Biomedical subjects

Edgar J Acosta

Publications and source records attributed to Edgar J Acosta.

4 recordsLinked to original sources

PubMed2006

Effect of humidity on lung surfactant films subjected to dynamic compression/expansion cycles.

The surface activity of bovine lipid extracted surfactant (BLES) preparations used in surfactant replacement therapy is studied in dynamic film compression/expansion cycles as a function of relative humidity, surfactant concentration, compression rate, and compression periodicity. BLES droplets were formed in a constrained sessile droplet configuration (CSD). Images obtained during cycling were analyzed using axisymmetric drop shape analysis (ADSA) to yield surface tension, surface area, and drop volume data. The experiments were conducted in a chamber that allowed both humid (100% RH), and "dry" air (i.e. less than 20% RH) environments. It was observed that in humid environments BLES films are not stable and tend to have poor surface activity compared to BLES films exposed to dry air. Further analysis of the data reveal that if BLES films are compressed fast enough (i.e. at physiological conditions) to avoid film hydration, lower minimum surface tensions are achieved. A film hydration-relaxation mechanism is proposed to explain these observations.

Animals↗

PubMed2005

Linker-based bio-compatible microemulsions.

In this work we have studied the formulation of biocompatible microemulsions using lecithin as the main surfactant and bio-compatible linker molecules (hexyl polyglucoside asthe hydrophilic linker and sorbitan monoleate as the lipophilic linker). These bio-compatible systems are discussed as potential substitutes for chlorinated solvents in dry-cleaning applications and as solvent delivery systems for pharmaceutical applications. Formulation parameters and conditions were evaluated using isopropyl myristate (IPM) as the model oil. It was found that the proposed linker-based formulations were able to form alcohol-free microemulsions while achieving higher solubilization capacity than similar systems reported in the literature. In addition, these lecithin/linker formulations were able to form microemulsions with a wide range of oils, from polar chlorinated hydrocarbons to hydrophobic oils such as squalene. These microemulsions were achieved under isotonic conditions (0.9% NaCl) by only varying the relative proportions of the linkers. The "solvency" power of these bio-compatible formulations was tested for the removal of hexadecane (used as model oil) from cotton fabrics and compared to the solvency power of a typical dry cleaning solvent tetrachloroethylene (PCE). While PCE and the linker-based lecithin formulation removed the same amount of hexadecane at low loading ratios (less than 1% oil volume fraction), at higher loading ratios the linker-based lecithin formulation retained its oil removal capacity while the efficiency of the PCE system declined rapidly. These initial results thus demonstrate the remarkable oil solubilization capacity of these bio-compatible linker-based lecithin formulations and illustrate their potential as environmentally friendly replacements for organic solvents.

Biocompatible Materials↗

PubMed2004

Self-assembly in linker-modified microemulsions.

Linker molecules are added to microemulsion systems to enhance the interaction between the surfactant and oil (lipophilic linkers) or water (hydrophilic linkers) phases. Previous results suggest that when lipophilic and hydrophilic linkers are combined they behave as a self-assembled surfactant at the oil/water interface. In this work we investigate this self-assembly phenomenon as a function of surfactant, linker and electrolyte concentration. We find that middle phase microemulsion appears at a specific concentration higher than the critical micelle concentration (CMC), which we denote as the critical middle phase microemulsion concentration (CmicroC). When the lipophilic linker dodecanol is added in equimolar ratio to the hydrophilic linker sodium mono- and dimethyl naphthalene sulfonate (SMDNS), the middle phase microemulsion did not appear until the surfactant sodium dihexyl sulfosuccinate (SDHS) concentration was larger than the CmicroC of the SDHS-alone system. Dodecanol is shown to segregate near the surfactant tails following a Langmuir-type adsorption process. This segregation is not affected by the electrolyte concentration but is significantly reduced when the surfactant (SDHS) concentration approaches the CmicroC. The data suggest that the self-assembly between hydrophilic and lipophilic linkers to form middle phase microemulsions is only possible if a minimum amount of surfactant is present.

Journal Article↗

PubMedDate not supplied

Microemulsions of triglyceride-based oils: The effect of co-oil and salinity on phase diagrams.

Microemulsification of triglyceride-based oil is challenging due to the formation of undesirable phases such as macroemulsions, liquid crystals, or sponge phases. This research evaluates the formation of artificial sebum microemulsions using linker molecules, with the addition of co-oil to help enhance sebum solubilization. The microemulsion consists of a lipophilic linker (sorbitan monooleate), a hydrophilic linker (hexylglucocide), a main surfactant (sodium dioctyl sulfosuccinate), a co-oil, and artificial sebum. The effect of adding co-oil to the phase behavior and the microstructure of the resulting microemulsion is described. The effect of several types of co-oil is also studied; the co-oils evaluated here are squalene, squalane, isopropyl myristate, and ethyl laurate. The effect of salinity on the microemulsion phase behavior is also presented. Fish diagrams are obtained by plotting total surfactant/linker concentration as a function of sebum fraction in the oil mixture (co-oil + sebum). Different microemulsion types (Winsor Types I, II, III, and IV) are formed, depending on the total surfactant/linker concentration and the fraction of co-oil in the oil mixture. Winsor Type IV (single-phase) microemulsions are observed at high surfactant/linker concentrations. These single-phase, isotropic, and low-viscous fluids are particularly useful for cleansing and delivery of functional ingredients in skin care products. Salt addition shifts the fish diagram towards more hydrophobic oil systems and higher surfactant/linker concentrations.

Cosmetics↗