Chitosan coated selenium: A versatile nano-delivery system for molecular cargoes

The use of nanoscale delivery platforms holds tremendous potential to overcome the current limitations associated with the conventional delivery of genetic materials and hydrophobic compounds. Therefore, there is an imperative need to develop a suitable alternative nano-enabled delivery platform to overcome these limitations. This work reports the first one-step hydrothermal synthesis of chitosan functionalized selenium nanoparticles (Selenium-chitosan, SeNP) that are capable of serving as a versatile nanodelivery platform for different types of active ingredients. The chitosan functionalization modified the surface charge to allow the loading of active ingredients and improve biocompatibility. The effective loading of the SeNP was demonstrated using genetic material, a hydrophobic small molecule, and an antibiotic. Furthermore, the loading of active ingredients showed no detrimental effect on the specific properties (fluorescence and bactericidal) of the studied active ingredients. In vitro antimicrobial inhibitory studies exhibited good compatibility between the SeNP delivery platform and Penicillin G (Pen), resulting in a reduction of the minimum inhibitory concentration (MIC) from 32 to 16 ppm. Confocal microscopy images showed the uptake of the SeNP by a macrophage cell line (J774A.1), demonstrating trackability and intracellular delivery of an active ingredient. In summary, the present work demonstrates the potential of SeNP as a suitable delivery platform for biomedical and agricultural applications.

Enhanced rheological and tribological properties of nanoenhanced greases by tuning interparticle contacts

HYPOTHESIS

Despite the wide spectrum of available nanoparticles, their utilization in lubricant and grease formulations remains challenging. To enhance their performance, an improved link between the interparticle contacts, brittleness of the resulting particle network, time-dependent rheology and tribology is required.

EXPERIMENTS

We systematically changed interparticle contacts and examined their effect on the colloidal stability, microstructure, rheological and tribological behavior of model greases by investigating four types of nanoclays: montmorillonite (Cloisite Na⁺), oleic-acid functionalized Cloisite Na⁺ (OA-Cloisite Na⁺), organomodified montmorillonite (C20A) and oleic-acid functionalized C20A (C20A-OA).

FINDINGS

We observed a range of behaviors, starting from the lack of colloidal stability in greases derived with Cloisite Na⁺ and OA-Cloisite Na⁺ to semi-solid type systems with C20A and C20A-OA. Consistent with previous studies, the rheological and tribological properties of C20A systems scale with nanoclay loadings. Surprisingly, the functionalized C20A-OA system exhibited a delayed transition towards hydrodynamic lubrication, and enhanced lubrication properties, both of which were largely independent of nanoclay loadings. Coupled microstructural investigation and time-dependent rheology reveal that this behavior is governed by increasing repulsive forces, decreasing inter-particle friction between C20A-OA nanoparticles, and faster reorganization of the C20A-OA nanoparticle network under shear. Increased interparticle repulsion enables C20A-OA nanoclays to pass each other under shear and align in direction of shear, which reduces the overall viscosity, while the presence of OA on nanoclays decreases inter-particle friction and particle-steel surface friction.

Aggregation of magnetic nanoparticles functionalized with trans-resveratrol in aqueous solution

In the framework of a protein-ligand-fishing strategy to identify proteins that bind to trans-resveratrol, a natural phenolic compound with pharmacological benefits, we have developed magnetic nanoparticles covalently linked to trans-resveratrol through three different derivatives and examined their aggregation behavior in aqueous solution. The monodispersed magnetic core (18 nm diameter) with its mesoporous silica shell (93 nm diameter) exhibited a notable superparamagnetic behavior useful for magnetic bioseparation. The hydrodynamic diameter, deduced from dynamic light scattering analysis, of the nanoparticle increased from 100 to 800 nm when the aqueous buffer changed from pH 10.0-3.0. A size polydispersion occurred from pH 7.0-3.0. In parallel, the value of the extinction cross section increased according to a negative power law of the UV wavelength. This was mainly due to light scattering by mesoporous silica, whereas the absorbance cross section remained very low in the 230-400 nm domain. The three types of resveratrol-grafted magnetic nanoparticles exhibited similar scattering properties, but their absorbance spectrum was consistent with the presence of trans-resveratrol. Their functionalization increased their negative zeta potential when pH increased from 3.0 to 10.0. The mesoporous nanoparticles were monodispersed in alkaline conditions, where their anionic surface strongly repulsed each other but aggregated progressively under van der Waals forces and hydrogen bonding when negative zeta potential decreased. The characterized results of nanoparticle behavior in aqueous solution provide critical insight for further study of nanoparticles with proteins in biological environment.

Effect of surface functionalization and loading on the mechanical properties of soft polymeric nanoparticles prepared by nano-emulsion templating

Drug and gene delivery systems based on polymeric nanoparticles offer a greater efficacy and a reduced toxicity compared to traditional formulations. Recent studies have evidenced that their internalization, biodistribution and efficacy can be affected, among other factors, by their mechanical properties. Here, we analyze by means of Atomic Force Microscopy force spectroscopy how composition, surface functionalization and loading affect the mechanics of nanoparticles. For this purpose, nanoparticles made of Poly(lactic-co-glycolic) (PLGA) and Ethyl cellulose (EC) with different functionalizations and loading were prepared by nano-emulsion templating using the Phase Inversion Composition method (PIC) to form the nano-emulsions. A multiparametric nanomechanical study involving the determination of the Young's modulus, maximum deformation and breakthrough force was carried out. The obtained results showed that composition, surface functionalization and loading affect the nanomechanical properties in a different way, thus requiring, in general, to consider the overall mechanical properties after the addition of a functionalization or loading. A graphical representation method has been proposed enabling to easily identify mechanically equivalent formulations, which is expected to be useful in the development of soft polymeric nanoparticles for pre-clinical and clinical use.

Nano-targeting lessons from the SARS-CoV-2

The lack of targeting efficacy has frequently led functionalized nanoparticles to accumulate in unwanted cells and tissues while boosting toxicity-related effects. Conversely, viruses are natural nanoparticles that precisely and responsively interact with the biological machinery through an effective-driven fashion. This interaction is enhanced by a meticulous spatial arrangement which results in a quasi-crystalline distribution of proteins on the viruses' surface. Amidst the COVID-19 pandemic, we propose to look at the SARS-CoV-2 nanoscale viral scaffold as an example of a highly-ordered architecture that must inspire and tailor the production of targeted synthetic nanoparticles.

Ligand Exchange and 1H NMR Quantification of Single- and Mixed-Moiety Thiolated Ligand Shells on Gold Nanoparticles

The use of nanoparticles in biomedicine critically depends on their surface chemistry. For metal nanoparticles, a common way to tune this surface chemistry is through mass action ligand exchange, where ligand exchange can be used to expand the functionality of the resulting nanoparticle conjugates. Specifically, the quantity, identity, and arrangement of the molecules in the resulting ligand shell each can be tuned significantly. Here, we describe methods to exchange and quantify thiolated and non-thiolated ligands on gold nanoparticle surfaces. Importantly, these strategies allow the quantification of multiple ligand types within a single ligand shell, simultaneously providing ligand composition and ligand density information. These results are crucial for both designing and assigning structure-function relationships in bio-functionalized nanoparticles, and these methods can be applied to a broad range of nanoparticle cores and ligand types including peptides, small molecule drugs, and oligonucleotides.

Aggregation kinetics and colloidal stability of functionalized nanoparticles

The functionalization of nanoparticles has primarily been used as a means to impart stability in nanoparticle suspensions. In most cases even the most advanced nanomaterials lose their function should suspensions aggregate and settle, but with the capping agents designed for specific solution chemistries, functionalized nanomaterials generally remain monodisperse in order to maintain their function. The importance of this cannot be underestimated in light of the growing use of functionalized nanomaterials for wide range of applications. Advanced functionalization schemes seek to exert fine control over suspension stability with small adjustments to a single, controllable variable. This review is specific to functionalized nanoparticles and highlights the synthesis and attachment of novel functionalization schemes whose design is meant to affect controllable aggregation. Some examples of these materials include stimulus responsive polymers for functionalization which rely on a bulk solution physicochemical threshold (temperature or pH) to transition from a stable (monodisperse) to aggregated state. Also discussed herein are the primary methods for measuring the kinetics of particle aggregation and theoretical descriptions of conventional and novel models which have demonstrated the most promise for the appropriate reduction of experimental data. Also highlighted are the additional factors that control nanoparticle stability such as the core composition, surface chemistry and solution condition. For completeness, a case study of gold nanoparticles functionalized using homologous block copolymers is discussed to demonstrate fine control over the aggregation state of this type of material.