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BACKGROUND:
Non-thermal atmospheric plasma (NTAP) offers a unique approach to sterilization of inanimate objects and potentially even wound disinfection. Currently, there is no reliable source of plasma-based free radical mixture to advance therapeutic sterilization in the biomedical field. We developed SteriFreeMed Plasma Processing Technology (SFM PPT), a novel, non-thermal plasma/free radical system that utilizes a remote source to deliver a sustained, highly active reactive oxygen and nitrogen species (RONS) mixture within a closed loop system. Our technology significantly reduces the footprint of traditional non-thermal plasma generators, and can be packaged into a "desktop" sized unit. Herein we demonstrate that SFM PPT reliably and rapidly sterilizes ubiquitous and sensitive electronic devices (cellphones) that are well known to harbor a variety of microorganisms, and does so within minutes without damaging the device itself or leaving behind any residue. Further, treatment of intact and wounded skin is not harmful.
METHODS:
To demonstrate SFM PPT sterilization, cellphone bacterial colonization pre- and post-treatment was evaluated. Cellphones from medical personnel were aseptically swabbed and streaked onto trypticase soy agar (TSA) pre- and post-10-minute treatment. Bacterial colony forming units (CFU) before and after SFM PPT treatment were quantified, and bacterial speciation was determined. To demonstrate SFM PPT's safety on wounds, two 8mm, full-thickness, splinted excisional wounds were created on both sides of dorsal midline of C57bl/6 mice. Experimental mice were placed in the SFM PPT sterilization compartment while their heads remained outside of the compartment via a snug exit site so as to prevent effluent inhalation while simultaneously maintaining the closed looped system. Mice were treated once for 10, 30 or 60 minutes and sacrificed 7 or 14 days after wounding.
RESULTS:
After 24 hours of incubation mean numbers of CFU grown from untreated cellphone swabs were: 8.18±9.41 CFU on blood, 7.64±5.73 CFU on chocolate, 2.91±3.91 CFU on CNA, and 0 CFU on MacConkey agar. Ten minute SFM PPT treatment eliminated bacterial growth on all cellphones, with 0 CFU grown from all TSA plates after 24 hours of incubation. Six staphylococcus species, including S. aureus, and Kocuria kristinae were grown from cellphones. SFM PPT did not physically or functionally damage any cellphone. After NTAP treatment of wounded mice there was no gross or histological evidence of residue, aberrant dermal architecture, infection, or edema. Harvested wounds were cut in half, and the mean length spanning dermal edge to opposite dermal edge was quantified. By day 7, wounds treated for 10 minutes demonstrated faster wound healing with statistically smaller wound widths than controls (4.8mm±0.3mm vs 7.1mm±0.4mm, p<0.01). There was no difference between control and 30 or 60 min treated wound widths. By day 14, all wounds demonstrated complete re-epithelialization/healing.
CONCLUSIONS:
Effective against a wide variety of microorganisms, SFM PPT is a novel, low cost, and portable technology that has the potential to revolutionize the current practice of device sterilization in both industrial and private settings. Further, NTAP appears safe when applied to living tissue and may even promote wound healing through a yet undiscovered mechanism.