Tailored-BODIPY/Amphiphilic Cyclodextrin Nanoassemblies with PDT Effectiveness

Amphiphilic cyclodextrins (aCDs) are an intriguing class of carrier systems which, recently, have been proposed to deliver porphyrinoids and anticancer drugs or combined dose of both for dual therapeutic applications. The design of nanoassemblies based on aCD and photosensitizers (PSs) aims to preserve the photodynamic therapy (PDT) efficacy of PS, reducing the tendency of PS to self-aggregate, without affecting the quantum yield of singlet oxygen (¹O₂) production, and, not less importantly, minimizing dark toxicity and reducing photosensitization effects. With this idea in mind, in this paper, we focus on nanoassemblies between a non-ionic aCD (SC6OH) and halo-alkyl tailored iodinated boron-dipyrromethenes (BODIPY) dye, a class of molecules which recently have been successfully proposed as a stimulating alternative to porphyrinoids for their high photodynamic efficacy. Nanoassemblies of BODIPY/aCD (BL01I@SC6OH) were prepared in different aqueous media by evaporation of mixed organic film of aCD and BODIPY, hydration, and sonication. The nanostructures were characterized, measuring their hydrodynamic diameter and ξ-potential and also evaluating their time-stability in biological relevant media. Taking advantage of emissive properties of the not-iodinated BODIPY analogue (BL01), nanoassemblies based on aCD and BL01 were investigated as model system to get insight on entanglement of BODIPY in the amphiphile in aqueous dispersion, pointing out that BODIPY is well-entrapped in monomeric form (τ ≅ 6.5 ns) within the colloidal carriers. Also morphology and fluorescence emission properties were elucidated after casting the solution on glass. BL01@SC6OH is easily detectable in cytoplasm of HCT116 cell lines, evidencing the remarkable intracellular penetration of this nanoassembly similar to free BODIPY. On the same cell lines, the photodynamically active assembly BL01I/aCD shows toxicity upon irradiation. Despite the fact that free BL01I is more PDT active than its assembly, aCD can modulate the cell uptake of BODIPY, pointing out the potential of this system for in vivo PDT application