A total synthesis of (()-stemodinone, a tetracyclic stemodane diterpene, from the known tricyclic... more A total synthesis of (()-stemodinone, a tetracyclic stemodane diterpene, from the known tricyclic methyl olefin 11 is described. The key steps involve an efficient ring-exchange reaction and palladium(0)-catalyzed lactone migration. The ring-exchange strategy for controlling the stereochemistry was based on an initial Diels-Alder reaction to form a new ring followed by cleavage of the original ring. Cleavage of the original ring of the Diels-Alder adduct 9 was achieved by an initial regio-and chemoselective Baeyer-Villiger oxidation followed by the Pd(0)-catalyzed lactonemigration reaction reported by us. 10.
Oligonucleotides modified with 2 &amp... more Oligonucleotides modified with 2 ',4 '-BNA(NC) (N-H)/(N-Me) monomers exhibited excellent hybridizing and nuclease resistance properties. Duplex and triplex thermal stabilities were greatly enhanced by incorporating 2',4'-BNA(NC) (N-H) and (N-Me) monomers and nuclease resistance was tremendously higher than that of natural oligonucleotide.
We examined the effect of 2'-O,4'-C-aminomethylene bridged nucleic acid (2',4'-BN... more We examined the effect of 2'-O,4'-C-aminomethylene bridged nucleic acid (2',4'-BNA(NC)) backbone modification of triplex-forming oligonucleotide (TFO) on the pyrimidine motif triplex formation at neutral pH, a condition where pyrimidine motif triplexes are unstable. The melting temperature of the pyrimidine motif triplex at pH 6.8 with 2',4'-BNA(NC) modified TFO was significantly higher than that observed with unmodified TFO. The 2',4'-BNA(NC) modification of TFO increased the thermal stability of the pyrimidine motif triplex at neutral pH. The present results certainly support the idea that the 2',4'-BNA(NC) backbone modification of TFO could be a key chemical modification and may eventually lead to progress in therapeutic applications of the antigene strategy in vivo.
We examined the effect of 3'-amino-2'-O,4'-C-methylene bridged nucleic acid (3'-a... more We examined the effect of 3'-amino-2'-O,4'-C-methylene bridged nucleic acid (3'-amino-2',4'-BNA) backbone modification of triplex-forming oligonucleotide (TFO) on the pyrimidine motif triplex formation at neutral pH, a condition where pyrimidine motif triplexes are unstable. The melting temperature of the pyrimidine motif triplex at pH 6.8 with 3'-amino-2',4'-BNA modified TFO was significantly higher than that observed with unmodified TFO. The 3'-amino-2',4'-BNA modification of TFO increased the thermal stability of the pyrimidine motif triplex at neutral pH. The present results certainly support the idea that the 3'-amino-2',4'-BNA modification of TFO could be a key chemical modification and may eventually lead to progress in therapeutic applications of the antigene strategy in vivo.
ABSTRACT Perovskites have gained attraction as electrode and interconnect materials for Solid Oxi... more ABSTRACT Perovskites have gained attraction as electrode and interconnect materials for Solid Oxide Fuel Cells (SOFCs) due to their catalytic, ionic and electrical conductivities, chemical and thermal stabilities at higher temperatures. The operation and efficiency of SOFC depends mainly on the electrodes. Each electrode, anode and cathode, has demanding materials selection criteria. State of the art nickel-yittria stabilized zirconia cermet anodes are unable to work efficiently with hydrocarbon fuels and at intermediate operating temperature range (600-800 degrees C). Hence, there is an increasing demand for the development of alternate anode materials to improve the fuel flexibility and efficiency of SOFCs. Perovskite based materials have oxygen ion vacancies depending on composition, temperature, and surrounding crystalline environment that impart mixed ionic and electronic conductivities to them. Since perovskite can accommodate all the elements in the periodic table they can offer excellent catalytic properties. The report is about the present status of perovskites based anode materials for SOFC application.
... Murtadhahadi 2,d and Mohd Nizam Ab. Rahman 2,e ... 21 (2001), p. 2843-2853 [6] KR Jamaludin, ... more ... Murtadhahadi 2,d and Mohd Nizam Ab. Rahman 2,e ... 21 (2001), p. 2843-2853 [6] KR Jamaludin, N. Muhamad, SYM Amin, MNA Rahman and Murtadhahadi: International Journal of Mechanical and Materials Engineering Vol. 3 No. ...
Journal of Education and Learning (EduLearn), 2012
... Kuala Lumpur: Utusan Publication and Distribution Sdn. Bhd. Purwanto, M. Ngalim. 1998. ... O... more ... Kuala Lumpur: Utusan Publication and Distribution Sdn. Bhd. Purwanto, M. Ngalim. 1998. ... Organizational Learning: the Key to Management Innovation. Spring: Sloan Management Review. Rivai, Veithzal, & Mulyadi, Dedy.2009. Leadership and Organizational Behavior. ...
2013 IEEE Asian Solid-State Circuits Conference (A-SSCC), 2013
ABSTRACT A fully integrated SoC for multimodality intracranial neuromonitoring is presented. This... more ABSTRACT A fully integrated SoC for multimodality intracranial neuromonitoring is presented. This SoC includes a capacitive MEMS pressure sensor, an electrochemical oxygen sensor, a solid-state temperature sensor and sensor interface circuits in a single chip. Chopper stabilization and dynamic element matching techniques are applied in sensor interface circuits to reduce circuit noise and offset. On-chip calibration is implemented for each sensor to compensate process variations. Measured accuracies of the pressure, oxygen, and temperature sensors are ±1 mmHg, ±1 mmHg, and ±0.2 oC, respectively. Implemented in 0.18-μm CMOS, the SoC occupies an area of 1.4 mm × 4mm and consumes 188-μW DC power.
This paper presents the development of a Twin-T oscillator comprising polymer coated parallel pla... more This paper presents the development of a Twin-T oscillator comprising polymer coated parallel plates as a sensor for ocean water salinity monitoring. This sensor employs a parallel plate capacitor design, with sea water serving as the medium between plates. Novalac resin and a proprietary commercial polymer (Accuflo™) were investigated as corrosion protective coatings for the copper electrodes of the capacitor. Electrochemical Impedance Spectroscopy (EIS) was employed to evaluate corrosion inhibition of polymer coating in sea water. A detection circuit was designed and simulated using P-spice and then implemented in Printed Circuit Board (PCB). EIS results indicate that Accuflo exhibits better corrosion inhibition in ocean water than Novolac. Further, the use of Twin-T oscillator based detection circuit resulted in enhanced sensitivity and better detection limit. Experiments performed using ocean water samples resulted in oscillator frequency shift of 410 Hertz/power supply unit (Hz/PSU). Oscillator frequency drift was reduced using frequency-to-voltage converters and sensitivity of 10 mV/PSU was achieved.
2013 IEEE International Electron Devices Meeting, 2013
ABSTRACT A highly sensitive label-free complementary-metal-oxide-semiconductor (CMOS) based high ... more ABSTRACT A highly sensitive label-free complementary-metal-oxide-semiconductor (CMOS) based high density micro-array for electrochemical detection and enumeration of breast tumor cell (MCF-7) is presented. The electrochemical impedance spectroscopy (EIS) based detection platform exhibited detection at single cell resolution (22 μm) and enumeration with mapping accuracy of ~80%. Maximum tumor-cell impedance increase of 28% was recorded.
We present a high-throughput label-free electrical-impedance spectroscopy (EIS) platform composed... more We present a high-throughput label-free electrical-impedance spectroscopy (EIS) platform composed of a 96×96 microelectrode array for counting and analysis of breast tumor cells (MCF-7). These Au-electrodes are densely packed within a 3.5 mm × 3.5 mm interrogation region. Each Au-electrode has an edge-length of 25 m designed to detect single tumor cell by electrical impedance spectroscopy. The detected signal is read out via an integrated circuit (IC) of addressable electrode-selection-switch array manufactured with 0.18 m CMOS technology.
A high-density electrical-impedance spectroscopy (EIS) biosensor array has been developed for hig... more A high-density electrical-impedance spectroscopy (EIS) biosensor array has been developed for highthroughput and automated counting of specific breast tumor MCF-7 cells. The biosensor array (96 × 96) consists of densely packed electrodes. Each of the square electrodes has an edge-length of 22 m to capture single MCF-7 cell. The electrodes are electrically addressable by decoding circuit built underneath by 0.18 m CMOS process. EIS spectra of electrodes were recorded over a wide frequency range with and without the presence of cell. Data were numerically fitted with the equivalent circuit model to extract important sensing parameters including cell impedance, electrode impedance, sealing resistance and spreading resistance. Results revealed a distinctive impedance increase from 50 kHz to 500 kHz, where the maximum (∼21% increment) occurs at 200 kHz. Enumeration of circulating tumor cells (CTCs) was performed by scanning an interrogation area of hundred electrodes at the optimum frequency. The developed EIS platform has demonstrated the electrical impedance detection with single cell resolution and enumeration with mapping accuracy of ∼90%.
... Taylor & Francis Group JasriI1,a, LY Moor', NH Lajis', ... more ... Taylor & Francis Group JasriI1,a, LY Moor', NH Lajis', AM Ali", MA Sukari', AA Rahman", AG Othman', H. Kikuzaki' and N. Nakatani' ... A decoction of the roots of H longicornutum Baker is used as a vermifuge and to treat earaches (Burkill, 1966; Perry, 1980). Previous studies onH. ...
Treatment of primary aliphatic amines with KOH in diethylene glycol at 210°C gives primary alcoho... more Treatment of primary aliphatic amines with KOH in diethylene glycol at 210°C gives primary alcohols directly in good yields. A synthetic application to a model study of (±)-scopadulin is also described.
Due to instability of pyrimidine motif triplex DNA at physiological pH, triplex stabilization at ... more Due to instability of pyrimidine motif triplex DNA at physiological pH, triplex stabilization at physiological pH is crucial in improving its potential in various triplex formation-based strategies in vivo, such as regulation of gene expression, mapping of genomic DNA, and gene-targeted mutagenesis. To this end, we investigated the effect of our previously reported chemical modification, 2'-O,4'-C-aminomethylene bridged nucleic acid (2',4'- BNA(NC)) modification, introduced into interrupted and continuous positions of triplex-forming oligonucleotide (TFO) on pyrimidine motif triplex formation at physiological pH. The interrupted 2',4'-BNA(NC) modifications of TFO increased the binding constant of the triplex formation at physiological pH by more than 10-fold, and significantly increased the nuclease resistance of TFO. On the other hand, the continuous 2',4'-BNA(NC) modification of TFO showed lower ability to promote the triplex formation at physiological pH than the interrupted 2',4'-BNA(NC) modifications of TFO, and did not significantly change the nuclease resistance of TFO. Selection of the interruptedly 2',4'-BNA(NC)-modified positions in TFO was more favorable for achieving the higher binding affinity of the pyrimidine motif triplex formation at physiological pH and the higher nuclease resistance of TFO than that of the continuously 2',4'-BNA(NC)-modified positions in TFO. We conclude that the interrupted 2',4'-BNA(NC) modification of TFO could be a key chemical modification to enhance pyrimidine motif triplex-forming ability and nuclease resistance under physiological condition, and may eventually lead to progress in various triplex formation-based strategies in vivo.
In the present work, the effect of a surface modification protocol along with the electrode size ... more In the present work, the effect of a surface modification protocol along with the electrode size has been investigated for developing an efficient, label-free electrochemical biosensing method for diagnosis of traumatic brain injury (TBI) biomarkers. A microdisk electrode array (MDEA) and a macroelectrode with a comb structure (MECS) were modified with an anti-GFAP (GFAP = glial fibrillary acidic protein) antibody using two protocols for optimum and label-free detection of GFAP, a promising acute-phase TBI biomarker. For the MDEA, an array of six microdisks with a 100 μm diameter and, for the MECS, a 3.2 mm × 5.5 mm electrode 5 μm wide with 10 μm spaced comb fingers were modified using an optimized protocol for dithiobis(succinimidyl propionate) (DSP) self-assembled monolayer formation. Anti-GFAP was covalently bound, and the remaining free DSP groups were blocked using ethanolamine (Ea). Sensors were exposed to solutions with different GFAP concentrations, and a label-free electrochemical impedance spectroscopy (EIS) technique was used to determine the concentration. EIS results confirmed that both types of Ea/anti-GFAP/DSP/Au electrodes modified with an optimized DSPbased protocol can accurately detect GFAP in the range of 1 pg mL −1 to 100 ng mL −1 with a detection limit of 1 pg mL −1 . However, the cross-use of the MDEA protocol on the MECS and vice versa resulted in very low sensitivity or poor signal resolution, underscoring the importance of proper matching of the electrode size and type and the surface modification protocol.
Gold micro-electrodes with various diameters (25, 50, 75, 100 and 250 mm) were manufactured using... more Gold micro-electrodes with various diameters (25, 50, 75, 100 and 250 mm) were manufactured using standard micro-fabrication techniques and optimized for counting of MCF-7 cells (breast tumor cells) with single cell resolution. For specific cell capture, anti-EpCAM was immobilized on 11mercaptoundecanoic acid (11-MUA)-3-mercaptopropionic acid (3-MPA) mixed self-assembled monolayer (SAM) modified gold surface of micro-electrodes. Electrodes were characterized using optical, cyclic voltammetry and electrochemical impedance spectroscopic (EIS) techniques. Cell capture response recorded using EIS suggested that optimum electrode dimensions should be analogous to desired cell size. For MCF-7 cells with an average diameter of 18 ¡ 2 mm, an electrode with 25 mm diameter was established as the optimum electrode size for precise single cell recognition and enumeration. In EIS investigation, the 25 mm electrode exhibited an impedance change of y2.2 6 10 7 V in response to a single tumor cell captured on its surface. On the other hand other electrodes (250, 100, 75 and 50 mm) showed much less response for a single tumor cell. In future, the use of high density arrays of such electrodes with surface modifications will result in miniaturized lab on a chip devices for precise counting of MCF-7 cells with single cell resolution.
A total synthesis of (()-stemodinone, a tetracyclic stemodane diterpene, from the known tricyclic... more A total synthesis of (()-stemodinone, a tetracyclic stemodane diterpene, from the known tricyclic methyl olefin 11 is described. The key steps involve an efficient ring-exchange reaction and palladium(0)-catalyzed lactone migration. The ring-exchange strategy for controlling the stereochemistry was based on an initial Diels-Alder reaction to form a new ring followed by cleavage of the original ring. Cleavage of the original ring of the Diels-Alder adduct 9 was achieved by an initial regio-and chemoselective Baeyer-Villiger oxidation followed by the Pd(0)-catalyzed lactonemigration reaction reported by us. 10.
Oligonucleotides modified with 2 &amp... more Oligonucleotides modified with 2 ',4 '-BNA(NC) (N-H)/(N-Me) monomers exhibited excellent hybridizing and nuclease resistance properties. Duplex and triplex thermal stabilities were greatly enhanced by incorporating 2',4'-BNA(NC) (N-H) and (N-Me) monomers and nuclease resistance was tremendously higher than that of natural oligonucleotide.
We examined the effect of 2'-O,4'-C-aminomethylene bridged nucleic acid (2',4'-BN... more We examined the effect of 2'-O,4'-C-aminomethylene bridged nucleic acid (2',4'-BNA(NC)) backbone modification of triplex-forming oligonucleotide (TFO) on the pyrimidine motif triplex formation at neutral pH, a condition where pyrimidine motif triplexes are unstable. The melting temperature of the pyrimidine motif triplex at pH 6.8 with 2',4'-BNA(NC) modified TFO was significantly higher than that observed with unmodified TFO. The 2',4'-BNA(NC) modification of TFO increased the thermal stability of the pyrimidine motif triplex at neutral pH. The present results certainly support the idea that the 2',4'-BNA(NC) backbone modification of TFO could be a key chemical modification and may eventually lead to progress in therapeutic applications of the antigene strategy in vivo.
We examined the effect of 3'-amino-2'-O,4'-C-methylene bridged nucleic acid (3'-a... more We examined the effect of 3'-amino-2'-O,4'-C-methylene bridged nucleic acid (3'-amino-2',4'-BNA) backbone modification of triplex-forming oligonucleotide (TFO) on the pyrimidine motif triplex formation at neutral pH, a condition where pyrimidine motif triplexes are unstable. The melting temperature of the pyrimidine motif triplex at pH 6.8 with 3'-amino-2',4'-BNA modified TFO was significantly higher than that observed with unmodified TFO. The 3'-amino-2',4'-BNA modification of TFO increased the thermal stability of the pyrimidine motif triplex at neutral pH. The present results certainly support the idea that the 3'-amino-2',4'-BNA modification of TFO could be a key chemical modification and may eventually lead to progress in therapeutic applications of the antigene strategy in vivo.
ABSTRACT Perovskites have gained attraction as electrode and interconnect materials for Solid Oxi... more ABSTRACT Perovskites have gained attraction as electrode and interconnect materials for Solid Oxide Fuel Cells (SOFCs) due to their catalytic, ionic and electrical conductivities, chemical and thermal stabilities at higher temperatures. The operation and efficiency of SOFC depends mainly on the electrodes. Each electrode, anode and cathode, has demanding materials selection criteria. State of the art nickel-yittria stabilized zirconia cermet anodes are unable to work efficiently with hydrocarbon fuels and at intermediate operating temperature range (600-800 degrees C). Hence, there is an increasing demand for the development of alternate anode materials to improve the fuel flexibility and efficiency of SOFCs. Perovskite based materials have oxygen ion vacancies depending on composition, temperature, and surrounding crystalline environment that impart mixed ionic and electronic conductivities to them. Since perovskite can accommodate all the elements in the periodic table they can offer excellent catalytic properties. The report is about the present status of perovskites based anode materials for SOFC application.
... Murtadhahadi 2,d and Mohd Nizam Ab. Rahman 2,e ... 21 (2001), p. 2843-2853 [6] KR Jamaludin, ... more ... Murtadhahadi 2,d and Mohd Nizam Ab. Rahman 2,e ... 21 (2001), p. 2843-2853 [6] KR Jamaludin, N. Muhamad, SYM Amin, MNA Rahman and Murtadhahadi: International Journal of Mechanical and Materials Engineering Vol. 3 No. ...
Journal of Education and Learning (EduLearn), 2012
... Kuala Lumpur: Utusan Publication and Distribution Sdn. Bhd. Purwanto, M. Ngalim. 1998. ... O... more ... Kuala Lumpur: Utusan Publication and Distribution Sdn. Bhd. Purwanto, M. Ngalim. 1998. ... Organizational Learning: the Key to Management Innovation. Spring: Sloan Management Review. Rivai, Veithzal, & Mulyadi, Dedy.2009. Leadership and Organizational Behavior. ...
2013 IEEE Asian Solid-State Circuits Conference (A-SSCC), 2013
ABSTRACT A fully integrated SoC for multimodality intracranial neuromonitoring is presented. This... more ABSTRACT A fully integrated SoC for multimodality intracranial neuromonitoring is presented. This SoC includes a capacitive MEMS pressure sensor, an electrochemical oxygen sensor, a solid-state temperature sensor and sensor interface circuits in a single chip. Chopper stabilization and dynamic element matching techniques are applied in sensor interface circuits to reduce circuit noise and offset. On-chip calibration is implemented for each sensor to compensate process variations. Measured accuracies of the pressure, oxygen, and temperature sensors are ±1 mmHg, ±1 mmHg, and ±0.2 oC, respectively. Implemented in 0.18-μm CMOS, the SoC occupies an area of 1.4 mm × 4mm and consumes 188-μW DC power.
This paper presents the development of a Twin-T oscillator comprising polymer coated parallel pla... more This paper presents the development of a Twin-T oscillator comprising polymer coated parallel plates as a sensor for ocean water salinity monitoring. This sensor employs a parallel plate capacitor design, with sea water serving as the medium between plates. Novalac resin and a proprietary commercial polymer (Accuflo™) were investigated as corrosion protective coatings for the copper electrodes of the capacitor. Electrochemical Impedance Spectroscopy (EIS) was employed to evaluate corrosion inhibition of polymer coating in sea water. A detection circuit was designed and simulated using P-spice and then implemented in Printed Circuit Board (PCB). EIS results indicate that Accuflo exhibits better corrosion inhibition in ocean water than Novolac. Further, the use of Twin-T oscillator based detection circuit resulted in enhanced sensitivity and better detection limit. Experiments performed using ocean water samples resulted in oscillator frequency shift of 410 Hertz/power supply unit (Hz/PSU). Oscillator frequency drift was reduced using frequency-to-voltage converters and sensitivity of 10 mV/PSU was achieved.
2013 IEEE International Electron Devices Meeting, 2013
ABSTRACT A highly sensitive label-free complementary-metal-oxide-semiconductor (CMOS) based high ... more ABSTRACT A highly sensitive label-free complementary-metal-oxide-semiconductor (CMOS) based high density micro-array for electrochemical detection and enumeration of breast tumor cell (MCF-7) is presented. The electrochemical impedance spectroscopy (EIS) based detection platform exhibited detection at single cell resolution (22 μm) and enumeration with mapping accuracy of ~80%. Maximum tumor-cell impedance increase of 28% was recorded.
We present a high-throughput label-free electrical-impedance spectroscopy (EIS) platform composed... more We present a high-throughput label-free electrical-impedance spectroscopy (EIS) platform composed of a 96×96 microelectrode array for counting and analysis of breast tumor cells (MCF-7). These Au-electrodes are densely packed within a 3.5 mm × 3.5 mm interrogation region. Each Au-electrode has an edge-length of 25 m designed to detect single tumor cell by electrical impedance spectroscopy. The detected signal is read out via an integrated circuit (IC) of addressable electrode-selection-switch array manufactured with 0.18 m CMOS technology.
A high-density electrical-impedance spectroscopy (EIS) biosensor array has been developed for hig... more A high-density electrical-impedance spectroscopy (EIS) biosensor array has been developed for highthroughput and automated counting of specific breast tumor MCF-7 cells. The biosensor array (96 × 96) consists of densely packed electrodes. Each of the square electrodes has an edge-length of 22 m to capture single MCF-7 cell. The electrodes are electrically addressable by decoding circuit built underneath by 0.18 m CMOS process. EIS spectra of electrodes were recorded over a wide frequency range with and without the presence of cell. Data were numerically fitted with the equivalent circuit model to extract important sensing parameters including cell impedance, electrode impedance, sealing resistance and spreading resistance. Results revealed a distinctive impedance increase from 50 kHz to 500 kHz, where the maximum (∼21% increment) occurs at 200 kHz. Enumeration of circulating tumor cells (CTCs) was performed by scanning an interrogation area of hundred electrodes at the optimum frequency. The developed EIS platform has demonstrated the electrical impedance detection with single cell resolution and enumeration with mapping accuracy of ∼90%.
... Taylor & Francis Group JasriI1,a, LY Moor', NH Lajis', ... more ... Taylor & Francis Group JasriI1,a, LY Moor', NH Lajis', AM Ali", MA Sukari', AA Rahman", AG Othman', H. Kikuzaki' and N. Nakatani' ... A decoction of the roots of H longicornutum Baker is used as a vermifuge and to treat earaches (Burkill, 1966; Perry, 1980). Previous studies onH. ...
Treatment of primary aliphatic amines with KOH in diethylene glycol at 210°C gives primary alcoho... more Treatment of primary aliphatic amines with KOH in diethylene glycol at 210°C gives primary alcohols directly in good yields. A synthetic application to a model study of (±)-scopadulin is also described.
Due to instability of pyrimidine motif triplex DNA at physiological pH, triplex stabilization at ... more Due to instability of pyrimidine motif triplex DNA at physiological pH, triplex stabilization at physiological pH is crucial in improving its potential in various triplex formation-based strategies in vivo, such as regulation of gene expression, mapping of genomic DNA, and gene-targeted mutagenesis. To this end, we investigated the effect of our previously reported chemical modification, 2'-O,4'-C-aminomethylene bridged nucleic acid (2',4'- BNA(NC)) modification, introduced into interrupted and continuous positions of triplex-forming oligonucleotide (TFO) on pyrimidine motif triplex formation at physiological pH. The interrupted 2',4'-BNA(NC) modifications of TFO increased the binding constant of the triplex formation at physiological pH by more than 10-fold, and significantly increased the nuclease resistance of TFO. On the other hand, the continuous 2',4'-BNA(NC) modification of TFO showed lower ability to promote the triplex formation at physiological pH than the interrupted 2',4'-BNA(NC) modifications of TFO, and did not significantly change the nuclease resistance of TFO. Selection of the interruptedly 2',4'-BNA(NC)-modified positions in TFO was more favorable for achieving the higher binding affinity of the pyrimidine motif triplex formation at physiological pH and the higher nuclease resistance of TFO than that of the continuously 2',4'-BNA(NC)-modified positions in TFO. We conclude that the interrupted 2',4'-BNA(NC) modification of TFO could be a key chemical modification to enhance pyrimidine motif triplex-forming ability and nuclease resistance under physiological condition, and may eventually lead to progress in various triplex formation-based strategies in vivo.
In the present work, the effect of a surface modification protocol along with the electrode size ... more In the present work, the effect of a surface modification protocol along with the electrode size has been investigated for developing an efficient, label-free electrochemical biosensing method for diagnosis of traumatic brain injury (TBI) biomarkers. A microdisk electrode array (MDEA) and a macroelectrode with a comb structure (MECS) were modified with an anti-GFAP (GFAP = glial fibrillary acidic protein) antibody using two protocols for optimum and label-free detection of GFAP, a promising acute-phase TBI biomarker. For the MDEA, an array of six microdisks with a 100 μm diameter and, for the MECS, a 3.2 mm × 5.5 mm electrode 5 μm wide with 10 μm spaced comb fingers were modified using an optimized protocol for dithiobis(succinimidyl propionate) (DSP) self-assembled monolayer formation. Anti-GFAP was covalently bound, and the remaining free DSP groups were blocked using ethanolamine (Ea). Sensors were exposed to solutions with different GFAP concentrations, and a label-free electrochemical impedance spectroscopy (EIS) technique was used to determine the concentration. EIS results confirmed that both types of Ea/anti-GFAP/DSP/Au electrodes modified with an optimized DSPbased protocol can accurately detect GFAP in the range of 1 pg mL −1 to 100 ng mL −1 with a detection limit of 1 pg mL −1 . However, the cross-use of the MDEA protocol on the MECS and vice versa resulted in very low sensitivity or poor signal resolution, underscoring the importance of proper matching of the electrode size and type and the surface modification protocol.
Gold micro-electrodes with various diameters (25, 50, 75, 100 and 250 mm) were manufactured using... more Gold micro-electrodes with various diameters (25, 50, 75, 100 and 250 mm) were manufactured using standard micro-fabrication techniques and optimized for counting of MCF-7 cells (breast tumor cells) with single cell resolution. For specific cell capture, anti-EpCAM was immobilized on 11mercaptoundecanoic acid (11-MUA)-3-mercaptopropionic acid (3-MPA) mixed self-assembled monolayer (SAM) modified gold surface of micro-electrodes. Electrodes were characterized using optical, cyclic voltammetry and electrochemical impedance spectroscopic (EIS) techniques. Cell capture response recorded using EIS suggested that optimum electrode dimensions should be analogous to desired cell size. For MCF-7 cells with an average diameter of 18 ¡ 2 mm, an electrode with 25 mm diameter was established as the optimum electrode size for precise single cell recognition and enumeration. In EIS investigation, the 25 mm electrode exhibited an impedance change of y2.2 6 10 7 V in response to a single tumor cell captured on its surface. On the other hand other electrodes (250, 100, 75 and 50 mm) showed much less response for a single tumor cell. In future, the use of high density arrays of such electrodes with surface modifications will result in miniaturized lab on a chip devices for precise counting of MCF-7 cells with single cell resolution.
Uploads
Papers by Abdur Rahman