Fe-encapsulated multiwall carbon nanotubes (Fe@MWCNTs) are candidates for magnetically targeted Drug Delivery Systems (mt-DDSs) against breast cancer. However, their full potential as versatile and biosafe vectors has yet to be developed. Key challenges that remain are relating surface functionalization to cytotoxicity and inducing selective cytotoxicity to cancer cells. We have studied quantitative uptake of pristine and functionalized Fe@MWCNTs (f-Fe@MWCNTs) in correlation to their in vitro cytotoxicity. Human monocyte macrophages (HMMs) and T47D breast cancer cells were selected as models to test selective cytotoxicity. [2+1]-Cycloaddition of nitrenes to Fe@MWCNTs yielded both effective functionalization and drug “tethering”. Hydrophilization of Fe@MWCNTs was critical for efficient active cell uptake. f-Fe@MWCNTs were considerably more toxic to T47D cells than HMMs, in spite of longer exposure times of the latter. Eventually, Fe@MWCNTs loaded with 5-fluorouracil in a β-cyclodextrin cage or with covalently linked purpurin emerged as the most cytotoxic and steerable in a magnetic field toward promising mt-DDSs.

Cell type, morphology, and functioning are key variables in the construction of efficient "drug-vehicle" hybrids in magnetic drug delivery. Iron-encapsulated multiwall carbon nanotubes (Fe@MWCNTs) appear as promising candidates for theranostics due to in situ chemical catalytic vapor deposition (c-CVD) synthesis, straightforward organic functionalization, and nanoneedle (1D) behavior. Here, model hybrids were synthesized by exploring C-sp 2 chemistry ((1+2)-cycloaddition of nitrenes and amidation) of the outer MWCNT walls combined with anticancer agents, that is, 5-fluorouracil (5FU), purpurin (Purp), and 1,8-naphthalimide DNA intercalators (NIDIs), via linkers. Analyses of the Fe@MWCNT vehicles by SEM, TEM, and Raman spectroscopy revealed their morphology while Mössbauer spectroscopy confirmed the presence of encapsulated ferromagnetic iron-based nanodomains. Cytotoxicity of the hybrids was studied using a 24 h MTS assay combined with the apoptosis and life cycle assays against human melanoma (Me45), colon carcinoma (HCT116+), and colon adenocarcinoma (Caco-2). The cells had different sensitivity to the vehicles themselves as well as to the hybrids. MWCNT-based covalent hybrids of 5FU and Purp emerged as the most promising systems against Me45 and HCT116+ cell lines with the highest in vitro cytotoxicity and proapoptotic activity. Furthermore, nanotubes bearing 4-nitro-and 4-(N-morpholinyl)-1,8-naphthalimide DNA intercalators appear as a promising candidate for the treatment of Caco-2.

Purpurin, 1,2,4-trihydroxyanthraquinone, was regioselectively alkylated under basic conditions using bromoalcohol of varying chain length. As a base, potassium carbonate, tetrabutylammonium hydroxide or 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) was used. The reaction of alkylation proceeded exclusively on the 2-hydroxyl group of the purpurin molecule. Addition of the obtained 2-( -hydroxyalkoxy)purpurins to protected D-glucal catalysed by triphenylphosphine hydrobromide gave an access to new glycoconjugates with high enantioselectivity. In parallel experiments, the same substrates reacted in the presence of boron trifluoride etherate yielding the appropriate unsaturated adducts as a result of Ferrier rearrangement.

No abstract