Smartphone-Enabled Quantification of Potassium in Blood Plasma.

This work describes a new method for determining K+ concentration, [K+], in blood plasma using a smartphone with a custom-built optical attachment. The method is based on turbidity measurement of blood plasma solutions in the presence of sodium tetraphenylborate, a known potassium precipitating reagent. The images obtained by a smartphone camera are analyzed by a custom image-processing algorithm which enables the transformation of the image data from RGB to HSV color space and calculation of a mean value of the light-intensity component (V). Analysis of images of blood plasma containing different amounts of K+ reveal a correlation between V and [K+]. The accuracy of the method was confirmed by comparing the results with the results obtained using commercial ion-selective electrode device (ISE) and atomic absorption spectroscopy (AAS). The accuracy of the method was within ± 0.18 mM and precision ± 0.27 mM in the [K+] range of 1.5-7.5 mM when using treated blood plasma calibration. Spike tests on a fresh blood plasma show good correlation of the data obtained by the smartphone method with ISE and AAS. The advantage of the method is low cost and integration with a smartphone which offers possibility to measure [K+] on demand and in remote areas where access to hospitals is limited.

Adsorption and Conformation of Bovine Serum Albumin with Blue-Emitting Gold Nanoclusters at the Air/Water and Lipid/Water Interfaces.

Protein-encapsulated nanoclusters (NCs) are emerging as a versatile platform for in-vivo imaging and other biomedical applications due to their ultrasmall size and excitation in the near-infrared region. Encapsulation may however affect protein structure, size, charge, and its interaction with lipid membranes. In this study, bulk characterization methods along with surface-sensitive vibrational sum-frequency generation (VSFG) spectroscopy were employed to study the secondary structure of bovine serum albumin (BSA) with blue-emitting Au8NCs at the air/water and 1,2-dipalmitoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (DPPG) lipid/water interfaces. With this approach, the difference in the adsorption behavior between native BSA and BSA with an increasing number of blue-emitting NCs was investigated under different pH conditions. At pH 7, at which both BSA and the lipid are negatively charged, protein molecules are found to associate with the DPPG monolayer via hydrophobic interactions with no preferential orientation across the lipid monolayer. At pH 3, adsorption of BSA at the DPPG monolayer occurs mainly due to electrostatic interactions between the negatively charged lipid headgroups and the positively charged protein, resulting in a uniform orientation of the protein across the lipid monolayer. Complimentary bulk studies by circular dichroism and particle size measurements show that the encapsulation of Au8NCs is associated with the loss of BSA helicity, which makes BSA-encapsulated Au8NCs prone to oligomerization, especially at a high content of Au8NCs at one BSA protein. The results indicate that the hydrodynamic diameter of BSA with Au8NCs strongly depends on the molar fraction of gold, the pH, and the storage time. A prolonged storage of Au8NCs@BSA at pH 7 increases the rate of protein oligomerization.

Inclined N2 desorption in a steady-state NO + CO reaction on Pt(100).

The angular and velocity distributions of desorbing products N2 and CO2 were studied in a steady-state NO + CO reaction on Pt(100). From the observation of the inclined N2 desorption, a contribution of the intermediate N2O decomposition pathway was first proposed on this surface. On the other hand, CO2 desorption collimated along the surface normal.