Rapid response oxygen-sensing nanofibers

Abstract

Molecular oxygen has profound effects on cell and tissue viability. Relevant sensor forms that can rapidly determine dissolved oxygen levels under biologically relevant conditions provide critical metabolic information. Using 0.5 μm diameter electrospun polycaprolactone (PCL) fiber containing an oxygen-sensitive probe, tris (4,7-diphenyl-1,10-phenanthroline) ruthenium(II) dichloride, we observed a response time of 0.9±0.12 seconds – 4–10 times faster than previous reports – while the t95 for the corresponding film was more than two orders of magnitude greater. Interestingly, the response and recovery times of slightly larger diameter PCL fibers were 1.79±0.23 s and 2.29±0.13 s, respectively, while the recovery time was not statistically different likely due to the more limited interactions of nitrogen with the polymer matrix. A more than 10-fold increase in PCL fiber diameter reduces oxygen sensitivity while having minor effects on response time; conversely, decreases in fiber diameter to less than 0.5 μm would likely decrease response times even further. In addition, a 50°C heat treatment of the electrospun fiber resulted in both increased Stern-Volmer slope and linearity likely due to secondary recrystallization that further homogenized the probe microenvironment. At exposure times up to 3600 s in length, photobleaching was observed but was largely eliminated by the use of either polyethersulfone (PES) or a PES-PCL core-shell composition. However, this resulted in 2- and 3-fold slower response times. Finally, even the non-core shell compositions containing the Ru oxygen probe result in no apparent cytotoxicity in representative glioblastoma cell populations.

Morphology impact on oxygen sensing ability of Ru(dpp)3Cl2 containing biocompatible polymers

“…A ruthenium dye with a luminescence that is sensitive to surrounding oxygen concentration was selected to prepare an oxygen-sensing biomaterial. Ru(dpp) 3 Cl 2 was chosen as the oxygen sensing moiety because previous cytotoxicity studies with Ru(dpp) 3 Cl 2 -containing PCL fibers exhibited no harmful effects, indicating that the luminophore itself does not cause significant toxicity on cultured cells [13]. Typically, the cast film cross-sections had dense, solid compositions, while the cross-sections of electrospun films exhibited fibrous structures.…”

“…Other studies show that increasing film thickness of 2D polymer films increases diffusion depth and correlates to greater oxygen response time [14]. An order of magnitude increase in PCL fiber diameter also reduced sensitivity and increased response time, imposing limits on oxygen diffusion through the polymer matrix [13]. Therefore, smaller electrospun fiber diameters are preferable in applications where rapid oxygen-sensing performance is desired.…”

“…One problem in using optical sensors is photobleaching, where the luminophore is photochemically destroyed by repeated light exposure needed to stimulate fluorescence [13]. All polymer samples tested showed good reversibility during alternating exposure to nitrogen and oxygen.…”

Ultra-fast opto-chemical sensors by using electrospun nanofibers as sensing layers

“…A precise real-time monitoring of the oxygen concentration in the exhaled breath allows resolving the dynamics of single breathing cycles and can give important indications regarding pulmonary diseases. Fast oxygen sensors without oxygen consumption are important in cell biology regarding the real time observation of cell metabolism and diffusion phenomena [30]. High-speed sensors are also highly relevant in many industrial applications for process control in high-speed mixing or diffusion processes, e.g.…”

Emission performance of optical fibre dissolved oxygen sensor using various optical fibre materials and parameters

“…In this paper, we report on the dissolved oxygen (DO) application. Several materials were reported to be used in DO sensor, for example [Ru(dpp) 3 ] 2+ , [Ru(bpy) 3 ] 2+ ,and Ru[(Phen) 3 ]Cl 2 [6]- [9]. For our work we have chosen ruthenium (II) dichloride, [Ru(dpp) 3 ] 2+ Cl 2 as the luminescence sensing material because of its high luminescence quantum yield, good photostability, good quenching efficiency and long lifetimes [10]- [12].…”