Molecular Investigation of The Interaction Between a Gold Nanoparticle and a Polymer in Aqueous Solution

Several experimental and theoretical challenges limit a more rational design of nanoparticles (NPs) with a specific target application, i.e., the preparation of NPs with different structures/properties for various final uses. The characterization of different nanoparticle suspensions in liquids has drawn significant attention in a wide range of engineering applications. Recently, many computational approaches concerning the interactions between soft materials and inorganic nanoparticles proved to be promising in guiding the experimental preparation of nano suspensions [1-3]. Due to their optical and electronic properties, gold nanoparticles (AuNPs) are interesting for several applications, ranging from energy (e.g., solar steam generation [4,5]) to medicine (e.g., cancer theranostics [6,7]). Regarding the latter, AuNPs often encounter biocompatibility and biodegradability issues that can be overcome by encapsulating them in a poly (lactic-co-glycolic acid) (PLGA) matrix. Understanding the self-assembly dynamics of PLGA on the AuNP surface is crucial to guide and optimize the design of AuNPs coated with a PLGA corona. In this work, we combine different computational techniques to understand the interactions of an AuNP with PLGAs, aiming at assessing the most efficient and effective AuNP shape for biological applications. Specifically, we first perform classical molecular dynamics simulations while tuning the PLGA concentration in an aqueous solution; second, relying on a recently developed unsupervised machine learning (ML) algorithm, we evaluate the time evolution and behavior of PLGA clusterization. Finally, we employ the umbrella sampling approach to explore the AuNP-PLGA free energy landscape; this, combined with a detailed analysis of the surface still accessible to the solvent, allow us to gain insight into the anisotropic adsorption behavior of PLGAs onto AuNP. Our results highlight that the shallow morphology, besides surface chemistry, can influence the adsorption phenomena: in particular, the tested AuNP topology present the Au {1 1 1} crystal planes as privileged adsorption sites. This modeling-based investigation offers a comprehensive methodological approach for the rational and functional design of PLGA-coated gold nanoparticles [8].<br/><br/><b>Acknowledgement: </b>Support of the Italian National Project PRIN Heat transfer and Thermal Energy Storage Enhancement by Foams and Nanoparticles (2017F7KZWS) is acknowledged.<br/><br/><b>References</b><br/>[1] T. D. Jorgenson, et al., Soft Matter, vol. 15, no. 37, pp. 7360–7368, 2019, doi: 10.1039/C9SM00426B.<br/>[2] Z. E. Hughes, et al., Nanoscale, vol. 9, no. 1, pp. 421–432, 2017, doi: 10.1039/C6NR07890G.<br/>[3] A. Cardellini, et al., Journal of Physics: Condensed Matter, vol. 28, no. 48, 2016, doi: 10.1088/0953-8984/28/48/483003.<br/>[4] M. Morciano, et al., Scientific reports, vol. 7, no. 11970, 2017, doi: 10.1038/s41598-017-12152-6.<br/>[5] E. Chiavazzo, et al., Nature Sustainability, vol. 1, pp. 763–772, 2018, doi: 10.1038/s41893-018-0186-x.<br/>[6] E. Chiavazzo, et al., Nature Communications, vol. 5, no. 3565, 2014, doi: 10.1038/ncomms4565.<br/>[7] A. Gizzatov, et al., Advanced functional materials, vol. 24, no. 29, 2014, doi: 10.1002/adfm.201400653.<br/>[8] R. Cappabianca, P. De Angelis, A.Cardellini, E. Chiavazzo, and P. Asinari, ACS Omega,<i> under review</i>