The Effect of Size and Geometry of Poly(acrylamide) Brush-Based Micropatterns on the Behavior of Cells

Autoantibodies immuno-mechanically modulate platelet contractile force and bleeding risk

Altered mechanotransduction has been proposed as a putative mechanism for disease pathophysiology, yet evidence remains scarce. Here we introduce a concept we call single cell immuno-mechanical modulation, which links immunology, integrin biology, cellular mechanics, and disease pathophysiology and symptomology. Using a micropatterned hydrogel-laden coverslip compatible with standard fluorescence microscopy, we conduct a clinical mechanobiology study, specifically focusing on immune thrombocytopenia (ITP), an autoantibody-mediated platelet disorder that currently lacks a reliable biomarker for bleeding risk. We discover that in pediatric ITP patients (n = 53), low single platelet contraction force alone is a "physics-based" biomarker of bleeding (92.3% sensitivity, 90% specificity). Mechanistically, autoantibodies and monoclonal antibodies drive increases and decreases of cell force by stabilizing integrins in different conformations depending on the targeted epitope. Hence, immuno-mechanical modulation demonstrates how antibodies may pathologically alter mechanotransduction to cause clinical symptoms and this phenomenon can be leveraged to control cellular mechanics for research, diagnostic, and therapeutic purposes.

Metallic Scaffold with Micron-Scale Geometrical Cues Promotes Osteogenesis and Angiogenesis via the ROCK/Myosin/YAP Pathway

The advent of precision manufacturing has enabled the creation of pores in metallic scaffolds with feature size in the range of single microns. In orthopedic implants, pore geometries at the micron scale could regulate bone formation by stimulating osteogenic differentiation and the coupling of osteogenesis and angiogenesis. However, the biological response to pore geometry at the cellular level is not clear. As cells are sensitive to curvature of the pore boundary, this study aimed to investigate osteogenesis in high- vs low-curvature environments by utilizing computer numerical control laser cutting to generate triangular and circular precision manufactured micropores (PMpores). We fabricated PMpores on 100 μm-thick stainless-steel discs. Triangular PMpores had a 30° vertex angle and a 300 μm base, and circular PMpores had a 300 μm diameter. We found triangular PMpores significantly enhanced the elastic modulus, proliferation, migration, and osteogenic differentiation of MC3T3-E1 preosteoblasts through Yes-associated protein (YAP) nuclear translocation. Inhibition of Rho-associated kinase (ROCK) and Myosin II abolished YAP translocation in all pore types and controls. Inhibition of YAP transcriptional activity reduced the proliferation, pore closure, collagen secretion, alkaline phosphatase (ALP), and Alizarin Red staining in MC3T3-E1 cultures. In C166 vascular endothelial cells, PMpores increased the VEGFA mRNA expression even without an angiogenic differentiation medium and induced tubule formation and maintenance. In terms of osteogenesis-angiogenesis coupling, a conditioned medium from MC3T3-E1 cells in PMpores promoted the expression of angiogenic genes in C166 cells. A coculture with MC3T3-E1 induced tubule formation and maintenance in C166 cells and tubule alignment along the edges of pores. Together, curvature cues in micropores are important stimuli to regulate osteogenic differentiation and osteogenesis-angiogenesis coupling. This study uncovered key mechanotransduction signaling components activated by curvature differences in a metallic scaffold and contributed to the understanding of the interaction between orthopedic implants and cells.

Highly stable cellulose nanofiber/polyacrylamide aerogel via in-situ physical/chemical double crosslinking for highly efficient Cu(II) ions removal

Water pollution by heavy metal ions is a global concern due to detrimental effects on the ecological environment and human health. To solve the problem of the stability and recyclability of the traditional adsorbents, we proposed three-dimensional lamellar porous cellulose nanofiber/polyacrylamide composite aerogel with outstanding pollutants adsorption, easy regeneration, and multiple recycling. The aerogel adsorbent was prepared by a two-step method via facile in-situ physical/chemical double cross-linking and freeze-drying processes. The resulting aerogels showed good thermal stability, superior water stability and excellent adsorption properties, with a maximum Langmuir adsorption capacity for Cu(II) ions up to 240 mg g^-1 due to the in-situ physical/chemical combination of anionic polyacrylamide and carbonylated cellulose nanofibers. The adsorption mechanism was the electrostatic attraction, chelating effect and complex formation driving forces for the fast and efficient adsorption of Cu(II) ions. The removal efficiency of the aerogels for Cu(II) remained above 80% after 10 adsorption/regeneration cycles, suggesting its outstanding recyclability. The proposed aerogel adsorbent shows noteworthy potential for the practical treatment of heavy metal ion wastewater.

Influences of Viscosity on the Osteogenic and Adipogenic Differentiation of Mesenchymal Stem Cells with Controlled Morphology

Matrix viscoelastic properties have been shown to have important effects on cell functions. However, the conventional culture methods for investigating the influences of viscoelastic properties on cell functions cannot exclude...

Spreading area and shape regulate the apoptosis and osteogenesis of mesenchymal stem cells on circular and branched micropatterned islands

The topography of extracellular matrix regulates the differentiation of mesenchymal stem cells (MSCs). In particular, the effect of spreading shape or area on cellular differentiation and viability of individual MSCs cultured in the confined adhesive regions is an interesting fundamental issue. In this study, the adhesive patterns with the circularity of 0.1 or 1 and the areas of 314; 628; 1,256; or 2,512 μm² were constructed using micropatterning technology. The expression of osteogenesis marker alkaline phosphatase and the apoptosis level of individual MSCs were measured using double fluorescent staining. Results indicated that individual MSCs confined in the small area showed an apoptotic tendency, and those in the large area might enter into osteogenesis. The branched shape with small circularity increased MSC viability but reduced their pluripotency compared with the circular shape. The expression of other osteogenesis markers, such as osteocalcin and Collagen I, confirmed that large and branched pattern promoted MSC osteogenesis. In addition, the transcriptional coactivator yes-associated protein (YAP) was transferred higher in the nuclei of the large and branched cells than other micropatterned groups. This study suggested that the spreading area and shape of individual MSCs regulate their viability and osteogenesis through the YAP pathway.

Actin Cytoskeleton-Disrupting and Magnetic Field-Responsive Multivalent Supramolecular Assemblies for Efficient Cancer Therapy

Actin cytoskeleton disruption is a promising and intriguing anticancer strategy, but their efficiency is frequently compromised by severe side effects of the actin cytoskeleton-disrupting agents. In this study, we constructed the biocompatible actin cytoskeleton-targeting multivalent supramolecular assemblies that specifically target and disrupt the tumor actin cytoskeleton for cancer therapy. The assemblies were composed of β-cyclodextrin-grafted hyaluronic acid (HACD) and iron oxide magnetic nanoparticles (MNPs) grafted by an actin-binding peptide (ABP) and adamantane (Ada)-modified polylysine. Owing to the multivalent binding between cyclodextrin and Ada, HACD, and peptide-grafted MNPs (MNP-ABP-Ada) could self-assemble to form MNP-ABP-Ada⊂HACD nanofibers in a geomagnetism-dependent manner. Furthermore, the presence of ABP rendered the assemblies to efficiently target the actin cytoskeleton. Interestingly, with the acid of a low-frequency alternating magnetic field (200 Hz), the actin cytoskeleton-targeting nanofibers could induce severe actin disruption, leading to a remarkable cell cycle arrest and drastic cell death of tumor cells both in vitro and in vivo, but showed no obvious toxicity to normal cells. The actin cytoskeleton-targeting/disrupting supramolecular assembly implies an excellent strategy for realizing efficient cancer therapy.

Influence of Cell Morphology on Mesenchymal Stem Cell Transfection

Gene transfection has broad applications in bioengineering and biomedical fields. Although many gene carrier materials and transfection methods have been developed, it remains unclear how cell morphology including cell spreading and elongation affects gene transfection. In this study, human bone marrow-derived mesenchymal stem cells (hMSCs) were cultured on micropatterns and transfected with cationic pAcGFP1-N1 plasmid complexes. The relationship between the cell morphology of hMSCs and gene transfection was investigated using micropatterning techniques. Spreading and elongation of hMSCs were precisely controlled by micropatterned surfaces. The results showed that well-spread and elongated hMSCs had high transfection efficiency. Analysis of the uptake of exogenous genes and DNA synthesis activity indicated that the well-spread and elongated cell morphology promoted gene transfection through enhanced uptake of the cationic complexes and accelerated DNA synthesis. The results should provide useful information for understanding of cell morphology on gene transfection and development of efficient gene transfection methods.

Asymmetric multifunctional 3D cell microenvironments by capillary force assembly

The fabrication and characterization of advanced 3D cell culture microenvironments that enable systematic structure–property relationship studies are reported.

Thickness-Encoded Micropatterns in One-Component Thermoresponsive Polymer Brushes for Culture and Triggered Release of Pancreatic Tumor Cell Monolayers and Spheroids

Fabrication, characterization, and application of micropatterned one-component poly(di(ethylene glycol)methyl ether methacrylate) (PDEGMA) brushes for monolayer cell and spheroid culture and temperature-triggered release are reported. Micropatterns of various shapes and sizes were designed to possess a unique functionality imparted by thermoresponsive thin PDEGMA patches, which are cell adhesive at 37 °C, embedded in a much thicker cell-resistant PDEGMA matrix that does not exhibit measurable thermoresponsive properties. Depending on the cell seeding density, PaTu 8988t human pancreatic tumor cells or spheroids were cultured area-selectively, confined by the 40 ± 4 nm thick passivating PDEGMA matrix, and could be released on demand by a mild thermally triggered brush swelling in the 5 ± 1 nm thin regions. As shown by surface plasmon resonance (SPR) measurements, in contrast to the thinner brushes, the thicker brushes exhibited virtually no fibronectin adhesive properties at 37 °C, whereas at 25 °C, both areas showed similar protein resistant behavior. The quasi-2D thickness-encoded micropatterns were shown to be useful templates for the growth of 3D multicellular aggregates. Thermally induced release after 5 days of incubation afforded 3D cell spheroids comprising up to 99% viable cells demonstrating that the system can be used as a 3D spheroid in vitro model for basic tumor research and anticancer drug screenings.

Enhanced cell adhesion on a bio-inspired hierarchically structured polyester modified with gelatin-methacrylate

Herein, fabrication and modification of novel bio-inspired microwell arrays with nanoscale topographic structures are reported. The natural nano- and microstructures present on the surface of rose petals were hypothesized to enhance cell-surface contacts. Thus hierarchically structured polyethylene terephthalate glycol modified (PETG) substrates were fabricated by replication from rose petals via nanoimprint lithography, followed by covalent modification and crosslinking with RGD-presenting gelatin-methacrylate (GelMA) for promoting cell adhesion and spreading. Cell culture experiments showed that the introduction of gelatin resulted in significantly enhanced cell adhesion and more than doubled cell areas on the GelMA modified surfaces. In addition, a slight preference was observed for concave compared to convex surfaces, which is tentatively attributed to the matching curvature of the micro-cavities and the cells, facilitating the accommodation of cells. These bioinspired hierarchically structured and gelatin functionalized substrates may provide new prospects for designing cell-based interfaces for advanced biomedical studies, e.g. for cell culture and biosensing in the future.

Regulation of mesenchymal stem cell functions by micro-nano hybrid patterned surfaces

Micro- and nano-structured substrates have been widely used in the biomedical engineering field. Their precise control of cell morphology makes them promising for investigating various cell behaviors. However, regulation of cell functions using micro-nano hybrid patterns is rarely achieved. Since the cell microenvironment in vivo has complex micro- and nano-structures, it is desirable to use micro-nano hybrid patterns to mimic the microenvironment to control cell morphology and disclose its influence on stem cell differentiation. In this study, poly(vinyl alcohol) (PVA) micro-stripes with different spacings (50 μm, 100 μm and 200 μm) were constructed on polystyrene (PS) nano-grooves to prepare micro-nano hybrid patterns where the direction of the PVA micro-stripes and PS nano-grooves was parallel or orthogonal. Human bone marrow-derived mesenchymal stem cells (hMSCs) cultured on the micro-nano hybrid patterns showed a different cell alignment and elongation dependent on the PVA micro-stripe spacing and orientation of the PS nano-grooves. Comparison of the influence of cell alignment and aspect ratio on differentiation of hMSCs indicated that myogenic differentiation was predominantly regulated by cell alignment and osteogenic differentiation by cell elongation, while adipogenic differentiation was regulated neither by cell alignment nor by cell elongation.

Fabrication of gelatin-micropatterned surface and its effect on osteogenic differentiation of hMSCs

Micropatterned surface with different surface chemistries was fabricated for the direct comparison of their effect on the behaviors of hMSCs and to avoid any batch to batch variations during cell culture.

Detailed Analysis of Pancreatic Tumor Cell Attachment on Gradient PDEGMA Brushes

Poly(di(ethylene glycol) methyl ether methacrylate) (PDEGMA) brushes show interesting thermoresponsive behavior that can be applied for cell release surfaces. Here it is shown that PDEGMA thickness gradients, which are synthesized by surface-initiated atom transfer radical polymerization, allow the systematic and precise analysis of the attachment of PaTu 8988 cells. By pumping the polymerization solution into the reactor with vertically fixed initiator samples, PDEGMA gradients with linearly increasing dry ellipsometric thickness with typical slopes of 2.5 nm cm^-1 are obtained. A very narrow transition of PaTu 8988t cell attachment is observed that starts for a thickness larger than 7.1 ± 0.2 nm. For PDEGMA layers thicker than 8.7 ± 0.2 nm no attached cells are found. This very narrow transition in brush properties within a thickness difference of <2 nm from cell-adherent to cell-nonadherent can be determined in much greater detail than before owing to the thickness gradients with shallow slope.

Electroassisted Functionalization of Nitinol Surface, a Powerful Strategy for Polymer Coating through Controlled Radical Surface Initiation

Coating Nitinol (NiTi) surfaces with a polymer layer has become very appealing in the past few years owing to its increased attraction in the biomedical field. Although its intrinsic properties helped ensure its popularity, its extensive implementation is still hampered by its nickel inclusion, making it sensitive to pitting corrosion and therefore leading to the release of carcinogenic Ni²⁺ ions. Among all recent ways to modify NiTi surfaces, elaboration of self-assembled monolayers is of great interest as their high order confers a reinforcement of the metal surface corrosion resistance and brings new functionalities to the metal for postmodification processes. In this work, we compare the electroassisted and thermally assisted self-assembling of 11-(2-bromoisobutyrate)-undecyl-1-phosphonic acid (BUPA) to the classical immersion process on NiTi surfaces initially submitted to a hydrothermal treatment. Among all tested conditions, the electroassisted grafting of BUPA at room temperature appears to be the most promising alternative, as it allows grafting in very short times (5-10 min), thus preventing its degradation. The thus-formed layer has been proven to be sufficient to enable the surface-initiated atom transfer radical polymerization (SI-ATRP) of 2-(dimethylamino)ethyl methacrylate.

Bioinspired Hierarchically Structured Surfaces for Efficient Capture and Release of Circulating Tumor Cells

The development of novel bioinspired surfaces with hierarchical micro- and nanoscale topographic structures for efficient capture and release of circulating tumor cells (CTCs) is reported. The capture of CTCs, facilitated by surface-immobilized epithelial cell adhesion molecule antibodies (anti-EpCAM), was shown to be significantly enhanced in novel three-dimensional hierarchically structured surfaces that were fabricated by replicating the natural micro- and nanostructures of rose petals. Under static conditions, these hierarchical capture substrates exhibited up to 6 times higher cell capture ability at concentrations of 100 cells mL^-1 in contrast to flat anti-EpCAM-functionalized polydimethylsiloxane (PDMS) surfaces. As indicated by scanning electron microscopy (SEM) and immunofluorescent images, this enhancement can be in large part attributed to the topographical interaction between nanoscale cell surface components and nanostructures on the substrate. Similarly, the increased surface area affords a higher nominal coverage of anti-EpCAM, which increases the number of available binding sites for cell capture. By treating the substrates with the biocompatible reductant glutathione (GSH), up to 85% of the captured cells were released, which displayed over 98% cell viability after culturing on tissue culture polystyrene (TCP) for 24 h. Therefore, these bioinspired hierarchically structured and functionalized substrates can be successfully applied to capture CTCs, as well as release CTCs for subsequent analysis. These findings provide new prospects for designing cell-material interfaces for advanced cell-based biomedical studies in the future.