Fabrication, characterization and application of phthalocyanine-magnetite hybrid nanofibers
- Authors: Modisha, Phillimon Mokanne
- Date: 2014
- Subjects: Nanofibers , Nanoparticles , Magnetite
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4500 , http://hdl.handle.net/10962/d1013223
- Description: Magnetic nanoparticles comprising magnetite (Fe3O4) were functionalized with 3-aminopropyl-triethoxysilane forming amino functionalized magnetite nanoparticles (AMNPs). The amino group allows for conjugation with zinc octacarboxyphthalocyanine (ZnOCPc) or zinc tetracarboxyphthalocyanine (ZnTCPc) via the carboxyl group to form an amide bond. A reduced aggregation of ZnTCPc is observed after conjugation with AMNPs. The thermal stability, conjugation, morphology and the sizes of the nanoparticles and their conjugates were confirmed using thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and Powder X-ray diffractometry (PXRD), respectively. The covalent linkage of AMNPs to ZnOCPc or ZnTCPc resulted in improvement in the photophysical behavior of the phthalocyanines. Improvement in the triplet quantum yield (ΦT), singlet oxygen quantum yield (ΦΔ), triplet lifetime (τT) and singlet oxygen lifetime (τΔ) of the ZnOCPc or ZnTCPc were observed, hence improving the photosensitizers efficiency. The conjugates comprising of zinc octacarboxyphthalocyanine (ZnOCPc) and AMNPs were electrospun into fibers using polyamide-6 (PA-6). This was used for the photodegradation of Orange-G and compared with ZnOCPc-AMNPs in suspension. For ZnOCPc-AMNPs in suspension, it is noteworthy that the catalyst can be easily recovered using an external magnetic field. The singlet oxygen generation increases as we increase the fiber diameter by increasing the ZnOCPc concentration. The singlet oxygen quantum yield is higher for PA-6/ZnOCPc-AMNPs nanofibers when compared to PA-6/ZnOCPc. The rate of degradation of Orange-G increased with an increase in the singlet oxygen quantum yield. Moreover, the kinetic analysis showed that the photodecomposition of Orange-G is a first-order reaction according to the Langmuir-Hinshelwood model.
- Full Text:
- Date Issued: 2014
- Authors: Modisha, Phillimon Mokanne
- Date: 2014
- Subjects: Nanofibers , Nanoparticles , Magnetite
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4500 , http://hdl.handle.net/10962/d1013223
- Description: Magnetic nanoparticles comprising magnetite (Fe3O4) were functionalized with 3-aminopropyl-triethoxysilane forming amino functionalized magnetite nanoparticles (AMNPs). The amino group allows for conjugation with zinc octacarboxyphthalocyanine (ZnOCPc) or zinc tetracarboxyphthalocyanine (ZnTCPc) via the carboxyl group to form an amide bond. A reduced aggregation of ZnTCPc is observed after conjugation with AMNPs. The thermal stability, conjugation, morphology and the sizes of the nanoparticles and their conjugates were confirmed using thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and Powder X-ray diffractometry (PXRD), respectively. The covalent linkage of AMNPs to ZnOCPc or ZnTCPc resulted in improvement in the photophysical behavior of the phthalocyanines. Improvement in the triplet quantum yield (ΦT), singlet oxygen quantum yield (ΦΔ), triplet lifetime (τT) and singlet oxygen lifetime (τΔ) of the ZnOCPc or ZnTCPc were observed, hence improving the photosensitizers efficiency. The conjugates comprising of zinc octacarboxyphthalocyanine (ZnOCPc) and AMNPs were electrospun into fibers using polyamide-6 (PA-6). This was used for the photodegradation of Orange-G and compared with ZnOCPc-AMNPs in suspension. For ZnOCPc-AMNPs in suspension, it is noteworthy that the catalyst can be easily recovered using an external magnetic field. The singlet oxygen generation increases as we increase the fiber diameter by increasing the ZnOCPc concentration. The singlet oxygen quantum yield is higher for PA-6/ZnOCPc-AMNPs nanofibers when compared to PA-6/ZnOCPc. The rate of degradation of Orange-G increased with an increase in the singlet oxygen quantum yield. Moreover, the kinetic analysis showed that the photodecomposition of Orange-G is a first-order reaction according to the Langmuir-Hinshelwood model.
- Full Text:
- Date Issued: 2014
Synthesis of silver nanoparticles and their role against a thiazolekinase enzyme from Plasmodium falciparum
- Yao, Jia
- Authors: Yao, Jia
- Date: 2014
- Subjects: Silver , Nanoparticles , Thiazoles , Plasmodium falciparum , Antimalarials , Malaria -- Chemotherapy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4168 , http://hdl.handle.net/10962/d1020894
- Description: Malaria, a mosquito-borne infectious disease, caused by the protozoan Plasmodium genus, is the greatest health challenges worldwide. The plasmodial vitamin B1 biosynthetic enzyme PfThzK diverges significantly, both structurally and functionally from its counterpart in higher eukaryotes, thereby making it particularly attractive as a biomedical target. In the present study, PfThzK was recombinantly produced as 6×His fusion protein in E. coli BL21, purified using nickel affinity chromatography and size exclusion chromatography resulting in 1.03% yield and specific activity 0.28 U/mg. The enzyme was found to be a monomer with a molecular mass of 34 kDa. Characterization of the PfThzK showed an optimum temperature and pH of 37°C and 7.5 respectively, and it is relatively stable (t₁/₂=2.66 h). Ag nanoparticles were synthesized by NaBH₄/tannic acid, and characterized by UV-vis spectroscopy and transmission electron microscopy. The morphologies of these Ag nanoparticles (in terms of size) synthesized by tannic acid appeared to be more controlled with the size of 7.06±2.41 nm, compared with those synthesized by NaBH₄, with the sized of 12.9±4.21 nm. The purified PfThzK was challenged with Ag NPs synthesized by tannic acid, and the results suggested that they competitively inhibited PfThzK (89 %) at low concentrations (5-10 μM) with a Ki = 6.45 μM.
- Full Text:
- Date Issued: 2014
- Authors: Yao, Jia
- Date: 2014
- Subjects: Silver , Nanoparticles , Thiazoles , Plasmodium falciparum , Antimalarials , Malaria -- Chemotherapy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4168 , http://hdl.handle.net/10962/d1020894
- Description: Malaria, a mosquito-borne infectious disease, caused by the protozoan Plasmodium genus, is the greatest health challenges worldwide. The plasmodial vitamin B1 biosynthetic enzyme PfThzK diverges significantly, both structurally and functionally from its counterpart in higher eukaryotes, thereby making it particularly attractive as a biomedical target. In the present study, PfThzK was recombinantly produced as 6×His fusion protein in E. coli BL21, purified using nickel affinity chromatography and size exclusion chromatography resulting in 1.03% yield and specific activity 0.28 U/mg. The enzyme was found to be a monomer with a molecular mass of 34 kDa. Characterization of the PfThzK showed an optimum temperature and pH of 37°C and 7.5 respectively, and it is relatively stable (t₁/₂=2.66 h). Ag nanoparticles were synthesized by NaBH₄/tannic acid, and characterized by UV-vis spectroscopy and transmission electron microscopy. The morphologies of these Ag nanoparticles (in terms of size) synthesized by tannic acid appeared to be more controlled with the size of 7.06±2.41 nm, compared with those synthesized by NaBH₄, with the sized of 12.9±4.21 nm. The purified PfThzK was challenged with Ag NPs synthesized by tannic acid, and the results suggested that they competitively inhibited PfThzK (89 %) at low concentrations (5-10 μM) with a Ki = 6.45 μM.
- Full Text:
- Date Issued: 2014
The interaction of silver nanoparticles with triosephosphate isomerase from human and malarial parasite (Plasmodium falciparum) : a comparative study
- De Moor, Warren Ralph Josephus
- Authors: De Moor, Warren Ralph Josephus
- Date: 2014
- Subjects: Silver , Nanoparticles , Triose-phosphate isomerase , Plasmodium falciparum , Nanotechnology , Antimalarials , Povidone
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4169 , http://hdl.handle.net/10962/d1020895
- Description: The advent of advanced modern nanotechnology techniques offers new and exciting opportunities to develop novel nanotech-derived antimalarial nanodrugs with enhanced selective and targeting abilities that allow for lower effective drug dosages, longer drug persistence and reduced drug degradation within the body. Using a nanodrug approach also has the advantage of avoiding drug resistance problems that plague reconfigured versions of already-existing antimalarial drugs. In this study recombinant triosephosphate isomerase enzymes from Plasmodium falciparum (PfTIM) and Humans (hTIM) were recombinantly expressed, purified and characterised. PfTIM was shown to have optimal pH stability at pH 5.0-5.5 and thermal stability at 25°C with Km 4.34 mM and Vmax 0.876 μmol.ml⁻ₑmin⁻ₑ. For hTIM, these parameters were as follows: pH optima of 6.5-7.0; temperature optima of 30°C, with Km 2.27 mM and Vmax 0.714 μmol.ml⁻ₑmin⁻ₑ. Recombinant TIM enzymes were subjected to inhibition studies using polyvinylpyrrolidone (PVP) stabilised silver nanoparticles (AgNPs) of 4-12 nm in diameter. These studies showed that the AgNPs were able to selectively inhibit PfTIM over hTIM with an 8-fold greater decrease in enzymatic efficiency (Kcat/Km) observed for PfTIM, as compared to hTIM, for kinetics tests done using 0.06 μM of AgNPs. Complete inhibition of PfTIM under optimal conditions was achieved using 0.25 μM AgNPs after 45 minutes while hTIM maintained approximately 31% of its activity at this AgNP concentration. The above results indicate that selective enzymatic targeting of the important, key metabolic enzyme TIM, can be achieved using nanotechnology-derived nanodrugs. It was demonstrated that the key structural differences, between the two enzyme variants, were significant enough to create unique characteristics for each TIM variant, thereby allowing for selective enzyme targeting using AgNPs. If these AgNPs could be coupled with a nanotechnology-derived, targeted localization mechanism – possibly using apoferritin to deliver the AgNPs to infected erythrocytes (Burns and Pollock, 2008) – then such an approach could offer new opportunities for the development of viable antimalarial nanodrugs. For this to be achieved further research into several key areas will be required, including nanoparticle toxicity, drug localization and testing the lethality of the system on live parasite cultures.
- Full Text:
- Date Issued: 2014
- Authors: De Moor, Warren Ralph Josephus
- Date: 2014
- Subjects: Silver , Nanoparticles , Triose-phosphate isomerase , Plasmodium falciparum , Nanotechnology , Antimalarials , Povidone
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4169 , http://hdl.handle.net/10962/d1020895
- Description: The advent of advanced modern nanotechnology techniques offers new and exciting opportunities to develop novel nanotech-derived antimalarial nanodrugs with enhanced selective and targeting abilities that allow for lower effective drug dosages, longer drug persistence and reduced drug degradation within the body. Using a nanodrug approach also has the advantage of avoiding drug resistance problems that plague reconfigured versions of already-existing antimalarial drugs. In this study recombinant triosephosphate isomerase enzymes from Plasmodium falciparum (PfTIM) and Humans (hTIM) were recombinantly expressed, purified and characterised. PfTIM was shown to have optimal pH stability at pH 5.0-5.5 and thermal stability at 25°C with Km 4.34 mM and Vmax 0.876 μmol.ml⁻ₑmin⁻ₑ. For hTIM, these parameters were as follows: pH optima of 6.5-7.0; temperature optima of 30°C, with Km 2.27 mM and Vmax 0.714 μmol.ml⁻ₑmin⁻ₑ. Recombinant TIM enzymes were subjected to inhibition studies using polyvinylpyrrolidone (PVP) stabilised silver nanoparticles (AgNPs) of 4-12 nm in diameter. These studies showed that the AgNPs were able to selectively inhibit PfTIM over hTIM with an 8-fold greater decrease in enzymatic efficiency (Kcat/Km) observed for PfTIM, as compared to hTIM, for kinetics tests done using 0.06 μM of AgNPs. Complete inhibition of PfTIM under optimal conditions was achieved using 0.25 μM AgNPs after 45 minutes while hTIM maintained approximately 31% of its activity at this AgNP concentration. The above results indicate that selective enzymatic targeting of the important, key metabolic enzyme TIM, can be achieved using nanotechnology-derived nanodrugs. It was demonstrated that the key structural differences, between the two enzyme variants, were significant enough to create unique characteristics for each TIM variant, thereby allowing for selective enzyme targeting using AgNPs. If these AgNPs could be coupled with a nanotechnology-derived, targeted localization mechanism – possibly using apoferritin to deliver the AgNPs to infected erythrocytes (Burns and Pollock, 2008) – then such an approach could offer new opportunities for the development of viable antimalarial nanodrugs. For this to be achieved further research into several key areas will be required, including nanoparticle toxicity, drug localization and testing the lethality of the system on live parasite cultures.
- Full Text:
- Date Issued: 2014
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