R22 - Bionanomatrix Coated Balloons promote faster endothelialization and demonstrate effective drug transfer

Introduction: : Cardiovascular disease (CVD) is one of the leading causes of death in the United States. CVD presents itself as lesions in the artery wall, commonly treated by stenting. However, in cases of femoropopliteal peripheral artery disease (PAD), stenting has a considerable risk of stent fracture resulting in restenosis and total stent occlusion. Balloon angioplasty has been developed as an alternative to stenting in cases of PAD. However, balloon angioplasty has issues with thrombosis and restenosis which may cause recurrences of clotting at the location. Therefore, drug coated balloons (DCBs) have been developed to address these issues. DCBs are coated with antiproliferative drugs such as paclitaxel or a drug in the -limus (sirolimus, everolimus) family of drugs. These types of drugs are meant to reduce the restenosis by reducing the uncontrolled proliferation of smooth muscle cells at the site of injury. However, there has been research that suggests paclitaxel could be toxic. The sirolimus drug has been shown to be able to effectively suppress restenosis and neointimal hyperplasia, however the sirolimus can also harm the endothelium at the injury site. This damaged endothelium may lead to late-stage restenosis. Therefore, it would be beneficial to develop a DCB that can simultaneously reduce restenosis and inflammation, while providing healing and promote re-endothelialization at the injury site. Thus, we have developed a dual action DCB combining a nitric oxide (NO) releasing peptide amphiphiles (PA), which can increase re-endothelialization and promote healing, with low dose of sirolimus liposomes to suppress neointimal hyperplasia and the restenosis.

Materials and

Methods: : The bionanomatrix consists of NO releasing nanomatrix and sirolimus encapsulated liposomes. The NO releasing nanomatrix is made of self-assembling peptide amphiphiles. Both parts of the bionanomatrix help recruit endothelial cells (ECs) while suppressing the proliferation of smooth muscle cells (SMCs). The bionanomatrix was evaluated in vitro and ex vivo. The in vitro study consisted of exposing ECs and SMCs to varying concentrations of sirolimus and NO and then assessing the proliferation of the cells via PCNA tests. The ex vivo study consisted of coating the bionanomatrix onto the DCB and expanding it into a vessel wall to measure drug transfer and retention of both the NO nanomatrix and the sirolimus liposomes. This was done by inflating the DCBs coated with the bionanomatrix inside of pig arteries while attached to a bioreactor to simulate circulation inside of the arteries. The NO releasing nanomatrix was conjugated to IR dye and the sirolimus liposomes were conjugated to DTAF liposomes so the retention time could be analyzed.

Results, Conclusions, and Discussions::

Results: In vitro cell proliferation studies on SMCs and ECs treated with sirolimus decreased EC and SMC proliferation, even at very low concentrations (1 ng/mL) (Figure 1A and B, blue bar). However, ECs treated with both sirolimus and the NO releasing bionanomatrix showed that treatment of NO at concentrations as low as 10-9 M concentration increased EC proliferation (Figure 1B, red bar), recovering the negative effects of proliferation by sirolimus treatment. DCBs coated with IR dye conjugated bionanomatrix were inflated into pig arteries and then exposed to physiological flow conditions for up to 14 days. Results of the ex vivo bioreactor model indicated that the bionanomatrix was present in the artery even after 14 days (Figure 1C).

Conclusion: In vitro cell proliferation studies on SMCs and ECs successfully indicated that the dual treatment of NO with sirolimus could still reduce the proliferation of SMCs while also recovering the proliferation of the ECs. This indicated that the NO treatment could have the potential to counteract the negative effects of sirolimus on the endothelium and potentially promote healing of the artery in vivo. Additionally, the bionanomatrix was successfully transferred into the pig artery and was retained there for at least 14 days. This indicates the potential of the bionanomatrix to release NO in the artery for and promote healing while reducing SMC proliferation for at least 14 days after the DCB treatment. This has the potential to heal the artery and reduce late-stage restenosis after balloon angioplasty.

Acknowledgements and/or References (Optional)::