Syntheses and photophysico-chemical properties of phthalocyanines in the presence of silica nanoparticles
- Authors: Peteni, Siwaphiwe
- Date: 2019
- Subjects: Phthalocyanines , Silica , Nanoparticles , Bioconjugates
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/67592 , vital:29118
- Description: This thesis reports on the syntheses and characterizationof symmetrical (charged and neutral), asymmetrical (neutral) metallophthalocyanines (MPcs) and subphthalocyanines (SubPcs). The charged and neutral Pcs were physically doped onto silica nanoparticles (SiNPs). The asymmetrical MPc was also chemically linked to SiNPs. Spectroscopic and microscopic techniques were used to confirm the formation of SiNPs-MPc conjugates. The photophysics and photochemistry of the MPcs were assessed when alone and in conjugates (with SiNPs). The studies showed no significant changes in fluorescence quantum yields (ϕF) and fluorescence lifetimes (ϕF) of MPcs following doping except for 2-SiNPs (2 = Zn tetraaminophenoxyphthalocyanines) and 6-SiNPs (doped) (6 = Zn tris[(4-(pyridine-4-ylthio)2-thio-4-methylthiazol-5yl) acetic acid phthalocyanine) where there was a decrease in the ϕF value. Also for 1-SiNPs (1 = unsubstituted ZnPc) there was an elongation in τF which could be due to the protection offered by SiNPs. Both charged/neutral MPcs displayed high triplet quantum yields (ϕT) and singlet quantum yields (ϕΔ) following doping except for 2-SiNPs where there was a decrease in the latter. For 1-SiNPs there was an increase in ϕT but a decrease inϕΔ .There wasa decrease in ϕT and an increase in ϕΔfor4-SiNPs (4 = Zn tetrasulfophenoxyphthalocyanine), the decrease in ϕT could be due to the orientation of theMPc in SiNPs. An increase in both ϕT and ϕΔ for 6-SiNPs (linked) compared to 6-SiNPs (doped) was observed. Complex 5 (5 = Zn tetra-kis-(dodecylmercapto) phthalocyanine) showed a low ϕΔ value.
- Full Text:
- Date Issued: 2019
- Authors: Peteni, Siwaphiwe
- Date: 2019
- Subjects: Phthalocyanines , Silica , Nanoparticles , Bioconjugates
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/67592 , vital:29118
- Description: This thesis reports on the syntheses and characterizationof symmetrical (charged and neutral), asymmetrical (neutral) metallophthalocyanines (MPcs) and subphthalocyanines (SubPcs). The charged and neutral Pcs were physically doped onto silica nanoparticles (SiNPs). The asymmetrical MPc was also chemically linked to SiNPs. Spectroscopic and microscopic techniques were used to confirm the formation of SiNPs-MPc conjugates. The photophysics and photochemistry of the MPcs were assessed when alone and in conjugates (with SiNPs). The studies showed no significant changes in fluorescence quantum yields (ϕF) and fluorescence lifetimes (ϕF) of MPcs following doping except for 2-SiNPs (2 = Zn tetraaminophenoxyphthalocyanines) and 6-SiNPs (doped) (6 = Zn tris[(4-(pyridine-4-ylthio)2-thio-4-methylthiazol-5yl) acetic acid phthalocyanine) where there was a decrease in the ϕF value. Also for 1-SiNPs (1 = unsubstituted ZnPc) there was an elongation in τF which could be due to the protection offered by SiNPs. Both charged/neutral MPcs displayed high triplet quantum yields (ϕT) and singlet quantum yields (ϕΔ) following doping except for 2-SiNPs where there was a decrease in the latter. For 1-SiNPs there was an increase in ϕT but a decrease inϕΔ .There wasa decrease in ϕT and an increase in ϕΔfor4-SiNPs (4 = Zn tetrasulfophenoxyphthalocyanine), the decrease in ϕT could be due to the orientation of theMPc in SiNPs. An increase in both ϕT and ϕΔ for 6-SiNPs (linked) compared to 6-SiNPs (doped) was observed. Complex 5 (5 = Zn tetra-kis-(dodecylmercapto) phthalocyanine) showed a low ϕΔ value.
- Full Text:
- Date Issued: 2019
Photophysicochemical and photodynamic antimicrobial chemotherapeutic studies of novel phthalocyanines conjugated to silver nanoparticles
- Authors: Rapulenyane, Nomasonto
- Date: 2013 , 2013-06-10
- Subjects: Phthalocyanines , Photochemistry , Photochemotherapy , Cancer -- Photochemotherapy , Anti-infective agents , Escherichia coli , Nanoparticles , Silver , Zinc
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4291 , http://hdl.handle.net/10962/d1003912 , Phthalocyanines , Photochemistry , Photochemotherapy , Cancer -- Photochemotherapy , Anti-infective agents , Escherichia coli , Nanoparticles , Silver , Zinc
- Description: This work reports on the synthesis, characterization and the physicochemical properties of novel unsymmetrically substituted zinc phthalocyanines: namely tris{11,19, 27-(1,2- diethylaminoethylthiol)-2-(captopril) phthalocyanine Zn ((ZnMCapPc (1.5)), hexakis{8,11,16,19,42,27-(octylthio)-1-(4-phenoxycarboxy) phthalocyanine} Zn (ZnMPCPc(1.7)) and Tris {11, 19, 27-(1,2-diethylaminoethylthiol)-1,2(caffeic acid) phthalocyanine} Zn ((ZnMCafPc (1.3)). Symmetrically substituted counterparts (tetrakis(diethylamino)zinc phthalocyaninato (3.8), octakis(octylthio)zinc phthalocyaninato (3.9) and tetrakis (carboxyphenoxy)zinc phthalocyaninato (3.10) complexes) were also synthesized for comparison of the photophysicochemical properties and to investigate the effect of the substituents on the low symmetry Pcs. The complexes were successfully characterized by IR, NMR, mass spectral and elemental analyses. All the complexes showed the ability to produce singlet oxygen, while the highest triplet quantum yields were obtained for 1.7, 1.5 and 3.9 (0.80, 0.65 and 0.62 respectively and the lowest were obtained for 1.3 and 3.10 (0.57 and 0.47 respectively). High triplet lifetimes (109-286 μs) were also obtained for all complexes, with 1.7 being the highest (286 μs) which also corresponds to its triplet and singlet quantum yields (0.80 and 0.77 respectively). The photosensitizing properties of low symmetry derivatives, ZnMCapPc and ZnMCafPc were investigated by conjugating glutathione (GSH) capped silver nanoparticles (AgNP). The formation of the amide bond was confirmed by IR and UV-Vis spectroscopies. The photophysicochemical behaviour of the novel phthalocyanine-GSH-AgNP conjugates and the simple mixture of the Ag NPs with low the symmetry phthalocyanines were investigated. It was observed that upon conjugation of the phthalocyanines to the GSH-AgNPs, a blue shift in the Q band was induced. The triplet lifetimes and quantum yields improved upon conjugation as compared to the phthalocyanines (Pc) alone. Complex 1.5 triplet lifetimes increased from 109 to 148 and triplet quantum yield from 0.65 to 0.86 upon conjugation. Fluorescence lifetimes and quantum yields decreased for the conjugates compared to the phthalocyanines alone, due to the quenching caused by the Ag NPs. The antimicrobial activity of the zinc phthalocyanines (complexes 1.3 and 1.5) and their conjugates against Escherichia coli was investigated. Only 1.3 and 1.5 complexes were investigated because of the availability of the sample. In general phthalocyanines showed increase in antibacterial activity with the increase in phthalocyanines concentration in the presence and absence of light. The Pc complexes and their Ag NP conjugates showed an increase in antibacterial activity, due to the synergistic effect afforded by Ag NP and Pcs. Improved antibacterial properties were obtained upon irradiation. 1.5-AgNPs had the highest antibacterial activity compared to 1.3-AgNPs conjugate; these results are in agreement with the photophysical behaviour. This work demonstrates improved photophysicochemical properties of low symm
- Full Text:
- Date Issued: 2013
- Authors: Rapulenyane, Nomasonto
- Date: 2013 , 2013-06-10
- Subjects: Phthalocyanines , Photochemistry , Photochemotherapy , Cancer -- Photochemotherapy , Anti-infective agents , Escherichia coli , Nanoparticles , Silver , Zinc
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4291 , http://hdl.handle.net/10962/d1003912 , Phthalocyanines , Photochemistry , Photochemotherapy , Cancer -- Photochemotherapy , Anti-infective agents , Escherichia coli , Nanoparticles , Silver , Zinc
- Description: This work reports on the synthesis, characterization and the physicochemical properties of novel unsymmetrically substituted zinc phthalocyanines: namely tris{11,19, 27-(1,2- diethylaminoethylthiol)-2-(captopril) phthalocyanine Zn ((ZnMCapPc (1.5)), hexakis{8,11,16,19,42,27-(octylthio)-1-(4-phenoxycarboxy) phthalocyanine} Zn (ZnMPCPc(1.7)) and Tris {11, 19, 27-(1,2-diethylaminoethylthiol)-1,2(caffeic acid) phthalocyanine} Zn ((ZnMCafPc (1.3)). Symmetrically substituted counterparts (tetrakis(diethylamino)zinc phthalocyaninato (3.8), octakis(octylthio)zinc phthalocyaninato (3.9) and tetrakis (carboxyphenoxy)zinc phthalocyaninato (3.10) complexes) were also synthesized for comparison of the photophysicochemical properties and to investigate the effect of the substituents on the low symmetry Pcs. The complexes were successfully characterized by IR, NMR, mass spectral and elemental analyses. All the complexes showed the ability to produce singlet oxygen, while the highest triplet quantum yields were obtained for 1.7, 1.5 and 3.9 (0.80, 0.65 and 0.62 respectively and the lowest were obtained for 1.3 and 3.10 (0.57 and 0.47 respectively). High triplet lifetimes (109-286 μs) were also obtained for all complexes, with 1.7 being the highest (286 μs) which also corresponds to its triplet and singlet quantum yields (0.80 and 0.77 respectively). The photosensitizing properties of low symmetry derivatives, ZnMCapPc and ZnMCafPc were investigated by conjugating glutathione (GSH) capped silver nanoparticles (AgNP). The formation of the amide bond was confirmed by IR and UV-Vis spectroscopies. The photophysicochemical behaviour of the novel phthalocyanine-GSH-AgNP conjugates and the simple mixture of the Ag NPs with low the symmetry phthalocyanines were investigated. It was observed that upon conjugation of the phthalocyanines to the GSH-AgNPs, a blue shift in the Q band was induced. The triplet lifetimes and quantum yields improved upon conjugation as compared to the phthalocyanines (Pc) alone. Complex 1.5 triplet lifetimes increased from 109 to 148 and triplet quantum yield from 0.65 to 0.86 upon conjugation. Fluorescence lifetimes and quantum yields decreased for the conjugates compared to the phthalocyanines alone, due to the quenching caused by the Ag NPs. The antimicrobial activity of the zinc phthalocyanines (complexes 1.3 and 1.5) and their conjugates against Escherichia coli was investigated. Only 1.3 and 1.5 complexes were investigated because of the availability of the sample. In general phthalocyanines showed increase in antibacterial activity with the increase in phthalocyanines concentration in the presence and absence of light. The Pc complexes and their Ag NP conjugates showed an increase in antibacterial activity, due to the synergistic effect afforded by Ag NP and Pcs. Improved antibacterial properties were obtained upon irradiation. 1.5-AgNPs had the highest antibacterial activity compared to 1.3-AgNPs conjugate; these results are in agreement with the photophysical behaviour. This work demonstrates improved photophysicochemical properties of low symm
- Full Text:
- Date Issued: 2013
Comparative study of the effect of silver nanoparticles on the hexokinase activity from human and Trypanosoma brucei
- Authors: Mlozen, Madalitso Martin
- Date: 2015
- Subjects: Nanoparticles , Silver , Glucokinase , Trypanosoma brucei , Drug resistance , African trypanosomiasis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4149 , http://hdl.handle.net/10962/d1017910
- Full Text:
- Date Issued: 2015
- Authors: Mlozen, Madalitso Martin
- Date: 2015
- Subjects: Nanoparticles , Silver , Glucokinase , Trypanosoma brucei , Drug resistance , African trypanosomiasis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4149 , http://hdl.handle.net/10962/d1017910
- Full Text:
- Date Issued: 2015
Investigating the enzymatic mechanism of platinum nanoparticle synthesis in sulfate-reducing bacteria
- Authors: Riddin, Tamsyn Louise
- Date: 2009
- Subjects: Platinum , Nanoparticles , Sulfate-reducing bacteria
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3965 , http://hdl.handle.net/10962/d1004024 , Platinum , Nanoparticles , Sulfate-reducing bacteria
- Description: Efforts to discover an efficient yet environmentally friendly mode of metal nanoparticle (NP) synthesis are increasing rapidly. A ‘green’ route that avoids the high costs, toxic wastes and complicated protocols associated with chemical synthesis methods is therefore highly sought after. A biologically based protocol will provide the possibility of gaining control over the mechanism merely by manipulating the experimental conditions of the system. Given that the properties of nanoparticles are highly dependant on the morphology of the particles themselves, this mechanistic control will provide significant industrial advantages with regards to tailoring specific properties of the nanoparticles produced. The key objectives of this study were to: a) determine whether a consortium of sulfate-reducing bacteria was capable of platinum nanoparticle synthesis, b) elucidate the bioreductive, enzymatic mechanism responsible, and c) attempt to control the morphologies of the particles produced. A consortium of sulfate-reducing bacteria (SRB), isolated from sewage sludge, was used in these investigations due to the advantages a consortium provides in comparison to pure cultures. The syntrophic relationships established within the constituent species not only prevent the growth of contaminant microbes, but increases the oxygen-tolerance of the system as a whole. The sulfate-reducing consortium was shown to possess an aerobic mechanism for Pt(IV) reduction which, though different from the anaerobic bioreductive mechanism previously identified in literature, did not require an exogenous electron donor. It was demonstrated that the Pt(IV) ion becomes reduced to Pt(0) via a two-cycle mechanism involving Pt(II) as the intermediate. Further investigation elucidated the reduction of Pt(IV) to Pt(II) to be dependant on a novel Pt(IV) reductase which becomes upregulated in the presence of Cu(II), while the reduction of Pt(II) to Pt(0) occurred by means of a periplasmic hydrogenase. To our knowledge, this is the first time a coupled mechanism for Pt(IV) reduction by micro-organisms has been proposed. A cell-free, crude protein solution from the consortium produced both geometric and irregular platinum nanoparticles. The wavelength of 334 nm was chosen as a nonquantitative indicator of Pt(0) nanoparticle formation over time. The optimum conditions for nanoparticle synthesis were pH 9.0, 65 ˚C and 0.75 mM Pt(IV) as H2PtCl6 salt. In the absence of a buffer a Pt(IV) concentration > 1 mM resulted in the precipitation of protein-nanoparticle bioconjugates, due to unfavourable acidic conditions. This demonstrated that the nanoparticles were binding to and becoming stabilised by general protein in the cell-free solution. Upon addition of a sodium-bicarbonate buffer, a general increase in Pt(IV) reduction to Pt(II) was observed. The addition of the buffer also resulted in an unexplained change in particle morphology and for this reason was not used in subsequent investigations. Polyvinylpyrrolidone (PVP) was shown to compromise the reduction rate of the Pt(IV) ion by SRB cells. The presence of extracellular NP’s was suggested by the colour of the supernatant turning brown and the A334 increasing over time. Attempts to visualise the particles by transmission electron microscopy (TEM) resulted in an unexpected phenomenon where nanoparticles could be observed to form dynamically upon irradiation by the electron beam. Extended irradiation by the electron beam also resulted in structural changes of the particles occurring during observation. An increase in temperature was shown to increase the reduction rate which in turn resulted in particles decreasing in size. The starting pH was shown to have a significant effect on the reduction rate and particle morphology although specific trends could not be identified. In conclusion, the cell-soluble extract from the sulfate-reducing consortium investigated, is capable of Pt(0) nanoparticle synthesis. Precise control over the particle morphology was not attained although the mechanism was further clarified and optimal conditions for nanoparticle synthesis were determined.
- Full Text:
- Date Issued: 2009
- Authors: Riddin, Tamsyn Louise
- Date: 2009
- Subjects: Platinum , Nanoparticles , Sulfate-reducing bacteria
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3965 , http://hdl.handle.net/10962/d1004024 , Platinum , Nanoparticles , Sulfate-reducing bacteria
- Description: Efforts to discover an efficient yet environmentally friendly mode of metal nanoparticle (NP) synthesis are increasing rapidly. A ‘green’ route that avoids the high costs, toxic wastes and complicated protocols associated with chemical synthesis methods is therefore highly sought after. A biologically based protocol will provide the possibility of gaining control over the mechanism merely by manipulating the experimental conditions of the system. Given that the properties of nanoparticles are highly dependant on the morphology of the particles themselves, this mechanistic control will provide significant industrial advantages with regards to tailoring specific properties of the nanoparticles produced. The key objectives of this study were to: a) determine whether a consortium of sulfate-reducing bacteria was capable of platinum nanoparticle synthesis, b) elucidate the bioreductive, enzymatic mechanism responsible, and c) attempt to control the morphologies of the particles produced. A consortium of sulfate-reducing bacteria (SRB), isolated from sewage sludge, was used in these investigations due to the advantages a consortium provides in comparison to pure cultures. The syntrophic relationships established within the constituent species not only prevent the growth of contaminant microbes, but increases the oxygen-tolerance of the system as a whole. The sulfate-reducing consortium was shown to possess an aerobic mechanism for Pt(IV) reduction which, though different from the anaerobic bioreductive mechanism previously identified in literature, did not require an exogenous electron donor. It was demonstrated that the Pt(IV) ion becomes reduced to Pt(0) via a two-cycle mechanism involving Pt(II) as the intermediate. Further investigation elucidated the reduction of Pt(IV) to Pt(II) to be dependant on a novel Pt(IV) reductase which becomes upregulated in the presence of Cu(II), while the reduction of Pt(II) to Pt(0) occurred by means of a periplasmic hydrogenase. To our knowledge, this is the first time a coupled mechanism for Pt(IV) reduction by micro-organisms has been proposed. A cell-free, crude protein solution from the consortium produced both geometric and irregular platinum nanoparticles. The wavelength of 334 nm was chosen as a nonquantitative indicator of Pt(0) nanoparticle formation over time. The optimum conditions for nanoparticle synthesis were pH 9.0, 65 ˚C and 0.75 mM Pt(IV) as H2PtCl6 salt. In the absence of a buffer a Pt(IV) concentration > 1 mM resulted in the precipitation of protein-nanoparticle bioconjugates, due to unfavourable acidic conditions. This demonstrated that the nanoparticles were binding to and becoming stabilised by general protein in the cell-free solution. Upon addition of a sodium-bicarbonate buffer, a general increase in Pt(IV) reduction to Pt(II) was observed. The addition of the buffer also resulted in an unexplained change in particle morphology and for this reason was not used in subsequent investigations. Polyvinylpyrrolidone (PVP) was shown to compromise the reduction rate of the Pt(IV) ion by SRB cells. The presence of extracellular NP’s was suggested by the colour of the supernatant turning brown and the A334 increasing over time. Attempts to visualise the particles by transmission electron microscopy (TEM) resulted in an unexpected phenomenon where nanoparticles could be observed to form dynamically upon irradiation by the electron beam. Extended irradiation by the electron beam also resulted in structural changes of the particles occurring during observation. An increase in temperature was shown to increase the reduction rate which in turn resulted in particles decreasing in size. The starting pH was shown to have a significant effect on the reduction rate and particle morphology although specific trends could not be identified. In conclusion, the cell-soluble extract from the sulfate-reducing consortium investigated, is capable of Pt(0) nanoparticle synthesis. Precise control over the particle morphology was not attained although the mechanism was further clarified and optimal conditions for nanoparticle synthesis were determined.
- Full Text:
- Date Issued: 2009
Synthesis of silver nanoparticles and their role against human and Plasmodium falciparum leucine aminopeptidase
- Authors: Mnkandhla, Dumisani
- Date: 2015
- Subjects: Silver , Nanoparticles , Plasmodium falciparum , Leucine aminopeptidase , Antimalarials , Nanotechnology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4150 , http://hdl.handle.net/10962/d1017911
- Description: Antimalarial drug discovery remains a challenging endeavour as malaria parasites continue to develop resistance to drugs, including those which are currently the last line of defence against the disease. Plasmodium falciparum is the most virulent of the malaria parasites and it delivers its deadliest impact during the erythrocytic stages of the parasite’s life cycle; a stage characterised by elevated catabolism of haemoglobin and anabolism of parasite proteins. The present study investigates the use of nanotechnology in the form of metallic silver nanoparticles (AgNPs) against P. falciparum leucine aminopeptidase (PfLAP), a validated biomedical target involved in haemoglobin metabolism. AgNPs were also tested against the human homolog cytosolic Homo sapiens leucine aminopeptidase (HsLAP) to ascertain their selective abilities. PfLAP and HsLAP were successfully expressed in Escherichia coli BL21(DE3) cells. PfLAP showed optimal thermal stability at 25 °C and optimal pH stability at pH 8.0 with a Km of 42.7 mM towards leucine-p-nitroanilide (LpNA) and a Vmax of 59.9 μmol.ml⁻¹.min⁻¹. HsLAP was optimally stable at 37 °C and at pH 7.0 with a Km of 16.7 mM and a Vmax of 17.2 μmol.ml⁻¹.min⁻¹. Both enzymes exhibited optimal activity in the presence of 2 mM Mn²⁺. On interaction with polyvinylpyrrolidone (PVP) stabilised AgNPs, both enzymes were inhibited to differing extents with PfLAP losing three fold of its catalytic efficiency relative to HsLAP. These results show the ability of AgNPs to selectively inhibit PfLAP whilst having much lesser effects on its human homolog. With the use of available targeting techniques, the present study shows the potential use of nanotechnology based approaches as “silver bullets” that can target PfLAP without adversely affecting the host. However further research needs to be conducted to better understand the mechanisms of AgNP action, drug targeting and the health and safety issues associated with nanotechnology use.
- Full Text:
- Date Issued: 2015
- Authors: Mnkandhla, Dumisani
- Date: 2015
- Subjects: Silver , Nanoparticles , Plasmodium falciparum , Leucine aminopeptidase , Antimalarials , Nanotechnology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4150 , http://hdl.handle.net/10962/d1017911
- Description: Antimalarial drug discovery remains a challenging endeavour as malaria parasites continue to develop resistance to drugs, including those which are currently the last line of defence against the disease. Plasmodium falciparum is the most virulent of the malaria parasites and it delivers its deadliest impact during the erythrocytic stages of the parasite’s life cycle; a stage characterised by elevated catabolism of haemoglobin and anabolism of parasite proteins. The present study investigates the use of nanotechnology in the form of metallic silver nanoparticles (AgNPs) against P. falciparum leucine aminopeptidase (PfLAP), a validated biomedical target involved in haemoglobin metabolism. AgNPs were also tested against the human homolog cytosolic Homo sapiens leucine aminopeptidase (HsLAP) to ascertain their selective abilities. PfLAP and HsLAP were successfully expressed in Escherichia coli BL21(DE3) cells. PfLAP showed optimal thermal stability at 25 °C and optimal pH stability at pH 8.0 with a Km of 42.7 mM towards leucine-p-nitroanilide (LpNA) and a Vmax of 59.9 μmol.ml⁻¹.min⁻¹. HsLAP was optimally stable at 37 °C and at pH 7.0 with a Km of 16.7 mM and a Vmax of 17.2 μmol.ml⁻¹.min⁻¹. Both enzymes exhibited optimal activity in the presence of 2 mM Mn²⁺. On interaction with polyvinylpyrrolidone (PVP) stabilised AgNPs, both enzymes were inhibited to differing extents with PfLAP losing three fold of its catalytic efficiency relative to HsLAP. These results show the ability of AgNPs to selectively inhibit PfLAP whilst having much lesser effects on its human homolog. With the use of available targeting techniques, the present study shows the potential use of nanotechnology based approaches as “silver bullets” that can target PfLAP without adversely affecting the host. However further research needs to be conducted to better understand the mechanisms of AgNP action, drug targeting and the health and safety issues associated with nanotechnology use.
- Full Text:
- Date Issued: 2015
Photodynamic antimicrobial chemotherapy activities of porphyrin- and phthalocyanine-platinum nanoparticle conjugates
- Authors: Managa, Muthumuni Elizabeth
- Date: 2015
- Subjects: Photochemotherapy , Anti-infective agents , Porphyrins , Phthalocyanines , Platinum , Nanoparticles , Bioconjugates , Electrospinning
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4539 , http://hdl.handle.net/10962/d1017919
- Description: This work reports on the conjugation of differently shaped Pt nanoparticles (PtNPs) with ClGa(III) 5,10,15,20-tetrakis-(4-carboxyphenyl) porphyrin (1) as well as chloro - (5,10,15,20-tetrakis (4- (4- carboxy phenycarbonoimidoyl) phenyl) porphyrinato) gallium(III) (2) The work also reports on platination of dihydroxosilicon octacarboxyphthalocyanine (OH)₂SiOCPc (3) to give dihydroxosilicontris(diaquaplatinum)octacarboxyphthalocyanine (OH)₂SiOCPc(Pt)₃ (4). The resulting conjugates were used for photodynamic antimicrobial chemotherapy against S. aureus, E. coli and C. albicans. The degree of photo-inactivation is dependent on concentration of the conjugates, light dose (fluence) and illumination time. The log reduction obtained for 1 when conjugated to cubic PtNPs was 4.64 log (which indicate 99.99 percent of the bacteria have been killed), which is much higher than 3.94 log unit for 1-hexagonal PtNPs and 3.31 log units for 1-unshaped PtNPs. Complex 2 conjugated to hexagonal PtNPs showed 18 nm red shift in the Soret band when compared to 2 alone. Complex 2 and 2-hexagonal PtNPs as well showed promising photodynamic antimicrobial chemotherapy (PACT) activity against S. aureus, E. coli and C. albicans in solution where the log reduction obtained was 4.92, 3.76, and 3.95 respectively for 2-hexagonal PtNPs. The singlet oxygen quantum yields obtained were higher at 0.56 for 2-hexagonl PtNPs in DMF while that of 2 was 0.52 in the same solvent. This resulted in improved PACT activity for 2-hexagonal PtNPs compared to 2. Complex 4 showed slight blue shifting of the absorption spectrum when compared to complex 3 The antimicrobial activity of 4 were promising as the highest log reduction value was observed when compared to the porphyrin conjugates.
- Full Text:
- Date Issued: 2015
- Authors: Managa, Muthumuni Elizabeth
- Date: 2015
- Subjects: Photochemotherapy , Anti-infective agents , Porphyrins , Phthalocyanines , Platinum , Nanoparticles , Bioconjugates , Electrospinning
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4539 , http://hdl.handle.net/10962/d1017919
- Description: This work reports on the conjugation of differently shaped Pt nanoparticles (PtNPs) with ClGa(III) 5,10,15,20-tetrakis-(4-carboxyphenyl) porphyrin (1) as well as chloro - (5,10,15,20-tetrakis (4- (4- carboxy phenycarbonoimidoyl) phenyl) porphyrinato) gallium(III) (2) The work also reports on platination of dihydroxosilicon octacarboxyphthalocyanine (OH)₂SiOCPc (3) to give dihydroxosilicontris(diaquaplatinum)octacarboxyphthalocyanine (OH)₂SiOCPc(Pt)₃ (4). The resulting conjugates were used for photodynamic antimicrobial chemotherapy against S. aureus, E. coli and C. albicans. The degree of photo-inactivation is dependent on concentration of the conjugates, light dose (fluence) and illumination time. The log reduction obtained for 1 when conjugated to cubic PtNPs was 4.64 log (which indicate 99.99 percent of the bacteria have been killed), which is much higher than 3.94 log unit for 1-hexagonal PtNPs and 3.31 log units for 1-unshaped PtNPs. Complex 2 conjugated to hexagonal PtNPs showed 18 nm red shift in the Soret band when compared to 2 alone. Complex 2 and 2-hexagonal PtNPs as well showed promising photodynamic antimicrobial chemotherapy (PACT) activity against S. aureus, E. coli and C. albicans in solution where the log reduction obtained was 4.92, 3.76, and 3.95 respectively for 2-hexagonal PtNPs. The singlet oxygen quantum yields obtained were higher at 0.56 for 2-hexagonl PtNPs in DMF while that of 2 was 0.52 in the same solvent. This resulted in improved PACT activity for 2-hexagonal PtNPs compared to 2. Complex 4 showed slight blue shifting of the absorption spectrum when compared to complex 3 The antimicrobial activity of 4 were promising as the highest log reduction value was observed when compared to the porphyrin conjugates.
- Full Text:
- Date Issued: 2015
Probing the biocompatibility of biomedical interfaces using the Quartz Crystal Microbalance with Dissipation
- Authors: Cromhout, Mary
- Date: 2011
- Subjects: Biomedical materials , Nanostructured materials , Biomedical engineering , Quartz crystal microbalances , Blood proteins , Nanoparticles
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4102 , http://hdl.handle.net/10962/d1010660
- Description: The biomedical application of nanotechnology has come into the spotlight, with the promise of ‘personalised’ therapeutics that couple early diagnosis with targeted therapeutic activity. Due to the rapid growth of the biomedical applications of nanoparticles, along with the lack of understanding concerning their interactions with biomolecules, there is a pressing need for the development of standard methods directed at investigating the effect of introducing these unique particles into the human body. The central aim of this research is to establish a platform directed at assessing the biological fate of pioneering therapeutic particulate agents, such as metallophthalocyanines (MPcs) and multi-walled carbon nanotubes (FMWCNTs). In particular, we proposed, that Quartz Crystal Microbalance with Dissipation (QCM-D) technology may be employed to assess the composition of blood protein corona deposited on the therapeutic surface, and subsequently assess the biocompatibility of such particles. The proposed method of protein detection utilises the nanogram sensitivity of QCM-D technology to monitor highly specific antibody-antigen interactions. In particular those interactions which occur when probe antibodies are used to detect adsorbed blood proteins deposited on target particle-modified sensor surfaces. Protein detection analysis was directed toward identification of surface bound human serum albumin, complement factor C3c, and human plasma fibrinogen. Preliminary analysis of generic biomedical surfaces indicated human serum albumin demonstrates a higher binding affinity towards positively charged surfaces (i.e. cysteamine self-assembled monolayer), followed by hydrophobic surfaces. Detection of complement C3c, corresponded with literature, where lower levels were detected on negatively charged surfaces (i.e. mercapto undecanoic acid self-assembled monolayer), and higher levels of more hydrophobic surfaces (i.e. 11-amino undecane thiol self-assembled monolayer). Human plasma fibrinogen was observed to favour hydrophilic over hydrophobic self-assembled monolayer surfaces, which was in accordance with literature. Application of the proposed protein detection method for biocompatibility analysis of target therapeutic molecules, namely metallophthalocyanines and acid functionalised multi-walled carbon nanotubes, demonstrated a dependence on modified-surface film characteristics, such as surface charge and topography with regards to human serum albumin and human plasma fibrinogen analysis representing new insights into their potential biomolecular interactions The highest levels of detected human serum albumin and complement C3c were detected on the GePcSmix-modified surfaces. AlPcSmix-modified surfaces analysis suggested the highest levels of human plasma fibrinogen. Two methods of acid functionalisation were employed, using both nitric and sulphuric acid, and pure nitric acid. A general increase in detected human serum albumin, corresponding with an increase in functionalisation time, was observed. Complement C3c detection suggested an increase in deposited complement C3c, with increasing functionalisation time, when assessing nitric acid functionalised multi-walled carbon nanotubes, and a decrease, with increasing functionalisation time, when assessing nitric and sulphuric acid functionalised multi-walled carbon nanotubes. Analysis of human plasma fibrinogen was inconclusive, as were cytotoxicity experiments utilising MCF-7 cells in the presence of metallophthalocyanine complexes, raising simultaneously important considerations for their application and study. In the first such detailed examination of its kind it was concluded that the proposed method of protein detection, using QCM-D, allows for the rudimentary but rapid means of analysis of select protein corona deposited on particulate biomedical surfaces.
- Full Text:
- Date Issued: 2011
- Authors: Cromhout, Mary
- Date: 2011
- Subjects: Biomedical materials , Nanostructured materials , Biomedical engineering , Quartz crystal microbalances , Blood proteins , Nanoparticles
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4102 , http://hdl.handle.net/10962/d1010660
- Description: The biomedical application of nanotechnology has come into the spotlight, with the promise of ‘personalised’ therapeutics that couple early diagnosis with targeted therapeutic activity. Due to the rapid growth of the biomedical applications of nanoparticles, along with the lack of understanding concerning their interactions with biomolecules, there is a pressing need for the development of standard methods directed at investigating the effect of introducing these unique particles into the human body. The central aim of this research is to establish a platform directed at assessing the biological fate of pioneering therapeutic particulate agents, such as metallophthalocyanines (MPcs) and multi-walled carbon nanotubes (FMWCNTs). In particular, we proposed, that Quartz Crystal Microbalance with Dissipation (QCM-D) technology may be employed to assess the composition of blood protein corona deposited on the therapeutic surface, and subsequently assess the biocompatibility of such particles. The proposed method of protein detection utilises the nanogram sensitivity of QCM-D technology to monitor highly specific antibody-antigen interactions. In particular those interactions which occur when probe antibodies are used to detect adsorbed blood proteins deposited on target particle-modified sensor surfaces. Protein detection analysis was directed toward identification of surface bound human serum albumin, complement factor C3c, and human plasma fibrinogen. Preliminary analysis of generic biomedical surfaces indicated human serum albumin demonstrates a higher binding affinity towards positively charged surfaces (i.e. cysteamine self-assembled monolayer), followed by hydrophobic surfaces. Detection of complement C3c, corresponded with literature, where lower levels were detected on negatively charged surfaces (i.e. mercapto undecanoic acid self-assembled monolayer), and higher levels of more hydrophobic surfaces (i.e. 11-amino undecane thiol self-assembled monolayer). Human plasma fibrinogen was observed to favour hydrophilic over hydrophobic self-assembled monolayer surfaces, which was in accordance with literature. Application of the proposed protein detection method for biocompatibility analysis of target therapeutic molecules, namely metallophthalocyanines and acid functionalised multi-walled carbon nanotubes, demonstrated a dependence on modified-surface film characteristics, such as surface charge and topography with regards to human serum albumin and human plasma fibrinogen analysis representing new insights into their potential biomolecular interactions The highest levels of detected human serum albumin and complement C3c were detected on the GePcSmix-modified surfaces. AlPcSmix-modified surfaces analysis suggested the highest levels of human plasma fibrinogen. Two methods of acid functionalisation were employed, using both nitric and sulphuric acid, and pure nitric acid. A general increase in detected human serum albumin, corresponding with an increase in functionalisation time, was observed. Complement C3c detection suggested an increase in deposited complement C3c, with increasing functionalisation time, when assessing nitric acid functionalised multi-walled carbon nanotubes, and a decrease, with increasing functionalisation time, when assessing nitric and sulphuric acid functionalised multi-walled carbon nanotubes. Analysis of human plasma fibrinogen was inconclusive, as were cytotoxicity experiments utilising MCF-7 cells in the presence of metallophthalocyanine complexes, raising simultaneously important considerations for their application and study. In the first such detailed examination of its kind it was concluded that the proposed method of protein detection, using QCM-D, allows for the rudimentary but rapid means of analysis of select protein corona deposited on particulate biomedical surfaces.
- Full Text:
- Date Issued: 2011