Plasmonic Enhancement of NIR to UV Upconversion by a Nanoengineered Interface Consisting of NaYF₄:Yb,Tm Nanoparticles and a Gold Nanotriangle Array for Optical Detection of Vitamin B12 in Serum

Abstract

A nanoengineered interface fabricated by self-assembly enables the online determination of vitamin B12 via a simple luminescence readout in serum without any pretreatment. The interplay of Tm3+-doped NaYF4 nanoparticles (UCNPs) and a gold nanotriangle array prepared by nanosphere lithography on a glass slide is responsible for an efficient NIR to UV upconversion. Hot spots of the gold assembly generate local electromagnetic-field enhancement, favoring the four-photon upconversion process at the low-power excitation of approximately 13 W·cm–2. An improvement by about 6 times of the intensity for the emission peaking at 345 nm is achieved. The nanoengineered interface has been applied in a proof-of-concept sensor for vitamin B12 in serum, which is known as a marker for the risk of cancer; Alzheimer disease; or, during pregnancy, neurological abnormalities in newborn babies. Vitamin B12 can be detected in serum down to 3.0 nmol·L–1 by a simple intensity-based optical readout, consuming only 200 μL of a sample, which qualifies as easy miniaturization for point-of-care diagnostics. Additionally, this label-free approach can be used for long-term monitoring because of the high photostability of the upconversion nanoparticles.

Current Nanocarrier Strategies Improve Vitamin B12 Pharmacokinetics, Ameliorate Patients’ Lives, and Reduce Costs

“…The use of enhanced Raman spectroscopy to quantify VitB12 in multivitamin complexes was also successfully demonstrated by Ibáñez et al, who realized screen-printed Au electrodes to be used in the electrochemical SERS detection of VitB12 with an LoD of 4-7 nM [103]. Wiesholler et al realized active substrates depositing Tm 3+ -doped NaYF 4 nanoparticles on arrays of Au nanotriangles on glass substrates, which were used to detect VitB12 in serum analyzing the near-infrared (NIR) to ultraviolet (UV) luminescence upconversion, obtaining an LoD of 3.0 nmol L −1 [104].…”

Upconversion-based nanosystems for fluorescence sensing of pH and H2O2

“…12 In contrast to conventional uorescence probes (such as organic dyes, carbon nanomaterials, and semiconductor quantum dots), upconversion nanoparticles featuring large anti-Stokes shis, excellent chemical-and photo-stability, sharp multicolor emissions, and low toxicity have been regarded as a promising class of luminophores. 13 Up to now, a variety of functional materials including organic dyes, [14][15][16] noble metals, [17][18][19] quantum dots, [20][21][22] carbon nanomaterials, [23][24][25] and two-dimensional materials [26][27][28] has been employed to couple with upconversion nanoparticles to construct uorescence probes, realizing quantitative detection of inorganic ions, [29][30][31] pH, [32][33][34] small molecules, [35][36][37][38] and nucleic acids. [39][40][41][42] Most of the upconversion-based probes rely on the uorescence resonance energy transfer (FRET) process, in which a very short distance between the upconversion nanoparticles and absorbers is required.…”

One-Pot, Solid-Phase Immunosensing Platform Consisting of a Nanometer-Thick Au/TiO2 Photocatalytic Film and Cy5/Capture Antibody/Gold Nanorod Conjugates

“…High-efficiency fluorescent probes are an attractive tool for improving the sensitivity of optical-based biosensors. Previous studies have shown that an increase in the quantum yield of fluorescent probes can enhance the sensitivity of FL-based biosensors. − The FL of probes can also be increased by inducing the surface plasmon of metals when the probes are near the metals [i.e., metal-enhanced fluorescence (MEF)]. , …”