Mechanical and Transport Properties of the Poly(ethylene oxide)−Poly(acrylic acid) Double Network Hydrogel from Molecular Dynamic Simulations

Not only in silico drug discovery: Molecular modeling towards in silico drug delivery formulations

The use of methods at molecular scale for the discovery of new potential active ligands, as well as previously unknown binding sites for target proteins, is now an established reality. Literature offers many successful stories of active compounds developed starting from insights obtained in silico and approved by Food and Drug Administration (FDA). One of the most famous examples is raltegravir, a HIV integrase inhibitor, which was developed after the discovery of a previously unknown transient binding area thanks to molecular dynamics simulations. Molecular simulations have the potential to also improve the design and engineering of drug delivery devices, which are still largely based on fundamental conservation equations. Although they can highlight the dominant release mechanism and quantitatively link the release rate to design parameters (size, drug loading, et cetera), their spatial resolution does not allow to fully capture how phenomena at molecular scale influence system behavior. In this scenario, the "computational microscope" offered by simulations at atomic scale can shed light on the impact of molecular interactions on crucial parameters such as release rate and the response of the drug delivery device to external stimuli, providing insights that are difficult or impossible to obtain experimentally. Moreover, the new paradigm brought by nanomedicine further underlined the importance of such computational microscope to study the interactions between nanoparticles and biological components with an unprecedented level of detail. Such knowledge is a fundamental pillar to perform device engineering and to achieve efficient and safe formulations. After a brief theoretical background, this review aims at discussing the potential of molecular simulations for the rational design of drug delivery systems.

The role of composition and structure of vanadium-doped nanosized titanium(iv) oxides (anatase and η-phase) in the realization of photocatalytic, adsorption and bactericidal properties

The photocatalytic, adsorption and bactericidal properties of vanadium-doped nanosized anatase and η-phase are influenced by their physiochemical parameters.

Aromatic ionene topology and counterion-tuned gelation of acidic aqueous solutions

Unusual gelation of acidic solutions was achieved using polycations bearing quaternary ammonium moieties. These ionene polymers are based on a disubstituted phenylene dibenzamide core, which allows the construction of different topomers (i.e. ortho-1, meta-2 and para-3). The topology of the polymers was found to play a key role on their aggregation behaviour both in pure water and in a variety of aqueous acidic solutions leading to the formation of stable acidic gels. Specifically, ortho-1 showed superior gelation ability than the analogues meta-2 and para-3 in numerous solutions of different pH and ionic strengths. Lower critical gelation concentrations, higher gel-to-sol transition temperatures and faster gelation were usually observed for ortho-1 regardless the solvent system. Detailed computational molecular dynamic simulations revealed a major role of the counterion (Cl^-) and specific polymerpolymer interactions. In particular, hydrogen bonds, N-Hπ interactions and intramolecular π-π stacking networks are distinctive in ortho-1. In addition, counterions located at internal hydration regions also affect to such polymerpolymer interactions, acting as binders and, therefore, providing additional stability.

Preparation and characterization of pH- and temperature-responsive nanocomposite double network hydrogels

A methodology is described for the preparation of pH- and temperature-responsive double network (DN) hydrogels with poly(N-isopropylacrylamide) (PNIPAM) as a tightly crosslinked 1st network, polyacrylic acid (PAA) as a loosely crosslinked 2nd network and graphene oxide (GO) as an additive. GO sheets were first prepared via an oxidation reaction and then dispersed in NIPAM aqueous solution via silanization. Free-radical polymerization of NIPAM was carried out at 20 °C in a water bath, and then subjected to UV light, leading to the formation of pH- and temperature-responsive PNIPAM/AA/GO DN hydrogels. The effects of GO sheets and AA contents on various physical properties were investigated. Results show that PNIPAM/AA/GO hydrogels undergo a large volumetric change in response to temperature. It also exhibits significantly fast swelling/deswelling compared with conventional PNIPAM hydrogel. Moreover, the PNIPAM/AA/GO hydrogels have a much better mechanical property than the conventional PNIPAM hydrogels.