Positive role of the long luminescence lifetime of upconversion nanophosphors on resonant surfaces for ultra-compact filter-free bio-assays

Abstract

We introduce a compact array fluorescence sensor principle that takes advantage of the long luminescence lifetimes of upconversion nanoparticles (UCNPs) to deploy a filter-free, optics-less contact geometry, advantageous for modern biochemical assays of biomolecules, pollutants or cells. Based on technologically mature CMOS chips for ∼10 kHz technical/scientific imaging, we propose a contact geometry between assayed molecules or cells and a CMOS chip that makes use of only a faceplate or direct contact, employing time-window management to reject the 975 nm excitation light of highly efficient UCNPs. The chip surface is intended to implement, in future devices, a resonant waveguide grating (RWG) to enhance excitation efficiency, aiming at the improvement of upconversion luminescence emission intensity of UCNP deposited atop of such an RWG structure. Based on mock-up experiments that assess the actual chip rejection performance, we bracket the photometric figures of merit of such a promising chip principle and predict a limit of detection around 10-100 nanoparticles.

A Synergy Approach to Enhance Upconversion Luminescence Emission of Rare Earth Nanophosphors with Million-Fold Enhancement Factor

“…For real useage in biological fields, an ideal fluoroprobe should generally meet several criteria, such as intense emission, monodispersity, small size, biocompatibility, and non−toxicity [13]. Recently, Ln 3+ −doped UCNPs are emerging as a booming material for biological applications [10][11][12][13][14][15][16]. Particularly with the development of facile and versatile strategies for surface modification [17], biocompatible and low biotoxicity UCNPs have opened a variety of applications in biomedical fields such as imaging [16,18,19], fluorescence assays [20], biosensing [21], molecular detection [22], drug delivery [23], and therapeutics [16,24].…”

Impact of Excitation Intensity-Dependent Fluorescence Intensity Ratio of Upconversion Nanoparticles on Wide-Field Thermal Imaging

“…(5) Er 3+ ions in the core served as activators to emit UCF through a multiphoton absorption process. (6) To prohibit UCF quench due to the deleterious energy transfer between Nd 3+ sensitizers and Er 3+ activators, they were spatially separated by putting Nd 3+ ions in the active shell and Er 3+ ions in the core. 10,29,30 As reported in our previous study, 10 NaYF 4 :Yb 3+ , Tm 3+ @NaYF 4 :Yb 3+ ,Nd 3+ @NaYF 4 core− double-shell UCNPs can produce stronger UCF emission than their core (NaYF 4 :Yb 3+ , Tm 3+ ) and core−shell (NaY-F 4 :Yb 3+ ,Tm 3+ @NaYF 4 :Yb 3+ , Nd 3+ ) counterparts under the Scheme 1.…”

“…Lanthanide-doped upconversion nanoparticles (UCNPs) can emit ultraviolet–visible (UV–Vis) fluorescent light through multiphoton absorption of near-infrared (NIR) light. UCNPs have attracted a lot of attention in research of photonics and biomedical applications − thanks to their unique properties, such as good photostability, no photobleaching, no autofluorescence, low scattering, no blinking, high signal-to-noise ratio, sharp emission line, large anti-Stokes shifts, long luminescence lifetimes, deep penetration in tissue, biocompatibility, low toxicity, and water dispersivity after appropriate surface modification. Furthermore, some lanthanide ion-doped UCNPs possess a temperature-dependent fluorescence intensity ratio (FIR) between two thermally coupled energy levels, making them suitable for nanoscale temperature sensing. − Lanthanide-doped UCNP-based fluorescence intensity ratiometric thermometers can provide outstanding properties, such as high sensitivity, noninvasiveness, and high spatial resolution.…”

Ultrasensitive Upconversion Nanoparticle Immunoassay for Human Serum Cardiac Troponin I Detection Achieved with Resonant Waveguide Grating

“…The use of UCNP fluorescent probes in bioassays can significantly reduce the limit of detection (LOD) to levels unattainable by conventional assays since UCNPs are excited by NIR light and assay biochemistry does not generate background luminescence . Therefore, they are more suitable as fluorescent probes in biosensing applications than conventionally used organic dyes and quantum dots. − ,− In addition, the UCL properties of UCNPs are inert to changes in buffer composition, sample matrix, and other environmental conditions . UCNP-based bioassay research is becoming a flourishing field and various types of UCNP-based bioassays have emerged over the past two decades. − ,− Sandwich-type heterogeneous biosensors are frequently developed because the use of a matched pair of antibodies provides the highest level of sensitivity and specificity. ,− Many studies have aimed to develop sandwich-type heterogeneous UCNP-based biosensors suitable for clinical and hospital diagnostic tools. − …”