Membrane-Mediated Interactions between Anisotropic Nanoparticles

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NONTECHNICAL SUMMARYNanoparticles have great potential in many biomedical applications including biosensing, diagnostics, gene therapy, drug delivery, magnetic hyperthermia and photothermal therapy. There are, however, also concerns associated with potential environmental and health hazards of many types of nanoparticles. Biomedical applications of nanoparticles and their potential toxicity necessitate their adhesion on a thin envelope encapsulating living cells known as the plasma membrane, and eventually their cellular entry. The plasma membrane, which is mainly composed of lipids, is an important component of all living cells. It is fluid and highly flexible. As a result, the adhesion of nanoparticles leads to deformation of the plasma membrane, which in turn leads to the aggregation of nanoparticles. While there have been studies on the effect of lipid membranes on the aggregation of spherical nanoparticles, the understanding of the effect of lipid membranes on interactions between nanoparticles with complex geometries or surface properties, and their resulting aggregation, remains lacking. This is despite nanoparticles with complex geometries or surface properties having more promising biomedical applications than spherical ones. This project aims at understanding the effect of membranes on interactions between nanoparticles with complex geometries or surface properties. During the course of this research, the principal investigator will train graduate and undergraduate students in various computational approaches, which will prepare them for careers in STEM fields. High school students will also be engaged in some aspects of the research through a summer program run by the Department of Physics and Materials Science at the University of Memphis. Aspects of the research will be integrated is some courses at the undergraduate and graduate levels that are taught by the principal investigator.TECHNICAL SUMMARYThis award supports an investigation of the two-body interaction and self-assembly of anisotropic nanoparticles induced by membrane deformations resulting from nanoparticles’ adhesion on lipid membranes. The research will be carried out through systematic and large-scale molecular dynamics simulations of an efficient coarse-grained model. The efficiency of this approach stems from the treatment of the solvent implicitly, softening the pair-wise interactions between beads, and the treatment of the nanoparticles as hollow tessellated surfaces. Two main types of anisotropic nanoparticles, corresponding to sphero-cylindrical nanoparticles and Janus nanoparticles, will be considered in this research. In the first part of the proposed research, the dimerisation threshold between anisotropic nanoparticles and the modes of dimerisation will be determined systematically as a function of the geometry of the nanoparticles and their surface heterogeneities. The modes of dimerisation of the nanoparticles will be investigated both in the case of planar tensionless lipid membranes and in the case of tensionless cylindrical membranes and closed vesicles, with the nanoparticles adhering either to the inner or outer side of the membrane. In the second part of the research, multi-body effects and self-assembly of the anisotropic nanoparticles will be investigated for varying parameters of the sphero-cylindrical nanoparticles and Janus nanoparticles and for varying values of the adhesion strength. The stability of the self-assemblies will be investigated by free-energy calculations of the results in conjunction with the Helfrich Hamiltonian.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.