Development of a Histidine-Targeted Spectrophotometric Sensor Using Ni(II)NTA-Functionalized Au and Ag Nanoparticles

Abstract

An antibody-free diagnostic reagent has been developed based on the aggregation-induced colorimetric change of Ni(II)NTA-functionalized colloidal gold and silver nanoparticles. This diagnostic strategy utilizes the high binding affinity of histidine-rich proteins with Ni(II)NTA to capture and cross-link the histidine-rich protein mimics with the silver and gold nanoparticles. In model studies, the aggregation behavior of the Ni(II)NTA nanoparticles was tested against synthetic targets including charged poly(amino acid)s (histidine, lysine, arginine, and aspartic acid) and mimics of Plasmodium falciparum histidine-rich protein 2 (pfHRP-II). Aggregation of the nanoparticle sensor was induced by all of the basic poly(amino acid)s including poly(l-histidine) within the pH range (5.5-9.0) tested, which is likely caused by the coordination between the multivalent polymer target and Ni(II)NTA groups on multiple particles. The peptide mimics induced aggregation of the nanoparticles only near their pK(a)'s with higher limits of detection. In addition, monomeric amino acids do not show any aggregation behavior, suggesting that multiple target binding sites are necessary for aggregation. Long-term stability studies showed that gold but not silver nanoparticles remained stable and exhibited similar aggregation behavior after 1 month of storage at room temperature and 37 °C. These results suggest that Ni(II)NTA gold nanoparticles could be further investigated for use as a sensor to detect histidine-rich proteins in biological samples.

Inorganic Complexes and Metal-Based Nanomaterials for Infectious Disease Diagnostics

“…Addition of a sample of target biomarker results in cross-linking of the functionalized nanoparticles, drastically decreasing the nanoparticle–nanoparticle distance and producing in a spectral shift. 244,245 AgNP aggregation assays in this format have been implemented for detection of both infectious disease protein 228 and nucleic acid 230 biomarkers; however, to the best of our knowledge, cross-linking-based AgNP aggregation has yet to be employed in paper diagnostics or other low-resource platforms.…”

Monolayer protected gold nanoparticles with metal-ion binding sites: functional systems for chemosensing applications

“…In a recent study by Wright et al this binding interaction was used to induce aggregation of the nanoparticles in multivalent biosystems detectable by spectrophotometric changes. 53 Li et al developed bifunctional Au-Fe 3 O 4 nanoparticles with Ni 2+ -coordinated N-[N a ,N a -bis(carboxymethyl)-Llysine]-16-mercaptohexadecanamide immobilized on the Au shell. This material was suitable for the purification of any 6-His tagged protein by chelation followed by magnetic separation.…”

Ni(II)NTA AuNPs as a low-resource malarial diagnostic platform for the rapid colorimetric detection of Plasmodium falciparum Histidine-Rich Protein-2

“…In this investigation, we aim to create a robust, low-resource colorimetric indicator for malaria diagnosis by selectively and rapidly aggregating Ni(II)NTA AuNPs only in the presence of a recombinant PfHRP-II (rcHRP-II) biomarker, triggering a spectrophotometric redshift and subsequently, a red-to-purple color change ( Figure 1). A custom, thiolated Ni(II)NTA recognition ligand has been previously synthesized and validated in our lab as a proof-of-concept design with Ni(II)NTA Au and AgNPs by detecting histidine-rich peptide mimics [20]. However, the activity of Ni(II)NTA AuNPs has never been assessed against PfHRP-II and the limits of detection for the peptide mimics are outside of the clinically relevant range for malaria diagnosis.…”