Abstract
Nowadays, thanks to nanotechnological progress, which itself guides us more and more closely toward not only the efficient design of innovative nanomaterials or nanostructures, but to the improvement of their functionality, we benefit from an important asset in the battle against pathogenic illnesses. Herein, we report a versatile biocompatible plasmonic nanoplatform based on a Whatman paper incorporating positively-charged gold nanospherical particles via the immersion approach. The morphological characterization of the as-engineered-plasmonic paper was examined by SEM (scanning electron microscopy) and HRTEM (high-resolution transmission electron microscopy) investigations, while its surface chemical modification with a synthetic polypeptide, specifically RRWHRWWRR-NH2 (P2), was proved by monitoring the plasmonic response of loaded gold nanospheres and the emission signal of P2 via fluorescence spectroscopy. The as-functionalized plasmonic paper is non-cytotoxic towards BJ fibroblast human cells at bactericidal concentrations. Finally, the antimicrobial activity of the P2-functionalized plasmonic paper on both planktonic bacteria and biofilms was tested against two reference strains: Gram-positive Bacteria, i.e., Staphylococcus aureus and the Gram-negative Bacteria, i.e., Escherichia coli, determining microbial inhibition of up to 100% for planktonic bacteria. In line with the above presented nanoplatform’s proper design, followed by their functionalization with active antimicrobial peptides, new roads can be open for determining antibiotic-free treatments against different relevant pathogens.
Highlights
Bacterial drug resistance can lead to serious health problems worldwide due to the long-term use of traditional antibiotics resulting in bacteria becoming immune to treatment [1]
Silver nanoparticles were proved to be very effective against bacteria strains [3], presenting antimicrobial activity both in the dark and under illumination [4,5], an important concern is still represented by their induced cytotoxicity, limiting their implementation in biological applications
Scaiano’s group, using amoxicillin coating of the gold nanoparticles surface, proved synergistic antimicrobial activity upon light irradiation against sensitive and antibiotic-resistant Staphylococcus aureus [12], while by employing lignin as a natural reducing and capping agent, they demonstrated that these formed non-toxic nanocomposites are able to act as bacteriostatic agents against bacterial biofilms [13]
Summary
Finding new antibiotics is becoming more and more difficult, and, new types of antibacterial compounds or novel innovative therapeutic approaches should be designed to solve this growing medical problem, being one of the top priorities for 2020, according to the World Health Organization (WHO) In this context, metal nanoparticles, based on their physical and chemical properties, have been recently proposed as versatile nanoplatforms of high research interest [2]. Gold nanoparticles exhibit low toxicity [8,9]; sometimes their intrinsic size and shape-dependent antibacterial activity seems to be insufficient To overcome this problem, the surface modification of the plasmonic nanoparticles could be an answer, through use of controlled grafting of different charged molecules facilitating specific binding to the bacterial membrane, and, generating an increase of their antibacterial activity [10]. The negatively-charged membrane permeability is a well-accepted mechanism to describe the action of the cationic AMPs [15], making them well suited for medical applications
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