Hysteresis and reversibility of a superhydrophobic photopatternable silicone elastomer.

We report upon the wetting property of layers of a micropatterned photodefinable silicon elastomer, PDSE, repetitively and alternatively treated with oxygen plasma and temperature cycles. At low power plasma treatments, we observed a hysteresis in terms of contact angle between phases lowering the contact angle and phases of recovery. As opposed to high power plasma for which we show that by generating fissures on the surface, the structure can be cycled between superhydrophobic and superhydrophilic states. The plasma-generated diffusion paths were characterized by electron microscopy and were found to be directly related to the recovery of the wetting properties of the plasma treated layers of PDSE. The cycling between the superhydrophobic and superhydrophilic states was dependent on the power of the applied plasma as well as the condition during the contact angle recovery amplified by a temperature-controlled baking step.

Integration of low-power microfluidic pumps with biosensors within a laboratory-on-a-chip device.

We describe the fabrication of a controllable microfluidic valve coupled with an electrochemical pump, which has been designed to deliver reagents to an integrated microfluidic biosensing system. Fluid, retained within an insertion reservoir using a stop valve, was pumped using electrochemical actuation, providing a low power, low voltage integrated Laboratory-on-a-Chip for reproducible, small volume fluidic manipulation. The properties of the valve were characterized using both X-ray photoelectron spectroscopy and contact angle measurements, enabling the calculation of the magnitude of the forces involved (which were subsequently verified through experimental measurement). Electrochemical generation of oxygen and hydrogen acted as an on-demand pressure system to force fluid over the stop valve barrier. The process of filling-up the biosensing chamber was characterized in terms of the time to fill, the energy used, and the peak power consumed. The potential of the device was illustrated using a glucose biosensor.

Colloidal particles for the delivery of steroid glycosides.

Water insoluble bioactive molecules with very high melting temperature and low solubility in water are difficult to formulate in food products. We demonstrate the synthesis of nanoscale particles from steroid glycosides using a facile liquid antisolvent precipitation method in the presence of various food grade stabilizers. Colloidal particles with sizes well below 200 nm are prepared from steroid glycosides containing extracts, as well as mixtures with phytosterol. In the mixtures, the formation of the typical for the phytosterol rod-like particles is suppressed. Particle size and structure are investigated by electron microscopy and dynamic light scattering. Due to the presence of surface charge and steric stabilization, colloidal particles do not display aggregation and are stable for a period of longer than one year. The results of this study are important for the formulation and delivery of steroid glycoside and phytosterol bioactive molecules in the fields of food, nutraceuticals, and medical applications.

Modeling the dose effects of soybean oil in salad dressing on carotenoid and fat-soluble vitamin bioavailability in salad vegetables.

Background: Previously, we showed that vegetable oil is necessary for carotenoid absorption from salad vegetables. Research is needed to better define the dose effect and its interindividual variation for carotenoids and fat-soluble vitamins.Objective: The objective was to model the dose-response relation between the amount of soybean oil in salad dressing and the absorption of 1) carotenoids, phylloquinone, and tocopherols in salad vegetables and 2) retinyl palmitate formed from the provitamin A carotenoids.Design: Women (n = 12) each consumed 5 vegetable salads with salad dressings containing 0, 2, 4, 8, or 32 g soybean oil. Blood was collected at selected time points. The outcome variables were the chylomicron carotenoid and fat-soluble vitamin area under the curve (AUC) and maximum content in the plasma chylomicron fraction (Cmax). The individual-specific and group-average dose-response relations were investigated by fitting linear mixed-effects random coefficient models.Results: Across the entire 0-32-g range, soybean oil was linearly related to the chylomicron AUC and Cmax values for α-carotene, lycopene, phylloquinone, and retinyl palmitate. Across 0-8 g of soybean oil, there was a linear increase in the chylomicron AUC and Cmax values for ß-carotene. Across a more limited 0-4-g range of soybean oil, there were minor linear increases in the chylomicron AUC for lutein and α- and total tocopherol. Absorption of all carotenoids and fat-soluble vitamins was highest with 32 g oil (P < 0.002). For 32 g oil, the interindividual rank order of the chylomicron AUCs was consistent across the carotenoids and fat-soluble vitamins (P < 0.0001).Conclusions: Within the linear range, the average absorption of carotenoids and fat-soluble vitamins could be largely predicted by the soybean oil effect. However, the effect varied widely, and some individuals showed a negligible response. There was a global soybean oil effect such that those who absorbed more of one carotenoid and fat-soluble vitamin also tended to absorb more of the others. This trial was registered at clinicaltrials.gov as NCT02867488.