Xia Hu

Background eliminated signal-on electrochemical aptasensing platform for highly sensitive detection of protein

Using platelet-derived growth factor B chain dimer (PDGF-BB) as the model target, a background current eliminated electrochemical aptameric sensing platform for highly sensitive and signal-on detection of protein is proposed in this paper. Successful fabrication of the biosensor depends on ingenious design of aptamer probe, which contains the aptamer sequence for PDGF-BB and the recognition sequence for EcoRI endonuclease. In the absence of PDGF-BB, the ferrocene labeled aptamer probe folds into a hairpin structure and forms a recognition site for EcoRI. By treatment with endonuclease, the specific and cleavable double-stranded region is cut off and redox-active ferrocene molecule is removed from the electrode surface, and almost no peak current is observed. When binding with target protein, the designed aptamer probe changes its conformation and dissociates the recognition double strand. The integrated aptamer probe is maintained when exposing to EcoRI endonuclease, resulting in obvious peak current. Therefore, a signal-on and sensitive sensing strategy for PDGF-BB detection is fabricated with eliminated background current. Under the optimized experimental conditions, a wide linear response range of 4 orders of magnitude from 20pgmL(-1) to 200ngmL(-1) is achieved with a detection limit of 10pgmL(-1). Moreover, the present aptameric platform is universal for the analysis of a broad range of target molecules of interest by changing and designing the sequence of aptamer probe.

DNA Interaction and Photocleavage Properties of Ru (II) Complexes [Ru(bpy)2(pibi)]2+ and [Ru(phen)2(pibi)]2+

A new asymmetry ligand pibi (pibi = 2-(pyridine-2-yl)-1-H-imidazo[4,5-f]benzo[d]imidazolone) and its ruthenium complexes with [Ru(L)2(pibi)]2+ (L = bpy (2, 2′-bipyridine), phen (1, 10-phenanthroline)), have been synthesized and characterized. The binding of two complexes with calf thymus DNA has been investigated by spectroscopic and viscosity measurement. The results indicate that both complexes can bind to CT-DNA through intercalative mode. Under irradiation at 365 nm, both complexes can partly promote the photocleavage of plasmid pBR322DNA. The low singlet oxygen generation abilities of the two complexes may be the factor for the low DNA photocleavage abilities.

Molecular Beacon-Based Fluorescent Biosensor for Sensitive Detection of Single Nucleotide Polymorphism

A sensitive fluorescent biosensing strategy based on structure-switching of molecular beacon for the detection of single nucleotide polymorphism is proposed in this study. In the absence of target DNA, only low background fluorescence can be detected since the formation of hairpin structure induces close proximity of fluorophore and quencher. On the contrary, the fluorescence intensity increases significantly after introduction of target DNA because structure-switching of molecular beacon results in separation of fluorophore and quencher. The change of fluorescence intensity is linear with concentration of target DNA, and a molecular beacon-based sensing system for fluorescent detection of single nucleotide polymorphism is fabricated. The target DNA can be sensitively detected in a linear dynamic range from 17.58nM-1.125μM with a low detection limit of 8 nM. Moreover, good reproducibility and high specificity are achieved.

Reusable Electrochemical Biosensor for Sensitive Detection of Single Nucleotide Polymorphisms Based on Gold Nanoparticle Self-Assembly

A reusable electrochemical biosensing strategy based on gold nanoparticle involved layer-by-layer self-assembly for sensitive detection of single nucleotide polymorphisms is proposed in this study. Making use of the strong sulfur-Au affinity, ethanthiol and capture probe modified gold nanoparticles are self-assembled onto the surface of gold electrode successively. The target DNA hybridizes with the capture probe and ferrocene labeled signaling probe successively via sandwich hybridization reaction. By measuring ac current voltammetry, the target DNA can be sensitively detected in a linear dynamic range from 4.1-410 nM with a low detection limit of 2 nM. Making use of self-assembled gold nanoparticles layer, a large amount of capture probes can be modified onto the gold electrode, supporting the high sensitivity of the proposed strategy. In addition, good reproducibility, high selectivity and stability are achieved. In particular, the biosensor can be easily regenerated by melting in hot water, making it reusable.

Electrochemical Aptasensor for Label-Free Detection of Protein Based on Gold Nanoparticle Involved Self-Assembly

A label-free electrochemical biosensing strategy based on gold nanoparticle involved layer-by-layer self assembly for the detection of protein is proposed using platelet derived growth factor-BB dimer (PDGF-BB) as the model analyte. Utilizing the strong sulfur-Au affinity, ethanthiol and capture probe modified gold nanoparticles are self-assembled onto the surface of gold electrode successively. The aptamer probe for target protein hybridizes with the capture probe and the biosensor is fabricated. By measuring ac current voltammetry, the target protein can be sensitively detected in a linear dynamic range from 1-1000 ng/mL with a low detection limit of 0.5 ng/mL. Making use of self-assembled gold nanoparticles layer, a large amount of capture probes can be modified onto the gold electrode, supporting the high sensitivity of the proposed strategy. In addition, good reproducibility, high selectivity and stability are achieved. In particular, the biosensor can be easily regenerated by melting in hot water, making it reusable.

Reusable Electrochemical Aptasensor for Sensitive Detection of Small Molecules Based on Structure-Switching Hairpin Probe

A reusable electrochemical biosensing strategy based on structure-switching hairpin probe for the detection of small molecules is proposed using cocaine as the model analyte. Aptamer probe hybridized with the immobilized signal probe to form DNA duplex. When target small molecule was added, competition between target molecule and the signal probe with the aptamer probe happened, which induced the signal probe from stretched duplex to hairpin structure. By measuring ac current voltammetry, the target molecule can be sensitively detected in a linear dynamic range from 1 nM-1000 nM with a low detection limit of 0.7 nM. In particular, the biosensor can be easily regenerated by melting in hot water, making it reusable.