Bisphosphonate-based strategies for bone tissue engineering and orthopedic implants

Biomaterial Cues for Regulation of Osteoclast Differentiation and Function in Bone Regeneration

Tissue regeneration involves dynamic dialogue between and among different cells and their surrounding matrices. Bone regeneration is specifically governed by reciprocity between osteoblasts and osteoclasts within the bone microenvironment. Osteoclast-directed resorption and osteoblast-directed formation of bone are essential to bone remodeling, and the crosstalk between these cells is vital to curating a sequence of events that culminate in the creation of bone tissue. Among bone biomaterial strategies, many have investigated the use of different material cues to direct the development and activity of osteoblasts. However, less attention has been given to exploring features that similarly target osteoclast formation and activity, with even fewer strategies demonstrating or integrating biomaterial-directed modulation of osteoblast-osteoclast coupling. This review aims to describe various biomaterial cues demonstrated to influence osteoclastogenesis and osteoclast function, emphasizing those that enhance a material construct's ability to achieve bone healing and regeneration. Additionally discussed are approaches that influence the communication between osteoclasts and osteoblasts, particularly in a manner that takes advantage of their coupling. Deepening our understanding of how biomaterial cues may dictate osteoclast differentiation, function, and influence on the microenvironment may enable the realization of bone-replacement interventions with enhanced integrative and regenerative capacities.

LL-37 and bisphosphonate co-delivery 3D-scaffold with antimicrobial and antiresorptive activities for bone regeneration

This study introduces a novel 3D scaffold for bone regeneration, composed of silk fibroin, chitosan, nano-hydroxyapatite, LL-37 antimicrobial peptide, and pamidronate. The scaffold addresses a critical need in bone tissue engineering by simultaneously combating bone infections and promoting bone growth. LL-37 was incorporated for its broad-spectrum antimicrobial properties, while pamidronate was included to inhibit bone resorption. The scaffold's porous structure, essential for cell infiltration and nutrient diffusion, was achieved through a freeze-drying process. In vitro assessments using SEM and FTIR confirmed the scaffold's morphology and chemical integrity. Antimicrobial efficacy was tested against pathogens of Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa). In vivo studies in a murine model of infectious bone defect revealed the scaffold's effectiveness in reducing inflammation and bacterial load, and promoting bone regeneration. RNA sequencing of treated specimens provided insights into the molecular mechanisms underlying these observations, revealing significant gene expression changes related to bone healing and immune response modulation. The results indicate that the scaffold effectively inhibits bacterial growth and supports bone cell functions, making it a promising candidate for treating infectious bone defects. Future studies should focus on optimizing the release of therapeutic agents and evaluating the scaffold's clinical potential.

Co-delivery of rhBMP-2 and zoledronic acid using calcium sulfate/hydroxyapatite carrier as a bioactive bone substitute to enhance and accelerate spinal fusion

Recombinant human bone morphogenetic protein-2 (rhBMP-2) has been FDA-approved for lumbar fusion, but supraphysiologic initial burst release due to suboptimal carrier and late excess bone resorption caused by osteoclast activation have limited its clinical usage. One strategy to mitigate the pro-osteoclast side effect of rhBMP-2 is to give systemic bisphosphonates, but it presents challenges with systemic side effects and low local bioavailability. The aim of this in vivo study was to analyze if posterolateral spinal fusion (PLF) could be improved by utilizing a calcium sulfate/hydroxyapatite (CaS/HA) carrier co-delivering rhBMP-2 and zoledronic acid (ZA). Six groups were allocated (CaS/HA, CaS/HA + BMP-2, CaS/HA + systemic ZA, CaS/HA + local ZA, CaS/HA + BMP-2 + systemic ZA, and CaS/HA + BMP-2 + local ZA). 10-week-old male Wistar rats, were randomly assigned to undergo L4-L5 PLF with implantation of group-dependent scaffolds. At 3 and 6 weeks, the animals were euthanized for radiography, μCT, histological staining, or biomechanical testing to evaluate spinal fusion. The results demonstrated that the CaS/HA biomaterial alone or in combination with local or systemic ZA didn't support PLF. However, the delivery of rhBMP-2 significantly promoted PLF. Combining systemic ZA with BMP-2 didn't enhance spinal fusion. Notably, the co-delivery of rhBMP-2 and ZA using the CaS/HA carrier significantly enhanced and accelerated PLF, without inhibiting systemic bone turnover, and potentially reduced the dose of rhBMP-2. Together, the treatment regimen of CaS/HA biomaterial co-delivering rhBMP-2 and ZA could potentially be a safe and cost-effective off-the-shelf bioactive bone substitute to enhance spinal fusion.

Ångstrom-scale gold particles loaded with alendronate via alpha-lipoic acid alleviate bone loss in osteoporotic mice

Osteoporosis is a highly prevalent metabolic disease characterized by low systemic bone mass and deterioration of bone microarchitecture, resulting in reduced bone strength and increased fracture risk. Current treatment options for osteoporosis are limited by factors such as efficacy, cost, availability, side effects, and acceptability to patients. Gold nanoparticles show promise as an emerging osteoporosis therapy due to their osteogenic effects and ability to allow therapeutic delivery but have inherent constraints, such as low specificity and the potential for heavy metal accumulation in the body. This study reports the synthesis of ultrasmall gold particles almost reaching the Ångstrom (Ång) dimension. The antioxidant alpha-lipoic acid (LA) is used as a dispersant and stabilizer to coat Ångstrom-scale gold particles (AuÅPs). Alendronate (AL), an amino-bisphosphonate commonly used in drug therapy for osteoporosis, is conjugated through LA to the surface of AuÅPs, allowing targeted delivery to bone and enhancing antiresorptive therapeutic effects. In this study, alendronate-loaded Ångstrom-scale gold particles (AuÅPs-AL) were used for the first time to promote osteogenesis and alleviate bone loss through regulation of the WNT signaling pathway, as shown through in vitro tests. The in vivo therapeutic effects of AuÅPs-AL were demonstrated in an established osteoporosis mouse model. The results of Micro-computed Tomography, histology, and tartrate-resistant acid phosphatase staining indicated that AuÅPs-AL significantly improved bone density and prevented bone loss, with no evidence of nanoparticle-associated toxicity. These findings suggest the possible future application of AuÅPs-AL in osteoporosis therapy and point to the potential of developing new approaches for treating metabolic bone diseases using Ångstrom-scale gold particles.

Modified-Hydroxyapatite-Chitosan Hybrid Composite Interfacial Coating on 3D Polymeric Scaffolds for Bone Tissue Engineering

Three dimensional (3D) scaffolds have huge limitations due to their low porosity, mechanical strength, and lack of direct cell-bioactive drug contact. Whereas bisphosphonate drug has the ability to stimulate osteogenesis in osteoblasts and bone marrow mesenchymal stem cells (hMSC) which attracted its therapeutic use. However it is hard administration low bioavailability, and lack of site-specificity, limiting its usage. The proposed scaffold architecture allows cells to access the bioactive surface at their apex by interacting at the scaffold's interfacial layer. The interface of 3D polycaprolactone (PCL) scaffolds has been coated with alendronate-modified hydroxyapatite (MALD) enclosed in a chitosan matrix, to mimic the native environment and stupulate the through interaction of cells to bioactive layer. Where the mechanical strength will be provided by the skeleton of PCL. In the MALD composite's hydroxyapatite (HAP) component will govern alendronate (ALD) release behavior, and HAP presence will drive the increase in local calcium ion concentration increases hMSC proliferation and differentiation. In results, MALD show release of 86.28 ± 0.22. XPS and SEM investigation of the scaffold structure, shows inspiring particle deposition with chitosan over the interface. All scaffolds enhanced cell adhesion, proliferation, and osteocyte differentiation for over a week without in vitro cell toxicity with 3.03 ± 0.2 kPa mechanical strength.

Bisphosphonate-incorporated coatings for orthopedic implants functionalization

Bisphosphonates (BPs), the stable analogs of pyrophosphate, are well-known inhibitors of osteoclastogenesis to prevent osteoporotic bone loss and improve implant osseointegration in patients suffering from osteoporosis. Compared to systemic administration, BPs-incorporated coatings enable the direct delivery of BPs to the local area, which will precisely enhance osseointegration and bone repair without the systemic side effects. However, an elaborate and comprehensive review of BP coatings of implants is lacking. Herein, the cellular level (e.g., osteoclasts, osteocytes, osteoblasts, osteoclast precursors, and bone mesenchymal stem cells) and molecular biological regulatory mechanism of BPs in regulating bone homeostasis are overviewed systematically. Moreover, the currently available methods (e.g., chemical reaction, porous carriers, and organic material films) of BP coatings construction are outlined and summarized in detail. As one of the key directions, the latest advances of BP-coated implants to enhance bone repair and osseointegration in basic experiments and clinical trials are presented and critically evaluated. Finally, the challenges and prospects of BP coatings are also purposed, and it will open a new chapter in clinical translation for BP-coated implants.

Bone Grafts in Dental Medicine: An Overview of Autografts, Allografts and Synthetic Materials

This review provides an overview of various materials used in dentistry and oral and maxillofacial surgeries to replace or repair bone defects. The choice of material depends on factors such as tissue viability, size, shape, and defect volume. While small bone defects can regenerate naturally, extensive defects or loss or pathological fractures require surgical intervention and the use of substitute bones. Autologous bone, taken from the patient's own body, is the gold standard for bone grafting but has drawbacks such as uncertain prognosis, surgery at the donor site, and limited availability. Other alternatives for medium and small-sized defects include allografts (from human donors), xenografts (from animals), and synthetic materials with osteoconductive properties. Allografts are carefully selected and processed human bone materials, while xenografts are derived from animals and possess similar chemical composition to human bone. Synthetic materials such as ceramics and bioactive glasses are used for small defects but may lack osteoinductivity and moldability. Calcium-phosphate-based ceramics, particularly hydroxyapatite, are extensively studied and commonly used due to their compositional similarity to natural bone. Additional components, such as growth factors, autogenous bone, and therapeutic elements, can be incorporated into synthetic or xenogeneic scaffolds to enhance their osteogenic properties. This review aims to provide a comprehensive analysis of grafting materials in dentistry, discussing their properties, advantages, and disadvantages. It also highlights the challenges of analyzing in vivo and clinical studies to select the most suitable option for specific situations.

Dual-crosslinked network of polyacrylamide-carboxymethylcellulose hydrogel promotes osteogenic differentiation in vitro

In our previous study, we successfully designed a dual-crosslinked network hydrogel by introducing the monomers acrylamide (AM), carboxymethylcellulose (CMC), zeolitic imidazolate framework-8 (ZIF-8), and alendronate (Aln). With the simultaneous presentation of physical and chemical crosslinks, the fabricated hydrogel with 10 % concentration of Aln@ZIF-8 (PAM-CMC-10%Aln@ZIF-8) exhibited excellent mechanical characteristics, high Aln loading efficiency (63.83 %), and a slow release period (6 d). These results demonstrate that PAM-CMC-10%Aln@ZIF-8 is a potential carrier for delaying Aln. In this study, we mainly focused on the biocompatibility and osteogenic ability of PAM-CMC-10%Aln@ZIF-8 in vitro, which is a continuation of our previous work. First, this study investigated the biocompatibility of dual-crosslinked hydrogels using calcein-AM/Propidium Iodide and cell counting kit-8. The morphology of rat bone mesenchymal stem cells was assessed using FITC-phalloidin/DAPI and vinculin immunostaining. Finally, osteogenic induction ability in vitro was assessed via alkaline phosphatase expression and alizarin red S staining, which was also confirmed using real-time PCR at the gene level and immunofluorescence at the protein level. The results indicated that the introduction of Aln enabled a dual-crosslinked hydrogel with superior biocompatibility and outstanding osteogenic differentiation ability in vitro, providing a solid foundation for subsequent animal experiments in vivo.

Cellular metabolism: a link connecting cellular behaviour with the physiochemical properties of biomaterials for bone tissue engineering

Biomaterial properties, such as surface roughness, morphology, stiffness, conductivity, and chemistry, significantly influence a cell's ability to sense and adhere to its surface and regulate cell functioning. Understanding how biomaterial properties govern changes in cellular function is one of the fundamental goals of tissue engineering. Still, no generalized rule is established to predict cellular processes (adhesion, spreading, growth and differentiation) on biomaterial surfaces. A few studies have highlighted that cells sense biomaterial properties at multiple length scales and regulate various intracellular biochemical processes like cytoskeleton organization, gene regulation, and receptor expression to influence cell function. However, recent studies have found cellular metabolism as another critical aspect of cellular processes that regulate cell behavior, co-relating metabolism to cellular functions like adhesion, proliferation, and differentiation. Now researchers have started to uncover previously overlooked factors on how biomaterial properties govern changes in cellular functions mediated through metabolism. This review highlights how different physiochemical properties of scaffolds designed from different biomaterials influence cell metabolism. The review also discusses the role of metabolism change in cellular functions and cell behavior in the context of bone tissue engineering. It also emphasizes the importance of cell metabolism as a missing link between the cellular behavior and physicochemical properties of scaffolds and serves as a guiding principle for designing scaffolds for tissue engineering.

Lipid Nanoparticles and Liposomes for Bone Diseases Treatment

Because of their outstanding biocompatibility, sufficient capacity to control drug release, and passive targeting capability, lipid nanoparticles are one of the world's most widely utilized drug delivery systems. However, numerous disadvantages limit the use of lipid nanoparticles in clinical settings, especially in bone regeneration, such as challenges in transporting, storing, and maintaining drug concentration in the local area. Scaffolds are frequently employed as implants to provide mechanical support to the damaged area or as diagnostic and imaging tools. On the other hand, unmodified scaffolds have limited powers in fostering tissue regeneration and curing illnesses. Liposomes offer a solid foundation for the long-term development of various commercial solutions for the effective drug delivery-assisted treatment of medical conditions. As drug delivery vehicles in medicine, adjuvants in vaccination, signal enhancers/carriers in medical diagnostics and analytical biochemistry, solubilizers for various ingredients as well as support matrices for various ingredients, and penetration enhancers in cosmetics are just a few of the industrial applications for liposomes. This review introduces and discusses the use of lipid nanoparticles and liposomes and the application of lipid nanoparticles and liposome systems based on different active substances in bone diseases.

Synthetic materials in craniofacial regenerative medicine: A comprehensive overview

The state-of-the-art approach to regenerating different tissues and organs is tissue engineering which includes the three parts of stem cells (SCs), scaffolds, and growth factors. Cellular behaviors such as propagation, differentiation, and assembling the extracellular matrix (ECM) are influenced by the cell's microenvironment. Imitating the cell's natural environment, such as scaffolds, is vital to create appropriate tissue. Craniofacial tissue engineering refers to regenerating tissues found in the brain and the face parts such as bone, muscle, and artery. More biocompatible and biodegradable scaffolds are more commensurate with tissue remodeling and more appropriate for cell culture, signaling, and adhesion. Synthetic materials play significant roles and have become more prevalent in medical applications. They have also been used in different forms for producing a microenvironment as ECM for cells. Synthetic scaffolds may be comprised of polymers, bioceramics, or hybrids of natural/synthetic materials. Synthetic scaffolds have produced ECM-like materials that can properly mimic and regulate the tissue microenvironment's physical, mechanical, chemical, and biological properties, manage adherence of biomolecules and adjust the material's degradability. The present review article is focused on synthetic materials used in craniofacial tissue engineering in recent decades.

New Insights into Amino-Functionalization of Magnetic Nanoplatelets with Silanes and Phosphonates

Magnetic nanoplatelets (NPLs) based on barium hexaferrite (BaFe₁₂O₁₉) are suitable for many applications because of their uniaxial magneto-crystalline anisotropy. Novel materials, such as ferroic liquids, magneto-optic composites, and contrast agents for medical diagnostics, were developed by specific surface functionalization of the barium hexaferrite NPLs. Our aim was to amino-functionalize the NPLs’ surfaces towards new materials and applications. The amino-functionalization of oxide surfaces is challenging and has not yet been reported for barium hexaferrite NPLs. We selected two amine ligands with two different anchoring groups: an amino-silane and an amino-phosphonate. We studied the effect of the anchoring group, backbone structure, and processing conditions on the formation of the respective surface coatings. The core and coated NPLs were examined with transmission electron microscopy, and their room-temperature magnetic properties were measured. The formation of coatings was followed by electrokinetic measurements, infrared and mass spectroscopies, and thermogravimetric analysis. The most efficient amino-functionalization was enabled by (i) amino-silanization of the NPLs precoated with amorphous silica with (3-aminopropyl)triethoxysilane and (ii) slow addition of amino-phosphonate (i.e., sodium alendronate) to the acidified NPL suspension at 80 °C.

The Use of Fibers in Bone Tissue Engineering

Bone tissue engineering aims to restore and maintain the function of bone by means of biomaterial-based scaffolds. This review specifically focuses on the use of fibers in biomaterials used for bone tissue engineering as suitable environment for bone tissue repair and regeneration. We present a bioinspired rationale behind the use of fibers in bone tissue engineering and provide an overview of the most common fiber fabrication methods, including solution, melt, and microfluidic spinning. Subsequently, we provide a brief overview of the composition of fibers that are used in bone tissue engineering, including fibers composed of (i) natural polymers (e.g., cellulose, collagen, gelatin, alginate, chitosan, and silk, (ii) synthetic polymers (e.g., polylactic acid [PLA], polycaprolactone, polyglycolic acid [PGA], polyethylene glycol, and polymer blends of PLA and PGA), (iii) ceramic fibers (e.g., aluminium oxide, titanium oxide, and zinc oxide), (iv) metallic fibers (e.g., titanium and its alloys, copper and magnesium), and (v) composite fibers. In addition, we review the most relevant fiber modification strategies that are used to enhance the (bio)functionality of these fibers. Finally, we provide an overview of the applicability of fibers in biomaterials for bone tissue engineering, with a specific focus on mechanical, pharmaceutical, and biological properties of fiber-functionalized biomaterials for bone tissue engineering. Impact statement Natural bone is a complex composite material composed of an extracellular matrix of mineralized fibers containing living cells and bioactive molecules. Consequently, the use of fibers in biomaterial-based scaffolds offers a wide variety of opportunities to replicate the functional performance of bone. This review provides an overview of the use of fibers in biomaterials for bone tissue engineering, thereby contributing to the design of novel fiber-functionalized bone-substituting biomaterials of improved functionality regarding their mechanical, pharmaceutical, and biological properties.

Design of 3D Scaffolds for Hard Tissue Engineering: From Apatites to Silicon Mesoporous Materials

Advanced bioceramics for bone regeneration constitutes one of the pivotal interests in the multidisciplinary and far-sighted scientific trajectory of Prof. Vallet Regí. The different pathologies that affect osseous tissue substitution are considered to be one of the most important challenges from the health, social and economic point of view. 3D scaffolds based on bioceramics that mimic the composition, environment, microstructure and pore architecture of hard tissues is a consolidated response to such concerns. This review describes not only the different types of materials utilized: from apatite-type to silicon mesoporous materials, but also the fabrication techniques employed to design and adequate microstructure, a hierarchical porosity (from nano to macro scale), a cell-friendly surface; the inclusion of different type of biomolecules, drugs or cells within these scaffolds and the influence on their successful performance is thoughtfully reviewed.

A Review on Re-Packaging of Bisphosphonates Using Biomaterials

The need for bone repair and insight into new regeneration therapies as well as improvement of existing regeneration routes is constantly increasing as a direct consequence of the rise in the number of trauma victims, musculoskeletal disorders, and increased life expectancy. Bisphosphonates (BPs) have emerged as a class of drugs with proven efficacy against many bone disorders. The most recent ability of this class of drugs is being explored in its anti-cancer ability. However, despite the pharmacological success, there are certain shortcomings that have circumvented this class of the drug. The mediation of biomaterials in delivering bisphosphonates has greatly helped in overcoming some of these shortcomings. This article is focused on reviewing the benefits the bisphosphonates have provided upon getting delivered via the use of biomaterials. Furthermore, the role of bisphosphonates as a potent anticancer agent is also accounted. It is witnessed that employing engineering tools in combination with therapeutics has the potential to provide solutions to bone loss from degenerative, surgical, or traumatic processes, and also aid in accelerating the healing of large bone fractures and problematic non-union fractures. The role of nanotechnology in enhancing the efficacy of the bisphosphonates is also reviewed and innovative approaches are identified.

Microsphere embedded hydrogel construct - binary delivery of alendronate and BMP-2 for superior bone regeneration

Biomimetic delivery of osteoinductive growth factors via an osteoconductive matrix is an interesting approach for stimulating bone regeneration. In this context, the bone extracellular matrix (ECM) has been explored as an optimal delivery system, since it releases growth factors in a spatiotemporal manner from the matrix. However, a bone ECM hydrogel alone is weak, unstable, and prone to microbial contamination and also has been reported to have significantly reduced bone morphogenic protein-2 (BMP-2) post decellularization. In the present work, a microsphere embedded osteoinductive decellularized bone ECM/oleoyl chitosan based hydrogel construct (BOC) was developed as a matrix allowing dual delivery of an anti-resorptive drug (alendronate, ALN, via the microspheres) and BMP-2 (via the hydrogel) for a focal tibial defect in a rabbit model. The synthesized gelatin microspheres (GMs) were spherical in shape with diameter ∼32 μm as assessed by SEM analysis. The BOC construct showed sustained release of ALN and BMP-2 under the studied conditions. Interestingly, amniotic membrane-derived stem cells (HAMSCs) cultivated on the hydrogel construct demonstrated excellent biocompatibility, cell viability, and active proliferation potential. Additionally, cell differentiation on the constructs showed an elevated expression of osteogenic genes in an RT-PCR study along with enhanced mineralized matrix deposition as demonstrated by alkaline phosphatase (ALP) assay and alizarin red assay. The hydrogel construct was witnessed to have improved neo-vascularization potential in a chick chorioalantoic membrane (CAM) assay. Also, histological and computed tomographic findings evidenced enhanced bone regeneration in the group treated with the BOC/ALN/BMP hydrogel construct in a rabbit tibial defect model. To conclude, the developed multifunctional hydrogel construct acts as an osteoinductive and osteoconductive platform facilitating controlled delivery of ALN and BMP-2, essential for stimulating bone tissue regeneration.

Mussel-Inspired Bisphosphonated Injectable Nanocomposite Hydrogels with Adhesive, Self-Healing, and Osteogenic Properties for Bone Regeneration

Injectable hydrogels have received much attention because of the advantages of simulation of the natural extracellular matrix, microinvasive implantation, and filling and repairing of complex shape defects. Yet, for bone repair, the current injectable hydrogels have shown significant limitations such as the lack of tissue adhesion, deficiency of self-healing ability, and absence of osteogenic activity. Herein, a strategy to construct mussel-inspired bisphosphonated injectable nanocomposite hydrogels with adhesive, self-healing, and osteogenic properties is developed. The nano-hydroxyapatite/poly(l-glutamic acid)-dextran (nHA/PLGA-Dex) dually cross-linked (DC) injectable hydrogels are fabricated via Schiff base cross-linking and noncovalent nHA-BP chelation. The chelation between bisphosphonate ligands (alendronate sodium, BP) and nHA favors the uniform dispersion of the latter. Moreover, multiple adhesion ligands based on catechol motifs, BP, and aldehyde groups endow the hydrogels with good tissue adhesion. The hydrogels possess excellent biocompatibility and the introduction of BP and nHA both can effectively promote viability, proliferation, migration, and osteogenesis differentiation of MC3T3-E1 cells. The incorporation of BP groups and HA nanoparticles could also facilitate the angiogenic property of endothelial cells. The nHA/PLGA-Dex DC hydrogels exhibited considerable biocompatibility despite the presence of a certain degree of inflammatory response in the early stage. The successful healing of a rat cranial defect further proves the bone regeneration ability of nHA/PLGA-Dex DC injectable hydrogels. The developed tissue adhesive osteogenic injectable nHA/PLGA-Dex hydrogels show significant potential for bone regeneration application.

Liposomes as multifaceted delivery system in the treatment of osteoporosis

Introduction: Treatment of osteoporosis with the available drug formulations is still challenging due to multiple associated limitations such as chronic treatment, off-target side effects, poor bone targeting, and low bioavailability. Adopting advanced bone-targeted drug delivery strategies like liposomes is one of the safe and effective approaches for osteoporosis treatment.Areas covered: This review summarizes the applications of liposomes in gene delivery, bone regeneration, bone-targeted delivery, and as a carrier for drug encapsulation in the treatment of osteoporosis. Details of all the supportive studies are discussed here and the bone-specific roles of the strategies like new generation liposomes in osteoporosis are elaborated. The future scope of performing in-depth research on the bone-targeted liposomes is discussed.Expert opinion: Liposomes-based bone-targeted delivery of therapeutics seems to be a promising approach for the effective treatment of osteoporosis. But till date, the tremendous in vitro and in vivo research on liposomes has failed to attain significant progress in their clinical translation. From bench to bedside success of the research an interdisciplinary collaboration between the preclinical and clinical experts engaged at different stages of liposomes development is required.

Using Alendronic Acid Coupled Fluorescently Labelled SM Liposomes as a Vehicle for Bone Targeting

Background:

We recently developed a liposomal nanoparticle system that can be used for drug delivery and simultaneously be monitored by optical or photoacoustic imaging devices. Here we tested the efficacy of alendronate as a homing molecule in SM-liposomes for bone targeting.

Methods:

Alendronate was immobilized covalently on the liposomal surface and the fluorescent dye indocyanine green was used as a payload in the liposomes. The indocyanine green delivery was analyzed by 3D optical tomography, optical fluorescence scanner, photoacoustic imaging, and by ex-vivo biodistribution studies.

Results:

The results show that the alendronate, coupled to the liposomal surface, increases sphingomyelin containing liposome targeting up to several-folds.

Conclusion:

The alendronate targeted liposomes open possibilities for an application in active bone targeting.

Histomorphometric Evaluation of Peri-Implant Bone Response to Intravenous Administration of Zoledronate (Zometa®) in an Osteoporotic Rat Model

We evaluated the response to peri-implant bone placed in the femoral condyle of osteoporotic rats, following intravenous zoledronate (ZOL) treatment in three settings: pre-implantation (ZOL-Pre), post-implantation (ZOL-Post), and pre- + post-implantation (ZOL-Pre+Post). Twenty-four female Wistar rats were ovariectomized (OVX). After 12 weeks, the rats received titanium implants in the right femoral condyle. ZOL (0.04 mg/kg, weekly) was administered to six rats 4 weeks pre-implantation and was stopped at implant placement. To another six rats, ZOL was given post-implantation and continued for 6 weeks. Additional six rats received ZOL treatment pre- and post-implantation. Control animals received weekly saline intravenous injections. At 6 weeks post-implantation, samples were retrieved for histological evaluation of the percentage of bone area (%BA) and of the percentage of bone-to-implant contact (%BIC). BA% for ZOL-Pre (29.6% ± 9.0%) and ZOL-Post (27.9% ± 5.6%) rats were significantly increased compared to that of the controls (17.3% ± 3.9%, p < 0.05). In contrast, ZOL-Pre+Post rats (20.4% ± 5.0%) showed similar BA% compared to Saline controls (p = 0.731). BIC% revealed a significant increase for ZOL-Post (65.8% ± 16.9%) and ZOL-Pre+Post (68.3% ± 10.0%) rats compared with that of Saline controls (43.3% ± 9.6%, p < 0.05), while ZOL-Pre rats (55.6% ± 19%) showed a BIC% comparable to that of Saline controls (p = 0.408). Our results suggest that receiving intravenous ZOL treatment before or after implant placement enhances peri-implant bone responses in terms of bone area. However, the effect of different ZOL treatment regimens on BIC% was found to be inconclusive.

The use of bisphosphonates to meet orthopaedic challenges

The anti-resorptive properties of bisphosphonates have been explored to manage several conditions that traditionally have required a surgical solution. In osteonecrosis, their use is predicated on the principle that bone collapse occurs during the revascularisation phase of the disease. If the associated resorptive activity were modulated, the resultant preserved joint architecture may improve clinical outcome and reduce the need for joint replacement. Pre-clinical and small-scale clinical studies have given non-conclusive support for this principle. Adequately powered clinical trials with relevant long-term endpoints are still required to firmly clarify the clinical efficacy of this treatment. Several clinical studies have shown that bisphosphonates can reduce periprosthetic bone loss and, in some situations, enhance implant fixation in the early period after joint replacement. This may be advantageous in settings where osseointegration is problematic. However, the ultimate goals of their use in joint replacement has been to reduce the incidence of late periprosthetic inflammatory osteolysis, the main cause of prosthesis failure. Population-based observational studies have associated bisphosphonate use with a lower incidence of revision surgery, supported by pre-clinical data. However, clinical trials have, to date, failed to demonstrate any efficacy for the human disease. The timing of bisphosphonate administration for secondary prevention after acute osteoporotic fracture has been subject to extensive investigation, with pre-clinical studies showing increased callus formation but decreased remodelling and no effect on the restoration of mechanical integrity of bone. Meta-analysis of clinical trial data indicates that early administration of bisphosphonate after acute fracture does not adversely affect fracture union, pain or functional outcomes. Finally, bisphosphonates have also been explored as a treatment for complex regional pain syndrome type-I. A recent meta-analysis has shown a beneficial effect on visual analogue scale pain scores, but an increase in mild adverse events.

Phosphate functionalization and enzymatic calcium mineralization synergistically enhance oligo[poly(ethylene glycol) fumarate] hydrogel osteoconductivity for bone tissue engineering

A current approach in bone tissue engineering is the implantation of polymeric scaffolds that promote osteoblast attachment and growth as well as biomineralization. One promising polymer is oligo[poly(ethylene glycol) fumarate] (OPF), a polyethylene glycol-based material that is biocompatible, injectable, and biodegradable, but in its native form does not support robust bone cell attachment or growth. To address this issue, this study evaluated the osteoconductivity of bis[02-(methacryloyloxy)ethyl] phosphate (BP) functionalized OPF hydrogels (OPF-BP) using MC3T3-E1 pre-osteoblast cells, both before and after enzymatic mineralization with a calcium solution. The inclusion of negatively charged functional groups allowed for the tailored uptake and release of calcium, while also altering the mechanical properties and surface topography of the hydrogel surface. In cell culture, OPF-BP hydrogels with 20 and 30% (w/w) BP optimized osteoblast attachment, proliferation, and differentiation after a 21-day in vitro period. In addition, the OPF-BP30 treatment, when mineralized with calcium, exhibited a 128% increase in osteocalcin expression when compared with the non-mineralized treatment. These findings suggest that phosphate functionalization and enzymatic calcium mineralization can act synergistically to enhance the osteoconductivity of OPF hydrogels, making this processed material an attractive candidate for bone tissue engineering applications.

The Potential of a Nanostructured Titanium Oxide Layer with Self-Assembled Monolayers for Biomedical Applications: Surface Properties and Biomechanical Behaviors

This study investigated the surface properties and biomechanical behaviors of a nanostructured titanium oxide (TiO) layer with different self-assembled monolayers (SAMs) of phosphonate on the surface of microscope slides. The surface properties of SAMs were analyzed using scanning electron microscopy, X-ray photoemission spectroscopy, and contact angle goniometry. Biomechanical behaviors were evaluated using nanoindentation with a diamond Berkovich indenter. Analytical results indicated that the homogenous nanostructured TiO surface was formed on the substrate surface after the plasma oxidation treatment. As the TiO surface was immersed with 11-phosphonoundecanoic acid solution (PUA-SAM/TiO), the formation of a uniform SAM can be observed on the sample surface. Moreover, the binding energy of O 1s demonstrated the presence of the bisphosphonate monolayer on the SAMs-coated samples. It was also found that the PUA-SAM/TiO sample not only possessed a higher wettability performance, but also exhibited low surface contact stiffness. A SAM surface with a high wettability and low contact stiffness could potentially promote biocompatibility and prevent the formation of a stress shielding effect. Therefore, the self-assembled technology is a promising approach that can be applied to the surface modification of biomedical implants for facilitating bone healing and osseointegration.

Bisphosphonate-Functionalized Scaffolds for Enhanced Bone Regeneration

The local sustained release of bioactive substances are attracting increasing attention in bone tissue engineering, which is beneficial to bone tissue formation and helps to improve the bone ingrowth ability of a scaffold. Bisphosphonates (BPs), as a representative kind of osteoclast inhibitors, are proven to possess excellent osteogenic induction capability. Accordingly, various physical and chemical strategies are developed to functionalize bone tissue scaffolds with BPs to achieve controlled release profiles. Compared with traditional treatment modalities, local release of BPs from these composite scaffolds will contribute to continuous bone integration without the risk of many complications. This review explores the molecular mechanisms of BPs on bone metabolism and analyzes the appropriate concentrations of BPs that promote bone regeneration. The advanced BP loading strategies, implant modification technologies, and BP-loaded composite scaffolds based on different matrices are summarized. Finally, the latest advances and the future development of BP-modified scaffolds for enhanced bone regeneration are discussed. This article provides leading-edge design strategies of the BP-functionalized bone engineering scaffolds for improved bone repairability.

Facile fabrication of the zoledronate-incorporated coating on magnesium alloy for orthopaedic implants

Background

Bisphosphonates (BPs) are known as a group of well-established drugs which are clinically used in metabolic bone disorder-related therapies. Recently increasing interests are focused on the application of BPs in the biodegradable Mg-based implants.

Methods

In this study a facile method was applied to fabricate a zoledronate loaded coating on AZ31 Mg alloy in comparison with the previous construction strategies, such as Ca-P chelation with BPs.

Results

The results showed that the fluoride pretreated coating could provide better corrosion resistance. Zoledronic acid (ZA) was successfully loaded on the surface of Mg alloy detected by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) analysis, and the release profile was quantified with Ultraviolet (UV) detection.

Conclusion

It is considered that this construction of ZA coated Mg-based orthopedic implants could be easily and efficiently used in clinic.

The translational potential of this article

Different from the traditional drug release mode, this paper used the hydrogen bond between drug molecules and drug carriers to not only realise the effective drug release in the early stage of drug release, but also meet the continuous effect of drugs in the later stage, providing a new possibility for clinical application.

Acceleration of Bone Fracture Healing through the Use of Natural Bovine Hydroxyapatite Implant on Bone Defect Animal Model

Bone is an important organ for supports the body that stores reserve of calcium, phosphorus, and other minerals. In fracture conditions where bleeding, soft tissue edema, nerve damage, and blood vessels around the bone damage happen, they can cause the mobilization of these minerals in the surrounding tissue. One of the efforts made in the treatment of these fractures is reconnection, in which it works by filling of bone defect with a matrix and administration of anti-infection. Biomaterial filling in defective bone is thought to accelerate the healing process of bone fracture and prevent osteomyelitis. For this reason, this study evaluates the acceleration of bone fracture healing using natural hydroxyapatite (NHA) bone filler in rabbits with bone defect model. Fracture modeling was performed by surgical technique and drilling of bones with a 4.2 mm diameter to form a defect in the rabbit femur. Bone implant contained bovine hydroxyapatite-gelatin-glutaraldehyde (BHA implant) or bovine hydroxyapatite-gelatin-glutaraldehyde-gentamicin (BHA-GEN implant) that was inserted in bone defects. 27 rabbits were divided into 3 groups: the control group who had bone defect, the bone defect group was given BHA implant and the bone defect group was given BHA-GEN implant. Observation of osteoclast, osteoblast, osteocyte, BALP level, and bone morphological integrity was carried out on the 14th, 28th, and 42nd days after surgery. Histological observation of rabbit femur showed a significant difference on the number of osteoclast, osteoblast and osteocyte in all three groups. The BALP level also showed a significant difference in the group given the natural BHA bone implant compared to the control group on day 14 (p = 0.0361). Based on the result of the X-ray, there was also a better integration of rabbit femur bone in groups with the use of BHA or BHA-GEN bone implant. Thus, it can be concluded that the use of a natural BHA implant can accelerate the process of bone repair in the fracture of rabbit femur. In addition, BHA implants were compatible as a matrix for supporting the bone cell growth.

Bone Regeneration Using Antiosteoporotic Drugs in Adjunction with Bone Grafting: A Meta-Analysis

The aim of this review was to systematically assess bone regeneration by using antiosteoporotic drugs in adjunction with bone grafting compared with controls (bone grafting without the administration of antiosteoporotic drugs). The review also evaluated statistical differences in the effect between systemic and local routes of drugs. Also, the effect of type of drugs (anticatabolic vs. anabolic) was subevaluated. PubMed and EMBASE (via OvidSP) resulted in inclusion of 60 animal studies. The studies were assessed for reporting quality and risk of bias. Outcome data from selected studies were categorized as either experimental (bone grafting with the administration of antiosteoporotic drugs) or control. Meta-analysis of selected studies was done for these outcomes: histomorphometrical bone area (BA%) and micro-CT bone volume (BV%). In this review, several animal models (52 healthy, 6 osteoporotic, and 2 both conditions) were subjected to examine the effect of antiosteoporotic drugs on bone grafting, with a predominant use of rodent species. Assessment indicates poor reporting quality and unclear risk of bias in the majority of studies. Random-effects meta-analysis revealed a significant increase in overall BA% (mean difference [MD]: 2.6, confidence interval [CI]: 2.25 to 2.92) and BV% (MD: 0.12, CI: 0.05 to 0.19) due to osteoporotic drug treatment compared with controls. For subgroups, both routes of antiosteoporotic drug administration showed similar effects on BA%. In contrast, systemic antiosteoporotic drug administration led to significantly higher BV% (MD: 6.75, CI: 5.30 to 8.19) compared with local administration (MD: 0.02, CI: -0.03 to 0.08). Further, administration of anabolic drugs significantly increased BA% (MD: 5.75, CI: 4.62 to 6.87) compared with anticatabolic drugs (MD: 1.86, CI: 1.47 to 2.26). In conclusion, both histomorphometrical and micro-CT scan analysis indicated an overall effect of using the antiosteoporotic drugs toward bone regeneration in adjunction with grafting. However, not all studies showed a positive effect and the present results need to be applied with care, as the included papers showed experimental heterogeneity for animal models. Further (pre)clinical research is warranted to explore whether drug-based strategies can be an effective adjunctive with bone grafting. Impact Statement The aim of this meta-analysis was to assess whether antiosteoporotic drugs can promote bone regeneration in adjunction with bone grafting by using preclinical animal models. Although the majority of included studies indicated poor reporting quality and unclear risk of bias, an overall positive effect of the antiosteoporotic drugs toward bone regeneration related to bone grafts can be highlighted.

Anti-Tumor Effects of Low Dose Zoledronate on Lung Cancer-Induced Spine Metastasis

Zoledronate (Zol) is an anti-resorptive/tumoral agent used for the treatment of many cancers including spinal bone metastasis. High systemic administration of a single dose is now the standard clinical care, yet it has been associated with several side effects. Here, we aimed to evaluate the effects of lower doses Zol on lung cancer and lung cancer-induced bone metastasis cells over a longer time period. Human lung cancer (HCC827) and three bone metastases secondary to lung cancer (BML1, BML3 and BML4) cells were treated with Zol at 1, 3 and 10 µM for 7 days and then assessed for cell proliferation, migration, invasion and apoptosis. Low Zol treatment significantly decreased cell proliferation (1, 3 and 10 µM), migration (3 and 10 µM) and invasion (10 µM) while increasing apoptosis (10 µM) in lung cancer and metastatic cells. Our data exploits the potential of using low doses Zol for longer treatment periods and reinforces this approach as a new therapeutic regimen to impede the development of metastatic bone cancer while limiting severe side effects following high doses of systemic drug treatment.

Synthetic Calcium Phosphate Ceramics as a Potential Treatment for Bisphosphonate-Related Osteonecrosis of the Jaw

(1) Background: Bisphosphonate-related osteonecrosis of the jaw (BRONJ) is one of the most often seen side effects in patients treated with nitrogen-containing bisphosphonates (BPs), a post-surgical non-healing wound condition. Since calcium phosphate (CP) compounds are able to adsorb zoledronate (ZOL) when used as a drug delivery vehicle, we aimed to verify if these ceramics might have a potential protective effect for soft tissues surrounding surgical osseous wounds. (2) Methods: The chemical reaction between ZOL and CP compounds was evaluated through ultraviolet-visible spectroscopy and elemental analysis. A primary culture of human gingival fibroblasts (HGF) was established as a model to evaluate the cytotoxicity of the association of ZOL (5–500 μM) and of ZOL/biphasic calcium phosphates (BCP). Metabolic activity, cell viability, types of cell death, the cell cycle through, and the migration ability of human gingival fibroblasts were evaluated. (3) Results: ZOL was adsorbed by biphasic calcium phosphate compounds in an aqueous solution. The HGF were sensitive to ZOL toxicity; nevertheless, ZOL/BCP showed a significant protective effect regarding metabolic activity, cell viability, and cell migration. (4) Conclusions: BCP interaction with ZOL reduces or abolishes its toxicity in HGF. This finding represents a potential solution for BRONJ in the case of patients undergoing therapy with ZOL.

Low-dose zoledronate for the treatment of bone metastasis secondary to prostate cancer

Background

Bisphosphonates (BPs) including zoledronate (zol) have become standard care for bone metastases as they effectively inhibit tumor-induced osteolysis and associated pain. Several studies have also suggested that zol has direct anti-tumor activity. Systemic administration at high doses is the current approach to deliver zol, yet it has been associated with debilitating side effects. Local therapeutic delivery offers the ability to administer much lower total dosage, while at the same time maintaining sustained high-local drug concentration directly at the target treatment site. Here, we aimed to assess effects of lower doses of zol on bone metastases over a longer time.

Methods

Prostate cancer cell line LAPC4 and prostate-induced bone metastasis cells were treated with zol at 1, 3 and 10 µM for 7 days. Following treatment, cell proliferation was assessed using Almarblue^®, Vybrant MTT^®, and Live/Dead^® viability/cytotoxicity assays. Additionally, cell migration and invasion were carried out using Falcon™ cell culture inserts and Cultrex^® 3D spheroid cell invasion assays respectively.

Results

We show that treatment with 3–10 µM zol over 7-days significantly decreased cell proliferation in both the prostate cancer cell line LAPC4 and cells from spine metastases secondary to prostate cancer. Using the same low-dose and longer time course for treatment, we demonstrate that 10 µM zol also significantly inhibits tumor cell migration and 3D-cell growth/invasion.

Conclusions

This project harnesses the potential of using zol at low doses for longer treatment periods, which may be a viable treatment modality when coupled with biomaterials or biodevices for local delivery.

Electronic supplementary material

The online version of this article (10.1186/s12935-019-0745-x) contains supplementary material, which is available to authorized users.

Hybrid particles derived from alendronate and bioactive glass for treatment of osteoporotic bone defects

Novel hybrid particles are synthesized using alendronate and bioactive glass, which can stimulate regeneration of osteoporotic bone defects.

Alendronate release from calcium phosphate cement for bone regeneration in osteoporotic conditions

Osteoporosis represents a major health problem in terms of compromising bone strength and increasing the risk of bone fractures. It can be medically treated with bisphosphonates, which act systemically upon oral or venous administration. Further, bone regenerative treatments in osteoporotic conditions present a challenge. Here, we focused on the development of a synthetic bone substitute material with local diminishing effects on osteoporosis. Composites were created using calcium phosphate cement (CPC; 60 wt%) and polylactic-co-glycolic acid (PLGA; 40 wt%), which were loaded with alendronate (ALN). In vitro results showed that ALN-loaded CPC/PLGA composites presented clinically suitable properties, including setting times, appropriate compressive strength, and controlled release of ALN, the latter being dependent on composite degradation. Using a rat femoral condyle bone defect model in osteoporotic animals, ALN-loaded CPC/PLGA composites demonstrated stimulatory effects on bone formation both within and outside the defect region.

Antiosteoporotic Drugs to Promote Bone Regeneration Related to Titanium Implants: A Systematic Review and Meta-Analysis

IMPACT STATEMENT

This meta-analysis was to investigate literature on the administration of antiosteoporotic drugs as an effective adjunct therapy for implant osseointegration using in vivo animal models.

Bisphosphonic Acid-Functionalized Cross-Linkers to Tailor Hydrogel Properties for Biomedical Applications

Two bisphosphonic acid-functionalized cross-linkers (one novel) with different spacer chain characteristics were synthesized and incorporated into hydrogels by copolymerization with 2-hydroxyethyl methacrylate at different ratios to control the hydrogels' swelling, mechanical properties, and ability to support mineralization for biomedical applications. The cross-linkers were synthesized by reaction of 2-isocyanatoethyl methacrylate and bisphosphonated diamines followed by selective dealkylation of the bisphosphonate ester groups. The hydrogels provide in vitro growth of carbonated apatite, morphology affected by the cross-linker structure. The hydrogels exhibit a high Young's modulus E (up to 400 kPa) and can sustain up to 10.2 ± 0.1 MPa compressive stresses. E and hence the cross-link density significantly increases upon mineralization reflecting the formation of many bisphosphonate BP-Ca2+ bonds acting as additional cross-links. Cyclic mechanical tests reveal self-recoverability of hydrogels because of reversible nature of BP-Ca2+ bonds. The results suggest that these cross-linkers can add calcium-binding abilities to hydrogels synthesized from any monomer and improve their mechanical, swelling, and mineralization properties and hence are potentially useful materials for biomedical applications.

A new synthetic granular calcium phosphate compound induces new bone in a sinus lift rabbit model

OBJECTIVES

The aim of this study was to investigate if a synthetic granular calcium phosphate compound (CPC) and a composite bisphosphonate-linked hyaluronic acid-calcium phosphate hydrogel (HABP·CaP) induced similar or more amount of bone as bovine mineral in a modified sinus lift rabbit model.

MATERIAL AND METHODS

Eighteen adult male New Zeeland White rabbits, received randomly one of the two test materials on a random side of the face, and bovine mineral as control on the contralateral side. In a sinus lift, the sinus mucosa was elevated and a titanium mini-implant was placed in the alveolar bone. Augmentation material (CPC, HABP·CaP or bovine bone) was applied in the space around the implant. The rabbits were euthanized three months after surgery and qualitative and histomorphometric evaluation were conducted. Histomorphometric evaluation included three different regions of interest (ROIs) and the bone to implant contact on each installed implant.

RESULTS

Qualitative assessment (p = <.05), histomorphometric evaluations (p = < .01), and implant incorporation (p = <.05) showed that CPC and bovine mineral induced similar amount of bone and more than the HABP·CaP hydrogel.

CONCLUSION

CPC induced similar amount of bone as bovine mineral and both materials induced more bone than HABP·CaP hydrogel.

CLINICAL SIGNIFICANCE

The CPC is suggested as a synthetic alternative for augmentations in the maxillofacial area.

Poly(vinylphosphonic acid-co-acrylic acid) hydrogels: The effect of copolymer composition on osteoblast adhesion and proliferation

There is a clinical need for a synthetic bone graft substitute that can be used at sites of surgical intervention to promote bone regeneration. Poly(vinylphosphonic acid-co-acrylic acid) (PVPA-co-AA) has recently been identified as a potential candidate for use in bone tissue scaffolds. It is hypothesized that PVPA-co-AA can bind to divalent calcium ions on bone mineral surfaces to control matrix mineralization and promote bone formation. In this study, hydrogels of PVPA-co-AA have been produced and the effect of copolymer composition on the structure and properties of the gels was investigated. It was found that an increase in VPA content led to the production of hydrogels with high porosities and greater swelling capacities. Consequently, improved cell adhesion and proliferation was observed on these hydrogels, as well as superior cell spreading morphologies. Furthermore, whereas poly(acrylic acid) gels were shown to be relatively brittle, an increase in VPA content created more flexible hydrogels that can be more easily molded into bone defect sites. Therefore, this work demonstrates that the mechanical and cell adhesion properties of PVPA-co-AA hydrogels can be tuned for the specific application by altering the copolymer composition. © 2017 The Authors Journal of Biomedical Materials Research Part A Published by Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 255-264, 2018.

Pamidronate-Conjugated Biodegradable Branched Copolyester Carriers: Synthesis and Characterization

The need for development of comprehensive therapeutic systems, (e.g., polymer-apatite composites) as a bone substitute material has previously been highlighted in many scientific reports. The aim of this study was to develop a new multifunctional composite based on hydroxyapatite porous granules doped with selenite ions (SeO₃^2-) and a biodegradable branched copolymer-bisphosphonate conjugate as a promising bone substitute material for patients with bone tumours or bone metastasis. A series of biodegradable and branched copolymer matrices, adequate for delivery of bisphosphonate in the bone-deficient area were synthesized and physico-chemically and biologically (cyto- and genotoxicity assays) characterized. Branched copolymers were obtained using a hyperbranched bis-MPA polyester-16-hydroxyl initiator and Sn(Oct)₂, a (co)catalyst of the ring-opening polymerization (ROP) of l,l-lactide (LLA) and ε-caprolactone (CL). A new amide bond was formed between the hydroxyl end groups of the synthesized copolymer carriers and an amine group of pamidronate (PAM)-the drug inhibiting bone resorption and osteoclast activity in bone. The dependence of the physico-chemical properties of the copolymer matrices on the kinetic release of PAM from the synthesized branched copolymer conjugate-coated hydroxyapatite granules doped with selenite ions was observed. Moreover, the correlation of these results with the hydrolytic degradation data of the synthesized matrices was evidenced. Therefore, the developed composite porous hydroxyapatite doped with SeO₃^2- ions/biodegradable copolymer-PAM conjugate appears most attractive as a bone substitute material for cancer patients.

Self-powered therapeutic release from conducting polymer/graphene oxide films on magnesium

Magnesium's complete in vivo degradation is appealing for medical implant applications. Rapid corrosion and hydrogen bubble generation along with inflammatory host tissue response have limited its clinical use. Here we electropolymerized a poly (3,4-ethylenedioxythiophene) (PEDOT) and graphene oxide (GO) film directly on Mg surface. GO acted as nano-drug carrier to carry anti-inflammatory drug dexamethasone (Dex). PEDOT/GO/Dex coatings improved Mg corrosion resistance and decreased the rate of hydrogen production. Dex could be released driven by the electrical current generated from Mg corrosion. The anti-inflammatory activity of the released Dex was confirmed in microglia cultures. This PEDOT/GO/Dex film displayed the ability to both control Mg corrosion and act as an on demand release coating that delivers Dex at the corrosion site to minimize detrimental effects of corrosion byproducts. Such multi-functional smart coating will improve the clinical use of Mg implants. Furthermore, the PEDOT/GO/Drug/Mg system may be developed into self-powered implantable drug delivery devices.

Study on critical-sized ultra-high molecular weight polyethylene wear particles loaded with alendronate sodium: in vitro release and cell response

The aim of this study was to investigate the in vitro release and the effect of RAW 264.7 macrophages of critical-sized wear particles of ultra-high molecular weight polyethylene (UHMWPE) loaded with alendronate sodium (ALN), one of the most effective drugs to treat osteoporosis in clinic. The critical-sized UHMWPE-ALN 0.5 wt.% wear particles were prepared by vacuum gradient filtration combined with Pluronic F-68. In vitro release of ALN from critical-sized UHMWPE-ALN wear particles was investigated in phosphate buffered saline (PBS) at 37 °C with a shaker. Cell morphology, proliferation, lactate dehydrogenase (LDH) leakage and secretions of cytokines were evaluated after co-cultured with critical-sized UHMWPE-ALN wear particles in vitro. Results showed that ALN released from critical-sized UHMWPE-ALN wear particles included burst release and slow release in vitro. Macrophages would be chemotaxis and aggregated around the critical-sized UHMWPE-ALN or UHMWPE wear particle, which was phagocytosed with time. The proliferation of macrophages co-cultured with critical-sized UHMWPE-ALN wear particles was significantly decreased compared with that of critical-sized UHMWPE group. Meanwhile, the critical-sized UHMWPE-ALN wear particles significantly induced the LDH leakage of macrophages, which indicated the cell death. The death of macrophages induced by ALN was one of pathways to inhibit their proliferation. The secretions of cytokines (interleukin-6 and tumor necrosis factor-alpha) in critical-sized UHMWPE-ALN group were significantly lower than those in critical-sized UHMWPE group due to the released ALN. The present results suggested that UHMWPE-ALN had the potential application in clinic to treat osteolysis induced by wear particles.

Intra-tumor delivery of zoledronate mitigates metastasis-induced osteolysis superior to systemic administration

Bisphosphonates (BPs) have recently been shown to have direct anti-tumor properties. Systemic treatment with BPs can have multiple adverse effects such as osteonecrosis of the jaw and BP induced bone fracturing and spine instability. While benefits of systemic BP treatments may outweigh risks, local treatment with BPs has been explored as an alternate strategy to reduce unwarranted risk. In the present study, we examined whether local delivery of BPs inhibits tumor-induced osteolysis and tumor growth more effectively than systemic treatment in an animal model of tumor-induced bone disease. Following establishment of an intra-tibial model of bone metastases in athymic mice, the experimental group was treated by local administration of zoledronate into the tibial lesion. A comparison of the effect of local versus systemic delivery of zoledronate on the formation of tumor-induced osteolysis was also carried out. A significant increase in mean bone volume/tissue volume % (BV/TV) of the locally treated group (12.30±2.80%) compared to the control group (7.13±1.22%) (P<0.001). Additionally, there was a significant increase in the BV/TV (10.90±1.25%) in the locally treated group compared to the systemically treated group (7.53±0.75%) (P=0.005). These preliminary results suggest that local delivery of BPs outperforms both systemic and control treatments to inhibit tumor-induced osteolysis.

Immobilization of alendronate on titanium via its different functional groups and the subsequent effects on cell functions

Immobilization of alendronate on orthopedic implants offers the possibility of enhancing osteogenesis without potentially adverse effects associated with systemic administration of this drug. In this work, alendronate was immobilized on titanium (Ti) via either its phosphate (Method 1) or amino (Method 2) groups, and responses of osteoblasts and human mesenchymal stem cells (hMSCs) on these surfaces were investigated. These modified substrates have similar surface roughness and are negatively charged. With similar amounts of immobilized alendronate, these two types of modified substrates showed comparable osteogenic stimulating effects in enhancing osteoblasts' alkaline phosphatase (ALP) activity and calcium deposition for the first 10days. However, alendronate immobilized via its phosphate groups was less stable, and gradually leached into the medium. As a result, its stimulating effect on osteoblast differentiation diminished with time. On the other hand, alendronate immobilized via its amino group stimulated osteoblast differentiation over 21days, and with 1655ng/cm2 of immobilized alendronate on the Ti substrate, calcium deposition by osteoblasts and hMSCs increased by 30% and 69%, respectively, compared to pristine Ti after 21days. The expressions of runt-related transcription factor 2, osterix, osteopontin and osteocalcin in hMSCs cultured on this substrate were monitored. The up-regulation of these genes is postulated to play a role in the acceleration of osteogenic differentiation of hMSCs cultured on the alendronate-modified substrate over those on pristine Ti.

Peptide coating applied on the spot improves osseointegration of titanium implants

On the spot osseointegrating peptide coating applicable to any size and shape of titanium bone implants.

Nanocomposite scaffolds with tunable mechanical and degradation capabilities: co-delivery of bioactive agents for bone tissue engineering

Novel multifunctional nanocomposite scaffolds made of nanobioactive glass and alginate crosslinked with therapeutic ions such as calcium and copper were developed for delivering therapeutic agents, in a highly controlled and sustainable manner, for bone tissue engineering. Alendronate, a well-known antiresorptive agent, was formulated into microspheres under optimized conditions and effectively loaded within the novel multifunctional scaffolds with a high encapsulation percentage. The size of the cation used for the alginate crosslinking impacted directly on porosity and viscoelastic properties, and thus, on the degradation rate and the release profile of copper, calcium and alendronate. According to this, even though highly porous structures were created with suitable pore sizes for cell ingrowth and vascularization in both cases, copper-crosslinked scaffolds showed higher values of porosity, elastic modulus, degradation rate and the amount of copper and alendronate released, when compared with calcium-crosslinked scaffolds. In addition, in all cases, the scaffolds showed bioactivity and mechanical properties close to the endogenous trabecular bone tissue in terms of viscoelasticity. Furthermore, the scaffolds showed osteogenic and angiogenic properties on bone and endothelial cells, respectively, and the extracts of the biomaterials used promoted the formation of blood vessels in an ex vivo model. These new bioactive nanocomposite scaffolds represent an exciting new class of therapeutic cell delivery carrier with tunable mechanical and degradation properties; potentially useful in the controlled and sustainable delivery of therapeutic agents with active roles in bone formation and angiogenesis, as well as in the support of cell proliferation and osteogenesis for bone tissue engineering.