Titania coating of mesoporous silica nanoparticles for improved biocompatibility and drug release within blood vessels.

Blood vessel disease is a major contributor to cardiovascular morbidity and mortality and is hallmarked by dysfunction of the lining endothelial cells (ECs). These cells play a significant role in vascular homeostasis, through the release of mediators to control vessel diameter, hence tissue perfusion. Mesoporous silica nanoparticles (MSNs) can be used as potential drug delivery platforms for vasodilator drugs. Here, using an ex vivo model of vascular function, we examine the use of titania coating for improved biocompatibility and release dynamics of MSN loaded sodium nitroprusside (SNP). MSNs (95 ± 23 nm diameter; pore size 2.7 nm) were synthesised and fully characterised. They were loaded with SNP and coated with titania (TiO2), using the magnetron sputtering technique. Pre-constricted aortic vessels were exposed to drug loaded MSNs (at 1.96 × 1012 MSN mL-1) and the time course of vessel dilation observed, in real time. Exposure of viable vessels to MSNs lead to their internalization into the cytoplasm of ECs, while TiMSNs were also observed in the elastic lamina and smooth muscle cell layers. We demonstrate that titania coating of MSNs significantly improves their biocompatibility and alters the dynamics of drug release. A slow and more sustained relaxation was evident after uptake of TiMSN-SNP, in comparison to uncoated MSN-SNP (rate of dilation was 0.08% per min over a 2.5 h period). The use of titania coated MSNs for drug delivery to the vasculature may be an attractive strategy for therapeutic clinical intervention in cardiovascular disease. STATEMENT OF SIGNIFICANCE: Cardiovascular disease is a major cause of mortality and morbidity worldwide, with a total global cost of over $918 billion, by 2030. Mesoporous silica nanoparticles (MSNs) have great potential for the delivery of drugs that can treat vessel disease. This paper provides the first description for the use of titania coated MSNs with increased vascular penetration, for the delivery of vasodilator drugs, without compromising overall vessel function. We demonstrate that titania coating of MSNs significantly improves their biocompatibility and uptake within aortic blood vessels and furthermore, enables a slower and more sustained release of the vasodilator drug, sodium nitroprusside within the vessel, thus making them an attractive strategy for the treatment of vascular disease.