Biocidal Efficiency Research Articles

Pyrazine-Based Iodine-Containing Biocidal Materials: Enhanced Energy Performance and Reduced Corrosion Risk.

Biosafety is crucial to the common interests of all humanity. Currently, global biosafety governance is a challenge and poses significant opportunities. With the escalating challenges posed by microorganisms, there is an urgent need to develop advanced biocidal materials. In this work, we introduce a class of iodine-containing high-energy biocidal materials, utilizing pyrazine rings with good thermal stability as nitrogen-rich high-energy backbones, to address the issues of corrosion and hygroscopicity associated with N-H acidic protons in traditional iodine-containing azole compounds. Employing nucleophilic substitution and coupling reactions, we successfully synthesized two distinct series of eight compounds (Series A: BQDI, BQFI, BQDIO; Series B: BBQ3I, BBQ4I, BBQNI, MBQ5I, and MBQDI), which exhibit a high iodine content and enhanced detonation pressure. Notably, compounds BQDIO and BBQNI show detonation pressures of 13.70 and 16.52 GPa, respectively, both exceeding the 10 GPa of traditional iodine-containing biocidal materials. This improvement is crucial for expanding the diffusion range of biocidal substances and enhancing the biocidal efficiency of these materials. Pyrazine-based iodine-containing compounds have revolutionized the performance of biocidal materials, addressing corrosion issues and paving the way for the development of efficient, stable, and safe biocidal materials.

In Vitro Viability Tests of New Ecofriendly Nanosystems Incorporating Essential Oils for Long-Lasting Conservation of Stone Artworks.

The study explores the application of natural biocides (oregano essential oil and eugenol, directly applied in solutions or encapsulated within silica nanocapsules) for safeguarding stone cultural heritage from biodeterioration, using green algae (Chlorococcum sp.) and cyanobacteria (Leptolyngbya sp.) as common pioneer biodeteriogens. Core-shell nanocontainers were built for a controlled release of microbicidal agents, a safe application of chemicals and a prolonged efficacy. The qualitative and quantitative evaluations of biocide efficiency at different doses were periodically performed in vitro, after six scheduled intervals of time (until 100 days). The release kinetics of composite biocide-embedding silica nanocapsules were characterized by the UV-Vis spectroscopy technique. Data showed both promising potential and some limitations. The comparative tests of different biocidal systems shed light on their variable efficacy against microorganisms, highlighting how encapsulation influences the release dynamics and the overall effectiveness. Both the essential oils showed a potential efficacy in protective antifouling coatings for stone artifacts. Ensuring compatibility with materials, understanding their differences in biocidal activity and their release rates becomes essential in tailoring gel, microemulsion or coating products for direct on-site application.

Isolation and Antibiogram Pattern of Bacteria Isolated from Automated Teller Machine (ATM) at Abuja Campus, University of Port Harcourt, Nigeria

The growing use of automated teller machines (ATMs) has sparked worries about possible microbial contamination on ATM keypads, which might be harmful to the general public's health. This study examines the antibiotic resistance characteristics of the bacterial infections linked to ATM keypads at the University of Port Harcourt's Abuja campus in Nigeria. Tests for antimicrobial susceptibility, bacterial isolation, and identification were carried out on swab samples obtained from different bank ATMs. Common contaminants found in the research were Staphylococcus, Bacillus, Enterobacter, Aerobacter, Photohabdus, and Micrococcus species. With a 40% prevalence, Bacillus species predominated, followed by Staphylococcus species at 30%. The range of total heterotrophic counts was 3.38–4.69 Log Cfu/ml. The necessity for efficient biocides was highlighted by the antimicrobial susceptibility tests, which showed different resistance patterns in Gram-positive and Gram-negative isolates. This study demonstrates the rise of antibiotic-resistant bacteria and emphasizes the importance of microbial contamination on ATM keypads for public health. Advocating for the slowing of the spread of resistant microbes, research promoting frequent surveillance, hygiene education, and the creation of antimicrobial measures is endorsed. All things considered, insightful information on the microbial environment of often-touched surfaces was provided by the results, emphasizing the advocacy for taking preventative measures to reduce the health hazards related to ATMs.

Biomimetic nanonet membranes with UV-driven self-cleaning performance for water remediation

Water pollution caused by industrial and natural contaminants has placed a significant burden on environment and human health. The present filtration membranes, however, suffer from a series of issues involving low permeation fluxes and easy fouling issue during long-term water remediation, which seriously restricts their practical applications. Herein, inspired by royal water lily leaf, we construct biomimetic nanonet membranes (BNMs) composed of fractal network and mastoid structures by one-step phase inversion of PVDF/TiO2 solution using electrospun fibrous membrane as substrates. Benefit from the distinct structures, the BNMs show sub-micro pores, high porosity, and intriguing hydrophilicity, which result in excellent removal performance for 0.3 μm solid particle (efficiency of 99.88%, permeation flux of 3439 L m−2 h−1), E. coli (log reduction value = 8.39, permeation flux of 1242 L m−2 h−1), and oil-in-water emulsions (efficiency of 99.0%, permeation flux of 8312 L m−2 h−1). Importantly, the presence of TiO2 nanoparticles with UV-driven catalytic activity effectively endows the BNMs with desirable biocidal efficiency (LRV = 8.5) and excellent self-cleaning properties (flux recovery ratio of 98.1%). The synthesis of such membranes may open new avenues in the design of high-performance filtration membranes for remediation of large volumes of wastewater.

Comprehensive Review on the Use of Biocides in Microbiologically Influenced Corrosion.

A microbiologically influenced corrosion (MIC) causes huge economic losses and serious environmental damage every year. The prevention and control measures for MIC mainly include physical, chemical, and biological methods. Among them, biocide application is the most cost-effective method. Although various biocides have their own advantages in preventing and treating MIC, most biocides have the problem of polluting the environment and increasing microorganism resistance. Therefore, it has stimulated the exploration of continuously developing new environmentally friendly and efficient biocides. In this review, the application advantages and research progress of various biocides used to prevent and control MIC are discussed. Also, this review provides a resource for the research and rational use of biocides regarding MIC mitigation and prevention.

Chemically Modified TiO2 Photocatalysts as an Alternative Disinfection Approach for Municipal Wastewater Treatment Plant Effluents

Among key issues in municipal wastewater treatment plants (MWTP) is the existence of pathogenic bacteria in the discarded effluents. Conventional disinfectants (ozone, UV irradiation, chlorine) have been insufficient in providing safe water due to the development of undesirable and noxious by-products. TiO2 comprises an attractive alternative to conventional methods because of its versatility and recently explored biocidal efficiency. As a result, within the framework of this study, chemically modified, visible active nanocrystalline TiO2 powders (N-TiO2, N,S-TiO2, and Ag@N-TiO2) were prepared via a low-cost, feasible sol-gel method for the treatment of real municipal wastewater effluents. Wastewater samples were acquired from the outlet of the treatment of Antiparos (Cyclades, Greece) MWTP during the summer period in which a great number of seasonal habitants and tourists usually visit the island, resulting in at least a doubling of the population. All synthesized powders were thoroughly characterized using various morphological and spectroscopic techniques, such as FE-SEM, XRD, micro-Raman, FTIR, DLS, UV-DRS, and XPS. Photocatalytic evaluation experiments were initially conducted towards Rhodamine B degradation under visible light irradiation. Among all studied powders, Ag@N-TiO2 indicated the highest efficiency, reaching total degradation (100%) of RhB within 240 min due to its smaller crystallite size (1.80 nm), enhanced surface area (81 m2g−1), and reduced energy band gap (Eg = 2.79 eV). The effect of the produced powders on the disinfection as assessed in terms of fecal indicator microorganisms (E. coli and total coliforms) inactivation was also examined in a semi-pilot scale-up photocatalytic reactor. Ag@N-TiO2 nanopowder was also found substantially more active for both groups of bacteria, leading to complete inactivation in less than 35 min, probably due to the higher production of H2O2/•OH, as emerged from the photocatalytic mechanism study. In addition, Ag@N-TiO2 nanoparticles demonstrated excellent photocatalytic and disinfection stability even after five subsequent recycling trials (8.34% activity loss and complete inactivation, respectively). The results of the present study demonstrate the feasibility for Ag@N-TiO2 to be utilized as a viable, eco-friendly approach for the photocatalytic pathogenic bacteria inactivation as an alternative disinfection approach for municipal wastewater treatment plant effluents with intense seasonal fluctuations in volume.

Multicationic Quaternary Ammonium Compounds: A Framework for Combating Bacterial Resistance.

During previous stages of research, high biocidal activity toward microorganism archival strains has been used as the main indicator in the development of new antiseptic formulations. Although this factor remains one of the most important characteristics of biocide efficiency, the scale of antimicrobial resistance spread causes serious concern. Therefore, focus shifts toward the development of formulations with a stable effect even in the case of prolonged contact with pathogens. Here, we introduce an original isocyanuric acid alkylation method with the use of available alkyl dichlorides, which opened access to a wide panel of multi-QACs with alkyl chains of various lengths between the nitrogen atoms of triazine and pyridine cycles. We used a complex approach for the resulting series of 17 compounds, including their antibiofilm properties, bacterial tolerance development, and antimicrobial activity toward multiresistant pathogenic strains. As a result of these efforts, available compounds have shown higher levels of antibacterial activity against ESKAPE pathogens than widely used commercial QACs. Hit compounds possessed high activity toward clinical bacterial strains and have also demonstrated a long-term biocidal effect without significant development of microorganism tolerance. The overall results indicated a high level of antibacterial activity and the broad application prospects of multi-QACs based on isocyanuric acid against multiresistant bacterial strains.

Thymol-Nanoparticles as Effective Biocides against the Quarantine Pathogen Xylella fastidiosa.

Quarantine pathogens require the investigation of new tools for effective plant protection. In particular, research on sustainable agrochemicals is the actual challenge. Plant extracts, essential oils, and gels are natural sources of efficient biocides, such as aromatic secondary metabolites. Thymol is the major phenolic constituent of thyme and oregano essential oils, and it can inhibit many pathogenic microbes. Thymol nanoparticles were obtained through adsorption on CaCO3 nanocrystals, exploiting their carrier action. High loading efficiency and capability were reached as verified through UV and TGA measurements. We report the first study of thymol effect on Xylella fastidiosa, conducing both fluorometric assay and in vitro inhibition assay. The first test confirmed the great antibacterial effect of this compound. Finally, an in vitro test revealed an interesting synergistic action of thymol and nanocarriers, suggesting the potential application of thymol-nanoparticles as effective biocides to control Xylella fastidiosa infection.

Fluorescence Analysis of Biocide Efficiency in Antifouling Coatings against Cyanobacteria.

This study focused on the antifouling effect of copper oxide (Cu2O)- and zineb-based coatings against Cyanothece sp. ATCC 51142 by analysing photosynthetic activity using chlorophyll fluorescence. The photoautotrophically grown cyanobacterium was exposed to toxic coatings over a short-term period of 32 h. The study showed that Cyanothece cultures are particularly sensitive to biocides (i) released from antifouling paints and (ii) exhibited by contact with the coated surfaces. Changes in the maximum quantum yield of photosystem II (FV/FM) were observed within the first 12 h of exposure to the coatings. Partial recovery of FV/FM in Cyanothece was revealed 24 h post exposure to a copper- and zineb-free coating. In this research, we proposed an analysis of the evaluation of fluorescence data to study the initial response of cyanobacterial cells to copper- and non-copper-based antifouling coatings formulated with zineb. We evaluated the dynamics of coating toxicity by determining the characteristic time constants of changes in the FV/FM. Within the most toxic paints studied, those formulated with the highest concentration of Cu2O and zineb, the estimated time constants were 3.9 times lower compared to the copper- and zineb-free paint. The use of zineb in copper-based antifouling coatings enhanced the toxic effect of paints and contributed to a faster decline in photosystem II activity in Cyanothece cells. The analysis we proposed, along with the fluorescence screening results, may be useful in evaluating the initial antifouling dynamic action against photosynthetic aquacultures.

In Vitro Investigation of the Antibacterial Activity of Nine Commercial Water Disinfectants, Acidifiers, and Glyceride Blends against the Most Important Poultry Zoonotic Bacteria.

Identifying and monitoring the efficiency of alternative biocides that are presently used in livestock is gaining vast attention. The objective of this study was to determine, in vitro, the antibacterial activity of nine commercial water disinfectants, acidifiers, and glyceride blends against clinical isolates or reference strains of zoonotic pathogens belonging to the genera Escherichia spp., Salmonella spp., Campylobacter spp., Listeria spp., and Staphylococcus spp. For each product, the antibacterial activity was tested in concentrations ranging from 0.002 to 1.136% v/v and expressed as the minimum concentration of the product that inhibits bacterial growth (MIC). Water disinfectants Cid 2000™ and Aqua-clean® recorded MICs ranging from 0.002 to 0.142% v/v, while the lowest MICs were recorded at two strains of Campylobacter (0.002-0.004% v/v). Virkon® S displayed various MICs (0.013-0.409% w/v) and was highly effective at suppressing the growth of Gram-positive bacteria such as S. aureus (0.013-0.026% w/v). The MICs of water acidifiers (Agrocid Super™Oligo, Premium acid, and Ultimate acid) and glyceride blends (CFC Floramix, FRA®LAC34, and FRA®Gut Balance) ranged from 0.036 to 1.136% v/v, and for most of these products, MICs were closely correlated by their ability to modify the pH of the culture medium close to 5. In conclusion, most of the tested products showed promising antibacterial activity; as a result, they would be good candidates for pathogen control in poultry farms and for reducing the emergence of antimicrobial resistance. However, further in vivo studies are recommended to provide relevant information for the underlying mechanisms, as well as for the establishment of the optimal dosage scheme for each product and their possible synergies.

Evaluation of the antifungal efficiency of biocides currently applied in the Coimbra UNESCO area limestone monuments

The application of biocides to control microbial proliferation in stone materials is nowadays a rather common practice. In the Coimbra´s UNESCO World heritage monuments, biocide treatments rely on the application of Biotin T and Preventol R80. However, the application of these formulations often occurs without the complete knowledge of microbial communities’ susceptibility to their application. The aim of this study was to evaluate the efficiency of these compounds and compare them with a commercial version of Ocimum basilicum essential oil, against various fungal species present in these areas. Through the application of in vitro antifungal activity assays, we were able to verify that, in general, Biotin T rather than Preventol R80 was more efficient against all tested fungi. In addition, the commercial version of the Ocimum basilicum essential oil also exhibited good results and might be an alternative option to be taken into consideration in future interventions in these monuments.

On the Use, Effectiveness, and Safety of Face Masks, Gloves, and Disinfectants to Prevent Transfer of Microbials between the Tattooist and the Customer: A Practical Review of Pros and Cons Including the Occupational Safety of the Tattooist.

Tattooists and their customers are under special risk of airborne infection because of the short distance during the procedure and the unavoidable exchange of expired and inhaled air potentially containing droplets holding pathogenic germs. Moreover, the manual procedure involves a significant risk of contamination through physical contact. A range of personal protective equipment (PPE) is available, including three-layered disposable surgical masks, cotton masks, respirators without or with expiration valve, visors and shields, goggles, medical gloves and aprons. Disinfectant fluids and wipes are used for skin and physical objects. Alcohol is used but may evaporate too fast and lose biocidal efficiency; it carries risk of fire. Alternatives such as chlorine and a range of new disinfectants listed in the EU biocide directive should be considered as alternatives. PPEs and disinfectants are subject to formal testing and classification. EU and US requirements are visited. No PPE and no disinfectant have 100% efficiency. Efficiency of masks is influenced negatively by the reduced breathability from masks and respirators with leakage of air between mask perimeter and the skin. Gloves have micro-porosity dependent on wear time and already after 30 min become less efficient. The humid microclimate under masks and gloves easily causes skin problems. Thus, there are many pros and cons to consider. Thoughts on ideal aim, sound sense and realistic application of PPE and disinfectants in daily routine in tattoo parlours are provided, the risk and health of the tattooist included.

The Influence of Viscosity on the Antimicrobial Activity of Simple Alcoholic-Based Hand Sanitizer for Infection of Covid-19 in Nigeria

Aim: This study was carried out to analyze and evaluate the influence of viscosity on the antimicrobial activity of simple alcoholic-based hand sanitizer preparations.
 Methods: The preparation of different viscosities of hand sanitizer was done by the introduction of carbomer to define its physicochemical stability. Two folds serial dilution of the test product using isopropyl alcohol and ethanol as alcohols and biocide efficiency to determine the antimicrobial activity using killing time assay were carried out.
 Results: The pH was adjusted to 7.29 and 7.11 respectively, which shows the neutrality of the products. More so, the pH of the two test products proved to be good and hence, stable. In terms of viscosity, it decreased as the concentration decreased at 0.07% for most of the organisms which indicated good antimicrobial activity on the bacterial and fungi strain used. However, concentrations of isopropyl-formulated test product were more effective than the ethanol-based product on the bacterial strains, with Pseudomonas aeruginosa having the highest percentage of microbial death at 92.5%. Although, the ethanol-based products showed higher antimicrobial activity against fungi strains than the isopropyl test product.
 Conclusion: Viscosity influences the activities of alcohol-based hand sanitizers since less viscous test product has a less concentration. Thus, more water denatures the proteins of the microorganism and limits the release of the active ingredient from the formulation. Sequel to this, viscosity enhancers like thickeners and gelling agents like carbomer should be used minimally in the formulation of these products.

Prussian Blue@Zeolitic imidazolate framework composite toward solar-triggered biodecontamination

Metal-organic frameworks (MOFs) featuring composition and bandstructure diversity, are an emerging class of photoresponsive disinfectants. In this study, we demonstrated the superiority of core–shell arranged photoactive MOFs (prussian blue (PB) and zeolitic imidazolate framework (ZIF-8)) for pathogen inactivation in terms of biocidal efficiency and broad-spectrum sensitivity. Reactive oxygen species (ROS) production was significantly promoted after the integration of PB due to the photosensitization effect and initiation of in situ Fenton reaction. Favorably, another inactivation channel was also opened owing to the unique photothermal effect of PB. Attributed to the facilitated ROS intracellular penetration by heat, the composite outperforms not only individual component but anatase TiO2 in pathogen elimination. Specifically, the Staphylococcus aureus (S. aureus) inactivation efficiency of the composite (6.6 log) is 2, 1.8 and 5.1 times higher than that of PB (3.3 log), ZIF-8 (3.7 log) and TiO2 (1.3 log) over 45 min of simulated sunlight illumination. Significantly, the infectivity of Bacillus anthracis and murine coronavirus in droplets on composite-coated filter surface could be greatly reduced (approximately 3 log reduction in colony number/coronavirus titer) within few minutes of solar exposure, indicative of the great potential of MOF composites toward life-threatening microbial infection prevention.

Disinfectant activities of extracts and metabolites from Baccharis dracunculifolia DC.

The concern regarding the harm caused by biocides to human health has been increasing over the years, making the natural products an alternative to less toxic and more efficient biocides. Therefore, this paper reports the investigation of the disinfectant potential of extracts and isolated compounds from Baccharis dracunculifolia. For this purpose, extracts of aerial parts (BD-C), tricomial wash (BD-L) and roots (BD-R) of B. dracunculifolia were obtained by maceration. The extracts were submitted to different chromatographic techniques, including high-speedy countercurrent chromatography (HSCCC) furnishing nine isolated compounds. The extracts and isolated compounds were evaluated regarding their antimicrobial activity by the broth microdilution method, according to the Clinical and Laboratory Standards Institute, and regarding their sanitizing activity according to Standard Operating Procedure No. 65·3210·007 (INCQS, 2011), developed by the National Institute for Quality Control in Health (INCQS) - Oswaldo Cruz Foundation (FIOCRUZ). In the antimicrobial evaluation the BD-C extract showed minimum inhibitory concentration (MIC) values of 200 and 100 µg/ml against Staphylococcus aureus and Tricophyton mentagrophytes, respectively. BD-L extract showed MIC value of 200 µg/ml against S. aureus. The isolated compounds caffeic acid (MBC 2·22 µmol l-1 ), ferulic acid (MBC 2·06 µmol l-1 ) and baccharin (MBC 0·27 µmol l-1 ) showed significant inhibitory activity against S. aureus. All B. dracunculifolia isolated compounds were active with exception of aromadrendin-4´-O-methyl-ether for T. mentagrophytes. Additionally, isosakuranetin was active against Salmonella choleraesuis (MIC 1·4 µmol l-1 ). Regarding the sanitizing activity, the hydroalcoholic solution containing 0·2% of B. dracunculifolia extract in 40°GL ethanol was effective in eliminating the microbial contamination on all carrier cylinders and against all microorganisms evaluated in the recommended exposure time of 10 min. Therefore, B. dracunculifolia has potential for the development of sanitizing agents to be used in hospitals, food manufactures and homes.

Polyphasic Characterization of Four Aspergillus Species as Potential Biocontrol Agents for White Mold Disease of Bean.

The genus Aspergillus comprises several species that play pivotal roles in agriculture. Herein, we morphologically and physiologically characterized four genetically distinct Aspergillus spp., namely A. japonicus, A. niger, A. flavus, and A. pseudoelegans, and examined their ability to suppress the white mold disease of bean caused by Sclerotinia sclerotiorum in vitro and under greenhouse conditions. Seriation type of Aspergillus spp. correlates with conidiospores discharge as detected on the Petri glass lid. Members of Nigri section cover their conidial heads with hard shells after prolonged incubation. In addition, sporulation of the tested Aspergillus isolates is temperature sensitive as it becomes inhibited at low temperatures and the colonies become white. Examined Aspergillus spp. were neither infectious to legumes nor aflatoxigenic as confirmed by HPLC except for A. flavus and A. pseudoelegans which, secreted 5 and 1 ppm of aflatoxin B1, respectively. Co-inoculations of Sclerotinia’s mycelium or sclerotia with a spore suspension of Aspergillus spp. inhibited their germination on PDA at 18 °C and 28 °C, and halted disease onset on detached common bean and soybean leaves. Similarly, plants treated with A. japonicus and A. niger showed the highest survival rates compared to untreated plants. In conclusion, black Aspergillus spp. are efficient biocides and safe alternatives for the management of plant diseases, particularly in organic farms.

Evaluating the Effect of Plants Extracts Against Varroa Mites (Varroa Destructors) of Honeybees (Apis Mellifera)

The honeybee is the most useful insect to man but their productive potential is reliant on their health conditions. The mites not only cause economic loss but also cause ecological problems related to the role of honey bees, as they are most vital pollinators of the World. The aim of this study was to evaluate and identify the efficiency of some plant-based biocides to develop alternative method of controlling Varroa destructors that is the safest to hive products. For this purpose, Euclaptus globulus, Calpurnia aurea, Ocimum basilicum, Allium sativum, Cymbopogon citratus, Mentha piperita and Ocimum gratissimum were collected, dried under shade and grinded and their oils were extracted by using Soxhlet apparatus and n-hexane as an extractor. The botanical extracted oils were prepared in different concentrations and applied on Varroa destructors and Apis mellifera . The effectiveness of the extracts against the mites and the safety to the honeybees was observed after 24 and 48 hours, respectively. Plants extracts showed variable responses to Varroa destructors . Results showed that A. sativum , E. globulus and C. aurea caused 100±0.0 percent mortality on V. destructor s after 24 hours. C. citratus extracts of 100 percent dose caused 100+0.0 percent mortality of the mites after application on the mites. C. aurea leaf extract may be safer to A. mellifera . Bio pesticides can be upcoming pest managing healthier choice. The n-hexane extracts of the E. globulus, A. sativum and C. aurea plants had insecticidal effects on the insect pests of bees and could be considered as bioactive candidate for management of the pests. Keywords: Effectiveness, Honeybee, Plant oils, Varroa destructors DOI: 10.7176/CMR/14-2-03 Publication date: May 31 st 2022

Assessment of cleaning techniques and its effectiveness for controlling biodeterioration fungi on wall paintings of Maijishan Grottoes

Biodeterioration is one of the main challenges in conservation of cultural heritage. This study tested and evaluated non-destructive methods to clean and control the microbial mycelia grown on the surface of wall paintings at the World Cultural Heritage Site of Maijishan Grottoes in China. Culture-dependent methods were used for isolation of fungi prior to identification by ITS rRNA gene sequences. The mycelia grown on the surface of wall paintings were removed with soft brushes under a negative pressure provided by a modified vacuum pump, and the pre-screened biocides were then selected and applied. Using a portable microscope, a microbial ATP bioluminescence detector, and a colorimeter, the effectiveness of cleaning and controlling against fungal mycelia on the wall paintings was evaluated. The results showed that the fungal isolates were dominated by Arachnomyces spp. with 92.28% sequence identity. Other major culturable fungal isolates were Parengyodontium album, Beauveria bassiana, and Scopulariopsis brumptii. The microscopic examination indicated the surface of the wall paintings was nearly free of visible fungal mycelia after the manual removal. There was a significant reduction of ATP bioluminescence before (43,303 ± 10, 280 RLU/cm2) and after (2,833 ± 388, RLU/cm2) the mechanical removal. The color difference (ΔE∗ab value) were less than 2.0 before and after biocide treatment, such difference could almost be ignored. Additionally, octylisothiazolinone was found to be the most efficient biocide for controlling fungal growth and could be an emergency protection measure. Furthermore, the key environmental factors that triggered periodic breakouts of the microorganisms on wall paintings were long-term higher relative humidity at the interface of earthen plaster layer and supporting sandstone during raining seasons and poor ventilation of the cave. This study provides a reference for the scientific conservation of biodeteriorated ancient wall paintings.

Biocides for the Control of Mosses on Stone Cultural Relics

ABSTRACT Controlling biodeterioration is a worldwide necessity for the preservation of cultural heritage. Biocides are the most effective compounds used for heritage protection of stone; however, their specific efficacy, performance over time, interference with cultural heritage materials, and potential hazards are still unclear. In this work, we test and evaluate a large number of biocides to address the degradation of stone cultural relics by mosses. The quantitative and qualitative evaluations of biocide efficiency were performed by chlorophyll fluorescence (ChlaF) measurements and confocal microscopy. Surprisingly, traditional herbicides (glyphosate, glufosinate-ammonium) and metal oxide nanoparticles (CuO, ZnO) with antibacterial effects do not affect mosses. However, some plant hormones and essential oils showed good effects at all stages of moss growth. Meanwhile, biocides were also tested on artificial simulated rocks to see if they change their properties. It turns out that biocides containing copper ions can cause chromaticity changes on the rock surfaces. In the end, a total of six efficient and safe biocides were obtained, which will play a good role in biological control for cultural heritage protection.

In English

The aim of this work is a comparative analysis of the biocidal efficiency of Ag nanoparticles (NPs) in the colloidal state, in the structure of films and dispersions of SiO2 and in the composition of textile fabrics, dependent on the method of synthesis, based on literature data and on own researches. Chemical reduction of silver (with borohydrides, hydrogen, hydrazine, etc.) allows one to adjust and control the size and shape of NPs. The shape of the NPs is mostly spherical, what is confirmed by the presence of a band of surface plasmon resonance in absorption spectra and by electron microscopy measurements. To prevent aggregation of NPs obtained by the method of chemical reduction in solution, the optimal ratio of two stabilizers based on surfactants and polymer at their minimum concentration was found, namely NaBH4 as a reductant and polyvinylpyrrolidone + sodium dodecyl sulfate as binary stabilizer of Ag NPs, with bactericidal activity of 99 % and stability for more than 3 years. Chemical reduction of silver ions was carried out also by the amino acid tryptophan (Trp) which has a dual function – a biocompatible reducing agent and stabilizer of silver NPs while maintaining their shape, size and stability for long-term use. Effective methods of photochemical synthesis of Ag NPs have been developed in different ways: by UV irradiation of Ag+ ions in solution in the presence of solid-state photosensitizer SiO2 with adsorbed benzophenone (SiO2/BPh); by UV irradiation of Ag+ ions in solution in the presence of the amino acid tryptophan (Trp); on silica surface when Ag/SiO2 sol-gel films production via irradiation of adsorbed Ag+ ions on SiO2 film (Ag+/SiO2) in the BPh solution. It is shown that when Ag NPs are adsorbed on the surface of highly dispersed SiO2, the logarithm of the reduction of microorganisms reduces and the time of their deactivation increases. A cheap and convenient way to modify of cotton textiles with Ag NPs by soft heat treatment of Ag+/cotton samples with high (90–95 %) efficiency of destruction of bacteria E. coli, K. pneumoniae, E. aerogenes, P. vulgaris, S. aureus, C. albicans, etc., with saving of biocidal activity after 5 cycles of washing has been developed. The dynamics of silver ions release from the surface of NPs in the structure of textile upon their contact with water for 72 hours and the number of irreversibly bound particles have been studied. The electrical resistance of the tissue is proportional to the quantity of NPs. That is NPs in the structure are in different degrees of binding, a certain part of them is retained (adsorbed) irreversibly, saving bactericidal properties after repeated contacts with water. On the basis of literature analysis it is shown that ecologically safe “green synthesis” is a promising way to silver NPs produce with pronounced bactericidal efficiency, which is becoming more common due to the large resource of cheap plant raw materials.