Nanochemistry and biotechnology

Synthesis of the conjugate of TMP3 porphyrin telomerase inhibitor with polyethylene glycol carrier
Dubey L.V., Kuziv Ia.B., Negrutska V.V., Dubey I.Ya.
Institute of Molecular Biology and Genetics, NAS of Ukraine, 150 Zabolotnogo str., 03143 Kyiv, Ukraine 
E-mail: dubey@imbg.org.ua
Telomerase is an enzyme performing the elongation of telomeric DNA. The majority of cancer cells are characterized by high telomerase activity, in contrast to normal somatic cells. So the telomerase system, including the enzyme itself and its substrate, telomeric DNA, is a promising target for modern anticancer therapy. 
Tetra(N-methylpyridinium)porphyrin TMPyP is a well-established antitumor telomerase inhibitor. We found its tricationic analog TMP3 to be just as efficient an inhibitor in vitro as TMPyP (IC50 6-6.5 µM for both compounds) [1]. 
To improve the specificity and bioavailability of antitumor drugs they can be attached to some biocompatible polymers that allow the targeted drug delivery and controlled drug release. We prepared a nanoconjugate of TMP3 with polyethylene glycol. Its monomethyl ether (mPEG, MW 6000) was functionalized with amino group by O-carboxylation with succinic anhydride followed by the coupling with cysteamine. Porphyrin bearing a COOH group was attached to this polymer via the active ester approach. TMP3 content in various samples of the conjugate was 80-115 μmol/g, as determined using its  426=2.0×105 M-1cm-1. Material is quite stable upon dry storage (no degradation in 4 months at 4°C) and soluble in water.
The linker contains two biolabile bonds, a disulfide bridge that can be cleaved by reducing agents like glutathione and ester bond cleavable by esterases, allowing the drug release inside the cell. The overnight treatment of the conjugate with 100 mM dithiothreitol (pH 7.5) resulted in complete S-S bond cleavage. The inhibitor is also cleaved from the carrier in alkaline medium due to the ester hydrolysis. 

1.	Negrutska V.V., Dubey L.V., Ilchenko M.M., Dubey I.Ya. Design and study of telomerase inhibitors based on G-quadruplex ligands // Biopolym Cell.– 2013.–29, N 3.–P. 169-176.