Growth of Escherichia coli on Biofunctionalized Surfaces of GaAs Elnaz Nazemi (1), Walid M. Hassen (1), Eric H. Frost (1,2), Jan J. Dubowski (1) 1. Interdisciplinary Institute for Technological Innovation (3IT), Laboratory for Quantum Semiconductors and Photon-based BioNanotechnology, Université de Sherbrooke, 3000, boul. de l'Université, Sherbrooke, Québec, J1K 0A5, Canada 2. Department of Microbiology and Infectiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, 3001, 12th Avenue North, Sherbrooke, Québec, J1H 5N4, Canada

Detection of bacteria and monitoring their ability to grow are of great importance in the fields of medicine, pharmaceutical research, water and food industries. In this report, we discuss the capture and growth of Escherichia coli on biofunctionalized GaAs and Au surfaces. We found that neither functionalized GaAs samples nor bare GaAs prevented bacterial growth when initial concentrations of bacteria were at least 105 CFU/mL. At the lower initial concentration of 104 CFU/mL, on the other hand, bacteria did not grow on Au or GaAs surfaces. The initial coverage with bacteria and the subsequent bacterial growth rate are dependent on the biofunctionalization architectures. We employed two architectures based on self-assembled monolayers: 1) polyethylene glycol (PEG) thiols; 2) 16-mercaptohexadecanoic acid thiols. In the first case, a network of biotinylated antibodies against E. coli was deposited on GaAs using biotinylated PEG thiols and neutravidin linkers. In the second case, we employed 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) and N-hydroxysuccinimide (NHS) linkers to facilitate covalent binding of antibodies to the carboxyl-functionalized surface or directly bound E. coli [1]. The PEG-biotin-Neutravidin architecture has been previously reported by

us to detect E. coli suspended in phosphate buffered saline solution [2]. With both of these architectures, we found that the antibody-coated surface was more efficient in capturing bacteria, and it permitted more efficient growth of bacteria, as illustrated in Fig. 1. These results are of importance to the development of photonic methods based, e.g., on the photoluminescence effect, for monitoring in situ biological activities of bacteria in different environments.

[1] R. L. Meyer, X. Zhou, L. Tang, A. Arpanaei, P. Kingshott, F. Besenbacher, "Immobilisation of living bacteria for AFM imaging under physiological conditions," Ultramicroscopy, vol. 110, pp. 1349-1357, 2010.

[2] E. Nazemi, S. Aithal, W. M. Hassen, E. H. Frost, and J. J. Dubowski, "GaAs/AlGaAs heterostructure photonic biosensor for rapid detection of Escherichia coli in phosphate buffered saline solution," Sensors and Actuators B: Chemical, vol. 207, pp. 556–562, 2015.

Keywords: Self-assembled monolayers, GaAs, gold surfaces, Escherichia coli, Bacteria growth, bacteria detection, photonic methods

Figure 1. A microscopic image of bacteria immobilized on the antibody functionalized surface of GaAs after 30 min exposure to bacteria at 106 CFU/mL and growth in Luria Bertani broth for 4.5 hours. The scale bar corresponds to 10 µm. The number of bacteria immobilized on the surface increased from 0.4 bacteria/100 µm2 initially to 3.06 bacteria/100 µm2 after 4.5 hours of growth.