Synthesis and characterization of novel BODIPYs and their antioxidant, antimicrobial, photodynamic antimicrobial, antibiofilm and DNA interaction activities

In the current study, we synthesized and characterized new BODIPY derivatives (1-4) having pyridine or thienyl-pyridine substituents at meso- position and 4-dibenzothienyl or benzo[b]thien-2-yl moieties at 2-,6- positions. We investigated fluorescence properties and the ability to form singlet oxygen. In addition, various biological activities of BODIPYs such as DPPH scavenging, DNA binding/cleavage ability, cell viability inhibition, antimicrobial activity, antimicrobial photodynamic therapy (aPDT) and biofilm inhibition properties were performed. BODIPY derivatives BDPY-3 (3) and BDPY-4 (4) have high fluorescence quantum yields as 0.50 and 0.61 and 1 O2 quantum yields were calculated as 0.83 for BDPY-1 (1), 0.12 for BDPY-2 (2), 0.11 for BDPY-3 and 0.23 for BDPY-4. BODIPY derivatives BDPY-2, BDPY-3 and BDPY-4 displayed 92.54 ± 5.41%, 94.20 ± 5.50%, and 95.03 ± 5.54% antioxidant ability, respectively. BODIPY compounds showed excellent DNA chemical nuclease activity. BDPY-2, BDPY-3 and BDPY-4 also exhibited 100% APDT activity against E. coli at all tested concentrations. In addition to these, they demonstrated a highly effective biofilm inhibition activity against Staphyloccous aureus and Pseudomans aeruginosa. BDPY-4 showed the most effective antioxidant and DNA cleavage activity, while BDPY-3 exhibited the most effective antimicrobial and antibiofilm activity.

Recent Progress and Trends in the Development of Electrospun and 3D Printed Polymeric-Based Materials to Overcome Antimicrobial Resistance (AMR)

Antimicrobial resistance (AMR) developed by microorganisms is considered one of the most critical public health issues worldwide. This problem is affecting the lives of millions of people and needs to be addressed promptly. Mainly, antibiotics are the substances that contribute to AMR in various strains of bacteria and other microorganisms, leading to infectious diseases that cannot be effectively treated. To avoid the use of antibiotics and similar drugs, several approaches have gained attention in the fields of materials science and engineering as well as pharmaceutics over the past five years. Our focus lies on the design and manufacture of polymeric-based materials capable of incorporating antimicrobial agents excluding the aforementioned substances. In this sense, two of the emerging techniques for materials fabrication, namely, electrospinning and 3D printing, have gained significant attraction. In this article, we provide a summary of the most important findings that contribute to the development of antimicrobial systems using these technologies to incorporate various types of nanomaterials, organic molecules, or natural compounds with the required property. Furthermore, we discuss and consider the challenges that lie ahead in this research field for the coming years.

Antimicrobial activity of photosensitizers: arrangement in bacterial membrane matters

Porphyrins are well-known photosensitizers (PSs) for antibacterial photodynamic therapy (aPDT), which is still an underestimated antibiotic-free method to kill bacteria, viruses, and fungi. In the present work, we developed a comprehensive tool for predicting the structure and assessment of the photodynamic efficacy of PS molecules for their application in aPDT. We checked it on a series of water-soluble phosphorus(V) porphyrin molecules with OH or ethoxy axial ligands and phenyl/pyridyl peripheral substituents. First, we used biophysical approaches to show the effect of PSs on membrane structure and their photodynamic activity in the lipid environment. Second, we developed a force field for studying phosphorus(V) porphyrins and performed all-atom molecular dynamics simulations of their interactions with bacterial lipid membranes. Finally, we obtained the structure-activity relationship for the antimicrobial activity of PSs and tested our predictions on two models of Gram-negative bacteria, Escherichia coli and Acinetobacter baumannii. Our approach allowed us to propose a new PS molecule, whose MIC₅₀ values after an extremely low light dose of 5 J/cm² (5.0 ± 0.4 μg/mL for E. coli and 4.9 ± 0.8 μg/mL for A. baumannii) exceeded those for common antibiotics, making it a prospective antimicrobial agent.

Antimicrobial Photodynamic Therapy against Escherichia coli and Staphylococcus aureus Using Nanoemulsion-Encapsulated Zinc Phthalocyanine

Multidrug-resistant microorganisms have become a significant public health threat, and traditional antibiotics are becoming ineffective. Photodynamic therapy (PDT) is a promising alternative that utilizes photosensitizers and light to produce Reactive Oxygen Species (ROS) that can kill microorganisms. Zinc phthalocyanine (ZnPc) is a promising photosensitizer due to its strong affinity for encapsulation in nanoemulsions and its antimicrobial properties. In this study, nanoemulsion was prepared using Miglyol 812N, a surfactant, and distilled water to dissolve hydrophobic drugs such as ZnPc. The nanoemulsion was characterized by its particle size, polydispersity index, Transmission Electron Microscope and Zeta potential, and the results showed that it was an efficient nanocarrier system that facilitated the solubilization of hydrophobic drugs in water. The use of ZnPc encapsulated in the nanoemulsion produced through the spontaneous emulsification method resulted in a significant reduction in cell survival percentages of gram-positive Staphylococcus aureus and gram-negative Escherichia coli by 85% and 75%, respectively. This may be attributed to the more complex cell membrane structure of E. coli compared to S. aureus. This demonstrates the potential of nanoemulsion-based PDT as an effective alternative to traditional antibiotics for treating multidrug-resistant microorganisms.

Photodynamic potential of hexadecafluoro zinc phthalocyanine in nanostructured lipid carriers: physicochemical characterization, drug delivery and antimicrobial effect against Candida albicans

This study aims to develop and characterize NCL loaded with ZnF16Pc (Pc) for application in antimicrobial photodynamic therapy. For the development of the NLC, the fusion-emulsification technique followed by sonication was applied. NLC and Pc-NLC were characterized in terms of mean diameter (Dm.n), polydispersity index (PdI), zeta potential (ZP), encapsulation efficiency (%EE), transmission electron microscopy (TEM), differential scanning (DSC), photobleaching and singlet oxygen generation in cellular systems (SOSG), and in vitro release assays performed by the beaker method, using dialysis membranes. Cell viability was performed by colony forming units (CFU/mL). The mean size of NLC and Pc-NLC was 158 nm ± 1.49 to 161.80 nm and showed PdI < 0.3 and ZP between -17.8 and -19.9, and stable during storage time (90 days). The TEM presented spherical particles, the Pc-NLC promoted the encapsulation of 75.57% ± 0.58. DSC analysis confirmed that there was no incompatibility between Pc and NLC. The analysis of the photodegradation profile proved to be photostable after encapsulation and this corroborates the data obtained by SOSG. In vitro release showed controlled and prolonged release. PDT Pc-NLC exhibited greater antifungal effect against C. albicans (3 log10 reduction) than Pc-NLC without light (1 log10 reduction). NLC can be an alternative to the application of Pc and improve the effect during PDT treatment.

Promising Photocytotoxicity of Water-Soluble Phtalocyanine against Planktonic and Biofilm Pseudomonas aeruginosa Isolates from Lower Respiratory Tract and Chronic Wounds

Alternative methods of killing microbes have been extensively researched in connection with the widespread appearance of antibiotic resistance among pathogenic bacteria. In this study, we report on in vitro antimicrobial phototoxicity research of cationic phthalocyanine with 2-(4-N-methylmorpholin-4-ium-4-yl)ethoxy substituents against selected clinical strains of Pseudomonas aeruginosa isolated from the lower respiratory tract and chronic wounds. The microorganisms tested in the research were analyzed in terms of drug resistance and biofilm formation. The photocytotoxic effect of phthalocyanine was determined by the reduction factor of bacteria. The studied cationic phthalocyanine at a concentration of 1.0 × 10−4 M, when activated by light, revealed a significant reduction factor, ranging from nearly 4 to 6 log, of P. aeruginosa cells when compared to the untreated control group. After single irradiation, a decrease in the number of bacteria in biofilm ranging from 1.3 to 4.2 log was observed, whereas the second treatment significantly improved the bacterial reduction factor from 3.4 to 5.5 log. It is worth mentioning that a boosted cell-death response was observed after the third irradiation, with a bacterial reduction factor ranging from 4.6 to 6.4 log. According to the obtained results, the tested photosensitizer can be considered as a potential antimicrobial photodynamic therapy against multidrug-resistant P. aeruginosa.

Composites based on graphite oxide and zirconium phthalocyanines with aromatic amino acids as photoactive materials

This article is a part of a scientific project focused on obtaining a new type of composite materials that are characterized by singlet oxygen generation upon irradiation with red light, which can be used as antibacterial agents. The composite material is nanoscale graphite oxide (GO) particles covalently bonded to an axially substituted zirconium phthalocyanine complex. For this purpose, two phthalocyanine zirconium complexes, axially mono-substituted with 4-aminosalicylic or 4-aminophthalic acids, were prepared and measured in terms of structure, morphology, and spectroscopic properties. The zirconium phthalocyanines are photosensitizers, and the axial ligands are bridging links connecting the complexes to the GO carrier (due to their terminal amino groups and carboxyl groups, respectively). The axial ligand in zirconium phthalocyanine complexes has a strong influence on the stability and optical properties of composite materials and, consequently, on reactive oxygen species (ROS) generation. In this paper, the effect of composite components (4-aminophthalato or 4-aminosalicylato substituted zirconium phthalocyanine complex as a photosensitizer and graphite oxide as a carrier and modulator of the action of active components) on ROS generation for potential antibacterial use is discussed.

Antimicrobial photodynamic therapy (aPDT) for biofilm treatments. Possible synergy between aPDT and pulsed electric fields

Currently, microbial biofilms have been the cause of a wide variety of infections in the human body, reaching 80% of all bacterial and fungal infections. The biofilms present specific properties that increase the resistance to antimicrobial treatments. Thus, the development of new approaches is urgent, and antimicrobial photodynamic therapy (aPDT) has been shown as a promising candidate. aPDT involves a synergic association of a photosensitizer (PS), molecular oxygen and visible light, producing highly reactive oxygen species (ROS) that cause the oxidation of several cellular components. This therapy attacks many components of the biofilm, including proteins, lipids, and nucleic acids present within the biofilm matrix; causing inhibition even in the cells that are inside the extracellular polymeric substance (EPS). Recent advances in designing new PSs to increase the production of ROS and the combination of aPDT with other therapies, especially pulsed electric fields (PEF), have contributed to enhanced biofilm inhibition. The PEF has proven to have antimicrobial effect once it is known that extensive chemical reactions occur when electric fields are applied. This type of treatment kills microorganisms not only due to membrane rupture but also due to the formation of reactive compounds including free oxygen, hydrogen, hydroxyl and hydroperoxyl radicals. So, this review aims to show the progress of aPDT and PEF against the biofilms, suggesting that the association of both methods can potentiate their effects and overcome biofilm infections.

The Impact of Graphite Oxide Nanocomposites on the Antibacterial Activity of Serum

Nanoparticles can interact with the complement system and modulate the inflammatory response. The effect of these interactions on the complement activity strongly depends on physicochemical properties of nanoparticles. The interactions of silver nanoparticles with serum proteins (particularly with the complement system components) have the potential to significantly affect the antibacterial activity of serum, with serious implications for human health. The aim of the study was to assess the influence of graphite oxide (GO) nanocomposites (GO, GO-PcZr(Lys)2-Ag, GO-Ag, GO-PcZr(Lys)2) on the antibacterial activity of normal human serum (NHS), serum activity against bacteria isolated from alveoli treated with nanocomposites, and nanocomposite sensitivity of bacteria exposed to serum in vitro (using normal human serum). Additionally, the in vivo cytotoxic effect of the GO compounds was determined with application of a Galleria mellonella larvae model. GO-PcZr(Lys)2, without IR irradiation enhance the antimicrobial efficacy of the human serum. IR irradiation enhances bactericidal activity of serum in the case of the GO-PcZr(Lys)2-Ag sample. Bacteria exposed to nanocomposites become more sensitive to the action of serum. Bacteria exposed to serum become more sensitive to the GO-Ag sample. None of the tested GO nanocomposites displayed a cytotoxicity towards larvae.

The antibacterial and antifungal properties of neutral, octacationic and hexadecacationic Zn phthalocyanines when conjugated to silver nanoparticles

The syntheses and characterization of novel octacationic and hexadecacationic Pcs is reported. With the aim of enhancing singlet oxygen generation efficiencies and hence antimicrobial activities, these Pcs (including their neutral counterpart) are conjugated to Ag nanoparticles (AgNPs). The obtained results show that the conjugate composed of the neutral Pc has a higher loading of Pcs as well as a greater singlet oxygen quantum yield enhancement (in the presence of AgNPs) in DMSO. The antimicrobial efficiencies of the Pcs and their conjugates were evaluated and compared on S. aureus, E. coli and C. albicans. The cationic Pcs possess better activity than the neutral Pc against all the microorganisms with the hexadecacationic Pc being the best. This work therefore demonstrates that increase in the number of cationic charges on the reported Pcs results in enhanced antimicrobial activities, which is maintained even when conjugated to Ag nanoparticles. The high activity and lack of selectivity of the cationic Pcs when conjugated to Ag NPs against different microorganisms make them good candidates for real life antimicrobial treatments.

BSA/DNA binding behavior and the photophysicochemical properties of novel water soluble zinc(II)phthalocyanines directly substituted with piperazine groups

In the current research, two novel zinc(II) phthalocyanines (ZnPcs) (1 and 2) directly connecting with 4-(4-methylpiperazin-1-yl)phenyl groups have been synthesized through the Suzuki-Miyaura coupling reaction. These ZnPcs 1 and 2 were converted to their water-soluble derivatives (1Q and 2Q) by quaternization. The photochemical and photophysical properties were determined in DMSO for the non-ionic zinc(II) phthalocyanines (1 and 2) and in both DMSO and aqueous solutions for the quaternized cationic derivatives (1Q and 2Q) to establish their photosensitizer capabilities in photodynamic therapy (PDT). The spectrofluorometric and spectrophotometric techniques were employed for the determination of interaction between water-soluble ZnPcs (1Q and 2Q) and BSA or ct-DNA. The binding constants of these compounds to BSA were found in the order of 10⁸ M^-1. The binding constant of the ct-DNA interaction with 2Q (1.09 × 10⁵ M^-1) was found higher than 1Q (6.87 × 10⁴ M^-1). The thermodynamic constants were determined for both 1Q and 2Q. The endothermic and spontaneous nature of interaction was observed with ct-DNA. Besides, the thermal denaturation and viscosity studies proved the non-intercalative mode of binding for both compounds to ct-DNA.

Carbonic Anhydrase Inhibition Potential and Some Bioactivities of the Peripherally Tetrasubstituted Cobalt(II), Titanium(IV), Manganese(III) Phthalocyanines

Background:

Peripherally tetrasubstituted cobalt(II), titanium(IV), manganese(III) phthalocyanines carrying redox-active metal centers were previously synthesized. Metallophthalocyanines (MPcs) exhibited the potential to use in medicinal applications due to biological activities, such as antibacterial, antioxidant and enzyme inhibition.

Objective:

This study's aim was to evaluate the previously synthesized metallophthalocyanines in terms of carbonic anhydrase inhibition, antioxidant, and antimicrobial activities.

Methods:

In this study, the inhibition potential of the metallophthallocyanines against carbonic anhydrase (CA) enzyme, which is important for treatments of many disorders, was evaluated. The metallophthalocyanines showed high CA inhibitory activity with IC50 values in the range of 74-317 nM, which was similar or better when compared with the standard CA inhibitors sulfanilamide and acetazolamide. In addition, antibacterial and antioxidant activities were determined. The metallophthallocyanines exhibited moderate antibacterial activity, especially against S. aureus and S. epidermis. The antioxidant activities of the compounds in both tests were quite high, even exceeding the standards Trolox and BHT, with SC50 values of 0.0048-0.0257 and TEAC values of 1143.3- 1543.7 μM, being 2 to 73 fold better activity.

Results:

In this study, the inhibition potential of the metallophthallocyanines against carbonic anhydrase (CA) enzyme, which is important for treatments of many disorders, was evaluated. The metallophthalocyanines showed high CA inhibitory activity with IC50 values in the range of 74-317 nM, which was similar or better when compared with the standard CA inhibitors sulfanilamide and acetazolamide. In addition, antibacterial and antioxidant activities were determined. The metallophthallocyanines exhibited moderate antibacterial activity, especially against S. aureus and S. epidermis. The antioxidant activities of the compounds in both tests were quite high, even exceeding the standards Trolox and BHT, with SC50 values of 0.0048-0.0257 and TEAC values of 1143.3- 1543.7 μM, being 2 to 73 fold better activity.

Conclusion:

In conclusion, all three metallophthalocyanines exhibit excellent carbonic anhydrase and antioxidant potential and deserve further interest for the synthesis of new derivatives.

In Vitro and In Vivo Demonstration of Ultraefficient and Broad-Spectrum Antibacterial Agents for Photodynamic Antibacterial Chemotherapy

Increasing threats from both pathogenic infections and antibiotic resistance highlight the pressing demand for nonantibiotic agents and alternative therapies. Herein, we report several new phenothiazinium-based derivatives, which could be readily synthesized via fragment-based assembly, which exhibited remarkable bactericidal activities both in vitro and in vivo. Importantly, in contrast to numerous clinically and preclinically used antibacterial photosensitizers, these compounds were able to eliminate various types of microorganisms, including Gram-(+) Staphylococcus aureus (S. aureus), Gram-(-) Escherichia coli, multidrug-resistant S. aureus, and their associated biofilms, at low drug and light dosages (e.g., 0.21 ng/mL in vitro and 1.63 ng/cm² in vivo to eradicate S. aureus at 30 J/cm²). This study thus unveils the potential of these novel phenothiaziniums as potent antimicrobial agents for highly efficient photodynamic antibacterial chemotherapy.

Light-Activated Zirconium(IV) Phthalocyanine Derivatives Linked to Graphite Oxide Flakes and Discussion on Their Antibacterial Activity

In search of an effective antibacterial agent that is useful in photodynamic therapy, new derivatives of zirconium(IV) phthalocyanine (ZrPc) complexes were obtained and linked to graphite oxide flakes. In the syntheses of ZrPc derivatives, two bis-axially substituted ligands with terminal amino group and different lengths of linear carbon chain (C4 in 4-aminobutyric acid or C11 in 11-aminoundecanoic acid) were used. The optical properties (absorption and photoluminescence spectra) of ZrPcs and the composites were examined. Broadband red–near-infrared lamp was tested as an external stimulus to activate ZrPcs and the composites. Optical techniques were used to show generation of singlet oxygen during irradiation. Considering the application of graphite oxide-based materials as bacteriostatic photosensitive additives for endodontic treatment of periapical tissue inflammation, the antibacterial activity was determined on one Escherichia coli strain isolated directly from an infected root canal of a human tooth and one strain with silver and antibiotic resistance. Looking at the obtained results, modified levels of activity toward different bacterial strains are discussed.

Graphene oxide nanohybrids for electron transfer-mediated antimicrobial activity

The rapid increase in the prevalence of antibiotic-resistant bacterial strains poses a global health risk. In this scenario, alternative strategies are needed to combat the alarming rise in multidrug-resistant bacterial populations. For example, metal-incorporated graphene derivatives have emerged as model nanomaterials owing to their intrinsic antibacterial activity together with their biocompatibility. Interestingly, photon-activated phthalocyanine sensitizers have also shown promising physiochemical biocidal effects against pathogenic bacteria populations when conjugated with diverse nanomaterials. Herein, we report the facile synthesis of graphene oxide incorporated zinc phthalocyanine (ZnPc-GO) nanohybrids showing bactericidal activity against Gram-negative Escherichia coli (E. coli) cells, in the absence of any photo-excitation. The ZnPc-GO hybrid nanomaterials were synthesized by the in situ deposition of GO flakes on ZnPc-coated indium tin oxide (ITO) substrates. Two types of morphologically different ZnPc molecules, potato-chip-like α-phase ZnPc, namely ZnPc(A), and nanorod-like β-phase ZnPc(B), were used for the synthesis of the ZnPc(A/B)-GO nanocomposites. The interactions of GO with the underlying ZnPc(A/B) entities in the ZnPc-GO systems were investigated using multiple characterization techniques. It was observed that the GO flakes in the ZnPc(B)-GO nanocomposite possess stronger π-π interactions and thus show a more efficient electron transfer mechanism when compared with the ZnPc(A) counterpart. Furthermore, the E. coli bacterial cells with an electronegative surface demonstrated a profound adherence to the electron-withdrawing ZnPc(B)-GO surface. The death kinetics of bacteria with ZnPc(B)-GO were further investigated using surface potential mapping and Kelvin probe force microscopy (KPFM) analysis. Upon direct contact with ZnPc(B)-GO, the adhered bacterial cells showed outer cell deformation and membrane protein leakage, induced by a proposed charge-transfer mechanism between negatively charged cells and the electron-withdrawing ZnPc(B)-GO surface. These new findings may provide insights into the design of potential ZnPc-GO-based novel antimicrobial nanomaterials or surface coatings.