Rational Design and Engineering of Graphene-Based Functional Nanocomposites as Effective Antimicrobial Reagents

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The rise and prevalence of antibiotic-resistant bacteria have significantly increased the costs of treatment and, more seriously, death rates. Thus, it is imperative that as these antibiotic-resistant bacteria evolve, so must the medicines that are utilized to treat them. In this research project, Professor Shaowei Chen from the University of California Santa Cruz proposes to use composite materials based on graphene oxide and metal/metal oxide nanoparticles as next-generation, low-cost, potent antimicrobial reagents. This is to take advantage of their synergistic interactions in the bactericidal actions, where the antimicrobial activity of the composites is markedly enhanced as compared to those of the individual components. The success of the proposed research will help establish a unique platform for the development of high-performance antimicrobial reagents. Additionally, the proposed research will offer an educational framework within which student researchers will acquire many complex skills by undertaking an interdisciplinary effort. Also, part of the research activities will be closely integrated with several outreach programs targeting minority, women, and disadvantaged undergraduate students and qualified high-school students. The students will acquire skills that are unattainable in a conventional classroom setting. The hands-on experience and intense training in laboratory research are anticipated to instill a strong sense of self-confidence and good work ethics in their future careers as part of the STEM workforce.The central goal of the proposed research is to advance our understanding of the mechanistic origin of graphene-based nanocomposites in antimicrobial applications and to develop a fundamental framework for the rational design and engineering of nanocomposites based on metal (oxide) nanoparticles and graphene derivatives as low-cost, high-efficiency antimicrobial reagents. There are three specific tasks: (a) design and engineering of graphene nanosheets, where the graphene structures (e.g., size, morphology, surface functionalization) will be systematically manipulated and the impacts on the antimicrobial activity will be carefully examined, (b) preparation of functional nanocomposites based on metal (oxide) nanoparticles deposited on graphene nanosheets, where the nanocomposite photo reactivity will be exploited as a powerful variable in the further manipulation and optimization of the antimicrobial activity, and (c) establishment of a structure-activity correlation by combining (nano)materials and molecular biology approaches, with a focus on unravelling the fundamental mechanisms in the bactericidal process. The proposed research is built upon recent progress in Professor Chen's laboratory where apparent antimicrobial activity was observed with transition-metal nanoparticles as well as graphene quantum dots, with the production of reactive oxygen species identified as the leading mechanism of action. A wide range of experimental tools will be employed in the research activities. For materials characterizations, these include transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, nuclear magnetic resonance, electron paramagnetic resonance, UV-visible, Raman, infrared, and photoluminescence spectroscopy. Using Escherichia coli as the illustrating example, the antimicrobial activity towards the inhibition of bacterial growth will be quantitatively assessed by UV-visible spectroscopic and fluorescence microscopic measurements, and the biochemical origins will be examined by RNA sequencing, within the context of reactive oxygen species generation and bacteria cell membrane damages. A direct, intimate correlation between these two efforts is anticipated to shed light on the mechanisms of action and lead to the establishment of a fundamental framework within which rational design and engineering of graphene-based nanocomposites can be achieved for optimal antimicrobial performance.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.