Surface photosterilization of implantable silicone biomaterials: structural and functional characterization

Hospital-acquired infections (HAIs) remain one of the major challenges faced by the global healthcare system. The increasing rate of pathogenic resistance against antibiotics suggests that alternative treatments are needed to control recurrent infections. Catheter-associated urinary tract infections (CAUTIs) are the third most common type of HAI worldwide, and this is mainly due to indwelling devices being excellent substrates for bacterial adhesion and growth. Subsequent biofilm formation on the implant surface acts as a constant nidus of bacteria and infection, thereby contributing to increased rates of patient morbidity and mortality. Here, we propose a simple and cost-effective method to sterilize silicone-based implant surfaces and prevent initial bacterial colonization, using Polydimethylsiloxane (PDMS) and an embedded ruthenium photosensitizer (PS). Exposure to LED light triggers potent photokilling action, resulting in significant bactericidal activity as evidenced by the number of adherent bacteria being below the level of detection (<10 CFU/mL) after 24 h. Live/dead staining studies using fluorescence microscopy indicated significant reduction in surface-adhered bacterial growth and biofilm formation. This potent antibacterial activity was verified in vivo, with exposure of contaminated PDMS coupons containing PS to LED prior to implantation resulting in over 99.5% reduction in adherent bacteria compared to controls over the 3-day implantation period. Histological analysis of the implantation site of PDMS+PS samples, in the absence of bacteria, revealed no adverse reactions. This was also confirmed using in vitro cytotoxicity studies. Tensile strength, surface roughness, hydrophobicity, and the development of encrustation of surface-treated groups exhibit comparable or improved properties to bare PDMS.

Mechanism of Oxygen Quenching of the Excited States of Heteroleptic Chromium(III) Phenanthroline Derivatives

In this study, we report the synthesis and characterization of some heteroleptic Cr(III) complexes of the form [Cr(Phen)2L](OTf)3, where Phen = 1,10-phenanthroline and L is either 2,2'-bipyridine (bpy) or its derivatives, such as 4,4'-dimethyl-2,2'-bipyridine (4,4'-DMB), 4,4'-dimethoxy-2,2'-bipyridine (4,4'-DMOB), 4,4'-ditert-butyl-2,2'-bipyridine (4,4'-dtbpy), 5,5'-dimethyl-2,2'-bipyridine (5,5'-DMB), 4,4'-dimethoxycarbonyl-2,2'-bipyridine (4,4'-dmcbpy) or 1,10-phenanthroline derivatives, such as 5-methyl-1,10-phenanthroline (5-Me-Phen) and 4,7-dimethyl-1,10-phenanthroline (4,7-DMP). Heteroleptic complexes were prepared in two stages via the intermediate [Cr(Phen)2(CF3SO3)2](CF3SO3) and five examples have been crystallographically characterized. Steady-state absorption and luminescence emission characteristics of these complexes were measured in 1 M HCl solutions. The luminescence quantum yield of these complexes was found to be the lowest for [Cr(Phen)2(4,4'-dmcbpy)](OTf)3 and the highest for [Cr(Phen)2(4,4'-DMB)](OTf)3 with values of 0.31 × 10-2 and 1.48 × 10-2, respectively. The calculated excited state energy, E0-0, was found to vary within the narrow range of 163.1-165.0 kJ mol-1 across the series. Transient absorption spectra in degassed, air-equilibrated, and oxygen-saturated 1 M HCl aqueous solutions were also measured at different time decays and demonstrated no significant differences, indicating the absence of any ion-separated species in the excited state. Excited-state decay traces at the wavelength of maximum absorption were used to calculate oxygen quenching rate constants, kq, which were found to be in the range 3.26-5.27 × 107 M-1 s-1. Singlet oxygen luminescence photosensitized by these complexes was observed in D2O, and its luminescence intensity at 1270 nm was used for the determination of singlet oxygen quantum yields for these complexes, which were in the range of 0.20-0.44, while the fraction of the excited 2E state quenched by oxygen was in the range of 0.22-0.68, and the efficiency of singlet oxygen production was in the range of 0.44-0.90. The mechanism by which the excited 2E state is quenched by oxygen is explained by a spin statistical model that predicts the balance between charge transfer and noncharge transfer deactivation pathways, which was represented by the parameter pCT that was found to vary from 0.35 to 0.68 for this series of Cr(III) complexes.

Development of water-soluble phenazine-2,3-diol-based photosensitizers for singlet oxygen generation

Phenazine-2,3-diol-based dyes, KY-1Na and KY-2Na bearing one and two carboxylic acid sodium salts, respectively, have been newly developed as water-soluble photosensitizers (PSs) possessing the ability to generate singlet oxygen (¹O₂). In order to evaluate the solubility of KY-1Na and KY-2Na in water, the hydrophobicity/hydrophilicity of the two PSs was investigated by experimental measurement of the logarithms (log P_o/w) of the 1-octanol/water partition coefficient (P_o/w) for the PS. The log P_o/w values of both KY-1Na and KY-2Na were determined to be -0.9, indicating that both the PSs are more hydrophilic than Rose Bengal (-0.6) and have hydrophilicity equivalent to methylene blue (-0.9). Both the PSs in water show a broad photoabsorption band in the range of 500 to 600 nm. Thus, we estimated the ¹O₂ quantum yields (Φ_Δ) of KY-1Na and KY-2Na in water by using 9,10-anthracenediyl-bis(methylene)dimalonic acid (ABDA) as a water-soluble ¹O₂ scavenger. It was found that in water the Φ_Δ value (0.19) of KY-2Na is higher than that of KY-1Na (0.06). Density functional theory (DFT) calculations suggested that the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) distributions for the molecular structure of KY-2Na are adequately separated, leading to a decrease in the energy gap (ΔE_ST) between the singlet state (S₁) and the triplet state (T₁) that causes efficient intersystem crossing (ISC), compared to that for the molecular structure of KY-1Na. Indeed, time-dependent DFT (TD-DFT) calculations demonstrated that the ΔE_ST(S₁-T₁) value (0.82 eV) of KY-2Na is smaller than that (0.98 eV) of KY-1Na, resulting in a relatively high Φ_Δ value of KY-2Na. Consequently, we demonstrate that phenazine-2,3-diol-based PSs bearing carboxylic acid salts possess high solubility and moderate ¹O₂ generation ability in water.

Photosensitization With Supramolecular Arrays for Enhanced Antimicrobial Photodynamic Treatments

Microbial infections represent a silent threat to health that has worsened in recent decades due to microbial resistance to multiple drugs, preventing the fight against infectious diseases. Therefore, the current postantibiotic era forces the search for new microbial control strategies. In this regard, antimicrobial photodynamic therapy (aPDT) using supramolecular arrays with photosensitizing capabilities showed successful emerging applications. This exciting field makes it possible to combine applied aspects of molecular photochemistry and supramolecular chemistry, together with the development of nano- and biomaterials for the design of multifunctional or "smart" supramolecular photosensitizers (SPS). This minireview aims to collect the concepts of the photosensitization process and supramolecular chemistry applied to the development of efficient applications of aPDT, with a brief discussion of the most recent literature in the field.

Recent Progress on Fullerene-Based Materials: Synthesis, Properties, Modifications, and Photocatalytic Applications

Solar light is an inexpensive energy source making up for energy shortage and solving serious environmental problems. For efficient utilization of solar energy, photocatalytic materials have attracted extensive attention over the last decades. As zero-dimensional carbon nanomaterials, fullerenes (C60, C70, etc.) have been extensively investigated for photocatalytic applications. Due to their unique properties, fullerenes can be used with other semiconductors as photocatalyst enhancers, and also as novel photocatalysts after being dispersed on non-semiconductors. This review summarizes fullerene-based materials (including fullerene/semiconductors and fullerene/non-semiconductors) for photocatalytic applications, such as water splitting, Cr (Ⅵ) reduction, pollutant degradation and bacterial disinfection. Firstly, the optical and electronic properties of fullerene are presented. Then, recent advances in the synthesis and photocatalytic mechanisms of fullerene-based photocatalysts are summarized. Furthermore, the effective performances of fullerene-based photocatalysts are discussed, mainly concerning photocatalytic H2 generation and pollutant removal. Finally, the current challenges and prospects of fullerene-based photocatalysts are proposed. It is expected that this review could bring a better understanding of fullerene-based photocatalysts for water treatment and environmental protection.

A Review of Theranostics Applications and Toxicities of Carbon Nanomaterials

BACKGROUND

In the last few years, the use of modified Carbon Nanomaterials (CNMs) for theranostics (therapeutic and diagnosis) applications is a new and rapidly growing area in pharmacy and medical fields. Owing to this, their specific physicochemical behaviors like high stability, drug loading, surface area to volume ratio, with low toxicity and immunogenicity are mainly responsible to be considered those as smart nanomaterials.

OBJECTIVES

This review describes the different dimensions of carbon-based nanocarriers including 0-D fullerene, 1-D Carbon Nanotubes (CNTs), and 2-D graphene and Graphene Oxide (GO) and their surface modification with different biocompatible and biodegradable molecules via covalent or non-covalent functionalization. The major focus of this article is on the different theranostics applications of CNMs like targeted drugs and genes delivery, photodynamic therapy, photothermal therapy, bioimaging, and biosensing. The therapeutic efficacy of drugs could be enhanced by delivering them directly on a specific site using different targeted ligands such as vitamins, peptide, carbohydrates, proteins, etc. A section of the article also discusses the toxicity of the CNMs to the living systems.

CONCLUSIONS

In brief, this review article discusses the numerous theranostics applications and toxicities of CNMs.

Revisiting Current Photoactive Materials for Antimicrobial Photodynamic Therapy

Microbial infection is a severe concern, requiring the use of significant amounts of antimicrobials/biocides, not only in the hospital setting, but also in other environments. The increasing use of antimicrobial drugs and the rapid adaptability of microorganisms to these agents, have contributed to a sharp increase of antimicrobial resistance. It is obvious that the development of new strategies to combat planktonic and biofilm-embedded microorganisms is required. Photodynamic inactivation (PDI) is being recognized as an effective method to inactivate a broad spectrum of microorganisms, including those resistant to conventional antimicrobials. In the last few years, the development and biological assessment of new photosensitizers for PDI were accompanied by their immobilization in different supports having in mind the extension of the photodynamic principle to new applications, such as the disinfection of blood, water, and surfaces. In this review, we intended to cover a significant amount of recent work considering a diversity of photosensitizers and supports to achieve an effective photoinactivation. Special attention is devoted to the chemistry behind the preparation of the photomaterials by recurring to extensive examples, illustrating the design strategies. Additionally, we highlighted the biological challenges of each formulation expecting that the compiled information could motivate the development of other effective photoactive materials.

Recent advances in nanomaterials for water protection and monitoring

Nanomaterials (NMs) for adsorption, catalysis, separation, and disinfection are scrutinized. NMs-based sensor technologies and environmental transformations of NMs are highlighted.

Photoactive antimicrobial nanomaterials

Nanomaterials for killing pathogenic bacteria under light irradiation.

Dual-Functionality Fullerene and Silver Nanoparticle Antimicrobial Composites via Block Copolymer Templates

We present the facile prepartion of C₇₀ and Ag nanoparticle (NP) loaded block copolymer (BCP) thin films, with C₇₀ and Ag NPs working in tandem to provide virucidal and bactericidal activities, respectively. Polystyrene-block-poly-4-vinylpyridine (PS-P4VP) was used as a template, allowing C₇₀ integration into PS domains and in situ formation of Ag NPs in P4VP domains, while providing control of the nanoscale spatial distribution of functionality as a function of BCP molecular weight (MW). C₇₀ loaded PS-P4VP films were found to generate significant amounts of ¹O₂ under visible light illumination with no apparent dependence on BCP MW. An analogous C₇₀ loaded PS homopolymer film produced notably less ¹O₂, highlighting a possible critical role of morphology on C₇₀ photoactivity. The antimicrobial activity of Ag NP and C₇₀ loaded composites against the model PR772 bacteriophage and Escherichia coli was assessed, finding synergistic inactivation afforded by the dual functionality. BCPs were demonstrated as versatile platforms for the preparation of multifunctional antimicrobial coatings toward combating diverse microbial communities.

Improving the Visible Light Photoactivity of Supported Fullerene Photocatalysts through the Use of [C₇₀] Fullerene

We herein present the first instance of employing [C₇₀] fullerene for photocatalytic ¹O₂ production in water, through covalent immobilization onto a mesoporous silica support via nucelophilic amine addition directly to fullerene's cage. This attachment approach prevents the aggregation of individual fullerene molecules in water, thus allowing fullerene to retain its photoactivity, yet is much less complex than other techniques commonly pursued to create such supported-fullerene materials, which typically rely on water-soluble fullerene derivatives and elaborate immobilization methods. The solid-supported C₇₀ material exhibits significantly improved aqueous visible-light photoactivity compared to previous C₆₀- and C₆₀-derivative-based supported fullerene materials. Further, this material rapidly inactivates MS2 bacteriophage under sunlight illumination, oxidizes various organic contaminants, and does not appear to be significantly fouled by natural organic matter (NOM), highlighting the potential of these materials in real-world applications. Collectively, the ease of preparation and significantly enhanced visible-light photoactivity of these materials advance fullerene-based technologies for water treatment.

Antimicrobial photodynamic inactivation in nanomedicine: small light strides against bad bugs

The relentless advance of drug-resistance among pathogenic microbes, mandates a search for alternative approaches that will not cause resistance. Photodynamic inactivation (PDI) involves the combination of nontoxic dyes with harmless visible light to produce reactive oxygen species that can selectively kill microbial cells. PDI can be broad-spectrum in nature and can also destroy microbial cells in biofilms. Many different kinds of nanoparticles have been studied to potentiate antimicrobial PDI by improving photosensitizer solubility, photochemistry, photophysics and targeting. This review will cover photocatalytic disinfection with titania nanoparticles, carbon nanomaterials (fullerenes, carbon nanotubes and graphene), liposomes and polymeric nanoparticles. Natural polymers (chitosan and cellulose), gold and silver plasmonic nanoparticles, mesoporous silica, magnetic and upconverting nanoparticles have all been used for PDI.