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

Educating EVs to Improve Bone Regeneration: Getting Closer to the Clinic

The incidence of bone-related disorders is continuously growing as the aging of the population in developing countries continues to increase. Although therapeutic interventions for bone regeneration exist, their effectiveness is questioned, especially under certain circumstances, such as critical size defects. This gap of curative options has led to the search for new and more effective therapeutic approaches for bone regeneration; among them, the possibility of using extracellular vesicles (EVs) is gaining ground. EVs are secreted, biocompatible, nano-sized vesicles that play a pivotal role as messengers between donor and target cells, mediated by their specific cargo. Evidence shows that bone-relevant cells secrete osteoanabolic EVs, whose functionality can be further improved by several strategies. This, together with the low immunogenicity of EVs and their storage advantages, make them attractive candidates for clinical prospects in bone regeneration. However, before EVs reach clinical translation, a number of concerns should be addressed. Unraveling the EVs’ mode of action in bone regeneration is one of them; the molecular mediators driving their osteoanabolic effects in acceptor cells are now beginning to be uncovered. Increasing the functional and bone targeting abilities of EVs are also matters of intense research. Here, we summarize the cell sources offering osteoanabolic EVs, and the current knowledge about the molecular cargos that mediate bone regeneration. Moreover, we discuss strategies under development to improve the osteoanabolic and bone-targeting potential of EVs.

Self-calcifying lipid nanocarrier for bone tissue engineering

BACKGROUND

A nanoemulsion with specific surface properties (such as charge and functional groups) can initiate the deposition of calcium phosphate (CaP) on its surface, leading to formation of CaP nanoparticles with a lipid core. The lipid core can carry lipophilic compounds based on the function of the nanoemulsion. Therefore, a dual purpose nanoemulsion of lipid nanoparticles (LNPs) exhibiting self-calcifying and carrier abilities can be developed.

METHODS

We employed an emulsification process to formulate LNPs with a specific charged surface. The LNPs were tested for their ability to calcify in simulated body fluid and encapsulate cholecalciferol (a model of active compound). The self-calcifying LNP was successfully fabricated using the emulsification process and stabilized using a mixture of polysorbate 80 and polysorbate 20.

RESULTS

The LNPs incubated in simulated body fluid bound to calcium and phosphate, subsequently forming CaP on the particle surface and resulting in approximately 180-nm CaP spheres with a lipid core. The LNPs facilitated calcium phosphate deposition in the collagen scaffolds. In addition, LNPs can be used as carriers of lipophilic compounds without impeding the self-calcifying ability.

Sandwiching Phosphorene with Iron Porphyrin Monolayer for High Stability and Its Biomimetic Sensor to Sensitively Detect Living Cell Released NO

Instability of 2D phosphorene material is the major obstacle for its broad applications. Herein phosphorene is sandwiched with self-assembled iron porphyrin monolayers on both sides (I-Phene) to significantly enhance stability. Iron porphyrin has strong interaction with phosphorene through formation of PFe bonds. The sandwich structure offers excellent stability of phosphorene by both-sided monolayer protections for an intact phosphorene structure more than 40 days under ambient conditions. Meanwhile, the electron transfer between iron porphyrin and phosphorene result in a high oxidation state of Fe, making I-Phene biomimetic sensitivity toward oxidation of nitric oxide (NO) for 2.5 and 4.0 times higher than phosphorene and iron-porphyrin alone, respectively. Moreover, I-Phene exhibits excellent selectivity, a wide detection range, and a low detection limit at a low oxidation potential of 0.82 V, which is comparable with the reported noble metal based biomimetic sensors while ranking the best among all non-noble biomimetic ones. I-Phene is further used for real-time monitoring NO released from cells. This work provides effective approach against phosphorene degrading for outstanding stability, which has universal significance for its various important applications, and holds a great promise for a highly sensitive biomimetic sensor in live-cell assays.

Matrix vesicles from dental follicle cells improve alveolar bone regeneration via activation of the PLC/PKC/MAPK pathway

Background

The regeneration of bone loss that occurs after periodontal diseases is a significant challenge in clinical dentistry. Extracellular vesicles (EVs)-based cell-free regenerative therapies represent a promising alternative for traditional treatments. Developmental biology suggests matrix vesicles (MVs), a subtype of EVs, contain mineralizing-related biomolecules and play an important role in osteogenesis. Thus, we explore the therapeutic benefits and expect to find an optimized strategy for MV application.

Methods

Healthy human dental follicle cells (DFCs) were cultured with the osteogenic medium to generate MVs. Media MVs (MMVs) were isolated from culture supernatant, and collagenase-released MVs (CRMVs) were acquired from collagenase-digested cell suspension. We compared the biological features of the two MVs and investigated their induction of cell proliferation, migration, mineralization, and the modulation of osteogenic genes expression. Furthermore, we investigated the long-term regenerative capacity of MMVs and CRMVs in an alveolar bone defect rat model.

Results

We found that both DFC-derived MMVs and CRMVs effectively improved the proliferation, migration, and osteogenic differentiation of DFCs. Notably, CRMVs showed better bone regeneration capabilities. Compared to MMVs, CRMVs-induced DFCs exhibited increased synthesis of osteogenic marker proteins including ALP, OCN, OPN, and MMP-2. In the treatment of murine alveolar bone defects, CRMV-loaded collagen scaffold brought more significant therapeutic outcomes with less unhealing areas and more mature bone tissues in comparison with MMVs and acquired the effects resembling DFCs-based treatment. Furthermore, the western blotting results demonstrated the activation of the PLC/PKC/MAPK pathway in CRMVs-induced DFCs, while this cascade was inhibited by MMVs.

Conclusions

In summary, our findings revealed a novel cell-free regenerative therapy for repairing alveolar bone defects by specific MV subtypes and suggest that PLC/PKC/MAPK pathways contribute to MVs-mediated alveolar bone regeneration.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02721-6.

PLGA-collagen-BPNS Bifunctional composite mesh for photothermal therapy of melanoma and skin tissue engineering

The treatment of melanoma requires not only the elimination of skin cancer cells but also skin regeneration to heal defects. To achieve this goal, a bifunctional composite scaffold of poly(DL-lactic-co-glycolic acid) (PLGA), collagen and black phosphorus nanosheets (BPNSs) was prepared by hybridizing a BPNS-embedded collagen sponge with a PLGA knitted mesh. The composite mesh increased the temperature under near-infrared laser irradiation. The incorporation of BPNSs provided the PLGA-collagen-BPNS composite mesh with excellent photothermal properties for the photothermal ablation of melanoma cells both in vitro and in vivo. The PLGA-collagen-BPNS composite mesh had high mechanical strength for easy handling. The PLGA-collagen-BPNS composite mesh facilitated the proliferation of fibroblasts, promoted the expression of angiogenesis-related genes and the genes of components of the extracellular matrix for skin tissue regeneration. The high mechanical strength, photothermal ablation capability and skin tissue regeneration effects demonstrate that the bifunctional PLGA-collagen-BPNS composite mesh is a versatile and effective platform for the treatment of melanoma and the regeneration of skin defects.

Electrospun Nanofibers for Bone Regeneration: From Biomimetic Composition, Structure to Function

In recent years, a variety of novel materials and processing technologies have been developed to prepare tissue engineering scaffolds for bone defect repair. Among them, nanofibers fabricated via electrospinning technology...

Electrospun PCL/MoS2 Nanofiber Membranes Combined with NIR-Triggered Photothermal Therapy to Accelerate Bone Regeneration

Electrospun nanofiber membranes have been widely used for guided bone regeneration (GBR). For assistance in bone healing, photothermal therapy which renders moderate heat stimulation to defect regions by near-infrared (NIR) light irradiation has attracted much attention in recent years. Combined with photothermal therapy, novel electrospun poly(ε-caprolactone)/molybdenum disulfide (PCL/MoS₂ ) nanofiber membranes are innovatively synthesized as GBR for bone therapy, wherein the exfoliated MoS₂ nanosheets served as osteogenic enhancers and NIR photothermal agents. With the doping of MoS₂ , the mechanical properties of nanofiber membranes got improved with the degradation unaffected. The composite PCL/MoS₂ membranes show enhanced cell growth and osteogenic performance compared with PCL alone. Under NIR-triggered mild photothermal therapy, osteogenesis and bone healing are accelerated by using PCL/MoS₂ nanofiber membranes for growth of bone mesenchymal stem cells in vitro and repair of rat tibia bone defect in vivo. The novel nanofiber membranes may be developed as intelligent GBR in the therapy of bone defects.

2D materials for bone therapy

Due to their prominent physicochemical properties, 2D materials are broadly applied in biomedicine. Currently, 2D materials have achieved great success in treating many diseases such as cancer and tissue engineering as well as bone therapy. Based on their different characteristics, 2D materials could function in various ways in different bone diseases. Herein, the application of 2D materials in bone tissue engineering, joint lubrication, infection of orthopedic implants, bone tumors, and osteoarthritis are firstly reviewed comprehensively together. Meanwhile, different mechanisms by which 2D materials function in each disease reviewed below are also reviewed in detail, which in turn reveals the versatile functions and application of 2D materials. At last, the outlook on how to further broaden applications of 2D materials in bone therapies based on their excellent properties is also discussed.

Calcium Phosphate-Reinforced Metal-Organic Frameworks Regulate Adenosine-Mediated Immunosuppression

Long-term accumulation of adenosine (Ado) in tumor tissues helps to establish the immunosuppressive tumor microenvironment and to promote tumor development. Regulation of Ado metabolism is particularly pivotal for blocking Ado-mediated immunosuppression. The activity of adenosine kinase (ADK) for catalyzing the phosphorylation of Ado plays an essential role in regulating Ado metabolism. Specifically, accumulated Ado in the tumor microenvironment occupies the active site of ADK, inhibiting the phosphorylation of Ado. Phosphate can protect ADK from inactivation and restore the activity of ADK. Herein, calcium phosphate-reinforced iron-based metal-organic frameworks (CaP@Fe-MOFs) are designed to reduce Ado accumulation and to inhibit Ado-mediated immunosuppressive response in the tumor microenvironment. CaP@Fe-MOFs are found to regulate the Ado metabolism by promoting ADK-mediated phosphorylation and relieving the hypoxic tumor microenvironment. Moreover, CaP@Fe-MOFs can enhance the antitumor immune response via Ado regulation, including the increase of T lymphocytes and dendritic cells and the decrease of regulatory T lymphocytes. Finally, CaP@Fe-MOFs are used for cancer treatment in mice, alleviating the Ado-mediated immunosuppressive response and achieving tumor suppression. This study may offer a general strategy for blocking the Ado-mediated immunosuppression in the tumor microenvironment and further for enhancing the immunotherapy efficacy in vivo.

Ca2+-supplying black phosphorus-based scaffolds fabricated with microfluidic technology for osteogenesis

Effective osteogenesis remains a challenge in the treatment of bone defects. The emergence of artificial bone scaffolds provides an attractive solution. In this work, a new biomineralization strategy is proposed to facilitate osteogenesis through sustaining supply of nutrients including phosphorus (P), calcium (Ca), and silicon (Si). We developed black phosphorus (BP)-based, three-dimensional nanocomposite fibrous scaffolds via microfluidic technology to provide a wealth of essential ions for bone defect treatment. The fibrous scaffolds were fabricated from 3D poly (l-lactic acid) (PLLA) nanofibers (3D NFs), BP nanosheets, and hydroxyapatite (HA)-porous SiO2 nanoparticles. The 3D BP@HA NFs possess three advantages: i) stably connected pores allow the easy entrance of bone marrow-derived mesenchymal stem cells (BMSCs) into the interior of the 3D fibrous scaffolds for bone repair and osteogenesis; ii) plentiful nutrients in the NFs strongly improve osteogenic differentiation in the bone repair area; iii) the photothermal effect of fibrous scaffolds promotes the release of elements necessary for bone formation, thus achieving accelerated osteogenesis. Both in vitro and in vivo results demonstrated that the 3D BP@HA NFs, with the assistance of NIR laser, exhibited good performance in promoting bone regeneration. Furthermore, microfluidic technology makes it possible to obtain high-quality 3D BP@HA NFs with low costs, rapid processing, high throughput and mass production, greatly improving the prospects for clinical application. This is also the first BP-based bone scaffold platform that can self-supply Ca2+, which may be the blessedness for older patients with bone defects or patients with damaged bones as a result of calcium loss.

3D-Printed Multifunctional Polyetheretherketone Bone Scaffold for Multimodal Treatment of Osteosarcoma and Osteomyelitis

In this work, we developed the first 3D-printed polyetheretherketone (PEEK)-based bone scaffold with multi-functions targeting challenging bone diseases such as osteosarcoma and osteomyelitis. A 3D-printed PEEK/graphene nanocomposite scaffold was deposited with a drug-laden (antibiotics and/or anti-cancer drugs) hydroxyapatite coating. The graphene nanosheets within the scaffold served as effective photothermal agents that endowed the scaffold with on-demand photothermal conversion function under near-infrared laser irradiation. The bioactive hydroxyapatite coating significantly boosted the stem cell proliferation in vitro and promoted new bone growth in vivo. The presence of antibiotics and anti-cancer drugs enabled eradication of drug-resistant bacteria and ablation of osteosarcoma cancer cells, the treatment efficacy of which can be further enhanced by on-demand laser-induced heating. The promising results demonstrate the strong potential of our multi-functional scaffold in applications such as bone defect repair and multimodal treatment of osteosarcoma and osteomyelitis.

Black Phosphorus/Polymers: Status and Challenges

As a newly emerged mono-elemental nanomaterial, black phosphorus (BP) has been widely investigated for its fascinating physical properties, including layer-dependent tunable band gap (0.3-1.5 eV), high ON/OFF ratio (10⁴ ), high carrier mobility (10³ cm² V^-1 s^-1 ), excellent mechanical resistance, as well as special in-plane anisotropic optical, thermal, and vibrational characteristics. However, the instability caused by chemical degradation of its surface has posed a severe challenge for its further applications. A focused BP/polymer strategy has more recently been developed and implemented to hurdle this issue, so at present BP/polymers have been developed that exhibit enhanced stability, as well as outstanding optical, thermal, mechanical, and electrical properties. This has promoted researchers to further explore the potential applications of black phosphorous. In this review, the preparation processes and the key properties of BP/polymers are reviewed, followed by a detailed account of their diversified applications, including areas like optoelectronics, bio-medicine, and energy storage. Finally, in accordance with the current progress, the prospective challenges and future directions are highlighted and discussed.

Calcium-Collagen Coupling is Vital for Biomineralization Schedule

Biomineralization is a chemical reaction that occurs in organisms in which collagen initiates and guides the growth and crystallization of matched apatite minerals. However, there is little known about the demand pattern for calcium salts and collagen needed by biomineralization. In this study, natural bone biomineralization is analyzed, and a novel interplay between calcium concentration and collagen production is observed. Any quantitative change in one of the entities causes a corresponding change in the other. Translocation-associated membrane protein 2 (TRAM2) is identified as an intermediate factor whose silencing disrupts this relationship and causes poor mineralization. TRAM2 directly interacts with the sarcoplasmic/endoplasmic reticulum calcium ATPase 2b (SERCA2b) and modulates SERCA2b activity to couple calcium enrichment with collagen biosynthesis. Collectively, these findings indicate that osteoblasts can independently and directly regulate the process of biomineralization via this coupling. This knowledge has significant implications for the developmentally inspired design of biomaterials for bone regenerative applications.

Functional biomedical materials derived from proteins in the acquired salivary pellicle

In the oral environment, the acquired salivary pellicle (ASP) on the tooth surface comprises proteins, glycoproteins, carbohydrates, and lipids. The ASP can specifically and rapidly adsorb on the enamel surface to provide effective lubrication, protection, hydration, and remineralisation, as well as be recognised by various bacteria to form a microbial biofilm (plaque). The involved proteins, particularly various phosphoproteins such as statherins, histatins, and proline-rich proteins, are vital to their specific functions. This review first describes the relationship between the biological functions of these proteins and their structures. Subsequently, recent advances in functional biomedical materials derived from these proteins are reviewed in terms of dental/bone therapeutic materials, antibacterial materials, tissue engineering materials, and coatings for medical devices. Finally, perspectives and challenges regarding the rational design and biomedical applications of ASP-derived materials are discussed.

A Stable Quaternized Chitosan-Black Phosphorus Nanocomposite for Synergetic Disinfection of Antibiotic-Resistant Pathogens

Antibiotics are widely used for treatment of bacterial infections, and their overuse has contributed to microbial resistance. Currently, an alternative antibiotic-free therapy for inactivating bacteria is of great interest. Black phosphorus (BP), a biocompatible and nontoxic rising-star two-dimensional layered material, has gained remarkable interest in many bioapplications including biosensing, cancer therapy, drug delivery, and also antibacterial treatment. However, BP nanosheets suffer from instability in ambient environments due to rapid oxidation and degradation. To address this issue, BP nanosheets were modified with quaternized chitosan (QCS) by electrostatic adsorption to prepare a BP-QCS composite for photothermal/pharmaco treatment of bacterial infection. The BP-QCS has obviously enhanced solubility and chemical stability in aqueous suspensions. We have demonstrated that under near-infrared (NIR) irradiation, the BP-QCS can synergistically inactivate more than 95% methicillin-resistant Staphylococcus aureus (S. aureus) (MRSA) and Escherichia coli within 10 min with a dose of only 75 μg/mL in vitro. Meanwhile, the BP-QCS composite under NIR can synergistically inactivate 98% S. aureus in vivo. Furthermore, the BP-QCS suspensions at effective antibacterial concentrations have negligible cytotoxicity and in vivo toxicity.

Recent advances in PLGA-based biomaterials for bone tissue regeneration

Bone regeneration is an interdisciplinary complex lesson, including but not limited to materials science, biomechanics, immunology, and biology. Having witnessed impressive progress in the past decades in the development of bone substitutes; however, it must be said that the most suitable biomaterial for bone regeneration remains an area of intense debate. Since its discovery, poly (lactic-co-glycolic acid) (PLGA) has been widely used in bone tissue engineering due to its good biocompatibility and adjustable biodegradability. This review systematically covers the past and the most recent advances in developing PLGA-based bone regeneration materials. Taking the different application forms of PLGA-based materials as the starting point, we describe each form's specific application and its corresponding advantages and disadvantages with many examples. We focus on the progress of electrospun nanofibrous scaffolds, three-dimensional (3D) printed scaffolds, microspheres/nanoparticles, hydrogels, multiphasic scaffolds, and stents prepared by other traditional and emerging methods. Finally, we briefly discuss the current limitations and future directions of PLGA-based bone repair materials. STATEMENT OF SIGNIFICANCE: As a key synthetic biopolymer in bone tissue engineering application, the progress of PLGA-based bone substitute is impressive. In this review, we summarized the past and the most recent advances in the development of PLGA-based bone regeneration materials. According to the typical application forms and corresponding crafts of PLGA-based substitutes, we described the development of electrospinning nanofibrous scaffolds, 3D printed scaffolds, microspheres/nanoparticles, hydrogels, multiphasic scaffolds and scaffolds fabricated by other manufacturing process. Finally, we briefly discussed the current limitations and proposed the newly strategy for the design and fabrication of PLGA-based bone materials or devices.

Composite scaffolds of black phosphorus nanosheets and gelatin with controlled pore structures for photothermal cancer therapy and adipose tissue engineering

Breast cancer treatment needs to eradicate cancer cells and restore breast defects after surgical intervention. Herein, bifunctional composite scaffolds of black phosphorus nanosheets (BPNSs) and gelatin were designed to kill breast cancer cells and induce adipose tissue reconstruction. The composite scaffolds were prepared by hybridizing photothermal BPNSs with porous gelatin matrices by adding pre-prepared ice particles to precisely adjust their pore structures. The composite scaffolds had large, well-interconnected spherical pores, which allowed cell migration and infiltration. Hybridization with BPNSs increased the compression strength of the scaffolds. The composite scaffolds possessed a high photothermal conversion capacity that was dependent on the amount of BPNSs. The composite scaffold with a high amount of BPNSs could completely kill breast cancer cells in vitro and in vivo under laser irradiation. Moreover, cell culture and animal experiment results showed that the composite scaffolds promoted lipid oil droplet formation and upregulated the expression of adipogenesis-related genes when hMSCs were cultured in the scaffolds. The composite scaffolds could offer a facile platform to exert anticancer effects against breast cancer cells and promote the reconstruction of adipose tissue.

A Cysteine-Mediated Synthesis of Red Phosphorus Nanosheets

Among phosphorus-based nanomaterials, layered black phosphorus and violet phosphorus have been actively explored in the past decade. However, methods for the synthesis of red phosphorus nanosheets (RPNSs) is lacking, even though red phosphorus (RP) is commercially available at low cost and has excellent chemical stability at room temperature. We report an efficient strategy for fabrication of RPNSs and doped RPNSs using cysteine as a reducing reagent. Data from in vitro and in vivo studies suggested that RPNSs can trigger production of reactive oxygen species, DNA damage, and subsequent autophagy-mediated cell death in a shape-dependent manner. Our findings provide a method for construction of layered RP nanomaterials and they present a unique mechanism for the application of phosphorus-based materials in nanomedicines.

Progress in the therapeutic applications of polymer-decorated black phosphorus and black phosphorus analog nanomaterials in biomedicine

Wonderful black phosphorus (BP) and some BP analogs (BPAs) have been increasingly studied for their biomedical applications owing to their fascinating properties and biodegradability, but opportunities and challenges have always coexisted in their study. Poor stability upon exposure to the natural environment is the major obstacle hampering their in vivo applications. BP/polymer and BPAs/polymer nanocomposites can not only efficiently prevent their oxidation and aggregation but also exhibit "biological activity" due to synergistic effects. In this review, we briefly describe the synthesis methods and stability strategies of BP/polymer and BPAs/polymer. Then, advances pertaining to their exciting therapeutic applications in various fields are systematically introduced, such as cancer therapy (phototherapy, drug delivery, and synergistic immunotherapy), bone regeneration, and neurogenesis. Some challenges for future clinical trials and possible directions for further study are finally discussed.

2D Nanomaterials for Tissue Engineering and Regenerative Nanomedicines: Recent Advances and Future Challenges

Regenerative medicine has become one of the hottest research topics in medical science that provides a promising way for repairing tissue defects in the human body. Due to their excellent physicochemical properties, the application of 2D nanomaterials in regenerative medicine has gradually developed and has been attracting a wide range of research interests in recent years. In particular, graphene and its derivatives, black phosphorus, and transition metal dichalcogenides are applied in all the aspects of tissue engineering to replace or restore tissues. This review focuses on the latest advances in the application of 2D-nanomaterial-based hydrogels, nanosheets, or scaffolds that are engineered to repair skin, bone, and cartilage tissues. Reviews on other applications, including cardiac muscle regeneration, skeletal muscle repair, nerve regeneration, brain disease treatment, and spinal cord healing are also provided. The challenges and prospects of applications of 2D nanomaterials in regenerative medicine are discussed.

Matrix Vesicles: Role in Bone Mineralization and Potential Use as Therapeutics

Bone is a complex organ maintained by three main cell types: osteoblasts, osteoclasts, and osteocytes. During bone formation, osteoblasts deposit a mineralized organic matrix. Evidence shows that bone cells release extracellular vesicles (EVs): nano-sized bilayer vesicles, which are involved in intercellular communication by delivering their cargoes through protein–ligand interactions or fusion to the plasma membrane of the recipient cell. Osteoblasts shed a subset of EVs known as matrix vesicles (MtVs), which contain phosphatases, calcium, and inorganic phosphate. These vesicles are believed to have a major role in matrix mineralization, and they feature bone-targeting and osteo-inductive properties. Understanding their contribution in bone formation and mineralization could help to target bone pathologies or bone regeneration using novel approaches such as stimulating MtV secretion in vivo, or the administration of in vitro or biomimetically produced MtVs. This review attempts to discuss the role of MtVs in biomineralization and their potential application for bone pathologies and bone regeneration.

Artificial Bioaugmentation of Biomacromolecules and Living Organisms for Biomedical Applications

The synergistic union of nanomaterials with biomaterials has revolutionized synthetic chemistry, enabling the creation of nanomaterial-based biohybrids with distinct properties for biomedical applications. This class of materials has drawn significant scientific interest from the perspective of functional extension via controllable coupling of synthetic and biomaterial components, resulting in enhancement of the chemical, physical, and biological properties of the obtained biohybrids. In this review, we highlight the forefront materials for the combination with biomacromolecules and living organisms and their advantageous properties as well as recent advances in the rational design and synthesis of artificial biohybrids. We further illustrate the incredible diversity of biomedical applications stemming from artificially bioaugmented characteristics of the nanomaterial-based biohybrids. Eventually, we aim to inspire scientists with the application horizons of the exciting field of synthetic augmented biohybrids.

A Review of the Functions of Matrix Vesicles in Periodontal Tissues

Periodontal tissues consist of cementum, periodontal ligaments, and alveolar bone, which provide indispensable support for physiological activities involving mastication, swallowing, and pronunciation. The formation of periodontal tissues requires a complex process, during which a close relationship with biomineralization is noticeable. Alveolar bone and cementum are physically hard, both of which are generated from biomineralization and possess the exact mechanical properties resembling other hard tissues. However, when periodontitis, congenital abnormalities, periapical diseases, and other pathological conditions affect the organism, the most common symptom, alveolar bone defect, is always unavoidable, which results in difficulties for current clinical treatment. Thus, exploring effective therapies to improve the prognosis is important. Matrix vesicles (MVs), a special subtype of extracellular vesicles related to histogenesis, are widely produced by the stem cells of developing hard tissues. With the assistance of the enzymes and transporters contained within them, MVs can construct the extracellular matrix and an adequate microenvironment, thus promoting biomineralization and periodontal development. Presently, MVs can be effectively extracted and delivered by scaffolds and generate hard tissues in vitro and in vivo, which are expected to be translated into therapies for alveolar bone defects. In this review, we generalize recent research progress on MV morphology, molecular composition, biological mechanism, and, in particular, the biological functions in periodontal development. In addition to the above unique roles of MVs, we further describe the available MV-related biotechnologies and achievements that make them promising for coping with existing problems and improving the treatment of alveolar bone defects.

Implantable multifunctional black phosphorus nanoformulation-deposited biodegradable scaffold for combinational photothermal/ chemotherapy and wound healing

Surgery is the mainstream treatment for melanoma, but its clinical implementation suffers from some major drawbacks including residual infiltrating melanoma cells at resection margins and severe tissue injury. In this study, a nanocomposite scaffold is developed for in-situ therapy after melanoma surgery as well as wound healing, which is fabricated by embedding photothermal-capable black phosphorus nanosheets (BPNSs) into bioresorbable Gelatin-PCL (GP) nanofibrous scaffold. GP scaffold is a clinically-tested biomaterial with temperature sensitivity and tissue-healing effect, while the BPNSs are loaded with the anticancer antibiotic of doxorubicin (DOX) and conjugated with NH₂-PEG-FA for tumor-targeted delivery. The GP scaffold could undergo a sol-gel transition upon NIR irritation and release the BPNSs in situ. During this process, most of the BP-based nanoformulations were selectively internalized by the melanoma cells for the cooperative photothermal therapy and heat-triggerable DOX therapy, while some of the loaded DOX was released into the wound tissue to create a tumor-suppressive microenvironment. Moreover, BPNSs could be gradually degraded to phosphates/phosphonates and thus enhance tissue repair by activating the ERK1/2 and PI3K/Akt pathway. Meanwhile, the detached DOX molecules would also enter the wound tissues for continuous melanoma inhibition. Considering the anti-melanoma and wound healing effect of this composite scaffold, it may offer a facile strategy for the wound treatment after melanoma surgery.

Black Phosphorus as Multifaceted Advanced Material Nanoplatforms for Potential Biomedical Applications

Black phosphorus is one of the emerging members of two-dimensional (2D) materials which has recently entered the biomedical field. Its anisotropic properties and infrared bandgap have enabled researchers to discover its applicability in several fields including optoelectronics, 3D printing, bioimaging, and others. Characterization techniques such as Raman spectroscopy have revealed the structural information of Black phosphorus (BP) along with its fundamental properties, such as the behavior of its photons and electrons. The present review provides an overview of synthetic approaches and properties of BP, in addition to a detailed discussion about various types of surface modifications available for overcoming the stability-related drawbacks and for imparting targeting ability to synthesized nanoplatforms. The review further gives an overview of multiple characterization techniques such as spectroscopic, thermal, optical, and electron microscopic techniques for providing an insight into its fundamental properties. These characterization techniques are not only important for the analysis of the synthesized BP but also play a vital role in assessing the doping as well as the structural integrity of BP-based nanocomposites. The potential role of BP and BP-based nanocomposites for biomedical applications specifically, in the fields of drug delivery, 3D printing, and wound dressing, have been discussed in detail to provide an insight into the multifunctional role of BP-based nanoplatforms for the management of various diseases, including cancer therapy. The review further sheds light on the role of BP-based 2D platforms such as BP nanosheets along with BP-based 0D platforms-i.e., BP quantum dots in the field of therapy and bioimaging of cancer using techniques such as photoacoustic imaging and fluorescence imaging. Although the review inculcates the multimodal therapeutic as well as imaging role of BP, there is still research going on in this field which will help in the development of BP-based theranostic platforms not only for cancer therapy, but various other diseases.

Jelly-Inspired Injectable Guided Tissue Regeneration Strategy with Shape Auto-Matched and Dual-Light-Defined Antibacterial/Osteogenic Pattern Switch Properties

Periodontitis is a bacterial infectious disease leading to the loss of periodontal supporting tissues and teeth. The current guided tissue regeneration (GTR) membranes for periodontitis treatments cannot effectively promote tissue regeneration for the limited antibacterial properties and the excessively fast degradation rate. Besides, they need extra tailoring according to variform defects before implantation, leading to imprecise match. This study proposed an injectable sodium alginate hydrogel composite (CTP-SA) doped with cubic cuprous oxide (Cu₂O) and polydopamine-coated titanium dioxide (TiO₂@PDA) nanoparticles for GTR. Inspired by the gelation process of the jelly, the phase change (liquid to solid) of CTP-SA after injection could automatch variform bone defects. Meanwhile, CTP-SA exhibited broad-spectrum antibacterial capabilities under blue light (BL) irradiation, including Streptococcus mutans (one of the most abundant bacteria in oral biofilms). Moreover, the reactive oxygen species released under BL excitation could accelerate the oxidation of Cu⁺ to Cu²⁺. Afterward, osteogenesis could be enhanced through two factors simultaneously: the stimulation of newly formed Cu²⁺ and the photothermal effect of CTP-SA under near-infrared (NIR) irradiation. Collectively, through this dual-light (blue and NIR) noninvasive regulation, CTP-SA could switch antibacterial and osteogenic modes to address requirements of patients at different healing stages, thereby realizing the customized GTR procedures.

Surface modification of black phosphorus-based nanomaterials in biomedical applications: Strategies and recent advances

Black phosphorus-based nanomaterials (BPNMs), an emerging member of two-dimensional (2D) nanomaterials, possess excellent physicochemical properties and hold great potential for application in advanced nanomedicines. However, the bare BPNMs easily decrease their biomedical activities due to their degradability and in vivo interactions with biological macromolecules such as plasma proteins, largely restricting their biomedical application. A variety of surface modifications, via chemical, physical or biological approaches, have been developed for BPNMs to avoid these limitations and achieve stable, long-lasting and safe therapeutic effects, thus enlighten the development of the multifunctional BPNMs for more practical application in the field of biomedicine. The present review summarizes the recent advances in the surface modification of BPNMs and the resultant expansion of their biomedical applications. Focus is put on the strategy and method of modification while the effects incurred on the behavior and potential toxicity of BPNMs are also included. The future and challenge of the surface modification of the therapeutic BPNMs are finally discussed.

Bioinspired Functional Black Phosphorus Electrospun Fibers Achieving Recruitment and Biomineralization for Staged Bone Regeneration

The ideal bone repair material should firstly recognize and recruit osteoblast precursor cells to initiate the repair process, then promote the differentiation of osteoblasts and accelerate the mineralization of the extracellular matrix (ECM). Here, a bioinspired staged bone regeneration strategy which loads bone morphogenetic protein₂ (BMP₂ )-modified black phosphorus (BP@BMP₂ ) nanosheets to a polylactic acid (PLLA) electrospun fibrous scaffold, with a combination of recruiting osteoblast precursor cells and biomineralization properties for bone regeneration, is constructed successfully by micro-sol electrospinning technique. BP, acting as carriers, can not only provide a negative surface and a strong BMP₂ loading ability but can also promote biomineralization in a 3D manner on the electrospun fibrous scaffold, while the BMP₂ is to target osteoblast precursor cells for recruitment and osteogenesis differentiation, which endows BP@BMP₂ nanosheets with staged bone regeneration ability. Furthermore, the in vitro and in vivo data showed that the BP@BMP₂ loaded electrospun fibrous scaffold have good biocompatibility and a strong osteogenesis ability resulting in rapid new bone tissue regeneration. Altogether, this newly developed bioinspired BMP₂ -modified BP electrospun fiber with staged bone regeneration properties via recruiting osteoblast precursor cells to the bone injured site and accelerating biomineralization can be a promising approach in physiologic bone repair.

Black phosphorus-based 2D materials for bone therapy

Since their discovery, Black Phosphorus (BP)-based nanomaterials have received extensive attentions in the fields of electromechanics, optics and biomedicine, due to their remarkable properties and excellent biocompatibility. The most essential feature of BP is that it is composed of a single phosphorus element, which has a high degree of homology with the inorganic components of natural bone, therefore it has a full advantage in the treatment of bone defects. This review will first introduce the source, physicochemical properties, and degradation products of BP, then introduce the remodeling process of bone, and comprehensively summarize the progress of BP-based materials for bone therapy in the form of hydrogels, polymer membranes, microspheres, and three-dimensional (3D) printed scaffolds. Finally, we discuss the challenges and prospects of BP-based implant materials in bone immune regulation and outlook the future clinical application.

Multifunctional layered black phosphorene-based nanoplatform for disease diagnosis and treatment: a review

As an outstanding two-dimensional material, black phosphorene, has attracted significant attention in the biomedicine field due to its large surface area, strong optical absorption, distinct bioactivity, excellent biocompatibility, and high biodegradability. In this review, the preparation and properties of black phosphorene are summarized first. Thereafter, black phosphorene-based multifunctional platforms employed for the diagnosis and treatment of diseases, including cancer, bone injuries, brain diseases, progressive oxidative diseases, and kidney injury, are reviewed in detail. This review provides a better understanding of the exciting properties of black phosphorene, such as its high drug-loading efficiency, photothermal conversion capability, high 1O2 generation efficiency, and high electrical conductivity, as well as how these properties can be exploited in biomedicine. Finally, the research perspectives of black phosphorene are discussed.

Bioactive Core-Shell CaF2 Upconversion Nanostructure for Promotion and Visualization of Engineered Bone Reconstruction

Inorganic ion metabolism plays significant roles in various life processes including signal transduction, substance exchange, and cellular constructions. Regulation and monitoring of ion metabolism offer great promise to modulate biological activities and provide insights into related mechanisms. Here, a synergistic nanodepot based on a bioactive core-shell CaF₂ upconversion nanostructure that integrates multiple mineral ions for metabolic regulation was built for the acceleration and monitoring of the biomineralization process. Multiple mineral ions released from the nanodepots can accelerate the growth of inorganic crystals and enhance the production of organic matrixes, synergistically facilitating the regeneration of bone defects in vivo. During the process, such a nanodepot can be constructed to specifically recognize osteoblasts for the monitoring of biomineralization. This nanoprobe represents an efficient strategy to promote and monitor biomineralization-related metabolic activities with applications in fundamental research, disease diagnosis, and regenerative medicine.

Extracellular vesicles: A bright star of nanomedicine

Extracellular vesicles (EVs) have unique structural, compositional, and morphological characteristics as well as predominant physiochemical stability and biocompatibility properties. They play a crucial role in pathophysiological regulation, and also have broad prospects for clinical application in the diagnosis, prognosis, and therapy of disease, and tissue regeneration and repair. Herein, the biosynthesis and physiological functions and current methods for separation and identification of EVs are summarized. Specifically, engineered EVs may be used to enhance targeted therapy in cancer and repair damaged tissues, and they may be developed as an individualized imaging diagnostic reagent, among other potential applications. We will focus on reviewing recent studies on engineered EVs in which alterations enhanced their therapeutic capability or diagnostic imaging potential via physical, chemical, and biological modification approaches. This review will clarify the superior biological functions and powerful therapeutic potential of EVs, particularly with regard to new designs based on EVs and their utilization in a new generation of nanomedicine diagnosis and treatment platforms.

Phototherapy-based combination strategies for bacterial infection treatment

The development of nanomedicine is expected to provide an innovative direction for addressing challenges associated with multidrug-resistant (MDR) bacteria. In the past decades, although nanotechnology-based phototherapy has been developed for antimicrobial treatment since it rarely causes bacterial resistance, the clinical application of single-mode phototherapy has been limited due to poor tissue penetration of light sources. Therefore, combinatorial strategies are being developed. In this review, we first summarized the current phototherapy agents, which were classified into two functional categories: organic phototherapy agents (e.g., small molecule photosensitizers, small molecule photosensitizer-loaded nanoparticles and polymer-based photosensitizers) and inorganic phototherapy agents (e.g., carbo-based nanomaterials, metal-based nanomaterials, composite nanomaterials and quantum dots). Then the development of emerging phototherapy-based combinatorial strategies, including combination with chemotherapy, combination with chemodynamic therapy, combination with gas therapy, and multiple combination therapy, are presented and future directions are further discussed. The purpose of this review is to highlight the potential of phototherapy to deal with bacterial infections and to propose that the combination therapy strategy is an effective way to solve the challenges of single-mode phototherapy.

Tremella-Like ZnO@Col-I-Decorated Titanium Surfaces with Dual-Light-Defined Broad-Spectrum Antibacterial and Triple Osteogenic Properties

The growing population of peri-implant diseases (PIDs) has become a public obsession, mainly due to the lack of antibacterial ability and osteogenic promotion of titanium (Ti) implants. Herein, inspired by tremella, we reported zinc oxide (ZnO)@collagen type I (Col-I)-decorated Ti for PIDs treatments. Compared with pure Ti implants, ZnO@Col-I-decorated Ti could be activated by a safe visible yellow light and showed excellent broad-spectrum antibacterial properties. The proliferation and osteogenic gene expression of bone marrow mesenchymal stem cells (BMSCs) indicated that the triple osseointegration of implants was realized through (I) the remarkedly improved surface hydrophilicity of ZnO@Col-I-decorated Ti, (II) the function of Col-I, and (III) the excellent near-infrared (NIR)-induced photothermal performance of ZnO. Collectively, the proposed dual-light-defined ZnO@Col-I coating was a promising implant surface modification system to provide customized treatments for each PID patient.

Photochemical Activity of Black Phosphorus for Near-Infrared Light Controlled In Situ Biomineralization

The photochemical activity of black phosphorus (BP) in near-infrared (NIR) light controlled in situ biomineralization is investigated. Owing to the excellent NIR absorption, irradiation with NIR light not only promotes degradation of BP into PO4 3-, but also enhances the chemical activity to accelerate the reaction between PO4 3- and Ca2+ and promote in situ biomineralization. Mineralization of hydrogels is demonstrated by the preparation of BP incorporated hydrogel (BP@Hydrogel) which delivers greatly improved biomineralization performance under NIR illumination. The biomineralization process which can be controlled by modulating the light irradiation time and location has a high potential in controlling the mechanical properties and osteoinductive ability in tissue engineering. This study also provides insights into the degradation, photochemical activity, and new biological/biomedical applications of BP.

The Construction of Biomimetic Cementum Through a Combination of Bioskiving and Fluorine-Containing Biomineralization

Despite tremendous attention is given to the construction of biomimetic cementum for regeneration of tooth cementum, the lack of recapitulating the composition and hierarchical structure of cementum often leads to the poor performance of constructed materials. How to highly mimic the sophisticated composition and hierarchy of cementum remains a longstanding challenge in constructing the biomimetic cementum. Inspired by cementum formation process, a novel construction approach via a combination of bioskiving and fluorine-containing biomineralization is developed in this study. The alternative collagen lamellae (ACL) that can highly mimic the rotated plywood structure of cementum collagen matrix is fabricated via bioskiving. Followed by biomineralization in the amorphous calcium phosphate (ACP) solution with different concentration of fluorine, a series of biomimetic cementum is constructed. Screened by physicochemical characterization, the biomimetic cementum with the composition and hierarchical structure highly similar to human cementum is selected. Through in vitro biological assay, this biomimetic cementum is proven to significantly promote the adhesion, proliferation, and cementogenic differentiation of periodontal ligament cells (PDLCs). Furthermore, in vivo study demonstrates that biomimetic cementum could induce cementogenesis. This biomimetic cementum constructed via combinatory application of bioskiving and fluorine-containing biomineralization stands as a promising candidate for achieving cementum regeneration.

Biomineral Precursor Formation Is Initiated by Transporting Calcium and Phosphorus Clusters from the Endoplasmic Reticulum to Mitochondria

Mineral granules in the mitochondria of bone-forming cells are thought to be the origin of biomineral precursors, which are transported to extracellular matrices to initiate cell-mediated biomineralization. However, no evidence has revealed how mitochondrial granules form. This study indicates that mitochondrial granules are initiated by transporting calcium and phosphorus clusters from the endoplasmic reticulum (ER) to mitochondria based on detailed observations of the continuous process of mouse parietal bone development as well as in vitro biomineralization in bone-forming cells. Nanosized biomineral precursors (≈30 nm in diameter), which originate from mitochondrial granules, initiate intrafibrillar mineralization of collagen as early as embryonic day 14.5. Both in vivo and in vitro studies further reveal that formation of mitochondrial granules is induced by the ER. Elevated levels of intracellular calcium or phosphate ions, which can be induced by treatment with ionomycin and black phosphorus, respectively, accelerate formation of the calcium and phosphorus clusters on ER membranes and ultimately promote biomineralization. These findings provide a novel insight into biomineralization and bone formation.

Advanced Black Phosphorus Nanomaterials for Bone Regeneration

Bone regeneration remains a great clinical challenge. Two-dimensional materials, especially graphene and its derivative graphene oxide, have been widely used for bone regeneration. Since its discovery in 2014, black phosphorus (BP) nanomaterials including BP nanosheets and BP quantum dots have attracted considerable scientific attention and are considered as prospective graphene substitutes. BP nanomaterials exhibit numerous advantages such as excellent optical and mechanical properties, electrical conductivity, excellent biocompatibility, and good biodegradation, all of which make them particularly attractive in biomedicine. In this review, we comprehensively summarize recent advances of BP-based nanomaterials in bone regeneration. The advantages are reviewed, the different synthesis methods of BP are summarized, and the applications to promote bone regeneration are highlighted. Finally, the existing challenges and perspectives of BP in bone regeneration are briefly discussed.

10-Fold Quantum Yield Improvement of Ag2S Nanoparticles by Fine Compositional Tuning

Ag₂S semiconductor nanoparticles (NPs) are near-infrared luminescent probes with outstanding properties (good biocompatibility, optimum spectral operation range, and easy biofunctionalization) that make them ideal probes for in vivo imaging. Ag₂S NPs have, indeed, made possible amazing challenges including in vivo brain imaging and advanced diagnosis of the cardiovascular system. Despite the continuous redesign of synthesis routes, the emission quantum yield (QY) of Ag₂S NPs is typically below 0.2%. This leads to a low luminescent brightness that avoids their translation into the clinics. In this work, an innovative synthetic methodology that permits a 10-fold increment in the absolute QY from 0.2 up to 2.3% is presented. Such an increment in the QY is accompanied by an enlargement of photoluminescence lifetimes from 184 to 1200 ns. The optimized synthetic route presented here is based on a fine control over both the Ag core and the Ag/S ratio within the NPs. Such control reduces the density of structural defects and decreases the nonradiative pathways. In addition, we demonstrate that the superior performance of the Ag₂S NPs allows for high-contrast in vivo bioimaging.

Photoluminescent biodegradable polyorganophosphazene: A promising scaffold material for in vivo application to promote bone regeneration

Tissue engineering scaffolds made of conventional aliphatic polyesters are inherently non-fluorescent, which results in their in vivo degradation hard to be visualized. Photoluminescent biodegradable polyorganophosphazenes (PPOPs) are synthesized by introducing fluorophores onto the polyphosphazene backbone via nucleophilic substitution reaction. In this study, a fluorophore (termed as TPCA), derived from citric acid and 2-aminoethanethiol, was co-substituted with alanine ethyl ester onto the polyphosphazene backbone to obtain a photoluminescent biodegradable POPP (termed as PTA). The scaffolds made of PTA demonstrated non-cytotoxicity and cell affinity, particularly, capacity in promoting osteogenic differentiation of bone marrow mesenchymal stromal cells (BMSCs). In vivo evaluations using the rat calvarial defect model confirmed its strong potential in enhancing osteogenesis, more importantly, the in vivo degradation of the PTA scaffold could be monitored via its fluorescence intensity alongside implantation time.

Exosomes promote pre-metastatic niche formation in ovarian cancer

Ovarian cancer is one of the most common gynecological malignancies. Upon initial diagnosis, the majority of patients present with widespread metastatic growth within the peritoneal cavity. This metastatic growth occurs in stages, with the formation of a pre-metastatic niche occurring prior to macroscopic tumor cell invasion. Exosomes released by the primary ovarian tumor are small extracellular vesicles which prepare the distant tumor microenvironment for accelerated metastatic invasion. They regulate intercellular communication between tumor cells and normal stroma, cancer-associated fibroblasts, and local immune cells within the tumor microenvironment. In this review, we highlight the emerging roles of ovarian cancer exosomes as coordinators of pre-metastatic niche formation, biomarkers amenable to liquid biopsy, and targets of chemotherapy.