Hybrid Plasmonic Photoreactors as Visible Light-Mediated Bactericides

Abstract

Photocatalytic compounds and complexes, such as tris(bipyridine)ruthenium(II), [Ru(bpy)3]2+, have shown promise as light-mediated bactericides. However, transition metal-based complexes require relatively high concentrations (ppm level) to achieve reliable antibacterial effects. There is consequently a need for new approaches that provide improved efficacy and control of the antibacterial function of these complexes. In this work, we demonstrate strong, visible light-dependent bacterial inactivation with a nanocomposite design that incorporates [Ru(bpy)3]2+ as photocatalyst and a Ag nanoparticle (NP) core as light-concentrating nanoantenna into a plasmonic hybrid photoreactor. The hybrid photoreactor platform is facilitated by a self-assembled lipid membrane that encapsulates the Ag NP and binds the photocatalyst. The lipid membrane renders the nanocomposite biocompatible in the absence of resonant illumination. Upon illumination, the plasmon-enhanced photoexcitation of the metal-toligand-charge-transfer band of [Ru(bpy)3]2+ prepares the reactive excited state of the complex that oxidizes the nanocomposite membrane and increases its permeability. The photooxidation induces the release of [Ru(bpy)3]2+, Ag+, and peroxidized lipids into the ambient medium, where they interact synergistically to inactivate bacteria. We measured seven orders of magnitude decrease in Gram-positive Arthrobacter sp. and four orders of magnitude decrease in Gramnegative Escherichia coli (E. coli) colony forming units (CFUs) with the photoreactor bactericides after 1-hour of visible light illumination. In both cases the photoreactor exceeds the bactericidal standard of a log reduction value (LRV) of 3, and surpasses the antibacterial effect of free Ag NPs or [Ru(bpy)3]2+ by more than four orders of magnitude. We also implement the inactivation of a bacterial thin film in a proof-of-concept study.

Cu(i) diimine complexes as immobilised antibacterial photosensitisers operating in water under visible light

“…[24][25][26][27][28][29][30] Metal ions such as Ag + , 31,32 metal oxides such as ZnO, 33 and complexes based on various metal ions including Cu(I), 34 have shown to be toxic to bacteria without light; 31,32,34 whilst inherently phototoxic metal nanoparticles have been used together with photosensitisers to promote the photoactivated production of ROS to initiate bacterial killing. 33,35 Other well-known photosensitisers include porphyrins, 36,37 such as derivatives of Zn(II) porphyrazine, or 5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin tetra-iodide (tetra-Py + -Me), which have also been used for water treatment with good results: for example, tetra-Py + -Me at 10 mM achieved a reduction of 99.999% of E. coli after 120 min of irradiation with artificial white light (380-700 nm).…”

Ruthenium‐based Photoactive Metalloantibiotics†

“…The Ag‐Ru/LDH hybrid was found to be more effective against Gram (+) bacteria than Gram (−) bacteria. Similarly, Reinhard and coworkers have designed a nanocomposite by coupling a [Ru(bpy) 3 ] 2+ and a silver nanoparticles core into a plasmonic photoreactor (96). Upon photoirradiation (<10 mW cm −2 ) of [Ru(bpy) 3 ] 2+ , a reactive state forms that oxidizes nanocomposite membrane and therefore increases its permeability (Fig.…”

Plasmonic photoreactors-coated plastic tubing as combined-active-and-passive antimicrobial flow sterilizer

“…9,12 The former typically involves nanostructured hydrophobic compounds to generate anti-fouling properties and trigger bacterial growth inhibition, [13][14][15] whereas the latter comprises a range of different strategies, including antibacterial polymers, proteins and peptides, 16,17 functional polymers or surfactants that lyse the microbes, [18][19][20][21][22] carbon-based materials such as graphene 23 and fullerene 24 for mechanical, photochemical, or photothermal inactivation, or metal-based nanostructures that can release metal cations as bactericides or that trigger photophysical inactivation pathways. 12,[25][26][27][28][29] Silver nanoparticles (NPs) are effective generic antibacterial agents [30][31][32][33][34] and represent the most commonly used metal-based antimicrobial coating. 12,24,27,29,35 Silver NPs were found to sustain not only light-independent antibacterial effects, such as the release of Ag + , 30,33,36 binding to bacterial surfaces, 37 permeation of bacteria cell bodies for inducing intracellular damages, 38 or synergistic enhancement of antibiotics, 39 but also light-dependent effects through plasmonic photodynamic chemotherapy (PDCT), [30][31][32] photothermal, 40 and...…”

“…12,[25][26][27][28][29] Silver nanoparticles (NPs) are effective generic antibacterial agents [30][31][32][33][34] and represent the most commonly used metal-based antimicrobial coating. 12,24,27,29,35 Silver NPs were found to sustain not only light-independent antibacterial effects, such as the release of Ag + , 30,33,36 binding to bacterial surfaces, 37 permeation of bacteria cell bodies for inducing intracellular damages, 38 or synergistic enhancement of antibiotics, 39 but also light-dependent effects through plasmonic photodynamic chemotherapy (PDCT), [30][31][32] photothermal, 40 and/or photocatalytic processes. 41 Microbicidal compound-releasing materials scaffolds are another notable example of active antimicrobial coatings.…”