Petroleum-based materials has become an increasingly problem for both the economy and the nature, since petroleum resources are finite, their prices are likely to rise in the future and polluting and global warming, caused in part by fossil resources extraction, are worsening the environment. The aim of this work was to produce newly conceived bio-inspired solutions towards the local treatment of dental diseases and the air filtra- tion in hospital mechanical ventilation.
Following concept of hierarchical organization combining microfabricated elementary building blocks that could be assembled into more complex structures, a scaffold chemi- cally and morphologically mimicking the dentin was developed. A biomineralization pro- cess was applied to nucleate magnesium-doped hydroxyapatite nanoparticles (MgHA) on gelatin molecules and obtain a biomimetic hybrid composite with an high content of mineral phase. Moreover, by blending the mineralized composite with alginate was possible to impart to the material the desired channel-like structure. My means of cross- linking and freeze-drying processes, it was possible to fabricate a 3D scaffold stable in physiological environment and mimicking the chemical and morphological features of dentin.
Chemically and morphologically graded construct was designed and developed thus mimicking the whole periodontium (cementum, periodontal ligament, alveolar bone). Hybrid composites endowed with superparamagnetic properties were synthetized to mimicry the hard tissues and further improve the regenerative potnetial, moreover a collagen-based porous layer was developed with analogous characteristic of the perio- dontal ligament.
Alveolar bone-like layer (FeHA/Coll) was realized through the biomineralization ap- proach, with a simultaneous nucleation of iron-doped hydroxyapatite (FeHA) and a pH-
dependent assembling of collagen fibers. The synthesis temperature and the introduc- tion of ferrous and ferric ions into the apatitic lattice during the stage of hydroxyapatite nucleation induces in the final composite chemic-physical, structural and morphological features close to those of bone along with superparamagnetic properties.
The cementum-like layer, was successfully obtained by processing a blend of cellulose acetate with FeHA nano-powder with electrospinning technique suitable to fabricate thin and dense but porous layers. . At this purpose, a synthetic procedure to obtain a magnetic (Fe2+/Fe3+)-lattice substituted hydroxyapatite have been optimized in order to induce superparamagnetic behavior and minimize the formation of magnetite as sec- ondary phase, potentially toxic once metabolized.
Finally the middle layer, the periodontal ligament-like one, was obtained by processing type I collagen properly cross-linked to control its durability in physiological conditions. Peculiar structural features, as open and interconnected pores were achieved through the applications of freeze-drying technique.
The three layer were than stacked together obtaining a 3D scaffold reproducing the chemical and morphological feature of the whole periodontium.
In vitro investigations performed on these biomimetic scaffolds demonstrate their bio-
compatibility, underlining their good ability to support cell adhesion and proliferation. Therefore, the biohybrid scaffolds developed in this work are promising candidates for the regeneration of dentin and periodontal region, since they have not only the poten- tial to provide a tissue-conductive system that mimics the tree-dimensional environ- ment of the tissues, but also thanks to their magnetic properties, they can furnish oste- oconductive stimuli necessary for a faster and effective tissue regeneration.
Employing biomimetic principles, also a Heat and Moisture Exchange air filter based on natural components was developed. A moisture exchange device was firstly optimized using the freeze-drying process on a cross-linked hydrogel based on a gelatin and chi- tosan blend. This filter section, which will represent the shell of the final device, was developed in order to minimize the air pressure drop and maximize the hygrometric exchange.
Separately, the synthetic procedure to obtain a magnetic (Fe2+/Fe3+)-substituted hy- droxyapatite was optimizing in order to maximize the magnetic behavior and therefore the hyperthermic effect. The achieved powder was then added into an alginate solution and thanks to cross-link and freeze-drying processes a magnetic core for the air filter was realized.
In this way it was realized an HME core-shell filter which offer the possibility of warming cold air from the artificial ventilator once subjected to an external magnetic field and high efficient in condensate vapor from the patient exhaled breath and release it into the inhaled air. A further function of this HME filters concerns the antibacterial and anti- viral filtering capabilities.This filter is completely made from renewable sources, that guarantee affordable prices, so it might find a new large and interesting market.
This work has thus led the development of scaffolds mimicking dentin which could be used to fill the cavities left by caries lesions and induce regeneration process, so that to be a solution in the case of superficial or deep and penetrating caries and prevent endo- dontic treatments and prolong the vitality of natural teeth.
While in patients with missing teeth, such innovative solutions could be beneficial in the primary stabilization of the titanium dental implants. Indeed, the amount of regenerat- ed bone is crucial for the implant stability over time.
A significant advantage of the collagen scaffold is that it is natural polymer and there- fore bioactive, allowing osteoblasts to maintain high metabolic rates that increase over- time.
Magnetic property of FeHA phase together with its biocompatibility open the door of the regenerative medicine to a conceptually newly family of biomimetic composites able to be manipulated or activated in situ by means of an external magnetic field.
The control mechanisms inherent in the whole process of self-assembling and minerali- zation, scaled at pilot plant, could allow to establish a technological platform based on
highly repeatable, scalable and cost-effective technology for the manufacturing of multi- functional devices with huge economic, environmental and social impact. In this respect, roadmaps addressing wider industrial exploitation could be prepared, basing on the knowledge gained in this PhD project.
These results can also represent a proof of concept for further development of smart devices obtained by biologically-inspired self-assembling processes.