Local delivery of zoledronate from a poly (D,L-lactide)-Coating increases fixation of press-fit implants

Osteogenic differentiation of human adipose-derived mesenchymal stem cells in a bisphosphonate-functionalized polycaprolactone/gelatin scaffold

Recent trends in bone tissue engineering have focused on the development of biomimetic constructs with appropriate mechanical and physiochemical properties. Here, we report the fabrication of an innovative biomaterial scaffold based on a new bisphosphonate-containing synthetic polymer combined with gelatin. To this end, zoledronate (ZA)-functionalized polycaprolactone (PCL-ZA) was synthesized by a chemical grafting reaction. After adding gelatin to the PCL-ZA polymer solution, the porous PCL-ZA/gelatin scaffold was fabricated by the freeze-casting method. A scaffold with aligned pores and a porosity of 82.04 % was obtained. During in vitro biodegradability test, 49 % of its initial weight lost after 5 weeks. The elastic modulus of the PCL-ZA/gelatin scaffold was 31.4 MPa, and its tensile strength was 4.2 MPa. Based on the results of MTT assay, the scaffold had good cytocompatibility with human Adipose-Derived Mesenchymal Stem Cells (hADMSCs). Furthermore, cells grown in PCL-ZA/gelatin scaffold showed the highest mineralization and ALP activity compared to other test groups. Results of the RT-PCR test revealed that RUNX2, COL 1A1, and OCN genes were expressed in PCL-ZA/gelatin scaffold at the highest level, suggesting its good osteoinductive capacity. These results revealed that PCL-ZA/gelatin scaffold could be considered a proper biomimetic platform for bone tissue engineering.

Zoledronic Acid Implant Coating Results in Local Medullary Bone Growth

Osteoarthritis (OA) can necessitate surgical interventions to restore the function of the joint in severe cases. Joint replacement surgery is one of the procedures implemented to replace the damaged joint with prosthetic implants in severe cases of OA. However, after successful implantation, a fraction of OA patients still require revision surgery due to aseptic prosthetic loosening. Insufficient osseointegration is one of the factors that contribute to such loosening of the bone implant, which is commonly made from titanium-based materials. Zoledronic acid (ZA), a potent bisphosphonate agent, has been previously shown to enhance osseointegration of titanium implants. Herein, we fabricated ZA/Ca composites using a reverse microemulsion method and coated them with 1,2-dioleoyl-sn-glycero-3-phosphate monosodium salt (DOPA) to form ZA/Ca/DOPA composites. Titanium alloy screws were subsequently dip-coated with a suspension of the ZA/Ca/DOPA composites and poly(lactic-co-glycolic) acid (PLGA) in chloroform to yield Za/PLGA-coated screws. The coated screws exhibited a biphasic in vitro release profile with an initial burst release within 48 h, followed by a sustained release over 1 month. To assess their performance in vivo, the Za/PLGA screws were then implanted into the tibiae of Sprague-Dawley rats. After 8 weeks, microCT imaging showed new bone growth along the medullary cavity around the implant site, supporting the local release of ZA to enhance bone growth around the implant. Histological staining further confirmed the presence of new mineralized medullary bone growth resembling the cortical bone. Such local medullary growth represents an opportunity for future studies with alternative coating methods to fine-tune the local release of ZA from the coating and enhance complete osseointegration of the implant.

Construction of Local Drug Delivery System on Titanium-Based Implants to Improve Osseointegration

Titanium and its alloys are the most widely applied orthopedic and dental implant materials due to their high biocompatibility, superior corrosion resistance, and outstanding mechanical properties. However, the lack of superior osseointegration remains the main obstacle to successful implantation. Previous traditional surface modification methods of titanium-based implants cannot fully meet the clinical needs of osseointegration. The construction of local drug delivery systems (e.g., antimicrobial drug delivery systems, anti-bone resorption drug delivery systems, etc.) on titanium-based implants has been proved to be an effective strategy to improve osseointegration. Meanwhile, these drug delivery systems can also be combined with traditional surface modification methods, such as anodic oxidation, acid etching, surface coating technology, etc., to achieve desirable and enhanced osseointegration. In this paper, we review the research progress of different local drug delivery systems using titanium-based implants and provide a theoretical basis for further research on drug delivery systems to promote bone–implant integration in the future.

Transcript-Activated Coatings on Titanium Mediate Cellular Osteogenesis for Enhanced Osteointegration

Osteointegration is one of the most important factors for implant success. Several biomolecules have been used as part of drug delivery systems to improve implant integration into the surrounding bone tissue. Chemically modified mRNA (cmRNA) is a new form of therapeutic that has been used to induce bone healing. Combined with biomaterials, cmRNA can be used to develop transcript-activated matrices for local protein production with osteoinductive potential. In this study, we aimed to utilize this technology to create bone morphogenetic protein 2 (BMP2) transcript-activated coatings for titanium (Ti) implants. Therefore, different coating methodologies as well as cmRNA incorporation strategies were evaluated. Three different biocompatible biomaterials were used for the coating of Ti, namely, poly-d,l-lactic acid (PDLLA), fibrin, and fibrinogen. cmRNA-coated Ti disks were assayed for transfection efficiency, cmRNA release, cell viability and proliferation, and osteogenic activity in vitro. We found that cmRNA release was significantly delayed in Ti surfaces previously coated with biomaterials. Consequently, the transfection efficiency was greatly improved. PDLLA coating improved the transfection efficiency in a concentration-dependent manner. Lower PDLLA concentration used for the coating of Ti resulted in higher transfection efficiency. Fibrin and fibrinogen coatings showed even higher transfection efficiencies compared to all PDLLA concentrations. In those disks, not only the expression was up to 24-fold higher but also the peak of maximal expression was delayed from 24 h to 5 days, and the duration of expression was also extended until 7 days post-transfection. For fibrin, higher transfection efficiencies were obtained in the coatings with the lowest thrombin amounts. Accordingly, fibrinogen coatings gave the best results in terms of cmRNA transfection. All biomaterial-coated Ti surfaces showed improved cell viability and proliferation, though this was more noticeable in the fibrinogen-coated disks. The latter was also the only coating to support significant amounts of BMP2 produced by C2C12 cells in vitro. Osteogenesis was confirmed using BMP2 cmRNA fibrinogen-coated Ti disks, and it was dependent of the cmRNA amount present. Alkaline phosphatase (ALP) activity of C2C12 increased when using fibrinogen coatings containing 250 ng of cmRNA or more. Similarly, mineralization was also observed that increased with increasing cmRNA concentration. Overall, our results support fibrinogen as an optimal material to deliver cmRNA from titanium-coated surfaces.

Total hip arthroplasty in patients with osteoporosis

There is a high prevalence of osteoporosis in patients undergoing total hip arthroplasty. There are several clinically relevant questions related to the management of such cases: the effect of ageing; the initial osseointegration of implants, especially when cementless THA is used; the effect of medical osteoporosis treatment on bone-implant interface; the incidence of intraoperative and late periprosthetic fractures, and the long-term survival of both cemented and cementless total hip arthroplasty performed for proximal femoral fractures and hip osteoarthritis. A critical review of the literature is presented in an attempt to draw practical conclusions.

Evaluation of zoledronate, cytochalasin-D, and desferrioxamine on osseointegration in an intra-medullary femoral implant model

OBJECTIVE

The rise in primary and revision surgeries utilizing joint replacement implants suggest the need for more reliable means of promoting implant fixation. Zoledronate-(Zol), cytochalasin-D-(cytoD), and desferrioxamine-(DFO) have been shown to enhance mesenchymal stem cell (MSC) differentiation into osteoblasts promoting bone formation. The objective was to determine whether Zol, cytoD, and DFO can improve fixation strength and enhance peri-implant bone volume about intra-medullary femoral implants.

METHODS

48 Sprague-Dawley female rats were randomized into four treatments, saline-control or experimental: Zol-(0.8 μg/μL), cytoD-(0.05 μg/μL), DFO-(0.4 μg/μL). Implants were placed bilaterally in the femoral canals following injection of treatment solution and followed for 28 days. Mechanical push-out testing and micro-CT were our primary evaluations, measuring load to failure and bone volume. Qualitative evaluation included histological assessment. Data was analyzed with a one-way ANOVA with Holm-Sidak mean comparison testing.

RESULTS

Significant results included pushout tests showing an increase in maximum energy for Zol (124%) and cytoD (82%); Zol showed an increase in maximum load by 48%; Zol micro-CT showed increase in BV/TV by 35%.

CONCLUSIONS

Our findings suggest that locally applied Zol and cytoD enhance implant mechanical stability. Bisphosphonates and actin regulators, like cytoD, might be further investigated as a new strategy for improving osseointegration.

Strontium ion reinforced bioceramic scaffold for load bearing bone regeneration

Bone defects in load bearing areas require bone reconstruction with strong biomaterial having mechanical characteristics like cortical bone. Bioceramics are biomaterials that support bone formation as well as provide adequate mechanical properties. A strontium substitution of the bioceramic is expected to further increase its bioactivity by enhancing osteogenesis and protect the bone from osteoclastic resorption. The study involves development, characterization and in vivo testing of a newly developed strontium substituted hydroxyapatite based bioceramic scaffold (SrHAB) with sufficient biomechanical properties. Optimal concentration of strontium ion required for enhanced osteogenic differentiation was identified by comparing three compositions of SrHAB scaffold; namely Sr10HAB, Sr30HAB and Sr50 HAB for their Alkaline phosphatase activity in vitro. The selected Sr10HAB scaffold demonstrated in vivo bone formation with osteogenic differentiation of stromal derived mesenchymal stem cells (MSC) from human and ovine sources in ectopic and ovine models. Thus, Sr10HAB scaffold has a potential for application in load bearing bone requirements of orthopaedics and dentistry.

Effect of local application of biphosphonates on improving peri-implant osseointegration in type-2 diabetic osteoporosis

Type 2 diabetes mellitus (T2DM), a leading cause of osteoporosis, remains a contraindication for bone implant therapy. Although associated with side effects when systemically administered, biphosphonates (BPs) play a positive role in diabetic osteoporosis treatment. We hypothesized that local BP therapy would prevent decayed implant osseointegration under T2DM conditions. To assess cell proliferation and determine the optimal BP concentration, bone marrow-derived mesenchymal stem cells (BMSCs) and bone marrow macrophages (BMMs) were treated with BPs at various relatively low concentrations (10^-9 mmol/L) for different periods of time. Our in vitro study results demonstrated that BP application reversed the process by which high glucose inhibits bone formation and stimulates bone resorption through osteoclast-specific gene and protein expression (P<0.05). In vivo, fat accumulation and insulin resistance were induced in T2DM rats. We used crosslinked hyaluronic acid as the drug delivery vehicle for BPs to ensure that BPs administered at a dose of 30 µg/kg could settle into the prepared hole in rats. Thereafter, implants were inserted into cylindrical holes of a specific size, created parallel to the long axis of the femora. The outcomes of the in vivo study revealed that BPs promoted bone formation, which reversed the reduction in the DM group according to double fluorescence labeling, micro-CT, biomechanical and histomorphometric analyses (P<0.05). Furthermore, intergroup comparisons revealed significant correlation coefficients (P<0.05) between the micro-CT and biomechanical parameters. Therefore, local administration of BPs could stimulation bone remodeling and represent an effective treatment strategy for preventing decayed implant osseointegration under T2DM conditions.

Local delivery of a zoledronate solution improves osseointegration of titanium implants in a rat distal femur model

This study aimed to determine whether locally applied anti-resorptive agents acetazolamide or zoledronic acid would improve mechanical stability in implant osseointegration when applied as a solution within the medullary canal. Thirty-three rats received titanium-implants bilaterally in their intramedullary femoral canals. Prior to implantation, animals received 0.1 ml saline, 1 mM acetazolamide solution, or 0.7 mM zoledronic acid solution directly into the medullary cavity. The control group only received saline within the medullary canal while the treatment groups only received the respective treatment to which they were randomized. Animals were allowed to heal 4 weeks, at which time they were euthanized and femurs isolated for mechanical and radiographic evaluation. Push-out force to failure increased 152% in the zoledronic acid group relative to the control. There was no significant difference in push-out force with acetazolamide relative to control. Also, zoledronic acid increased metaphyseal bone volume fraction 46% and increased metaphyseal bone-implant contact 58% relative to the control. Recent research exploring local injection of medications to improve implant osseointegration and minimize systemic-effects has failed to quantitatively evaluate implant fixation strength on non-hydroxyapatite coated implants or implants without previous bone compaction. This study demonstrated that a simple injection of zoledronic acid into the medullary canal, rather than coatings or commercial gels, can increase fixation strength of an uncoated titanium-implant. Our findings indicate simple injection of zoledronic acid in saline solution has the potential for improving fixation of uncemented joint implants. Clinical Significance: Intramedullary injection of local bisphosphonate solutions could be implemented to improve osseointegration in cementless arthroplasty. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:3294-3298, 2018.

Anabolic and antiresorptive actions of locally delivered bisphosphonates for bone repair: A review

During the last decades, several research groups have used bisphosphonates for local application to counteract secondary bone resorption after bone grafting, to improve implant fixation or to control bone resorption caused by bone morphogenetic proteins (BMPs). We focused on zoledronate (a bisphosphonate) due to its greater antiresorptive potential over other bisphosphonates. Recently, it has become obvious that the carrier is of importance to modulate the concentration and elution profile of the zoledronic acid locally. Incorporating one fifth of the recommended systemic dose of zoledronate with different apatite matrices and types of bone defects has been shown to enhance bone regeneration significantly in vivo. We expect the local delivery of zoledronate to overcome the limitations and side effects associated with systemic usage; however, we need to know more about the bioavailability and the biological effects. The local use of BMP-2 and zoledronate as a combination has a proven additional effect on bone regeneration. This review focuses primarily on the local use of zoledronate alone, or in combination with bone anabolic factors, in various preclinical models mimicking different orthopaedic conditions.

Cite this article: I. Qayoom, D. B. Raina, A. Širka, Š. Tarasevičius, M. Tägil, A. Kumar, L. Lidgren. Anabolic and antiresorptive actions of locally delivered bisphosphonates for bone repair: A review. Bone Joint Res 2018;7:548–560. DOI: 10.1302/2046-3758.710.BJR-2018-0015.R2.

Healing in peri-implant gap with BMP-2 and systemic bisphosphonate is dependent on BMP-2 dose-A canine study

The bone-implant interface of cementless orthopedic implants can be described as a series of uneven sized gaps with discontinuous areas of direct bone-implant contact. Bridging these voids and crevices by addition of an anabolic stimulus to increase new bone formation can potentially improve osseointegration of implants. Bone morphogenetic protein 2 (BMP-2) stimulates osteoblast formation to increase new bone formation but also indirectly stimulates osteoclast activity. In this experiment, we investigate the hypothesis that osseointegration, defined as mechanical push-out and histomorphometry, depends on the dose of BMP-2 when delivered as an anabolic agent with systemic administration of the anti-resorptive agent zoledronate to curb an increase in osteoclast activity. Four porous coated titanium implants (one with each of three doses of surface-applied BMP-2 (15 µg; 60 µg; 240 µg) and untreated) surrounded by a 0.75 mm empty gap, were inserted into the distal femurs of each of twelve canines. Zoledronate IV (0.1 mg/kg) was administered 10 days into the observation period of 4 weeks. Bone-implant specimens were evaluated by mechanical push-out test and histomorphometry. The 15 µg implants had the best fixation on all mechanical parameters and largest surface area covered with new bone compared to the untreated, 60 and 240 µg implants, as well as the highest volume of new bone in the implant gap compared to 60 and 240 µg implants. The results in a canine implant model demonstrated that a narrow range of BMP-2 doses have opposite effects in bridging an empty peri-implant gap with bone, when combined with systemic zoledronate. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1406-1414, 2018.

Effect of local zoledronate delivery on osseointegration: a systematic review of preclinical studies

PURPOSE

The aim of the present systematic review was to assess the effect of local zoledronate (ZOL) delivery (topical or as implant surface coatings) on osseointegration.

MATERIALS AND METHODS

In this systematic review, the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed. To address the focused question, 'Does local zoledronate delivery enhance osseointegration?' indexed databases were searched without time or language restrictions up to and including April 2017 using various combination of the following keywords: 'zoledronate', 'bisphosphonates', 'osseointegration' and 'topical administration'. Letters to the Editor, historic reviews, commentaries, case-series and case-reports were excluded.

RESULTS

Initially, 383 articles were identified out of which, 23 experimental studies fulfilled the inclusion criteria. In 18 studies, ZOL was incorporated into implants surfaces as a coating and in five studies ZOL was applied topically (bone graft or irrigation) into the bone cavities. Results from 87% studies reported that local delivery of ZOL (coating or topical) is effective in enhancing osseointegration or new bone formation around implants.

CONCLUSIONS

Local ZOL delivery (coating or topical) seems to enhance osseointegration in animals; however, from a clinical perspective, further randomized control trials with long-term follow-up are needed in this regard.

Local delivery of zoledronate from a poly (d,l-lactide)-coating increases fixation of hydroxy-coated implants

Initial secure implant fixation predicts long-term survival. Bisphosphonates are anti-resorptive agents. They have been shown to increase implant fixation. We investigated whether local delivery of zoledronate from a poly-d,l-lactide (PDLLA)-coating could improve fixation and osseointegration of hydroxy-apatite coated implants. Cylindrical hydroxy-apatite coated implants were bilaterally inserted press-fit into the proximal tibiae of 10 dogs. On one side the implant was coated with PDLLA containing zoledronate. The PDLLA coating was applied upon the hydroxy-apatite coating. We used the contralateral implant as control. This implant was not coated with a poly-d,l-lactide. Observation period was 12 weeks. We evaluated implant fixation with histomorphometry and biomechanical push-out test. Zoledronate resulted in an approximately threefold increase in all biomechanical parameters when comparing data with their respective controls. We found that zoledronate increased preservation of old lamellar bone and increased formation of new woven bone. This study indicates that local delivery of zoledronate from a PDDLA coating has the potential to increase implant fixation. Studies investigating different doses of zoledronate and longer follow-up are needed. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:974-979, 2017.

Recent coating developments for combination devices in orthopedic and dental applications: A literature review

Orthopedic and dental implants have been used successfully for decades to replace or repair missing or damaged bones, joints, and teeth, thereby restoring patient function subsequent to disease or injury. However, although device success rates are generally high, patient outcomes are sometimes compromised due to device-related problems such as insufficient integration, local tissue inflammation, and infection. Many different types of surface coatings have been developed to address these shortcomings, including those that incorporate therapeutic agents to provide localized delivery to the surgical site. While these coatings hold enormous potential for improving device function, the list of requirements that an ideal combination coating must fulfill is extensive, and no single coating system today simultaneously addresses all of the criteria. Some of the primary challenges related to current coatings are non-optimal release kinetics, which most often are too rapid, the potential for inducing antibiotic resistance in target organisms, high susceptibility to mechanical abrasion and delamination, toxicity, difficult and expensive regulatory approval pathways, and high manufacturing costs. This review provides a survey of the most recent developments in the field, i.e., those published in the last 2-3years, with a particular focus on technologies that have potential for overcoming the most significant challenges facing therapeutically-loaded coatings. It is concluded that the ideal coating remains an unrealized target, but that advances in the field and emerging technologies are bringing it closer to reality. The significant amount of research currently being conducted in the field provides a level of optimism that many functional combination coatings will ultimately transition into clinical practice, significantly improving patient outcomes.