Evaluation of zeta potential of nanomaterials by electrophoretic light scattering: Fast field reversal versus Slow field reversal modes.

Zeta potential of nanomaterials designed to be used in nanomedicine is an important parameter to evaluate as it influences in vivo behaviour hence biological activity, efficacy and safety. As mentioned by the International Organization for Standardization (ISO), electrophoretic light scattering is a relevant method for evaluating zeta potential. The present work aimed to validate a new protocol based on the application of Fast Field Reversal mode and to explore its scope with nanomaterials investigated as nanomedicines. Its scope was then compared with that of an already validated protocol which uses both Fast Field Reversal and Slow Field Reversal modes. The new protocol was validated within the framework of the application of the Smoluchowski approximation. Its performances complied with the ISO standard. The protocol could be applied to evaluate mean zeta potential of soft nanomaterials including polymer-based nanoparticles and liposomes. However, it appeared unsuitable to evaluate zeta potential of dense nanomaterials including rutile titanium dioxide nanoparticles. Compared with the previously validated protocol which only applied to the determination of zeta potential of polymer nanoparticles, this new validated protocol gives access to the determination of zeta potential to a wider range of nanomedicines under conditions complying with quality control assessments.

Burned bodies: post-mortem computed tomography, an essential tool for modern forensic medicine.

Currently, post-mortem computed tomography (PMCT) has become an accessible and contemporary tool for forensic investigations. In the case of burn victims, it provides specific semiologies requiring a prudent understanding to differentiate between the normal post-mortem changes from heat-related changes. The aim of this pictorial essay is to provide to the radiologist the keys to establish complete and focused reports in cases of PMCT of burn victims. Thus, the radiologist must discern all the contextual divergences with the forensic history, and must be able to report all the relevant elements to answer to the forensic pathologist the following questions: Are there tomographic features that could help to identify the victim? Is there evidence of remains of biological fluids in liquid form available for toxicological analysis and DNA sampling? Is there another obvious cause of death than heat-related lesions, especially metallic foreign bodies of ballistic origin? Finally, what are the characteristic burn-related injuries seen on the corpse that should be sought during the autopsy? TEACHING POINTS: • CT is highly useful to find features permitting the identification of a severely burned body. • PMCT is a major asset in gunshot injuries to depict ballistic foreign bodies in the burned cadavers. • CT is able to recognise accessible blood for tests versus heat clot (air-crescent sign). • Heat-related fractures are easily differentiated from traumatic fractures. • Epidural collections with a subdural appearance are typical heat-related head lesions.

Characterization of nanomedicines' surface coverage using molecular probes and capillary electrophoresis.

A faithful characterization of nanomedicine (NM) is needed for a better understanding of their in vivo outcomes. Size and surface charge are studied with well-established methods. However, other relevant parameters for the understanding of NM behavior in vivo remain largely inaccessible. For instance, the reactive surface of nanomedicines, which are often grafted with macromolecules to decrease their recognition by the immune system, is excluded from a systematic characterization. Yet, it is known that a subtle modification of NMs' surface characteristics (grafting density, molecular architecture and conformation of macromolecules) is at the root of major changes in the presence of biological components. In this work, a method that investigates the steric hindrance properties of the NMs' surface coverage based on its capacity to exclude or allow adsorption of well-defined proteins was developed based on capillary electrophoresis. A series of proteins with different molecular weights (MW) were used as molecular probes to screen their adsorption behavior on nanoparticles bearing different molecular architectures at their surface. This novel strategy evaluating to some degree a functionality of NMs can bring additional information about their shell property and might allow for a better perception of their behavior in the presence of biological components. The developed method could discriminate nanoparticles with a high surface coverage excluding high MW proteins from nanoparticles with a low surface coverage that allowed high MW proteins to adsorb on their surface. The method has the potential for further standardization and automation for a routine use. It can be applied in quality control of NMs and to investigate interactions between proteins and NM in different situations.

Towards quality assessed characterization of nanomaterial: Transfer of validated protocols for size measurement by dynamic light scattering and evaluation of zeta potential by electrophoretic light scattering.

Quality control analysis of nanomaterials has been identified as a major issue to pursue their development in different industrial fields including nanomedicine. One difficulty is the lack of standardized and validated protocols suitable to achieve their characterization. In a previous work, we have developed standardized protocols for the evaluation of the size and zeta potential of nanomaterials based on methods described in the ISO standard and have performed validation of each one. The present work was aimed to transfer these protocols in three independent receiving laboratories. No official guideline was described in the literature to achieve such a transfer. A comparative study for receiving laboratories equipped with the same instrument as the sending laboratory was designed based on the Code of Federal Regulation edited by the Food and Drug Administration. For the receiving laboratory equipped with an instrument working at a different wavelength, a new validation was designed and applied. Corresponding statistical methods were used for the analysis of the results. A successful transfer of the protocols in all receiving laboratories was achieved. All laboratories recorded consistent results applying in blind the protocol of size measurements on two samples of nanomaterials from which included one reference.