Hao Fan

A new electrochemical biosensor for DNA detection based on molecular recognition and lead sulfide nanoparticles

In this paper, we constructed a new electrochemical biosensor for DNA detection based on a molecule recognition technique. In this sensing protocol, a novel dual-labeled DNA probe (DLP) in a stem-loop structure was employed, which was designed with dabcyl labeled at the 3 end as a guest molecule, and with a Pb nanoparticle labeled at the 5 end as electrochemical tag to indicate hybridization. One α-cyclodextrin-modified electrode (α-CD/MCNT/GCE) was used for capturing the DNA hybridization. Initially, the DLP was in the closed state in the absence of the target, which shielded dabcyl from the bulky α-CD/MCNT/GCE conjugate due to a steric effect. After hybridization, the loop sequence (16 bases) formed a rigid duplex with the target, breaking the relatively shorter stem duplex (6 bases). Consequently, dabcyl was forced away from the Pb nanoparticle and became accessible by the electrode. Therefore, the target hybridization event can be sensitively transduced via detecting the electrochemical reduction current signal of Pb. Using this method, as low as 7.1×10(-10)M DNA target had been detected with excellent differentiation ability for even a single mismatch.

A New Electrochemical Aptasensor for Protein Detection Based on Target Protein-Induced Strand Displacement

A sensitive electrochemical aptasensor for detection of thrombin based on target protein-induced strand displacement is presented. For this proposed aptasensor, dsDNA which is from immobilized probe DNA (IP) which has a hybridized with aptamer(Apt) initially was immobilized on the Au electrode through thiol group of IP，while a DNA labeled with PdS nanoparticles was used as a detection probe (DP-PdS). When Au electrode immersed into solution which contain target protein and DP-PdS, the aptamer preferred to form G-quarter structure with the present target protein and dsDNA was released into immobilized probe DNA (IP) which could be hybridized with DP-PdS. After dissolving PdS from electrode, a mercury-film electrode was used for electrochemical detection of these Pd2+ ions which offered excellent electrochemical signal transduction. Detection of thrombin was specific without being affected by the coexistence of other proteins such as BSA and lysozyme, and as low as 2.3×10-11 mol/L of thrombin was detected.

A ZnS-Nanoparticle-Label-Based Electrochemical Codeine Sensor

Codeine (3-methylmorphine) is an opiate that is widely used to treat mild or moderate pain and cough suppression. It is the second predominant alkaloid in opium with a mild sedative effect. In the present study, we describe an electrochemical sensor for codeine detection by using the DNA aptamers against codeine. In the sensing protocol, a dually-labeled DNA aptamer probe was designed to be labeled at one end with HS, and at its another end with dabcyl as an electrochemical tag to produce electrochemical signal via recognization occurrence. One special electrochemical marker was prepared by modifying ZnS nanoparticle with-cyclodextrins (ab. ZnS-CDs), which employed as electrochemical signal provider and would conjunct with the codeine probe modified electrode through the host–guest recognition of CDs to dabcyl. With codeine adding, aptamer folding allows the ZnS-CDs into soultion that caused an increase of current signal. This sensor has the ability to detect 37pM codeine. Our study demonstrates that the biosensor has good specificity and stability. It can be used to detect codeine.

Synthesis, Crystal Structure and Electrochemical Property of New Ferrocenyl Schiffbase

s: A novel Schiff-base compound based on ferrocene I has been synthesized and characterized by X-ray diffraction. Electrochemical measurements exhibit that this new ferrocenyl schiffbase undergoes a reversible one-electron redox process.

A New Electrochemical Sensor for DNA Detection Based on Au Nanoparticles Surface-Modified with β-Cyclodextrins

We herein constructed a sensor that converts target DNA hybridization-induced conformational transformation of the probe DNA to electrochemical response based on host-guest recognition and nanoparticle label. In the sensor, the hairpin DNA terminal-labeled with 4-((4-(dimethylamino)phenyl)azo)benzoic acid (dabcyl) and NH2 group was immobilized on multi-walled carbon nanotube modified glassy carbon electrode (MCNTs/GCE) surface, and the Au nanoparticles surface-modified with b-cyclodextrins (CD-AuNPs) were employed as electrochemical signal provider and host-guest recognition element. Initially, the probe DNA immobilized on electrode kept the stem-loop configuration, which shielded dabcyl from docking with the CD-AuNPs in solution due to the steric effect. After target hybridization, the probe DNA underwent a significant conformational change, which forced dabcyl away from the electrode. As a result, formerly-shielded dabcyl became accessible to host-guest recognition between b-cyclodextrin (b-CD) and dabcyl, thus the target hybridization event could be sensitively transduced to electrochemical signal provided by CD-AuNPs. This host-guest recognition-based electrochemical sensor has been able to detect as low as picomolar DNA target with excellent differentiation ability for even single mismatch.

An Electrochemical Sensor for DNA Detection Based Metal Nanoparticle Modified with Cyclodextrins

We herein constructed a sensor that converts target DNA hybridization-induced conformational transformation of the probe DNA to electrochemical response based on host-guest recognition and nanoparticle label. In the sensor, the hairpin DNA terminal-labeled with 4-((4-(dimethylamino) phenyl) azo) benzoic acid (dabcyl) and thiol group was immobilized on Au electrode surface as the probe DNA by Au-S bond, and the PdS nanoparticles surface-modified with β-cyclodextrins (PdS-CDs) were employed as electrochemical signal provider and host-guest recognition element. Initially, the probe DNA immobilized on electrode kept the stem-loop configuration, which shielded dabcyl from docking with the PdS-CDs in solution due to the steric effect. After target hybridization, the probe DNA underwent a significant conformational change, which forced dabcyl away from the electrode. As a result, formerly shielded dabcyl became accessible to host-guest recognition between β-cyclodextrin and dabcyl, thus the target hybridization event could be sensitively transduced to electrochemical signal provided by PdS-CDs. This host guest recognition-based electrochemical sensor has been able to detect as low as picomolar DNA target with excellent differentiation ability for even single mismatch

A New Electrochemical Host-Guest Recognition Sensor for DNA Detection

This communication reports on a new electrochemical method to detect the hybridization specificity in homogenous solution by using host-guest recognition technique. A hairpin DNA with a dabcyl molecule which is typical guest molecule to b-CD at the 3’-terminus and a NH2 linked at the 5’-terminus as the probe DNA. The probe DNA was immobilized on the PdS nanoparticle to construct a double-labeled probe (DLP) and could selectively hybridize with its target DNA in homogenous solution. A b-CD modified Poly(N-acetylaniline) glassy carbon electrode was used for capturing dabcyl in DLP. Without binding with target DNA, the DLP keep stem-loop structure and block dabcyl enter into the cavity of b-CD on electrode. However, a target-binding DLP is incorporated into double stranded DNA, causing loop-stem structure opened and dabcyl could be easy captured by b-CD which brought DLP on electrode surface. With electrochemical measurement, the signal come from Pd2+ be used for target DNA quantitative analysis.

Double Aza-Michael Addition of Thiols to Dienones Catalyzed by L-Proline

In the presence of L-proline, an efficient and direct double aza-Michael addition of thiols with dienones has been realized, affording functionalized sulfur-containing products in excellent yields (94%-97%).

Amino Acid Catalyzed Conjugate Addition of Thiol to Dienone

Double conjugate addition of thiols with dienones was catalyzed by amino acids at room temperature in methanol, to afford the corresponding addition product in good to excellent yields.

Synthesis and Characterization of Binuclear Ruthenium Vinyl Complexes with Dithienylethene Unit

A novel binuclear ruthenium vinyl complexes with dithienylethene unit II [RuCl (CO)(PMe3)3]2(μ-CH=CH-DTE-CH=CH) has been synthesized and characterized by elemental analysis and NMR spectra. Meanwhile, the crystal of II was obtained and determined by X-ray single-crystal diffraction.