Covalent Immobilization of Organic Photosensitizers on the Glass Surface: Toward the Formation of the Light-Activated Antimicrobial Nanocoating

Abstract

Two highly efficient commercial organic photosensitizers—azure A (AA) and 5-(4-aminophenyl)-10,15,20-(triphenyl)porphyrin (APTPP)—were covalently attached to the glass surface to form a photoactive monolayer. The proposed straightforward strategy consists of three steps, i.e., the initial chemical grafting of 3-aminopropyltriethoxysilane (APTES) followed by two chemical postmodification steps. The chemical structure of the resulting mixed monolayer (MIX_TC_APTES@glass) was widely characterized by X-ray photoelectron (XPS) and Raman spectroscopies, while its photoactive properties were investigated in situ by UV–Vis spectroscopy with α-terpinene as a chemical trap. It was shown that both photosensitizers retain their activity toward light-activated generation of reactive oxygen species (ROS) after immobilization on the glassy surface and that the resulting nanolayer shows high stability. Thanks to the complementarity of the spectral properties of AA and APTPP, the effectiveness of the ROS photogeneration under broadband illumination can be optimized. The reported light-activated nanocoating demonstrated promising antimicrobial activity toward Escherichia coli (E. coli), by reducing the number of adhered bacteria compared to the unmodified glass surface.

Light-Induced Anti-Bacterial Effect Against Staphylococcus aureus of Porphyrin Covalently Bonded to a Polyethylene Terephthalate Surface

“…This was achieved through a C–H insertion mechanism wherein diazirine moieties lose dinitrogen after thermal-, photo-, or electro-activation and form a carbon–carbon bond with the substrate. The use of diazirine-based molecules as cross-linkers of aliphatic polymer materials was previously reported by our group. , Chemical approaches based on the formation of covalent bonds between a photosensitizer and the surface can increase the stability of the material . Additionally, since the porphyrin is covalently attached to a surface, the molecule is prevented from leaching into the environment, meaning that bioaccumulation will not be a concern and it will not be necessary to develop a method for the removal of the molecule.…”

“… 24 , 26 , 29 − 38 Different physical methods have been applied to incorporate porphyrins and other photosensitizers into surfaces. 26 , 39 − 42 Building on previous work by Spontak, where a zinc porphyrin embedded within a polymer effectively inactivated both Gram-negative and Gram-positive bacteria, 26 we designed a zinc porphyrin molecule 1 , zinc(II) 5,10,15,20-tetrakis(( N -4-[3-(trifluoromethyl)-3 H -diazirin-3-yl]benzyl)-4-pyridyl)-21 H ,23 H -porphine tetrabromide, that could be covalently attached to carbon-based polymers ( Figure 1 ). This was achieved through a C–H insertion mechanism wherein diazirine moieties lose dinitrogen after thermal-, photo-, or electro-activation and form a carbon–carbon bond with the substrate.…”

“… 43 , 44 Chemical approaches based on the formation of covalent bonds between a photosensitizer and the surface can increase the stability of the material. 39 Additionally, since the porphyrin is covalently attached to a surface, the molecule is prevented from leaching into the environment, meaning that bioaccumulation will not be a concern and it will not be necessary to develop a method for the removal of the molecule. Recently, the use of a tetra-substituted diazirine porphyrin covalently bonded to nonwoven melt-blown polypropylene textiles was demonstrated by our group to be efficient for virus inactivation.…”

“…A particularly promising method for producing nonspecific antimicrobial activity is the use of photosensitizers to produce singlet oxygen in the presence of light . The singlet oxygen disrupts the cell membrane in a nonselective manner and does not trigger an oxidative stress response, meaning bacteria are not likely to develop a resistance to singlet oxygen. , At this point, it is debatable whether or not a resistance to singlet oxygen can be developed, but photodynamic inactivation has demonstrated success as an antimicrobial approach. , There is precedent for using cationic porphyrin molecules, a known group of photosensitizers, in antimicrobial materials. ,,− Different physical methods have been applied to incorporate porphyrins and other photosensitizers into surfaces. ,− Building on previous work by Spontak, where a zinc porphyrin embedded within a polymer effectively inactivated both Gram-negative and Gram-positive bacteria, we designed a zinc porphyrin molecule 1 , zinc­(II) 5,10,15,20-tetrakis­(( N -4-[3-(trifluoromethyl)-3 H -diazirin-3-yl]­benzyl)-4-pyridyl)-21 H ,23 H -porphine tetrabromide, that could be covalently attached to carbon-based polymers (Figure ). This was achieved through a C–H insertion mechanism wherein diazirine moieties lose dinitrogen after thermal-, photo-, or electro-activation and form a carbon–carbon bond with the substrate.…”

Antimicrobial photodynamic inactivation of planktonic and biofilm cells by covalently immobilized porphyrin on polyethylene terephthalate surface

“…These supports include cellulose, chitosan, cotton, multi-walled carbon nanotubes, polystyrene and nylon films (Spagnul et al, 2015). Moreover, these porphyrin-enhanced surfaces demonstrated antimicrobial effect against different Gram negative and Gram positive bacteria including E. coli ( Ringot et al, 2011;Castro et al, 2017;Nyga et al, 2021), and S. aureus (Ringot et al, 2011;Dastgheyb et al, 2015).…”