Source: GEORGE WASHINGTON UNIVERSITY submitted to NRP
DEVELOPMENT OF GRAPHITIC-CARBON-NITRIDE-BASED ANTIMICROBIAL NANOMATERIALS FOR SAFE FOOD PROCESSING AND PACKAGING
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
COMPLETE
Funding Source
AFRI COMPETITIVE GRANT
Reporting Frequency
Annual
Accession No.
1012305
Grant No.
2017-67021-26602
Cumulative Award Amt.
$450,200.00
Proposal No.
2016-08785
Multistate No.
(N/A)
Project Start Date
Jul 1, 2017
Project End Date
Jun 30, 2021
Grant Year
2017
Program Code
[A1511]- Agriculture Systems and Technology: Nanotechnology for Agricultural and Food Systems
Recipient Organization
GEORGE WASHINGTON UNIVERSITY
2121 EYE STREET NW SUITE 601
WASHINGTON,DC 20052
Performing Department
CIVIL & ENVIRONMENTAL ENGINEER
Non Technical Summary
Foodborne pathogens raise significant concerns in public health and cause severe economic losses. In the food industry, microbial cross-contamination compromises processed food safety, potentially affecting a very large portion of the population. Food packaging is critical for food storage, handling, and transport, but defected or soiled packages and packaged food spoilage promote further pathogen propagation. We aim to design, fabricate, characterize, and evaluate photocatalytic graphitic carbon nitride (g-C3N4) nanomaterials and their polymer composites as effective, broad-spectrum, sustainable antimicrobials for processing-surface-coating and packaging materials to improve food safety. g-C3N4 activates oxygen gas under indoor visible lighting, producing oxidative species that inactivate a broad range of foodborne pathogens without any net consumption of the photocatalyst. g-C3N4 will also be loaded with silver or copper nanoparticles, enabling antimicrobial activity in the dark when light is not available. The proposed project will not only provide fundamental insights in nanotechnology and microbiology, but will also lay out a systematic design-fabrication-application-evaluation strategy with integrated simulation and experimental approaches for improved food safety and biosecurity.
Animal Health Component
60%
Research Effort Categories
Basic
40%
Applied
60%
Developmental
0%
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
71240992020100%
Knowledge Area
712 - Protect Food from Contamination by Pathogenic Microorganisms, Parasites, and Naturally Occurring Toxins;

Subject Of Investigation
4099 - Microorganisms, general/other;

Field Of Science
2020 - Engineering;
Goals / Objectives
We aim to design, fabricate, and characterize g-C3N4-based photocatalytic nanomaterials and composites for food processing and packaging, and evaluate their antimicrobial performance for foodborne pathogen control under both indoor lighting and dark conditions, as follows: (1) design g-C3N4 nanomaterials and composites by molecular simulations to enhance photocatalytic inactivation of pathogens; (2) determine the key properties of g-C3N4-based photocatalytic nanomaterials and composites that impact performance for pathogen inactivation; (3) understand the mechanisms of nano-g-C3N4-based materials for inactivating pathogens; and (4)predict the development and control of pathogenic biofilms on nano-g-C3N4-based polymer composites according to reactive-transport modeling.
Project Methods
To accomplish the stated objectives, we will undertake the following tasks and methods: (1)tailoring the molecular structure of g-C3N4 nanomaterials to enhance photocatalytic performance through density functional theory based molecular simulations;(2)synthesis of g-C3N4-based photocatalytic nanomaterialsvia thermal polycondensation and solovthermal methods, synthesis ofg-C3N4-based photocatalytic nanocomposites via physical blending, chemical covalent binding, andelectrospinning, and characterization of the nanomaterials and composites;(3)evaluation of antimicrobial performance of nano-g-C3N4-based materials for the inactivation of foodborne pathogens, including planktonic bacteria and biofilms; and (4)reactive-transport model prediction of the development and the control of pathogenic biofilms on nano-g-C3N4 polymer composites.

Progress 07/01/20 to 06/30/21

Outputs
Target Audience:We present our work in 2021 ACS Spring conference by giving an oral presentation. We have also published one research article on the Journal of Hazardous Materials. The audiences include the researchers who attend the conference and who read our paper. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?The project has trained one Ph.D. student. How have the results been disseminated to communities of interest?The results have been published on the Journal of Hazardous Materials and presented in 2021 ACS Spring Meeting. What do you plan to do during the next reporting period to accomplish the goals?The project is ended this year.

Impacts
What was accomplished under these goals? We have fabricated chitosan-graphitic carbon nitride composite films to inactivate a broad spectrum of pathogenics, including Staphylococcus epidermidis, Pseudomonas aerugionosa, and Escherichia coli O157:H7 that is an important foodborne pathogen. We have also evaluated the antimicrobial performance of the composite films for inactivating complex biofilms (developed from urine) to demontraste the reactivity of these films. We characterize composite properties, biofilm properties, and composite-biofilm interactions to identify the key properties that determine the antimicrobial performance.

Publications

  • Type: Journal Articles Status: Published Year Published: 2021 Citation: Shen, H., Durkin, D. P., Aiello, A., Diba, T., Lafleur, J., Zara, J. M., Shen, Y., Shuai, D. Photocatalytic Graphitic Carbon Nitride-Chitosan Composites for Pathogenic Biofilm Control under Visible Light Irradiation. J. Hazard. Mater. 2021, 408, 124890.


Progress 07/01/17 to 04/02/21

Outputs
Target Audience:We have published four research articles on ACS Applied Materials & Interfaces, Nanoscale, Applied Catalysis B: Environmental, and Journal of Hazardous Materials, and we have given several conference presentations in ACS, AEESP, Gordon conference, ASM conferences, MoBE conference, etc. The broad audiences include scientists and engineers in agricultural engineering, food microbiology, food safety, environmental engineering, nanotechnology, and catalysis. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?We have trained two Ph.D. students in environmental engineering. How have the results been disseminated to communities of interest?We have published four research articles in ACS Applied Materials & Interfaces, Applied Catalysis B: Environmental, Nanoscale, and Journal of Hazardous Materials, and have presented our research in a number of conferences including ACS, AEESP, ASM, Gordon, and MoBE conferences. The audiences include scientists and engineers from diverse fields, including but not limited to agricultural engineering, food safety, food microbiology, environmental engineering, nanotechnology, and catalysis. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? We have design graphici carbon nitride nanomaterials and composites that show enhanced performance for pathogen control, and we have also systematically characterize the nanomaterials/composites and biofilms, including physical, chemical, biological, and mechanical properties, to understand how and why the nanomaterial/composites can kill pathogenic biofilms. Pathogenic biofilms raise significant health and economic concerns, because these bacteria are persistent and can lead to foodborne diseases or diseas outbreaks. Compared with conventional antimicrobial strategies, photocatalysis holds promise for biofilm control because of its broad-spectrum effectiveness under ambient conditions, low cost, easy operation, and reduced maintenance. In our study, we first investigated the performance and mechanism of Staphylococcus epidermidis biofilm control and eradication on the surface of an innovative photocatalyst, graphitic carbon nitride (g-C3N4), under visible light irradiation, which overcame the need for ultraviolet (UV) light for many current photocatalysts (e.g., titanium dioxide (TiO2)). Optical coherence tomography (OCT) and confocal laser scanning microscopy (CLSM) suggested that g-C3N4 coupons inhibited biofilm development and eradicated mature biofilms under the irradiation of white light-emitting diodes (LEDs). Biofilm inactivation was observed occurring from the surface towards the center of the biofilms, suggesting that the diffusion of reactive species into the biofilms played a key role. By taking advantage of scanning electron microscopy (SEM), CLSM, and atomic force microscopy (AFM) for biofilm morphology, composition, and mechanical property characterization, we demonstrated that photocatalysis destroyed the integrated and cohesive structure of biofilms and facilitated biofilm eradication by removing the extracellular polymeric substances (EPS). Moreover, reactive oxygen species (ROS) generated during g-C3N4 photocatalysis were quantified via reactions with radical probes, and 1O2 was believed to be responsible for biofilm control and removal. We next fabricated visible-light-responsive composites of carbon-doped graphitic carbon nitride and chitosan with high reactivity and processability. The broad-spectrum biofilm inhibition and eradication of the photocatalytic composites against Staphylococcus epidermidis, Pseudomonas aeruginosa PAO1, and Escherichia coli O157: H7 under visible light irradiation were demonstrated. Extracellular polymeric substances in Escherichia coli O157: H7 biofilms were most resistant to photocatalytic oxidation, which led to reduced performance for biofilm removal. 1O2 produced by the composites was believed to dominate biofilm inactivation. Moreover, the composites exhibited excellent performance for inhibiting biofilm development in urine, highlighting the promise for inactivating environmental biofilms developed from multiple bacterial species. Our study provides fundamental insights into the development of new photocatalytic composites, and elucidates the mechanism of how the photocatalyst reacts with a microbiological system. Moreover, we explored the mechanism of biofilm removal with respect to biofilm mechanical properties. Biofilms are a cluster of bacteria embedded in EPSthat contain a complex composition of polysaccharides, proteins, and extracellular DNA (eDNA). Desirable mechanical properties of the biofilms are critical for their survival, propagation, and dispersal, and the response of mechanical properties to different treatment conditions also sheds light on biofilm control and eradication in vivo and on engineering surfaces. However, it is challenging yet important to interrogate mechanical behaviors of biofilms with a high spatial resolution because biofilms are very heterogeneous. Moreover, biofilms are viscoelastic, and their time-dependent mechanical behavior is difficult to capture. Herein, we developed a powerful technique that combines the high spatial resolution of the atomic force microscope (AFM) with a rigorous history-dependent viscoelastic analysis to deliver highly spatial-localized biofilm properties within a wide time-frequency window. By exploiting the use of static force spectroscopy in combination with an appropriate viscoelastic framework, we highlight the intensive amount of time-dependent information experimentally available that has been largely overlooked. It is shown that this technique provides a detailed nanorheological signature of the biofilms even at the single-cell level. We share the computational routines that would allow any user to perform the analysis from experimental raw data. The detailed localization of mechanical properties in space and in time-frequency domain provides insights on the understanding of biofilm stability, cohesiveness, dispersal, and control. Our work highlights the promise of using g-C3N4 for a broad range of antimicrobial applications, especially for the eradication of persistent biofilms under visible light irradiation, which holds promise for food industry applications. We have also elucidate the mechanism of biofilm removal, in terms of ROS production, bacterial inactivation and EPS removal, and reduced cohesiveness of biofilms.

Publications

  • Type: Journal Articles Status: Published Year Published: 2021 Citation: Shen, H., Durkin, D. P., Aiello, A., Diba, T., Lafleur, J., Zara, J. M., Shen, Y., Shuai, D. Photocatalytic Graphitic Carbon Nitride-Chitosan Composites for Pathogenic Biofilm Control under Visible Light Irradiation. J. Hazard. Mater. 2021, 408, 124890.
  • Type: Journal Articles Status: Published Year Published: 2019 Citation: Shen, H., Lo?pez-Guerra, E. A., Zhu, R., Diba, T., Zheng, Q., Solares, S. D., Zara, J. M., Shuai, D., Shen, Y. Visible-light-responsive Photocatalyst of Graphitic Carbon Nitride for Pathogenic Biofilm Control. ACS Appl. Mater. Interfaces 2019, 11 (1), 373384.
  • Type: Journal Articles Status: Published Year Published: 2019 Citation: Zheng, Q., Xu, E., Park, E., Chen, H., Shuai, D. Looking at the Overlooked Hole Oxidation: Photocatalytic Transformation of Organic Contaminants on Graphitic Carbon Nitride under Visible Light Irradiation. Appl. Catal. B 2019, 240, 262-269.
  • Type: Conference Papers and Presentations Status: Accepted Year Published: 2021 Citation: Shen, H., Shuai, D., Durkin, D. P., Aiello, A., Diba, T., Lafleur, J., Zara, J. M., Shen, Y. Visible-light-responsive Graphitic Carbon Nitride/Chitosan Composite Films for Antimicrobial Packaging, ACS Spring Meeting, USA, 04/2021. ORAL
  • Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: Shen, H., Shuai, D., Shen, Y. Visible-Light-Responsive Photocatalytic Nanomaterial Graphitic Carbon Nitride for Biofilm Control, AEESP Conference, Tempe, AZ, USA, 05/2019. ORAL
  • Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: Shen, H., Shuai, D., Shen, Y. Visible-light-responsive Photocatalyst of Graphitic Carbon Nitride for Biofilm Control, ACS Spring Meeting, Orlando, FL, USA, 04/2019. ORAL
  • Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Shen, H., Shuai, D., Shen, Y. Visible-light-responsive Photocatalyst of Graphitic Carbon Nitride Nanomaterials for Pathogenic Biofilm Control, 2018 SNO Conference, Washington, DC, USA, 11/2018. ORAL
  • Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Lo?pez-Guerra, E. A., Shen, H., Solares, S. D., Shuai, D. Measuring the Viscoelastic Properties of Biofilms with 4D Atomic Force Microscopy, 8th ASM Conference on Biofilms, Washington, DC, USA, 10/2018. POSTER
  • Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Shen, H., Lo?pez-Guerra, E. A., Zhu, R., Diba, T., Zheng, Q., Solares, S. D., Zara, J. M., Shuai, D., Shen, Y. Visible-light-responsive Photocatalyst of Graphitic Carbon Nitride for Pathogenic Biofilm Control, 8th ASM Conference on Biofilms, Washington, DC, USA, 10/2018. POSTER
  • Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Shen, H., L�pez-Guerra, E. A., Diba, T., Solares, S. D., Zara, J. M., Shuai, D. Visible-light-responsive Graphitic Carbon Nitride Nanomaterials for Biofilm Control, Gordon Research Conference: Nanoscale Science and Engineering for Agriculture and Food Systems, South Hadley, MA, USA, 06/2018. POSTER
  • Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Shen, H., L�pez-Guerra, E. A., Diba, T., Solares, S. D., Zara, J. M., Shuai, D. Visible-light-responsive Graphitic Carbon Nitride Nanomaterials for Biofilm Control, Gordon Research Seminar: Nanoscale Science and Engineering for Agriculture and Food Systems, South Hadley, MA, USA, 06/2018. ORAL
  • Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Shen, H., Shuai, D. Visible-Light-Responsive Photocatalytic Graphitic Carbon Nitride for Antimicrobial Applications, ACS Spring Meeting, New Orleans, LA, USA, 03/2018. ORAL
  • Type: Conference Papers and Presentations Status: Published Year Published: 2017 Citation: Shen, H., Shuai, D. Graphitic Carbon Nitride Nanomaterials for Sustainable Antimicrobial Applications, MoBE 2017, Washington, DC, USA, 10/2017. POSTER
  • Type: Conference Papers and Presentations Status: Published Year Published: 2017 Citation: Shen, H., Shuai, D. Visible-Light-Responsive Photocatalytic Graphitic Carbon Nitride for Antimicrobial Applications, AEESP Conference, Ann Arbor, MI, USA, 06/2017. ORAL
  • Type: Conference Papers and Presentations Status: Published Year Published: 2017 Citation: Shen, H., Shuai, D. Antimicrobial Applications of Visible-Light-Responsive Photocatalysts, ACS Spring Meeting, San Francisco, CA, USA, 04/2017. ORAL
  • Type: Journal Articles Status: Published Year Published: 2019 Citation: Lo?pez-Guerra, E. A., Shen, H., Solares, S. D., Shuai, D. Acquisition of Time-frequency Localized Mechanical Properties of Biofilms and Single Cells with High Spatial Resolution. Nanoscale 2019, 11, 8918-8929.


Progress 07/01/19 to 06/30/20

Outputs
Target Audience:The knowledge of nanotechnology for food safety has been integrated in some lectures for CE 3520 Environmental Engineering I for undergraduate students at The George Washington University (GW). The project has also trained a Ph.D. student in the Department of Civil and Environmental Engineering at GW. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?We have trained one graduate studentunder the project, for the fabrication of graphitic carbon nitride-chitosan composite filmand the application for antimicrobial applications. The graduate student has learned the techniques for material fabrication and characterization, and biofilm development and characterization. How have the results been disseminated to communities of interest?We have presented our work at several conferences, such as 2019 AEESP conference, in front of the communities of environmental scientists and engineers, agricutural and food scientists and engineers, microbiologists, and chemists. The PD was also invited to present the work at different universities, and the audient includes the faculty, undergraduates, and graduates in chemical and biochemical engineering, environmental engineering, and civil engineering. What do you plan to do during the next reporting period to accomplish the goals?We are planning to utilize transcriptomics to understand how photocatalyst interact with pathogenic biofilms, which will provide guidelines for rational material design for biofilm control.

Impacts
What was accomplished under these goals? We have fabricated a highly reactive composite film with graphitic carbon nitride and chitosan, and it has the potential for being used as an anitmicrobial food packaging material. Briefly, chitosan was mixed withgraphitic carbon nitride from melamine, cyanuric acid, and barbituric acid, and the polymer composite was casted to form an antimicrobial film. We have tested the performance of the film for biofilm control and eradication forStaphylococcus epidermidis, Pseudomonas aeruginosa, and Escherichia coli O157:H7 (a well-known foodborne pathogen), and they also showed promising results in both PBS and nutrient rich conditions under the irradiation of white LED lights.By taking advantage of scanning electron microscopy and confocal laser scanning microscopyfor biofilm morphology and compositioncharacterization, we demonstrated that photocatalysis destroyed the integrated and cohesive structure of biofilms and facilitated biofilm eradication by removing the extracellular polymeric substances.Moreover, reactive oxygen species generated during photocatalysis were quantified via reactions with radical probes and 1O2 was believed to be responsible for biofilm control and removal. The radical production of the composite film is on par with that of pure graphitic carbon nitride coupons.

Publications

  • Type: Journal Articles Status: Other Year Published: 2020 Citation: Graphitic Carbon Nitride-Chitosan Composite for Broad-Spectrum Pathogenic Biofilm Control (To be submitted)
  • Type: Conference Papers and Presentations Status: Accepted Year Published: 2019 Citation: Shen, H., Shuai, D., Shen, Y. Visible-Light-Responsive Photocatalytic Nanomaterial Graphitic Carbon Nitride for Biofilm Control, AEESP Conference, Tempe, AZ, USA


Progress 07/01/18 to 06/30/19

Outputs
Target Audience:The knowledge of nanotechnology for food safety has been integrated in some lectures for CE 3520 Environmental Engineering I for undergraduate students at The George Washington University (GW). Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?We have trained one graduate studentunder the project, for the fabrication of graphitic carbon nitride and the application for antimicrobial applications, as well as atomic force microscopic characterization of biofilms. The graduate student haslearned the techniques for material fabrication and characterization, and biofilm development and characterization. How have the results been disseminated to communities of interest?We have presented our work at several conferences, including 2018 SNO conference, 2018 Gordon conference, and 2019 ACS conference,in front of the communities of environmental scientists and engineers, agricutural and food scientists and engineers,microbiologists, and chemists. The PD was also invited to present the work at different universities, and the audient includes the faculty, undergraduates, and graduates in chemical and biochemical engineering, environmental engineering, and civil engineering. What do you plan to do during the next reporting period to accomplish the goals?1. We will fabricate graphtiic carbon nitride-polymer composite for antimicrobial applications, including the inactivation of bacterial and viral pathogens; 2. We will understand the physical, chemical, and biological response of biofilms under oxdative stress in photocatalysis.

Impacts
What was accomplished under these goals? We have fabricated a highly reactive photocatalytic graphitic carbon nitride from melamine, cyanuric acid, and barbituric acid, and tested its antimicrobial performance forbiofilm Staphylococcus epidermidis (S. epidermidis). Key properties of the photocatalytic material has been identified, and the mechanisms of biofilm control has been elucidated.Optical coherence tomography and confocal laser scanning microscopy (CLSM) suggested that g-C3N4coupons inhibited biofilm development and eradicated mature biofilms under the irradiation of white light-emitting diodes. Biofilm inactivation was observed occurring from the surface toward the center of the biofilms, suggesting that the diffusion of reactive species into the biofilms played a key role. By taking advantage of scanning electron microscopy, CLSM, and atomic force microscopy for biofilm morphology, composition, and mechanical property characterization, we demonstrated that photocatalysis destroyed the integrated and cohesive structure of biofilms and facilitated biofilm eradication by removing the extracellular polymeric substances. Moreover, reactive oxygen species generated during g-C3N4 photocatalysis were quantified via reactions with radical probes and1O2was believed to be responsible for biofilm control and removal. In addition,we developed a powerful technique that combines the high spatial resolution of the atomic force microscope(AFM) with a rigorous history-dependent viscoelastic analysis to deliver highly spatial-localized biofilm properties within a wide time-frequency window. By exploiting the use of static force spectroscopy incombination with an appropriate viscoelastic framework, we highlight the intensive amount of timedependent information experimentally available that has been largely overlooked. It is shown that this technique provides a detailed nanorheological signature of the biofilms even at the single-cell level. We share the computational routines that would allow any user to perform the analysis from experimental rawdata. The detailed localization of mechanical properties in space and in time-frequency domain providesinsights on the understanding of biofilm stability, cohesiveness, dispersal, and control.

Publications

  • Type: Journal Articles Status: Published Year Published: 2019 Citation: Shen, H., Lo?pez-Guerra, E. A., Zhu, R., Diba, T., Zheng, Q., Solares, S. D., Zara, J. M., Shuai, D., Shen, Y. Visible-light-responsive Photocatalyst of Graphitic Carbon Nitride for Pathogenic Biofilm Control. ACS Appl. Mater. Interfaces 2019, 11 (1), 373384.
  • Type: Journal Articles Status: Published Year Published: 2019 Citation: Lo?pez-Guerra, E. A., Shen, H., Solares, S. D., Shuai, D. Acquisition of Time-frequency Localized Mechanical Properties of Biofilms and Single Cells with High Spatial Resolution. Nanoscale. DOI: 10.1039/C8NR10287B
  • Type: Conference Papers and Presentations Status: Published Year Published: 2019 Citation: Shen, H., Shuai, D., Shen, Y. Visible-light-responsive Photocatalyst of Graphitic Carbon Nitride for Biofilm Control, ACS Spring Meeting, Orlando, FL, USA, 04/2019. ORAL
  • Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Shen, H., Shuai, D., Shen, Y. Visible-light-responsive Photocatalyst of Graphitic Carbon Nitride Nanomaterials for Pathogenic Biofilm Control, 2018 SNO Conference, Washington, DC, USA, 11/2018. ORAL
  • Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Lo?pez-Guerra, E. A., Shen, H., Solares, S. D., Shuai, D. Measuring the Viscoelastic Properties of Biofilms with 4D Atomic Force Microscopy, 8th ASM Conference on Biofilms, Washington, DC, USA, 10/2018. POSTER
  • Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Shen, H., Lo?pez-Guerra, E. A., Zhu, R., Diba, T., Zheng, Q., Solares, S. D., Zara, J. M., Shuai, D., Shen, Y. Visible-light-responsive Photocatalyst of Graphitic Carbon Nitride for Pathogenic Biofilm Control, 8th ASM Conference on Biofilms, Washington, DC, USA, 10/2018. POSTER
  • Type: Conference Papers and Presentations Status: Accepted Year Published: 2018 Citation: Shen, H., L�pez-Guerra, E. A., Diba, T., Solares, S. D., Zara, J. M., Shuai, D. Visible-light-responsive Graphitic Carbon Nitride Nanomaterials for Biofilm Control, Gordon Research Seminar: Nanoscale Science and Engineering for Agriculture and Food Systems, South Hadley, MA, USA, 06/2018. ORAL


Progress 07/01/17 to 06/30/18

Outputs
Target Audience: The knowledge of nanotechnology for food safety has been integrated in some lectures for CE 3520 Environmental Engineering I for undergraduate students at The George Washington University (GW). Our research group started the collaboration with Behmis Company, Inc, a leading manufacturer of packaing for healthcare and food, and is incoporating our photocatalytic nanomaterials into the packaging materials and testing their performance for antimicrobial applications. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?We have trained two graduate students under the project, for the fabrication of graphitic carbon nitride and the application for antimicrobial applications. The graduate students have learned the techniques for material fabrication and characterization, and biofilm development and characterization. How have the results been disseminated to communities of interest?We have presented our work at several conferences, including 2017 AEESP conference, 2017 MoBE conference, and 2018 ACS conference, in front of the communities of environmental scientists and engineers, microbiologists, and chemists. The PD was also invited to present the work at different universities, and the audient includes the faculty, undergraduates, and graduates in chemical and biochemical engineering, environmental engineering, earth sciences, and civil engineering. Graduate students also presented the work in GW SEAS 2018 showcase, where a broad range of audiences from engineering attended. What do you plan to do during the next reporting period to accomplish the goals? We will look into biofilm mechanics (characterized by atomic force microscopy), and correlate it with biofilm control on graphitic carbon nitride. We will identify how biofilm mechanical properties respond to ROS (via chemical oxidation of EPSs or biological control of EPS production) and how photocatalysis can inactivate biofilms. We will fabricate new graphitic nitride that produces more hydrogen peroxide for biofilm control. We will explore how bacteria that produce different amount of EPSs respond to ROS in photocatalysis.

Impacts
What was accomplished under these goals? We have fabricated a highly reactive photocatalytic graphitic carbon nitride from melamine, cyanuric acid, and barbituric acid, and tested its antimicrobial performance for planktonic bacterial Escherichia coli (E. coli)and biofilm Staphylococcus epidermidis (S. epidermidis). Key properties of the photocatalytic material has been identified, and the mechanisms of biofilm control is being elucidated. The photocatalytic material was fabricated from 2 g of melamine, 2 g of cyanuric acid, and 0.07 g of barbituric acid under heating at 520 oC, and it exhibited the best performance for bacterial inactivation. The surface area and charge separation rate were the most important factors that determined photocatalytic activity, and the introduction of cyanuric acid and barbituric acid improved these two properties. PlanktonicE. coli was observed for 2.27 log inactivation under visible light irradiation (white LED irradiation), whereas no inactivation was observed in control experiments when the photocatalyst or light was absent. Biofilms were developed in dark on the surface of the photocatalyst, however no biofilm was formed under continous white LED irradiation and the mature biofilm was eradicated and killed under the exposure of white LED irradiation. These experiments demonstrated that the photocatalytic graphitic carbon nitride inactivated planktonic cells and biofilms under visible light irradiation or potential indoor lighting. Biofilm eradiation kinetics was evaluated, by evaluating biofim viability under visible light irradiation on graphitic carbon nitride for different durations. The results suggested that reactive oxygen species (ROS) generated by graphitic carbon nitride diffused into and killed the biofilm. The key ROS were evaluated, and we believed that hydrogen peroxide was the critical ROS that inactivated biofilms. Extracellular polymeric substances (EPSs) were also investigated, and the results indicated that the content of EPSs decreased in biofilm eradication. These results highlighted the mechanism of biofilm control on graphitic carbon nitride under visible light irradiation, and they provide insights for advancing material design for food safety control applications.

Publications

  • Type: Conference Papers and Presentations Status: Published Year Published: 2017 Citation: Visible-Light-Responsive Photocatalytic Graphitic Carbon Nitride for Antimicrobial Applications, 2017 AEESP Conference
  • Type: Conference Papers and Presentations Status: Published Year Published: 2017 Citation: Graphitic Carbon Nitride Nanomaterials for Sustainable Antimicrobial Applications, MoBE 2017
  • Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Visible-Light-Responsive Photocatalytic Graphitic Carbon Nitride for Antimicrobial Applications, 2018 ACS Spring Meeting