Polypeptide-Based Molecular Platform and Its Docetaxel/Sulfo-Cy5-Containing Conjugate for Targeted Delivery to Prostate Specific Membrane Antigen.

A strategy for stereoselective synthesis of molecular platform for targeted delivery of bimodal therapeutic or theranostic agents to the prostate-specific membrane antigen (PSMA) receptor was developed. The proposed platform contains a urea-based, PSMA-targeting Glu-Urea-Lys (EuK) fragment as a vector moiety and tripeptide linker with terminal amide and azide groups for subsequent addition of two different therapeutic and diagnostic agents. The optimal method for this molecular platform synthesis includes (a) solid-phase assembly of the polypeptide linker, (b) coupling of this linker with the vector fragment, (c) attachment of 3-aminopropylazide, and (d) amide and carboxylic groups deprotection. A bimodal theranostic conjugate of the proposed platform with a cytostatic drug (docetaxel) and a fluorescent label (Sulfo-Cy5) was synthesized to demonstrate its possible sequential conjugation with different functional molecules.

Synthesis and biological evaluation of Doxorubicin-containing conjugate targeting PSMA.

Prostate-specific membrane antigen (PSMA), also known as glutamate carboxypeptidase II (GCPII), has recently emerged as a prominent biomarker of prostate cancer (PC) and as an attractive protein trap for drug targeting. At the present time, several drugs and molecular diagnostic tools conjugated with selective PSMA ligands are actively evaluated in different preclinical and clinical trials. In the current work, we discuss design, synthesis and a preliminary biological evaluation of PSMA-specific small-molecule carrier equipped by Doxorubicin (Dox). We have introduced an unstable azo-linker between Dox and the carrier hence the designed compound does release the active substance inside cancer cells thereby providing a relatively high Dox concentration in nuclei and a relevant cytotoxic effect. In contrast, we have also synthesized a similar conjugate with a stable amide linker and it did not release the drug at all. This compound was predominantly accumulated in cytoplasm and did not cause cell death. Preliminary in vivo evaluation has showed good efficiency for the degradable conjugate against PC3-PIP(PSMA+)-containing xenograft mine. Thus, we have demonstrated that the conjugate can be used as a template to design novel analogues with improved targeting, anticancer activity and lower rate of potential side effects. 3D molecular docking study has also been performed to elucidate the underlying mechanism of binding and to further optimization of the linker area for improving the target affinity.

Magnetocontrollability of Fe7C3@C superparamagnetic nanoparticles in living cells.

BACKGROUND: A new type of superparamagnetic nanoparticles with chemical formula Fe7C3@C (MNPs) showed higher value of magnetization compared to traditionally used iron oxide-based nanoparticles as was shown in our previous studies. The in vitro biocompatibility tests demonstrated that the MNPs display high efficiency of cellular uptake and do not affect cyto-physiological parameters of cultured cells. These MNPs display effective magnetocontrollability in homogeneous liquids but their behavior in cytoplasm of living cells under the effect of magnetic field was not carefully analyzed yet. RESULTS: In this work we investigated the magnetocontrollability of MNPs interacting with living cells in permanent magnetic field. It has been shown that cells were capable of capturing MNPs by upper part of the cell membrane, and from the surface of the cultivation substrate during motion process. Immunofluorescence studies using intracellular endosomal membrane marker showed that MNP agglomerates can be either located in endosomes or lying free in the cytoplasm. When attached cells were exposed to a magnetic field up to 0.15 T, the MNPs acquired magnetic moment and the displacement of incorporated MNP agglomerates in the direction of the magnet was observed. Weakly attached or non-attached cells, such as cells in mitosis or after cytoskeleton damaging treatments moved towards the magnet. During long time cultivation of cells with MNPs in a magnetic field gradual clearing of cells from MNPs was observed. It was the result of removing MNPs from the surface of the cell agglomerates discarded in the process of exocytosis. CONCLUSIONS: Our data allow us to conclude for the first time that the magnetic properties of the MNPs are sufficient for successful manipulation with MNP agglomerates both at the intracellular level, and within the whole cell. The structure of the outer shells of the MNPs allows firmly associate different types of biological molecules with them. This creates prospects for the use of such complexes for targeted delivery and selective removal of selected biological molecules from living cells.