Vertical electric field induced bacterial growth inactivation on amorphous carbon electrodes Shilpee Jain a,d , Ashutosh Sharma b, * , Bikramjit Basu a,c,d, * a Department of Materials Science and Engineering, Indian Institute of Technology, Kanpur, India b Department of Chemical Engineering, Indian Institute of Technology, Kanpur, India c Laboratory for Biomaterials, Materials Research Centre, Indian Institute of Science, Bangalore, India d Interdisciplinary Bio-Engineering Program, Indian Institute of Science, Bangalore, India ARTICLE INFO Article history: Received 29 April 2014 Accepted 16 September 2014 Available online 28 September 2014 ABSTRACT The objective of the present work is to understand the vertical electric field stimulation of the bacterial cells, when grown on amorphous carbon substrates in vitro. In particular, the antibacterial activity against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli are studied using MTT assay, live/dead assay and inner membrane permeabi- lization assays. In our experiments, the carbon substrate acts as one electrode and the counter electrode is positioned outside the culture medium, thus suppressing the current, electrokinetic motions and chemical reactions. Guided by similar experiments conducted in our group on neuroblastoma cells, the present experimental results further establish the interdependence of field strength and exposure duration towards bacterial growth inac- tivation in vitro. Importantly, significant reduction in bacterial viability was recorded at the 2.5 V/cm electric field stimulation conditions, which does not reduce the neural cell viabil- ity to any significant extent on an identical substrate. Following electrical stimulation, the bacterial growth is significantly inhibited for S. aureus bacterial strain in an exposure time dependent manner. In summary, our experiments establish the effectiveness of the vertical electric field towards bacterial growth inactivation on amorphous carbon substrates, which is a cell type dependent phenomenon (Gram-positive vs. Gram-negative). Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction The failure of various biomedical devices is often caused by prosthetic infection mediated by bacterial cell attachment, growth and biofilm formation [1,2]. The retention and survival of adhered bacteria depend on the surface charge, hydropho- bicity/hydrophilicity, chemical composition and surface roughness of the implant [3–5]. Due to adhesion of bacterial cells, eukaryotic cells in the host human tissue need to com- pete with prokaryotic cells (bacterial cells) for the implanted material surface [6,7]. Due to faster growth rate (rate of divi- sion), the formation of a mature biofilm often precede the neotissue formation in vivo, making the implantation sites extremely resistant to antibiotics or host defense mecha- nisms [8]. Thus, in order to achieve appropriate host response, it is essential to design surfaces and processes with dual performance that encourage eukaryotic cell functional- ity (adhesion, proliferation, differentiation etc.) and at the same time prevent bacterial cell attachment. Apart from developing new biomaterial with antibacterial property, a http://dx.doi.org/10.1016/j.carbon.2014.09.048 0008-6223/Ó 2014 Elsevier Ltd. All rights reserved. * Corresponding authors. Address: Materials Research Center, Indian Institute of Science, Bangalore, India (B. Basu). E-mail addresses: ashutos@iitk.ac.in (A. Sharma), bikram@mrc.iisc.ernet.in (B. Basu). CARBON 81 (2015) 193 – 202 Available at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/carbon