Cold atmospheric plasmas (CAPs) within recent years have shown great promise in the field of plasma medicine, encompassing a variety of treatments from wound healing to the treatment of cancerous tumors. For each subsequent treatment, a different application of CAPs has been postulated and attempted to best treat the target for the most effective results. These treatments have varied through the implementation of control parameters such as applied settings, electrode geometries, gas flow, and the duration of the treatment. However, with such an extensive number of variables to consider, scientists and engineers have sought a means to accurately control CAPs for the best-desired effects in medical applications. This paper seeks to investigate and characterize the historical precedent for the use of plasma control mechanisms within the field of plasma medicine. Current control strategies, plasma parameters, and control schemes will be extrapolated through recent developments and successes to gain better insight into the future of the field and the challenges that are still present in the overall implementation of such devices. Proposed approaches, such as data-driven machine learning, and the use of closed-loop feedback controls, will be showcased as the next steps toward application.

Introduction. Aspergillus flavus and Fusarium keratoplasticum are common causative pathogens of fungal keratitis (FK), a severe corneal disease associated with significant morbidity and vision loss. Escalating incidence of antifungal resistance to available antifungal drugs poses a major challenge to FK treatment. Cold atmospheric plasma (CAP) is a pioneering nonpharmacologic antimicrobial intervention that has demonstrated potential as a broad-spectrum antifungal treatment. Gap statement. Previous research highlights biofilm-associated resistance as a critical barrier to effective FK treatment. Although CAP has shown promise against various fungal infections, its efficacy against biofilm and conidial forms of FK pathogens remains inadequately explored. Aim. This study aims to investigate the antifungal efficacy of CAP against clinical fungal keratitis isolates of A. flavus and F. keratoplasticum in vitro. Methodology. Power parameters (22–27 kV_pp, 300–400 Hz and 20–80 mA) of a dielectric barrier discharge CAP device were optimized for inactivation of A. flavus biofilms. Optimal applied voltage and total current were applied to F. keratoplasticum biofilms and conidial suspensions of A. flavus and F. keratoplasticum. The antifungal effect of CAP treatment was investigated by evaluating fungal viability through means of metabolic activity, c.f.u. enumeration (c.f.u. ml⁻¹) and biofilm formation. Results. For both fungal species, CAP exhibited strong time-dependent inactivation, achieving greater than 80 % reduction in metabolic activity and c.f.u. ml⁻¹ within 300 s or less, and complete inhibition after 600 s of treatment. Conclusion. Our findings indicate that CAP is a promising broad-spectrum antifungal intervention. CAP treatment effectively reduces fungal viability in both biofilm and conidial suspension cultures of A. flavus and F. keratoplasticum, suggesting its potential as an alternative treatment strategy for fungal keratitis.

The purpose of this study is to evaluate sublethal cold atmospheric plasma (CAP) treatment of filamentous fungal pathogen susceptibility to commonly used antifungal drugs in vitro. Response to CAP in combination with voriconazole, fluconazole, amphotericin B, and caspofungin was evaluated in Aspergillus flavus and Fusarium keratoplasticum conidia and mycelium; conidial response to fluconazole was also assessed in three strains of F. falciforme. Conidial susceptibility to antifungal drugs alone or in combination with CAP was assessed using a modified CLSI broth microdilution assay with MIC determination and colony-forming unit (CFU) enumeration. Mycelial viability and biofilm thickness changes in response to antifungal drugs alone or in combination with CAP were assessed over 24 hours post treatment. CAP enhanced antifungal drug efficacy against all fungal species, though effects differed by drug and growth form. CAP enhanced antifungal drug susceptibility in conidia, with the strongest effect observed for F. keratoplasticum conidia, where caspofungin MIC decreased fourfold (from 16 to 4−8 μg/mL) and sensitivity to fluconazole, which exerted no effect in absence of CAP, was restored when combined with sublethal CAP treatment. In A. flavus, CAP lowered the MIC of voriconazole (from 0.25 to 0.06–0.125 μg/mL) but increased the MIC of amphotericin B (from 4 to >4 μg/mL), despite reductions in viable cell counts. Differential responses to CAP and fluconazole were observed across three strains of F. falciforme, suggesting variability in CAP response. In treated biofilms, CAP alone initially reduced mycelial viability and biofilm thickness, but partial recovery of the fungus was observed over time in most cases. When combined with antifungal drugs, CAP significantly enhanced reduction of mycelial viability and thickness beyond antifungal treatment alone. In F. keratoplasticum biofilms, the combination of CAP and antifungal drugs produced sustained reductions in mycelial viability and biofilm thickness, whereas A. flavus biofilms were more resistant to CAP treatment and exhibited consistent recovery after 24 hours.

Cold atmospheric plasmas (CAP) are a versatile tool in medical applications like wound healing. Its therapeutic benefits are partially attributed to the generation of biologically active reactive oxygen and nitrogen species (RONS). Characterization of RONS, however, typically only occurs after treatment. Here we report the first real-time in situ detection of CAP-generated nitric oxide (NO), and the simultaneous detection of cellular calcium ions (Ca²⁺) release using electrochemical sensors during CAP treatment of murine wounds. In vivo, NO rose rapidly within the first minute of CAP treatment but accumulated less overall than in PBS, reflecting reactions with wound-bed targets. In situ measurements revealed nearly double the concentrations of static endpoint assays, underscoring the importance of real-time detection. Ca²⁺ signals displayed transient, burst-like increases, likely due to CAP-induced membrane permeability and as response to oxidative stress. We also investigated the sensitivity, selectivity, and stability of the graphene oxide coated NO sensors and ion-selective Ca²⁺ sensors. Interference studies showed that the NO sensor also responds to H ₂ O ₂ and NO ₂ ⁻ yet remains most sensitive to NO. Raman microscopy revealed progressive degradation of the graphene oxide layer after only one hour of CAP exposure, drastically reducing sensor currents. Improvements in NO sensor design will enable more accurate measurements for feedback control for plasma-based wound therapies. Ca²⁺ sensors are more robust and retained full functionality after three hours and repeated use providing a reliable diagnostic for immediate biological response. The results establish real-time electrochemical sensing as a powerful approach to monitor CAP-tissue interactions.