Solid-phase microextraction: a fit-for-purpose technique in biomedical analysis

The impact of normothermic and hypothermic preservation methods on kidney lipidome-comparative study using chemical biopsy with microextraction probes

Introduction

Normothermic ex vivo kidney perfusion (NEVKP) is designed to replicate physiological conditions to improve graft outcomes. A comparison of the impact of hypothermic and normothermic preservation techniques on graft quality was performed by lipidomic profiling using solid-phase microextraction (SPME) chemical biopsy as a minimally invasive sampling approach.

Methods

Direct kidney sampling was conducted using SPME probes coated with a mixed-mode extraction phase in a porcine autotransplantation model of the renal donor after cardiac death, comparing three preservation methods: static cold storage (SCS), NEVKP, and hypothermic machine perfusion (HMP). The lipidomic analysis was done using ultra-high-performance liquid chromatography coupled with a Q-Exactive Focus Orbitrap mass spectrometer.

Results

Chemometric analysis showed that the NEVLP group was separated from SCS and HMP groups. Further in-depth analyses indicated significantly (p < 0.05, VIP > 1) higher levels of acylcarnitines, phosphocholines, ether-linked and longer-chain phosphoethanolamines, triacylglycerols and most lysophosphocholines and lysophosphoethanolamines in the hypothermic preservation group. The results showed that the preservation temperature has a more significant impact on the lipidomic profile of the kidney than the preservation method's mechanical characteristics.

Conclusion

Higher levels of lipids detected in the hypothermic preservation group may be related to ischemia-reperfusion injury, mitochondrial dysfunction, pro-inflammatory effect, and oxidative stress. Obtained results suggest the NEVKP method's beneficial effect on graft function and confirm that SPME chemical biopsy enables low-invasive and repeated sampling of the same tissue, allowing tracking alterations in the graft throughout the entire transplantation procedure.

Emerging technologies: analytical lab vs. clinical lab perspective. Common goals and gaps to be filled in the pursuit of green and sustainable solutions

Analytical chemistry is a broad area of science comprised of many sub-disciplines. Although each sub-discipline has its own dominant trends, one trend is common to all of them: greenness and sustainability. Efforts to develop more ecological and environmentally friendly methods have been ongoing for over a decade with initial attempts largely focusing on limiting the necessary volume of solvents required and eliminating the use of toxic solvents. Over time, the miniaturization of analytical devices gained popularity as a way of not only reducing chemical usage, but also enabling analyses using smaller sample volumes and more "remote" applications (e.g., on-site sampling and analysis). Of course, miniaturization poses numerous challenges for researchers, for instance, in relation to the method's sensitivity and reproducibility. Developments in the design of detection systems have largely helped to mitigate these issues, but they also often restrict the potential for on-site analysis. Therefore, attempts have been made to improve analysis throughout the entire analytical process, from sampling through sample preparation and instrumental analysis to data handling. Furthermore, clinical chemistry labs must adhere to certain regulations and use certified protocols and materials, which precludes the rapid implementation of solutions developed in research labs. What are the obstacles in translating such innovations to practical applications, and what inventions can make a difference in the future? The answers to these two questions define the trends in analytical chemistry in the field of medical analysis.

Microextraction based on liquid-solid phase transition of benzoic acid: Extraction of statins from human urine followed by chromatographic analysis

Herein, a microextraction method was reported based on the liquid-solid phase transition of benzoic acid to quantify two statins, namely lovastatin and simvastatin in authentic human urine. The principle of the method is based on the phase transition of benzoic acid by altering the pH of the sample solution enabling efficient dispersion and phase separation in one step. Due to the moderate melting point of benzoic acid, its solidification is performed at ambient temperature without the need for sample cooling. Various experimental parameters that affect the performance of the analytes (i.e. extractant type and its concentration, acid type and concentration, and sample volume) have been examined and optimized. The method was validated based on the total error concept. For this purpose, accuracy profiles were constructed in the concentration range of 100-5000 ng mL-1 while β-expectation tolerance intervals fell within ±15% demonstrating that 95% of future results will not exceed the defined bias limits. The intra-day and inter-day method precision was less than 4.7% and 4.3% for both analytes, while the limit of detection was 15 ng mL-1 for both analytes. It was also proved that the usage of benzoic acid is advantageous in minimizing the potential inter-conversion of the analytes during the acidification step of the extraction procedure. The green potential of the proposed analytical scheme was examined based on Green Analytical Procedure index. The proposed sample pretreatment technique proved to be a valuable tool offering selectivity and rapidness. The developed method was used for the analysis of real human urine obtained after the administration of statin-based pharmaceutical formulations.

Solid Phase Microextraction—A Promising Tool for Graft Quality Monitoring in Solid Organ Transplantation

Solid organ transplantation is a life-saving intervention for patients suffering from end-stage organ failure. Although improvements in surgical techniques, standards of care, and immunosuppression have been observed over the last few decades, transplant centers have to face the problem of an insufficient number of organs for transplantation concerning the growing demand. An opportunity to increase the pool of organs intended for transplantation is the more frequent use of organs from extended criteria and the development of analytical methods allowing for a better assessment of the quality of organs to minimize the risk of post-transplant organ injury and rejection. Therefore, solid-phase microextraction (SPME) has been proposed in various studies as an effective tool for determining compounds of significance during graft function assessment or for the chemical profiling of grafts undergoing various preservation protocols. This review summarizes how SPME addresses the analytical challenges associated with different matrices utilized in the peri-transplant period and discusses its potential as a diagnostic tool in future work.