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Sensitive determination of plasma protein binding of cationic drugs using mixed-mode solid-phase microextraction.
J Pharm Biomed Anal. 2015 Nov 10; 115:534-42.JP

Abstract

Freely dissolved concentrations are considered to be the most relevant concentration in pharmacology and toxicology, as they represent the active concentration available for interaction with its surroundings. Here, a solid-phase microextraction (SPME) coating that combines octadecyl and propylsulfonic acid groups as strong cation exchange sites, known as C18/SCX or "mixed-mode" SPME, is used to measure freely dissolved concentrations of amitriptyline, amphetamine, diazepam and tramadol to different binding matrices, including bovine serum albumin (BSA), human serum albumin (HSA), human plasma and human whole blood. A potential confounding factor in binding studies is that proteins may sorb to the fiber coating leading to incorrect measurement of protein sorption or changes in uptake kinetics to the fiber coating. Sorption of bovine serum albumin (BSA) was observed and quantified using a Lowry assay. BSA binds to the C18/SCX fiber in small amounts, but large changes in uptake kinetics were not observed. All experiments were performed at equilibrium. In addition, however, the effect of depletion and non-equilibrium extraction on the estimation of protein binding affinities was also studied. Binding affinities to BSA and human serum albumin (HSA) were calculated as log KBSA or log KHSA. These values were very similar to reported literature values. Sampling at either equilibrium or non-equilibrium resulted in similar binding affinities. Furthermore, SPME fibers were used to measure freely dissolved concentrations in undiluted human plasma and whole blood. Analysis of SPME extracts could be performed using HPLC-UV or HPLC with fluorescence detection without prior clean-up of the samples. Measured bound fractions in plasma using this SPME approach were comparable to literature reference values. Bound fractions in whole blood were always higher than in plasma, due to red blood cell partitioning. This work shows the potential of SPME as sampling tool for freely dissolved concentrations, especially for highly protein-bound compounds. Conventional SPME coatings such as polyacrylate (PA) or polydimethylsiloxane (PDMS) might be lacking sensitivity when sampling the small neutral fraction of highly protein-bound positively charged compounds, but the C18/SCX fiber is able to sorb the charged species of organic cations, thereby improving sensitivity for these types of compounds.

Authors+Show Affiliations

Institute for Risk Assessment Sciences, Utrecht University, P.O. Box 80177, 3508 TD Utrecht, The Netherlands. Electronic address: H.Peltenburg@uu.nl.Netherlands Forensic Institute, P.O. Box 24044, 2490 AA The Hague, The Netherlands.Institute for Risk Assessment Sciences, Utrecht University, P.O. Box 80177, 3508 TD Utrecht, The Netherlands.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

26313333

Citation

Peltenburg, Hester, et al. "Sensitive Determination of Plasma Protein Binding of Cationic Drugs Using Mixed-mode Solid-phase Microextraction." Journal of Pharmaceutical and Biomedical Analysis, vol. 115, 2015, pp. 534-42.
Peltenburg H, Bosman IJ, Hermens JL. Sensitive determination of plasma protein binding of cationic drugs using mixed-mode solid-phase microextraction. J Pharm Biomed Anal. 2015;115:534-42.
Peltenburg, H., Bosman, I. J., & Hermens, J. L. (2015). Sensitive determination of plasma protein binding of cationic drugs using mixed-mode solid-phase microextraction. Journal of Pharmaceutical and Biomedical Analysis, 115, 534-42. https://doi.org/10.1016/j.jpba.2015.08.002
Peltenburg H, Bosman IJ, Hermens JL. Sensitive Determination of Plasma Protein Binding of Cationic Drugs Using Mixed-mode Solid-phase Microextraction. J Pharm Biomed Anal. 2015 Nov 10;115:534-42. PubMed PMID: 26313333.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Sensitive determination of plasma protein binding of cationic drugs using mixed-mode solid-phase microextraction. AU - Peltenburg,Hester, AU - Bosman,Ingrid J, AU - Hermens,Joop L M, Y1 - 2015/08/04/ PY - 2015/05/29/received PY - 2015/07/30/revised PY - 2015/08/01/accepted PY - 2015/8/28/entrez PY - 2015/8/28/pubmed PY - 2016/7/7/medline KW - Cation exchange KW - Free concentration KW - Ionized pharmaceuticals KW - Mixed-mode SPME KW - Organic cations KW - Plasma protein binding SP - 534 EP - 42 JF - Journal of pharmaceutical and biomedical analysis JO - J Pharm Biomed Anal VL - 115 N2 - Freely dissolved concentrations are considered to be the most relevant concentration in pharmacology and toxicology, as they represent the active concentration available for interaction with its surroundings. Here, a solid-phase microextraction (SPME) coating that combines octadecyl and propylsulfonic acid groups as strong cation exchange sites, known as C18/SCX or "mixed-mode" SPME, is used to measure freely dissolved concentrations of amitriptyline, amphetamine, diazepam and tramadol to different binding matrices, including bovine serum albumin (BSA), human serum albumin (HSA), human plasma and human whole blood. A potential confounding factor in binding studies is that proteins may sorb to the fiber coating leading to incorrect measurement of protein sorption or changes in uptake kinetics to the fiber coating. Sorption of bovine serum albumin (BSA) was observed and quantified using a Lowry assay. BSA binds to the C18/SCX fiber in small amounts, but large changes in uptake kinetics were not observed. All experiments were performed at equilibrium. In addition, however, the effect of depletion and non-equilibrium extraction on the estimation of protein binding affinities was also studied. Binding affinities to BSA and human serum albumin (HSA) were calculated as log KBSA or log KHSA. These values were very similar to reported literature values. Sampling at either equilibrium or non-equilibrium resulted in similar binding affinities. Furthermore, SPME fibers were used to measure freely dissolved concentrations in undiluted human plasma and whole blood. Analysis of SPME extracts could be performed using HPLC-UV or HPLC with fluorescence detection without prior clean-up of the samples. Measured bound fractions in plasma using this SPME approach were comparable to literature reference values. Bound fractions in whole blood were always higher than in plasma, due to red blood cell partitioning. This work shows the potential of SPME as sampling tool for freely dissolved concentrations, especially for highly protein-bound compounds. Conventional SPME coatings such as polyacrylate (PA) or polydimethylsiloxane (PDMS) might be lacking sensitivity when sampling the small neutral fraction of highly protein-bound positively charged compounds, but the C18/SCX fiber is able to sorb the charged species of organic cations, thereby improving sensitivity for these types of compounds. SN - 1873-264X UR - https://www.unboundmedicine.com/medline/citation/26313333/Sensitive_determination_of_plasma_protein_binding_of_cationic_drugs_using_mixed_mode_solid_phase_microextraction_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0731-7085(15)30100-X DB - PRIME DP - Unbound Medicine ER -