Smart air filters for moisture exchange and capture of nanoparticles in biomedical applications

Hybrid porous nano-composites to be used as filtering devices and moisture exchange systems are developed with complex geometry contributing to the water and nano-particles trapping (including the unrestrainable particle with dimensions in the range of 30-100 nm) without excessive pressure drop.
The hybrid composites are developed through a biomineralization process induced starting from a suspension of blended natural polymers (e.g. gelatine, chitosan, alginate) in the presence of Ca2+ and PO43- ions at controlled temperature and pH. This will achieve the simultaneous fibration and heterogeneous nucleation of defined amounts of low crystallinity nano-apatite-like phases.
The obtained mineralized gels will be subjected to freeze-drying processes where the kinetics of freezing and sublimation are controlled to achieve tailored microstructure and pore orientation. The mineralized 3-D constructs exhibit highly open and interconnected porosity. The formation of the mineralized constructs will be controlled by large amounts of cross-linking agents to regulate mechanical stability and stiffness as well as pore size and orientation. This in compliance with the hydrophilicity and hydrophobicity of the involved polymers will in turn influence the permeability of the device.
The filtering devices can be also endowed with interference system nucleating on the polymeric phase superparamagnetic mineral phases like Fe-doped hydroxyapatite (Fe-HA). Indeed, by controlling the Fe2+/Fe3+ ratio and the coordination state inside the apatitic lattice it is possible to induce intrinsic superparamagnetism that could be exploited to increase the capture of ferromagnetic-like nanoparticles during filtration.
Moreover, hyperthermia, as a side effect of superparamagnetism in Fe-HA, is exploit to produce temperature gradients inside the filtering media: the thermophoretic force can cause the displacement of the aerosol particles towards the cold part of the internal composite surfaces, thus increasing the filter capture efficiency.
Bacteriostatic/bactericide functionality will be achieved by inducing the biomineralization process to nucleate Ag-substituted HA with its known effects against bacteria. Such filters can be adapted for use as HME filters which, as a unique sterile item providing both filtering and humidification, will limit infections and consequently serious diseases.