2, University of California, Riverside, Riverside, California, United States
3, University of California, Riverside, Riverside, California, United States
Polymer/virus composite fibers have the potential to combine the structural properties of a polymer with the site-specific chemistry of viral proteins. Because viruses can be genetically modified to display a range of high affinity peptides, they can be tailored to different applications. One such virus, the filamentous M13 bacteriophage, has found utility in cellular scaffolds, biotemplates, biosensors and drug release. For these polymer/M13 composite fibers, enriching specific fiber interfaces can enhance functionality. For example, in biosensing and cellular scaffold applications, the surface of the fiber is the critical interface; biomolecule surface enrichment can improve sensor sensitivity and encourage cell growth. For controlled-release applications, the important interface is within the volume of the fiber; biomolecule core enrichment can help to sustain or delay drug delivery.
One method of producing polymer/M13 fibers is near-field electrospinning, a scalable direct write fabrication method utilizing a strong applied voltage to fabricate fibers quickly and precisely. The electric field generated during the near field electrospinning process has the potential to interact with the pH-modified surface charge of the M13 virus and enrich the fiber interface.
In this work, we characterized the spatial distribution of a streptavidin-binding M13 bacteriophage encapsulated within near-field electrospun polyvinyl alcohol (PVA) fibers as a function of spinning solution pH. The viral spatial distribution was evaluated with confocal fluorescence microscopy by covalently tagging M13 with fluorescent molecules. At pH values above the isoelectric point (pI), the electric field generated during electrospinning attracted the negatively charged M13 to the fiber surface, resulting in surface-enriched fibers. Conversely, at pH below the pI, the positively charged M13 were drawn to the fiber core, resulting in core-enriched fibers. To further evaluate the polymer/M13 interface, the fibers were crosslinked and incubated with streptavidin-conjugated gold nanoparticles. Surface-enriched PVA/M13 fibers demonstrated greater streptavidin affinity than core-enriched fibers. These results show that M13 virus distribution can be controlled via pH during the near-field electrospinning process to produce enhanced functional PVA/M13 fibers.