Chemical functionalization of bone implants with nanoparticle-stabilized chitosan and methotrexate for inhibiting both osteoclastoma formation and bacterial infection†
A great challenge in orthopedic tumor operation faced by orthopedic implants is the high recurrence and metastasis of bone tumor as well as the bacterial infection associated with the implants. Thus ideal titanium (Ti)-based bone implants should be able to not only inhibit cancer cell adhesion and proliferation, and promote cancer cell apoptosis, but also resist bacterial infections. Towards this end, we developed a new approach to modify the surface of Ti-based bone implants so that they can restrain functions of osteoclastoma (giant cell tumor of bone) cancer cells (GCTs) and inhibit the adhesion of bacteria. First, the surface of pristine Ti substrates was functionalized with dopamine (DA) to form DA–Ti substrates. Then nanoparticles electrostatically assembled from poly-lysine (PLL) and heparin (Hep) were chemically immobilized onto the DA–Ti substrates to form PLL/Hep–Ti substrates. Chitosan (CH) and methotrexate (MTX) were then electrostatically immobilized onto the PLL/Hep–Ti substrates to generate CH–MTX–Ti substrates. The successful functionalization of the Ti substrates was confirmed by X-ray photoelectron spectroscopy. GCTs cultured on differently functionalized Ti substrates were investigated in terms of cell adhesion, cytoskeleton, proliferation, cytotoxicity and apoptosis. The growth of Staphylococcus aureus bacteria in the presence of different substrates was also assayed. Our results showed that CH–MTX–Ti substrates not only significantly inhibited the adhesion, proliferation and viability of GCTs, and promoted the apoptosis of GCTs, but also prevented the adhesion of the bacteria and the subsequent formation of bacterial biofilms, when compared to other Ti substrates. Thus CH–MTX–Ti substrates are expected to be used as orthopedic prostheses in bone tumor surgery that can inhibit both osteoclastoma formation and bacterial infection.