Evaluation of the Immunosafety of Cucurbit[n]uril on Peripheral Blood Mononuclear Cells In Vitro

Overcoming barriers with non-covalent interactions: supramolecular recognition of adamantyl cucurbit[n]uril assemblies for medical applications

Adamantane, a staple in medicinal chemistry, recently became a cornerstone of a supramolecular host-guest drug delivery system, ADA/CB[n]. Owing to a good fit between the adamantane cage and the host cavity of the cucurbit[n]uril macrocycle, formed strong inclusion complexes find applications in drug delivery and controlled drug release. Note that the cucurbit[n]uril host is not solely a delivery vehicle of the ADA/CB[n] system but rather influences the bioactivity and bioavailability of drug molecules and can tune drug properties. Namely, as host-guest interactions are capable of changing the intrinsic properties of the guest molecule, inclusion complexes can become more soluble, bioavailable and more resistant to metabolic conditions compared to individual non-complexed molecules. Such synergistic effects have implications for practical bioapplicability of this complex system and provide a new viewpoint to therapy, beyond the traditional single drug molecule approach. By achieving a balance between guest encapsulation and release, the ADA/CB[n] system has also found use beyond just drug delivery, in fields like bioanalytics, sensing assays, bioimaging, etc. Thus, chemosensing in physiological conditions, indicator displacement assays, in vivo diagnostics and hybrid nanostructures are just some recent examples of the ADA/CB[n] applicability, be it for displacements purposes or as cargo vehicles.

Evaluation of the Immunosafety of Cucurbit[n]uril In Vivo

Cucurbiturils are a family of macrocyclic oligomers capable of forming host-guest complexes with various molecules. Due to noncovalent binding to drug molecules and low toxicity, cucurbiturils has been extensively investigated as potential carriers for drug delivery. However, the immune system's interactions with different drug carriers, including cucurbiturils, are still under investigation. In this study, we focused on cucurbiturils' immunosafety and immunomodulation properties in vivo. We measured blood counts and lymphocyte subpopulations in blood, spleen, and bone marrow, and assessed the in vivo toxicity to spleen and bone marrow cells after intraperitoneal administration to BALB/c mice. When assessing the effect of cucurbit[6]uril on blood parameters after three intraperitoneal injections within a week in laboratory animals, a decrease in white blood cells was found in mice after injections of cucurbit[6]util, but the observed decrease in the number of white blood cells was within the normal range. At the same time, cucurbit[7]uril and cucurbit[8]uril did not affect the leukocyte counts of mice after three injections. Changes in the number of platelets, erythrocytes, and monocytes, as well as in several other indicators, such as hematocrit or erythrocyte volumetric dispersion, were not detected. We show that cucurbiturils do not have immunotoxicity in vivo, with the exception of a cytotoxic effect on spleen cells after сucurbit[7]uril administration at a high dosage. We also evaluated the effect of cucurbiturils on cellular and humoral immune responses. We founded that cucurbiturils in high concentrations affect the immune system in vivo, and the action of various cucurbiturils differs in different homologues, which is apparently associated with different interactions in the internal environment of the body.

Influence of Cucurbiturils on the Production of Reactive Oxygen Species by T- and B-Lymphocytes, Platelets and Red Blood Cells

Reactive oxygen species (ROS) are highly reactive chemical molecules containing oxygen. ROS play an important role in signaling and cell homeostasis at low and moderate concentrations. ROS could be a cause of damage to proteins, nucleic acids, lipids, membranes and organelles at high concentrations. There are a lot of cells that can produce ROS to maintain functional activity. It is known that metal nanoparticles can increase production of ROS in cells. However, the effect of cucurbiturils on ROS production is still unknown. In our study, we evaluated production of ROS by the immune (T-, B-lymphocytes, NK-cells) and non-immune cells (red blood cells, platelets), as well as tumor cells line (1301, K562) after treatment with cucurbiturils in vitro. Assessment of reactive oxide species (ROS) were provided by using dihydrorhodamine 123 (DHR 123). Fluorescence intensity and percentage DHR123 were measured by flow cytometry. Platelets, erythrocytes and activated T-helpers were changed the level of ROS production in response to stimulation with cucurbiturils. It was found that the percentage of these ROS-producing cells was reduced by cucurbiturils. Thus, cucurbiturils may affect the production of ROS by cells, but further research is needed in this area.

Production of reactive oxygen species by neutrophils and macrophages of F1 hybrid mice (C57Bl6xCBA) in response to stimulation with cucurbit(n)urils (n = 6, 7, 8)

   Background. Due to their very small size, nanomaterials, in particular cucurbiturils, have unique physical and chemical properties that find their application in medicine. However, the toxicity of cucurbiturils is not fully understood; in particular, we are interested in the immunological safety of their use. One of the mechanisms of nanotoxicity is the formation of reactive oxygen species (ROS) by macrophages and neutrophils. Hyperproduction of ROS can lead to oxidative stress and further damage to cell DNA with loss of physiological function and development of pathology.   The aim. Evaluation of the effect of cucurbit[n]urils (n = 6, 7, 8) on the production of reactive oxygen species by mice macrophages and neutrophils.   Materials and methods. F1 hybrid mice (CBAxC57Bl/6) aged 2 months (n = 11) were used in the work. Evaluation of superoxide radical production by peritoneal mouse neutrophils and macrophages was carried out by spectrophotometric method for determining the reduction of p-nitroblue tetrazolium (NBT) to formazan.   Results. It was shown that CB[6] and CB[7] at concentrations of 0.5 and 0.3 mM do not have an inhibitory effect on ROS synthesis, but, on the contrary, significantly increase ROS production by macrophages. In addition, CB[6] 0.3 mM increases the level of ROS in neutrophils.   Conclusion. Cucurbiturils can lead to an increase in the production of ROS in immunocompetent cells, depending on the concentration used (0.3 mM and higher).

Assessment of the Biocompatibility of Cucurbiturils in Blood Cells

Currently, cucurbiturils are being actively researched all over the world. Research is focused on the ways of improving the solubility and selectivity of cucurbiturils, increasing the stability of the complexes with other particles in various media and enhancing their ability to bind and release various substances. The most significant area of our research is the assessment of safety, studying the biological properties and synergistic effects of cucurbiturils during complexation with drugs. In this article, the hemocompatibility of erythrocytes and leukocytes with cucurbiturils was investigated. We demonstrated that cucurbiturils have no cytotoxic effect, even at high concentrations (1 mM) and do not affect the viability of PBMCs. However, cucurbiturils can increase the level of the early apoptosis of lymphocytes and cucurbit[7]uril enhances hemolysis in biologically relevant media. Despite this, cucurbiturils are fairly safe organic molecules in concentrations up to 0.3 mM. Thus, we believe that it will become possible to use polymer nanostructures as drug delivery systems in clinical practice, since cucurbiturils can be modified to improve pharmacological properties.