Bioinspired extracellular vesicles embedded with black phosphorus for molecular recognition-guided biomineralization

Fostering tissue engineering and regenerative medicine to treat musculoskeletal disorders in bone and muscle

The musculoskeletal system, which is vital for movement, support, and protection, can be impaired by disorders such as osteoporosis, osteoarthritis, and muscular dystrophy. This review focuses on the advances in tissue engineering and regenerative medicine, specifically aimed at alleviating these disorders. It explores the roles of cell therapy, particularly Mesenchymal Stem Cells (MSCs) and Adipose-Derived Stem Cells (ADSCs), biomaterials, and biomolecules/external stimulations in fostering bone and muscle regeneration. The current research underscores the potential of MSCs and ADSCs despite the persistent challenges of cell scarcity, inconsistent outcomes, and safety concerns. Moreover, integrating exogenous materials such as scaffolds and external stimuli like electrical stimulation and growth factors shows promise in enhancing musculoskeletal regeneration. This review emphasizes the need for comprehensive studies and adopting innovative techniques together to refine and advance these multi-therapeutic strategies, ultimately benefiting patients with musculoskeletal disorders.

Enzyme-Activated Biomimetic Vesicles Confining Mineralization for Bone Maturation

Inspired by the crucial role of matrix vesicles (MVs), a series of biomimetic vesicles (BVs) fabricated by calcium glycerophosphate (CaGP) modified polyurethane were designed to mediate the mineralization through in situ enzyme activation for bone therapy. In this study, alkaline phosphatase (ALP) was harbored in the porous BVs by adsorption (Ad-BVs) or entrapment (En-BVs). High encapsulation of ALP on En-BVs was effectively self-activating by calcium ions of CaGP-modified PU that specifically hydrolyzed the organophosphorus (CaGP) to inorganic phosphate, thus promoting the formation of the highly oriented bone-like apatite in vitro. Enzyme-catalyzed kinetics confirms the regulation of apatite crystallization by the synergistic action of self-activated ALP and the confined microcompartments of BVs. This leads to a supersaturated microenvironment, with the En-BVs group exhibiting inorganic phosphate (Pi) levels 4.19 times higher and Ca2+ levels 3.67 times higher than those of simulated body fluid (SBF). Of note, the En-BVs group exhibited excellent osteo-inducing differentiation of BMSCs in vitro and the highest maturity with reduced bone loss in rat femoral defect in vivo. This innovative strategy of biomimetic vesicles is expected to provide valuable insights into the enzyme-activated field of bone therapy.

ZIF-8-Modified Black Phosphorus Nanosheets Incorporated into Injectable Dual-Component Hydrogels for Enhanced Photothermal Antibacterial and Osteogenic Activities

The development of growth factor-free biomaterials for bone tissue regeneration with anti-infection and anti-inflammatory activities remains challenging. Black phosphorus nanosheets (BPNs), with distinctive attributes, including photothermal conversion and calcium ion chelation, offer potential for use in bone tissue engineering and infection prevention. However, BPNs are prone to oxidation and degradation in aqueous environments, and methods to stabilize BPNs for long-term bone repair remain insufficient. Herein, zeolitic imidazolate framework-8 (ZIF-8) was used to stabilize BPNs via in situ crystallization onto the surface of BPNs (BP@ZIF-8 nanocomposite). A novel injectable dual-component hydrogel comprising gelatin methacryloyl (GelMA) and methacrylate-modified hyaluronic acid (HAMA) was used as a BP@ZIF-8 nanocomposite carrier (GelMA/HAMA/BP@ZIF-8). The BP@ZIF-8 nanocomposite could effectively protect internal BPNs from oxidation and enhance the long-term photothermal performance of the hydrogel in both in vitro and in vivo settings. The GelMA/HAMA/BP@ZIF-8 hydrogel was injectable and exhibited outstanding performance for photothermal conversion, mechanical strength, and biodegradability, as well as excellent photothermal antibacterial activity against Staphylococcus aureus and Escherichia coli in vitro and in an in vivo rat model. The GelMA/HAMA/BP@ZIF-8 hydrogel also provided a microenvironment conducive to osteogenic differentiation, promoting the transformation of M2 macrophages and inhibiting inflammatory responses. Furthermore, the hydrogel promoted bone regeneration and had a synergistic effect with near-infrared irradiation in a rat skull-defect model. Transcriptome sequencing analysis revealed that the PI3K-AKT- and calcium-signaling pathways may be involved in promoting osteogenic differentiation induced by the GH-BZ hydrogel. This study presents an innovative, multifaceted solution to the challenges of bone tissue regeneration with antibacterial and anti-inflammatory effects, providing insights into the design of smart biomaterials with dual therapeutic capabilities.

Functionalized BP@(Zn+Ag)/EPLA Nanofibrous Scaffolds Fabricated by Cryogenic 3D Printing for Bone Tissue Engineering

This study fabricates a functionalized scaffold by cryogenic three-dimensional (3D) printing using an aminated poly-L-lactic acid (EPLA) solution containing nanosilver/zinc-coated black phosphorus (BP@(Zn+Ag)) nanocomposites. The nanocomposites are prepared by a green method of in situ photodeposition of silver and zinc nanoparticles (AgNPs and ZnNPs) on BP nanosheets (BPNs) under visible light irradiation without any chemical reductant. Scanning electron microscope (SEM) and X-ray energy dispersive spectrometer (EDS) confirm the uniform distribution of BP@(Zn+Ag) nanoparticles in the EPLA nanofibrous matrix. The in vitro tests show that the fabricated BP@(Zn+Ag)/EPLA nanofibrous scaffold exhibits excellent antibacterial activity (over 96%) against E. coli and S. aureus, as well as enhanced cell viability and osteogenic activity to facilitate the growth and differentiation of osteoblasts. The in vivo rat calvarial defect model also demonstrates that the BP@(Zn+Ag)/EPLA nanofibrous scaffold promotes new bone tissue formation around the implant site. Therefore, the prepared multifunctional 3D printed BP@(Zn+Ag)/EPLA nanofibrous scaffold has great potential for bone tissue engineering (BTE) applications.

Multifunctional Biodegradable Conductive Hydrogel Regulating Microenvironment for Stem Cell Therapy Enhances the Nerve Tissue Repair

The nerve guidance conduits incorporated with stem cells, which can differentiate into the Schwann cells (SCs) to facilitate myelination, shows great promise for repairing the severe peripheral nerve injury. The innovation of advanced hydrogel materials encapsulating stem cells, is highly demanded for generating supportive scaffolds and adaptive microenvironment for nerve regeneration. Herein, this work demonstrates a novel strategy in regulating regenerative microenvironment for peripheral nerve repair with a biodegradable conductive hydrogel scaffold, which can offer multifunctional capabilities in immune regulation, enhancing angiogenesis, driving SCs differentiation, and promoting axon regrowth. The biodegradable conductive hydrogel is constructed by incorporation of polydopamine-modified silicon phosphorus (SiP@PDA) nanosheets into a mixture of methacryloyl gelatin and decellularized extracellular matrix (GelMA/ECM). The biomimetic electrical microenvironment performs an efficacious strategy to facilitate macrophage polarization toward a pro-healing phenotype (M2), meanwhile the conductive hydrogel supports vascularization in regenerated tissue through sustained Si element release. Furthermore, the MSCs 3D-cultured in GelMA/ECM-SiP@PDA conductive hydrogel exhibits significantly increased expression of genes associated with SC-like cell differentiation, thus facilitating the myelination and axonal regeneration. Collectively, both the in vitro and in vivo studies demonstrates that the rationally designed biodegradable multifunctional hydrogel significantly enhances nerve tissues repair.

Strategies and Challenges of Mesenchymal Stem Cells-Derived Extracellular Vesicles in Infertility

Having genetically related offspring remains an unattainable dream for couples with reproductive failure. Mesenchymal stem cells (MSCs) are multipotent stromal cells derived from various human tissues and organs. As critical paracrine effectors of MSCs, extracellular vesicles (EVs) can carry and deliver bioactive content, thereby participating in intercellular communication and determining cell fate. Mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) have shown promising therapeutic effects, including repairing injured endometria, restoration of ovarian functions, and improving sperm quantity, morphology, and motility, owing to their regenerative potential, abundant sources, high proliferation rates, low immunogenicity, and lack of ethical issues. However, limited knowledge on purification and isolation of MSC-EVs, therapeutic effects, and unpredictable safety have caused challenges in overcoming female and male infertility. To overcome them, future studies should focus on modification/engineering of MSC-EVs with therapeutic biomolecules and combining attractive biomaterials and MSC-EVs. This review highlights the latest studies on MSC-EVs therapies in infertility and the major challenges that must be overcome before clinical translation.

Photoacoustic Imaging-Guided Self-Adaptive Hyperthermia Supramolecular Cascade Nano-Reactor for Diabetic Periodontal Bone Regeneration

Commencing with the breakdown of the diabetic osteoimmune microenvironment, multiple pathogenic factors, including hyperglycemia, inflammation, hypoxia, and deleterious cytokines, are conjointly involved in the progression of diabetic periodontal bone regeneration. Based on the challenge of periodontal bone regeneration treatment and the absence of real-time feedback of blood oxygen fluctuation in diabetes mellitus, a novel self-adaptive hyperthermia supramolecular cascade nano-reactor ACFDG is constructed via one-step supramolecular self-assembly strategy to address multiple factors in diabetic periodontal bone regeneration. Hyperthermia supramolecular ACFDG possesses high photothermal conversion efficiency (32.1%), and it can effectively inhibit the vicious cycle of ROS-inflammatory cascade through catalytic cascade reactions, up-regulate the expression of heat shock proteins (HSPs) under near-infrared (NIR) irradiation, which promotes periodontal bone regeneration. Remarkably, ACFDG can provide real-time non-invasive diagnosis of blood oxygen changes during periodontal bone regeneration through photoacoustic (PA) imaging, thus can timely monitor periodontal hypoxia status. In conclusion, this multifunctional supramolecular nano-reactor combined with PA imaging for real-time efficacy monitoring provides important insights into the biological mechanisms of diabetic periodontal bone regeneration and potential clinical theranostics.

In Situ Mitochondrial Biomineralization for Drug-Free Cancer Therapy

The common clinical chemotherapy often brings serious side effects to patients, mainly due to the off-target and leakage of toxic drugs. However, this is fatal for some specific clinical tumors, such as brain tumors and neuroma. This study performs a drug-free approach by encapsulating black phosphorus (BP) and calcium peroxide (CaO2) in liposomes with surface-modified triphenylphosphonium (BCLT) to develop mitochondria targeting calcification for cancer therapy without damaging normal cells. BCLT preferentially accumulates inside tumor mitochondria and then is activated by near-infrared (NIR) laser irradiation to produce abundant PO4 3- and Ca2+ to accelerate in situ mitochondrial mineralization, leading to mitochondrial dysfunction and cancer cell death. More importantly, both PO4 3- and Ca2+ are essential components of metabolism in the body, and random gradient diffusion or premature leakage does not cause damage to adjacent normal cells. This achievement promises to be an alternative to conventional chemotherapy in clinical practice for many specific tumor types.

Multifunctional Conductive and Electrogenic Hydrogel Repaired Spinal Cord Injury via Immunoregulation and Enhancement of Neuronal Differentiation

Spinal cord injury (SCI) is a refractory neurological disorder. Due to the complex pathological processes, especially the secondary inflammatory cascade and the lack of intrinsic regenerative capacity, it is difficult to recover neurological function after SCI. Meanwhile, simulating the conductive microenvironment of the spinal cord reconstructs electrical neural signal transmission interrupted by SCI and facilitates neural repair. Therefore, a double-crosslinked conductive hydrogel (BP@Hydrogel) containing black phosphorus nanoplates (BP) is synthesized. When placed in a rotating magnetic field (RMF), the BP@Hydrogel can generate stable electrical signals and exhibit electrogenic characteristic. In vitro, the BP@Hydrogel shows satisfactory biocompatibility and can alleviate the activation of microglia. When placed in the RMF, it enhances the anti-inflammatory effects. Meanwhile, wireless electrical stimulation promotes the differentiation of neural stem cells (NSCs) into neurons, which is associated with the activation of the PI3K/AKT pathway. In vivo, the BP@Hydrogel is injectable and can elicit behavioral and electrophysiological recovery in complete transected SCI mice by alleviating the inflammation and facilitating endogenous NSCs to form functional neurons and synapses under the RMF. The present research develops a multifunctional conductive and electrogenic hydrogel for SCI repair by targeting multiple mechanisms including immunoregulation and enhancement of neuronal differentiation.

A theragenerative bio-nanocomposite consisting of black phosphorus quantum dots for bone cancer therapy and regeneration

Recently, the term theragenerative has been proposed for biomaterials capable of inducing therapeutic approaches followed by repairing/regenerating the tissue/organ. This study is focused on the design of a new theragenerative nanocomposite composed of an amphiphilic non-ionic surfactant (Pluronic F127), bioactive glass (BG), and black phosphorus (BP). The nanocomposite was prepared through a two-step synthetic strategy, including a microwave treatment that turned BP nanosheets (BPNS) into quantum dots (BPQDs) with 5 ± 2 nm dimensions in situ. The effects of surfactant and microwave treatment were assessed in vitro: the surfactant distributes the ions homogenously throughout the composite and the microwave treatment chemically stabilizes the composite. The presence of BP enhanced bioactivity and promoted calcium phosphate formation in simulated body fluid. The inherent anticancer activity of BP-containing nanocomposites was tested against osteosarcoma cells in vitro, finding that 150 μg mL-1 was the lowest concentration which prevented the proliferation of SAOS-2 cells, while the counterpart without BP did not affect the cell growth rate. Moreover, the apoptosis pathways were evaluated and a mechanism of action was proposed. NIR irradiation was applied to induce further proliferation suppression on SAOS-2 cells through hyperthermia. The inhibitory effects of bare BP nanomaterials and nanocomposites on the migration and invasion of bone cancer, breast cancer, and prostate cancer cells were assessed in vitro to determine the anticancer potential of nanomaterials against primary and secondary bone cancers. The regenerative behavior of the nanocomposites was tested with healthy osteoblasts and human mesenchymal stem cells; the BPQDs-incorporated nanocomposite significantly promoted the proliferation of osteoblast cells and induced the osteogenic differentiation of stem cells. This study introduces a new multifunctional theragenerative platform with promising potential for simultaneous bone cancer therapy and regeneration.

Black Phosphorus-Based Dynamic Self-Healing Hydrogel to Integrate Demineralized Bone Matrix and Noggin-Targeting siRNA for Synergistic Osteogenesis

Although a demineralized bone matrix (DBM) is often used as an alternative to an autologous bone graft, its clinical application is still hampered by easy dispersion of DBM particles and insufficient osteoinductivity in the defect site. Herein, we designed a self-healing hydrogel for DBM that can rapidly restore its structural integrity after damage based on amino-rich black phosphorus (BP) nanosheets and aldehyde-functionalized hyaluronic acid (AHA). Given the increased expression of bone morphogenetic protein (BMP) antagonists by DBM stimulation, the osteogenic potency of DBM in the hydrogel carrier was further enhanced by abrogating the BMP antagonism. The BP/AHA hydrogel provided dynamic polymer-nanosheet networks that combine injectability, modability, and physical stability with high DBM loading, where the BP nanosheets served as osteogenic cross-linkers to promote biomineralization and deliver siRNA to suppress undesirable expression of BMP antagonist noggin by DBM. As a result, the BP/AHA hydrogel integrated with DBM and noggin-targeting siRNA synergistically promoted osteogenic differentiation of mesenchymal stem cells by enhancing BMP/Smad signaling. This work demonstrates a promising strategy to improve the efficacy of bone regeneration using bone graft.

Preparation of black phosphorus@sodium alginate microspheres with bone matrix vesicle structure via electrospraying for bone regeneration

Bone matrix vesicles are commonly acknowledged as the primary site of biomineralization in human skeletal tissue. Black phosphorus has exhibited favorable properties across various chemical and physical domains. In this investigation, a novel composite microsphere was synthesized through the amalgamation of sodium alginate (ALG) with black phosphorus nanosheets (BP) utilizing the electrospray (ES) technique. These microspheres were tailored to mimic the regulatory function of matrix vesicles (MV) upon exposure to a biomimetic mineralization fluid (SBF) during the biomineralization process. Results revealed that black phosphorus nanosheets facilitated the generation of hydroxyapatite (HA) on the microsphere surface. Live-dead assays and cell proliferation experiments showcased a cell survival rate exceeding 85 %. Moreover, wound healing assessments unveiled that M-ALG-BP microspheres exhibited superior migration capacity, with a migration rate surpassing 50 %. Furthermore, after 7 days of osteogenic induction, M-ALG-BP microspheres notably stimulated osteoblast differentiation. Particularly noteworthy, M-ALG-BP microspheres significantly enhanced osteogenic differentiation of osteoblasts and induced collagen production in vitro. Additionally, experiments involving microsphere implantation into mouse skeletal muscle demonstrated the potential for ectopic mineralization by ALG-BP microspheres. This investigation underscores the outstanding mineralization properties of ALG-BP microspheres and their promising clinical prospects in bone tissue engineering.

Macrophage membrane (MMs) camouflaged near-infrared (NIR) responsive bone defect area targeting nanocarrier delivery system (BTNDS) for rapid repair: promoting osteogenesis via phototherapy and modulating immunity

Bone defects remain a significant challenge in clinical orthopedics, but no targeted medication can solve these problems. Inspired by inflammatory targeting properties of macrophages, inflammatory microenvironment of bone defects was exploited to develop a multifunctional nanocarrier capable of targeting bone defects and promoting bone regeneration. The avidin-modified black phosphorus nanosheets (BP-Avidin, BPAvi) were combined with biotin-modified Icaritin (ICT-Biotin, ICTBio) to synthesize Icaritin (ICT)-loaded black phosphorus nanosheets (BPICT). BPICT was then coated with macrophage membranes (MMs) to obtain MMs-camouflaged BPICT (M@BPICT). Herein, MMs allowed BPICT to target bone defects area, and BPICT accelerated the release of phosphate ions (PO43-) and ICT when exposed to NIR irradiation. PO43- recruited calcium ions (Ca2+) from the microenvironment to produce Ca3(PO4)2, and ICT increased the expression of osteogenesis-related proteins. Additionally, M@BPICT can decrease M1 polarization of macrophage and expression of pro-inflammatory factors to promote osteogenesis. According to the results, M@BPICT provided bone growth factor and bone repair material, modulated inflammatory microenvironment, and activated osteogenesis-related signaling pathways to promote bone regeneration. PTT could significantly enhance these effects. This strategy not only offers a solution to the challenging problem of drug-targeted delivery in bone defects but also expands the biomedical applications of MMs-camouflaged nanocarriers.

Advances in the Application of Black Phosphorus-Based Composite Biomedical Materials in the Field of Tissue Engineering

Black Phosphorus (BP) is a new semiconductor material with excellent biocompatibility, degradability, and optical and electrophysical properties. A growing number of studies show that BP has high potential applications in the biomedical field. This article aims to systematically review the research progress of BP composite medical materials in the field of tissue engineering, mining BP in bone regeneration, skin repair, nerve repair, inflammation, treatment methods, and the application mechanism. Furthermore, the paper discusses the shortcomings and future recommendations related to the development of BP. These shortcomings include stability, photothermal conversion capacity, preparation process, and other related issues. However, despite these challenges, the utilization of BP-based medical materials holds immense promise in revolutionizing the field of tissue repair.

Incorporation of black phosphorus nanosheets into poly(propylene fumarate) biodegradable bone cement to enhance bioactivity and osteogenesis

BACKGROUND

Injectable bone cement is commonly used in clinical orthopaedics to fill bone defects, treat vertebral compression fractures, and fix joint prostheses during joint replacement surgery. Poly(propylene fumarate) (PPF) has been proposed as a biodegradable and injectable alternative to polymethylmethacrylate (PMMA) bone cement. Recently, there has been considerable interest in two-dimensional (2D) black phosphorus nanomaterials (BPNSs) in the biomedical field due to their excellent photothermal and osteogenic properties. In this study, we investigated the biological and physicochemical qualities of BPNSs mixed with PPF bone cement created through thermal cross-linking.

METHODS

PPF was prepared through a two-step process, and BPNSs were prepared via a liquid phase stripping method. BP/PPF was subsequently prepared through thermal cross-linking, and its characteristics were thoroughly analysed. The mechanical properties, cytocompatibility, osteogenic performance, degradation performance, photothermal performance, and in vivo toxicity of BP/PPF were evaluated.

RESULTS

BP/PPF exhibited low cytotoxicity levels and mechanical properties similar to that of bone, whereas the inclusion of BPNSs promoted preosteoblast adherence, proliferation, and differentiation on the surface of the bone cement. Furthermore, 200 BP/PPF demonstrated superior cytocompatibility and osteogenic effects, leading to the degradation of PPF bone cement and enabling it to possess photothermal properties. When exposed to an 808-nm laser, the temperature of the bone cement increased to 45-55 °C. Furthermore, haematoxylin and eosin-stained sections from the in vivo toxicity test did not display any anomalous tissue changes.

CONCLUSION

BP/PPF exhibited mechanical properties similar to that of bone: outstanding photothermal properties, cytocompatibility, and osteoinductivity. BP/PPF serves as an effective degradable bone cement and holds great potential in the field of bone regeneration.

Preparation of genetically or chemically engineered exosomes and their therapeutic effects in bone regeneration and anti-inflammation

The treatment of bone or cartilage damage and inflammation-related diseases has been a long-standing research hotspot. Traditional treatments such as surgery and cell therapy have only displayed limited efficacy because they can't avoid potential deterioration and ensure cell activity. Recently, exosomes have become a favorable tool for various tissue reconstruction due to their abundant content of proteins, lipids, DNA, RNA and other substances, which can promote bone regeneration through osteogenesis, angiogenesis and inflammation modulation. Besides, exosomes are also promising delivery systems because of stability in the bloodstream, immune stealth capacity, intrinsic cell-targeting property and outstanding intracellular communication. Despite having great potential in therapeutic delivery, exosomes still show some limitations in clinical studies, such as inefficient targeting ability, low yield and unsatisfactory therapeutic effects. In order to overcome the shortcomings, increasing studies have prepared genetically or chemically engineered exosomes to improve their properties. This review focuses on different methods of preparing genetically or chemically engineered exosomes and the therapeutic effects of engineering exosomes in bone regeneration and anti-inflammation, thereby providing some references for future applications of engineering exosomes.

NIR light-facilitated bone tissue engineering

In the last decades, near-infrared (NIR) light has attracted considerable attention due to its unique properties and numerous potential applications in bioimaging and disease treatment. Bone tissue engineering for bone regeneration with the help of biomaterials is currently an effective means of treating bone defects. As a controlled light source with deeper tissue penetration, NIR light can provide real-time feedback of key information on bone regeneration in vivo utilizing fluorescence imaging and be used for bone disease treatment. This review provides a comprehensive overview of NIR light-facilitated bone tissue engineering, from the introduction of NIR probes as well as NIR light-responsive materials, and the visualization of bone regeneration to the treatment of bone-related diseases. Furthermore, the existing challenges and future development directions of NIR light-based bone tissue engineering are also discussed. This article is categorized under: Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Implantable Materials and Surgical Technologies > Nanotechnology in Tissue Repair and Replacement.

Double-Network DNA Macroporous Hydrogel Enables Aptamer-Directed Cell Recruitment to Accelerate Bone Healing

Recruiting endogenous bone marrow mesenchymal stem cells (BMSCs) in vivo to bone defect sites shows great promise in cell therapies for bone tissue engineering, which tackles the shortcomings of delivering exogenous stem cells, including limited sources, low retention, stemness loss, and immunogenicity. However, it remains challenging to efficiently recruit stem cells while simultaneously directing cell differentiation in the dynamic microenvironment and promoting neo-regenerated tissue ingrowth to achieve augmented bone regeneration. Herein, a synthetic macroporous double-network hydrogel presenting nucleic acid aptamer and nano-inducer enhances BMSCs recruitment, and osteogenic differentiation is demonstrated. An air-in-water template enables the rapid construction of highly interconnective macroporous structures, and the physical self-assembly of DNA strands and chemical cross-linking of gelatin chains synergistically generate a resilient double network. The aptamer Apt19S and black phosphorus nanosheets-specific macroporous hydrogel demonstrate highly efficient endogenous BMSCs recruitment, cell differentiation, and extracellular matrix mineralization. Notably, the enhanced calvarial bone healing with promising matrix mineralization and new bone formation is accompanied by adapting this engineered hydrogel to the bone defects. The findings suggest an appealing material approach overcoming the traditional limitations of cell-delivery therapy that can inspire the future design of next-generation hydrogel for enhanced bone tissue regeneration.

3D Printing Drug-Free Scaffold with Triple-Effect Combination Induced by Copper-Doped Layered Double Hydroxides for the Treatment of Bone Defects

Tissue-engineered poly(l-lactide) (PLLA) scaffolds have been widely used to treat bone defects; however, poor biological activities have always been key challenges for its further application. To address this issue, introducing bioactive drugs or factors is the most commonly used method, but there are often many problems such as high cost, uncontrollable and monotonous drug activity, and poor bioavailability. Here, a drug-free 3D printing PLLA scaffold with a triple-effect combination induced by surface-modified copper-doped layered double hydroxides (Cu-LDHs) is proposed. In the early stage of scaffold implantation, Cu-LDHs exert a photothermal therapy (PTT) effect to generate high temperature to effectively prevent bacterial infection. In the later stage, Cu-LDHs can further have a mild hyperthermia (MHT) effect to stimulate angiogenesis and osteogenic differentiation, demonstrating excellent vascularization and osteogenic activity. More importantly, with the degradation of Cu-LDHs, the released Cu2+ and Mg2+ provide an ion microenvironment effect and further synergize with the MHT effect to stimulate angiogenesis and osteogenic differentiation, thus more effectively promoting the healing of bone tissue. This triple-effect combined scaffold exhibits outstanding antibacterial, osteogenic, and angiogenic activities, as well as the advantages of low cost, convenient procedure, and long-term efficacy, and is expected to provide a promising strategy for clinical repair of bone defects.

Biodegradable nano black phosphorus based SDF1-α delivery system ameliorates Erectile Dysfunction in a cavernous nerve injury rat model by recruiting endogenous stem/progenitor cells

Stem cell (SC) therapy has been shown high prospects in erectile dysfunction (ED) treatment. Without ethical issues and risks of immune rejection and tumorigenesis of exogenous SC therapy, endogenous stem/progenitor cells (S/PCs) have a better potential for ED management, and their homing and redistribution are controlled by SDF1-α/CXCR4 axis. Considering black phosphorus nanosheet (BPNS) has emerged as an efficient and safe drug vehicle due to its large surface area, biodegradability, and the ability to retain and slowly release its loaded drugs, BPNS is utilized to load SDF1-α, a chemokine for S/PCs, to construct the BP@SDF1-α complex to efficiently recruit stem cells (SCs) by injury-site injection and thus ameliorate ED within the bilateral cavernous nerve injury (BCNI) rat models. We find that BP@SDF1-α can efficiently recruit exogenous SCs and endogenous S/PCs to corpus cavernosum and main pelvic ganglion (MPG) by local administration. Of note, ascribing to endogenous S/PCs recruitment, it also successfully alleviates ED in BCNI rat models by enhancing the protein expression levels of α-SMA, CD31, and nNOs, and eliciting less collagen deposition in the penis after its combined injection at corpus cavernosum and MPG. Thus, this study provides a new insight into the treatment of ED with endogenous S/PCs. BIODEGRADABLE NANO BLACK PHOSPHORUS BASED SDF1-α DELIVERY SYSTEM AMELIORATES ERECTILE DYSFUNCTION IN A CAVERNOUS NERVE INJURY RAT MODEL BY RECRUITING ENDOGENOUS STEM/PROGENITOR CELLS.

Phototherapy techniques for the management of musculoskeletal disorders: strategies and recent advances

Musculoskeletal disorders (MSDs), which include a range of pathologies affecting bones, cartilage, muscles, tendons, and ligaments, account for a significant portion of the global burden of disease. While pharmaceutical and surgical interventions represent conventional approaches for treating MSDs, their efficacy is constrained and frequently accompanied by adverse reactions. Considering the rising incidence of MSDs, there is an urgent demand for effective treatment modalities to alter the current landscape. Phototherapy, as a controllable and non-invasive technique, has been shown to directly regulate bone, cartilage, and muscle regeneration by modulating cellular behavior. Moreover, phototherapy presents controlled ablation of tumor cells, bacteria, and aberrantly activated inflammatory cells, demonstrating therapeutic potential in conditions such as bone tumors, bone infection, and arthritis. By constructing light-responsive nanosystems, controlled drug delivery can be achieved to enable precise treatment of MSDs. Notably, various phototherapy nanoplatforms with integrated imaging capabilities have been utilized for early diagnosis, guided therapy, and prognostic assessment of MSDs, further improving the management of these disorders. This review provides a comprehensive overview of the strategies and recent advances in the application of phototherapy for the treatment of MSDs, discusses the challenges and prospects of phototherapy, and aims to promote further research and application of phototherapy techniques.

Annexin A5 derived from matrix vesicles protects against osteoporotic bone loss via mineralization

Matrix vesicles (MVs) have shown strong effects in diseases such as vascular ectopic calcification and pathological calcified osteoarthritis and in wound repair of the skeletal system due to their membranous vesicle characteristics and abundant calcium and phosphorus content. However, the role of MVs in the progression of osteoporosis is poorly understood. Here, we report that annexin A5, an important component of the matrix vesicle membrane, plays a vital role in bone matrix homeostasis in the deterioration of osteoporosis. We first identified annexin A5 from adherent MVs but not dissociative MVs of osteoblasts and found that it could be sharply decreased in the bone matrix during the occurrence of osteoporosis based on ovariectomized mice. We then confirmed its potential in mediating the mineralization of the precursor osteoblast lineage via its initial binding with collagen type I to achieve MV adhesion and the subsequent activation of cellular autophagy. Finally, we proved its protective role in resisting bone loss by applying it to osteoporotic mice. Taken together, these data revealed the importance of annexin A5, originating from adherent MVs of osteoblasts, in bone matrix remodeling of osteoporosis and provided a new strategy for the treatment and intervention of bone loss.

Copper Ion-Modified Germanium Phosphorus Nanosheets Integrated with an Electroactive and Biodegradable Hydrogel for Neuro-Vascularized Bone Regeneration

Severe bone defects accompanied by vascular and peripheral nerve injuries represent a huge orthopedic challenge and are often accompanied by the risk of infection. Thus, biomaterials with antibacterial and neurovascular regeneration properties are highly desirable. Here, a newly designed biohybrid biodegradable hydrogel (GelMA) containing copper ion-modified germanium-phosphorus (GeP) nanosheets, which act as neuro-vascular regeneration and antibacterial agents, is designed. The copper ion modification process serves to improve the stability of the GeP nanosheets and offers a platform for the sustained release of bioactive ions. Study findings show that GelMA/GeP@Cu has effective antibacterial properties. The integrated hydrogel can significantly boost the osteogenic differentiation of bone marrow mesenchymal stem cells, facilitate angiogenesis in human umbilical vein endothelial cells, and up-regulate neural differentiation-related proteins in neural stem cells in vitro. In vivo, in the rat calvarial bone defect mode, the GelMA/GeP@Cu hydrogel is found to enhance angiogenesis and neurogenesis, eventually contributing to bone regeneration. These findings indicate that in the field of bone tissue engineering, GelMA/GeP@Cu can serve as a valuable biomaterial for neuro-vascularized bone regeneration and infection prevention.

Hybrid Polymer Vesicles: Controllable Preparation and Potential Applications

Hybrid polymer vesicles contain functional nanoparticles (NPs) in their walls, interfaces, coronae, or cavities. NPs render the hybrid vesicles with specific physical properties, while polymers endow them with structural stability and may significantly reduce the high toxicity of NPs. Therefore, hybrid vesicles integrate fascinating multifunctions from both NPs and polymeric vesicles, which have gained tremendous attention because of their diverse promising applications. Various types of delicate hybrid polymeric vesicles with size control and tunable localization of NPs in different parts of vesicles have been constructed via in situ and ex situ strategies, respectively. Their potential applications have been widely explored, as well. This review presents the progress of block copolymer (BCP) vesicle systems containing different types of NPs including metal NPs, magnetic NPs, and semiconducting quantum dots (QDs), etc. The strategies for controlling the location of NPs within hybrid vesicles are discussed. Typical potential applications of the elegant hybrid vesicles are also highlighted.

FePSe3 -Nanosheets-Integrated Cryogenic-3D-Printed Multifunctional Calcium Phosphate Scaffolds for Synergistic Therapy of Osteosarcoma

Clinical treatment of osteosarcoma encounters great challenges of postsurgical tumor recurrence and extensive bone defect. To develop an advanced artificial bone substitute that can achieve synergistic bone regeneration and tumor therapy for osteosarcoma treatment, a multifunctional calcium phosphate composite enabled by incorporation of bioactive FePSe3 -nanosheets within the cryogenic-3D-printed α-tricalcium phosphate scaffold (TCP-FePSe3 ) is explored. The TCP-FePSe3 scaffold exhibits remarkable tumor ablation ability due to the excellent NIR-II (1064 nm) photothermal property of FePSe3 -nanosheets. Moreover, the biodegradable TCP-FePSe3 scaffold can release selenium element to suppress tumor recurrence by activating of the caspase-dependent apoptosis pathway. In a subcutaneous tumor model, it is demonstrated that tumors can be efficiently eradicated via the combination treatment with local photothermal ablation and the antitumor effect of selenium element. Meanwhile, in a rat calvarial bone defect model, the superior angiogenesis and osteogenesis induced by TCP-FePSe3 scaffold have been observed in vivo. The TCP-FePSe3 scaffold possesses improved capability to promote the repair of bone defects via vascularized bone regeneration, which is induced by the bioactive ions of Fe, Ca, and P released during the biodegradation of the implanted scaffolds. The TCP-FePSe3 composite scaffolds fabricated by cryogenic-3D-printing illustrate a distinctive strategy to construct multifunctional platform for osteosarcoma treatment.

Inhibiting Osteolytic Breast Cancer Bone Metastasis by Bone-Targeted Nanoagent via Remodeling the Bone Tumor Microenvironment Combined with NIR-II Photothermal Therapy

Bone is one of the prone metastatic sites of patients with advanced breast cancer. The "vicious cycle" between osteoclasts and breast cancer cells plays an essential role in osteolytic bone metastasis from breast cancer. In order to inhibit bone metastasis from breast cancer, NIR-II photoresponsive bone-targeting nanosystems (CuP@PPy-ZOL NPs) are designed and synthesized. CuP@PPy-ZOL NPs can trigger the photothermal-enhanced Fenton response and photodynamic effect to enhance the photothermal treatment (PTT) effect and thus achieve synergistic anti-tumor effect. Meanwhile, they exhibit a photothermal enhanced ability to inhibit osteoclast differentiation and promote osteoblast differentiation, which reshaped the bone microenvironment. CuP@PPy-ZOL NPs effectively inhibited the proliferation of tumor cells and bone resorption in the in vitro 3D bone metastases model of breast cancer. In a mouse model of breast cancer bone metastasis, CuP@PPy-ZOL NPs combined with PTT with NIR-II significantly inhibited the tumor growth of breast cancer bone metastases and osteolysis while promoting bone repair to achieve the reversal of osteolytic breast cancer bone metastases. Furthermore, the potential biological mechanisms of synergistic treatment are identified by conditioned culture experiments and mRNA transcriptome analysis. The design of this nanosystem provides a promising strategy for treating osteolytic bone metastases.

Natural Chlorogenic Acid Planted Nanohybrids with Steerable Hyperthermia for Osteosarcoma Suppression and Bone Regeneration

Surgical resection is the most common approach for the treatment of osteosarcoma. However, two major complications, including residual tumor cells and large bone defects, often arise from the surgical resection of osteosarcoma. Discovering new strategies for programmatically solving the two above-mentioned puzzles has become a worldwide challenge. Herein, a novel one-step strategy is reported for natural phenolic acid planted nanohybrids with desired physicochemical properties and steerable photothermal effects for efficacious osteosarcoma suppression and bone healing. Nanohybrids are prepared based on the self-assembly of chlorogenic acid and gold nanorods through robust Au-catechol interface actions, featuring precise nanostructures, great water solubility, good stability, and adjustable hyperthermia generating capacity. As expected, on the one hand, these integrated nanohybrids can severely trigger apoptosis and suppress tumor growth with strong hyperthermia. On the other hand, with controllable mild NIR irradiation, the nanohybrids promote the expression of heat shock proteins and induce prominent osteogenic differentiation. This work initiates a brand-new strategy for assisting osteosarcoma surgical excision to resolve the blockage of residual tumor cells elimination and bone regeneration.

Sam68 promotes osteogenic differentiation of aortic valvular interstitial cells by TNF-α/STAT3/autophagy axis

Calcified aortic valve disease (CAVD) is a major non-rheumatic heart valve disease in the world, with a high mortality rate and without suitable pharmaceutical therapy due to its complex mechanisms. Src-associated in mitosis 68-KD (Sam68), an RNA binding protein, has been reported as a signaling adaptor in numerous signaling pathways (Huot in Mol Cell Biol, 29(7), 1933-1943, 2009), particularly in inflammatory signaling pathways. The effects of Sam68 on the osteogenic differentiation process of hVICs and its regulation on signal transducer and activator of transcription 3 (STAT3) signaling pathway have been investigated in this study. Human aortic valve samples detection found that Sam68 expression was up-regulated in human calcific aortic valves. We used tumor necrosis factor α (TNF-α) as an activator for osteogenic differentiation in vitro and the result indicated that Sam68 was highly expressed after TNF-α stimulation. Overexpression of Sam68 promoted osteogenic differentiation of hVICs while Sam68 knockdown reversed this effect. Sam68 interaction with STAT3 was predicted by using String database and was verified in this study. Sam68 knockdown reduced phosphorylation of STAT3 activated by TNF-α and the downstream gene expression, which further influenced autophagy flux in hVICs. STAT3 knockdown alleviated the osteogenic differentiation and calcium deposition promoted by Sam68 overexpression. In conclusion, Sam68 interacts with STAT3 and participates in its phosphorylation to promote osteogenic differentiation of hVICs to induce valve calcification. Thus, Sam68 may be a new therapeutic target for CAVD. Regulatory of Sam68 in TNF-α/STAT3/Autophagy Axis in promoting osteogenesis of hVICs.

Harnessing Nucleic Acids Nanotechnology for Bone/Cartilage Regeneration

The effective regeneration of weight-bearing bone defects and critical-sized cartilage defects remains a significant clinical challenge. Traditional treatments such as autologous and allograft bone grafting have not been successful in achieving the desired outcomes, necessitating the need for innovative therapeutic approaches. Nucleic acids have attracted significant attention due to their ability to be designed to form discrete structures and programmed to perform specific functions at the nanoscale. The advantages of nucleic acid nanotechnology offer numerous opportunities for in-cell and in vivo applications, and hold great promise for advancing the field of biomaterials. In this review, the current abilities of nucleic acid nanotechnology to be applied in bone and cartilage regeneration are summarized and insights into the challenges and future directions for the development of this technology are provided.

Recent Advances in the Biological Responses to Nano-black Phosphorus: Understanding the Importance of Intrinsic Properties and Cell Types

The production scalability and increasing demand for nano-black phosphorus materials (nano-BPs) inevitably lead to their environmental leakage, thereby raising the risk of human exposure through inhalation, ingestion, dermal, and even intravenous pathways. Consequently, a systematic evaluation of their potential impacts on human health is necessary. This Review outlines recent progress in the understanding of various biological responses to nano-BPs. Attention is particularly given to the inconsistent toxicological findings caused by a wide variation of nano-BPs' physicochemical properties, toxicological testing methods, and cell types examined in each study. Additionally, cellular uptake and intracellular trafficking, cell death modes, immunological effects, and other biologically relevant processes are discussed in detail, providing evidence for the potential health implications of nano-BPs. Finally, we address the remaining challenges related to the health risk evaluation of nano-BPs and propose a broader range of applications for these promising nanomaterials.

Bioinspired Mild Photothermal Effect-Reinforced Multifunctional Fiber Scaffolds Promote Bone Regeneration

Bone fractures are often companied with poor bone healing and high rates of infection. Early recruitment of mesenchymal stem cells (MSCs) is critical for initiating efficient bone repair, and mild thermal stimulation can accelerate the recovery of chronic diseases. Here, a bioinspired, staged photothermal effect-reinforced multifunctional scaffold was fabricated for bone repair. Uniaxially aligned electrospun polycaprolactone nanofibers were doped with black phosphorus nanosheets (BP NSs) to endow the scaffold with excellent near-infrared (NIR) responsive capability. Apt19S was then decorated on the surface of the scaffold to selectively recruit MSCs toward the injured site. Afterward, microparticles of phase change materials loaded with antibacterial drugs were also deposited on the surface of the scaffold, which could undergo a solid-to-liquid phase transition above 39 °C, triggering the release of payload to eliminate bacteria and prevent infection. Under NIR irradiation, photothermal-mediated up-regulation of heat shock proteins and accelerated biodegradation of BP NSs could promote the osteogenic differentiation of MSCs and biomineralization. Overall, this strategy shows the ability of bacteria elimination, MSCs recruitment, and bone regeneration promotion with the assistance of photothermal effect in vitro and in vivo, which emphasizes the design of a bioinspired scaffold and its potential for a mild photothermal effect in bone tissue engineering.

Radical-Scavenging and Subchondral Bone-Regenerating Nanomedicine for Osteoarthritis Treatment

Osteoarthritis (OA) is characterized by cartilage degradation and subchondral bone remodeling. However, most available studies focus on either cartilage degradation or subchondral bone lesion, alone, and rarely pay attention to the synergy of these two pathological changes. Herein, a dual-functional medication is developed to simultaneously protect cartilage and achieve subchondral bone repair. Black phosphorus nanosheets (BPNSs), with a strong reactive oxygen species (ROS)-scavenging capability and high biocompatibility, also present a notable promoting effect in osteogenesis. BPNSs efficiently eliminate the intracellular ROS and, thus, protect the inherent homeostasis between cartilage matrix anabolism and catabolism. RNA sequencing results of BPNSs-treated OA chondrocytes further reveal the restoration of chondrocyte function, activation of antioxidant enzymes, and regulation of inflammation. Additional in vivo assessments solidly confirm that BPNSs inhibit cartilage degradation and prevent OA progression. Meanwhile, histological evaluation and microcomputed tomography (micro-CT) scanning analysis verify the satisfying disease-modifying effects of BPNSs on OA. Additionally, the excellent biocompatibility of BPNSs enables them as a competitive candidate for OA treatment. This distinct disease-modifying treatment of OA on the basis of BPNSs provides an insight and paradigm on the dual-functional treatment strategy focusing on both cartilage degradation and subchondral bone lesion in OA and explores a broader biomedical application of BPNS nanomedicine in orthopedics.

Anti-BCMA surface engineered biomimetic photothermal nanomissile enhances multiple myeloma cell apoptosis and overcomes the disturbance of NF-κB signaling in vivo

Conventional chemotherapy for multiple myeloma (MM) faces the challenges of a low complete remission rate and transformation to recurrence/refractory. The current MM first-line clinical drug Bortezomib (BTZ) faces the problem of enhanced tolerance and nonnegligible side effects. B cell maturation antigen (BCMA), for its important engagement in tumor signaling pathways and novel therapy technologies such as Chimeric antigen receptor T-Cell immunotherapy (CAR-T) and Antibody Drug Conjugate (ADC), has been identified as an ideal target and attracted attention in anti-MM therapy. Emerging nanotechnology provided feasible methods for drug delivery and new therapeutic strategies such as photothermal therapy (PTT). Herein, we developed a BCMA-Targeting biomimetic photothermal nanomissile BTZ@BPQDs@EM @anti-BCMA (BBE@anti-BCMA) by integration of BTZ, black phosphorus quantum dots (BPQDs), Erythrocyte membrane (EM) and BCMA antibody (anti-BCMA). We hypothesized that this engineered nanomissile could attack tumor cells in triple ways and achieve effective treatment of MM. Consequently, the intrinsic biomimetic nature of EM and the active targeting property of anti-BCMA enhanced the accumulation of therapeutic agents in the tumor site. Besides, owing to the decrease in BCMA abundance, the potential apoptosis-inducing ability was revealed. With the support of BPQDs' photothermal effect, Cleaved-Caspase-3 and Bax signal increased significantly, and the expression of Bcl-2 was inhibited. Furthermore, the synergistic photothermal/chemo therapy can effectively inhibit tumor growth and reverse the disorder of NF-κB in vivo. Importantly, this biomimetic nanodrug delivery system and antibody induced synergistic therapeutic strategy efficiently killed MM cells with ignorable systemic toxicity, which is a promising method for the future anticancer treatment of hematological malignancies in clinics.

Silk-Based Biomaterials for Designing Bioinspired Microarchitecture for Various Biomedical Applications

Biomaterial research has led to revolutionary healthcare advances. Natural biological macromolecules can impact high-performance, multipurpose materials. This has prompted the quest for affordable healthcare solutions, with a focus on renewable biomaterials with a wide variety of applications and ecologically friendly techniques. Imitating their chemical compositions and hierarchical structures, bioinspired based materials have elevated rapidly over the past few decades. Bio-inspired strategies entail extracting fundamental components and reassembling them into programmable biomaterials. This method may improve its processability and modifiability, allowing it to meet the biological application criteria. Silk is a desirable biosourced raw material due to its high mechanical properties, flexibility, bioactive component sequestration, controlled biodegradability, remarkable biocompatibility, and inexpensiveness. Silk regulates temporo-spatial, biochemical and biophysical reactions. Extracellular biophysical factors regulate cellular destiny dynamically. This review examines the bioinspired structural and functional properties of silk material based scaffolds. We explored silk types, chemical composition, architecture, mechanical properties, topography, and 3D geometry to unlock the body's innate regenerative potential, keeping in mind the novel biophysical properties of silk in film, fiber, and other potential forms, coupled with facile chemical changes, and its ability to match functional requirements for specific tissues.

Multifunctional inorganic biomaterials: New weapons targeting osteosarcoma

Osteosarcoma is the malignant tumor with the highest incidence rate among primary bone tumors and with a high mortality rate. The anti-osteosarcoma materials are the cross field between material science and medicine, having a wide range of application prospects. Among them, biological materials, such as compounds from black phosphorous, magnesium, zinc, copper, silver, etc., becoming highly valued in the biological materials field as well as in orthopedics due to their good biocompatibility, similar mechanical properties with biological bones, good biodegradation effect, and active antibacterial and anti-tumor effects. This article gives a comprehensive review of the research progress of anti-osteosarcoma biomaterials.

Extracellular vesicles: emerging anti-cancer drugs and advanced functionalization platforms for cancer therapy

Increasing evidences show that unmodified extracellular vesicles (EVs) derived from various cells can effectively inhibit the malignant progression of different types of tumors by delivering the bioactive molecules. Therefore, EVs are expected to be developed as emerging anticancer drugs. Meanwhile, unmodified EVs as an advanced and promising nanocarrier that is frequently used in targeted delivery therapeutic cargos and personalized reagents for the treatment and diagnosis of cancer. To improve the efficacy of EV-based treatments, researchers are trying to engineering EVs as an emerging nanomedicine translational therapy platform through biological, physical and chemical approaches, which can be broaden and altered to enhance their therapeutic capability. EVs loaded with therapeutic components such as tumor suppressor drugs, siRNAs, proteins, peptides, and conjugates exhibit significantly enhanced anti-tumor effects. Moreover, the design and preparation of tumor-targeted modified EVs greatly enhance the specificity and effectiveness of tumor therapy, and these strategies are expected to become novel ideas for tumor precision medicine. This review will focus on reviewing the latest research progress of functionalized EVs, clarifying the superior biological functions and powerful therapeutic potential of EVs, for researchers to explore new design concepts based on EVs and build next-generation nanomedicine therapeutic platforms.

Black phosphorous-based biomaterials for bone defect regeneration: a systematic review and meta-analysis

Critical-sized bone defects are always difficult to treat, and they are associated with a significant burden of disease in clinical practice. In recent decades, due to the fast development of biomaterials and tissue engineering, many bioinspired materials have been developed to treat large bone defects. Due to the excellent osteoblastic ability of black phosphorous (BP), many BP-based biomaterials have been developed to treat bone defects. Therefore, there are abundant studies as well as a tremendous amount of research data. It is urgent to conduct evidence-based research to translate these research data and results into validated scientific evidence. Therefore, in our present study, a qualitative systematic review and a quantitative meta-analysis were performed. Eighteen studies were included in a systematic review, while twelve studies were included in the meta-analysis. Our results showed that the overall quality of experimental methods and reports of biomaterials studies was still low, which needs to be improved in future studies. Besides, we also proved the excellent osteoblastic ability of BP-based biomaterials. But we did not find a significant effect of near-infrared (NIR) laser in BP-based biomaterials for treating bone defects. However, the quality of the evidence presented by included studies was very low. Therefore, to accelerate the clinical translation of BP-based biomaterials, it is urgent to improve the quality of the study method and reporting in future animal studies. More evidence-based studies should be conducted to enhance the quality and clinical translation of BP-based biomaterials.

The Application of Black Phosphorus Nanomaterials in Bone Tissue Engineering

Recently, research on and the application of nanomaterials such as graphene, carbon nanotubes, and metal-organic frameworks has become increasingly popular in tissue engineering. In 2014, a two-dimensional sheet of black phosphorus (BP) was isolated from massive BP crystals. Since then, BP has attracted significant attention as an emerging nanomaterial. BP possesses many advantages such as light responsiveness, electrical conductivity, degradability, and good biocompatibility. Thus, it has broad prospects in biomedical applications. Moreover, BP is composed of phosphorus, which is a key bone tissue component with good biocompatibility and osteogenic repair ability. Thereby, BP exhibits excellent advantages for application in bone tissue engineering. In this review, the structure and the physical and chemical properties of BP are described. In addition, the current applications of BP in bone tissue engineering are reviewed to aid the future research and application of BP.

Biomolecule-mimetic nanomaterials for photothermal and photodynamic therapy of cancers: Bridging nanobiotechnology and biomedicine

Nanomaterial-based phototherapy has become an important research direction for cancer therapy, but it still to face some obstacles, such as the toxic side effects and low target specificity. The biomimetic synthesis of nanomaterials using biomolecules is a potential strategy to improve photothermal therapy (PTT) and photodynamic therapy (PDT) techniques due to their endowed biocompatibility, degradability, low toxicity, and specific targeting. This review presents recent advances in the biomolecule-mimetic synthesis of functional nanomaterials for PTT and PDT of cancers. First, we introduce four biomimetic synthesis methods via some case studies and discuss the advantages of each method. Then, we introduce the synthesis of nanomaterials using some biomolecules such as DNA, RNA, protein, peptide, polydopamine, and others, and discuss in detail how to regulate the structure and functions of the obtained biomimetic nanomaterials. Finally, potential applications of biomimetic nanomaterials for both PTT and PDT of cancers are demonstrated and discussed. We believe that this work is valuable for readers to understand the mechanisms of biomimetic synthesis and nanomaterial-based phototherapy techniques, and will contribute to bridging nanotechnology and biomedicine to realize novel highly effective cancer therapies.

Chloroplast-inspired Scaffold for Infected Bone Defect Therapy: Towards Stable Photothermal Properties and Self-Defensive Functionality

Bone implant-associated infections induced by bacteria frequently result in repair failure and threaten the health of patients. Although black phosphorus (BP) material with superior photothermal conversion ability is booming in the treatment of bone disease, the development of BP-based bone scaffolds with excellent photothermal stability and antibacterial properties simultaneously remains a challenge. In nature, chloroplasts cannot only convert light into chemical energy, but also hold a protective and defensive envelope membrane. Inspired by this, a self-defensive bone scaffold with stable photothermal property is developed for infected bone defect therapy. Similar to thylakoid and stroma lamella in chloroplasts, BP is integrated with chitosan and polycaprolactone fiber networks. The mussel-inspired polydopamine multifunctional "envelope membrane" wrapped above not only strengthens the photothermal stability of BP-based scaffolds, but also realizes the in situ anchoring of silver nanoparticles. Bacteria-triggered infection of femur defects in vivo can be commendably inhibited at the early stage via these chloroplast-inspired implants, which then effectively promotes endogenous repair of the defect area under mild hyperthermia induced by near-infrared irradiation. This chloroplast-inspired strategy shows outstanding performance for infected bone defect therapy and provides a reference for the functionality of other biomedical materials.

Black-Phosphorus-Nanosheet-Reinforced Coating of Implants for Sequential Biofilm Ablation and Bone Fracture Healing Acceleration

Incurable implant-related infection may cause catastrophic consequences due to the existence of a biofilm that resists the infiltration of host immune cells and antibiotics. Innovative approaches inspired by nanomedicine, e.g., engineering innovative multifunctional bionic coating systems on the surface of implants, are becoming increasingly attractive. Herein, 2D black phosphorus nanosheets (BPs) were loaded onto a hydroxyapatite (HA)-coated metal implant to construct a BPs@HA composite coating. With its photothermal conversion effect and in situ biomineralization, the BPs@HA coating shows excellent performances in ablating the bacterial biofilm and accelerating fracture healing, which were verified through both in vitro and in vivo studies. Moreover, differentially expressed genes of bone formation and bone mesenchymal stem cells (BMSCs) regulated by the BPs@HA coating were identified using absolute quantitative transcriptome sequencing followed by the screening of gene differential expressions. A functional enrichment analysis reveals that the expression of core markers related to BMSC differentiation and bone formation could be effectively regulated by BPs through a metabolism-related pathway. This work not only illustrates the great potential in clinical application of the BPs@HA composite coating to eliminate bacteria and accelerate bone fracture healing but also contributes to an understanding of the underlying molecular mechanism of osteogenesis physiological function regulation based on an analysis of absolute quantitative transcriptome sequencing.

Black phosphorous nanomaterials as a new paradigm for postoperative tumor treatment regimens

Surgery is currently a mainstream treatment modality for various solid tumor indications. However, aggressive resection of tumor tissues frequently causes postoperative complications, which severely undermine the well-being of patients. Moreover, the residue tumor cells may substantially increase the risk of local and distant tumor relapse. The recent development in black phosphorus (BP)-based nanomaterials offers a promising opportunity to address these clinical challenges. BP is an emerging nanomaterial with excellent biocompatibility and versatile functionality, which has already demonstrated great potential for a variety of biomedical applications including tumor therapy and tissue engineering. In this review, the recent advances in BP-based nanobiomaterials for the post-surgery treatment of solid tumor have been summarized, while specific emphasis was placed on their capability to continuously inhibit residue tumor growth at the surgery site as well as stimulating various healing mechanisms, aiming to preventing tumor relapse while promoting the healing of surgery-induced traumatic soft/hard tissue injuries. It is anticipated that the nanoengineered BP-based materials may open new avenues to tackle those clinical challenges in surgical treatment of solid tumors.

Matrix Vesicle-Mediated Mineralization and Potential Applications

Hard tissues, including the bones and teeth, are a fundamental part of the body, and their formation and homeostasis are critically regulated by matrix vesicle-mediated mineralization. Matrix vesicles have been studied for 50 y since they were first observed using electron microscopy. However, research progress has been hampered by various technical barriers. Recently, there have been great advancements in our understanding of the intracellular biosynthesis of matrix vesicles. Mitochondria and lysosomes are now considered key players in matrix vesicle formation. The involvement of mitophagy, mitochondrial-derived vesicles, and mitochondria-lysosome interaction have been suggested as potential detailed mechanisms of the intracellular pathway of matrix vesicles. Their main secretion pathway may be exocytosis, in addition to the traditionally understood mechanism of budding from the outer plasma membrane. This basic knowledge of matrix vesicles should be strengthened by novel nano-level microscopic technologies, together with basic cell biologies, such as autophagy and interorganelle interactions. In the field of tissue regeneration, extracellular vesicles such as exosomes are gaining interest as promising tools in cell-free bone and periodontal regenerative therapy. Matrix vesicles, which are recognized as a special type of extracellular vesicles, could be another potential alternative. In this review, we outline the recent significant progress in the process of matrix vesicle-mediated mineralization and the potential clinical applications of matrix vesicles for tissue regeneration.

Engineered 2D materials for optical bioimaging and path toward therapy and tissue engineering

Two-dimensional (2D) layered materials as a new class of nanomaterial are characterized by a list of exotic properties. These layered materials are investigated widely in several biomedical applications. A comprehensive understanding of the state-of-the-art developments of 2D materials designed for multiple nanoplatforms will aid researchers in various fields to broaden the scope of biomedical applications. Here, we review the advances in 2D material-based biomedical applications. First, we introduce the classification and properties of 2D materials. Next, we summarize surface and structural engineering methods of 2D materials where we discuss surface functionalization, defect, and strain engineering, and creating heterostructures based on layered materials for biomedical applications. After that, we discuss different biomedical applications. Then, we briefly introduced the emerging role of machine learning (ML) as a technological advancement to boost biomedical platforms. Finally, the current challenges, opportunities, and prospects on 2D materials in biomedical applications are discussed.

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Cell-specific aptamers as potential drugs in therapeutic applications: A review of current progress

Cell-specific aptamers are a promising emerging player in the field of disease therapy. This paper reviews the multidimensional research progress made in terms of their classification, modification, and application. Based on the target location of cell-specific aptamers, it is defined and classified cell-specific aptamers into three groups including aptamers for cell surface markers, aptamers for intracellular components, and aptamers for extracellular components. Moreover, the modification methods of aptamers to achieve improved stability and affinity are concluded. In addition, recent advances in the application of cell-specific aptamers are discussed, mainly focusing on the increasing research attraction of cell state improving helpers and cell recruitment mediators in the improvement of cellular microenvironments to achieve successful disease therapy. This review also highlights 11 types of clinical aptamer drugs. Finally, the challenges and future directions of potential clinical applications are presented. In summary, we believe that cell-specific aptamers are promising drugs in disease therapy.

Two-dimensional nanomaterials-added dynamism in 3D printing and bioprinting of biomedical platforms: Unique opportunities and challenges

The nanomaterials research spectrum has seen the continuous emergence of two-dimensional (2D) materials over the years. These highly anisotropic and ultrathin materials have found special attention in developing biomedical platforms for therapeutic applications, biosensing, drug delivery, and regenerative medicine. Three-dimensional (3D) printing and bioprinting technologies have emerged as promising tools in medical applications. The convergence of 2D nanomaterials with 3D printing has extended the application dynamics of available biomaterials to 3D printable inks and bioinks. Furthermore, the unique properties of 2D nanomaterials have imparted multifunctionalities to 3D printed constructs applicable to several biomedical applications. 2D nanomaterials such as graphene and its derivatives have long been the interest of researchers working in this area. Beyond graphene, a range of emerging 2D nanomaterials, such as layered silicates, black phosphorus, transition metal dichalcogenides, transition metal oxides, hexagonal boron nitride, and MXenes, are being explored for the multitude of biomedical applications. Better understandings on both the local and systemic toxicity of these materials have also emerged over the years. This review focuses on state-of-art 3D fabrication and biofabrication of biomedical platforms facilitated by 2D nanomaterials, with the comprehensive summary of studies focusing on the toxicity of these materials. We highlight the dynamism added by 2D nanomaterials in the printing process and the functionality of printed constructs.

Platelet-Activating Biominerals Enhanced Injectable Hydrogels With Superior Bioactivity for Bone Regeneration

Refractory bone fracture, which is difficult to be treated, is a common clinical disease. Taking inspiration from the natural process of bone regeneration, we provide a biomimetic strategy to develop a new injectable biomaterial for repairing bone defects, which is mainly composed of platelets, fibrins, and biominerals. Biomineral nanoparticles (EACPNs) with an amorphous phase are prepared by an enzyme-catalyzed route and display a platelet-activating property. The composite hydrogel (EPH) of EACPNs, fibrins, and platelets is injectable, and has similar chemical properties to natural materials in bone regeneration. The dried EPH samples display a highly porous structure, which would be favorable for cell attachment and growth. The results from in vitro studies indicate that EPH has high biocompatibility and superior bioactivity in promoting the osteogenic differentiation of rat bone marrow stem cells (rBMSCs). Furthermore, the results from in vivo studies clearly indicate that EPH can induce the formation of new collagen and vessels in the defect area, thus leading to faster regeneration of bone defects at 2 weeks. Our study provides a strategy for designing new biomimetic materials, which may be favorable in the treatment of refractory bone fracture.

Silicon-Phosphorus-Nanosheets-Integrated 3D-Printable Hydrogel as a Bioactive and Biodegradable Scaffold for Vascularized Bone Regeneration

Natural bone is a highly vascularized tissue that relies on the vasculature for blood and nutrients supply to maintain skeletal integrity. Bioactive nanomaterials with the capability of improving vascularized bone regeneration are highly demanded for bone tissue engineering. In this work, 2D silicon phosphorus (SiP) is explored as a new kind of bioactive and biodegradable nanomaterial with excellent angiogenesis and osteogenesis, and a 3D printed biohybrid hydrogel of GelMA-PEGDA incorporated with photocrosslinkable SiP-nanosheet (GelMA-PEGDA/SiPAC) is developed to apply on bone tissue engineering. Findings show that the GelMA-PEGDA/SiPAC possessess excellent biocompatibility and biodegradability, and can sustainably release Si and P elements. Compared with the biohybrid hydrogel scaffolds incorporated with black phosphorus nanosheets, the GelMA-PEGDA/SiPAC can further enhance the osteogenesis of mesenchymal stem cells, and tubular networking of human umbilical vascular endothelial cells. In a rat calvarial bone defect model, the superior angiogenesis and osteogenesis induced by GelMA-PEGDA/SiPAC have been confirmed in vivo. The current strategy paves a new way to design a multifunctional SiP nanocomposite scaffold on mediating the osteogenesis and angiogenesis in one system, and provides a bioactive and biodegradable alternative nanomaterial for tissue engineering and regenerative medicine.