title: Antibiotic gold: tethering of antimicrobial peptides to gold nanoparticles maintains conformational flexibility of peptides and improves trypsin susceptibility.
abstract: Peptide-coated nanoparticles are valuable tools for diverse biological applications, such as drug delivery, molecular recognition, and antimicrobial action. The functionalization of pre-fabricated nanoparticles with free peptides in solution is inefficient either due to aggregation of the particles or due to the poor ligand exchange reaction. Here, we present a one-pot synthesis for preparing gold nanoparticles with a homogeneous distribution that are covered in situ with cationic peptides in a site-selective manner via Cys-residue at the N-terminus. Five representative peptides were selected, which are known to perturb cellular membranes and exert their antimicrobial and/or cell penetrating activity by folding into amphiphilic α-helical structures. When tethered to the nanoparticles at a single site, all peptides were found to switch their conformation from unordered state (in aqueous buffers) to their functionally relevant α-helical conformation in the presence of model membranes, as shown by circular dichroism spectroscopy. The conjugated peptides also maintained the same antibacterial activity as in the free form. Most importantly, when tethered to the gold nanoparticles the peptides showed an enormous increase in stability against trypsin digestion compared to the free forms, leading to a dramatic improvement of their lifetimes and activities. These findings suggest that site-selective surface tethering of peptides to gold nanoparticles has several advantages: (i) it does not prevent the peptides from folding into their biologically active conformation, (ii) such conjugation protects the peptides against protease digestion, and (iii) this way it is possible to prepare stable, water soluble antimicrobial nanoparticles as promising antibacterial agents.
authors.affiliation: Karlsruhe Institute of Technology (KIT), 1Institute of Biological Interfaces (IBG-2) P.O.B. 3640, D 76021 Karlsruhe, Germany. Anne.Ulrich@kit.edu.
authors.forename: Parvesh
authors.initials: P
authors.lastname: Wadhwani
authors.affiliation: KIT, 2Institute of Organic Chemistry & CFN, Fritz-Haber-Weg 6, D-76131 Karlsruhe, Germany.
authors.forename: Nico
authors.initials: N
authors.lastname: Heidenreich
authors.affiliation: KIT, 2Institute of Organic Chemistry & CFN, Fritz-Haber-Weg 6, D-76131 Karlsruhe, Germany.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Podeyn
authors.affiliation: Karlsruhe Institute of Technology (KIT), 1Institute of Biological Interfaces (IBG-2) P.O.B. 3640, D 76021 Karlsruhe, Germany. Anne.Ulrich@kit.edu.
authors.forename: Jochen
authors.initials: J
authors.lastname: Bürck
authors.affiliation: Karlsruhe Institute of Technology (KIT), 1Institute of Biological Interfaces (IBG-2) P.O.B. 3640, D 76021 Karlsruhe, Germany. Anne.Ulrich@kit.edu and KIT, 2Institute of Organic Chemistry & CFN, Fritz-Haber-Weg 6, D-76131 Karlsruhe, Germany.
authors.forename: Anne S
authors.identifier: http://orcid.org/0000-0001-5571-9483
authors.initials: AS
authors.lastname: Ulrich
mesh_terms: D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000008:administration & dosage* / Q000737:chemistry; D023181:Antimicrobial Cationic Peptides / Q000008:administration & dosage* / Q000737:chemistry; D001419:Bacteria / Q000187:drug effects; D001424:Bacterial Infections / Q000188:drug therapy; D004337:Drug Carriers / Q000737:chemistry*; D004355:Drug Stability; D006046:Gold / Q000737:chemistry*; D006801:Humans; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D000072756:Protein Conformation, alpha-Helical; D014357:Trypsin / Q000737:chemistry
chemical_list: D000900:Anti-Bacterial Agents; D023181:Antimicrobial Cationic Peptides; D004337:Drug Carriers; D006046:Gold; D014357:Trypsin