Repellent Agent Research Articles

Investigation of Membrane Emulsification for the Scaled Production of Microcapsules for Self-sealing Cementitious Systems

Capsule-based self-sealing in cementitious systems is an advantageous methodology which has the potential to decrease water ingress and thus enhance a system’s durability and extend its lifespan. If capsule-based self-sealing is to be considered as an industrial solution, production must be scaled while capsule quality and batch reproducibility are maintained. In this study, polyurethane-shelled microcapsules containing a commercially available water repellent agent were produced using membrane emulsification equipment, supplied by Micropore Technologies, followed by interfacial polymerisation. Production was scaled across three different cross-flow membrane emulsification devices, the AXF-1, the AXF-3, and the AXF-4, increasing production output to a maximum of 850 L/hr of capsule suspension. Following production, capsules were characterised, measuring average size and size distribution, as well as integrated into a cementitious matrix. The results highlight the key parameters that govern capsule size, the versatility of the equipment, and the consistent quality of capsules produced. It is hoped that this scaled production of capsules will help to develop the commercial viability of capsule-based self-sealing cementitious systems.

Polymethyl methacrylate resin containing ε-poly-L-lysine and 2-methacryloyloxyethyl phosphorylcholine with antimicrobial effects

Statement of problemPolymethyl methacrylate (PMMA) is commonly used in dentistry, including as a denture base material. However, the colonization of a PMMA surface by microbial microorganisms could increase the risk of oral diseases such as denture stomatitis and gingivitis. The development of PMMA with antibacterial properties should improve its clinical application, but whether adding ε-poly-L-lysine (ε-PL) and 2-methacryloyloxyethyl phosphorylcholine (MPC) provides antimicrobial effects is unclear. PurposeThis in vitro study aimed to develop a novel antibacterial PMMA resin containing the natural nontoxic antibacterial agent ε-PL and the protein repellent agent MPC. The mechanical properties, protein repellency, and antimicrobial activities of the resin were then evaluated. Material and methodsDifferent mass fractions of ε-PL and MPC were mixed into PMMA as the experimental groups, with unaltered PMMA as the control group. The flexural strength (n=10) and surface roughness (n=6) of the resulting mixtures were measured to determine their mechanical properties. The antiprotein properties were measured by using the micro bicinchoninic acid method (n=6). The antimicrobial effect of the resin was assessed using live/dead staining (n=6) and methyltransferase (MTT) assays (n=10). According to the variance homogeneity and normal distribution results, 1-way analysis of variance followed by the Tukey honestly significant difference test or the Welch test and the Games-Howell test were used (α=.05 for all tests). ResultsNo significant differences were found in the flexural strength values and surface roughness of the specimens containing 1.5% MPC and 1.5% ε-PL compared with those of the control (P>.05). The addition of ε-PL to the PMMA resin alone significantly increased its bactericidal properties (P<.05). Adding both ε-PL and MPC further increased the antibacterial activity of the PMMA resin without increasing protein adhesion more than in the control group. ConclusionsThe incorporation of both ε-PL and MPC into PMMA improved its antibacterial capacity without affecting its mechanical properties and did not increase protein adhesion. Therefore, the novel PMMA fabricated in this study shows promise for dental applications.

An overview of the potential of &lt;i&gt;Citrus hystrix&lt;/i&gt; (kaffir lime) essential oil as mosquito repellent

&lt;span&gt;A chemical-based insect repellent such as N, N-diethyl-3-methylbenzamide (DEET) is commonly used against all insects despite its toxicity in humans. Hence, a repellent agent from natural sources of plant essential oil was introduced. Some of the plants which have the repellent potential are catnip, hairy basil, citronella, vetiver, clove, and citrus. Citronellal, citronellol, geraniol, eugenol, eugenol-acetate, and beta-caryophyllene are among the repellent active components in these plants. &lt;em&gt;Citrus hystrix&lt;/em&gt; (kaffir lime) was known for several applications in food, health, and skincare, but its potential as mosquito repellent is still new. This overview paper highlights the potential of kaffir lime essential oil as a mosquito repellent and the encapsulation of essential oil related to mosquito repellent. Several studies on kaffir lime essential oil as mosquito repellent was conducted and revealed that the major repellent active components are citronellol and limonene. Pure kaffir lime essential oil provides one-hour repellent protection against the mosquito. However, an addition of 5% vanillin prolongs the protection time to three hours. Essential oil is easily vaporized at room temperature which shortens its effectiveness time. Encapsulation of the essential oil would control the vaporization process and hence prolong its efficiency. Nonetheless, almost no research work reported on the encapsulation of kaffir lime essential oil and the release mechanism of the encapsulated kaffir lime.&lt;/span&gt;

Nanogels Containing Foeniculum vulgare Mill. and Mentha piperita L. Essential Oils: Mosquitoes' Repellent Activity and Antibacterial Effect.

Foeniculum vulgare Mill. and Mentha piperita L. are two common medicinally important plants with a wide range of biological activities such as insecticide and antibacterial effects. In this study, the chemical composition of their essential oils was investigated using GC-MS analysis. After that, their nanoemulsions were prepared; optimum samples with droplet sizes of 74 ± 7 and 136 ± 5 nm were gelified. The viscosity of the prepared nanogels and the successful loading of the essential oil in them were investigated. The efficacy of the nanogel containing M. piperita essential oil as a repellent and antibacterial agent was more potent than the nanogel containing F. vulgare essential oil. Its completely protected time against Anopheles stephensi, the main malaria mosquito vector, was 120 ± 8 min. Moreover, the growth of Escherichia coli and Staphylococcus aureus after treatment with 5000 µg/mL of nanogel containing M. piperita essential oil was reduced by 100 and 65%, respectively. Considering natural constituents, a straightforward preparation method, and high efficacy, the nanogel containing M. piperita essential oil could be introduced for further investigation against other mosquitoes and bacterial species.

Ovicidal and repellent activities of several plant essential oils against Periplaneta americana L. and enhanced activities from their combined formulation

Natural ovicidal and repellent agents against Periplaneta americana L. are urgently needed, and plant essential oils (EOs) can assume this role quite readily. In this study, ovicidal and repellent activities against Periplaneta americana of EOs from Cymbopogon citratus (Stapf.), Cinnamomum verum (J. Presl.), Eucalyptus globulus (Labill.), Illicium verum (Hook.f.), and Zanthoxylum limonella (Alston) in soybean oil and in ethyl alcohol were determined by topical and dual-choice assays, as well as 10% cypermethrin and a combined formulation of 5% C. verum EO + 5% I. verum EO. Cypermethrin at 10% provided the highest toxicity (100% inhibition rate) against the eggs, but only slightly higher than that (99.3%) provided by the combined EO formulation, while the highest repellent activity against the adults was provided by the combined formulation (89.5% repelled cockroaches at 48 h after treatment). In addition, all EO formulations in soybean oil provided higher ovicidal and repellent activities than those in ethyl alcohol. To conclude, the combined EO formulation in soybean oil can replace cypermethrin because their efficacy was nearly equivalent, but the combination should be much safer to use.

Fabrication of fluoride-free water repellency cotton fabrics with water-borne polyurethane/acrylate dispersion

In this work, a new fluoride-free awaterborne polyurethane (WPUA) water repellent agent was synthesized and used for cotton fabrics with the concerns of environmental and human safety. Specifically, the WPUA was prepared by isophorone diisocyanate (IPDI), poly(tetrahydrofuran) (PTMG), 2,2-bis(hydroxymethyl)butyric acid (DMBA), and 2-hydroxyethyl acrylate (HEA), followed by polymerization of long-chain alkyl acrylate monomers by a seed emulsion method. After being treated with the water repellent agent via a dip-pad-curing process, cotton fabrics could gain desired water repellent (contact angel at 145° and hydrostatic pressure up to 264 mm). Atomic force microscope (AFM) and scanning electron microscope (SEM) analysis showed that the low surface energy WPUA polymers coated the fabric and formed a concavo-convex structure. Benefiting from the robust formation of coatings, the cotton fabrics could obtain good durability for daily laundry. After 50 home laundering cycles, the static water contact angle of the fabric coated with the WPUA could be maintained at 127°. Moreover, the addition of the WPUA to cotton fabrics also exhibited minimally impacting breaking strength and whiteness of the cotton fabric. All the results showed that the new WPUA dispersion is a promising water repellent for textile due to its environment-friendly and cost-effective nature and could be used as a substitute for fluorocarbons water repellent agent.

Chemical Composition and Insecticidal Properties of Essential Oil Obtained from Artemesia songarica Schrenk

Artemisia songarica Schrenk is a dominant sand fixation plant growing in the People's Republic of China. At present, there are rare studies on the chemical composition and biological activity of A. songarica. The chemical composition of the original oil was analyzed by gas chromatography-mass spectrometry, and 16 compounds were determined. The main compounds were bisabolol oxide II (28.7%), nerolidol (18.6%), bisabolol (12.9%), bisaboloxide A (10.0%), and spathulenol (6.0%). The contact toxicity and repellent activity of A. songarica essential oil and four selected compounds (bisabolol, geranyl butyrate, nerolidol, and santalol) were assessed against Tribolium castaneum Herbst and Liposcelis bostrychophila Badonnel. Bioassays showed that the crude essential oil exhibited strong insecticide and repellent activities against both pests. Santalol possessed the strongest contact toxicity (50% lethal dose [LD50] = 1.29 μg per adult) against T. castaneum. Nerolidol, santalol, and geranyl butyrate showed fair contact activity against L. bostrychophila. In particular, geranyl butyrate exhibited outstanding activity (LD50 = 11.53 μg/cm2). In addition, all of the four compounds did not detect a difference between compounds and the positive control (P > 0.05) against two pests at five tested concentrations. These results indicated that A. songarica and its selected compounds could be used as prospective insecticidal and repellent agents for further development and use.

How Effective Are Antimicrobial Agents on Preventing the Adhesion of Candida albicans to Denture Base Acrylic Resin Materials? A Systematic Review.

Denture stomatitis is a common oral infection caused by Candid albicans. It occurs under removable dentures due to several causative and contributing factors. If not treated, it can lead to fatal systemic candida infections. Different materials and techniques have been used to treat denture stomatitis; however, no single treatment has succeeded. The purpose of this study was to review novel techniques for incorporating antimicrobial and protein repellent agents into denture acrylic resin materials and their effect on the adhesion of Candida albicans to denture base acrylic resin materials to prevent and/or treat denture stomatitis. A systematic review was conducted in which an electronic search was undertaken using different databases and relevant keywords. The literature search revealed numerous studies describing different antifungal materials incorporated into different denture acrylic resin materials. The investigated materials showed significant antimicrobial activity with slight or no effect on the physical and mechanical properties; however, the optical properties were particularly affected with higher concentrations. The incorporation of antimicrobial agents to reduce or prevent Candida albicans biofilm formation on acrylic resin proved to be very effective, and this effect was found to be proportional to the percentage of the material used. The latter should be considered carefully not to alter the physical, mechanical or optical characteristics of the denture base material.

Intracellular Ca2+ accumulation triggered by caffeine provokes resistance against a broad range of biotic stress in rice.

Chemical pesticides are still frequently overused to diminish such crop loss caused by biotic stress despite the threat to humans and the environment. Thus, it is urgent to find safer and more effective defense strategies. In this study, we report that caffeine, implanted through a transgenic approach, enhances resistance against variable biotic stresses in rice without fitness cost. Caffeine-producing rice (CPR) was generated by introducing three N-methyltransferase genes involved in the biosynthesis of caffeine in coffee plants. The CPR plants have no differences in morphology and growth compared to their wild-type counterparts, but they show strongly enhanced resistance to both bacterial leaf blight, rice blast, and attack of white-backed planthoppers. Caffeine acts as a repellent agent against rice pathogens. Moreover, caffeine triggers a series of Ca2+ signalling-like processes to synthesize salicylic acid (SA), a hormone associated with plant resistance. In CPR, phosphodiesterase was inhibited by caffeine, cAMP and cGMP increased, intracellular Ca2+ increased, phenylalanine lyase (PAL) was activated by OsCPK1, and SA synthesis was activated. This finding is a novel strategy to improve resistance against the biotic stresses of crops with a special type of defense inducer.

Denture Acrylic Resin Material with Antibacterial and Protein-Repelling Properties for the Prevention of Denture Stomatitis.

Denture stomatitis is a multifactorial pathological condition of the oral mucosa that affects up to 72% of denture wearers. It is commonly seen on the palatal mucosa and characterized by erythema on the oral mucosa that are in contact with the denture surface. The aim of this study was to incorporate 2-methacryloyloxyethyl phosphorylcholine (MPC) and dimethylaminohexadecyl methacrylate (DMAHDM) into a high impact polymethylmethacrylate heat-cured denture base acrylic resin as a potential treatment for denture stomatitis. We used a comparative study design to examine the effect of incorporating MPC as a protein repellent agent and DMAHDM as an antifungal agent to prevent the adherence of Candida albicans to the denture base material. The dual incorporation of MPC and DMAHDM reduced C. albicans biofilm colony-forming unit by two orders of magnitude when compared to the control group devoid of the bioactive agents. Although the addition of MPC and DMAHDM alone or in combination significantly reduced the flexural strength of the material, they showed reduced roughness values when compared to control groups. This new denture acrylic resin provides the benefit of enhancing C. albicans biofilm elimination through dual mechanisms of action, which could potentially reduce the prevalence of denture stomatitis.

The composition, pharmacological and economic importance of essential oil of Litsea cubeba (Lour.) Pers

Litsea cubeba (Lour.) Pers. is a valuable essential oil-producing plant species. It is a shrub and is mostly found in India, China, Japan, Taiwan, and, Northern Thailand. L. cubeba essential oil, which is rich in citral, has been used as a traditional medicine to treat several diseases. The fresh fruits of L. cubeba are used for the extraction of essential oil, and the oil is intense yellowish in color, fresh and has a sweet aromatic flavor. The composition of essential oil varies based on the extraction method, cultivar, plant parts, time of sampling and processing. The current manuscript summarizes the composition as well as pharmacological and economic importance of L. cubeba essential oil. The literature review revealed that the essential oil of L. cubeba exhibited antioxidant, antimicrobial, and antiproliferative activities; also, it can be used as pesticide, repellent and fragrance agent in cosmetics. However, further studies are required to bridge the scientific gap of transferring the scientific findings into commercially valuable products. Also, studies on the potential of L. cubeba essential oil in other possible fields like aromatherapy and cognition are desirable.

Characterisation and Evaluation of Antimicrobial, Antioxidant and Antibiofilm Activities of Silver Nanoparticles Biosynthesised from Harpullia arborea Bark Extract

Introduction: In recent years, plant-based antibacterial substance has replaced the conventional chemical synthesis method. Harpullia arborea belongs to the Sapindaceae family; its bark, fruit, and seeds are used by Indians as leech repellent, hair wash, and antirheumatic agents. Plant-mediated green synthesis of nanomaterials is gaining popularity due to its environmental friendliness and cost-effectiveness. Aim: To synthesise Silver Nanoparticles (AgNPs) using bark extract of Harpullia arborea and evaluate their antibacterial efficacy against food borne pathogens. Materials and Methods: The in-vitro study of antimicrobial activity of Harpullia arborea bark extract was utilised for the synthesis of nanoparticles with 2 mM of silver nitrate. The study was conducted from March 2017 to April 2017. The synthesised nanoparticles were confirmed and characterised using Ultraviolet-Visible (UV-Vis) spectroscopy, while Fourier transform infrared, and electron microscopy utilised for the determination of shape and size of the synthesised particle. The synthesised AgNPs were subjected to antibacterial activity against food isolates using agar well diffusion method. Furthermore, Minimal Inhibitory Concentration (MIC) and antioxidant were also measured with titre plate and 2,2-diphenyl-1-picryl-hydrazylhydrate (DPPH) method, respectively. Results: The UV-Vis spectra showed conformation of AgNPs with surface resonance peak of 430 nm, and Fourier-transform Infrared Spectroscopy (FTIR) spectra confirmed the involvement of biological molecules in AgNPs synthesis. In addition, Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray (EDX) analysis confirmed AgNPs with a spherical shape with diameters from 26.3-40.6 nm. The well diffusion method showed the antibacterial activity of AgNPs against bacterial isolates. The results showed that AgNPs possess higher antimicrobial potency than non AgNPs. The lowest Minimum Inhibitory Concentration (MIC) was observed against Staphylococcus aureus [3.5 mg] and followed by Enterococcus faecalis and Pseudomonas aeruginosa [4.5 mg]. The DPPH method has confirmed that silver nanoparticles have a similar antioxidant activity compared to ascorbic acid. Conclusion: It can be concluded that Harpullia arborea bark extract can be used effectively in the production of potent antimicrobial and antioxidants for commercial use.

An investigation on the performance of 1200 kg/m3 lightweight foamed concrete incorporated with calcium stearate

Lightweight foamed concrete (LFC) is normally used on the exterior of buildings such as walls and roof slabs, which causes it to be often exposed to natural weathering such as rain. Since water is an agent of deterioration towards the durability of LFC in long term, calcium stearate, is introduced into LFC. Calcium stearate (CS) is a type of water repellent agent that reduces the penetration of water into LFC. This research aims to investigate the effect of incorporating CS into the LFC mix in terms of its strength performance. Four types of LFC containing different percentages of CS ranging from 0 % to 0.6 % of cement weight were cast and water cured for 7, 28 and 56 days before being tested for its strength properties. It was found that adding CS into the LFC does not affect the workability of fresh concrete. The finding also showed that CS only retards the strength development rate of LFC during the early ages of LFC instead of reducing its overall strength. Under continuous curing, LFC with CS can achieve strength similar to the strength obtained by the control mix. If the early strength of LFC is not a major concern, incorporating CS into LFC will have an added advantage of lower water absorption which improves the durability of LFC.

Novel acylpiperidine analogues as potential aphid repellent agents: Rational design, synthesis and repellent activity

Odorant-binding protein (OBP) is a promising potential target and can be used as a template for developing insect control agents due to its ability to bind to and transport semiochemicals to olfactory receptors, thus triggering behavioural responses among insects. In this study, 27 novel acylpiperidine analogues were designed and synthesised by introducing the hydrophobic long chain of the aphid alarm pheromone (E)-β-farnesene (EβF) into the polar acylpiperidine group of the commercial insect repellent icaridine based on the binding cavity characteristics of an OBP of the pea aphid Acyrthosiphon pisum, ApisOBP3. Compound 14c displayed good repellent activity against the pea aphids with a repellence rate of 61.5% at a concentration of 6 μg/μL. The equilibrium dissociation constant (Ki) of compound 14c against ApisOBP3 was 20.92 μM in competitive fluorescence binding assays; this value is similar to the Ki of the commercial insect repellent icaridine (20.56 μM). Molecular dynamics simulation revealed that the EβF long chain of compound 14c showed considerable hydrophobic interactions with the binding domain of ApisOBP3. Moreover, the acylpiperidine moiety of compound 14c formed one hydrogen bond and multiple carbon–hydrogen bonds with the Phe2 and Asn109 residues, respectively. The binding free energy analysis indicated that the contribution of the van der Waals force to the binding affinity was approximately twice as great as that of the electrostatic force. These studies provide significant guidance for the rational designing and efficient identification of novel insect repellent agents.

Acaricidal and repellent activities of Litsea cubeba (Lour.) oil and 3,7-dimethyl-2,6-octadienal against Haemaphysalis longicornis (Acari: Ixodidae)

The bioactivity of the essential oil extracted from Litsea cubeba fruits against tick vectors of severe fever with thrombocytopenia syndrome is unknown. In this study, L. cubeba oil and its main constituents, 3,7-dimethyl-2,6-octadienal and its similar structures, were evaluated for their acaricidal and repellent activities on the unfed nymphs and adults of Haemaphysalis longicornis. L. cubeba oil displayed both acaricidal and repellent activities against both life stages. Among the constituents of L. cubeba oil, only 3,7-dimethyl-2,6-octadienal exhibited both acaricidal and repellent activities against both life stages. In a repellent bioassay, 3,7-dimethyl-2,6-octadienal and L. cubeba oil at dose of 0.08 mg/cm2 provided excellent repellence (100%) against the nymphs and adults for over 60 min post-application. When the acaricidal and repellent activities of 3,7-dimethyl-2,6-octadienal and its similar structures were compared, activities of all tested derivatives were significantly less potent than those of 3,7-dimethyl-2,6-octadienal. The strong acaricidal and repellent activities of 3,7-dimethyl-2,6-octadienal in L. cubeba oil suggests that it is a promising natural candidate for developing new sustainable acaricidal and repellent agents.

Analysis of chemical compositions and larvicidal activity of nut extracts from Areca catechu Linn against Aedes (Diptera: Culicidae).

BackgroundThere is a growing need to use green alternative larvicidal control for Aedes larvae compared to chemical insecticides. Substantial reliance on chemical insecticides caused insecticide resistance in mosquito populations. Thus, research for alternate chemical compounds from natural products is necessary to control Aedes larvae. This study explores the analysis of chemical compositions from Areca catechu nut as a potential larvicide for Aedes (Diptera: Culicidae).MethodsThe Areca catechu nut collected from Ipoh, Perak, Malaysia was grounded into powder and used for Soxhlet extraction. The chemical analysis of the extracts and their structures were identified using the GCMS-QP2010 Ultra (Shimadzu) system. National Institute of Standards and Technology (NIST) Chemistry WebBook, Standard Reference Database 69 (https://webbook.nist.gov/chemistry/) and PubChem (https://pubchem.ncbi.nlm.nih.gov/), the two databases used to retrieve the synonyms, molecular formula, molecular weight, and 2-dimensional (2D) structure of chemical compounds. Next, following WHO procedures for larval bioassays, the extracts were used to asses larvicidal activity against early 4th instar larvae of Aedes aegypti and Aedes albopictus.ResultsThe larvicidal activities were observed against early 4th stage larvae with different concentrations in the range from 200 mg/L to 1600 mg/L. The LC50 and LC95 of Aedes aegypti were 621 mg/L and 2264 mg/L respectively; whereas the LC50 and LC95 of Aedes albopictus were 636 mg/L and 2268 mg/L respectively. Mortality was not observed in the non-target organism test. The analysis using gas chromatography and mass spectrometer recovered several chemical compounds such as Arecaidine, Dodecanoic acid, Methyl tetradecanoate, Tetradecanoic acid <n->, and n-Hexadecanoic acid bioactive components. These chemical constituents were used as additive formulations in pesticides, pest control, insect repellent, and insecticidal agents.ConclusionsOur study showed significant outcomes from the extract of Areca catechu nut and it deserves further investigation in relation to chemical components and larvicidal actions between different species of Aedes mosquitoes. Even though all these findings are fundamental, it may have some interesting potentials to be developed as natural bio-larvicidal products.

Manual Application versus Autonomous Release of Water Repellent Agent to Prevent Reinforcement Corrosion in Cracked Concrete

Cracks in reinforced concrete are preferential ingress paths for aggressive substances such as chlorides. As soon as a critical amount of chlorides has reached the steel reinforcement, corrosion will occur. Therefore, crack healing is of utmost importance. However, manual crack repair is very labour intensive. Therefore, the potential of self-healing through the release of a water repellent agent from embedded capsules was compared with the effectiveness of applying this agent on the concrete surface before or after cracking and the effectiveness of injection of the agent into a crack. From the electrochemical corrosion measurements, it was shown that only uncracked samples were able to withstand 135 weekly cycles of exposure to a 33 g/L chloride solution without corrosion initiation of the reinforcement. While samples with manually injected and autonomously healed cracks resisted the exposure conditions for about 50 cycles or more, samples for which the water repellent agent was applied onto the surface after cracking resisted the exposure conditions for 5–42 cycles, while samples for which the agent was applied onto the surface before cracking showed an immediate corrosion initiation similar as was noted for the untreated cracks. From a visualization of the chloride ingress front and determination of the chloride content in the vicinity of the crack, it was noticed that none of the crack treatment techniques performed as well as the uncracked series. Visual inspection of the corroded rebars and determination of the corroded volume of the rebars through computed tomography and macro-cell corrosion current measurements proved again that the uncracked series outperformed the other series. While the corroded volume of the rebars from the uncracked series was almost zero, this value ranged from 15–95 mm3 for the rebars of the other series. However, the latter investigations also showed that release of the agent into the crack, whether this was done in a manual way or autonomously through release from embedded capsules, resulted in a delayed corrosion initiation and lower corrosion propagation rate compared to the application of a water repellent agent onto the surface. This is a beneficial outcome for the further implementation of self-healing approaches, more specifically though the release of encapsulated water repellent agent, in the market.

An Investigation of Suitable Healing Agents for Vascular-Based Self-Healing in Cementitious Materials

Self-healing cementitious materials can extend the service life of structures, improve safety during repair activities and reduce costs with minimal human intervention. Recent advances in self-healing research have shown promise for capsule-based and intrinsic healing systems. However, limited information is available regarding vascular-based self-healing mechanisms. The aim of this work is to compare different commercially available healing agents regarding their suitability in a self-healing vascular network system by examining a regain in durability and mechanical properties. The healing agents investigated include sodium silicate, two polyurethanes, two water repellent agents and an epoxy resin. Sealing efficiencies above 100% were achieved for most of the healing agents, and both polyurethanes and the epoxy resin showed high regain in strength. The results obtained from this study provide a framework for selecting a healing agent given a specific application, as a healing agent’s rheology and curing properties can affect the optimal geometry and design of a vascular network.

Repellent activity of three essential oils against dengue and filarial vector mosquitoes

Cymbopogon nardus, Syzygium aromaticum, and Citrus sinensis have been well known to possess insecticidal activity. Here, we investigated the repellent activity of individual of three essential oils (C. nardus, S. aromaticum, C. sinensis) and a combination of essential oils (C. nardus + C. sinensis, C. nardus + S. aromaticum, and C. sinensis + S. aromaticum) against a dengue vector, Aedes aegypti and a filarial vector, Culex quinquefasciatus. The essential oils (1 mg) were smeared evenly on the surface of the left arm (three volunteers) and then subjected to 25 females of A. aegypti and C. quinquefasciatus in the cage. The number of landed mosquitos was observed every hour for 7 hours to determine the protection index (PI). The result showed that individuals of three essential oils and a combination of essential oils generated > 90% of PI until 7 hours of application for both mosquitos species tested. Overall, the data demonstrated that individual of three essential oils, i.e., C. nardus, S. aromaticum, C. sinensis, and various combinations of essential oils (C. nardus + C. sinensis; C. nardus + S. aromaticum; C. sinensis + S. aromaticum) are promising as repellent agents against A. aegypti and C. quinquefasciatus.

Methodological approaches to assessment of the decline for health risk reduction from mosquito bites due to the application of repellents and insecticides

Introduction. The use of repellents and insecticides is the most important method of protection against mosquitoes. In the scientific literature, there is practically no information about the risk from mosquito bitesl to human health due to the non-use of these funds. The information on the prevalence, infection of mosquito-carriers of infectious agents was studied; biological risks from non-use of repellents and insecticides. The aim of the study is to develop methodological approaches to assessing the reduction of health risk from mosquito bites due to the use of repellent and insecticidal agents. Materials and methods. The methods of studying relevant scientific literature, analysis of statistical reporting data, the main stages of the methodology for assessing health risks were used. Results. The proposed methodological approaches have been tested in various scenarios for the use of repellents and insecticides in comparison with the averted risks associated with the development of infectious diseases carried by mosquitoes. Conclusion. For the implementation of methodological approaches, scenarios and parameters of the development of the situation with the use of repellents and insecticides or their non-use are proposed. Indicators of individual, population and prevented health risks were calculated, considering the severity of harm to health. The personal health risk of West Nile fever (WNF) and dirofilariasis in non-endemic areas without application repellents and insecticides is assessed as acceptable - 1.2•10-8 and 1.7•10-5, respectively. At the territory with constantly recorded WNV incidence, the application of repellents or insecticides diminished the population risk of contracting fever by ten times. The averted health risk is 0.297 cases per 2.8 million population. When using repellents or insecticides, the population risk of dirofilariasis is significantly reduced. The averted health risk is 8.8 cases per population of 579 103 people.