Eunjoo Kim 1 , Young Chae Chu 2 , Jee Young Han 2 , Don Haeng Lee 3,4 , Ye Ji Kim 2 , Hyun-Chul Kim 1 , Se Geun Lee 1 , Sung Jun Lee 1 , Sang Won Jeong 1 & Joon Mee Kim 2 1 Division of Nano & Bio Research, Daegu Gyeongbuk Institute of Science and Technology, Hosan-dong, Daegu 704-230, Korea 2 Department of Pathology, Inha University Hospital, Sinheung-dong, Incheon 400-711, Korea 3 Department of Gastroenterology, Inha University Hospital, Sinheung-dong, Incheon 400-711, Korea 4 Utah-Inha DDS & Advanced Therapeutic Research Center, 50 Michuhol Tower SongdoTechnoPark, Songdo-dong, Yeonsu-gu, Incheon 406-840, Korea Correspondence and requests for materials should be addressed to E. Kim (ejkim@dgist.ac.kr), J. M. Kim (jmkpath@inha.ac.kr) Accepted 9 October 2010 Abstract Silver nanoparticles (SNPs) have received consider- able attention recently, because SNPs with different shapes and sizes exhibit variable antimicrobial activi- ty, which makes them useful for medical and hygienic purposes. SNPs have been detected in various tis- sues and organisms after inhalation, oral ingestion, and contact with the skin, indicating that SNPs can be distributed to different body tissues after uptake. Thus, the toxicity of SNPs to different body tissues after their uptake needs to be studied. In this study, we performed a proteomic analysis of liver, lung, and kidney tissues in rats exposed to approximately 50 nm SNPs by intravascular injection. Then, the differ- entially expressed proteins representing a dose-de- pendent response were identified. The differentially expressed proteins were mostly related to the known toxicity of SNPs, such as apoptosis, increased reac- tive oxygen species, thrombus formation, and inflam- mation. Additionally, proteins related to metabolic disorders including diabetes were identified as differ- entially expressed proteins in kidney, based solely on the analysis of the protein profile and related dis- ease pathway. In conclusion, the differentially express- ed proteins identified in this study could provide basic data for understanding the toxic and pathologi- cal responses of SNP-exposed tissues and to identi- fy candidate SNP toxicity biomarkers. Keywords: Silver nanoparticle, Toxicoproteomics, Biomarker, Apoptosis, Reactive oxygen species, Blood coagulation Introduction Nanotechnology is a rapidly growing science of pro- ducing and utilizing nano-sized particles. It provides a modern and innovative approach to develop and test new nanoparticle formulations for electronics, biomedi - cal and therapeutic applications, and various necessi- ties of life 1,2 . Silver nanoparticles (SNPs) represent a prominent nanoproduct with potential applications in medicine and hygiene. SNPs have antimicrobial activ- ity resulting in their widespread use in bedding, wash- ers, water purification, toothpaste, shampoo and rinse, infant nipples and nursing bottles, fabrics, deodorants, filters, kitchen utensils, toys, and humidifiers 3 . SNPs are also used for treating wounds and burns 4 . The anti- microbial properties of silver have been known for thousands of years 5 , but SNPs have gained attention recently, because different formulations of SNPs with different shapes and sizes exhibit variable antimicro- bial activity, which offers their possible use for medi- cal and hygienic purposes 6 . Comparing the antimicrobial effect of silver ions and SNPs is an interesting field of research, and some stu- dies have been performed in this area. Silver ions and SNPs also have inhibitory and lethal effects on bacte- rial species such as E. coli 7 , Staphylococcus aureus, and yeast 8 . However, Morones et al. 5 indicated that the mechanism of SNP antimicrobial activity is different than the mechanism induced by silver ions. Gade et al. 9 observed complete disruption of the bacterial mem- brane after a few minutes in contact with SNPs and Raffi et al. 10 proposed that the high efficiency of SNPs was due to the large surface area available for interac- tions, resulting in their effectiveness against bacteria. This high efficiency occurs at nanomolar concentra- tions in the case of SNPs and in the micromolar range in the case of silver ions 11 . In addition to antimicrobial activity, the mechanisms of toxicity in the human body are also of paramount importance to understand the pathology caused by SNPs. Hussain et al. 12 evaluated the acute toxicity of SNPs in a rat liver cell line (BRL 3A) at concentrations Proteomic Analysis of Silver Nanoparticle Toxicity in Rat Available online at www.ehs.or.kr