Solid-Phase Covalent Immobilization of Upconverting Nanoparticles for Biosensing by Luminescence Resonance Energy Transfer

Abstract

Monodisperse water-soluble upconverting nanoparticles (UCNPs) were immobilized onto modified glass substrates for development of biosensing surfaces that operated using luminescence resonance energy transfer (LRET). Amine modified UCNPs were prepared from oleic acid capped UCNPs by ligand exchange using o-phosphorylethanolamine (PEA). PEA-UCNPs were covalently immobilized on aldehyde functionalized coverslips. Environmental scanning electron microscopy (ESEM) images indicated a homogeneous distribution of UCNPs on surfaces with a high immobilization density of approximately 1.3 × 10(11) UCNP cm(-2). This is the first account of covalent immobilization of UCNPs for bioassay and biosensor development where the density is on par with the high immobilization densities reported for other types of nanoparticles. The functionality and stability of the immobilized NPs were demonstrated by examining an LRET-based bioassay. The well-known sandwich assay for the detection of thrombin was selected as a model in which UCNPs were used as donors and quantum dots (QDs) as acceptors. The closely packed UCNPs on the glass surface showed a 2.5-fold enhancement in assay sensitivity compared to less-densely packed surfaces. In addition, a 1.5-fold enhancement in energy transfer efficiency was shown for solid-phase compared to solution-phase LRET.

Lanthanide Nanoparticles: From Design toward Bioimaging and Therapy

“…Apart from the low LOD of 230 fmol (in buffer solution) this nanoprobe afforded, it is also the first example of covalent immobilization of UCNPs for the applications of biosensing. 389 A similar thrombin aptamer assisted specific biosensing carried out by Wang's group used AuNRs to quench the NIR UCL at 804 nm of NaYF 4 :Yb,Tm UCNPs. This system was used in human serum and gave a LOD of 0.129 nM.…”

Resonance Energy Transfer-Based Nucleic Acid Hybridization Assays on Paper-Based Platforms Using Emissive Nanoparticles as Donors

“…The broad absorbance band of QDs that stretches into the UV region of the spectrum makes them susceptible to direct excitation in the process of exciting the RET donor. We have recently paired QDs as RET acceptors with UCNP donors [7,8]. UCNPs are excited in the near-IR and IR region and emit in the UV to near-IR region of the spectrum.…”

“…This permits the excitation of the RET donor without the direct excitation of the QDs. We have previously shown the utility UCNP/QD RET pair for bioassay development using analytes such as proteins [7] and nucleic acids [8].…”

Oligonucleotide Sensor Based on Selective Capture of Upconversion Nanoparticles Triggered by Target-Induced DNA Interstrand Ligand Reaction

“…19,20 In addition, these nanoparticles have interesting photoluminescent properties, like high photostability, the absence of blinking and photobleaching, along with large anti-Stokes shifts, which allow the creation of robust analytical systems with low backgrounds and high signal-to-noise ratios. 19,21−26 Furthermore, the narrow emission bands exhibited by these nanoparticles and the possibility to tune their emission wavelengths make them ideal candidates to be used for multiplexed analytical systems 27−29 in immunoassays (ULISA) 30 where the upconversion nanoparticles (UCNPs) are linked to antibodies or aptamers 25 as reporters. In these analytical systems, the target and the functionalized UCNP are captured on a solid support giving a signal proportional to the amount of target.…”