Physico-mechanical reinforcement and antimicrobial efficiency of green-synthesized Ca/bentonite/chitosan nanocomposites

Bone tissue engineering necessitates the utilization of scaffolds that amalgamate biocompatibility, mechanical robustness, and antimicrobial properties to effectively address the challenges of regeneration and infection control. Natural polymers, such as chitosan, inherently offer bioactivity; however, they require reinforcement to achieve optimal functionality. To formulate an eco-friendly calcium/exfoliated bentonite/chitosan (Ca/EXF-BE/CS) nanocomposite scaffold with enhanced mechanical strength and antimicrobial efficacy for applications in bone tissue engineering. Calcium oxide was derived from waste eggshells through the process of calcination at 600 °C. The Egyptian bentonite was subjected to purification and exfoliation via CTAB-assisted ultrasonication. Ca/EXF-BE nanocomposites were synthesized employing green tea-mediated precipitation, followed by the encapsulation with chitosan through ionic gelation utilizing tripolyphosphate as a crosslinking agent. Characterization was conducted using XRD, FE-SEM, FTIR, BET analysis, and mechanical testing. The antimicrobial efficacy was evaluated against E. coli, S. aureus, and C. albicans using well diffusion and MIC/MBC assays. The Ca/EXF-BE/CS exhibited the highest surface area value of 134.6 m2/g, coupled with an average pore width of 44.5 Å. The mechanical properties of EXF-BE were significantly enhanced with the addition of Ca and CS, as evidenced by the ultimate tensile strength (σuts) values of 15.38 ± 0.40MPa, 16.19 ± 0.38 MPa, and 17.84 ± 0.42 MPa; toughness measurements of 1.435 ± 0.23 MJ/m3, 1.713 ± 0.25 MJ/m3, and 2.067 ± 0.31 MJ/m3; and strain at breakdown percentages of approximately 28.5 ± 0.31%, 28.69 ± 0.3%, and 30.1 ± 0.33% for EXF-BE, Ca/EXF-BE, and Ca/EXF-BE/CS, respectively. The antimicrobial properties, evaluated through the well diffusion method, revealed inhibition zones measuring 27.13, 21.25, and 23 mm against E. coli, S. aureus, and Candida albicans, respectively, at 1000 µg/mL of Ca/EXF-BE, thereby demonstrating promising multifunctional capabilities. The Ca/BE/CS nanocomposite, produced via sustainable synthesis from eggshell waste, demonstrates enhanced strength, toughness, porosity, and antimicrobial activity. Its multifunctional performance makes it a promising scaffold for load-bearing bone tissue engineering and infection control in orthopedic applications.