Burcu Gumuscu

Light‐responsive liquid crystal elastomers (LCEs) have emerged as promising materials for generating dynamic surface topographies for use in haptic, self‐cleaning, and biomedical applications. However, the programmability and predictability of such topography formation under biomedically relevant conditions remain largely unexplored, which limits their practical use. In this work, we present a combined experimental and simulation analysis of light‐responsive LCE surfaces operating under physiological conditions, enabling programmable, highly spatially controlled topography formation through bottom photomask exposure. Using a cholesteric LCE film and a mask geometry consisting of 50 µm pillars with a 4‐min ultraviolet (UV)‐light exposure, the maximum achievable topography height was obtained. By shorter and longer exposure times, and variations in mask geometry, maximum topography heights can be programmed. The resulting surface topographies can be erased under visible (vis)‐light, with the switching process being reversible. Moreover, employing photomasks of different geometries enables the generation of a wide range of alternative topographical patterns. Experimental findings are corroborated by simulations. The combined experimental and simulation results provide a predictive model for (re)programmable dynamic surface topography formation. Taken together, these findings establish a foundation for light‐responsive dynamic bio surfaces with potential for applications in controlled cellular modulation, tissue engineering, and regenerative medicine.

Most conventional digital microfluidic (DMF) chips face challenges in balancing low actuation voltage, dielectric robustness, and minimal current leakage, thereby limiting their effectiveness and use for biological applications. In this work, we present a multilayered digital microfluidic (mDMF) chip incorporating a multilayer dielectric stack of silicon nitride and parylene C to achieve an optimal balance of these properties. The multilayered and compact electrode design creates two‐fold more operational space, while the multilayer dielectric structure reduces actuation voltages down to 50 V, which demotes a stable two‐fold reduction to conventional standards. Finite element analysis was employed to optimize the dielectric thicknesses, ensuring minimal current leakage under 10 nA, which is 100‐fold below the biological detection threshold. Experimental validation was conducted through droplet actuation and water contact angle characterizations, identifying the optimal dielectric composition as 400‐nm thick silicon nitride and 1‐µm thick parylene C layer. The utility of mDMF chips in biological assays was demonstrated by culturing human‐derived macrophages and fibroblasts under varying concentrations of cytochalasin D. Results indicated comparable experimental performance to conventional well plate assays, while utilizing over 2 orders of magnitude less sample volume. This advancement highlights the efficiency of DMF for cell‐based assays and facilitates wider biomedical applications.

Understanding macrophage phenotype regulation by mechanical stimuli is a promising way to elucidate the body's inflammatory response and design new therapies. However, creating dynamic interfaces that allow precise, real-time, and reversible control over mechanical cues remains a challenge. In this study, we report the immunomodulatory effects of dynamic liquid crystal (LC) polymer films on in vitro macrophage responses. By utilizing reversible light-induced LC surface topographies, we generate dynamic mechanical stimuli on cells during topography formation and removal, enabling on-demand and reversible reprogramming of cell behavior. Our findings reveal a strong topographical shape-dependent cell response by examining the effects of flat, pillared, and grooved LC films on THP-1-derived macrophages. A strong increase in both pro- and anti-inflammatory markers is observed on grooves, while pillars maintain the anti-inflammatory profile without broad activation. Macrophages on LC film-generated topographies furthermore present distinct cytokine expression profiles. Notably, light-induced grooves triggered a stronger pro-remodeling cellular response, while pillars appeared to exert an inhibitory effect on macrophage activation. The dynamic topographies remarkably induced distinct changes in the macrophage membrane morphology, triggering migration-associated blebbing of the cell membrane in all cases except for grooves that promoted an increased degree of lamellipodia and filopodia formation. Overall, these results demonstrate that light-responsive LC surfaces provide a controllable platform for topography-dependent and adaptive immune modulation, opening opportunities for rational design of immunoregulatory scaffolds that exploit macrophage plasticity for regenerative medicine.

Understanding macrophage phenotype regulation by mechanical stimuli is a promising way to elucidate the body's inflammatory response and design new therapies. However, creating dynamic interfaces that allow precise, real‐time, and reversible control over mechanical cues remains a challenge. In this study, we report the immunomodulatory effects of dynamic liquid crystal (LC) polymer films on in vitro macrophage responses. By utilizing reversible light‐induced LC surface topographies, we generate dynamic mechanical stimuli on cells during topography formation and removal, enabling on‐demand and reversible reprogramming of cell behavior. Our findings reveal a strong topographical shape‐dependent cell response by examining the effects of flat, pillared, and grooved LC films on THP‐1‐derived macrophages. A strong increase in both pro‐ and anti‐inflammatory markers is observed on grooves, while pillars maintain the anti‐inflammatory profile without broad activation. Macrophages on LC film‐generated topographies furthermore present distinct cytokine expression profiles. Notably, light‐induced grooves triggered a stronger pro‐remodeling cellular response, while pillars appeared to exert an inhibitory effect on macrophage activation. The dynamic topographies remarkably induced distinct changes in the macrophage membrane morphology, triggering migration‐associated blebbing of the cell membrane in all cases except for grooves that promoted an increased degree of lamellipodia and filopodia formation. Overall, these results demonstrate that light‐responsive LC surfaces provide a controllable platform for topography‐dependent and adaptive immune modulation, opening opportunities for rational design of immunoregulatory scaffolds that exploit macrophage plasticity for regenerative medicine.

This Perspective discusses the potential of stimuli‐responsive liquid crystal polymer (LCP) bio‐interfaces in modulating cell behavior as next generation dynamic artificial scaffolds. Unlike current artificial biomaterials that have static properties, LCPs offer fast, reversible, and spatially programmable deformation that reflects the dynamic properties of the natural materials and systems. In this Perspective, we first outline static materials and key interface properties known to influence cellular processes, then provide an overview of LCPs operating under physiological conditions, crosslinking strategies, and alignment mechanisms relevant for designing responsive systems. Subsequently, we reorganize existing findings on LCP bio‐interfaces into two conceptual categories: (1) static LCPs that demonstrate baseline biocompatibility and cellular alignment effects, and (2) dynamic LCPs that enable externally triggered dynamics for on‐demand mechanomodulation. The categorization highlights that, despite their intrinsic stimuli‐responsiveness, LCP‐based dynamic bio‐polymer interfaces remain scarcely explored in cellular studies. Finally, we discuss current material limitations, operational challenges under physiological conditions, and technological barriers such as stiffness mismatch, biocompatibility, and stimulus compatibility, and propose future research directions for unlocking adaptive, multi‐stimuli‐responsive, and integrated‐readout LCP platforms for cell modulation.

Cancer development is increasingly associated with changes in tissue curvature, which influence dynamic cellular behaviors such as polarization and migration. However, the mechanisms by which curved tissue architectures contribute to cancer progression remain poorly understood, partly due to the lack of adequate research tools. Here, we fabricated magnetic Acrylamide hydrogel constructs to investigate the effect of curvature and dynamic movement induced by external magnetic fields of low intensity (100 mT) in the phenotype and gene expression of MDA-MB-231 metastatic breast cancer cells. We found that combining the magnetic hydrogel (MACrylamide) with an applied magnetic field significantly reduced the area occupied by the cells, from 55% to 33%, compared to conditions without magnetic field exposure. In addition, exposure to the magnetic field in combination with the magnetic scaffold had a statistically significant effect on the expression of specific genes associated with anti-inflammatory responses and tumor proliferation and metastasis (NMO1, OCT4, SOX4). These findings suggest that the cells altered their behavior after 7 days of culture on the magnetic hydrogel and 24 h of magnetic stimulation. As a control, NHDF dermal fibroblasts were cultured under the same conditions. Comparison of the two cell lines confirms the selectivity of the approach for cancer cells while ensuring minimal impact on healthy skin cells. This work underscores the importance of dynamic tissue curving during carcinogenesis using a biocompatible surface that mimics physiologically relevant curved tissues.

Cardiovascular diseases are the leading cause of global mortality. These conditions are associated with cardiac cell death and loss of vascularization, potentially progressing to fatal myocardial infarction. However, the lack of accurate models to simulate the complex cardiac tissue microenvironment and explore alternative therapeutics contributes to heart disease still being regarded as irreversible. In this work, we developed a unique organ-on-chip platform that integrates electrical, magnetic, and mechanical stimulation to replicate the cardiac microenvironment and investigate the impact of electrical and magnetic stimulation on cardiac cell fate. Our micromodel integrated triple stimulating inputs using hybrid stimuli-responsive materials. Electromagnetic scaffolds were obtained by coating with conductive poly(3,4-ethylenedioxythiophene) polystyrenesulfonate (PEDOT:PSS) electrospun coaxial fibers comprising a polycaprolactone (PCL) shell and a core of gelatin embedded with iron oxide nanoparticles (MNPs). These scaffolds were incorporated in the chip, and the properties and biological effects of these aligned electromagnetic fibers were compared with those of PEDOT:PSS-coated gelatin hydrogels with aligned magnetic particles. In the presence of an external magnetic field, both materials became more hydrophilic. PEDOT:PSS coaxial fibers demonstrated higher electroconductivity (7.9 S·cm^-1) than the conductive hydrogels (0.83 S·cm^-1). Induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) were successfully cultured on the PEDOT:PSS coaxial fibers, as shown by cell metabolic activity assays over 8 days. Additionally, a 24-h of electric and magnetic combined stimulation significantly enhanced cell viability, with viable cell area increasing from 21% (control) to 54% in the stimulated condition. As proof of concept, we cocultured iPSC-CMs and human vascular endothelial cells (HUVECs) on the materials. Cardiac contraction, which ceased after seeding on the scaffolds, was restored through combined electric and magnetic stimulation and HUVEC culture on-chip. This approach modulates cardiac cell mechanotransduction and offers insights for modeling cardiac tissue, opening future avenues in cardiac repair and remodeling.

Functional hepatocytes play a crucial role in drug screening and cytotoxicity studies. However, primary hepatocytes quickly lose their differentiated state and specialized functions within hours to days after seeding, limiting the utility of in vitro models for long-term drug response and toxicity assessments. To overcome this limitation, we developed a microfluidic system designed to sustain the long-term culture of hepatocytes by optimizing flow conditions and incorporating microtopography to support cell-specific functions. A microfluidic chip with integrated topography was fabricated using soft lithography and characterized through numerical studies. Flow parameters were refined using HepaRG cells, which served as a model to optimize conditions. Hepatocyte-specific functions of HepaRG cells and primary macaque hepatocytes were evaluated under static and flow conditions over time using albumin and urea assays. The system demonstrated its ability to support HepaRG cells for up to 25 days and primary macaque hepatocytes for up to 5 days. Notably, flow conditions enhanced metabolic activity, with HepaRG cells showing a 70-fold increase in albumin secretion and a 40% rise in urea production by day 14, compared to static cultures. Similarly, primary macaque hepatocytes exhibited a 120-fold increase in albumin secretion under flow by day 8 relative to static conditions. These results highlight the potential of this optimized microfluidic platform for long-term hepatocyte culture, making it a valuable tool for future applications in drug screening and toxicity testing.

This tutorial review covers mammalian cell culture integration within digital microfluidic devices, exploring scaffolds, AC/DC effects on cell behavior, physical/biochemical stimuli delivery, on-chip analytics, sorting, and organ-on-chip aspects.

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.