Encapsulation of rat bone marrow stromal cells using a poly-ion complex gel of chitosan and succinylated poly(Pro-Hyp-Gly)

Advancements in Three Dimensional In-Vitro Cell Culture Models

The scientific field is observing a gradual shift from monolayer cultures to three-dimensional (3D) models, as they give a more relevant data in pre-clinical stages. This review summarizes the major techniques and materials used to develop 3D platforms, especially for cancer. It also discusses the challenges and some unresolved issues of the field and highlights some techniques that have made it to the market.

Effect of chitosan addition on the properties of low-density polyethylene blend as potential bioplastic

Plastics based on low-density polyethylene (LDPE) blends generally have limited miscibility, and it is difficult to obtain a homogeneous blend. Although they show excellent properties, their thermal degradation rate is a concern. This work aims to realize a homogeneous blend with higher chitosan concentration, thus expected to increase its degradation properties. An extrusion technique successfully synthesized LDPE and chitosan blends. The mixtures were prepared by adding maleic anhydride (MA) and tert-butyl peroxybenzoate (TBPB) as a compatibilizer and initiator, respectively. The addition of MA and TBPB resulted in homogeneous blends and using chitosan concentration of 40 %wt resulted in better tensile strength and elongation at break. The water uptake increased along with chitosan concentration in the blends. The thermal behavior analysis of the blends conducted by simultaneous TG/DTA revealed that the increase of chitosan concentration tends to improve the blend's thermal degradation slightly. Moreover, chitosan addition resulted in approximately a hundred times larger biodegradability compared to plastics based on LDPE alone.

Optical control of cell differentiation on synthetic collagen-like scaffolds

We have developed biocompatible scaffolds that enable cell fate control with visible light. The scaffolds are based on synthetic collagen-like polypeptide, poly(prolyl-hydroxyprolyl-glycyl) {poly(Pro-Hyp-Gly)} which has been used for cosmetics and other healthcare applications. Bioactive peptides were conjugated to the scaffolds via photoactivation reaction utilizing 488 nm visible light. In addition, the use of a photocleavable crosslinker enables dissociation of chemical moieties by 405 nm laser irradiation. The synthesis scheme enables optical control to attach and detach functional peptides in pre-patterned shapes. Using bone forming peptide (BFP), we demonstrate that calcium deposition by rat bone stromal cells can be directed on the scaffold. Using other signaling molecules and three-dimensional scaffolds, controlled differentiation of stem cells can be achieved by spatio-temporally specific irradiation of confocal microscope laser.

Cell-Surface Engineering for Advanced Cell Therapy

Stem cells opened great opportunity to overcome diseases that conventional therapy had only limited success. Use of scaffolds made from biomaterials not only helps handling of stem cells for delivery or transplantation but also supports enhanced cell survival. Likewise, cell encapsulation can provide stability for living animal cells even in a state of separateness. Although various chemical reactions were tried to encapsulate stolid microbial cells such as yeasts, a culture environment for the growth of animal cells allows only highly biocompatible reactions. Therefore, the animal cells were mostly encapsulated in hydrogels, which resulted in enhanced cell survival. Interestingly, major findings of chemistry on biological interfaces demonstrate that cell encapsulation in hydrogels have a further a competence for modulating cell characteristics that can go beyond just enhancing the cell survival. In this review, we present a comprehensive overview on the chemical reactions applied to hydrogel-based cell encapsulation and their effects on the characteristics and behavior of living animal cells.

Cytocompatible polyion complex gel of poly(Pro-Hyp-Gly) for simultaneous rat bone marrow stromal cell encapsulation

Polyion complex (PIC) gel of poly(Pro-Hyp-Gly) was successfully fabricated by simply mixing polyanion and polycation derivatives of poly(Pro-Hyp-Gly), a collagen-like polypeptide. The polyanion, succinylated poly(Pro-Hyp-Gly), and the polycation, arginylated poly(Pro-Hyp-Gly), contain carboxy (pK_a = 5.2) and guanidinium (pK_a = 12.4) groups, respectively. Mixing the polyanion and the polycation at physiological pH (pH = 7.4) resulted in PIC gel. The hydrogel formation was optimum at an equimolar ratio of carboxy to guanidinium groups, suggesting that ionic interaction is the main determinant for the hydrogel formation. The hydrogel was successfully used for simultaneous rat bone marrow stromal cell encapsulation. The encapsulated cells survived and proliferated within the hydrogel. In addition, the cells exhibited different morphology in the hydrogel compared with cells cultured on a tissue culture dish as a two-dimensional (2D) control. At day one, a round morphology and homogeneous single cell distribution were observed in the hydrogel. In contrast, the cells spread and formed a fibroblast-like morphology on the 2D control. After three days, the cells in the hydrogel maintained their morphology and some of them formed multicellular aggregates, which is similar to cell morphology in an in vivo microenvironment. These results suggest that the PIC gel of poly(Pro-Hyp-Gly) can serve as a cytocompatible three-dimensional scaffold for stem cell encapsulation, supporting their viability, proliferation, and in vivo-like behavior.