ABSTRACT
Nano hydroxyapatite (nHAp), a main component of the inorganic composition of human bones and teeth, is widely used in bone tissue engineering, bone defect repair and replacement, for example, for its biocompatibility, bioactivity, bioaffinity and the ability to induce bone regeneration. Nano hydroxyapatite contains calcium and phosphorus, elements that can be replaced through the normal metabolic channels of the human body. Therefore, after implantation, it can be partially or completely absorbed and replaced by human tissues and can effectively assist bone regeneration, which makes it an ideal material for bone repair. However, traditional nHAp material is brittle and hard to be degraded in human body. In addition, nHAp has poor stability due to its high surface energy and tendency for agglomeration, which causes rapid attenuation of its mechanical strength and limits its clinical application. At present, the mechanical properties and biocompatibility of nHAp can be effectively improved by loading the related growth factors, proteins, peptides and other bioactive molecules, so as to better meet the biological requirements of bone repair materials. However, the traditional physicochemical modification methods are complicated and may interfere with the bioactivity of nHAp. It is simple to biomimetically synthesize nanomaterials by direct utilization of the molecular recognition and self-assemble capabilities of biomolecules or living microorganisms. Furthermore, the properties of the synthesized nanomaterials are stable, and the method has been extensively studied in recent years. Due to the unique crystaline structure and physicochemical properties of nHAp, results of a large number of studies have shown that its affinity with biological molecules can be used to produce bioactive nHAp by biomimetic synthesis methods. Biomimetically synthesized nHAp is expected to become the mainstream bone tissue engineering scaffold material. Analyzing and summarizing the biomimetic synthetic process and the characteristics of different nHAp materials will facilitate further development of bone defect repair materials with better mechanical and biological properties. Herein we reviewed methods of biomimetic synthesis of nHAp based on different biomolecular templates. Furthermore, we also discussed applications of biomimetic synthesized nHAp in bone tissue engineering, which can used as reference information for further research and development of new-generation bone repair biomaterials.
Subject(s)
Durapatite , Tissue Engineering , Biomimetics , Bone and Bones , Humans , Tissue ScaffoldsABSTRACT
Nitrogen dioxide (NO2) detection is of great importance because the emission of NO2 gas profoundly endangers the natural environment and human health. However, a few challenges, including lowering detection limit, improving response/recovery kinetics, and reducing working temperature, should be further addressed before practical applications. Herein, a series of N-doped graphene quantum dot (N-GQD)-modified three-dimensional ordered macroporous (3DOM) In2O3 composites are constructed and their NO2 response properties are studied. The results show that compared to pure 3DOM In2O3, reduced graphene oxide (rGO)/3DOM In2O3, and N-doped graphene sheets (NS)/3DOM In2O3, the N-GQDs/3DOM In2O3 sensing materials exhibit higher NO2 responses with fast response and recovery speed and low working temperature (100 °C). In addition, the detection limit of NO2 response for the optimal N-GQDs/In2O3 sensor is as low as 100 ppb. Upon exposure to CO, CH4, NH3, acetone, ethanol, toluene, and formaldehyde, only very weak responses could be observed, indicating good selectivity for the synthesized material. More attractively, the responses of the optimized N-GQDs/In2O3 sensor exhibit no obviously big fluctuation over 60 days, implying good long-term stability. We suggest that the formation of heterojunctions between 3DOM In2O3 and N-GQDs and the doping N atoms in N-GQDs play crucial roles in improving the NO2 sensing properties.
