Use of EPR and FTIR to detect biological effects of ultrasound and microbubbles on a fibroblast cell line.

Structural and functional effects of exposing murine fibroblasts (NIH 3T3) to therapeutic ultrasound at 1 MHz frequency are described. These bioeffects can be attributed to the formation of free radical species by sonolysis of water. When cavitation occurs, dissociation of water vapor into H atoms and OH radicals is observed; these H atoms and OH radicals combine to form H(2), H(2)O(2), and HO(2).

Radiation-induced signals analysed by EPR spectrometry applied to fortuitous dosimetry.

Dosimetry based on the detection by electron paramagnetic resonance (EPR) spectroscopy of ionizing radiation-induced radicals is an established method for the retrospective dosimetry of past exposures and the dosimetry of potentially exposed persons in radiological emergencies. The dose is estimated by measuring the physical damage induced in materials contained in objects placed on or next to the potentially exposed person. The aim of this paper is to survey the current literature about methodologies and materials that have been proposed for EPR dosimetry, in order to identify those that could be suitable for population triage according to criteria such as ubiquity, non invasiveness and easy sample collection, presence of a post-irradiation EPR signal, negligible background signal, linearity of dose-response relationship, minimum detection limit and post-irradiation signal stability.

Radiofrequency dielectric loss relaxation in polyion-induced liposome aggregates.

In this note, we present a set of dielectric loss relaxation measurements of aqueous charged liposome suspensions during the whole aggregation process induced by oppositely charged adsorbing polyions. The system experiences two concomitant effects known as "reentrant condensation" and "charge inversion," resulting in the formation of liposome aggregates whose average size reaches a maximum in the vicinity of the electroneutrality condition, accompanied to a progressive reduction of their overall electrical charge. Far from the neutrality, from both sides, polyion-coated liposomes exist with a charge of opposite sign.

Polyion-induced liposomal vesicle aggregation: a radiowave dielectric relaxation study.

The radiowave dielectric properties of aqueous heterogeneous systems during the complexation of charged polyions and oppositely charged liposomal particles have been measured in a wide frequency range, between 100 Hz and 2 GHz. The formation of a polyion-liposome complex driven by the correlated polyion adsorption at the particle surface implies two concomitant effects referred to as reentrant condensation and charge inversion. Both of them are governed by electrostatic interactions and there is now strong evidence, based on experiments and simulations, that counterion release is the driving force of the aggregation process.

Counterion release in overcharging of polyion-liposome complexes.

We present a set of electrical conductivity measurements of a mesoscopic equilibrium cluster phase in the aggregation process of charged particles induced by oppositely charged polyions. These measurements supply strong experimental evidence that correlated adsorption of polyions is driven by the counterion release. This phenomenon, known to occur in DNA-liposome mixtures in lamellar phase, i.