The application of Sn(IV)Cl2 and In(III)Cl porphyrin-dyed TiO2 nanofibers in photodynamic antimicrobial chemotherapy for bacterial inactivation in water.

The World Health Organization has reported that antimicrobial resistance is one of the top 10 health threats that humanity faces today. Due to this, alternative therapies to the common antimicrobials are being explored and among these is photodynamic antimicrobial chemotherapy, where a combination of light, a photosensitizer and reactive oxygen species can be used to target microbial cells. In this research, free base, tin (IV) and indium (III) tetramethoxyporphyrins photosensitizers are adsorbed onto inorganic titanium dioxide nanofibers in an effort to create reusable fibers that are effective against Staphylococcus aureus. The photodynamic antimicrobial chemotherapy studies indicate that the metalloporphyrin adsorbed nanofibers exhibit good photodynamic antimicrobial activity against Staphylococcus aureus where the Cl2Sn(IV) tetramethoxyporphyrin dyed TiO2 exhibited 100% bacterial inhibition after a 30 min irradiation period.

Understanding the Principles and Applications of Dual Z-Scheme Heterojunctions: How Far Can We Go?

In the past seven years, dual Z-scheme heterojunctions evolved as favorable approaches for enhanced charge carrier separation through direct or indirect charge transfer transportation mechanisms. The dynamics of the charge transfer is the major strategy for understanding their photoactivity and stability through the formation of distinctive redox centers. The understanding of currently recognized principles for successful fabrication and classification in different energy and pollution remediation strategies is discussed, and a universal charge transfer-type-based classification of dual Z-schemes that can be adopted for Z-scheme and S-scheme heterojunctions is proposed. Methods used for determining the charge transfer as proof of dual Z-scheme existence are outlined. Most importantly, a new macroscopic N-scheme and a triple Z-scheme that can also be adopted as triple S-scheme heterostructures composed of four semiconductors are proposed for generating both oxidatively and reductively empowered systems. The proposed systems are expected to possess properties that enable them to harvest solar light to drive important chemical reactions for different applications.

Porphyrins developed for photoinactivation of microbes in wastewater.

Photodynamic antimicrobial chemotherapy (PACT) is extensively studied as a strategic method to inactivate pathogenic microbes in wastewater for addressing the limitations associated with chlorination, ozonation, and ultraviolet irradiation as disinfection methods, which generally promote the development of resistant genes and harmful by-products such as trihalomethanes. PACT is dependent on photons, oxygen, and a photosensitizer to induce cytotoxic effects on various microbes by generating reactive oxygen species. Photosensitizers such as porphyrins have demonstrated significant microbial inactivation through PACT, hence now explored for wastewater phototreatment. This review aims to evaluate the efficacy of porphyrins and porphyrin-conjugates as photosensitizers for wastewater photoinactivation. Concerns relating to the application of photosensitizers in water treatment are also evaluated. This includes recovery and reuse of the photosensitizer when immobilized on solid supports.

Modulation of Z-scheme photocatalysts for pharmaceuticals remediation and pathogen inactivation: Design devotion, concept examination, and developments.

The recent outbreak of Covid-19 guarantees overconsumption of different drugs as a necessity to reduce the symptoms caused by this pandemic. This triggers the proliferation of pharmaceuticals into drinking water systems. Is there any hope for access to safe drinking water? Photocatalytic degradation using artificial Z-scheme photocatalysts that has been employed for over a decade conveys a prospect for sustainable clean water supply. It is compelling to comprehensively summarise the state-of-the-art effects of Z-scheme photocatalytic systems towards the removal of pharmaceuticals in water. The principle of Z-scheme and the techniques used to validate the Z-scheme interfacial charge transfer are explored in detail. The application of the Z-scheme photocatalysts towards the degradation of antibiotics, NSAIDs, and bacterial/viral inactivation is deliberated. Conclusions and stimulating standpoints on the challenges of this emergent research direction are presented. The insights and up-to-date information will prompt the up-scaling of Z- scheme photocatalytic systems for commercialization.

Photophysical and in vitro photoinactivation of Escherichia coli using cationic 5,10,15,20-tetra(pyridin-3-yl) porphyrin and Zn(II) derivative conjugated to graphene quantum dots.

Pathogenic microorganisms may continue causing infection through the transfer of antibiotic resistance genes. As a result, the efficacy of pharmaceuticals in microbial inactivation is deteriorating. The present study was conducted to investigate the antimicrobial activity of neutral and quaternized free base and Zn 5,10,15,20-tetra(pyridin-3-yl) porphyrins on Escherichia coli (E. coli), a gram-negative bacterium that causes cholecystitis, pneumonia and urinary tract infections. Conjugation of the porphyrin to graphene quantum dots (GQDs) was implemented to enhance photocatalysis and reactive oxygen species generation. Density functional theory (DFT) geometry optimizations for free base and Zn porphyrin based on the B3LYP (Becke 3-Parameter (Exchange), Lee, Yang and Parr) functional of the Gaussian09 program package and Time-dependent density-functional theory (TD-DFT) calculations of the associated UV-visible absorption spectra are reported to analyse the electronic structure and optical properties of the porphyrins. The TD-DFT calculations showed that for both porphyrins the value of highest occupied molecular orbital (ΔHOMO) is greater than that of lowest unoccupied molecular orbital (ΔLUMO) which tells that there is no unusual splitting of (LUMO) orbitals which may be caused by systematic error in TD-DFT calculations. Due to the red shift in the spectrum of ZnT(3-Py)P and the ΔLUMO being higher, the HOMO-LUMO gap was expected to be lower than that of H2T(3-Py)P. The photophysical properties and Photodynamic antimicrobial chemotherapy activities of these nanoconjugates were investigated. The highest ΦΔ was that of Q-ZnT(3-Py)P- GDQs at 0.69 with the log reduction of 9.42.

Photodynamic therapy characteristics of phthalocyanines in the presence of boron doped detonation nanodiamonds: Effect of symmetry and charge.

The synthesis, photophysicochemical and photodynamic therapy (PDT) activities of benzothiazole substituted zinc phthalocyanine (Pc): 1 (asymmetrically substituted and composed of no charges), 2 (asymmetrically substituted and composed of three positive charges), and 3 (symmetrically substituted and composed of four positive charges), are presented. The triplet and singlet oxygen quantum yields were highest for complex 2 showing the importance of asymmetry and charge. The complexes are covalently and non-covalently linked to B doped detonation nanodiamonds (B@DNDs) to yield nanohybrids (B@DNDs-1, B@DNDs-2, B@DNDs-3). The presence of B@DNDs, asymmetry and positive charge resulted in improved PDT with the lowest cell viability being observed for B@DNDs-2 at 5%. The cell viability ranged from 5% to 7% for the nanohybrids compared to 19-26% for Pcs alone.

Symmetrically Substituted Zn and Al Phthalocyanines and Polymers for Photodynamic Therapy Application.

N4 macrocyclic complexes of Al and Zn phthalocyanines with symmetrical imine and imidazole moiety at the periphery were synthesized. The synthesized ligands, complexes, and polymers were purified and characterized to study the structure of the molecule. These synthesized complexes were used for photodynamic therapy application as the diamagnetic Zn and Al have the ability to produce and stabilize singlet oxygen species. The synthesized N4 molecules of aluminum iminomethoxy phenyl phthalocyanine and aluminum ethyl phenyl benzimidazolephthalocyanine showed better activity against MCF-7 cells. These results suggest that this assay may be used as an early biomarker of clinical response.

Enhancement of photodynamic antimicrobialtherapy through the use of cationic indium porphyrin conjugated to Ag/CuFe2O4 nanoparticles.

Photodynamic antimicrobial chemotherapy (PACT) is being actively researched as a possible alternative for antimicrobial agents. This study focuses on the application of neutral indium 5-p-carboxyphenyl-10-15-20-(tri-4-pyridyl)porphyrin and cationic indium 5-p-carboxyphenyl-10-15-20-(tris-4-methylpyridyl)-porphyrin triiodide conjugated to 6-mercapo-1-hexanol functionalized Ag/CuFe2O4 magnetic nanoparticles for photo-inactivation of S. aureus bacteria. Comparative studies were done on quaternized and unquaternized indium porphyrin complexes conjugated to Ag/CuFe2O4, where log reduction of 9.27 was obtained for quaternized conjugate and 0.83 for unquaternized conjugate.

Acetophenone substituted phthalocyanines and their graphene quantum dots conjugates as photosensitizers for photodynamic antimicrobial chemotherapy against Staphylococcus aureus.

This work reports on the synthesis and characterization of novel acetophenone substituted phthalocyanines along with the self-assembled nanoconjugates formed via π-π stacking interaction between the synthesized unmetalated (2), zinc (3) and indium (4) phthalocyanines and graphene quantum dots (GQDs) to form 2@GQDs, 3@GQDs and 4@GQDs. The complexes and conjugates exhibited high singlet oxygen ranging from 0.20 to 0.79 in DMSO for Pcs and nanoconjugates where in all cases, the indium complexes showed the highest singlet oxygen quantum yields. The photodynamic antimicrobial chemotherapy activity of both phthalocyanines and nanoconjugates were tested against Staphylococcus aureus. 4@GQDs was found to be highly effective causing a 9.68 log reduction of the bacteria at 10 µM (based on Pc) when compared to 3.77 log reduction of 3@GQDs.

Photophysical properties and photodynamic therapy activities of detonated nanodiamonds-BODIPY-phthalocyanines nanoassemblies.

This work reports on the synthesis of nanoassemblies of supramolecular hybrids containing detonated nanodiamonds (DNDs) covalently linked to halogenated BODIPY (DNDs-BODIPY) by an amide bond, followed by π-π stacking of 2,9,16,23-tetrakis[4-(N-methylpyridyloxy)]-phthalocyanine (ZnTPPcQ) on the DNDs-BODIPY conjugate, to form nanoassembly represented as ZnTPPcQ-DNDs-BODIPY. ZnTPPcQ-DNDs-BODIPY has a higher singlet oxygen quantum yield of 0.50 in water. Therefore, the construction of a three component photodynamic therapy agent (ZnTPPcQ-DNDs-BODIPY) as a single photosentisiser improved singlet quantum yields of the Pc. Zeta potential studies of ZnTPPcQ-DNDs-BODIPY under various temperatures, concentrations and pH conditions, showed the conjugate is more stable at pHs 2, 4 and 7 and at high concentrations (50 µg/mL) and temperatures (80 °C). ZnTPPcQ-DNDs-BODIPY showed high photodynamic therapy (PDT) activity with a low MCF-7 cell viability of 21 ± 5% when compared to 31 ± 2%, 30 ± 2% and 28 ± 2% cell viability at the highest tested concentration of 50 µg/mL for DNDs, ZnTPPcQ-DND and DNDs-BODIPY, respectively.

Effect of symmetry and metal nanoparticles on the photophysicochemical and photodynamic therapy properties of cinnamic acid zinc phthalocyanine.

In this study, a novel asymmetric cinnamic acid zinc phthalocyanine (ZnPc, 1) containing three tert-butyl substituents is reported. The asymmetric ZnPc (1) is further linked to amino functionalized magnetic nanoparticles (AMNPs) (1-AMNPs) and to cysteine functionalized silver nanoparticles (cys-AgNPs) (1-cys-AgNPs) through an amide bond. 1-AMNPs and 1-cys-AgNPs improved the triplet and singlet oxygen quantum yields of complex 1, this was also observed with the previously reported 2-AMNPs when compared to 2 while 3-AMNPs yielded an unexpected decrease in triplet quantum yield as compared to 3. The silver nanoparticles (1-cys-AgNPs) had a better effect on improving the singlet oxygen quantum yield of complex 1 than the magnetic nanoparticles (1-AMNPs). The Pcs and conjugates recorded low cell cytotoxicity in the dark and high photocytotoxicity against MCF-7 cells in-vitro. MCF-7 cell viabilities of less than 50% were recorded at 80 µg/mL making the Pcs and conjugates under study potential candidates for use as photosensitizers in cancer therapy.

Photodynamic antimicrobial chemotherapy activity of (5,10,15,20-tetrakis(4-(4-carboxyphenycarbonoimidoyl)phenyl)porphyrinato) chloro gallium(III).

(5,10,15,20-Tetrakis(4-(4-carboxyphenycarbonoimidoyl)phenyl)porphyrinato) chloro gallium(III) (complex 1) was conjugated to platinum nanoparticles (PtNPs) (represented as 1-PtNPs). The resulting conjugate showed 18 nm red shift in the Soret band when compared to 1 alone. Complex 1 and 1-PtNPs showed promising photodynamic antimicrobial chemotherapy (PACT) activity against Staphylococcus aureus, Escherichia coli and Candida albicans in solution where the log reductions obtained were 4.92, 3.76, and 3.95, respectively for 1-PtNPs. The singlet oxygen quantum yields obtained were higher at 0.56 for 1-PtNPs in DMF while that of 1 was 0.52 in the same solvent. This resulted in improved PACT activity for 1-PtNPs compared to 1 alone.

Photophysicochemical behavior and antimicrobial activity of dihydroxosilicon tris(diaquaplatinum)octacarboxyphthalocyanine.

Platination of dihydroxosilicon octacarboxyphthalocyanine (OH)2SiOCPc was successfully carried out to give dihydroxosilicon tris(diaquaplatinum)octacarboxyphthalocyanine (OH)2SiOCPc(Pt)3 conjugate. Slight blue shifting of the absorption spectrum of (OH)2SiOCPc(Pt)3 was observed on conjugation with platinum. Comparative photophysicochemical behavior and antimicrobial photo-activities of (OH)2SiOCPc(Pt)3 conjugate with (OH)2SiOCPc or Pt nanoparticles revealed that the heavy atom, Pt on the periphery of the phthalocyanine significantly enhanced its singlet oxygen generation with a quantum yield of 0.56 obtained for the (OH)2SiOCPc(Pt)3 conjugate. The (OH)2SiOCPc(Pt)3 conjugate showed highest antimicrobial activity towards Candida albicans and Escherichia coli compared to (OH)2SiOCPc and Pt nanoparticles alone under illumination.