Impact of negative Gaussian curvature of nanoparticles on cellular uptake

Abstract

Nanoparticles (NPs) have proven effective for delivering drugs, genes, diagnostics, and vaccines into target cells. Cellular uptake of NPs usually involves endocytosis mechanisms. Inspired by cell-penetrating peptides like TAT, which generate negative Gaussian membrane curvature that enables the uptake of cargo attached to the peptide, we hypothesized that designing NPs with negative curvature could lower the energy barrier for endocytosis, improving cellular uptake and reducing extracellular accumulation, impacting NP effectiveness and toxicity.

In order to accomplish the goal, we focused on gold nanoparticles, versatile for imaging, photothermal therapy, and drug delivery. We synthesized two NP types: gold nanorods (AuNRs) with zero gaussian curvature and gold dogbones (AuDBs) with negative gaussian curvature. We assessed NP uptake using MD simulations and experiments.

For AuDBs, the double gyroid template was used, with biodegradable poly (styrene-block-methyl methacrylate) (PS-PMMA) copolymer self-assembly. AuDBs were grown inside the PS gyroid nanopores and the template etched out. AuNRs were synthesized using a binary surfactant and seed-mediated growth. Various characterization techniques were employed to confirm the successful synthesis of AuNPs and to evaluate their cellular uptake.

FE-SEM showed particle formation, with AuNR lengths of 98.35±12.45 nm and AuDBs at 100.89±18.85 nm. Gaussian curvature was 0 for AuNRs and -14.5/nm² for AuDBs. These NPs exhibited strong fluorescence for cellular uptake assessment through confocal laser scanning microscopy (CLSM) without fluorescent probes. A549 lung cancer cells and NIH3T3 fibroblast cells were chosen for in-vitro uptake analysis.

Cytotoxicity assays established safe AuNP concentrations, with IC50 values of over 100 ppm for AuNRs and 3 ppm for AuDBs after 24 hours. CLSM observations after a 2 hour treatment showed significantly higher uptake (****p<0.0001) of AuDBs compared to AuNRs, supported by ICP-MS and flow cytometry analysis. MD simulations further validated enhanced AuDB uptake.

In conclusion, NPs with negative Gaussian curvature exhibit superior cellular uptake compared to those with zero curvature, offering significant implications for designing NPs for various biomedical applications.