Determination of caffeine, paraxanthine, theophylline and theobromine in premature infants by HILIC-MS/MS

From "wet" matrices to "dry" blood spot sampling strategy: a versatile LC-MS/MS assay for simultaneous monitoring caffeine and its three primary metabolites in preterm infants

OBJECTIVES

To update traditional "wet" matrices to dried blood spot (DBS) sampling, based on the liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) technique, and develop a method for simultaneous analyzing caffeine and its three primary metabolites (theobromine, paraxanthine, and theophylline), supporting routine therapeutic drug monitoring (TDM) for preterm infants.

METHODS

DBS samples were prepared by a two-step quantitative sampling method, i.e., volumetric sampling of a quantitative 10 μL volume of peripheral blood and an 8 mm diameter whole punch extraction by a methanol/water (80/20, v/v) mixture containing 125 mM formic acid. Four paired stable isotope labeled internal standards and a collision energy defect strategy were applied for the method optimization. The method was fully validated following international guidelines and industrial recommendations on DBS analysis. Cross validation with previously developed plasma method was also proceeded. The validated method was then implemented on the TDM for preterm infants.

RESULTS

The two-step quantitative sampling strategy and a high recovery extraction method were developed and optimized. The method validation results were all within the acceptable criteria. Satisfactory parallelism, concordance, and correlation were observed between DBS and plasma concentrations of the four analytes. The method was applied to provide routine TDM services to 20 preterm infants.

CONCLUSIONS

A versatile LC-MS/MS platform for simultaneous monitoring caffeine and its three primary metabolites was developed, fully validated, and successfully applied into the routine clinical TDM practices. Sampling method switching from "wet" matrices to "dry" DBS will facilitate and support the precision dosing of caffeine for preterm infants.

A novel fluorescent aptasensor for the detection of theophylline based on cryonase-driven signal amplification strategy

In the study, we have developed an expedient and efficient method for the detection of theophylline based on the amplification of the signal intensity of fluorescence based on oxidized single-walled carbon nanohorns (oxSWCNHs)/cryonase. When theophylline was not present in the system, oxSWCNHs can adequately adsorb nucleic acid probes labeled by carboxyfluorescein (FAM). In the presence of theophylline, the nucleic acid probe forms the tertiary probe-theophylline complex, which detaches from the surface of the oxSWCNHs. Then, upon reaction with cryonase, the complex can release the FAM and theophylline into the next cycle. The fluorescence signal of the system exhibits a 1:N magnification, enabling quantitative detection of theophylline. The linear range was 30-150 ng/mL, and the limit of detection (LOD) was 6.04 ng/mL. At the same time, it can also be used to detect theophylline in mouse serum.