Development of ultrasound-triggered antibiotic release clip to prevent spinal fusion infection

Alex Michael Sevit

doi:10.17918/etd-6506

Surgical site infection (SSI) is a devastating outcome of lumbar fusion surgery arising in 8.5% of primary procedures. This infection is often marked by the formation of biofilm, which is highly resistant to antibiotics, thus the only treatment for SSI is secondary surgery. Ultrasound has been recently found to mechanically disrupt biofilm, increasing its antibiotic susceptibility, and is often used to trigger drug release. In this study, an ultrasound-triggered antibiotic release device has been developed. The device is made of selective laser sintered polyetheretherketone (PEEK) and clips to a standard 5.5 mm lumbar fusion rod. Initially, the clip will be loaded with antibiotic and sealed with a poly(lactic acid) (PLA) membrane, however, with application of ultrasound, the membrane will rupture, releasing antibiotic directly into the surgical site. Dimensional accuracy was verified using computer tomography and the SLS PEEK material was found to be 38% porous. A model was developed to understand the mechanism of release from the clip. The model supported the hypothesis that release occurred through the walls of the clip as well as from the drug delivery channel, highlighting the necessity of a robust membrane to retain drug. The membrane was applied via submersion in a PLAchloroform solution. The amount of PLA deposited on the clip was varied by changing the number of dips and the concentration of PLA. To assess membrane drug retention and responsiveness to ultrasound-triggered release, clips were incubated for 7 days in physiological conditions, then sonicated at day 7. The high concentration membrane showed the greatest retention, retaining 81% of the loaded drug over 7 days, however, it was unperturbed by ultrasound. The low concentration clips only retained 62% of their drug, but showed an increase in release rate after ultrasound. Further investigation should focus on membrane optimization: finding the precise number of dips and PLA concentration to fulfill the design criteria. The next step would then be to assess the antibacterial effectiveness of the device. This study has demonstrated promising initial feasibility of the drug delivery clip. With further development, this device could be implemented with current clinical antibiotic prophylaxis, to provide another layer of protection. This staged treatment with antibiotics could further reduce the incidence of surgical site infection, decreasing health care costs, disability of this serious complication.

Development of ultrasound-triggered antibiotic release clip to prevent spinal fusion infection

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Development of ultrasound-triggered antibiotic release clip to prevent spinal fusion infection

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