Optimization of a validated stability-indicating RP-LC method for the determination of fulvestrant from polymeric based nanoparticle systems, drugs and biological samples Mehmet Gumustas a , Ceyda Tuba Sengel-Turk b , Canan Hascicek b * and Sibel A. Ozkan a ABSTRACT: Fulvestrant is used for the treatment of hormone receptor-positive metastatic breast cancer in postmenopausal women with disease progression following anti-estrogen therapy. Several reversed-phase columns with variable silica mate- rials, diameters, lengths, etc., were tested for the optimization study. A good chromatographic separation was achieved using a Waters X-Terra RP 18 column (250 × 4.6 mm i.d. × 5 μm) and a mobile phase, consisting of a mixture of acetonitrile–water (65:35; v/v) containing phosphoric acid (0.1%). The separation was carried out 40°C with detection at 215 nm.The calibration curves were linear over the concentration range between 1.0–300 and 1.0–200 μg/mL for standard solutions and biological media, respectively. The proposed method is accurate and reproducible. Forced degradation studies were also realized. This fully validated method allows the direct determination of fulvestrant in dosage form and biological samples. The average recovery of the added fulvestrant amount in the samples was between 98.22 and104.03%. The proposed method was also applied for the determination of fulvestrant from the polymeric-based nanoparticle systems. No interference from using polymers and other excipients was observed in in vitro drug release studies. Therefore an incorporation efficiency of fulvestrant-loaded nanoparticle could be determined accurately and specifically. Copyright © 2014 John Wiley & Sons, Ltd. Keywords: fulvestrant; RP-LC; validation; nanoparticles; optimization; biological samples Introduction Fulvestrant (FLV) (Scheme 1), chemically known as (7α,17β)-7-{9- [(4,4,5,5,5-pentafluoropentyl) sulfinyl]nonyl}estra-1,3,5(10)-tri- ene-3,17-diol (Sweetman, 2009), is a new estrogen receptor antagonist that is active in models of tamoxifen resistance and lacks cross-resistance with other anti-estrogens. Many breast cancers have estrogen receptors and the growth of these types of tumors can be stimulated by estrogen. Fulvestrant is an estro- gen receptor antagonist that binds to the estrogen receptor in a competitive manner with affinity comparable to that of estradiol and down-regulates the estrogen receptor protein in breast cancer cells. FLV has also a specific mode of action since it blocks and accelerates degradation of estrogen and progesterone receptor protein, leading to an inhibition of estrogen signaling. It has no estrogen agonist effects. The action effectively lowers the estrogen receptor activity in the cell so that it acts more like a normal cell (Valachis et al., 2010; Vergote and Abram, 2006). In the open literature, few methods have been reported for the determination of FLV in pharmaceutical dosage forms using spectrophotometric and voltammetric methods (Balaram et al., 2007; Dogan-Topal and Ozkan, 2011; Kul et al., 2011). A review of the literature revealed that only one LC-MS/MS method has been reported for the determination of FLV in rat plasma (Liu et al., 2011). However, the proposed procedure also presents the stability-indicating degradation behavior of FLV. No reported methods were selective enough to resolve the active ingredients from their potential impurities and forced-degradation products and, consequently, none of these studies can be considered stability indicating. Nanomedicine has been regarded as one of the most promis- ing approaches for the medical application of nanotechnology as an alternative to conventional drug delivery systems. Nanoparticle-based drug delivery systems is a rapidly develop- ing area within cancer, which is still a leading cause of death all over the world (Nafee et al., 2009; Liu et al., 2010). Polymeric nanoparticles are colloidal drug delivery systems that range in size from 10 to 1000 nm in diameter and are formulated from a biodegradable polymer in which the therapeutic agent is incorporated in, adsorbed or chemically coupled onto the polymeric matrix structure. Among the biodegradable polymers approved by the US Food and Drug Administration, poly[D,L- lactide-co-glycolide] (PLGA) and poly(ethylene glycol)-block- * Correspondence to: Canan Hascicek, Ankara University, Faculty of Pharmacy, Department of Pharmaceutical Technology, Ankara, Turkey. Email: cogan@pharmacy.ankara.edu.tr a Ankara University, Faculty of Pharmacy, Department of Analytical Chemistry, Ankara, Turkey b Ankara University, Faculty of Pharmacy, Department of Pharmaceutical Technology, Ankara, Turkey Abbreviations used: FLV, fulvestrant; PEG-block-PCL, poly(ethylene glycol)- block-poly(ε-caprolactone)methyl ether; PLGA, poly[D,L-lactide-co-glycolide]; PVA, poly(vinyl alcohol). Biomed. Chromatogr. 2014; 28: 1409–1417 Copyright © 2014 John Wiley & Sons, Ltd. Research article Received: 14 November 2013, Revised: 13 January 2014, Accepted: 17 February 2014 Published online in Wiley Online Library: 27 May 2014 (wileyonlinelibrary.com) DOI 10.1002/bmc.3183 1409