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Cellular mechanics plays an important role in physiological processes such as cell growth, differentiation, apoptosis and gene expression. Herein, we present a nano-imprinted structural color graphene film with anisotropic microgroove and two-dimensional (2D) photonic crystal structures for cardiomyocytes dynamic displaying. The anisotropic structural color graphene film was generated by a “sandwich” mold in one step with the assistance of two designed templates. Because of the microgroove structure and biocompatibility of the film, the cardiomyocytes could be induced into a highly ordered arrangement with recoverable autonomous beating. Meanwhile, the opposite surface of the film was imparted with defect-free 2D photonic crystal structures, giving it a vivid structural color and photonic band gap (PBG). We demonstrated that the flexible film would undergo synchronous volume or shape changes with the cardiomyocytes’ elongation and contraction during the beating process, showing cyclic changes of the structural color, which in turn could be converted into force. In addition, by integrating this anisotropic structural color graphene film with microfluidic channels, a novel and accurate heart-on-a-chip platform was established for real-time cell monitoring and drug screening. These characteristics of the present anisotropic structural color graphene films make them extremely valuable in the field of biomedicine.

The first bench-stable triple-diazonium reagent (TDA-1) was rationally designed and synthesized for coupling and crosslinking. The three reactive sites of TDA-1 can react with phenol-containing molecules as well as plant viruses in aqueous buffers efficiently. In addition, a new-type azo-linked cage was constructed by the direct reaction of TDA-1 with a triple-phenol molecule and was characterized by X-ray crystallography.

Silk fibroin (SF) is considered biocompatible and biodegradable for osteochondral repair. However, it lacks a bioactive domain for cell adhesion, proliferation and differentiation, limiting its therapeutic efficacy. To revamp SF as a biomimicking and bioactive microenvironment to regulate cell behaviours, we engineered an elastin-like polypeptide (ELP, Val-Pro-Gly-Xaa-Gly) to modify SF fibers via simple and green dehydrothermal (DHT) treatment. Our results demonstrated that the ELP successfully bound to SF, and the scaffold was reinforced by the fusion of the silk fiber intersections with ELP (S-ELP-DHT) via the DHT treatment. Both bone mesenchymal stem cells (BMSCs) and chondrocytes exhibited improved spreading and proliferation on the S-ELP-DHT scaffolds. The ex vivo and in vivo experiments further demonstrated enhanced mature bone and cartilage tissue formation using the S-ELP-DHT scaffolds compared to the naked SF scaffolds. These results indicated that a recombinant ELP-modified silk scaffold can mimic three-dimensional (3D) cell microenvironment, and improve bone and cartilage regeneration. We envision that our scaffolds have huge clinical potential for osteochondral repair., Graphical abstract Schematic illustration showing the S-ELP-DHT scaffolds can be fabricated into fibrocartilage or bone mimic by seeding with chondrocytes or BMSCs for osteochondral regeneration.Image 1, Highlights • Elastin-like polypeptide (ELP) modified silk fibroin (SF) scaffold was developed via dehydrothermal treatment (S-ELP-DHT). • The S-ELP-DHT scaffold provided a beneficial cell microenvironment for osteochondral repair. • Greater mature bone and cartilage tissue formation were achieved. • Improved repair efficacy for articular osteochondral defects was confirmed.

Stem-cell based in vitro differentiation for disease modeling offers great value to explore the molecular and functional underpinnings driving many types of cardiomyopathy and congenital heart diseases. Nevertheless, one major caveat in the application of in vitro differentiation of human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes (hiPSC-CMs) involves the immature phenotype of the CMs. Most of the existing methods need complex apparatus and require laborious procedures in order to monitor the cardiac differentiation/maturation process and often result in cell death. Here we developed an intrinsic color sensing system utilizing a microgroove structural color methacrylated gelatin film, which allows us to monitor the cardiac differentiation process of hiPSC-derived cardiac progenitor cells in real time. Subsequently this system can be employed as an assay system to live monitor induced functional changes on hiPSC-CMs stemming from drug treatment, the effects of which are simply revealed through color diversity. Our research shows that early intervention of cardiac differentiation through simple physical cues can enhance cardiac differentiation and maturation to some extent. Our system also simplifies the previous complex experimental processes for evaluating the physiological effects of successful differentiation and drug treatment and lays a solid foundation for future transformational applications.

H2S is a well-known toxic gas and also a gaseous signaling molecule involved in many biological processes. Advanced chemical tools that can regulate H2S levels in vivo are useful for understanding H2S biology as well as its potential therapeutic effects. To this end, we have developed a series of 7-nitro-1,2,3-benzoxadiazole (NBD) amines as potential H2S scavengers. The kinetic studies of thiolysis reactions revealed that incorporation of positively-charged groups onto the NBD amines greatly increased the rate of the H2S-specific thiolysis reaction. We demonstrate that these reactions proceed effectively, with second order rate constants (k2) of >116 M−1 s−1 at 37 °C for NBD-S8. Additionally, we demonstrate that NBD-S8 can effectively scavenge enzymatically-produced and endogenous H2S in live cells. Furthering the biological significance, we demonstrate NBD-S8 mediates scavenging of H2S in mice., We demonstrate that positively-charged NBD amines can effectively scavenge biological H2S in live cells and in mice.

Recently, organ-on-chips have become a fast-growing research field with the widespread development of microfluidic chips and synthetic materials in tissue engineering. Due to the existing cardiotoxicity of many cardiovascular drugs, heart-on-chips which are promising to replace traditional animal models have been extensively researched and developed to mimic human organ functions in vitro. The heart-on-chips mainly focus on cardiac mechanics, which is regarded as the central indicator of in vitro heart models and drug testing. Traditional methods for the detection of myocardial mechanics have been demonstrated complex and inefficient in heart-on-chips. Therefore, photonic crystal materials with unique optical properties have attracted interests and have been introduced into the heart-on-chips, developing a visualized self-reporting system for cardiomyocytes activity monitoring. In this review, photonic crystal-based heart-on-chips for biosensing are introduced, as well as the fabrication methods and design criteria of them. The characterizations of the photonic crystal materials are classified into optical properties and structural properties, and their applications in cell culture and biosensing are further discussed. Then, several representative examples and developments of the integration of photonic crystal materials into microfluidic chips are described in detail. Finally, potentials and limitations are put forward to promote the development of the photonic crystal-based intelligent heart-on-chips.

With the development of the materials science, biosensors tend to be thin, flexible, versatile, and are extensively employed in biotechnology, clinical diagnosis, biochips, etc. However, most existing biosensors are single-functionalized and destitute in contrivable microstructure, which result in some inherent limitations. In this work, a novel thin-film sensor that had dual response generated from one stimulus was designed based on the colloidal crystal templates and devisable circuit system. Benefiting from designed platinum coating, the thin-film appeared as a flexible strain sensor which presented corresponding resistance changes with the slight deformation of the thin-film. In addition, with the sacrificial template method, the porous thin-film derived from the colloidal crystal template was endowed with manageable porous structure and splendid structural color, and the resultant color could be various when the environment changed. These features laid the foundation for the construction of multifunctional thin-film biosensor and presented potential applicability for a variety of biological research and flexible sensing devices.

The basic fibroblast growth factor (bFGF) plays an important role in the wound repair process. However, lacking of better biomaterials to carry bFGF still is a challenge in skin repair and regeneration. In this study, the human-like collagen (HLC) cross-linked with transglutaminase (TG) to fabricate a HLC/TG hydrogel to load bFGF. The physical properties of hydrogel, such as interior structure, mechanical property, were characterized

Structural color materials with the property of angle-independence have attracted increasing interest in recent years because of their applications in various research fields. In this paper, inspired by the anisotropic lattice microstructure of the Parides sesostris butterfly, we present a novel angle-independent structural material by simply doping spinous pollen particles into the colloidal crystal arrays to interfere their self-assembling process. The resultant composited materials have anisotropic close-packed colloidal crystal domains around the spikes of the pollens. These differently oriented domains could reflect the light to a wide range of viewing angles, and thus imparted the composite materials with the same wide angle of structural colors. Attractively, the materials were endowed with light-controlled reversible structural color changing behavior by incorporating photothermal responsive graphene-tagged hydrogels. These features of the bioinspired angle-independent structural color materials showed their potential values in constructing intelligent sensors, anti-counterfeiting barcode labels, and so on.

Three-dimensional (3D) cell spheroids have a demonstrated value for in vitro biological research and therapeutics development. Attempts to this technique focus on the development of effective methods for fabricating cell spheroids. Here, inspired by the heterogeneously textured wettability bumps (with hydrophilic peaks and hydrophobic bases) of Stenocara beetle, we present a biotemplated substrate with wettable hydrogel arrays for culturing the cell spheroids. The biotemplates were Morpho butterfly wings with chitin and protein components, which could provide a natural superhydrophobic surface without any modification. The droplet microarrays could be formed for cell spheroid culture on this bioinspired wing substrate by using the hydrogel patterns to hanging droplets. The hanging drop culture method on hydrogel-covered wings has the advantages of high speed, uniform size, and controllable diameter for the formation of 3D cell spheroids. It was demonstrated that drugs produced distinct responses in the 3D cell spheroids compared to conventional two-dimensional cell cultures. As the presented system does not require complex instruments and chemical modifications, our method can simply construct the desired wettability substrates with high biocompatibility for cell culture, drug testing, and other biomedical applications.

An intelligent structural color hydrogel with photo-controllable capability was developed by adding graphene oxide (GO) into colloidal particle solutions. The high charge characteristic of GO could significantly enhance the electrostatic repulsion effect between adjacent particles and promote the ordered assembly of the colloidal particles. The resultant colloidal crystal arrays (CCAs) with a small amount of GO additive were imparted with vivid angle-dependent structural colors due to the enhanced photon absorption of the hybrid materials, whereas their structural colors became dull and angle-independent with a high GO concentration, which contributes to the isotropic short-range ordered CAA nanostructures. It was demonstrated that the GO hybrid structural color hydrogels with temperature-sensitive polymer components featured photo-responsive properties, which provided remotely controllable dynamic structural colors for different patterns. These features of the GO hybrid structural color hydrogels make them promising for the applications of anti-counterfeiting barcode and other related fields.

Treating serious bone trauma with an osteo-inductive agent such as bone morphogenetic proteins (BMPs) has been considered as an optimized option when delivered via a collagen sponge (CS). Previous works have shown that the BMP concentration and release rate from approved CS carriers is difficult to control with precision. Here we presented the fabrication of a recombinant fusion protein from recombinant human-like collagen (HLC) and human BMP-2 (hBMP2). The fusion protein preserved the characteristic of HLC allowing the recombinant protein to be expressed in Yeast (such as Pichia pastoris GS115) and purified rapidly and easily with mass production after methanol induction. It also kept the stable properties of HLC and hBMP2 in the body fluid environment with good biocompatibility and no cytotoxicity. Moreover, the recombinant fusion protein fabricated a vertical through-hole structure with improved mechanical properties, and thus facilitated migration of bone marrow mesenchymal stem cells (MSCs) into the fusion materials. Furthermore, the fusion protein degraded and released hBMP-2 in vivo allowing osteoinductive activity and the enhancement of utilization rate and the precise control of the hBMP2 release. This fusion protein when applied to cranial defects in rats was osteoinductively active and improved bone repairing enhancing the repairing rate 3.5- fold and 4.2- fold when compared to the HLC alone and the control, respectively. There were no visible inflammatory reactions, infections or extrusions around the implantation sites observed. Our data strongly suggests that this novel recombinant fusion protein could be more beneficial in the treatment of bone defects than the simple superposition of the hBMP2/collagen sponge.

Natural animal collagen and its recombinant collagen are favorable replacements in human tissue engineering due to their remarkable biomedical property. However, this exploitation is largely restricted due to the potential of immunogenicity and virus contamination. Exploring new ways to produce human collagen is a fundamental key to its biomedical and clinical application. All human fibrillar collagen molecules have three polypeptide chains constructed from a repeating Gly-Xaa-Yaa triplet, where Xaa and Yaa represent one random amino acid. Using cDNA techniques to modify several repeat sequences of the cDNA fragment, a novel human collagen named recombinant human-like collagen (HLC), with low immunogenicity and little risk from hidden virus can be engineered and notably tailored to specific applications. HLC was initially used as a coating to modify the tissue engineering scaffold, and then used as the scaffold after cross link agents were added to increase its mechanical strength. Due to its good biocompatibility, low immunogenicity, stabilised property and the ability of mass production, HLC has been widely considered to use in skin injury treatments, vascular scaffolds engineering, cartilage, bone defect repair, skincare, haemostatic sponge, and drug delivery including coating with medical nanoparticles. In this review, we symmetrically reviewed the development, recent advances in design and application of HLC, and other recombinant human collagen-based biomedicine potentials. For comparison and providing basic background information about the techniques, we start with recombinant human collagens. In the end, future improvements in using HLC are also discussed.

Bionic electronic skin (E-skin) that could convert external physical or mechanical stimuli into output signals has a wide range of applications including wearable devices, artificial prostheses, software robots, etc. Here, we present a chameleon-inspired multifunctional E-skin based on hydroxypropyl cellulose (HPC), Poly(Acrylamide-co-Acrylic acid) (PACA), and carbon nanotubes (CNTs) composited liquid-crystal hydrogel. We found that the HPC could still form cholesteric liquid-crystal photonic structures with the CNTs additive for enhancing their color saturation and PACA polymerization for locating their assembled periodic structures. As the composite hydrogel containing HPC elements and the PACA scaffold responds to different stimuli, such as temperature variations, mechanical pressure, and tension, it could correspondingly change its volume or internal nanostructure and report these as visible color switches. In addition, due to the additive of CNTs, the composite hydrogel could also output these stimuli as electrical resistance signals. Thus, the hydrogel E-skins had the ability of quantitatively feeding back external stimuli through electrical resistance as well as visually mapping the stimulating sites by color variation. This dual-signal sensing provides the ability of visible-user interaction as well as antiinterference, endowing the multifunctional E-skin with great application prospects.

As simulators of organisms in Nature, soft robots have been developed over the past few decades. In particular, biohybrid robots constructed by integrating living cells with soft materials demonstrate the unique advantage of simulating the construction and functions of human tissues or organs, thus attracting extensive attention and research interest. Here, we present up-to-date studies concerning biohybrid robots with various biological actuators such as contractile cells and microorganisms. After presenting the basic components including biological components and synthetic materials, the controlling methods and locomotion modalities of biohybrid robots are clarified and summarized. We then focus on the applications, especially the biomedical applications, of the biohybrid robots including drug delivery, bioimaging, and tissue engineering. The challenges and prospects for the future development of biohybrid robots are also presented.

Drug discovery through a large number of candidates with nearly unlimited possibilities is laborious, time-consuming, and incurs massive costs. It thus calls for fast and robust methods that allow for handling small amounts of reagents, automation, and high-throughput analysis. In this regard, droplet-based microfluidic platforms provide several unique advantages. Highly monodispersed droplets can be generated in a high frequency and serve as microcontainers with just a few femtoliter to nanoliter volume. Furthermore, each of them can be manipulated to initiate specific reactions in parallel. Consequently, droplet microfluidics is emerging as a useful tool for drug discovery and development.The authors provide a brief overview of the latest developments of droplet-based microfluidic techniques for drug discovery and emphasize their applications at different stages, covering target selection, drug candidate identification, and preclinical research.Droplet-based microfluidics holds great potential in drug discovery due to its capability of reaction miniaturization and high-throughput analysis. However, its commercial applications are still at an early stage as the experiments are mostly implemented utilizing custom-built instruments in laboratory environments. Thus, joint efforts from scientists and engineers with multidisciplinary backgrounds are required to optimize the standardization and stability of droplet-based microfluidic platforms.

Anisotropic structural color particles from colloidal phase separation are developed for dynamic cell monitoring and sensing., Structural color materials have been studied for decades because of their fascinating properties. Effects in this area are the trend to develop functional structural color materials with new components, structures, or morphologies for different applications. In this study, we found that the coassembled graphene oxide (GO) and colloid nanoparticles in droplets could form component phase separations, and thus, previously unknown anisotropic structural color particles (SCPs) with hemispherical colloidal crystal cluster and oblate GO component could be achieved. The anisotropic SCPs, as well as their inverse opal hydrogel derivatives, were endowed with brilliant structural colors and controllable capabilities of fixation, location, orientation, and even responsiveness due to their specific structure, morphology, and components. We have also demonstrated that the anisotropic hydrogel SCPs with these features were ideal candidates for dynamic cell monitoring and sensing. These properties indicate that the anisotropic SCPs and their derivatives have huge potential values in biomedical areas.

Microbial fuel cells (MFCs) are attractive because they can harvest energy from sewage, but challenge remains in achieving valuable power density. To address this issue, we develop a novel binder-free anode, Nano-Fe3C@2D-NC@CC, by assembling 2D Zn-Fe-MOF arrays on the fibers of carbon cloth and subsequently carbonizing MOF. This fabrication results in a unique configuration that nano-Fe3C particles are highly dispersed on N-doped carbon arrays vertically standing on carbon fibers. The standing 2D arrays not only benefit bacterial adhesion but also guarantee nano-Fe3C particles with abundant sites for the charge transfer between bacteria and anode. Consequently, a superior power density (1606 ± 52 mW m−2) is harvested when the resultant Nano-Fe3C@2D-NC@CC is evaluated as the anode in MFCs based on a mixed bacterium culture. The facile fabrication of Nano-Fe3C@2D-NC@CC paves a promising path for the application of MFCs in large scale.

Particle-based delivery systems demonstrate a pregnant value in the fields of drug research and development. Efforts to advance this technology focus on the fabrication of functional particles with enhanced efficiency and performance for drug delivery. Here, we present a new type of mesoporous colloidal photonic crystal particle (MCPCP)-based drug-delivery system with distinct features. As the MCPCPs were constructed by self-assembling monodisperse mesoporous nanoparticles in microfluidic droplet templates, they were composed of hierarchical macro- and mesoporous structures and could provide plenty of nanopores and interconnected nanochannels for synergistic loading of both micro- and macromolecule drugs with large quantity and sustained release. In addition, by integrating the stimuli-responsive poly( N-isopropylacrylamide) hydrogel into the MCPCPs and employing it as a "gating" to control the opening of the macro- and mesopores, the MCPCP delivery systems were imparted with the function of controllable release. More attractively, as the average refractive index of the MCPCPs was decreased during the release of the loaded actives, the photonic band gaps of the MCPCPs blue-shifted correspondingly; this provided a novel stratagem for real-time self-reporting of the therapeutic agent release process of the MCPCPs. Hence, the MCPCPs are ideal for intelligent drug delivery because of these dramatical features.

Facial approximation plays a vital role in personal identification when other methods cannot be applied, and the study on facial soft tissue thickness (FSTT) is important to allow more accurate facial approximation. The Cone-Beam CT (CBCT) is considered to be an accurate approach in assessing FSTT, however only few studies have assessed the FSTT norms by CBCT in Chinese populations. The aim of this study was to (1) establish forensic measurement approach on a 3D model reconstructed by CBCT image; (2) obtain FSTT norms from the adults of Yangtze River delta Han population; (3) determine the impacts of sex, age, BMI as well as malocclusion type on FSTT and (4) form a FSTT database through CBCT. A total of 60 facial landmarks were primarily established from 3D reconstructed models from CBCT images of 424 healthy Han adults (130 males and 294 females) aged from 21 to 50 years in Yangtze River delta region and measurements were carried out. The multivariate analysis of variance test and multiple linear regressions test showed that the FSTT values on most landmarks were significantly different between sexes and BMI, and males showed greater values, expect for the landmarks distributed in malarzygomatic areas. Simultaneously, BMI mostly affected the landmarks located in zygomatic region. Besides, only a few landmarks were influenced by age. Interestingly, several periodontal landmarks were influenced by malocclusion types, thus the impact of malocclusion types on FSTT requires attention. Finally, the validation analysis suggested that measurement approach is an important factor for FSTT.

Osteoinductive activity of the implant in bone healing and regeneration is still a challenging research topic. Therapeutic application of recombinant human bone morphogenetic protein-2 (BMP-2) is a promising approach to enhance osteogenesis. However, high dose and uncontrolled burst release of BMP-2 may introduce edema, bone overgrowth, cystlike bone formation, and inflammation. In this study, low-dose BMP-2 of 1 μg was used to design PLA-PD-BMP for functionalization of polylactic acid (PLA) implants via mussel-inspired polydopamine (PD) assist. For the first time, the binding property and efficiency of the PD coating with BMP-2 were directly demonstrated and analyzed using an antigen-antibody reaction. The obtained PLA-PD-BMP surface immobilized with this low BMP-2 dose can endow the implants with abilities of introducing strong stem cell adhesion and enhanced osteogenicity. Furthermore, in vivo osteoinduction of the PLA-PD-BMP-2 scaffolds was confirmed by a rat ectopic bone model, which is marked as the "gold standard" for the evidence of osteoinductive activity. The microcomputed tomography, Young's modulus, and histology analyses were also employed to demonstrate that PLA-PD-BMP grafted with 1 μg of BMP-2 can induce bone formation. Therefore, the method in this study can be used as a model system to immobilize other growth factors onto various different types of polymer substrates. The highly biomimetic mussel-derived strategy can therefore improve the clinical outcome of polymer-based medical implants in a facile, safe, and effective way.

Tissue-engineered skin equivalent (TESE) is an optimized alternative for the treatment of skin defects. Designing and fabricating biomaterials with desired properties to load cells is critical for the approach. In this study, we aim to develop a novel TESE with recombinant human collagen (rHC) hydrogel and fibroblasts to improve full-thickness skin defect repair. First, the bioactive effect of rHC on fibroblast proliferation, migration and phenotype was assayed. The results showed that rHC had good biocompatibility and could stimulate fibroblasts migration and secrete various growth factors. Then, rHC was cross-linked with transglutaminase (TG) to prepare rHC hydrogel. Rheometer tests indicated that 10% rHC/TG hydrogel could reach a oscillate stress of 251 Pa and remained stable. Fibroblasts were seeded into rHC/TG hydrogel to prepare TESE. Confocal microscope and scanning electronic microscope observation showed that seeded fibroblasts survived well in the hydrogel. Finally, the therapeutic effect of the newly prepared TESE was tested in a mouse full-thickness skin defect model. The results demonstrated that TESE could significantly improve skin defect repair in vivo. Conclusively, TESE prepared from rHC and fibroblasts in this study exhibits great potential for clinical application in the future.

Spiral ganglion neuron (SGN) degeneration can lead to severe hearing loss, and the directional regeneration of SGNs has shown great potential for improving the efficacy of auditory therapy. Here, a novel 3D conductive microstructure with surface topologies is presented by integrating superaligned carbon-nanotube sheets (SA-CNTs) onto Morpho Menelaus butterfly wings for SGN culture. The parallel groove-like topological structures of M. Menelaus wings induce the cultured cells to grow along the direction of its ridges. The excellent conductivity of SA-CNTs significantly improves the efficiency of cellular information conduction. When integrating the SA-CNTs with M. Menelaus wings, the SA-CNTs are aligned in parallel with the M. Menelaus ridges, which further strengthens the consistency of the surface topography in the composite substrate. The SA-CNTs integrated onto butterfly wings provide powerful physical signals and regulate the behavior of SGNs, including cell survival, adhesion, neurite outgrowth, and synapse formation. These features indicate the possibility of directed regeneration after auditory nerve injury.

Near-infrared (NIR) fluorescent probes are attractive tools for bioimaging applications because of their low auto-fluorescence interference, minimal damage to living samples, and deep tissue penetration. H2S is a gaseous signaling molecule that is involved in redox homeostasis and numerous biological processes in vivo. To this end, we have developed a new red shifted fluorescent probe 1 to detect physiological H2S in live cells. The probe 1 is based on a rhodamine derivative as the red shifted fluorophore and the thiolysis of 7-nitro 1,2,3-benzoxadiazole (NBD) amine as the H2S receptor. The probe 1 displays fast fluorescent enhancement at 660 nm (about 10-fold turn-ons, k2 = 29.8 M−1s−1) after reacting with H2S in buffer (pH 7.4), and the fluorescence quantum yield of the activated red shifted product can reach 0.29. The probe 1 also exhibits high selectivity and sensitivity towards H2S. Moreover, 1 is cell-membrane-permeable and mitochondria-targeting, and can be used for imaging of endogenous H2S in living cells. We believe that this red shifted fluorescent probe can be a useful tool for studies of H2S biology.

New bench-stable reagents with two diazonium sites were designed and synthesized for protein crosslinking. Because of the faster diazonium-tyrosine coupling reaction, hydrogels from the crosslinking of tobacco mosaic virus and the reagent DDA-3 could be prepared within 1 min at room temperature. Furthermore, hydrogels with the introduction of disulfide bonds via DDA-4 could be chemically degraded by dithiothreitol. Our results provided a facile approach for the direct construction of virus-based hydrogels.

Structural color hydrogels with healable capability are of great significance in many fields, however the controllability of these materials still needs optimizing. Thus, this work presents a healable structural color hydrogel with photocontrolling properties. The component parts of the hydrogel are a graphene oxide (GO) integrated inverse opal hydrogel scaffold and a hydrogel filler with reversible phase transition. The inverse opal scaffold provides stable photonic crystal structure and the hydrogel filler is the foundation of healing. Taking advantage of the prominent photothermal conversion efficiency of GO, the healable structural color material is imparted with photocontrolled properties. It is found that the structural color hydrogel shaped in complex patterns can heal under near-infrared (NIR) irradiation. These features indicate that the optical controllable healable structural color hydrogel can be employed in various applications, such as constructing complex objects, repairing tissues, and so on.

RADA16 (RADARADARADARADA) is an amphiphilic polypeptide composed of 16 amino acids, which is composed of alternating positively charged arginine (R), hydrophobic alanine (A) and negatively charged aspartic acid (D) that repeat periodically throughout the composition. This structure allows RADA16 to form an extremely stable and highly ordered β-sheet structure by noncovalent bonding (ionic bonds, hydrogen bonds, hydrophobic action, π-π bonds, etc.). Moreover, it can form a three-dimensional (3D) nanofiber hydrogel scaffold in neutral pH with water content higher than 99% and with a physiological saline solution, having excellent biocompatibility and low immunogenicity, etc. Its degradation products are amino acids, which can reduce the possibility of an inflammatory reaction and have little effect on the normal healing process of damaged tissue. In addition, the special 3D structure of RADA16 facilitates the proliferation and differentiation of cells, making it widely used in cell culture scaffolds. Subsequent studies have found that the C-terminus or N-terminus of RADA16 is modified by a specific functional peptide, which not only retains the original function of RADA16 but also gives the RADA16 self-assembling hydrogel a more powerful function. In recent years, RADA16 and RADA16-based fusion peptides have been applied in biomedical fields, such as 3D cell culture, tissue repair, rapid hemostasis, and delivery systems, which have broad prospects. This review focuses on recent research and applications of RADA16 and RADA16-based self-assembling peptide nanofiber scaffold (SAPNS) in biomedicine.

Natural fiber systems provide inspirations for artificial fiber spinning and applications. Through a long process of trial and error, great progress has been made in recent years. The natural fiber itself, especially silks, and the formation mechanism are better understood, and some of the essential factors are implemented in artificial spinning methods, benefiting from advanced manufacturing technologies. In addition, fiber-based materials produced via bioinspired spinning methods find an increasingly wide range of biomedical, optoelectronic, and environmental engineering applications. This paper reviews recent developments in the spinning and application of bioinspired fiber systems, introduces natural fiber and spinning processes and artificial spinning methods, and discusses applications of artificial fiber materials. Views on remaining challenges and the perspective on future trends are also proposed.

Hypothesis Ultrasensitive detections with enrichment approaches based on hydrophilic-hydrophobic patterns have attracted increasing attention in the early diagnosis and treatment of diseases. However, most of these techniques involve complicated micro-fabrications and chemical modifications to achieve their specific pattern substrate wettability. Hence, the development of a simple and effective approach for the construction of new surface wettability techniques for ultrasensitive detection is with great expectations. Experiments We present a simple approach to fabricate the superwettable colloidal crystal (CC) micropatterns on superhydrophobic Morpho butterfly wing surface for the ultrasensitive detection. The superwettable CC micropatterns were easily obtained by infiltrating and self-assembling monodispersed silica colloidal nanoparticles on the plasma treated butterfly wing patterns. The analytes could be enriched onto the hydrophilic CC area due to the wettability difference between the hydrophilic CC area and the superhydrophobic substrate. Findings It was demonstrated that the detection limit of thrombin was down to 1.8 × 10−13 mol L−1 based on the fluorophore-labeled aptamer. Moreover, with two-dimensional position codes of these CC micropatterns for different probes, the multiplex detection capability was also demonstrated with great accuracy. As the elimination of complex instruments and chemical modifications, this proposed platform offers a simple strategy for ultrasensitive multiplex detection in practical applications.

Biohybrid actuators composed of living tissues and artificial materials have attracted increasing interest in recent years because of their extraordinary function of dynamically sensing and interacting with complex bioelectrical signals. Here, a compound biohybrid actuator with self-driven actuation and self-reported feedback is designed based on an anisotropic inverse opal substrate with periodical elliptical macropores and a hydrogel filling. The benefit of the anisotropic surface topography and high biocompatibility of the hydrogel is that the planted cardiomyocytes could be induced into a highly ordered alignment with recovering autonomic beating ability on the elastic substrate. Because of the cell elongation and contraction during cardiomyocyte beating, the anisotropic inverse opal substrates undergo a synchronous cycle of deformation actuations, which can be reported as corresponding shifts of their photonic band gaps and structural colors. These self-driven biohybrid actuators could be used as elements for the construction of a soft-bodied structural color robot, such as a biomimetic guppy with a swinging tail. Besides, with the integration of a self-driven biohybrid actuator and microfluidics, the advanced heart-on-a-chip system with the feature of microphysiological visuality has been developed for integrated cell monitoring and drug testing. This anisotropic inverse opal-derived biohybrid actuator could be widely applied in biomedical engineering.