In this paper we report a label-free detection method of unmodified DNA using polypyrrole as an immobilization matrix by impedance measurement. A probe and a target complementary DNA sequence specific for the bacteria...In this paper we report a label-free detection method of unmodified DNA using polypyrrole as an immobilization matrix by impedance measurement. A probe and a target complementary DNA sequence specific for the bacterial pathogen, Bacillus cereus are used. Impedance measurements are performed without using additional redox probes. The effects of hybridization and non-specific binding are compared when the Probe DNA molecules were immobilized by two different methods: electrochemical adsorption and entrapment. The probe DNA immobilized using electrochemical adsorption yielded better hybridization signals compared to that immobilized using the entrapment method. Control experiments were also performed to prove the specificity of the biosensor in the presence of non complementary DNA. Negligible unspecific binding with the immobilized probe was observed with the electrochemically adsorbed probe, whereas the entrapped probe responded to the non complementary target. The performance of the DNA sensor was characterized using both cyclic voltammetry and impedance spectroscopy techniques and proved to be effective in terms of specificity of hybridization events.展开更多
Rheumatoid factors(RFs) are the characteristic autoantibodies of rheumatoid arthritis. Recent researches in our laboratory showed that the immobilized single-stranded DNA(ss-DNA) immunoadsorbent can selectively remove...Rheumatoid factors(RFs) are the characteristic autoantibodies of rheumatoid arthritis. Recent researches in our laboratory showed that the immobilized single-stranded DNA(ss-DNA) immunoadsorbent can selectively remove RFs from the serum of patients. In the present paper are studied the modification of argininine, tryptophan, lysine residues and carboxyl terminus of IgGRF, which was separated from patients′ serum, with 1,2-cyclohexanedione(CHD), N-bromosuccinimide(NBS), pyridoxal 5′-phosphate(PP) and 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide(EDC) respectively, and their effects on the adsorption capacity of the immobilized ss-DNA immunoadsorbent for IgGRF. After the specific modification, the corresponding adsorption capacities of the adsorbents were changed from 48%, 46%, 44% and 54% to 84%, 14%, 21% and 81%, respectively. These results indicate that the electrostatic or ionic-bonding is essential for the interaction between ss-DNA and IgGRF.展开更多
Carboxyl was formed on the surface of glassy carbon electrode(GCE) by electrochemical oxidation. Ethylenediamine(En) was used as the arm molecule to link carboxyl with dsDNA using 1-ethyl-3-(3-dimethylaminopropyl)-car...Carboxyl was formed on the surface of glassy carbon electrode(GCE) by electrochemical oxidation. Ethylenediamine(En) was used as the arm molecule to link carboxyl with dsDNA using 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride(EDC) and N-hydroxysuccinimide(NHS) as the activators to prepare dsDNA modified electrode(dsDNA/En/GCE). It was shown that dsDNA could be covalently immobilized on the surface of GCE. ssDNA modified electrode(ssDNA/En/GCE) was obtained via the thermal denaturation of dsDNA/En/GCE. The dsDNA/En/GCE and ssDNA/En/GCE were characterized by voltammetry with methylene blue(MB) as the indicator. The results indicated that the currents of the redox peaks of MB at ssDNA/En/GCE were larger than those at dsDNA/En/GCE, and the currents of the redox peaks at En/GCE were the smallest. The peak-currents of MB at the DNA modified electrode had good reproducibility after multi-denaturation and hybridization cycles.展开更多
DNA immobilization on electrode surfaces has been widely used for fabricating sensors since DNA can interact with a wide variety of biomolecules. Recendy, DNA has been demonstrated as an electronic super conductor... DNA immobilization on electrode surfaces has been widely used for fabricating sensors since DNA can interact with a wide variety of biomolecules. Recendy, DNA has been demonstrated as an electronic super conductor and become the most promising biomolecule for application of chemical sensing in biological system. Calf thymus DNA (ct-DNA) is a most popularly used native DNA in many applications. An electrochemical deposition on carbon fiber micro electrode can provide sensitive detection of dopamine in presence of large amount of ascorbic acid.……展开更多
文摘In this paper we report a label-free detection method of unmodified DNA using polypyrrole as an immobilization matrix by impedance measurement. A probe and a target complementary DNA sequence specific for the bacterial pathogen, Bacillus cereus are used. Impedance measurements are performed without using additional redox probes. The effects of hybridization and non-specific binding are compared when the Probe DNA molecules were immobilized by two different methods: electrochemical adsorption and entrapment. The probe DNA immobilized using electrochemical adsorption yielded better hybridization signals compared to that immobilized using the entrapment method. Control experiments were also performed to prove the specificity of the biosensor in the presence of non complementary DNA. Negligible unspecific binding with the immobilized probe was observed with the electrochemically adsorbed probe, whereas the entrapped probe responded to the non complementary target. The performance of the DNA sensor was characterized using both cyclic voltammetry and impedance spectroscopy techniques and proved to be effective in terms of specificity of hybridization events.
基金Key Projectof National Basic Science and Developm ent(No.G19990 6 4 70 7) and Tianjin- Nankai U niversi-ty Co- Construction Foundation and China- UK Collaboration Project
文摘Rheumatoid factors(RFs) are the characteristic autoantibodies of rheumatoid arthritis. Recent researches in our laboratory showed that the immobilized single-stranded DNA(ss-DNA) immunoadsorbent can selectively remove RFs from the serum of patients. In the present paper are studied the modification of argininine, tryptophan, lysine residues and carboxyl terminus of IgGRF, which was separated from patients′ serum, with 1,2-cyclohexanedione(CHD), N-bromosuccinimide(NBS), pyridoxal 5′-phosphate(PP) and 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide(EDC) respectively, and their effects on the adsorption capacity of the immobilized ss-DNA immunoadsorbent for IgGRF. After the specific modification, the corresponding adsorption capacities of the adsorbents were changed from 48%, 46%, 44% and 54% to 84%, 14%, 21% and 81%, respectively. These results indicate that the electrostatic or ionic-bonding is essential for the interaction between ss-DNA and IgGRF.
文摘Carboxyl was formed on the surface of glassy carbon electrode(GCE) by electrochemical oxidation. Ethylenediamine(En) was used as the arm molecule to link carboxyl with dsDNA using 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride(EDC) and N-hydroxysuccinimide(NHS) as the activators to prepare dsDNA modified electrode(dsDNA/En/GCE). It was shown that dsDNA could be covalently immobilized on the surface of GCE. ssDNA modified electrode(ssDNA/En/GCE) was obtained via the thermal denaturation of dsDNA/En/GCE. The dsDNA/En/GCE and ssDNA/En/GCE were characterized by voltammetry with methylene blue(MB) as the indicator. The results indicated that the currents of the redox peaks of MB at ssDNA/En/GCE were larger than those at dsDNA/En/GCE, and the currents of the redox peaks at En/GCE were the smallest. The peak-currents of MB at the DNA modified electrode had good reproducibility after multi-denaturation and hybridization cycles.
基金supported by National Natural Science Foundation of China(6091000260974112+4 种基金6097108530970969)the National High Technology Research and Development Program(863 Program) (2009AA012413)Ph.D.Programs Foundation of Ministry of Education of China(20070001020)Postdoctoral Science Foundation of China(No .20080440257)
文摘 DNA immobilization on electrode surfaces has been widely used for fabricating sensors since DNA can interact with a wide variety of biomolecules. Recendy, DNA has been demonstrated as an electronic super conductor and become the most promising biomolecule for application of chemical sensing in biological system. Calf thymus DNA (ct-DNA) is a most popularly used native DNA in many applications. An electrochemical deposition on carbon fiber micro electrode can provide sensitive detection of dopamine in presence of large amount of ascorbic acid.……
