Polymer/Surfactant Interaction in Applied Systems
E. Desmond Goddard, James V. Gruber in Principles of Polymer Science and Technology in Cosmetics and Personal Care, 1999
Traditionally, flocculation of aqueous suspensions has been achieved by addition of electrolyte (in which case the effect would currently be termed “coagulation”) or, recently and more often, by addition of a suitable polymer. A” “controlled” level of flocculation is sometimes a desired target to develop “structure” within a particular system. Flocculation by a polymer generally allows much more flexibility in this respect than does partial coagulation with an added electrolyte. In flocculation the process usually entails the adsorption of segments of one polymer molecule onto several different particles, so it is
Nanosuspensions as Nanomedicine: Current Status and Future Prospects
Debarshi Kar Mahapatra, Sanjay Kumar Bharti in Medicinal Chemistry with Pharmaceutical Product Development, 2019
Flocculation, a type of sedimentation, results from attractive interactions between particles. Flocculation of nanosuspensions may occur by polymer bridging, charge neutralization, polymer–particle surface complex formation or depletion flocculation, or by a combination of these mechanisms [103]. Depending on the nature of the polymer and the character of its interaction with the nanocrystal surface, there are two main possible mechanisms of flocculation: [1] bridging as a result of adsorption of a macromolecule onto the surface of nanocrystals and [2] surface charge neutralization [104].
Exopolysaccharide Production from Marine Bacteria and Its Applications
Se-Kwon Kim in Marine Biochemistry, 2023
Rapid development in industrialization and anthropogenic activities has led to an increase in the discharge of waste and wastewater containing organic and inorganic pollutants. Bioflocculant is a kind of biodegradable macromolecular flocculant produced by microorganisms. Because of their biodegradability, harmlessness and inability to produce secondary pollutants, bioflocculants have gained much wider attention in research (Gong et al., 2008). Flocculation is an essential process in the treatment of wastewater and dye effluents (Fujita, 2000).
Mortality and physiological impacts of the tea saponin against Ephestia kuehniella Zeller (Lepidoptera: Pyralidae)
Published in Toxin Reviews, 2022
Morteza Shahriari, Arash Zibaee, Seyyedeh Kimia Mirhaghparast, Sarah Aghaeepour Pour, Samar Ramzi, Hassan Hoda
Tea saponin was extracted based on the procedure of Li et al. (2012). C. sinensis seeds were collected from Langroud tea gardens (Guilan Province, Northern Iran), powdered, and sifted. The powder was stirred in warm water (liquid to the solid ratio: 6:1; the water temperature: 80 °C; soaking time 6 h). Then, the samples were centrifuged at 5000 rpm, for 30 min at 25 °C to obtain the primary extracted solution. The concentration of 30% of flocculant of polyaluminum chloride was added into the content of 1% of the primary extracted liquid by weight and kept at 25 °C for 2 h to remove impurities. Afterward, centrifugation was performed at 5000 rpm, at 25 °C for 30 min to get the demanded supernatant. Ten grams of calcium oxide as the settlement agent was added to the earlier supernatant and stirred for 4 h before being centrifuged at 5000 rpm for 30 min at 25 °C. The present supernatant was removed, and ammonium bicarbonate was added (30% of the total mixture) to remove calcium from the TS. The samples stirring for 2 h at 60 °C and centrifugated at 5000 rpm for 30 min at 25 °C. Afterward, tubes containing the samples were put in a boiling water bath for 5 min and incubated at 80 °C for 12 h within an oven to gain TS powder (75% purity).
Biopredictive tools for the development of injectable drug products
Published in Expert Opinion on Drug Delivery, 2022
Mônica Villa Nova, Kennard Gan, Matthias G. Wacker
Together with agitation and hydrodynamics (section 4.1), the medium volume has a strong impact on the release behavior. Smaller liquid volumes increase the particle density and may reduce the physical stability of the dispersion [6]. This becomes even more apparent when high concentrations of particles are stabilized by flocculation, a formulation strategy seen with many long-acting injectables [84]. Under these conditions, more attention must be paid to the presence of macromolecular solutes (e.g. proteins and collagen) [6]. They can play a key role in the physical stabilization of suspensions in-situ [6]. Additionally, whenever the injected dose accounts for a significant volume fraction at the injection site, excipients can influence the physiological microenvironment as well. PLGA microspheres, for instance, are known to reduce the pH at the injection site, leading to accelerated degradation processes [89,90].
Chitosan caged liposomes for improving oral bioavailability of rivaroxaban: in vitro and in vivo evaluation
Published in Pharmaceutical Development and Technology, 2021
Maged K. Elsayad, Hammam A. Mowafy, Alaa A Zaky, Ahmed M. Samy
With 0.3% CS coating (RVX-CL3), the average particle size was found to be 92.1 nm. This could be supported by the observation that with the increasing level of CS, a condensed coating layer was formed on the particle surface and by the small range aggregation of liposomes. However, further aggregation in a large range was prevented by the surface charge and steric hindrance from the CS chain. In the coating process, the CS solution was added to the liposome suspension drop wisely. We observed that flocculation emerged temporarily in the instillation process, but quickly disappeared under agitation. This revealed that a condensed coating layer was constructed as the CS strength increased, and consequently the liposome particles were re-dispersed from aggregation by electrostatic repelling force. This comes in close agreement with the previous results reported by Li et al. (Li et al. 2009).
Related Knowledge Centers
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