Introduction: Titanium dioxide (TiO2) is renowned for its photocatalytic properties: exposure to UV light of titanium dioxide containing materials gives rise to a more hydrophilic surface and production of free radicals. The addition of titanium dioxide thereby reduces both protein adsorption and cell adhesion on the surface of biomaterials. Ventricular shunt catheters for the treatment of hydrocephalus are commonly made from poly (di-methyl) siloxane (PDMS), despite their high incidence of failure, with infection and shunt obstruction being the most serious. For this reason, the use of a micro-porous catheter with increased hydrophilicity has been proposed[1],[2]. The characterisation of a hybrid shunt catheter material is herein reported, based on titanium dioxide embedded in an electrospun polymeric matrix.
Materials and Methods: TiO2 was synthesized in situ via a sol-gel reaction starting from an alkoxide precursor (Ti(OnBu)4) mixed with an excess of acetic acid, and dispersed in a poly(caprolactone) solution, which was electrospun to yield a microfibrous mat comprised of nonaligned fibres. Similarly, electrospun titanium dioxide-polyurethane composite material was prepared from a medical grade polyurethane elastomer (Z6A1, Biomer Technology Ltd., Runcorn, UK).
The electrospun hybrid materials were characterized by means of DSC, XRD, SEM and EDS, and have been used as scaffolds in preliminary cell viability tests.
Results and Discussion: The addition of titanium dioxide alters the physical-chemical properties of the polymeric matrix. Whereas pure polyurethane fibres tend to separate, and show a bimodal distribution in terms of fibre diameter, titanium dioxide-loaded fibres exhibit a narrower, more uniform, distribution.
Thermal studies highlight a general broadening in the size distribution of the crystallites and a shift towards lower melting temperatures with an increase in titania content.
TiO2 seems to be well dispersed throughout the polymeric matrix. While XRD reveals a small and broad peak for the pure cast polymer, no peaks are present in either the electrospun or in the hybrid samples, which suggests that titanium dioxide is in an amorphous form.
Both electrospinning process and the addition of titanium dioxide seem to contribute towards the disruption of crystalline domains within the polymer.
After being exposed to UV irradiation, titanium dioxide triggers photocatalytic reactions.
Conclusion: The properties conferred on the polymer by the presence of TiO2 in the matrix is expected to give rise to increased wettability and therefore a reduction in cell viability. Further studies are warranted to determine the individual contribution of factors such as fibre morphology, mechanical properties, enhanced wettability and photocatalytic activity to the decrease in cell viability.
The authors wish to acknowledge the support of the UK Engineering & Physical Sciences Research Council (EPSRC) Doctoral Training Centre in Medical Devices, University of Strathclyde (EPSRC Grant Ref. EP/F50036X/1) for the studentship awarded to DE.
References:
[1] Suresh S, Black RA. J Biomaterial Applications, 2015; 29(7):1028-1038.
[2] Harris CA, et al. Journal of biomedical materials research Part A, 2011;98:425-33.