A major challenge in tissue engineering is to develop robust protocols for differentiating ES and iPS cells to functional adult tissues at a clinically relevant scale. The goal of this study is to develop a high throughput platform for generating bioactive, stem cell-laden microgels to direct differentiation in a well-defined microenvironment. We describe a droplet microfluidics system for fabricating microgels composed of polyethylene glycol and heparin, with tunable geometric, mechanical, and chemical properties, at kHz rates. Heparin-containing hydrogel particles sequestered growth factors Nodal and FGF-2, which are implicated in specifying pluripotent cells to definitive endoderm. Mouse ESCs were encapsulated into heparin microgels with a single dose of Nodal and FGF-2, and expressed high levels of endoderm markers Sox17 and FoxA2 after 5 days. These results highlight the use of microencapsulation for tailoring the stem cell microenvironment to promote directed differentiation, and may provide a straightforward path to large scale bioprocessing in the future.

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Introdution: Wound healing is a complex and dynamic process, which requires to be prepared a suitable environment to promote healing process. Wound dressing is one of the most important external factors affecting the wound healing process. With the advancement in technology, more than 1000 types of modern wound dressings have been developed. Wound dressings are either based on natural materials or on the basis of synthetic and chemical materials. In addition to the protective and covering role, which modern wound dressings play, they have a chemical and physical interaction with wound bed addition. They carry antibiotics, drugs and nanoparticles and play an important role in maintaining moisture or hydration the wound; all of these factors can facilitate the wound healing process. In this study, the wound healing process and the properties of wound dressings were presented first and then the types of wound dressings and their applications were investigated. This study, with comprehensive information on the types of modern wound dressings and their advantages and drawbacks, will help a physician in the proper selection of an appropriate wound dressing.