ORIGINAL PAPER Characterization of gold nanorods in vivo by integrated analytical techniques: their uptake, retention, and chemical forms Liming Wang & Yu-Feng Li & Liangjun Zhou & Ying Liu & Li Meng& Ke Zhang & Xiaochun Wu & Lili Zhang& Bai Li & Chunying Chen Received: 15 July 2009 / Revised: 20 October 2009 / Accepted: 6 November 2009 / Published online: 17 December 2009 # Springer-Verlag 2009 AbstractIntegrated analytical techniques wereused to study the tissue distribution and structural information of gold nanorods (Au NRs) in Sprague-Dawley rats through tail intravenous injection. Before in vivo experiments were conducted,carefulcharacterization of Au NRs was performed. The zeta potential proved that adsorption of bovineserum albumin on Au NRsturned thesurface chargesfrom positiveto negativeas in an in vitro simulation. The biodistribution of Au NRs was investigated quantitatively by inductively coupled plasma mass spec- trometry at differentime points after injection. As target tissues,both liverand spleen werechosen to further demonstrate the intracellular localization of Au NRs by the combination of transmission electron microscopy and energy-dispersiveX-ray spectroscopy.Moreover, synchrotron-radiation-based X-ray absorption spectroscopy was employed and it was observed that long-term retention of Au NRs in liver and spleen did not induce obvious changes in the oxidation states of gold. Therefore, the present systematic method can provide important informa- tion abouthe fates of Au NRs in vivo and can also be extended to study the biological effects ofothermetallic nanomaterials in the future. Keywords Gold nanorods . Biodistribution . Characterization in vivo . Transmission electron microscopy . Inductively coupled plasma mass spectrometry . X-ray absorption spectroscopy Introduction With the development of nanotechnology, many kinds of nanomaterials are manufactured and some have potential applications in the fields of biology and medicine. With the success in the controlled synthesis and owing to their properties, gold nanorods(Au NRs) arebecominga promising candidate for medical applications such as tumo thermotherapy, near-infrared imaging, molecular detection and diagnosis, and drug and gene delivery [ 1, 2]. Their unique optical properties are closely related to the tunable surface plasmon resonance (SPR) in the visible and near- infrared regions, which endows the Au NRs with optical properties thatcan betailored in termsof absorption, fluorescence, and scattering of visible and near-infrared light[3]. A gold atom can also coordinate with a thiol group,which makesit convenientto modify some functional molecules through this group [ 4, 5]. Recently, researchers have been focusing on the biolog effects ofAu NRs, such as cytotoxicity, biocompatibility, uptake and clearance by cells, and biodistribution in vivo [6–9].Gold materials are reported to be inert and safe on the basis of the safety evaluation of bulk materials. L. Wang : L. Zhou : Y. Liu : L. Meng : L. Zhang : C. Chen CAS Key Laboratory for Biological Effects of Nanomaterials and Nanosafety, National Center for Nanoscience and Technology of China, Beijing 100190, China Y.-F.Li : B. Li : C. Chen (*) CAS Key Laboratory for Nuclear Analytical Techniques, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China e-mail: chenchy@nanoctr.cn K. Zhang : X. Wu (*) Laboratory for Nanoscale Measurement and Standardization, National Center for Nanoscience and Technology of China, Beijing 100190, China e-mail: wuxc@nanoctr.cn Anal Bioanal Chem (2010) 396:1105–1114 DOI 10.1007/s00216-009-3302-y