Quantum sensing in a physiological-like cell niche using fluorescent nanodiamonds embedded in electrospun polymer nanofibers

Fluorescent nanodiamonds (fNDs) containing Nitrogen Vacancy (NV) centres are promising candidates for quantum sensing in biological environments. However, to date, there has been little progress made to combine the sensing capabilities of fNDs with biomimetic substrates used in the laboratory to support physiologically representative cell behaviour. This work describes the fabrication and implementation of electrospun Poly Lactic-co-Glycolic Acid (PLGA) nanofibers embedded with fNDs for optical quantum sensing in an environment, which recapitulates the nanoscale architecture and topography of the cell niche. A range of solutions for electrospinning was prepared by mixing fNDs in different combinations of PLGA and it was shown that fND distribution was highly dependent on PLGA and solvent concentrations. The formulation that produced uniformly dispersed fNDs was identified and subsequently electrospun into nanofibers. The resulting fND nanofibers were characterised using fluorescent microscopy and Scanning Electron Microscopy (SEM). Quantum measurements were also performed via optically detected magnetic resonance (ODMR) and longitudinal spin relaxometry. Time varying magnetic fields external to the fND nanofibers were detected using continuous wave ODMR to demonstrate the sensing capability of the embedded fNDs. The potential utility of fND embedded nanofibers for use as biosensors in physiological environments was demonstrated by their ability to support highly viable populations of differentiated neural stem cells, a major therapeutic population able to produce electrically active neuronal circuits. The successful acquisition of ODMR spectra from the fNDs in the presence of live cells was also demonstrated on cultures of differentiating neural stem cells.