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Biosensors by Demet Ataman Sadık

Research paper thumbnail of Mixed-monolayer of N-hydroxysuccinimide-terminated cross- linker and short alkanethiol to improve the efficiency of biomolecule binding for biosensing

Surface and Interface Analysis, 2018

The goal of this study was to use a novel surface chemistry for modifying gold surfaces to decrea... more The goal of this study was to use a novel surface chemistry for modifying gold surfaces to decrease the steric hindrance, minimize the nonspecific bindings while providing directed immobilization of proteins for advancing the transducer property and to provide a biosensing platform for surface plasmon resonance (SPR) applications. Mixed self-assembled monolayers (mSAMs) were prepared using 3,3′-Dithiodipropionic acid di (N-hydroxysuccinimide ester) (DSP) and 6-mercapto-1-hexanol (MCH) and the selected model proteins bovine serum albumin (BSA) and lysozyme were tested for binding efficiency. First, binding of these two proteins at constant concentration to different DSP:MCH mSAMs were compared to deduce the best molar ratio for forming mSAM using a continuous flow system coupled to SPR. Coincidently the maximum protein binding DSP:MCH mSAM were the same for both proteins. The change in Response Unit (ΔRU) signal due to protein binding between DSP SAM and maximum protein binding DSP:MCH mSAM for lysozyme binding was more in comparison to BSA binding. Second, the effect of BSA and lysozyme concentration on binding efficiency to maximum protein binding DSP: MCH mSAM were compared and discussed. Lysozyme and BSA were shown to reach saturations on the same monolayer at concentrations of 5.7x10 −5 and 8.96x10 −6 [M] respectively, hence the molar ratio for limit concentrations is 6:1. The DSP SAM, MCH SAM, and DSP:MCH mSAMs where maximum and minimum protein binding occurs were also characterized with XPS and Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. Blank gold surface, maximum protein binding DSP:MCH mSAM and BSA immobilized DSP:MCH mSAM on gold surface were also investigated utilizing tapping mode AFM.

Research paper thumbnail of Nanofabrication and plasma polymerization assisted surface modification of a transducer based on localized surface plasmon resonance of gold nanostructure arrays for biosensorapplications

J Nanophotonics, 2013

The nanofabrication and surface modification of a transducer based on localized surface plasmon r... more The nanofabrication and surface modification of a transducer based on localized surface plasmon resonance (LSPR) of gold nanostructure arrays for biosensing was studied. We used electron beam lithography for the nanopatterning technique, which let us choose LSPR sensor properties by providing immense control over nanostructural geometry. A critical step in the utilization of this transducer is to form a selective biolayer over the gold nanostructures. We applied plasma polymerization and wet chemistry techniques for ethylenediamine (EDA) modification and glutaraldehyde immobilization as intermediate layers, respectively. The gold nanostructure arrays were primarily modified using EDA in order to activate the surface with amine groups that are cross-linked with later added avidin molecules by the help of glutaraldhyde layer residing in between. The success of plasma polymerization was validated with x-ray photoelectron spectroscopy measurements. As a last step, we introduced biotin to the surface (biotin has a high affinity for avidin). We were able to detect the LSPR resonance wavelength shift in the transmission spectra at each step of modification, including the avidin-biotin interaction, which acts as a model for specific molecule detection using LSPR.

Papers by Demet Ataman Sadık

Research paper thumbnail of Yüzey Plazmon Rezonans Temelli Trombin Biyosensörünün Geliştirilmesi

Enhancing the performance of biosensors has become an important task. Some of the requirements fo... more Enhancing the performance of biosensors has become an important task. Some of the requirements for improving the sensitivity and selectivity of these systems includes overcoming the steric hinderance issue, providing resistance to nonspecific binding, stable biological recognition layer formation and providing upright position while retaining the biological activity of the biological recognition element during the surface immobilization process. Formation of mixed self-assembled monolayers (mSAMs) is a commonly used procedure for diluting thiol modified biological recognition elements, so that target recognition is enhanced due to reduction in steric hinderance. In this study, a surface plasmon resonance (SPR) based sensor was developed for thrombin detection via forming 3,3’ Dithiodipropionic acid di (N-hydroxysuccinimide ester) (DSP) :6-mercapto-1-hexanol (MCH) mSAMs on gold surface. During the development of the sensor surface, DSP was utilized together with MCH 1) To decrease th...

Research paper thumbnail of Nanofabrication and plasma polymerization assisted surface modification of a transducer based on localized surface plasmon resonance of gold nanostructure arrays for biosensor applications

The nanofabrication and surface modification of a transducer based on localized surface plasmon r... more The nanofabrication and surface modification of a transducer based on localized surface plasmon resonance (LSPR) of gold nanostructure arrays for biosensing was studied. We used electron beam lithography for the nanopatterning technique, which let us choose LSPR sensor properties by providing immense control over nanostructural geometry. A critical step in the utilization of this transducer is to form a selective biolayer over the gold nanostructures. We applied plasma polymerization and wet chemistry techniques for ethylenediamine (EDA) modification and glutaraldehyde immobilization as intermediate layers, respectively. The gold nanostructure arrays were primarily modified using EDA in order to activate the surface with amine groups that are cross-linked with later added avidin molecules by the help of glutaraldhyde layer residing in between. The success of plasma polymerization was validated with x-ray photoelectron spectroscopy measurements. As a last step, we introduced biotin to the surface (biotin has a high affinity for avidin). We were able to detect the LSPR resonance wavelength shift in the transmission spectra at each step of modification, including the avidin-biotin interaction, which acts as a model for specific molecule detection using LSPR.

Research paper thumbnail of Mixed monolayer decorated SPR sensing surface for thrombin detection

Journal of Pharmaceutical and Biomedical Analysis

Keywords: Biosensor Gold surfaces 3,3 Dithiodipropionic acid di (N-hydroxysuccinimide ester) DSP:... more Keywords: Biosensor Gold surfaces 3,3 Dithiodipropionic acid di (N-hydroxysuccinimide ester) DSP:6-mercapto-1-hexanol (MCH) Mixed self-assembled monolayers (mSAMs) Biological recognition element immobilization Surface plasmon resonance (SPR) a b s t r a c t The development of surface plasmon resonance (SPR) based immunosensor for thrombin detection was aimed. For this purpose, 3,3 Dithiodipropionic acid di (N-hydroxysuccinimide ester) (DSP):6-mercapto-1-hexanol (MCH) mixed self-assembled monolayers (mSAMs) were formed on gold surfaces for immobilization of anti-thrombin antibody. The performance of the immunosensor was determined against the target protein thrombin at various concentrations using flow cell coupled SPR. The linear detection range of the immunosensor was 30.0-100.0 nM with an R 2 value of 0,992. Limit of Detection (LOD) and Limit of Quantification (LOQ) were determined to be 6.0 nM and 30.0 nM, respectively. The selectivity of the immunosensor was tested against a non-target model protein, human serum albumin (HSA) and the obtained RU value was found to be below the RU value corresponding to the LOQ concentration for thrombin. The immunosensor's capability to detect thrombin in diluted complex serum matrix was also tested and the obtained RU value (159 ± 16) was compared with RU value obtained for thrombin detection in PBS solution (137 ± 19). Based on the results, it was shown that DSP:MCH interface is a promising immobilization platform for binding biological recognition elements for the development of biosensors.

Research paper thumbnail of Mixed-monolayer of N-hydroxysuccinimide-terminated cross-linker and short alkanethiol to improve the efficiency of biomolecule binding for biosensing

Surface and Interface Analysis

The goal of this study was to use a novel surface chemistry for modifying gold surfaces to decrea... more The goal of this study was to use a novel surface chemistry for modifying gold surfaces to decrease the steric hindrance, minimize the nonspecific bindings while providing directed immobilization of proteins for advancing the transducer property and to provide a biosensing platform for surface plasmon resonance (SPR) applications. Mixed self-assembled monolayers (mSAMs) were prepared using 3,3′-Dithiodipropionic acid di (N-hydroxysuccinimide ester) (DSP) and 6-mercapto-1-hexanol (MCH) and the selected model proteins bovine serum albumin (BSA) and lysozyme were tested for binding efficiency. First, binding of these two proteins at constant concentration to different DSP:MCH mSAMs were compared to deduce the best molar ratio for forming mSAM using a continuous flow system coupled to SPR. Coincidently the maximum protein binding DSP:MCH mSAM were the same for both proteins. The change in Response Unit (ΔRU) signal due to protein binding between DSP SAM and maximum protein binding DSP:MCH mSAM for lysozyme binding was more in comparison to BSA binding. Second, the effect of BSA and lysozyme concentration on binding efficiency to maximum protein binding DSP: MCH mSAM were compared and discussed. Lysozyme and BSA were shown to reach saturations on the same monolayer at concentrations of 5.7x10 −5 and 8.96x10 −6 [M] respectively, hence the molar ratio for limit concentrations is 6:1. The DSP SAM, MCH SAM, and DSP:MCH mSAMs where maximum and minimum protein binding occurs were also characterized with XPS and Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. Blank gold surface, maximum protein binding DSP:MCH mSAM and BSA immobilized DSP:MCH mSAM on gold surface were also investigated utilizing tapping mode AFM.

Research paper thumbnail of Mixed-monolayer of N-hydroxysuccinimide-terminated cross-linker and short alkanethiol to improve the efficiency of biomolecule binding for biosensing

Surface and Interface Analysis

The goal of this study was to use a novel surface chemistry for modifying gold surfaces to decrea... more The goal of this study was to use a novel surface chemistry for modifying gold surfaces to decrease the steric hindrance, minimize the nonspecific bindings while providing directed immobilization of proteins for advancing the transducer property and to provide a biosensing platform for surface plasmon resonance (SPR) applications. Mixed self-assembled monolayers (mSAMs) were prepared using 3,3′-Dithiodipropionic acid di (N-hydroxysuccinimide ester) (DSP) and 6-mercapto-1-hexanol (MCH) and the selected model proteins bovine serum albumin (BSA) and lysozyme were tested for binding efficiency. First, binding of these two proteins at constant concentration to different DSP:MCH mSAMs were compared to deduce the best molar ratio for forming mSAM using a continuous flow system coupled to SPR. Coincidently the maximum protein binding DSP:MCH mSAM were the same for both proteins. The change in Response Unit (ΔRU) signal due to protein binding between DSP SAM and maximum protein binding DSP:MCH mSAM for lysozyme binding was more in comparison to BSA binding. Second, the effect of BSA and lysozyme concentration on binding efficiency to maximum protein binding DSP: MCH mSAM were compared and discussed. Lysozyme and BSA were shown to reach saturations on the same monolayer at concentrations of 5.7x10 −5 and 8.96x10 −6 [M] respectively, hence the molar ratio for limit concentrations is 6:1. The DSP SAM, MCH SAM, and DSP:MCH mSAMs where maximum and minimum protein binding occurs were also characterized with XPS and Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. Blank gold surface, maximum protein binding DSP:MCH mSAM and BSA immobilized DSP:MCH mSAM on gold surface were also investigated utilizing tapping mode AFM.

Research paper thumbnail of Mixed-monolayer of N-hydroxysuccinimide-terminated cross-linker and short alkanethiol to improve the efficiency of biomolecule binding for biosensing

Surface and Interface Analysis

The goal of this study was to use a novel surface chemistry for modifying gold surfaces to decrea... more The goal of this study was to use a novel surface chemistry for modifying gold surfaces to decrease the steric hindrance, minimize the nonspecific bindings while providing directed immobilization of proteins for advancing the transducer property and to provide a biosensing platform for surface plasmon resonance (SPR) applications. Mixed self-assembled monolayers (mSAMs) were prepared using 3,3′-Dithiodipropionic acid di (N-hydroxysuccinimide ester) (DSP) and 6-mercapto-1-hexanol (MCH) and the selected model proteins bovine serum albumin (BSA) and lysozyme were tested for binding efficiency. First, binding of these two proteins at constant concentration to different DSP:MCH mSAMs were compared to deduce the best molar ratio for forming mSAM using a continuous flow system coupled to SPR. Coincidently the maximum protein binding DSP:MCH mSAM were the same for both proteins. The change in Response Unit (ΔRU) signal due to protein binding between DSP SAM and maximum protein binding DSP:MCH mSAM for lysozyme binding was more in comparison to BSA binding. Second, the effect of BSA and lysozyme concentration on binding efficiency to maximum protein binding DSP: MCH mSAM were compared and discussed. Lysozyme and BSA were shown to reach saturations on the same monolayer at concentrations of 5.7x10 −5 and 8.96x10 −6 [M] respectively, hence the molar ratio for limit concentrations is 6:1. The DSP SAM, MCH SAM, and DSP:MCH mSAMs where maximum and minimum protein binding occurs were also characterized with XPS and Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. Blank gold surface, maximum protein binding DSP:MCH mSAM and BSA immobilized DSP:MCH mSAM on gold surface were also investigated utilizing tapping mode AFM.

Research paper thumbnail of Mixed-monolayer of N-hydroxysuccinimide-terminated cross-linker and short alkanethiol to improve the efficiency of biomolecule binding for biosensing

Surface and Interface Analysis

The goal of this study was to use a novel surface chemistry for modifying gold surfaces to decrea... more The goal of this study was to use a novel surface chemistry for modifying gold surfaces to decrease the steric hindrance, minimize the nonspecific bindings while providing directed immobilization of proteins for advancing the transducer property and to provide a biosensing platform for surface plasmon resonance (SPR) applications. Mixed self-assembled monolayers (mSAMs) were prepared using 3,3′-Dithiodipropionic acid di (N-hydroxysuccinimide ester) (DSP) and 6-mercapto-1-hexanol (MCH) and the selected model proteins bovine serum albumin (BSA) and lysozyme were tested for binding efficiency. First, binding of these two proteins at constant concentration to different DSP:MCH mSAMs were compared to deduce the best molar ratio for forming mSAM using a continuous flow system coupled to SPR. Coincidently the maximum protein binding DSP:MCH mSAM were the same for both proteins. The change in Response Unit (ΔRU) signal due to protein binding between DSP SAM and maximum protein binding DSP:MCH mSAM for lysozyme binding was more in comparison to BSA binding. Second, the effect of BSA and lysozyme concentration on binding efficiency to maximum protein binding DSP: MCH mSAM were compared and discussed. Lysozyme and BSA were shown to reach saturations on the same monolayer at concentrations of 5.7x10 −5 and 8.96x10 −6 [M] respectively, hence the molar ratio for limit concentrations is 6:1. The DSP SAM, MCH SAM, and DSP:MCH mSAMs where maximum and minimum protein binding occurs were also characterized with XPS and Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. Blank gold surface, maximum protein binding DSP:MCH mSAM and BSA immobilized DSP:MCH mSAM on gold surface were also investigated utilizing tapping mode AFM.

Research paper thumbnail of Mixed-monolayer of N-hydroxysuccinimide-terminated cross- linker and short alkanethiol to improve the efficiency of biomolecule binding for biosensing

Surface and Interface Analysis, 2018

The goal of this study was to use a novel surface chemistry for modifying gold surfaces to decrea... more The goal of this study was to use a novel surface chemistry for modifying gold surfaces to decrease the steric hindrance, minimize the nonspecific bindings while providing directed immobilization of proteins for advancing the transducer property and to provide a biosensing platform for surface plasmon resonance (SPR) applications. Mixed self-assembled monolayers (mSAMs) were prepared using 3,3′-Dithiodipropionic acid di (N-hydroxysuccinimide ester) (DSP) and 6-mercapto-1-hexanol (MCH) and the selected model proteins bovine serum albumin (BSA) and lysozyme were tested for binding efficiency. First, binding of these two proteins at constant concentration to different DSP:MCH mSAMs were compared to deduce the best molar ratio for forming mSAM using a continuous flow system coupled to SPR. Coincidently the maximum protein binding DSP:MCH mSAM were the same for both proteins. The change in Response Unit (ΔRU) signal due to protein binding between DSP SAM and maximum protein binding DSP:MCH mSAM for lysozyme binding was more in comparison to BSA binding. Second, the effect of BSA and lysozyme concentration on binding efficiency to maximum protein binding DSP: MCH mSAM were compared and discussed. Lysozyme and BSA were shown to reach saturations on the same monolayer at concentrations of 5.7x10 −5 and 8.96x10 −6 [M] respectively, hence the molar ratio for limit concentrations is 6:1. The DSP SAM, MCH SAM, and DSP:MCH mSAMs where maximum and minimum protein binding occurs were also characterized with XPS and Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. Blank gold surface, maximum protein binding DSP:MCH mSAM and BSA immobilized DSP:MCH mSAM on gold surface were also investigated utilizing tapping mode AFM.

Research paper thumbnail of Nanofabrication and plasma polymerization assisted surface modification of a transducer based on localized surface plasmon resonance of gold nanostructure arrays for biosensorapplications

J Nanophotonics, 2013

The nanofabrication and surface modification of a transducer based on localized surface plasmon r... more The nanofabrication and surface modification of a transducer based on localized surface plasmon resonance (LSPR) of gold nanostructure arrays for biosensing was studied. We used electron beam lithography for the nanopatterning technique, which let us choose LSPR sensor properties by providing immense control over nanostructural geometry. A critical step in the utilization of this transducer is to form a selective biolayer over the gold nanostructures. We applied plasma polymerization and wet chemistry techniques for ethylenediamine (EDA) modification and glutaraldehyde immobilization as intermediate layers, respectively. The gold nanostructure arrays were primarily modified using EDA in order to activate the surface with amine groups that are cross-linked with later added avidin molecules by the help of glutaraldhyde layer residing in between. The success of plasma polymerization was validated with x-ray photoelectron spectroscopy measurements. As a last step, we introduced biotin to the surface (biotin has a high affinity for avidin). We were able to detect the LSPR resonance wavelength shift in the transmission spectra at each step of modification, including the avidin-biotin interaction, which acts as a model for specific molecule detection using LSPR.

Research paper thumbnail of Yüzey Plazmon Rezonans Temelli Trombin Biyosensörünün Geliştirilmesi

Enhancing the performance of biosensors has become an important task. Some of the requirements fo... more Enhancing the performance of biosensors has become an important task. Some of the requirements for improving the sensitivity and selectivity of these systems includes overcoming the steric hinderance issue, providing resistance to nonspecific binding, stable biological recognition layer formation and providing upright position while retaining the biological activity of the biological recognition element during the surface immobilization process. Formation of mixed self-assembled monolayers (mSAMs) is a commonly used procedure for diluting thiol modified biological recognition elements, so that target recognition is enhanced due to reduction in steric hinderance. In this study, a surface plasmon resonance (SPR) based sensor was developed for thrombin detection via forming 3,3’ Dithiodipropionic acid di (N-hydroxysuccinimide ester) (DSP) :6-mercapto-1-hexanol (MCH) mSAMs on gold surface. During the development of the sensor surface, DSP was utilized together with MCH 1) To decrease th...

Research paper thumbnail of Nanofabrication and plasma polymerization assisted surface modification of a transducer based on localized surface plasmon resonance of gold nanostructure arrays for biosensor applications

The nanofabrication and surface modification of a transducer based on localized surface plasmon r... more The nanofabrication and surface modification of a transducer based on localized surface plasmon resonance (LSPR) of gold nanostructure arrays for biosensing was studied. We used electron beam lithography for the nanopatterning technique, which let us choose LSPR sensor properties by providing immense control over nanostructural geometry. A critical step in the utilization of this transducer is to form a selective biolayer over the gold nanostructures. We applied plasma polymerization and wet chemistry techniques for ethylenediamine (EDA) modification and glutaraldehyde immobilization as intermediate layers, respectively. The gold nanostructure arrays were primarily modified using EDA in order to activate the surface with amine groups that are cross-linked with later added avidin molecules by the help of glutaraldhyde layer residing in between. The success of plasma polymerization was validated with x-ray photoelectron spectroscopy measurements. As a last step, we introduced biotin to the surface (biotin has a high affinity for avidin). We were able to detect the LSPR resonance wavelength shift in the transmission spectra at each step of modification, including the avidin-biotin interaction, which acts as a model for specific molecule detection using LSPR.

Research paper thumbnail of Mixed monolayer decorated SPR sensing surface for thrombin detection

Journal of Pharmaceutical and Biomedical Analysis

Keywords: Biosensor Gold surfaces 3,3 Dithiodipropionic acid di (N-hydroxysuccinimide ester) DSP:... more Keywords: Biosensor Gold surfaces 3,3 Dithiodipropionic acid di (N-hydroxysuccinimide ester) DSP:6-mercapto-1-hexanol (MCH) Mixed self-assembled monolayers (mSAMs) Biological recognition element immobilization Surface plasmon resonance (SPR) a b s t r a c t The development of surface plasmon resonance (SPR) based immunosensor for thrombin detection was aimed. For this purpose, 3,3 Dithiodipropionic acid di (N-hydroxysuccinimide ester) (DSP):6-mercapto-1-hexanol (MCH) mixed self-assembled monolayers (mSAMs) were formed on gold surfaces for immobilization of anti-thrombin antibody. The performance of the immunosensor was determined against the target protein thrombin at various concentrations using flow cell coupled SPR. The linear detection range of the immunosensor was 30.0-100.0 nM with an R 2 value of 0,992. Limit of Detection (LOD) and Limit of Quantification (LOQ) were determined to be 6.0 nM and 30.0 nM, respectively. The selectivity of the immunosensor was tested against a non-target model protein, human serum albumin (HSA) and the obtained RU value was found to be below the RU value corresponding to the LOQ concentration for thrombin. The immunosensor's capability to detect thrombin in diluted complex serum matrix was also tested and the obtained RU value (159 ± 16) was compared with RU value obtained for thrombin detection in PBS solution (137 ± 19). Based on the results, it was shown that DSP:MCH interface is a promising immobilization platform for binding biological recognition elements for the development of biosensors.

Research paper thumbnail of Mixed-monolayer of N-hydroxysuccinimide-terminated cross-linker and short alkanethiol to improve the efficiency of biomolecule binding for biosensing

Surface and Interface Analysis

The goal of this study was to use a novel surface chemistry for modifying gold surfaces to decrea... more The goal of this study was to use a novel surface chemistry for modifying gold surfaces to decrease the steric hindrance, minimize the nonspecific bindings while providing directed immobilization of proteins for advancing the transducer property and to provide a biosensing platform for surface plasmon resonance (SPR) applications. Mixed self-assembled monolayers (mSAMs) were prepared using 3,3′-Dithiodipropionic acid di (N-hydroxysuccinimide ester) (DSP) and 6-mercapto-1-hexanol (MCH) and the selected model proteins bovine serum albumin (BSA) and lysozyme were tested for binding efficiency. First, binding of these two proteins at constant concentration to different DSP:MCH mSAMs were compared to deduce the best molar ratio for forming mSAM using a continuous flow system coupled to SPR. Coincidently the maximum protein binding DSP:MCH mSAM were the same for both proteins. The change in Response Unit (ΔRU) signal due to protein binding between DSP SAM and maximum protein binding DSP:MCH mSAM for lysozyme binding was more in comparison to BSA binding. Second, the effect of BSA and lysozyme concentration on binding efficiency to maximum protein binding DSP: MCH mSAM were compared and discussed. Lysozyme and BSA were shown to reach saturations on the same monolayer at concentrations of 5.7x10 −5 and 8.96x10 −6 [M] respectively, hence the molar ratio for limit concentrations is 6:1. The DSP SAM, MCH SAM, and DSP:MCH mSAMs where maximum and minimum protein binding occurs were also characterized with XPS and Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. Blank gold surface, maximum protein binding DSP:MCH mSAM and BSA immobilized DSP:MCH mSAM on gold surface were also investigated utilizing tapping mode AFM.

Research paper thumbnail of Mixed-monolayer of N-hydroxysuccinimide-terminated cross-linker and short alkanethiol to improve the efficiency of biomolecule binding for biosensing

Surface and Interface Analysis

The goal of this study was to use a novel surface chemistry for modifying gold surfaces to decrea... more The goal of this study was to use a novel surface chemistry for modifying gold surfaces to decrease the steric hindrance, minimize the nonspecific bindings while providing directed immobilization of proteins for advancing the transducer property and to provide a biosensing platform for surface plasmon resonance (SPR) applications. Mixed self-assembled monolayers (mSAMs) were prepared using 3,3′-Dithiodipropionic acid di (N-hydroxysuccinimide ester) (DSP) and 6-mercapto-1-hexanol (MCH) and the selected model proteins bovine serum albumin (BSA) and lysozyme were tested for binding efficiency. First, binding of these two proteins at constant concentration to different DSP:MCH mSAMs were compared to deduce the best molar ratio for forming mSAM using a continuous flow system coupled to SPR. Coincidently the maximum protein binding DSP:MCH mSAM were the same for both proteins. The change in Response Unit (ΔRU) signal due to protein binding between DSP SAM and maximum protein binding DSP:MCH mSAM for lysozyme binding was more in comparison to BSA binding. Second, the effect of BSA and lysozyme concentration on binding efficiency to maximum protein binding DSP: MCH mSAM were compared and discussed. Lysozyme and BSA were shown to reach saturations on the same monolayer at concentrations of 5.7x10 −5 and 8.96x10 −6 [M] respectively, hence the molar ratio for limit concentrations is 6:1. The DSP SAM, MCH SAM, and DSP:MCH mSAMs where maximum and minimum protein binding occurs were also characterized with XPS and Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. Blank gold surface, maximum protein binding DSP:MCH mSAM and BSA immobilized DSP:MCH mSAM on gold surface were also investigated utilizing tapping mode AFM.

Research paper thumbnail of Mixed-monolayer of N-hydroxysuccinimide-terminated cross-linker and short alkanethiol to improve the efficiency of biomolecule binding for biosensing

Surface and Interface Analysis

The goal of this study was to use a novel surface chemistry for modifying gold surfaces to decrea... more The goal of this study was to use a novel surface chemistry for modifying gold surfaces to decrease the steric hindrance, minimize the nonspecific bindings while providing directed immobilization of proteins for advancing the transducer property and to provide a biosensing platform for surface plasmon resonance (SPR) applications. Mixed self-assembled monolayers (mSAMs) were prepared using 3,3′-Dithiodipropionic acid di (N-hydroxysuccinimide ester) (DSP) and 6-mercapto-1-hexanol (MCH) and the selected model proteins bovine serum albumin (BSA) and lysozyme were tested for binding efficiency. First, binding of these two proteins at constant concentration to different DSP:MCH mSAMs were compared to deduce the best molar ratio for forming mSAM using a continuous flow system coupled to SPR. Coincidently the maximum protein binding DSP:MCH mSAM were the same for both proteins. The change in Response Unit (ΔRU) signal due to protein binding between DSP SAM and maximum protein binding DSP:MCH mSAM for lysozyme binding was more in comparison to BSA binding. Second, the effect of BSA and lysozyme concentration on binding efficiency to maximum protein binding DSP: MCH mSAM were compared and discussed. Lysozyme and BSA were shown to reach saturations on the same monolayer at concentrations of 5.7x10 −5 and 8.96x10 −6 [M] respectively, hence the molar ratio for limit concentrations is 6:1. The DSP SAM, MCH SAM, and DSP:MCH mSAMs where maximum and minimum protein binding occurs were also characterized with XPS and Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. Blank gold surface, maximum protein binding DSP:MCH mSAM and BSA immobilized DSP:MCH mSAM on gold surface were also investigated utilizing tapping mode AFM.

Research paper thumbnail of Mixed-monolayer of N-hydroxysuccinimide-terminated cross-linker and short alkanethiol to improve the efficiency of biomolecule binding for biosensing

Surface and Interface Analysis

The goal of this study was to use a novel surface chemistry for modifying gold surfaces to decrea... more The goal of this study was to use a novel surface chemistry for modifying gold surfaces to decrease the steric hindrance, minimize the nonspecific bindings while providing directed immobilization of proteins for advancing the transducer property and to provide a biosensing platform for surface plasmon resonance (SPR) applications. Mixed self-assembled monolayers (mSAMs) were prepared using 3,3′-Dithiodipropionic acid di (N-hydroxysuccinimide ester) (DSP) and 6-mercapto-1-hexanol (MCH) and the selected model proteins bovine serum albumin (BSA) and lysozyme were tested for binding efficiency. First, binding of these two proteins at constant concentration to different DSP:MCH mSAMs were compared to deduce the best molar ratio for forming mSAM using a continuous flow system coupled to SPR. Coincidently the maximum protein binding DSP:MCH mSAM were the same for both proteins. The change in Response Unit (ΔRU) signal due to protein binding between DSP SAM and maximum protein binding DSP:MCH mSAM for lysozyme binding was more in comparison to BSA binding. Second, the effect of BSA and lysozyme concentration on binding efficiency to maximum protein binding DSP: MCH mSAM were compared and discussed. Lysozyme and BSA were shown to reach saturations on the same monolayer at concentrations of 5.7x10 −5 and 8.96x10 −6 [M] respectively, hence the molar ratio for limit concentrations is 6:1. The DSP SAM, MCH SAM, and DSP:MCH mSAMs where maximum and minimum protein binding occurs were also characterized with XPS and Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. Blank gold surface, maximum protein binding DSP:MCH mSAM and BSA immobilized DSP:MCH mSAM on gold surface were also investigated utilizing tapping mode AFM.