Influence of Gold/Silver Ratio in Ablative Nanoparticles on Their Interaction with Aptamers and Functionality of the Obtained Conjugates

Abstract

Nano-bio-conjugates, featuring noble metal gold− silver alloy nanoparticles, represent a versatile tool in diagnostics and therapeutics due to their plasmonic and antimicrobial properties tunable by the particle's gold molar fraction. However, little is known about how the binding of thiolated biomolecules to noble metal nanoparticles is influenced by the fraction of gold and silver atoms on the nanoparticle's surface and to which extend this would affect the functionality of the conjugated biomolecules. In this work, we generated gold−silver alloy nanoparticles with average diameters of 7−8 nm using the modern, surfactant-free laser ablation in liquids (LAL) synthesis approach. We conjugated them with thiolated miniStrep aptamer ligands at well-controlled aptamer-to-nanoparticle surface area ratios with maxima between 12 and 27 pmol aptamer/cm 2 particle surface area. The results revealed a clear correlation between surface coverage and the nanoparticles' nominal gold/silver ratio, with maximum coverage reached for gold-rich alloys and a pronounced maximum for silverrich alloys. However, the conjugates' functionality, evaluated by binding of streptavidin, was surprisingly robust and hardly affected by the nominal composition. However, 1.5 times higher surface coverage was needed to obtain maximum functionality in the silverrich conjugates. Based on these results, it may be concluded that the nominal composition of gold−silver alloy nano-bioconjugates is freely tunable without a pronounced impact on the attached ligands' functionality, a finding highly relevant for the flexible design of nano-bio-conjugates for future biomedical applications. This study's results may facilitate the design of alloy nano-bio-conjugates for future applications in therapeutics and diagnostics.

Bacteria‐Epithelial Cell Interaction Influences Cytotoxicity and Antibacterial Effect of Silver‐Gold Alloy Nanoparticles on a Species‐Specific Level

“…Regarding chemical composition, the UV‐Vis spectrum (Figure 1C) displays a single peak with a maximum at λ=418 nm. This is in fair accordance with other studies synthesizing AgAu alloy nanoparticles by laser synthesis in liquids and verified that the bulk AgAu atomic ratio of 80 : 20 is retained within the studied particles [20,21] . To evaluate the colloidal stability of the AgAu nanoparticles and to gain further information on their surface chemistry, zeta potential measurements were conducted for representative Ag 80 Au 20 samples at pH=7.8.…”

“…A sample volume of 0.1 mL was utilized and sedimentation was homogenized with a D(+)‐sucrose density gradient. In conjunction with the mass concentrations from gravimetry, these distributions were utilized to calculate the overall surface concentration in cm 2 /ml in every colloid, a procedure described in more detail in our previous works [15,21] …”

“…This is in fair accordance with other studies synthesizing AgAu alloy nanoparticles by laser synthesis in liquids and verified that the bulk AgAu atomic ratio of 80 : 20 is retained within the studied particles. [20,21] To evaluate the colloidal stability of the AgAu nanoparticles and to gain further information on their surface chemistry, zeta potential measurements were conducted for representative Ag 80 Au 20 samples at pH = 7.8. This data clearly showed an overall negative zeta potential, with an average value (mean from triplicates) of À 56 � 3.9 mV, which indicates good colloidal stability.…”

The Origin of the Intracellular Silver in Bacteria: A Comprehensive Study using Targeting Gold–Silver Alloy Nanoparticles

“…[ 40 ] Concerning functionality (affinity for the bacterial surface), the authors assumed that a high surface coverage on the NP surface coincided with a maximum functionality for ligand‐free AgAu alloy NP conjugates. [ 41 ] The vial was subsequently centrifuged at 125 000 g for 20 min. The supernatant was carefully removed to avoid disturbance of the particle‐aptamer sediment and then centrifuged at 125 000 g for 20 min.…”

Nanoscale bioconjugates: A review of the structural attributes of drug-loaded nanocarrier conjugates for selective cancer therapy

“…The main advantage of these advanced drug delivery systems (DDS) is their ability to increase the maximum tolerated dose (MTD) and decrease the minimum effective dose (MED) in cancer patients to enlarge the therapeutic window [ 74 , 75 ]. These nanobioconjugates (NBCs) (here defined as a nanoscale carrier attached to a biologically active component) allow selective targeted delivery to the intended cells or tissues [ 76 ]. The nanocarriers can incorporate an anticancer cytotoxic drug, such as docetaxel, paclitaxel, doxorubicin (DOX), etc., which are used in conventional chemotherapy but can have undesirable side effects, including signaling pathways blockage, liver cancers cells proliferation inhibition, bone marrow, and hair follicle cell growth deterrence when the drug accumulates in healthy tissues [ 77 ].…”