Ciprofloxacin implants for bone infection. In vitro-in vivo characterization

Chitosan nanofibrous scaffold with graded and controlled release of ciprofloxacin and BMP-2 nanoparticles for the conception of bone regeneration

The repair of bone defects using grafts is commonly employed in clinical practice. However, the risk of infection poses a significant concern. Tissue engineering scaffolds with antibacterial functionalities offer a better approach for bone tissue repair. In this work, firstly, two kinds of nanoparticles were prepared using chitosan to complex with ciprofloxacin and BMP-2, respectively. The ciprofloxacin complex nanoparticles improved the dissolution efficiency of ciprofloxacin achieving a potent antibacterial effect and cumulative release reached 95 % in 7 h. For BMP-2 complexed nanoparticles, the release time points can be programmed at 80 h, 100 h or 180 h by regulating the number of coating chitosan layers. Secondly, a functional scaffold was prepared by combining the two nanoparticles with chitosan nanofibers. The microscopic nanofiber structure of the scaffold with 27.28 m2/g specific surface area promotes cell adhesion, high porosity provides space for cell growth, and facilitates drug loading and release. The multifunctional scaffold exhibits programmed release function, and has obvious antibacterial effect at the initial stage of implantation, and releases BMP-2 to promote osteogenic differentiation of mesenchymal stem cells after the antibacterial effect ends. The scaffold is expected to be applied in clinical bone repair and graft infection prevention.

Bovine Serum Albumin - Hydroxyapatite Nanoflowers as Potential Local Drug Delivery System of Ciprofloxacin

Introduction

Hybrid nanoflowers are structures consisting of organic (enzymes, proteins, nucleic acids) and inorganic components (mostly metal phosphates) with a flower-like hierarchical structure. Novel hybrid nanoflowers based on bovine serum albumin (BSA) and hydroxyapatite (HA) were obtained and characterized. Study on BSA-HA nanoflowers as potential drug delivery system is reported for the first time.

Methods

Embedding ciprofloxacin in the structure of hybrid nanoflowers was confirmed by ATR-FTIR and thermogravimetric analysis. The inorganic phase of the nanoflowers was determined by X-ray diffraction. UV‒Vis spectroscopy was used to evaluate the release profiles of ciprofloxacin from nanoflowers in buffer solutions at pH 7.4 and 5. The agar disk diffusion method was used to study the antibacterial activity of the synthesized nanoflowers against Staphylococcus aureus and Pseudomonas aeruginosa.

Results

Bovine serum albumin - hydroxyapatite nanoflowers were obtained with diameters of ca. 1-2 µm. The kinetics of ciprofloxacin release from nanoflowers were described by the Korsmeyer-Peppas model. The antibacterial activity of the synthesized nanoflowers was demonstrated against S. aureus and P. aeruginosa, two main pathogens found in osteomyelitis.

Conclusion

The formulated nanoflowers may act as an efficient local antibiotic delivery system. Due to the use of nonhazardous, biodegradable components and benign synthesis, hybrid nanoflowers are very promising drug delivery systems that could be applied in the treatment of skeletal system infections.

Fabrication and evaluation of customized implantable drug delivery system for orthopedic therapy based on 3D printing technologies

A customized implantable drug delivery system with the dual functions of playing a supporting role and providing continuous bacteriostasis is of great importance during the treatment of bone defect diseases. The main objective of this study was to explore the potential of using three-dimensional (3D) printing technologies to fabricate customized implants. Ciprofloxacin hydrochloride (Cipro) was chosen as the model drug, and two printing technologies, semisolid extrusion (SSE) and fused deposition modeling (FDM) were introduced. Six kinds of implants with customized irregular shapes were printed via FDM technology. Two kinds of implants with customized dosages were constructed via SSE technology. In addition, three kinds of implants with customized internal structures were produced via FDM and SSE technologies. The data for morphology, dimensions and mechanical properties demonstrated satisfactory printability and good printing accuracy when applying SSE and FDM technologies to produce the customized implants. The dissolution curves indicated that the desired customized drug release could be achieved by designing the specific internal structures. The biocompatibility examination showed that the printed implants possessed outstanding biocompatibility. In conclusion, all results suggested that 3D printing technologies provide a feasible method and novel strategy to fabricate customized implantable drug delivery systems.

Exploration and Preparation of Patient-specific Ciprofloxacin Implants Drug Delivery System Via 3D Printing Technologies

A suitable drug-loaded implant delivery system that can effectively release antibacterial drug in the postoperative lesion area and help repair bone infection is very significant in the clinical treatment of bone defect. The work was aimed to investigate the feasibility of applying three-dimensional (3D) printing technology to prepare drug-loaded implants for bone repair. Semi-solid extrusion (SSE) and Fuse deposition modeling® (FDM) technologies were implemented and ciprofloxacin (CIP) was chosen as the model drug. All of the implants exhibited a smooth surface, good mechanical properties and satisfactory structural integrity as well as accurate dimensional size. In vitro drug release showed that the implants made by 3D printing technologies slowed down the initial drug burst effect and expressed a long-term sustained release behavior, compared with the implants prepared with traditional method. In addition, the patient-specific macrostructure implants, consisting of interconnected and different shapes pores, were created using unique lay down patterns. As a result, the weakest burst release effect and the sustained drug release were achieved in the patient-specific implants with linear pattern. These results clearly stated that 3D printing technology offers a viable approach to prepare control-releasing implants with patient-specific macro-porosity and presents novel strategies for treating bone infections.

Stretch-responsive adhesive microcapsules for strain-regulated antibiotic release from fabric wound dressings

Bacterial infection of a wound is a major complication that can significantly delay proper healing and even necessitate surgical debridement. Conventional non-woven fabric dressings, including gauzes, bandages and cotton wools, often fail in treating wound infections in a timely manner due to their passive release mechanism of antibiotics. Here, we propose adhesive mechanically-activated microcapsules (MAMCs) capable of strongly adhering to a fibrous matrix to achieve a self-regulated release of antibiotics upon uniaxial stretching of non-woven fabric dressings. To achieve this, a uniform population of polydopamine (PDA)-coated MAMCs (PDA-MAMCs) are prepared using a microfluidics technique and subsequent oxidative dopamine polymerization. The PDA-MAMC allows for robust mechano-activation within the fibrous network through high retention and effective transmission of mechanical force under stretching. By validating the potential of a PDA-MAMCs-laden gauze to release antibiotics in a tensile strain-dependent manner, we demonstrate that PDA-MAMCs can be successfully incorporated into a woven material and create a smart wound dressing for control of bacterial infections. This new mechano-activatable delivery approach will open up a new avenue for a stretch-triggered, on-demand release of therapeutic cargos in skin-mountable or wearable biomedical devices.

Natural medicine delivery from biomedical devices to treat bone disorders: A review

With an increasing life expectancy and aging population, orthopedic defects and bone graft surgeries are increasing in global prevalence. Research to date has advanced the understanding of bone biology and defect repair mechanism, leading to a marked success in the development of synthetic bone substitutes. Yet, the quest for functionalized bone grafts prompted the researchers to find a viable alternative that regulates cellular activity and supports bone regeneration and healing process without causing serious side-effects. Recently, researchers have introduced natural medicinal compounds (NMCs) in bone scaffold that enables them to release at a desirable rate, maintains a sustained release allowing sufficient time for tissue in-growth, and guides bone regeneration process with minimized risk of tissue toxicity. According to World Health Organization (WHO), NMCs are gaining popularity in western countries for the last two decades and are being used by 80% of the population worldwide. Compared to synthetic drugs, NMCs have a broader range of safety window and thus suitable for prolonged localized delivery for bone regeneration. There is limited literature focusing on the integration of bone grafts and natural medicines that provides detailed scientific evidences on NMCs, their toxic limits and particular application in bone tissue engineering, which could guide the researchers to develop functionalized implants for various bone disorders. This review will discuss the emerging trend of NMC delivery from bone grafts, including 3D-printed structures and surface-modified implants, highlighting the significance and potential of NMCs for bone health, guiding future paths toward the development of an ideal bone tissue engineering scaffold. STATEMENT OF SIGNIFICANCE: To date, additive manufacturing technology provids us with many advanced patient specific or defect specific bone constructs exhibiting three-dimensional, well-defined microstructure with interconnected porous networks for defect-repair applications. However, an ideal scaffold should also be able to supply biological signals that actively guide tissue regeneration while simultaneously preventing post-implantation complications. Natural biomolecules are gaining popularity in tissue engineering since they possess a safer, effective approach compared to synthetic drugs. The integration of bone scaffolds and natural biomolecules exploits the advantages of customized, multi-functional bone implants to provide localized delivery of biochemical signals in a controlled manner. This review presents an overview of bone scaffolds as delivery systems for natural biomolecules, which may provide prominent advancement in bone development and improve defect-healing caused by various musculoskeletal disorders.

Formulation and characterization of hydroxyapatite-based composite with enhanced compressive strength and controlled antibiotic release

A composite based on hydroxyapatite (HA) and chitosan (CS) combined with ciprofloxacin (CIP) was formulated by the solid-liquid mixing method. The optimization of the solid to the liquid ratio and the use of chitosan in a small amount (≤5 wt%) promoted the preparation of stable and rigid monoliths. A synergistic effect of CS and CIP contents on the compressive strength of the CIP-loaded composite was evidenced. The compressive strength of the fabricated biocomposite ranged in values from 1 to 6 MPa, comparable to those reported for cancellous bone. The improvement of the mechanical properties with the increase of the rate of organic components was correlated with the diminution of the surface area and the reduction in the pore volume of the specimens. On the other hand, the in vitro release experiments of the antibiotic indicated a sustained and controlled release of CIP over 10 days. Moreover, in vitro antibacterial tests performed on the biocomposite HA-CS5-CIP showed significant inhibition of Staphylococcus aureus and Escherichia coli pathogens. According to the showed results, the formulated composite with three-phase components could be a promising material for bone repair and local antibiotic release for the treatment of bone infections.

Ibuprofen-loaded calcium phosphate granules: A new bone substitute for local relieving symptoms of osteoarthritis

Musculoskeletal diseases often demand a drug treatment at the specific site of injury or defect site. In this context, the use of calcium phosphates is attractive as it allows both the bone substitution and the local delivery of a drug substance. In this work, we present a drug delivery device that combines calcium phosphate bioceramic granules and ibuprofen, a widely used anti-inflammatory drug. After verifying in vitro biocompatibility of the ibuprofen-loaded calcium phosphate granules on murine preosteoblastic cells (MC3T3), we evaluated in vitro efficiency of the drug substance released from the bioceramic using rheumatoid arthritis synoviocytes. Our data document that ibuprofen-loaded calcium phosphate granules reduced inflammatory response and increased apoptosis of synoviocytes. In vivo study showed that both unloaded, and ibuprofen-loaded calcium phosphate granules induced a progressive osteogenesis, but in the case of ibuprofen-loaded implants, bone ingrowth was more limited in first weeks. However, as far as concerns inflammation, while unloaded granules showed inflammation up to 4 weeks, ibuprofen loaded granules did not show any significant inflammation. Ibuprofen concentration determination in blood samples showed that a very small amount of the drug reached the general circulation which render this drug delivery system suitable for both bone substitution and reduction of inflammation at the implantation site. Thus, this new drug carrier could be used to locally relieve inflammatory bone diseases symptoms including rheumatoid arthritis but, beyond this study, this kind of granules could be considered for the delivery of therapeutic agents such as antibiotic, analgesic or anticancer drugs.

Clinically established biodegradable long acting injectables: An industry perspective

Long acting injectable formulations have been developed to sustain the action of drugs in the body over desired periods of time. These delivery platforms have been utilized for both systemic and local drug delivery applications. This review gives an overview of long acting injectable systems that are currently in clinical use. These products are categorized in three different groups: biodegradable polymeric systems, including microparticles and implants; micro and nanocrystal suspensions and oil-based formulations. Furthermore, the applications of these drug delivery platforms for the management of various chronic diseases are summarized. Finally, this review addresses industrial challenges regarding the development of long acting injectable formulations.

Development of antibacterial, ciprofloxacin-eluting biodegradable coatings on Ti6Al7Nb implants to prevent peri-implant infections

Various types of biodegradable polymers containing lactide, glycolide, caprolactone, and trimethylene carbonate units have been used to obtain ciprofloxacin (CFX)-enriched coatings developed on the Ti6Al7Nb alloy, intended for short-term therapy. In the first step, the surface of the Ti6Al7Nb alloy was modified, mostly according to sandblasting and anodic oxidation to obtain the TiO₂ layer. Anodizing can be an effective method for preparing TiO₂ coatings with osteoconductive properties. The polymer containing CFX molecules was deposited on the modified alloy, and Polymer + CFX/TiO ₂ /Ti6Al7Nb systems were developed. CFX-enriched coatings adhered well to the surface of the previously modified alloy. Polymer layers maintain the topography of the alloy due to the development of the surface during the sandblasting method. As polymers intended for the study possess degradation ability, they are capable of releasing the incorporated drug. Antibacterial activity of CFX-enriched coatings was examined to verify the functionality of designed Polymer + CFX/TiO ₂ /Ti6Al7Nb systems, and the bactericidal effect was confirmed for all cases. The presented study is an extension of previous, initial research and creates an overview of polyester or polyestercarbonate CFX-eluting coatings.

Adsorption/desorption study of antibiotic and anti-inflammatory drugs onto bioactive hydroxyapatite nano-rods

The use of high doses of antibacterial and anti-inflammatory drugs for patients with bone diseases, associated to implants or bone filling, can develop adverse effects; and consequently, it promotes to think new strategies to avoid this problem. In this work, it has been described the adsorption/release (or desorption) behavior of two drugs, ciprofloxacin (CIP) and ibuprofen (IBU), onto hydroxyapatite (nano-HA) at 37 °C. Through Ultraviolet-Visible (UV-Vis) spectroscopy, the concentrations of both drugs in adsorption, kinetic and desorption processes were obtained. The Fourier Transformed-Infrared (FT-IR) spectroscopy, Zeta-potential (ζ-potential), High-Resolution Transmission Electron Microscopy (H-TEM) and x-Ray Diffraction (xRD) were also used to characterize bared nanoparticles and those with adsorbed drugs. Five adsorption models (Langmuir, Freundlich, Sips, Temkin and Dubinin-Radushkevich) were used for describing the behavior of both active compounds. The adsorption processes (CIP/nano-HA and IBU/nano-HA) were better predicted by the Sips model than by the others. The kinetic adsorption data were processed, for both active agents, by application of Avrami's model. Desorption/release process (of both drugs) was evaluated though Korsmeyer-Peppas (K-P) model. Owing to the predictability of these systems, we propose the use of these active ceramics as potential bone filler for improving the treatment against bacterial bone infections and to avoid its associated inflammatory process.

Synthesis and characterization of nanoscale zeolitic imidazolate frameworks with ciprofloxacin and their applications as antimicrobial agents

The present study investigated antibiotic drug loading in metal–organic frameworks (MOFs).

A therapeutic delivery system for chronic osteomyelitis via a multi-drug implant based on three-dimensional printing technology

Chronic osteomyelitis is difficult to be cured and often relapses, which presents to be a great challenge to clinicians. We conducted this original study to explore the efficiency of therapeutic alliance for chronic osteomyelitis by a multi-drug implant based on three-dimensional printing technology. We designed and fabricated preciously a multi-drug implant with a multi-layered concentric cylinder construction by three-dimensional (3D) printing technology. Levofloxacin and tobramycin were incorporated into the drug implant in a specific sequence. The drug release property of the drug implant was assayed in vitro We also developed an animal model of chronic osteomyelitis to estimate the effect of the 3D printed multi-drug implant. The results showed that the multi-drug implant had a sustained and programmed drug release property. Levofloxacin and tobramycin which were released from the multi-drug implant worked in tandem to enhance pharmacodynamic action which was similar to a tumor chemotherapy program and were sufficient to treat chronic osteomyelitis. These findings imply that the administration of 3D printed multi-drug implant would be a potential therapeutic method for chronic osteomyelitis. Further studies are required.

In vivo quantification of gentamicin released from an implant coating

Drug-releasing implants are gaining increasing interest. The present study reports a detailed physicochemical analysis of a polymeric coating based on poly(D,L-lactide) and the incorporated gentamicin combined with an in vitro and in vivo study of the gentamicin release. Differential scanning calorimeter, Fourier transform infrared spectroscopy, gel permeation chromatography and high-performance liquid chromatography showed no effect of the gamma sterilisation on the coating components or an interaction of the polymer and the gentamicin. Microbiological analysis revealed an inhibition of bacterial growth on the implant surface. For the in vivo study, gentamicin-coated wires were implanted into the tibiae of rats and harvested at different time points up to day 42. To monitor the release in vivo, gentamicin was quantified in serum, bone, endosteum, kidney, and on the explanted wires. Gentamicin was detectable over a time period of 42 days in the endosteum, up to seven days in the kidney, up to 4 h in the bone and at the end of the experiment on one of eight wires. The locally released gentamicin caused no histological changes of the kidney. Microbiologically active concentrations of released gentamicin were found in the endosteum up to 4 h after implantation. The combination of different methods supports the individual results, where quantification is complemented by visualisation or antimicrobial activity. This work demonstrates that the coating procedure results in no substantial alteration of the incorporated drug and that the in vitro burst release occurs also in vivo.

Ciprofloxacin monoolein water gels as implants for the treatment of chronic osteomyelitis: In vitro characterization

This work investigated the possibility of using the biodegradable gentamicin-monoolein-water gels as models, in order to obtain a similar sustained release of ciprofloxacin hydrochloride. Four gels containing antibiotics were prepared and were examined with regard to their physicochemical properties and in vitro drug release characteristics. Ciprofloxacin, unlike gentamicin, which was dissolved in the matrix, was in dispersed form. However, despite its insolubility, microscopic observation, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and X-ray diffraction showed that the developed gel was in the cubic liquid crystalline structure and have maintained their ability to progressively release ciprofloxacin. ciprofloxacin-monoolein-water (5:80:15% w/w), which released in vitro approximately 85% of ciprofloxacin after 16 days could possibly be considered as an alternative to a gentamicin-monoolein-water gel for the treatment of chronic osteomyelitis.

A systematic review of animal models for Staphylococcus aureus osteomyelitis

Staphylococcus aureus (S. aureus) osteomyelitis is a significant complication for orthopaedic patients undergoing surgery, particularly with fracture fixation and arthroplasty. Given the difficulty in studying S. aureus infections in human subjects, animal models serve an integral role in exploring the pathogenesis of osteomyelitis, and aid in determining the efficacy of prophylactic and therapeutic treatments. Animal models should mimic the clinical scenarios seen in patients as closely as possible to permit the experimental results to be translated to the corresponding clinical care. To help understand existing animal models of S. aureus, we conducted a systematic search of PubMed and Ovid MEDLINE to identify in vivo animal experiments that have investigated the management of S. aureus osteomyelitis in the context of fractures and metallic implants. In this review, experimental studies are categorised by animal species and are further classified by the setting of the infection. Study methods are summarised and the relevant advantages and disadvantages of each species and model are discussed. While no ideal animal model exists, the understanding of a model's strengths and limitations should assist clinicians and researchers to appropriately select an animal model to translate the conclusions to the clinical setting.

Processing and sustained in vitro release of rifampicin containing composites to enhance the treatment of osteomyelitis

The objective in this study was to develop an osteoconductive, biodegradable and rifampicin releasing bone filling composite material for the treatment of osteomyelitis, a bacterial infection of bone that is very difficult and expensive to treat. The composite material will be used together with a ciprofloxacin releasing composite, because of the rapid development of resistant bacteria when rifampicin is used alone. Three composites were manufactured by twin-screw extrusion. The polymer matrix for the composites was poly(L-lactide-co-ε-caprolactone) 70/30 and all the composites contained 8 wt% (weight percent) of rifampicin antibiotic. The β-TCP contents of the composites were 0 wt%, 50 wt% and 60 wt%. The composites were sterilized by gamma irradiation before in vitro degradation and drug release tests. The hydrolytical degradation of the studied composites proceeded quickly and the molecular weight of the polymer component of the composites decreased rapidly. Rifampicin release occurred in four phases in which the high β-TCP content of the samples, polymer degradation and mass loss all played a role in determining the phases. The ceramic component was seen to have a positive effect on the drug release. The composite with 50 wt% of β-TCP showed the most promising rifampicin release profile and it also showed activity against a common osteomyelitis causing bacteria Pseudomonas aeruginosa. A clear inhibition zone was formed in 16 h incubation. Overall, the tested materials showed great potential to be developed into a bone filler material for the treatment of osteomyelitis or other bone related infections in combination with the ciprofloxacin releasing materials.

In situ synthesis, characterization and in vitro studies of ciprofloxacin loaded hydroxyapatite nanoparticles for the treatment of osteomyelitis

A series of ciprofloxacin loaded hydroxyapatite nanoparticles has been synthesized by anin situprecipitation method for osteomyelitis treatment.

Formulation of ciprofloxacin hydrochloride loaded biodegradable nanoparticles: optimization of technique and process variables

Poly lactic-co-glycolic acid (PLGA 502 H) nanoparticles incorporating ciprofloxacin HCl (CP) were prepared by double emulsion solvent diffusion technique.

METHODS

The influence of the application of probe sonication besides the high pressure homogenization in the preparation of the secondary emulsion and its application during the solidification step were studied. Their effect on the particle size, Zeta potential and the percent encapsulation efficiency of the drug (EE %) were investigated. The effect of the addition of polyvinyl alcohol (PVA) during the preparation of the primary emulsion was studied. Moreover, the effect of the addition of 0.1 M sodium chloride and/or adjusting the external and extracting phases to pH 7.4 were investigated. The selected formula was examined using IR, X-ray, DSC and SEM and in vitro drug release.

RESULTS

These formulations showed an appropriate particle size ranges between 135.7-187.85 nm, a mean zeta potential ranging from -0.839 to -6.81 mV and a mean EE% which ranged from 35% to 69%.

CONCLUSION

The presented data revealed the superiority of using probe sonication besides high pressure homogenization during the formation of secondary emulsion. Moreover, the results indicated that the tested factors had a pronounced significant effect on the EE%.

Release behavior and toxicity profiles towards A549 cell lines of ciprofloxacin from its layered zinc hydroxide intercalation compound

Background

Layered hydroxides salts (LHS), a layered inorganic compound is gaining attention in a wide range of applications, particularly due to its unique anion exchange properties. In this work, layered zinc hydroxide nitrate (LZH), a family member of LHS was intercalated with anionic ciprofloxacin (CFX), a broad spectrum antibiotic via ion exchange in a mixture solution of water:ethanol.

Results

Powder x-ray diffraction (XRD), Fourier transform infrared (FTIR) and thermogravimetric analysis (TGA) confirmed the drug anions were successfully intercalated in the interlayer space of LZH. Specific surface area of the obtained compound was increased compared to that of the host due to the different pore textures between the two materials. CFX anions were slowly released over 80 hours in phosphate-buffered saline (PBS) solution due to strong interactions that occurred between the intercalated anions and the host lattices. The intercalation compound demonstrated enhanced antiproliferative effects towards A549 cancer cells compared to the toxicity of CFX alone.

Conclusions

Strong host-guest interactions between the LZH lattice and the CFX anion give rise to a new intercalation compound that demonstrates sustained release mode and enhanced toxicity effects towards A549 cell lines. These findings should serve as foundations towards further developments of the brucite-like host material in drug delivery systems.

An in vitro study of composites of poly(L-lactide-co-ε-caprolactone), β-tricalcium phosphate and ciprofloxacin intended for local treatment of osteomyelitis

Osteomyelitis is a bacterial disease that can become chronic, and treatment often includes a surgical operation to remove infected bone. The aim of this study was to develop and investigate in vitro bone filling composite materials that release ciprofloxacin to kill any remaining bacteria and contain bioceramic to help the bone to heal. Three composites of poly(L-lactide-co-ε-caprolactone), β-tricalcium phosphate and ciprofloxacin were compounded using twin-screw extrusion and sterilized by gamma irradiation. Drug release and degradation of the composites were investigated in vitro for 52 weeks. The composite with 50 wt% of β-TCP had the most promising ciprofloxacin release profile. The ceramic component accelerated the drug release that occurred in three phases obeying first-order kinetics. Inhibition zone testing using bioluminescence showed that the released ciprofloxacin had effect in eradicating a common osteomyelitis causing bacteria Pseudomonas aeruginosa. During the in vitro degradation test series, molar weight of the polymer matrix of the composites decreased rapidly. Additionally, ¹H-NMR analysis showed that the polymer had blocky structure and the comonomer ratio changed during hydrolysis. The tested composites showed great potential to be developed into bone filler materials for the treatment of osteomyelitis or other bone related infections.

Bisphosphonate-based strategies for bone tissue engineering and orthopedic implants

Bisphosphonates (BPs) are a group of well-established drugs that are applied in the development of metabolic bone disorder-related therapies. There is increasing interest also in the application of BPs in the context of bone tissue engineering, which is the topic of this review, in which an extensive overview of published studies on the development and applications of BPs-based strategies for bone regeneration is provided with special focus on the rationale for the use of different BPs in three-dimensional (3D) bone tissue scaffolds. The different alternatives that are investigated to address the delivery and sustained release of these therapeutic drugs in the nearby tissues are comprehensively discussed, and the most significant published approaches on bisphosphonate-conjugated drugs in multifunctional 3D scaffolds as well as the role of BPs within coatings for the improved fixation of orthopedic implants are presented and critically evaluated. Finally, the authors' views regarding the remaining challenges in the fields and directions for future research efforts are highlighted.

Development of 3D wet-spun polymeric scaffolds loaded with antimicrobial agents for bone engineering

Three-dimensional wet-spun microfibrous meshes of a star poly(∈-caprolactone) were developed as potential scaffolds endowed with antimicrobial activity. The in vitro release kinetics of the meshes, under physiological conditions, was initially fast and then a sustained release for more than one month was observed. Cell cultures of a murine pre-osteoblast cell line showed good cell viability and adhesion on the wet-spun star poly(∈-caprolactone) fiber scaffolds. These promising results indicate a potential application of the developed meshes as engineered bone scaffolds with antimicrobial activity.

Macro-to-micro porous special bioactive glass and ceftriaxone-sulbactam composite drug delivery system for treatment of chronic osteomyelitis: an investigation through in vitro and in vivo animal trial

A systematic and extensive approach incorporating in vitro and in vivo experimentation to treat chronic osteomyelitis in animal model were made using antibiotic loaded special bioactive glass porous scaffolds. After thorough characterization for porosity, distribution, surface charge, a novel drug composite were infiltrated by using vacuum infiltration and freeze-drying method which was subsequently analyzed by SEM-EDAX and studied for in vitro drug elution in PBS and SBF. Osteomyelitis in rabbit was induced by inoculation of Staphylococcus aureus and optimum drug-scaffold were checked for its efficacy over control and parenteral treated animals in terms of histopathology, radiology, in vivo drug concentration in bone and serum and implant-bone interface by SEM. It was optimized that 60P samples with 60-65% porosity (bimodal distribution of macro- to micropore) with average pore size ~60 μm and higher interconnectivity, moderately high antibiotic adsorption efficiency (~49%) was ideal. Results after 42 days showed antibiotic released higher than MIC against S. aureus compared to parenteral treatment (2 injections a day for 6 weeks). In vivo drug pharmacokinetics and SEM on bone-defect interface proved superiority of CFS loaded porous bioactive glass implants over parenteral group based on infection eradication and new bone formation.

Functionalized Bridged Silsesquioxane-based Nanostructured Microspheres: Performance as Novel Drug-delivery Devices in Bone Tissue-related Applications

Two kinds of functionalized nanostructured hybrid microspheres, based on the bridged silsesquioxane family, were synthesized by employing the sol–gel method via self-assembly of two different organic–inorganic bridged monomers. The architecture reached at molecular level allowed the incorporation of acetylsalicylic acid (ASA) as an anti-inflammatory model drug. The ASA-functionalized microspheres were characterized as delivery devices in simulated body fluid (SBF). The release behaviors of the synthesized microspheres (Fickian or anomalous diffusion mechanisms) were shown to be dependent on the chemical nature of the bridged monomers employed to synthesize the hybrid materials. The functionalized microspheres were proposed as delivery systems into calcium phosphate cements (CPCs), in order to slow down the characteristic drug-delivery kinetics of this kind of bone tissue-related materials. The incorporation of the new functionalized microparticles into the CPCs represented a viable methodology to modify the ASA-release kinetics in comparison to a conventional CPC containing the drug dispersed into the solid phase. The ASA-delivery profiles obtained from the microsphere-loaded CPCs showed that 40–60% of drug can be released after 2 weeks of testing in SBF. The inclusion of the microspheres into the CPC matrices allowed modification of the release profiles through a mechanism that involved two stages: (1) the diffusion of the drug through the organic–inorganic matrix of the microspheres (according to a Fickian or anomalous diffusion, depending on the nanostructuring) and (2) the subsequent diffusion of the drug through the ceramic matrix of the hardened cements. The release behavior of the composite cements was shown to be dependent on the nanostructuring of the hybrid microspheres, which can be selectively tailored by choosing the desired chemical structure of the bridged precursors employed in the sol–gel synthesis. The obtained results demonstrated the ability of this new class of functionalized hybrid microdevices as delivery systems into calcium phosphate materials with potential bone tissue-related drug-delivery applications.

A programmed release multi-drug implant fabricated by three-dimensional printing technology for bone tuberculosis therapy

In the world, bone tuberculosis is still very difficult to treat and presents a challenge to clinicians. In this study, we utilized 3D printing technology to fabricate a programmed release multi-drug implant for bone tuberculosis therapy. The construction of the drug implant was a multi-layered concentric cylinder divided into four layers from the center to the periphery. Isoniazid and rifampicin were distributed individually into the different layers in a specific sequence of isoniazid-rifampicin-isoniazid-rifampicin. The drug release assays in vitro and in vivo showed that isoniazid and rifampicin were released orderly from the outside to the center to form the multi-drug therapeutic alliance, and the peak concentrations of drugs were detected in sequence at 8 to 12 day intervals. In addition, no negative effect on the proliferation of rabbit bone marrow mesenchymal stem cells was detected during the cytocompatibility assay. Due to its ideal pharmacologic action and cytocompatibility, the programmed release multi-drug implant with a complex construction fabricated by 3D printing technology could be of interest in prevention and treatment of bone tuberculosis.

Bone tissue engineering therapeutics: controlled drug delivery in three-dimensional scaffolds

This paper provides an extensive overview of published studies on the development and applications of three-dimensional bone tissue engineering (TE) scaffolds with potential capability for the controlled delivery of therapeutic drugs. Typical drugs considered include gentamicin and other antibiotics generally used to combat osteomyelitis, as well as anti-inflammatory drugs and bisphosphonates, but delivery of growth factors is not covered in this review. In each case reviewed, special attention has been given to the technology used for controlling the release of the loaded drugs. The possibility of designing multifunctional three-dimensional bone TE scaffolds for the emerging field of bone TE therapeutics is discussed. A detailed summary of drugs included in three-dimensional scaffolds and the several approaches developed to combine bioceramics with various polymeric biomaterials in composites for drug-delivery systems is included. The main results presented in the literature are discussed and the remaining challenges in the field are summarized with suggestions for future research directions.

Organic-inorganic composites for bone drug delivery

This review paper attempts to provide an overview in the fabrication and application of organic-inorganic based composites in the field of local drug delivery for bone. The concept of local drug delivery exists for a few decades. However, local drug delivery in bone and specially application of composites for delivery of drugs to bone is an area for potential research interest in the recent time. The advantages attained by an organic-inorganic composite when compared to its individual components include their ability to release drug, adopting to the natural environment and supporting local area until complete bone regeneration, which make them carriers of interest for local drug delivery for bone.

Treatment of experimental osteomyelitis by methicillin resistant Staphylococcus aureus with bone cement system releasing grepafloxacin

The authors examined the effectiveness of the local anti-microbial treatment on methicillin resistant Staphylococcus aureus (MRSA) experimental osteomyelitis. Thirty-six rabbits with chronic MRSA osteomyelitis of the right femur were treated with local grepafloxacin delivery system prepared by a mixture of acrylic bone cement (polymethyl methacrylate, PMMA) plus 4% grepafloxacin. Osteomyelitis was induced by inoculating MRSA (100 microl of cultured bacteria; 10(7)) and the local insertion of a needle, serving as a foreign body, at the upper third of the femur. The course of the infection was followed by clinical, radiographic and microbiological examination. In the third week, all animals were re-operated, needles were removed, and antibiotic containing acrylic cement was implanted. Thereafter, one control and five treated animals were sacrificed per week, within 6 weeks. Osteomyelitis was found in all rabbits. In vitro grepafloxacin levels remained high throughout the 6 weeks of the experiment. Histologically tissue reaction against the cement was not observed. Osteomyelitis lesions and bone structure were progressively repaired after cement implantation. Biomechanical analysis showed no significant influence on the mechanical properties of acrylic cement due to grepafloxacin. The above mixture could prove to be an important supplementary method for the treatment of bone infections. Such a system could replace the use of gentamycin PMMA beads in the treatment of patients with chronic osteomyelitis due to MRSA. Furthermore, the proposed method could be used as a spacer after removal septic loosened prostheses in combination with systemic administration of antibiotics.

Sodium fusidate-poly(D,L-lactide-co-glycolide) microspheres: Preparation, characterisation andin vivoevaluation of their effectiveness in the treatment of chronic osteomyelitis

PURPOSE

The aim of this study was to prepare poly(D,L-lactide-co-glycolide) (PLGA) microspheres containing sodium fusidate (SF) using a double emulsion solvent evaporation method with varying polymer:drug ratios (1:1, 2.5:1, 5:1) and to evaluate its efficiency for the local treatment of chronic osteomyelitis.

METHODS

The particle size and distribution, morphological characteristics, thermal behaviour, drug content, encapsulation efficiency and in vitro release assessments of the formulations had been carried out. Sterilized SF-PLGA microspheres were implanted in the proximal tibia of rats with methicillin-resistant Staphylococcus aureus (MRSA) osteomyelitis. After 3 weeks of treatment, bone samples were analysed with a microbiological assay.

RESULTS

PLGA microspheres between the size ranges of 2.16-4.12 microm were obtained. Production yield of all formulations was found to be higher than 79% and encapsulation efficiencies of 19.8-34.3% were obtained. DSC thermogram showed that the SF was in an amorphous state in the microspheres and the glass transition temperature (T(g)) of PLGA was not influenced by the preparation procedure. In vitro drug release studies had indicated that these microspheres had significant burst release and their drug release rates were decreased upon increasing the polymer:drug ratio (p < 0.05). Based on the in vivo data, rats implanted with SF-PLGA microspheres and empty microspheres showed 1987 +/- 1196 and 55526 +/- 49086 colony forming unit of MRSA in 1 g bone samples (CFU/g), respectively (p < 0.01).

CONCLUSION

The in vitro and in vivo studies had shown that the implanted SF loaded microspheres were found to be effective for the treatment of chronic osteomyelitis in an animal experimental model. Hence, these microspheres may be potentially useful in the clinical setting.

Linking bisphosphonates to the free amino groups in fluoroquinolones: preparation of osteotropic prodrugs for the prevention of osteomyelitis

Osteomyelitis is an infection located in bone and a notoriously difficult disease to manage, requiring frequent and heavy doses of systemically administered antibiotics. Targeting antibiotics to the bone after systemic administration may provide both greater efficacy of treatment and less frequent administration. By taking advantage of the affinity of the bisphosphonate group for bone mineral, we have prepared a set of 13 bisphosphonated antibacterial prodrugs based on eight different linkers tethered to the free amino functionality on fluoroquinolone antibiotics. While all but one of the prodrugs were shown in vitro to be effective and rapid bone binders (over 90% in 1 h), only eight of them demonstrated the capacity to significantly regenerate the parent drug. In a rat model of the disease, a selected group of agents demonstrated their ability to prevent osteomyelitis when used in circumstances under which the parent drug had already been cleared and is thus inactive.