ZIF-8 induced hydroxyapatite-like crystals enabled superior osteogenic ability of MEW printing PCL scaffolds.

ZIF-8 may experience ion-responsive degradation in ionic solutions, which will change its initial architecture and restrict its direct biological use. Herein, we report an abnormal phenomenon in which ZIF-8 induces large hydroxyapatite-like crystals when soaked directly in simulated body fluid. These crystals grew rapidly continuously for two weeks, with the volume increasing by over 10 folds. According to Zn2+ release and novel XRD diffraction peak presence, ZIF-8 particles can probably show gradual collapse and became congregate through re-nucleation and competitive coordination. The phenomenon could be found on ZIF-8/PCL composite surface and printed ZIF-8/PCL scaffold surface. ZIF-8 enhanced PCL roughness through changing the surface topography, while obviously improving the in-vivo and in-vitro osteoinductivity and biocompatibility. The pro-biomineralization property can make ZIF-8 also applicable in polylactic acid-based biomaterials. In summary, this study demonstrates that ZIF-8 may play the role of a bioactive additive enabling the surface modification of synthetic polymers, indicating that it can be applied in in-situ bone regeneration.

Immunochromatographic fluorometric determination of clenbuterol with enhanced sensitivity.

A method is described to enhance the sensitivity of an immunochromatographic assay for clenbuterol (CLE) by making use of dually-labeled gold nanoparticles (GNPs), background fluorescence blocking, and immunomagnetic separation. The GNPs were labeled with biotinylated antibody and streptavidin, respectively, and dually labeled GNPs were obtained via the biotin-streptavidin interaction to amplify the detection signal. The fluorescent signal was blocked by dually labeled GNPs and decreased as the dually labeled GNPs aggregation increases on nitrocellulose membrane, which derived from fluorescent polyvinylchloride card. However, fluorescence (measured at excitation/emission wavelengths of 518/580 nm) recovers when CLE reacts with dually labeled GNPs. Immunomagnetic separation was first applied for sample pretreatment. This can offset the matrix effect and improves the sensitivity and accuracy of the assay. Under the optimal conditions, the limits of detection of CLE visually were 0.25 µg·L-1. In addition, clenbuterol can be quantified in swine urine with a 0.03 µg·L-1 detection limit. This is 60-fold lower than current immunochromatography. Response is linear in the 0.06-0.59 µg·L-1 concentration range, and the recoveries from spiked swine urine range from 81 to 115%." Graphical abstract Schematic presentation of the strategies for improving sensitivity of immunochromatographic assay. It includes immunomagnetic separations, dually-labeled gold nanoparticles and background fluorescence blocking. The assay was applied to detect clenbuterol (CLE) in swine urine with an excellent performance.

A biocompatible vascularized graphene oxide (GO)-collagen chamber with osteoinductive and anti-fibrosis effects promotes bone regeneration in vivo.

The survival of transplanted cells and tissues in bone regeneration requires a microenvironment with a vibrant vascular network. A tissue engineering chamber can provide this in vivo. However, the commonly used silicone chamber is biologically inert and can cause rejection reactions and fibrous capsule. Studies have revealed that collagen is highly biocompatible and graphene oxide (GO) could regulate osteogenic activity in vivo. Besides, GO can be cross-linked with natural biodegradable polymers to construct scaffolds. Methods: A vascularized GO-collagen chamber model was built by placing vessels traversing through the embedded tissue-engineered grafts (osteogenic-induced bone mesenchymal stem cells -gelatin) in the rat groin area. Osteogenic activity and inflammatory reactions were assessed using different methods including micro-CT scanning, Alizarin red staining, and immunohistochemical staining. Results: After one month, in vivo results showed that bone mineralization and inflammatory responses were significantly pronounced in the silicone model or no chamber (control) groups. Vascular perfusion analysis confirmed that the GO-collagen chamber improved the angiogenic processes. Cells labeled with EdU revealed that the GO-collagen chamber promoted the survival and osteogenic differentiation of bone mesenchymal stem cells. Conclusion: Overall, the novel biocompatible GO-collagen chamber exhibited osteoinductive and anti-fibrosis effects which improved bone regeneration in vivo. It can, therefore, be applied to other fields of regenerative medicine.

Multi-Layered Polyamide/Collagen Scaffolds with Topical Sustained Release of N-Acetylcysteine for Promoting Wound Healing.

BACKGROUND: Impaired wound healing might be associated with many issues, especially overactive of reactive oxygen species (ROS), deficiency of blood vessels and immature of epidermis. N-acetylcysteine (NAC), as an antioxidant, could solve these problems by inhibiting overreactive of ROS, promoting revascularization and accelerating re-epithelialization. How to deliver NAC in situ with a controllable releasing speed still remain a challenge. MATERIALS AND METHODS: In this study, we combined collagen (Col) with N-acetylcysteine to perform the characteristics of sustained release and chemically crosslinked Col/NAC composite with polyamide (PA) nanofibers to enhance the mechanical property of collagen and fabricated this multi-layered scaffold (PA-Col/NAC scaffold). The physical properties of the scaffolds such as surface characteristics, water absorption and tensile modulus were tested. Meanwhile, the ability to promote wound healing in vitro and in vivo were investigated. RESULTS: These scaffolds were porous and performed great water absorption. The PA-Col/NAC scaffold could sustainably release NAC for at least 14 days. After cell implantation, PA-Col/NAC scaffold showed better cell proliferation and cell migration than the other groups. In vivo, PA-Col/NAC scaffolds could promote wound healing best among all the groups. CONCLUSION: The multi-layered scaffolds could obviously accelerate the process of wound healing and exert better and prolonged effects.

Self-Assembled Human Adipose-Derived Stem Cell-Derived Extracellular Vesicle-Functionalized Biotin-Doped Polypyrrole Titanium with Long-Term Stability and Potential Osteoinductive Ability.

Mesenchymal stem cell-derived extracellular vesicles (MSC-EVs), containing proteins or microRNAs (miRNAs), possessing various biological activity and low immunogenicity, are considered promising for surface modification of bone grafts. However, the modification efficiency is not satisfied yet, resulting in compromised therapy effects. Here, we report a novel immobilized method by self-assembling biotinylated MSC-EVs onto the surface of biotin-doped polypyrrole titanium (Bio-Ppy-Ti) to improve its biofunctions in vitro and in vivo. Using this method, the amount of human adipose-derived stem cell-EVs (hASC-EVs) anchored onto the Bio-Ppy-Ti surface was 185-fold higher than that of pure Ti after ultrasonic concussion for 30 s and it remained stable on the Bio-Ppy-Ti surface for 14 days at 4 °C. Compared to pristine Ti, EV-Bio-Ppy-Ti exhibited enhanced cell compatibility and osteoinductivity for osteoblasts in vitro and anti-apoptosis ability in the ectopic bone formation mode. Gene chip analysis further demonstrated that several osteoinductive miRNAs were encapsulated in hASC-EVs, which may explain the high bone regeneration ability of EV-Bio-Ppy-Ti. Thus, this MSC-EV biotin-immobilized method appears to be highly efficient and long-term stable for bone graft bioactive modification, demonstrating its potential for clinical metal implants.

Biocompatible graphene oxide-collagen composite aerogel for enhanced stiffness and in situ bone regeneration.

The developing bone graft substitutes have become a promising strategy for repairing large bone loss. Aerogels that made from natural polymers were widely investigated for synthetic bone graft due to their high porosity and great biocompatibility. However, the mechanical properties of natural polymer aerogel are extremely poor for large bone repair. Graphene oxide (GO) is one of the nanomaterials with great mechanical properties as well as biocompatibility, making it a promising component when constructing hybrid aerogels for bone regeneration. In the present study, we have developed a highly porous aerogel consist of GO and type I collagen (COL) using sol-gel process (concentrations of GO: 0%, 0.05%, 0.1%, and 0.2% w/v). Results indicated that GO-COL aerogels were highly porous and hydrophilic. Furthermore, the compressive modulus of GO-COL aerogels was enhanced with the GO concentration increased. For in vitro experiment, 0.1% GO-COL aerogel exhibited better biomineralization rate and cell compatibility than other groups of aerogels. For in vivo study, a better bone repair effect was observed in 0.1% GO-COL aerogels than COL aerogel in rat cranial defect models. This study indicated that 0.1% GO-COL aerogel exhibited good biocompatibility and osteogenic ability in vivo, which make it a promising biocompatible scaffold for bone regeneration and tissue engineering.

Giant spontaneous exchange bias triggered by crossover of superspin glass in Sb-doped Ni50Mn38Ga12 Heusler alloys.

A spontaneous exchange bias (SEB) discovered by Wang et al. [Phys. Rev. Lett. 106 (2011) 077203.] after zero-field cooling (ZFC) has attracted recent attention due to its interesting physics. In this letter, we report a giant SEB tuned by Sb-doping in Ni50Mn38Ga12-xSbx Heusler alloys. Such an SEB was switched on below the blocking temperature of approximately 50 K. The maximum exchange bias HE can arrive at 2930 Oe in a Ni50Mn38Ga10Sb2 sample after ZFC to 2 K. Further studies showed that this SEB was attributable to interaction of superspin glass (SSG) and antiferromagnetic matix, which was triggered by the crossover of SSG from canonical spin glass to a cluster spin glass. Our results not only explain the underlying physics of SEB, but also provide a way to tune and control the SEB performance.