Bo Yu

It has been stated clearly that nanofillers could make an enhancement on the mechanical performances of dental composites. In order to address current shortage of traditional dental composites, fillers in forms of nanofibers or nanotubes are broadly regarded as ideal candidates to greatly increase mechanical performances of dental composites with low content of fillers. In this review, the efforts using nanofibers and nanotubes to reinforce mechanical performances of dental composites, including polymeric nanofibers, metallic nanofibers or nanotubes, and inorganic nanofibers or nanotubes, as well as their researches related, are demonstrated in sequence. The first purpose of current paper was to confirm the enhancement of nanofibers or nanotubes’ reinforcement on the mechanical performances of dental restorative composite. The second purpose was to make a general description about the reinforcement mechanism of nanofibers and nanotubes, especially, the impact of formation of interphase boundary interaction and nanofibers themselves on the advanced mechanical behaviors of the dental composites. By means of the formation of interface interaction and poststretching nanofibers, reinforced effect of dental composites by sorts of nanofibers/nanotubes has been successfully obtained.

Nanofibers and nanotubes have recently gained substantial interest for potential applications in tissue engineering due to their large ratio of surface area to volume and unique microstructure. It has been well proved that the mechanical property of matrix could be largely enhanced by the addition of nanoscaled fibers or tubes. At present, more and more researches have shown that the biocompatibility and bioactivity of biomedical materials could be improved by the addition of nanofibers or nanotubes. In this review, the efforts using nanofibers and nanotubes to improve biocompatibility and bioactivity of biomedical materials, including polymeric nanofibers/nanotubes, metallic nanofibers/nanotubes, and inorganic nanofibers/nanotubes, as well as their researches related, are demonstrated in sequence. Furthermore, the possible mechanism of improving biocompatibility and bioactivity of biomedical materials by nanofibers or nanotubes has been speculated to be that the specific protein absorption on the nanoscaled fibers or tubes plays important roles.

Injectable biomaterials, which can be physically inserted into a target site without the use of surgery, have received increasing attention in tissue engineering during the last decade. There is also a growing need for quantitative evaluation of the injectable biomaterial directly and noninvasively. The objectives of this study are to originate a quantitative noninvasive technique for evaluation of in situ forming bone biomaterials and to validate the feasibility of diagnostic ultrasound images analysis technique. The potential of ultrasound for quantitative evaluation of tissue development was compared with computed tomography (CT) in vivo. A strong correlation was witnessed between ultrasound gray‐scale values (GV) and volumetric mean of CT value (HU_m) (r = 0.95). Meanwhile, the volume of the material area could be estimated by ultrasound maximum cross‐section pixel, which demonstrates a certain consistency with CT mask volume in 3D reconstruction images (r = 0.87). In conclusion, ultrasound imaging, which is corresponding with the traditional CT, can be used to evaluate osteogenesis capability and degradation property of injectable biomaterials. It may be a noninvasive, nonradioactive, and effective aid to monitor ossification and reconstruction of biomaterials at the implant region for bone defect repair.

To meet the challenges of designing an in situ forming scaffold and regenerating bone with complex three‐dimensional (3D) structures, an in situ forming hydrogel scaffold based on nano‐hydroxyapatite (nHA), collagen (Col), and chitosan (CS) was synthesized. Currently, only a limited number of techniques are available to mediate and visualize the injection process of the injectable biomaterials directly and noninvasively. In this study, the potential of ultrasound for the quantitative in vivo evaluation of tissue development in CS/nHAC scaffold was evaluated. The CS/nHAC scaffold was injected into rat subcutaneous tissue and evaluated for 28 days. Quantitative measurements of the gray‐scale value, volume, and blood flow of the scaffold were evaluated using diagnostic technique. This study demonstrates that ultrasound can be used to noninvasively and nondestructively monitor and evaluate the in vivo characteristics of injectable bone scaffold. In comparison to the CS, the CS/nHAC scaffold showed a greater stiffness, less degradation rate, and better blood supply in the in vivo evaluation. In conclusion, the diagnostic ultrasound method is a good tool to evaluate the in vivo formation of injectable bone scaffolds and facilitates the broad use to monitor tissue development and remodeling in bone tissue engineering.

The purpose of this study was to evaluate the in vitro cell biocompatibility of an in situ forming composite consisting of chitosan (CS), nano‐hydroxyapatite and collagen (nHAC), which has a complex hierarchical structure similar to natural bone. MC3T3‐E1 mouse calvarial preosteoblasts were cultured on the surface of the injectable CS/nHAC and CS scaffold. The proliferations of seeded MC3T3‐E1 were investigated for 10 days. Cytotoxicity, cell proliferation, and cell expression of osteogenic markers such as alkaline phosphatase (ALP), type 1 collagen (COL‐1), RUNX‐2, and osteocalcin (OCN) were examined by biochemical assay and reverse transcription polymerase chain reaction. Cell viability and total cellularity (measured by dsDNA) were similar between the two scaffold groups. However, ALP, COL‐1, OCN, and RUNX‐2 production were significantly greater when osteoblasts were cultured on CS/nHAC scaffolds. The increase in osteogenic markers production on CS/nHAC scaffolds indicated that these scaffolds were superior to chitosan‐only scaffolds in facilitating osteoblast mineralization. These results demonstrate the potential of the CS/nHAC scaffolds to be used in bone tissue engineering.