Au nanowire-on-film SERRS sensor for ultrasensitive Hg2+ detection

We report an ultrasensitive and selective single nanowire-on-film (SNOF) surface-enhanced resonance Raman scattering (SERRS) sensor for Hg(2+) detection based on structure-switching double stranded DNAs (dsDNAs). Binding of Hg(2+) induces conformational changes of the dsDNAs and let a Raman reporter get close to the SNOF structure, thereby turning on SERRS signal. The well-defined SNOF structure provides a detection limit of 100 pM with improved accuracy in Hg(2+) detection. This sensor is stable over a considerable amount of time and reusable after simple treatment. Since this SNOF sensor is composed of a single Au NW on a film, development of a multiplex sensor would be possible by employing NWs modified by multiple kinds of aptamers.     

Development of a Novel Electrochemical Biosensor for Detection and Discrimination of DNA Sequence and Single Base Mutation in dsDNA Samples Based on PNA‐dsDNA Hybridization – a new Platform Technology

In spite of the extensive attention paid on the development of various DNA detection strategies, very few studies have been reported regarding direct detection of DNA sequence and mutation in dsDNA. Here, we describe the feasibility of detection and discrimination of target DNA sequences and single base mutations (SBM) directly in double‐stranded oligonucleotides and PCR products without the need for denaturation of the target dsDNA samples. This goal was achieved by employing a peptide nucleic acid (PNA) chain, self‐assembled on the gold electrode as a probe, which binds to dsDNA and forms PNA‐dsDNA hybrid.     

Stereoselective Interaction between DNA and Stable Chiral Surfaces Modified with 1,2‐Diphenylethylenediamine Enantiomers

This work described an interesting phenomenon of the stereoselective adsorption behaviors of DNA on stable chiral surfaces which were modified with 1,2‐diphenylethylenediamine enantiomers on gold electrodes. The modification process and electrochemical characterization of the chiral surfaces were measured by cyclic voltammetry (CV). The stereoselective adsorption behaviors of DNA on the two chiral surfaces were investigated via atomic force microscopy (AFM), CV, electrochemical impedance spectroscopy (EIS) and quartz crystal microbalance (QCM). All results confirmed that (1R,2R)‐1,2‐diphenylethylenediamine modified surface had stronger interaction with DNA molecules than (1S,2S)‐1,2‐diphenylethylenediamine modified surface, and the chirality of the surfaces created an different effect on the morphology and adsorption quantity of DNA.     

Structure–Function Relationships of New Lipids Designed for DNA Transfection

Cationic liposome/DNA complexes can be used as nonviral vectors for direct delivery of DNA‐based biopharmaceuticals to damaged cells and tissues. To obtain more effective and safer liposome‐based gene transfection systems, two cationic lipids with identical head groups but different chain structures are investigated with respect to their in vitro gene‐transfer activity, their cell‐damaging characteristics, and their physicochemical properties. The gene‐transfer activities of the two lipids are very different. Differential scanning calorimetry and synchrotron small‐ and wide‐angle X‐ray scattering give valuable structural insight. A subgel‐like structure with high packing density and high phase‐transition temperature from gel to liquid‐crystalline state are found for lipid 7 (N′‐2‐[(2,6‐diamino‐1‐oxohexyl)amino]ethyl‐2,N‐bis(hexadecyl)propanediamide) containing two saturated chains. Additionally, an ordered head‐group lattice based on formation of a hydrogen‐bond network is present. In contrast, lipid 8 (N′‐2‐[(2,6‐diamino‐1‐oxohexyl)amino]ethyl‐2‐hexadecyl‐N‐[(9Z)‐octadec‐9‐enyl]propanediamide) with one unsaturated and one saturated chain shows a lower phase‐transition temperature and a reduced packing density. These properties enhance incorporation of the helper lipid cholesterol needed for gene transfection. Both lipids, either pure or in mixtures with cholesterol, form lamellar phases, which are preserved after addition of DNA. However, the system separates into phases containing DNA and phases without DNA. On increasing the temperature, DNA is released and only a lipid phase without intercalated DNA strands is observed. The conversion temperatures are very different in the two systems studied. The important parameter seems to be the charge density of the lipid membranes, which is a result of different solubility of cholesterol in the two lipid membranes. Therefore, different binding affinities of the DNA to the lipid mixtures are achieved.     

Radiolysis of 5,10,15,20-tetrakis(N-methyl-4-pyridyl)-porphyrin or 5,10,15,20-tetrakis(4-sulfonatophenyl)-porphyrin in aqueous solution in the presence and in the absence of DNA or human serum albumin

The reduction of two free-base ionic porphyrins: 5,10,15,20-tetrakis(N-methyl-4-pyridyl)-porphyrin (TMPyP) and 5,10,15,20-tetrakis(4-sulfonatophenyl)-porphyrin (TSPP) by the hydrated electron was studied under neutral pH in aqueous solution in the absence and in the presence of biomolecules, DNA or HSA. Pulse radiolysis studies provided the spectra of the short-lived π-radical anions and steady-state radiolysis led to formation of stable phlorin or chlorin, the products of two-electron reduction and protonation at a meso and a pyrrolic nitrogen positions or at two β-pyrrole positions, respectively. Identification of the final reduction products was based on their reactivity to molecular oxygen—the phlorin, contrary to chlorine, was oxidized rapidly by O₂ to recover the original porphyrin. The stable product of TMPyP reduction was the phlorin, whereas for TSPP the chlorine and the phlorin were obtained. Addition of biomolecules to the solution resulted in changes of the porphyrins spectroscopic properties and in the decrease in rates of the occurring reduction processes proceeding with participation of the porphyrins.     

硅表面分子刷图案化及生长DNA纳米管

结合“自上而下”和“自下而上”技术构建微纳米器件是目前纳米科学和技术领域追逐的目标之一。本文首先采用硅氢化反应在硅表面共价偶联引发聚合的活性基团,接着实施表面原子转移自由基聚合（ATRP）反应形成高分子刷poly（PEGMA）,采用“自上而下”的光刻技术在硅表面制备功能化的图案,最后利用“自下而上”的DNA自组装技术在图案部分原位生长DNA纳米管。上述组装过程通过多次透射反射红外光谱、凝胶电泳、透射电镜和扫描电镜进行了检测,证实了硅芯片表面定位生长DNA纳米管的可行性。     

两个带呋喃悬臂不对称大环双核铜配合物的合成、结构及性质

合成并表征了2个不对称大环双核铜配合物[Cu₂（L¹）Cl₂]·CH₃CN（1）和[Cu₂（L²）Br₂]·CH₃CN·H₂O（2）。配合物与CT-DNA的作用通过紫外-可见光谱,粘度实验,圆二色谱和凝胶电泳实验进行了研究。紫外-可见光谱的结果表明配合物与DNA的结合常数分别为6.2×10⁵和7.2×10⁵,圆二色谱的实验表明配合物能与DNA较好的结合,粘度实验表明配合物与DNA的结合为非典型的插入模式,凝胶电泳实验显示配合物通过氧化机理对DNA有较强的切割活性。