π‐Extended Donor–Acceptor Porphyrins and Metalloporphyrins for Antimicrobial Photodynamic Inactivation

Free base, zinc and palladium π‐extended porphyrins containing fused naphthalenediamide units were employed as photosensitizers in antimicrobial photodynamic therapy (aPDT). Their efficacy, assessed by photophysical and in vitro photobiological studies on Gram‐positive bacteria, was found to depend on metal coordination, showing a dramatic enhancement of photosensitizing activity for the palladium complex

Dye extract of calyces of Hibiscus sabdariffa has photodynamic antibacterial activity: A prospect for sunlight‐driven fresh produce sanitation

Abstract Photodynamic sanitation of fresh produce could help reduce spoilage and disease transmissions where conventional methods of sanitation are not available, and sunlight is available for free. In this study, we evaluated the photostability and photodynamic antibacterial activity of the dye extracts of calyces of Hibiscus sabdariffa. The dye extracts were very photostable in water but bleached in acetate‐HCl buffer (pH 4.6), phosphate buffer saline (pH 7.2), and tris base‐HCl buffer (pH 8.6). The photostability correlated with the photodynamic antibacterial activity of the dye extracts. Both the methanol and water dye extracts at the concentration of 0.0625 mg/ml caused complete inactivation of Bacillus subtilis (reductions of 8.5 log CFU/ml) within 2 min either with the visible light exposure at 10 mW/cm2 or in the dark without the light exposure. Reductions of 4.8 log CFU/ml and 2.2 log CFU/ml of Escherichia coli were observed when 1 mg/ml of methanol and water dye extracts were used, respectively, in water with the light exposure at 10 mW/cm2 for 20 min. Discussions are included about the ease of the dye extractions of the calyces of H. sabdariffa even in water without the need of energy for heating and the suitability of the dye extracts for the fresh produce sanitation. Dye extract of calyces of H. sabdariffa has photodynamic and nonphotodynamic antibacterial activity which could be exploited for the development of a low‐tech sunlight‐driven fresh produce sanitation system that is cheap, sustainable, and environmentally friendly

Dye extract of calyces of 'Hibiscus sabdariffa' has photodynamic antibacterial activity: A prospect for sunlight-driven fresh produce sanitation

Photodynamic sanitation of fresh produce could help reduce spoilage and disease transmissions where conventional methods of sanitation are not available, and sunlight is available for free. In this study, we evaluated the photostability and photodynamic antibacterial activity of the dye extracts of calyces of 'Hibiscus sabdariffa'. The dye extracts were very photostable in water but bleached in acetate-HCl buffer (pH 4.6), phosphate buffer saline (pH 7.2), and tris base-HCl buffer (pH 8.6). The photostability correlated with the photodynamic antibacterial activity of the dye extracts. Both the methanol and water dye extracts at the concentration of 0.0625 mg/ml caused complete inactivation of 'Bacillus subtilis' (reductions of 8.5 log CFU/ml) within 2 min either with the visible light exposure at 10 mW/cm2 or in the dark without the light exposure. Reductions of 4.8 log CFU/ml and 2.2 log CFU/ml of Escherichia coli were observed when 1 mg/ml of methanol and water dye extracts were used, respectively, in water with the light exposure at 10 mW/cm2 for 20 min. Discussions are included about the ease of the dye extractions of the calyces of 'H. sabdariffa' even in water without the need of energy for heating and the suitability of the dye extracts for the fresh produce sanitation. Dye extract of calyces of 'H. sabdariffa' has photodynamic and nonphotodynamic antibacterial activity which could be exploited for the development of a low-tech sunlight-driven fresh produce sanitation system that is cheap, sustainable, and environmentally friendly

Regulation of photo triggered cytotoxicity in electrospun nanomaterials: role of photosensitizer binding mode and polymer identity

Although electrospun nanomaterials containing photoactive dyes currently compete with the present state of art antimicrobial materials, relatively few structure–activity relationships have been established to identify the role of carrier polymer and photosensitizer binding mode on the performance of the materials. In this study scaffolds composed of poly(vinyl alcohol), polyacrylonitrile, poly(caprolactone), and tailor-made phthalocyanine-based photosensitizers are developed utilizing electrospinning as a simple, time and cost-effective method. The photoinduced activity of nanofibrous materials was characterized in vitro against E. coli and B. subtilis as models for Gram-negative and Gram-positive bacteria respectively, as well as against bacteriophages phi6 and MS2 as models for enveloped and non-enveloped viruses respectively. For the first time, we show how polymer-specific properties affect antifouling and antimicrobial activity of the nanofibrous material, indicating that the most promising way to increase efficiency is likely via methods that focus on increasing the number of short, but strong and reversible bacteria–surface interactions

Oxygen-Insensitive Aggregates of Pt(II) Complexes as Phosphorescent Labels of Proteins with Luminescence Lifetime-Based Readouts

The synthesis and photophysical properties of a tailored Pt(II) complex are presented. The phosphorescence of its monomeric species in homogeneous solutions is quenched by interaction with the solvent and therefore absent even upon deoxygenation. However, aggregation-induced shielding from the environment and suppression of rotovibrational degrees of freedom trigger a phosphorescence turn-on that is not suppressed by molecular oxygen, despite possessing an excited-state lifetime ranging in the microsecond scale. Thus, the photoinduced production of reactive oxygen species is avoided by the suppression of diffusion-controlled Dexter-type energy transfer to triplet molecular oxygen. These aggregates emit with the characteristic green luminescence profile of monomeric complexes, indicating that Pt-Pt or excimeric interactions are negligible. Herein, we show that these aggregates can be used to label a model biomolecule (bovine serum albumin) with a microsecond-range luminescence. The protein stabilizes the aggregates, acting as a carrier in aqueous environments. Despite spectral overlaps, the green phosphorescence can be separated by time-gated detection from the dominant autofluorescence of the protein arising from a covalently bound green fluorophore that emits in the nanosecond range. Interestingly, the aggregates also acted as energy donors able to sensitize the emission of a fraction of the fluorophores bound to the protein. This resulted in a microsecond-range luminescence of the fluorescent acceptors and a shortening of the excited-state lifetime of the phosphorescent aggregates. The process that can be traced by a 1000-fold increase in the acceptor's lifetime mirrors the donor's triplet character. The implications for phosphorescence lifetime imaging are discussed.Fil: Delcanale, Pietro. Università di Parma; ItaliaFil: Galstyan, Anzhela. Westfalische Wilhelms Universitat; AlemaniaFil: Daniliuc, Constantin G.. Westfalische Wilhelms Universitat; AlemaniaFil: Grecco, Hernan Edgardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Abbruzzetti, Stefania. Università di Parma; ItaliaFil: Faust, Andreas. Westfalische Wilhelms Universitat; AlemaniaFil: Viappiani, Cristiano. Università di Parma; ItaliaFil: Strassert, Cristian A.. Westfalische Wilhelms Universitat; Alemani

π‐Extended Donor–Acceptor Porphyrins and Metalloporphyrins for Antimicrobial Photodynamic Inactivation

Free base, zinc and palladium π‐extended porphyrins containing fused naphthalenediamide units were employed as photosensitizers in antimicrobial photodynamic therapy (aPDT). Their efficacy, assessed by photophysical and in vitro photobiological studies on Gram‐positive bacteria, was found to depend on metal coordination, showing a dramatic enhancement of photosensitizing activity for the palladium complex