This research offers fundamental and possible breakthrough results that will benefit practical applications in public health and environmental nanotechnology. For first time, mitigation of the negative effects of a common nanoparticle will be studied from the organism side. Results of the work can be adapted to other nanoparticles, such as zero-valent nanoparticles silver nanoparticles, that come into contact with beneficial bacteria commonly present in wastewater treatment systems. This research involves integration of engineering applications, biotechnology, and cellular and molecular microbiology. Broader impacts of the work include support of an institution in an EPSCOR state, training of students inunderrepresented groups inluding native Americans. The research aslso involves the development of novel new technolgy that builds the infrastrucure of science.
Intellectual Merit The project provided fundamental and breakthrough research that benefits practical applications. Currently, impact of nanomaterials on the environment is being investigated widely. The project focused on the next stage which is finding the solution to the impact. For the first time, a mitigation of the negative effect of a common nanomaterial from the organism side was studied. Major factors influencing the protection of microbial cells through polymeric entrapment from carbon nanotubes (CNTs) were elucidated. The results enhanced understanding on the interactions between microbial cells and CNTs, which could lead to more prevention and protection methods, and stimulation of research in different fields. In addition, the results could be adapted to other nanoparticles that could come into contact with beneficial bacteria such as zero-valent iron nanoparticles applied for site remediation and silver nanoparticles commonly present in wastewater treatment systems. Broader Impact The outcomes from the project have an impact on the environment and in turn public health. Nanomaterials are pollutants that could negatively affect ecosystems and engineered systems that involve the beneficial uses of microorganisms. Cell entrapment studied in the project is a biotechnology that could potentially reduce the impact of nanomaterials on microbial cells. The project enhanced the participation of underrepresented groups in science, technology, engineering, and mathematics. A female doctoral student was trained. A research experience was offered to a Native American junior college student. The project required integrated knowledge in engineering applications of biotechnology, and cellular and molecular microbiology. As a result, it promoted a collaborative partnership between a process engineer (main PI) and a microbiologist (co-PI) that are in two different departments and colleges at North Dakota State University. Results from the project will be disseminated via one to two publications (under preparation) in widely circulated journals. Summary The project provided several important outcomes. It offered more understanding on adverse impact of CNTs on bacterial cells. Multiple evidences indicate that both short and long CNTs are toxic to bacterial cells. Long CNTs reduced the viability of bacterial cells more than short CNTs. The negative effects of both short and long CNTs on the viability of cells increase with concentration of CNTs. The degree of impact of CNTs on cell viability was not greatly influenced by the concentration of cells. CNTs physically damage the cells by puncturing cell membrane (Figure 1) and in turn causing the loss of fluid inside the cell and eventually viability. Entrapping cells in porous polymers such as polyvinyl alcohol and alginate can reduce the negative effects from short and long CNTs on cells particularly when the CNT concentration is high. Polyvinyl alcohol can provide better protection to the cells than alginate. The degree of protection of cells by the entrapment decreases with increasing CNT concentration. Entrapped cells are more resistant to short CNTs than long CNTs. The deposition and straining of CNTs on the surface and in the pores of the entrapment matrix limit the physical contact between CNTs and the cells leading to no or less effect on cell viability (Figure 2). Cells that are possibly affected by CNTs can be identified due to an ability to tag CNTs with fluorescence signal (Figure 3). This identification ability is an important step towards more discoveries on the impact of CNTs on cells. The project provided an opportunity for the two PIs that are in two different fields to work together to advance discovery on prevention of impact of CNTs on bacterial cells. A female doctoral student was trained in this project. A Native American college student from a reservation was able to gain research experience through this project (Figure 4).
