The development of electrochemical aptamer biosensors based on polyamidoamine dendrimer-streptavidin supramolecular architecture
- Authors: Soda, Narshone
- Date: 2017
- Subjects: Supramolecular electrochemistry , Molecular structure , Nanomedicine
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/235917 , uj:24136
- Description: M.Tech. (Chemistry) , Abstract: This dissertation reports on the development of an electrochemical aptasensor for hydrogen peroxide and thrombin based on a novel polyamidoamine dendrimer-streptavidin supramolecular architecture. Polyamidoamine dendrimer (PAMAM) was electrodeposited on a glassy carbon electrode using cyclic voltammetry at a potential window of -200 mV to +1100 mV at scan rate 50 mV s-1. The electrode was labelled GCE/PAMAM. A 50 μL volume of 100 μg/mL streptavidin (strept) was drop coated on the GCE/PAMAM electrode for 2 h. The electrode was labelled GCE/PAMAM/Strept and also referred to as the supramolecular platform. The platform was characterised using various techniques such as voltammetry, electrochemical impedance spectroscopy, electron microscopy etc. The supramolecular architecture (GCE, PAMAM)/ strept) was conjugated to an enzyme called horseradish peroxidase (HRP) to make the biosensor GCE/PAMAM/Strept-HRP. The biosensor i.e. GCE/PAMAM/Strept-HRP was used for the detection of hydrogen peroxide. The GCE/PAMAM/Strept-HRP biosensor was studied using electrochemical techniques (CV, SWV, EIS and chronoamperometry) and microscopic techniques (HR-SEM). The platform was conducting and electroactive exhibiting reversible electrochemistry (E°′ = 450 mV and Ipa/Ipc ≈ 1 in Fe(CN)63-/4-). The second part of the work involves the detection of thrombin using a GCE/PAMAM/Strept/TBA modified electrode. Biotinylated aptamer probe was immobilised on the platform through biotin-streptavidin interaction. The aptasensor was monitored using CV, SWV and EIS. The selectivity of the GCE/PAMAM/Strept/TBA based aptasensor was evaluated using interfering proteins of BSA, lysozyme, and haemoglobin that also co-exist with thrombin in the blood. The relative response obtained shows insignificant effect for the interfering proteins with BSA and haemoglobin having a relative response of 9.2% and 7.6% respectively. This confirms the excellent specificity of the proposed aptasensor.
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- Authors: Soda, Narshone
- Date: 2017
- Subjects: Supramolecular electrochemistry , Molecular structure , Nanomedicine
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/235917 , uj:24136
- Description: M.Tech. (Chemistry) , Abstract: This dissertation reports on the development of an electrochemical aptasensor for hydrogen peroxide and thrombin based on a novel polyamidoamine dendrimer-streptavidin supramolecular architecture. Polyamidoamine dendrimer (PAMAM) was electrodeposited on a glassy carbon electrode using cyclic voltammetry at a potential window of -200 mV to +1100 mV at scan rate 50 mV s-1. The electrode was labelled GCE/PAMAM. A 50 μL volume of 100 μg/mL streptavidin (strept) was drop coated on the GCE/PAMAM electrode for 2 h. The electrode was labelled GCE/PAMAM/Strept and also referred to as the supramolecular platform. The platform was characterised using various techniques such as voltammetry, electrochemical impedance spectroscopy, electron microscopy etc. The supramolecular architecture (GCE, PAMAM)/ strept) was conjugated to an enzyme called horseradish peroxidase (HRP) to make the biosensor GCE/PAMAM/Strept-HRP. The biosensor i.e. GCE/PAMAM/Strept-HRP was used for the detection of hydrogen peroxide. The GCE/PAMAM/Strept-HRP biosensor was studied using electrochemical techniques (CV, SWV, EIS and chronoamperometry) and microscopic techniques (HR-SEM). The platform was conducting and electroactive exhibiting reversible electrochemistry (E°′ = 450 mV and Ipa/Ipc ≈ 1 in Fe(CN)63-/4-). The second part of the work involves the detection of thrombin using a GCE/PAMAM/Strept/TBA modified electrode. Biotinylated aptamer probe was immobilised on the platform through biotin-streptavidin interaction. The aptasensor was monitored using CV, SWV and EIS. The selectivity of the GCE/PAMAM/Strept/TBA based aptasensor was evaluated using interfering proteins of BSA, lysozyme, and haemoglobin that also co-exist with thrombin in the blood. The relative response obtained shows insignificant effect for the interfering proteins with BSA and haemoglobin having a relative response of 9.2% and 7.6% respectively. This confirms the excellent specificity of the proposed aptasensor.
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Density Functional Theory (DFT) studies for the ring opening mechanism of tetraethyl 2-aryl-1,2-epoxygembisphosphonates
- Authors: Marondedze, Epraim F.
- Date: 2016
- Subjects: Density functionals , Molecular structure , Molecules - Models - Data processing
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/84634 , uj:19246
- Description: Abstract: The study reported in this thesis was aimed at investigating the ring opening mechanism(s) associated with the breaking of the carbon-oxygen oxirane bond of tetraethyl 2-aryl-1,2-epoxygembisphosphonate. Density Functional Theory (DFT) was employed to theoretically determine the mechanism(s) of the oxirane ring opening for tetraethyl 2-aryl-1,2-epoxy-2-phenylbisphosphonate. Simulations were carried out using the Gaussian09 version D01 software whereas visualisations were performed in GaussView 5.0.8, a graphic user interface compatible and part of the Gaussian software packages. The generalized gradient approximation functional BP86 in combination with the 6-31+G(d,p) and aug-cc-pVTZ basis sets was used for investigating the proposed reaction pathways. The method was selected after comparing energies and geometries obtained at both the BP86 and B3LYP functionals on selected local minima. Two transition states were obtained and found to be associated with opening on carbon 1 and 2 of the oxirane ring. These transition states were verified by running a frequency calculation and an intrinsic reaction coordinate (IRC) calculation at the same level of theory. Solvent effects were incorporated implicitly using the conductor-like polarised continuum model (CPCM) to investigate the effects on the energy and structures involved in the proposed mechanistic pathways. The effect of both electron donating and electron withdrawing groups on the transition state energies was also investigated. The ring opening at C2 was found to be the most favoured pathway both in vacuum and in the selected solvents. , M.Sc. (Chemistry)
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- Authors: Marondedze, Epraim F.
- Date: 2016
- Subjects: Density functionals , Molecular structure , Molecules - Models - Data processing
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/84634 , uj:19246
- Description: Abstract: The study reported in this thesis was aimed at investigating the ring opening mechanism(s) associated with the breaking of the carbon-oxygen oxirane bond of tetraethyl 2-aryl-1,2-epoxygembisphosphonate. Density Functional Theory (DFT) was employed to theoretically determine the mechanism(s) of the oxirane ring opening for tetraethyl 2-aryl-1,2-epoxy-2-phenylbisphosphonate. Simulations were carried out using the Gaussian09 version D01 software whereas visualisations were performed in GaussView 5.0.8, a graphic user interface compatible and part of the Gaussian software packages. The generalized gradient approximation functional BP86 in combination with the 6-31+G(d,p) and aug-cc-pVTZ basis sets was used for investigating the proposed reaction pathways. The method was selected after comparing energies and geometries obtained at both the BP86 and B3LYP functionals on selected local minima. Two transition states were obtained and found to be associated with opening on carbon 1 and 2 of the oxirane ring. These transition states were verified by running a frequency calculation and an intrinsic reaction coordinate (IRC) calculation at the same level of theory. Solvent effects were incorporated implicitly using the conductor-like polarised continuum model (CPCM) to investigate the effects on the energy and structures involved in the proposed mechanistic pathways. The effect of both electron donating and electron withdrawing groups on the transition state energies was also investigated. The ring opening at C2 was found to be the most favoured pathway both in vacuum and in the selected solvents. , M.Sc. (Chemistry)
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