Oxygen sensing performance of biodegradable electrospun nanofibers: Influence of fiber composition and core-shell geometry

Abstract Implantable optical oxygen sensors can be constructed through incorporation of an oxygen-sensitive chromophore within a biocompatible polymer host. In this work, a Pd (II) benzoporphyrin that absorbs (630 nm) and phosphoresces (810 nm) within the optical tissue window was incorporated into various biodegradable polymer matrices via electrospinning. A unique in situ fluorimeter setup was constructed and used to rigorously characterize the sensor performance in the physiologically relevant dissolved oxygen range (∼0-90 μM) in 37 °C phosphate buffered saline. Single-component polycaprolactone (PCL) fibers exhibited high sensitivity (KSV: 1.25 × 105 M-1) and monoexponential decay curves, indicating a homogenous chromophore environment. The ability to move from a single-component composition (PCL) to blended (PCL:gelatin) and core-shell systems (PCL:gelatin-PCL) without compromising the desirable properties of the single-component sensor was demonstrated. These variations may offer the potential to tune degradation time of the resulting sensor while maintaining high sensitivity and monoexponential decays. In contrast, blended 50:50 PCL:poly(d,l-lactide-co-glycolide) (PLGA) exhibited significantly reduced sensitivity (KSV: 6.66 × 104 M-1) and biexponential decays. Despite the observation of biexponential lifetime decays for PCL:PLGA, all electrospun sensors exhibited linear Stern-Volmer behavior over the physiologically relevant dissolved oxygen range. This work rigorously evaluated biodegradable candidates for in vivo oxygen sensing under physiologically relevant conditions in which the character of the individual phosphorescence decay curves offered insight into the nature of the chromophore environment.