Microplasma Jet Arrays as a Therapeutic Choice for Fungal Keratitis

A miniature and efficient colorimetric system assisted by the microplasma jet array for Cr (VI) detection

Microplasma jet (MPJ), serving as excitation sources in miniaturized systems, has been widely used for contaminant detection. However, the employment of the MPJ is conditioned due to the limit generation of the radicals. Here, a novel 4-channel microplasma jet array (MPJA) is designed for 3,3,5,5-tetramethylbenzidine (TMB) rapid oxidation without oxidizing reagents and catalysts. The jet array, generated from a ceramic tube, allows direct contact with the sample. A colorimetric system containing the MPJA has been developed for the detection of hexavalent chromium. Compared to the MPJ, the employment of MPJA significantly makes the detection system effective and sensitive. Under optimal operating condition, the system exhibits a linear response for Cr (VI) detection within the range of 0.3-1.2 μmol L-1, with a detection limit (LOD) of 0.11 μmol L-1. The practicality of the system is validated through the analysis of real-world samples. The system can be packed into a case with 40 cm in length, 30 cm in width and 30 cm in height. The power consumption is 0.052 W. The system provides a potential method for samples determination in emergency.

Low-temperature plasma jet suppresses bacterial colonisation and affects wound healing through reactive species

An argon-based low-temperature plasma jet (LTPJ) was used to treat chronically infected wounds in Staphylococcus aureus-laden mice. Based on physicochemical property analysis and in vitro antibacterial experiments, the effects of plasma parameters on the reactive nitrogen and oxygen species (RNOS) content and antibacterial capacity were determined, and the optimal treatment parameters were determined to be 4 standard litre per minute and 35 W. Additionally, the plasma-treated activation solution had a bactericidal effect. Although RNOS are related to the antimicrobial effect of plasma, excess RNOS may be detrimental to wound remodelling. In vivo studies demonstrated that medium-dose LTPJ promoted MMP-9 expression and inhibited bacterial growth during the early stages of healing. Moreover, LTPJ increased collagen deposition, reduced inflammation, and restored blood vessel density and TGF-β levels to normal in the later stages of wound healing. Therefore, when treating chronically infected wounds with LTPJ, selecting the medium dose of plasma is more advantageous for wound recovery. Overall, our study demonstrated that low-temperature plasma jets may be a potential tool for the treatment of chronically infected wounds.

The efficacy of a device-based approach to microorganism disinfection and protein removal for orthokeratology lenses in varied clinical circumstances

PURPOSE

RigidCare is an electrolysis-based device that recently obtained approval from the US's FDA to sterilise microorganisms and remove proteins for orthokeratology (O-K) lenses. The study was conducted to investigate the device's performance in varied clinical circumstances.

METHODS

Trial lenses and private lenses were employed by O-K lens wearers from five hospitals for an evaluation of disinfection and sterilisation and an assessment of protein removal, respectively. Menicon multipurpose solution and protein remover were selected for use with the control group. Following the instructions, pre-cleaning lens samples, post-cleaning lens samples and residual solution samples of trial lenses of the experimental and control groups were collected for microorganism examinations by an experienced third-party testing organisation. The levels of protein deposition for these two approaches were rated by senior O-K experts. Categorical variables were analysed using statistical tests, such as the chi-squared test and Fisher's exact test.

RESULTS

The microbial positive rate detected from the pre-cleaning and post-cleaning lens samples and the residual solution of the trial lenses for the experimental and control group was 4/76 vs 1/74 (P = 0.37), 1/76 vs 0/74 (P = 1.00) and 0/76 vs 8/74 (P = 0.006), respectively. Following protein removal, the experimental group exhibited a significantly higher overall proportion of lenses rated as 'clean' or with a 'mild deposit' (96.4 %, 79/82) compared to the control group (85.7 %, 66/77), with a significant difference (P < 0.05).

CONCLUSION

This multi-center study demonstrated that RigidCare exhibited superior efficacy in disinfection, sterilisation and protein removal as compared to Menicon multipurpose solution and protein remover.

Low-Temperature Plasma Techniques in Biomedical Applications and Therapeutics: An Overview

Plasma, the fourth fundamental state of matter, comprises charged species and electrons, and it is a fascinating medium that is spread over the entire visible universe. In addition to that, plasma can be generated artificially under appropriate laboratory techniques. Artificially generated thermal or hot plasma has applications in heavy and electronic industries; however, the non-thermal (cold atmospheric or low temperature) plasma finds its applications mainly in biomedicals and therapeutics. One of the important characteristics of LTP is that the constituent particles in the plasma stream can often maintain an overall temperature of nearly room temperature, even though the thermal parameters of the free electrons go up to 1 to 10 keV. The presence of reactive chemical species at ambient temperature and atmospheric pressure makes LTP a bio-tolerant tool in biomedical applications with many advantages over conventional techniques. This review presents some of the important biomedical applications of cold-atmospheric plasma (CAP) or low-temperature plasma (LTP) in modern medicine, showcasing its effect in antimicrobial therapy, cancer treatment, drug/gene delivery, tissue engineering, implant modifications, interaction with biomolecules, etc., and overviews some present challenges in the field of plasma medicine.

Construction of a Compact Array of Microplasma Jet Devices and Its Application for Random Mutagenesis of Rhodosporidium toruloides

A small and efficient DNA mutation-inducing machine was constructed with an array of microplasma jet devices (7 × 1) that can be operated at atmospheric pressure for microbial mutagenesis. Using this machine, we report disruption of a plasmid DNA and generation of mutants of an oleaginous yeast Rhodosporidium toruloides. Specifically, a compact-sized microplasma channel (25 × 20 × 2 mm3) capable of generating an electron density of greater than 1013 cm-3 was constructed to produce reactive species (N2*, N2+, O, OH, and Hα) under helium atmospheric conditions to induce DNA mutagenesis. The length of microplasma channels in the device played a critical role in augmenting both the volume of plasma and the concentration of reactive species. First, we confirmed that microplasma treatment can linearize a plasmid by creating nicks in vitro. Second, we treated R. toruloides cells with a jet device containing 7 microchannels for 5 min; 94.8% of the treated cells were killed, and 0.44% of surviving cells showed different colony colors as compared to their parental colony. Microplasma-based DNA mutation is energy-efficient and can be a safe alternative for inducing mutations compared to conventional methods using toxic mutagens. This compact and scalable device is amenable for industrial strain improvement involving large-scale mutagenesis.

Clinical Observation of Low-Temperature Plasma Ablation Combined with Drug Therapy in the Treatment of Fungal Keratitis

Objective

To observe the efficacy and prognosis of low-temperature plasma ablation + drug therapy in the treatment of fungal corneal ulcers.

Methods

The present paper presents a retrospective clinical study with a subject base of 34 eyes. Patients with a fungal corneal ulcer who visited the Affiliated Eye Hospital of Nanchang University between August 2019 and December 2021 were selected as the study participants. They were found to have highly reflective fungal hyphae in the corneal stroma layer via confocal microscope examination, which were revealed to be positive on etiology examination, with the ulcer and infiltration depths ≤1/2 of the corneal thickness. The efficacy and prognosis were observed after treatment with low-temperature plasma ablation + drug therapy.

Results

A total of 34 cases (34 eyes) had clinical manifestations of corneal infiltration and corneal ulcer formation, with a corneal lesion diameter of 1.31-8.64 mm (average = 4.79 ± 2.03 mm). The average healing time of corneal ulcers was 6.2 ± 1.7 days. Among a total of 34 cases (34 eyes) in patients with fungal keratitis, the infection was controlled and the ulcers gradually healed after treatment with low-temperature plasma system + drug therapy in a total of 30 cases (30 eyes, 88%). A total of three cases (3 eyes, 9%) exhibited no clear improvement after the treatment, and the patients underwent conjunctival flap covering surgery. One case (one eye, 3%) exhibited no clear improvement after further treatment, with the patient experiencing corneal perforation and ultimately undergoing penetrating keratoplasty.

Conclusion

Low-temperature plasma ablation + drug therapy can effectively control the progression of fungal keratitis infection, as well as significantly shorten the ulcer healing time, and is, therefore, an effective method.

Clinical Investigation of the Safety and Efficacy of Low-temperature Plasma as an Adjuvant Treatment for Mild to Moderate Fungal Keratitis: A Pilot Study

PURPOSE

This pilot study assessed the safety and efficacy of low-temperature plasma (LTP) as an adjuvant treatment for mild to moderate fungal keratitis (FK).

METHODS

Thirty FK patients were randomized into LTP (n = 15) and control (n = 15) groups. Patients were followed up for 3 months. The best-corrected visual acuity (BCVA), ulcer size, and hypopyon height were measured; healing time or complications were documented and compared.

RESULTS

More patients in the LTP group healed completely (11/15 in 48 days) compared with the control group (4/15 in 59.5 days), and those patients had a deeper initial ulcer depth and exhibited better BCVA improvements. Four patients failed after LTP treatment due to perforation, increased inflammatory infiltration, or hypopyon; those with more hypopyon were more likely to fail.

CONCLUSIONS

LTP could be a promising adjuvant therapy to topical antifungal drugs for mild to moderate FK.

The Nanosecond Impulsive Breakdown Characteristics of Air, N2 and CO2 in a Sub-mm Gap

The present paper investigates the breakdown characteristics—breakdown voltage, with breakdown occurring on the rising edge of the applied HV impulses, and time to breakdown—for gases of significance that are present in the atmosphere: air, N2 and CO2. These breakdown characteristics have been obtained in a 100 µm gap between an HV needle and plane ground electrode, when stressed with sub-µs impulses of both polarities, with a rise time up to ~50 ns. The scaling relationships between the reduced breakdown field Etip/N and the product of the gas number density and inter-electrode gap, Nd, were obtained for all tested gases over a wide range of Nd values, from ~1020 m−2 to ~1025 m−2. The breakdown field-time to breakdown characteristics obtained at different gas pressures are presented as scaling relationships of Etip/N, Nd, and Ntbr for each gas, and compared with data from the literature.

Treatment of Fungal-Infected Diabetic Wounds with Low Temperature Plasma

Diabetes mellitus renders patients susceptible to chronic wounds and various infections. Regarding the latter, fungal infections are of particular concern since, although they are the source of significant morbidity and mortality in immunocompromised patients, they are generally resistant to conventional treatment and a definite treatment strategy has not yet been established. Herein, we report the treatment of skin wounds in a diabetic rat model, infected by Candida albicans, with low temperature helium plasma generated in a hand-held atmospheric jet device. A fungal infection was induced on two dorsal skin wounds of the diabetic rats, and one wound was treated with the plasma jet whereas the other served as a control. Histological analysis revealed accelerated skin wound healing and decreased evidence of fungal infection in the plasma-treated group, as compared to the control group. Regeneration of the epidermis and dermis, collagen deposition, and neovascularization were all observed as a result of plasma treatment, but without wound contraction, scar formation or any evidence of thermal damage to the tissue. These findings demonstrate that the He plasma jet is remarkably effective in diabetic skin wounds infected by Candida albicans, thereby providing a promising medical treatment option for diabetes mellitus patients with skin wound and fungal infections.

Inactivation and sensitization of Pseudomonas aeruginosa by microplasma jet array for treating otitis media

Otitis media (OM), known as a middle ear infection, is the leading cause of antibiotic prescriptions for children. With wide-spread use of antibiotics in OM, resistance to antibiotics continues to decrease the efficacy of the treatment. Furthermore, as the presence of a middle ear biofilm has contributed to this reduced susceptibility to antimicrobials, effective interventions are necessary. A miniaturized 3D-printed microplasma jet array has been developed to inactivate Pseudomonas aeruginosa, a common bacterial strain associated with OM. The experiments demonstrate the disruption of planktonic and biofilm P. aeruginosa by long-lived molecular species generated by microplasma, as well as the synergy of combining microplasma treatment with antibiotic therapy. In addition, a middle ear phantom model was developed with an excised rat eardrum to investigate the antimicrobial effects of microplasma on bacteria located behind the eardrum, as in a patient-relevant setup. These results suggest the potential for microplasma as a new treatment paradigm for OM.

The Antifungal and Ocular Permeation of Ketoconazole from Ophthalmic Formulations Containing Trans-Ethosomes Nanoparticles

Ketoconazole (KET), a synthetic imidazole broad-spectrum antifungal agent, is characterized by its poor aqueous solubility and high molecular weight, which might hamper its corneal permeation. The aim was to develop an ophthalmic formulation loaded with optimized trans-ethosomal vesicles to enhance KET ocular permeation, antifungal activity, rapid drug drainage, and short elimination half-life. Four formulation factors affecting the vesicles' size, zeta potential, entrapment efficiency, and flexibility of the trans-ethosomes formulations were optimized. The optimum formulation was characterized, and their morphological and antifungal activity were studied. Different ophthalmic formulations loaded with the optimized vesicles were prepared and characterized. The ocular irritation and in vivo corneal permeation were investigated. Results revealed that the drug-to-phospholipid-molar ratio, the percentage of edge activator, the percentage of ethanol, and the percentage of stearyl amine significantly affect the characteristics of the vesicles. The optimized vesicles were spherical and showed an average size of 151.34 ± 8.73 nm, a zeta potential value of +34.82 ± 2.64 mV, an entrapment efficiency of 94.97 ± 5.41%, and flexibility of 95.44 ± 4.33%. The antifungal activity of KET was significantly improved following treatment with the optimized vesicles. The developed in situ gel formulations were found to be nonirritating to the cornea. The trans-ethosomes vesicles were able to penetrate deeper into the posterior eye segment without any toxic effects. Accordingly, the in situ developed gel formulation loaded with KET trans-ethosomes vesicles represents a promising ocular delivery system for the treatment of deep fungal eye infections.

Evaluation of the Safety and Efficacy of a Low-Temperature Plasma Surgical System for Pterygium

Purpose:

Surgical excision is the standard treatment for pterygium. This study was conducted to evaluate the safety and efficacy of a novel technique using low-temperature plasma (LTP) for excision and hemostasis in pterygium surgery.

Methods:

A prospective, comparative, and randomized clinical trial was conducted on 60 patients (60 eyes) undergoing pterygium excision with conjunctival autografts using fibrin glue. Patients were equally divided into the following 2 groups: a control group and a LTP group. Postoperative follow-up visits were scheduled on day 1, week 1, and months 1 and 3, and recurrence was evaluated at 1 year. Patients were examined for operative time, best corrected visual acuity, conjunctival autograft inflammation (CAI), graft stability (GS), pain, recurrence, and final appearance. Factors related to pterygium recurrence and final appearance were analyzed.

Results:

Mean operative times were shorter in the LTP group (16.7 ± 3.4 min) than those in the control group (20.1 ± 4.7 min, P = 0.002). LTP eyes had milder CAI than control eyes at postoperative day 1 (P = 0.000) and week 1 (P = 0.000). Patients in the LTP group exhibited better GS (P = 0.01) and milder pain (P = 0.04) than those in the control group on day 1. Two control patients (6.7%) and no (0%) LTP patients experienced recurrence (P = 0.08). GS and CAI were the significant factors contributing to recurrence (GS: R = 0.425, P = 0.001; CAI: R = 0.309, P = 0.016).

Conclusions:

LTP to replace surgical blades and disposable cautery for ablation and hemostasis is safe and efficient for pterygium surgery, resulting in shorter operative time, milder inflammation, and better graft stability without increasing complication risk.

Revealing Plasma-Surface Interaction at Atmospheric Pressure: Imaging of Electric Field and Temperature inside the Targeted Material

The plasma-surface interaction is studied for a low temperature helium plasma jet generated at atmospheric pressure using Mueller polarimetry on an electro-optic target. The influence of the AC kHz operating frequency is examined by simultaneously obtaining images of the induced electric field and temperature of the target. The technique offers high sensitivity in the determination of the temperature variation on the level of single degrees. Simultaneously, the evolution of the electric field in the target caused by plasma-driven charge accumulation can be measured with the threshold of the order of 10⁵ V/m. Even though a specific electro-optic crystal is used to obtain the results, they are generally applicable to dielectric targets under exposure of a plasma jet when they are of 0.5 mm thickness, have a dielectric constant greater than 4 and are at floating potential. Other techniques to examine the induced electric field in a target do not exist to the best of our knowledge, making this technique unique and necessary. The influence of the AC kHz operating frequency is important because many plasma jet designs used throughout the world operate at different frequency which changes the time between the ionization waves and hence the leftover species densities and stability of the plasma. Results for our jet show a linear operating regime between 20 and 50 kHz where the ionization waves are stable and the temperature increases linearly by 25 K. The charge deposition and induced electric fields do not increase significantly but the surface area does increase due to an extended surface propagation. Additionally, temperature mapping using a 100 μm GaAs probe of the plasma plume area has revealed a mild heat exchange causing a heating of several degrees of the helium core while the surrounding air slightly cools. This peculiarity is also observed without plasma in the gas plume.