Alginate-chitosan core-shell microcapsule cultures of hepatic cells in a small scale stirred bioreactor: impact of shear forces and microcapsule core composition

Fabrication of alginate-based hydrogel microparticle via ruthenium-catalyzed photocrosslinking

In this study, we developed an alginate-based microparticle production process via sodium ruthenium(II) tris-bipyridyl dication (Ru)/ammonium persulfate (SPS)-mediated visible light crosslinking system using a microfluidic device. Microparticles were prepared by crosslinking phenolic-substituted alginate (AlgPh) and incorporated gelatin (GelPh) in an aqueous solution containing SPS, which flowed into an ambient immiscible liquid paraffin-containing Ru using coaxial double orifice microfluidic device. The hydrogel microparticles appeared with the desired geometries and dimensions under optimal conditions. The concentration of AlgPh and light intensity were the most critical parameters for harvesting spherical microparticles with homogeneous size distribution. The physical properties of the prepared AlgPh microparticles were characterized and compared with Alg-Ca microparticles. Cell viability and proliferation preserved on AlgPh/GelPh hydrogel surfaces. Also, encapsulated cells in microparticles were also viable and proliferated well over 13 days after encapsulation. In brief, the results proved the feasibility of fabricating AlgPh vehicles via Ru/SPS-mediated system and visible light irradiation as a simple and efficient three-dimensional platform, which are applicable for various tissue engineering and cell delivery purposes.

Sustain release of dexamethasone from polyvinyl alcohol microparticle produced via coaxial microfluidic system

OBJECTIVE

Polyvinyl alcohol (PVA) as a synthetic biopolymer has unique physicochemical properties to achieve an efficient drug carrier. In this study phenol-substituted polyvinyl alcohol (PVAPh) microparticle was made through a microfluidic system and peroxidase-mediated reaction in the presence of hydrogen peroxide and in following dexamethasone (Dex) release characteristics from this vehicle were elaborated for sustained drug delivery applications.

RESULTS

PVAPh was synthesized by esterification and amidation reactions respectively. Then, the synthesized PVAPh solution containing peroxidase and Dex flowed within the inner channel of the coaxial microfluidic device while liquid paraffin saturated with H2O2 flowed from the outer channel. The monodisperse microparticles were produced in a spherical shape with an average diameter of 160 μm. The Dex was successfully encapsulated in PVAPh MP and its sustained release profile was maintained for up to 7 days. It was found that exposure of Dex-loaded PVAPh MPs to subcultured mouse embryonic fibroblast 10T1/2 cells had no deleterious effects on cell viability, morphology and growth rate. Moreover, the sustained release of Dex and the high mechanical durability of PVAPh MPs suggest an excellent prospect for the synthesized PVAPh and the developed method as a biocompatible carrier required for drug delivery and regenerative medicine.

Influence of shear force on ex vivo expansion of hematopoietic model cells in a stirred tank bioreactor

To evaluate shear stress influence on ex vivo expansion of hematopoietic cell lineages for clinical application, in this study, human pro-monocytic cell (namely U937 cell line) was selected as a hematopoietic stem cell (HSC) model and cultured in suspension mode at two different agitation rates (50, 100 rpm) in the stirred bioreactor. At the agitation rate of 50 rpm, the cells achieved higher expansion folds (27.4 fold) with minimal morphological changes as well as apoptotic cell death, while at 100 rpm the expansion fold decreased after 5-day of culture in suspension culture in comparison with static culture and reached 24.5 fold at the end of the culture. The results of glucose consumption and lactate production were also in agreement with the data of fold expansion and indicated the preference of culture in the stirred bioreactor when agitated at 50 rpm. This study indicated the stirred bioreactor system with an agitation rate of 50 rpm and surface aeration may be used as a potential dynamic culture system for clinical applications of hematopoietic cell lineage. The current experiments shed data related to the effect of shear stress on human U937 cells, as a hematopoietic cell model, to set a protocol for expansion of HSCs for biomedical applications.

Synthesis, optimization, and cell response investigations of natural-based, thermoresponsive, injectable hydrogel: An attitude for 3D hepatocyte encapsulation and cell therapy

For the purpose of developing a 3D vehicle for the delivery of hepatocytes in cell therapy, the improved system of crosslinker and new gelling agent combinations consisting of glycerophosphate and sodium hydrogen carbonate have been employed to produce injectable, thermoresponsive hydrogels based on chitosan and silk fibroin. Adjusting the polymer-to-gelling agent ratio and utilizing a chemical crosslinker developed hydrogel scaffolds with optimal gelling time and pH. Applying sodium hydrogen carbonate neutralizes chitosan while keeping its thermoresponsive characteristics and decreases glycerophosphate from 60% to 30%. Genipin boosts the mechanical properties of hydrogel without affecting the gel time. Due to their stable microstructure and lower amine availability, genipin-containing materials have a low swelling ratio, around six compared to eight for those without genipin. Hydrogels that are crosslinked degrade about half as fast as those that are not. The slowerr degradation of Silk fibroin compared to chitosan makes it an efficient degradation inhibitor in silk-containing formulations. All of the optimized samples showed less than 5% hemolytic activity, indicating that they lacked hemolytic characteristics. The acceptable cell viability in crosslinked hydrogels ranges from 72% to 91% due to the decreasing total salt concentration, which protects cells from hyperosmolality. The pH of hydrogels and their interstitial pores kept most encapsulated cells alive and functioning for 24 h. Urea levels are higher in the encapsulation condition compared to HepG2 cultivated alone, and this may be due to cell-matrix interactions that boost liver-specific activity. Urea synthesis in genipin crosslinked hydrogels increased dramatically from day 1 (about 4 mg dl^-1) to day 3 (approximately 6 mg dl^-1), suggesting the enormous potential of these hydrogels for cell milieu preparation. All mentioned findings represent that the optimized system may be a promising candidate for liver regeneration.

Current strategies with implementation of three-dimensional cell culture: the challenge of quantification

From growing cells in spheroids to arranging them on complex engineered scaffolds, three-dimensional cell culture protocols are rapidly expanding and diversifying. While these systems may often improve the physiological relevance of cell culture models, they come with technical challenges, as many of the analytical methods used to characterize traditional two-dimensional (2D) cells must be modified or replaced to be effective. Here we review the advantages and limitations of quantification methods based either on biochemical measurements or microscopy imaging. We focus on the most basic of parameters that one may want to measure, the number of cells. Precise determination of this number is essential for many analytical techniques where measured quantities are only meaningful when normalized to the number of cells (e.g. cytochrome p450 enzyme activity). Thus, accurate measurement of cell number is often a prerequisite to allowing comparisons across different conditions (culturing conditions or drug and treatment screening) or between cells in different spatial states. We note that this issue is often neglected in the literature with little or no information given regarding how normalization was performed, we highlight the pitfalls and complications of quantification and call for more accurate reporting to improve reproducibility.

Design considerations of benchtop fluid flow bioreactors for bio-engineered tissue equivalents in vitro

One of the major aims of bio-engineering tissue equivalents in vitro is to create physiologically relevant culture conditions to accurately recreate the cellular microenvironment. This often includes incorporation of factors such as the extracellular matrix, co-culture of multiple cell types and three-dimensional culture techniques. These advanced techniques can recapitulate some of the properties of tissue in vivo, however fluid flow is a key aspect that is often absent. Fluid flow can be introduced into cell and tissue culture using bioreactors, which are becoming increasingly common as we seek to produce increasingly accurate tissue models. Bespoke technology is continuously being developed to tailor systems for specific applications and to allow compatibility with a range of culture techniques. For effective perfusion of a tissue culture many parameters can be controlled, ranging from impacts of the fluid flow such as increased shear stress and mass transport, to potentially unwanted side effects such as temperature fluctuations. A thorough understanding of these properties and their implications on the culture model can aid with a more accurate interpretation of results. Improved and more complete characterisation of bioreactor properties will also lead to greater accuracy when reporting culture conditions in protocols, aiding experimental reproducibility, and allowing more precise comparison of results between different systems. In this review we provide an analysis of the different factors involved in the development of benchtop flow bioreactors and their potential biological impacts across a range of applications.

Influence of Technological Factors on the Quality of Chitosan Microcapsules with Boswellia serata L. Essential Oil

Essential oils contain many volatile compounds that are not stable and lose their pharmacological effect when exposed to the environment. The aim of this study is to protect Boswellia serrata L. essential oil from environmental factors by encapsulation and determine the influence of chitosan concentration and types (2%, 4%; medium and high molecular weights), essential oil concentration, different emulsifiers (Tween and Span), and technological factors (stirring time, launch height, drip rate) on the physical parameters, morphology, texture, and other parameters of the generated gels, emulsions, and microcapsules. For the first time, Boswellia serrata L. essential oil microcapsules with chitosan were prepared by coacervation. Hardness, consistency, stickiness, viscosity, and pH of chitosan gels were tested. Freshly obtained microcapsules were examined for moisture, hardness, resistance to compression, size, and morphology. Results show that different molecular weights and concentrations of chitosan affected gel hardness, consistency, stickiness, viscosity, mobility, and adhesion. An increase in chitosan concentration from 2% to 4% significantly changed the appearance of the microcapsules. It was found that spherical microcapsules were formed when using MMW and HMW 80/1000 chitosan. Chitosan molecular weight, concentration, essential oil concentration, and stirring time all had an impact on the hardness of the microcapsules and their resistance to compression.

Effect of Shellac Waterborne Coating Microcapsules on the Optical, Mechanical and Self-Healing Properties of Waterborne Primer on Tilia europaea L. Wood

Microcapsules of melamine formaldehyde-coated shellac and waterborne coating were prepared by in situ polymerization at 400, 600, 800 and 1000 rpm. The microcapsules prepared at four different stirring rates were added into the waterborne primer at a concentration of 5.0%, 10.0%, 15.0%, 20.0% and 25.0%. The effects of microcapsules prepared at different stirring rates and the concentration of microcapsules added into the paint film on the optical, mechanical and liquid resistance properties of the paint film were investigated. The results showed that the comprehensive performance of Tilia europaea L. waterborne primer film was the best when the concentration of microcapsules obtained at 600 rpm was 5.0%. On this basis, the aging resistance and self-healing performance of waterborne primer film on Tilia europaea L. with the best comprehensive performance were explored to lay the foundation for optimizing the preparation process of self-healing coating.