PAH/DAS covalently cross-linked layer-by-layer multilayers: a "nano-net" superstratum immobilizes nanoparticles and remains permeable to small molecules

Development of functionalized core-shell nanohybrid/synthetic rubber nanocomposites with enhanced performance

Regulating the interfacial interaction between fillers and matrices is crucial for fabricating high-performance polymer composites. In this research, a functionalized core-shell hybrid silica@graphene oxide was produced by the charge attraction method, and then added to a trans-1,4-polyisoprene matrix as a neoteric filler to obtain a brand-new silica@graphene oxide/trans-1,4-polyisoprene polymer nanocomposite. The hybrid incorporation simultaneously improved the fracture toughness, mechanical strength and heat resistance of the nanocomposites. We examined the thermal, mechanical and shape memory properties of the nanocomposites via methodical measurements from the microscale to the macroscale. The experimental results demonstrated that, compared with other samples, the nanocomposite sample with 1.0 wt% silica@graphene oxide exhibited the best mechanical and thermal performance, and the fabricated nanocomposites showed good shape memory properties. This new and feasible approach is likely to enable a new strategy for the design of interfaces for developing nanocomposites with high performance.

A self-powered delivery substrate boosts active enzyme delivery in response to human movements

Stimulated drug releases in response to human movements are highly appealing in medical therapy and various daily uses. However, the design of a mechanically responsive substrate that presents high delivery capacities and can also preserve the activities of sensitive molecules such as enzymes is still challenging. Taking advantage of the recent development in effective piezoelectric flexible films and in molecular delivery devices, we propose a composite delivery substrate that preserves enzyme activities and enhances molecular delivery in response to human movements such as finger presses or massages. The substrate is achieved by combining two parts, which are the energy converting unit and the molecular loading and releasing unit. The energy converting unit is a piezoelectric-dielectric flexible composite film that produces enhanced electricity and preserves the electricity longer compared to a pure piezoelectric polymer. The molecular delivery unit is a layer-by-layer multilayer containing mesoporous silica particles that are assembled at pH 9 but used in neutral solutions. The releases of molecules including small molecules, peptides, and proteins are all accelerated in response to finger presses irrespective of the signs or densities of their charges. More importantly, the enzyme CAT preserves its activity after release from the composite substrates, meaning that the CAT-loaded (PAH/MS)n(PAH/DAS)n@rGO-TFB/PVDF-HFP composite substrate holds promise as a self-powered soothing pad that effectively removes residue H2O2.

Controlled allylation of polyelectrolytes: a deep insight into chemical aspects and their applicability as building blocks for robust multilayer coatings

Polyelectrolytes (PEs) bearing easily derivatizable functions for possible post-modification under mild conditions can find a broad range of applications in various fields. The present paper describes the successful controlled side-chain allylation of two types of PEs: polyamine-based polycations, i.e. poly(allylamine hydrochloride) (PAH) and branched polyethyleneimine (PEI), and strong polyanions, i.e. poly(sodium vinyl sulfonate) (PVS) and poly(sodium 4-styrene sulfonate) (PSS). PSS has been largely investigated in the literature, while PVS is much less commonly explored. The allylation of each type presents its own drawback, i.e. heterogeneous reaction in the case of strong polyanions and instability of partially protonated allylated polyamine products. Nevertheless, all encountered difficulties could be solved and thoroughly elucidated by different experimental tests. This partial allyl-functionalization does not affect the electrolytic properties of the newly allylated PEs, as evidenced by the effective construction of two series of polyelectrolyte multilayer (PEM) films, namely PEI-ene (PSS-ene/PAH-ene)4 and PEI-ene (PVS-ene/PAH-ene)4, the latter being one of the rare examples developed in the literature. The presence of allyl groups on the PE side-chains allows for the stabilization of the resulting PEM films via thiol-ene photo-crosslinking in the presence of a water-soluble dithiol crosslinker. In order to fix permanently the resulting crosslinked PEM films on substrates, the covalent crosslinking occurs not only between different C=C bonds on PE layers but also with those present on substrates preliminarily functionalized with allyl groups via sulfur–gold chemistry. The robustness of both resulting crosslinked PEM films under strongly basic solution (pH 14) is validated by Quartz Crystal Microbalance (QCM) measurements. The versatility and effectiveness of the present approach is expected to find potential applications in different scientific and technological fields.

Layer by Layer Mesoporous Silica-Hyaluronic Acid-Cyclodextrin Bifunctional "Lamination": Study of the Application of Fluorescent Probe and Host⁻Guest Interactions in the Drug Delivery Field

The layer-by-layer technique was exploited to adjust the magnitude of the host⁻guest interactions between adamantane and cyclodextrin. The effect depends on numerous complex and changeable growth profiles of the films and the number of bilayers. These composite films of mesoporous silica nanoparticles and hyaluronic acid⁻cyclodextrin(HA-CD) were constructed to load the fluorescent dyes and peptides. The release rates of these molecules would decrease with an increase in the number of layers. A laser scanning confocal microscope was utilized to obtain the diffusion coefficient of fluorescein isothiocyanate. Hybrid films could be applied to increase the loading of different kinds of molecules and could also be integrated into the lamination to delay the rate of release.

Using a biocompatible diazidecrosslinker to fabricate a robust polyelectrolyte multilayer film with enhanced effects on cell proliferation

Due to the noncovalent interactions between the layers of polyelectrolyte films, the layer-by-layer assembled multilayered films always face the challenge of low film stiffness and chemical stability under extreme conditions. To handle this issue, we incorporated 4,4'-diazostilbene-2,2'-disulfonic acid disodium salt (DAS) as a crosslinker and subsequently photocrosslinked the layers of a poly(allylamine hydrochloride)/catalase multilayered film. The results showed that DAS could stabilize the prepared film in a manner similar to the traditional cross-linker glutaraldehyde. The multilayered film showed good biocompatibility with a positive effect on cell proliferation. Therefore, by using the commercially available DAS crosslinker, we provide a synthesis-free and biocompatible method to stabilize polyelectrolyte multilayers for broad and significant applications in biological fields, e.g., varying crosslinking density to adjust the mechanical strength of biomaterials, stabilizing susceptible biofilms, or introducing functional groups onto cell membranes.

A functional protein retention and release multilayer with high stability

Effective and robust interfacial protein retention lies at the heart of the fabrication of protein-based functional interfaces, which is potentially applicable in catalysis, medical therapy, antifouling, and smart devices, but remains challenging due to the sensitive nature of proteins. This study reports a general protein retention strategy to spatial-temporally confine various types of proteins at interfacial regions. The proteins were preserved in mesoporous silica nanoparticles embedded in covalently woven multilayers. It is worth noting that the protein retention strategy effectively preserves the catalytic capabilities of the proteins, and the multilayer structure is robust enough to withstand the bubbling catalytic reactions and could be repeatedly used due to conservation of proteins. The spatiotemporal retention of proteins could be adjusted by varying the number of capping layers. Furthermore, we demonstrate that the protein-loaded interfacial layers could not only be used to construct catalytic-active interfaces, but also be integrated as the power-generating unit to propel a macroscopic floating device.