Recently, we detected a previously unknown Ser-Pro-Cys
(SPC) tripeptide
in the blood serum of multiple sclerosis patients. Its role as a biomarker
of the autoimmune disease was suggested, although its origin and real
biological activity remained unclear. Here, we created a biocompatible
PEGylated comb-like polymer that was used as a platform for covalent
immobilization of the SPC, which provided a possibility to explore
the biological activity of this tripeptide. This macromolecular conjugate
was synthesized via a reaction of the terminal epoxide group of the
biocompatible copolymer of dimethyl maleate (DMM) and polyethylene
glycol methyl ether methacrylate (PEGMA) with the amino group of the
SPC tripeptide. Unexpectedly, the resulting conjugate containing SPC
demonstrated anticancer activity in vitro. It possessed
pro-apoptotic action toward human tumor cells, while there was no
cytotoxic effect of that conjugate toward normal lymphocytes of human
peripheral blood. The detected biological effects of the created conjugate
inspired us to carry out a thorough study of structural and colloidal-chemical
characteristics of this surface-active copolymer containing side PEG
chains and a terminal nontoxic synthetic fragment. The copolymer composition,
in particular, the content of the peptide fragment, was determined
via elemental analysis and NMR spectroscopy. At CMC, it formed polymeric
micelle-like structures with a hydrodynamic diameter of 180 ±
60 nm. The conjugation of the peptide fragment to the initial comb-like
copolymer caused a change of zeta-potential of the formed micelle-like
structures from −0.15 to 0.32 mV. Additional structural modification
of the created polymeric nanoplatform was performed via attachment
of fluorescein isothiocianate (FITC) dye that permitted monitoring
of the behavior of the bioactive SPC-functionalized conjugate in the
treated tumor cells. Its penetration into those cells and localization
in their cytoplasm were revealed. The principal novelty of this study
consists in finding that covalent conjugation of two nontoxic compoundsSPC
tripeptide and comb-like PEGylated polymerled to an unexpected
synergy which appeared in the distinct cytotoxic action of the macromolecular
complex toward human tumor cells. A potential role of peculiarities
of the colloidal-chemical properties of the novel conjugate in its
cytotoxic effect are discussed. Thus, synthesized comb-like PEGylated
polymers can provide a prospective nanoplatform for drug delivery
in anticancer chemotherapy.