Self-assembly of maltoheptaose-block-polystyrene into micellar nanoparticles and encapsulation of gold nanoparticles

Properties, Applications and Toxicities of Organotrialkoxysilane-Derived Functional Metal Nanoparticles and Their Multimetallic Analogues

Sol-gel chemistry offers a very unique tool for nanoscale mastering of material preparation from metal alkoxides [...].

Carbohydr Polym Special Issue Invited contribution: Click chemistry for block polysaccharides with dihydrazide and dioxyamine linkers - A review

Engineered block polysaccharides is a relatively new class of biomacromolecules consisting of chemical assembly of separate block structures at the chain termini. In contrast to conventional, laterally substituted polysaccharide derivatives, the block arrangement allows for much higher preservation of inherent chain properties such as biodegradability and stimuli-responsive self-assembly, while at the same time inducing new macromolecular properties. Abundant, carbon neutral, and even recalcitrant biomass is an excellent source of blocks, opening for numerous new uses of biomass for a wide range of novel biomaterials. Among a limited range of methodologies available for block conjugation, bifunctional linkers allowing for oxyamine and hydrazide 'click' reactions have recently proven useful additions to the repertoire. This article focuses the chemistry and kinetics of these reactions. It also presents some new data with the aim to provide useful protocols and methods for general use towards new block polysaccharides.

Trialkoxyheptazine-Based Glyconanoparticles for Fluorescence in Aqueous Solutions and on Surfaces via Controlled Binding in Space

The fluorescent organic 2,5,8-tris((adamantan-1-yl)-methoxy)-heptazine (HTZ-Ad) was solubilized in water by inclusion of adamantane groups into free β-cyclodextrins or a cyclodextrin shell of glyconanoparticles. These glyconanoparticles with average diameters between 40 and 60 nm result from the self-assembly of polystyrene-block-β-cyclodextrin copolymers. Under UV irradiation at 365 nm, the modified nanoparticles exhibit fluorescence emission in aqueous media as well as in their adsorbed state. This constitutes the first spectroscopic characterization of a trialkoxyheptazine in aqueous medium. The specific binding of the glyconanoparticles to a surface was achieved via host-guest interactions with an electrochemically generated poly(pyrrole-adamantane) film. An interdigitated microelectrode modified with poly(pyrrole-adamantane) film and glyconanoparticles was incubated in HTZ-Ad, resulting in a substrate with spatially controlled fluorescence. The same modified electrode was incubated with an aqueous suspension of glyconanoparticles previously functionalized by HTZ-Ad, resulting in a fluorescent 3D assembly.

Design and Characterization of Maltoheptaose-b-Polystyrene Nanoparticles, as a Potential New Nanocarrier for Oral Delivery of Tamoxifen

Tamoxifen citrate (TMC), a non-steroidal antiestrogen drug used for the treatment of breast cancer, was loaded in a block copolymer of maltoheptaose-b-polystyrene (MH-b-PS) nanoparticles, a potential drug delivery system to optimize oral chemotherapy. The nanoparticles were obtained from self-assembly of MH-b-PS using the standard and reverse nanoprecipitation methods. The MH-b-PS@TMC nanoparticles were characterized by their physicochemical properties, morphology, drug loading and encapsulation efficiency, and release kinetic profile in simulated intestinal fluid (pH 7.4). Finally, their cytotoxicity towards the human breast carcinoma MCF-7 cell line was assessed. The standard nanoprecipitation method proved to be more efficient than reverse nanoprecipitation to produce nanoparticles with small size and narrow particle size distribution. Moreover, tamoxifen-loaded nanoparticles displayed spherical morphology, a positive zeta potential and high drug content (238.6 ± 6.8 µg mL-1) and encapsulation efficiency (80.9 ± 0.4 %). In vitro drug release kinetics showed a burst release at early time points, followed by a sustained release profile controlled by diffusion. MH-b-PS@TMC nanoparticles showed higher cytotoxicity towards MCF-7 cells than free tamoxifen citrate, confirming their effectiveness as a delivery system for administration of lipophilic anticancer drugs.

Functionalizable Glyconanoparticles for a Versatile Redox Platform

A series of new glyconanoparticles (GNPs) was obtained by self-assembly by direct nanoprecipitation of a mixture of two carbohydrate amphiphilic copolymers consisting of polystyrene-block-β-cyclodextrin and polystyrene-block-maltoheptaose with different mass ratios, respectively 0–100, 10–90, 50–50 and 0–100%. Characterizations for all these GNPs were achieved using dynamic light scattering, scanning and transmission electron microscopy techniques, highlighting their spherical morphology and their nanometric size (diameter range 20–40 nm). In addition, by using the inclusion properties of cyclodextrin, these glyconanoparticles were successfully post-functionalized using a water-soluble redox compound, such as anthraquinone sulfonate (AQS) and characterized by cyclic voltammetry. The resulting glyconanoparticles exhibit the classical electroactivity of free AQS in solution. The amount of AQS immobilized by host–guest interactions is proportional to the percentage of polystyrene-block-β-cyclodextrin entering into the composition of GNPs. The modulation of the surface density of the β-cyclodextrin at the shell of the GNPs may constitute an attractive way for the elaboration of different electroactive GNPs and even GNPs modified by biotinylated proteins.

Redox-Active Carbohydrate-Coated Nanoparticles: Self-Assembly of a Cyclodextrin-Polystyrene Glycopolymer with Tetrazine-Naphthalimide

The controlled self-assembly of precise and well-defined photochemically and electrochemically active carbohydrate-coated nanoparticles offers the exciting prospect of biocompatible catalysts for energy storage/conversion and biolabeling applications. Here an aqueous nanoparticle system has been developed with a versatile outer layer for host-guest molecule encapsulation via β-cyclodextrin inclusion complexes. A β-cyclodextrin-modified polystyrene polymer was first obtained by copper nanopowder click chemistry. The glycopolymer enables self-assembly and controlled encapsulation of tetrazine-naphthalimide, as a model redox-active agent, into nanoparticles via nanoprecipitation. Cyclodextrin host-guest interactions permit encapsulation and internanoparticle cross-linking for the formation of fluorescent compound and clustered self-assemblies with chemically reversible electroactivity in aqueous solution. Light scattering experiments revealed stable particles with hydrodynamic diameters of 138 and 654 nm for nanoparticles prepared with tetrazine, of which 95% of the nanoparticles represent the smaller objects by number. Dynamic light scattering revealed differences as a function of preparation method in terms of size, 3-month stability, polydispersity, radius of gyration, and shape factor. Individual self-assemblies were visualized by atomic force microscopy and fluorescence microscopy and monitored in real-time by nanoparticle tracking analysis. UV-vis and fluorescence spectra provided insight into the optical properties and critical evidence for host-guest encapsulation as evidenced by solvachromatism and enhanced tetrazine uptake. Cyclic voltammetry was used to investigate the electrochemical properties and provided further support for encapsulation and an estimate of the tetrazine loading capacity in tandem with light scattering data.

Self-Assembly of Oligosaccharide-b-PMMA Block Copolymer Systems: Glyco-Nanoparticles and Their Degradation under UV Exposure

This paper discusses the self-assembly of oligosaccharide-containing block copolymer and the use of ultraviolet (UV) to obtain nanoporous glyco-nanoparticles by photodegradation of the synthetic polymer block. Those glyco-nanoparticles consisting of oligosaccharide-based shell and a photodegradable core domain were obtained from the self-assembly of maltoheptaose-block-poly(methyl methacrylate) (MH-b-PMMA48) using the nanoprecipitation protocol. MH-b-PMMA48 self-assembled into well-defined spherical micelles (major compound) with a hydrodynamic radius (Rh) of ca. 10 nm and also into large compound micellar aggregates (minor compound) with an Rh of ca. 65 nm. The oligosaccharide shells of these glyco-nanoparticles were cross-linked through the Michael-type addition of divinyl sulfone under dilute conditions to minimize the intermicellar cross-linking. The core domain photodegradation of the cross-linked glyco-nanoparticles was induced under exposure to 254 nm UV radiation, resulting in porous glyco-nanoparticles with an Rh of ca. 44 nm. The morphology of the cross-linked shell and the core photodegradation of these glyco-nanoparticles were characterized using static light scattering, dynamic light scattering, Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, field-emission gun-scanning electron microscopy, and transmission electron microscopy. The innovative aspect of this approach concerns the fact that after removing the PMMA domains the porous nanoparticles are mostly composed of biocompatible and nontoxic oligosaccharides.

Redox tunable delivery systems: sweet block copolymer micelles via thiol–(bromo)maleimide conjugation

A tunable release of encapsulated Nile Red from xyloglucan-oligosaccharides-block-polycaprolactone obtained by thiol–(bromo)maleimide click reaction was successfully achieved by mixing their Gluathione-responsiveness.

Oligosaccharide-based block copolymers: metal-free thiol-maleimide click conjugation and self-assembly into nanoparticles

Amphiphilic oligosaccharide-based block copolymers (OBCPs) are able to self-assemble either into nanoparticles with biocompatible oligosaccharides corona in aqueous solution or in sub-nanopatterned thin-films originating from the high incompatibility between the different blocks. For these reasons, these biosourced OBCPs are valuable structures for applications in nanomedicine and nanoelectronics. Up to now, the synthesis of those OBCPs was obtained through grafting-onto method using Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC). However, complete removal of metal catalyst residues from the resultant copolymer chains is critical and hampers electronic and biomedical applications. In this study, we report an efficient and convenient metal-free click chemistry approach consisting in coupling thiol-containing oligosaccharide blocks to maleimide-terminated polystyrenes. Upon self-assembly in water, spherical micelles of similar size than those obtained by Cu(I)-catalyzed azide-alkyne cycloaddition were formed as evidenced using dynamic light scattering and transmission electron microscopy techniques.

Self-assembly of phosphorous containing oligomers: morphological features and pH-sensitiveness in suspension

Methacrylamide-based oligomers bearing phosphonate pending groups at the end of a long alkyl chain and originating from undecylenic acid synthons were subjected to direct oligomer dissolution. Size improvement towards much smaller objects was reached using the nanoprecipitation method: the oligomers were first dissolved in an organic solvent, and then precipitated in water using a syringe pump. Dynamic light scattering (DLS) showed phosphorous containing monomodal and quite narrow-sized self-assemblies in water with hydrodynamic diameters (DH) ranging from 80 to 280 nm (depending on the oligomer system). Direct visualization using transmission electron microscopy (TEM) and atomic force microscopy (AFM) showed filled and almost individual particles with spherical shape. They were considerably shrunk, suggesting the highly swollen character of the self-assemblies in suspension. Morphological information on the multi-scale self-assembled structures was complementarily obtained using static light scattering (SLS). Thus, at a low length-scale, highly segregated sub-units having sharp boundaries surrounded by water (Porod behaviour) were observed, whereas at a high length-scale random non-compact organization of these sub-units via weak interactions was found, forming a chaplet-like structure (Gaussian behaviour). Furthermore, the pH-sensitiveness of the suspensions obtained after the nanoprecipitation method was studied. Particularly, at pH = 12, the characteristic size drastically increased within few hours from typically ∼280 nm to 2 μm due to electrostatic repulsion between deprotonated hydroxyl groups. At longer times, the observed peculiar behaviour corresponded to the model of diffusion-limited cluster aggregation (DLCA) where the particles stuck easily together upon contact [continuation of the article by C. Bouilhac, C. Travelet, A. Graillot, S. Monge, R. Borsali and J.-J. Robin, Polym. Chem., 2014, 5, 2756-2767].