While the infection rate after primary total joint replacements (TJR) sits at 1–2%, for trauma-related surgery, it can be as high as 3.6 to 21.2% based on the type of trauma; the risk of reinfection after revision surgery is even higher. Current treatments with antibiotic-releasing PMMA-based bone cement/ beads and/or systemic antibiotic after surgical debridement do not provide effective treatment due to fluctuating antibiotic levels at the site of infection, leading to insufficient local antibiotic concentration. In addition, non-biodegradable PMMA does not support bone regrowth in the debrided void spaces and often must be removed in an additional surgery. Here, we report a bioactive glass or bioglass (BG) substrate-based biodegradable, easy to fabricate “press fitting” antibiotic-releasing bone void filling (ABVF-BG) putty to provide effective local antibiotic release at the site of infection along with support for bone regeneration. The ABVF-BG putty formulation had homogenously distributed BG particles, a porous structure, and showed putty-like ease of handling. Furthermore, the ABVF-BG putty demonstrated in vitro antibacterial activity for up to 6 weeks. Finally, the ABVF-BG putty was biodegradable in vivo and showed 100% bacterial eradication (as shown by bacterial cell counts) in the treatment group, which received ABVF-BG putty, compared to the infection control group, where all the rats had a high bacterial load (4.63 × 10⁶ ± 7.9 × 10⁵ CFU/gram bone) and sustained osteomyelitis. The ABVF-BG putty also supported bone growth in the void space as indicated by a combination of histology, µCT, and X-ray imaging. The potential for simultaneous infection treatment and bone healing using the developed BG-based ABVF-BG putty is promising as an alternative treatment option for osteomyelitis.

Frequent and inappropriate usage of antibiotics has changed the natural evolution of bacteria by reducing susceptibility and increasing resistance towards antibacterial agents. New resistance mechanisms evolved in the response to host defenses and pharmaceutical interventions are threatening our ability to treat common infections, resulting in increased mortality. In the face of this rising epidemic, antibiotic drug discovery, which has long been overlooked by big pharma, is reaching a critical low. Thus, the development of an infection-responsive drug delivery system, which may mitigate multidrug resistance and preserve the lifetime of our current antibiotic arsenal, has garnered the attention of both popular science and funding agencies. The present work describes the development of a thrombin-sensitive linker embedded into a recombinant spider silk copolymer to create a nanosphere drug delivery vehicle. Recent studies have suggested that there is an increase in thrombin-like activity during Staphylococcus aureus infection; thus, drug release from this new “smart” nanosphere can be triggered in the presence of infection. A thrombin sensitive peptide (TSP) was synthesized, and the thrombin cleavage sensitivity was determined by HPLC. The results showed no cleavage of the peptide when exposed to human serum whereas the peptide was cleaved when incubated with S. aureus exudate. Subsequently, the peptide was coupled with a silk copolymer via EDC-NHS chemistry and formulated into nanospheres encapsulating antibiotic vancomycin. These nanospheres were evaluated for in vitro infection-responsive drug release and antimicrobial activity. Finally, the drug responsive nanospheres were assessed for efficacy in an in vivo septic arthritis model. Our study provides evidence that the protein conjugate was enzyme responsive and can be used to formulate targeted drug release to combat infections against multidrug-resistant bacterial strains.

The number of total joint replacements (TJR) is on the rise with a corresponding increase in the number of infected TJR, which necessitates revision surgeries. Current treatments with either non-biodegradable, antibiotic-releasing polymethylmethacrylate (PMMA) based bone cement, or systemic antibiotic after surgical debridement do not provide effective treatment due to fluctuating antibiotic levels at the site of infection. Here, we report a biodegradable, easy-to-use “press-fitting” antibiotic-releasing bone void filling (ABVF) putty that not only provides efficient antibiotic release kinetics at the site of infection but also allows efficient osseointegration. The ABVF formulation was prepared using poly (D,L-lactide-co-glycolide) (PLGA), polyethylene glycol (PEG), and polycaprolactone (PCL) as the polymer matrix, antibiotic vancomycin, and osseointegrating synthetic bone PRO OSTEON for bone-growth support. ABVF was homogenous, had a porous structure, was moldable, and showed putty-like mechanical properties. The ABVF putty released vancomycin for 6 weeks at therapeutic level. Furthermore, the released vancomycin showed in vitro antibacterial activity against Staphylococcus aureus for 6 weeks. Vancomycin was not toxic to osteoblasts. Finally, ABVF was biodegradable in vivo and showed an effective infection control with the treatment group showing significantly higher bone growth (p < 0.001) compared to the control group. The potential of infection treatment and osseointegration makes the ABVF putty a promising treatment option for osteomyelitis after TJR.

In spite of advances in Total Joint Replacements (TJR), infection remains a major concern and a primary causative factor for revision surgery. Current clinical standards treat these osteomyelitis infections with antibiotic-laden poly(methyl methacrylate) (PMMA)-based cement, which has several disadvantages, including inadequate local drug release kinetics, antibiotic leaching for a prolonged period and additional surgical interventions to remove it, etc. Moreover, not all antibiotics (e.g., rifampicin, a potent antibiofilm antibiotic) are compatible with PMMA. For this reason, treatment of TJR-associated infections and related complications remains a significant concern. The objective of this study was to develop a polymer-controlled dual antibiotic-releasing bone void filler (ABVF) with an underlying osseointegrating substrate to treat TJR implant-associated biofilm infections. An ABVF putty was designed to provide sustained vancomycin and rifampicin antibiotic release for 6 weeks while concurrently providing an osseointegrating support for regrowth of lost bone. The reported ABVF showed efficient antibacterial and antibiofilm activity both in vitro and in a rat infection model where the ABVF both showed complete bacterial elimination and supported bone growth. Furthermore, in an in vivo k-wire-based biofilm infection model, the ABVF putty was also able to eliminate the biofilm infection while supporting osseointegration. The retrieved k-wire implants were also free from biofilm and bacterial burden. The ABVF putty delivering combination antibiotics demonstrated that it can be a viable treatment option for implant-related osteomyelitis and may lead to retention of the hardware while enabling single-stage surgery.

With the rising tide of antibiotic resistant bacteria, extending the longevity of the current antibiotic arsenal is becoming a necessity. Developing local, controlled release antibiotic strategies, particularly for difficult to penetrate tissues such as bone, may prove to be a better alternative. Previous efforts to develop an osteoconductive local antibiotic release device for bone were created as solid molded composites; however, intimate contact with host bone was found to be critical to support host bone regrowth; thus, an osteocondconductive antibiotic releasing bone void filling putty was developed. Furthermore, a controlled releasing polymer matrix was refined using pendant-functionalized diols to provide tailorable pharmacokinetics. In vitro pharmacokinetic and bioactivity profiles were compared for a putty formulation with an analogous composition as its molded counterpart as well as four new pendant-functionalized polymers. A best-fit analysis of polymer composition in either small cylindrical disks or larger spheres revealed that the new pendant-functionalized polymers appear to release vancomycin via both diffusion and erosion regardless of the geometry of the putty. In silico simulations, a valuable technique for diffusion mediated controlled release models, will be used to confirm and optimize this property.