Sustain release of loaded insulin within biomimetic hydrogel microsphere for sciatic tissue engineering in vivo.

We developed insulin loaded biomimetic microsphere by laccase-mediated crosslinking using a microfluidic device in the water-in-oil emulsion system as an injectable vehicle for the repair of sciatic tissue. Aqueous polymeric solution of phenol-substituted hyaluronic acid (HAPh) and collagen (ColPh) containing insulin and laccase flowed from the inner channel into oil flow within an outer channel which leads formation of hydrogel microsphere. The physical properties of prepared specimens including swelling rate, mechanical resistance and the prolonged release rate of microspheres proved applicability of fabricated vehicles for tissue engineering and drug delivery systems. The growth profile and behavior of cells in microspheres indicated cytocompatibility of the method and prepared vehicles for microtissue development. Histopathological examination revealed a significant increase in axonal regeneration, and remyelination process in injured sciatic nerve following treatment with HAPh/ColPh microspheres containing insulin compared to control groups. Also, the functional characteristic of sciatic tissue showed that the presence of biomimetic microsphere and insulin simultaneously had improved sciatic tissue functions including functional sciatic index (SFI) values, reaction to hot plate and muscle weight of rats. In summary, the results proved that composite biomimetic microspheres containing insulin effectively improved nerve regeneration in the rat model.

Cell encapsulation in core-shell microcapsules through coaxial electrospinning system and horseradish peroxidase-catalyzed crosslinking.

Cellular growth of enclosed cells in core-shell microcapsules is a key element for the practical use of the device in tissue engineering and biopharmaceutical fields. We developed alginate derivative microcapsules with a liquid core template by horseradish peroxidase crosslinking using an integrated coaxial microfluidic device by electrospray system. The cells and gelatin solution were extruded from the inner channel of coaxial microfluidic device and alginate possessing phenolic moieties (Alg-Ph) and horseradish peroxidase (HRP) flowed from the outer channel. In open electric filed, concentric drops of the two coaxial fluids broken up into microdrops and sprayed into the gelling bath containing hydrogen peroxide to instantly gel alginate in the shell fluid before the two fluids got mixed or gelatin dispersed in a gelling bath. The core-shell structure of about 350 µm in diameter and gel membrane of 42 µm was developed by optimization of operational parameters including electrical voltage, flow rate and concentration of polymers. The physical properties of microcapsules including swelling and mechanical resistance proved the applicability of fabricated vehicles for cell culture systems in vitro and in vivo. The viability of enclosed fibroblast cells in generated core-shell microcapsule was more than 90% which is sufficiently high compared with it before encapsulation. The growth profile and behavior of cells in microcapsules showed appropriate cell growth and the possibility of fabrication of spherical tissue was confirmed through degradation of hydrogel membrane. These results validate the significant potential of coaxial electrospray system and HRP-mediated hydrogelation in the fabrication of cell-laden core-shell microcapsule for tissue engineering and regenerative medicine.