Calcium phosphate-phosphorylated adenosine hybrid microspheres for anti-osteosarcoma drug delivery and osteogenic differentiation

In vitro evaluation of doxorubicin release from diopside particles on MG-63 and HF spheroids as a 3D model of tumor and healthy tissues

Local drug delivery systems based on bioceramics ensure safe and effective treatment of bone defects and anticancer therapy. A promising drug delivery scaffold material for bone treatment applications is diopside (CaMgSi2O6) which is bioactive, degradable, and possesses drug-release ability. Currently, in vitro assessment of drug release from biomaterials is performed mostly on a 2D cell monolayer. However, to interpret and integrate biochemical signals, cells need a 3D microenvironment that provides cell-cell and cell-extracellular matrix interactions. In this regard, 3D cell models are gaining popularity. In this work, we proposed the protocol for evaluation of the effect of doxorubicin released from diopside on MG-63 cells and primary human fibroblasts in 3D culture conditions. Tissue spheroids with similar diameters were incubated with doxorubicin-loaded diopside for 72 h, the amount of diopside was calculated in accordance with the required doxorubicin concentration. We demonstrated that doxorubicin is gradually released from diopside and exhibits an activity similar to that of the pure drug at the same total concentration. It is important to note that doxorubicin was more potent on MG-63 spheroids compared to HF spheroids, which confirmed the reliability of spheroids as 3D models of tumor and healthy tissues.

Osteosarcoma cell death induced by innovative scaffolds doped with chemotherapeutics

Osteosarcoma (OS) cancer treatments include systemic chemotherapy and surgical resection. In the last years, novel treatment approaches have been proposed, which employ a drug-delivery system to prevent offside effects and improves treatment efficacy. Locally delivering anticancer compounds improves on high local concentrations with more efficient tumour-killing effect, reduced drugs resistance and confined systemic effects. Here, the synthesis of injectable strontium-doped calcium phosphate (SrCPC) scaffold was proposed as drug delivery system to combine bone tissue regeneration and anticancer treatment by controlled release of methotrexate (MTX) and doxorubicin (DOX), coded as SrCPC-MTX and SrCPC-DOX, respectively. The drug-loaded cements were tested in an in vitro model of human OS cell line SAOS-2, engineered OS cell line (SAOS-2-eGFP) and U2-OS. The ability of doped scaffolds to induce OS cell death and apoptosis was assessed analysing cell proliferation and Caspase-3/7 activities, respectively. To determine if OS cells grown on doped-scaffolds change their migratory ability and invasiveness, a wound-healing assay was performed. In addition, the osteogenic potential of SrCPC material was evaluated using human adipose derived-mesenchymal stem cells. Osteogenic markers such as (i) the mineral matrix deposition was analysed by alizarin red staining; (ii) the osteocalcin (OCN) protein expression was investigated by enzyme-linked immunosorbent assay test, and (iii) the osteogenic process was studied by real-time polymerase chain reaction array. The delivery system induced cell-killing cytotoxic effects and apoptosis in OS cell lines up to Day 7. SrCPC demonstrates a good cytocompatibility and it induced upregulation of osteogenic genes involved in the skeletal development pathway, together with OCN protein expression and mineral matrix deposition. The proposed approach, based on the local, sustained release of anticancer drugs from nanostructured biomimetic drug-loaded cements is promising for future therapies aiming to combine bone regeneration and anticancer local therapy.

Black phosphorus, an advanced versatile nanoparticles of antitumor, antibacterial and bone regeneration for OS therapy

Osteosarcoma (OS) is the most common primary malignant bone tumor. In the clinic, usual strategies for OS treatment include surgery, chemotherapy, and radiation. However, all of these therapies have complications that cannot be ignored. Therefore, the search for better OS treatments is urgent. Black phosphorus (BP), a rising star of 2D inorganic nanoparticles, has shown excellent results in OS therapy due to its outstanding photothermal, photodynamic, biodegradable and biocompatible properties. This review aims to present current advances in the use of BP nanoparticles in OS therapy, including the synthesis of BP nanoparticles, properties of BP nanoparticles, types of BP nanoparticles, and modification strategies for BP nanoparticles. In addition, we have discussed comprehensively the application of BP in OS therapy, including single, dual, and multimodal synergistic OS therapies, as well as studies about bone regeneration and antibacterial properties. Finally, we have summarized the conclusions, limitations and perspectives of BP nanoparticles for OS therapy.

Calcium-based biomaterials: Unveiling features and expanding applications in osteosarcoma treatment

Calcium, an indispensable element in bone tissues, plays a crucial role in various cellular processes involved in cancer progression. Its ubiquitous yet spatially distinct distribution in the body presents an opportunity to target calcium homeostasis as a novel strategies for cancer treatment, with specific advantages in osteosarcoma therapy. In this comprehensive review, we retrospect the calcium biology intersected with cancer progression, highlight the unveiling features of calcium-based biomaterials in regulating both bone homeostasis and cancer development. We also provide an overview of recent breakthroughs in cancer therapy that leverage calcium biomaterials, showcasing their potential to serve as versatile, customizable platforms for osteosarcoma treatment and as reservoirs for supporting bone reconstruction.

Zeolitic Imidazolate Framework (ZIF-8) Decorated Iron Oxide Nanoparticles Loaded Doxorubicin Hydrochloride for Osteosarcoma Treatment - in vitro and in vivo Preclinical Studies

Background

As a broad-spectrum antitumorigenic agent, doxorubicin (DOX) is commonly used as a chemotherapeutic drug for treating osteosarcoma (OS). Still, it is associated with significant cell toxicity and ineffective drug delivery, whereas the zeolite imidazolate framework is extensively applied in the biomedical field as a carrier owing to its favorable biocompatibility, high porosity, and pH-responsiveness. Therefore, we need to develop a drug delivery platform that can effectively increase the antitumorigenic effect of the loaded drug and concurrently minimize drug toxicity.

Methods

In this study, a Fe3O4@ZIF-8 nanocomposite carrier was prepared with ZIF-8 as the shell and encapsulated with Fe3O4 by loading DOX to form DOX- Fe3O4@ZIF-8 (DFZ) drug-loaded magnetic nanoparticles. Then, we characterized and analyzed the morphology, particle size, and characteristics of Fe3O4@ZIF-8 and DFZ by TEM, SEM, and Malvern. Moreover, we examined the inhibitory effects of DFZ in vitro and in vivo. Meanwhile, we established a tumor-bearing mouse model, evaluating its tumor-targeting by external magnetic field guidance.

Results

DFZ nanoparticles possessed have a size of ~110 nm, with an encapsulation rate of 21% and pH responsiveness. DFZ exerted a superior cytostatic effect and apoptosis rate on K7M2 cells in vitro compared to DOX(p<0.01). In animal experiments, DFZ offers up to 67% tumor inhibition and has shown a superior ability to induce apoptosis than DOX alone in TUNEL results(p<0.01). Tumor-targeting experiments have validated that DFZ can be effectively accumulated in the tumor tissue and enhance anticancer performance.

Conclusion

In summary, the DFZ nano-delivery system exhibited a more substantial anti-tumorigenic effect as well as superior active tumor targeting of DOX- Fe3O4@ZIF-8 compared to that of DOX alone in terms of biocompatibility, drug loading capacity, pH-responsiveness, tumor-targeting, and anti-tumorigenic effect, indicating its chemotherapeutic application potential.

Hierarchically Structured Hydroxyapatite Particles Facilitate the Enhanced Integration and Selective Anti-Tumor Effects of Amphiphilic Prodrug for Osteosarcoma Therapy

Efficient delivery of cargo into target cells is a formidable challenge in modern medicine. Despite the great promise of biomimetic hydroxyapatite (HA) particles in tissue engineering, their potential applications in bone tumor therapy, particularly their structure-function relationships in cargo delivery to target cells, have not yet been well explored. In this study, biomimetic multifunctional composite microparticles (Bm-cMPs) are developed by integrating an amphiphilic prodrug of curcumin with hierarchically structured HA microspheres (Hs-hMPs). Then, the effects of the hierarchical structure of vehicles on the integration and delivery of cargo as well as the anti-osteosarcoma (OS) effect of the composite are determined. Different hierarchical structures of the vehicles strongly influence the self-assembly behavior of the prodrug. The flake-like crystals of Hs-hMPs enable the highest loading capacity and enhance the stability of the cargo. Compared to the normal cells, OS cells exhibit 3.56-times better uptake of flake-like Hs-hMPs, facilitating the selective anti-tumor effect of the prodrug. Moreover, Bm-cMPs suppress tumor growth and metastasis by promoting apoptosis and inhibiting cell proliferation and tumor vascularization. The findings shed light on the potential application of Bm-cMPs and suggest a feasible strategy for developing an effective targeted therapy platform using hierarchically structured minerals for OS treatment.

Localized Nanoparticle-Mediated Delivery of miR-29b Normalizes the Dysregulation of Bone Homeostasis Caused by Osteosarcoma whilst Simultaneously Inhibiting Tumor Growth

Patients diagnosed with osteosarcoma undergo extensive surgical intervention and chemotherapy resulting in dismal prognosis and compromised quality of life owing to poor bone regeneration, which is further compromised with chemotherapy delivery. This study aims to investigate if localized delivery of miR-29b-which is shown to promote bone formation by inducing osteoblast differentiation and also to suppress prostate and cervical tumor growth-can suppress osteosarcoma tumors whilst simultaneously normalizing the dysregulation of bone homeostasis caused by osteosarcoma. Thus, the therapeutic potential of microRNA (miR)-29b is studied to promote bone remodeling in an orthotopic model of osteosarcoma (rather than in bone defect models using healthy mice), and in the context of chemotherapy, that is clinically relevant. A formulation of miR-29b:nanoparticles are developed that are delivered via a hyaluronic-based hydrogel to enable local and sustained release of the therapy and to study the potential of attenuating tumor growth whilst normalizing bone homeostasis. It is found that when miR-29b is delivered along with systemic chemotherapy, compared to chemotherapy alone, the therapy provided a significant decrease in tumor burden, an increase in mouse survival, and a significant decrease in osteolysis thereby normalizing the dysregulation of bone lysis activity caused by the tumor.

Reduction-responsive dextran-based Pt(IV) nano-prodrug showed a synergistic effect with doxorubicin for effective melanoma treatment

Melanoma, the deadliest skin cancer with high metastasis potential, has posed a great threat to human health. Accordingly, early efficient blocking of melanoma progression is vital in antitumor treatment. Herein, a reduction-responsive dextran-based Pt(IV) nano-prodrug (PDPN) was synthesized and used for doxorubicin (DOX) delivery to combat melanoma synergistically. First, PDPN was prepared by one-pot chemical coupling of carboxylated methoxy poly(ethylene glycol) (mPEG), dextran (Dex), and the crosslinking agent cisPt (IV)-COOH. PDPN had a spherical structure (R_h = 34 ± 11.3 nm). Then, DOX was encapsulated into the PDPN core to form DOX-loaded PDPN (PDPN-DOX). The obtained PDPN-DOX displayed reduction-responsive release of DOX and Pt, thus showing a synergistic anticancer effect in B16F10 cells (combination index, 0.46). Furthermore, in vivo experiments demonstrated that PDPN-DOX was effective for the synergistic treatment of subcutaneous melanoma. Collectively, the as-prepared PDPN could serve as a promising and versatile nano-prodrug carrier for the co-delivery of chemotherapeutics in tumor combination therapy.

Synthetic biodegradable polymer materials in the repair of tumor-associated bone defects

The repair and reconstruction of bone defects and the inhibition of local tumor recurrence are two common problems in bone surgery. The rapid development of biomedicine, clinical medicine, and material science has promoted the research and development of synthetic degradable polymer anti-tumor bone repair materials. Compared with natural polymer materials, synthetic polymer materials have machinable mechanical properties, highly controllable degradation properties, and uniform structure, which has attracted more attention from researchers. In addition, adopting new technologies is an effective strategy for developing new bone repair materials. The application of nanotechnology, 3D printing technology, and genetic engineering technology is beneficial to modify the performance of materials. Photothermal therapy, magnetothermal therapy, and anti-tumor drug delivery may provide new directions for the research and development of anti-tumor bone repair materials. This review focuses on recent advances in synthetic biodegradable polymer bone repair materials and their antitumor properties.

Recent advances on small molecules in osteogenic differentiation of stem cells and the underlying signaling pathways

Bone-related diseases are major contributors to morbidity and mortality in elderly people and the current treatments result in insufficient healing and several complications. One of the promising areas of research for healing bone fractures and skeletal defects is regenerative medicine using stem cells. Differentiating stem cells using agents that shift cell development towards the preferred lineage requires activation of certain intracellular signaling pathways, many of which are known to induce osteogenesis during embryological stages. Imitating embryological bone formation through activation of these signaling pathways has been the focus of many osteogenic studies. Activation of osteogenic signaling can be done by using small molecules. Several of these agents, e.g., statins, metformin, adenosine, and dexamethasone have other clinical uses but have also shown osteogenic capacities. On the other hand, some other molecules such as T63 and tetrahydroquinolines are not as well recognized in the clinic. Osteogenic small molecules exert their effects through the activation of signaling pathways known to be related to osteogenesis. These pathways include more well-known pathways including BMP/Smad, Wnt, and Hedgehog as well as ancillary pathways including estrogen signaling and neuropeptide signaling. In this paper, we review the recent data on small molecule-mediated osteogenic differentiation, possible adjunctive agents with these molecules, and the signaling pathways through which each small molecule exerts its effects.

Injectable, Anti-Cancer Drug-Eluted Chitosan Microspheres against Osteosarcoma

The purpose of this study is to fabricate different anti-cancer drug-eluted chitosan microspheres for combination therapy of osteosarcoma. In this study, electrospray in combination with ground liquid nitrogen was utilized to manufacture the microspheres. The size of obtained chitosan microspheres was uniform, and the average diameter was 532 μm. The model drug release rate and biodegradation rate of chitosan microspheres could be controlled by the glutaraldehyde vapor crosslinking time. Then the 5-fluorouracil (5-FU), paclitaxel (PTX), and Cis-dichlorodiammine-platinum (CDDP) eluted chitosan microspheres were prepared, and two osteosarcoma cell lines, namely, HOS and MG-63, were selected as cell models for in vitro demonstration. We found the 5-FU microspheres, PTX microspheres, and CDDP microspheres could significantly inhibit the growth and migration of both HOS and MG-63 cells. The apoptosis of both cells treated with 5-FU microspheres, PTX microspheres, and CDDP microspheres was significantly increased compared to the counterparts of control and blank groups. The anti-cancer drug-eluted chitosan microspheres show great potential for the treatment of osteosarcoma.

Milk Protein-Based Nanohydrogels: Current Status and Applications

Milk proteins are excellent biomaterials for the modification and formulation of food structures as they have good nutritional value; are biodegradable and biocompatible; are regarded as safe for human consumption; possess valuable physical, chemical, and biological functionalities. Hydrogels are three-dimensional, cross-linked networks of polymers capable of absorbing large amounts of water and biological fluids without dissolving and have attained great attraction from researchers due to their small size and high efficiency. Gelation is the primary technique used to synthesize milk protein nanohydrogels, whereas the denaturation, aggregation, and gelation of proteins are of specific significance toward assembling novel nanostructures such as nanohydrogels with various possible applications. These are synthesized by either chemical cross-linking achieved through covalent bonds or physical cross-linking via noncovalent bonds. Milk-protein-based gelling systems can play a variety of functions such as in food nutrition and health, food engineering and processing, and food safety. Therefore, this review highlights the method to prepare milk protein nanohydrogel and its diverse applications in the food industry.

An instantly fixable and self-adaptive scaffold for skull regeneration by autologous stem cell recruitment and angiogenesis

Limited stem cells, poor stretchability and mismatched interface fusion have plagued the reconstruction of cranial defects by cell-free scaffolds. Here, we designed an instantly fixable and self-adaptive scaffold by dopamine-modified hyaluronic acid chelating Ca²⁺ of the microhydroxyapatite surface and bonding type I collagen to highly simulate the natural bony matrix. It presents a good mechanical match and interface integration by appropriate calcium chelation, and responds to external stress by flexible deformation. Meanwhile, the appropriate matrix microenvironment regulates macrophage M2 polarization and recruits endogenous stem cells. This scaffold promotes the proliferation and osteogenic differentiation of BMSCs in vitro, as well as significant ectopic mineralization and angiogenesis. Transcriptome analysis confirmed the upregulation of relevant genes and signalling pathways was associated with M2 macrophage activation, endogenous stem cell recruitment, angiogenesis and osteogenesis. Together, the scaffold realized 97 and 72% bone cover areas after 12 weeks in cranial defect models of rabbit (Φ = 9 mm) and beagle dog (Φ = 15 mm), respectively.

Limited stem cells and mismatched interface fusion have plagued biomaterial-mediated cranial reconstruction. Here, the authors engineer an instantly fixable and self-adaptive scaffold to promote calcium chelation and interface integration, regulate macrophage M2 polarization, and recruit endogenous stem cells.

Physically-crosslinked hydroxyethyl cellulose-g-poly (acrylic acid-co-acrylamide)-Fe3+/silver nanoparticles for water disinfection and enhanced adsorption of basic methylene blue dye

In this study, we report the development of physically cross-linked hydroxyethyl cellulose grafted polyacrylic acid-co-polyacrylamide/silver nanocomposite [Ag@HEC-g-P(AA-co-AM)-Fe³⁺] possesses excellent antimicrobial and enhanced MB adsorption. A green in-situ reduction process was used to prepare silver nanoparticles. UV-Vis spectroscopy, TEM, ATR-IR, XRD, SEM-EDS were used to analyze the green produced silver nanoparticles and Ag@HEC-g-P(AA-co-AM)-Fe³⁺. The swelling ratio of Ag@HEC-g-P(AA-co-AM)-Fe³⁺ is dependent on AgNPs content and pH. The swelling kinetics fitted with Pseudo-second order. The cumulative release#% of AgNPs was 29.63 ± 1.7%, respectively up to 10 h and its kinetics obey Korsmeyer-Peppas model. The grafting to HEC and incorporation of AgNPs into HEC-g-P(AA-co-AM)-Fe³⁺ enhances the thermal stabilities and increases total activation energies from 19,122.2 to 66,287.1 KJ mol. Ag@HEC-g-P(AA-co-AM)-Fe³⁺ has powerful antimicrobial activity against Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, Micrococcus leutus, Staphyllococus aureus. The maximum adsorption capacity of MB was 133.38 ± 1.25 mg/g at nanocomposite concentration (300 mg/L), pH (9.0), and MB concentration (5 mg/L). To anticipate the adsorption mechanism, Pseudo-first and second-order models, as well as three isotherm models (Langmuir, Freundlich, and Temkin) were used to model adsorption kinetics. The nonlinear Langmuir models and second-order kinetics were the most appropriate.

Calcium Phosphate-Based Bioceramics in the Treatment of Osteosarcoma: Drug Delivery Composites and Magnetic Hyperthermia Agents

The use of biomaterials in medicine is not recent, and in the last few decades, the research and development of biocompatible materials had emerged. Hydroxyapatite (HAp), a calcium phosphate that constitutes a large part of the inorganic composition of human bones and teeth, has been used as an interesting bioceramic material. Among its applications, HAp has been used to carry antitumor drugs, such as doxorubicin, cisplatin, and gemcitabine. Such HAp-based composites have an essential role in anticancer drug delivery systems, including the treatment of osteosarcoma. In addition, the association of this bioceramic with magnetic nanoparticles (MNPs) has also been used as an effective agent of local magnetic hyperthermia. Further, the combined approach of the aforementioned techniques (HAp scaffolds combined with anti-tumor drugs and MNPs) is also an attractive therapeutical alternative. Considering the promising role of the use of bioceramics in modern medicine, we proposed this review, presenting an updated perspective on the use of HAp in the treatment of cancer, especially osteosarcoma. Finally, after giving the current progress in this field, we highlight the urgent need for efforts to provide a better understanding of their potential applications.

Biomineralization-inspired synthesis of amorphous manganese phosphates for GLUT5-targeted drug-free catalytic therapy of osteosarcoma

Osteosarcoma, occurring most frequently in children, teens, and young adults, is a lethal bone cancer with a high incidence of distant metastases and drug resistance. Developing a therapeutic platform that integrates targeting, curing and imaging is highly desirable for enhanced osteosarcoma therapy, yet quite challenging. In this work, we demonstrate a novel biomineralization-inspired strategy for the synthesis of a fructose incorporated manganese phosphate (Fru-MnP) nanoplatform for tumour targeting, drug-free therapy, and MRI imaging. Benefitting from the glucose transporter 5 (GLUT5)-mediated endocytosis, our Fru-MnP nanoplatform produces a high level of reactive oxygen species (ROS) via the Mn²⁺-driven Fenton reaction within osteosarcoma cells, leading to efficient cancer cell killing due to caspase-mediated apoptosis. By virtue of the T1 signal enhancement of Mn²⁺, our Fru-MnP nanoplatform also acts as an effective tumour-specific MRI contrast agent, realizing the MRI-monitored chemodynamic therapy. The proposed synergistic therapeutic platform opens new possibilities for high efficacy therapy for osteosarcoma.

Hydroxyapatite-binding albumin nanoclusters for enhancing bone tumor chemotherapy

Hydroxyapatite-binding albumin nanoclusters (NCs) were developed for improving the anticancer agent accumulation in bone tumors. Human serum albumin (HSA) was decorated with alendronate (AD), and doxorubicin (DOX)-loaded NCs (HSA-AD/DOX) were fabricated via the ball-milling technology, an innovative nano-fabrication method by which more than 90% of the secondary structures of albumin can be preserved. The targeting ability of NCs was confirmed using a novel in vitro bone cancer model, wherein hydroxyapatite and collagen, the major components of the bone matrix representing the highly mineralized bone tumor microenvironment, were co-cultured with HOS/MNNG, a human osteosarcoma cell line. The binding affinity of HSA-AD/DOX to hydroxyapatite was evaluated based on the DOX binding efficiency. HSA-AD/DOX showed a 5.04-fold higher affinity than HSA/DOX. The enhanced distribution of HSA-AD/DOX to bone tumors was verified using a newly developed mouse model bearing HOS/MNNG tumors with hydroxyapatite beads. HSA-AD/DOX led to a 52.0% increase in tumor accumulation compared to that of the unmodified HSA/DOX. This is mainly due to the hydroxyapatite-binding affinity of the AD moiety, which is supported by histological analyses performed on the dissected tumors. Furthermore, HSA-AD/DOX changed the protein expression patterns of the tumors, implying the enhanced apoptotic process. Overall, the targeting ability of HSA-AD/DOX are effectively translated into improved therapeutic efficacy in bone tumor-xenografted mice, suggesting that the developed NCs are a promising delivery system for bone tumor treatment.

Tumor Diagnosis and Therapy Mediated by Metal Phosphorus-Based Nanomaterials

Metal phosphorus-based nanomaterials (Metal-P NMs) including metal phosphate nanomaterials, metal phosphide nanomaterials, and metal-black phosphorus (Metal-BP) nanocomposite are widely used in the field of biomedicine owing to their excellent physical and chemical properties, biocompatibility, and biodegradability. In recent years, metal phosphate nanomaterials and Metal-BP nanocomposite acted as medicine delivery system have made breakthroughs in tumor diagnosis including magnetic resonance imaging, fluorescence imaging, photoacoustic imaging, nuclear imaging, and therapies including chemotherapy, gene therapy, photothermal therapy, photodynamic therapy, and radiation therapy. Metal phosphate nanomaterials have good biodegradability, especially calcium-based metal phosphate nanomaterials can be dissolved into nontoxic ions and participate in the metabolisms of normal organs. Compared with metal phosphate nanomaterials, metal phosphide nanomaterials have excellent optical, magnetic, and catalytic properties, which can be used as multifunctional diagnostic nanoplatforms and therapeutic agents for chemodynamic therapy, photothermal therapy, or immunotherapy. The latest developments in Metal-P NMs, covering the range of preparation methods and biological applications, such as serving as drug carriers, tumor diagnosis, and therapy, are focused. All in all, the current trends, key issues, future prospects and challenges of Metal-P NMs are concluded and discussed, which are important for the development of this research field and shining more lights on this direction.

Amorphous calcium phosphate nanoparticles using adenosine triphosphate as an organic phosphorus source for promoting tendon-bone healing

Background

Rotator cuff tear (RCT) is a common problem of the musculoskeletal system. With the advantage of promoting bone formation, calcium phosphate materials have been widely used to augment tendon-bone healing. However, only enhancing bone regeneration may be not enough for improving tendon–bone healing. Angiogenesis is another fundamental factor required for tendon–bone healing. Therefore, it’s necessary to develop a convenient and reliable method to promote osteogenesis and angiogenesis simultaneously, thereby effectively promoting tendon–bone healing.

Methods

The amorphous calcium phosphate (ACP) nanoparticles with dual biological activities of osteogenesis and angiogenesis were prepared by a simple low-temperature aqueous solution method using adenosine triphosphate (ATP) as an organic phosphorus source. The activities of osteogenesis and angiogenesis and the effect on the tendon–bone healing of ACP nanoparticles were tested in vitro and in a rat model of acute RCT.

Results

The ACP nanoparticles with a diameter of tens of nanometers were rich in bioactive adenosine. In vitro, we confirmed that ACP nanoparticles could enhance osteogenesis and angiogenesis. In vivo, radiological and histological evaluations demonstrated that ACP nanoparticles could enhance bone and blood vessels formation at the tendon–bone junction. Biomechanical testing showed that ACP nanoparticles improved the biomechanical strength of the tendon–bone junction and ultimately promoted tendon–bone healing of rotator cuff.

Conclusions

We successfully confirmed that ACP nanoparticles could promote tendon–bone healing. ACP nanoparticles are a promising biological nanomaterial in augmenting tendon–bone healing.

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-01007-y.

Sustained and controlled delivery of doxorubicin from an in-situ setting biphasic hydroxyapatite carrier for local treatment of a highly proliferative human osteosarcoma

Doxorubicin (DOX) is a cornerstone drug in the treatment of osteosarcoma. However, achieving sufficient concentration in the tumor tissue after systemic administration with few side effects has been a challenge. Even with the most advanced nanotechnology approaches, less than 5% of the total administered drug gets delivered to the target site. Alternatives to increase the local concentration of DOX within the tumor using improved drug delivery methods are needed. In this study, we evaluate a clinically approved calcium sulfate/hydroxyapatite (CaS/HA) carrier, both in-vitro and in-vivo, for local, sustained and controlled delivery of DOX to improve osteosarcoma treatment. In-vitro drug release studies indicated that nearly 28% and 36% of the loaded drug was released over a period of 4-weeks at physiological pH (7.4) and acidic pH (5), respectively. About 63% of the drug had been released after 4-weeks in-vivo. The efficacy of the released drug from the CaS/HA material was verified on two human osteosarcoma cell lines MG-63 and 143B. It was demonstrated that the released drug fractions functioned the same way as the free drug without impacting its efficacy. Finally, the carrier system with DOX was assessed using two clinically relevant human osteosarcoma xenograft models. Compared to no treatment or the clinical standard of care with systemic DOX administration, the delivery of DOX using a CaS/HA biomaterial could significantly hinder tumor progression by inhibiting angiogenesis and cell proliferation. Our results indicate that a clinically approved CaS/HA biomaterial containing cytostatics could potentially be used for the local treatment of osteosarcoma. STATEMENT OF SIGNIFICANCE: The triad of doxorubicin (DOX), methotrexate and cisplatin has routinely been used for the treatment of osteosarcoma. These drugs dramatically improved the prognosis, but 45-55% of the patients respond poorly to the treatment with low 5-year survival. In the present study, we repurpose the cornerstone drug DOX by embedding it in a calcium sulfate/hydroxyapatite (CaS/HA) biomaterial, ensuring a spatio-temporal drug release and a hypothetically higher and longer lasting intra-tumoral concentration of DOX. This delivery system could dramatically hinder the progression of a highly aggressive osteosarcoma compared to systemic administration, by inhibiting angiogenesis and cell proliferation. Our data show an efficient method for supplementary osteosarcoma treatment with possible rapid translational potential due to clinically approved constituents.

Precise engineering of acorn-like Janus nanoparticles for cancer theranostics

The anisotropic Janus nanoparticles (JNPs) provide synergistic effects by concentrating multiple properties on a single carrier. Herein, we reported a novel and simple approach to fabricate acorn-like poly(acrylic acid)-mesoporous calcium phosphate/polydopamine (PAA-mCaP/PDA) JNPs, which were selectively functionalized with methoxy-poly(ethylene glycol)thiol (PEG-SH) on PDA domains to obtain superior stability, while the other mCaP sides served as a storage space and passage for the anti-cancer drug of doxorubicin (DOX). The unique acorn-like PAA-mCaP/PDA-PEG JNPs were utilized as novel theranostic agents for photoacoustic (PA) imaging-guided synergistic cancer chemo-phototherapy. More importantly, this synthetic strategy can be applied to synthesize various mesoporous Janus nanocarriers, paving the way toward designed synthesis of acorn-like JNPs in nanomedicine, biosensing and catalysis. STATEMENT OF SIGNIFICANCE: The distinct acorn-like poly(acrylic acid)-mesoporous calcium phosphate/polydopamine Janus nanoparticles (PAA-mCaP/PDA JNPs) with a spherical-shaped PAA-mCaP core and PDA half-shell were fabricated for the first time. To achieve superior stability, the acorn-like PAA-mCaP/PDA JNPs were selectively functionalized with methoxy-poly(ethylene glycol)thiol (PEG-SH) on PDA domains to obtain acorn-like PAA-mCaP/PDA-PEG JNPs. The resultant acorn-like PAA-mCaP/PDA-PEG JNPs own an excellent biocompatibility, high drug-loading contents, good photothermal conversion efficiency, photoacoustic (PA) imaging capacity and pH/NIR dual-responsive properties, enabling the acorn-like JNPs to be applied for PA imaging-guided synergistic cancer chemo-phototherapy. More importantly, the synthetic approach could be extended to prepare acorn-like mesoporous inorganic substances/PDA JNPs for specific applications.

Innovative Biomaterials for the Treatment of Bone Cancer

Bone cancer is a demanding challenge for contemporary medicine due to its high frequency of presentation and significant heterogeneity of malignant lesions developing within the bone. To date, available treatments are rarely curative and are primarily aimed at prolonging patients' survival and ameliorating their quality of life. Furthermore, both pharmacological and surgical therapies are aggravated by a consistent burden of adverse events and subsequent disability due to the loss of healthy bone structural and functional properties. Therefore, great research efforts are being made to develop innovative biomaterials able to selectively inhibit bone cancer progression while reducing the loss of bone structural properties secondary to local tissue invasion. In this review, we describe the state of the art of innovative biomaterials for the treatment of bone cancer. Along with physiological bone remodeling, the development of bone metastasis and osteosarcoma will be depicted. Subsequently, recent advances on nanocarrier-based drug delivery systems, as well as the application of novel, multifunctional biomaterials for the treatment of bone cancer will be discussed. Eventually, actual limitations and promising future perspectives regarding the employment of such approaches in the clinical scenario will be debated.

Progress of biomaterials for bone tumor therapy

Bone tumors are currently a major clinical challenge. In recent decades, strategies using well-designed versatile biomaterials for the treatment of bone tumors have emerged and attracted extensive research interest. Suitable biomaterials not only facilitate repair for bone defects aroused by surgical intervention but also help deliver antineoplastic drugs to the target site or provide photothermal/magnetothermal therapy to kill bone tumor cells. Thus, the development of biomaterials exhibits a great perspective for future bone tumor treatment.We summarize the recent progress of versatile biomaterials for bone tumor therapy, with an emphasis on photothermal/magnetothermal therapy and drug delivery.With the further understanding and development of biomaterials, multifunctional biomaterials have been proposed for bone tumor treatment. Through the interdisciplinary cooperation from the fields of biomedicine, clinical medicine and engineering, multifunctional biomaterials will perfectly match individual bone defects in the clinic with low cost in the future.

Smart Cargo Delivery System based on Mesoporous Nanoparticles for Bone Disease Diagnosis and Treatment

Bone diseases constitute a major issue for modern societies as a consequence of progressive aging. Advantages such as open mesoporous channel, high specific surface area, ease of surface modification, and multifunctional integration are the driving forces for the application of mesoporous nanoparticles (MNs) in bone disease diagnosis and treatment. To achieve better therapeutic effects, it is necessary to understand the properties of MNs and cargo delivery mechanisms, which are the foundation and key in the design of MNs. The main types and characteristics of MNs for bone regeneration, such as mesoporous silica (mSiO2 ), mesoporous hydroxyapatite (mHAP), mesoporous calcium phosphates (mCaPs) are introduced. Additionally, the relationship between the cargo release mechanisms and bone regeneration of MNs-based nanocarriers is elucidated in detail. Particularly, MNs-based smart cargo transport strategies such as sustained cargo release, stimuli-responsive (e.g., pH, photo, ultrasound, and multi-stimuli) controllable delivery, and specific bone-targeted therapy for bone disease diagnosis and treatment are analyzed and discussed in depth. Lastly, the conclusions and outlook about the design and development of MNs-based cargo delivery systems in diagnosis and treatment for bone tissue engineering are provided to inspire new ideas and attract researchers' attention from multidisciplinary areas spanning chemistry, materials science, and biomedicine.

Synthesis, Structural, Morphological and Thermal Characterization of Five Different Silica-Polyethylene Glycol-Chlorogenic Acid Hybrid Materials

The present study investigated the structure, morphology, thermal behavior, and bacterial growth analysis of novel three-component hybrid materials synthesized by the sol-gel method. The inorganic silica matrix was weakly bonded to the network of two organic components: a well-known polymer such as polyethylene glycol (PEG, average molar mass of about 4000 g/mol), and an antioxidant constituted by chlorogenic acid (CGA). In particular, a first series was made by a 50 wt% PEG-based (CGA-free) silica hybrid along with two 50 wt% PEG-based hybrids containing 10 and 20 wt% of CGA (denoted as SP50, SP50C10 and SP50C20, respectively). A second series contained a fixed amount of CGA (20 wt%) in silica-based hybrids: one was the PEG-free material (SC20) and the other two contained 12 and 50 wt% of PEG, respectively (SP12C20 and SP50C20, respectively), being the latter already included in the first series. The X-ray diffraction (XRD) patterns and scanning electron microscope (SEM) images of freshly prepared materials confirmed that all the materials were amorphous and homogeneous regardless of the content of PEG or CGA. The thermogravimetric (TG) analysis revealed a higher water content was adsorbed into the two component hybrids (SP50 and SC20) because of the availability of a larger number of H-bonds to be formed with water with respect to those of silica/PEG/CGA (SPC), where silica matrix was involved in these bonds with both organic components. Conversely, the PEG-rich materials (SP50C10 and SP50C20, both with 50 wt% of the polymer) retained a lower content of water. Decomposition of PEG and CGA occurred in almost the same temperature interval regardless of the content of each organic component. The antibacterial properties of the SiO₂/PEG/CGA hybrid materials were studied in pellets using either Escherichia coli and Enterococcus faecalis, respectively. Excellent antibacterial activity was found against both bacteria regardless of the amount of polymer in the hybrids.

Nanocarrier-based drug delivery systems for bone cancer therapy: a review

Bone cancer is a malignant tumor that originates in the bone and destroys the healthy bone tissues. Of the various types of bone tumors, osteosarcoma is the most commonly diagnosed primary bone malignancy. The standard treatment for primary malignant bone tumors comprises surgery, chemotherapy and radiotherapy. Owing to the lack of proven treatments, different forms of alternative therapeutic approaches have been examined in recent decades. Among the new therapeutic methodologies, nanotechnology-based anticancer therapy has paved the way for new targeted strategies for bone cancer treatment and bone regeneration. They include approaches such as the co-delivery of multiple drug cargoes, the enhancement of their biodistribution and transport properties, normalizing accumulation and the optimization of drug release profiles to overcome shortcomings of the existing therapy. This review examines the standard treatments for osteosarcoma, their lacunae, and the evolving therapeutic strategies based on nanocarrier-mediated combinational drug delivery systems, and future perspectives for osteosarcoma therapy.

In situ pocket-type microcarrier (PMc) as a therapeutic composite: Regeneration of cartilage with stem cells, genes, and drugs

We prepared pocket-type micro-carriers (PMc) with pores larger than 30 μm for use in cell delivery by adding 40 mg pluronic F-127 copolymers (F-127) to biodegradable PLGA dissolved in dichloromethane solution. The controlling the size of the pockets in this way facilitates the adhesion of cells by regulating the size of the pockets according to the cells having various sizes. The size of PMc pores could be controlled within a range of 2 to 30 μm by varying the F-127 content. The ratio of F-127 to DOPA-bPEI was most appropriate at 1: 1, and the pocket size at 10 mg/ml of F-127 was appropriate for adhering 20-30 μm stem cells. F-127 containing SOX9 pDNA, in combination with DOPA-polyethylene-coated gold nanoparticles and dexamethasone loaded in PMcs, promoted cartilage differentiation. Gold nanoparticles complex and dexamethasone (DEX) loaded in PMcs were identified by micro-CT imaging and fluorescence imaging, respectively. By captured in pore generated on/in microspheres, the stem cells were safe and stable for use in delivery, both in vitro and in an animal model. Thus, microsphere pores can safely capture stem cells, and at the same time provide a microenvironment in which the captured stem cells can differentiate into chondrocytes.

Review of a new bone tumor therapy strategy based on bifunctional biomaterials

Bone tumors, especially those in osteosarcoma, usually occur in adolescents. The standard clinical treatment includes chemotherapy, surgical therapy, and radiation therapy. Unfortunately, surgical resection often fails to completely remove the tumor, which is the main cause of postoperative recurrence and metastasis, resulting in a high mortality rate. Moreover, bone tumors often invade large areas of bone, which cannot repair itself, and causes a serious effect on the quality of life of patients. Thus, bone tumor therapy and bone regeneration are challenging in the clinic. Herein, this review presents the recent developments in bifunctional biomaterials to achieve a new strategy for bone tumor therapy. The selected bifunctional materials include 3D-printed scaffolds, nano/microparticle-containing scaffolds, hydrogels, and bone-targeting nanomaterials. Numerous related studies on bifunctional biomaterials combining tumor photothermal therapy with enhanced bone regeneration were reviewed. Finally, a perspective on the future development of biomaterials for tumor therapy and bone tissue engineering is discussed. This review will provide a useful reference for bone tumor-related disease and the field of complex diseases to combine tumor therapy and tissue engineering.

Design strategies and evolving role of biomaterial assisted treatment of osteosarcoma

Osteosarcoma is the most commonly diagnosed form of bone cancer. It is characterized by a high risk of developing lung metastasis as the disease progresses. Standard treatment includes combination of surgical intervention, chemotherapy and radiotherapy. However, the non-specificity of potent chemotherapeutic agents often leads to major side effects. In this review, we discuss the role of various classes of biomaterials, including both organic as well as inorganic in realizing the local and systemic delivery of therapeutic agents like drugs, radioisotopes and even gene silencing agents to treat osteosarcoma. Biomaterial assisted unconventional therapies such as targeted therapy, nanotherapy, magnetic hyperthermia, gene therapy, photothermal and photodynamic therapies are also being explored. A wide variety of biomaterials including lipids, carbon-based materials, polymers, silica, bioactive glass, hydroxyapatite and metals are designed as delivery systems with the desired loading efficiency, release profile, and on-demand delivery. Among others, liposomal carriers have attracted a great deal of attention due to their capability to encapsulate both hydrophobic and hydrophilic drugs. Polymeric systems have high drug loading efficiency and stability and can even be tailored to achieve desired size and physiochemical properties. Carbon-based systems can also be seen as an upcoming class of therapeutics with great potential in treating different types of cancer. Inorganic materials like silica nanoparticles have high drug payload owing to their mesoporous structure. On the other hand, ceramic materials like bioactive glass and hydroxyapatite not only act as excellent delivery vectors but also participate in osteo-regeneration activity. These multifunctional biomaterials are also being investigated for their theranostic abilities to monitor cancer ablation. This review systematically discusses the vast landscape of biomaterials along with their challenges and respective opportunities for osteosarcoma therapy.

A novel multifunctional carbon aerogel-coated platform for osteosarcoma therapy and enhanced bone regeneration

Nowadays, groundbreaking strategies are urgently needed to address drug resistance, osteolysis, bone defects and other predicaments impeding the therapeutic efficacy of osteosarcoma. Among them, photothermal therapy (PTT), using systematically administrated nanoagents, exhibits attractive therapeutic efficacy, yet is powerless in bone defect regeneration. Herein, a novel multifunctional beta-tricalcium phosphate (β-Ca3(PO4)2, β-TCP) bioceramic platform-coated with carbon aerogel (CA), which was initially developed for tumor therapy, was fabricated. On account of the desirable photothermal capabilities of CA, sufficient hyperthermia is generated under the irradiation of an 808 nm laser to achieve a thorough ablation of osteosarcoma tumors. Furthermore, CA-coated surfaces provide extra roughness and a higher specific surface area, which promoted the protein recruitment ability and osteogenesis via a fibronectin (FN)-mediated signaling pathway. The photothermal therapeutic efficacy and osteogenesis capability of CA-coated β-TCP-C suggests a novel approach for the treatment of osteosarcoma and provides provoking inspiration for the prospective bio-application of CA.

Tripeptide-based macroporous hydrogel improves the osteogenic microenvironment of stem cells

Due to the ability to combine multiple osteogenic induction "cues" at the same time, hydrogels are widely used in the three-dimensional (3D) culture of human mesenchymal stem cells (hMSCs) and osteoinduction. However, the survival and proliferation of stem cells in a 3D culture system are limited, which reduces their osteogenic differentiation efficiency. In addition, the cells inside the hydrogel are prone to apoptosis due to hypoxia, which is a serious challenge for tissue engineering based on stem cells. In this study, a tripeptide-based macroporous alginate hydrogel was prepared to improve the osteogenic microenvironment of stem cells. The arginine-glycine-aspartate (RGD) peptide promoted the adhesion and proliferation of stem cells, and the degradation of gelatin microspheres (GMs) produced a macroporous structure to enhance further the migration and aggregation of stem cells. Mesoporous silica nanoparticles (MSNs) sustained-release bone-forming peptide-1 (BFP-1) induced osteogenic differentiation, and the sustained release of the QK peptide from the GMs promoted angiogenesis. In vitro experiments have shown that this functionalized hydrogel stimulates the proliferation of hMSCs, encourages larger cell cluster formation, and enhances the osteogenic differentiation efficiency. The released QK facilitates the proliferation and migration of endothelial cells. In vivo experiments have also verified that this system has a better osteogenic effect, and more blood vessels were observed inside the hydrogel, than in other systems. In general, this research has led to the development of a tripeptide macroporous hydrogel that can simultaneously promote osteogenesis and angiogenesis, showing great promise for applications of 3D cultures and stem cell-based tissue engineering.

M-keratin nano-materials create a mineralized micro-circumstance to promote proliferation and differentiation of DPSCs

As traditional root canal obturation leads to the loss of the biological activity of the tooth, it is necessary to develop a material that promotes the regeneration of dental tissue. However, this remains a challenging task. Our study aims to construct a mineralized material to support the proliferation and differentiation of dental pulp stem cells (DPSCs), and to explore a new strategy for the treatment of pulp tissue necrosis. Mineralized keratin (M-keratin), defined as keratin that has been mineralized in simulated body fluid, was first harvested to construct the root canal filling material. Characterizations indicated that new substances or components were formed on the surface of keratin particles after mineralization, and the morphology of the keratin was changed. M-keratin promoted the growth, proliferation, and differentiation of DPSCs. After cultivation with M-keratin, DPSCs exhibited more extracellular matrix proteins interacting with the culture interface, the number of these cells increased significantly, and the 3-[4,5-dimethylthiazol-2-yl-]-2,5-diphenyltetrazolium bromide values of cells in the experimental group also increased. Meanwhile, signs that the DPSCs began to differentiate into odontoblasts were observed or detected by alizarin red S staining, ELISA, RNA-Seq, and western blot. We hope that this study will contribute to the development of a new material that promotes the regeneration of dental tissue as well as providing new ideas and strategies for the treatment of dental pulp disease.

Selenium-doped calcium phosphate biomineral reverses multidrug resistance to enhance bone tumor chemotherapy

The construction of a functional drug delivery system to reverse the multidrug resistance (MDR) of bone tumors in cases of failed chemotherapy remains a challenge. Herein, we demonstrate a selenium-doped calcium phosphate (Se-CaP) biomineral with high biocompatibility, biodegradability and pH-sensitive drug release properties. Se-CaP may not only serve as an effective drug-carrier to enhance the uptake of doxorubicin (DOX), but may also synchronously induce caspases-mediated apoptosis of osteosarcoma by generating intracellular reactive oxygen species (ROS). Furthermore, in vitro and in vivo studies obviously demonstrate that Se-CaP can reverse the MDR of osteosarcoma by down-regulating the expression of MDR-related ABC (ATP binding cassette) transporters proteins (ABCB1 and ABCC1). Finally, DOX-loaded Se-CaP can significantly inhibit DOX-resistant MG63 (MG63/DXR) tumor growth in nude mice. Considering its biomimetic chemical properties, the Se-CaP biomineral, with the multiple functions mentioned above, could be a promising candidate for treating bone tumors with MDR characteristics.

pH-responsive silk fibroin-based CuO/Ag micro/nano coating endows polyetheretherketone with synergistic antibacterial ability, osteogenesis, and angiogenesis

Polyetheretherketone has been widely used for bone defect repair, whereas failures may happen due to implant loosening and infection. Thus, PEEK implant with multi-function (osteogenesis, angiogenesis, and bacteria-killing) is essential to solve this problem. Herein, copper oxide microspheres (µCuO) decorated with silver nanoparticles (nAg) were constructed on porous PEEK surface via silk fibroin. In vitro studies highlighted the pH controlled release ability of this coating. It liberated a high dose of Cu²⁺ and Ag⁺ at low pH environment (pH 5.0), leading to 99.99% killing of planktonic bacteria and complete eradication of sessile bacteria, avoiding biofilm formation. Under physiological environment (pH 7.4), a lower amount of leaked metal ions induced promoted ALP production, collagen secretion, and calcium deposition, as well as NO production, which indicated potentiated osteogenesis and angiogenesis. In vivo results displayed the highest new bone volume around, and the appearance of new bone inside porous structure of, PEEK implant with this coating in rabbit tibia, signified the abilities of this coating to promote bone regeneration and osseointegration. Our study established solid support for implants with this coating to be a successful bone defect repair solution. STATEMENT OF SIGNIFICANCE: In this study, CuO/Ag micro/nano particles were incorporated into the porous surface of PEEK through polydopamine and silk fibroin layers. The design of this coating conferred pH-controlled release behavior to Cu²⁺ and Ag⁺. High dose of metal ions were released at pH 5.0, which presented synergistic antibacterial ability and killed 99.99% of planktonic bacteria. Low concentration of metal ions were controlled by this coating at physiological environment, which potentiated osteodifferentiation of Ad-MSC in vitro and led to complete integration of implant with bone tissue in vivo.

Improved Osteogenesis of Selective-Laser-Melted Titanium Alloy by Coating Strontium-Doped Phosphate With High-Efficiency Air-Plasma Treatment

Surface treatment and bioactive metal ion incorporation are effective methods for the modification of titanium alloys to be used as biomaterials. However, few studies have demonstrated the use of air-plasma treatment in orthopedic biomaterial development. Additionally, no study has performed a direct comparison between unmodified titanium alloys and air-plasma-treated alloys with respect to their biocompatibility and osteogenesis. In this study, the biological activities of unmodified titanium alloys, air-plasma-treated titanium alloys, and air-plasma-treated strontium-doped/undoped calcium phosphate (CaP) coatings were compared. The strontium-doped CaP (Sr-CaP) coating on titanium alloys were produced by selective laser melting (SLM) technology as well as micro-arc oxidation (MAO) and air-plasma treatment. The results revealed that rapid air-plasma treatment improved the biocompatibility of titanium alloys and that Sr-CaP coating together with air-plasma treatment significantly enhanced both the biocompatibility and osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). Overall, this study demonstrated that low temperature air-plasma treatment is a fast and effective surface modification which improves the biocompatibility of titanium alloys. Additionally, air-plasma-treated Sr-CaP coatings have numerous practical applications and may provide researchers with new tools to assist in the development of orthopedic implants.

Bone Diseases: Current Approach and Future Perspectives in Drug Delivery Systems for Bone Targeted Therapeutics

Bone diseases include a wide group of skeletal-related disorders that cause mobility limitations and mortality. In some cases, e.g., in osteosarcoma (OS) and metastatic bone cancer, current treatments are not fully effective, mainly due to low patient compliance and to adverse side effects. To overcome these drawbacks, nanotechnology is currently under study as a potential strategy allowing specific drug release kinetics and enhancing bone regeneration. Polymers, ceramics, semiconductors, metals, and self-assembled molecular complexes are some of the most used nanoscale materials, although in most cases their surface properties need to be tuned by chemical or physical reactions. Among all, scaffolds, nanoparticles (NPs), cements, and hydrogels exhibit more advantages than drawbacks when compared to other nanosystems and are therefore the object of several studies. The aim of this review is to provide information about the current therapies of different bone diseases focusing the attention on new discoveries in the field of targeted delivery systems. The authors hope that this paper could help to pursue further directions about bone targeted nanosystems and their application for bone diseases and bone regeneration.

Biodegradable calcium phosphate nanoparticles for cancer therapy

Calcium phosphate is the inorganic mineral of hard tissues such as bone and teeth. Due to their similarities to the natural bone, calcium phosphates are highly biocompatible and biodegradable materials that have found numerous applications in dental and orthopedic implants and bone tissue engineering. In the form of nanoparticles, calcium phosphate nanoparticles (CaP's) can also be used as effective delivery vehicles to transfer therapeutic agents such as nucleic acids, drugs, proteins and enzymes into tumor cells. In addition, facile preparation and functionalization of CaP's, together with their inherent properties such as pH-dependent solubility provide advantages in delivery and release of these bioactive agents using CaP's as nanocarriers. In this review, the challenges and achievements in the intracellular delivery of these agents to tumor cells are discussed. Also, the most important issues in the design and potential applications of CaP-based biominerals are addressed with more focus on their biodegradability in tumor microenvironment.

Controlled Delivery of Curcumin and Vitamin K2 from Hydroxyapatite-Coated Titanium Implant for Enhanced in Vitro Chemoprevention, Osteogenesis, and in Vivo Osseointegration

Successful repair of critical-sized tumor-resection defects, especially in load-bearing bones, still remains a major challenge in clinical orthopedics. Titanium (Ti) implants have been increasingly used in the past few decades because of titanium's suitable mechanical properties and biocompatibility; however, it shows insufficient integration with the surrounding bone. In this study, the plasma spray technique is utilized to form homogeneous hydroxyapatite (HA) coating on the surface of the Ti implant to enhance osseointegration at the tissue-implant interface. These coated implants are loaded with curcumin and vitamin K2 to introduce chemopreventive and osteogenesis ability via controlled release of these biomolecules. The synergistic effect of these two biomolecules showed enhanced in vitro osteoblast (hFOB) cell attachment and proliferation for 11 days. Moreover, these biomolecules showed lower in vitro osteosarcoma (MG-63) cell proliferation after 3, 7, and 11 days. An in vivo study was carried out to evaluate the bone bonded zone in a rat distal femur model at an early wound healing stage of 5 days. Modified Masson Goldner staining of the tissue-implant section showed improved contact between tissue and implant in dual drug-loaded HA-coated Ti implants compared to control implants. This work presents a successful fabrication of a mechanically competent functional Ti implant with the advantages of enhanced in vitro osteoblast proliferation, osteosarcoma inhibition, and in vivo osseointegration, indicating the potential for load-bearing bone-defect repair after tumor resection.

In Situ Precipitation of Cluster and Acicular Hydroxyapatite onto Porous Poly(γ-benzyl-l-glutamate) Microcarriers for Bone Tissue Engineering

Bone tissue engineering scaffold based on microcarriers provides an effective approach for the repair of irregular bone defects. The implantation of microcarriers by injection can reduce surgical trauma and fill various irregular shaped bone defects. Microcarriers with porous structure and osteogenic properties have shown great potential in promoting the repair of bone defects. In this study, two kinds of hydroxyapatite/poly-(γ-benzyl-l-glutamate) (HA/PBLG) microcarriers were constructed by emulsion/in situ precipitation method and their structures and properties were studied. First, PBLG porous microcarriers were prepared by an emulsion method. Surface carboxylation of PBLG microcarriers was performed to promote the deposition of HA on PBLG microcarriers. Next, the modified porous PBLG microcarriers were used as the matrix, combined with the in situ precipitation method; the cluster HA and acicular HA were precipitated onto the surface of porous microcarriers in the presence of ammonia water and tri(hydroxymethyl)aminomethane (Tris) solution, respectively. The micromorphology, composition, and element distribution of the two kinds of microcarriers were characterized by TEM, SEM, and AFM. Adipose stem cells (ADSCs) were cultured on the cluster HA/PBLG and acicular HA/PBLG microcarriers, respectively. ADSCs could grow and proliferate normally on both kinds of microcarriers wherein the acicular HA/PBLG microcarriers were more favorable for early cell adhesion and showed a beneficial effect on mineralization and osteogenic differentiation of ADSCs. Successful healing of a rabbit femur defect verified the bone regeneration ability of acicular HA/PBLG microcarriers.

In vivo behavior of biomicroconcretes based on α-tricalcium phosphate and hybrid hydroxyapatite/chitosan granules and sodium alginate

The current studies provide insights into how predictions based on results of physicochemical and in vitro tests are consistent with the results of in vivo studies. The new biomicroconcrete type materials were obtained by mixing the solid phase, composed of hybrid hydroxyapatite/chitosan granules and highly reactive α-tricalcium phosphate powder, used as the setting agent. This approach guaranteed a good adhesion of the continuous cement phase to the surface of granules. It has been demonstrated that developed biomicroconcretes are surgically handy, possessed favorable physicochemical and biological properties and can be considered as effective bone implant material. The hierarchical porosity and compressive strength (2-6 MPa) similar to cancellous bone made them suitable for low-load bearing applications. Despite the fact that final setting times of biomicroconcretes were longer than recommended in the literature (i.e., exceeded 15 min), their short cohesion time allows for a successful implantation in a rabbit femoral defect model. Histological analysis and Raman studies revealed newly formed bone tissues around the sides of implanted materials. Furthermore, the process of neovascularization and reconstruction of the bone tissue, as well as a reverse scaffolding process, was visible. No signs of inflammation or adverse tissue reactions were observed during the experiment.

The mineralization, drug release and in vivo bone defect repair properties of calcium phosphates/PLA modified tantalum scaffolds

Calcium phosphate based biomaterials have been widely studied in biomedical areas. Herein, amorphous calcium phosphate (ACP) nanospheres and hydroxyapatite (HA) nanorods were separately prepared and used for coating tantalum (Ta) scaffolds with a polymer of polylactide (PLA). We have found that different crystal phases of calcium phosphate coated on Ta scaffolds displayed different effects on the surface morphologies, mineralization and bovine serum albumin (BSA) release. The ACP-PLA and HA-PLA coated on Ta scaffold were more favorable for in vitro mineralization than bare and PLA coated Ta scaffolds, and resulted in a highly hydrophilic surfaces. Meanwhile, the osteoblast-like cells (MG63) showed favorable properties of adhesion and spreading on both ACP-PLA and HA-PLA coated Ta scaffolds. The ACP-PLA and HA-PLA coated Ta scaffolds showed a high biocompatibility and potential applications for in vivo bone defect repair.

Calcium phosphate modified tantalum scaffolds displayed high performance on mineralization, sustained drug release and in vivo bone defect repair.

Nanomedicine in osteosarcoma therapy: Micelleplexes for delivery of nucleic acids and drugs toward osteosarcoma-targeted therapies

Osteosarcoma(OS) represents the main cancer affecting bone tissue, and one of the most frequent in children. In this review we discuss the major pathological hallmarks of this pathology, its current therapeutics, new active biomolecules, as well as the nanotechnology outbreak applied to the development of innovative strategies for selective OS targeting. Small RNA molecules play a role as key-regulator molecules capable of orchestrate different responses in what concerns cancer initiation, proliferation, migration and invasiveness. Frequently associated with lung metastasis, new strategies are urgent to upgrade the therapeutic outcomes and the life-expectancy prospects. Hence, the prominent rise of micelleplexes as multifaceted and efficient structures for nucleic acid delivery and selective drug targeting is revisited here with special emphasis on ligand-mediated active targeting. Future landmarks toward the development of novel nanostrategies for both OS diagnosis and OS therapy improvements are also discussed.

On-demand storage and release of antimicrobial peptides using Pandora's box-like nanotubes gated with a bacterial infection-responsive polymer

Background: Localized delivery of antimicrobial agents such as antimicrobial peptides (AMPs) by a biomaterial should be on-demand. Namely, AMPs should be latent and biocompatible in the absence of bacterial infection, but released in an amount enough to kill bacteria immediately in response to bacterial infection. Methods: To achieve the unmet goal of such on-demand delivery, here we turned a titanium implant with titania nanotubes (Ti-NTs) into a Pandora's box. The box was loaded with AMPs (HHC36 peptides, with a sequence of KRWWKWWRR) inside the nanotubes and "closed" (surface-modified) with a pH-responsive molecular gate, poly(methacrylic acid) (PMAA), which swelled under normal physiological conditions (pH 7.4) but collapsed under bacterial infection (pH ≤ 6.0). Thus, the PMAA-gated Ti-NTs behaved just like a Pandora's box. The box retarded the burst release of AMPs under physiological conditions because the gate swelled to block the nanotubes opening. However, it was opened to release AMPs to kill bacteria immediately when bacterial infection occurred to lowering the pH (and thus made the gate collapse). Results: We demonstrated such smart excellent bactericidal activity against a panel of four clinically important bacteria, including Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus. In addition, this box was biocompatible and could promote the osteogenic differentiation of human mesenchymal stem cells. Both in vitro and in vivo studies confirmed the smart "on-demand" bactericidal activity of the Pandora's box. The molecularly gated Pandora's box design represents a new strategy in smart drug delivery.