Cell Type and Nuclear Size Dependence of the Nuclear Deformation of Cells on a Micropillar Array

Engineering the Cellular Microenvironment: Integrating Three-Dimensional Nontopographical and Two-Dimensional Biochemical Cues for Precise Control of Cellular Behavior

The development of biomaterials capable of regulating cellular processes and guiding cell fate decisions has broad implications in tissue engineering, regenerative medicine, and cell-based assays for drug development and disease modeling. Recent studies have shown that three-dimensional (3D) nanoscale physical cues such as nanotopography can modulate various cellular processes like adhesion and endocytosis by inducing nanoscale curvature on the plasma and nuclear membranes. Two-dimensional (2D) biochemical cues such as protein micropatterns can also regulate cell function and fate by controlling cellular geometries. Development of biomaterials with precise control over nanoscale physical and biochemical cues can significantly influence programming cell function and fate. In this study, we utilized a laser-assisted micropatterning technique to manipulate the 2D architectures of cells on 3D nanopillar platforms. We performed a comprehensive analysis of cellular and nuclear morphology and deformation on both nanopillar and flat substrates. Our findings demonstrate the precise engineering of single cell architectures through 2D micropatterning on nanopillar platforms. We show that the coupling between the nuclear and cell shape is disrupted on nanopillar surfaces compared to flat surfaces. Furthermore, our results suggest that cell elongation on nanopillars enhances nanopillar-induced endocytosis. We believe our platform serves as a versatile tool for further explorations into programming cell function and fate through combined physical cues that create nanoscale curvature on cell membranes and biochemical cues that control the geometry of the cell.

Epithelial-Mesenchymal Transition of Cancer Cells on Micropillar Arrays

Epithelial-mesenchymal transition (EMT) is critical for tumor invasion and many other cell-relevant processes. While much progress has been made about EMT, no report concerns the EMT of cells on topological biomaterial interfaces with significant nuclear deformation. Herein, we prepared a poly(lactide-co-glycolide) micropillar array with an appropriate dimension to enable significant deformation of cell nuclei and examined EMT of a human lung cancer epithelial cell (A549). We show that A549 cells undergo serious nuclear deformation on the micropillar array. The cells express more E-cadherin and less vimentin on the micropillar array than on the smooth surface. After transforming growth factor-β1 (TGF-β1) treatment, the expression of E-cadherin as an indicator of the epithelial phenotype is decreased and the expression of vimentin as an indicator of the mesenchymal phenotype is increased for the cells both on smooth surfaces and on micropillar arrays, indicating that EMT occurs even when the cell nuclei are deformed and the culture on the micropillar array more enhances the expression of vimentin. Expression of myosin phosphatase targeting subunit 1 is reduced in the cells on the micropillar array, possibly affecting the turnover of myosin light chain phosphorylation and actin assembly; this makes cells on the micropillar array prefer the epithelial-like phenotype and more sensitive to TGF-β1. Overall, the micropillar array exhibits a promoting effect on the EMT.

Coupling of static ultramicromagnetic field with elastic micropillar-structured substrate for cell response

Micropillars have emerged as promising tools for a wide range of biological applications, while the influence of magnetic fields on cell behavior regulation has been increasingly recognized. However, the combined effect of micropillars and magnetic fields on cell behaviors remains poorly understood. In this study, we investigated the responses of H9c2 cells to ultramicromagnetic micropillar arrays using NdFeB as the tuned magnetic particles. We conducted a comparative analysis between PDMS micropillars and NdFeB/PDMS micropillars to assess their impact on cell function. Our results revealed that H9c2 cells exhibited significantly enhanced proliferation and notable cytoskeletal rearrangements on the ultramicromagnetic micropillars, surpassing the effects observed with pure PDMS micropillars. Immunostaining further indicated that cells cultured on ultramicromagnetic micropillars displayed heightened contractility compared to those on PDMS micropillars. Remarkably, the ultramicromagnetic micropillars also demonstrated the ability to decrease reactive oxygen species (ROS) levels, thereby preventing F-actin degeneration. Consequently, this study introduces ultramicromagnetic micropillars as a novel tool for the regulation and detection of cell behaviors, thus paving the way for advanced investigations in tissue engineering, single-cell analysis, and the development of flexible sensors for cellular-level studies.

Recent advances in regenerative biomaterials

Nowadays, biomaterials have evolved from the inert supports or functional substitutes to the bioactive materials able to trigger or promote the regenerative potential of tissues. The interdisciplinary progress has broadened the definition of 'biomaterials', and a typical new insight is the concept of tissue induction biomaterials. The term 'regenerative biomaterials' and thus the contents of this article are relevant to yet beyond tissue induction biomaterials. This review summarizes the recent progress of medical materials including metals, ceramics, hydrogels, other polymers and bio-derived materials. As the application aspects are concerned, this article introduces regenerative biomaterials for bone and cartilage regeneration, cardiovascular repair, 3D bioprinting, wound healing and medical cosmetology. Cell-biomaterial interactions are highlighted. Since the global pandemic of coronavirus disease 2019, the review particularly mentions biomaterials for public health emergency. In the last section, perspectives are suggested: (i) creation of new materials is the source of innovation; (ii) modification of existing materials is an effective strategy for performance improvement; (iii) biomaterial degradation and tissue regeneration are required to be harmonious with each other; (iv) host responses can significantly influence the clinical outcomes; (v) the long-term outcomes should be paid more attention to; (vi) the noninvasive approaches for monitoring in vivo dynamic evolution are required to be developed; (vii) public health emergencies call for more research and development of biomaterials; and (viii) clinical translation needs to be pushed forward in a full-chain way. In the future, more new insights are expected to be shed into the brilliant field-regenerative biomaterials.

A static force model to analyze the nuclear deformation on cell adhesion to vertical nanostructures

Vertical nanostructures have been found to induce the deformation of the nuclear envelope during cell adhesion. However, there has been a lack of quantitative analysis of the influence of nanostructures morphology on the degree of nuclear deformation. Here, a theoretical model was proposed to investigate the mechanism of nuclear deformation by analyzing the mechanical force balance. Based on the established model, we analyzed the effects of the morphology of the nanopillar array on nuclear deformation and gave the quantitative relationship of the deformation depth of the nucleus with the pitch and radius of nanopillars. Our theoretical results seem to show broad agreements with experimental observations, which implies that the work can provide useful guidance to the design of nanostructures for biomedical applications.

A Cell Culture Chip with Transparent, Micropillar-Decorated Bottom for Live Cell Imaging and Screening of Breast Cancer Cells

In the recent years, microfabrication technologies have been widely used in cell biology, tissue engineering, and regenerative medicine studies. Today, the implementation of microfabricated devices in cancer research is frequent and advantageous because it enables the study of cancer cells in controlled microenvironments provided by the microchips. Breast cancer is one of the most common cancers in women, and the way breast cancer cells interact with their physical microenvironment is still under investigation. In this study, we developed a transparent cell culture chip (Ch-Pattern) with a micropillar-decorated bottom that makes live imaging and monitoring of the metabolic, proliferative, apoptotic, and morphological behavior of breast cancer cells possible. The reason for the use of micropatterned surfaces is because cancer cells deform and lose their shape and acto-myosin integrity on micropatterned substrates, and this allows the quantification of the changes in morphology and through that identification of the cancerous cells. In the last decade, cancer cells were studied on micropatterned substrates of varying sizes and with a variety of biomaterials. These studies were conducted using conventional cell culture plates carrying patterned films. In the present study, cell culture protocols were conducted in the clear-bottom micropatterned chip. This approach adds significantly to the current knowledge and applications by enabling low-volume and high-throughput processing of the cell behavior, especially the cell–micropattern interactions. In this study, two different breast cancer cell lines, MDA-MB-231 and MCF-7, were used. MDA-MB-231 cells are invasive and metastatic, while MCF-7 cells are not metastatic. The nuclei of these two cell types deformed to distinctly different levels on the micropatterns, had different metabolic and proliferation rates, and their cell cycles were affected. The Ch-Pattern chips developed in this study proved to have significant advantages when used in the biological analysis of live cells and highly beneficial in the study of screening breast cancer cell–substrate interactions in vitro.

Automated Cell Mechanical Characterization by On-Chip Sequential Squeezing: From Static to Dynamic

The mechanical properties of cells are harmless biomarkers for cell identification and disease diagnosis. Although many systems have been developed to evaluate the static mechanical properties of cells for biomedical research, their robustness, effectiveness, and cost do not meet clinical requirements or the experiments with a large number of cell samples. In this paper, we propose an approach for on-chip cell mechanical characterization by analyzing the dynamic behavior of cells as they pass through multiple constrictions. The proposed serpentine microfluidic channel consisted of 20 constrictions connected in series and divided into five rows for tracking cell dynamic behavior. Assisted by computer vision, the squeezing time of each cell through five rows of constrictions was automatically collected and filtered to evaluate the cell's mechanical deformability. We observed a decreasing passage time and increasing dynamic deformability of the cells as they passed through the multiple constrictions. The deformability increase rate of the HeLa cells was eight times greater than that of MEF cells. Moreover, the weak correlation between the deformability increase rate and the cell size indicated that cell recognition based on measuring the deformability increase rate could hardly be affected by the cell size variation. These findings showed that the deformability increase rate of the cell under on-chip sequential squeezing as a new index has great potential in cancer cell recognition.

Exploration of possible cell chirality using material techniques of surface patterning

Consistent left-right (LR) asymmetry or chirality is critical for embryonic development and function maintenance. While chirality on either molecular or organism level has been well established, that on the cellular level has remained an open question for a long time. Although it remains unclear whether chirality exists universally on the cellular level, valuable efforts have recently been made to explore this fundamental topic pertinent to both cell biology and biomaterial science. The development of material fabrication techniques, surface patterning, in particular, has afforded a unique platform to study cell-material interactions. By using patterning techniques, chirality on the cellular level has been examined for cell clusters and single cells in vitro in well-designed experiments. In this review, we first introduce typical fabrication techniques of surface patterning suitable for cell studies and then summarize the main aspects of preliminary evidence of cell chirality on patterned surfaces to date. We finally indicate the limitations of the studies conducted thus far and describe the perspectives of future research in this challenging field. STATEMENT OF SIGNIFICANCE: While both biomacromolecules and organisms can exhibit chirality, it is not yet conclusive whether a cell has left-right (LR) asymmetry. It is important yet challenging to study and reveal the possible existence of cell chirality. By using the technique of surface patterning, the recent decade has witnessed progress in the exploration of possible cell chirality within cell clusters and single cells. Herein, some important preliminary evidence of cell chirality is collected and analyzed. The open questions and perspectives are also described to promote further investigations of cell chirality in biomaterials.

Tailoring Cellular Function: The Contribution of the Nucleus in Mechanotransduction

Cells sense a variety of different mechanochemical stimuli and promptly react to such signals by reshaping their morphology and adapting their structural organization and tensional state. Cell reactions to mechanical stimuli arising from the local microenvironment, mechanotransduction, play a crucial role in many cellular functions in both physiological and pathological conditions. To decipher this complex process, several studies have been undertaken to develop engineered materials and devices as tools to properly control cell mechanical state and evaluate cellular responses. Recent reports highlight how the nucleus serves as an important mechanosensor organelle and governs cell mechanoresponse. In this review, we will introduce the basic mechanisms linking cytoskeleton organization to the nucleus and how this reacts to mechanical properties of the cell microenvironment. We will also discuss how perturbations of nucleus-cytoskeleton connections, affecting mechanotransduction, influence health and disease. Moreover, we will present some of the main technological tools used to characterize and perturb the nuclear mechanical state.

Chromosomal Repositioning and Gene Regulation of Cells on a Micropillar Array

While various cell responses on material surfaces have been examined, relatively few reports are focused on significant self-deformation of cell nuclei and corresponding chromosomal repositioning. Herein, we prepared a micropillar array of poly(lactide-co-glycolide) (PLGA) and observed significant nuclear deformation of HeLa cells on the polymeric micropillars. In particular, we detected the territory positioning of chromosomes 18 and 19 and gene expression profiles of HeLa cells on the micropillar array using fluorescence in situ hybridization and a DNA microarray. Chromosome 18 was found to be translocated closer to the nuclear periphery than chromosome 19 on the micropillar array. With the repositioning of chromosomal territories, HeLa cells changed their gene expressions on the micropillar array with 180 genes upregulated and 255 genes downregulated for all of the 23 pairs of chromosomes under the experimental conditions and the employed Bioinformatics criteria. Hence, this work deepens the understanding on cell-material interactions by revealing that material surface topography can probably influence chromosomal repositioning in the nuclei and gene expressions of cells.

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.

Self-Assembly of Integrin Ligands on the Apical Membrane Inhibits the Migration of Glioma Cells

Malignant brain cancer remains challenging in treatment due to the highly invasive quality of gliomas. Inspired by the upregulated expression of integrin β1 subunits in tumors, we designed and synthesized an integrin-targeting self-assembling ligand based on a laminin-derived peptide that selectively forms nanofibrous microdomains on the apical membrane of glioma cells, inhibiting their migration and invasion.

Critical Areas of Proliferation of Single Cells on Micropatterned Surfaces and Corresponding Cell Type Dependence

Material cues to influence cell proliferation are a fundamental issue in the fields of biomaterials, cell biology, tissue engineering, and regenerative medicine. This paper aims to investigate the proliferation of single mammal cells on micropatterned material surfaces. To this end, we prepared cell-adhesive circular microislands with 20 areas on the nonfouling background and systematically examined adhesion and proliferation behaviors of different kinds of single cells (primary stem and nonstem cells, cancer and normal cell lines) on micropatterns. On the basis of the analysis of experimental data, we found two critical areas about cell proliferation: (1) the critical spreading area of cells from almost no proliferation to confined proliferation, denoted as A_P and (2) the critical spreading area of cells from confined proliferation to almost free proliferation, denoted as A_FP. We further summarized the relative size relationship between these two critical areas and the characteristic areas of cell adhesion on both patterned and nonpatterned surfaces. While proliferation of single primary cells was affected by cell spreading, those cell lines, irrespective of normal and cancer cells, did not exhibit significant cell-spreading effects. As a result, this study reveals that proliferation of single cells is dependent upon spreading area, in particular for primary cells on material surfaces.

Square prism micropillars on poly(methyl methacrylate) surfaces modulate the morphology and differentiation of human dental pulp mesenchymal stem cells

Use of soluble factors is the most common strategy to induce osteogenic differentiation of mesenchymal stem cells (MSCs) in vitro, but it may raise potential side effects in vivo. The topographies of the substrate surfaces affect cell behavior, and this could be a promising approach to guide stem cell differentiation. Micropillars have been reported to modulate cellular and subcellular shape, and it is particularly interesting to investigate whether these changes in cell morphology can modulate gene expression and lineage commitment without chemical induction. In this study, poly(methyl methacrylate) (PMMA) films were decorated with square prism micropillars with different lateral dimensions (4, 8 and 16 μm), and the surface wettability of the substrates was altered by oxygen plasma treatment. Both, pattern dimensions and hydrophilicity, were found to affect the attachment, proliferation, and most importantly, gene expression of human dental pulp mesenchymal stem cells (DPSCs). Decreasing the pillar width and interpillar spacing of the square prism pillars enhanced cell attachment, cell elongation, and deformation of nuclei, but reduced early proliferation rate. Surfaces with 4 or 8 μm wide pillars/gaps upregulated the expression of early bone-marker genes and mineralization over 28 days of culture. Exposure to oxygen plasma increased wettability and promoted cell attachment and proliferation but delayed osteogenesis. Our findings showed that surface topography and chemistry are very useful tools in controlling cell behavior on substrates and they can also help create better implants. The most important finding is that hydrophobic micropillars on polymeric substrate surfaces can be exploited in inducing osteogenic differentiation of MSCs without any differentiation supplements.

Polydopamine-mediated covalent functionalization of collagen on a titanium alloy to promote biocompatibility with soft tissues

The clinical success of a titanium (Ti) percutaneous implant requires the integration with soft tissues to form a biological seal, which effectively combats marsupialization, premigration and infection after implantation. However, the bioinert surface of Ti or its alloys prevents the material from sufficient biological sealing and limits the application of Ti or its alloys as percutaneous implants. In this study, we achieved a collagen coating to bioactivate the surface of Ti-6Al-4V. In order to enable covalent functionalization, we first deposited a polydopamine (PDA) coating on Ti-6Al-4V based on dopamine self-polymerization and then immobilized collagen chains on PDA. Compared with physical absorption, such a chemical bonding method through mussel-inspired chemistry showed better stability of the coating. Meanwhile, the cellular tests in vitro indicated that collagen functionalization on the Ti-6Al-4V surface showed better adhesion of human foreskin fibroblasts (HFFs) and human immortal keratinocytes (HaCaTs). The subcutaneous implantation tests in rats indicated that the collagen modification attenuated soft tissue response and improved tissue compatibility compared with either pure Ti-6Al-4V or merely PDA coated samples. The facile bioinspired approach enables a persistent modification of metals by macromolecules under aqueous environments, and the PDA-collagen coated titanium alloy is worthy of further investigation as a percutaneous implant.

Proliferation of Cells with Severe Nuclear Deformation on a Micropillar Array

Cellular responses on a topographic surface are fundamental topics about interfaces and biology. Herein, a poly(lactide- co-glycolide) (PLGA) micropillar array was prepared and found to trigger significant self-deformation of cell nuclei. The time-dependent cell viability and thus cell proliferation was investigated. Despite significant nuclear deformation, all of the examined cell types (Hela, HepG2, MC3T3-E1, and NIH3T3) could survive and proliferate on the micropillar array yet exhibited different proliferation abilities. Compared to the corresponding groups on the smooth surface, the cell proliferation abilities on the micropillar array were decreased for Hela and MC3T3-E1 cells and did not change significantly for HepG2 and NIH3T3 cells. We also found that whether the proliferation ability changed was related to whether the nuclear sizes decreased in the micropillar array, and thus the size deformation of cell nuclei should, besides shape deformation, be taken into consideration in studies of cells on topological surfaces.