Evaluation of a Chitosan Hemostat in a Porcine Laparoscopic Partial Nephrectomy Model: A Pilot Study

Background and Objective: The ideal hemostatic agent for laparoscopic partial nephrectomy (LPN) would provide complete hemostasis and sealing of the collecting system at a low cost. Chitosan (CS) is an established topical hemostatic agent, but standard sterilization techniques affect its functional and biologic properties, thereby preventing parenteral uses. This study sought to characterize the safety and efficacy of an implanted CS hemostat sterilized with either a standard technique, electron beam (e-beam) irradiation, or a novel technique, nonthermal nitrogen plasma, in a porcine LPN model. Methods: Laparoscopic partial nephrectomies were performed on six farm pigs and hemostasis achieved using only a CS hemostatic agent (Clo-Sur P.A.D.) that was e-beam (n = 3) or plasma sterilized (PS) (n = 3). Number of pads needed to achieve hemostasis, estimated blood loss, operative time, mass of kidney resection, and warm ischemia time were measured. Animals were monitored for 14 weeks and at harvest, retrograde ureteropyelography and histologic analysis were performed. Results: Complete hemostasis and collection system sealing were achieved in both groups. There was a trend toward less pads required for hemostasis (p = 0.056) and reduced blood loss (p = 0.096) with PS pads, although this did not achieve statistical significance. No complications were observed for 14 weeks and gross examination showed the implanted CS was encapsulated in a fibrous capsule. Histologic analysis revealed a healed nephrectomy site with residual CS and associated chronic inflammation, reactive fibrosis, and foreign body giant cell formation. Importantly, the adjacent renal tissue was intact and viable with no residual parenchymal inflammation or cytologic damage. Conclusion: CS pads alone provided safe and effective hemostasis in a porcine LPN model. PS may enhance hemostatic efficacy and resorption compared with e-beam.

Effects of Low-Temperature Plasma-Sterilization on Mars Analog Soil Samples Mixed with Deinococcus radiodurans

We used Ar plasma-sterilization at a temperature below 80 °C to examine its effects on the viability of microorganisms when intermixed with tested soil. Due to a relatively low temperature, this method is not thought to affect the properties of a soil, particularly its organic component, to a significant degree. The method has previously been shown to work well on spacecraft parts. The selected microorganism for this test was Deinococcus radiodurans R1, which is known for its remarkable resistance to radiation effects. Our results showed a reduction in microbial counts after applying a low temperature plasma, but not to a degree suitable for a sterilization of the soil. Even an increase of the treatment duration from 1.5 to 45 min did not achieve satisfying results, but only resulted in in a mean cell reduction rate of 75% compared to the untreated control samples.

Acid etching and plasma sterilization fail to improve osseointegration of grit blasted titanium implants

Interaction between implant surface and surrounding bone influences implant fixation. We attempted to improve the bone-implant interaction by 1) adding surface micro scale topography by acid etching, and 2) removing surface-adherent pro-inflammatory agents by plasma cleaning. Implant fixation was evaluated by implant osseointegration and biomechanical fixation.

The study consisted of two paired animal sub-studies where 10 skeletally mature Labrador dogs were used. Grit blasted titanium alloy implants were inserted press fit in each proximal tibia. In the first study grit blasted implants were compared with acid etched grit blasted implants. In the second study grit blasted implants were compared with acid etched grit blasted implants that were further treated with plasma sterilization. Implant performance was evaluated by histomorphometrical investigation (tissue-to-implant contact, peri-implant tissue density) and mechanical push-out testing after four weeks observation time.

Neither acid etching nor plasma sterilization of the grit blasted implants enhanced osseointegration or mechanical fixation in this press-fit canine implant model in a statistically significant manner.

Plasma sterilization of poly lactic acid ultrasound contrast agents: surface modification and implications for drug delivery

Poly lactic acid (PLA) ultrasound contrast agents (CA) have been developed previously in our laboratory for ultrasound (US) imaging, as well as surface coated with doxorubicin to create a potential targeted platform of chemotherapeutic delivery using focused US. However, we have previously found it impossible to sterilize these agents while at the same time maintaining their acoustic properties, a task that would probably require fabrication within a clean facility. The purpose of this paper is to investigate the feasibility of using plasma to sterilize these CA while maintaining maximum echogenicity, a step that would greatly facilitate in vivo investigations. Effects of plasma exposure time (1, 3 and 6 min) and intensity (low-10 mA, 6.8 W; medium-15 mA, 10.5 W; and high-25 mA, 18 W) on the CAs' acoustic properties, surface morphology, zeta potential, capacity to carry chemotherapeutics and overall sterility are described. Both increases in plasma intensity and exposure time increased CA zeta potential and also significantly increased drug payload. High-intensity plasma exposure for 3 min was found to be an optimal sterilization protocol for maximal (100%) preservation of CA echogenicity. Plasma exposure resulted in sterile samples and maintained original CA enhancement of 20 dB and acoustic half-life over 75 min, while increasing CA zeta potential by 11 mV and doxorubicin loading efficiency by 10%. This study not only shows how a highly temperature- and pressure-sensitive agent can be sterilized using plasma, but also that surface modification can be used to increase surface binding of the drug.