Development and Evaluation of a Solid-Phase Microextraction Probe for in Vivo Pharmacokinetic Studies

Abstract

Simplified procedures and a reduction in sampling errors are important advantages for performing as many chemical analysis steps as possible at the site where a sample or subject is located. Solid-phase microextraction technology addresses this goal, and for our purposes, it also allows for in vivo monitoring of a dynamic living system with minimal disturbance of the system. Here we report the development of a solid-phase microextraction application for in vivo monitoring of circulating blood concentrations of benzodiazepines. A probe based on a polypyrrole extraction phase was developed and used for extraction of drug molecules directly from a peripheral vein with subsequent instrumental quantification. The probe provides good sensitivity and selectivity for the drugs versus the blood matrix, while eliminating the need to draw blood. After sampling, the extracted drugs are quantified by liquid chromatography-tandem mass spectrometry. The limit of detection of the method is ∼3-7 ng/mL for analysis of the benzodiazepines from whole blood, and the method is linear to 1000 ng/mL. The method was used to monitor the pharmacokinetic profiles of diazepam and its metabolites in dogs, and the results compared favorably with profiles determined by conventional methods. Because no blood and only very small amounts of drugs are removed, minimal disruption to the chemical balance in blood occurs. This approach offers the potential for reduced exposure to blood for analytical personnel, simplified, less disruptive sampling, and lower stress levels on animals for pharmacokinetic studies. It also allows for a significant reduction in animal usage for these studies, which is important both ethically and for improving data quality.

Making biosamples compatible with instrumental analysis

“…On-site measurement cannot be applied to every target analyte due to selectivity and sensitivity issues. Prof. Pawliszyn`s group is the pioneer of in-vivo microextraction that solves this shortcoming [20]. As the name well indicates, this approach consists on the integration of sampling and microextraction and presents the following advantages: a) is faster than con-ventional approaches; b) minimizes error associated to sample treatment and c) minimizes the error associated to sample storage since the analysis is performed after the in-vivo extraction [21].…”

Current Developments and Future Trends in Solid-phase Microextraction Techniques for Pharmaceutical and Biomedical Analyses

“…The method has been successfully utilized for the in vivo and in vitro pharmacokinetic measurements of free concentrations of ligand. 113,[117][118][119][120][121][122][123][124][125] Whole-blood and free concentrations of ligand, easily measured by SPME, are of utmost importance in therapeutics, since they correlate with the pharmacological effects of drug and are more significant than plasma concentrations. Using PDMS and PA coatings, the binding of several drugs with different polarities and binding constants to human plasma and serum albumin has been determined, indicating that this method is thermodynamically sound, requiring a small volume of sample and a short analysis time.…”

“…24,25,27,30,35,39,40,87,[117][118][119][120][121][122][123][124][125] Two configurations of proposed in vivo SPME sampling systems are illustrated (Fig. 4).…”

Low invasive in vivo tissue sampling for monitoring biomarkers and drugs during surgery

“…12,13 Recently, the feasibility of the method was also shown for global screening purposes. [14][15][16][17] The main advantages of in vivo SPME, being a low invasive and nondisturbing method to the system under study, were demonstrated for pharmacokinetics and metabolomics in blood, [18][19][20][21][22][23] whereas in vivo tissue analyses were conducted for analysis of pharmaceuticals in living fish. 24,25 In addition, with the SPME technique, blood sampling can be performed directly from a vein by using a hypodermic needle-assembled SPME probe (Figure 1) or by insertion of the probe to the vein through the i.v.…”

“…catheter. 18 This approach can be successfully employed in larger animals (dogs, pigs, and so on) and humans. For small animals such as rodents, because of the small size of their vessels, a number of interfaces facilitating the use of a SPME probe were developed.…”