Porous microcapsule formation with microsieve emulsification

Engineering Synthetic Erythrocytes as Next-Generation Blood Substitutes

Blood scarcity is one of the main causes of healthcare disruptions worldwide, with blood shortages occurring at an alarming rate. Over the last decades, blood substitutes has aimed at reinforcing the supply of blood, with several products (e.g., hemoglobin-based oxygen carriers, perfluorocarbons) achieving a limited degree of success. Regardless, there is still no widespread solution to this problem due to persistent challenges in product safety and scalability. In this Review, we describe different advances in the field of blood substitution, particularly in the development of artificial red blood cells, otherwise known as engineered erythrocytes. We categorize the different strategies into natural, synthetic, or hybrid approaches, and discuss their potential in terms of safety and scalability. We identify synthetic engineered erythrocytes as the most powerful approach, and describe erythrocytes from a materials engineering perspective. We review their biological structure and function, as well as explore different methods of assembling a material-based cell. Specifically, we discuss how to recreate size, shape, and deformability through particle fabrication, and how to recreate the functional machinery through synthetic biology and nanotechnology. We conclude by describing the versatile nature of synthetic erythrocytes in medicine and pharmaceuticals and propose specific directions for the field of erythrocyte engineering.

One-step emulsification for controllable preparation of ethyl cellulose microcapsules and their sustained release performance

A simple and versatile strategy for controlled production of monodisperse ethyl cellulose (EC) microcapsules by a single-stage emulsification method has been developed. Monodisperse oil-in-water emulsions, obtained by a microfluidic device, are used as templates for preparing EC microcapsules. Oil-soluble ethyl acetate (EA) is miscible with water, so the interfacial mass transfer between EA and water occurs sufficiently, which leads to water molecules pass through the phase interface and diffuse into emulsion interior. Water molecules aggregate at the interface, and some merge into a large water drop in the central position of the emulsion. After evaporation of EA solvent, monodisperse EC microcapsules create large numbers of pits on the surface with a hollow structure. Curcumin is used as a model drug and embedded in the hollow structure. EC microcapsules have good, sustained drug release efficacy in a simulated intestinal environment, and the release process of EC microcapsules containing 6.14% drug-loaded capacity is fully consistent with the vitro drug release model. Such simple techniques for making EC microcapsules may open a window to the controlled preparation of other multifunctional microcapsules. Besides, it offers theoretical guidance for the study of EC microcapsules as drug carriers and expanding clinical application of curcumin.

Facile fabrication of shell crosslinked microcapsule by visible light induced graft polymerization for enzyme encapsulation

A strategy to encapsulate enzymes into microcapsule fabricated by visible light-induced graft polymerization using CaCO₃microparticles as template was developed.

Facile fabrication of tea tree oil-loaded antibacterial microcapsules by complex coacervation of sodium alginate/quaternary ammonium salt of chitosan

In this study, flavoured tea tree oil (TTO)-loaded antibacterial microcapsules were developed based on the complex coacervation of sodium alginate (SA) and a quaternary ammonium salt of chitosan (HACC).

Structured microparticles with tailored properties produced by membrane emulsification

This paper provides an overview of membrane emulsification routes for fabrication of structured microparticles with tailored properties for specific applications. Direct (bottom-up) and premix (top-down) membrane emulsification processes are discussed including operational, formulation and membrane factors that control the droplet size and droplet generation regimes. A special emphasis was put on different methods of controlled shear generation on membrane surface, such as cross flow on the membrane surface, swirl flow, forward and backward flow pulsations in the continuous phase and membrane oscillations and rotations. Droplets produced by membrane emulsification can be used for synthesis of particles with versatile morphology (solid and hollow, matrix and core/shell, spherical and non-spherical, porous and coherent, composite and homogeneous), which can be surface functionalised and coated or loaded with macromolecules, nanoparticles, quantum dots, drugs, phase change materials and high molecular weight gases to achieve controlled/targeted drug release and impart special optical, chemical, electrical, acoustic, thermal and magnetic properties. The template emulsions including metal-in-oil, solid-in-oil-in-water, oil-in-oil, multilayer, and Pickering emulsions can be produced with high encapsulation efficiency of encapsulated materials and narrow size distribution and transformed into structured particles using a variety of solidification processes, such as polymerisation (suspension, mini-emulsion, interfacial and in-situ), ionic gelation, chemical crosslinking, melt solidification, internal phase separation, layer-by-layer electrostatic deposition, particle self-assembly, complex coacervation, spray drying, sol-gel processing, and molecular imprinting. Particles fabricated from droplets produced by membrane emulsification include nanoclusters, colloidosomes, carbon aerogel particles, nanoshells, polymeric (molecularly imprinted, hypercrosslinked, Janus and core/shell) particles, solder metal powders and inorganic particles. Membrane emulsification devices operate under constant temperature due to low shear rates on the membrane surface, which range from (1-10)×10(3) s(-1) in a direct process to (1-10)×10(4) s(-1) in a premix process.

Advances in membrane emulsification. Part A: recent developments in processing aspects and microstructural design approaches

Modern emulsion processing technology is strongly influenced by the market demands for products that are microstructure-driven and possess precisely controlled properties. Novel cost-effective processing techniques, such as membrane emulsification, have been explored and customised in the search for better control over the microstructure, and subsequently the quality of the final product. Part A of this review reports on the state of the art in membrane emulsification techniques, focusing on novel membrane materials and proof of concept experimental set-ups. Engineering advantages and limitations of a range of membrane techniques are critically discussed and linked to a variety of simple and complex structures (e.g. foams, particulates, liposomes etc.) produced specifically using those techniques.

Porous polymer membranes via selectively wetted surfaces

Here, we show that porous polymeric membranes can be prepared using the principles of offset printing: an offset printing plate is structured into hydrophobic and hydrophilic regions with the help of photolithography and is selectively wetted with a solution of calcium chloride in water at the hydrophilic regions. Then, a polymer solution (poly(methyl methacrylate) in chloroform) is applied to this surface and forms a hydrophobic layer that is structured by the aqueous droplets. Deviating from standard offset printing, this layer is not transferred to another surface in its liquid state but is solidified and subsequently is separated from the printing plate. The thickness of the polymer film is chosen in such a way that the aqueous droplets on the surface protrude from the film. Thus, we obtain polymer membranes with pores in the size of the protruding aqueous droplets. These membranes are then characterized by the filtration of model dispersions.

Microcapsules with a pH responsive polymer: influence of the encapsulated oil on the capsule morphology

Microcapsules were prepared by microsieve membrane cross flow emulsification of Eudragit FS 30D/dichloromethane/edible oil mixtures in water, and subsequent phase separation induced by extraction of the dichloromethane through an aqueous phase. For long-chain triglycerides and jojoba oil, core-shell particles were obtained with the oil as core, surrounded by a shell of Eudragit. Medium chain triglyceride (MCT oil) was encapsulated as relatively small droplets in the Eudragit matrix. The morphology of the formed capsules was investigated with optical and SEM microscopy. Extraction of the oil from the core-shell capsules with hexane resulted in hollow Eudragit capsules with porous shells. It was shown that the differences are related to the compatibility of the oils with the shell-forming Eudragit. An oil with poor compatibility yields microcapsules with a dense Eudragit shell on a single oil droplet as the core; oils having better compatibility yield porous Eudragit spheres with several oil droplets trapped inside.