Disinfection Potential Research Articles

The potential of Moringa oleifera seeds for fungal disinfection in water

Water contamination by fungi has earned more attention by numerous researchers, while disinfection is one of the primary methods used in drinking water treatment process to remove bacteria or fungi. In this work, a pilot study on the characterization and the performance of the regrowth fungal spores on Moringa oleifera (MO) disinfection process were investigated. Firstly, an active compound in MO seeds was extracted and characterized via Fourier-transform infrared (FTIR) and scanning electron microscopy (SEM) analyses. The extract MO then underwent a comparison set of disinfection studies without any disinfectant at different time to evaluate its performance in reducing the growth of fungal spores in water. The disinfection study reveals that fungi's spore’s growth decreased from 71% to 60% from day two until day seven. In addition, these findings indicate that extract MO seeds may be a potential disinfectant for the growth of fungi in drinking water.

Comparative Evaluation of Antimicrobial Activity of Irreversible Hydrocolloid Impression Material Incorporated with Various Disinfectants – An In-vitro Study

Background: Blood and saliva can easily contaminate the dental impressions. It contains variety of bacteria, fungi, and viruses which causes cross infection to health personnel & environment. Therefore, sterilizing the impression material is the best way to avoid disease transmission. Spraying and Immersion technique are conventional methods of disinfection of irreversible hydrocolloid impression material but in both of these techniques impression is disinfected only on the surface. Self-disinfecting impression are disinfected throughout the impression material. This study categorized various disinfectants into Chemical, Herbal & Physical. Nanoparticles and herbal disinfectants are mixed with irreversible hydrocolloid impression material, which will suggest its antimicrobial activity.
 Aim & Objectives: To evaluate and compare antimicrobial-activity of irreversible hydrocolloid impression materials incorporated with various disinfectants.
 Methodology: Commercially existing irreversible hydrocolloid impression materials will be used in the study. The disinfectants used will be chlorhexidine, silver nanoparticles and cinnamon. The selected disinfectants will be added into the irreversible hydrocolloid at the manipulation stage and their antimicrobial activity will be evaluated using the “Kirby Bauer Disk Diffusion Method” against the selected microorganisms.
 Expected Outcome: Differential Antimicrobial activity of Chlorhexidine, Silver Nanoparticle and Cinnamon when added to irreversible hydrocolloid for disinfection of impressions.
 Conclusion: Addition of various disinfectants in irreversible hydrocolloid may imbibe the antimicrobial activity within the impression materialand with the comparative investigations, more potent disinfectant can be applicable for clinical use as per findings of the present study.

Microbiome response to foam fractionation and ozonation in RAS

Efficient water treatment is required to maintain high water quality and control microbial growth in recirculating aquaculture systems (RAS). Here, we examined the effects of two treatment methods, ozonation and foam fractionation, separately and combined, on the microbiology in twelve identical experimental RAS with rainbow trout (Oncorhyncus mykiss) during 8 weeks. Microbes suspended in water and growing in biofilter biofilms were examined using flow cytometry analysis and high throughput sequencing of the 16S rRNA gene. The results showed that foam fractionation did not cause large changes in abundance or overall community composition of free-living microbes. Instead, through decreasing the organic matter availability in water, it targeted specific microbial taxa, leading to e.g. decreased potential for off-flavor production. In contrast, ozonation was found to have a profound impact on the system microbiology, by reducing the overall cell abundance, increasing microbial dead/live ratio, and changing the community composition of both free-living and biofilm microbes. Ozonation increased the abundance of certain key microbial taxa adapted to low carbon conditions, which might form a stable and more abundant community under a prolonged ozone dosing. Combining the two treatment methods did not provide any additional benefits as compared to ozonation solely, corroborating the high disinfection potential of ozone. However, ozone had only a minor impact on biofilter microbial communities, which were, in general, more resistant to water treatment than water communities. Water treatment had no effect on the overall genetic nitrification potential in the biofilter biofilms. However, foam fractionation led to changes in the nitrifying microbial community in biofilter, increasing the abundance of Nitrospira conducting complete ammonia oxidation to nitrate (comammox). Altogether, the results obtained indicate that although these two water treatment methods have similar outcomes on physico-chemical water quality and microbial activity, their underlying mechanisms are different, potentially leading to different outcomes under the long-term application.

Corrosion Inhibition of Peracetic Acid‐Based Disinfectants

AbstractPeracetic acid (PAA) is a highly potent disinfectant, exhibiting an outstandingly broad spectrum of activity against various microorganisms and viruses. Nevertheless, one disadvantage when applying PAA for disinfection purposes is the strongly corrosive effect due to its oxidizing properties. The employment of a nonionic surfactant as corrosion inhibitor was evaluated in addition to adjustment of the pH value of the solution, regarding the materials aluminum, stainless steel, copper, brass, polyvinyl chloride, wood, and ceramics. Whereas unmodified PAA solution led to strong corrosive effects on the material surface, this impact was significantly lowered when the pH value was shifted to 7. When in addition a nonionic surfactant was applied, no corrosion phenomena at all were observed.

Photocatalytic disinfection of micro-organisms: Mechanisms and applications

Microbial contamination has globally represented an extreme health risk to human beings. Bacteria, fungi, algae and viruses being minuscule possess excessive ecological toxicity and a wide range of diseases to an aquatic and terrestrial existence Recently, photocatalytic disinfection has acquired ever-growing worldwide attention due to its energy conversion and disinfection potential. Diverse factors such as the type of photocatalytic material employed for the disinfection process and micro-organisms significantly influence the disinfection technique. There are different novel photocatalysts including TiO2, graphitic carbon nitride (g-C3N4), nanocomposites and membranes that have been developed for microbial disinfection in land and water surfaces. Photocatalytic disinfection is majorly dependent on different operational parameters such as photocatalysts dosage, pH, light source, and temperature. Photocatalysts possess antimicrobial properties which might also contribute to the expulsion of micro-organisms from surfaces. Cell membrane degradation mechanism which governs the performance of photocatalytic disinfection is reviewed in detail. The review describes the fundamental mechanism of photocatalytic disinfection. The development of novel photocatalysts for the disinfection of bacteria, fungi, viruses and algae has been reviewed in detail. In addition, different parameters that affect the performance of photocatalytic disinfection are reviewed. Applications of photocatalytic disinfection of microorganisms and future perspectives are discussed.

Assessment of Disinfection Potential of Q-Switch Nd: YAG Laser on Contaminated Titanium Implant Surfaces.

Peri-implantitis (PI) is a relatively frequent pathology that compromises the overall survival of the dental implant. Adjunctive approaches for the conventional mechanical debridement are being suggested to optimize the treatment of PI. The goal of the study was the assessment of the disinfection potential of the Q-Switch Nd: YAG laser on contaminated titanium implant surfaces. A total of 72 sterile titanium discs were used and divided into three groups: 24 contaminated titanium discs treated with the laser (study Group L), 24 contaminated titanium discs with no treatment (control 1—Group C), and 24 sterile titanium discs with no treatment (control 2—Group S). Multi-species biofilm was used: Porphyromonas gingivalis, Fusobacterium nucleatum, Aggregatibacter actinomycetemcomitans, Streptococcus mutans, Streptococcus sobrinus, and Prevotella intermedia. Commensal bacteria were included also: Actinomyces naeslundii, Actinomyces viscosus, Streptococcus cristatus, Streptococcus gordonii, Streptococcus mitis, Streptococcus oralis, Streptococcus sanguinis, Streptococcus parasanguinis, and Veillonella parvula. Parameters delivered per pulse on the targeted surfaces of the titanium discs were an energy density of 0.597 J/cm2 each pulse, a pulse power of 270 mW, a laser beam spot of 2.4 mm in diameter, and a rate of repetition of 10 Hertz (Hz) for a pulse duration of 6 nanoseconds (ns). The mode was no contact, and a distance of 500 micrometers was used with a total time of irradiation equal to 2 s (s). The collection of microbiological samples was made for all groups; colony-forming units (CFU) were identified by two different practitioners, and the average of their examinations was considered for each sample. The average of the TBC (CFU/mL) was calculated for each group. Values were 0.000 CFU/mL, 4767 CFU/mL, and 0.000 CFU/mL for Group L, Group C, and Group S, respectively. Therefore, the suggested treatment protocol was able to provoke a total disinfection of the contaminated titanium surfaces. A statistical difference was only found between Group L vs. Group C and between Group S vs. Group C. The difference was not significant between Group S and Group L. In conclusion, the present study confirmed that the Q-Switch Nd: YAG laser under our specific conditions can provide a total disinfection of the contaminated titanium surfaces.

The electrochemical oxidation of chloride on Pt-Ni-Co-G electrodes and its application in in-situ disinfection of water

In-situ chlorine generation has high disinfection potential for small to medium scale water treatment systems. Electrodes were prepared by coating Pt-, Ni-, Co-oxides on graphite substrate using electrodeless deposition method and characterized with SEM, EDS, XRD, XPS and cyclic voltammetry. Results showed that the molar ratio of Ni- and Co-oxides on graphite surface influenced surface structure and in-situ chlorine generation capacity. Pt0.01Ni0.24Co0.75 electrode exhibited a unique surface structure and the highest in-situ chlorine generation capability. The Pt0.01Ni0.24Co0.75-G electrode exhibited highly porous 3D structure and high oxygen deficit, which significantly promoted the formation of M-Cl− binding on electrode surface and enhanced chlorine generation. The onset of chlorine evolution potential was lower than that of oxygen on Pt0.01Ni0.24Co0.75-G electrode. Moreover, the transfer coefficient of chloride oxidation was smaller than that of water oxidation, which would enhance chloride oxidation current efficiency. The in-situ chlorine generation capability increased with NaCl concentration. The kinetics of chlorine generation was well described by the Langmuir-Hinsheldwood mechanism. The in-situ disinfection rate decreased with the increase in initial E. coli density. A 7.5-log disinfection was achieved in 15 min in the presence of 0.01 M NaCl under 5 mA/cm2 current density at room temperature. The lipid peroxide, morphology changes and destruction of E. coli cell membrane were observed in the in-situ disinfection process, indicating that reactive species such as chlorine radical in addition to free chlorine played the main role of in-situ disinfection.

Copper/Carbon Core/Shell Nanoparticles: A Potential Material to Control the Fish Pathogen Saprolegnia parasitica.

Copper-based fungicides have a long history of usage in agriculture and aquaculture. With the rapid development of metal-based nanoparticles, copper-based nanoparticles have attracted attention as a potential material for prevention and control of Saprolegnia parasitica. The present study investigated the effectiveness of copper/carbon core/shell nanoparticles (CCCSNs) and a commercial CCCSNs filter product (COPPERWARE®) against S. parasitica in a recirculating system. Results showed that the growth of agar plugs with mycelium was significantly suppressed after exposure to both CCCSNs powder and COPPERWARE® filters. Even the lowest concentration of CCCSNs used in our study (i.e., 100 mg/mL) exhibited significant inhibitory effects on S. parasitica. The smallest quantity of the filter product COPPERWARE® (3.75 × 3.7 × 1.2 cm, 2.58 g) used in our aquarium study also demonstrated significant inhibition compared with the control group. However, we observed leaching of copper into the water especially when larger quantities of COPPERWARE® were used. Water turbidity issues were also observed in tanks with the filter material. Besides these issues, which should be further investigated if the product is to be used on aquatic species sensitive to copper, CCCSNs has promising potential for water disinfection.

Spatial disinfection potential of slightly acidic electrolyzed water.

Slightly acidic electrolyzed water (SAEW) was developed by Japanese companies over 20 years ago. SAEW has the advantage of potent sterilizing action while being relatively safe. This study evaluated the potential application of SAEW in spatial disinfection. Prior to experiments involving spatial spraying, the ability of SAEW to remove seven type of microorganisms that cause food poisoning was studied in vitro. Results indicated that free chlorine in SAEW, even at a low concentration (30 mg/L), was able to remove Cladosporium cladosporioides, a typical airborne fungus that degrades food, and spores such as Bacillus subtilis, a hardy bacterium. In an experiment involving spatial spraying, 3.43 log10 CFU/100 L of Staphylococcus epidermidis was sprayed in a room-sized space; the same space was then sprayed with SAEW. The number of settling microbes was measured and the sterilizing ability of SAEW was assessed. Results indicated that the concentration of S. epidermidis in the space was completely removed after 20 minutes of SAEW spraying. The above findings indicate that SAEW may be used to remove airborne microorganisms via spatial spraying.

Facile fabrication of antibacterial and antiviral perhydrolase-polydopamine composite coatings

In situ generation of antibacterial and antiviral agents by harnessing the catalytic activity of enzymes on surfaces provides an effective eco-friendly approach for disinfection. The perhydrolase (AcT) from Mycobacterium smegmatis catalyzes the perhydrolysis of acetate esters to generate the potent disinfectant, peracetic acid (PAA). In the presence of AcT and its two substrates, propylene glycol diacetate and H2O2, sufficient and continuous PAA is generated over an extended time to kill a wide range of bacteria with the enzyme dissolved in aqueous buffer. For extended self-disinfection, however, active and stable AcT bound onto or incorporated into a surface coating is necessary. In the current study, an active, stable and reusable AcT-based coating was developed by incorporating AcT into a polydopamine (PDA) matrix in a single step, thereby forming a biocatalytic composite onto a variety of surfaces. The resulting AcT-PDA composite coatings on glass, metal and epoxy surfaces yielded up to 7-log reduction of Gram-positive and Gram-negative bacteria when in contact with the biocatalytic coating. This composite coating also possessed potent antiviral activity, and dramatically reduced the infectivity of a SARS-CoV-2 pseudovirus within minutes. The single-step approach enables rapid and facile fabrication of enzyme-based disinfectant composite coatings with high activity and stability, which enables reuse following surface washing. As a result, this enzyme-polymer composite technique may serve as a general strategy for preparing antibacterial and antiviral surfaces for applications in health care and common infrastructure safety, such as in schools, the workplace, transportation, etc.

Formation of bio-responsive nanocomposites for targeted bacterial bioimaging and disinfection

The increasing emergence of pathogenic bacterial infection have been regarded as urgent threats. Notwithstanding, developing simplified and effective means for accurate bacterial target diagnosis and therapy remains a considerable challenge. Here we report a reasonable method for accurate and rapid theranostic of bacteria by in situ self-assembly strategy. By introducing aqueous gold and zinc ions into E.coli cells, the gold and zinc nanoclusters (NCs) could be spontaneously constructed by utilizing the in situ self-assemble biosynthetic strategy that takes advantage of the unique microenvironment of pathogenic bacteria and efficiently enhanced the uptake of DNA into the bacteria cells in the presence of Herring sperm DNA. The self-assembling biosynthetic approach improved image sensitivity and specificity toward the bacterial and exhibited highly efficient disinfection activities coupled with NIR light irradiation. This may raise the possibility of establishing a unique theranostic nanoplatform that possess great potential for accurate bacteria bioimaging and disinfection.

Efficiency of a digital electrofulguration system in contaminated root canals in vitro.

Decontamination of the root canal (RC) system is essential for successful endodontic therapy. In this in vitro study, it was evaluated the disinfection potential of an electrofulguration device, the Endox® Endodontic System (EES), in RC infected with Enterococcus faecalis. Sixty-five human lower premolars were instrumented with MTwo® system. The specimens were distributed into six experimental groups (n = 10), according to the irrigation protocol: 2% chlorhexidine gel (CHX); CHX + EES; 5.25% sodium hypochlorite (NaOCl); NaOCl + EES; saline solution (SS); and SS + EES. Five specimens were untreated (control). RC samples were collected before (C1) and after EES treatment (C2), after chemo-mechanical preparation (CMP) (C3), and after final EES treatment (C4). All samples were plated for colony forming units (CFU/mL) onto solid media. The data were analyzed by Wilcoxon and Friedman tests for intragroup comparisons and by Kruskal Wallis test followed by Dunn's test for intergroup comparisons (α = 0.05). Treatment with the EES did not significantly reduce the number of CFU/mL as compared to baseline levels (C1 vs. C2, p> 0.05). After CMP (C3), all groups showed a significantly reduced amount of CFU/mL (p <0.05), with no difference between CHX- and NaOCl-treated samples (p >0.05). Lastly, treatment with the EES following CMP (C4) did not significantly reduce the amount of CFU/mL (C3 vs. C4, p> 0.05). To conclude, the use of the Endox® Endodontic System did not result in considerable bacterial reduction at all operative times, while treatment with NaOCl and CHX was equally efficient for this purpose.

Effect of Relative Humidity in Air on the Transmission of Respiratory Viruses

Viral respiratory infections have plagued mankind over its known history. Unfortunately, there has been a lack of meaningful progress in preventing the spread of viral respiratory infections globally. The central dogma appears to be that viruses are the villains. This framing focuses on a viral load balance (VLB) in the air. It follows that physical dilution through various means have been the primary focus of attempts to reduce the spread of infections. The problem of obesity provides a good example of how paradigm blindness can slow down progress in a field. Obesity has been framed as an energy balance disorder that blames overeating and lack of exercise for weight gain. Reframing obesity as a disorder of fat metabolism and storage caused by the quantity and quality of carbohydrates in the diet, referred to as the carbohydrate-insulin model (CIM), opened an alternative line of questioning with a testable hypothesis. Similarly, we postulate an alternative way to frame the spread of viral respiratory infections that would lead to new insights and potentially new ways to prevent infections. It has long been recognized that viral respiratory infections show a pronounced seasonal variation, referred to as seasonal forging, such that they increase in the winter but decrease or virtually disappear in the summer. In temperate regions, people spend over 90% of their time indoors. This is, therefore, where most respiratory infections are expected to occur. Evidence has been accumulating for decades on the strong correlation between variations in indoor relative humidity (RH) and variations in infection rates. Within a RH Goldilocks zone of 40%-60%, encapsulated viruses like influenza and SARS are optimally inactivated outside the infected host. Below 40% and above 80%, viruses can survive for extended periods in the air or on surfaces. This may explain in part the seasonality of infections as the indoor level of RH in winter is typically about 20% and above 40% in summer in temperate regions. However, the mechanism for the inactivation at midrange RH (in summer) is not well understood. This paper offers a hypothesis that could explain these observations. We have demonstrated that H2O2 and other reactive oxygen species (ROS) are formed spontaneously at the water-air interface of pure water microdroplets. Using only water and a nebulizing gas in the presence of oxygen, we have demonstrated the significant disinfectant potential of pure water microdroplets caused by the activity of H2O2 and other ROS. We postulate that spontaneous H2O2 and ROS formation in viruses containing exhaled microdroplets have a similar virucidal effect at mid-range RH. The droplet evaporation rate is sufficient to concentrate the solutes and provide enough time for reactions to occur at significantly higher rates than in bulk solutions. The concentration of H2O2 has also been shown to be positively correlated to RH. In addition, several other ROS/RNS may be present or formed through interactions with H2O2 that may act as even more effective virucide disinfectants to inactivate the virus. Below RH 40% evaporation happens too rapidly for these reactions to make an impact before the droplet is desiccated, and above RH 80% the solutes remain too diluted. Rapid inactivation of viruses at midrange RH may therefore play a greater role in preventing infections than physical dilution of virus load in the air through excessive mechanical ventilation. Similar to obesity, we suggest that a new paradigm that considers virus infectivity outside the host rather than the virus load balance in the air alone could greatly contribute to our understanding of respiratory infections. The proposed new “Relative Humidity Infectivity” RHI paradigm could explain the causal mechanisms underlying seasonal respiratory infections. This can point to better prevention strategies that avoid further distortion of our indoor environment and create conditions within which humans can thrive and be optimally protected. We need more focus on testing the various hypotheses and more data to determine which of the two paradigms will lead us in the right direction or how to use the best of both in an optimal combination. The stakes cannot be higher, and the potential for eradicating future viral respiratory pandemics with nature-based solutions may be right under our noses, literally.

SARS-CoV-2 Disinfection of Air and Surface Contamination by TiO2 Photocatalyst-Mediated Damage to Viral Morphology, RNA, and Protein.

SARS-CoV-2 is the causative agent of COVID-19, which is a global pandemic. SARS-CoV-2 is transmitted rapidly via contaminated surfaces and aerosols, emphasizing the importance of environmental disinfection to block the spread of virus. Ultraviolet C radiation and chemical compounds are effective for SARS-CoV-2 disinfection, but can only be applied in the absence of humans due to their toxicities. Therefore, development of disinfectants that can be applied in working spaces without evacuating people is needed. Here we showed that TiO2-mediated photocatalytic reaction inactivates SARS-CoV-2 in a time-dependent manner and decreases its infectivity by 99.9% after 20 min and 120 min of treatment in aerosol and liquid, respectively. The mechanistic effects of TiO2 photocatalyst on SARS-CoV-2 virion included decreased total observed virion count, increased virion size, and reduced particle surface spike structure, as determined by transmission electron microscopy. Damage to viral proteins and genome was further confirmed by western blotting and RT-qPCR, respectively. The multi-antiviral effects of TiO2-mediated photocatalytic reaction implies universal disinfection potential for different infectious agents. Notably, TiO2 has no adverse effects on human health, and therefore, TiO2-induced photocatalytic reaction is suitable for disinfection of SARS-CoV-2 and other emerging infectious disease-causing agents in human habitation.

Controllable drilling by corrosive Cu1Ox to access highly accessible single-site catalysts for bacterial disinfection

Precise modulation of local structure will improve the catalytic performance for single-site catalysts (SSCs), by taming electronic structure of supported metals and impacting the adsorption energy of reaction intermediates. In order to modify and strengthen the metal-support interaction, a controllable drilling process induced by atomic Cu1Ox is presented for fabrication of accessible SSCs. First, the bulk Cu2O was thermally driven to migrate and diffuse within the tangent graphene oxide membranes (GOM) interface, drilling plenty of channels in the GOM. Then, the volatile and atomic Cu1Ox species would diffuse through the corroded channels. At last, the Cu1Ox species with strong causticity would corrode the C-N support by breaking the Cu-O bonds and releasing CO2. Hence, the atomic Cu species were eventually anchored in the C-N support by coordination with dangling N-rich defects, forming the Cu SSCs. The fabricated Cu SSCs exhibited an excellent performance in sterilizing bacteria. As our results displayed, Escherichia coli (E. coli.) was almost sterilized by Cu SSCs via activating persulfate. Compared to the traditional approaches employed by wastewater treatment plant, our Cu SSCs exhibit much better antibacterial effect, holding a great potential for practical bacterial disinfection.

Recent development in antimicrobial activity of biopolymer-inorganic nanoparticle composites with water disinfection potential: a comprehensive review.

Nowadays, water-borne diseases including hepatitis remain the critical health challenge due to the inadequate supply of potable and safe water for human activities. The major cause is that the pathogenic microorganisms causing diseases have developed resistance against common techniques used by sewage water treatment plants for water disinfection. Therefore, there is a need to improve these conventional water treatment techniques by taking into consideration the application of nanotechnology for wastewater purification. The main aim of this paper is to provide a review on the synthesis of biopolymer-inorganic nanoparticle composites (BINCs), their used as antimicrobial compounds for water disinfection, as well as to elaborate on their antimicrobial mechanism of action. The microbial properties affecting the activity of antimicrobial compounds are also evaluated.

“Dew-of-Leaf” structure multiple synergetic antimicrobial modality hybrid: A rapid and long lasting bactericidal material

• Ag-PCN@Ti 3 C 2 -BC was fabricated achieving MSAM hybrid material. • A Rapid and long lasting antibacterial hybrid material was provided. • Rapid antibacterial effect was achieved by photodynamic and photothermal effect. • Long lasting antibacterial effect was achieved by Ag + ions releasing. • 1 O 2 and heat pushed the Ag + ions releasing from the sputtered silver under light illumination. Multiple synergetic antimicrobial modality (MSAM) platform is a novel approach which has highly advocated recently to meet the challenge of bacterial infection. In this research, we constructed a “Dew-of-Leaf” like hybrid material (Ag-PCN@Ti 3 C 2 -BC) with multiple design features that integrated photodynamic, photothermal and silver ion releasing effects. Porphyrinic MOFs (PCN-224) grown on Ti 3 C 2 nanosheets was first filtered onto BC, then nanosilver was sputtered using magnetron sputtering technique. Interestingly, the light-driven singlet oxygen produced by PCN-224 and the heat produced by Ti 3 C 2 not only synergistically enhanced the antibacterial effect, but also promoted the sputtered nanosilver to be degraded to release silver ions, achieving rapid bacterial inactivation and long lasting bacterial inhibition effects. Moreover, after two rounds of bacterial inactivation and 6 months of room environment preservation, an antibacterial inactivation study still demonstrated 99.9999% elimination of Gram-negative Escherichia coli ATCC-8099 and Gram-positive Staphylococcus aureus ATCC-6538 with Ag-PCN@Ti 3 C 2 -BC. Taken together, this nanofiber hybrid material permits an effective way to inactivate bacteria rapidly at first and long lasting bacterial inhibition followed, showing great potential for microbial disinfection.

Potential of essential oil combinations for surface and air disinfection.

In this study, it was aimed to develop a novel disinfectant from various essential oils containing active components with antimicrobial activity. The mixture of oregano, cinnamon and clove oils (1:1:1) with 10% oil concentration (SOM) was used as potential disinfectant on various areas and showed the highest antimicrobial activity among oil combinations tested. SOM reduced the numbers of total mesophilic aerobic bacteria (TMAB; 2·27 log CFU per 25cm2 ) and Escherichia coli (4·60 log CFU per 25cm2 ) under the detection limits. Application of SOM (1, 2, 3, 4 and 6%) into incubators reduced TMAB and mould-yeast counts of incubator air by 82·9 and 100% respectively. SOM application (3%) into ambient air also reduced its TMAB and mould-yeast counts by 92 and 84·6% respectively. While ethanol is commonly used for the disinfection of environments, equipment and surfaces, SOM is an important alternative that may also be used for the disinfection of various surfaces as well as air.

Kinetics of Bacterial Inactivation by Peroxynitric Acid in the Presence of Organic Contaminants.

Low-temperature atmospheric-pressure plasma has been studied for disinfection purposes. When plasma is exposed to water, reactive oxygen and nitrogen species are generated and preserved in the water fraction (plasma-treated water [PTW]), which consequently exhibits bactericidal activity. At low temperatures, one of the bactericidal components of PTW is peroxynitric acid (PNA). Importantly, PNA can also be synthesized by chemical reaction, without exposure to plasma. In this study, we evaluated the bactericidal properties of PNA based on reaction kinetics in comparison with other disinfectants. The analysis, based on dose-dependent effects, showed that PNA exhibited about 1 and 10 times the bactericidal activity of hypochlorous acid (HOCl) and peracetic acid, respectively. In addition, we evaluated the influence of organic contaminants on the bactericidal effects of PNA and HOCl. The bactericidal potential of both disinfectants was reduced by bovine serum albumin (BSA); however, PNA showed about 30-times-higher resistance against BSA inhibition than HOCl. Analysis of the dose-dependent effects of PNA revealed that the inhibition of bactericidal effect was caused by its consumption. Further experiments using model substrates containing particular amino acid residues (Met, Cys, Lys, and Leu) suggested that the bacterial inactivation by PNA is less affected by BSA due to the low reactivity and narrow reactivity spectrum of PNA for amino acid residues. Overall, our results suggest that PNA has a great disinfection potential, especially in the presence of organic contaminants (e.g., on the surface of the human body and on medical instruments contaminated with biological fluids).IMPORTANCE A good disinfectant for the human body should have various properties, such as strong bactericidal activity, harmlessness to living tissues, and resistance against biological fluids (or other organic contaminants). Peroxynitric acid (PNA) showed a bactericidal effect that was several tens up to several hundred times higher per unit of molarity than that of sodium hypochlorite and peracetic acid, which are used as general disinfectants for medical equipment. Moreover, the high resistance of PNA to organic load was confirmed, indicating that PNA will inactivate bacteria effectively even on contaminated surfaces, such as used medical devices or the human body surface. Therefore, we propose that PNA can be used as a strong disinfectant for the human body.

Ag functionalized SnS2 with enhanced photothermal activity for safe and efficient wound disinfection.

Severe bacterial infections have brought an urgent threat to our daily life, and photothermal therapy (PTT) has acted as an effective method to kill bacteria. Herein we decorated Ag on the surface of SnS2 (Ag@SnS2), which has outstanding photothermal conversion capability and good biocompatibility. The decoration of Ag on SnS2 improved the absorption of near-infrared (NIR) light in comparison to SnS2, resulting in a temperature increase of 50 °C after 5 min of NIR light irradiation (1.9 W cm-2) and a photothermal conversion efficiency of 31.3%. Ag@SnS2 exhibits almost 100% growth inhibition of E. coli and S. aureus bacteria due to hyperthermia, with a concentration larger than 0.5 mg mL-1 and 5 min of NIR irradiation. Meanwhile, SEM images of treated bacterial cells showed the attachment of Ag@SnS2 on the cell surface and obvious cellular membrane destruction. Ag@SnS2 can also accelerate in vivo wound healing through PTT-induced bacterial disinfection. Therefore, Ag@SnS2 exhibits great potential for photothermal antibacterial application and wound disinfection.