Platinum metallodrug-protein binding studies by capillary electrophoresis-inductively coupled plasma-mass spectrometry: characterization of interactions between Pt(II) complexes and human serum albumin.
Characterizing how platinum metallocomplexes bind to human serum albumin (HSA) is essential in evaluating anticancer drug candidates. Using cisplatin as a reference complex, the application of capillary electrophoresis (CE) to reliably assess drug/HSA interactions was validated. Since this complex is small compared to the size of the protein, the binding response could only be recognized when applying CE coupled to a (platinum) metal-specific mode of detection, namely inductively coupled plasma-mass spectrometry (ICP-MS). This coupling allowed for confirmation of a specific affinity of cisplatin and novel Pt complexes to HSA, measurement of the kinetics of binding reactions, and determination of the number of drug molecules attached to the protein. As the cisplatin/HSA molar ratio increased, the reaction rate became faster with a maximum on the kinetic curve appearing at about 50 h of incubation at 20 times excess of cisplatin. The reaction was characterized as a pseudo-first order reaction with the rate constant k = 0.003 min(-1) at 37 degrees C. When incubated with a 20-fold excess of cisplatin, HSA bound up to 10 mol of Pt per mol of the protein. This is indicative for a strong metal-protein coordination occurring at several HSA sites other than the only protein cysteine residue. Structural analogs of cisplatin, bearing aminoalcohol ligands, showed comparable protein binding reactivity and stoichiometry but a common equilibrium was not reached even after one week of incubation. Also apparent was a two-step mechanism of the binding reaction. Results demonstrated the suitability of CE-ICP-MS as a rapid assay for high-throughput studying of drug/HSA interactions.
Timerbaev
Andrei R
AR
Institute of Inorganic Chemistry, University of Vienna, Vienna, Austria.|Permanent address: Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, 117975 Moscow, Russia Fax: +43-1-4277-52680.
Aleksenko
Svetlana S
SS
Department of Analytical Chemistry, Warsaw University of Technology, Warsaw, Poland.
Polec-Pawlak
Kasia
K
Department of Analytical Chemistry, Warsaw University of Technology, Warsaw, Poland.
Ruzik
Rafal
R
Department of Analytical Chemistry, Warsaw University of Technology, Warsaw, Poland.
Semenova
Olga
O
Institute of Inorganic Chemistry, University of Vienna, Vienna, Austria.
Hartinger
Christian G
CG
Institute of Inorganic Chemistry, University of Vienna, Vienna, Austria.
Oszwaldowski
Slawomir
S
Department of Analytical Chemistry, Warsaw University of Technology, Warsaw, Poland.
Galanski
Markus
M
Institute of Inorganic Chemistry, University of Vienna, Vienna, Austria.
Jarosz
Maciej
M
Department of Analytical Chemistry, Warsaw University of Technology, Warsaw, Poland.
Keppler
Bernhard K
BK
Institute of Inorganic Chemistry, University of Vienna, Vienna, Austria.
D000970:Antineoplastic Agents / Q000737:chemistry / Q000494:pharmacology; D002945:Cisplatin / Q000032:analysis* / Q000737:chemistry; D004347:Drug Interactions; D004573:Electrolytes / Q000737:chemistry; D019075:Electrophoresis, Capillary / Q000379:methods*; D006801:Humans; D007700:Kinetics; D013058:Mass Spectrometry / Q000379:methods*; D004364:Pharmaceutical Preparations / Q000032:analysis / Q000737:chemistry; D010984:Platinum / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D012709:Serum Albumin / Q000737:chemistry* / Q000378:metabolism
D000970:Antineoplastic Agents; D004573:Electrolytes; D004364:Pharmaceutical Preparations; D012709:Serum Albumin; D010984:Platinum; D002945:Cisplatin