Multifunctional CuS nanoparticle deposition for enhanced dentin bonding: Synergistic dehydration, MMP inhibition and antibacterial action

Objective To develop a multifunctional strategy based on in-situ copper sulfide (CuS) nanoparticle deposition, aiming to simultaneously mitigate interface-confined water to improve adhesive infiltration, suppress enzymatic degradation, and prevent bacterial colonization. Methods Demineralized dentin matrices (DDM) were sequentially treated with CuSO₄ and Na₂S solutions at three concentrations (0.0015, 0.015, 0.15 mol/L), with conventional wet-bonding as a control. Nanoparticle distribution, matrix dehydration, matrix metalloproteinase (MMP) activity, antibacterial efficacy ( Streptococcus mutans , Staphylococcus aureus and Escherichia coli ), and bonding performance (nanoleakage, microtensile bonding strength) were systematically evaluated. Results Uniform CuS deposition significantly reduced DDM hydration to release the interface-confined water. The 0.015 and 0.15 groups showed enhanced mechanical properties. Moreover, all concentrations of CuS deposition inhibited MMP and showed antibacterial effect. As a result, the 0.015 and 0.15 groups showed improved adhesive infiltration, reduced nanoleakage ( p  < 0.05) and increased both immediate and aged microtensile bonding strength ( p  < 0.01). Conclusion In-situ CuS nanoparticle deposition synergistically enhances bond durability, through DDM dehydration, MMP inhibition, and antibacterial action. This approach effectively minimizes hybrid layer defects and collectively prolongs bonding longevity. Clinical significance The Cu-assisted bonding technique provides a clinically feasible solution to address multifactorial failure modes in dentin bonding, leveraging nanomaterial synergy for durable adhesive restorations.