Photodynamic anticancer and antimicrobial activities of novel bacteriochlorins
- Authors: Tauyakhale, Kaisano Goodness
- Date: 2024-10-11
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/464587 , vital:76524
- Description: The World Health Organization cautioned that the major contributing factors of cancer amongst people are the excessive usage of alcohol, smoking, lack of exercise and low intake of fruits, vegetables, and high-fibre foods. Furthermore, cancer by far is reported to be the most common and leading cause of death worldwide (1 in 6 deaths is due to cancer). Moreover, it is reported that cancer kills more people than tuberculosis, malaria and AIDS combined every year. Chemotherapy has been utilised as a mode of rehabilitation for complete being used in conjunction with surgery or to improve the state of well-being of patients until their point of death. However, it is well known for its adverse effects, such as loss of hair, altered gastric metabolism, vomiting and nausea, dehydration, weight loss, and loss of appetite. For this reason, photodynamic therapy (PDT) was developed as an alternative. A molecular dye (photosensitiser/PS) and light of a specific wavelength produce cytotoxic singlet oxygen species, which induce cell death. The aim of this project is to prepare novel structurally modified porphyrin-type dyes that absorb far into the near-infrared region. Identifying suitable dyes that absorb significantly in the 700−800 nm region is particularly important from an African perspective, since melanin significantly limits the penetration of laser light into human tissue in the 600−700 nm region, where first- and second-generation photosensitiser dyes usually absorb. The porphyrin analogues that will be investigated in this regard are bacteriochlorins (BChls), which are known to have suitable optical properties that are potentially suitable in this regard. The first step of the study would be to synthesise tetraarylporphyrins with electron- withdrawing meso-aryl rings because their reduction to BChls is more readily attainable than is the case with electron-donating rings. However, these contrasting properties can be combined to tailor the BChls for effective photodynamic therapy, so the type of porphyrins synthesised will be tetraarylBChls with different meso-aryl groups to first analyze the induction of different chemical properties in this case, the impact of introducing electron donating (4- and 3-quinoline substituents) or electron-withdrawing (pentafluorophenyl substituents) groups on the meso-positions of the dyes and more specifically whether the position of the quinoline nitrogen atom relative to the core of the BChl has any significant impact on the reactivity of the dye (the 4- or 3-position of the quinoline). The next factor to be considered is the induction of the heavy atom effect by introducing a metal in the centre of the dye in order to try to increase the singlet oxygen quantum yields for high production of reactive oxygen species and singlet oxygen and further red shift the lowest energy absorption band of the BChls in the therapeutic window for deep tissue penetration for effective. Lastly, the goal will be to explore whether the delivery of bacteriochlorin photosensitisers to cancer cells can be enhanced by introducing quaternised nitrogen atoms to the meso-aryl ligands. , Thesis (MSc) -- Faculty of Science, Chemistry, 2024
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- Date Issued: 2024-10-11
Phthalocyanine-based bio-functional conjugates: photodynamic therapy and photoantimicrobial chemotherapeutic efficacy evaluation in-vitro
- Authors: Magadla, Aviwe
- Date: 2024-04-05
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/435918 , vital:73212 , DOI 10.21504/10962/435918
- Description: This thesis reports on the syntheses and characterisation of symmetrical and asymmetrical phthalocyanines (Pcs) with different ring substituents derived to form either cationic styryl pyridine, cationic styryl pyridine triphenylphosphonium (TPP+)-based, benzothiazole, cationic pyridyl-dihydrothiazole and other closely related groups. The starting Pc complex of the synthesised Pc derivatives was typically obtained through the cyclotetramerisation of a substituted phthalonitrile. Then, depending on the desired final complex, the desired complexes were synthesised through the Knoevenagel condensation, alkylation reaction, and Schiff base reaction. Furthermore, silica nanoparticles (SiNPs) were also used to encapsulate Pcs. Following aminopropyl triethoxysilane amino (APTES) functionalisation of the surface of the Pc@SiNPs-APTES, biomolecules such as gallic acid, folic acid, and ampicillin were covalently attached to the surface. Additionally, Pc@SiNPs-APTES is protonated with 1,3-propanesultone. The pair of synthesised asymmetric Pcs is attached to ciprofloxacin (CIP) via an amide bond. Different analytical methods were used to characterise the Pcs and their conjugates. The photophysics and photochemistry of the Pcs both by themselves and in their conjugate form when doped with SiNPs. The cationic Pcs were able to produce sufficient singlet oxygen on their own in most cases. This is explained by the Pcs greater solubility in water. Since singlet oxygen is produced from the triplet state, singlet oxygen quantum yield (Δ) values complement triplet quantum yield (T) values. Low Δ values could be attributed to ineffective energy transfer; screening effects may have prevented the excited triplet state of the Pcs from interacting with the ground state molecular oxygen, lowering the Δ values. In other instances, the Pcs' protection by the SiNPs could be credited with extending the triplet lifetime. The direct connection of Pcs with CIP increased the formation of T and Δ in ABSTRACT comparison to Pcs alone. Both in planktonic and biofilm form, the cationic Pcs and conjugates showed enhanced bacterial elimination. The Pcs and conjugates demonstrated significant activity in photodynamic therapy treatment (PDT) experiments at the tested doses. In both PDT and photodynamic antimicrobial chemotherapy (PACT) treatment, the cationic Pcs outperformed the neutral Pc in terms of biological activity. , Thesis (PhD) -- Faculty of Science, Chemistry, 2024
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- Date Issued: 2024-04-05
Development of graphene materials and phthalocyanines for application in dye-sensitized solar cells
- Authors: Chindeka, Francis
- Date: 2020
- Subjects: Dye-sensitized solar cells , Graphene , Phthalocyanines , Molecular orbitals , Impedance spectroscopy
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/166092 , vital:41328
- Description: Two sets of dye-sensitized solar cells (DSSCs) were fabricated. In the first set, dye-sensitized solar cells (DSSC) were fabricated by incorporating graphene materials as catalysts at the counter electrode. Platinum was also used as a catalyst for comparative purposes. Different phthalocyanines: hydroxyl indium tetracarboxyphenoxy phthalocyanine (1), chloro indium octacarboxy phthalocyanine (2) and dibenzoic acid silicon phthalocyanine (3) were used as dyes. Complex 3 gave the highest power conversion efficiency (η) of 3.19% when using nitrogen doped reduced graphene oxide nanosheets (NrGONS) as a catalyst at the counter electrode, and TiO2 containing rGONS at the anode. The value obtained is close to 3.8% obtained when using Pt catalyst instead of NrGONS at the cathode, thus confirming that NrGONS is a promising candidate to replace the more expensive Pt. The study also shows that placing rGONS on both the anode and cathode improves efficiency. In the second set, DSSCs were fabricated by using 2(3,5-biscarboxyphenoxy), 9(10), 16(17), 23(24)-tri(tertbutyl) phthalocyaninato Cu (4) and Zn (5) complexes as dyes on the ITO-TiO2 photoanodes containing reduced graphene oxide nanosheets (rGONS) or nitrogen-doped rGONS (NrGONS). The evaluation of the assembled DSSCs revealed that using ITO-TiO2-NrGONS-CuPc (4) photoanode had the highest fill factor (FF) and power conversion efficiency (ɳ) of 69 % and 4.36 % respectively. These results show that the asymmetrical phthalocyanine complexes (4) and (5) showed significant improvement on the performance of the DSSC compared to previous work on symmetrical carboxylated phthalocyanines with ɳ = 3.19%.
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- Date Issued: 2020