With controlled nanometre-sized pores and surface areas of thousands of square metres per gram, metal-organic frameworks (MOFs) may have an integral role in future catalysis, filtration and sensing applications. In general, for MOF-based device fabrication, well-organized or patterned MOF growth is required, and thus conventional synthetic routes are not suitable. Moreover, to expand their applicability, the introduction of additional functionality into MOFs is desirable. Here, we explore the use of nanostructured poly-hydrate zinc phosphate (α-hopeite) microparticles as nucleation seeds for MOFs that simultaneously address all these issues. Affording spatial control of nucleation and significantly accelerating MOF growth, these α-hopeite microparticles are found to act as nucleation agents both in solution and on solid surfaces. In addition, the introduction of functional nanoparticles (metallic, semiconducting, polymeric) into these nucleating seeds translates directly to the fabrication of functional MOFs suitable for molecular size-selective applications.

Scaffolds with gradients of physico-chemical properties and controlled 3D architectures are crucial for engineering complex tissues. These can be produced using multi-material additive manufacturing (AM) techniques. However, they typically only achieve discrete gradients using separate printheads to vary compositions. Achieving continuous composition gradients, to better mimic tissues, requires material dosing and mixing controls. No such AM solution exists for most biomaterials. Existing AM techniques also cannot selectively modify scaffold surfaces to locally stimulate cell adhesion. A hybrid AM solution to cover these needs is reported here. A dosing- and mixing-enabled, dual-material printhead and an atmospheric pressure plasma jet to selectively activate/coat scaffold filaments during manufacturing were combined on one platform. Continuous composition gradients in both 2D hydrogels and 3D thermoplastic scaffolds were fabricated. An improvement in mechanical properties of continuous gradients compared to discrete gradients in the 3D scaffolds, and the ability to selectively enhance cell adhesion were demonstrated.

Bone infections following open bone fracture or implant surgery remain a challenge in the orthopedics field. In order to avoid high doses of systemic drug administration, optimized local antibiotic release from scaffolds is required. 3D additive manufactured (AM) scaffolds made with biodegradable polymers are ideal to support bone healing in non-union scenarios and can be given antimicrobial properties by the incorporation of antibiotics. In this study, ciprofloxacin and gentamicin intercalated in the interlamellar spaces of magnesium aluminum layered double hydroxides (MgAl) and α-zirconium phosphates (ZrP), respectively, are dispersed within a thermoplastic polymer by melt compounding and subsequently processed via high temperature melt extrusion AM (~190 °C) into 3D scaffolds. The inorganic fillers enable a sustained antibiotics release through the polymer matrix, controlled by antibiotics counterions exchange or pH conditions. Importantly, both antibiotics retain their functionality after the manufacturing process at high temperatures, as verified by their activity against both Gram + and Gram - bacterial strains. Moreover, scaffolds loaded with filler-antibiotic do not impair human mesenchymal stromal cells osteogenic differentiation, allowing matrix mineralization and the expression of relevant osteogenic markers. Overall, these results suggest the possibility of fabricating dual functionality 3D scaffolds via high temperature melt extrusion for bone regeneration and infection prevention.

Implantable devices need specific tailored surface morphologies and chemistries to interact with the living systems or to actively induce a biological response also by the release of drugs or proteins. These customised requirements foster technologies that can be implemented in additive manufacturing systems. Here we present a novel approach based on spraying processes that allows to control separately topographic features in the submicron range (∽ 60 nm - 2 µm), ammine or carboxylic chemistry and fluorophore release even on temperature sensitive biodegradable polymers such as polycaprolactone (PCL). We developed a two-steps process with a first deposition of 220 nm silica and poly(lactic-co-glycolide) (PLGA) fluorescent nanoparticles by aerosol followed by the deposition of a fixing layer by atmospheric pressure plasma jet (APPJ). The nanoparticles can be used to create the nano-roughness and to include active molecule release, while the capping layer ensures stability and the chemical functionalities. The process is enabled by a novel APPJ which allows deposition rates of 10 - 20 nm·s^-1 at temperatures lower than 50 °C using argon as process gas. This approach was assessed on titanium alloys for dental implants and on PCL films. The surfaces were characterized by FT-IR, AFM and SEM. Titanium alloys were tested with pre-osteoblasts murine cells line, while PCL film with fibroblasts. Cell behaviour was evaluated by viability and adhesion assays, protein adsorption, cell proliferation, focal adhesion formation and SEM. The release of a fluorophore molecule was assessed in the cell growing media, simulating a drug release. Osteoblast adhesion on the plasma treated materials increased by 20% with respect to commercial titanium alloys implants. Fibroblast adhesion increased by a 100% compared to smooth PCL substrate. The release of the fluorophore by the dissolution of the PLGA nanoparticles was verified and the integrity of the encapsulated drug model confirmed.

An efficient way to increase the gas barrier properties of polymers is the development of silica barrier coatings; in fact inorganic barrier layers like SiN_x and SiO_x, usually obtained by PECVD, can decrease the gas permeation through polymeric substrates by several orders of magnitude. Nevertheless, the known costs of vacuum systems and in‐line processing needs have generated increasing interest to develop atmospheric condition alternatives. In this work results on deposition of SiO_x on thin layers obtained by an atmospheric plasma jet as well as results on the gas permeation behaviour are presented. Obtained results, on the thickness and composition of the coatings, are evaluated under several deposition conditions.