Enhanced anti-microbial effect through cationization of a mono-triazatricyclodecane substituted asymmetric phthalocyanine

Inactivation of Nosema spp. with zinc phthalocyanine

Most honey bee pathogens, such as Vairimorpha (Nosema), cannot be rapidly and definitively diagnosed in a natural setting, consequently there is typically the spread of these diseases through shared and re-use of beekeeping equipment. Furthermore, there are no viable treatment options available for Nosema spores to aid in managing the spread of this bee disease. We therefore aimed to develop a new method using novel Zinc Phthalocyanine (ZnPc) as a photosensitizer for the photodynamic inactivation of Nosema spores that could be used for the decontamination of beekeeping equipment. Nosema spores were propagated for in vitro testing using four caged Apis mellifera honey bees. The ZnPc treatment was characterized, encapsulated with a liposome, and then used as either a 10 or 100 µM treatment for the freshly harvested Nosema spores, for either a 30 and or 60-minute time period, under either light or dark conditions, in-vitro, in 96-well plates. In the dark treatment, after 30-min, the ZnPc 100 µM treatment, caused a 30 % Nosema mortality, while this increased to 80 % at the same concentration after the light treatment. The high rate of anti-spore effects, in a short period of time, supports the notion that this could be an effective treatment for managing honey bee Nosema infections in the future. Our results also suggest that the photo activation of the treatment could be applied in the field setting and this would increase the sterilization of beekeeping equipment against Nosema.

From disinfectants to antibiotics: Enhanced biosafety of quaternary ammonium compounds by chemical modification

The excessive use of quaternary ammonium compounds (QACs) following the COVID-19 pandemic has raised substantial concerns regarding their biosafety. Overuse of QACs has been associated with chronic biological adverse effects, including genotoxicity or carcinogenicity. In particular, inadvertent intravascular administration or oral ingestion of QACs can lead to fatal acute toxicity. To enhance the biosafety and antimicrobial efficacy of QACs, this study reports a new series of QACs, termed as PACs, with the alkyl chain of benzalkonium substituted by a phthalocyanine moiety. Firstly, the rigid phthalocyanine moiety enhances the selectivity of QACs to bacteria over human cells and reduces alkyl chain's entropic penalty of binding to bacterial membranes. Furthermore, phthalocyanine neutralizes hemolysis and cytotoxicity of QACs by binding with albumin in plasma. Our experimental results demonstrate that PACs inherit the optical properties of phthalocyanine and validate the broad-spectrum antibacterial activity of PACs in vitro. Moreover, the intravascular administration of the most potent PAC, PAC1a, significantly reduced bacterial burden and ameliorated inflammation level in a bacteria-induced septic mouse model. This study presents a new strategy to improve the antimicrobial efficacy and biosafety of QACs, thus expanding their range of applications to the treatment of systemic infections.

Double-Grafted PET Fiber Material to Remove Airborne Bacteria with High Efficiency

Air pollution caused by bacteria and viruses has posed a serious threat to public health. Commercial air purifiers based on dense fibrous filters can remove particulate matter, including airborne pathogens, but do not kill them efficiently. Here, we developed a double-grafted antibacterial fiber material for the high-efficiency capture and inactivation of airborne microorganisms. Tetracarboxyl phthalocyanine zinc, a photosensitizer, was first grafted onto the polyester (PET) fiber, followed by coating with chitosan on the surface of PET fiber to make a double-grafted fiber material. Under the irradiation of light with a specific wavelength (680 nm), double-grafted fiber materials killed up to 99.99% of Gram-positive bacteria and Gram-negative bacteria and had a significant antibacterial effect on drug-resistant bacteria. The double-grafted PET fiber showed broad-spectrum antibacterial activities and was capable to inactivate drug-resistant bacteria. Notably, in filtration experiments for airborne bacteria, this double-grafted PET fiber demonstrated a high bacteria capture efficiency (95.68%) better than the untreated PET fiber (64.87%). Besides, the double-grafted PET fiber was capable of efficiently killing airborne bacteria. This work provides a new idea for the development of air filtration materials that can efficiently kill airborne pathogen and has good biosafety.

Latest trends on photodynamic disinfection of Gram-negative bacteria: photosensitizer's structure and delivery systems

Antimicrobial resistance is threatening to overshadow last century's medical advances. Etiological agents of previously eradicated infectious diseases are now resurgent as multidrug-resistant strains, especially for Gram-negative strains. Finding new therapeutic solutions is a real challenge for our society. In this framework, Photodynamic Antimicrobial ChemoTherapy relies on the generation of toxic reactive oxygen species in the presence of light, oxygen, and a photosensitizer molecule. The use of reactive oxygen species is common for disinfection processes, using chemical agents, such as chlorine and hydrogen peroxide, and as they do not have a specific molecular target, it decreases the potential of tolerance to the antimicrobial treatment. However, light-driven generated reactive species result in an interesting alternative, as reactive species generation can be easily tuned with light irradiation and several PSs are known for their low environmental impact. Over the past few years, this topic has been thoroughly studied, exploring strategies based on single-molecule PSs (tetrapyrrolic compounds, dipyrrinate derivatives, metal complexes, etc.) or on conjunction with delivery systems. The present work describes some of the most relevant advances of the last 6 years, focusing on photosensitizers design, formulation, and potentiation, aiming for the disinfection of Gram-negative bacteria.

Photodynamic and Photothermal Ce6-Modified Gold Nanorod as a Potent Alternative Candidate for Improved Photoinactivation of Bacteria

The global rise of antibiotic resistance of pathogenic bacteria has become an increasing medical and public concern, which is further urging the development of antimicrobial channels for treating infectious diseases. The combination of photodynamic therapy (PDT) with photothermal therapy (PTT) has been considered as a promising alternative way for the replacement of traditional antibiotic therapy. In this research, the newly fabricated Chlorin-e6 (Ce6) conjugated mesoporous silica-coated AuNRs, designated AuNR@SiO₂-NH₂-Ce6, exhibited synergistic photothermal effects and single oxygen localized generation property, and showed stronger photoinactivation for bacteria compared with Ce6. AuNR@SiO₂-NH₂-Ce6 can anchor to the cell membrane and accumulate in the interior of cells. Furthermore, the unique porous structure of AuNR@SiO₂NH₂ enabled Ce6 encapsulation in the mesopores and was subsequently released and activated by photothermic effect, allowing the generated single oxygen to penetrate into the cytoplasmic membrane or directly enter the interior of bacteria cells, thus overcoming the inherent defects of single oxygen. AuNR@SiO₂-NH₂-Ce6 not only damaged the integrity of the cell membrane of bacteria but also facilitated the cellular permeation and accumulation of external nanoagents in the bacteria upon light irradiation. In addition, AuNR@SiO₂-NH₂-Ce6 exhibited negligible cytotoxicity toward mammalian cells and hemolytic activity. Therefore, AuNR@SiO₂-NH₂-Ce6 may be highly promising candidates as topical antibacterial agents, and this study has wide implications on the design of next-generation antimicrobial agents.

A3B type unsymmetrical and amphiphilic phthalocyanines: Synthesis, characterization, thermal stability and aggregation studies

This study reports the preparation, analysis, aggregation statuses and thermal properties of five phthalocyanines. The preparation of all molecules includes two steps: the first step is the preparation of phthalocyanine precursor molecules (A and B coded phthalonitriles); the second step is the synthesis of one metal-free and four metalled phthalocyanines (A₃B-Co, A₃B-Cu, A₃B-H, A₃B-Ni, and A₃B-Zn coded compounds). Compound A holds a hydrophobic chain (cetyl alcohol); compound B holds a hydrophilic chain (tetraethylene glycol). Phthalocyanines include three hydrophobic chains and one hydrophilic chain (A₃B type phthalocyanine). Characterization methods which were used to determine the structure of these compounds are Fourier Transform Infrared (FTIR), Proton Nuclear Magnetic Resonance (¹H NMR), Carbon-13 Nuclear Magnetic Resonance (¹³C NMR), and Ultraviolet Visible (UV Vis) spectroscopies and elemental analysis. The phthalocyanines have high stability up to 260 °C as a minimum value. Aggregation statuses of the phthalocyanines change to the metal from the metal or to the solvent from the solvent.