A novel, multi-barrier, drug eluting calcium sulfate/biphasic calcium phosphate biodegradable composite bone cement for treatment of experimental MRSA osteomyelitis in rabbit model

Incorporation of calcium phosphate cement into decellularized extracellular matrix enhances its bone regenerative properties

Decellularized extracellular matrix (dECM) hydrogels are engineered constructs that are widely-used in the field of regenerative medicine. However, the development of ECM-based hydrogels for bone tissue engineering requires enhancement in its osteogenic properties. For this purpose, we initially employed bone-derived dECM hydrogel (dECM-Hy) in combination with calcium phosphate cement (CPC) paste to improve the biological and structural properties of the dECM hydrogel. A decellularization protocol for bovine bone was developed to prepare dECM-Hy, and the mechanically-tuned dECM/CPC-Hy was built based on both rheological and mechanical characteristics. The dECM/CPC-Hy displayed a double swelling ratio and compressive strength. An interconnected structure with distinct hydroxyapatite crystals was evident in dECM/CPC-Hy. The expression levels of Alp, Runx2 and Ocn genes were upregulated in dECM/CPC-Hy compared to the dECM-Hy. A 14-day follow-up of the rats receiving subcutaneous implanted dECM-Hy, dECM/CPC-Hy and mesenchymal stem cells (MSCs)-embedded (dECM/CPC/MSCs-Hy) showed no toxicity, inflammatory factor expression or pathological changes. Radiography and computed tomography (CT) of the calvarial defects revealed new bone formation and elevated number of osteoblasts-osteocytes and osteons in dECM/CPC-Hy and dECM/CPC/MSCs-Hy compared to the control groups. These findings indicate that the dECM/CPC-Hy has substantial potential for bone tissue engineering.

Design and Improvement of Bone Adhesive in response to Clinical Needs

Fracture represents one of the most common diagnoses in contemporary medical practice, with the majority of cases traditionally addressed through metallic device fixation. However, this approach is marred by several drawbacks, including prolonged operative durations, considerable expenses, suboptimal applicability to comminuted fractures, increased infection risks, and the inevitable requirement for secondary surgery. The inherent advantages of bone adhesives in these fields have garnered the attention of orthopedic surgeons, who have commenced utilizing biocompatible and biodegradable bone adhesives to bond and stabilize bone fragments. Regrettably, the current bone adhesives generally exhibit insufficient adhesive strength in vivo environments, and it is desirable for them to possess effective osteogenesis to facilitate fracture healing. Consequently, aligning bone adhesives with practical clinical demands remains a significant hurdle, which has catalyzed a surge in research endeavors. Within this review, the conceptual framework, characteristics, and design ideas of bone adhesives based on clinical needs are delineated. Recent advancements in this domain, specifically focusing on the enhancement of two pivotal characteristics-adhesive strength and osteogenic potential are also reviewed. Finally, a prospective analysis of the future advancements in bone adhesives, offering new insights into solutions for diverse clinical problems is presented.

Formulation of three tailed bacteriophages by spray-drying and atomic layer deposition for thermal stability and controlled release

Deep infection is the second most common complication of arthroplasty following loosening of the implant. Antibiotic-loaded bone cements (ALBCs) and high concentrations of systemic broad-spectrum antibiotics are commonly used to prevent infections following injury and surgery. However, clinical data fails to show that ALBCs are effective against deep infection, and negative side effects can result following prolonged administration of antibiotics. Additionally, the rise of multidrug resistant (MDR) bacteria provides an urgent need for alternatives to broad-spectrum antibiotics. Phage therapy, or the use of bacteriophages (viruses that infect bacteria) to target pathogenic bacteria, might offer a safe alternative to combat MDR bacteria. Application of phage therapy in the setting of deep infections requires formulation strategies that would stabilize bacteriophage against chemical and thermal stress during bone-cement polymerization, that maintain bacteriophage activity for weeks or months at physiological temperatures, and that allow for sustained release of phage to combat slow-growing, persistent bacteria. Here, we demonstrate the formulation of three phages that target diverse bacterial pathogens, which includes spray-drying of the particles for enhanced thermal stability at 37 °C and above. Additionally, we use atomic layer deposition (ALD) to coat spray-dried powders with alumina to allow for delayed release of phage from the dry formulations, and potentially protect phage against chemical damage during bone cement polymerization. Together, these findings present a strategy to formulate phages that possess thermal stability and sustained release properties for use in deep infections.

Decoding antimicrobial resistance: unraveling molecular mechanisms and targeted strategies

Antimicrobial resistance poses a significant global health threat, necessitating innovative approaches for combatting it. This review explores various mechanisms of antimicrobial resistance observed in various strains of bacteria. We examine various strategies, including antimicrobial peptides (AMPs), novel antimicrobial materials, drug delivery systems, vaccines, antibody therapies, and non-traditional antibiotic treatments. Through a comprehensive literature review, the efficacy and challenges of these strategies are evaluated. Findings reveal the potential of AMPs in combating resistance due to their unique mechanisms and lower propensity for resistance development. Additionally, novel drug delivery systems, such as nanoparticles, show promise in enhancing antibiotic efficacy and overcoming resistance mechanisms. Vaccines and antibody therapies offer preventive measures, although challenges exist in their development. Non-traditional antibiotic treatments, including CRISPR-Cas systems, present alternative approaches to combat resistance. Overall, this review underscores the importance of multifaceted strategies and coordinated global efforts to address antimicrobial resistance effectively.

Current application and future perspectives of antimicrobial degradable bone substitutes for chronic osteomyelitis

Chronic osteomyelitis remains a persistent challenge for the surgeons due to its refractory nature. Generally, treatment involves extensive debridement of necrotic bone, filling of dead space, adequate antimicrobial therapy, bone reconstruction, and rehabilitation. However, the optimal choice of bone substitute to manage the bone defect remains debatable. This paper reviewed the clinical evidence for antimicrobial biodegradable bone substitutes in the treatment of osteomyelitis in recent years. Indeed, this combination was proved to eradicate infection and facilitate bone reconstruction, which might reduce the cost and hospital stay. Handling was associated with increased risk of unwanted side effect to affect bone healing. The study provides some valuable insights into the clinical evaluation of treatment outcomes in the aspects of infection eradication, bone reconstruction, and complications caused by materials. However, achieving complete infection eradication and subsequently perfect bone reconstruction remains challenging in compromised conditions, hence advanced innovative bone substitutes are imperative. In this review, we mainly focus on the desired functional effects of advanced bone substitutes on infection eradication and bone reconstruction from the future perspective. Handling property was optimized to simplify surgery process. It is expected that this review will provide an important opportunity to enhance the understanding of the design and application of innovative biomaterials to synergistically eradicate infection and restore integrity and function of bone.

Research Progress of Design Drugs and Composite Biomaterials in Bone Tissue Engineering

Bone, like most organs, has the ability to heal naturally and can be repaired slowly when it is slightly injured. However, in the case of bone defects caused by diseases or large shocks, surgical intervention and treatment of bone substitutes are needed, and drugs are actively matched to promote osteogenesis or prevent infection. Oral administration or injection for systemic therapy is a common way of administration in clinic, although it is not suitable for the long treatment cycle of bone tissue, and the drugs cannot exert the greatest effect or even produce toxic and side effects. In order to solve this problem, the structure or carrier simulating natural bone tissue is constructed to control the loading or release of the preparation with osteogenic potential, thus accelerating the repair of bone defect. Bioactive materials provide potential advantages for bone tissue regeneration, such as physical support, cell coverage and growth factors. In this review, we discuss the application of bone scaffolds with different structural characteristics made of polymers, ceramics and other composite materials in bone regeneration engineering and drug release, and look forward to its prospect.

Triple-functional bone adhesive with enhanced internal fixation, bacteriostasis and osteoinductive properties for open fracture repair

At present, effective fixation and anti-infection implant materials represent the mainstay for the treatment of open fractures. However, external fixation can cause nail tract infections and is ineffective for fixing small fracture fragments. Moreover, closed reduction and internal fixation during the early stage of injury can lead to potential bone infection, conducive to bone nonunion and delayed healing. Herein, we designed a bone adhesive with anti-infection, osteogenic and bone adhesion fixation properties to promote reduction and fixation of open fractures and subsequent soft tissue repair. It was prepared by the reaction of gelatin (Gel) and oxidized starch (OS) with vancomycin (VAN)-loaded mesoporous bioactive glass nanoparticles (MBGNs) covalently cross-linked with Schiff bases. Characterization and adhesion experiments were conducted to validate the successful preparation of the Gel-OS/VAN@MBGNs (GOVM-gel) adhesive. Meanwhile, in vitro cell experiments demonstrated its good antibacterial effects with the ability to stimulate bone marrow mesenchymal stem cell (BMSCs) proliferation, upregulate the expression of alkaline phosphatase (ALP) and osteogenic proteins (RunX2 and OPN) and enhance the deposition of calcium nodules. Additionally, we established a rat skull fracture model and a subcutaneous infection model. The histological analysis showed that bone adhesive enhanced osteogenesis, and in vivo experiments demonstrated that the number of inflammatory cells and bacteria was significantly reduced. Overall, the adhesive could promote early reduction of fractures and antibacterial and osteogenic effects, providing the foothold for treatment of this patient population.

Implantable biomedical materials for treatment of bone infection

The treatment of bone infections has always been difficult. The emergence of drug-resistant bacteria has led to a steady decline in the effectiveness of antibiotics. It is also especially important to fight bacterial infections while repairing bone defects and cleaning up dead bacteria to prevent biofilm formation. The development of biomedical materials has provided us with a research direction to address this issue. We aimed to review the current literature, and have summarized multifunctional antimicrobial materials that have long-lasting antimicrobial capabilities that promote angiogenesis, bone production, or "killing and releasing." This review provides a comprehensive summary of the use of biomedical materials in the treatment of bone infections and a reference thereof, as well as encouragement to perform further research in this field.

Antibacterial intraosseous implant surface coating that responds to changes in the bacterial microenvironment

Bone implant-associated infection is one of the most challenging problems encountered by orthopedic surgeons. There is considerable interest in the development of drug-loaded antibacterial coatings for the surfaces of metal implants. However, it is difficult to achieve the stable local release of an effective drug dose for many antibacterial coatings. In the present study, analyses of the thickness and water contact angle of multiple layers confirmed the successful assembly of multilamellar membrane structures. Measurement of the zone of bacterial inhibition indicated gradual degradation of the (montmorillonite [MMT]/hyaluronic acid [HA])₁₀ multilamellar film structure with concentration-dependent degradation during incubation with hyaluronidase solution and Staphylococcus aureus. In vivo results resembled the in vitro results. Overall, the findings confirm that the (MMT/HA-rifampicin)₁₀ multilamellar film structure exhibits good antibacterial properties and excellent biocompatibility. Further studies of the clinical potential of the antibacterial coating prepared in this experiment are warranted.

Treatment of long bone infection by a biodegradable bone cement releasing antibiotics in human

Repair of methicillin-resistant Staphylococcal (MRSA) chronic osteomyelitis and resulting bone defect is one of the major challenges in orthopaedics. Previous study has shown the effectiveness of antibiotic loaded biodegradable composite bone cement with in vitro tests and in the treatment of experimental osteomyelitis. The cement is composed of poly(lactide-co-glycolide) encapsulated antibiotic-biphasic calcium phosphate granule complex and additive antibiotic powder in gypsum binder. In this study, the cement was studied further to evaluate its in vitro biological properties (cytocompatibility, platelet activation), anti-infective, and bone regenerative potential in comparison to poly(methyl methacrylate) (PMMA) cement and parenteral therapy in 43 patients (age 5-57 years) with chronic MRSA osteomyelitis by analyzing the results of histopathology, radiographs, magnetic resonance imaging, scanning electron microscopy, and serum drug concentrations for 1 year. The composite cement showed superior cytocompatibility and coagulant activity compared to PMMA cement. Moreover, the results of different postoperative clinical and radiological examinations also proved the supremacy of composite cement over the other treatment modalities in terms of success rate, faster sepsis control and bone regeneration. Low serum antibiotic concentrations and normal serum calcium levels indicate that the calcium-rich composite cement is safe for application in human. Therefore, we conclude that the composite bone cement is a promising candidate for the treatment of chronic osteomyelitis.

3D-printed composite scaffold with anti-infection and osteogenesis potential against infected bone defects

In the field of orthopedics, an infected bone defect is a refractory disease accompanied by bone infection and defects as well as aggravated circulation. There are currently no personalized scaffolds that can treat bone infections using local stable and sustained-release antibiotics while providing mechanical support and bone induction to promote bone repair in the process of absorption in vivo. In our previous study, rifampicin/moxifloxacin-poly lactic-co-glycolic acid (PLGA) microspheres were prepared and tested for sustained release and antibacterial activity. The composite scaffold of poly-l-lactic acid (PLLA)/Pearl had a positive effect on mechanics supports and promoted osteogenesis. Therefore, in this study, the personalized scaffolds of PLLA/Pearl were first prepared by 3D printing. Then, rifampicin/moxifloxacin-PLGA (RM-P) microspheres were loaded into the scaffold pores to prepare the PLLA/Pearl/RM-P scaffolds. In this in vitro study, we investigated the structural characteristics and cytocompatibility of 3D-printed composite scaffolds, which indicates the integrity of the components in the scaffolds. The PLLA/Pearl and PLLA/Pearl/RM-P composite scaffolds can promote adhesion, proliferation, and differentiation of human bone marrow mesenchymal stem cells. Moreover, a rabbit model of infected bone defects of the radius was established. PLLA, PLLA/Pearl, and PLLA/Pearl/RM-P scaffolds were implanted into the bone nidus. The therapeutic effect of the three scaffolds on the infected bone defects was evaluated through imaging and microbiological and histological analysis after surgery. Among the three scaffolds, only the PLLA/Pearl/RM-P scaffold had anti-infection and bone defect repair in vivo. 3D printing provides support for personalized scaffold structures, and composite materials ensure that the scaffolds exert anti-infection and bone repair effects. Our study suggests that the PLLA/Pearl/RM-P scaffold is a promising new material in the clinical treatment of infected bone defects.

Indication the mechanism of dual-functional scaffold in the treatment of infected bone defects.

Controlled and localized antibiotics delivery using magnetic-responsive beads for synergistic treatment of orthopedic infection

Antibiotic-loaded bone cement beads have been a reliable passive delivery system for the localized treatment of osteomyelitis; however, low, and unregulated drug release rates limit the ability of this system to maintain therapeutic concentrations. This problem is further amplified by drug-resistant pathogens that might invade or evolve under these conditions. Furthermore, currently available bone cements are incompatible with some antibiotics. The proposed device resembles conventional bone cement beads but contains an on-demand drug delivery magnetic sponge that provides actively controlled release of antibiotics. The slightly porous structure facilitates some drug diffusion while further drug release may be controlled remotely via magnetic actuation. Additionally, a combination of silver nitrate and gentamicin are used in the device as these agents are shown to display a synergistic antibacterial activity in vitro using checkerboard and time-kill assays. The device releases gentamicin and silver in both actuation and diffusion modes over 7 days. The in vitro bacterial studies demonstrate the efficacy of the released agents alone, and synergistically in combination, against Methicillin-resistant Staphylococcus aureus and Escherichia coli. The proposed device offers a facile fabrication process which allows control of the release profile by engineering hole configurations or manipulating magnetic field strength to provide the most effective therapy.

Multi-stage controllable degradation of strontium-doped calcium sulfate hemihydrate-tricalcium phosphate microsphere composite as a substitute for osteoporotic bone defect repairing: degradation behavior and bone response

Various requirements for the repair of complex bone defects have motivated to development of scaffolds with adjustable degradation rates and biological functions. Tricalcium phosphate (TCP) and calcium sulfate are the most commonly used bone repair materials in the clinic, how to better combine TCP and calcium sulfate and play their greatest advantages in the repair of osteoporotic bone defect is the focus of our research. In this study, a series of scaffolds with multistage-controlled degradation properties composed of strontium-doped calcium sulfate (SrCSH) and strontium-doped tricalcium phosphate (Sr-TCP) microspheres scaffolds were prepared, and their osteogenic activity,in vivodegradation and bone regeneration ability in tibia of osteoporotic rats were evaluated.In vitrostudies revealed that different components of SrCSH/Sr-TCP scaffolds significantly promoted the proliferation and differentiation of MC3T3-E1 cells, which showed a good osteogenic induction activity.In vivodegradation results showed that the degradation time of composite scaffolds could be controlled in a large range (6-12 months) by controlling the porosity and phase composition of Sr-TCP microspheres. The results of osteoporotic femoral defect repair showed that when the degradation rate of scaffold matched with the growth rate of new bone, the parameters such as bone mineral density, bone volume/total volume ratio, trabecular thickness, angiogenesis marker platelet endothelial cell adhesion molecule-1 and new bone formation marker osteocalcin expression were higher, which promoted the rapid repair of osteoporotic bone defects. On the contrary, the slow degradation rate of scaffolds hindered the growth of new bone to a certain extent. This study elucidates the importance of the degradation rate of scaffolds for the repair of osteoporotic bone defects, and the design considerations can be extended to other bone repair materials, which is expected to provide new ideas for the development of tissue engineering materials in the future.

Recent Advances in the Evaluation of Antimicrobial Materials for Resolution of Orthopedic Implant-Associated Infections In Vivo

While orthopedic implant-associated infections are rare, revision surgeries resulting from infections incur considerable healthcare costs and represent a substantial research area clinically, in academia, and in industry. In recent years, there have been numerous advances in the development of antimicrobial strategies for the prevention and treatment of orthopedic implant-associated infections which offer promise to improve the limitations of existing delivery systems through local and controlled release of antimicrobial agents. Prior to translation to in vivo orthopedic implant-associated infection models, the properties (e.g., degradation, antimicrobial activity, biocompatibility) of the antimicrobial materials can be evaluated in subcutaneous implant in vivo models. The antimicrobial materials are then incorporated into in vivo implant models to evaluate the efficacy of using the material to prevent or treat implant-associated infections. Recent technological advances such as 3D-printing, bacterial genomic sequencing, and real-time in vivo imaging of infection and inflammation have contributed to the development of preclinical implant-associated infection models that more effectively recapitulate the clinical presentation of infections and improve the evaluation of antimicrobial materials. This Review highlights the advantages and limitations of antimicrobial materials used in conjunction with orthopedic implants for the prevention and treatment of orthopedic implant-associated infections and discusses how these materials are evaluated in preclinical in vivo models. This analysis serves as a resource for biomaterial researchers in the selection of an appropriate orthopedic implant-associated infection preclinical model to evaluate novel antimicrobial materials.

Bacterial virulence factors: a target for heterocyclic compounds to combat bacterial resistance

Antibiotic resistance is one of the most important challenges of the 21st century. However, the growing understanding of bacterial pathogenesis and cell-to-cell communication has revealed many potential strategies for the discovery of drugs that can be used for the treatment of bacterial infections. Interfering with bacterial virulence and/or quorum sensing could be a particularly interesting approach, because it is believed to exert less selective pressure on the bacterial resistance than with traditional strategies, geared toward killing bacteria or preventing their growth. Here, we discuss the mechanism of bacterial virulence, presenting promising strategies and recently synthesized heterocyclic compounds to combat future bacterial infections.

In vitro and in vivo effectiveness of a novel injectable calcitonin-loaded collagen/ceramic bone substitute

This study aimed to evaluate the effectiveness of a novel calcitonin-loaded calcium phosphate composite bone cement in vitro and in vivo. The novel composite bone cements were composed of NuROs injectable bone graft substitute, type I collagen, and/or salmon calcitonin. The setting time, porosity, wettability, compressive strength, compressive modulus, and crystallographic structures of cement specimens were determined. Degradation rate, calcitonin release rate, and osteoinductivity were assessed in vitro. In addition, osteogenic effect was examined in a rabbit model of femoral defect. The results revealed that addition of collagen/calcitonin did not substantially alter physical properties and degradation rate of bone cement specimens. Calcitonin was released into culture medium in a two-phase manner. Osteogenic effect of conditioned medium derived from calcitonin containing bone cement was observed. Finally, de novo bone growth and bone mineralization across the bone defect area were observed in rabbits after implantation of composite bone cement specimens. In conclusion, this novel calcitonin-loaded composite calcium phosphate bone cement exhibits biocompatibility, bioresorbability, osteoinductivity, and osteoconductivity, which may be suitable for clinical use.

Sequential release of double drug (graded distribution) loaded gelatin microspheres/PMMA bone cement

Drugs are loaded into PMMA bone cement to reduce the risk of infection in freshly implanted prostheses or to promote the differentiation and growth of osteoblasts. However, the same method of loading of drugs in the bone cement cannot simultaneously achieve an effective antibacterial response and long-term treatment outcomes for osteoporosis based on a patient's clinical needs. In the present study, gentamicin sulfate (GS)/alendronate (ALN)-dual-loaded gelatin modified PMMA bone cement (GAPBC) was fabricated to provide rapid and continuous antibiotic release and long-term anti-osteoporotic therapy. Specifically, the gelatin microspheres were loaded with the drugs using separate methodologies, namely, ALN was loaded during fabrication of the gelatin microspheres after which GS was absorbed onto the gelatin from solution. The results demonstrate that sequential release of the GS and ALN was achieved, GS release playing a major role over the first 24 hours and ALN release dominant after 3 weeks of immersion in PBS, resulting from the graded distribution within the gelatin microspheres, and the final drug release ratio of GS (73.6%) and ALN (68.5%) from the modified bone cement was significantly higher than from PMMA bone cement. Therefore, GAPBC represents a potential drug carrier for future clinical applications.

Therapeutics and delivery vehicles for local treatment of osteomyelitis

Osteomyelitis, or the infection of the bone, presents a major complication in orthopedics and may lead to prolonged hospital visits, implant failure, and in more extreme cases, amputation of affected limbs. Typical treatment for this disease involves surgical debridement followed by long-term, systemic antibiotic administration, which contributes to the development of antibiotic-resistant bacteria and has limited ability to eradicate challenging biofilm-forming pathogens including Staphylococcus aureus-the most common cause of osteomyelitis. Local delivery of high doses of antibiotics via traditional bone cement can reduce systemic side effects of an antibiotic. Nonetheless, growing concerns over burst release (then subtherapeutic dose) of antibiotics, along with microbial colonization of the nondegradable cement biomaterial, further exacerbate antibiotic resistance and highlight the need to engineer alternative antimicrobial therapeutics and local delivery vehicles with increased efficacy against, in particular, biofilm-forming, antibiotic-resistant bacteria. Furthermore, limited guidance exists regarding both standardized formulation protocols and validated assays to predict efficacy of a therapeutic against multiple strains of bacteria. Ideally, antimicrobial strategies would be highly specific while exhibiting a broad spectrum of bactericidal activity. With a focus on S. aureus infection, this review addresses the efficacy of novel therapeutics and local delivery vehicles, as alternatives to the traditional antibiotic regimens. The aim of this review is to discuss these components with regards to long bone osteomyelitis and to encourage positive directions for future research efforts.

Osteomyelitis: Focus on Conventional Treatments and Innovative Drug Delivery Systems

Osteomyelitis is a bone marrow infection which generally involves cortical plates and which may occur after bone trauma, orthopedic/maxillofacial surgery or after vascular insufficiency episodes. It mostly affects people from the Third World Countries, the elderly and patients affected by systemic diseases e.g. autoimmune disorders, AIDS, osteoporosis and microvascular disease. The highest percentage of osteomyelitis cases (almost 75%) is caused by Staphylococcus spp., and in particular by Staphylococcus aureus (more than 50%). The ideal classification and the diagnosis of osteomyelitis are two important tools which help the physicians to choose the best therapeutic strategies. Currently, common therapies provide an extensive debridement in association with intravenous administration of antibiotics (penicillin or clindamycin, vancomycin and fluoroquinolones among all for resistant microorganisms), to avoid the formation of sequestra. However, conventional therapeutic approach involves several drawbacks like low concentration of antibiotics in the infected site, leading to resistance and adverse effects due to the intravenous administration. For these reasons, in the last years several studies have been focused on the development of drug delivery systems such as cements, beads, scaffolds and ceramics made of hydroxyapatite (HA), calcium phosphate (CaP) and β-tricalcium phosphate (β-TCP) which demonstrated to be biocompatible, poorly toxic and capable to allow osteointegration and a prolonged drug release. The aim of this review is to provide a focus on current therapies and latest developed drug delivery systems with particular attention on those based on CaP and its derivatives, hoping that this work could allow further direction in the field of osteomyelitis.

A Facile Synthesis Process and Evaluations of α-Calcium Sulfate Hemihydrate for Bone Substitute

Alpha-calcium sulfate hemihydrate (α-HH) has been used effectively in grafting through its desired features to support bone regeneration. In recent years, many synthetic methods have been proposed. Among them, the autoclave method for manufacturing α-HH is best suited for cost-savings due to its simple operation and limited use of additives. Despite these advantages, the synthesis of surgical grade products without the use of any additives has not yet been clearly discussed. In this study, surgical grade α-HH was successfully produced from calcium sulfate dihydrate (DH) using the autoclave method at an elevated temperature and pressure. The synthesized powder had a high purity of about 98.62% α-HH with a prismatic morphology (20.96 ± 8.83 µm in length and 1.30 ± 0.71 µm in diameter). The screening tests, in simulated body fluid (SBF) solution, for the product properties showed no bioactivity, and fast degradation accompanied by a slight decrease in pH. The lactate dehydrogenase (LDH) assay showed good biocompatibility of the material, however, its potential for cytotoxicity was also observed in NIH 3T3 cells. Briefly, despite some unfavorable properties, the autoclave-synthesized α-HH is a promising bone graft substitute that can be applied in orthopedic and maxillofacial surgeries.

Filling the Gap: A Correlation between Objective and Subjective Measures of Injectability

Various injectable biomaterials are developed for the minimally invasive delivery of therapeutics. Typically, a mechanical tester is used to ascertain the force required to inject these biomaterials through a given syringe-needle system. However, currently there is no method to correlate the force measured in the laboratory to the perceived effort required to perform that injection by the end user. In this article, the injection force (F) for a variety of biomaterials, displaying a range of rheological properties, is compared with the effort scores from a 50 person panel study. The maximum injection force measured at crosshead speed 1 mm s^-1 is a good proxy for injection effort, with an R² of 0.89. This correlation leads to the following conclusions: participants can easily inject 5 mL of substance for F < 12 N; considerable effort is required to inject 5 mL for 12 N < F < 38 N; great effort is required and <5 mL can be injected for 38 N < F < 64 N; and materials are entirely non-injectable for F > 64 N. These values may be used by developers of injectable biomaterials to make decisions about formulations and needle sizes early in the translational process.

Strategies to Overcome Antimicrobial Resistance (AMR) Making Use of Non-Essential Target Inhibitors: A Review

Antibiotics have always been considered as one of the most relevant discoveries of the twentieth century. Unfortunately, the dawn of the antibiotic era has sadly corresponded to the rise of the phenomenon of antimicrobial resistance (AMR), which is a natural process whereby microbes evolve in such a way to withstand the action of drugs. In this context, the identification of new potential antimicrobial targets and/or the identification of new chemical entities as antimicrobial drugs are in great demand. To date, among the many possible approaches used to deal with antibiotic resistance is the use of antibiotic adjuvants that hit bacterial non-essential targets. In this review, the author focuses on the discovery of antibiotic adjuvants and on new tools to study and reduce the prevalence of resistant bacterial infections.

Use of Antibiotic Loaded Biomaterials for the Management of Bone Prosthesis Infections: Rationale and Limits

BACKGROUND

Periprosthetic joint infection still represents a challenging issue for the orthopedic community. In the United States approximately a million joint arthroplasties are performed each year, with infection rates ranging from 1 to 2%: revisions has significant implications on health care costs and appropriate resource management. The use of locally applied antibiotics as a prophylaxis measure or as a component of the therapeutic approach in primary or revision surgery is finalized at eliminating any microorganism and strengthening the effectiveness of systemic therapy.

OBJECTIVE

The present review of clinical and preclinical in vivo studies tried to identify advantages and limitations of the materials used in the clinical orthopedic practice and discuss developed biomaterials, innovative therapeutic approaches or strategies to release antibiotics in the infected environment.

METHODS

A systematic search was carried out by two independent observers in two databases (www.pubmed.com and www.scopus.com) in order to identify pre-clinical and clinical reports in the last 10 years.

RESULTS

71 papers were recognized eligible: 15 articles were clinical studies and 56 in vivo studies.

CONCLUSION

Polymethylmethacrylate was the pioneer biomaterial used to manage infections after total joint replacement. Despite its widespread use, several issues still remain debated: the methods to combine materials and antibiotics, the choice of antibiotics, releasing kinetics and antibiotics efficacy. In the last years, the interest was directed towards the selection of different antibiotics, loaded in association with more than only one class and biomaterials with special focus on delivery systems as implant surface coatings, hydrogels, ceramics, micro-carriers, microspheres or nanoparticles.

Animal models of orthopaedic infections. A review of rabbit models used to induce long bone bacterial infections

The development of infections is one of the main complications in orthopaedics, especially in the presence of implants for the osteosynthesis of compound fractures and joint prosthesis. Indeed, foreign materials and implants act as substrates for the adhesion and proliferation of bacterial strains able to produce biofilm, causing peri-implant osteomyelitis. The eradication of biofilm remains a great challenge for the host immune system, as well as for medical and surgical approaches, thus imposing the need for new prophylactic and/or therapeutic strategies in which animal models have an essential role. In vivo orthopaedic models have mainly been used to study the pathogenesis of infections, biofilm behaviour and the efficacy of antimicrobial strategies, to select diagnostic techniques and test the efficacy of novel materials or surface modifications to impede both the establishment of bone infections and the associated septic loosening of implants. Among several models of osteomyelitis and implant-related infections described in small rodents and large animals, the rabbit has been widely used as a reliable and reproducible model of orthopaedic infections. This review examines the relevance of rabbits for the development of clinically representative models by analysing the pros and cons of the different approaches published in the literature. This analysis will aid in increasing our knowledge concerning orthopaedic infections by using this species. This review will be a tool for researchers who need to approach pre-clinical studies in the field of bone infection and have to identify the most appropriate animal model to verify their scientific hypothesis.

Polylactic-co-glycolic acid microspheres added to fixative cements and its role on bone infected architecture

Joint prostheses are an essential element to improve quality of life. However, prostheses may fail due to several factors, including the most frequent cause, Staphylococcus aureus infection. The identification of new fixing bone cements with less reactivity on bone tissue and an adequate response to infection remains a primary challenge. The aim of this study is to evaluate the response of bone tissue in rabbits after introduction of a hydroxyapatite‐coated titanium rod with a commercial fixative cement (Palacos®) compared to a modified experimental cement (EC) containing polylactic‐co‐glycolic acid (PLGA) microspheres in the presence or absence of contaminating germs. This study used 20 New Zealand rabbits which were divided into four groups (n = 5) depending on the presence or absence of S. aureus and the use of commercial (Palacos®) or EC. A histological method, based on bone architecture damage, was proposed to evaluate from 1 to 9 the histological results and the response of the infected tissue. The macrophage response was also evaluated using monoclonal antibody RAM‐11. The study showed better bone conservation with the use of EC with PLGA microspheres against the Palacos® commercial cement, including the noncontaminated and contaminated groups. © 2019 The Authors. Journal of Biomedical Materials Research Part B: Applied Biomaterials published by Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B:2517–2526, 2019.

Chronic Osteomyelitis - Bacterial Flora, Antibiotic Sensitivity and Treatment Challenges

Background:

Chronic osteomyelitis is a catastrophic sequel of delayed diagnosis of acute osteomyelitis.

Objectives:

The objectives of the study were to determine bacterial flora and antibiotic sensitivity, and to evaluate the outcome of an aggressive surgical approach to chronic osteomyelitis.

Methods:

This is a single surgeon, prospective cohort study on 30 consecutive patients with clinically and radiologically diagnosed chronic osteomyelitis presented to a hospital. We prospectively recorded demographic, clinical, radiological features, treatment protocol, microbiologic results of culture and sensitivity. The main treatment outcome measures were clinical signs of eradication of infection.

Results:

Microbiologic results showed that Gram-negative and mixed flora accounts for more than half of chronic osteomyelitis cases while Staphylococcus aureus was a dominating single pathogen (39%). We detected a high resistance rate to common antibiotics, e.g. 83% of S. aureus isolates were resistant to oxacillin (MRSA). The mean duration of bone infection was 4.2 years (3 months to 30 years) and the mean number of operations was 1.5 (1-5) . The mean follow-up was 15 months (12-18 months). Infection was eradicated in 95% (21 out of 22) treated by a single procedure and in all patients (n=8) by double procedure.

Conclusion:

Presented the high rate of MRSA strains is alarming and calls for updating of the antibiotic therapy guidelines in the country. Good results in treatment of chronic osteomyelitis can be achieved by a single-stage protocol including radical debridement combined with systemic and topical antibiotic.

Effects of alkaloids from Sophora flavescens on osteoblasts infected with Staphylococcus aureus and osteoclasts

Chronic osteomyelitis is primarily caused by infection with Staphylococcus aureus (S. aureus). Antibiotics are commonly administered; however, it is a challenge to promote bone healing. The aim of this study was to investigate the in vitro effects of alkaloids from the herbal remedy Sophora flavescens (ASF) on rat calvarial osteoblasts (ROBs) infected with S. aureus and healthy osteoclasts. Cell proliferation and alkaline phosphatase, interleukin-6, and tumour necrosis factor-α activity was measured in infected ROBs; tartrate-resistant acid phosphatase was evaluated in osteoclasts via enzyme-linked immunosorbent assay. The mRNA and protein expression levels of bone morphogenetic protein 2, runt-related transcription factor 2, osteoprotegerin, and receptor activator of nuclear factor kappa-B ligand were assessed in infected ROBs through reverse transcription-polymerase chain reaction and western blotting analysis, respectively. Results indicated that ASF increased the viability of uninfected ROBs and infected ROBs treated with vancomycin via regulation of bone morphogenetic protein 2, runt-related transcription factor, osteoprotegerin, and receptor activator of nuclear factor kappa-B ligand mRNA and protein expression levels. In addition, the secretion of the inflammatory factor tumour necrosis factor-α was decreased and alkaline phosphatase activity was increased, inhibiting the viability of osteoclasts and tartrate-resistant acid phosphatase activity. Therefore, the herbal remedy ASF has potential as a new treatment for chronic osteomyelitis.

Effect of Low-Frequency Pulsed Ultrasound on Drug Delivery, Antibacterial Efficacy, and Bone Cement Degradation in Vancomycin-Loaded Calcium Phosphate Cement

Background

Calcium phosphate cement (CPC) has been applied as a biodegradable antibiotic carrier in osteomyelitis. However, the drug delivery, antibacterial efficacy, and degradation rate of CPC are insufficient and require further improvement in clinical application.

Material/Methods

Vancomycin-loaded CPC columns were prepared, and eluted in simulated body fluid. The drug delivery was assessed in the ultrasound group and control group by fluorescence polarization immunoassay. The antibacterial efficacy of vancomycin in the ultrasound group and control groups was investigated by standard plate count method. Low-frequency pulsed ultrasound (46.5 kHz, 900 mW/cm²) was used to produce a sinusoidal wave in the ultrasound groups. The percentage of residual weight was evaluated to assess the degradation of CPC.

Results

The concentration and cumulatively released percentage of vancomycin in the ultrasound group were higher than that in the control group at each time point (p<0.05). The duration of vancomycin concentration over the level of minimum inhibitory concentration was significantly prolonged in the ultrasound group (p<0.05). Antibacterial efficacy of vancomycin in the ultrasound group was significantly greater than that in the control group with same concentration of vancomycin (p<0.05). The percentage of residual weight in the ultrasound group was significantly less than that in the control group (p<0.05).

Conclusions

Low-frequency pulsed ultrasound can enhance vancomycin release, prolong the duration of vancomycin concentration at high levels, and accelerate the degradation rate of vancomycin-loaded CPC.

Nanocements produced from mesoporous bioactive glass nanoparticles

Biomedical cements are considered promising injectable materials for bone repair and regeneration. Calcium phosphate composition sized with tens of micrometers is currently one of the major powder forms. Here we report a unique cement form made from mesoporous bioactive glass nanoparticles (BGn). The nanopowder could harden in reaction with aqueous solution at powder-to-liquid ratios as low as 0.4-0.5 (vs. 2.0-3.0 for conventional calcium phosphate cement CPC). The cementation mechanism investigated from TEM, XRD, FT-IR, XPS, and NMR analyses was demonstrated to be the ionic (Si and Ca) dissolution and then reprecipitation to form Si-Ca-(P) based amorphous nano-islands that could network the particles. The nanopowder-derived nanocement exhibited high surface area (78.7 m²/g); approximately 9 times higher than conventional CPC. The immersion of nanocement in simulated body fluid produced apatite nanocrystallites with ultrafine size of 10 nm (vs. 55 nm in CPC). The ultrafine nanocement adsorbed protein molecules (particularly positive charged proteins) at substantial levels; approximately 160 times higher than CPC. The nanocement released Si and Ca ions continuously over the test period of 2 weeks; the Si release was unique in nanocement whereas the Ca release was in a similar range to that observed in CPC. The release of ions significantly stimulated the responses of cells studied (rMSCs and HUVECs). The viability and osteogenesis of rMSCs were significantly enhanced by the nanocement ionic extracts. Furthermore, the in vitro tubular networking of HUVECs was improved by the nanocement ionic extracts. The in vivo neo-blood vessel formation in CAM model was significantly higher by the nanocement implant when compared with the CPC counterpart, implying the Si ion release might play a significant role in pro-angiogenesis. Furthermore, the early bone forming response of the nanocement, based on the implantation in a rat calvarial bone defect, demonstrated a sign of osteoinductivity along with excellent osteocondution and bone matrix formation. Although more studies remain to confirm the potential of nanocement, some of the intriguing physico-chemical properties and the biological responses reported herein support the promise of the new 'nanopowder-based nanocement' for hard tissue repair and regeneration.

Stem Cell and Advanced Nano Bioceramic Interactions

Bioceramics are type of biomaterials generally used for orthopaedic applications due to their similar structure with bone. Especially regarding to their osteoinductivity and osteoconductivity, they are used as biodegradable scaffolds for bone regeneration along with mesenchymal stem cells. Since chemical properties of bioceramics are important for regeneration of tissue, physical properties are also important for cell proliferation. In this respect, several different manufacturing methods are used for manufacturing nano scale bioceramics. These nano scale bioceramics are used for regeneration of bone and cartilage both alone or with other types of biomaterials. They can also act as carrier for the delivery of drugs in musculoskeletal infections without causing any systemic toxicity.

Targeting microbial biofilms: current and prospective therapeutic strategies

Biofilm formation is a key virulence factor for a wide range of microorganisms that cause chronic infections. The multifactorial nature of biofilm development and drug tolerance imposes great challenges for the use of conventional antimicrobials and indicates the need for multi-targeted or combinatorial therapies. In this Review, we focus on current therapeutic strategies and those under development that target vital structural and functional traits of microbial biofilms and drug tolerance mechanisms, including the extracellular matrix and dormant cells. We emphasize strategies that are supported by in vivo or ex vivo studies, highlight emerging biofilm-targeting technologies and provide a rationale for multi-targeted therapies aimed at disrupting the complex biofilm microenvironment.