Urine Chemistries

Designing stimuli-responsive upconversion nanoparticles based on an inner filter effect mimetic immunoassay for phenylketonuria accuracy diagnosis

Phenylketonuria (PKU) is the most common inborn error of amino acid metabolism caused by an inherited deficiency in L-phenylalanine-4-hydroxylase (PAH) activity. It is usually controlled by diet and monitored regularly with markers, as PKU is not curable. However, conventional methods for target biomarker analysis are invasive and labor intensive. Here, we report a rapid and sensitive, mimetic immunoassay for detecting phenylpyruvate (PhPY) based on stimuli-responsive upconversion nanoparticles with an inner filter effect (IFE). The strong and specific binding of PhPY and Fe³⁺ forms a complex with maximum absorption at approximately 640 nm. Upon the addition of LiYF₄:Er,Ho@LiYF₄ UCNPs (maximum emission at 699 nm), the inner filter effect is triggered along with a concurrent decrease in fluorescence. The proposed method demonstrates ultra sensitivity with a detection limit of 79.63 μg L^-1, which is superior to most reported methods, thereby enabling phenylpyruvate assays on human urine.

Development of a selective chloride sensing platform using a screen-printed platinum electrode

A new and selective voltammetric method for chloride determination is proposed, based on platinum and chloride interactions. A screen-printed platinum electrode (SPPtE) functions as a sensing platform, which promotes the formation of chloro-adsorbed species on the electrode surface, acting as an effective means of anion-determination in several matrices. The pretreatment of the SPPtE and careful control of the cathodic stripping voltammetric parameters yielded a well-defined electrochemical signal. This cathodic peak was due to the adsorption of chlorine, which had previously been oxidized from chloride anions in the initial anodic deposition step. It offers a simple, low-cost, fast, reproducible (RSD < 6%) and precise method for selective chloride determination, with limit of detection of 0.76 mM, and a sensitivity of - 24.147 µA mM ^-1 for a broad determination range of up to 150 mM. Chloride determination was correctly performed with single drops of environmental, pharmaceutical and food samples. In addition, the sensor was successfully adapted as a flexible screen-printed platinum electrode sensor using Gore-Tex^® as support for printing.