Surface passivation improves the synthesis of highly stable and specific DNA-functionalized gold nanoparticles with variable DNA density.

We report a novel and multifaceted approach for the quick synthesis of highly stable single-stranded DNA (ssDNA) functionalized gold nanoparticles (AuNPs). The method is based on the combined effect of surface passivation by (1-mercaptoundec-11-yl)hexa(ethylene glycol) and low pH conditions, does not require any salt pretreatment or high excess of ssDNA, and can be generalized for oligonucleotides of any length or base sequence. The synthesized ssDNA-coated AuNPs conjugates are stable at salt concentrations as high as 3.

Development of stable and reproducible biosensors based on electrochemical impedance spectroscopy: three-electrode versus two-electrode setup.

This work focuses on the development of electrochemical impedance biosensors based on capacitance readout, for the detection of biomolecules in small sample volumes. We performed electrochemical impedance spectroscopy (EIS) measurements of DNA hybridization in electrochemical cells with microfabricated gold electrodes. The time stability of the device was tested in two different configurations: two microelectrodes in a microfluidic channel; two microelectrodes plus a reference electrode in an electrochemical cell.

Universality of protein reentrant condensation in solution induced by multivalent metal ions.

The effective interactions and phase behavior of protein solutions under strong electrostatic coupling conditions are difficult to understand due to the complex charge pattern and irregular geometry of protein surfaces. This distinguishes them from related systems such as DNA or conventional colloids. In this work, we discuss the question of universality of the reentrant condensation (RC) of proteins in solution induced by multivalent counterions, i.

Protein-protein interactions in ovalbumin solutions studied by small-angle scattering: effect of ionic strength and the chemical nature of cations.

The influence of ionic strength and of the chemical nature of cations on the protein-protein interactions in ovalbumin solution was studied using small-angle X-ray and neutron scattering (SAXS/SANS). The globular protein ovalbumin is found in dimeric form in solutions as suggested by SANS/SAXS experiments. Due to the negative charge of the proteins at neutral pH, the protein-protein interactions without any salt addition are dominated by electrostatic repulsion.