Spectroscopic methods such as circular dichroism and steady state fluorescence spectroscopy were used to monitor the conformation of BIOLOGY AND HEALTH SCIENCES SYNCHROTRON SOLEIL HIGHLIGHTS 2020 the bovine serum and evaluate its interactions with the nanoparticles (FIGURE3). Overall, these experiments demonstrated that BSA and the squalene-adenosine monomer form a complex. The stoichiometry of this complex is between 1 and 2 squalene-adenosine monomer per protein DISCO BEAMLINE and the binding constants place the prodrug among mild BSA binders. Associated publication FIGURE 3 Albumin-driven disassembly of lipidic nanoparticles: the specific case of the squalene-adenosine nanodrug. F. Gobeaux, J. Bizeau, F. Samson, L. Marichal, I. Grillo, F. Wien, S. O. Yesylevsky, C. Ramseyer, M. Rouquette, S. Lepêtre-Mouelhi, D. Desmaële, P. Couvreur, P. Guenoun, J. P. Renault, F. Testard. Nanoscale, 12(4), 2793 (2020). References [1] J. K. Patra et al. , J Nanobiotechnology 16, (2018). These experiments have been completed by molecular docking simulations [2] S. Soares et al., 6, 360 (2018). confirming the values of the binding energy. Moreover, these simulation [3] A. Gaudin et al., Nature shows that although the binding is unspecific, the highest probability of Nanotechnology 9, 1054 (2014). binding of SQAd monomer is in the grooves on the protein surface and [4] P. Couvreur et al., Nano Lett. 6, in the interdomain cleft of albumin. 2544 (2006). Overall, our study shows that the albumin in the blood serum is able to disassemble SQAd nanoassemblies by extracting the SQAd monomers Corresponding authors to form a complex with one or two molecules of SQAd. This mechanism Frédéric Gobeaux seems to be generic to any squalene-based prodrug since the binding & Fabienne Testard occurs through the squalene moiety and that several observations were CEA Saclay, reproduced with other prodrugs. NIMBE-LIONS bâtiment 546 91191 Gif-sur-Yvette, France CONCLUSIONS AND PERSPECTIVES frederic.gobeaux@cea.fr fabienne.testard@cea.fr These observations depart from the common view that proteins adsorb on all nanoparticles to form a passive corona around them. In the case Captions of soft nano-assemblies such as those formed by squalene-based FIGURE 1: Top: scheme of the nanoprecipitation process prodrugs, it appears that serum albumin disassemble these supramolecular of the SQAd bioconjugate prodrug into nanoparticles. assemblies and contribute to the transport of the prodrug in the blood Bottom: possible interactions between the components of the system. stream by forming a small complex. The nanoparticles thus act as circulating reservoirs in the blood stream. It remains to be seen if this FIGURE 2: Left: two SQAd nanoparticles observed by mechanism applies to other promising lipid nano-assemblies such as cryo-TEM. Middle: SANS pattern of SQAd nanoparticles (blue), bovine serum albumin (red) and the mixture thereof cubosomes and hexosomes. In the meantime, we are studying the (purple). The decrease of the signal at small q indicates role of lipoproteins, another important serum component involved in a loss of the nanoparticle contribution. Right: shift of the uptake of lipids, as well as the consequences of the flow through in the size distribution of the SQAd nanoparticles in the presence of albumin. situexperiments in the laboratory or at the synchrotron. FIGURE 3: Left: quenching of the albumin fluorescence in the presence of increasing amount of SQAd This work was supported by a public grant overseen by the French nanoparticles. Right: Modification of the albumin National Research Agency (ANR) as part of the “Investissements d’Avenir” conformation in the presence of increasing amount ofSQAd nanoparticles monitored by circular dichroism. program (Labex NanoSaclay, reference: ANR-10-LABX-0035) SANS experiment were performed at the Institut Laue-Langevin (Grenoble, France). 49