Chirality Controls Mesenchymal Stem Cell Lineage Diversification through Mechanoresponses

Chirality Regulates Bone Regeneration through Mechanoresponse and Immunoregulation

As an omnipresent occurrence in the natural world, chirality plays a crucial role in numerous biological and physiological processes. Therefore, incorporation of chirality into biointerface materials has been emerging as a research hotspot in the development of regenerative biomaterials. Nevertheless, how chiral biointerface materials interact with biological organisms remains poorly understood. In the current study, a bioinspired chiral self-assembled nanohydroxyapatite material is developed for bone regeneration using a distraction osteogenesis model. We found that the left-handed chirality, rather than the right-handed chirality, possessed the greatest heightened ability for bone regeneration. Molecular mechanism research reveals that the left-handed chirality can activate mechanosensitive pathways to promote Ca2+ influx, subsequently enhancing macrophage type-2 polarization through phosphorylation of signal transducer and activator of transcription (STAT6), which eventually stimulates bone regeneration by harnessing the synergistic effects of angiogenesis and osteogenesis. These findings provide additional insights into the underlying mechanism of chiral recognition between biological systems and biointerface materials, offering alternative pathways for the development of biomaterials.

Enantiomer-Dependent Supramolecular Antibacterial Therapy for Drug-Resistant Bacterial Keratitis

Bacteria have the potential to exhibit divergent stereochemical preferences for different levels of chiral structures, including from molecule, supramolecule, to nanomicroscale helical structure. Accordingly, the structure-activity relationship between chirality and bactericidal activity remains uncertain. In this study, we seek to understand the multivalent molecular chirality effect of chiral supramolecular polymers on antibacterial activity. Two n-butylazobenzene-modified l- and d-tripeptides (abbreviated C4Azo-l-VKK-OH and C4Azo-d-VKK-OH) were synthesized and subsequently self-assembled in water into chiral supramolecular polymers (designated l-Fiber and d-Fiber, respectively). The l-Fiber and d-Fiber displayed comparable nonhelical nanofiber morphologies but exhibited opposite multivalent molecular chirality. A comparative study demonstrated that the l-Fiber exhibited a markedly higher affinity for bacteria, thereby demonstrating significantly enhanced bactericidal efficiency against methicillin-resistant Staphylococcus aureus (MRSA) in comparison to that of the d-Fiber. Following disassembly into monomers via host-guest chemistry, the bactericidal potency of both the l-Fiber and d-Fiber was found to be almost lost, suggesting the multivalent molecular chirality effect. Of note, the l-Fiber exhibited superior efficacy in curing MRSA-infected keratitis in comparison to the d-Fiber. These findings highlight the importance of multivalent molecular chirality in the design and development of chiral supramolecular polymers for antibacterial applications. This research also presents an effective chiral supramolecular antibacterial strategy for the treatment of drug-resistant bacteria-infected keratitis.

Metabolic Reprogramming of Neural Stem Cells by Chiral Nanofiber for Spinal Cord Injury

Exogenous neural stem cells (NSCs) have great potential to reconstitute damage spinal neural circuitry. However, regulating the metabolic reprogramming of NSCs for reliable nerve regeneration has been challenging. This report discusses the biomimetic dextral hydrogel (DH) with right-handed nanofibers that specifically reprograms the lipid metabolism of NSCs, promoting their neural differentiation and rapid regeneration of damaged axons. The underlying mechanism is the intrinsic stereoselectivity between DH and fatty acid-binding protein 5 (FABP5), which facilitates the transportation of fatty acids bound to FABP5 into the mitochondria and endoplasmic reticulum, subsequently augmenting fatty acid oxidation (FAO) levels and enriching sphingosine biosynthesis. In the rat SCI model, DH significantly improved the Basso-Beattie-Bresnahan (BBB) locomotor scores (over 3-fold) and the hindlimbs' compound muscle action potential (over 4-fold) compared with the untreated group, conveying a significant return of functional recovery. This finding of nanoscale chirality-dependent NSCs metabolic reprogramming provides insights into understanding stem cell physiology and presents opportunities for regenerative medicine.

Chirality-Induced Hydroxyapatite Manipulates Enantioselective Bone-Implant Interactions Toward Ameliorative Osteoporotic Osseointegration

Inspired by the fundamental attribute of chirality in nature, chiral-engineered biomaterials now represent a groundbreaking frontier in biomedical fields. However, the integration of chirality within inorganic materials remains a critical challenge and developments of chirality-induced bionic bone implants are still in infancy. In this view, novel chiral hydroxyapatite (CHA) coated Ti alloys are successfully synthesized by a sophisticated chiral molecule-induced self-assembly method for the first time. The obtained samples are characterized by stereospecific L-/D-/Rac-chiral hierarchical morphology, nanotopography rough surfaces, improved hydrophilicity, and bioactivity. Following implantation into rat femoral condyle defects, the distinct stereospecific chiral hierarchical structures exhibit highly enantioselective bone-implants interactions, wherein the left-handed chirality of L-CHA strongly promotes osteoporotic osseointegration and vice versa for right-handed chirality of D-CHA. Consistently, in vitro assays further validate the superior enantiomer-dependent osteoporotic osseointegration ability of L-CHA, mainly by manipulating desired immunomodulation coupled with enhanced neurogenesis, angiogenesis, and osteogenesis. Moreover, as analyzed by transcriptomic RNA-seq, a new discovery of down-regulated IL-17 signaling pathway is considered predominately responsible for the desired immunomodulation ability of L-CHA. These results provide new insights into biological multifunctionality and mechanism underlying L-chirality's roles for bone healing, thus may inspiring developments of new generation of chiral biomaterials.

Chiral polypeptide hydrogels regulating local immune microenvironment and anti-tumor immune response

The impact of chirality on immune response has attracted great interest in cancer vaccine research recently. However, the study of chiral synthetic polypeptide hydrogels as cancer vaccines as well as of the impact of biomaterials themselves for antitumor immunotherapy has rarely been reported. Here, we show the key role of residue chirality of polypeptide hydrogels in antitumor immunity and local immune microenvironment regulation. Compared to poly(γ-ethyl-L-glutamate)-based hydrogels (L-Gel), poly(γ-ethyl-D-glutamate)-based hydrogels (D-Gel) induces enhanced level of immune cell infiltration. However, D-Gel causes higher levels of suppressive markers on antigen-presenting cells and even induces stronger T cell exhaustion than L-Gel. Finally, D-Gel establishes a local chronic inflammatory and immunosuppressive microenvironment and shows insufficient anti-tumor effects. Conversely, the milder host immune responses induced by L-Gel leads to more effective tumor inhibition. This study provides insights on the role of residue chirality in the regulation of local immune microenvironment and affecting antitumor immune response.

Chiral Engineered Biomaterials: New Frontiers in Cellular Fate Regulation for Regenerative Medicine

Chirality, the property of objects that are nonsuperimposable on their mirror images, plays a crucial role in biological processes and cellular behaviors. Chiral engineered biomaterials have emerged as a promising approach to regulating cellular fate in regenerative medicine. However, few reviews provide a comprehensive examination of recent advancements in chiral biomaterials and their applications in cellular fate regulation. Herein, various fabrication techniques available for chiral biomaterials, including the use of chiral molecules, surface patterning, and self‐assembly are discussed. The mechanisms through which chiral biomaterials influence cellular responses, such as modulation of adhesion receptors, intracellular signaling, and gene expression, are explored. Notably, chiral biomaterials have demonstrated their ability to guide stem cell differentiation and augment tissue‐specific functions. The potential applications of chiral biomaterials in musculoskeletal disorders, neurodegenerative diseases, cardiovascular diseases, and wound healing are highlighted. Challenges and future perspectives, including standardization of fabrication methods and translation to clinical settings, are addressed. In conclusion, chiral engineered biomaterials offer exciting prospects for precisely controlling cellular fate, advancing regenerative medicine, and enabling personalized therapeutic strategies.

Effect of supramolecular chirality on nano-protein/cell interaction: An experimental and computational investigation

Understanding the unique role of supramolecular chirality in nano-protein/cell interactions, as opposed to molecular chirality, is crucial for elucidating the origin of life. However, this aspect has received inadequate attention. In this study, L/D-glutamic acid-based amphiphiles (L/D-GluC16), which possess molecular chirality, were synthesized. Additionally, through the manipulation of solvent effects, left/right-handed helical nanofibers (M/P-GluC16), endowed with supramolecular chirality, were assembled from L/D-GluC16. With the aid of molecular dynamics (MD) simulations, the interaction between M/P-GluC16, L/D-GluC16, and a model protein (bovine serum albumin, BSA) was investigated at the thermodynamic and spatial orientational levels. Combined with the experimental result of protein adsorption efficiency, a more favorable chirality-dependent binding of M/P-GluC16 to protein compared to L/D-GluC16 was confirmed. Furthermore, driven by the binding-induced conformational changes and subsequent functional disruptions of proteins, M/P-GluC16 exhibited a greater chirality-specific cancer cell inhibitory efficacy compared to L/D-GluC16, highlighting the more significant impact of supramolecular chirality on nano-protein/cell interactions than molecular chirality.

Chiral Hydrogel Nerve Conduit Boosts Peripheral Nerve Regeneration via Regulation of Schwann Cell Reprogramming

The Schwann cell (SC) is essential in peripheral nerve regeneration by reprogramming into a stem-like "repair Schwann cell" (rSC) phenotype; however, maintaining the rSC stemness remains an unmet challenge. Chirality is a fundamental factor controlling cell fate, and its potential role in regulation of SC reprogramming has long been ignored and remains poorly understood. Herein, inspired by natural chiral components in the SC microenvironment, chiral hydrogel nerve conduits are prepared by supramolecular assembly of l/d-phenylalanine derivatives (l/d-Phe) in polymeric chitosan-gelatin conduits. Right-handed l-Phe fibers within hydrogel conduits maintain the stemness of rSC through enhanced stereoselective interaction between collagen IV and l-Phe fibers triggered by collagen IV-Integrin α1β1, MAPK, and YAP/TAZ signaling pathways and finally activate the key regulator of SC reprogramming, the c-Jun pathway. In the rat model of a sciatic nerve defect, the l-Phe hydrogel nerve conduit significantly enhances nerve regeneration, exhibiting markedly improved histological, electrophysiological, and functional outcomes. The findings reveal the chirality-dependent regulation of SC reprogramming in a pioneering way, offering potential strategies for nerve regeneration therapies.

Hierarchical Chiral Calcium Silicate Hydrate Films Promote Vascularization for Tendon-to-Bone Healing

Revascularization after rotator cuff repair is crucial for tendon-to-bone healing. The chirality of materials has been reported to influence their performance in tissue repair. However, data on the use of chiral structures to optimize biomaterials as a revascularization strategy remain scarce. Here, calcium silicate hydrate (CSO) films with hierarchical chirality on the atomic to micrometer scale are developed. Interestingly, levorotatory CSO (L-CSO) films promote the migration and angiogenesis of endothelial cells, whereas dextral and racemic CSO films do not induce the same effects. Molecular analysis demonstrates that L-chirality can be recognized by integrin receptors and leads to the formation of focal adhesion, which activates mechanosensitive ion channel transient receptor potential vanilloid 4 to conduct Ca2+ influx. Consequently, the phosphorylation of serum response factor is biased by Ca2+ influx to promote the vascular endothelial growth factor receptor 2 signaling pathway, resulting in enhanced angiogenesis. After implanted in a rat rotator cuff tear model, L-CSO films strongly enhance vascularization at the enthesis, promoting collagen maturation, increasing bone and fibrocartilage formation, and eventually improving the biomechanical strength. This study reveals the mechanism through which chirality influences angiogenesis in endothelial cells and provides a critical theoretical foundation for the clinical application of chiral biomaterials.

Amino acid-based supramolecular chiral hydrogels promote osteogenesis of human dental pulp stem cells via the MAPK pathway

Critical-size defects (CSDs) of the craniofacial bones cause aesthetic and functional complications that seriously impact the quality of life. The transplantation of human dental pulp stem cells (hDPSCs) is a promising strategy for bone tissue engineering. Chirality is commonly observed in natural biomolecules, yet its effect on stem cell differentiation is seldom studied, and little is known about the underlying mechanism. In this study, supramolecular chiral hydrogels were constructed using L/d-phenylalanine (L/D-Phe) derivatives. The results of alkaline phosphatase expression analysis, alizarin red S assay, as well as quantitative real-time polymerase chain reaction and western blot analyses suggest that right-handed D-Phe hydrogel fibers significantly promoted osteogenic differentiation of hDPSCs. A rat model of calvarial defects was created to investigate the regulation of chiral nanofibers on the osteogenic differentiation of hDPSCs in vivo. The results of the animal experiment demonstrated that the D-Phe group exhibited greater and faster bone formation on hDPSCs. The results of RNA sequencing, vinculin immunofluorescence staining, a calcium fluorescence probe assay, and western blot analysis indicated that L-Phe significantly promoted adhesion of hDPSCs, while D-Phe nanofibers enhanced osteogenic differentiation of hDPSCs by facilitating calcium entry into cells and activate the MAPK pathway. These results of chirality-dependent osteogenic differentiation offer a novel therapeutic strategy for the treatment of CSDs by optimising the differentiation of hDPSCs into chiral nanofibers.

Chiral nanomaterials in tissue engineering

Addressing significant medical challenges arising from tissue damage and organ failure, the field of tissue engineering has evolved to provide revolutionary approaches for regenerating functional tissues and organs. This involves employing various techniques, including the development and application of novel nanomaterials. Among them, chiral nanomaterials comprising non-superimposable nanostructures with their mirror images have recently emerged as innovative biomaterial candidates to guide tissue regeneration due to their unique characteristics. Chiral nanomaterials including chiral fibre supramolecular hydrogels, polymer-based chiral materials, self-assembling peptides, chiral-patterned surfaces, and the recently developed intrinsically chiroptical nanoparticles have demonstrated remarkable ability to regulate biological processes through routes such as enantioselective catalysis and enhanced antibacterial activity. Despite several recent reviews on chiral nanomaterials, limited attention has been given to the specific potential of these materials in facilitating tissue regeneration processes. Thus, this timely review aims to fill this gap by exploring the fundamental characteristics of chiral nanomaterials, including their chiroptical activities and analytical techniques. Also, the recent advancements in incorporating these materials in tissue engineering applications are highlighted. The review concludes by critically discussing the outlook of utilizing chiral nanomaterials in guiding future strategies for tissue engineering design.

Multi-Omics Reveals the Genetic and Metabolomic Architecture of Chirality Directed Stem Cell Lineage Diversification

Chirality-directed stem-cell-fate determination involves coordinated transcriptional and metabolomics programming that is only partially understood. Here, using high-throughput transcriptional-metabolic profiling and pipeline network analysis, the molecular architecture of chirality-guided mesenchymal stem cell lineage diversification is revealed. A total of 4769 genes and 250 metabolites are identified that are significantly biased by the biomimetic chiral extracellular microenvironment (ECM). Chirality-dependent energetic metabolism analysis has revealed that glycolysis is preferred during left-handed ECM-facilitated osteogenic differentiation, whereas oxidative phosphorylation is favored during right-handed ECM-promoted adipogenic differentiation. Stereo-specificity in the global metabolite landscape is also demonstrated, in which amino acids are enriched in left-handed ECM, while ether lipids and nucleotides are enriched in right-handed ECM. Furthermore, chirality-ordered transcriptomic-metabolic regulatory networks are established, which address the role of positive feedback loops between key genes and central metabolites in driving lineage diversification. The highly integrated genotype-phenotype picture of stereochemical selectivity would provide the fundamental principle of regenerative material design.

Low temperature synthesis of chiral carbon dots for reducing H2O2 damage

Recently, researches focused towards the chiral nanostructures have attracted vast attention. However, the synthesis of chiral carbon dots (CDs) through one-step method is still rather scarce. Herein, a universal approach to green synthesis of chiral CDs at low temperature was proposed. In brief, L-FruCDs and D-FruCDs were obtained by only heating the fructose and chiral cysteine molecules in the sodium hydroxide aqueous solution under atmospheric pressure. Circular dichroism spectra show that these prepared CDs exhibit opposite chirality ranging from 210 to 260 nm. Specially, the prepared L-FruCDs could reduce the intracellular oxidative damage induced by hydrogen peroxide and display a superior performance than that of D-FruCDs. Mechanism studies indicate that the probably protect mechanism is ascribed to the directly consumption the intracellular ROS. And the clearance efficiency of intracellular reactive oxygen species of L-FruCDs is 3-times than that of D-FruCDs. Furthermore, this newly synthesized method is scalable by replacing fructose precursor with ascorbic acid, sucrose or lactose. In sum, our work provides a new method for the preparation of chiral CDs and achieve a great success in exploring the chiral biological effects at nanoscale.

Enantiomer-Dependent Supramolecular Immunosuppressive Modulation for Tissue Reconstruction

Modulating the properties of biomaterials in terms of the host immune response is critical for tissue repair and regeneration. However, it is unclear how the preference for the cellular microenvironment manipulates the chiral immune responses under physiological or pathological conditions. Here, we reported that in vivo and in vitro oligopeptide immunosuppressive modulation was achieved by manipulation of macrophage polarization using chiral tetrapeptide (Ac-FFFK-OH, marked as FFFK) supramolecular polymers. The results suggested that chiral FFFK nanofibers can serve as a defense mechanism in the restoration of tissue homeostasis by upregulating macrophage M2 polarization via the Src-STAT6 axis. More importantly, transiently acting STAT6, insufficient to induce a sustained polarization program, then passes the baton to EGR2, thereby continuously maintaining the M2 polarization program. It is worth noting that the L-chirality exhibits a more potent effect in inducing macrophage M2 polarization than does the D-chirality, leading to enhanced tissue reconstruction. These findings elucidate the crucial molecular signals that mediate chirality-dependent supramolecular immunosuppression in damaged tissues while also providing an effective chiral supramolecular strategy for regulating macrophage M2 polarization and promoting tissue injury repair based on the self-assembling chiral peptide design.

Graphene oxide-doped chiral dextro-hydrogel promotes peripheral nerve repair through M2 polarization of macrophages

Dextro-chirality is reported to specifically promote the proliferation and survival of neural cells. However, applying this unique performance to nerve repair remains a great challenge. Graphite oxide (GO)-phenylalanine derivative hydrogel system was constructed through doping 5% GO into self-assembly dextro- or levo-hydrogels (named as dextro and levo group, respectively), which exhibited identical physical and chemical properties, cyto-compatibility, and mirror-symmetrical chirality. In vivo experiments using rat sciatic nerve repair models showed that the functional recovery and histological restoration of regenerating nerves in the dextro group were significantly improved, approaching that of autograft implantation. The doped GO promoted M2 polarization of macrophages, increasing the expression of platelet-derived growth factor BB chain and vascular endothelial growth factor, thereby improving angiogenesis in regenerating nerves. A mechanism is proposed for the facilitated nerve repair through the synergistic effect of GO and dextro-hydrogel, involving dextro-chirality selection of neural cells and GO-induced M2 polarization, which promotes microvascular regeneration and myelination. This study showcases the immense potential of chirality in addressing neurological issues by providing a compelling demonstration of the development of effective therapies that leverage the unique matrix chirality selection of nerve cells to promote peripheral nerve regeneration.

3D Chiral Self-Assembling Matrixes for Regulating Polarization of Macrophages and Enhance Repair of Myocardial Infarction

The regulation of inflammatory response at the site of injury and macrophage immunotherapy is critical for tissue repair. Chiral self-assemblies are one of the most ubiquitous life cues, which is closely related to biological functions, life processes, and even the pathogenesis of diseases. However, the role of supramolecular chiral self-assemblies in the regulation of immune functions in the internal environment of tissues has not been fully explored yet. Herein, 3D supramolecular chiral self-assembling matrixes are prepared to regulate the polarization of macrophages and further enhance the repair of myocardial infarction (MI). Experiments studies show that M-type (left-handed) self-assembling matrixes significantly inhibit inflammation and promote damaged myocardium repair by upregulating M2 macrophage polarization and downstream immune signaling compared with P-type (right-handed), and R-type (non-chirality) self-assembling matrixes. Classical molecular dynamics (MD) simulation demonstrates that M-type self-assembling matrixes display higher stereo-affinity to cellular binding, which enhances the clustering of mechanosensitive integrin β1 (Itgβ1) and activates focal adhesion kinase (FAK) and Rho-associated protein kinase (ROCK), as well as downstream PI3K/Akt1/mTOR signaling axes to promote M2 polarization. This study of designing a 3D chiral self-assembling matrixes microenvironment suitable for regulating the polarization of macrophages will provide devise basis for immunotherapy with biomimetic materials.

Chiral Cell Nanomechanics Originated in Clockwise/Counterclockwise Biofunctional Microarrays to Govern the Nuclear Mechanotransduction of Mesenchymal Stem Cells

Cell chirality is extremely important for the evolution of cell morphogenesis to manipulate cell performance due to left-right asymmetry. Although chiral micro- and nanoscale biomaterials have been developed to regulate cell functions, how cell chirality affects cell nanomechanics to command nuclear mechanotransduction was ambiguous. In this study, chiral engineered microcircle arrays were prepared by photosensitive cross-linking synthesis on cell culture plates to control the clockwise/counterclockwise geometric topology of stem cells. Asymmetric focal adhesion and cytoskeleton structures could induce chiral cell nanomechanics measured by atomic force microscopy (AFM) nanoindentation in left-/right-handed stem cells. Cell nanomechanics could be enhanced when the construction of mature focal adhesion and the assembly of actin and myosin cytoskeletons were well organized in chiral engineered stem cells. Curvature angles had a negative effect on cell nanomechanics, while cell chirality did not change cytoskeletal mechanics. The biased cytoskeleton tension would engender different nuclear mechanotransductions by yes-associated protein (YAP) evaluation. The chiral stimuli were delivered into the nuclei to oversee nuclear behaviors. A strong cell modulus could activate high nuclear DNA synthesis activity by mechanotransduction. The results will bring the possibility of understanding the interplay of chiral cell nanomechanics and mechanotransduction in nanomedicines and biomaterials.

Unique Chirality Selection in Neural Cells for D-Matrix Enabling Specific Manipulation of Cell Behaviors

Manipulating neural cell behaviors is a critical issue to various therapies for neurological diseases and damages, where matrix chirality has long been overlooked despite the proven adhesion and proliferation improvement of multiple non-neural cells by L-matrixes. Here, it is reported that the D-matrix chirality specifically enhances cell density, viability, proliferation, and survival in four different types of neural cells, contrasting its inhibition in non-neural cells. This universal impact on neural cells is defined as "chirality selection for D-matrix" and is achieved through the activation of JNK and p38/MAPK signaling pathways by the cellular tension relaxation resulting from the weak interaction between D-matrix and cytoskeleton proteins, particularly actin. Also, D-matrix promotes sciatic nerve repair effectively, both with or without non-neural stem cell implantation, by improving the population, function, and myelination of autologous Schwann cells. D-matrix chirality, as a simple, safe, and effective microenvironment cue to specifically and universally manipulate neural cell behaviors, holds extensive application potential in addressing neurological issues such as nerve regeneration, neurodegenerative disease treatment, neural tumor targeting, and neurodevelopment.

3D micropattern force triggers YAP nuclear entry by transport across nuclear pores and modulates stem cells paracrine

Biophysical cues of the cellular microenvironment tremendously influence cell behavior by mechanotransduction. However, it is still unclear how cells sense and transduce the mechanical signals from 3D geometry to regulate cell function. Here, the mechanotransduction of human mesenchymal stem cells (MSCs) triggered by 3D micropatterns and its effect on the paracrine of MSCs are systematically investigated. Our findings show that 3D micropattern force could influence the spatial reorganization of the cytoskeleton, leading to different local forces which mediate nucleus alteration such as orientation, morphology, expression of Lamin A/C and chromatin condensation. Specifically, in the triangular prism and cuboid micropatterns, the ordered F-actin fibers are distributed over and fully transmit compressive forces to the nucleus, which results in nuclear flattening and stretching of nuclear pores, thus enhancing the nuclear import of YES-associated protein (YAP). Furthermore, the activation of YAP significantly enhances the paracrine of MSCs and upregulates the secretion of angiogenic growth factors. In contrast, the fewer compressive forces on the nucleus in cylinder and cube micropatterns cause less YAP entering the nucleus. The skin repair experiment provides the first in vivo evidence that enhanced MSCs paracrine by 3D geometry significantly promotes tissue regeneration. The current study contributes to understanding the in-depth mechanisms of mechanical signals affecting cell function and provides inspiration for innovative design of biomaterials.

Chirality-biased protein expression profile during early stages of bone regeneration

Introduction: Chirality is a crucial mechanical cue within the extracellular matrix during tissue repair and regeneration. Despite its key roles in cell behavior and regeneration efficacy, our understanding of chirality-biased protein profile in vivo remains unclear. Methods: In this study, we characterized the proteomic profile of proteins extracted from bone defect areas implanted with left-handed and right-handed scaffold matrices during the early healing stage. We identified differentially-expressed proteins between the two groups and detected heterogenic characteristic signatures on day 3 and day 7 time points. Results: Proteomic analysis showed that left-handed chirality could upregulate cell adhesion-related and GTPase-related proteins on day 3 and day 7. Besides, interaction analysis and in vitro verification results indicated that the left-handed chiral scaffold material activated Rho GTPase and Akt1, ultimately leading to M2 polarization of macrophages. Discussion: In summary, our study thus improved understanding of the regenerative processes facilitated by chiral materials by characterizing the protein atlas in the context of bone defect repair and exploring the underlying molecular mechanisms of chirality-mediated polarization differences in macrophages.

Chiral Supramolecular Assemblies: Controllable Construction and Biological Activity

Chiral supramolecular assemblies with helical structures (e. g., proteins with α-helix, DNA with double helix, collagen with triple-helix) as the central structure motifs in biological systems play a crucial role in various physiological activities of living organisms. Variations in chiral structure can cause many abnormal physiological activities. To gain insight into the construction, structural transition, and related physiological functions of these complex helix in natural systems, it is necessary to fabricate artificial supramolecular assemblies with controllable helix orientation as research platform. This review discusses recent advances in chiral supramolecular assembly, including the precise construction and regulation of assembled chiral nanostructures with tunable chirality. Chiral structure-dependent biological activities, including cell proliferation, cell differentiation, antibacterial activity and tissue regeneration, are also discussed. This review not only contributes to further understanding of the importance of chirality in the physiological environment, but also plays an important role in the development of chiral biomedical materials for the treatment of diseases (e. g., tissue engineering regeneration, stem cell transplantation therapy).

Manipulation of Heterogeneous Surface Electric Potential Promotes Osteogenesis by Strengthening RGD Peptide Binding and Cellular Mechanosensing

The heterogeneity of extracellular matrix (ECM) topology, stiffness, and architecture is a key factor modulating cellular behavior and osteogenesis. However, the effects of heterogeneous ECM electric potential at the micro- and nanoscale on osteogenesis remain to be elucidated. Here, the heterogeneous distribution of surface potential is established by incorporating ferroelectric BaTiO₃ nanofibers (BTNF) into poly(vinylidene fluoridetrifluoroethylene) (P(VDF-TrFE)) matrix based on phase-field and first-principles simulation. By optimizing the aspect ratios of BTNF fillers, the anisotropic distribution of surface potential on BTNF/P(VDF-TrFE) nanocomposite membranes can be achieved by strong spontaneous electric polarization of BTNF fillers. These results indicate that heterogeneous surface potential distribution leads to a meshwork pattern of fibronectin (FN) aggregation, which increased FN-III7-10 (FN fragment) focal flexibility and anchor points as predicted by molecular dynamics simulation. Furthermore, integrin clustering, focal adhesion formation, cell spreading, and adhesion are enhanced sequentially. Increased traction of actin fibers amplifies mechanotransduction by promoting nuclear translocation of YAP/Runx2, which enhances osteogenesis in vitro and bone regeneration in vivo. The work thus provides fundamental insights into the biological effects of surface potential heterogeneity at the micro- and nanoscale on osteogenesis, and also develops a new strategy to optimize the performance of electroactive biomaterials for tissue regenerative therapies.

Assessing Biomaterial-Induced Stem Cell Lineage Fate by Machine Learning-Based Artificial Intelligence

Current functional assessment of biomaterial-induced stem cell lineage fate in vitro mainly relies on biomarker-dependent methods with limited accuracy and efficiency. Here a "Mesenchymal stem cell Differentiation Prediction (MeD-P)" framework for biomaterial-induced cell lineage fate prediction is reported. MeD-P contains a cell-type-specific gene expression profile as a reference by integrating public RNA-seq data related to tri-lineage differentiation (osteogenesis, chondrogenesis, and adipogenesis) of human mesenchymal stem cells (hMSCs) and a predictive model for classifying hMSCs differentiation lineages using the k-nearest neighbors (kNN) strategy. It is shown that MeD-P exhibits an overall accuracy of 90.63% on testing datasets, which is significantly higher than the model constructed based on canonical marker genes (80.21%). Moreover, evaluations of multiple biomaterials show that MeD-P provides accurate prediction of lineage fate on different types of biomaterials as early as the first week of hMSCs culture. In summary, it is demonstrated that MeD-P is an efficient and accurate strategy for stem cell lineage fate prediction and preliminary biomaterial functional evaluation.

Regulation of Macrophage Polarization on Chiral Potential Distribution of CFO/P(VDF-TrFE) Films

Surface potentials of biomaterials have been shown to regulate cell fate commitment. However, the effects of chirality-patterned potential distribution on macrophage polarization are still only beginning to be explored. In this work, we demonstrated that the chirality-patterned potential distribution of CoFe₂O₄/poly(vinylidene fluoride-trifluoroethylene) (CFO/P(VDF-TrFE)) films could significantly down-regulate the M1 polarization of bone marrow-derived macrophages (BMDMs). Specifically, the dextral-patterned surface potential distribution simultaneously up-regulated the expression of M2-related markers of BMDMs. The results were attributed to the sensitive difference of integrin subunits (α₅β₁ and α_vβ₃) to the dextral- and sinistral-patterned surface potential distribution, respectively. The interaction difference between the integrin subunits and surface potential distribution altered the cell adhesion and cytoskeletal structure and thereby the polarization behavior of BMDMs. This work, therefore, emphasizes the importance of chirality of potential distribution on cell behavior and provides a new strategy to regulate the immune response of biomaterials.

Chiral fiber supramolecular hydrogels for tissue engineering

Tissue engineering (TE), as a new interdisciplinary discipline, aims to develop biological substitutes for repairing damaged tissues and organs. For the success of tissue regeneration, such biomaterials need to support the physiological activities of cells and allow the growth and maturation of tissues. Naturally, this regulation is achieved through the dynamic remodeling of the extracellular matrix (ECM) of cells. In recent years, chiral supramolecular hydrogels have shown higher application potential in the TE field than traditional polymer hydrogels due to their dynamic noncovalent interactions, adjustable self-assembly structure, and good biocompatibility. These advantages make it possible to construct hydrogels under physiological conditions with structure and function similar to those of the natural ECM. Meanwhile, the chiral characteristics of hydrogels play an important role in regulating cellular activities such as differentiation, adhesion, and proliferation, which is beneficial for tissue formation. In this review, a brief introduction is presented to highlight the importance of chiral fiber supramolecular hydrogels for TE at first. Afterward, the considerations for chiral supramolecular hydrogel design, as well as the influence of external stimuli on chiral hydrogel construction, are discussed. Finally, the potential application prospects of these materials in TE and the significant contribution made by our group in this field are summarized. This review not only helps to reveal the importance of chiral properties in TE but also provides new strategies for TE research based on chiral bionic microenvironments. This article is categorized under: Implantable Materials and Surgical Technologies > Nanotechnology in Tissue Repair and Replacement Biology-Inspired Nanomaterials > Peptide-Based Structures Nanotechnology Approaches to Biology > Cells at the Nanoscale Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Chiral-Selective Antigen-Presentation by Supramolecular Chiral Polymer Micelles

Chirality is ubiquitous in biological systems, which is closely related to biological functions, life processes, and even the pathogenesis of diseases. However, the interface between the chirality of synthetic materials and organisms, particularly the immune system, remains poorly understood. Here, supramolecular chiral polymer micelles (SCPMs) are prepared by complexing antigenic proteins with chiral amino acid-modified polyethyleneimine. The introduction of chirality not only reduces the toxicity of cationic polymer, but also benefits cell uptake and antigen presentation. Especially, D-chirality presents the lowest cytotoxicity, while promoting the highest expression level of costimulatory molecules on dendritic cells compared to L-chirality and achirality. The superiority of D-chirality to stimulate dendritic cell maturation is supported by immunization with D-SCPMs, which achieves significant antigen-specific proliferation of T cells in the spleen, lymph nodes, and tumor of mice. Chirality-mediated antigen processing and presentation are demonstrated by D-SCPMs self-assembled from chiral alkaline histidine or neutral phenylalanine modified polyethyleneimine and tumor associated ovalbumin or severe acute respiratory syndrome coronavirus 2 spike 1 antigenic protein. Immunoactivation enabled by D-chirality opens a window to prepare potent nanotherapeutics for disease prevention and treatment.

The PCK2-glycolysis axis assists three-dimensional-stiffness maintaining stem cell osteogenesis

Understanding mechanisms underlying the heterogeneity of multipotent stem cells offers invaluable insights into biogenesis and tissue development. Extracellular matrix (ECM) stiffness has been acknowledged as a crucial factor regulating stem cell fate. However, how cells sense stiffness cues and adapt their metabolism activity is still unknown. Here we report the novel role of mitochondrial phosphoenolpyruvate carboxykinase (PCK2) in enhancing osteogenesis in 3D ECM via glycolysis. We experimentally mimicked the physical characteristics of 3D trabeculae network of normal and osteoporotic bone with different microstructure and stiffness, observing that PCK2 promotes osteogenesis in 3D ECM with tunable stiffness in vitro and in vivo. Mechanistically, PCK2 enhances the rate-limiting metabolic enzyme pallet isoform phosphofructokinase (PFKP) in 3D ECM, and further activates AKT/extracellular signal-regulated kinase 1/2 (ERK1/2) cascades, which directly regulates osteogenic differentiation of MSCs. Collectively, our findings implicate an intricate crosstalk between cell mechanics and metabolism, and provide new perspectives for strategies of osteoporosis.

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As the key rate-limiting enzyme of gluconeogenesis, PCK2 manipulates osteogenesis in stiff and soft ECM in vitro and in vivo.

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PCK2 regulates osteogenic capacity of BMMSCs in 3D ECM with different stiffness, via modulating glycolysis and regulating PFKP-AKT/ERK signaling pathways.

Chiral Hydrogel Accelerates Re-Epithelization in Chronic Wounds via Mechanoregulation

Chronic wounds, such as diabetic foot ulcers (DFU), are a serious clinical problem. It is a challenge for the conventional wound dressings to achieve the desirable therapeutic efficacy due to the lack of biomimetic structural environment for rapid re-epithelization. Inspired by the naturally existing chiral structures in skin, a novel amino acid-based chiral hydrogel dressing is developed, consisting of left-handed or right-handed helical fibers self-assembled by l/d-phenylalanine derivatives. Compared to the levorotatory chiral hydrogel (LH), the dextral chiral hydrogel (DH) shows the ability to enhance cell adhesion, proliferation, and migration, and strongly promotes diabetic wound healing and re-epithelialization with a drug-free mode. Interestingly, the dextral chiral hydrogel is able to actively increase adsorption of type I collagen and promote proliferation and migration of keratinocyte in an integrin and YAP-mediated manner. This study not only provides a novel strategy for treatment of chronic wounds by utilizing dextral chiral hydrogel dressings, but also unveils the molecular mechanism for effect of dextral chiral structures on the promoted proliferation of keratinocyte.

Recognition of 3D Chiral Microenvironments for Myoblast Differentiation

Cell chirality plays a critical role in the linkage between molecular chirality and the asymmetrical biological functions of body organs. However, enantioselective interactions between cell chirality and the extracellular environment are not yet fully understood. In this study, we investigated the effects of structurally chiral extracellular microenvironments on cellular alignments and differentiations. Twisted wrinkle-shaped chiral micropatterns were prepared using biaxial and asymmetric buckling methods, wherein structural handedness was determined from the orientation of the tilt angle between the first and second microwrinkles. Myoblasts were separately cultured on two enantiomeric chiral micropatterns in a mirror-reflected shape. Cells cultured on the left-handed chiral micropatterns preferred alignments along the direction of the second microwrinkle, with a relatively deeper valley than that of the first microwrinkle. The aligned cells on the left-handed pattern showed higher differentiation rates, as assessed by fusion indices and marker protein expression levels, than those cultured on right-handed chiral micropatterns. These results suggest that myoblasts exhibit enantioselective recognition of structurally chiral microenvironments, which can promote cellular alignments and differentiation.

Chiral Biomaterials for Nanomedicines: From Molecules to Supraparticles

Chirality, the property whereby an object or a system cannot be superimposed on its mirror image, prevails amongst nature over various scales. Especially in biology, numerous chiral building blocks and chiral-specific interactions are involved in many essential biological activities. Despite the prevalence of chirality in nature, it has been no longer than 70 years since the mechanisms of chiral-specific interactions drew scientific attention and began to be studied. Owing to the advent of chiral-sensitive equipment such as circular dichroism spectrometers or chiral liquid columns for chromatography, it has recently been possible to achieve a deeper understanding of the chiral-specific interactions and consequential impacts on the functionality and efficiency of nanomedicine. From this point of view, it is worthwhile to examine previously reported chiral biomaterials with their compositions and possible applications to achieve new paradigms of biomaterials. This review discusses chiral materials on various scales and their biological applications.

A chiral microenvironment promotes retinal progenitor cell proliferation by activating the Akt and ERK pathways

Retinal progenitor cell (RPC) transplantation has been proposed as a potential strategy for the treatment of retinal degeneration, which is a leading cause of vision loss. However, a major obstacle is the poor proliferation of RPCs. Accumulating evidence suggests that the chiral features of the extracellular microenvironment are closely related to cell proliferation. Inspired by this, L/D-phenylalanine-derived molecules (LP and DP) are employed to construct a biomimetic chiral microenvironment for enhancing RPC proliferation. LP and DP self-assemble into left-handed and right-handed helical fibrous networks, respectively. It is found that DP nanofibrous films show an excellent ability in promoting RPC proliferation via the activation of the Akt and extracellular signal-regulated kinase (ERK) pathways. In addition, both LP and DP nanofibrous films have the advantage of attenuating inflammation, and LP films can maintain the stem potential of RPCs. Thus, the promotion of RPC proliferation using a bioinspired chiral fibrous microenvironment is a promising strategy for RPC-based therapies for retinal degeneration.

Chiral Supramolecular Hydrogel Loaded with Dimethyloxalyglycine to Accelerate Chronic Diabetic Wound Healing by Promoting Cell Proliferation and Angiogenesis

Chronic refractory wounds are one of the most serious complications of diabetes, and the effects of common treatments are limited. Chiral hydrogel combined with dimethyloxalyglycine (DMOG) as a dressing is a promising strategy for the treatment of chronic wounds. In this research, we have developed a DMOG-loaded supramolecular chiral amino-acid-derivative hydrogel for wound dressings for full-thickness skin regeneration of chronic wounds. The properties of the materials, the ability of sustained release drugs, and the ability to promote angiogenesis were tested in vitro, and the regeneration rate and repair ability of full-thickness skin were tested in vivo. The chiral hydrogel had the ability to release drugs slowly. It can effectively promote cell migration and angiogenesis in vitro, and promote full-thickness skin regeneration and angiogenesis in vivo. This work offers a new approach for repairing chronic wounds completely through a supramolecular chiral hydrogel loaded with DMOG.

Chirality-induced bionic scaffolds in bone defects repair-a review

Due to lack of amino sugar with aging, people will suffer from various epidemic bone diseases called "undead cancer" by the World Health Organization. The key problem in bone tissue engineering that has not been completely resolved is the repair of critical large-scale bone and cartilage defects. The chirality of the extracellular matrix plays a decisive role in the physiological activity of bone cells and the occurrence of bone tissue, but the mechanism of chirality in regulating cell adhesion and growth is still in the early stage of exploration. This paper reviews the application progress of chirality-induced bionic scaffolds in bone defects repair based on "soft" and "hard" scaffolds. The aim is to summarize the effects of different chiral structures (L-shaped and D-shaped) in the process of inducing bionic scaffolds in bone defects repair. In addition, many technologies and methods as well as issues worthy of special consideration for preparing chirality-induced bionic scaffolds are also introduced. We expect that this work can provide inspiring ideas for designing new chirality-induced bionic scaffolds and promote the development of chirality in bone tissue engineering. This article is protected by copyright. All rights reserved.

Reconstructable Uterus-Derived Materials for Uterus Recovery toward Efficient Live Births

Uterine factor infertility is increasingly common in modern society and has severely affected human life and health. However, the existing biomaterial scaffold-mediated systems remain limited in efficient uterus recovery, leading to low pregnancy rate and live births. Here, reconstructable uterus-derived materials (RUMs) are demonstrated by combining uterus-derived extracellular matrix and seeded chorionic villi mesenchymal stem cells for uterus recovery, achieving highly efficient live births in rats with severe uterine injury. The RUMs can be designed into different states (such as, liquid RUMs and solid RUMs) and shapes (such as, cuboid, triangular-prism, and cube) in terms of requirements. The RUMs can effectively prevent intrauterine adhesion, and promote endometrial regeneration and muscle collagen reconstruction, as well as, accelerate wound healing by constructing a physical barrier and secreting cytokines, allowing efficient uterus recovery. The injured uterus nearly achieves complete recovery after treating with the RUMs and has normal pregnancies for supporting fetal development and live births, similar to the normal rats. The study provides a regenerative medicine therapeutics for uterine factor infertility.

Effect of Polymer Topology and Residue Chirality on Biodegradability of Polypeptide Hydrogels

Polypeptide-based injectable hydrogels have attracted the attention of biomedical researchers due to their unique biocompatibility and biodegradability, tunable residue chirality, and secondary conformation of polypeptide chains. In the present study, four types of poly(ethylene glycol)-block-poly(glutamic acid)s with different topological structures and residue chirality of polypeptide segments were developed, which were grafted with tyramine side groups for further cross-linking. The results demonstrated that the covalent conjugation between the tyramine groups in the presence of horseradish peroxidase and hydrogen peroxide could form porous hydrogels rapidly. Additionally, the gelation time and mechanical strength of the hydrogels were measured. All the polymer precursors and hydrogels exhibited good cytocompatibility in vitro. Further assessment of the enzymatic degradability of the hydrogels and copolymers in vitro revealed that the degradation rate was influenced by the adjustment of polymer topology or residue chirality of polypeptide copolymers. Subsequently, the effect of copolymer topology and polypeptide chirality on in vivo biodegradability and biocompatibility was assessed. This study will provide insights into the relationship between copolymer structures and hydrogel properties and benefit future polypeptide-based hydrogel studies in biomedical applications.

Scaffold geometry modulation of mechanotransduction and its influence on epigenetics

The dynamics of cell mechanics and epigenetic signatures direct cell behaviour and fate, thus influencing regenerative outcomes. In recent years, the utilisation of 2D geometric (i.e. square, circle, hexagon, triangle or round-shaped) substrates for investigating cell mechanics in response to the extracellular microenvironment have gained increasing interest in regenerative medicine due to their tunable physicochemical properties. In contrast, there is relatively limited knowledge of cell mechanobiology and epigenetics in the context of 3D biomaterial matrices, i.e., hydrogels and scaffolds. Scaffold geometry provides biophysical signals that trigger a nucleus response (regulation of gene expression) and modulates cell behaviour and function. In this review, we explore the potential of additive manufacturing to incorporate multi length-scale geometry features on a scaffold. Then, we discuss how scaffold geometry direct cell and nuclear mechanosensing. We further discuss how cell epigenetics, particularly DNA/histone methylation and histone acetylation, are modulated by scaffold features that lead to specific gene expression and ultimately influence the outcome of tissue regeneration. Overall, we highlight that geometry of different magnitude scales can facilitate the assembly of cells and multicellular tissues into desired functional architectures through the mechanotransduction pathway. Moving forward, the challenge confronting biomedical engineers is the distillation of the vast knowledge to incorporate multiscaled geometrical features that would collectively elicit a favourable tissue regeneration response by harnessing the design flexibility of additive manufacturing. STATEMENT OF SIGNIFICANCE: It is well-established that cells sense and respond to their 2D geometric microenvironment by transmitting extracellular physiochemical forces through the cytoskeleton and biochemical signalling to the nucleus, facilitating epigenetic changes such as DNA methylation, histone acetylation, and microRNA expression. In this context, the current review presents a unique perspective and highlights the importance of 3D architectures (dimensionality and geometries) on cell and nuclear mechanics and epigenetics. Insight into current challenges around the study of mechanobiology and epigenetics utilising additively manufactured 3D scaffold geometries will progress biomaterials research in this space.

The osteogenic response to chirality-patterned surface potential distribution of CFO/P(VDF-TrFE) membranes

Piezoelectric poly(vinylidene fluoride-trifluoroethylene) has demonstrated an ability to promote osteogenesis, and the biomaterials with a chirality-patterned topological surface could enhance cellular osteogenic differentiation. In this work, we created a chirality-patterned...

Dynamic Ligand Screening by Magnetic Nanoassembly Modulates Stem Cell Differentiation

In native microenvironment, diverse physical barriers exist to dynamically modulate stem cell recruitment and differentiation for tissue repair. In this study, nanoassembly-based magnetic screens of various sizes are utilized, and they are elastically tethered over an RGD ligand (cell-adhesive motif)-presenting material surface to generate various nanogaps between the screens and the RGDs without modulating the RGD density. Large screens exhibiting low RGD distribution stimulate integrin clustering to facilitate focal adhesion, mechanotransduction, and differentiation of stem cells, which are not observed with small screens. Magnetic downward pulling of the large screens decreases the nanogaps, which dynamically suppress the focal adhesion, mechanotransduction, and differentiation of stem cells. Conversely, magnetic upward pulling of the small screens increases the nanogaps, which dynamically activates focal adhesion, mechanotransduction, and differentiation of stem cells. This regulation mechanism is also shown to be effective in the microenvironment in vivo. Further diversifying the geometries of the physical screens can further enable diverse modalities of multifaceted and safe unscreening of the distributed RGDs to unravel and modulate stem cell differentiation for tissue repair.

Chirality Bias Tissue Homeostasis by Manipulating Immunological Response

The physiological chirality of extracellular environments is substantially affected by pathological diseases. However, how this stereochemical variation drives host immunity remains poorly understood. Here, it is reported that pathology-mimetic M-nanofibrils-but not physiology-mimetic P-nanofibrils-act as a defense mechanism that helps to restore tissue homeostasis by manipulating immunological response. Quantitative multi-omics in vivo and in vitro shows that M-nanofibrils significantly inhibit inflammation and promote tissue regeneration by upregulating M2 macrophage polarization and downstream immune signaling compared with P-nanofibrils. Molecular analysis and theoretical simulation demonstrate that M-chirality displays higher stereo-affinity to cellular binding, which induces higher cellular contractile stress and activates mechanosensitive ion channel PIEZOl to conduct Ca²⁺ influx. In turn, the nuclear transfer of STAT is biased by Ca²⁺ influx to promote M2 polarization. These findings underscore the structural mechanisms of disease, providing design basis for immunotherapy with bionic functional materials.

Use of Electrospun Phenylalanine/Poly-ε-Caprolactone Chiral Hybrid Scaffolds to Promote Endothelial Remodeling

The fabrication of tissue-engineered vascular grafts to replace damaged vessels is a promising therapy for cardiovascular diseases. Endothelial remodeling in the lumen of TEVGs is critical for successful revascularization. However, the construction of well-functioning TEVGs remains a fundamental challenge. Herein, chiral hybrid scaffolds were prepared by electrospinning using D/L-phenylalanine based gelators [D(L)PHEG] and poly-ε-caprolactone (PCL). The chirality of scaffolds significantly affected the endothelial remodeling progress of TEVGs. Compared with L-phenylalanine based gelators/poly-ε-caprolactone (L/PCL) and PCL, D-phenylalanine based gelators/poly-ε-caprolactone (D/PCL) scaffolds enhanced cell adhesion, and proliferation and upregulated the expression of fibronectin-1, and vinculin. These results suggests that chiral hybrid scaffolds can promote endothelial remodeling of TEVGs by upregulating adhesion-associated protein levels. This study offers an innovative strategy for endothelial remodeling of TEVGs by fabricating chiral hybrid scaffolds, and provides new insight for the treatment of cardiovascular diseases.

Biofunctionality with a twist: the importance of molecular organisation, handedness and configuration in synthetic biomaterial design

The building blocks of life - nucleotides, amino acids and saccharides - give rise to a large variety of components and make up the hierarchical structures found in Nature. Driven by chirality and non-covalent interactions, helical and highly organised structures are formed and the way in which they fold correlates with specific recognition and hence function. A great amount of effort is being put into mimicking these highly specialised biosystems as biomaterials for biomedical applications, ranging from drug discovery to regenerative medicine. However, as well as lacking the complexity found in Nature, their bio-activity is sometimes low and hierarchical ordering is missing or underdeveloped. Moreover, small differences in folding in natural biomolecules (e.g., caused by mutations) can have a catastrophic effect on the function they perform. In order to develop biomaterials that are more efficient in interacting with biomolecules, such as proteins, DNA and cells, we speculate that incorporating order and handedness into biomaterial design is necessary. In this review, we first focus on order and handedness found in Nature in peptides, nucleotides and saccharides, followed by selected examples of synthetic biomimetic systems based on these components that aim to capture some aspects of these ordered features. Computational simulations are very helpful in predicting atomic orientation and molecular organisation, and can provide invaluable information on how to further improve on biomaterial designs. In the last part of the review, a critical perspective is provided along with considerations that can be implemented in next-generation biomaterial designs.

Cell-subpopulation alteration and FGF7 activation regulate the function of tendon stem/progenitor cells in 3D microenvironment revealed by single-cell analysis

Three dimensional (3D) microenvironments more accurately replicate native microenvironments for stem cell maintenance and function compared with two dimensional (2D) microenvironments. However, the molecular mechanisms by which 3D microenvironments regulate stem cell function remain largely unexplored at the single-cell level. Here, using a single-cell analysis and functional analysis, we found not all cell-subpopulations respond to 3D microenvironments based on a systematically 3D gelatin microcarrier culture system we developed for the expansion and function maintenance of hTSPCs. 3D microenvironments alter the cell-subpopulation distribution of human tendon stem/progenitor cells (hTSPCs) by improving the proportion of ICAM1+ITGB8+ and FGF7+CYGB+ subpopulations. We also revealed the activated FGF7 signaling in the two subpopulations is responsible for the enhanced tenogenesis of hTSPCs through cell-cell interactions. The hTSPCs cultured in 3D niche with a specific cell-subpopulation structure exhibited superior stem-cell characteristics and functions both in vitro and in vivo. Together, our study demonstrates that 3D microenvironments can regulate stem-cell function by modulating the critical cell subpopulation and identifies FGF7 as a novel regulator for tenogenic differentiation and tendon regeneration.

An Amorphous Peri-Implant Ligament with Combined Osteointegration and Energy-Dissipation

Progress toward developing metal implants as permanent hard-tissue substitutes requires both osteointegration to achieve load-bearing support, and energy-dissipation to prevent overload-induced bone resorption. However, in existing implants these two properties can only be achieved separately. Optimized by natural evolution, tooth-periodontal-ligaments with fiber-bundle structures can efficiently orchestrate load-bearing and energy dissipation, which make tooth-bone complexes survive extremely high occlusion loads (>300 N) for prolonged lifetimes. Here, a bioinspired peri-implant ligament with simultaneously enhanced osteointegration and energy-dissipation is presented, which is based on the periodontium-mimetic architecture of a polymer-infiltrated, amorphous, titania nanotube array. The artificial ligament not only provides exceptional osteoinductivity owing to its nanotopography and beneficial ingredients, but also produces periodontium-similar energy dissipation due to the complexity of the force transmission modes and interface sliding. The ligament increases bone-implant contact by more than 18% and simultaneously reduces the effective stress transfer from implant to peri-implant bone by ≈30% as compared to titanium implants, which as far as is known has not previously been achieved. It is anticipated that the concept of an artificial ligament will open new possibilities for developing high-performance implanted materials with increased lifespans.

Roe-inspired stem cell microcapsules for inflammatory bowel disease treatment

Mesenchymal stem cells (MSCs), which exert regulatory effects on various immune cells, have been a promising therapy for inflammatory bowel disease treatment. However, their therapeutic effects are limited by lack of nutritional supply, immune system attack, and low accumulation on the target site. Here, inspired by the natural incubation mechanism of roe, we present immune-isolating, wet-adhesive, and nutrient-rich microcapsules for therapeutic MSCs encapsulation. The adhesive shells were fabricated by ionic cross-linking of alginate and visible curing of epsilon-poly-L-lysine-graft-methacrylamide and dopamine methacrylamide, which encapsulated the liquid core of the MSCs and roe proteins. Due to the core-shell construction of the resultant microcapsules, the MSCs might escape from attack of the immune system while still maintaining immunomodulating functions. In addition, the roe proteins encapsulated in the core phase offered sufficient nutrient supply for MSCs' survival and proliferation. Furthermore, after intraperitoneal transplantation, the wet-adhesive radicals on the shell surface could immobilize the MSCs-encapsulating microcapsules onto the bowel. Based on these features, practical values of the roe-inspired microcapsules with MSCs encapsulation were demonstrated by applying them to treat dextran sulfate sodium (DSS)-induced colitis through increasing residence time, regulating immune imbalance, and relieving disease progression. We believe that the proposed roe-inspired microcapsules with MSCs encapsulation are potential for clinical application.

Crucial Impact of Residue Chirality on the Gelation Process and Biodegradability of Thermoresponsive Polypeptide Hydrogels

Thermosensitive polypeptide hydrogels have gained considerable attention in potential biomedical applications, of which the polymer structure may be tuned by residue chirality. In this study, polypeptide-based block copolymers with different chiralities were synthesized by ring-opening polymerization of γ-ethyl-l-glutamate N-carboxyanhydride and/or γ-ethyl-d-glutamate N-carboxyanhydride using amino-terminated monomethoxy poly(ethylene glycol) as a macroinitiator. All mPEG-polypeptide copolymers underwent sol-gel transition with an increase in temperature. The block copolymers with mixed enantiomeric residues of γ-ethyl-l-glutamate (ELG) and γ-ethyl-d-glutamate (EDG) in the polypeptide blocks exhibited lower critical gelation concentrations and lower critical gelation temperatures compared with those composed of pure ELG or EDG residues. We established that the difference in gelation properties between the copolymers was derived from the distinction of the secondary structures. We further demonstrated the influence of polypeptide chirality on the degradability and biocompatibility of hydrogels in vivo. Our findings provide insights into the design of hydrogels having tailored secondary conformation, gelation property, and biodegradability.

Macroscopic Supramolecular Assembly Strategy to Construct 3D Biocompatible Microenvironments with Site-Selective Cell Adhesion

Three-dimensional (3D) scaffolds with chemical diversity are significant to direct cell adhesion onto targeted surfaces, which provides solutions to further control over cell fates and even tissue formation. However, the site-specific modification of specific biomolecules to realize selective cell adhesion has been a challenge with the current methods when building 3D scaffolds. Conventional methods of immersing as-prepared structures in solutions of biomolecules lead to nonselective adsorption; recent printing methods have to address the problem of switching multiple nozzles containing different biomolecules. The recently developed concept of macroscopic supramolecular assembly (MSA) based on the idea of "modular assembly" is promising to fabricate such 3D scaffolds with advantages of flexible design and combination of diverse modules with different surface chemistry. Herein we report an MSA method to fabricate 3D ordered structures with internal chemical diversity for site-selective cell adhesion. The 3D structure is prepared via 3D alignment of polydimethylsiloxane (PDMS) building blocks with magnetic pick-and-place operation and subsequent interfacial bindings between PDMS based on host/guest molecular recognition. The site-specific cell affinity is realized by distributing targeted building blocks that are modified with polylysine molecules of opposite chiralities: PDMS modified with films containing poly-l-lysine (PLL) show higher cell density than those with poly-d-lysine (PDL). This principle of selective cell adhesion directed simply by spatial distribution of chiral molecules has been proven effective for five different cell lines. This facile MSA strategy holds promise to build complex 3D microenvironment with on-demand chemical/biological diversities, which is meaningful to study cell/material interactions and even tissue formation.