Corrigendum Corrigendum to ‘‘The role of ROS generation from magnetic nanoparticles in an alternating magnetic field on cytotoxicity” [Acta Biomater. 25 (2015) 284–290] Anastasia K. Hauser a , Robert J. Wydra a , Rohit Bhandari a , Piotr G. Rychahou b , B. Mark Evers b,c , Kimberly W. Anderson a , Thomas D. Dziubla a , J. Zach Hilt a,⇑ a Department of Chemical and Materials Engineering, University of Kentucky, Lexington, KY 40506, USA b Department of Surgery, College of Medicine, University of Kentucky, Lexington, KY 40506, USA c Markey Cancer Center, University of Kentucky, Lexington, KY 40506, USA The authors regret that the flow cytometry studies and associ- ated data (Figs. 5 and 6) in the above-mentioned article were found to have errors during follow-up work. Thus, these studies have been repeated. Since there were adjustments to the methods, the new section 2.6. that accurately describes the updated procedures is included below. 2.6. Cellular response to alternating magnetic field CT26 cells were seeded in 6 well plates at 110,000 cells/ml (2 ml/well). Nanoparticle suspensions of 5 mg/ml in DMSO were diluted in cell culture media to a concentration of 200 lg/ml iron oxide. These were new batches of the three nanoparticle systems that were characterized and found to have similar properties as those reported in the original paper, with minor differences attrib- uted to batch-to-batch variability. The cells were exposed to the nanoparticle systems for 2 h followed by media removal, washing 2 with PBS, and detachment with trypsin. Cells were split into samples with and without field exposure and exposed to 50 lM 6-carboxy-2 0 -7 0 -dichlorodihydro fluorescein diacetate (carboxy- DCFDA) (Invitrogen). Cells were incubated at 37 °C for 30 min to facilitate stain internalization, exposed to the alternating magnetic field for 30 min (Taylor Winfield magnetic induction source; approximately 60 kA/m in strength at 292 kHz frequency), then returned to the incubator for 30 min post incubation. Cells were analyzed using Accuri C6 flow cytometer (BD Biosciences, San Jose, CA). A ratio of the mean fluorescence between samples exposed to the AMF and the samples that remained in the incubator was used to determine the enhanced ROS generation attributed to the nanoparticles in the AMF. To determine the effects of the combined treatment, a caspase 3/7 apoptosis assay (Invitrogen) was utilized. Following cell exposure to the iron oxide nanoparticles (IONP) systems (same procedure as previously described), the cells were detached and half were treated with an AMF (60 kA/m and 292 kHz) for 30 min while the other half remained in the incubator. After treatment, the cells were incubated for 30 min, 12 or 24 h. At the specified time points, the cells were centrifuged, re-suspended in PBS, and the caspase 3/7 assay was completed per manufacturer’s instruc- tions. Caspase 3/7 activity was analyzed using flow cytometry (FL-1). After further investigation into the apoptosis assay, the analysis method stated in the original manuscript was altered. A non-apoptotic (low FL-1) and an apoptotic (high FL-1) population resulted, and these two populations were gated appropriately. Therefore, the data in Fig. 6 is reported as percent apoptosis at the various time points following treatment. The updated Figs. 5 and 6 and the associated discussion are included below. Fig. 5 displays the ROS enhancement ratio via AMF exposure of CT26 exposed to the various IONP systems. Exposure of control cells to the AMF does not result in an increase in ROS generation. There appears to be an increase in ROS generation in cells exposed to uncoated IONPs and glucose coated IONPs although not statisti- cally significant. Upon exposure to the AMF, cells exposed to citric acid coated IONPs experienced the greatest ROS enhancement, and this was significantly greater ROS production than the control. The caspase 3/7 apoptosis assay was completed to determine the effects of increased ROS production via cells containing IONPs in the presence of an AMF. Fig. 6 displays the percent apoptosis of cells exposed to the various IONP systems with and without 30 min AMF exposure when analyzed 30 min, 12 and 24 h post treatment. At the original apoptosis analysis time of 30 min post treatment, the combination of IONPs and AMF did not enhance apoptosis in CT26 cells exposed to any of the IONP systems. There- fore, the time after treatment was increased to allow the cells time to respond to the injury and for cells at different stages of the cell cycle to enter apoptosis upon reaching G1 or G2 checkpoints [1]. All the IONP systems combined with AMF exposure significantly increase apoptosis in CT26 cells compared to no AMF exposure http://dx.doi.org/10.1016/j.actbio.2015.10.009 1742-7061/Ó 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. DOI of original article: http://dx.doi.org/10.1016/j.actbio.2015.06.037 ⇑ Corresponding author at: Department of Chemical and Materials Engineering, University of Kentucky, 177 F. Paul Anderson Tower, Lexington, KY 40506-0046, USA. E-mail address: hilt@engr.uky.edu (J.Z. Hilt). Acta Biomaterialia 33 (2016) 322–323 Contents lists available at ScienceDirect Acta Biomaterialia journal homepage: www.elsevier.com/locate/actabiomat