Near-field electrospinning of polymer/phage whispering gallery mode microfiber resonators for label-free biosensing

Abstract

Whispering gallery mode (WGM) resonators have attracted attention as optical biosensors due to their capacity for rapid label-free detection. Separately, the M13 bacteriophage has been investigated as an alternative biorecognition element. In this work, a novel polymer WGM biosensor functionalized with filamentous virus biocapture agents was fabricated using near-field electrospinning (NFES) in a single step. Polyvinyl alcohol (PVA) was mixed with streptavidin-binding M13 bacteriophage and rhodamine 6 G in aqueous solution for blend electrospinning of active cavity microfiber-based resonators. Confocal fluorescence microscopy revealed alignment of M13 bioreceptors along the fiber axis, while x-ray photoelectron spectroscopy (XPS) and streptavidin-conjugated nanoparticle binding studies indicated that bioactive M13 bacteriophage were on the fiber surface. Dye-doped, crosslinked PVA/M13 fibers supported moderate quality (Q) factor first order WGM resonances within their cross-sections that exhibited a spectral shift in response to streptavidin binding. Composite PVA/M13 microfibers demonstrated specific label-free biosensing of streptavidin with a theoretical limit of detection of 3 nM and a maximum surface coverage of 21 ± 5%. These results demonstrate the potential of NFES to fabricate WGM resonators from PVA/M13 microfibers and use them as a platform for rapid, sensitive label-free sensing.