Physica B 385–386 (2006) 725–727 Mean square hydrogen fluctuations in chitosan/lecithin nanoparticles from elastic neutron scattering experiments Fabio Sonvico a , Maria Teresa Di Bari b , Livia Bove c , Antonio Deriu b,Ã , Fabrizio Cavatorta b , Gianfranco Albanese b a Dipartimento di Farmacia,Universita` di Parma and INFM, Parma I-43100, Italy b Dipartimento di Fisica,Universita` di Parma, INFM and CNISM, Parma I-43100, Italy c INFM-OGG and CRS-SOFT, c/o Institue Laue-Langevin, 38042 Grenoble, France Abstract Recently, we have started a systematic study of the structure and dynamics of nano- and microparticles of interest as highly biocompatible drug carriers. For these particles, that are composed of polymeric and lipid material, a detailed understanding of the particle–solvent interactions is of key importance in order to tailor their characteristics for delivering drugs with specific chemical properties. Here we report results of elastic neutron scattering (ENS) investigations on lecithin/chitosan nanoparticles. They were first prepared by autoassembling the two components in aqueous solution; the samples were then freeze-dried and re-hydrated in a D 2 O atmosphere. The experiments were performed in the temperature range of 20–50 K using the backscattering spectrometer IN13 at ILL (Grenoble, France). The comparison of samples in the dry state with similar ones at an hydration level of about 0.3–0.4 (g D 2 O/g hydrated sample), indicates that the presence of an outer chitosan ‘‘coating’’ reduces the mean square fluctuations of the hydrogens in the lipid component, leading thus to a stiffer nanoparticle structure. r 2006 Elsevier B.V. All rights reserved. PACS: 61.12.Ex; 82.35.Np; 87.14.Cc; 82.37.Rs Keywords: Elastic neutron scattering; Nanoparticles; Lipids; Polysaccharides; Drug delivery 1. Introduction In pharmaceutical sciences, nano- and microparticles have been proposed to improve the bioavailability and efficacy of drugs with promising results. The use of carriers allows the modification of the biopharmaceutic properties of the drug without modifying its molecular structure; it is therefore an interesting approach for the administration of drugs presenting some hindering problems, such as low water solubility, rapid metabolism/elimination, narrow therapeutic index, poor specificity [1,2]. For the production of these delivery systems, a number of different materials have been proposed, such as polysaccharides, synthetic polymers, lipids, etc. Among them, phospholipids and polysaccharides have received considerable attention due to their biocompatibility, biodegradability, low cost, and safety [3,4]. The understanding of the structure and of the interac- tions involved in nanoparticle formation has major relevance for tailoring the release of the drug in order to obtain specific therapeutic effects. Recently, we have started a systematic study of the structure and dynamics of nano- and microparticles of interest as highly biocom- patible drug carriers. For these particles, that are made up from polymeric and lipid materials, a detailed study of the interaction between the components as well as of the particle–solvent (H 2 O) interactions is of key importance in order to foretell the encapsulation and delivery of drugs with specific chemical properties. Here we report results of an elastic neutron scattering (ENS) investigation on nanoparticles composed of lipids and polysaccharides. The lipid part, soybean lecithin, a mixture of different phospholipids, enables an efficient ARTICLE IN PRESS www.elsevier.com/locate/physb 0921-4526/$ - see front matter r 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.physb.2006.06.034 Ã Corresponding author. Tel.: +39 0521 905267; fax: +39 0521 906022. E-mail address: Antonio.Deriu@fis.unipr.it (A. Deriu).