Magnetic nanoparticle clusters as actuators of ssDNA release.

One of the major areas of research in nanomedicine is the design of drug delivery systems with remotely controllable release of the drug. Despite the enormous progress in the field, this aspect still poses a challenge, especially in terms of selectivity and possible harmful interactions with biological components other than the target. We report an innovative approach for the controlled release of DNA, based on clusters of core-shell magnetic nanoparticles. The primary nanoparticles are functionalized with a single-stranded oligonucleotide, whose pairing with a half-complementary strand in solution induces clusterization. The application of a low frequency (6 KHz) alternating magnetic field induces DNA melting with the release of the single strand that induces clusterization. The possibility of steering and localizing the magnetic nanoparticles, and magnetically actuating the DNA release discloses new perspectives in the field of nucleic-acid based therapy.

A rational approach in probe design for nucleic acid-based biosensing.

Development of nucleic acid-based sensing attracts the interest of many researchers in the field of both basic and applied research in chemistry. Major factors for the fabrication of a successful nucleic acid sensor include the design of probes for target sequence hybridization and their immobilization on the chip surface. Here we demonstrate that a rational choice of bioprobes has important impact on the sensor's analytical performances. Computational evaluations, by a simple and freely available program, successfully led to the design of the best probes for a given target, with direct application to nucleic acid-based sensing. We developed here an optimized and reproducible strategy for in silico probe design supported by optical transduction experiments. In particular Surface Plasmon Resonance imaging (SPRi), at the forefront of optical sensing, was used here as proof of principle. Five probes were selected, immobilized on gold chip surfaces by widely consolidated thiol chemistry and tested to validate the computational model. Using SPRi as the transducting component, real-time and label free analysis was performed, taking the Homo sapiens actin beta (ACTB) gene fragment as model system in nucleic acid detection. The experimental sensor behavior was further studied by evaluating the strength of the secondary structure of probes using melting experiments. Dedicated software was also used to evaluate probes' folding, to support our criteria. The SPRi experimental results fully validate the computational evaluations, revealing this approach highly promising as a useful tool to design biosensor probes with optimized performances.

Catalytic properties of serum albumin.

In this work it has been observed that human blood plasma is able to catalyse the reaction between tert.butyl hydroperoxide and 2-nitro-5-mercaptobenzoic acid. The purification of a proteic fraction responsible for this activity indicated it is due to plasma albumin; this is also demonstrated using various purified commercial albumins. We have determined the Vmax and the Km of the reaction and the effect of some substances of pharmacological or physiological importance on the same reaction. Some antiinflammatory non-steroidal drugs showed an inhibitory effect on the phenomenon, similar to that of endogenous substances such as fatty acids, bilirubin and arachidonic acid. The ability of other physiological substances such as cytochrome c, hemoglobin and hemin to catalyze the same reaction has also been observed.