Research Article Thymoquinone-Loaded Nanostructured Lipid Carrier Exhibited Cytotoxicity towards Breast Cancer Cell Lines (MDA-MB-231 and MCF-7) and Cervical Cancer Cell Lines (HeLa and SiHa) Wei Keat Ng, 1 Latifah Saiful Yazan, 1,2 Li Hua Yap, 2 Wan Abd Ghani Wan Nor Hafiza, 2 Chee Wun How, 3 and Rasedee Abdullah 3,4 1 Laboratory of Molecular Biomedicine, Institute of Bioscience, Universiti Putra Malaysia (UPM), 43400 Serdang, Selangor, Malaysia 2 Department of Biomedical Science, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia (UPM), 43400 Serdang, Selangor, Malaysia 3 Laboratory of Vaccine and Immunotherapeutics, Institute of Bioscience, Universiti Putra Malaysia (UPM), 43400 Serdang, Selangor, Malaysia 4 Department of Veterinary Pathology and Microbiology, Faculty of Veterinary Medicine, Universiti Putra Malaysia (UPM), 43400 Serdang, Selangor, Malaysia Correspondence should be addressed to Latifah Saiful Yazan; latifahsy@upm.edu.my Received 10 August 2014; Revised 24 November 2014; Accepted 27 November 2014 Academic Editor: Wan-Liang Lu Copyright © 2015 Wei Keat Ng et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Tymoquinone (TQ) has been shown to exhibit antitumor properties. Tymoquinone-loaded nanostructured lipid carrier (TQ- NLC) was developed to improve the bioavailability and cytotoxicity of TQ. Tis study was conducted to determine the cytotoxic efects of TQ-NLC on breast cancer (MDA-MB-231 and MCF-7) and cervical cancer cell lines (HeLa and SiHa). TQ-NLC was prepared by applying the hot high pressure homogenization technique. Te mean particle size of TQ-NLC was 35.66 ± 0.1235 nm with a narrow polydispersity index (PDI) lower than 0.25. Te zeta potential of TQ-NLC was greater than −30 mV. Polysorbate 80 helps to increase the stability of TQ-NLC. Diferential scanning calorimetry showed that TQ-NLC has a melting point of 56.73 ∘ C, which is lower than that of the bulk material. Te encapsulation efciency of TQ in TQ-NLC was 97.63 ± 0.1798% as determined by HPLC analysis. TQ-NLC exhibited antiproliferative activity towards all the cell lines in a dose-dependent manner which was most cytotoxic towards MDA-MB-231 cells. Cell shrinkage was noted following treatment of MDA-MB-231 cells with TQ-NLC with an increase of apoptotic cell population (P < 0.05). TQ-NLC also induced cell cycle arrest. TQ-NLC was most cytotoxic towards MDA-MB-231 cells. It induced apoptosis and cell cycle arrest in the cells. 1. Introduction Cancer is one of the major causes of death in the world [1]. Breast cancer and cervical cancer are the two most common malignancies among women worldwide. It is estimated that over 1.3 million new cases of breast cancer are diagnosed every year globally, of which over 450,000 of the patients would die from the disease. Although the cervical cancer inci- dence and mortality rate have declined, more than 520,000 cervical cancer new cases and over 275,000 deaths have been reported in 2008 worldwide [2]. Nigella sativa (also known as black seed or habbatus sauda) appears as one of the important herbs among various medicinal plants. Majority of the biological activities of Nigella sativa are associated with the presence of thymo- quinone (TQ), the major bioactive compound found in the seeds of the plant [3]. TQ or 2-isopropyl-5-methyl-1,4- benzoquinone (C 10 H 12 O 2 ) with relative molecular mass of 164.2 exhibited strong cytotoxic activities against several cancer cell lines including human cervical adenocarcinoma (HeLa) [4], human squamous carcinoma (SiHa) [5], human oestrogen receptor negative breast adenocarcinoma (MDA- MB-231), and human oestrogen receptor positive breast adenocarcinoma (MCF-7) [6, 7]. Intraperitoneal route has been used to administer TQ. Nevertheless, this route of administration in preclinical and clinical use is restricted by Hindawi Publishing Corporation BioMed Research International Volume 2015, Article ID 263131, 10 pages http://dx.doi.org/10.1155/2015/263131