the molecules takes place (Figure 2(a)). Subsequently, further swelling of the polymer leads to gelation of the system [14,19]. Regarding the development of in situ gelling formulations based on these polymers, however, the need for an acidic pH of the formulation in order to maintain low viscosity has to be taken into account that might cause stability problems especially of pH-sensitive drugs. Furthermore, ocular application of such systems can elicit discomfort and induce lacrimation [20].
Tailor-made pH-sensitive polyacrylic acid functionalized mesoporous silica nanoparticles for efficient and controlled delivery of anti-cancer drug Etoposide
Published in Drug Development and Industrial Pharmacy, 2018
Seema Saroj, Sadhana J. Rajput
Presence of large amount of silanol groups on MCM-41 lead to a highly negative Zeta potential value of −36.86 mV. After amine functionalization, the zeta potential increased to +33.92 mV. This could be attributed to the presence of free positively charged amino groups. After functionalization with PAA, the value dropped to −31.15 mV due to the occurrence of large number of acidic carboxylic groups in polyacrylic acid. Thus, it was confirmed that there occurred a successful grafting of PAA chains on MCM-41 NPs. Notably, loading of ETS into MCM-41 and MCM-41-PAA did not alter the nature of surface charges. The details of various zeta potential values are given in Figure 6. The size of NPs was determined by zeta sizer. MCM-41 NPs had z average diameter of 110.2 nm, whereas the PAA decorated MSNs exhibited z average diameter of 142.85 nm (Figure 7).
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