  Citation: Hallfors, N.G.; Teo, J.C.M.; Bertone, P.M.; Joshi,C.P.; Orozaliev, A.; Martin, M.N.; Isakovic, A.F. Electrodeformation of White Blood Cells Enriched with Gold Nanoparticles. Processes 2022, 10, 134. https://doi.org/10.3390/pr10010134 Academic Editor: Fabio Carniato Received: 30 November 2021 Accepted: 5 January 2022 Published: 10 January 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). processes Article Electrodeformation of White Blood Cells Enriched with Gold Nanoparticles Nicholas G. Hallfors 1 , Jeremy C. M. Teo 2 , Peter M. Bertone 3,4 , Chakra P. Joshi 5 , Ajymurat Orozaliev 2 , Matthew N. Martin 5 and A. F. Isakovic 4, * 1 Biomedical Engineering Department, Khalifa University, Abu Dhabi P.O. Box 127788, United Arab Emirates; nicholas.hallfors@ku.ac.ae 2 Mechanical and Biomedical Engineering Department, New York University Abu Dhabi, Abu Dhabi P.O. Box 129188, United Arab Emirates; jeremy.teo@nyu.edu (J.C.M.T.); ajymurat.orozaliev@nyu.edu (A.O.) 3 Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104, USA; pbertone@seas.upenn.edu 4 Department of Physics and Astronomy, Colgate University, Hamilton, NY 13346, USA 5 Physics Department, Khalifa University, Abu Dhabi, P.O. Box 127788, United Arab Emirates; chakraprasadjoshi@yahoo.com (C.P.J.); matthew.martin@ku.ac.ae (M.N.M.) * Correspondence: aisakovic@colgate.edu or iregx137@gmail.com Abstract: The elasticity of white blood cells (WBCs) provides valuable insight into the condition of the cells themselves, the presence of some diseases, as well as immune system activity. In this work, we describe a novel process of refined control of WBCs’ elasticity through a combined use of gold nanoparticles (AuNPs) and the microelectrode array device. The capture and controlled deformation of gold nanoparticles enriched white blood cells in vitro are demonstrated and quantified. Gold nanoparticles enhance the effect of electrically induced deformation and make the DEP-related processes more controllable. Keywords: leukocytes; electrodeformation; lab-on-chip; nanoparticles; Young’s modulus 1. Introduction Cells are subjected to a variety of mechanical forces in vivo, and the way they deform in response to mechanical, electrical, and biochemical stimuli relies on a combination of passive and active processes [1]. Red blood cells significantly deform as they travel throughout the body’s capillary networks, which are at times smaller than the cells’ resting size. Diseases such as malaria and sickle cell anemia are associated with disruption of the cell membrane elasticity, leading to capillary blockages and a loss of oxygenation [2]. The deformability of cells has even been linked to cancer, where highly metastatic cells have been shown to be soft and deformable, allowing them to migrate through tissue into the blood stream [3–5]. In white blood cells (WBC), quantification of a cell’s elastic modulus via deformability measurements could provide insights into the physiological state of the cell. HL60 cells can differentiate into monocytes, granulocytes, or macrophages, and mechanical deformation alone can distinguish which pathway the HL60 cell will take [6]. Neutrophil activation leads to reduced deformability, which has been demonstrated by morpho-rheological (MORE) analysis [7]. Monocytes from individuals afflicted by Respiratory Tract Infection (RTI) or Acute Lung Injury (ALI) both increased in size with staphylococcus stimulation, but only viral RTI monocytes displayed any measurable increase in deformation. These results indicate that size and deformation studies may be able to identify the presence of viral, bacterial, or other inflammatory diseases through lymphocyte mechanical analysis, implying a need for fast, reliable methods to measure mechanical properties. Processes 2022, 10, 134. https://doi.org/10.3390/pr10010134 https://www.mdpi.com/journal/processes