Three-dimensional printed sample load/inject valves enabling online monitoring of extracellular calcium and zinc ions in living rat brains.

We have developed a simple and low-cost flow injection system coupled to a quadruple ICP-MS for the direct and continuous determination of multi-element in microdialysates. To interface microdialysis sampling to an inductively coupled plasma mass spectrometer (ICP-MS), we employed 3D printing to manufacture an as-designed sample load/inject valve featuring an in-valve sample loop for precise handling of microliter samples with a dissolved solids content of 0.9% NaCl (w/v). To demonstrate the practicality of our developed on-line system, we applied the 3D printed valve equipped a 5-µL sample loop to minimize the occurrence of salt matrix effects and facilitate an online dynamic monitoring of extracellular calcium and zinc ions in living rat brains. Under the practical condition (temporal resolution: 10h(-1)), dynamic profiling of these two metal ions in living rat brain extracellular fluid after probe implantation (the basal values for Ca and Zn were 12.11±0.10mg L(-1) and 1.87±0.05µg L(-1), respectively) and real-time monitoring of the physiological response to excitotoxic stress elicited upon perfusing a solution of 2.5mM N-methyl-d-aspartate were performed.

Quantitatively profiling the dissolution and redistribution of silver nanoparticles in living rats using a knotted reactor-based differentiation scheme.

Whether silver nanoparticles (AgNPs) degrade and release silver ions (Ag(+)) in vivo has remained an unresolved issue. To evaluate the biodistribution and dissolution behavior of intravenously administered AgNPs in living rats, we employed a knotted reactor (KR) device to construct a differentiation scheme for quantitative assessment of residual AgNPs and their released Ag(+) ions in complicated animal tissues; to do so, we adjusted the operating parameters of the KR, namely, the presence/absence of a rinse solution and the sample acidity. After optimization, our proposed differentiation system was confirmed to be tolerant to rat tissue and organ matrix and provide superior reliability of differentiating AgNPs/Ag(+) than the conventional centrifugal filtration method. We then applied this differentiation strategy to investigate the biodistribution and dissolution of AgNPs in rats 1, 3, and 5 days postadministration, and it was found that the administered AgNPs accumulated predominantly in the liver and spleen, then dissolved and released Ag(+) ions that were gradually excreted, resulting in almost all of the Ag(+) ions becoming deposited in the kidney, lung, and brain. Histopathological data also indicated that toxic responses were specifically located in the AgNP-rich liver, not in the Ag(+)-dominated tissues and organs. Thus, the full-scale chemical fate of AgNPs in vivo should be integrated into future assessments of the environmental health effects and utilization of AgNP-containing products.

A high-throughput microdialysis-parallel solid phase extraction-inductively coupled plasma mass spectrometry hyphenated system for continuous monitoring of extracellular metal ions in living rat brain.

To significantly improve the temporal resolving power of in vivo trace brain metal monitoring system, in this paper we describe a novel analytical configuration combining the dual functions of online segmentation of the rat brain microdialysate and parallel solid phase extraction (SPE) of multiple segmented samples. In contrast to traditional SPE procedures, in this study the three pumped media-the buffered rat brain microdialysate, the eluent, and the air stream-were converted to a series of segmented streams through the manipulation of a flow-through stream selector. After optimizing this online automatic MD/parallel poly(vinyl chloride) SPE/inductively coupled plasma mass spectrometry hyphenated system for the analysis of ultra-trace metal ions, the sample volume of the microdialysate was set at 0.83µL, the analytical sequence was repeatable every 20s, and the detection limits were in the range 0.03-0.24µgL(-1), with spike analyses of Mn, Co, Ni, Cu, and Zn in a rat brain ECF sample agreeing well with expected values (88-107%). To further examine the system's practicability, we also performed (i) in vivo dynamic monitoring of these trace metal ions in living rat brain extracellular fluid post-probe implantation (the basal values for Mn, Co, Ni, Cu, and Zn were 1.17±0.18, 1.27±0.36, 2.46±0.62, 0.86±0.37, and 2.35±0.55µgL(-1), respectively) and (ii) real-time visualization of the physiological response to acute neural depolarization elicited upon perfusing a high-K(+) medium through the MD probe.