Near infrared with principal component analysis as a novel analytical approach for nanoparticle technology

Purpose. To progress in the characterization of a poly(MePEGcyanoacrylate-c o-hexadecylcyanoacrylate) (poly(PEGCA-co-HDCA) copolymer and the nanopartic les formed from this copolymer. Methods. Poly(PEGCA-co-HDCA) at a MePEG/hexadecyl ratio of 1:4 was investig ated by H-1-NMR and near infrared spectroscopy. The nanoparticle suspension s, obtained by the methods of nanoprecipitation or emulsion-solvent evapora tion, as well as the crude nanoparticles and their dispersion medium-were a nalyzed by MePEG measurement, H-1-NMR, and near infrared spectroscopy. Results, The H-1-NMR results showed that the (poly(PEGCA-co-HDCA) copolymer obtained bore lateral hydrophilic MePEG chains and lateral hydrophobic hex adecyl chains in a final ratio of 1:4. How ever, this ratio, although repro ducible from batch to batch, represented only a mean value for different mo lecular species. Indeed, our results demonstrated the formation of more hyd rophobic poly(alkylcyanoacrylate) oligomers (with a higher content of hexad ecyl chains) and other more hydrophilic oligomers (with a higher MePEG cont ent). Only the more hydrophobic oligomers were able to form solid pegylated nanoparticles. As far as these nanoparticles were concerned, determination of their MePEG content allowed the calculation of a distance of 1.2 nm and 1.05 nm between 2 grafted MePEG chains at the nanoparticle surface, when o btained by nanoprecipitation and emulsion-solvent evaporation, respectively . Moreover, when the same copolymer batch was used, different nanoparticles were obtained according to the preparation method, as seen by near infrare d spectroscopy. Conclusions. The nanoparticles obtained by nanoprecipitation or emulsion-so lvent evaporation of poly(PEGCA-co-HDCA) 1:4 copolymer displayed a differen t supramolecular organization, as evidenced by the near infrared spectrosco py results. Moreover, these nanoparticles showed surface characteristics co mpatible with a long circulating carrier.