Antimicrobial PMMA Bone Cement Containing Long Releasing Multi-Walled Carbon Nanotubes

Antibiotic-Loaded Nano-Sized Delivery Systems: An Insight into Gentamicin and Vancomycin

The fight against infectious disease has remained an ever-evolving challenge in the landscape of healthcare. The ability of pathogens to develop resistance against conventional drug treatments has decreased the effectiveness of therapeutic interventions, and antibiotic resistance is recognized as one of the main challenges of our time. The goal of this systematic review paper is to provide insight into the research papers published on innovative nanosized drug delivery systems (DDSs) based on gentamycin and vancomycin and to discuss the opportunity of their repurposing through nano DDS formulations. These two antibiotics are selected because (i) gentamicin is the first-line drug used to treat suspected or confirmed infections caused by Gram-negative bacterial infections and (ii) vancomycin is used to treat serious Gram-positive bacterial infections. Moreover, both antibiotics have severe adverse effects, and one of the purposes of their formulation as nanosized DDSs is to overcome them. The review paper includes an introduction focusing on the challenges of infectious diseases and traditional therapeutic treatments, a brief description of the chemical and pharmacological properties of gentamicin and vancomycin, case studies from the literature on innovative nanosized DDSs as carriers of the two antibiotic drugs, and a discussion of the results found in the literature.

Preparation and characterizations of antibacterial poly(methyl methacrylate) bone cement via copolymerization with a quaternary ammonium monomer of dimethylaminotriclosan methacrylate

Poly (methyl methacrylate) (PMMA) bone cement relies on the loaded antibiotic to realize the antibacterial purpose. But the exothermic behavior during setting often makes temperature-sensitive antibiotics inactivated. It is necessary to develop new material candidates to replace antibiotics. In this study, a new quaternary ammonium methacrylate (QAM) monomer called dimethylaminetriclosan methacrylate (DMATCM) was designed by the quaternization between 2-(Dimethylamino)ethyl methacrylate and triclosan, then employed as the modifier to explore the feasibility of equipping bone cement with antibacterial activity, and to investigate the variations on the physical and biological performances brought by the substitution ratio of DMATCM to MMA. Results showed that DMATCM opened its C=C bonding to participate in the MMA polymerization, and the quaternary ammonium group helped it to perform broad-spectrum antibacterial property against both Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli. With an increased substitution ratio of DMATCM to MMA, the glass transition temperatures, the maximum exothermic temperatures, and the contact angles of bone cements declined, but the residual monomer contents, the fluid uptakes, and the setting times under Vical indentation increased. Long-term soaking made almost no changes to the weight loss and the mechanical properties of DMATCM-modified cements with lower substitution ratios of 0∼20%, and the activation rather enhanced the strengths of uncured AMBC-4 and AMBC-5 samples. Owing to more DMATCM exposed on the cement surface, the inhibition ring diameter produced by modified cement was improved to a maximum of 28.09 mm, and MC3T3-E1 cells performed the cell viabilities all beyond 70% and healthy adhesion after 72 h co-culturing. Taking all measured properties and ISO standards into account, the antibacterial bone cement under the ratio of 10% performed better, besides its good bactericidal effect, the other properties satisfied the requirements for clinical application.

Comparison of the Therapeutic Efficacy of Antibiotic-Loaded Polymeric Tissue Scaffold and Bone Cement in the Regeneration of Infected Bone Tissue

Background Local antibiotic applications have been used in chronic osteomyelitis and have been defined as an adjunctive treatment method. Biodegradable materials are also used for the same purpose by adding antibiotics. The fact that it does not require additional surgery to be removed is an important advantage. In this study, we intended to develop a new biodegradable drug-loaded polymeric scaffold with good antibiotic release and compare the microbiological results with antibiotic-impregnated bone cement. Methodology A tissue scaffold containing poly(2-hydroxyethyl methacrylate) (PHEMA) was prepared in our laboratory and loaded with ertapenem and daptomycin antibiotics. The surface morphology and pore geometries of drug-loaded and unloaded scaffolds were analyzed by a scanning electron microscope under vacuum. The dose-dependent antiproliferative effects of PHEMA scaffold, drug-loaded scaffold, cement, and drug-loaded cement on osteoblast cells were investigated. To evaluate drug release kinetics, the absorbance values of the scaffold loaded with ertapenem and daptomycin were measured with the spectrometer. For microbiological tests, ertapenem and daptomycin-impregnated cement and scaffold, as well as the control scaffold and cement samples, were investigated for their antibacterial activities on Staphylococcus aureus and Klebsiella pneumoniae strains using the disc diffusion method. These microorganisms are one of the most common microorganisms in osteomyelitis. Results The efficacy of antibiotic-impregnated scaffold and cement on both gram-negative and gram-positive microorganisms was investigated. The daptomycin zone diameter in S. aureus ATCC 29233 strain was 17 mm, whereas it was 24 mm for scaffold and 22 mm for cement. Scaffold was found to be more effective than cement against S. aureus strain. The K. pneumoniae ATCC BAA-2814 strain was found to be resistant to ertapenem, but the zone diameter was 21 mm for scaffold and 20 mm for cement. Ertapenem-loaded scaffold was found to be more effective than cement. It was found that the antimicrobial activity of the scaffold was higher than cement. When we evaluated the release profiles, for the daptomycin-loaded cement group, 98% of daptomycin was cumulatively released within 30 minutes, and for the daptomycin-loaded scaffold group, 100% of daptomycin was cumulatively released in six days. To compare ertapenem-loaded cement and scaffold, 98% of ertapenem was cumulatively released within 10 minutes in the cement group. For the scaffold group, 100% of ertapenem was cumulatively released in 17 days. We found that the scaffold released the antibiotic more slowly and for a longer duration. Therefore, it was thought that the scaffold would be more effective on biofilm and the treatment of osteomyelitis would be more successful. Conclusions The produced scaffold was compared with cement, and it was concluded that the scaffold had better release and antimicrobial efficacy. Scaffold is more advantageous than cement because it is bioeliminable. Thus, there is no need for a second surgical intervention with the likely prevention of mortality and morbidity. Because of all these features, the scaffold seems promising in the local treatment of osteomyelitis.

Composite Bone Cements with Enhanced Drug Elution

Antibiotic-loaded bone cement (ALBC) has become an indispensable material in orthopedic surgery in recent decades, owing to the possibility of drugs delivery to the surgical site. It is applied for both infection prophylaxis (e.g., in primary joint arthroplasty) and infection treatment (e.g., in periprosthetic infection). However, the introduction of antibiotic to the polymer matrix diminishes the mechanical strength of the latter. Moreover, the majority of the loaded antibiotic remains embedded in polymer and does not participate in drug elution. Incorporation of the various additives to ALBC can help to overcome these issues. In this paper, four different natural micro/nanoscale materials (halloysite, nanocrystalline cellulose, micro- and nanofibrillated cellulose) were tested as additives to commercial Simplex P bone cement preloaded with vancomycin. The influence of all four materials on the polymerization process was comprehensively studied, including the investigation of the maximum temperature of polymerization, setting time, and monomer leaching. The introduction of the natural additives led to a considerable enhancement of drug elution and microhardness in the composite bone cements compared to ALBC. The best combination of the polymerization rate, monomer leaching, antibiotic release, and microhardness was observed for the sample containing nanofibrillated cellulose (NFC).

Comparison of antibacterial activity and biocompatibility of non-leaching nitrofuran bone cement loaded with vancomycin, gentamicin, and tigecycline

BACKGROUND

Non-leaching antibacterial bone cement can generate long-term antibacterial activity, it cannot treat serious infections that have occurred like antibiotic-loaded bone cement. Currently, the antibacterial activity and biocompatibility of non-leaching cement when loaded with antibiotics have yet to be determined.

METHODS

Non-leaching antibacterial nitrofuran bone cement (NFBC) specimens were prepared with low-dose and high-dose antibiotics. The antibacterial activity and biocompatibility of NFBC loaded with vancomycin, gentamicin, and tigecycline were compared. The agar diffusion method was employed to observe the inhibition zone of the samples against two bacterial strains from day one to day seven. The CCK-8 assay and acute liver and kidney toxicity test were conducted to assess the effects of the samples on mouse embryo osteoblast precursor cells and C57 mice, respectively.

RESULTS

Gentamicin-loaded cement exhibited the most potent antibacterial activity, effectively inhibiting both bacterial strains at a low dose. Tigecycline-loaded cement demonstrated superior biocompatibility, showing no acute liver and kidney toxicity in mice and minimal cytotoxicity to osteoblasts.

CONCLUSIONS

NFBC loaded with gentamicin, vancomycin, and tigecycline not only maintains sustained antibacterial activity but also exhibits excellent biocompatibility.

3D printed-electrospun PCL/hydroxyapatite/MWCNTs scaffolds for the repair of subchondral bone

Osteochondral defect caused by trauma or osteoarthritis exhibits a major challenge in clinical treatment with limited symptomatic effects at present. The regeneration and remodeling of subchondral bone play a positive effect on cartilage regeneration and further promotes the repair of osteochondral defects. Making use of the strengths of each preparation method, the combination of 3D printing and electrospinning is a promising method for designing and constructing multi-scale scaffolds that mimic the complexity and hierarchical structure of subchondral bone at the microscale and nanoscale, respectively. In this study, the 3D printed-electrospun poly(ɛ-caprolactone)/nano-hydroxyapatites/multi-walled carbon nanotubes (PCL/nHA/MWCNTs) scaffolds were successfully constructed by the combination of electrospinning and layer-by-layer 3D printing. The resulting dual-scale scaffold consisted of a dense layer of disordered nanospun fibers and a porous microscale 3D scaffold layer to support and promote the ingrowth of subchondral bone. Herein, the biomimetic PCL/nHA/MWCNTs scaffolds enhanced cell seeding efficiency and allowed for higher cell-cell interactions that supported the adhesion, proliferation, activity, morphology and subsequently improved the osteogenic differentiation of bone marrow mesenchymal stem cells in vitro. Together, this study elucidates that the construction of 3D printed-electrospun PCL/nHA/MWCNTs scaffolds provides an alternative strategy for the regeneration of subchondral bone and lays a foundation for subsequent in vivo studies.