Silver Nanoparticle Formation in Different Sizes Induced by Peptides Identified within Split‐and‐Mix Libraries

Abstract

Silver nanoparticles (AgNPs) are becoming increasingly important for manifold applications in, for example, imaging, catalysis, electronics, and the development of antimicrobial coatings. [1][2][3] The formation of AgNPs is typically accomplished by chemical reduction or irradiation of Ag + ions with visible light in the presence of additives, such as polymers or surfactants, which induce the formation of AgNPs and stabilize the NPs. [1,2] Recently, peptides bearing functional groups that coordinate to Ag + ions have become popular as additives. [4][5][6][7][8] Their large structural and functional diversity also renders peptides attractive for the controlled formation of AgNPs of defined sizes, which still presents a challenge to date. Since the rational design of peptides that induce metal NP formation is difficult, combinatorial approaches are attractive for the identification of suitable peptides. [7,8] We envisaged that colorimetric on-bead screening of split-andmix libraries could be a particularly powerful tool that would allow the testing of diverse libraries, which contain both natural and unnatural amino acids. [9] The typical size-and shape-dependent coloration of AgNPs [1] was anticipated to allow for a facile identification of active library members.Herein, we introduce the use of combinatorial split-andmix libraries for the identification of peptides that are capable of inducing the formation of AgNPs. In conjunction with scanning electron microscopy (SEM) studies, we also demonstrate that the method allows for the identification of certain types of peptides that induce the formation of AgNPs of specific sizes.We started our investigations by testing the members of peptide library 1 for their ability to induce AgNP formation in the presence of either light or the chemical reducing agent sodium ascorbate (Figure 1 a). Within the library, the amino acids serine (Ser), aspartic acid (Asp), histidine (His), and tyrosine (Tyr), bearing functional groups that were envisaged for Ag + ion coordination, were employed in positions AA1 and AA2 (Figure 1). Tyr was included in the library as it is a well-known photoactive residue. [6] Linkers of varying flexibility and geometry were used to connect the amino acids in order to allow for diverse spatial arrangements of their sidechain functional groups. trans-2-Aminohexanoic acid (Achc), Pro-Aib (Aib = aminoisobutyric acid) and Pro-Gly were chosen as turn-inducing linkers, and 6-aminohexanoic acid (Ahx) and b-alanine as flexible linkers. The library was prepared by encoded [10] split-and-mix synthesis [11] on TentaGel resin by utilizing seven different linkers and seven different l-and d-amino acids in positions AA1 and AA2, hence the library consisted maximally of 7 3 = 343 different peptides (Figure 1 a). Amino acid couplings were performed by following the standard Fmoc/tBu protocol for peptide synthesis using HBTU/iPr 2 NEt as the coupling reagent and piperidine for Fmoc deprotections (Fmoc = 9-fluorenylmethyloxycarbonyl, HBTU = O-(benzotriazol-l-yl)-N,N,N'...

Nanobio Silver: Its Interactions with Peptides and Bacteria, and Its Uses in Medicine

“…122 Also, Adhikari and Banerjee 123 reported that in a short peptide-based hydrogel, the light-induced formation of silver nanowires is possible due to the combination of a carboxylic acid-containing peptide (Fmoc-Val-Asp-OH) and sunlight. 123 These observations are in agreement with the results reported by Belser et al 118 who showed that a tetrapeptide containing Asp and Ser linked by a rigid linker that does not spontaneously form AgNPs upon incubation with silver nitrate is able to mineralize silver only in the presence of light. The suggested influence of the complexation with a peptide on the redox potential of silver is discussed controversially since the work of Carter et al 124 showed that the silver redox potential does not change in the presence of a glutamate hexamer.…”

“…Interestingly, these results imply that cysteine is a better ligand for Ag(I) than lysine, which is not in agreement with the calculated binding affinities discussed previously in section 2.1.1 (see Table 1). A similar system was investigated by Belser et al 118 who observed that a tripeptide containing both tyrosine and histidine as a strong silver binder is able to mineralize silver only after irradiation. The above summarized results for the involvement of tyrosine in the reduction process of silver clearly indicate that there is still a long way to go to understand the mechanistic pathways involved in the mineralization of silver, and it has to be seen whether the formation of dityrosine takes place in response to the presence of silver ions.…”

Silver coordination polymers with isonicotinic acid derived short polyethylene glycol – Synthesis, structures, anion effect and solution behavior

“…In our hands, we focus on several applications in the context of silver chemistry on one hand and the ligand Lin on the other. One is concerned with the generation of silver nanoparticles [19,20], as we were able to show that our compounds possess good light stability in the cases where the silver ions are spaced from each other [15,7], or poor light stability if silver ions are arranged close to each other [7]. Another application deals with the antimicrobial properties of the silver ions, for which we were able to show that compounds e.g.…”

From Alkaline Earth Ion Aggregates via Transition Metal Coordination Polymer Networks towards Heterometallic Single Source Precursors for Oxidic Materials

“…[36,37] Furthermore, the ligand has to be easily synthesized and available in large quantities at a low cost, because it rently in development as coatings for implant materials. [44][45][46][47] With the longer ligand L2, mainly metallacycles based on two silver ions and two ligands are observed, with the exception of a one-dimensional simple helical compound (Fig. 4) [48] and a two-dimensional polycatenated structure.…”