Glycosaminoglycans (GAGs) are key elements of the pericellular space, where they are involved in
several signalling pathways determining cell fate [1,2]. The main transmitters of GAGs bioactivity are
their cell surface receptors, such as CD44 for hyaluronan (HA) and tyrosine-protein phosphatase S,
PTPσ, for chondroitin sulfate (CS) [3,4]. While overexpression of CD44 is a hallmark of various
malignant tumours, the interaction of CS with PTPσ is associated with inhibition of the axons growth
and reduced neural regeneration. In this study, we modified HA and CS with a short (C9) alkane thiol.
The functionalization was performed in an end-on fashion using oxime click chemistry at the reducing
end of the GAG thus, preserving its bioactivity. The obtained novel amphiphilic GAGs (HA-C9 and
CS-C9) self-assemble into micelles at physiological conditions. We explored the redox-sensitivity
(due to the presence of the thiol group) and the encapsulation ability in both hydrophobic and
hydrophilic compartments of the generated micelles. The synthesis of the aminooxy-alkylthiol was
preformed following previously described procedures [5]. Oxime coupling was carried out in 1/1
mixtures of ethanol or DMSO/phospohate buffer (pH 4.5) right after in situ deprotection of the
aminooxy group from the n-hidroxyphatalimide precursor. The obtained amphiphilic GAGs were
purified by dialysis against ethanol and characterized by 1H NMR (modification degree and purity).
Critical micellar concentration (CMC) was determined by fluorescence spectroscopy using Nile Red.
Size of micelles was determined through dynamic light scattering (DLS) and atomic force
microscopy, -potential was accessed by electrophoretic light scattering. Redox-sensitivity was
evaluated by monitoring the particle disassembleing upon addition of redox agent 1,4-Dithiothreitol
(DTT) by DLS and confirmed by Nile Red fluorescence quenching. The ability to encapsulate both
hydrophobic and hydrophilic compounds was demonstrated by determining the encapsulation
efficacy of Nile Red and Dextran-FITC respectively. Both HA-C9 (99% modified) and CS-C9 (68%
modified) formed aggregates with 150 nm and 200 nm of diameter, respectively, and a negative
superficial charge -30 mV. Importantly, the CMC did not change significantly upon increasing the
temperature to the physiological one. Upon the addition of DTT, we observe a micelle disaggregation
of HA-C9 as a result of the cleavage of sulphide bridges between polymers. This effect was not
observed when CS-C9 was used instead. Finally, we were able to entrap either hydrophilic (shell) or
hydrophobic (core) compound in the HA-C9 micelles and release them upon stimulus (redox
environments) relevant for tumour therapeutics. The obtained HA-C9 micelles are prominent as
tumour therapeutics as they (i) can target cells overexpressing the CD44 via the HA presented on
the surface; (ii) response to the tumour relevant redox stimulus; and (iii) allow entrapment of either
hydrophilic or hydrophobic drugs.
1. Fuster M. M. and Esko J. D., Nature Rev Cancer. 2005, 5, 526-542;
2. Bulow H. E. and Hobert O, Annu Rev Cell Dev Biol. 2006, 22, 375-407;
3. Shen Y. J. et al., Science. 2009, 326, 592-596;
4. Isacke, C. M. and Yarwood, H., Int J Biochem Cell Biol. 2002, 34,718–721;
5. Chan E. et al., Langmuir 2001, 18, 311–313;
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