Nanoscale upconversion for oxygen sensing

Abstract

Optical oxygen sensors have many promising qualities but rely on excitation by violet or blue wavelengths that suffer from high levels of scattering and absorption in biological tissues. Here we demonstrate an alternative method using 980nm near-infrared light to initially stimulate ceramic upconverting nanoparticles (UCNPs) contained within a novel form, electrospun core-shell fibers. The emission of the UCNPs excites a molecular optical oxygen sensor, the subsequent phosphorescent emission being dynamically quenched by the presence of molecular oxygen. The potential for use of such an energy transfer within electrospun fibers widely used in biological applications is promising. However, current knowledge of such 'handshake' interactions is limited. Fiber-based carriers enabling such optical conversions provide unique opportunities for biosensing as they recapitulate the topography of the extracellular matrix. This creates a wide array of potential theranostic, fiber-based applications in disease diagnosis/imaging, drug delivery and monitoring of therapeutic response. Using a fiber-based vehicle, we observed gaseous oxygen sensing capabilities and a linear Stern-Volmer response allowing highly accurate calibration. Configurational aspects were also studied to determine how to maximize the efficiency of this 'handshake' interaction.

Simple Self-Referenced Luminescent pH Sensors Based on Upconversion Nanocrystals and pH-Sensitive Fluorescent BODIPY Dyes

“…This sensitized excitation is either achieved by distance-dependent nonradiative processes such as luminescence resonance energy transfer (LRET) or by inner-filter-effect-based reabsorption. 131,140,[237][238][239] So far, the ratiometric approach featuring UCNPs was used for several sensing applications, such as temperature sensing, 240,241 oxygen sensing utilizing iridium-or ruthenium-based metallorganic complexes, 242,243 Depending on the optical properties of the analyte-responsive compound to be either colorimetrically or fluorogenically detected, there are two main principles for the readout of the ratiometric response, namely the readout of the quotient of the luminescence intensities of an analyte-responsive and a target-inert emission band. While one approach features a colorimetric analyte-responsive compound, the other approach presents a fluorogenic analyteresponsive compound with the UCNPs acting as intrinsic nanolamp (see Figure 11).…”

Injectable, dispersible polysulfone‐polysulfone core‐shell particles for optical oxygen sensing

“…A response time (deoxygenated to oxygenated conditions) shorter than the recovery time (oxygenated to deoxygenated conditons) has been previously observed for other luminescent dissolved oxygen sensors. 14,15,[60][61][62] This difference is likely the result of the matrices (e.g., polysulfone) exhibiting enhanced permeability and diffusivity for oxygen versus nitrogen. 63,64 Also, note that the measured response and recovery times are significantly faster than those commonly observed for other dissolved oxygen sensors.…”

Recent Advances on Functionalized Upconversion Nanoparticles for Detection of Small Molecules and Ions in Biosystems

“…In their system, ruthenium complexes were employed as oxygen indicators, which can selectively react with oxygen. Lannutti and co‐workers demonstrated an O 2 probe with a core–shell fiber structure and same ruthenium complexes as energy acceptors . Song and co‐workers employed platinum complexes as energy acceptors to construct O 2 probe.…”