Microscale Sensing of Oxygen via Encapsulated Porphyrin Nanofibers: Effect of Indicator and Polymer “Core” Permeability

Abstract

Biomimetic polymer nanofibers integrate sensing capabilities creating utility across many biological and biomedical applications. We created fibers consisting of either a poly(ether sulfone) (PES) or a polysulfone (PSU) core coated by a biocompatible polycaprolactone (PCL) shell to facilitate cell attachment. Oxygen sensitive luminescent probes Pt(II) meso-tetra(pentafluorophenyl)porphine (PtTFPP) or Pd(II) meso-tetra(pentafluorophenyl)porphine (PdTFPP), were incorporated in the core via single-step coaxial electrospinning providing superior sensitivity, high brightness, linear response, and excellent stability. Both PES−PCL and PSU−PCL fibers provide more uniform probe distribution than polydimethylsiloxane (PDMS). PSU-based sensing fibers possessed optimum sensitivity due to their relatively higher oxygen permeability. During exposure to 100% nitrogen and 100% oxygen, PES−PCL fiber displayed an I 0 /I 100 value of 6.7; PSU−PCL exhibited a value of 8.9 with PtTFPP as the indicator. In contrast, PdTFPP-containing fibers possess higher sensitivity due to the long porphyrin lifetime. The corresponding I 0 /I 100 values were 80.6 and 106.7 for the PES−PCL and PSU−PCL matrices, respectively. The response and recovery times were 0.24/0.39 s for PES−PCL and 0.38/0.83 s for PSU−PCL which are 0.12 and 0.11 s faster, respectively, than the Pt-based porphyrin in the same matrices. Paradoxically, lower oxygen permeabilities make these polymers better suited to measuring higher (i. e., ∼20%) oxygen contents than PDMS. Individual fiber sensing was studied by fluorescence spectrometry and at a sub-micrometer scale by total internal reflection fluorescence (TIRF). Specific polymer blends relate polymer composition to the resulting sensor properties. All compositions displayed linear Stern−Volmer plots; sensitivity could be tailored by matrix or the sensing probe selection.

Nanoscale upconversion for oxygen sensing

“…Using well-established techniques, the N2 to O2 and O2 to N2 response times were found to be 0.202±0.050 s and 0.404±0.100 s, respectively. This response is largely controlled by the relative O2/N2 affinity of the polymers [25] and the amount of time it takes to exchange the gas content in the cuvette containing the fibers.…”

“…We have incorporated UCNPs (LiYF4:Yb,Tm) with the oxygen-sensitive molecule tris (4,7-diphenyl-1,10-phenanthroline) ruthenium (II) dichloride (Ru(dpp)3Cl2) into electrospun core-shell fibers. Despite the longer lifetimes and, therefore, increased oxygen-sensitivity of such porphyrins as palladium (II) and platinum (II) tetrakis(pentafluorophenyl)porphyrin (PdTFPP and PtTFPP), [4,25] Ru(dpp)3Cl2 was chosen due to its broad absorption peak that overlaps efficiently with the upconverter emission at 480 nm. [26][27][28] The detailed electronic interactions between the UCNPs and the ruthenium complex are shown in Figure 1.…”

Electrochemical Conversion of Carbon Dioxide into CHO‐Containing Compounds on Multimetallic Porphyrins

“…The synergy between the metalloporphyrin and the polymer could find use in molecular electronics because it allows for both electronic and photonic conduction and also the development of anisotropic functional materials . Also, important properties for clinical use, such as fluorescence and the photosensitive ability to generate singlet oxygen, which enables porphyrin to be used as an anticancer drug ,. Moreover, a cobalt(II) porphyrin was successfully incorporated into polymer membranes for the optical sensing of imidazole and its derivatives .…”

“…[29] Also, important properties for clinical use, such as fluorescence and the photosensitive ability to generate singlet oxygen, which enables porphyrin to be used as an anticancer drug. [30,31] Moreover, a cobalt(II) porphyrin was successfully incorporated into polymer membranes for the optical sensing of imidazole and its derivatives. [32] Finally, metalloporphyrins (Fe, Co)-based conjugated porous polymer frameworks are new high-surface-area porous materials consisting of an extended conjugated skeleton and inherent mesoporous.…”

The Development of a Highly Sensitive Fiber-Optic Oxygen Sensor

“…There are many oxygen-sensitive dyes which can be used for optical oxygen sensing. Pd(II) complexes [14][15][16][17][18][19][20] have been used in recent years in preference to organic dye complexes with Ru(II) and Pt(II), because they can be easily excited with a compact and low-cost LED light source.…”