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The rise of bacterial infections has become a serious problem in human societies. As a result, the development of nanocomposite materials based on biocompatible and non-hazardous materials, besides having antimicrobial and biocompatibility or non-cytotoxicity, associated with unique structural properties, possesses a great importance. Research approach: In this study, bacterial cellulose (BC)/polypyrrole (PPy) and zinc nanoparticles (ZnO), which simultaneously have antimicrobial properties and cell proliferation, were introduced as a new generation of nanocomposite scaffolds produced by freeze-drying. To begin with, ZnO with different weight percentages of 1%, 3% and 5% was added to BC and then PPy in the amount of 2 mmol was embedded in the structure by in situ polymerization. FESEM images proved that the nanofibrous and porous structure of BC was also preserved in the presence of PPy and ZnO. However, after adding PPy and ZnO, they formed a dense structure and microstructure of grape clusters. By adding 2 mmol PPy into BC and upon in situ synthesizing, the tensile strength and Young modulus of BC were significantly reduced to 71 MPa and 2.5 GPa, respectively. On the other hand, with the addition of ZnO nanoparticles, the mechanical properties significantly increased (both of Young modulus and tensile strength compared to BC/PPy samples) due to the compaction of the nanocomposite aerogel’s structure and the formation of the interface of ZnO nanoparticles with both polymers of BC and PPy. The observation of the inhibition zone in the culture medium containing two gram-positive and negative bacteria, well proved the antibacterial ability of ternary nanocomposite scaffolds. The results of MT9 related to L929 on aerogels showed that by adding 3% of ZnO nanoparticles, adhesion and cell proliferation increased significantly during different days of 1 day, 5 days and 7 days of culture.

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Research subject: This study aims to improve the biocompatibility, bioactivity, and mechanical properties of gelatin-based composite scaffolds by coating them with polyethylene glycol (PEG) doped with bioactive glasses (BGs) containing zinc and magnesium.
Research approach: A response surface methodology (RSM) was used to model and evaluate the effects of two independent variables: the PEG/Gel weight ratio (X1) and the BG weight percentage (X2). The responses investigated included ultimate strength, Young's modulus, elongation at break, swelling percentage, erosion percentage, and moisture absorption percentage.
Main results: Optimal conditions were determined to obtain scaffolds with suitable mechanical strength, biocompatibility and degradability. Analysis of variance (ANOVA) was used to obtain the best model describing the influence of each independent variable on the responses. The optimal scaffold formulation was selected based on software-defined parameters. The FTIR spectrum was used to analyze the functional groups present on the surface of the samples. The FTIR spectrum of the synthesized BGs showed a broad vibrational band in the range of 900 to 1100 cm^-1, which is attributed to the asymmetric Si-O-Si stretching band. The FTIR spectrum of the PEG/Gel/BG composite confirmed the presence of BG in the scaffolds and the interaction between the polymer matrix and BG. Increasing the amount of BG relative to the polymer scaffold led to a decrease in pore size and consequently, a decrease in the scaffold's swelling percentage. The effect of varying the BG weight percentage on tensile strength was greater than that of the PEG/Gel weight ratio. The tensile strength increased significantly due to the good interaction between the polymer scaffold and BG, as well as the uniform dispersion of BG within the polymer matrix. SEM images indicated that cells penetrated well into the scaffolds and formed a suitable three-dimensional cellular network. Cytotoxicity, cell attachment and proliferation, and osteogenic differentiation were evaluated using the MTT test and by culturing MG-63 cells on the scaffold. Cell viability showed no significant difference between the tested and control samples.
 

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Since one of the main problems in bone tissue repair is the bacterial infections, recently the development of drug-eluting nanocomposite scaffolds for bone regenerative medicine applications has attracted significant attention. In this study Polycaprolactone (PCL)-based composite scaffolds containing 10vol% of titanium dioxide nanoparticles (~21nm), and bioactive glass particles (~6µm), were prepared without drug and also loaded by Tetracycline hydrochloride (TCH) antibiotic (0.57, 1.15 mg/mL) through solvent casting method for bone tissue engineering applications. Structural characterizations based on Scanning Electron Microscopy (SEM), and FTIR analysis were utilized to study the chemical bonds of glass/ceramic particles, and antibiotic crystals on the surface. In addition, in vitro cytotoxicity, and antibacterial analysis were performed by MTT, and Agar well-diffusion assays, respectively. In this study polymeric and composite scaffolds were fabricated with TCH clusters decorated on the surface. It was shown that the bioactive glass/PCL scaffolds loaded by 0.57 mg/mL of TCH revealed significant antibacterial effect, despite the acceptable cell viability. These scaffolds seem to be of interest as a potential candidate in drug-eluting scaffolds for bone tissue engineering applications.