Cucurbit[10]uril-Encapsulated Cationic Porphyrins with Enhanced Fluorescence Emission and Photostability for Cell Imaging

Abstract

Porphyrins are widely applied for imaging, diagnosis, and treatment of diseases because of their excellent photophysical properties. However, porphyrins easily tend to aggregate driven by hydrophobic interaction and π-π stacking in an aqueous medium, which causes fluorescence quenching of the porphyrins as well as limitation of cell uptake and intracellular accumulation. Herein, cucurbit[10]uril (CB[10]) was used to fully encapsulate cationic porphyrin (CPor) in the large cavity with strong binding affinity in aqueous solutions, and the CPor aggregates were efficient disassembled, companying remarkable enhancing its fluorescence intensity. The CB[10]-based host− guest complex provided excellent protection to CPor, resulting in less susceptibility to oxidation and imparting higher photostability to CPor for cell imaging. In addition, by complexation with CB[10], it was found that the fluorescence signals and photostability of CPor were also effectively improved in cells with different reactive oxygen species levels. It is highly anticipated that the large macrocyclic host cavity-triggered large-guest encapsulation strategy in this work will provide a convenient and efficient method for designing supramolecular porphyrin dyes, thus broadening the diagnosis and imaging application in cells and microorganisms.

A hypoxia-responsive supramolecular formulation for imaging-guided photothermal therapy

“…These results explicitly proved that the photostability of IR780 was observably improved by SAC4A and NH 2 C4A. The probable mechanism was that SAC4A and NH 2 C4A encapsulated IR780, which could make IR780 trapped in the complex and isolated from environment or solvent, and protect IR780 from light irradiation and oxidation 24 , 66 .…”

A Bacteria‐Responsive Porphyrin for Adaptable Photodynamic/Photothermal Therapy

“…To reduce the cytotoxicity, as shown in Figure 5a, a supramolecular approach to form a host‐guest complex between TMPyP and CB[7] was employed. CB[7] preferentially interacted with the N ‐methylpyridyl moieties of TMPyP in a 1 : 4 stoichiometry (TMPyP : 4 CB[7]) with a binding constant of 8.2×10 4 M −1 for each step [58, 59] . By forming the host‐guest complex of TMPyP/(CB[7]) 4 , as shown in Figure 5b, the cell viability maintained over 85 % even at a relatively high concentration of 0.20 mM, which was twice the concentration used for in vitro antibacterial experiments.…”

“…CB [7] preferentially interacted with the N-methylpyridyl moieties of TMPyP in a 1 : 4 stoichiometry (TMPyP : 4 CB [7]) with a binding constant of 8.2 × 10 4 M À 1 for each step. [58,59] By forming the host-guest complex of TMPyP/(CB [7]) 4 , as shown in Figure 5b, the cell viability maintained over 85 % even at a relatively high concentration of 0.20 mM, which was twice the concentration used for in vitro antibacterial experiments. Therefore, the biocompatibility of TMPyP can be significantly improved by the introduction of CB [7].…”

Targeted Delivery and Site-Specific Activation of β-Cyclodextrin-Conjugated Photosensitizers for Photodynamic Therapy through a Supramolecular Bio-orthogonal Approach

“…For applications in PDT, supramolecular photosensitizers assembled by metal coordination, electrostatic forces, or host–guest interactions have been reported. − ,, For the host–guest complexes, the aforementioned macrocyclic hosts have been adopted to encapsulate a wide range of photosensitizers for anticancer and antimicrobial applications. , The hydrophilic hosts can generally increase the water solubility of the guest photosensitizers, reduce their aggregation, and enhance their photostability and photodynamic efficacy . In some of these systems, amphiphilic hosts or guests are used and the resulting host–guest complexes further self-assemble to form nanostructured materials, while discrete host–guest photosensitizing systems have also been reported.…”

“…22,23 The hydrophilic hosts can generally increase the water solubility of the guest photosensitizers, reduce their aggregation, and enhance their photostability and photodynamic efficacy. 24 In some of these systems, amphiphilic hosts or guests are used and the resulting host−guest complexes further self-assemble to form nanostructured materials, while discrete host−guest photosensitizing systems have also been reported. Owing to the adjustable host−guest interactions, these supramolecular photosensitizers can undergo reversible assembly and disassembly through displacement of the guest species, which provides a mechanism for activation of the photodynamic activity.…”