Peptide-Induced Fractal Assembly of Silver Nanoparticles for Visual Detection of Disease Biomarkers

Abstract

We report the peptide-programmed fractal assembly of silver nanoparticles (AgNPs) in a diffusion-limited aggregation (DLA) mode, and this change in morphology generates a significant color change. We show that peptides with specific repetitions of defined amino acids (i.e., arginine, histidine, or phenylalanine) can induce assembly and coalescence of the AgNPs (20 nm) into a hyperbranched structure (AgFSs) (∼2 μm). The dynamic process of this assembly was systematically investigated, and the extinction of the nanostructures can be modulated from 400 to 600 nm by varying the peptide sequences and molar ratio. According to this rationale, two strategies of SARS-CoV-2 detection were investigated. The activity of the main protease (Mpro) involved in SARS-CoV-2 was validated with a peptide substrate that can bridge the AgNPs after the proteolytic cleavage. A sub-nanomolar limit of detection (0.5 nM) and the capacity to distinguish by the naked eye in a wide concentration range (1.25–30 nM) were achieved. Next, a multichannel sensor-array based on multiplex peptides that can visually distinguish SARS-CoV-2 proteases from influenza proteases in doped human samples was investigated.

Spacer Matters: All-Peptide-Based Ligand for Promoting Interfacial Proteolysis and Plasmonic Coupling

“…16 Although effective at measuring proteases, this approach and others adapt a stepwise strategy: (i) incubation of enzyme with substrate and (ii) NP introduction. 10,17,32,33 This complicates the instructed processes for end-users from using the point-of- care diagnostic kit. Strategies that render proteolysis and plasmonic coupling in one pot have mainly focused on conjugating substrates onto polymeric ligands such as poly(ethylene glycol) (PEG) and extending the spatial distance for biointeractions.…”

“…For instance, the coupled metallic NPs in close proximity leads to a collective plasmon and red-shifts the resonant wavelength relative to individual nanoparticlesthis in turn causes color change . In addition, coating molecules can cause NPs to respond to biomolecular stimuli via changes in affinity, − hydrophilicity, − charge valence, − or reactivity, , which subsequently induce colloidal aggregation and color changes suitable for sensing applications. Previous studies have provided some insights to guide the rationale design of coating ligand for better bionanoscale recognition, revealing that the collective architecture presented on nanosurfaces determines the accessibility, homogeneity, orientation, and functionality, etc . , …”

Surfactant-Assisted Assembly of Dipeptide Forming a Broom-like Structure

“…The behavior of peptides, which can self-assemble into various nanostructures, has attracted much attention because of their applications in biomedical, bioengineering and drug production [ 4 , 5 , 6 , 7 , 8 ]. In contrast to other supramolecular structural motifs, the unique and desirable features of peptides include their chemical diversity, sequence-specific secondary structures, biomolecular recognition, high biocompatibility, and ease of synthesis [ 9 , 10 , 11 , 12 , 13 , 14 , 15 ]. As a minimal-recognition module, the dipeptide Phe-Phe (FF), which can easily assemble into various ordered structures, is the most studied because of its mechanical, electrical and optical properties [ 16 , 17 , 18 , 19 , 20 , 21 ].…”

A di-arginine additive for dissociation of gold nanoparticle aggregates: A matrix-insensitive approach with applications in protease detection

“…17 Also, dramatic background signals are usually observed in biofluids because there is significant charge screening, thus leading to a reduction in repulsive forces and aggregation of the AuNPs due to the VdW interaction. Extreme dilution of the biological sample 16 or extraction of the analyte from the matrix are thus often needed. 18 Only a few examples of nanoparticle aggregation-based assays in biological fluids have been reported.…”

“…15 Thermodynamically, AuNPs colloids are not stable and tend to aggregate over time, which results in non-desired aggregation of the particles that reduces the color difference between a positive sample (analyte present) and a negative sample (analyte absent). 8,16 Another limitation is the difficulty to operate in biofluids such as plasma, saliva, urine, bile or cell lysates. The presence of background matrix compounds can interfere with the colorimetric detection, e.g., via a protein corona that prevents the AuNPs cross-linking.…”