Microplastics in human urine: Characterisation using µFTIR and sampling challenges using healthy donors and endometriosis participants.

Microplastics (MPs) are found in all environments, within the human food chain, and have been recently detected in several human tissues. The objective herein was to undertake an analysis of MP contamination in human urine samples, from healthy individuals and participants with endometriosis, with respect to their presence, levels, and the characteristics of any particles identified. A total of 38 human urine samples and 15 procedural blanks were analysed. MPs were characterised using µFTIR spectroscopy (size limitation of 5 µm) and SEM-EDX. In total, 123 MP particles consisting of 22 MP polymer types were identified within 17/29 of the healthy donor (10 mL) urine samples, compared with 232 MP particles of differing 16 MP polymer types in 12/19 urine samples from participants with endometriosis. Healthy donors presented an unadjusted average of 2589 ± 2931 MP/L and participants with endometriosis presented 4724 ± 9710 MP/L. Polyethylene (PE)(27%), polystyrene (PS)(16%), resin and polypropylene (PP)(both 12%) polymer types were most abundant in healthy donor samples, compared with polytetrafluoroethylene (PTFE) (59%), and PE (16%) in samples from endometriosis participants. The MP levels within healthy and endometriosis participant samples were not significantly different. However, the predominant polymer types varied, and the MPs from the metal catheter-derived endometriosis participant samples and healthy donors were significantly smaller than those observed in the procedural blanks. The procedural blank samples comprised 62 MP particles of 10 MP polymer types, mainly PP (27%), PE (21%), and PS (15%) with a mean ± SD of 17 ± 18, highlighting the unavoidable contamination inherent in measurement of MPs from donors. This is the first evidence of MP contamination in human urine with polymer characterisation and accounting for procedural blanks. These results support the phenomenon of transport of MPs within humans, specifically to the bladder, and their characterisation of types, shapes and size ranges identified therein.

Capillary Structured Suspensions from In Situ Hydrophobized Calcium Carbonate Particles Suspended in a Polar Liquid Media.

We demonstrate that capillary suspensions can be formed from hydrophilic calcium carbonate particles suspended in a polar continuous media and connected by capillary bridges formed of minute amounts of an immiscible secondary liquid phase. This was achieved in two different polar continuous phases, water and glycerol, and three different oils, oleic acid, isopropyl myristate, and peppermint oil as a secondary liquid phase. The capillary structuring of the suspension was made possible through local in situ hydrophobization of the calcium carbonate particles dispersed in the polar media by adding very small amounts of oleic acid to the secondary liquid phase. We observed a strong increase in the viscosity of the calcium carbonate suspension by several orders of magnitude upon addition of the secondary oil phase compared with the same suspension without secondary liquid phase or without oleic acid. The stability and the rheological properties of the obtained capillary structured materials were studied in relation to the physical properties of the system such as the particle size, interfacial tension between the primary and secondary liquid phases, as well as the particle contact angle at this liquid-liquid interface. We also determined the minimal concentrations of the secondary liquid phase at fixed particle concentration as well as the minimal particle concentration at fixed secondary phase concentration needed to form a capillary suspension. Capillary suspensions formed by this method can find application in structuring pharmaceutical and food formulations as well as a variety of home and personal care products.

High internal phase emulsions: catastrophic phase inversion, stability, and triggered destabilization.

We have investigated the formation, drop sizes, and stability of emulsions prepared by hand shaking in a closed vessel in which the emulsion is in contact with a single type of surface during its formation. The emulsions undergo catastrophic phase inversion from oil-in-water (o/w) to water-in-oil (w/o) as the oil volume fraction is increased. We find that the oil volume fraction required for catastrophic inversion exhibits a linear correlation with the oil-water-solid surface contact angle. W/o high internal phase emulsions (HIPEs) prepared in this way contain water drops of diameters in the range 10-100 µm; emulsion drop size depends on the surfactant concentration and method of preparation. W/o HIPEs with large water drops show water separation but w/o HIPEs with small water drops are stable with respect to water separation for more than 100 days. The destabilization of the w/o HIPEs can be triggered by either evaporation of the oil continuous phase or by contact the emulsion with a solid surface of the "wrong" wettability.

Compartmentalization and separation of aqueous reagents in the water droplets of water-in-oil high internal phase emulsions.

We have compartmentalized aqueous reagents and indicator species within the micrometer-sized water droplets of mixed high internal phase emulsions (HIPEs). Mass transport of the reagents across the micrometer-thickness oil films separating the water droplets followed by reaction with the indicator species produces a visible color change which provides a simple method to measure the trapping times of the reagents. Trapping times have been measured for an uncharged reagent (hydrogen peroxide) and charged reagents (HCl and NaClO) in different HIPEs. The trapping times are discussed in terms of a model in which the transferring species partitions from the water to the oil film followed by a rate-determining step of diffusion across the oil film. Rather surprisingly, it is found that trapping times are of similar orders of magnitude for both uncharged and charged aqueous species transferring across liquid oil films.

Thermally Responsive Capillary Suspensions.

We demonstrate that stimulus-responsive capillary-structured materials can be formed from hydrophobized calcium carbonate particles suspended in a non-polar phase (silicone oil) and bridged by very small amounts of a hydrogel as the secondary aqueous phase. Inclusion of thermally responsive polymers into the aqueous phase yielded a capillary-structured suspension whose rheology is controlled by a change in temperature and can increase its complex modulus by several orders of magnitude because of the gelation of the capillary bridges between the solid particles. We demonstrate that the rheology of the capillary suspension and its response upon temperature changes can be controlled by the gelling properties as little as 0.1 w/w % of the secondary aqueous phase containing 2 wt % of the gelling carbohydrate. Doping the secondary (aqueous) phase with methyl cellulose, which gels at elevated temperatures, gave capillary-structured materials whose viscosity and structural strength can increase by several orders of magnitude as the temperature is increased past the gelling temperature of the methyl cellulose solution. Increasing the methyl cellulose concentration from 0 to 2 w/w % in the secondary (aqueous) phase increases the complex modulus and the yield stress of the capillary suspension of 10 w/w % hydrophobized calcium carbonate in silicone oil by 2 orders of magnitude at a fixed temperature. By using an aqueous solution of a low melting point agarose as a secondary liquid phase, which melts as the temperature is raised, we produced capillary-structured materials whose viscosity and structural strength can decrease by several orders of magnitude as the temperature is increased past the melting temperature of the agarose solution. The development of thermally responsive capillary suspensions can find potential applications in structuring of smart home and personal care products as well as in temperature-triggered change in rheology and release of flavors in foods and actives in pharmaceutical formulations.