CAREER: Nanoscale Interactions of Stimuli-responsive Nanoparticles with Enzymes

About This Grant

Living cells use enzymes to perform numerous biological functions. These enzymes work on cellular targets which are extremely small in size, oftentimes measured at the nanometer (one billionth of a meter) length scale. This CAREER project aims to understand the fundamental mechanisms of how enzyme-sensitive, nanoscale materials interact with an enzyme. This goal will be realized by developing nanoparticles, which respond to a particular class of enzymes by changing particle size and function. Further, these particles will mimic the function of a naturally occurring, enzyme-sensitive protein – histone – that is found in cells. The developed platform will therefore answer several fundamental questions related to enzyme actions at the nanoscale, such as (1) How nanoparticles selectively interact with a target enzyme and reject interactions with other macromolecules in the complex biological environment ? and (2) How to regulate the rate and extent of enzyme responsivity of nanoscale materials via engineering their size, shape, surface properties, and chemical composition? An in-depth understanding of the structure and function of enzyme-sensitive nanoparticles will open the gateway to designing smart nanomaterials capable of selectively recognizing a specific enzyme. These nano-platforms would then provide tools and techniques to prepare cancer drug delivery systems, diagnostic agents for neurodegenerative diseases, biosensing technologies, and mechanisms for pollution control. The educational goal of the CAREER project has three-pronged approaches centered on Tribal Colleges and Primary Undergraduate Institutes across North Dakota. The approach is aimed to increase inclusivity and minimize the loss of Native American students in higher education. The educational activity will include (1) peer-to-peer collaboration with at least eight Tribal College and Primarily Undergraduate Institution mentors over the project period to revitalize the learning resources of these institutes for STEM education, (2) curriculum development for the North Dakota State University engineering graduate program, and (3) increased research involvement of undergraduates from underprivileged areas across North Dakota. The research activity delineated in this project will thus expand the scope of training in nanoscale interactions and contribute to a robust supply of professionals needed in STEM research at the national level. The overarching goal of this CAREER project is to deconvolute and understand the events occurring when an enzyme interacts with an Enzyme-Responsive Polymersome. Polymersomes are nanoscale, membrane-bound vesicles formed via the self-assembly of amphiphilic block copolymers that constitutes their membranes. Using a model enzyme with epigenetic activity, histone deacetylase, the principal investigator aims to study the effect of chemical composition and nanoscale features of polymersomes that are capable of recognizing target enzymes and rejecting interactions with off-target biomacromolecules. Developing platforms to study enzyme interactions with dynamically-responsive nanosystems is challenging because (1) accessibility of an enzyme to its nanoparticle-bound substrates depends not only on the particle size and charge but also on molecular crowding and conformation; (2) the mechanism of enzyme interactions with substrates at the nanoscale is transient downstream of specific environmental cues, and (3) extracting molecular level structure/dynamics information at the nano-bio interface under the interference of surrounding molecules is non-trivial. Given the increasing need for biomolecular delivery platforms for therapeutics, agrochemicals, environmental remediation, and synthetic materials that mimic cellular organelles, there is a critical need to overcome these challenges. Three strategies will be realized to achieve the goal of this CAREER project: first, the PI will mimic the enzyme-responsivity pattern of a histone — an acetylated lysine-bearing natural protein of well-defined size and structure, found in living cells that interacts with different epigenetic enzymes, such as histone deacetylase; second, the mechanism of the enzyme interactions on this histone-mimetic nanoplatform, mediated by deacetylation reaction (removal of acetyl groups from primary amines of lysine residues) will be structurally followed and established. third, synthetic and experimental techniques capable of orthogonally detecting molecular-level interactions will be used to dissect the interactions of nanoparticles with enzymes in contact with each other. The central hypothesis of this research activity is that structural and functional changes of enzyme-responsive polymersomes in response to epigenetic enzymes are mediated mechanistically via the inversion of solubility of the hydrophobic and hydrophilic segment of the amphiphilic block copolymers in water and governed by the enzyme accessibility to its substrate located within the nanostructure. The main teaching philosophy of PI’s educational plan involves connecting with mentors serving tribal colleges and primary undergraduate institutes across the state of North Dakota via an immersive ‘Mentor- to-Mentor” program for the continuation and reinforcement of STEM training in these institutes. Further, the research elements of nanoparticle-enzyme interactions will be bridged with engineering graduate curriculum development in the PI’s home institute that will be harnessed to improve enrollments of under-represented minorities in 4-year graduate schools. 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.