Contact angle hysteresis of bovine serum albumin (BSA) solution/metal (Au-Cr) coated glass substrate

Regulation Mechanism of Phenolic Hydroxyl Number on Self-Assembly and Interaction between Edible Dock Protein and Hydrophobic Flavonoids

In this study, galangin (Gal), kaempferol (Kae), quercetin (Que), and myricetin (Myr) were chosen as the representative flavonoids with different phenolic hydroxyl numbers in the B-ring. The edible dock protein (EDP) was chosen as the new plant protein. Based on this, the regulation mechanism of the phenolic hydroxyl number on the self-assembly behavior and molecular interaction between EDP and flavonoid components were investigated. Results indicated that the loading capacity order of flavonoids within the EDP nanomicelles was Myr (10.92%) > Que (9.56%) > Kae (6.63%) > Gal (5.55%). Moreover, this order was consistent with the order of the hydroxyl number in the flavonoid's B ring: Myr (3) > Que (2) > Kae (1) > Gal (0). The micro morphology exhibited that four flavonoid-EDP nanomicelles had a core-shell structure. In the meantime, the EDP encapsulation remarkably improved the flavonoids' water solubility, storage stability, and sustained release characteristics. During the interaction of EDP and flavonoids, the noncovalent interactions including van der Waals forces, hydrophobic interaction, and hydrogen bonding were the main binding forces. All of the results demonstrated that the hydroxyl number of bioactive compounds is a critical factor for developing a delivery system with high loading ability and stability.

A new polymer lab-on-a-chip (LOC) based on a microfluidic capillary flow assay (MCFA) for detecting unbound cortisol in saliva

Unbound cortisol in saliva, which can be detected with non-invasive sampling, is now considered as one of the most effective biomarkers for the biochemical evaluation of common mental disorders. In this work, a new polymer lab-on-a-chip (LOC) based on a microfluidic capillary flow assay (MCFA) with on-chip dried reagents was newly developed and fully characterized for the detection of unbound cortisol in saliva. The new MCFA device consisted of serially connected microchannels for sample loading, dried detection antibodies, time delay for incubation time control, a spiral reaction chamber for testing, positive and negative controls, and a capillary pump for waste fluid collection. In addition, a portable fluorescence analyzer was also developed for the rapid quantitative measurement of salivary cortisol with high accuracy. A linear dynamic range of 7.0 pg mL-1-16.0 ng mL-1 was achieved from spiked artificial saliva samples with an inter-chip CV of around 4.0% using the developed LOC and fluorescence analyzer. The achieved results support the effective biochemical analysis of common mental disorders such as chronic stress, depression, anxiety and post traumatic stress disorder (PTSD). The new LOC based on a microfluidic capillary flow assay (MCFA) developed in this work can be one of the most promising LOC platforms for high-sensitivity and quantitative POCT with saliva and blood plasma/serum samples.

VT, Nguyen T, Han J, Ahn CH. A new microchannel capillary flow assay (MCFA) platform with lyophilized chemiluminescence reagents for a smartphone-based POCT detecting malaria

There has been a considerable development in microfluidic based immunodiagnostics over the past few years which has greatly favored the growth of novel point-of-care-testing (POCT). However, the realization of an inexpensive, low-power POCT needs cheap and disposable microfluidic devices that can perform autonomously with minimum user intervention. This work, for the first time, reports the development of a new microchannel capillary flow assay (MCFA) platform that can perform chemiluminescence based ELISA with lyophilized chemiluminescent reagents. This new MCFA platform exploits the ultra-high sensitivity of chemiluminescent detection while eliminating the shortcomings associated with liquid reagent handling, control of assay sequence and user intervention. The functionally designed microchannels along with adequate hydrophilicity produce a sequential flow of assay reagents and autonomously performs the ultra-high sensitive chemiluminescence based ELISA for the detection of malaria biomarker such as PfHRP2. The MCFA platform with no external flow control and simple chemiluminescence detection can easily communicate with smartphone via USB-OTG port using a custom-designed optical detector. The use of the smartphone for display, data transfer, storage and analysis, as well as the source of power allows the development of a smartphone based POCT analyzer for disease diagnostics. This paper reports a limit of detection (LOD) of 8 ng/mL by the smartphone analyzer which is sensitive enough to detect active malarial infection. The MCFA platform developed with the smartphone analyzer can be easily customized for different biomarkers, so a hand-held POCT for various infectious diseases can be envisaged with full networking capability at low cost.

Drops That Change Their Mind: Spontaneous Reversal from Spreading to Retraction

A liquid drop may spread faster on surfaces when surfactants are added. Here we show that after some time the spreading in such systems can, under certain conditions, spontaneously reverse to retraction and the droplet pulls itself back, receding from areas it has just recently wetted, elevating its center of mass in a jerklike motion. The duration from drop placement to the onset of retraction ranges from hours to less than a second primarily as a function of surfactant concentration. When the retraction is asymmetric, it results in drop motion, and when it is symmetric, the mass of the drop collects itself on its spot. This phenomenon, which was predicted theoretically in 2014, is apparently a general one for drops with surfactants; however, other factors, such as evaporation and contamination, prevented its observance so far.