Electric Field PolarityControls Distribution of ViralBioreceptors within Near-Field Electrospun Biohybrid Microfiber OpticalBiosensors

Microorganisms (e.g., bacteria, fungi, and viruses) add indispensable functionality to a range of electrospun polymer materials and devices. The optimal distribution of bioactive agents on either the interior or exterior of the fiber is application-specific. Current microbe surface immobilization strategies and core-confinement techniques continue to pose a number of challenges. Here, we explore a simple strategy, utilizing electrostatic forces, to control the migration and surface concentration of the M13 bacteriophage within near-field electrospun poly(vinyl alcohol) (PVA) microfibers. Both the surface charge of the electrospun virus and the applied electric field polarity altered microbe placement. When doped with Rhodamine 6G (R6G), the circular microfiber cross sections formed active whispering gallery mode (WGM) resonators. These relatively high-quality (<i>Q</i>) optical cavities enabled us to sensitively probe the virus content of their outer layer, while functioning as label-free optical biosensors with phage-based streptavidin biorecognition elements. Coulomb forces displayed significant control over M13 surface coverage during near-field electrospinning, increasing biosensor response by nearly a factor of 4 to 1310 nM streptavidin. These findings are an important demonstration of electrostatic forces as a simple, yet adaptable method to enhance biohybrid fiber functionality and performance by tailoring microbe distribution.