|Ph.D Student||Soll Matan|
|Subject||Bioconjugated Corroles for Treating Diseases|
|Department||Department of Chemistry||Supervisor||Professor Zeev Gross|
Recent work has shown that metallocorroles are a very promising for drug development against various diseases. This includes the antineoplastic activity of water soluble gallium corroles, which has been reported extensively and disclosed great therapeutic potential. The first new finding in this thesis was the relationship between cytotoxicity and affinity to VLDL (very low density lipoprotein) of different metal complexes of the same corrole. Consequently, we considered much more lipophilic derivatives of corroles (VLDL is considered a “carrier” of lipophilic drugs) for displaying better efficacy towards malignant tissue. Testing this hypothesis required a solution for introducing non-water-soluble corroles into aqueous environment.
An increasing attention to albumin as a drug delivering vehicle, together with previous findings about albumin/corrole host/guest interactions, initiated the investigation regarding the utility of albumin for the introduction of lipophilic corroles into biological media. This was performed by a very simple methodology: co-solvation of albumin and lipophilic metallocorroles in a mixed water/organic solvent, followed by dialysis against PBS to remove the organic solvent. This approach yielded non-covalent conjugates of nanoparticular corrole with the protein, which we termed bionanocages (BNC’s). The novelty relative to other albumin nanoparticles fabrication techniques is that those require extreme to minor covalent or quaternary structure modifications of the protein. Following the characterization of the BNC’s, we have disclosed that their rates of clearance from intracellular compartments are very slow, which might be of great promise for bio-imaging. Further investigation disclosed that the specific corrole 5,10,15-tris(pentafluorophenyl)corrole gallium(III), (2)Ga, used for BNC’s formation is cytostatic rather than cytotoxic.
In parallel, a novel synthetic procedure for the synthesis of 5,10,15-tris(trifluoromethyl)corrole, (4)H3, was developed in order to test the corresponding gallium chelate (4)Ga. One main difference is the almost 50% smaller molecular weight of (4)Ga relative to (2)Ga. Cancer cells treated with (4)Ga-based BNC’s did undergo programmed cell death (apoptosis) in vitro within a few hours of exposure, accompanied by phenotypes of lysosomal fission, elevated calcium levels, increased reactive oxygen species (ROS) content, mitochondrial depolarization and membranal blabbing. These phenotypes are reminiscent of necrosis and apoptosis altogether, implying that the activity of (4)Ga might be attributed to the emerging form of cellular controlled death termed necroptosis. Assessment of in vitro cellular uptake of (4)Ga disclosed disassembly of the BNC structure and release of its cargo extracellularly, fast absorbance of (4)Ga on the surface of cells and uptake of the corrole through what appears to be facilitated diffusion.
Initial preclinical assessment of a series of BNC’s disclosed that albumin conjugates of (2)Ga, (4)Ga and the water soluble (1)Ga impose no apparent physiological and hematological effects at the tested doses. The (4)Ga BNC’s displayed the most promising pharmacokinetics profile, a fast redistribution phase followed by a very slow clearance phase, identifying it as the best candidate for therapeutics and imaging.
We conclude by stating that we have introduced a facile and novel formulation of non-water soluble corroles with native proteins, together with the introduction of a new corrole subfamily that displays improved antineoplastic activity.