Goldilocks Energy Minimum: Peptide-Based Reversible Aggregation and Biosensing

Abstract

Colorimetric biosensors based on gold nanoparticle (AuNP) aggregation are often challenged by matrix interference in biofluids, poor specificity, and limited utility with clinical samples. Here, we propose a peptide-driven nanoscale disassembly approach, where AuNP aggregates induced by electrostatic attractions are dissociated in response to proteolytic cleavage. Initially, citrate-coated AuNPs were assembled via a short cationic peptide (RRK) and characterized by experiments and simulations. The dissociation peptides were then used to reversibly dissociate the AuNP aggregates as a function of target protease detection, i.e., main protease (M pro ), a biomarker for severe acute respiratory syndrome coronavirus 2. The dissociation propensity depends on peptide length, hydrophilicity, charge, and ligand architecture. Finally, our dissociation strategy provides a rapid and distinct optical signal through M pro cleavage with a detection limit of 12.3 nM in saliva. Our dissociation peptide effectively dissociates plasmonic assemblies in diverse matrices including 100% human saliva, urine, plasma, and seawater, as well as other types of plasmonic nanoparticles such as silver. Our peptide-enabled dissociation platform provides a simple, matrix-insensitive, and versatile method for protease sensing.

Silver Nanoparticle Sensor Array for the Detection of SARS-CoV-2

“…The decrease in the ratiometric absorbance was fitted to a sigmoidal dose–response curve using GraphPad Prism 10 because the shift in absorbance often yields a sigmoidal curve as the concentration becomes diluted. ,, The sensitivity of each peptide to the viral particles was compared via the viral concentration, signifying the inflection point of the sigmoidal curve. (RRK) 2 was the most sensitive peptide because it had the lowest inflection point for all of the virus types except for the Delta variant.…”

“…The peptides RR, RRK, HHK, (RRK) 2 , FFK, and GG were synthesized through solid-phase peptide synthesis. 33 R represents the amino acid arginine, K represents the amino acid lysine, H represents the amino acid histidine, F represents the amino acid phenylalanine, and G represents the amino acid glycine. This was done by using an Aapptec Eclipse peptide synthesizer.…”

Activatable prodrug for controlled release of an antimicrobial peptide via the proteases overexpressed inCandida albicansandPorphyromonas gingivalis

“…The colloidal state of the AuNPs-citrate suspension was defined as the ratio of the absorbance: A700 nm/A520 nm. [36,37] High and low ratios correspond to assembled or monodispersed NPs, respectively. The maximum ratio was obtained for concentrations of 25 µM and 5 µM of S1 and G1, respectively.…”

“…This color change is based on precious metal nanoparticles and plasmonic coupling leading to a change in optical behavior in the visible region. [34][35][36][37] In the work below, we characterize the prodrugs, their toxicity profiles, their selectivity to fungi and bacteria in vitro, and finally show the diagnostic performance of the sensor.…”

Activatable prodrug for controlled release of an antimicrobial peptide via the proteases overexpressed in Candida albicans and Porphyromonas gingivalis

“…Finally, we used the zwitterionic peptide-prodrugs to produce a colorimetric signal that reports the presence of C. albicans or P. gingivalis proteases 36 , 37 . This color change is based on precious metal nanoparticles and plasmonic coupling leading to a change in optical behavior in the visible region 35 , 38 - 40 . In the work below, we characterize the prodrugs, their toxicity profiles, their selectivity to fungi and bacteria in vitro , and finally, show the diagnostic performance of the sensor.…”