Browsing by Author "Fernández-Fraguas, Cristina"

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    Bulk and interfacial interactions between hydroxypropyl-cellulose and bile salts: Impact on the digestion of emulsified lipids
    Zornjak, Jennifer; Liu, Jianzhao; Esker, Alan R.; Lin, Tiantian; Fernández-Fraguas, Cristina (2020-09)
    Hydroxypropyl-cellulose (HPC) is a surface-active, non-digestible polysaccharide, commonly used in food emulsions as thickener and/or emulsifier. Due to these dual characteristics, HPC is a potential ingredient to modulate lipid digestion. Since bile salts (BS) are key players during lipid digestion, the aim of this work was to investigate the impact that interactions of HPC with BS has on the digestion of emulsified lipids. We studied the effect of two BS species differing in bile-acid moiety, sodium-taurocholate (NaTC) and sodium-taurodeoxycholate (NaTDC). A Quartz-Crystal-Microbalance (QCM-D) was used to evaluate HPC-BS interfacial interactions during the sequential and simultaneous adsorption of both components at a hydrophobic surface, while microDifferential-Scanning-Calorimetry was used to examine bulk interactions. In vitro lipid digestion was studied by using a pH-stat method. Results showed that, under fed-state conditions, NaTDC micelles were more effective at displacing a pre-adsorbed HPC layer from the surface than NaTC monomers. Nevertheless, HPC was resistant to complete displacement by both BS. Additionally, HPC was more susceptible to interact with NaTDC in the bulk, compared to NaTC, which made the adsorption more competitive for NaTDC. The reduced amount of free NaTDC in solution could explain the delayed lipolysis shown by HPC-stabilized emulsions when NaTDC was used to simulate duodenal conditions. These findings show that the delay of lipid digestion by HPC is due to the combined effect of HPC-BS interfacial and bulk interactions, with BS-binding in solution mostly contributing to this effect, and the BS molecular and micellar structure playing essential roles on both situations.
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    A fast and simple ion-pair high performance liquid chromatography method for analysis of primary bile salts in in vitro digested bean samples
    Lin, Tiantian; O'Keefe, Sean F.; Fernández-Fraguas, Cristina (Elsevier, 2021-05-15)
    Bile salts (BS) play a key role in cholesterol and lipid metabolism as well as in many other key metabolic pathways. High performance liquid chromatography (HPLC) is the most common technique used to analyze BS in diverse type of samples. However, current HPLC analysis methods used to analyze and quantify single BS in in vitro digested samples showed poor separation of a complex mixture of BS. In this article, we improved a standard method originally used for quantifying individual BS in food samples subjected to in vitro digestion. We also adapted a method previously developed for BS examination in human blood samples to the analysis of these molecules in chyme samples obtained during simulated gastrointestinal digestion. Our method was simple and achieved a fast and successful separation and quantification of four primary BS (sodium salts of taurocholic, glycocholic, taurochenodeoxycholic and glycochenodeoxycholic acids). •A method used to analyze bile salts in human blood samples has been adapted to separate and quantify four primary bile salts in in vitro digested bean samples. •Addition of an ion-pair reagent led to complete separation of glycine and taurine conjugates of chenodeoxycholic and cholic acids within 10 min, and achieved good peak symmetry. •The minimum BS concentration that could be measured was as low as 0.03125mM.
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    Novel Electrospun Pullulan Fibers Incorporating Hydroxypropyl-β-Cyclodextrin: Morphology and Relation with Rheological Properties
    Poudel, Deepak; Swilley-Sanchez, Sarah; O'Keefe, Sean F.; Matson, John B.; Long, Timothy E.; Fernández-Fraguas, Cristina (MDPI, 2020-10-31)
    Fibers produced by electrospinning from biocompatible, biodegradable and naturally occurring polymers have potential advantages in drug delivery and biomedical applications because of their unique functionalities. Here, electrospun submicron fibers were produced from mixtures containing an exopolysaccharide (pullulan) and a small molecule with hosting abilities, hydroxypropyl-β-cyclodextrin (HP-β-CD), thus serving as multi-functional blend. The procedure used water as sole solvent and excluded synthetic polymers. Rheological characterization was performed to evaluate the impact of HP-β-CD on pullulan entanglement concentration (CE); the relationship with electrospinnability and fiber morphology was investigated. Neat pullulan solutions required three times CE (~20% w/v pullulan) for effective electrospinning and formation of bead-free nanofibers. HP-β-CD (30% w/v) facilitated electrospinning, leading to the production of continuous, beadless fibers (average diameters: 853-1019 nm) at lower polymer concentrations than those required in neat pullulan systems, without significantly shifting the polymer CE. Rheological, Differential Scanning Calorimetry (DSC) and Dynamic Light Scattering (DLS) measurements suggested that electrospinnability improvement was due to HP-β-CD assisting in pullulan entanglement, probably acting as a crosslinker. Yet, the type of association was not clearly identified. This study shows that blending pullulan with HP-β-CD offers a platform to exploit the inherent properties and advantages of both components in encapsulation applications.