Disposable screen-printed electrochemical sensing strips for rapid decentralized measurements of salivary ketone bodies: Towards therapeutic and wellness applications.

The interest in ketone bodies (KBs) has intensified recently as they play significant roles in healthcare, nutrition, and wellness applications. We present a disposable electrochemical sensing strip for rapid decentralized detection of ß-hydroxybutyrate (HB), one of the dominant physiological KBs, in saliva. The new salivary enzymatic HB sensor strip relies on a gold-coated screen-printed carbon electrode modified with a reagent layer containing toluidine blue O (TBO mediator), ß-hydroxybutyrate dehydrogenase (HBD enzyme), and the HBD cofactor nicotinamide adenine dinucleotide (NAD+ coenzyme), along with carbon nanotubes (CNTs) and chitosan (Chit) for enhancing the sensor's sensitivity and for encapsulating the enzyme and its cofactor, respectively. The systematic optimization resulted in an attractive analytical performance, with a rapid response time within 60 s, a wide HB dynamic detection range from 0.1 to 3.0 mM along with a low limit of detection (50 µM HB) in an artificial saliva medium. The strip displays high selectivity for HB over acetoacetate (AcAc) and other interferences (i.e., acetaminophen, ascorbic acid, glucose, lactic acid, and uric acid), good reproducibility, and high stability towards temperature or pH effects. The new disposable sensing strip system, coupled with a hand-held electrochemical analyzer, showed rapid HB monitoring in human saliva samples collected from healthy volunteers, with similar temporal profiles to those obtained in parallel capillary blood measurements in response to the intake of keto supplements. This strip enables efficient, reliable, and near real-time salivary HB detection to track non-invasively the dynamics of HB concentrations after intaking commercial supplements towards diverse healthcare and nutrition applications.

Decentralized vitamin C & D dual biosensor chip: Toward personalized immune system support.

Combating the ongoing COVID-19 pandemic has put the spotlight on nutritional support of the immune system through consumption of vitamins C and D. Accordingly, there are urgent demands for an effective on-the-spot multi-vitamin self-testing platform that monitors the levels of these immune-supporting micronutrients for guiding precision nutrition recommendations. Herein, we present a compact bioelectronic dual sensor chip aimed at frequent on-the-spot simultaneous monitoring of the salivary vitamin C and D dynamics. The new bioelectronic chip combines a new electrocatalytic vitamin C amperometric assay along with competitive vitamin D immunoassay on neighboring electrodes, to perform selective and cross-talk free detection of both vitamins in a 10-µL saliva sample within 25 min. The distinct vitamin C or D temporal profiles obtained for different individuals after vitamin supplementation indicate the potential of the new bioelectronic chip strategy for enhancing personalized nutrition towards guiding dietary interventions to meet individual nutrition needs and promote immune system health.

Determination of antioxidant activity in foods and beverages by reaction with 2,2'-diphenyl-1-picrylhydrazyl (DPPH): collaborative study First Action 2012.04.

A colorimetric method for the determination of total antioxidant activity in a variety of foods and beverages was validated in both a single-laboratory validation and a collaborative laboratory validation study. The procedure involved extraction of the antioxidants directly into a methanol-water solution containing a known amount of 2,2'-diphenyl-1-picrylhydrazyl (DPPH), thus promoting the rapid reaction of extracted materials with DPPH. The reaction was monitored by spectrophotometric measurement of the absorbance loss at 517 nm. Antioxidant activity was quantified relative to a dilution series of vitamin E analog standards (Trolox), which were analyzed in parallel simultaneously with the food and beverage samples. The antioxidant activities of the samples ranged from 131 to 131 000 micromole Trolox equivalents/100 g. Statistical analysis of the results showed that nine of the 11 matrixes gave acceptable HorRat values, indicating that the method performed well in these cases. The acceptable matrixes include pomegranate juice, blueberry juice, carrot juice, green tea, wine, rosemary spice, ready-to-eat cereal, and yogurt. Two samples failed the HorRat test: the first was an almond milk that had an antioxidant level below the practical LOQ for the method; the second was a sample of canola oil with added omega-3 fatty acid that was immiscible in the reaction medium.