The objective of the study is to analyze the biological characteristics and stability of the linear derivative Bac2a from bactenecin, compared with the control peptide melittin. The secondary structure, antibacterial activity, hemolytic activity, cell toxicity and stability of the Bac2a were determined by circular dichroism spectroscopy, broth micro-dilution method and MTT assay. The results showed that Bac2a was a nonregular curl in aqueous solution, however, it was an α-helix structure in the hydrophobic environment. The minimal inhibitory concentration (MIC) of Bac2a ranged from 2 to 32 μmol/L, so the bacteriostatic activity of Bac2a was strong. The hemolytic rate was only 14.81% when the concentration of Bac2a was 64 μmol/L, which showed that the hemolytic rate of Bac2a was low. The therapy index of Bac2a was 3.26, and the cytotoxicity was relatively low, thus the cell selectivity was relatively high. In addition, with the heating treatment of 100℃ for 1 h, Bac2a still possessed rather a high antibacterial activity and showed a good heating stability. In a word, Bac2a has good application prospects in food, medicine and other fields, and is expected as a substitute for traditional antibiotics.
Objective To investigate the effects of tannic acid (TA) doping on the physicochemical properties, biocompatibility, in vitro osteogenic performance, and antibacterial activity of Brushite bone cement, and to evaluate its feasibility for bone defect repair. MethodsTA was incorporated into Brushite bone cement at concentrations of 0, 1.0, 3.0, 5.0, and 10.0 mg/g of solid powder, designated as Brushite, Brushite/TA-1, Brushite/TA-2, Brushite/TA-3, and Brushite/TA-4, respectively. The compressive strength and microstructure of each group were evaluated. The extracts of the bone cements were prepared and co-cultured with MC3T3-E1 cells. Cell proliferation was assessed using the cell counting kit 8 (CCK-8) assay. The cytotoxicity was observed by Calcein/propidium iodide live/dead cell staining. Cell adhesion was observed via scanning electron microscopy. After osteogenic induction, alkaline phosphatase (ALP) activity was measured and ALP staining was performed. The expression levels of osteogenic-related genes, including runt-related transcription factor 2 (Runx2), osteocalcin (OCN), osteopontin (OPN), collagen type Ⅰ (Col-Ⅰ), and integrin-binding sialoprotein (IBSP), were detected by real-time fluorescent quantitative PCR (qRT-PCR). The antibacterial activity of the bone cement against Escherichia coli was assessed using the inhibition zone method. ResultsCompared with the Brushite group, the Brushite/TA-3 and Brushite/TA-4 groups exhibited significantly increased compressive strength (P<0.05). TA doping resulted in a higher crystal content and a more regular and dense crystal arrangement. Regarding cytocompatibility, the Brushite/TA-3 group demonstrated the most pronounced enhancement of cell proliferation (P<0.05), whereas the Brushite/TA-4 group showed relatively lower cell proliferative activity (P<0.05). All groups exhibited low cytotoxicity with good cell viability. Cell adhesion density and pseudopodia extension were superior in all TA-doped groups compared with the Brushite group. Regarding osteogenic activity, after 14 days of osteogenic induction, ALP activity was higher in all TA-doped groups than in the Brushite group (P<0.05) in a dose-dependent manner. The relative expression of Runx2, OCN, OPN, Col-Ⅰ, and IBSP mRNA also increased to varying degrees in a dose-dependent manner compared with the Brushite group. Regarding antibacterial performance, only the Brushite/TA-4 group exhibited inhibitory effects against Escherichia coli, with an inhibition zone diameter of approximately 7 mm. ConclusionDoping with an appropriate concentration of TA (3.0-5.0 mg/g) improves the mechanical properties, cytocompatibility, and osteogenic activity of Brushite bone cement. A higher concentration (10.0 mg/g) confers antibacterial properties but may partially inhibit cell proliferation. TA-doped Brushite bone cement demonstrates good application potential in the field of bone defect repair.