Molecular dynamics of carbon nanohorns and their complexes with cisplatin in aqueous solution

The medication with Pt-based antitumor drug cisplatin has demonstrated effective results against cancer cells, despite the severe side effects due to the high toxicity associated with the low selectivity of these anticancer agents. An alternative to overcome or decrease the side effects is to use drug delivery systems, which can carry high doses of the anticancer drug and promote its slow and targeted release to the tumor sites. Herein, we used molecular dynamics to study prototypes of the complexes formed by the encapsulated cisplatin and carbon nanohorns (CNH), with the purpose to characterize its structures and dynamical behavior in aqueous solution, an important feature to assess the potentiality of using CNH as carrier systems. The results indicated the presence of up to 36 water molecules inside the empty CNH cavity, depending on the cone angle and the presence of the cisplatin. Some of these solvent molecules are expelled out to the bulk upon cisplatin inclusion, although more than 10 molecules remain even for the narrow structures. Moreover, the calculated binding free energy (Δ_bG) pointed out that the inclusion complexes formation between CNH structures and up to two cisplatin molecules was thermodynamically favorable in aqueous media, which suggests the potentiality of these carbon nanostructures as drug carriers. For the most likely and narrow host structure the average Δ_bG was -92.0 kcal mol^-1 for inclusion of two cisplatin, with most of the complex stability coming from the van der Waals contribution.