Journal of Pharmaceutical and Biomedical Analysis 44 (2007) 1147–1153 Determination of methylprednisolone acetate in biological fluids at gold nanoparticles modified ITO electrode Rajendra N. Goyal a,∗ , Munetaka Oyama b , Akrajas A. Umar b , Anuradha Tyagi c , Neeta Bachheti a a Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee 247667, India b Division of Research Initiatives, International Innovation Center, Kyoto University, Nishikyo-Ku, Kyoto 615-8520, Japan c Amity Institute of Nanotechnology, Amity University, Noida-201301, India Received 22 March 2007; received in revised form 10 May 2007; accepted 29 May 2007 Available online 2 June 2007 Abstract The electrochemical behavior of a corticosteroid methylprednisolone (MP), used for doping, has been studied at gold nanoparticles modified indium tin oxide (nanoAu/ITO) electrode. The nanoAu/ITO electrode exhibited an effective catalytic response towards its oxidation and lowered its oxidation potential by ∼127 mV when compared with bare ITO electrode. Oxidation of MP has been carried out in phosphate containing electrolyte in the pH range 2.13–10.00 and a well-defined oxidation peak was noticed. Linear concentration curves are obtained over the concentration range 0.01–1.0 M with a detection limit of 2.68 × 10 -7 M at nanoAu/ITO electrode. A diffusion coefficient of 2.36 × 10 -6 cm 2 /s is calculated for MP using chronoamperometry. The proposed method is effectively applied to detect the concentration of MP in pharmaceutical formulations and human blood plasma and urine samples. A comparison of MP concentration determined in blood plasma and urine by the proposed method and GC/MS indicated that the results are essentially similar. It is believed that the method will be useful in determining this drug in case of doping. © 2007 Elsevier B.V. All rights reserved. Keywords: Indium tin oxide; Gold nanoparticles; Methylprednisolone; Blood plasma; Urine; Voltammetry 1. Introduction Methylprednisolone (MP) [(6,11)-11,17,21-trihydroxy-6- methyl-pregna-1,4-diene-3,20-dione] is a synthetic corticos- teroid drug typically used for its anti-inflammatory property [1]. MP(I) is used to achieve prompt suppression of inflam- mation in different parts of the body [2] and for the treatment of certain forms of arthritis, skin, blood, kidney (glomeru- lonephritis), eye (graves ophthalmopathy), thyroid and intestinal disorders (e.g., colitis) and asthma [3–10]. Certain types of can- cer [11,12] have also been treated with methylprednisolone. MP is one of the commonly used medicines in acute lung injury caused by acid aspiration [13]. Lin et al. reported that MP is also effective in the cases of head injury [14]. Direct infusion of MP into perilymphatic space accelerates hearing recovery and reduces hair cell losses after impulse noise trauma ∗ Corresponding author. Tel.: +91 1332 285794; fax: +91 1332 273560. E-mail address: rngcyfcy@iitr.ernet.in (R.N. Goyal). [15]. Being a performance-enhancing drug, World Anti-Doping Agency (WADA) has banned the use of MP in sports when administered orally, rectally, intravenously or intramuscularly [16,17]. Its illicit use has prompted considerable interest during last few years in the development of methods for the testing of this drug in plasma and urine samples of athletes. MP(I) has been determined by relatively few techniques, such as high performance liquid chromatography (HPLC), HPLC with UV detection, spectrophotometry, gas chromatography–mass spec- trometry and colorimetry [18–22]. Electrochemical methods have been widely applied for the determination of pharmaceuti- cal formulations since they offer high sensitivity, low detection limit and use of simple instrumentation. However, there appears to be no electrochemical method reported for the determination of MP in literature till date. Gold nanoparticles exhibit attractive properties in elec- trode modification by improving the electrode conductivity and enhancing the analytical sensitivity and selectivity [23]. This work aimed to study the voltammetric behavior of MP and its determination in pharmaceutical preparations as well as in 0731-7085/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jpba.2007.05.033