Microencapsulation of rifampicin: A technique to preserve the mechanical properties of bone cement

The tale of microencapsulated rifampicin: is it useful for the treatment of periprosthetic joint infection?

Purpose

Microencapsulation techniques have allowed the addition of rifampicin to bone cement, but its in vivo efficacy has not been proven. The aim of our study is to determine the superiority of cement containing gentamicin and rifampicin microcapsules in the treatment of PJI versus cement exclusively containing gentamicin.

Methods

An S. aureus PJI was induced in 15 NZW rabbits. A week after inoculation, the first stage of replacement was carried out, and the animals were divided into two groups: group R received a spacer containing gentamicin and rifampicin microcapsules, and group C received a spacer containing gentamicin. Intra-articular release curve of rifampicin and infection and toxicity markers were monitored for four weeks post-operatively, when microbiological analysis was performed.

Results

The microbiological cultures showed a significantly lower growth of S. aureus in soft tissue (2.3·10⁴ vs 0; p = 0.01) and bone (5.7·10² vs 0; p = 0.03) in the group with rifampicin microcapsules. No differences were found in systemic toxicity markers. Rifampicin release from the cement spacer showed higher concentrations than the staphylococcal MIC throughout the analysis.

Conclusion

The in vivo analyses demonstrated the superiority of cement containing gentamicin and rifampicin microcapsules versus the isolated use of gentamicin in the treatment of PJI in the rabbit model without serious side effects due to the systemic absorption of rifampicin. Given the increasing incidence of staphylococci-related PJI, the development of new strategies for intra-articular administration of rifampicin for its treatment has a high clinical impact.

[Salvage procedure for chronic periprosthetic infection : Use of a rifampicin-loaded polymethyl methacrylate spacer]

Periprosthetic infections with problematic and multiresistant pathogens represent a great challenge for trauma surgeons, especially when repetitive surgical débridement combined with calculated i.v. antibiotic treatment does not lead to resolution of the infection. This can necessitate a deviation from state of the art treatment concepts, such as the additive implementation of a rifampicin-loaded polymethyl methacrylate (PMMA) spacers.

3D-Printed Porous Tantalum Coated with Antitubercular Drugs Achieving Antibacterial Properties and Good Biocompatibility

Treatment of bone and joint tuberculosis remains a challenge. The development of tissue-engineered drug-loaded biomaterials has increased the therapeutic options. However, for the treatment of osteoarticular tuberculosis with severe local infection risks and high weight-bearing requirements, it is still necessary to design materials consistent with bone biomechanics, cytocompatibility, and osteogenesis and to provide more effective antimicrobial functions. The antitubercular drugs isoniazid and rifampicin are loaded with gellan gum, and a 3D-printed porous tantalum surface is treated with polydopamine to increase adhesion. The osteogenic induction and differentiation are tested using alkaline phosphatase, alizarin red staining, sirius red staining, and polymerase chain reaction testing. Bone regeneration in vivo is measured by X-ray, micro-computerized tomography, hard tissue sections, and fluorescence staining. The drug is released slowly in vitro and in vivo, increasing the duration of antibacterial action. The composite bio-scaffolds inhibit Staphylococcus aureus growth, have good biocompatibility, and does not inhibit the induction of osteogenic differentiation of rat bone marrow mesenchymal stem cells. The composite bio-scaffold can simultaneously achieve localized long-term controlled drug release and bone regeneration and is a promising route for bone and joint tuberculosis treatment.

Preparation of Poly(ethylene glycol)@Polyurea Microcapsules Using Oil/Oil Emulsions and Their Application as Microreactors

The development process of catalytic core/shell microreactors, possessing a poly(ethylene glycol) (PEG) core and a polyurea (PU) shell, by implementing an emulsion-templated non-aqueous encapsulation method, is presented. The microreactors' fabrication process begins with an emulsification process utilizing an oil-in-oil (o/o) emulsion of PEG-in-heptane, stabilized by a polymeric surfactant. Next, a reaction between a poly(ethylene imine) (PEI) and a toluene-2,4-diisocyanate (TDI) takes place at the boundary of the emulsion droplets, resulting in the creation of a PU shell through an interfacial polymerization (IFP) process. The microreactors were loaded with palladium nanoparticles (NPs) and were utilized for the hydrogenation of alkenes and alkynes. Importantly, it was found that PEG has a positive effect on the catalytic performance of the developed microreactors. Interestingly, besides being an efficient green reaction medium, PEG plays two crucial roles: first, it reduces the palladium ions to palladium NPs; thus, it avoids the unnecessary use of additional reducing agents. Second, it stabilizes the palladium NPs and prevents their aggregation, allowing the formation of highly reactive palladium NPs. Strikingly, in one sense, the suggested system affords highly reactive semi-homogeneous catalysis, whereas in another sense, it enables the facile, rapid, and inexpensive recovery of the catalytic microreactor by simple centrifugation. The durable microreactors exhibit excellent activity and were recycled nine times without any loss in their reactivity.

A Novel Antimicrobial Peptide Scyreprocin From Mud Crab Scylla paramamosain Showing Potent Antifungal and Anti-biofilm Activity

Natural antimicrobial peptides (AMPs) are potential antibiotic alternatives. Marine crustaceans are thought to generate more powerful and various AMPs to protect themselves from infections caused by pathogenic microorganisms in their complex aquatic habitat, thus becoming one of the most promising sources of AMPs or other bioactive substances. In the study, a novel protein was identified as an interacting partner of male-specific AMP SCY2 in Scylla paramamosain and named scyreprocin. The recombinant product of scyreprocin (rScyreprocin) was successfully expressed in Escherichia coli. rScyreprocin exerted potent, broad-spectrum antifungal, antibacterial, and anti-biofilm activity (minimum inhibitory concentrations from 0.5 to 32 μM) through differential modes of action, including disruption of cell membrane integrity and induction of cell apoptosis, and has rapid bactericidal (in 0.5–2 h) and fungicidal (in 8–10 h) kinetics. In addition to its fungicidal activity against planktonic fungi, rScyreprocin also prevented the adhesion of fungal cells, inhibited biofilm formation, and eradicated the mature biofilms. Moreover, rScyreprocin showed a profound inhibitory effect on spore germination of Aspergillus spp. (minimum inhibitory concentrations from 4 to 8 μM). This peptide was not cytotoxic to murine and mammalian cells and could increase the survival rate of Oryzias melastigma under the challenge of Vibrio harveyi. Taken together, the novel AMP scyreprocin would be a promising alternative to antibiotics used in aquaculture and medicine.

Self-healing biomaterials: The next generation is nano

The U.S. Agency for Healthcare Research and Quality estimates that there are over 1 million total hip and total knee replacements each year in the U.S. alone. Twenty five percent of those implants will experience aseptic loosening, and bone cement failure is an important part of this. Bone cements are based on poly(methyl methacrylate) (PMMA) systems that are strong but brittle polymers. PMMA-based materials are also essential to modern dental fillings, and likewise, the failure rates are high with lifetimes of 3-10 years. These brittle polymers are an obvious target for self-healing systems which could reduce revision surgeries and visits to dentist. Self-healing polymers have been described in the literature since 1996 and examples from Roman times are known, but their application in medicine has been challenging. This review looks at the development of self-healing biomaterials for these applications and the challenges that lie between development and the clinic. Many of the most promising formulations involve introducing nanoscale components which offer substantial potential benefits over their microscale counterparts especially in composite systems. There is substantial promise for translation, but issues with toxicity, robustness, and reproducibility of these materials in the complex environment of the body must be addressed. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Implantable Materials and Surgical Technologies > Nanomaterials and Implants.

PMMA-Based Bone Cements and the Problem of Joint Arthroplasty Infections: Status and New Perspectives

Polymethyl methacrylate (PMMA)-based bone cement is a biomaterial that has been used over the last 50 years to stabilize hip and knee implants or as a bone filler. Although PMMA-based bone cement is widely used and allows a fast-primary fixation to the bone, it does not guarantee a mechanically and biologically stable interface with bone, and most of all it is prone to bacteria adhesion and infection development. In the 1970s, antibiotic-loaded bone cements were introduced to reduce the infection rate in arthroplasty; however, the efficiency of antibiotic-containing bone cement is still a debated issue. For these reasons, in recent years, the scientific community has investigated new approaches to impart antibacterial properties to PMMA bone cement. The aim of this review is to summarize the current status regarding antibiotic-loaded PMMA-based bone cements, fill the gap regarding the lack of data on antibacterial bone cement, and explore the progress of antibacterial bone cement formulations, focusing attention on the new perspectives. In particular, this review highlights the innovative study of composite bone cements containing inorganic antibacterial and bioactive phases, which are a fascinating alternative that can impart both osteointegration and antibacterial properties to PMMA-based bone cement.

Antibiotic-Loaded Polymethylmethacrylate Beads and Spacers in Treatment of Orthopedic Infections and the Role of Biofilm Formation

Polymethylmethacrylate (PMMA) also referred as (acrylic) bone cement is a non-degradable biomaterial that has been used in clinical orthopedic practice for several decades. PMMA can be used in a plain formulation, but is often used in an antibiotic-loaded formulation in (primary and revision) arthroplasty and in treatment of orthopedic infections as prosthetic joint infections (PJI) and chronic osteomyelitis. In treatment of PJIs antibiotic-loaded PMMA is often used as a carrier material for local antibiotic delivery in addition to treatment with systemic antibiotics. In this case, the antibiotic-loaded PMMA is often used as a spacer or as a bead chain. Since the introduction of PMMA as an antibiotic carrier there is a tremendous amount of scientific and clinical papers published, which studied numerous different aspects of antibiotic-loaded PMMA. This paper will review the research regarding basic principles of antibiotic-loaded PMMA as mechanism of action, antibiotic-release capacities, choice of antibiotics and influences on mechanical properties of PMMA. Subsequently, concerns regarding the application of antibiotic-loaded PMMA, biofilm formation, antibiotic resistance and local or systemic toxicity will be discussed. In addition to these subjects, the role of antibiotic loaded PMMA in clinical treatment of PJIs and chronic osteomyelitis is discussed in the final part of this paper.

Radical scavenging of poly(methyl methacrylate) bone cement by rifampin and clinically relevant properties of the rifampin-loaded cement

Objectives

The objective of this study was to characterize the effect of rifampin incorporation into poly(methyl methacrylate) (PMMA) bone cement. While incompatibilities between the two materials have been previously noted, we sought to identify and quantify the cause of rifampin’s effects, including alterations in curing properties, mechanical strength, and residual monomer content.

Methods

Four cement groups were prepared using commercial PMMA bone cement: a control; one with 1 g of rifampin; and one each with equimolar amounts of ascorbic acid or hydroquinone relative to the amount of rifampin added. The handling properties, setting time, exothermic output, and monomer loss were measured throughout curing. The mechanical strength of each group was tested over 14 days. A radical scavenging assay was used to assess the scavenging abilities of rifampin and its individual moieties.

Results

Compared with control, the rifampin-incorporated cement had a prolonged setting time and a reduction in exothermic output during polymerization. The rifampin cement showed significantly reduced strength and was below the orthopaedic weight-bearing threshold of 70 MPa. Based on the radical scavenging assay and strength tests, the hydroquinone structure within rifampin was identified as the polymerization inhibitor.

Conclusion

The incorporation of rifampin into PMMA bone cement interferes with the cement’s radical polymerization. This interference is due to the hydroquinone moiety within rifampin. This combination alters the cement’s handling and curing properties, and lowers the strength below the threshold for weight-bearing applications. Additionally, the incomplete polymerization leads to increased toxic monomer output, which discourages its use even in non-weight-bearing applications.

Cite this article: G. A. Funk, E. M. Menuey, K. A. Cole, T. P. Schuman, K. V. Kilway, T. E. McIff. Radical scavenging of poly(methyl methacrylate) bone cement by rifampin and clinically relevant properties of the rifampin-loaded cement. Bone Joint Res 2019;8:81–89. DOI: 10.1302/2046-3758.82.BJR-2018-0170.R2.