Figure 9. Schematic representation of blood cellular uptake of VGALG and VGCB8ALG hydrogels. Chemical structures of VG, ALG, and CB8 are also shown. The 2:1 binary complex of CB8 with the viologen dimers is not shown for simplicity.
As described in the introduction, employing supramolecular hydrogels based on polysaccharides for biomedical applications and utilizing cucurbituril macromolecules is not original and has received significant attention. It has also been described for various biological and clinical applications. Hydrogels are themselves a widely researched field of (bio)materials. They have been enormously reported, and the field is not novel.[12] For example, hydrogel drug delivery has already implemented the host-guest association between cucurbit[7]uril (CB7) and cisplatin.[35]Nonetheless, elucidating the effects of macromolecules on the mechanism of cellular uptake is still motivated.
The biocompatibility and low toxicity have been confirmed for the modified ALG in the present work. The translation of the unmodified ALG has already been explored in literature.[36] The research concluded the significant role of size. Three different size-dependent mechanisms for cellular uptake were suggested. Oleoyl ALG ester nanoparticles whose sizes are 50, 120, or 730 nm enter the colon cancer cells via Clathrin-Mediated Endocytosis (CME), CvME, or micropinocytosis, respectively.[36] From Figure 4, the CB8-modified ALG has a size that is 165 nm compared to 1540 nm for the undecorated ALG. The uptake mechanism was confirmed to be CvME which agrees with the literature. In another account, the authors highlighted the effect of charges on the uptake of nanoparticles. Because the lung cancer cell’s surface has a negative charge, cationic cerium oxide nanoparticles[37] were better internalized than neutrally or negatively charged ones, such as the cellular internalization of polyplexes, lipoplexes, and lipopolyplexes into a myoblast cell line.[38] From Figure 4, the modified VGCB8ALG has a positive charge (viz. +14.4 mV) compared to the negatively charged VGALG (-19.8 mV) and thus was better internalized into leukemia cancer in agreement with those reports. The rigidity factor was demonstrated to modulate the type of cellular uptake, in which rigid nanoparticles of N ,N -diethyl acrylamide, and 2-hydroxyethyl methacrylate cross-linked with N ,N ′-methylene-bis-acrylamide were better internalized to RAW 264.7 murine macrophage cells compared to soft nanoparticles.[39] From Figure S5 in the Supporting Information, adding CB8 renders the modified hydrogels more rigid than VGALG. Thus, the increase in endocytosis is unsurprising. The exciting point remains the straightforward elucidation of how CB8 has modulated the cellular uptake, which can be further utilized for other clinical applications in the future.
Collectively these data unfold the factors that biomedical researchers need to consider (among others) to get more efficient drug delivery systems in cancer therapy that involves a macromolecular system or other drug vehicles. Although, nowadays, the field of application, material type, and drug loading need to be precisely selected and extensively studied, we envisage that the successful modulation of cellular internalization upon the addition of CB8 on VGALG must have a wide impact in the broader research field and benefits similar cellular studies performed on other macrocycle-based biomaterials for other biomedical applications. The technology is patentable, which would then be of interest to international pharmaceutical companies for commercial development.
CONCLUSION
The present work offers a supramolecular strategy to modulate the cellular uptake and intracellular processing of drug delivery systems, paving the way for a more remarkable improvement in the development of drug therapeutics of alginates in cancer therapy. We showed that supramolecular encapsulation is the key required for the efficient delivery of a model drug system via CvME, as manifested in the substantial decrease in the size of the alginate hydrogels. The employment of a supramolecular approach to modify drug carriers is not new. Still, the results here confirm a distinct, unique modulation of the intracellular processing of alginate carriers, unfolding a thorough understanding of the macrocyclic effects on drug delivery compared to previous reports.
Supplementary Information The online version contains supplementary material available at XXXXXX .
Author Contributions
F.C.; optical data (UV, PL, TRPL) acquisition and analysis and writing the initial draft, V. P.; material characterization by FTIR, DLS, TGA, DSC, and NMR, P.L.; data analysis, M.B., A.A., O.B., M.B., and E.P.; clinical studies and contribute to manuscript writing, N.S. created the idea, conceptualization, supervision, and final manuscript writing. All authors have approved the final version of the manuscript.
Funding Sources
This study was supported by Grant 12R113 from UAE University.
Data availability: All relevant data are within the paper.