August 1, 2021
* P?0.05. B isothiocyanate (MNPs@SiO2(RITC)), even at 0.1?g/L. These protruded structures are involved in a cells rigidity sensing, but how these NPs impact rigidity sensing is usually unknown. Results Here, we statement that this rigidity sensing of human embryonic kidney (HEK293) cells was impaired even kb NB 142-70 at 0.1?g/L kb NB 142-70 of MNPs@SiO2(RITC). At this concentration, cells were unable to discern the stiffness difference between soft (5?kPa) and rigid (2?MPa) flat surfaces. The impairment of rigidity sensing was further supported by observing the disappearance of locally contracted elastomeric submicron pillars (900?nm in diameter, 2?m in height, 24.21 nN/m in stiffness k) under MNPs@SiO2(RITC) treated cells. A decrease in the phosphorylation of paxillin, which is usually involved in focal adhesion dynamics, may cause cells to be insensitive to stiffness differences when they are treated with MNPs@SiO2(RITC). Conclusions Our results suggest that NPs may impair the rigidity sensing of cells even at low concentrations, thereby affecting cell adhesion and distributing. Keywords: Lamellipodia, Filopodia, Rigidity sensing, Silica-coated magnetic nanoparticles, Traction force Background In recent years, the use of nanoparticles (NPs) has been rapidly growing in medical research, especially for diagnostic and therapeutic purposes. The size of NPs enables them to enter cells and accumulate, causing cellular dysfunction [1C4]. Moreover, because of their high surface-to-volume ratios, NPs are highly reactive and Rabbit polyclonal to SUMO3 potentially have side effects, like generating reactive oxygen species (ROS), compared to bulk material [5C7]. ROS damages cell membranes, cytoskeletons, etc. [8C12]. Magnetic nanoparticles (MNPs) are widely used in diagnostics and as biosensors in biotechnology and biomedicine [13, 14]. To reduce the adverse effect of MNPs, they are coated with biocompatible components such as polyethylenimine, polysaccharide, and silica [15C18]. Among these MNPs, silica-coated magnetic nanoparticles incorporating rhodamine B isothiocyanate (MNPs@SiO2(RITC)) composed of silica shells and MNP cores in the range from 1 to 10?g/l are used for cell labeling , hyperthermia  and magnetic resonance imaging (MRI) . MNPs@SiO2(RITC) have been evaluated to be nontoxic by standard methods for assessment of toxicity [21C23]. It was reported that MNPs@SiO2(RITC) did not cause apparent toxicity in mice when administrated into them at the concentration of 25?mg to 100?mg/kg . Unlike these results, we reported that MNPs@SiO2(RITC) induce the production ROS, that leads to ER stress, decreased proteasome activity, and altered cellular metabolism [4, 9, 24], suggesting that careful studies are required before the applications of MNPs@SiO2(RITC) in vivo. During their initial contact, cells sense extracellular matrix (ECM) rigidity, in a phenomenon called rigidity sensing. Rigidity sensing is required for cells to translate the mechanical properties of the ECM into biochemical signals that can regulate the genes and proteins of the cell [25C27]. Biochemical signaling is usually involved in determining cell behaviors and fates, such as cell differentiation, migration, apoptosis, proliferation, and tissue development [28C30]. NPs disrupt the cytoskeleton, affecting focal adhesion kb NB 142-70 (FA) proteins and their subsequent adhesion , which are initiated beneath lamellipodia (branched actin filaments) and filopodia (finger-like protrusions) as focal complexes . Previously, we reported that the formation of lamellipodia and filopodia were inhibited at 0.1 and 1?g/L of MNPs@SiO2(RITC) . However, it is still unknown how these NPs impact the cell’s ability to sense the stiffness of the ECM. Conventionally, cell rigidity sensing is usually studied by observing changes in cell morphology using smooth polydimethylsiloxane (PDMS) surfaces with stiffness of 5?kPa (soft) and 2?MPa (rigid). Cells respond to a rigid surface by forming polarized designs with a large FA area . Furthermore, polarized cells often show filopodia that probe the substrate rigidity before distributing . Recently, rigidity sensing has been studied by measuring local contractions on elastomeric submicron pillars [34, 35]. Local contractions are detected kb NB 142-70 by observing the bending of adjacent pillars toward each other when cells were seeded around the pillars . In this statement,.