(4dt) Multifunctional Polymeric Nanomaterials for Environmental and Biomedical Applications

Simple and accurate detection of heavy metals and biomolecules including DNA, protein, and microorganisms are of interest in environmental and biomedical applications.  Use of nanotechnology is especially promising for advances in this area.  My current and past work has combined polymer science, nanotechnology and biotechnology in order to functionalize nanomaterials with biomolecules.   Building on this experience, the goal of my proposed research is to develop multifunctional polymer-based nanomaterials for detection of heavy metals and biomolecules based on fundamental understanding of material interactions.  These advanced functional materials may have a variety of potential applications ranging from water purification to clinical lab diagnostics i.e. in biomarker research, cancer diagnostics, and detection of infectious diseases. 

In my graduate work at North Carolina State University working under the direction of Dr. Saad Khan, the goal of my research was to capitalize on the high specific surface area of nanofibers as well as the advantages of biocatalysts by immobilizing proteins/enzymes within chemically crosslinked polymer nanofibers.  Surprisingly, despite the short length scale, the catalytic activity of the enzyme within the nanofiber was significantly affected by diffusion limitations.  Thus, surface modification of nanofibers should provide a route to improved performance of the biomolecule.  Based on the understanding gained, nanofibers with various surface chemistries can be produced by electrospinning and functionalization with biomolecules such as oligionucleotides or antibodies for highly specific capture of molecules of interest e.g. bacterial pathogens.  For example, nanofibers can be produced from polymers with an amine containing backbone such as chitosan which can used to attach antibodies of interest through bifunctional reagents such as glutaraldehyde.  Chelators can also be employed for capture of heavy metals, e.g. deferoxamine for detection of iron can be attached using the same chemistry.  The surface chemistry of the fibers can be modified to accommodate other molecules of interest. Further, by combining the biomolecules of interest or chelators with fluorophores, bifunctional materials capable of capture and detection can be achieved. 

Multifunctional polymer nanoparticles are also of potential use in sensing applications.  As a Postdoctoral Associate working with Dr. Prud’homme at Princeton University, I have been developing nanoparticles for use as contrast agents in diagnostic medical imaging applications using Flash Nanoprecipitation (FNP).  In FNP, amphiphilic block copolymers direct self-assembly of biocompatible nanoparticles with high concentrations of encapsulated components.  The precipitation process is controlled by carefully tuning the time scales of micromixing, self-assembly, and nucleation and growth. Further, the surface of the nanoparticles can be functionalized with desired surface chemistries or ligands of interest.  Building on this experience, FNP may prove a promising route to multifunctional materials that combine the unique attributes of inorganic nanoparticles. For example, gold nanoparticles functionalized with recognition molecules such as antibodies, antigens, or oligonucleotides can be used for colorimetric detection of biomolecules as the optical properties of the nanoparticles which will change upon interactions with the target biomolecules. Magnetic nanoparticles can be used to capture and manipulate a target biomolecule.  By designing a nanoparticle with a magnetic core, and then functionalizing the surface with gold nanoparticles, sensing capabilities may be enhanced as the magnetic core should facilitate separation and/or concentration while the gold nanoparticles provide optical detection.  By attaching ligands of interest to the polymer nanoparticle or the gold nanoparticle, specific detection of molecules may be achieved.    

The methodologies developed using nanofibers and nanoparticles are versatile and can be adapted for detection of a number of analytes.  Detection and removal of heavy metals for water purification as well as detection of bacterial pathogens for biodefense applications are of particular interest.