Polysaccharide based supramolecular injectable hydrogels for in situ treatment of bladder cancer

Implantable system maximizes drug concentration and continuously releases drugs near the tumor,which is an effective tool to solve the difficult retention of chemotherapy drugs in bladder cancer.In this work,a novel polysaccharide supramolecular injectable hydrogel(CCA hydrogels for short)is rapidly constructed by simply mixing cationic chitosan,anionic sulfobutyl etherβ-cyclodextrin(SBE-β-CD)and a trace amount of silver ions.The injected hydrogel reconstituted and regained its shape in less than 1 h,and it can still maintain the elasticity suitable for the human body.By packaging the drug directly,the gel achieves a high concentration of doxorubicin,an anticancer drug.Using MB49-luc cells as the model of bladder tumor for anti-tumor in vivo,the CCA-DOX gel has obvious inhibitory effect on bladder tumor,and its inhibitory effect is much greater than that of free DOX.Therefore,this self-healing injectable hydrogel has great potential for in situ treatment of bladder cancer.

Therapeutic neovascularization promoted by injectable hydrogels

The aim of therapeutic neovascularization is to repair ischemic tissues via formation of new blood vessels by delivery of angiogenic growth factors,stem cells or expansion of pre-existing cells.For efficient neovascularization,controlled release of growth factors is particularly necessary since bolus injection of molecules generally lead to a poor outcome due to inadequate retention within the injured site.In this regard,injectable hydrogels,made of natural,synthetic or hybrid biomaterials,have become a promising solution for efficient delivery of angiogenic factors or stem and progenitor cells for in situ tissue repair,regeneration and neovascularization.This review article will broadly discuss the state-of-the-art in the development of injectable hydrogels from natural and synthetic precursors,and their applications in ischemic tissue repair and wound healing.We will cover a wide range of in vitro and in vivo studies in testing the functionalities of the engineered injectable hydrogels in promoting tissue repair and neovascularization.We will also discuss some of the injectable hydrogels that exhibit self-healing properties by promoting neovascularization without the presence of angiogenic factors.

Injectable Self‑Healing Adhesive pH‑Responsive Hydrogels Accelerate Gastric Hemostasis and Wound Healing

Endoscopic mucosal resection(EMR)and endoscopic submucosal dissection(ESD)are well-established therapeutics for gastrointestinal neoplasias,but complications after EMR/ESD,including bleeding and perforation,result in additional treatment morbidity and even threaten the lives of patients.Thus,designing biomaterials to treat gastric bleeding and wound healing after endoscopic treatment is highly desired and remains a challenge.Herein,a series of injectable pH-responsive selfhealing adhesive hydrogels based on acryloyl-6-aminocaproic acid(AA)and AA-g-N-hydroxysuccinimide(AA-NHS)were developed,and their great potential as endoscopic sprayable bioadhesive materials to efficiently stop hemorrhage and promote the wound healing process was further demonstrated in a swine gastric hemorrhage/wound model.The hydrogels showed a suitable gelation time,an autonomous and efficient self-healing capacity,hemostatic properties,and good biocompatibility.With the introduction of AA-NHS as a micro-cross-linker,the hydrogels exhibited enhanced adhesive strength.A swine gastric hemorrhage in vivo model demonstrated that the hydrogels showed good hemostatic performance by stopping acute arterial bleeding and preventing delayed bleeding.A gastric wound model indicated that the hydrogels showed excellent treatment effects with significantly enhanced wound healing with type I collagen deposition,α-SMA expression,and blood vessel formation.These injectable self-healing adhesive hydrogels exhibited great potential to treat gastric wounds after endoscopic treatment.

“Ferrero-like”nanoparticles knotted injectable hydrogels to initially scavenge ROS and lastingly promote vascularization in infarcted hearts

Myocardial infarction(MI)exhibits a complicated and ever-accelerated pathological change involving excessive reactive oxygen species(ROS)and the up-regulation of pro-inflammatory cytokines in the initial stage,and a permanently inadequate blood supply.Herein,an injectable hydrogel fabricated by nanoparticles(NPs)knotted thiolated hyaluronic acid(HA-SH)was reported to reverse the hostile microenvironment and rebuild the heart functions after MI.Inspired by the composite shell-core structure of Ferrero chocolate sphere,a mimetic nanocarrier was designed to consist of the hydrophobic dimethyloxalylglycine(DMOG)NPs core and a thick polydopamine(PDA)shell formed by the self-polymerization of dopamine embedded with watersoluble drug epigallocatechin-3-gallate(EGCG)throughπ-πinteractions.The resulted"Ferrero-like"NPs exhibited a"three-inone"capacity,namely loading two distinct drugs,elimination of ROS,and serving a crosslinker to knot HA-SH."Ferrero-like"NPs and HA-SH could rapidly form a hydrogel that exhibited a stable mechanical property,high capability to capture ROS,and programmed release of EGCG and DMOG.Four weeks after deploying the"Ferrero-like"NPs knotted hydrogels into rat infarcted hearts,the ejection fraction(EF)increased by 23.7%,and the infarct size decreased by 21.1%,and the fibrotic area reduced by 24.4%.The outcomes of immunofluorescence staining and reverse transcription-polymerase chain reaction(RTPCR)demonstrated a down-regulation of inflammatory factors(tumor necrosis factor-α(TNF-α),interleukin-1β(IL-1β),interferon-γ(IFN-γ)),up-regulation of vascular related growth factors(hypoxia inducible factor-1α(HIF-1α),vascular endothelial growth factor A(VEGFA),von Willebrand factor(vWF),angiopoietin-1(Ang-1))and cardiac-related m RNAs(gap junction protein(Cx43),Cadherin 2).All in all,in this report,a very simple approach to intertemporally address the intricate and ongoing pathological changes after MI by injecting"Ferrero-like"NPs knotted hydrogels is developed to reverse hostile microenvironment,with an ability to scavenge ROS,down-regulate pro-inflammation factors in the first stage,and promote angiogenesis in a long term,thereby contributing to a significant improvement of heart functions.

Injectable hydrogels for spinal cord injury repair

Spinal cord injury(SCI)often causes severe functional impairment of body,which leads to a huge burden to the patient and the whole society.Many strategies,especially biomaterials,have been employed for SCI repair.Among various biomaterials,injectable hydrogels have attracted much attention because of their ability to load functional components and be injected into the lesioned area without surgeries.In this review,we summarize the recent progress in injectable hydrogels for SCI repair.We firstly introduce the pathophysiology of SCI,which reveals the mechanism of clinical manifestations and determines the therapeutic schedule.Then,we describe the original sources of polymers and the crosslinking manners in forming hydrogels.After that,we focus on the in vivo therapeutic strategies and effects of injectable hydrogels.Finally,the recent challenges and future outlook of injectable hydrogel for SCI repair are concluded and discussed.We believe this review can be helpful and inspire the further development of injectable hydrogels for SCI repair.

Multimodal therapy strategies based on hydrogels for the repair of spinal cord injury

Spinal cord injury(SCI)is a serious traumatic disease of the central nervous system,which can give rise to the loss of motor and sensory function.Due to its complex pathological mechanism,the treatment of this disease still faces a huge challenge.Hydrogels with good biocompatibility and biodegradability can well imitate the extracellular matrix in the microenvironment of spinal cord.Hydrogels have been regarded as promising SCI repair material in recent years and continuous studies have confirmed that hydrogel-based therapy can effectively eliminate inflammation and promote spinal cord repair and regeneration to improve SCI.In this review,hydrogel-based multimodal therapeutic strategies to repair SCI are provided,and a combination of hydrogel scaffolds and other therapeutic modalities are discussed,with particular emphasis on the repair mechanism of SCI.

Bioinspired Injectable Self-Healing Hydrogel Sealant with Fault-Tolerant and Repeated Thermo-Responsive Adhesion for Sutureless Post-Wound-Closure and Wound Healing

Hydrogels with multifunctionalities,including sufficient bonding strength,injectability and self-healing capacity,responsive-adhesive ability,fault-tolerant and repeated tissue adhesion,are urgently demanded for invasive wound closure and wound healing.Motivated by the adhesive mechanism of mussel and brown algae,bioinspired dynamic bonds cross-linked multifunctional hydrogel adhesive is designed based on sodium alginate(SA),gelatin(GT)and protocatechualdehyde,with ferric ions added,for sutureless post-wound-closure.The dynamic hydrogel cross-linked through Schiff base bond,catechol-Fe coordinate bond and the strong interaction between GT with temperature-dependent phase transition and SA,endows the resulting hydrogel with sufficient mechanical and adhesive strength for efficient wound closure,injectability and self-healing capacity,and repeated closure of reopened wounds.Moreover,the temperature-dependent adhesive properties endowed mispositioning hydrogel to be removed/repositioned,which is conducive for the fault-tolerant adhesion of the hydrogel adhesives during surgery.Besides,the hydrogels present good biocompatibility,near-infrared-assisted photothermal antibacterial activity,antioxidation and repeated thermo-responsive reversible adhesion and good hemostatic effect.The in vivo incision closure evaluation demonstrated their capability to promote the post-wound-closure and wound healing of the incisions,indicating that the developed reversible adhesive hydrogel dressing could serve as versatile tissue sealant.

Preparation and Evaluation of an Injectable Chitosan-Hyaluronic Acid hydrogel for Peripheral Nerve Regeneration

The aim of this study was to obtain the fillers in the lumen of hollow nerve conduits（NCs） to improve the microenvironment of nerve regeneration. A p H-induced injectable chitosan（CS）-hyaluronic acid（HA） hydrogel for nerve growth factor（NGF） sustained release was developed. Its properties were characterized by gelation time, FT-IR, SEM, in vitro swelling and degradation. Furthermore, the in vitro NGF release profiles and cell biocompatibility were also investigated. The experimental results show that the CS-HA aqueous solution can undergo a rapid gelation 3 minutes after its environmental p H is changed to 7.4. The CSHA hydrogel has interconnected channels with a controllable pore diameter and with a porosity of about 80%. It has a favorable swelling behavior and can be degraded by about 70% within 8 weeks in vitro and is suitable for NGF release. The CS-HA/NGF hydrogel exhibits a lower cytotoxicity and is in favor of the adhesion and proliferation of the BMMSCs cells. It is indicated that the CS-HA/NGF will be a promising candidate for neural tissue engineering.

Injectable“cocktail”hydrogel with dual-stimuli-responsive drug release,photothermal ablation,and drug-antibody synergistic effect

The combination of the first-line standard chemotherapeutic drug doxorubicin hydrochloride(DOX)and the molecular-targeted drug Herceptin(HCT)has emerged as a promising strategy for human epidermal growth receptor 2(HER-2)overexpressing breast cancer treatment.However,insufficient drug accumulation and severe cardiotoxicity are two major challenges that limit its clinical application.Herein,an in situ forming gold nanorods(AuNRs)-sodium alginate(ALG)hybrid hydrogel encapsulating DOX and HCT was engineered for tumor synergistic therapy involving injectable,dual-stimuli-responsive drug release,photothermal ablation,and drug-antibody synergistic therapy.The photothermal agent AuNRs,anticancer drug DOX,and anticancer antibody HCT were mixed in ALG solution,and after injection,the soluble ALG was quickly transformed into a hydrogel in the presence of Ca^(2+)in the body.Significantly,the hybrid hydrogel exhibits an extremely high photothermal conversion efficiency of 70%under 808 nm laser irradiation.The thermal effect can also provide photothermal stimulation to trigger the drug release from the gel matrix.In addition,the drug release rate and the releasing degree are also sensitive to the pH.In vitro studies demonstrated that the PEI-AuNR/DOX/HCT/ALG hydrogel has facilitated the therapeutic efficiency of each payload and demonstrated a strong synergistic killing effect on SK-BR-3 cells.In vivo imaging results showed that the local drug delivery system can effectively reduce the nonspecific distribution in normal tissues and increase drug concentration at tumor sites.The proposed hydrogel system shows significant clinical implications by easily introducing a sustainable photothermal therapy and a potential universal carrier for the local delivery of multiple drugs to overcome the challenges faced in HER-2 overexpressing cancer therapy.

Injectable reactive oxygen and nitrogen species-controlling hydrogels for tissue regeneration:current status and future perspectives

The dual role of reactive oxygen and nitrogen species(RONS)in physiological and pathological processes in biological systems has been widely reported.It has been recently suggested that the regulation of RONS levels under physiological and pathological conditions is a potential therapy to promote health and treat diseases,respectively.Injectable hydrogels have been emerging as promising biomaterials for RONS-related biomedical applications owing to their excellent biocompatibility,three-dimensional and extracellular matrix-mimicking structures,tunable properties and easy functionalization.These hydrogels have been developed as advanced injectable platforms for locally generating or scavenging RONS,depending on the specific conditions of the target disease.In this review article,the design principles and mechanism by which RONS are generated/scavenged from hydrogels are outlined alongside a discussion of their in vitro and in vivo evaluations.Additionally,we highlight the advantages and recent developments of these injectable RONS-controlling hydrogels for regenerativemedicines and tissue engineering applications.

An injectable bioactive dressing based on platelet-rich plasma and nanoclay:Sustained release of deferoxamine to accelerate chronic wound healing

Delayed diabetic wound healing has placed an enormous burden on society.The key factors limiting wound healing include unresolved inflammation and impaired angiogenesis.Platelet-rich plasma(PRP)gel,a popular biomaterial in the field of regeneration,has limited applications due to its non-injectable properties and rapid release and degradation of growth factors.Here,we prepared an injectable hydrogel(DPLG)based on PRP and laponite by a simple one-step mixing method.Taking advantages of the non-covalent interactions,DPLG could overcome the limitations of PRP gels,which is injectable to fill irregular injures and could serve as a local drug reservoir to achieve the sustained release of growth factors in PRP and deferoxamine(an angiogenesis promoter).DPLG has an excellent ability in accelerating wound healing by promoting macrophage polarization and angiogenesis in a full-thickness skin defect model in typeⅠdiabetic rats and normal rats.Taken together,this study may provide the ingenious and simple bioactive wound dressing with a superior ability to promote wound healing.

Promoting lacunar bone regeneration with an injectable hydrogel adaptive to the microenvironment

Injectable hydrogel is suitable for the repair of lacunar bone deficiency.This study fabricated an injectable,self-adaptive silk fibroin/mesoporous bioglass/sodium alginate(SMS)composite hydrogel system.With controllable and adjustable physical and chemical properties,the SMS hydrogel could be easily optimized adaptively to different clinical applications.The SMS hydrogel effectively showed great injectability and shapeability,allowing defect filling with no gap.Moreover,the SMS hydrogel displayed self-adaptability in mechanical reinforcement and degradation,responsive to the concentration of Ca2+and inflammatory-like pH value in the microenvi-ronment of bone deficiency,respectively.In vitro biological studies indicated that SMS hydrogel could promote osteogenic differentiation of bone marrow mesenchymal stem cells by activation of the MAPK signaling pathway.The SMS hydrogel also could improve migration and tube formation of human umbilical vein endothelial cells.Investigations of the crosstalk between osteoblasts and macrophages confirmed that SMS hydrogel could regulate macrophage polarization from M1 to M2,which could create a specific favorable environment to induce new bone formation and angiogenesis.Meanwhile,SMS hydrogel was proved to be antibacterial,especially for gram-negative bacteria.Furthermore,in vivo study indicated that SMS could be easily applied for maxillary sinus elevation,inducing sufficient new bone formation.Thus,it is convincing that SMS hydrogel could be potent in a simple,minimally invasive and efficient treatment for the repair of lacunar bone deficiency.

An injectable conductive hydrogel restores electrical transmission at myocardial infarct site to preserve cardiac function and enhance repair

Myocardial infarction(MI)leads to massive cardiomyocyte death and deposition of collagen fibers.This fibrous tissue disrupts electrical signaling in the myocardium,leading to cardiac systolic and diastolic dysfunction,as well as arrhythmias.Conductive hydrogels are a promising therapeutic strategy for MI.Here,we prepared a highly water-soluble conductive material(GP)by grafting polypyrrole(PPy)onto non-conductive gelatin.This component was added to the gel system formed by the Schiff base reaction between oxidized xanthan gum(OXG)and gelatin to construct an injectable conductive hydrogel.The prepared self-healing OGGP3(3 wt%GP)hydrogel had good biocompatibility,elastic modulus,and electrical conductivity that matched the natural heart.The prepared biomaterials were injected into the rat myocardial scar tissue 2 days after MI.We found that the cardiac function of the rats treated with OGGP3 was improved,making it more difficult to induce arrhythmias.The electrical resistivity of myocardial fibrous tissue was reduced,and the conduction velocity of myocardial tissue was increased.Histological analysis showed reduced infarct size,increased left ventricular wall thickness,increased vessel density,and decreased inflammatory response in the infarcted area.Our findings clearly demonstrate that the OGGP3 hydrogel attenuates ventricular remodeling and inhibits infarct dilation,thus showing its potential for the treatment of MI.

Injectable bioorthogonal hydrogel (BIOGEL) accelerates tissue regeneration in degenerated intervertebral discs

Intervertebral disc(IVD)degeneration is a leading cause of back pain and precursor to more severe conditions,including disc herniation and spinal stenosis.While traditional growth factor therapies(e.g.,TGFβ)are effective at transiently reversing degenerated disc by stimulation of matrix synthesis,it is increasingly accepted that bioscaffolds are required for sustained,complete IVD regeneration.Current scaffolds(e.g.,metal/polymer composites,non-mammalian biopolymers)can be improved in one or more IVD regeneration demands:biodegradability,noninvasive injection,recapitulated healthy IVD biomechanics,predictable crosslinking,and matrix repair induction.To meet these demands,tetrazine-norbornene bioorthogonal ligation was combined with gelatin to create an injectable bioorthogonal hydrogel(BIOGEL).The liquid hydrogel precursors remain free-flowing across a wide range of temperatures and crosslink into a robust hydrogel after 5-10 min,allowing a human operator to easily inject the therapeutic constructs into degenerated IVD.Moreover,BIOGEL encapsulation of TGFβpotentiated histological repair(e.g.,tissue architecture and matrix synthesis)and functional recovery(e.g.,high water retention by promoting the matrix synthesis and reduced pain)in an in vivo rat IVD degeneration/nucleotomy model.This BIOGEL procedure readily integrates into existing nucleotomy procedures,indicating that clinical adoption should proceed with minimal difficulty.Since bioorthogonal crosslinking is essentially non-reactive towards biomolecules,our developed material platform can be extended to other payloads and degenerative injuries.

An injectable alginate/fibrin hydrogel encapsulated with cardiomyocytes and VEGF for myocardial infarction treatment

Myocardial infarction(MI)is one of the typical cardiovascular diseases,which persist as the leading cause of death globally.Due to the poor regenerative capability of endogenous cardiomyocytes(CMs),the transplantation of exogenous CMs becomes a promising option for MI treatment.However,the low retention and survival of transplanted cells still limit the clinical translation of cell therapy.Herein,an alginate/fibrin-based injectable hydrogel was prepared for the delivery of neonatal CMs and an angiogen-esis agent vascular endothelial growth factor(VEGF)locally to the infarcted area of the heart.This hydro-gel combined the specific advantages of alginate and fibrin with proper mechanical properties and cell affinity,showing good biocompatibility to support the retention and integration of the transplanted CMs to the host myocardium.Moreover,the delivered VEGF was favorable for the blood recovery to mitigate the ischemic microenvironment of the infarcted area and thus improved the survival of the transplanted CMs.Intramyocardial injection of this hydrogel to the infarcted area of the heart promoted angiogenesis,inhibited fibrosis,and improved cardiac function,exhibiting great potential for MI treatment.

Thermosensitive injectable hydrogel loaded with hypoxia-induced exosomes maintains chondrocyte phenotype through NDRG3-mediated hypoxic response

Current clinical treatments cannot effectively delay the progression of osteoarthritis(OA).Consequently,joint replacement surgery is required for late-stage OA when patients cannot tolerate pain and joint dysfunction.Therefore,the prevention of OA progression in the early and middle stages is an urgent clinical problem.In a previous study,we demonstrated that NDRG3-mediated hypoxic response might be closely related to the development and progression of OA.In this study,an injectable thermosensitive hydrogel was established by cross-linking Pluronic F-127 and hyaluronic acid(HA)for the sustained release of hypoxia-induced exosomes(HExos)derived from adipose-derived mesenchymal stem cells.We demonstrated that for OA at the early and middle stages,the HExos-loaded HP hydrogel could maintain the chondrocyte phenotype by enhancing chondrocyte autophagy,reducing chondrocyte apoptosis,and promoting chondrocyte activity and proliferation through the NDRG3-mediated hypoxic response.This novel composite hydrogel,which could activate the NDRG3-mediated hypoxic response,may provide new ideas and a theoretical basis for the treatment of early-and mid-stage OA.

Shear-responsive boundary-lubricated hydrogels attenuate osteoarthritis

Lipid-based boundary layers formed on liposome-containing hydrogels can facilitate lubrication.However,these boundary layers can be damaged by shear,resulting in decreased lubrication.Here,a shear-responsive boundary-lubricated drug-loaded hydrogel is created by incorporating celecoxib(CLX)-loaded liposomes within dynamic covalent bond-based hyaluronic acid(HA)hydrogels(CLX@Lipo@HA-gel).The dynamic cross-linked network enables the hydrogel to get restructured in response to shear,and the HA matrix allows the accumulation of internal liposome microreservoirs on the sliding surfaces,which results in the formation of boundary layers to provide stable lubrication.Moreover,hydration shells formed surrounding the hydrogel can retard the degradation process,thus helping in sustaining lubrication.Furthermore,in vitro and in vivo experiments found that CLX@Lipo@HA-gels can maintain anabolic-catabolic balance,alleviate cartilage wear,and attenuate osteoarthritis progression by delivering CLX and shear-responsive boundary lubrication.Overall,CLX@Lipo@HA-gels can serve as shear-responsive boundary lubricants and drug-delivery vehicles to alleviate friction-related diseases like osteoarthritis.

A novel degradable injectable HLC-HPA hydrogel with antiinflammatory activity for biomedical materials:Preparation,characterization,in vivo and in vitro evaluation

In situ injectable hydrogels,which have great potential in tissue engineering,are characterized by simple preparation,minimal invasiveness and adaptation to complex shapes.However,injectable hydrogels have higher requirements for biocompatibility and safety due to their use in vivo implantation.Therefore,in this study,a human-like collagen(HLC)-based in situ gel-forming injectable HLC-HPA hydrogel was synthesized by combining the amino group of HLC with the carboxyl group of HPA activated using 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride(EDC)and N-hydroxysuccinimide(NHS),followed by crosslinking by horseradish peroxidase(HRP)and H_2O_2,and used as scaffold material for tissue engineering.The hydrogel stiffness,gel time and biodegradation rate could be easily and independently adjusted by varying the H_2O_2 and HRP concentrations.Scanning electron microscope(SEM)clarified the homogeneous porous and interconnected internal structures of the hydrogel.In vitro cell viability and in vivo degradation experiments confirmed that the HLC-HPA hydrogel had good biodegradability and excellent biocompatibility.Interestingly,in cultured macrophages,the HLC-HPA hydrogel showed anti-inflammatory activity by reducing the amount of the pro-inflammatory cytokines tumor necrosis factor-α(TNF-α)and interleukin-6(IL-6)and increasing the secretion of the anti-inflammatory cytokine interleukin-10(IL-10)induced by lipopolysaccharide(LPS).Meanwhile,in animal experiments,HLC-HPA hydrogels exhibit excellent biocompatibility and have properties of hemostasis and reduction of inflammatory response.Therefore,the HLC-HPA hydrogel prepared in this study has great potential for development for use in the biomedical field.

Advances of injectable hydrogel-based scaffolds for cartilage regeneration

Articular cartilage is an important load-bearing tissue distributed on the surface of diarthrodial joints.Due to its avascular,aneural and non-lymphatic features,cartilage has limited self-regenerative properties.To date,the utilization of biomaterials to aid in cartilage regeneration,especially through the use of injectable scaffolds,has attracted considerable attention.Various materials,therapeutics and fabrication approaches have emerged with a focus on manipulating the cartilage microenvironment to induce the formation of cartilaginous structures that have similar properties to the native tissues.In particular,the design and fabrication of injectable hydrogel-based scaffolds have advanced in recent years with the aim of enhancing its therapeutic efficacy and improving its ease of administration.This review summarizes recent progress in these efforts,including the structural improvement of scaffolds,network cross-linking techniques and strategies for controlled release,which present new opportunities for the development of injectable scaffolds for cartilage regeneration.

Release of VEGF and BMP9 from injectable alginate based composite hydrogel for treatment of myocardial infarction

Myocardial infarction(MI)is one of cardiovascular diseases that pose a serious threat to human health.The pathophysiology of MI is complex and contains several sequential phases including blockage of a coronary artery,necrosis of myocardial cells,inflammation,and myocardial fibrosis.Aiming at the treatment of different stages of MI,in this work,an injectable alginate based composite hydrogel is developed to load vascular endothelial active factor(VEGF)and silk fibroin(SF)microspheres containing bone morphogenetic protein 9(BMP9)for releasing VEGF and BMP9 to realize their respective functions.The results of in vitro experiments indicate a rapid initial release of VEGF during the first few days and a relatively slow and sustained release of BMP9 for days,facilitating the formation of blood vessels in the early stage and inhibiting myocardial fibrosis in the long-term stage,respectively.Intramyocardial injection of such composite hydrogel into the infarct border zone of mice MI model via multiple points promotes angiogenesis and reduces the infarction size.Taken together,these results indicate that the dual-release of VEGF and BMP9 from the composite hydrogel results in a collaborative effect on the treatment of MI and improvement of heart function,showing a promising potential for cardiac clinical application.