Regulation of stem cell fate using nanostructure-mediated physical signals

Wrapping stem cells with wireless electrical nanopatches for traumatic brain injury therapy

Electrical stimulation holds promise for enhancing neuronal differentiation of neural stem cells to treat traumatic brain injury. However, once the stem cells leave the stimulating material and migrate post transplantation, electrical stimulation on them is diminished. Here, we wrap the stem cells with wireless electrical nanopatches, the conductive graphene nanosheets. Under electromagnetic induction, electrical stimulation can thus be applied in-situ to individual nanopatch-wrapped stem cells on demand, stimulating their neuronal differentiation through a MAPK/ERK signaling pathway. Consequently, 41% of the nanopatch-wrapped stem cells differentiate into functional neurons in 5 days, as opposed to only 16.3% of the unwrapped ones. The brain injury male mice implanted with the nanopatch-wrapped stem cells and exposed to a rotating magnetic field 30 min/day exhibit significant recovery of brain tissues, behaviors, and cognitions, within 28 days. This study opens up an avenue to individualized electrical stimulation of transplanted stem cells for treating neurodegenerative diseases.

Photothermal driven BMSCs osteogenesis and M2 macrophage polarization on polydopamine-coated Ti3C2 nanosheets/poly(vinylidene fluoride trifluoroethylene) nanocomposite coatings

Mild thermal stimulation plays an active role in bone tissue repair and regeneration. In this work, a bioactive polydopamine/Ti3C2/poly(vinylidene fluoride trifluoroethylene) (PDA/Ti3C2/P(VDF-TrFE)) nanocomposite coating with excellent near-infrared light (NIR)-triggered photothermal effect was designed to improve the osteogenic ability of implants. By incorporating dopamine (DA)-modified Ti3C2 nanosheets into the P(VDF-TrFE) matrix and combining them with alkali initiated in situ polymerization, the resulting PDA/Ti3C2/P(VDF-TrFE) nanocomposite coating gained high adhesion strength on Ti substrate, excellent tribological and corrosion resistance properties, which was quite important for clinical application of implant coatings. Cell biology experiments showed that NIR-triggered mild thermal stimulation on the coating surface promoted cell spreading and growth of BMSCs, and also greatly upregulated the osteogenic markers, including Runt-Related Transcription Factor 2 (RUNX2), alkaline phosphatase (ALP), osteopontin (OPN), osteocalcin (OCN). Simultaneously, the synthesis of heat shock protein 47 (HSP47) was significantly promoted by the mild thermal stimulation, which strengthened the specific interaction between HSP47 and collagen Ⅰ (COL-Ⅰ), thereby activating the integrin-mediated MEK/ERK osteogenic differentiation signaling pathway. In addition, the results also showed that the mild thermal stimulation induced the polarization of macrophages towards M2 phenotype, which can attenuate the inflammatory response of injured bone tissue. Antibacterial results indicated that the coating exhibited an outstanding antibacterial ability against S. aureus and E. coli. Conceivably, the versatile implant bioactive coatings developed in this work will show great application potential for implant osseointegration.

Piezocatalytically-induced controllable mineralization scaffold with bone-like microenvironment to achieve endogenous bone regeneration

Orderly hierarchical structure with balanced mechanical, chemical, and electrical properties is the basis of the natural bone microenvironment. Inspired by nature, we developed a piezocatalytically-induced controlled mineralization strategy using piezoelectric polymer poly-L-lactic acid (PLLA) fibers with ordered micro-nano structures to prepare biomimetic tissue engineering scaffolds with a bone-like microenvironment (pcm-PLLA), in which PLLA-mediated piezoelectric catalysis promoted the in-situ polymerization of dopamine and subsequently regulated the controllable growth of hydroxyapatite crystals on the fiber surface. PLLA fibers, as analogs of mineralized collagen fibers, were arranged in an oriented manner, and ultimately formed a bone-like interconnected pore structure; in addition, they also provided bone-like piezoelectric properties. The uniformly sized HA nanocrystals formed by controlled mineralization provided a bone-like mechanical strength and chemical environment. The pcm-PLLA scaffold could rapidly recruit endogenous stem cells, and promote their osteogenic differentiation by activating cell membrane calcium channels and PI3K signaling pathways through ultrasound-responsive piezoelectric signals. In addition, the scaffold also provided a suitable microenvironment to promote macrophage M2 polarization and angiogenesis, thereby enhancing bone regeneration in skull defects of rats. The proposed piezocatalytically-induced controllable mineralization strategy provides a new idea for the development of tissue engineering scaffolds that can be implemented for multimodal physical stimulation therapy.

Biomechanics of Macrophages on Disordered Surface Nanotopography

Macrophages are involved in every stage of the innate/inflammatory immune responses in the body tissues, including the resolution of the reaction, and they do so in close collaboration with the extracellular matrix (ECM). Simplified substrates with nanotopographical features attempt to mimic the structural properties of the ECM to clarify the functional features of the interaction of the ECM with macrophages. We still have a limited understanding of the macrophage behavior upon interaction with disordered nanotopography, especially with features smaller than 10 nm. Here, we combine atomic force microscopy (AFM), finite element modeling (FEM), and quantitative biochemical approaches in order to understand the mechanotransduction from the nanostructured surface into cellular responses. AFM experiments show a decrease of macrophage stiffness, measured with the Young's modulus, as a biomechanical response to a nanostructured (ns-) ZrOx surface. FEM experiments suggest that ZrOx surfaces with increasing roughness represent weaker mechanical boundary conditions. The mechanical cues from the substrate are transduced into the cell through the formation of integrin-regulated focal adhesions and cytoskeletal reorganization, which, in turn, modulate cell biomechanics by downregulating cell stiffness. Surface nanotopography and consequent biomechanical response impact the overall behavior of macrophages by increasing movement and phagocytic ability without significantly influencing their inflammatory behavior. Our study suggests a strong potential of surface nanotopography for the regulation of macrophage functions, which implies a prospective application relative to coating technology for biomedical devices.

Research progress in cell therapy for oral diseases: focus on cell sources and strategies to optimize cell function

In recent years, cell therapy has come to play an important therapeutic role in oral diseases. This paper reviews the active role of mesenchymal stem cells, immune cell sources, and other cells in oral disorders, and presents data supporting the role of cell therapy in oral disorders, including bone and tooth regeneration, oral mucosal disorders, oral soft tissue defects, salivary gland dysfunction, and orthodontic tooth movement. The paper will first review the progress of cell optimization strategies for oral diseases, including the use of hormones in combination with stem cells, gene-modified regulatory cells, epigenetic regulation of cells, drug regulation of cells, cell sheets/aggregates, cell-binding scaffold materials and hydrogels, nanotechnology, and 3D bioprinting of cells. In summary, we will focus on the therapeutic exploration of these different cell sources in oral diseases and the active application of the latest cell optimization strategies.

Mechanically induced pyroptosis enhances cardiosphere oxidative stress resistance and metabolism for myocardial infarction therapy

Current approaches in myocardial infarction treatment are limited by low cellular oxidative stress resistance, reducing the long-term survival of therapeutic cells. Here we develop a liquid-crystal substrate with unique surface properties and mechanical responsiveness to produce size-controllable cardiospheres that undergo pyroptosis to improve cellular bioactivities and resistance to oxidative stress. We perform RNA sequencing and study cell metabolism to reveal increased metabolic levels and improved mitochondrial function in the preconditioned cardiospheres. We test therapeutic outcomes in a rat model of myocardial infarction to show that cardiospheres improve long-term cardiac function, promote angiogenesis and reduce cardiac remodeling during the 3-month observation. Overall, this study presents a promising and effective system for preparing a large quantity of functional cardiospheres, showcasing potential for clinical application.

Adult tissue-specific stem cell interaction: novel technologies and research advances

Adult tissue-specific stem cells play a dominant role in tissue homeostasis and regeneration. Various in vivo markers of adult tissue-specific stem cells have been increasingly reported by lineage tracing in genetic mouse models, indicating that marked cells differentiation is crucial during homeostasis and regeneration. How adult tissue-specific stem cells with indicated markers contact the adjacent lineage with indicated markers is of significance to be studied. Novel methods bring future findings. Recent advances in lineage tracing, synthetic receptor systems, proximity labeling, and transcriptomics have enabled easier and more accurate cell behavior visualization and qualitative and quantitative analysis of cell-cell interactions than ever before. These technological innovations have prompted researchers to re-evaluate previous experimental results, providing increasingly compelling experimental results for understanding the mechanisms of cell-cell interactions. This review aimed to describe the recent methodological advances of dual enzyme lineage tracing system, the synthetic receptor system, proximity labeling, single-cell RNA sequencing and spatial transcriptomics in the study of adult tissue-specific stem cells interactions. An enhanced understanding of the mechanisms of adult tissue-specific stem cells interaction is important for tissue regeneration and maintenance of homeostasis in organisms.

Wireless Electrical Signals Induce Functional Neuronal Differentiation of BMSCs on 3D Graphene Framework Driven by Magnetic Field

Bone marrow mesenchymal stem cells (BMSCs) are suggested as candidates for neurodegeneration therapy by autologous stem cells to overcome the lack of neural stem cells in adults. However, the differentiation of BMSCs into functional neurons is a major challenge for neurotherapy. Herein, a methodology has been proposed to induce functional neuronal differentiation of BMSCs on a conductive three-dimensional graphene framework (GFs) combined with a rotating magnetic field. A wireless electrical signal of about 10 μA can be generated on the surface of GFs by cutting the magnetic field lines based on the well-known electromagnetic induction effect, which has been proven to be suitable for inducing neuronal differentiation of BMSCs. The enhanced expressions of the specific genes/proteins and apparent Ca2+ intracellular flow indicate that BMSCs cultured on GFs with 15 min/day rotating magnetic field stimulation for 15 days can differentiate functional neurons without any neural inducing factor. The animal experiments confirm the neural differentiation of BMSCs on GFs after transplantation in vivo, accompanied by stimulation of an external rotating magnetic field. This study overcomes the lack of autologous neural stem cells for adult neurodegeneration patients and provides a facile and safe strategy to induce the neural differentiation of BMSCs, which has potential for clinical applications of neural tissue engineering.

Bioinspired Adaptable Indwelling Microneedles for Treatment of Diabetic Ulcers

Microneedles provide an effective strategy for transdermal drug delivery. Many endeavors have been devoted to developing smart microneedles that can respond to and interact with pathophysiological environments. Here, novel bioinspired adaptable indwelling microneedles with therapeutic exosome encapsulation are presented for diabetic wound healing by a combined fabrication strategy of template replication and 3D transfer printing. Such microneedles are composed of mesenchymal stem cell (MSC)-exosomes-encapsulated adjustable poly(vinyl alcohol) (PVA) hydrogel needle tips and detachable 3M medical tape supporting substrate. As the mechanical strength of the PVA hydrogel is ionically responsive due to Hofmeister effects, the hardness of the resultant microneedle tips can be upregulated by sulfate ions to ensure skin penetration and be softened by nitrate ions after tip-substrate detachment to adapt to the surrounding tissue and release exosomes. Because the MSC-exosomes can effectively activate fibroblasts, vascular endothelial cells, and macrophages, the indwelling microneedles are demonstrated with the function of promoting tissue regeneration and diabetic wound healing in full-thickness cutaneous wounds of diabetic rat models. These features indicate that the bioinspired adaptable indwelling microneedles are with practical values and clinical prospects in tissue and wound regeneration.

Engineering Female Germline Stem Cells with Exocytotic Polymer Dots

Germline stem cells (GSCs) are the only cell population capable of passing genetic information to offspring, making them attractive targets in reproductive biology and fertility research. However, it is generally more difficult to introduce exogenous biomolecules into GSCs than other cell types, impeding the exploration and manipulation of these cells for biomedical purposes. Herein, semiconductor polymer dots (Pdots)-based nanocomplex Pdot-siRNA is developed and achieves effective knockdown of target genes in female germline stem cells (FGSCs). Advantage of high fluorescence brightness of Pdots is taken for comprehensive investigation of their cellular uptake, intracellular trafficking, and exocytosis in FGSCs. Importantly, Pdots show excellent biocompatibility and minimally disturb the differentiation of FGSCs. Intracellular Pdots escape from the lysosomes and undergo active exocytosis, which makes them ideal nanocarriers for bioactive cargos. Moreover, Pdot-siRNA can penetrate into 3D ovarian organoids derived from FGSCs and down-regulate the expression levels of target genes. This study investigates the interface between a type of theranostic nanoparticles and FGSCs for the first time and sheds light on the manipulation and medical application of FGSCs.

Surface-modified Ti3C2 MXene nanosheets for mesenchymal stem cell osteogenic differentiation via photothermal conversion

In the field of bone tissue engineering, the practical application of growth factors is limited by various factors such as systemic toxicity, instability, and the potential to induce inflammation. To circumvent these limitations, the use of physical signals, such as thermal stimulation, to regulate stem cells has been proposed as a promising alternative. The present study aims to investigate the potential of the two-dimensional nanomaterial Ti₃C₂ MXene, which exhibits unique photothermal properties, to induce osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BMSCs) via photothermal conversion. Surface modification of Ti₃C₂ MXene nanosheets with PVP (Ti₃C₂-PVP) was employed to enhance their colloidal stability in physiological solutions. Characterization and cellular experiments showed that Ti₃C₂-PVP nanosheets have favorable photothermal properties and biocompatibility. Our study demonstrated that the induction of photothermal stimulation by co-culturing Ti₃C₂-PVP nanosheets with BMSCs and subsequent irradiation with 808 nm NIR significantly promoted cell proliferation, adhesion and osteogenic differentiation of BMSCs. In conclusion, the results of this study suggest that Ti₃C₂-PVP is a promising material for bone tissue engineering applications as it can modulate the cellular functions of BMSCs through photothermal conversion.

Nervous tract-bioinspired multi-nanoyarn model system regulating neural differentiation and its transcriptional architecture at single-cell resolution

Bioinspired by native nervous tracts, a spinal cord-mimicking model system that was composed of multiple nanofibrous yarns (NYs) ensheathed in a nanofibrous tube was constructed by an innovative electrospinning-based fabrication and integration strategy. The infilling NYs exhibited uniaxially aligned nanofibrous architecture that had a great resemblance to spatially-arranged native nervous tracts, while the outer nanofibrous tubes functioned as an artificial dura matter to provide a stable intraluminal microenvironment. The three-dimensional (3D) NYs were demonstrated to induce alignment, facilitate migration, promote neuronal differentiation, and even phenotypic maturation of seeded neural stem and progenitor cells (NSPCs), while inhibiting gliogenesis. Single-cell transcriptome analysis showed that the NSPC-loaded 3D NY model shared many similarities with native spinal cords, with a great increase in excitatory/inhibitory (EI) neuron ratio. Curcumin, as a model drug, was encapsulated into nanofibers of NYs to exert an antioxidant effect and enhanced axon regeneration. Overall, this study provides a new paradigm for the development of a next-generation in vitro neuronal model system via anatomically accurate nervous tract simulation and constructs a blueprint for the research on NSPC diversification in the biomimetic microenvironment.

Conductive fibers for biomedical applications

Bioelectricity has been stated as a key factor in regulating cell activity and tissue function in electroactive tissues. Thus, various biomedical electronic constructs have been developed to interfere with cell behaviors to promote tissue regeneration, or to interface with cells or tissue/organ surfaces to acquire physiological status via electrical signals. Benefiting from the outstanding advantages of flexibility, structural diversity, customizable mechanical properties, and tunable distribution of conductive components, conductive fibers are able to avoid the damage-inducing mechanical mismatch between the construct and the biological environment, in return to ensure stable functioning of such constructs during physiological deformation. Herein, this review starts by presenting current fabrication technologies of conductive fibers including wet spinning, microfluidic spinning, electrospinning and 3D printing as well as surface modification on fibers and fiber assemblies. To provide an update on the biomedical applications of conductive fibers and fiber assemblies, we further elaborate conductive fibrous constructs utilized in tissue engineering and regeneration, implantable healthcare bioelectronics, and wearable healthcare bioelectronics. To conclude, current challenges and future perspectives of biomedical electronic constructs built by conductive fibers are discussed.

Nanostructure Mediated Piezoelectric Effect of Tetragonal BaTiO3 Coatings on Bone Mesenchymal Stem Cell Shape and Osteogenic Differentiation

In recent years, porous titanium (Ti) scaffolds with BaTiO3 coatings have been designed to promote bone regeneration. However, the phase transitions of BaTiO3 have been understudied, and their coatings have yielded low effective piezoelectric coefficients (EPCs < 1 pm/V). In addition, piezoelectric nanomaterials bring many advantages in eliciting cell-specific responses. However, no study has attempted to design a nanostructured BaTiO3 coating with high EPCs. Herein, nanoparticulate tetragonal phase BaTiO3 coatings with cube-like nanoparticles but different effective piezoelectric coefficients were fabricated via anodization combining two hydrothermal processes. The effects of nanostructure-mediated piezoelectricity on the spreading, proliferation, and osteogenic differentiation of human jaw bone marrow mesenchymal stem cells (hJBMSCs) were explored. We found that the nanostructured tetragonal BaTiO3 coatings exhibited good biocompatibility and an EPC-dependent inhibitory effect on hJBMSC proliferation. The nanostructured tetragonal BaTiO3 coatings of relatively smaller EPCs (<10 pm/V) exhibited hJBMSC elongation and reorientation, broad lamellipodia extension, strong intercellular connection and osteogenic differentiation enhancement. Overall, the improved hJBMSC characteristics make the nanostructured tetragonal BaTiO3 coatings promising for application on implant surfaces to promote osseointegration.

Extrafibrillarly Demineralized Dentin Matrix for Bone Regeneration

Dentin is a natural extracellular matrix, but its availability in bone grafting and tissue engineering applications is underestimated due to a lack of proper treatment. In this study, the concept of extrafibrillar demineralization is introduced into the construction of dentin-derived biomaterials for bone regeneration for the first time. Calcium chelating agents with large molecular weights are used to selectively remove the extrafibrillar apatite minerals without disturbing the intrafibrillar minerals within dentin collagen, resulting in the formation of an extrafibrillarly demineralized dentin matrix (EDM). EDM with distinctive nanotopography and bone-like mechanical properties is found to significantly promote cell adhesion, migration, and osteogenic differentiation in vitro while enhancing in vivo bone healing of rat calvarial defects. The outstanding osteogenic performance of EDM is further confirmed to be related to the activation of the focal adhesion-cytoskeleton-nucleus mechanotransduction axis. Overall, this study shows that extrafibrillar demineralization of dentin has great potential to produce hierarchical collagen-based scaffolds for bone regeneration, and this facile top-down fabrication method brings about new ideas for the biomedical application of naturally derived bioactive materials.

Fiber diameters and parallel patterns: proliferation and osteogenesis of stem cells

Due to the innate extracellular matrix mimicking features, fibrous materials exhibited great application potential in biomedicine. In developing excellent fibrous biomaterial, it is essential to reveal the corresponding inherent fiber features' effects on cell behaviors. Due to the inevitable 'interference' cell adhesions to the background or between adjacent fibers, it is difficult to precisely reveal the inherent fiber diameter effect on cell behaviors by using a traditional fiber mat. A single-layer and parallel-arranged polycaprolactone fiber pattern platform with an excellent non-fouling background is designed and constructed herein. In this unique material platform, the 'interference' cell adhesions through interspace between fibers to the environment could be effectively ruled out by the non-fouling background. The 'interference' cell adhesions between adjacent fibers could also be excluded from the sparsely arranged (SA) fiber patterns. The influence of fiber diameter on stem cell behaviors is precisely and comprehensively investigated based on eliminating the undesired 'interference' cell adhesions in a controllable way. On the SA fiber patterns, small diameter fiber (SA-D1, D1 means 1 μm in diameter) may seriously restrict cell proliferation and osteogenesis when compared to the middle (SA-D8) and large (SA-D56) ones and SA-D8 shows the optimal osteogenesis enhancement effect. At the same time, the cells present similar proliferation ability and even the highest osteogenic ability on the densely arranged (DA) fiber patterns with small diameter fiber (DA-D1) when compared to the middle (DA-D8) and large (DA-D56) ones. The 'interference' cell adhesion between adjacent fibers under dense fiber arrangement may be the main reason for inducing these different cell behavior trends along with fiber diameters. Related results and comparisons have illustrated the effects of fiber diameter on stem cell behaviors more precisely and objectively, thus providing valuable reference and guidance for developing effective fibrous biomaterials.

Nanoenabled Trainable Systems: From Biointerfaces to Biomimetics

In the dynamic biological system, cells and tissues adapt to diverse environmental conditions and form memories, an essential aspect of training for survival and evolution. An understanding of the biological training principles will inform the design of biomimetic materials whose properties evolve with the environment and offer routes to programmable soft materials, neuromorphic computing, living materials, and biohybrid robotics. In this perspective, we examine the mechanisms by which cells are trained by environmental cues. We outline the artificial platforms that enable biological training and examine the relationship between biological training and biomimetic materials design. We place emphasis on nanoscale material platforms which, given their applicability to chemical, mechanical and electrical stimulation, are critical to bridging natural and synthetic systems.

Recent Advances in Electrochemical Biosensors for Monitoring Animal Cell Function and Viability

Redox reactions in live cells are generated by involving various redox biomolecules for maintaining cell viability and functions. These qualities have been exploited in the development of clinical monitoring, diagnostic approaches, and numerous types of biosensors. Particularly, electrochemical biosensor-based live-cell detection technologies, such as electric cell-substrate impedance (ECIS), field-effect transistors (FETs), and potentiometric-based biosensors, are used for the electrochemical-based sensing of extracellular changes, genetic alterations, and redox reactions. In addition to the electrochemical biosensors for live-cell detection, cancer and stem cells may be immobilized on an electrode surface and evaluated electrochemically. Various nanomaterials and cell-friendly ligands are used to enhance the sensitivity of electrochemical biosensors. Here, we discuss recent advances in the use of electrochemical sensors for determining cell viability and function, which are essential for the practical application of these sensors as tools for pharmaceutical analysis and toxicity testing. We believe that this review will motivate researchers to enhance their efforts devoted to accelerating the development of electrochemical biosensors for future applications in the pharmaceutical industry and stem cell therapeutics.

Modulating the surface potential of microspheres by phase transition in strontium doped barium titanate to restore the electric microenvironment for bone regeneration

The endogenous electrical potential generated by native bone and periosteum plays a key role in maintaining bone mass and quality. Inspired by the electrical properties of bone, different negative surface potentials are built on microspheres to restore electric microenvironment for powerful bone regeneration, which was prepared by the combination of strontium-doped barium titanate (Sr-BTO) nanoparticles and poly (lactic-co-glycolic acid) (PLGA) with high electrostatic voltage field (HEV). The surface potential was modulated through regulating the phase composition of nanoparticles in microspheres by the doping amount of strontium ion (Sr2+). As a result, the 0.1Sr-BTO/PLGA group shows the lowest surface potential and its relative permittivity is closer to natural bone. As expected, the 0.1Sr-BTO/PLGA microspheres performed cytocompatibility, osteogenic activity in vitro and enhance bone regeneration in vivo. Furthermore, the potential mechanism of Sr-BTO/PLGA microspheres to promote osteogenic differentiation was further explored. The lower surface potential generated on Sr-BTO/PLGA microspheres regulates cell membrane potential and leads to an increase in the intracellular calcium ion (Ca2+) concentration, which could activate the Calcineurin (CaN)/Nuclear factor of activated T-cells (NFAT) signaling pathway to promote osteogenic differentiation. This study established an effective method to modulate the surface potential, which provides a prospective exploration for electrical stimulation therapy. The 0.1Sr-BTO/PLGA microsphere with lower surface potential and bone-matched dielectric constant is expected to have great potential in the field of bone regeneration.

Construction of magnetic nanochains to achieve magnetic energy coupling in scaffold

Background

Fe₃O₄ nanoparticles are highly desired for constructing endogenous magnetic microenvironment in scaffold to accelerate bone regeneration due to their superior magnetism. However, their random arrangement easily leads to mutual consumption of magnetic poles, thereby weakening the magnetic stimulation effect.

Methods

In this study, magnetic nanochains are synthesized by magnetic-field-guided interface co-assembly of Fe₃O₄ nanoparticles. In detail, multiple Fe₃O₄ nanoparticles are aligned along the direction of magnetic force lines and are connected in series to form nanochain structures under an external magnetic field. Subsequently, the nanochain structures are covered and fixed by depositing a thin layer of silica (SiO₂), and consequently forming linear magnetic nanochains (Fe₃O₄@SiO₂). The Fe₃O₄@SiO₂ nanochains are then incorporated into poly l-lactic acid (PLLA) scaffold prepared by selective laser sintering technology.

Results

The results show that the Fe₃O₄@SiO₂ nanochains with unique core–shell structure are successfully constructed. Meanwhile, the orderly assembly of nanoparticles in the Fe₃O₄@SiO₂ nanochains enable to form magnetic energy coupling and obtain a highly magnetic micro-field. The in vitro tests indicate that the PLLA/Fe₃O₄@SiO₂ scaffolds exhibit superior capacity in enhancing cell activity, improving osteogenesis-related gene expressions, and inducing cell mineralization compared with PLLA and PLLA/Fe₃O₄ scaffolds.

Conclusion

In short, the Fe₃O₄@SiO₂ nanochains endow scaffolds with good magnetism and cytocompatibility, which have great potential in accelerating bone repair.

Polythiophene-mediated light modulation of membrane potential and calcium signalling in human adipose-derived stem/stromal cells

Recent progress in the fields of regenerative medicine and tissue engineering has been strongly fostered both by the investigation of crucial cues, able to trigger the regeneration of damaged tissues, and by the development of ad hoc functional materials, capable of selectively (re-)activating relevant physiological pathways. In parallel to the successful realization of biochemical cues and the optimization of delivery protocols, the use of biophysical stimuli has been emerging as an alternative, highly effective strategy. Techniques based on electrical, magnetic and mechanical stimulation have been reported to efficiently direct differentiation of stem cells and modulate cell physiology at different developmental stages. In this framework, the use of optical stimulation represents a valuable approach, possibly overcoming current limitations of chemical cues, like limited spatial and temporal resolution and poor control over the extracellular environment. Surprisingly, the effects of light on the physiological properties (light toxicity, cell membrane potential, and cell ionic trafficking) of undifferentiated cells, as well as on their differentiation pathways, were investigated to a very limited extent and rarely quantified in a systematic way. In this work, we aim at clarifying the effects of optical excitation on the physiological behaviour of undifferentiated human adipose-derived stem cells (hASC), cultured on top of a light-sensitive conjugated polymer, region-regular poly-3-hexyl-thiophene (P3HT). Interestingly, we observe statistically significant modulation of the cell membrane potential, as well as noticeable effects on intracellular calcium signalling, triggered by P3HT excitation upon green light stimuli. Possible mechanisms involved in the signal transduction pathways are considered and critically discussed. The capability to modulate the physiological response of hASC upon photoexcitation, in a highly controlled and selective manner, provides a promptly available and non invasive diagnostic tool, thus contributing to the understanding of the complex machinery behind stem cells and material interfaces. Moreover, it may open the route to novel techniques to drive the differentiation path with unprecedented versatility and operational easiness.

Bone Repairment via Mechanosensation of Piezo1 Using Wearable Pulsed Triboelectric Nanogenerator

Bone repair in real time is a challenging medical issue for elderly patients; this is mainly because aged bone marrow mesenchymal stem cells (BMSCs) possess limited osteogenesis potential and repair capacity. In this study, triboelectric stimulation technology is used to achieve bone repair via mechanosensation of Piezo1 by fabricating a wearable pulsed triboelectric nanogenerator (WP-TENG) driven by human body movement. A peak value of 30 µA has the optimal effects to rejuvenate aged BMSCs, enhance their osteogenic differentiation, and promote human umbilical vein endothelial cell tube formation. Further, previous studies demonstrate that triboelectric stimulation of a WP-TENG can reinforce osteogenesis of BMSCs and promote the angiogenesis of human umbilical vein endothelial cells (HUVECs). Mechanistically, aged BMSCs are rejuvenated by triboelectric stimulation via the mechanosensitive ion channel Piezo1. Thus, the osteogenesis potential of BMSCs is enhanced and the tube formation capacity of HUVECs is improved, which is further confirmed by augmented bone repair and regeneration in in vivo investigations. This study provides a potential signal transduction mechanism for rejuvenating aged BMSCs and a theoretical basis for bone regeneration using triboelectric stimulation generated by a WP-TENG.

Stemness Maintenance and Massproduction of Neural Stem Cells on Poly L-Lactic Acid Nanofibrous Membrane Based on Piezoelectriceffect

Neural stem cells (NSCs) therapy is promising for treating neurodegenerative disorders and neural injuries. However, the limited in vitro expansion, spontaneous differentiation, and decrease in stemness obstruct the acquisition of high quantities of NSCs, restricting the clinical application of cell-based therapies and tissue engineering. This article reports a facile method of promoting NSCs expansion and maintaining stemness using wireless electrical stimulation triggered by piezoelectric nanomaterials. A nanofibrous membrane of poly L-lactic acid (PLLA) is prepared by electrostatic spinning, and the favorable piezoelectric property of PLLA facilitates the freeing of electrons after transformation. These self-powered electric signals generated by PLLA significantly enhance NSCs proliferation. Further, an undifferentiated cellular state is maintained in the NSCs cultured on the surfaces of PLLA nanofibers exposed to ultrasonic vibration. In addition, the neural differentiation potencies and functions of NSCs expanded by piezoelectric-driven localized electricity are not attenuated. Moreover, cell stemness can be maintained by wireless electric stimulation. Taken together, the electronic signals mediated by PLLA nanofibers facilitate NSCs proliferation. This efficient and simple strategy can maintain the stemness of NSCs during proliferation, which is essential for their clinical application, and opens up opportunities for the mass production of NSCs for use in cell therapy.