Mechanical, material, and antimicrobial properties of acrylic bone cement impregnated with silver nanoparticles Josh Slane a, ⁎, Juan Vivanco b,d , Warren Rose c , Heidi-Lynn Ploeg b , Matthew Squire a a Department of Orthopedics and Rehabilitation, University of Wisconsin–Madison, Madison, WI, USA b Department of Mechanical Engineering, University of Wisconsin-Madison, Madison, WI, USA c School of Pharmacy, University of Wisconsin–Madison, Madison, WI, USA d Facultad de Ingeniería y Ciencias, Universidad Adolfo Ibáñez, Viña del Mar, Chile abstract article info Article history: Received 24 August 2014 Received in revised form 22 October 2014 Accepted 28 November 2014 Available online 2 December 2014 Keywords: Bone cement Infection Nanoparticles Antimicrobial Mechanical properties Prosthetic joint infection is one of the most serious complications that can lead to failure of a total joint replace- ment. Recently, the rise of multidrug resistant bacteria has substantially reduced the efficacy of antibiotics that are typically incorporated into acrylic bone cement. Silver nanoparticles (AgNPs) are an attractive alternative to traditional antibiotics resulting from their broad-spectrum antimicrobial activity and low bacterial resistance. The purpose of this study, therefore, was to incorporate metallic silver nanoparticles into acrylic bone cement and quantify the effects on the cement's mechanical, material and antimicrobial properties. AgNPs at three loading ratios (0.25, 0.5, and 1.0% wt/wt) were incorporated into a commercial bone cement using a probe sonication technique. The resulting cements demonstrated mechanical and material properties that were not substantially different from the standard cement. Testing against Staphylococcus aureus and Staphylococcus epidermidis using Kirby-Bauer and time-kill assays demonstrated no antimicrobial activity against planktonic bacteria. In contrast, cements modified with AgNPs significantly reduced biofilm formation on the surface of the cement. These results indicate that AgNP-loaded cement is of high potential for use in primary arthroplasty where prevention of bac- terial surface colonization is vital. © 2014 Elsevier B.V. All rights reserved. 1. Introduction The development of prosthetic joint infection (PJI) is one of the most devastating complications that can arise after total joint arthroplasty. Although the current incidence rates are 2.0 and 2.4% for hip and knee replacement procedures, these values are projected to steadily increase [1]. The development of PJI can cause severe physical and emotional pain to a patient while simultaneously placing a significant burden on the healthcare system in terms of cost and resource allocation. Often times, PJI is attributable to bacterial colonization through biofilm forma- tion on the implant's surface, which makes treatment with traditional systemic antibiotics exceedingly difficult [2]. In response, one of the most common prophylactic techniques against PJI is to incorporate antibiotics into acrylic (PMMA) bone cement to prevent bacterial colo- nization and proliferation by providing local antibiotic delivery directly at the implant site [3]. The recent rise and spread of multidrug resistant (MDR) microor- ganisms has become a problem of significant importance worldwide. The widespread use of antibiotics over the past several decades has re- sulted in the development of genetic and biochemical mechanisms that allow bacteria to survive in antibiotic environments [4]. There has been significant concern over the efficacy of commonly used antibiotics with- in bone cement, particularly gentamicin, due to the aforementioned rise in MDR microorganisms [5,6]. For example, Hellmark et al. [7] obtained 33 clinical isolates of Staphylococcus epidermidis during PJI revision pro- cedures and found a 79% resistance to gentamicin. Similar results were confirmed by Thornes et al. [8] who noted an increased resistance to gentamicin-loaded Palacos bone cement in a rat model. It is generally accepted that while the use of antibiotic-loaded bone cement reduces the possibility of PJI, there is an increase in the possibility of bacterial re- sistance development [9]. Thus, the problem of reduced antibiotic effi- cacy has created the need to investigate the potential of incorporating new antimicrobials into bone cement [5]. The use of metallic silver as an antimicrobial agent dates back to an- tiquity where it was commonly utilized to preserve drinking water and wine [10], however, the development of more potent antibiotics even- tually displaced the utility of silver in the clinical setting. The availability of silver nanoparticles (AgNPs) has reopened the use of silver in medical applications since the high surface to volume ratio of nanoparticles im- parts unique chemical and physical properties which greatly enhance the antimicrobial effects of silver [11]. Within recent decades, AgNPs have been incorporated into a wide array of consumer and medical products such as fabrics, textiles, plastics, cosmetics, catheters, stents, and wound dressings [12]. Despite this wide usage, the exact mecha- nism behind the antimicrobial properties of silver is still debated. Materials Science and Engineering C 48 (2015) 188–196 ⁎ Corresponding author at: 1513 University Ave, Room 3046, Madison, WI 53706, USA. E-mail address: jaslane@wisc.edu (J. Slane). http://dx.doi.org/10.1016/j.msec.2014.11.068 0928-4931/© 2014 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Materials Science and Engineering C journal homepage: www.elsevier.com/locate/msec