Electrospinning of composite biomaterials: incorporation of bioactive agents and formation of hierarchical nanostructures

This PhD focused on promotion of bioactivity of electrospun fibres. Two methods were used to achieve this objective: using antimicrobial agents and, creating hierar-chical structures.

Antimicrobial agents, essential oils and zinc oxide nanoparticles, were encapsulat-ed in polymer nanofibres to promote antimicrobial properties.

Tea tree and Manuka essential oils were encapsulated in poly (lactic acid) (PLA) by dissolving in their common solvent acetone and then electrospin. Plasticising effect of essential oils was observed in differential scanning calorimetry (DSC)test. Glass transition temperature of PLA fibres decreased with increasing essential oil concen-tration. This corresponded with mechanical results. Manuka/PLA fibres showed successful result in inhibition of E. coli in antimicrobial test.

Zinc oxide nanoparticles have previously been used in electrospun fibres for anti-microbial purpose. To my knowledge, previous studies have only achieved to en-capsulate zinc oxide nanoparticles directly in electrospun fibres. In this thesis, for the first time, zinc oxide nanoparticles were first in-situ synthesised in polyethylene-imine (PEI) and then combined with zein to electrospin fibres. Resulting fibres showed better mechanical properties when compared to pure electrospun zein fi-bres.

The second method, creating hierarchical structure, was achieved by phase separa-tion. An unique dual-porosity structure of electrospun poly(ethyl cyanoacry-late)/polycaprolactone (PECA/PCL) was demonstrated. Composition of fibres was confirmed by Fourier-transform infrared spectroscopy (FTIR). Hierarchical structures are believed to favour cell attachment and proliferation by increasing fibre surface roughness and surface-to-volume ratio.