Peptide-Functionalized Nanostructured Microarchitectures Enable Rapid Mechanotransductive Differentiation

Mechanoactivation of Single Stem Cells in Microgels Using a 3D-Printed Stimulation Device

In this study, the novel 3D-printed pressure chamber for encapsulated single-cell stimulation (3D-PRESS) platform is introduced for the mechanical stimulation of single stem cells in 3D microgels. The custom-designed 3D-PRESS, allows precise pressure application up to 400 kPa at the single-cell level. Microfluidics is employed to encapsulate single mesenchymal stem cells within ionically cross-linked alginate microgels with cell adhesion RGD peptides. Rigorous testing affirms the leak-proof performance of the 3D-PRESS device up to 400 kPa, which is fully biocompatible. 3D-PRESS is implemented on mesenchymal stem cells for mechanotransduction studies, by specifically targeting intracellular calcium signaling and the nuclear translocation of a mechanically sensitive transcription factor. Applying 200 kPa pressure on individually encapsulated stem cells reveals heightened calcium signaling in 3D microgels compared to conventional 2D culture. Similarly, Yes-associated protein (YAP) translocation into the nucleus occurs at 200 kPa in 3D microgels with cell-binding RGD peptides unveiling the involvement of integrin-mediated mechanotransduction in singly encapsulated stem cells in 3D microgels. Combining live-cell imaging with precise mechanical control, the 3D-PRESS platform emerges as a versatile tool for exploring cellular responses to pressure stimuli, applicable to various cell types, providing novel insights into single-cell mechanobiology.

Nanoscale surface coatings and topographies for neural interfaces

With the lack of minimally invasive tools for probing neuronal systems across spatiotemporal scales, understanding the working mechanism of the nervous system and limited assessments available are imperative to prevent or treat neurological disorders. In particular, nanoengineered neural interfaces can provide a solution to this technological barrier. This review covers recent surface engineering approaches, including nanoscale surface coatings, and a range of topographies from the microscale to the nanoscale, primarily focusing on neural-interfaced biosystems. Specifically, the immobilization of bioactive molecules to fertilize the neural cell lineage, topographical engineering to induce mechanotransduction in neural cells, and enhanced cell-chip coupling using three-dimensional structured surfaces are highlighted. Advances in neural interface design will help us understand the nervous system, thereby achieving the effective treatments for neurological disorders. STATEMENT OF SIGNIFICANCE: • This review focuses on designing bioactive neural interface with a nanoscale chemical modification and topographical engineering at multiscale perspective. • Versatile nanoscale surface coatings and topographies for neural interface are summarized. • Recent advances in bioactive materials applicable for neural cell culture, electrophysiological sensing, and neural implants are reviewed.

Silicon microfabrication technologies for biology integrated advance devices and interfaces

Miniaturization is the trend to manufacture ever smaller devices and this process requires knowledge, experience, understanding of materials, manufacturing techniques and scaling laws. The fabrication techniques used in semiconductor industry deliver an exceptionally high yield of devices and provide a well-established platform. Today, these miniaturized devices are manufactured with high reproducibility, design flexibility, scalability and multiplexed features to be used in several applications including micro-, nano-fluidics, implantable chips, diagnostics/biosensors and neural probes. We here provide a review on the microfabricated devices used for biology driven science. We will describe the ubiquity of the use of micro-nanofabrication techniques in biology and biotechnology through the fabrication of high-aspect-ratio devices for cell sensing applications, intracellular devices, probes developed for neuroscience-neurotechnology and biosensing of the certain biomarkers. Recently, the research on micro and nanodevices for biology has been progressing rapidly. While the understanding of the unknown biological fields -such as human brain- has been requiring more research with advanced materials and devices, the development protocols of desired devices has been advancing in parallel, which finally meets with some of the requirements of biological sciences. This is a very exciting field and we aim to highlight the impact of micro-nanotechnologies that can shed light on complex biological questions and needs.

Assessing Tumorigenicity in Stem Cell-Derived Therapeutic Products: A Critical Step in Safeguarding Regenerative Medicine

Stem cells hold promise in regenerative medicine due to their ability to proliferate and differentiate into various cell types. However, their self-renewal and multipotency also raise concerns about their tumorigenicity during and post-therapy. Indeed, multiple studies have reported the presence of stem cell-derived tumors in animal models and clinical administrations. Therefore, the assessment of tumorigenicity is crucial in evaluating the safety of stem cell-derived therapeutic products. Ideally, the assessment needs to be performed rapidly, sensitively, cost-effectively, and scalable. This article reviews various approaches for assessing tumorigenicity, including animal models, soft agar culture, PCR, flow cytometry, and microfluidics. Each method has its advantages and limitations. The selection of the assay depends on the specific needs of the study and the stage of development of the stem cell-derived therapeutic product. Combining multiple assays may provide a more comprehensive evaluation of tumorigenicity. Future developments should focus on the optimization and standardization of microfluidics-based methods, as well as the integration of multiple assays into a single platform for efficient and comprehensive evaluation of tumorigenicity.

Efficient Delivery of Biological Cargos into Primary Cells by Electrodeposited Nanoneedles via Cell-Cycle-Dependent Endocytosis

Nanoneedles are a useful tool for delivering exogenous biomolecules to cells. Although therapeutic applications have been explored, the mechanism regarding how cells interact with nanoneedles remains poorly studied. Here, we present a new approach for the generation of nanoneedles, validated their usefulness in cargo delivery, and studied the underlying genetic modulators during delivery. We fabricated arrays of nanoneedles based on electrodeposition and quantified its efficacy of delivery using fluorescently labeled proteins and siRNAs. Notably, we revealed that our nanoneedles caused the disruption of cell membranes, enhanced the expression of cell-cell junction proteins, and downregulated the expression of transcriptional factors of NFκB pathways. This perturbation trapped most of the cells in G2 phase, in which the cells have the highest endocytosis activities. Taken together, this system provides a new model for the study of interactions between cells and high-aspect-ratio materials.

Magnetic Nanobubble Mechanical Stress Induces the Piezo1-Ca2+ -BMP2/Smad Pathway to Modulate Neural Stem Cell Fate and MRI/Ultrasound Dual Imaging Surveillance for Ischemic Stroke

Neural stem cells (NSCs) are used to treat various nervous system diseases because of their self-renewal ability and multidirectional differentiation potential. However, an insufficient ability to track their migration in vivo and poor control over their survival and differentiation efficiency are two major critical challenges for clinical application. Here, it is shown that when magnetic nanobubbles (MNBs), which are assembled from magnetic nanoparticles, are internalized by NSCs, intramembrane volumetric oscillation of the MNBs induces an increase in intracellular hydrostatic pressure and cytoskeleton force, resulting in the activation of the Piezo1-Ca²⁺ mechanosensory channel. This subsequently triggers the BMP2/Smad biochemical signaling pathway, leading to differentiation of NSCs into the neuronal phenotype. Signaling through the Piezo1-Ca²⁺ -BMP2/Smad pathway can be further accelerated by application of an external shear stress force using low-intensity pulsed ultrasound. More importantly, magnetic resonance imaging and ultrasound imaging surveillance of NSCs based on MNB labeling can be leveraged to provide NSC therapeutic outcomes. Both the in vitro and in vivo findings demonstrate that a bubble nanostructure-induced physical force can modulate and control the mechanical signaling pathway regulating stem cell development.

Mechano-Nanoarchitectonics: Design and Function

Mechanical stimuli have rather ambiguous and less-specific features among various physical stimuli, but most materials exhibit a certain level of responses upon mechanical inputs. Unexplored sciences remain in mechanical responding systems as one of the frontiers of materials science. Nanoarchitectonics approaches for mechanically responding materials are discussed as mechano-nanoarchitectonics in this review article. Recent approaches on molecular and materials systems with mechanical response capabilities are first exemplified with two viewpoints: i) mechanical control of supramolecular assemblies and materials and ii) mechanical control and evaluation of atom/molecular level structures. In the following sections, special attentions on interfacial environments for mechano-nanoarchitectonics are emphasized. The section entitled iii) Mechanical Control of Molecular System at Dynamic Interface describes coupling of macroscopic mechanical forces and molecular-level phenomena. Delicate mechanical forces can be applied to functional molecules embedded at the air-water interface where operation of molecular machines and tuning of molecular receptors upon macroscopic mechanical actions are discussed. Finally, the important role of the interfacial media are further extended to the control of living cells as described in the section entitled iv) Mechanical Control of Biosystems. Pioneering approaches on cell fate regulations at liquid-liquid interfaces are discussed in addition to well-known mechanobiology.

Arg-Gly-Asp peptide functionalized poly-amino acid/ poly (p-benzamide) copolymer with enhanced mechanical properties and osteogenicity

Poly-amino acid (PAA) is a promising biomaterial in biomedical engineering due to its similar amide bond structure to collagen and excellent biocompatibility, but the lack of osteogenic activity and inferior mechanical strength limit its long-term application in orthopedics. In this study, a poly-amino acid/poly (p-benzamide) (PAA-PBA) copolymer with high mechanical strength was designed and fabricated by the method of solution polymerization. The chain structures, thermal properties and mechanical properties of these polymers were evaluated and results showed that PBA greatly promoted the mechanical properties of PAA, and the copolymer performed the maximum mechanical strengths with compressive strength, bending strength and tensile strength of 123 MPa, 107 MPa and, 95 MPa, respectively. To increase the bioactivity of surface, a bioactive coating that consists of poly-(dopamine) (PDA) nanolayers and tripeptide Arginine-Glycine-Aspartic acid (RGD) on sulfonated PAA-PBA copolymer was created. A porous structure appeared on the surface after modification, the surface roughness and hydrophilicity of copolymer has been improved obviously after introducing PDA and RGD peptide coating. The in vitro bioactivity evaluation demonstrated that the RGD-functionalized sample showed a significantly improved ability to promote bone apatite mineralization, cell adhesion, proliferation and osteogenic differentiation. In a word, such a strategy of material synthesis and surface modification method shows a great potential for broadening the use of PAA in the application of load-bearing bone substitute biomaterials.

Conformal Self-Assembly of Nanospheres for Light-Enhanced Airtightness Monitoring and Room-Temperature Gas Sensing

The fabrication of conformal nanostructures on microarchitectures is of great significance for diverse applications. Here a facile and universal method was developed for conformal self-assembly of nanospheres on various substrates including convex bumps and concave holes. Hydrophobic microarchitectures could be transferred into superhydrophilic ones using plasma treatment due to the formation of numerous hydroxyl groups. Because of superhydrophilicity, the nanosphere suspension spread on the microarchitectures quickly and conformal self-assembly of nanospheres can be realized. Besides, the feature size of the conformal nanospheres on the substrates could be further regulated by plasma treatment. After transferring two-dimensional tungsten disulfide sheets onto the conformal nanospheres, the periodic nanosphere array was demonstrated to be able to enhance the light harvesting of WS2. Based on this, a light-enhanced room-temperature gas sensor with a fast recovery speed (<35 s) and low detecting limit (500 ppb) was achieved. Moreover, the WS2-covered nanospheres on the microarchitectures were very sensitive to the changes in air pressure due to the formation of suspended sheets on the convex bumps and concave holes. A sensitive photoelectronic pressure sensor that was capable of detecting the airtightness of vacuum devices was developed using the WS2-decorated hierarchical architectures. This work provides a simple method for the fabrication of conformal nanospheres on arbitrary substrates, which is promising for three-dimensional microfabrication of multifunctional hierarchical microarchitectures for diverse applications, such as biomimetic compound eyes, smart wetting surfaces and photonic crystals.

Unpatterned Bioactive Poly(Butylene 1,4-Cyclohexanedicarboxylate)-Based Film Fast Induced Neuronal-Like Differentiation of Human Bone Marrow-Mesenchymal Stem Cells

Herein, we present poly(butylene 1,4-cyclohexanedicarboxylate) (PBCE) films characterized by an unpatterned microstructure and a specific hydrophobicity, capable of boosting a drastic cytoskeleton architecture remodeling, culminating with the neuronal-like differentiation of human bone marrow-mesenchymal stem cells (hBM-MSCs). We have used two different filming procedures to prepare the films, solvent casting (PBCE) and compression-moulding (PBCE*). PBCE film had a rough and porous surface with spherulite-like aggregations (Ø = 10-20 μm) and was characterized by a water contact angle = 100°. PBCE* showed a smooth and continuous surface without voids and visible spherulite-like aggregations and was more hydrophobic (WCA = 110°). Both surface characteristics were modulated through the copolymerization of different amounts of ether-oxygen-containing co-units into PBCE chemical structure. We showed that only the surface characteristics of PBCE-solvent-casted films steered hBM-MSCs toward a neuronal-like differentiation. hBM-MSCs lost their canonical mesenchymal morphology, acquired a neuronal polarized shape with a long cell protrusion (≥150 μm), expressed neuron-specific class III β-tubulin and microtubule-associated protein 2 neuronal markers, while nestin, a marker of uncommitted stem cells, was drastically silenced. These events were observed as early as 2-days after cell seeding. Of note, the phenomenon was totally absent on PBCE* film, as hBM-MSCs maintained the mesenchymal shape and behavior and did not express neuronal/glial markers.

Nanostructured Architectures Promote the Mesenchymal-Epithelial Transition for Invasive Cells

Dynamic modulation of cellular phenotypes between the epithelial and mesenchymal states-the epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition (MET)-plays an important role in cancer progression. Nanoscale topography of culture substrates is known to affect the migration and EMT of cancer cells. However, existing platforms heavily rely on simple geometries such as grooved lines or cylindrical post arrays, which may oversimplify the complex interaction between cells and nanotopography in vivo. Here, we use electrodeposition to construct finely controlled surfaces with biomimetic fractal nanostructures as a means of examining the roles of nanotopography during the EMT/MET process. We found that nanostructures in the size range of 100 to 500 nm significantly promote MET for invasive breast and prostate cancer cells. The "METed" cells acquired distinct expression of epithelial and mesenchymal markers, displayed perturbed morphologies, and exhibited diminished migration and invasion, even after the removal of a nanotopographical stimulus. The phosphorylation of GSK-3 was decreased, which further tuned the expression of Snail and modulated the EMT/MET process. Our findings suggest that invasive cancer cells respond to the geometries and dimensions of complex nanostructured architectures.