Supercritical Fluid Technology Assisted Incorporation of Antimicrobials into Medical Devices

Baru, Sarn-ii (2022) Supercritical Fluid Technology Assisted Incorporation of Antimicrobials into Medical Devices. Doctoral thesis, SETU Waterford.

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Catheter-associated infections (CAIs) are a serious concern worldwide. In the United States alone, about 80,000 catheter line-associated bloodstream infections (CLABSIs) are recorded each year with increased mortality rates for seriously ill patients. Current means used for incorporating antimicrobials include coating, impregnation, engineered surface topography and hot-melt extrusion (HME). However, the major problems associated with these methods are leaching, uncontrolled drug delivery and degradation of thermosensitive drugs. The aim of this research work was to produce antimicrobial loaded thermoplastic polyurethanes for delivering a proven solution to the current unmet need of eliminating the occurrence of biofilm formation. The incorporation of selected antimicrobial agents in polyurethanes was approached in two different fashions. Firstly, the use of sub-critical carbon dioxide (sbCO2) to assist the single HME process, which successfully lowered melt process temperature of Quadrathane polyurethane from 190 to 175 °C. Unfortunately, it was higher than the melting temperature of chlorhexidine diacetate (CHX-A) at which CHX lost its antimicrobial properties. Graphene oxide (GO), was also selected to incorporate into Quadrathane polyurethane by using the single step HME processing with the assistance of sbCO2. The results demonstrated that the incorporation of GO into Quadrathane polyurethane resulted in a change in mechanical, thermal, and rheological properties of the composites. The incorporation of GO also imparted more strength to the Quadrathane matrix. Another medical grade polyurethane, Pellethane polyurethane, was chosen to be extruded using a two-step HME processing approach with pressurized CO2 at the subcritical point. The results showed that under both conditions, pressurised CO2 could change the rheological properties of the Pellethane in the barrel of the extruder. The melt viscosity decreased to 36.36 percent and 40.04 percent at 600 and 1000 psi, respectively. The process temperature of Pellethane polyurethane was reduced from 185 °C to 160 °C. The processing window temperature was raised by 25 °C and may be extended for other polymers. Crystallinity and thermal decomposition kinetics and behaviour of the Pellethane polyurethane extrudates were also investigated. The activation energy (Ea) values of the polyurethane treated with pressurised CO2 at 600 and 1000 psi were 155 and 150 kJ·mol-1 , respectively. Both were higher than that of untreated samples which was 135 kJ·mol-1. The greater Ea values for thermal decomposition provided higher thermal stability of the Pellethane polyurethane. A second technique proposed to incorporate the antimicrobials into Quadrathane polyurethane using sbCO2 assisted impregnation technique. CHX-A was impregnated into Quadrathane polyurethane by using sbCO2 at 400 and 600 psi and methanol as a co-solvent. The highest CHX-A uptake was1.23 mg (0.13%) for the Quadrathane sample treated at 600 psi, 5 wt%, the distribution of CHX-A in the matrix was not homogeneous which decreases from the outer part to the inner part of the matrix. Gram-positive bacteria, S. aureus were chosen for antimicrobial performance test. At the experimental time points, the CHX-A impregnated Quadrathane samples outperformed the negative control. Log 10 value increased from 0.00 to 2.83 for the samples treated at 400 and 600 psi. Unfortunately, the GO composite samples at all scenarios for both sbCO2 assisted impregnation and HME did not perform any efficacy against S. aureus. The elution study demonstrates that CHX was not eluted from the Quadrathane matrix because a very small amount of CHX-A was found in the Quadrathane matrix.

Item Type: Thesis (Doctoral)
Uncontrolled Keywords: Antimicrobials, Medical Devices
Departments or Groups: *NONE OF THESE*
Divisions: School of Engineering > Department of Engineering Technology
Depositing User: Derek Langford
Date Deposited: 06 Oct 2022 11:10
Last Modified: 06 Oct 2022 11:10

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