Hydroxyapatite (HA) is widely used in bone tissue engineering for its bioactivity and biocompatibility, and a growing number of researchers are exploring ways to improve the physical properties and biological functions of hydroxyapatite. Up to now, HA has been used as inorganic building blocks for tissue engineering or as nanofillers to blend with polymers, furthermore, various methods such as ion doping or surface modification have been also reported to prepare functionalized HA. In this review, we try to give a brief and comprehensive introduction about HA-based materials, including ion-doped HA, HA/polymer composites and surface modified HA and their applications in bone tissue engineering. In addition, the prospective of HA is also discussed. This review may be helpful for researchers to get a general understanding about the development of hydroxyapatite based materials.

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Collagen gel scaffolds can potentially be utilized as cell seeded systems for skin tissue engineering. However, its dramatic contraction after being mixed with cells and its mechanical weakness are the drawbacks for its application to skin engineering. In this study, a compressed collagen gel scaffold was fabricated through the rapid expulsion of liquid from reconstituted gels by the application of 'plastic compression'(PC) technique. Both compressed and uncompressed gels were characterized with their gel contraction rate, morphology, the viability of seeded cells, their mechanical properties and the feasibility as a scaffold for constructing tissue-engineered skin. The results showed that the compression could significantly reduce the contraction of the collagen gel and improve its mechanical property. In addition, seeded dermal fibroblasts survived well in the compressed gel and seeded epidermal cells gradually developed into a stratified epidermal layer, and thus formed tissue engineered skin. This study reveals the potential of using compressed collagen gel as a scaffold for skin engineering.

Myocardial infarction (MI) constitutes the first cause of morbidity and mortality in our life, so using highly conductive and elastic materials to produce an engineered cardiac patch is an effective way to improve the myocardium infarction area function. Here, shape memory polymers of the polyurethane/polyaniline/silicon oxide (PU/PANI/SiO2) electrospinning sub-micron fiber patch were precisely produced in the case of the hydrogen bonding effect and interaction between the carboxyl groups to provide compatibility, phase mixing/miscibility, and stability. The sub-micron fiber patch prepared by our group has some remarkable characteristics, such as sub-micron fibers, 3D porous structure, special thickness to simulate the extracellular matrix (ECM), elastic deformation, good properties in conducting weak electrical signals, stability to maintain the whole structure, and self-adhesion. This sub-micron fiber material has been proven to be effective, easy, and reliable. Through precise design of the material system, structure regulation, and performance optimization, the aim is to produce a sub-micron fiber cardiac patch to simulate the myocardium ECM and improve conductive signal transduction for potential MI therapy.