Preparation of Monodisperse Calcium Alginate Micro-/Nanospheres via Shirasu Porous Glass Membrane Emulsification Followed by Classification Using Microfiltration Membranes

Polymeric microcarriers for minimally-invasive cell delivery

Tissue engineering (TE) aims at restoring tissue defects by applying the three-dimensional (3D) biomimetic pre-formed scaffolds to restore, maintain, and enhance tissue growth. Broadly speaking, this approach has created a potential impact in anticipating organ-building, which could reduce the need for organ replacement therapy. However, the implantation of such cell-laden biomimetic constructs based on substantial open surgeries often results in severe inflammatory reactions at the incision site, leading to the generation of a harsh adverse environment where cell survival is low. To overcome such limitations, micro-sized injectable modularized units based on various biofabrication approaches as ideal delivery vehicles for cells and various growth factors have garnered compelling interest owing to their minimally-invasive nature, ease of packing cells, and improved cell retention efficacy. Several advancements have been made in fabricating various 3D biomimetic microscale carriers for cell delivery applications. In this review, we explicitly discuss the progress of the microscale cell carriers that potentially pushed the borders of TE, highlighting their design, ability to deliver cells and substantial tissue growth in situ and in vivo from different viewpoints of materials chemistry and biology. Finally, we summarize the perspectives highlighting current challenges and expanding opportunities of these innovative carriers.

Characterization of Sodium Alginate-Locust Bean Gum Films Reinforced with Daphnetin Emulsions for the Development of Active Packaging

In this study, we characterized an active film made of sodium alginate (SA)—locust bean gum (LBG) containing daphnetin-based film. Physicochemical characteristics, as well as antioxidant and antibacterial properties, were investigated. The results showed that the addition of a low concentration of daphnetin increased the flexibility of SA–LBG cling film, leading to an improvement in elongation at break and tensile strength. As the daphnetin content increased, solubility, brightness and transparency of the cling film decreased, and the moisture permeability increased. The antioxidant capacity and antibacterial activity of films with daphnetin were improved compared to those of the basal film. In addition, the cling film formed by adsorption had higher bacterial (Shewanella putrefaciens and Pseudomonas fluorescens) inhibition and antioxidant activity rates than direct film formation. The results indicate that the combination of daphnetin in SA–LBG film provides an active film with antioxidant and antibacterial properties, with potential for the development of food-grade packaging material.

Sub-100-micron calcium-alginate microspheres: Preparation by nitrogen flow focusing, dependence of spherical shape on gas streams and a drug carrier using acetaminophen as a model drug

We developed a miniature gas-liquid coaxial flow device using glass capillaries, aiming to produce sub-100-μm Ca-alginate microspheres. Depending on collecting distance and the flow rates of nitrogen gas and alginate solution, however, Ca-alginate microparticles of different shapes were obtained. Spherical, monodisperse microparticles (microspheres) could only be obtained at certain gas flow rates and within a corresponding range of collecting distance. The result suggests that, for particles of this size, the gas flow rate and collecting distance are crucial for the formation of the spherical shape. We evaluated, as an example of its applications, the microsphere as a drug carrier using acetaminophen as a model drug. Large (~150 μm) and small (~70 μm) drug-loaded microspheres were prepared using two respective devices. Specifically, the drug-loaded microspheres were complexed with chitosan of different molecular weights. The dependence of in vitro drug release on the microsphere size and the chitosan molecular weight was examined. CHEMICAL COMPOUNDS STUDIED IN THIS ARTICLE: Alginic acid sodium salt (PubChem CID: 5102882); Chitosan (PubChem CID: 71853); Calcium chloride (PubChem CID: 5284359); Sodium chloride (PubChem CID: 5234); Acetaminophen (PubChem CID: 1983); Polydimethylsiloxane (PubChem CID: 24771); n-Octadecyltrimethoxysilane (PubChem CID: 76486).

Aqueous Two-Phase System Formation in Small Droplets by Shirasu Porous Glass Membrane Emulsification Followed by Water Extraction

By utilizing water transport phenomena between two different water-in-oil (W/O) emulsion droplets through continuous oil phase, we developed a novel method of aqueous two-phase system (ATPS) formation in small droplets prepared by Shirasu porous glass (SPG) membrane emulsification technique. When we mixed W/O emulsion droplets containing poly(ethylene glycol) (PEG) and dextran (DEX) at concentrations below the threshold of the phase separation, with droplets containing other solutes at high concentrations, water extraction from the droplets containing PEG and DEX to those containing the other solutes occurred, owing to the osmotic pressure difference. This effect increased the concentrations of PEG and DEX in the droplets above the phase separation threshold. We demonstrated the feasibility of the preparation method by varying the pore sizes of the SPG membranes, the solutes, and their concentrations. Only when the concentration of the solute was high enough to extract sufficient amounts of water did the homogeneous disperse phase consisting of PEG and DEX in droplets turn into a PEG-rich phase and DEX-rich phase, showing ATPS. This result was irrespective of the solute itself and pore size of the SPG membrane. In particular, we successfully demonstrated monodisperse ATPS droplets with diameters of approximately 10 μm under a certain condition.