Imaging of proteins in biological tissues by fluorescence microscopy and laser ablation-ICP-MS using natural and isotopically enriched silver nanoclusters

Abstract

Antibodies conjugated with naturally abundant and isotopically enriched AgNCs are used for bioimaging of proteins in human retinal layers by LA-ICP-MS.

Immunoassays based on inductively coupled plasma mass spectrometry detection: So far so good, so what?

“…A large variety of NPs have been proposed (AgNPs [52][53][54][55], PtNPs [53,56], PbSNPs [57], metal/dye-doped silica NPs [58], Cs-doped magnetic NPs [58,59], UCNPs [30,31], EuPO 4 /LuPO 4 NPs [32], Quantum Dots (QDs) [60][61][62][63][64][65], etc.) but AuNPs [34,[53][54][55]63,[66][67][68][69][70][71][72][73][74][75][76] are usually preferred due to their lower cost and greater commercial availability.…”

“…For instance, after immunoassay completion, it is feasible to enlarge NPs size through metal deposition thus improving analytical figures of merit without compromising antibody recognition capabilities [65]. Third, given the optical properties of some NPs, they allow the development of dual detection immunoassays by fluorescence and mass spectrometry [30,31,52,53,56,72]. Lores-Padín et al [56] have proposed the use of Pt nanoclusters (NCs) for immunoglobulin E dual detection by fluorometry and ICP-MS. As expected, ICP-MS detection affords lower LoDs (10-fold) than those obtained by fluorescence, but the latter approach is more straightforward and cheaper when sensitivity requirements are not critical.…”

“…UCNPs [31] and QDs [64]) and proteins bioimaging in tissue sections by LA-ICP-MS (i.e. Au, Ag and PtNCs) [52,53,72,73]. Finally, analyte quantification could not only be performed by means ionic signal calibration curve but operating single particle analysis mode (SP-ICP-MS) [62,63,71].…”

Synthesis of Size Monodisperse Water-Soluble Metal Nanoclusters for Protein Quantification by Elemental Mass Spectrometry

“…Concerning the analysis of tissues and cells, the use of LA solid sampling technique allows to determine the sough proteins concentration and their distribution along the micrometer structures of the samples (lateral resolution in the range of 1-5 μm has been reported). In this case, AuNCs, AgNCs and PtNCs have been successfully investigated as elemental tags for proteins determination in human brain and ocular tissues [6][7][8]. However, the main limitation of using MNCs for quantification purposes is related to their size variability.…”

“…In previous studies, we successfully synthesized water-soluble AuNCs following a bottom-up approach by chemical reduction of the Au (III) to Au (I, 0) in the presence of a thiolated ligand [7]. Nevertheless, the deviation associated with the AuNCs diameter must be decreased in order to apply them for quantification of biomolecules in single cells by elemental MS detection.…”