Cells Dynamically Adapt to Surface Geometry by Remodeling Their Focal Adhesions and Actin Cytoskeleton

Harnessing the power of physicochemical material property screening to direct breast epithelial and breast cancer cells

Understanding cell-material interactions is crucial for advancing biomedical applications, influencing cellular behavior and medical device performance. Material properties can be manipulated to direct cell responses, benefiting applications from regenerative medicine to implantable devices such as silicone breast implants. Knowledge about the interaction differences between healthy and cancer cells with implants may guide implant design to more precisely influence cell adhesion and proliferation of healthy cells while inhibiting cancer cells, tailoring outcomes to specific cellular responses. To show-case this potential, breast epithelial cells and breast cancer cells were investigated regarding their interaction with a broad range of combined physicochemical properties. This study employed a silicone-based high-throughput screening method utilizing Double Orthogonal Gradients (DOGs) to investigate the influence of topography, stiffness, and wettability on breast epithelial cells (MCF10a) and breast cancer cells (MCF7). Results show distinct cellular responses, including decreased proliferation rates in both MCF10a and MCF7 cells with the introduction of surface topography and the dominant influence of wettability on cell adhesion, proliferation, and cluster formation. The screening identified specific regions of interest (ROIs) where MCF10a cell proliferation outperformed MCF7 cells and that topography inhibits cluster formation (tumorigenesis), offering potential prospects for the creation of novel implant surfaces.

Tailoring Cell Behavior and Antibacterial Properties on Zirconia Biomaterials through Femtosecond Laser-Induced Micropatterns and Nanotopography

This study explores the potential of ultrashort pulsed-direct laser interference patterning (USP-DLIP) to fabricate micropatterns on zirconia surfaces, aimed at enhancing their cell-instructive and antibacterial properties for biomedical applications. A femtosecond laser was employed to fabricate 3 and 10 μm periodic linear (L3 and L10) and grid (G3 and G10) patterns on tetragonal zirconia polycrystal stabilized with 3% molar yttrium oxide (3Y-TZP). The patterns exhibited homogeneous, high-aspect-ratio structures with laser-induced nanotopography within the grooves while maintaining minimal surface damage. All patterns significantly enhanced human mesenchymal stem cell (hMSCs) adhesion, spreading, and migration through topographical guidance and nanotopography-induced cell anchoring. Pattern geometry influenced cell morphology and migration: linear patterns induced high elongation and alignment along the grooves, leading to unidirectional migration, while grid structures promoted widespread cells with bidirectional alignment, promoting bidirectional migration. Antibacterial assessment using Pseudomonas aeruginosa (P. aeruginosa) (Gram-negative) and Staphylococcus aureus (S. aureus) (Gram-positive) revealed a size-dependent bacterial response. The patterns of lower periodicity (L3 and G3) showed superior antibacterial properties, reducing bacterial colonization through distinct mechanisms: mechanical trapping for P. aeruginosa (25% reduction) and disruption of bacterial aggregation for S. aureus (30% reduction). Coculture experiments with hMSCs and bacteria confirmed that L3 and G3 surfaces effectively combined enhanced cell adhesion with reduced bacterial colonization, highlighting the potential of USP-DLIP for developing multifunctional cell-instructive and antibacterial biomaterial surfaces.

Light-Responsive Liquid Crystal Surface Topographies for Dynamic Stimulation of Cells

All biological surfaces possess distinct dynamic surface topographies. Due to their versatility, these topographies play a crucial role in modulating cell behavior and, when intentionally designed, can precisely guide cellular responses. So far, biomechanical responses have predominantly been studied on static surfaces, overlooking the dynamic environment in the body, where cells constantly interact with shifting biomechanical cues. In this work, we designed and fabricated a light-responsive liquid crystal polymer film to study the effect of micrometer-scale, dynamic surface topographies on cells under physiologically relevant conditions. The light-responsive liquid crystal polymers enable on-demand surface topographical changes, reaching pillar heights of 800 nm and grooved topographies with 700 nm height differences at 37 °C in water. The light-induced surface topographies increased mechanosensitive cell signaling by up to 2-fold higher yes-associated protein (YAP) translocation to the nucleus, as well as up to 3-fold more heterogeneity in distribution of focal adhesions, in a topography-related manner. The pillared topography was seen to cause a lower cellular response, while the grooved topography caused an increased mechanical activation, as well as cell alignment due to a more continuous and aligned physical cue that enhances cell organization. Excitingly, we observed that subsequent surface topography changes induced a 3-fold higher YAP nuclear translocation in fibroblast cells, as well as a 5-fold higher vinculin heterogeneity distribution, indicating that multiple cycles of topography exposure ampliated the cell response. Our work emphasizes the potential of light-responsive liquid crystal polymer films generating dynamic biomechanical cues that allow us to modulate and steer cells in vitro.

Chromatin-site-specific accessibility: A microtopography-regulated door into the stem cell fate

Biomaterials that mimic extracellular matrix topography are crucial in tissue engineering. Previous research indicates that certain biomimetic topography can guide stem cells toward multiple specific lineages. However, the mechanisms by which topographic cues direct stem cell differentiation remain unclear. Here, we demonstrate that microtopography influences nuclear tension in mesenchymal stem cells (MSCs), shaping chromatin accessibility and determining lineage commitment. On aligned substrates, MSCs exhibit high cytoskeletal tension along the fiber direction, creating anisotropic nuclear stress that opens chromatin sites for neurogenic, myogenic, and tenogenic genes via transcription factors like Nuclear receptor TLX (TLX). In contrast, random substrates induce isotropic nuclear stress, promoting chromatin accessibility for osteogenic and chondrogenic genes through Runt-related transcription factors (RUNX). Our findings reveal that aligned and random microtopographies direct site-specific chromatin stretch and lineage-specific gene expression, priming MSCs for distinct lineages. This study introduces a novel framework for understanding how topographic cues govern cell fate in tissue repair and regeneration.

Modulation of Biomaterial-Associated Fibrosis by Means of Combined Physicochemical Material Properties

Biomaterial-associated fibrosis remains a significant challenge in medical implants. To optimize implant design, understanding the interplay between biomaterials and host cells during the foreign body response (FBR) is crucial. Material properties are known to influence cellular behavior and can be used to manipulate cell responses, but predicting the right combination for the desired outcomes is challenging. This study explores how combined physicochemical material properties impact early myofibroblast differentiation using the Biomaterial Advanced Cell Screening (BiomACS) technology, which assesses hundreds of combinations of surface topography, stiffness, and wettability in a single experiment. Normal human dermal fibroblasts (NHDFs) are screened for cell density, area, and myofibroblast markers α-smooth muscle actin (α-SMA) and Collagen type I (COL1) after 24 h and 7 days of culture, with or without transforming growth factor-beta (TGF-β). Results demonstrated that material properties influence fibroblast behavior after 7 days with TGF-β stimulation, with wettability emerging as the predominant factor, followed by stiffness. The study identified regions with increased cell adhesion while minimizing myofibroblast differentiation, offering the potential for implant surface optimization to prevent fibrosis. This research provides a powerful tool for cell-material studies and represents a critical step toward enhancing implant properties and reducing complications, ultimately improving patient outcomes.

Evaluation of the In Vitro Behavior of Electrochemically Deposited Plate-like Crystal Hydroxyapatite Coatings

The purpose of coatings is to protect or enhance the functionality of the substrate material, irrespective of the field in which the material was designed. The use of coatings in medicine is rapidly expanding with the objective of enhancing the osseointegration ability of metallic materials such as titanium. The aim of this study was to obtain biomimetic hydroxyapatite (HAp)-based coatings on titanium by using the pulsed galvanostatic method. The morphology of the HAp-based coatings revealed the presence of very thin and wide plate-like crystals, grown perpendicular to the Ti substrate, while the chemical composition highlighted a Ca/P ratio of 1.66, which is close to that of stoichiometric HAp (1.67). The main phases and chemical bonds identified confirmed the presence of the HAp phase in the developed coatings. A roughness of 228 nm and a contact angle of approx. 17° were obtained for the HAp coatings, highlighting a hydrophilic character. In terms of biomineralization and electrochemical behavior, it was shown that the HAp coatings have significantly enhanced the titanium properties. Finally, the in vitro cell tests carried out with human mesenchymal stem cells showed that the Ti samples coated with HAp have increased cell viability, extracellular matrix, and Ca intracellular deposition when compared with the uncoated Ti, indicating the beneficial effect.

DNA Nanoparticle Based 2D Biointerface to Study the Effect of Dynamic RGD Presentation on Stem Cell Adhesion and Migration

The native extracellular matrix (ECM) undergoes constant remodeling, where adhesive ligand presentation changes over time and in space to control stem cell function. As such, it is of interest to develop 2D biointerfaces able to study these complex ligand stem-cell interactions. In this study, a novel dynamic bio interface based on DNA hybridization is developed, which can be employed to control ligand display kinetics and used to study dynamic cell-ligand interaction. In this approach, mesoporous silica nanoparticles (MSN) are functionalized with single-strand DNA (MSN-ssDNA) and spin-coated on a glass substrate to create the 2D bio interface. Cell adhesive tripeptide RGD is conjugated to complementary DNA strands (csDNA) of 9, 11, or 20 nucleotides in length, to form csDNA-RGD. The resulting 3 csDNA-RGD conjugates can hybridize with the ssDNA on the MSN surface, presenting RGD with increased ligand dissociation rates as DNA length is shortened. Slow RGD dissociation rates led to enhanced stem cell adhesion and spreading, resulting in elongated cell morphology. Cells on surfaces with slow RGD dissociation rates also exhibited higher motility, migrating in multiple directions compared to cells on surfaces with fast RGD dissociation rates. This study contributes to the existing body of knowledge on dynamic ligand-stem cell interactions.

Biointerfaces with ultrathin patterns for directional control of cell migration

In the context of wound healing and tissue regeneration, precise control of cell migration direction is deemed crucial. To address this challenge, polydimethylsiloxane (PDMS) platforms with patterned 10 nm thick TiOx in arrowhead shape were designed and fabricated. Remarkably, without tall sidewall constraints, MC3T3-E1 cells seeded on these platforms were constrained to migrate along the tips of the arrowheads, as the cells were guided by the asymmetrical arrowhead tips which provided large contact areas. To the best of our knowledge, this is the first study demonstrating the use of thin TiOx arrowhead pattern in combination with a cell-repellent PDMS surface to provide guided cell migration unidirectionally without tall sidewall constraints. Additionally, high-resolution fluorescence imaging revealed that the asymmetrical distribution of focal adhesions, triggered by the patterned TiOx arrowheads with arm lengths of 10, 20, and 35 μm, promoted cell adhesion and protrusion along the arrowhead tip direction, resulting in unidirectional cell migration. These findings have important implications for the design of biointerfaces with ultrathin patterns to precisely control cell migration. Furthermore, microelectrodes were integrated with the patterned TiOx arrowheads to enable dynamic monitoring of cell migration using impedance measurement. This microfluidic device integrated with thin layer of guiding pattern and microelectrodes allows simultaneous control of directional cell migration and characterization of the cell movement of individual MC3T3-E1 cells, offering great potential for the development of biosensors for single-cell monitoring.

Microfluidically Aligned Collagen to Maintain the Phenotype of Tenocytes In Vitro

Tendon is a highly organized tissue that transmits forces between muscle and bone. The architecture of the extracellular matrix of tendon, predominantly from collagen type I, is important for maintaining tenocyte phenotype and function. Therefore, in repair and regeneration of damaged and diseased tendon tissue, it is crucial to restore the aligned arrangement of the collagen type I fibers of the original matrix. To this end, a novel, user-friendly microfluidic piggyback platform is developed allowing the controlled patterned formation and alignment of collagen fibers simply on the bottom of culture dishes. Rat tenocytes cultured on the micropatterns of aligned fibrous collagen exhibit a more elongated morphology. The cells also show an increased expression of tenogenic markers at the gene and protein level compared to tenocytes cultured on tissue culture plastic or non-fibrillar collagen coatings. Moreover, using imprinted polystyrene replicas of aligned collagen fibers, this work shows that the fibrillar structure of collagen per se affects the tenocyte morphology, whereas the biochemical nature of collagen plays a prominent role in the expression of tenogenic markers. Beyond the controlled provision of aligned collagen, the microfluidic platform can aid in developing more physiologically relevant in vitro models of tendon and its regeneration.

Silicon Nanoneedle-Induced Nuclear Deformation: Implications for Human Somatic and Stem Cell Nuclear Mechanics

Cell nuclear size and shape are strictly regulated, with aberrations often leading to or being indicative of disease. Nuclear mechanics are critically responsible for intracellular responses to extracellular cues, such as the nanotopography of the external environment. Silicon nanoneedle (SiNN) arrays are tunable, engineered cell culture substrates that permit precise, nanoscale modifications to a cell's external environment to probe mechanotransduction and intracellular signaling. We use a library of four different SiNN arrays to investigate the immediate and downstream effects of controlled geometries of nanotopographical cues on the nuclear integrity/dynamics of human immortalized somatic and renewing stem cell types. We quantify the significant, albeit different, nuclear shape changes that both cell types undergo, which suggest that cellular responses to SiNN arrays are more comparable to three-dimensional (3D) environments than traditional flat cultureware. We show that nanotopography-induced effects on nuclear envelope integrity, protein localization, and focal adhesion complex formation are cell-dependent. Migration is shown to be dramatically impeded for human neural progenitor cells (hNPCs) on nanotopographies compared to flat substrates but not for somatic cells. Our results indicate an additional layer of complexity in cellular mechanotransduction, which warrants closer attention in the context of engineered substrates and scaffolds for clinical applications.