Developing materials with remote controllability of macroscale ligand presentation can mimic extracellular matrix (ECM) remodeling to regulate cellular adhesion in vivo. Herein, we designed charged mobile nanoligands with superparamagnetic nanomaterials amine-functionalized and conjugated with polyethylene glycol linker and negatively charged RGD ligand. We coupled negatively a charged nanoligand to a positively charged substrate by optimizing electrostatic interactions to allow reversible planar movement. We demonstrate the imaging of both macroscale and in situ nanoscale nanoligand movement by magnetically attracting charged nanoligand to manipulate macroscale ligand density. We show that in situ magnetic control of attracting charged nanoligand facilitates stem cell adhesion, both in vitro and in vivo, with reversible control. Furthermore, we unravel that in situ magnetic attraction of charged nanoligand stimulates mechanosensing-mediated differentiation of stem cells. This remote controllability of ECM-mimicking reversible ligand variations is promising for regulating diverse reparative cellular processes in vivo.

The development of heat-generating magnetic nanostructures is critical for the effective management of tumors using magnetic hyperthermia. Herein, we demonstrate that polyethylene glycol (PEG)-coated iron oxide (magnetite, Fe3O4) multigranule nanoclusters (PEG-MGNCs) can enhance the efficiency of hyperthermia-based tumor suppression in vitro and in vivo. MGNCs consisting of granules (crystallites) measuring 22.9 nm in diameter were prepared via the hydrothermal polyol method, followed by the surface modification of MGNCs with PEG-dopamine. The freshly prepared PEG-MGNCs exhibit 145.9 ± 10.2 nm diameter on average under aqueous conditions. The three-dimensional structures of PEG-MGNCs enhance the hyperthermic efficacy compared with PEGylated single iron-oxide nanoparticles (NPs), resulting in severe heat damage to tumor cells in vitro. In the SCC7 tumor-bearing mice, near-infrared fluorescence dye (Cy5.5)-labeled PEG-MGNCs are successfully accumulated in the tumor tissues because of NP-derived enhanced permeation and retention effect. Finally, the tumor growth is significantly suppressed in PEG-MGNC-treated mice after two-times heat generation by using a longitudinal solenoid, which can generate an alternating magnetic field under high-frequency (19.5 kA/m, 389 kHz) induction. This study shows for the first time that the PEG-MGNCs greatly enhance the hyperthermic efficacy of tumor treatment both in vitro and in vivo.

Barcode nanowires (BNWs) composed of multiple layered segments of different materials are attractive to bioengineering field due to their characteristics that allow the adjustment of physicochemical properties and conjugation with two or more types of biomolecules to facilitate multiple tasks. Here, we report a metallic Fe (iron)−Au (gold) BNW-based platform for capturing CD8 T cells and the interferon-γ (γ) they secrete, both of which play key roles in controlling infectious diseases such as tuberculosis, at the single-cell level. We also describe an efficient approach for conjugating distinct antibodies, which recognize different epitopes to appropriate materials. The platform achieved detection even with 4.45−35.6 μg mL −1 of BNWs. The T cell capture efficiency was close to 100% and the detection limit for interferon-γ was 460 pg mL −1 . This work presents a potential guideline for the design of single-cell immunoassay platforms for eliminating diagnostic errors by unambiguously identifying disease-relevant immune mediators.

Natural extracellular matrix (ECM) can regulate the interactions between cells and ligands by exhibiting heterogeneous nano-sequences periodically displaying adhesive ligands, such as RGD ligand in vivo. [1,2] Cell-adhesive ECM proteins, such as fibronectin, vitronectin, and collagen, were shown to form periodically sequenced RGD ligand-bearing nanostructures (67-100 nm). [1] Periodic structure in reflectance was also observed from native tissues. [2] The ligation of integrin with adhesive ligand mediates the assembly of cytoskeletal actin filaments and focal adhesion (FA) complexes to activate mechanosensing signaling pathways that can regulate cellular differentiation. [3,4] Strategically developing materials with heterogeneously sequenced ligand nanostructures can emulate ECM [5] microenvironment to help elucidate the interactions between cells and nano-ligands with tunable frequency and sequences. This can effectively regulate diverse cellular adhesion and functionality in vivo, such as FA, mechanosensing, and differentiation of stem cells. [6] The native extracellular matrix (ECM) can exhibit heterogeneous nanosequences periodically displaying ligands to regulate complex cell-material interactions in vivo. Herein, an ECM-emulating heterogeneous barcoding system, including ligand-bearing Au and ligand-free Fe nano-segments, is developed to independently present tunable frequency and sequences in nano-segments of cell-adhesive RGD ligand. Specifically, similar exposed surface areas of total Fe and Au nano-segments are designed. Fe segments are used for substrate coupling of nanobarcodes and as ligand-free nanosegments and Au segments for ligand coating while maintaining both nanoscale (local) and macroscale (total) ligand density constant in all groups. Low nano-ligand frequency in the same sequences and terminally sequenced nano-ligands at the same frequency independently facilitate focal adhesion and mechanosensing of stem cells, which are collectively effective both in vitro and in vivo, thereby inducing stem cell differentiation. The Fe/RGD-Au nanobarcode implants exhibit high stability and no local and systemic toxicity in various tissues and organs in vivo. This work sheds novel insight into designing biomaterials with heterogeneous nano-ligand sequences at terminal sides and/or low frequency to facilitate cellular adhesion. Tuning the electrodeposition conditions can allow synthesis of unlimited combinations of ligand nano-sequences and frequencies, magnetic elements, and bioactive ligands to remotely regulate numerous host cells in vivo.

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Native extracellular matrix (ECM) can exhibit cyclic nanoscale stretching and shrinking of ligands to regulate complex cell–material interactions. Designing materials that allow cyclic control of changes in intrinsic ligand‐presenting nanostructures in situ can emulate ECM dynamicity to regulate cellular adhesion. Unprecedented remote control of rapid, cyclic, and mechanical stretching (“ON”) and shrinking (“OFF”) of cell‐adhesive RGD ligand‐presenting magnetic nanocoils on a material surface in five repeated cycles are reported, thereby independently increasing and decreasing ligand pitch in nanocoils, respectively, without modulating ligand‐presenting surface area per nanocoil. It is demonstrated that cyclic switching “ON” (ligand nanostretching) facilitates time‐regulated integrin ligation, focal adhesion, spreading, YAP/TAZ mechanosensing, and differentiation of viable stem cells, both in vitro and in vivo. Fluorescence resonance energy transfer (FRET) imaging reveals magnetic switching “ON” (stretching) and “OFF” (shrinking) of the nanocoils inside animals. Versatile tuning of physical dimensions and elements of nanocoils by regulating electrodeposition conditions is also demonstrated. The study sheds novel insight into designing materials with connected ligand nanostructures that exhibit nanocoil‐specific nano‐spaced declustering, which is ineffective in nanowires, to facilitate cell adhesion. This unprecedented, independent, remote, and cytocompatible control of ligand nanopitch is promising for regulating the mechanosensing‐mediated differentiation of stem cells in vivo.

Scheme 1. Schematic of submolecular tuning ligand size and spacing to regulate integrin binding and clustering. Descriptions of the proposed model of independently unraveling the effect of ligand size and spacing on integrin ligation and the clustering of macrophages: "7-18", "13-17", "7-3", and "gold shell". In the "A-B" notation, "A" indicates the liganded GNP size in nm and "B" indicates the liganded GNP edge-to-edge spacing in nm. The "7-3" arrays stimulate the binding of integrin across neighboring liganded GNPs, resulting in robust macrophage adhesion comparable to fully liganded gold shells as a positive control. Relative to the "7-3" ligand arrays, increasing the "ligand spacing only" or "both ligand size and spacing" in the "7-18" and "13-17" liganded sites, respectively, yields binding sites for integrin but suppresses multiple integrin molecules joining the neighboring liganded sites due to the "ligand spacing" playing a dominant role, resulting in poor macrophage adhesion.

Macrophages can associate with extracellular matrix (ECM) demonstrating nanosequenced cell-adhesive RGD ligand. In this study, we devised barcoded materials composed of RGD-coated gold and RGD-absent iron nanopatches to show various frequencies and position of RGD-coated nanopatches with similar areas of iron and RGD-gold nanopatches that maintain macroscale and nanoscale RGD density invariant. Iron patches were used for substrate coupling. Both large (low frequency) and externally positioned RGD-coated nanopatches stimulated robust attachment in macrophages, compared with small (high frequency) and internally positioned RGD-coated nanopatches, respectively, which mediate their regenerative/anti-inflammatory M2 polarization. The nanobarcodes exhibited stability in vivo. We shed light into designing ligand-engineered nanostructures in an external position to facilitate host cell attachment, thereby eliciting regenerative host responses.