Understand the molecular-level interactions between organisms and nanoparticles to guide the development of environmentally benign nanotechnology
Nanoparticles are increasingly incorporated into everyday consumer goods, such as electric cars and personal electronics batteries (ACS Cent. Sci. 2015, 1, 117-123). They are also utilized in many human health applications, including drug delivery and diagnostics (ACS Infect. Dis. 2018, 12, 1432-1435). Although nanomaterials have helped to advance the fields of energy generation and storage, as well as medicine, little is understood about the downstream effects after they are disposed of or accidently released into the environment. Research in the last decade has found that nanomaterials can be toxic to microorganisms through mechanisms such as heavy metal poisoning, ROS generation, and membrane disruption. Furthermore, nanoparticles often transform after release into the environment through dissolution of the metals and the adsorption of a biomolecular corona. Through a combination of chemical and biological methods, we are working to characterize the molecular-level interactions between nanoparticles and biological systems, ranging from metabolites and proteins to microbes. (Figure 1). This knowledge will inform future disposal policies and enable the design of novel materials that are less toxic and made from greener, more sustainable elements.
In an environmental matrix, pristine nanomaterials transform and acquire a corona of biomolecules, such as proteins, which can sheild the identity of a nanoparticle. Understanding the composition of the corona can provide a better predictor for nanoparticle cellular uptake than bulk properties such as ζ-potential. While the orientation and conformation of bound proteins are thought to be strong indicators of cellular uptake, characterization of corona composition and display remains challenging. We have combined molecular dynamics simulations and mass spectrometry-based protein footprinting to characterize binding of the peripheral membrane protein Cyt c to anionic gold nanoparticles with amino-acid specificity (Figure 2; ACS Nano, 2019, 13, 6856-6866). Both approaches identified specific Cyt c binding sites that facilitated attachment to the nanoparticle surface. We continue to push the boundaries of understanding the relationship between the physicochemical properties of nanoparticles and corona molecules.
Silver-containing particles are widely used as antimicrobial agents and recent evidence indicates that bacteria rapidly become resistant to these nanoparticles. Much less studied is the chronic exposure of bacteria to particles that were not designed to interact with microorganisms. For example, previous work has demonstrated that the lithium intercalated battery cathode nanosheet, nickel manganese cobalt oxide (NMC), is cytotoxic and causes a significant delay in growth of Shewanella oneidensis MR-1 upon acute exposure. Upon chronic exposure, we found that S. oneidensis MR-1 rapidly adapts to NMC and is subsequently able to survive in much higher concentrations of these particles, providing the first evidence of permanent bacterial resistance following exposure to nanoparticles that were not intended as antibacterial agents (Chem. Sci. 2019, 10, 9768-9781). We also found that when NMC-adapted bacteria were subjected to only the metal ions released from this material, their specific growth rates were higher than when exposed to the nanoparticle. As such, were the first to demonstrate bacterial resistance to complex metal oxide nanoparticles with an adaptation mechanism that cannot be fully explained by multi-metal adaptation. Moving forward, we are working to develop a molecular-level understanding of the adaptation process, as well as to evaluate the importance of the genes we found to be mutated in the resistant strain. We will do this through the use of multiple -omics techniques (Figure 3), including activity-based protein profiling, as well as microscopy, biochemistry, cell biology, and genetics to piece together all of the biochemical changes required for bacteria to survive prolonged exposure to toxic nanomaterials.
This work is performed as part of a unique collaborative group, the Center for Sustainable Nanotechnology, which is funded as a Center for Chemical Innovation by the NSF. This multi-investigator project provides the opportunity to collaborate with institutions across the country.
What types of methods will you learn/use on this project?
Mass spectrometry-based proteomics and metabolomics, transcriptomics, nanomaterial characterization, microscopy, microbiology, and biochemistry.