Solvent-filled matrix polyelectrolyte capsules: preparation, structure and dynamics

Advances in polysaccharide-based nano/microcapsules for biomedical applications: A review

Biocompatible and biodegradable polysaccharides are abundant and renewable natural materials. Polysaccharides and their derivatives are developed into various carrier materials for biomedical applications. In particular, advanced polysaccharide-based nano/microcapsules have received extensive attention in biomedical applications due to their good encapsulation ability and tunability. In recent years, polysaccharide-based nano/microcapsules have been widely used in drug carriers, gene carriers, antigen carriers, wound dressings, bioimaging and biosensors. Numerous research results have confirmed the feasibility, safety, and effectiveness of polysaccharide-based nano/microcapsules in the above-mentioned biomedical applications. This review discussed and analyzed the latest research strategies and design considerations for these applications in detail. The preparation methods, application strategies, and design considerations of polysaccharide-based nano/microcapsules are summarized and analyzed, and their challenges and future research prospects in biomedicine are further discussed. It is expected to provide researchers with inspiration and design ideas.

Designing Natural Polymer-Based Capsules and Spheres for Biomedical Applications-A Review

Natural polymers, such as polysaccharides and polypeptides, are potential candidates to serve as carriers of biomedical cargo. Natural polymer-based carriers, having a core-shell structural configuration, offer ample scope for introducing multifunctional capabilities and enable the simultaneous encapsulation of cargo materials of different physical and chemical properties for their targeted delivery and sustained and stimuli-responsive release. On the other hand, carriers with a porous matrix structure offer larger surface area and lower density, in order to serve as potential platforms for cell culture and tissue regeneration. This review explores the designing of micro- and nano-metric core-shell capsules and porous spheres, based on various functions. Synthesis approaches, mechanisms of formation, general- and function-specific characteristics, challenges, and future perspectives are discussed. Recent advances in protein-based carriers with a porous matrix structure and different core-shell configurations are also presented in detail.

Undulatory Locomotion of Magnetic Multilink Nanoswimmers

Micro- and nanorobots operating in low Reynolds number fluid environments require specialized swimming strategies for efficient locomotion. Prior research has focused on designs mimicking the rotary corkscrew motion of bacterial flagella or the planar beating motion of eukaryotic flagella. These biologically inspired designs are typically of uniform construction along their flagellar axis. This work demonstrates for the first time planar undulations of composite multilink nanowire-based chains (diameter 200 nm) induced by a planar-oscillating magnetic field. Those chains comprise an elastic eukaryote-like polypyrrole tail and rigid magnetic nickel links connected by flexible polymer bilayer hinges. The multilink design exhibits a high swimming efficiency. Furthermore, the manufacturing process enables tuning the geometrical and material properties to specific applications.

LbL coated microcapsules for delivering lipid-based drugs

Nowadays, more than 40% of new pharmacologically active compounds exhibit poor water solubility, which requires the development of the new methods for their administration and delivery. One of the most promising approaches for the development of such delivery systems is the use of layer-by-layer assembly technology for encapsulation of the lipid-based drugs. This technique permits the step-wise adsorption of various components as the layer growth is governed by their electrostatic attraction and allows the formation of multilayer shells with nanometer-scale precision. The proposed review surveys the application of layer-by-layer assembly for emulsions, nanoparticles, and capsule-based delivery systems for lipid-based drugs.

Tuning swelling pH and permeability of hydrogel multilayer capsules

We report on tuning swelling pH transitions of hydrogel hollow capsules that were derived from hydrogen-bonded multilayers via chemical cross-linking. The capsules were either of a single component - a weak poly(carboxylic acid), such as poly(acrylic acid) (PAA), poly(methacrylic acid) (PMAA), or poly(ethacrylic acid) (PEAA) - or contained two hydrogen-bonding polymers, such as in poly(carboxylic acid)/poly(N-vinylpyrrolidone-co-NH2) (PVPON-co-NH2) or in poly(carboxylic acid)/poly(N-vinylcaprolactam-co-NH2) (PVCL-co-NH2) systems. By varying the acidity of weak polyelectrolytes, the capsule swelling can be tuned over a wide pH range from 5 to 10. We show that differently from one-component capsules, the swelling amplitude of two-component capsules is limited by the number of cross-links provided by amino-containing units of a PVCL-co-NH2 copolymer. For two-component capsules with the same degree of cross-linking, permeability at the minimum swelling pH was decreased for PMAA-neutral copolymer capsules as compared to those of PAA-neutral copolymer. We also demonstrate that swelling pH of one-component capsules in the acidic region can be modulated via reversible association with a polycation. The fine control over the swelling pH transitions and permeability of hydrogel capsules enables their use in biomedical applications.