A facile method for the construction of covalently cross-linked layered double hydroxides layer-by-layer films: Enhanced stability and delayed release of guests

Molecular Design of Layer-by-Layer Functionalized Liposomes for Oral Drug Delivery

Liposomes are small spherical vesicles composed mainly of phospholipids and cholesterol. Over the years, a number of liposomal formulations have shown clinical promise, but the use of liposomes in oral drug delivery is limited. This is partly due to the vulnerability of conventional liposomes to the detrimental effect of gastrointestinal destabilizing factors and also to the poor efficiency in intestinal absorption of liposomes. Some of these issues can be ameliorated using the layer-by-layer (LbL) assembly technology, which has been widely applied to modify the surface of various nanoparticulate systems. Discussions about LbL functionalization of liposomes as oral drug carriers, however, are scant in the literature. To fill this gap, this review presents an overview of the roles of LbL functionalization in the development of liposomes, followed by a discussion about major principles of molecular design and engineering of LbL-functionalized liposomes for oral drug delivery. Regarding the versatility offered by LbL assembly, it is anticipated that LbL-functionalized liposomes may emerge as one of the important carriers for oral drug administration in the future.

Biologically responsive, long-term release nanocoating on an electrospun scaffold for vascular endothelialization and anticoagulation

A critical challenge to the development of tissue engineering small-diameter vascular grafts is to achieve rapid endothelialization and long-term anticoagulation. It is necessary to graft both adhesion and antithrombus factors onto the surface of polycaprolactone without burst release to promote endothelial cell affinity and antithrombogenicity. A bionic structure with a nanocoating that allows a biologically responsive, long-term release was employed in this work to enable the grafting of various bioactive molecules such as gelatin, polylysine, and heparin. This approach involved orienting the biomimetic vascular structures; the self-assembly grafting of gelatin, polylysine, and heparin nanoparticles; and genipin crosslinking to form a multiphase crosslinked nanocoating. In this biologically inspired design, vascular endothelialization and long-term anticoagulation were successfully induced through a matrix metallopeptidase 2 regulative mechanism by delivering both adhesion and antithrombus factors with a responsive, long-term release without burst release. The method provided a simple and effective approach for delivering dual factors for tissue engineering small-diameter vascular grafts.

Covalent layer-by-layer films: chemistry, design, and multidisciplinary applications

Covalent layer-by-layer (LbL) assembly is a powerful method used to construct functional ultrathin films that enables nanoscopic structural precision, componential diversity, and flexible design. Compared with conventional LbL films built using multiple noncovalent interactions, LbL films prepared using covalent crosslinking offer the following distinctive characteristics: (i) enhanced film endurance or rigidity; (ii) improved componential diversity when uncharged species or small molecules are stably built into the films by forming covalent bonds; and (iii) increased structural diversity when covalent crosslinking is employed in componential, spacial, or temporal (labile bonds) selective manners. In this review, we document the chemical methods used to build covalent LbL films as well as the film properties and applications achievable using various film design strategies. We expect to translate the achievement in the discipline of chemistry (film-building methods) into readily available techniques for materials engineers and thus provide diverse functional material design protocols to address the energy, biomedical, and environmental challenges faced by the entire scientific community.

Controlled Interfacial Permeation, Nanostructure Formation, Catalytic Efficiency, Signal Enhancement Capability, and Cell Spreading by Adjusting Photochemical Cross-Linking Degrees of Layer-by-Layer Films

Interfacial properties including permeation, catalytic efficiency, Raman signal enhancement capabilities, and cell spreading efficiencies are important features that determine material functionality and applications. Here, we propose a facile method to adjust the above-mentioned properties by controlling the cross-linking degrees of multilayer using a photoactive molecule. After treating the cross-linked films in basic solutions, films with different cross-linking degrees presented varying residue thicknesses and film morphologies. As a result, these different films possessed distinct molecular loading and release characteristics. In addition, gold nanoparticles (AuNPs) of different morphological traits were generated by redox reactions coupled with diffusion within these films. The AuNP-polyelectrolyte obtained from the polyelectrolyte films of the medium cross-linking degrees displayed the highest catalytic efficiency and signal enhancement capabilities. Furthermore, cells responded to the variation of film cross-linking degrees, and on the films with the highest cross-linking degree, cells adhered with the highest speed. We expect this report to provide a general interfacial material engineering strategy for material designs.