Additive manufacturing has facilitated fabrication of complex and patient-specific metallic meta-biomaterials that offer an unprecedented collection of mechanical, mass transport, and biological properties as well as a fully interconnected porous structure. However, applying meta-biomaterials for addressing unmet clinical needs in orthopedic surgery requires additional surface functionalities that should be induced through tailor-made coatings. Here, we developed multi-functional layer-by-layer coatings to simultaneously prevent implant-associated infections and stimulate bone tissue regeneration. We applied multiple layers of gelatin- and chitosan-based coatings containing either bone morphogenetic protein (BMP)-2 or vancomycin on the surface of selective laser melted porous structures made from commercial pure Titanium (CP Ti) and designed using a triply periodic minimal surface (i.e., sheet gyroid). The additive manufacturing process resulted in a porous structure and met the the design values comparatively. X-ray photoelectron spectroscopy spectra confirmed the presence and composition of the coating layers. The release profiles showed a continued release of both vancomycin and BMP-2 for 2–3 weeks. Furthermore, the developed meta-biomaterials exhibited a very strong antibacterial behavior with up to 8 orders of magnitude reduction in both planktonic and implant-adherent bacteria and no signs of biofilm formation. The osteogenic differentiation of mesenchymal stem cells was enhanced, as shown by two-fold increase in the alkaline phosphatase activity and up to four-fold increase in the mineralization of all experimental groups containing BMP-2. Eight-week subcutaneous implantation in vivo showed no signs of a foreign body response, while connective tissue ingrowth was promoted by the layer-by-layer coating. These results unequivocally confirm the superior multi-functional performance of the developed biomaterials.

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Application of bio-functionalized coatings on bone implantable devices is a promising approach to direct rapid bone-implant integration. Plasma polymer (PP) films have become increasingly popular as platforms for surface bio-functionalization of implantable devices. However, the production of a reactive, yet stable PP film represents a technological challenge; as achieving a balance between the film's stability and functional group density is not trivial. Here we report the development of highly reactive and stable radical-functionalized PP films, using a combination of plasma polymerization and plasma immersion ion implantation. We provide new insights into the role of energetic ion bombardment on the growth mechanisms of plasma polymers by measuring the hydrogen content of PP structures using elastic recoil detection analysis. Nano-indentation and nano-scratch tests, as well as stability studies in simulated body fluid show a strong correlation between the degree of energetic ion bombardment and physico-chemical stability of the coatings. The potential of such ion-treated PP films to fabricate biofunctionalized implants that promote the functionality of primary osteoprogenitor cells is confirmed by studying cellular interactions after covalent attachment of fibronectin or bone morphogenetic protein (BMP)-2. We found that covalent attachment of fibronectin improved adhesion, spreading and proliferation of primary osteoblasts; whereas covalent attachment of BMP-2 enhanced the osteocalcin expression in bone-marrow isolated mesenchymal stem cells (MSC). These results present great promise for the fabrication of a new class of robust, biologically-functionalized interfaces for the surface engineering of biomaterials, particularly implants that need to be overgrown with bone-producing cells and thereby become firmly attached to host tissue.

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Prevention and treatment of biomaterial-associated infections (BAI) are imperative requirements for the effective and long-lasting function of orthopedic implants. Surface-functionalization of these materials with antibacterial agents, such as antibiotics, nanoparticles and peptides, is a promising approach to combat BAI. The well-known silver nanoparticles (AgNPs) in particular, although benefiting from strong and broad-range antibacterial efficiency, have been frequently associated with mammalian cell toxicity when physically adsorbed on biomaterials. The majority of irreversible immobilization techniques employed to fabricate AgNP-functionalized surfaces are based on wet-chemistry methods. However, these methods are typically substrate-dependent, complex, and time-consuming. Here we present a simple and dry strategy for the development of polymeric coatings used as platforms for the direct, linker-free covalent attachment of AgNPs onto solid surfaces using ion-assisted plasma polymerization. The resulting coating not only exhibits long-term antibiofilm efficiency against adherent Staphylococcus aureus (S. aureus), but also enhances osteoblast adhesion and proliferation. High resolution X-ray photoelectron spectroscopy (XPS), before and after sodium dodecyl sulfate (SDS) washing, confirms covalent bonding. The development of such silver-functionalized surfaces through a simple, plasma-based process holds great promise for the fabrication of implantable devices with improved tissue-implant integration and reduced biomaterial associated infections.@en