ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING Asia-Pac. J. Chem. Eng. 2011; 6: 563–568 Published online 4 April 2011 in Wiley Online Library (wileyonlinelibrary.com) DOI:10.1002/apj.581 Commentary The potential biohazards of nanosized wear particles at bone–prosthesis interface Y. F. Zhang, 1 Y.F. Zheng 1 * and L. Qin 2 1 State Key Laboratory for Turbulence and Complex System and Department of Advanced Materials and Nanotechnology, College of Engineering, Peking University, Beijing 100871, P. R. China 2 Musculoskeletal Research Laboratory, Department of Orthopaedics and Traumatology, The Chinese University of Hong Kong, Hong Kong Received 12 January 2011; Revised 24 February 2011; Accepted 28 February 2011 INTRODUCTION Much attention has been paid to the nanoparticles (NPs) that are produced for applications in various areas, such as semiconductor or metallic NPs used in the fabrication of components, polymer additives in packaging, tires or NPs for catalysts or in sun- screen formulations, and oxide NPs applied in our daily life. These NPs are produced in the envi- ronment and may penetrate into the human body through outer-in routes, such as respiratory inhala- tion, gastrointestinal (GL) tract, or dermal and blood circulation. [1,2] However, there are some other ways in which NPs are generated in vivo and make the exposure of NPs different from the external environment and cause dis- tinctive bioeffects. Less well realized by those interested in nanotoxicology is that there is also the possibil- ity of an internal exposure to particles from surgical implants in the orthopedic field (Fig. 1). In this paper, we will mainly address wear debris continuously gen- erated from motion taking place at the articulating sur- faces. Artificial hip joints have been used for endoprosthe- ses since the middle of the last century. Approximately 1 000 000 joints are replaced annually worldwide, with a rising tendency. Metals, ultra high molecular weight polyethylene (UHMWPE), and ceramics are the three main materials used in the design of implant compo- nents for hip and knee replacement. In early 1976, Harris already reported the extensive localized bone resorption resulting in implant loosening without result- ing in infection in hip arthroplasty. After that, aseptic loosening became the most common cause of revision of major arthroplasties. Among various causes result- ing in aseptic loosening, wear particles is the major one *Correspondence to : Y.F. Zheng, State Key Laboratory for Turbu- lence and Complex System and Department of Advanced Materials and Nanotechnology, College of Engineering, Peking University, Beijing 100871, P. R. China. E-mail: yfzheng@pku.edu.cn considered by a majority of orthopedists. The forma- tion and related biological responses of wear particles are major factors determining the longevity of hip and knee arthroplasties. [4] Wear particles from the articulation interface dis- persing into the joint fluid and directly coming in contact with the implant-bed and bone is the major cause leading to the alteration in osteoblast func- tions. It eventually results in abnormal bone for- mation and remodeling between implant and bone. Therefore, research in this area has largely focused on the properties of the retrieved implants. Peripros- thetic tissues; in vivo and in vitro models of implant loosening; and the activities of major participating cells, such as osteoblasts, macrophages, and fibrob- lasts, also become the focus of the related stud- ies. Understanding the NP–cell interaction is critical for the safe development of nanomaterials, and the bio- logical evaluation of NPs have been prone to be a necessity or a pioneering step in interdisciplinary nan- otechnological fields. Much work has been performed to challenge the issue of how to assess the biosafety of these diverse chemicals that humans are potentially exposed to. In this review, we retrospect on the stud- ies dedicated to biological response in joint tissues irritated by particulate debris that consist of metals, polyethylene (PE), and ceramics as the primary cause of periprosthetic osteolysis and the subsequent implant loosening in total joint replacements. Then we also sur- vey the osteo-effects of nanosized wear particles and discuss the NPs’ biohazards when they are exposed within the privileged sites in the human body. We suggest potential future directions in biosafety eval- uations of NPs with attention to nanotoxicology not only from the angle of environmental science but also based on the aspect of biomedical applications, espe- cially in orthopedic surgeries involving metal implanta- tions.  2011 Curtin University of Technology and John Wiley & Sons, Ltd. Curtin University is a trademark of Curtin University of Technology