This work is supported by Summer Research Grant and Research Fund from The University of New Haven. Effect of Size of Gold Nanoparticles (GNP) on Intracellular Uptake and Cytotoxicity in Breast Cancer Cells Yuwen Zhao Department of Mechanical and Biomedical Engineering University of New Haven West Haven, CT yzhao6@unh.newhavem.edu Rui Yang Department of Mechanical and Biomedical Engineering University of New Haven West Haven, CT ryang3@unh.newhavem.edu Shue Wang * Department of Mechanical and Biomedical Engineering University of New Haven West Haven, CT swang@unh.newhavem.edu Abstract—We investigated the effects of intracellular uptake of different sizes of gold nanoparticles (GNP) ranging from 10 nm to 100 nm on breast cancer cells (MDA-MB-231). The experimental results showed the cell cytotoxicity is high dose- and dimension- dependent. We further investigated the effect of intracellular uptake of GNP on cell morphology, including cell area, perimeter, and aspect ratio. We showed GNP with a diameter of 20 nm enhanced cell proliferation with a low concentration of GNP (2 μg/mL, 4 μg/mL, and 10 μg/mL). To evaluate the specific sizes of GNP affection in wound healing, we investigated the cell migration ability after GNP uptake. Also, we detect the Dll4 expression when the GNP works as a probe, in which the 10 nm GNP-LNA complex reveals significant signal intensity. Keywords— gold nanoparticles, intracellular affection, cytotoxicity, dll4 expression I. INTRODUCTION Gold nanoparticles (GNPs) have been investigated and demonstrated to be an effective tool as therapeutic delivery vectors, intracellular imaging agents due to their favorable chemical and optical properties in the field of developmental biology and clinical study[1]. The capability of endocytosis of GNPs enables it to be applied in the field of drug delivery, gene delivery, and nanobiosensor. For example, previous studies have shown the combination of Locked Nucleic Acid (LNA) probes and gold nanorods (GNRs) or GNPs can be applied to detect mRNA gene expression dynamics at the single cell level[2]. Although several groups have investigated the effects of GNP uptake on cell cytotoxicity, the effects of GNP uptake on cell morphology and motility have not been adequately addressed[3]. Here, we investigated the effects of different sizes of GNP on the breast cancer cell line (MDA- MB-231). First, we evaluated the cell viability after endocytic uptake of GNP with a concentration of 2 μg/mL, 4 μg/mL, 10 μg/mL, and 20 μg/mL. Next, we further investigated the cell morphology change after the intracellular uptake of GNP with the incubation time of 72 hours and 168 hours. Our results indicated that the cytotoxicity of GNP uptake is dose- and size-dependent. The cell area, perimeter, and aspect ratio after GNP uptake is dependent on the dimension, concentration, and incubation duration. To show how MDA-MB-231 cells migrate and test the difference between healthy MDA-MB-231 cells and the cells after scratching, we detected Dll4 expression in the cells. By previous studies, the leader cells usually show higher expression with Dll4, so in our research, the cells leading to cover the scratched area can show different genetic expression with other cells[4]. The double-stranded locked nucleic acid (dsLNA) complex is used to monitor the dynamic expression of target mRNA near the border as a probe. A donor probe composed of a nucleic acid sequence complementary to the target mRNA is labeled with a 6-FAM fluorophore at the 5' end. In its complementary sequence, we placed a quencher (Iowa Black RQ) on the 3' end. By using Dll4 dsLNA donate - quencher (DQ) complex probes, we can detect the Dll4 mRNA expression in a single cell. Also, the MDA-MB-231 cells with scratching and without scratching behave different migration tendency, the cells after scratch will be more involved in the migration, with the mRNA expression proved this hypothesis. As we concern, we choose 10 nm and 20 nm GNP with (11-Mercaptoundecyl)- N, N, N-trimethylammonium bromide (MUTAB) coated in the concentration of 2 μg/ml and 4 μg/ml. Based on these particles, we found they have less cytotoxic and small affection with cell morphology changes. Then we test the cell migration ability on wound healing assay by using DQ probe. Due to the toxicity of the lipofectamine-2000 with the cells during the transfection process, due to the property of MUTAB coated GNP, we use GNP as a vector to reduce the toxicity when transfection[5]. Meanwhile, GNP has a greater surface ratio. Thus, it brings a higher amount of Dll4 sequence into the cells, and we can get an apparent signal intensity. 978-1-7281-7230-9/20/$31.00 © 2020 IEEE 402 Proceedings of the 15th Annual IEEE International Conference on Nano/Micro Engineered and Molecular Systems September 27-30, 2020 Authorized licensed use limited to: UNIVERSITY OF CONNECTICUT. Downloaded on December 22,2020 at 19:59:52 UTC from IEEE Xplore. Restrictions apply.