Volatile carbonyl metabolites analysis of nanoparticle exposed lung cells in an organ-on-a-chip system.

The evaluation of nanoparticles (NPs) cytotoxicity is crucial for advancing nanotechnology and assessing environmental pollution. However, existing methods for NPs cytotoxicity evaluation suffer from limited accuracy and inadequate information content. In the study, we developed a novel detection platform that enables the identification of cellular carbonyl metabolites at the organ level. The platform is integrated with a cell co-culture lung organ chip (LOC) and a micropillar concentrator. Notably, our work represents the successful measurement of the amounts of cellular metabolites on LOC system. The volatile carbonyl metabolites (VCMs) generated by cells exposure to various types of NPs with different concentrations were captured and detected by high-resolution mass spectrometry (MS). Compared with conventional cell viability and reactive oxygen species (ROS) analysis, our method discerns the toxicological impact of NPs at low concentrations by analyzed VCM at levels as low as ppb level. The LOC system based metabolic gas detection confirmed that low concentrations of NPs have a toxic effect on the cell model, which was not reflected in the fluorescence detection, and the effect of NP material is more significant than the size effect. Furthermore, this method can distinguish different NPs acting on cell models through cluster analysis of multiple VCMs.

Reliability and validity of the COSMED K5 portable metabolic system during walking.

PURPOSE: Portable methods for assessing energy expenditure outside the laboratory and clinical environments are becoming more widely used. As such, it is important to understand the accuracy of such devices. Therefore, the purpose was to determine the reliability and validity of the COSMED K5 portable metabolic system. METHODS: Reliability and validity were assessed in 27 adults (age: 27 ± 5 years; n = 15 women) using a walking protocol. The protocol consisted of a 5-min walk/2-min rest cycle starting at 1.5 mph and increasing in 0.5-mph increments to 4.0 mph. During visit one, participants wore the K5 to assess oxygen consumption ([Formula: see text]O2), carbon dioxide production ([Formula: see text]CO2), and other metabolic variables. Two to seven days later, the protocol was repeated twice with the COSMED K5 and K4b2 systems in a randomized, counterbalanced order. RESULTS: Intraclass correlation coefficients (ICC) revealed that the K5 reliably measured [Formula: see text]O2 (ICC 0.64-0.85) and [Formula: see text]CO2 across all walking speeds (ICC 0.50-0.80), with stronger reliability at faster walking speeds compared with slower speeds. Moderate-to-strong relationships were observed for measured gases between the K5 and K4b2. Specifically, [Formula: see text]O2 exhibited a moderately high-to-high relationship between devices (r = 0.72-0.82), and a similarly moderately high-to-high relationship was observed for [Formula: see text]CO2 (r = 0.68-0.82). While there were no differences in [Formula: see text]O2 measured between devices (p ≥ 0.10), the K5 provided lower [Formula: see text]CO2 readings than the K4b2 during the 3.0, 3.5, and 4.0 mph walking speeds (p ≤ 0.02). CONCLUSIONS: The K5 provided reliable and valid measures of metabolic variables, with greater reliability and validity at faster walking speeds.