Biodegradable poly(D,L-lactide) coating of implants for continuous release of growth factors

Highly Adhesive Antimicrobial Coatings for External Fixation Devices

Pin site infections arise from the use of percutaneous pinning techniques (as seen in skeletal traction, percutaneous fracture pinning, and external fixation for fracture stabilization or complex deformity reconstruction). These sites are niduses for infection because the skin barrier is disrupted, allowing for bacteria to enter a previously privileged area. After external fixation, the rate of pin site infections can reach up to 100%. Following pin site infection, the pin may loosen, causing increased pain (increasing narcotic usage) and decreasing the fixation of the fracture or deformity correction construct. More serious complications include osteomyelitis and deep tissue infections. Due to the morbidity and costs associated with its sequelae, strategies to reduce pin site infections are vital. Current strategies for preventing implant-associated infections include coatings with antibiotics, antimicrobial polymers and peptides, silver, and other antiseptics like chlorhexidine and silver-sulfadiazine. Problems facing the development of antimicrobial coatings on orthopedic implants and, specifically, on pins known as Kirschner wires (or K-wires) include poor adhesion of the drug-eluting layer, which is easily removed by shear forces during the implantation. Development of highly adhesive drug-eluting coatings could therefore lead to improved antimicrobial efficacy of these devices and ultimately reduce the burden of pin site infections. In response to this need, we developed two types of gel coatings: synthetic poly-glycidyl methacrylate-based and natural-chitosan-based. Upon drying, these gel coatings showed strong adhesion to pins and remained undamaged after the application of strong shear forces. We also demonstrated that antibiotics can be incorporated into these gels, and a K-wire with such a coating retained antimicrobial efficacy after drilling into and removal from a bone. Such a coating could be invaluable for K-wires and other orthopedic implants that experience strong shear forces during their implantation.

The management of fracture related infections: What practices can be supported by high-level evidence?

Fracture related infections (FRIs) are a disabling condition causing significant concern within the orthopaedic community. FRIs have a huge societal and economic burden leading to prolonged recovery times and the potential for becoming chronic conditions or being life-threatening. Despite its importance in our field, the surgical community has just recently agreed on a definition which, added to the lack of surgical trials assessing preventive and treatment interventions have limited our understanding and precipitated wide variations in surgeons' practice. This article aims to review the current practices that can be supported with high-quality evidence. Currently, we have a limited body of high-quality evidence on FRI prevention and treatment. A handful of measures have proven effective, such as the use of prophylactic antibiotics, the use of saline and low pressure as the preferred irrigation solution and the safety of delaying initial surgical débridement more than 6 hours without impacting infection rates for open fracture wounds débridement. Future multicentre trials, properly powered, will shed light on current areas of controversy regarding the benefit of different preoperative and perioperative factors for the prevention and treatment of FRIs. Higher quality evidence is needed to guide surgeons to offer an evidence-based approach to prevent FRI occurrence and to treat patients suffering from them.

Functional and radiological outcomes of primary ring fixator versus antibiotic nail in open tibial diaphyseal fractures: A prospective study

BACKGROUND

Management of open fractures of tibia is still a matter of debate due to high incidence of infections. Traditionally external fixators have been advocated in managing open tibial fractures. Due to limited efficacy of systemic antibiotics, recently antibiotic coated intramedullary interlocking nails have been developed for the management of open tibia fractures. Therefore, we conducted this prospective randomized study to compare the functional and radiological outcomes of primary ring fixator versus antibiotic coated nail in open diaphyseal tibial fractures.

METHODS

The study included 32 patients with Gustilo-Anderson type II and type IIIA fractures of tibial diaphysis. Out of them 16 patients were managed with Ring External Fixator (Group I) and 16 were managed with Ossipro^Ò gentamicin intramedullary interlocking tibial nail (Group II). The radiological and functional outcomes were assessed at final follow-up according to and SMFA criteria. Statistical analysis of the data was performed using IBM SPSS statistics 2.0 software. Chi square test and independent student t-test were used and a P value <0.05 was considered statistically significant RESULTS: Union was achieved in 15 patients (93.8%) in group I and 13 patients (81.2%) in group II. Pin tract infection was seen in 6 patients (37.5%) in group I, whereas infection was present in 2 patients (12.5%) in group II. Bone results were excellent in 13 patients (81.3%), good in 2 patients (12.5%), poor in one patient (6.3%). In group II, bone results were excellent in 12 patients (75%), good in one patient (6.2%), poor in 3 patients (18.8%). At 1 year of final follow up, mean SMFA score was 24.41±5.87 in group I, whereas mean SMFA score was 23.703±8.02 in group II.

CONCLUSION

Ring fixator as well as antibiotic coated tibial interlocking nail achieved comparable rates of union in the present study. Complication rates were similar in both the groups and the functional and radiological outcomes were comparable in both groups. Results of this study indicate that although ring fixation is an established option for management of open tibial fractures, antibiotic-coated intramedullary nail is also a reliable option in open Grade II and grade IIIA injuries.

LEVEL OF EVIDENCE

Level II.

Surgical Applications of Materials Engineered with Antimicrobial Properties

The infection of surgically placed implants is a problem that is both large in magnitude and that broadly affects nearly all surgical specialties. Implant-associated infections deleteriously affect patient quality-of-life and can lead to greater morbidity, mortality, and cost to the health care system. The impact of this problem has prompted extensive pre-clinical and clinical investigation into decreasing implant infection rates. More recently, antimicrobial approaches that modify or treat the implant directly have been of great interest. These approaches include antibacterial implant coatings (antifouling materials, antibiotics, metal ions, and antimicrobial peptides), antibacterial nanostructured implant surfaces, and antibiotic-releasing implants. This review provides a compendium of these approaches and the clinical applications and outcomes. In general, implant-specific modalities for reducing infections have been effective; however, most applications remain in the preclinical or early clinical stages.

Antibiotic-Coated Nail in Open Tibial Fracture: A Retrospective Case Series

Implant-associated infections still represent one of the main problems in treatment of open fracture. The role of systemic antibiotic prophylaxis is now agreed and accepted; however, recent literature seems to underline the importance of local antibiotic therapy at the fracture site, and antibiotic nails have been shown to play a role in the treatment of open fractures in terms of fracture healing and lower risk of infection. We retrospectively analyzed our results, from January 2016 to March 2020, with the use of coated nails in the treatment of open tibial fractures, evaluating the rates of infection and fracture healing as primary outcomes and the rate of reoperations, time from trauma to nailing and hospital stay as secondary outcomes. Thirty-eight patients treated with coated nail (ETN ProtectTM, Synthes) were included in the study. Minimum follow-up was of 18 months. Thirty-four of 38 patients achieved bone union and 2 patients underwent septic non-union. In our series, no systemic toxicity or local hypersensitivity to antibiotics were recorded. From this study, use of antibiotic-coated nails appears to be a valid and safe option for treatment of open tibial fractures and prevention of implant-related infections, particularly in tibial fractures with severe soft tissue exposure and impairment.

Antibiotics- and Heavy Metals-Based Titanium Alloy Surface Modifications for Local Prosthetic Joint Infections

Prosthetic joint infection (PJI) is the second most common cause of arthroplasty failure. Though infrequent, it is one of the most devastating complications since it is associated with great personal cost for the patient and a high economic burden for health systems. Due to the high number of patients that will eventually receive a prosthesis, PJI incidence is increasing exponentially. As these infections are provoked by microorganisms, mainly bacteria, and as such can develop a biofilm, which is in turn resistant to both antibiotics and the immune system, prevention is the ideal approach. However, conventional preventative strategies seem to have reached their limit. Novel prevention strategies fall within two broad categories: (1) antibiotic- and (2) heavy metal-based surface modifications of titanium alloy prostheses. This review examines research on the most relevant titanium alloy surface modifications that use antibiotics to locally prevent primary PJI.

Surface Modification of Porous Polyethylene Implants with an Albumin-Based Nanocarrier-Release System

BACKGROUND

Porous polyethylene (PPE) implants are used for the reconstruction of tissue defects but have a risk of rejection in case of insufficient ingrowth into the host tissue. Various growth factors can promote implant ingrowth, yet a long-term gradient is a prerequisite for the mediation of these effects. As modification of the implant surface with nanocarriers may facilitate a long-term gradient by sustained factor release, implants modified with crosslinked albumin nanocarriers were evaluated in vivo.

METHODS

Nanocarriers from murine serum albumin (MSA) were prepared by an inverse miniemulsion technique encapsulating either a low- or high-molar mass fluorescent cargo. PPE implants were subsequently coated with these nanocarriers. In control cohorts, the implant was coated with the homologue non-encapsulated cargo substance by dip coating. Implants were consequently analyzed in vivo using repetitive fluorescence microscopy utilizing the dorsal skinfold chamber in mice for ten days post implantation.

RESULTS

Implant-modification with MSA nanocarriers significantly prolonged the presence of the encapsulated small molecules while macromolecules were detectable during the investigated timeframe regardless of the form of application.

CONCLUSIONS

Surface modification of PPE implants with MSA nanocarriers results in the alternation of release kinetics especially when small molecular substances are used and therefore allows a prolonged factor release for the promotion of implant integration.

Clinical Application of Antibacterial Hydrogel and Coating in Orthopaedic and Traumatology Surgery

Implant related infection is one of the most frequent complications in orthopaedic and trauma surgery. Local antibiotic treatment strategies are becoming part of the prevention and treatment methodology for this fearful complication. To date, there are two coatings available on the market, both with a polylactic acid base. Current evidence supports the use of these types of coatings in the prophylaxis of periprosthetic infections and fracture-related infections. However, their therapeutic use has been less investigated. The purpose of this article is to summarise recent evidence relating to the clinical application of antibacterial hydrogels and coatings in orthopaedic and traumatology surgery and indicating which future applications may benefit from it.

Review on Surface Treatment for Implant Infection via Gentamicin and Antibiotic Releasing Coatings

Surface treatment of metallic implants plays a crucial role in orthopedics and orthodontics. Metallic implants produce side-effects such as physical, chemical/electro-chemical irritations, oligodynamic/catalytic and carcinogenic effects. These effects cause bacterial infections and account for huge medical expenses. Treatment for these infections comprises repeated radical debridement, replacement of the implant device and intravenous or oral injection antibiotics. Infection is due to the presence of bacteria in the patient or the surrounding environment. The antibiotic-based medication prevents prophylaxis against bacterial colonization, which is an emphatic method that may otherwise be catastrophic to a patient. Therefore, preventive measures are essential. A coating process was developed with its drug infusion and effect opposing biofilms. Modification in the medical implant surface reduces the adhesion of bacterial and biofilms, the reason behind bacterial attachment. Other polymer-based and nanoparticle-based carriers are used to resolve implant infections. Therefore, using an implant coating is a better approach to prevent infection due to biofilm.

Antibiotic-loaded amphora-shaped pores on a titanium implant surface enhance osteointegration and prevent infections

Artificial prostheses for joint replacement are indispensable in orthopedic surgery. Unfortunately, the implanted surface is attractive to not only host cells but also bacteria. To enable better osteointegration, a mechanically stable porous structure was created on a titanium surface using laser treatment and metallic silver particles were embedded in a hydrophilic titanium oxide layer on top. The laser structuring resulted in unique amphora-shaped pores. Due to their hydrophilic surface conditions and capillary forces, the pores can be loaded preoperative with the antibiotic of choice/need, such as gentamicin. Cytotoxicity and differentiation assays with primary human osteoblast-like cells revealed no negative effect of the surface modification with or without gentamicin loading. An in vivo biocompatibility study showed significantly enhanced osteointegration as measured by push-out testing and histomorphometry 56 days after the implantation of the K-wires into rat femora. Using a S. aureus infection model, the porous, silver-coated K-wires slightly reduced the signs of bone destruction, while the wires were still colonized after 28 days. Loading the amphora-shaped pores with gentamicin significantly reduced the histopathological signs of bone destruction and no bacteria were detected on the wires. Taken together, this novel surface modification can be applied to new or established orthopedic implants. It enables preoperative loading with the antibiotic of choice/need without further equipment or post-coating, and supports osteointegration without a negative effect of the released dug, such as gentamicin.

Intramedullary nail: the past, present and the future - a review exploring where the future may lead us

BACKGROUND

Intramedullary nails (IMNs) are the current gold standard treatment for long bone diaphyseal and selected metaphyseal fractures. The design of IMNs has undergone many revisions since its invention in the 16th century, with a dramatic increase in novel designs in recent years aiming to further improve intramedullary fixation techniques.

AIMS

To map the evolution of IMNs in orthopedic surgery, discuss the limitations and complications of current IMNs and identify novel IMNs that may influence future design innovations.

METHODS

We undertook a scoping review on the status of orthopedic IMNs by reviewing Google Scholar with the following keywords. Publications and patents selected for retrieval were initially assessed on the title and abstract by five independent reviewers. 52 papers were retrieved for complete text examination, and secondary references were checked from these papers. The results were discussed within the research group and consensus was obtained describing novel IMNs.

RESULTS

Novel IMN designs include growth factor and/or antimicrobial coatings targeting fracture healing and perioperative infection risk, respectively; minimally invasive expandable IMNs to avoid the need for interlocking screws; and novel materials such as carbon fiber for their theoretically superior biomechanical properties and avoidance of artifact on CT and MRI imaging.

CONCLUSION

The novel IMNs proposed in recent years collectively aim to improve intramedullary fixation techniques by reducing operative time and radiation exposure, improving fracture healing or monitoring bone cancer progression. However, more research and development are necessary to solve these complex problems.

Gentamicin-Coated Tibia Nail in Fractures and Nonunion to Reduce Fracture-Related Infections: A Systematic Review

The incidence of a fracture-related infection (FRI) can reach 30% of open tibia fractures (OTF). The use of antibiotic-coated implants is one of the newest strategies to reduce the risk of infection in orthopedic surgery. The aim of this study was to investigate the efficacy and safety of a gentamicin-coated tibia nail in primary fracture fixation (FF) and revision surgery (RS) of nonunion cases in terms of FRI incidence. We conducted a systematic review according to the PRISMA checklist on Pub-Med, Cochrane, and EMBASE. Of the 32 studies, 8 were included, for a total of 203 patients treated: 114 were FF cases (63% open fractures) and 89 were RS cases, of which 43% were infected nonunion. In the FF group, four FRI were found (3.8%): three OTF (Gustilo-Anderson III) and one closed fracture; bone healing was achieved in 94% of these cases. There were four relapses of infection and one new onset in the RS group; bone healing occurred in 88% of these cases. No side effects were found. There were no significant differences in terms of FRI, nonunion, and healing between the two groups. Gentamicin-coated tibia nail is an effective therapeutic option in the prophylaxis of high-risk fracture infections and in complex nonunion cases.

Engineering Anisotropic Meniscus: Zonal Functionality and Spatiotemporal Drug Delivery

Human meniscus is a fibrocartilaginous structure that is crucial for an adequate performance of the human knee joint. Degeneration of the meniscus is often followed by partial or total meniscectomy, which enhances the risk of developing knee osteoarthritis. The lack of a satisfactory treatment for this condition has triggered a major interest in drug delivery (DD) and tissue engineering (TE) strategies intended to restore a bioactive and fully functional meniscal tissue. The aim of this review is to critically discuss the most relevant studies on spatiotemporal DD and TE, aiming for a multizonal meniscal reconstruction. Indeed, the development of meniscal tissue implants should involve a provision for adequate active molecules and scaffold features that take into account the anisotropic ultrastructure of human meniscus. This zonal differentiation is reflected in the meniscus biochemical composition, collagen fiber arrangement, and cell distribution. In this sense, it is expected that a proper combination of advanced DD and zonal TE strategies will play a key role in the future trends in meniscus regeneration. Impact statement Meniscus degeneration is one of the main causes of knee pain, inflammation, and reduced mobility. Currently used suturing procedures and meniscectomy are far from being ideal solutions to the loss of meniscal function. Therefore, drug delivery (DD) and tissue engineering (TE) strategies are currently under investigation. DD systems aim at an in situ controlled release of growth factors, whereas TE strategies aim at mimicking the anisotropy of native meniscus. The goal of this review is to discuss these two main approaches, as well as synergies between them that are expected to lead to a real breakthrough in the field.

Adjuvant Drug-Assisted Bone Healing: Advances and Challenges in Drug Delivery Approaches

Bone defects of critical size after compound fractures, infections, or tumor resections are a challenge in treatment. Particularly, this applies to bone defects in patients with impaired bone healing due to frequently occurring metabolic diseases (above all diabetes mellitus and osteoporosis), chronic inflammation, and cancer. Adjuvant therapeutic agents such as recombinant growth factors, lipid mediators, antibiotics, antiphlogistics, and proangiogenics as well as other promising anti-resorptive and anabolic molecules contribute to improving bone healing in these disorders, especially when they are released in a targeted and controlled manner during crucial bone healing phases. In this regard, the development of smart biocompatible and biostable polymers such as implant coatings, scaffolds, or particle-based materials for drug release is crucial. Innovative chemical, physico- and biochemical approaches for controlled tailor-made degradation or the stimulus-responsive release of substances from these materials, and more, are advantageous. In this review, we discuss current developments, progress, but also pitfalls and setbacks of such approaches in supporting or controlling bone healing. The focus is on the critical evaluation of recent preclinical studies investigating different carrier systems, dual- or co-delivery systems as well as triggered- or targeted delivery systems for release of a panoply of drugs.

Prevention of infection in open fractures: Where are the pendulums now?

Soft tissue management and fracture fixation including initial external fixation in Gustilo-Anderson type II and type III open fractures are cornerstones in the treatment but details on timing and type of wound closure, irrigation and debridement, systemic and local antibiotics, antimicrobial-coated implants and the use of Bone Morphogenetic Protein-2 remain controversial. This article looks at current clinical evidence of these items for the management of open fractures. Timing of debridement and wound closure remains critical. Early debridement by an experienced team within 24 h seems adequate while gross contamination, a devascularized limb, a multi-injured patient and compartment syndrome require immediate surgical intervention. Wound closure during the first surgery was shown to result in reduced rates for infections and nonunion. If soft-tissue reconstruction is needed, it should be performed within the first 7 days. Regarding types of irrigation fluid, antiseptic and antibacterial solutions did not prove to be superior to saline. High pressure irrigation has not been demonstrated to be beneficial whereas antibiotic administration as soon as possible has been proven to be favorable. Administration of more than 72 h was not superior to shorter systemic antibiotic intervals. For Gustilo-Anderson type I and II, broad spectrum antibiotic therapy is reasonable. Additional aminoglycosides for broader coverage are recommended in Gustilo-Anderson type III fractures. There is newer literature on the beneficial effects of the use of local antibiotics, e.g. by antibiotic beads. Coating of internal fixation devices is a modern approach to improve infection prophylaxis and gentamicin-coated implants have been demonstrated to be safe in clinical application. Vacuum assisted closure (VAC) could not evidence negative pressure wound therapy to reduce infection risk, improve self-rated disability or quality of life in open fractures, however, enhance treatment costs. Recombinant human bone morphogenetic proteins (rhBMP)-2 showed promising data in Gustilo-Anderson type III open tibial shaft fractures with lower rates of invasive secondary procedures. In conclusion, there is evidence for thorough debridement and irrigation with saline, early soft tissue coverage and the use of systemic and local antibiotics. Except for a short-term soft tissue coverage VAC seems not to be beneficial and rhBMP-2 is an additional tool in Gustilo-Anderson type III open fractures.

Allogenic Bone Graft Enriched by Periosteal Stem Cell and Growth Factors for Osteogenesis in Critical Size Bone Defect in Rabbit Model: Histopathological and Radiological Evaluation

Background & Objective:

This study aimed to investigate the effect of decellularized allogeneic bone graft enriched by periosteal stem cells (PSCs) and growth factors on the bone repair process in a rabbit model, which could be used in many orthopedic procedures.

Methods:

In this experimental study, a critical size defect (CSD) (10 mm) was created in the radial diaphysis of 40 rabbits. In group A, the defect was left intact with no medical intervention. In group B, the defect was filled by a decellularized bone graft. In group C, the defect was implanted by a decellularized bone graft enriched with platelet growth factors. In group D, the defect was treated by a decellularized bone graft seeded by periosteal mesenchymal stem cells (MSCs). Also, in group E, the defect was filled by a decellularized bone graft enriched with platelet growth factors and periosteal MSCs. Radiological evaluation was done on the first day and then in the second, fourth, and eighth weeks after the operation. The specimens were harvested on the 28th and 56th postoperative days and evaluated for histopathological criteria.

Results:

The radiologic and microscopic analysis of the healing process in bone defects of the treated groups (C, D, and E) revealed more advanced repair criteria than those of groups A and B significantly (P<0.05).

Conclusion:

Based on this study, it appears that implantation of concentrated PSCs in combination with growth factors and allogeneic cortical bone graft is an effective therapy for the repair of large bone defects.

Polymer Membranes Sonocoated and Electrosprayed with Nano-Hydroxyapatite for Periodontal Tissues Regeneration

Diseases of periodontal tissues are a considerable clinical problem, connected with inflammatory processes and bone loss. The healing process often requires reconstruction of lost bone in the periodontal area. For that purpose, various membranes are used to prevent ingrowth of epithelium in the tissue defect and enhance bone regeneration. Currently-used membranes are mainly non-resorbable or are derived from animal tissues. Thus, there is an urgent need for non-animal-derived bioresorbable membranes with tuned resorption rates and porosity optimized for the circulation of body nutrients. We demonstrate membranes produced by the electrospinning of biodegradable polymers (PDLLA/PLGA) coated with nanohydroxyapatite (nHA). The nHA coating was made using two methods: sonocoating and electrospraying of nHA suspensions. In a simulated degradation study, for electrosprayed membranes, short-term calcium release was observed, followed by hydrolytic degradation. Sonocoating produced a well-adhering nHA layer with full coverage of the fibers. The layer slowed the polymer degradation and increased the membrane wettability. Due to gradual release of calcium ions the degradation-associated acidity of the polymer was neutralized. The sonocoated membranes exhibited good cellular metabolic activity responses against MG-63 and BJ cells. The collected results suggest their potential use in Guided Tissue Regeneration (GTR) and Guided Bone Regeneration (GBR) periodontal procedures.

Comparative study of the efficacy of gentamicin-coated intramedullary interlocking nail versus regular intramedullary interlocking nail in Gustilo type I and II open tibia fractures

PURPOSE

Open tibia fracture is prone to infection, consequently causing significant morbidity and increasing the hospital stay, occupational loss and onset of chronic osteomyelitis. Intramedullary nailing is one choice for treating tibia shaft fractures. To improve the delivery of antibiotics at the tissue-implant interface, many methods have been proposed as a part of prophylaxis against infection. This study was conducted to study the role of gentamicin-impregnated intramedullary interlocking (IMIL) nail in the prevention of infection in Gustilo type I and II open tibia fractures and to compare the results with regular intramedullary nail.

METHODS

The study included 28 patients with open tibia fractures (Gustilo type 1 or type 2); of them 14 underwent regular IMIL nailing and the other 14 were treated with gentamicin-coated nailing. Randomization was done by alternate allocation of the patients. Follow-up was done postoperatively (day 1), 1 week, 6 weeks, and 6 months for bone union, erythrocyte sedimentation rate (ESR), hemoglobin and C-reactive protein (CRP). Statistical significance was tested using unpaired t-test. A p value less than 0.05 was considered significant.

RESULTS

There were 4 cases of infection in controls (regular IMIL nail) and no infection among patients treated with gentamicin-coated nail during the follow up (X² = 4.66, p = 0.031). At 6 months postoperatively, CRP (p = 0.031), ESR (p = 0.046) and hemoglobin level (p = 0.016) showed significant difference between two groups. The bone healing rate was better with gentamicin-coated nail in comparison to regular IMIL nail at 6 months follow-up (p = 0.016).

CONCLUSION

Gentamicin-coated IMIL nail has a positive role in preventing infection in Gustilo type I and II open tibia fractures.

Antibacterial coating of implants: are we missing something?

Implant-related infection is one of the leading reasons for failure in orthopaedics and trauma, and results in high social and economic costs. Various antibacterial coating technologies have proven to be safe and effective both in preclinical and clinical studies, with post-surgical implant-related infections reduced by 90% in some cases, depending on the type of coating and experimental setup used. Economic assessment may enable the cost-to-benefit profile of any given antibacterial coating to be defined, based on the expected infection rate with and without the coating, the cost of the infection management, and the cost of the coating. After reviewing the latest evidence on the available antibacterial coatings, we quantified the impact caused by delaying their large-scale application. Considering only joint arthroplasties, our calculations indicated that for an antibacterial coating, with a final user's cost price of €600 and able to reduce post-surgical infection by 80%, each year of delay to its large-scale application would cause an estimated 35 200 new cases of post-surgical infection in Europe, equating to additional hospital costs of approximately €440 million per year. An adequate reimbursement policy for antibacterial coatings may benefit patients, healthcare systems, and related research, as could faster and more affordable regulatory pathways for the technologies still in the pipeline. This could significantly reduce the social and economic burden of implant-related infections in orthopaedics and trauma. Cite this article: C. L. Romanò, H. Tsuchiya, I. Morelli, A. G. Battaglia, L. Drago. Antibacterial coating of implants: are we missing something? Bone Joint Res 2019;8:199-206. DOI: 10.1302/2046-3758.85.BJR-2018-0316.

Implant Coating Manufactured by Micro-Arc Oxidation and Dip Coating in Resorbable Polylactide for Antimicrobial Applications in Orthopedics

Prophylaxis and the treatment of implant-related infections has become a key focus area for research into improving the outcome of orthopedic implants. Functional resorbable coatings have been developed to provide an antimicrobial surface on the implant and reduce the risk of infection. However, resorbable coatings developed to date still suffer from low adhesive strength and an inadequate release rate of antibiotics. This study presents a novel double-coating of micro-arc oxidation and resorbable polylactide copolymer on a Ti-6Al-4V implant with the aim of reducing the risk of infection post-implantation. The adhesive strength, rate of coating degradation, and antibiotic release rate were investigated. A key finding was that the micro-arc oxidation coating with the addition of antibiotics increased the adhesive strength of the poly-l-lactide-co-ε-caprolactone (PLC) coatings. The adhesive strength was influenced by the concentration of the PLC solution, the surface structure of the titanium substrate, and the composition of the coatings. The antibiotics blended into the PLC coating had a release cycle of approximately 10 days, which would be long enough to reduce the risk of developing an infection after implantation. The double coatings presented in this study have an excellent potential for reducing the incidence and severity of implants-related early infections.

Current development of biodegradable polymeric materials for biomedical applications

In the last half-century, the development of biodegradable polymeric materials for biomedical applications has advanced significantly. Biodegradable polymeric materials are favored in the development of therapeutic devices, including temporary implants and three-dimensional scaffolds for tissue engineering. Further advancements have occurred in the utilization of biodegradable polymeric materials for pharmacological applications such as delivery vehicles for controlled/sustained drug release. These applications require particular physicochemical, biological, and degradation properties of the materials to deliver effective therapy. As a result, a wide range of natural or synthetic polymers able to undergo hydrolytic or enzymatic degradation is being studied for biomedical applications. This review outlines the current development of biodegradable natural and synthetic polymeric materials for various biomedical applications, including tissue engineering, temporary implants, wound healing, and drug delivery.

Cellular Response of Anodized Titanium Surface by Poly(Lactide-co-Glycolide)/Bone Morphogenic Protein-2

Background

The purpose of this study is to examine physical characteristics of and initial biological properties to anodized titanium treated with poly(d,l-lactide-co-glycolide) (PLG) mixed with recombinant human bone morphogenic protein-2 (rhBMP-2).

Methods

Titanium specimens were prepared in groups of four as follows: group NC was anodized under 300 V as control; group PC was anodized then dropped and dried with solution 0.02 ml PLG; group D was anodized then dropped and dried with solution 0.02 ml PLG/rhBMP-2 (3.75 μg per disc); and group E was anodized then coated with 0.02 ml PLG/rhBMP-2 (3.75 μg per disc) by electrospray. Human osteoblastic-like sarcoma cells were cultured. Cell proliferation and alkaline phosphatase (ALP) activity test were carried out. Runx-2 gene was investigated by the reverse transcription-polymerase chain reaction. Immunofluorescence outcome of osteogenic proteins was observed.

Results

After 3 days, there were significantly higher proliferations compared rhBMP-2 loaded titanium discs with rhBMP-2 unloaded discs. The ALPase activity on rhBMP-2 loaded titanium discs was significantly higher than in rhBMP-2 unloaded discs. The expression level of Runx2 mRNA presented the highest on the PLG/rhBMP-2-coated surface.

Conclusion

PLG polymers mixed with rhBMP-2 might improve proliferation, differentiation and osteogenic protein formation of cells on the anodized titanium.

Easily Accessible Protein Nanostructures via Enzyme Mediated Addressing

Site-specific formation of nanoscaled protein structures is a challenging task. Most known structuring methods are either complex and hardly upscalable or do not apply to biological matter at all. The presented combination of enzyme mediated autodeposition and nanosphere lithography provides an easy-to-apply approach for the buildup of protein nanostructures over a large scale. The key factor is the tethering of enzyme to the support in designated areas. Those areas are provided via prepatterning of enzymatically active antidots with variable diameters. Enzymatically triggered protein addressing occurs exclusively at the intended areas and continues until the entire active area is coated. After this, the reaction self-terminates. The major advantage of the presented method lies in its easy applicability and upscalability. Large-area structuring of entire support surfaces with features on the nanometer scale is performed efficiently and without the necessity of harsh conditions. These are valuable premises for large-scale applications with potentials in biosensor technology, nanoelectronics, and life sciences.

Application of Materials as Medical Devices with Localized Drug Delivery Capabilities for Enhanced Wound Repair

The plentiful assortment of natural and synthetic materials can be leveraged to accommodate diverse wound types, as well as different stages of the healing process. An ideal material is envisioned to promote tissue repair with minimal inconvenience for patients. Traditional materials employed in the clinical setting often invoke secondary complications, such as infection, pain, foreign body reaction, and chronic inflammation. This review surveys the repertoire of surgical sutures, wound dressings, surgical glues, orthopedic fixation devices and bone fillers with drug eluting capabilities. It highlights the various techniques developed to effectively incorporate drugs into the selected material or blend of materials for both soft and hard tissue repair. The mechanical and chemical attributes of the resultant materials are also discussed, along with their biological outcomes in vitro and/or in vivo. Perspectives and challenges regarding future research endeavors are also delineated for next-generation wound repair materials.

Printing amphotericin B on microneedles using matrix-assisted pulsed laser evaporation

Transdermal delivery of amphotericin B, a pharmacological agent with activity against fungi and parasitic protozoa, is a challenge since amphotericin B exhibits poor solubility in aqueous solutions at physiologic pH values. In this study, we have used a laser-based printing approach known as matrix-assisted pulsed laser evaporation to print amphotericin B on the surfaces of polyglycolic acid microneedles that were prepared using a combination of injection molding and drawing lithography. In a modified agar disk diffusion assay, the amphotericin B-loaded microneedles showed concentration-dependent activity against the yeast Candida albicans. The results of this study suggest that matrix-assisted pulsed laser evaporation may be used to print amphotericin B and other drugs that have complex solubility issues on the surfaces of microneedles.

Current treatment of infected non-union after intramedullary nailing

Non-union is a devastating consequence of a fracture. Non-unions cause substantial patient morbidity with patients suffering from loss of function of the affected extremity, increased pain, and a substantial decrease in the quality of life. The management is often associated with repeated, unsuccessful operations resulting in prolonged hospital stays, which has social and economic consequences to both the patient and the healthcare system. The rates of non-union following intramedullary (IM) nailing vary according to anatomical location. There is currently no consensus regarding the treatment of infected non-unions following IM nailing, but the most common procedures reported are; exchange IM nail with antibiotic suppression or excision of the non-union, (stabilisation with external fixation or less commonly plate or IM nail) and then reconstruction of the bone defect with distraction osteogenesis or the Masquelet technique. This article explores the general principles of treatment, fixation modalities and proposes a treatment strategy for the management of infected non-unions following intramedullary nailing.

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

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

Antimicrobial coated implants in trauma and orthopaedics-A clinical review and risk-benefit analysis

Implant-associated infections remain a major issue in orthopaedics and antimicrobial functionalization of the implant surface by antibiotics or other anti-infective agents have gained interest. The goal of this article is to identify antimicrobial coatings, for which clinical data are available and to review their clinical need, safety profile, and their efficacy to reduce infection rates. PubMed database of the National Library of Medicine was searched for clinical studies on antimicrobial coated implants for internal fracture fixation devices and endoprostheses for bone surgery, for which study design, level of evidence, biocompatibility, development of resistance, and effectiveness to reduce infection rates were analyzed. Four different coating technologies were identified: gentamicin poly(d, l-lactide) coating for tibia nails, one high (MUTARS^®) and one low amount silver (Agluna) technology for tumor endoprostheses, and one povidone-iodine coating for titanium implants. There was a total of 9 published studies with 435 patients, of which 7 studies were case series (level IV evidence) and 2 studies were case control studies (level III evidence). All technologies were reported with good systemic and local biocompatibility, except the development of local argyria with blue to bluish grey skin discoloration after the use of silver MUTARS^® megaendoprostheses. For the local use of gentamicin, there is contradictory data on the risk of emergence of gentamicin-resistance strains, a risk that does not seem to exist for silver and iodine based technologies. Regarding reduction of infection rates, one case control study showed a significant reduction of infection rates by Agluna silver coated tumor endoprostheses. Based on socio-economic data, there is a strong need for improvement of infection prevention and treatment strategies, including implant coatings, in fracture care, primary and revision arthroplasty, and bone tumor surgery. The reviewed gentamicin, silver Agluna, and povidone-iodine technologies have shown a good risk benefit ratio for patients. Further data from randomized control trials are desirable, although this will remain challenging in the context of infection prevention due to the required large sample size of such studies.

Fosfomycin Addition to Poly(D,L-Lactide) Coating Does Not Affect Prophylaxis Efficacy in Rat Implant-Related Infection Model, But That of Gentamicin Does

Gentamicin is the preferred antimicrobial agent used in implant coating for the prevention of implant-related infections (IRI). However, the present heavy local and systemic administration of gentamicin can lead to increased resistance, which has made its future use uncertain, together with related preventive technologies. Fosfomycin is an alternative antimicrobial agent that lacks the cross-resistance presented by other classes of antibiotics. We evaluated the efficacy of prophylaxis of 10% fosfomycin-containing poly(D,L-lactide) (PDL) coated K-wires in a rat IRI model and compared it with uncoated (Control 1), PDL-coated (Control 2), and 10% gentamicin-containing PDL-coated groups with a single layer of coating. Stainless steel K-wires were implanted and methicillin-resistant Staphylococcus aureus (ATCC 43300) suspensions (103 CFU/10 μl) were injected into a cavity in the left tibiae. Thereafter, K-wires were removed and cultured in tryptic soy broth and then 5% sheep blood agar mediums. Sliced sections were removed from the tibiae, stained with hematoxylin-eosin, and semi-quantitatively evaluated with X-rays. The addition of fosfomycin into PDL did not affect the X-ray and histopathological evaluation scores; however, the addition of gentamicin lowered them. The addition of gentamicin showed a protective effect after the 28th day of X-ray evaluations. PDL-only coating provided no protection, while adding fosfomycin to PDL offered a 20% level protection and adding gentamicin offered 80%. Furthermore, there were 103 CFU level growths in the gentamicin-added group, while the other groups had 105. Thus, the addition of fosfomycin to PDL does not affect the efficacy of prophylaxis, but the addition of gentamicin does. We therefore do not advise the use of fosfomycin as a single antimicrobial agent in coating for IRI prophylaxis.

Testing of antibiotic releasing implant coatings to fight bacteria in combat-associated osteomyelitis - an in-vitro study

PURPOSE

Surgical procedures to prevent osteomyelitis after trauma can be supported by local application of antibiotics. This in-vitro study investigated the release and impact of antibiotics from implant coatings against bacteria associated with combat-related osteomyelitis.

METHODS

K-wires were coated with poly(D,L-lactide) and ciprofloxacin, gentamicin, colistin, daptomycin or cefoxitin in different concentrations. The release was quantified and antimicrobial activity tested for different gram-positive or gram-negative bacteria, alone and in combination. To exclude toxic effects, primary osteoblast-like cells were exposed to antibiotic coating concentrations.

RESULTS

All antibiotics alone and in combination showed an initial burst release with dose dependent antimicrobial activity and no negative effects on osteoblast-like cells, except for cefoxitin.

CONCLUSIONS

Implant coatings can be customized with single or double antibiotic coatings to effectively fight different bacteria and also mixed infections in the treatment of a combat-acquired osteomyelitis. However, optimal drug load and degradation behaviour of individual antibiotics have to be considered.

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.

Importance of dual delivery systems for bone tissue engineering

Bone formation is a complex process that requires concerted function of multiple growth factors. For this, it is essential to design a delivery system with the ability to load multiple growth factors in order to mimic the natural microenvironment for bone tissue formation. However, the short half-lives of growth factors, their relatively large size, slow tissue penetration, and high toxicity suggest that conventional routes of administration are unlikely to be effective. Therefore, it seems that using multiple bioactive factors in different delivery systems can develop new strategies for improving bone tissue regeneration. Combination of these factors along with biomaterials that permit tunable release profiles would help to achieve truly spatiotemporal regulation during delivery. This review summarizes the various dual-control release systems that are used for bone tissue engineering.

Hyaluronic acid-coated poly(d,l-lactide) (PDLLA) nanofibers prepared by electrospinning and coating

Process of preparation of HA/PDLLA nanohybrids.

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

Early secure fixation of total joint replacements is crucial for long-term survival. Antiresorptive agents such as bisphosphonates have been shown to increase implant fixation. We investigated whether local delivery of zoledronate from poly-D, L-lactide (PDLLA)-coated implants could improve implant fixation and osseointegration. Experimental titanium implants were bilaterally inserted press-fit into the proximal tibiae of 10 dogs. On one side the implant was coated with PDLLA containing zoledronate. The contralateral implant was uncoated and used as control. Observation period was 12 weeks. Implant fixation was evaluated with histomorphometry and biomechanical push-out test. We found an approximately twofold increase in all biomechanical parameters when comparing data from the zoledronate group with their respective controls. Histomorphometry showed increased amount of preserved bone and increased bone formation around the zoledronate implants. This study indicates that local delivery of zoledronate from a PDDLA coating has the potential to increase implant fixation.

The use of gentamicin-coated nails in complex open tibia fracture and revision cases: A retrospective analysis of a single centre case series and review of the literature

INTRODUCTION

Despite modern advances in fracture care, deep (implant-related) infection remains a problem in the treatment of tibia fractures. There is some evidence that antibiotic-coated implants are beneficial in the prevention of this sometimes devastating complication. In the following study we describe our results using a gentamicin-coated intramedullary tibia nail (Expert Tibia Nail (ETN) PROtect™) for the surgical treatment of complex open tibia fracture and revision cases.

MATERIALS AND METHODS

We describe the outcome of patients treated between January 2012 and September 2013, using a gentamicin-coated intramedullary tibia nail. Treatment indications included acute, Gustilo grade II-III, open tibia fractures or closed tibia fractures with long-term external fixation prior to intramedullary nailing and complex tibia fracture revision cases with a mean of three prior surgical interventions. Outcome parameters in this study were deep infection and nonunion.

RESULTS

In total, 16 consecutive patients with 16 tibia fractures were treated with a gentamicin-coated intramedullary nail. The overall patient population was subdivided into two groups. The first group consisted of 11 patients (68.8%) with acute fractures who were treated with a gentamicin-coated intramedullary nail. The second group consisted of 5 complex revision cases (31.2%). In our patient population no deep infections could be noted after the treatment with a gentamicin-coated tibia nail. Nonunion was diagnosed in 4 patients (25.0%), 1 of these was a revision case.

CONCLUSIONS

Musculoskeletal complications place a cost burden on total healthcare expenditure. Better understanding of the epidemiology and pathogenesis is essential because this can lead to prevention rather than treatment strategies. The purpose of the study was to evaluate a gentamicin-coated tibia nail in the prevention of deep (implant-related) infection. In our patient population no deep infections occurred after placement of the gentamicin-coated nail. Following this study and literature data, antibiotic-coated implants seem a potential option for prevention of deep infection in trauma patients. In the future this statement needs to be confirmed by large randomised clinical trials.

Osteogenic differentiation and proliferation of bone marrow-derived mesenchymal stromal cells on PDLLA + BMP-2-coated titanium alloy surfaces

RhBMP-2 is clinically applied to enhance bone healing and used in combination with titanium fixation implants. The purpose of this in vitro study was to compare the osteogenic differentiation and proliferation of hMSC on native polished versus sandblasted titanium surfaces (TS) and to test their behavior on pure poly-D,L-lactide (PDLLA) coated as well as PDLLA + rhBMP-2 coated TS. Furthermore, the release kinetics of PDLLA + rhBMP-2-coated TS was investigated. Human bone marrow cells were obtained from three different donors (A: male, 16 yrs; B: male, 27 yrs, C: male, 49 yrs) followed by density gradient centrifugation and flow cytometry with defined antigens. The cells were seeded on native polished and sandblasted TS, PDLLA-coated TS and PDLLA + rhBMP-2-coated TS. Osteogenic differentiation (ALP specific activity via ALP and BCA assay) and proliferation (LDH cytotoxicity assay) was examined on day 7 and 14 and release kinetics of rhBMP-2 was investigated on day 3, 7, 10, and 14. We found significant higher ALP specific activity and LDH activity on native polished compared to native sandblasted surfaces. PDLLA led to decreased ALP specific and LDH activity on both surface finishes. Additional rhBMP-2 slightly diminished this effect. RhBMP-2-release from coated TS decreased nearly exponentially with highest concentrations at the beginning of the cultivation period. The results of this in vitro study suggest that native TS stimulate hMSC significantly stronger toward osteogenic differentiation and proliferation than rhBMP-2 + PDLLA-layered TS in the first 14 days of cultivation. The PDLLA-layer seems to inhibit local hMSC differentiation and proliferation.

Induction of Angiogenesis by Matrigel Coating of VEGF-Loaded PEG/PCL-Based Hydrogel Scaffolds for hBMSC Transplantation

hBMSCs are multipotent cells that are useful for tissue regeneration to treat degenerative diseases and others for their differentiation ability into chondrocytes, osteoblasts, adipocytes, hepatocytes and neuronal cells. In this study, biodegradable elastic hydrogels consisting of hydrophilic poly(ethylene glycol) (PEG) and hydrophobic poly(ε-caprolactone) (PCL) scaffolds were evaluated for tissue engineering because of its biocompatibility and the ability to control the release of bioactive peptides. The primary cultured cells from human bone marrow are confirmed as hBMSC by immunohistochemical analysis. Mesenchymal stem cell markers (collagen type I, fibronectin, CD54, integrin1β, and Hu protein) were shown to be positive, while hematopoietic stem cell markers (CD14 and CD45) were shown to be negative. Three different hydrogel scaffolds with different block compositions (PEG:PCL=6:14 and 14:6 by weight) were fabricated using the salt leaching method. The hBMSCs were expanded, seeded on the scaffolds, and cultured up to 8 days under static conditions in Iscove's Modified Dulbecco's Media (IMDM). The growth of MSCs cultured on the hydrogel with PEG/PCL= 6/14 was faster than that of the others. In addition, the morphology of MSCs seemed to be normal and no cytotoxicity was found. The coating of the vascular endothelial growth factor (VEGF) containing scaffold with Matrigel slowed down the release of VEGF in vitro and promoted the angiogenesis when transplanted into BALB/c nude mice. These results suggest that hBMSCs can be supported by a biode gradable hydrogel scaffold for effective cell growth, and enhance the angiogenesis by Matrigel coating.

Longitudinal analysis of osteogenic and angiogenic signaling factors in healing models mimicking atrophic and hypertrophic non-unions in rats

Impaired bone healing can have devastating consequences for the patient. Clinically relevant animal models are necessary to understand the pathology of impaired bone healing. In this study, two impaired healing models, a hypertrophic and an atrophic non-union, were compared to physiological bone healing in rats. The aim was to provide detailed information about differences in gene expression, vascularization and histology during the healing process. The change from a closed fracture (healing control group) to an open osteotomy (hypertrophy group) led to prolonged healing with reduced mineralized bridging after 42 days. RT-PCR data revealed higher gene expression of most tested osteogenic and angiogenic factors in the hypertrophy group at day 14. After 42 days a significant reduction of gene expression was seen for Bmp4 and Bambi in this group. The inhibition of angiogenesis by Fumagillin (atrophy group) decreased the formation of new blood vessels and led to a non-healing situation with diminished chondrogenesis. RT-PCR results showed an attempt towards overcoming the early perturbance by significant up regulation of the angiogenic regulators Vegfa, Angiopoietin 2 and Fgf1 at day 7 and a further continuous increase of Fgf1, -2 and Angiopoietin 2 over time. However µCT angiograms showed incomplete recovery after 42 days. Furthermore, lower expression values were detected for the Bmps at day 14 and 21. The Bmp antagonists Dan and Twsg1 tended to be higher expressed in the atrophy group at day 42. In conclusion, the investigated animal models are suitable models to mimic human fracture healing complications and can be used for longitudinal studies. Analyzing osteogenic and angiogenic signaling patterns, clear changes in expression were identified between these three healing models, revealing the importance of a coordinated interplay of different factors to allow successful bone healing.

Lysostaphin-coated titan-implants preventing localized osteitis by Staphylococcus aureus in a mouse model

The increasing incidence of implant-associated infections induced by Staphylococcus aureus (SA) in combination with growing resistance to conventional antibiotics requires novel therapeutic strategies. In the current study we present the first application of the biofilm-penetrating antimicrobial peptide lysostaphin in the context of bone infections. In a standardized implant-associated bone infection model in mice beta-irradiated lysostaphin-coated titanium plates were compared with uncoated plates. Coating of the implant was established with a poly(D,L)-lactide matrix (PDLLA) comprising lysostaphin formulated in a stabilizing and protecting solution (SPS). All mice were osteotomized and infected with a defined count of SA. Fractures were fixed with lysostaphin-coated locking plates. Plates uncoated or PDLLA-coated served as controls. All mice underwent debridement and lavage on Days 7, 14, 28 to determine the bacterial load and local immune reaction. Fracture healing was quantified by conventional radiography. On Day 7 bacterial growth in the lavages of mice with lysostaphin-coated plates showed a significantly lower count to the control groups. Moreover, in the lysostaphin-coated plate groups complete fracture healing were observed on Day 28. The fracture consolidation was accompanied by a diminished local immune reaction. However, control groups developed an osteitis with lysis or destruction of the bone and an evident local immune response. The presented approach of terminally sterilized lysostaphin-coated implants appears to be a promising therapeutic approach for low grade infection or as prophylactic strategy in high risk fracture care e.g. after severe open fractures.

Bone tissue engineering scaffolding: computer-aided scaffolding techniques

Tissue engineering is essentially a technique for imitating nature. Natural tissues consist of three components: cells, signalling systems (e.g. growth factors) and extracellular matrix (ECM). The ECM forms a scaffold for its cells. Hence, the engineered tissue construct is an artificial scaffold populated with living cells and signalling molecules. A huge effort has been invested in bone tissue engineering, in which a highly porous scaffold plays a critical role in guiding bone and vascular tissue growth and regeneration in three dimensions. In the last two decades, numerous scaffolding techniques have been developed to fabricate highly interconnective, porous scaffolds for bone tissue engineering applications. This review provides an update on the progress of foaming technology of biomaterials, with a special attention being focused on computer-aided manufacturing (Andrade et al. 2002) techniques. This article starts with a brief introduction of tissue engineering (Bone tissue engineering and scaffolds) and scaffolding materials (Biomaterials used in bone tissue engineering). After a brief reviews on conventional scaffolding techniques (Conventional scaffolding techniques), a number of CAM techniques are reviewed in great detail. For each technique, the structure and mechanical integrity of fabricated scaffolds are discussed in detail. Finally, the advantaged and disadvantage of these techniques are compared (Comparison of scaffolding techniques) and summarised (Summary).

Hydrophilization of poly(caprolactone) copolymers through introduction of oligo(ethylene glycol) moieties

In this study, a new family of poly(ε-caprolactone) (PCL) copolymers that bear oligo(ethylene glycol) (OEG) moieties is described. The synthesis of three different oligo(ethylene glycol) functionalized epoxide monomers derived from 2-methyl-4-pentenoic acid, and their copolymerization with ε-caprolactone (CL) to poly(CL-co-OEG-MPO) copolymers is presented. The statistical copolymerization initiated with SnOct2/BnOH yielded the copolymers with varying OEG content and composition. The linear relationship between feed ratio and incorporation of the OEG co-monomer enables control over backbone functional group density. The introduction of OEG moieties influenced both the thermal and the hydrophilic characteristics of the copolymers. Both increasing OEG length and backbone content resulted in a decrease in static water contact angle. The introduction of OEG side chains in the PCL copolymers had no adverse influence on MC-3TE3-E1 cell interaction. However, changes to cell form factor (Φ) were observed. While unmodified PCL promoted elongated (anisotropic) morphologies (Φ = 0.094), PCL copolymer with tri-ethylene glycol side chains at or above seven percent backbone incorporation induced more isotropic cell morphologies (Φ = 0.184) similar to those observed on glass controls (Φ = 0.151).

BMP-functionalised coatings to promote osteogenesis for orthopaedic implants

The loss of bone integrity can significantly compromise the aesthetics and mobility of patients and can be treated using orthopaedic implants. Over the past decades; various orthopaedic implants; such as allografts; xenografts and synthetic materials; have been developed and widely used in clinical practice. However; most of these materials lack intrinsic osteoinductivity and thus cannot induce bone formation. Consequently; osteoinductive functionalisation of orthopaedic implants is needed to promote local osteogenesis and implant osteointegration. For this purpose; bone morphogenetic protein (BMP)-functionalised coatings have proven to be a simple and effective strategy. In this review; we summarise the current knowledge and recent advances regardingBMP-functionalised coatings for orthopaedic implants.