Evaluation of the surface properties of dextran-coated poly(isobutylcyanoacrylate) nanoparticles by spin-labelling coupled with electron resonance spectroscopy

Poly(alkylcyanoacrylate) nanoparticles are developed as carrier for the in vivo delivery of drugs. In this area of research, one of the major challenges is to design nanoparticles able to carry a drug to a specific site in the body. This appears to be mainly governed by the surface properties of the carrier. Results from previous independent studies suggest that the way dextran chains are arranged at the nanoparticle surface can affect the in vivo fate of the carrier. Thus, the purpose of the present study was to investigate for the first time whether electronic paramagnetic resonance (EPR) could highlight a difference between the physico-chemical surface properties of dextran-coated nanoparticles obtained by two different emulsion polymerisation mechanisms of isobutylcyanoacrylate. Poly(isobutylcyanoacrylate) nanoparticles were prepared either by anionic or by radical polymerisation, initiated in both cases by dextran. The respective copolymers self-organised as nanoparticles. Dextran chains located at the nanoparticle surface could be labelled with a free nitroxide radical containing a probe and EPR analysis could be performed on freeze-dried nanoparticles, rehydrated nanoparticles and dispersed nanoparticles in water. The mobility of dextran chains appeared to differ according to the degree of hydration of the systems. More interestingly, EPR spectra clearly highlighted differences in dextran chain mobility comparing the nanoparticles obtained by radical and anionic polymerisation. Therefore, this technique opens an interesting prospect of investigating surface properties of polysaccharide-coated nanoparticles by a new physico-chemical approach to further correlate the mobility of the polysaccharide chains with the fate of the nanoparticles in biological systems.