Irregular Defects Research Articles

Microsphere-Gel Composite System with Mesenchymal Stem Cell Recruitment, Antibacterial, and Immunomodulatory Properties Promote Bone Regeneration via Sequential Release of LL37 and W9 Peptides.

Various types of biomaterials have been widely used to treat complex bone defects. However, potential infection risks and inappropriate host immune responses induced by biomaterials can adversely affect the final bone repair outcome. Therefore, the development of novel bone biomaterials with antibacterial and immunomodulatory capabilities is conducive to achieving a good interaction between the host and material, thereby creating a local microenvironment favorable for osteogenesis and ultimately accelerating bone regeneration. In this study, we fabricated a porcine small intestinal submucosa (SIS) hydrogel containing LL37 peptides and polylactic-glycolic acid (PLGA) microspheres encapsulated with WP9QY(W9) peptide (LL37-W9/PLGA-SIS), which can fill irregular bone defects and exhibits excellent mechanical properties. In vitro experiments showed that the microsphere-gel composite system had sequential drug release characteristics. The LL37 peptide released first had good antibacterial performance and BMSC recruitment ability, which could prevent infection at an early stage and increase the number of BMSCs at the injured site. In addition, it also has immunomodulatory properties, showing both pro-inflammatory and anti-inflammatory activities, but its early pro-inflammatory properties are more inclined to activate the M1 phenotype of macrophages. Moreover, the subsequently released W9 peptide not only reduced the expression of pro-inflammatory genes to alleviate inflammation and induced more macrophages to convert to M2 phenotypes but also promoted the osteogenic differentiation of BMSCs. This finely regulated immune response is considered to be more closely related to the physiological bone healing process. When studying the interaction between macrophages and BMSCs mediated by the material, it was found that the immunomodulatory and osteogenic effects were enhanced. In vivo experiments, we constructed rat skull defect models, which further proved that LL37-W9/PLGA-SIS gel can properly regulate the immune response, and has a good ability to promote osteogenesis in situ. In conclusion, the LL37-W9/PLGA-SIS hydrogel has great application prospects in immune regulation and bone therapy.

Numerical and experimental investigation on the defect formation in lithium-ion-battery electrode-slot coating

• Three types of defects in lithium-ion-battery electrode-slot coating are found. • Defect formation is related to static or dynamic contact line location movement. • A larger maximum coating speed can be obtained for a lower coating gap. • The maximum coating speed of the underbite die configuration increases by 25.6%. Defect-free slot coating is important in the design and manufacturing of lithium-ion-battery electrodes. However, the defect formation in electrode-slot coating is not clearly understood because of the involvement and coupling of many parameters. Here, we investigate the defect formation mechanisms in electrode-slot coating by using numerical and experimental methodologies. Three defects, namely, striped, spotted, and irregular, are observed. The striped defect is related to downstream menisci contraction; however, the spotted and irregular defects are associated with the unstable development of the sawtooth dynamic contact line. In addition, three regions for the capillary number and minimum-thickness-based coating window are found, and the dominant force in each region is clarified. The results indicate that a higher maximum coating speed can be obtained for a lower coating gap, and the maximum coating speed of the underbite die configuration increases by 25.6% compared with that of the normal die configuration.

Injectable composite hydrogel based on carbon particles for photothermal therapy of bone tumor and bone regeneration

• Injectable composite hydrogel based on carbon particles is developed. • Carbon particles can serve as photothermal agents to ablate osteosarcoma tissues. • Injectable composite hydrogel facilitates the conformal therapy of bone defects. • Composite hydrogel promotes the new bone formation with a high BV/TV ratio of 76.2%. Surgical resection, as the most efficient treatment for bone tumor, still faces a dilemma between the complete removal of tumor tissue and the maximum reservation of healthy bone tissue. In response to this, an injectable composite hydrogel with chitosan/hyaluronic acid/ β -sodium glycerophosphate as the matrix and carbon particles as the photothermal agent is developed. Owing to the temperature sensitivity, the composite hydrogel can be injected into the irregular bone defect and exhibit the sol-gel phase transition upon body temperature, facilitating the conformal therapy. The composite hydrogel can ablate the human osteosarcoma on Balb/c nude mice model with the tumor inhibition rate of 98.4% after near-infrared laser irradiation (808 nm). The assessment of bone regeneration on calvarial-defect model of Sprague-Dawley rats reveals that the composite hydrogel can promote new bone formation with the bone volume/total volume ratio of 76.2% after 8 weeks, in sharp contrast to the control group of 23.9%.

Automatic reconstruction of irregular shape defects in pulsed thermography using deep learning neural network

Quantitative defect and damage reconstruction play a critical role in industrial quality management. Accurate defect characterisation in Infrared Thermography (IRT), as one of the widely used Non-Destructive Testing (NDT) techniques, always demands adequate pre-knowledge which poses a challenge to automatic decision-making in maintenance. This paper presents an automatic and accurate defect profile reconstruction method, taking advantage of deep learning Neural Networks (NN). Initially, a fast Finite Element Modelling (FEM) simulation of IRT is introduced for defective specimen simulation. Mask Region-based Convolution NN (Mask-RCNN) is proposed to detect and segment the defect using a single thermal frame. A dataset with a single-type-shape defect is tested to validate the feasibility. Then, a dataset with three mixed shapes of defect is inspected to evaluate the method’s capability on the defect profile reconstruction, where an accuracy over 90% on Intersection over Union (IoU) is achieved. The results are compared with several state-of-the-art of post-processing methods in IRT to demonstrate the superiority at detailed defect corners and edges. This research lays solid evidence that AI deep learning algorithms can be utilised to provide accurate defect profile reconstruction in thermography NDT, which will contribute to the research community in material degradation analysis and structural health monitoring.

Three‐dimensional printinghydrogel scaffold with bioactivity and shape‐adaptability for potential application in irregular bone defect regeneration

AbstractComplex shaped bone defects that need to be filled are very common in clinic. But after filling, gaps are inevitably left between substitutes and host bone due to the poor conformability of preformed implants, hence hindering bone regeneration. Therefore, based on our previous study, we here used the bioink (named PPG) composed of polyurethane, polyacrylamide, and gelatin with optimized composition ratio to three‐dimensionally (3D) print an inorganic/organic composite hydrogel scaffold with self‐expandability to fill irregular bone defects and bioactivity to accelerate bone healing through adjusting the content of bioactive ceramic (BC). The results indicated that, the 3D printed BC/PPG scaffold had a rough surface on each fiber; with the incorporation of BC powders, the composite hydrogel scaffolds in swelling experiments could perform a comparable self‐adaptability to PPG hydrogel scaffold; the bioactive ions including Ca, Mg, and Si could be released from the composite scaffold and induce the rapid deposition of bone‐like apatite. The mechanical tests proved that the BC(10%)/PPG scaffold was the top performer under compression. The in vitro cell assessment illustrated that compared with PPG hydrogel scaffold, the BC/PPG composite scaffolds were more favorable to the proliferation and spreading of bone mesenchymal stem cells (BMSCs).

A novel flexible, conductive, and three-dimensional reduced graphene oxide/polyurethane scaffold for cell attachment and bone regeneration

Development of conductive and three-dimensional scaffolds with elastic properties and shape-recovery capability for bone regeneration within irregular bone cavities has been challenging. Polyurethanes (PUs) are intrinsically elastic polymers; however, their mechanical performance, biocompatibility, and functionality need to be improved for application as implants and biomedical devices. Herein, application of a novel flexible, conductive, and three-dimensional polyurethane scaffold (3DPU), fabricated through coating a commercial PU foam with graphene oxide (GO) and its subsequent reduction with ascorbic acid, described as 3DrGO/PU, is investigated for bone regeneration. The 3DrGO/PU scaffold supported the growth and proliferation of mouse osteoblast cells (MG-63) with strong mineralization and cell attachment. It is likely that the electrically conductive macro-porous 3DrGO/PU scaffold, provides bioactivity and promote nucleation and growth of hydroxyapatite (HA) in the simulated body fluid. Experiments assessing in vivo bone formation in rat calvarial skull defects provided clear evidence for efficacy of the 3D scaffold for treatment of irregular bone defects. The results of this study are promising, as they present easy production of a cost-effective green fabricated scaffold. It also offers a potential for cell attachment and capture, to be used in future tissue engineering and even biosensing applications.

3D Contour Printing of Anatomically Mimetic Cartilage Grafts with Microfiber-Reinforced Double-Network Bioink.

Bioprinting is an emerging technology for fabricating cell-laden scaffolds with custom shapes that resemble the complex architecture of human tissues, however, construction of mechanically competent tissue grafts which mimic irregular cartilage defect is still a big challenge. Here, 3D printing of short fiber-reinforced double-network bioink to generate anatomically accurate and mechanical tunable scaffold for cartilage regeneration is reported. Poly(lactic acid) (PLLA) short fibers are first prepared by electrospinning and then fragmented through aminolysis reaction. Composite inks are constructed with an incorporation of fragmented microfibers with varied amounts and lengths into oxidized alginate bioink. The results show that incorporation of PLLA short fibers not only improves the printing fidelity but also facilitates in generating mechanically strong constructs. By incorporating gelatin methacryloyl (GelMA) and optimizing the bioink composition, the fabricated constructs with a compressive stress of ≈150 kPa even after 100 cyclical compression loading (up to 40% of strain) are achieved. In addition, this mechanically reinforced alginate/GelMA double-network bioink displays good biocompatibility and supports bone marrow-derived stromal cell chondrogenesis in vitro. Collectively, these findings demonstrate this approach is capable of printing engineered grafts which resemble the irregular size and mechanical properties of cartilage and thus hold potential for functional tissue regeneration.

Triple-functional injectable liposome–hydrogel composite enhances bacteriostasis and osteo/angio-genesis for advanced maxillary sinus floor augmentation

Bone-grafting biological materials are commonly used to increase the height of the alveolar bone in the maxillary posterior region during maxillary sinus floor augmentation. However, there has been little research on the development of an injectable bone-grafting material with bacteriostatic, angiogenic, and osteogenic properties. In this work, we developed a triple-functional vancomycin/deferoxamine/dexamethasone (Van/DFO/Dex) liposome–hydrogel composite with desirable injectability. The release kinetics confirmed orderly sustained release of Van (a bacteriostat), DFO (a vascularised small molecule), and Dex (an osteogenic small molecule). In vitro findings demonstrated the favourable cytocompatibility and antibacterial ability of this composite against Staphylococcus aureus. Additionally, the angiogenic ability of human umbilical vein endothelial cells and osteogenic differentiation activity of MC3T3-E1 cells were enhanced. An in vivo bacteriostasis assay and rabbit maxillary sinus floor augmentation model corroborated the enhanced bacteriostasis and vascularised bone regeneration properties of this functionalised composite. Overall, the favourable injectability to be fit for the minimally invasive procedure, locally sustained release property, and prominent biological functions underscore the clinical potential of Van/DFO/Dex as an ideal bone-grafting material for irregular bone defect repairs, such as maxillary sinus floor augmentation.

Construction of poly-(γ-benzyl‐l‐glutamate) composite microcarriers with osteogenic and angiogenic properties for the restoration of alveolar bone defects

The repair of alveolar bone defects is one of the urgent clinical problems to be solved. Injectable microcarriers show great potential for bone repair due to their ability to fill irregular bone defects. In this study, the ICA@nCP/nHA-g-PBLG composite microcarriers with osteogenic and angiogenic properties were fabricated via double emulsion (W/O/W) method. Firstly, poly-(γ-benzyl‐l‐glutamate) (PBLG) was linkaged onto the surface of nano copper hydroxyphosphate (nCP) and nano hydroxyapatite (nHA) to construct nCP-g-PBLG and nHA-g-PBLG nanohybrids by chemical grafting, respectively. Then, nCP/nHA-g-PBLG porous microcarriers were fabricated via double emulsion (W/O/W) method and immersed in icariin (ICA) solution to obtain ICA@nCP/nHA-g-PBLG composite microcarriers. The composite microcarriers were more conducive to the proliferation of bone marrow mesenchymal stem cells (BMSCs) when the content of nCP and ICA in the composite microcarriers were 0.5 wt% and 0.1 wt%, respectively. The release of Cu2+ in nCP could promote angiogenesis, while the release of ICA could promote the osteogenic differentiation of BMSCs. The ability of ICA@nCP/nHA-g-PBLG microcarriers to restore alveolar bone defects was proved in a rabbit model. In conclusion, the ICA@nCP/nHA-g-PBLG microcarriers exhibited two functions: osteogenesis and angiogenesis, which could be served as a promising implant for alveolar bone defects repair.

Hybrid electrochemical additive and subtractive manufacturing (HEASM) based on simultaneous mask electrochemical deposition and dissolution

This paper proposed a method for hybrid electrochemical additive and subtractive manufacturing (HEASM) to fabricate microstructures with high-dimensional accuracy and good surface quality. Electrochemical additive manufacturing is achieved by applying positive pulses between the electrodes and then negative pulses are subsequently applied to achieve electrochemical finishing of the shape and surface. In this study, the formation of irregular surface defects was investigated, and a verification experiment was carried out. The inter-electrode pulse waveform and machining process were observed to characterize the electrochemical deposition and dissolution machining. The effects of pure electrodeposition, HEASM, and excessive electrolysis on the surface morphology were compared experimentally. The results indicate that HEASM can reduce the surface roughness by 45.5% but excessive electrolysis can cause a collapse of edge regions. Finally, Taguchi optimization experiments were carried out, and an optimized parameter combination for HEASM was obtained. A microstructure manufactured with an optimized pulse number ratio 0.6 × 10−2, peak current ratio 0.5, and pulse width ratio 1.0 had the best surface morphology and dimensional accuracy. And its surface roughness and height were 0.343 μm and 33.563 μm, respectively.

A novel sprayable thermosensitive hydrogel coupled with zinc modified metformin promotes the healing of skin wound.

A novel sprayable adhesive is established (ZnMet-PF127) by the combination of a thermosensitive hydrogel (Pluronic F127, PF127) and a coordination complex of zinc and metformin (ZnMet). Here we demonstrate that ZnMet-PF127 potently promotes the healing of traumatic skin defect and burn skin injury by promoting cell proliferation, angiogenesis, collagen formation. Furthermore, we find that ZnMet could inhibit reactive oxygen species (ROS) production through activation of autophagy, thereby protecting cell from oxidative stress induced damage and promoting healing of skin wound. ZnMet complex exerts better effects on promoting skin wound healing than ZnCl2 or metformin alone. ZnMet complex also displays excellent antibacterial activity against Staphylococcus aureus or Escherichia coli, which could reduce the incidence of skin wound infections. Collectively, we demonstrate that sprayable PF127 could be used as a new drug delivery system for treatment of skin injury. The advantages of this sprayable system are obvious: (1) It is convenient to use; (2) The hydrogel can cover irregular skin defect sites evenly in a liquid state. In combination with this system, we establish a novel sprayable adhesive (ZnMet-PF127) and demonstrate that it is a potential clinical treatment for traumatic skin defect and burn skin injury.

Classification of computed thermal tomography images with deep learning convolutional neural network

Thermal tomography (TT) is a computational method for the reconstruction of depth profile of the internal material defects from Pulsed Infrared Thermography (PIT) nondestructive evaluation. The PIT method consists of recording material surface temperature transients with a fast frame infrared camera, following thermal pulse deposition on the material surface with a flashlamp and heat diffusion into material bulk. TT algorithm obtains depth reconstructions of thermal effusivity, which has been shown to provide visualization of the subsurface internal defects in metals. In many applications, one needs to determine the defect shape and orientation from reconstructed effusivity images. Interpretation of TT images is non-trivial because of blurring, which increases with depth due to the heat diffusion-based nature of image formation. We have developed a deep learning convolutional neural network (CNN) to classify the size and orientation of subsurface material defects in TT images. CNN was trained with TT images produced with computer simulations of 2D metallic structures (thin plates) containing elliptical subsurface voids. The performance of CNN was investigated using test TT images developed with computer simulations of plates containing elliptical defects, and defects with shapes imported from scanning electron microscopy images. CNN demonstrated the ability to classify radii and angular orientation of elliptical defects in previously unseen test TT images. We have also demonstrated that CNN trained on the TT images of elliptical defects is capable of classifying the shape and orientation of irregular defects.

Customized Design 3D Printed PLGA/Calcium Sulfate Scaffold Enhances Mechanical and Biological Properties for Bone Regeneration

Polylactic glycolic acid copolymer (PLGA) has been widely used in tissue engineering due to its good biocompatibility and degradation properties. However, the mismatched mechanical and unsatisfactory biological properties of PLGA limit further application in bone tissue engineering. Calcium sulfate (CaSO4) is one of the most promising bone repair materials due to its non-immunogenicity, well biocompatibility, and excellent bone conductivity. In this study, aiming at the shortcomings of activity-lack and low mechanical of PLGA in bone tissue engineering, customized-designed 3D porous PLGA/CaSO4 scaffolds were prepared by 3D printing. We first studied the physical properties of PLGA/CaSO4 scaffolds and the results showed that CaSO4 improved the mechanical properties of PLGA scaffolds. In vitro experiments showed that PLGA/CaSO4 scaffold exhibited good biocompatibility. Moreover, the addition of CaSO4 could significantly improve the migration and osteogenic differentiation of MC3T3-E1 cells in the PLGA/CaSO4 scaffolds, and the PLGA/CaSO4 scaffolds made with 20 wt.% CaSO4 exhibited the best osteogenesis properties. Therefore, calcium sulfate was added to PLGA could lead to customized 3D printed scaffolds for enhanced mechanical properties and biological properties. The customized 3D-printed PLGA/CaSO4 scaffold shows great potential for precisely repairing irregular load-bearing bone defects.

Precision medicine strategies for spinal degenerative diseases: Injectable biomaterials with in situ repair and regeneration.

As the population ages, spinal degeneration seriously affects quality of life in middle-aged and elderly patients, and prevention and treatment remain challenging for clinical surgeons. In recent years, biomaterials-based injectable therapeutics have attracted much attention for spinal degeneration treatment due to their minimally invasive features and ability to perform precise repair of irregular defects. However, the precise design and functional control of bioactive injectable biomaterials for efficient spinal degeneration treatment remains a challenge. Although many injectable biomaterials have been reported for the treatment of spinal degeneration, there are few reviews on the advances and effects of injectable biomaterials for spinal degeneration treatment. This work reviews the current status of the design and fabrication of injectable biomaterials, including hydrogels, bone cements and scaffolds, microspheres and nanomaterials, and the current progress in applications for treating spinal degeneration. Additionally, registered clinical trials were also summarized and key challenges and clinical translational prospects for injectable materials for the treatment of spinal degenerative diseases are discussed.

Development of Biodegradable Osteopromotive Citrate-Based Bone Putty.

The burden of bone fractures demands development of effective biomaterial solutions, while additional acute events such as noncompressible bleeding further motivate the search for multi-functional implants to avoid complications including osseous hemorrhage, infection, and nonunion. Bone wax has been widely used in orthopedic bleeding control due to its simplicity of use and conformation to irregular defects; however, its nondegradability results in impaired bone healing, risk of infection, and significant inflammatory responses. Herein, a class of intrinsically fluorescent, osteopromotive citrate-based polymer/hydroxyapatite (HA) composites (BPLP-Ser/HA) as a highly malleable press-fit putty is designed. BPLP-Ser/HA putty displays mechanics replicating early nonmineralized bone (initial moduli from ≈2-500kPa), hydration induced mechanical strengthening in physiological conditions, tunable degradation rates (over 2 months), low swelling ratios (<10%), clotting and hemostatic sealing potential (resistant to blood pressure for >24h) and significant adhesion to bone (≈350-550kPa). Simultaneously, citrate's bioactive properties result in antimicrobial (≈100% and 55% inhibition of S. aureus and E. coli) and osteopromotive effects. Finally, BPLP-Ser/HA putty demonstrates in vivo regeneration in a critical-sized rat calvaria model equivalent to gold standard autograft. BPLP-Ser/HA putty represents a simple, off-the-shelf solution to the combined challenges of acute wound management and subsequent bone regeneration.

Photonic crystal based biosensor with the irregular defect for detection of blood plasma

Truncated 1D photonic crystals-based biosensors with aperiodic defects under the Kretschmann configuration are investigated for sensing the refractive index changes in an aqueous solution polluted with blood components like plasma (n=1.35). The aperiodic defect cells are three types of Fibonacci sequences (S2, S3, and S4) made of two Dirac semimetal and dielectric materials. Dirac semimetal materials have considerably tunable permittivities and conductivities and evidence have shown that light-matter coupling is stronger than previously known materials like graphene. The Bloch surface waves and defect modes are the results of breaking the periodicity in an ordinary 1D photonic crystal that appeared in the photonic band gaps. The influence of the irregular, periodic defect layer on the hybridization of the defect and surface modes and the performance of the proposed biosensors are investigated by using the well-known transfer matrix method. The effect of the defect layer thicknesses is also taken into account. Plotting the electric field profile shows that the modes in the crossing region change their roles and those following the slope of the modes in the defectless structure have better sensing performance than farther ones. In addition, results show that the figure of merit of the structures (N′=2, N=4) using the aperiodic defect with mentioned Fibonacci sequences (FOM(S3)=525 and FOM(S4)=508) is considerably better than those made of periodic defects (FOM(S2)=406).

A novel protocol for injectable artificial cartilage constructs based on programmed shape-morphing hydrogels for cartilage regeneration

Direct contact between cells is of great significance to the formation of natural tissues, especially in regard to cartilage differentiation, which begins with the biological process of cell aggregation. Herein, based on the preparation of microspheres via microwells, we prepared functional hydrogel-based microwells by using cobalt ionic crosslinking. The preparation of functional microwells can not only induce the upregulation of genes and proteins related to cartilage differentiation but also greatly reduce markers related to hypertrophy and mineralization, which play a significant role in the formation of hyaline cartilage. Importantly, we combined microwell cultures with the later preparation of injectable artificial cartilage grafts. In vitro, microwell culture and cartilage differentiation induction can be achieved through the preparation of microwells crosslinked by ions. Via the partial removal of ions, the hydrogel and microtissues can be injected into the defect through the shape recovery of the gel in the later stage and through the stable gel formed by covalent crosslinking to repair irregular cartilage defects. This study not only broadens the application of microwells but also promotes the progress of material-based tissue engineering strategies through the design of intelligent materials.

A novel porous granular scaffold for the promotion of trabecular bone repair by time-dependent alteration of morphology.

Granular scaffolds have been extensively used in the clinic to repair irregular maxillofacial defects. There remain some challenges for the repair of trabecular structures in cancellous bone due to the reticular lamella-like morphology. In this study, we fabricated a novel granular scaffold by rational design of components with different degradation rates so that the morphology of the novel scaffold can evolve to match the growth period of bone cells. Here, polycaprolactone (PCL) was used to fabricate porous microspheres as a skeleton with slow degradation. The macropores were filled with quick degraded gelatin to form complete microspheres. Asynchronous degradation of the two components altered the morphology of the evolutive scaffold from compact to porous, gradually exposing the ridge-like skeletons. This scaffold reversed the decline of cellular adhesion to simple porous skeletons during the initial adhesion. Furthermore, the cells were able to grow into the pores and adhere onto the skeletons with an elongated cellular morphology, facilitating osteogenic differentiation. This novel scaffold was experimentally proven to promote the regeneration of alveolar bone along with a good percentage of bone volume and the formation of trabecular structures. We believe this morphology-evolved scaffold is highly promising for regenerative applications in the clinic.

Study of oxygen-deficient W18O49-based drug delivery system readily absorbed through cellular internalization pathways in tumor-targeted chemo-/photothermal therapy.

W18O49-mediated photothermal therapy (PTT) is affected by the easily oxidized property and its direct exposure to physiological environment can cause biological events, which limit its development in the biomedical field. Herein, a composite nanoparticle PVP-W18O49@C (PW@C), with significant antioxidant and excellent biocompatibility, was constructed to overcome the limitations of W18O49 in the medical field. Oxygen-deficient W18O49, with irregular defect structure, was combined with hollow carbon nanospheres treated by reflux to obtain W18O49@C (W@C) similar to sea urchins. Compared with W18O49, W@C shows stronger antioxidant properties, and it still has the ability to convert light energy to heat energy after 6months. In addition, polyvinyl pyrrolidone is coated on the surface of W@C to construct PW@C, which significantly improves biocompatibility of W@C. The photothermal conversion efficiency of PW@C was 42.9±1.3. PWD (PW@C loaded with DOX·HCl) showed controllable drug release behavior under pH and NIR stimulation, and the drug release rate reached 69.1±1.6% at pH=5.0. Notably, PWD was readily absorbed by cells through clathrin/caveolae-mediated internalization channels, and the viability of HeLa cells treated with PWD+NIR was only 21.5±1.0%. Through photothermal, drug delivery/release and cytotoxicity evaluation, PWD was proved to be an effective platform for chemo-/photothermal combinational tumor therapy.

Conjugated cobalt polyphthalocyanine with defective π-π extended structure for enhanced rechargeable li-oxygen batteries

The urgent demand for high-energy and high-power energy storage devices initiates considerable interest for Li-O2 batteries. Considering the catalytic reaction that happened on the cathode, the electrocatalyst plays a key role in deciding the performance of Li-O2 batteries. Herein, a cobalt polyphthalocyanine with defective polymeric layered structure (D-CoPPc) is prepared by an annealing treatment. The macromolecular structure of D-CoPPc overcomes the dissolution of cobalt phthalocyanine (CoPc) therefore guarantying structural stability. Such a distinctive structure provides imperative features for Li-O2 batteries involving the intrinsic high catalytic activity of CoPc unit, high conductivity given by π-π extended conjugated skeleton. Moreover, the introduced irregular structural defects are expected to promote the diffusion of oxygen. As a result, Li-O2 battery with D-CoPPc as a catalyst achieves a high specific capacity of 4.0 mA h cm−2 at a current density of 50 μA cm−2, a remarkable rate capability with the discharge voltage reached at 2.55 V at a current density of 500 μA cm−2, and a superior cycling stability of more than 1000 h at 20 μA cm−2. As such, the presented framework tailoring and defect engineering strategy open new avenues to regulate the catalytic activity for high-performance metal–oxygen batteries.