Highly Sensitive in vitro Biosensor for Enterotoxigenic Escherichia coli Detection Based on ssDNA Anchored on PtNPs‐Chitosan Nanocomposite

Detection of Enterotoxigenic Escherichia coli in various biological samples has tremendous importance in human health. In this direction, we have designed a label free electrochemical biosensor for highly selective detection of Escherichia coli through detecting ST gene. The ability of sensor probe to detect ST_G was confirmed using polymerase chain reaction. The biosensor was fabricated based on ST_G specific probes immobilized on platinum nanoparticles chitosan nanocomposite on screen printed carbon electrode, which was characterized by cyclic voltammetry, transmission electron microscopy, and fourier transform infrared spectroscopy. A highly sensitive label free sensing was achieved by analyzing ST_G hybridization using electrochemical impedance spectroscopy (EIS) technique. The EIS analysis showed a significant increase in charge transfer resistance after ST_G interaction with the highly selective ssDNA probe immobilized on the nanocomposite film. The increase in charge transfer resistance was evaluated for varying concentrations of ST_G, which shows a dynamic range between 1.0×10⁻¹² and 1.0×10⁻⁴ with the detection limit of 3.6×10⁻¹⁴ M (RSD<4.5 %). The regeneration of sensor probe was also studied and interference due to non‐target sequences was evaluated to ensure the selectivity of the designed sensor. The practical applicability of sensor probe was also analyzed by detecting the ST_G from the bacteria present in surface water.     

Counting of Escherichia coli by a microflow cytometer based on a photonic–microfluidic integrated device

Counting of Escherichia coli DH5α‐cell suspensions in PBS is performed using a microflow cytometer based on a photonic–microfluidic integrated device. Side‐scattered light signals are used to count the E. coli cells. A detection efficiency of 92% is achieved when compared with the expected count from a hemocytometer. The detection efficiency is correlated to the ratio of sample to sheath flow rates. It is demonstrated that E. coli can be easily distinguished from beads of similar sizes (2–4 μm) as their scattering intensities are different.     

Recognition of Artificial Nucleobases by E. coli Purine Nucleoside Phosphorylase versus its Ser90Ala Mutant in the Synthesis of Base‐Modified Nucleosides

A wide range of natural purine analogues was used as probe to assess the mechanism of recognition by the wild‐type (WT) E. coli purine nucleoside phosphorylase (PNP) versus its Ser90Ala mutant. The results were analyzed from viewpoint of the role of the Ser90 residue and the structural features of the bases. It was found that the Ser90 residue of the PNP 1) plays an important role in the binding and activation of 8‐aza‐7‐deazapurines in the synthesis of their nucleosides, 2) participates in the binding of α‐D ‐pentofuranose‐1‐phosphates at the catalytic site of the PNP, and 3) catalyzes the dephosphorylation of intermediary formed 2‐deoxy‐α‐D ‐ribofuranose‐1‐phosphate in the trans‐2‐deoxyribosylation reaction. 5‐Aza‐7‐deazaguanine manifested excellent substrate activity for both enzymes, 8‐amino‐7‐thiaguanine and 2‐aminobenzothiazole showed no substrate activity for both enzymes. On the contrary, the 2‐amino derivatives of benzimidazole and benzoxazole are substrates and are converted into the N1‐ and unusual N2‐glycosides, respectively. 9‐Deaza‐5‐iodoxanthine showed moderate inhibitory activity of the WT E. coli PNP, whereas 9‐deazaxanthine and its 2′‐deoxyriboside are weak inhibitors.     

Nano-ZnO微叉指电极生物传感器检测大肠杆菌

设计了一种基于纳米ZnO材料检测大肠杆菌(E.coli O157:H7)的微叉指阻抗生物传感器,利用电化学方法在氧化铟锡(ITO)叉指电极表面沉积上纳米ZnO,然后将链霉亲和素固定在纳米ZnO表面,利用生物素亲和素的高亲和性原理将大肠杆菌抗体绑定在传感器表面,完成传感器的构建。实验表明,传感器检测E.coli O157:H7线性范围为40~4×10^6cfu/mL,检出限为40 cfu/mL,传感器的特异性、重现性、实用性较好。     

Synthesis of Ag/AgCl-mesoporous silica nanocomposites using a simple aqueous solution-based chemical method and a study of their antibacterial activity on E. coli

Simple aqueous solution-based chemical methods have been developed for the synthesis of Ag/AgCl nanoparticle-mesoporous silica nanocomposites. Ag loading in the mesoporous silica was accomplished using a wet-impregnation method. The AgCl-mesoporous silica nanocomposite material(AgCl-mSi) was synthesized by using a 'one pot' method. Synthesized materials were characterized using X-ray diffraction,N2 adsorption-desorption analysis and high-resolution transmission electron microscopy. Antibacterial activity of...     

微流控芯片上大肠杆菌的电化学阻抗检测方法研究

基于细菌悬浮液的阻抗特性和微流控芯片电化学阻抗检测技术,采用所构建的微流控芯片电化学阻抗分析系统,以大肠杆菌为样本,优化了扰动振幅、缓冲溶液电导率、扫描频率和新制大肠杆菌标本静置时间等参数,对大肠杆菌标本、大肠杆菌标准合成样本进行电化学阻抗检测,建立了一种大肠杆菌快速定量检测方法.在扰动振幅500 mV、缓冲溶液电导率...     

A Sensitive Nanoporous Gold-Based Electrochemical DNA Biosensor for Escherichia coli Detection

A sensitive electrochemical DNA biosensor based on a mixed monolayer structure self-assembled at nanoporous gold (NPG) electrode surface was prepared for Escherichia coli (E. coli) detection. The NPG was fabricated on gold electrode, onto which thiolated oligonucleotides (SH-DNA) and mercaptohexanol (MCH) were covalently linked forming a mixed self-assembled monolayer (SAM). The hybridization between the SH-DNA/MCH modified biosensor and E. coli DNA was monitored with differential pulse voltammetry measurement using methylene blue (MB) as the hybridization indicator. The biosensor can detect 1 × 10^?12 M DNA target and 50 cfu/μL E. coli without any nucleic acid amplification steps. The detection limit was lowered to 50 cfu/mL after 5.0 h of incubation.     

Piezoelectric Crystal Biosensor System for Detection of Escherichia Coli

Abstract

A piezoelectric crystal biosensor system was applied to the detection of Escherichia coli. the system consists of an oscillator, a frequency counter, a flow cell and a modified piezoelectric crystal. Anti-E. coli antibody is immobilized on the surface of the crystal. It is used as an E. coli detection by measuring its resonant frequency shift due to a mass change caused by specific binding of the micro organisms to the surface. the frequency shift correlates with an E. coli concentration in the range of 10⁶?10⁸ cells·cm^?3. the resonant frequency shift is increased by further treatment to bind micro-particles modified with anti-E. coli antibody. This method allows us to improve the determination limit to 10⁵ cells · cm^?3.     

亲水作用色谱/质谱联用方法用于大肠杆菌代谢组分析

建立了两性离子亲水作用色谱/质谱联用方法用于大肠杆菌胞内极性代谢物的分离分析。选取52个代表性极性物质对方法进行考察,发现此方法有较好的线性范围,且大部分物质最低检测限均在ng/mL数量级。平行制备6份样品进行分析,结果显示85%以上代谢物峰面积的RSD值小于30%。6个内标物质在低、中、高3个浓度下的日内精密度（RSD）均小于20%,大部分物质的相对回收率都在可接受的范围内（70%~130%）。把此方法用于yfcC基因改造的3株大肠杆菌代谢组分析,发现一些小肽、氨基酸、核苷、有机酸、磷脂等物质在基因改造后发生明显变化。此研究结果表明,建立的两性离子亲水作用色谱/质谱方法检测到的物质化学性质分布广,跨越了极性磷脂到小肽的各个范围,且具有良好的重复性、稳定性和适用性。