Browsing by Subject "Surfactants"

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    Elemental sulfur coarsening kinetics
    (Springer (Biomed Central Ltd.), 2014) Garcia, Angel A.; Druschel, Gregory K.; Department of Earth Sciences, School of Science
    BACKGROUND: Elemental sulfur exists is a variety of forms in natural systems, from dissolved forms (noted as S8(diss) or in water as S8(aq)) to bulk elemental sulfur (most stable as α-S8). Elemental sulfur can form via several biotic and abiotic processes, many beginning with small sulfur oxide or polysulfidic sulfur molecules that coarsen into S8 rings that then coalesce into larger forms: [Formula: see text] Formation of elemental sulfur can be possible via two primary techniques to create an emulsion of liquid sulfur in water called sulfur sols that approximate some mechanisms of possible elemental sulfur formation in natural systems. These techniques produce hydrophobic (S8(Weimarn)) and hydrophilic (S8(polysulfide)) sols that exist as nanoparticle and colloidal suspensions. These sols begin as small sulfur oxide or polysulfidic sulfur molecules, or dissolved S8(aq) forms, but quickly become nanoparticulate and coarsen into micron sized particles via a combination of classical nucleation, aggregation processes, and/or Ostwald ripening. RESULTS: We conducted a series of experiments to study the rate of elemental sulfur particle coarsening using dynamic light scattering (DLS) analysis under different physical and chemical conditions. Rates of nucleation and initial coarsening occur over seconds to minutes at rates too fast to measure by DLS, with subsequent coarsening of S8(nano) and S8(sol) being strongly temperature dependent, with rates up to 20 times faster at 75°C compared to 20°C. The addition of surfactants (utilizing ionic and nonionic surfactants as model compounds) results in a significant reduction of coarsening rates, in addition to known effects of these molecules on elemental sulfur solubility. DLS and cryo-SEM results suggest coarsening is largely a product of ripening processes rather than particle aggregation, especially at higher temperatures. Fitting of the coarsening rate data to established models for Ostwald ripening additionally support this as a primary mechanism of coarsening. CONCLUSIONS: Elemental sulfur sols coarsen rapidly at elevated temperatures and experience significant effects on both solubility and particle coarsening kinetics due to interaction with surfactants. Growth of elemental sulfur nanoparticles and sols is largely governed by Ostwald ripening processes.
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    Surfactants: Role in biofilm management and cellular behaviour
    (Wiley, 2019-06) Percival, Steven L.; Mayer, Dieter; Kirsner, Robert S.; Schultz, Greg; Weir, Dot; Roy, Sashwati; Alavi, Afsaneh; Romanelli, Marco; Surgery, School of Medicine
    Appropriate and effective wound cleaning represents an important process that is necessary for preparing the wound for improved wound healing and for helping to dislodge biofilms. Wound cleaning is of paramount importance to wound bed preparation for helping to enhance wound healing. Surfactant applications in wound care may represent an important area in the cleaning continuum. However, understanding of the role and significance of surfactants in wound cleansing, biofilm prevention and control, and enhancing cellular viability and proliferation is currently lacking. Despite this, some recent evidence on poloxamer-based surfactants where the surfactants are present in high concentration have been shown to have an important role to play in biofilm management; matrix metalloproteinase modulation; reducing inflammation; and enhancing cellular proliferation, behaviour, and viability. Consequently, this review aims to discuss the role, mode of action, and clinical significance of the use of medically accepted surfactants, with a focus on concentrated poloxamer-based surfactants, to wound healing but, more specifically, the role they may play in biofilm management and effects on cellular repair.