Comparison of the short- and long-term effects of zinc ions on the anaerobic mesophilic co-digestion of food waste and waste activated sludge: Digester performance, antibiotic resistance gene reduction and the microbial community.

Heavy metals contained in waste activated sludge (WAS), especially zinc ions, have an inhibitory effect on the anaerobic digestion. However, the effects of zinc ions on digester performance, antibiotic resistance genes (ARGs) reduction, and the microbial community involved in the anaerobic mesophilic co-digestion (AcoD) of WAS and food waste (FW) have not been fully characterized. Therefore, batch trials and continuous stirred tank reactors were used under different zinc-ion concentrations. Findings showed that the AcoD system can tolerate a maximum zinc ion of 540 mg/L in a short-term batch and 470 mg/L in a long-term AcoD system, promoting methane production of approximately 1.0-17.0 %. Metagenomic analysis revealed that syntrophic H2 transfer occurred between Syntrophomonas and Methanoculleus and the aceticlastic and hydrogenotrophic methanogenic pathways were both enhanced by 1.18- and 1.16 times, respectively. Moreover, the relative abundance of Methanosarcina increased from 58.4 % to 72.5 % at 470 mg/L to adapt to the high zinc ion concentration during long-term continuous operation. These results revealed that AcoD with a low zinc ion concentration can effectively increase the removal percentage of ARGs. The results provide guidance for biogas recovery and use of mesophilic AcoD with FW and WAS containing high zinc ion concentrations without pretreatment process.

Fabrication of gelatin methacryloyl/graphene oxide conductive hydrogel for bone repair.

The ideal bone repair materials possess a series of properties, such as injectability, good mechanical properties and bone inducibility. In the present study, gelatin methacryloyl (GelMA) and graphene oxide (GO) were selected to prepare conductive hydrogel by changing the concentration of GelMA and GO during the cross-link process. The effects of different contents of GelMA and GO to the hydrogel performance were investigated. The results showed that the mechanical properties of the hydrogel kept 16.37 ± 1.89 KPa after adding 0.1% GO, while the conductivity was improved to 1.36 ± 0.09 µS/cm. The porosity of hydrogel before and after mineralization could reach more than 90%. The mechanical properties of mineralized hydrogel was improved significantly, could reach 26.38 ± 2.29 KPa. Cell experiments indicated that the mineralized hydrogel with electrical stimulation obviously improve the alkaline phosphatase activity of the cells. GelMA/GO conductive hydrogel could be a promising candidate for bone repair and bone tissue engineering.

Nanocatalytic Hydrogel with Rapid Photodisinfection and Robust Adhesion for Fortified Cutaneous Regeneration.

Chronic inflammation caused by invasive bacterial infections severely interferes with the normal healing process of skin regeneration. Hypoxia of the infection microenvironment (IME) seriously affects the antibacterial effect of photodynamic therapy in phototherapy. To address this serious issue, a nanocatalytic hydrogel with an enhanced phototherapy effect consisting of a hydrogel polyvinyl alcohol (PVA) scaffold, MXene/CuS bio-heterojunction, and polydopamine (PDA) for photothermal antibacterial effects and promoting skin regeneration is designed. The MXene/CuS bio-heterojunction has a benign photothermal effect. Singlet oxygen (1O2) and hydroxyl radicals (·OH) were generated under near-infrared light, which made the hydrogel system have good antioxidant and antibacterial properties. The addition of PDA further improves the biocompatibility and endows the nanocatalytic hydrogel with adhesion. Additionally, in vivo assays display that the nanocatalytic hydrogel has good skin regeneration ability, including ability to kill bacteria, and promotes capillary angiogenesis and collagen deposition. This work proposes an approach for nanocatalyzed hydrogels with an activated IME response to treat wound infections by enhancing the phototherapeutic effects.

Biomimetic, biodegradable and osteoinductive treated dentin matrix/α-calcium sulphate hemihydrate composite material for bone tissue engineering.

It is still a huge challenge for bone regenerative biomaterial to balance its mechanical, biological and biodegradable properties. In the present study, a new composite material including treated dentin matrix (TDM) and α-calcium sulphate hemihydrate (α-CSH) was prepared. The optimal composition ratio between TDM and α-CSH was explored. The results indicate that both components were physically mixed and structurally stable. Its compressive strength reaches up to 5.027 ± 0.035 MPa for 50%TDM/α-CSH group, similar to human cancellous bone tissues. Biological experiments results show that TDM/α-CSH composite exhibits excellent biocompatibility and the expression of osteogenic related genes and proteins (ALP, RUNX2, OPN) is significantly increased. In vivo experiments suggest that the addition of TDM for each group (10%, 30%, 50%) effectively promotes cell proliferation and osteomalacia. In addition, 50% of the TDM/α-CSH combination displays optimal osteoconductivity. The novel TDM/α-CSH composite is a good candidate for certain applications in bone tissue engineering.