Remote Control of Multimodal Nanoscale Ligand Oscillations Regulates Stem Cell Adhesion and Differentiation

Abstract

Cellular adhesion is regulated by the dynamic ligation process of surface receptors, such as integrin, to adhesive motifs, such as Arg-Gly-Asp (RGD). Remote control of adhesive ligand presentation using external stimuli is an appealing strategy for the temporal regulation of cell-implant interactions in vivo and was recently demonstrated using photochemical reaction. However, the limited tissue penetration of light potentially hampers the widespread applications of this method in vivo. Here, we present a strategy for modulating the nanoscale oscillations of an integrin ligand simply and solely by adjusting the frequency of an oscillating magnetic field to regulate the adhesion and differentiation of stem cells. A superparamagnetic iron oxide nanoparticle (SPION) was conjugated with the RGD ligand and anchored to a glass substrate by a long flexible poly(ethylene glycol) linker to allow the oscillatory motion of the ligand to be magnetically tuned. In situ magnetic scanning transmission electron microscopy and atomic force microscopy imaging confirmed the nanoscale motion of the substrate-tethered RGD-grafted SPION. Our findings show that ligand oscillations under a low oscillation frequency (0.1 Hz) of the magnetic field promoted integrin-ligand binding and the formation and maturation of focal adhesions and therefore the substrate adhesion of stem cells, while ligands oscillating under high frequency (2 Hz) inhibited integrin ligation and stem cell adhesion, both in vitro and in vivo. Temporal switching of the multimodal ligand oscillations between low- and high-frequency modes reversibly regulated stem cell adhesion. The ligand oscillations further induced the stem cell differentiation and mechanosensing in the same frequency-dependent manner. Our study demonstrates a noninvasive, penetrative, and tunable approach to regulate cellular responses to biomaterials in vivo. Our work not only provides additional insight into the design considerations of biomaterials to control cellular adhesion in vivo but also offers a platform to elucidate the fundamental understanding of the dynamic integrin-ligand binding that regulates the adhesion, differentiation, and mechanotransduction of stem cells.

Remote Control of Intracellular Calcium Using Upconversion Nanotransducers Regulates Stem Cell Differentiation In Vivo

“…For example, Du and others showed magnetic field‐mediated aggregation and stretching of stem cells with magnetic nanoparticles to induce their cardiac differentiation in vitro . Our own studies have shown that the magnetic field tuned the tether compliance or oscillation of ligand with magnetic nanoparticles to modulate stem cell differentiation into osteoblasts in vitro. Alternatively, among light stimuli in various wavelength, NIR light that can activate nanomaterials offers benefits of reduced phototoxicity and deep tissue penetration.…”

Pattern-Dependent Mammalian Cell (Vero) Morphology on Tantalum/Silicon Oxide 3D Nanocomposites

“…Recent studies have used micro- and nanometer-scale engineered structures to mimic extracellular matrices and other biological structures, which have led to a groundbreaking understanding of the physical cues and molecular signal transduction pathways for integrin activated focal adhesion, protein adsorption, and pseudopodia formation [1,2,3,4,5,6,7,8,9]. Results have shown that cellular responses often depend on the mechanical properties, pattern structures, and surface chemistry of the microenvironment surrounding the cells [1,3,4,5,7,8,10,11,12,13,14,15,16,17,18,19,20]; however, work done thus far has been conducted with structures composed of monolithic materials having uniform surface chemical composition.…”

Magnetic Nanomaterials for Advanced Regenerative Medicine: The Promise and Challenges

“…Besides ion channels, mechanosensitive receptors such as integrins and the Wnt receptor Frizzled have been targeted and magnetically activated to directly regulate cell proliferation and differentiation . Recently, Bian and co‐workers reported both in vitro and in vivo regulation of stem cell adhesion and differentiation using integrin ανβ 3‐targeting MIONs tethered with the RGD peptide under a low AMF (0.1 Hz). Rotherham et al designed MIONs functionalized with an anti‐Frizzled protein which were able to activate Wnt signaling in MSCs under an external magnetic field.…”