Dirty Conditions Research Articles

Inactivation of Avian Influenza Virus Using Commercial Chemical Disinfectants in Small Scale Poultry Production

Two commercial chemical disinfectants which are commonly used currently in the Egyptian markets were tested individually for effectiveness against High pathogenic avian influenza virus (HPAIV), which currently hit the Egyptian poultry farms at 2013, A/chicken/Egypt/13VIR3729/4/2013 (H5N1). The tested agents were sodium hypochlorite 5% available chlorine (NaOCL) and PERACLEAN 5%® (Peroxyacetic Acid 4.9% and hydrogen peroxide 26.5%). The test was performed in accordance to the guidelines of American environmental protection agency (EPA), using a carrier test with surfaces (coupons) designed specially to mimic the poultry house floor and made from concrete cement, (under dirty condition resemble Phase two, step two of CEN). At room temperature which mimic the field condition in the Egyptian poultry farms. Both sodium hypochlorite with concentration (250ppm), and PERACLEAN 5%® with concentration (1%), were not able to inactivate the virus after 5 minutes contact time, while inactivation was achieved within 30 minutes contact time. , which prove one of the golden roles when applying a disinfectant, is allowing the increase of contact time between the disinfectant and avian pathogen.

An Investigation of the Aerosol Indirect Effect on Convective Intensity Using Satellite Observations

AbstractThe effect of the environment on individual clouds makes it difficult to isolate the signal of the aerosol indirect effect, particularly at larger spatial and temporal scales. This study uses observations from the Tropical Rainfall Measuring Mission (TRMM), CloudSat, and Aqua satellites to identify convective cloud systems in clean and dirty environments. The Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol index is collocated with radar precipitation features (RPFs) from TRMM and congestus cloud features (CFs) from CloudSat. The Interim ECMWF Re-Analysis (ERA-Interim) is interpolated to identify the environmental profile surrounding each feature. Regions in Africa, the Amazon, the Atlantic Ocean, and the southwestern United States are examined. TRMM features in the Africa and Amazon regions are more intense and have higher lightning flash rates under dirty background conditions. RPFs in the southwestern United States are more intense under clean background conditions. The Atlantic region shows little difference in intensity. The differences found in the mean thermodynamic profile for RPFs forming in clean and dirty environments could explain these differences in convective intensity.Congestus identified with CloudSat show smaller differences between clouds forming in clean and dirty environments in Africa and the Amazon. Congestus in clean environments have higher reflectivities and generally larger widths, but no trend is seen in cloud-top height. The signal of the aerosol indirect effect is so small that it is very difficult to detect confidently using these methods. The environment must be considered in any study of the aerosol indirect effect, because important environmental changes can occur as aerosols are introduced to an air mass.

DiamondFace-coated seals ensure pumps run smoothly at remote oilfield in Ecuador

This brief case study reveals that DiamondFace mechanical seals from EagleBurgmann Germany GmbH & Co Kg are being used to keep multiphase booster pumps – used at a remote oilfield in Ecuador – running smoothly, even during periods of inadequate lubrication and under dirty operating conditions.

A practical evaluation of detergent and disinfectant solutions on cargo container surfaces for bacteria inactivation efficacy and effect on material corrosion

Cleaning and disinfection agents were evaluated against selected bacteria on three surfaces: aluminium, stainless steel and fibre re-enforced plastic, used as cargo container linings and to access their effect on the surface integrity. Nine sanitation chemical solutions: benzalkonium chloride, sodium hypochlorite, nitric acid, levulinic acid, peracetic acid sodium hydroxide, sodium dodecyl sulphate, AT special (commercial detergent) and Disinfect Maxi (commercial disinfectant) were tested against seven bacteria strains: Escherichia coli K12, E. coli DSM 682, Salmonella Senftenberg DSM 10062, Salmonella Typhimurium P6, Pseudomonas aeruginosa DSM 939, Listeria monocytogenes Scott A and Listeria innocua P577 in dirty condition as described by standard bactericidal test both in suspension and on the three surfaces. With the exception of sodium dodecyl sulphate (SDS) and AT Special (ATS), the others were efficient in reducing the live bacteria counts as required by the standards for six of the bacteria both in suspension and on the three surfaces; L. monocytogenes Scott A was the exception. Only peracetic acid was able to disinfect all seven strains on all surfaces (> 4 log CFU reduction) as well as in suspension (> 5 log CFU reduction) as required by the standards. Accelerated corrosion tests also showed that most of the disinfectant will likely compromise the integrity of the surfaces. Only peracetic acid at the concentration used had minimal corrosion effect. A novel index for practical usability was created to take into account disinfection efficacy and low corrosiveness; peracetic acid had the highest usability index from the chemicals tested. Peracetic acid based disinfectants will be appropriate for an environment with the composite materials studied as found in some cargo containers. Combining disinfection studies, corrosion studies and the index of the two can assist the food and allied industries in making cost-effective choices for disinfectants depending on surface materials present. Keywords: Detergents, bacteria, cargo container surfaces, disinfectant African Journal of Biotechnology Vol. 12(23), pp. 3689-3698

Dirty love: the effect of cleanliness of the environment on perceived susceptibility for sexually transmitted infections

AbstractRisk for sexually transmitted infections (STIs) is perceived to be less when the potential partner is sexually appealing. Is it possible that cleanliness of the room in which intercourse takes place also affects perceived risk for STIs? In scenario studies, participants were asked to imagine having had unsafe sex with a person they just met in that person's apartment (Study 1) or in a hotel room (Study 2) and that the next day they wake up in a room that is either quite dirty or very clean. Participants in the dirty room condition rated their susceptibility to STI higher, and had lower intentions to act the same way again. Results are discussed in terms of deductive processes, emotions, and magical contagion.

Enzymatic transformation of tyrosol by Trametes trogii laccases: Identification of the product and study of its biological activities

Abstract Oxidative transformation of tyrosol catalysed by Trametes trogii laccases in aqueous solution was investigated. LC–MS analysis shows that tyrosol was converted to its dimer. The enzymatic reaction was also investigated by 1 H and 13 C nuclear magnetic resonance, and the product formed was identified as a dimeric tetracyclic ketone. The bactericidal and fungicidal properties of tyrosol dimer were investigated using the NCCLS broth dilution and EN 1276 standard methods. High bactericidal and fungicidal effect of concentrations ranged between 1–0.5 g L −1 and 8–4 g L −1 were obtained. Dimer concentrations of 33 g L −1 and 66 g L −1 allowed reductions in viability higher than 5 log units per mL for Pseudomonas aeruginosa ATCC 15442, Escherichia coli ATCC 10536 and Enterococcus hirae ATCC 10541, Staphylococcus aureus ATCC 9144 respectively, within a contact time of 5 min under dirty conditions. The effect of this product on Tuta absoluta , a harmful pest of tomato in the world, was also evaluated. The results showed high insecticidal activity against this insect at a concentration of 16.5 g L −1 . Germinability experiments on Lycopersicum esculetum were conducted in order to evaluate the potential of a laccase treatment in removing tyrosol phytotoxicity. The results showed that tyrosol dimer was nonphytotoxic. This study presents the first comprehensive results of biological characterisation of the product obtained by the action of laccase on tyrosol transformation with T. trogii laccases.

Assessment of the efficacy of benzalkonium chloride and sodium hypochlorite against Acanthamoeba polyphaga and Tetrahymena spp.

The efficacy of benzalkonium chloride and sodium hypochlorite against Acanthamoeba polyphaga and two Tetrahymena spp. was determined based on the European Standard EN 1276:2009 suspension test. Trophozoite viability was assessed by determination of the membrane integrity using flow cytometry as a fast screening technique. Bovine serum albumin was added to simulate clean (0.3 g/liter) and dirty (3 g/liter) conditions. Benzalkonium chloride caused cell lysis at concentrations above 50 mg/liter under clean and dirty conditions. A concentration of 50 mg of free chlorine per liter had a strong biocidal effect on acanthamoebae and tetrahymenae after 15 min under clean and dirty conditions. Our results suggest that benzalkonium chloride and sodium hypochlorite were effective against the three microorganisms at concentrations commonly applied in the food industry.

Efficacy of decontaminants and disinfectants against Clostridium difficile

Clostridium difficile is a common nosocomial pathogen transmitted mainly via its spores. These spores can remain viable on contaminated surfaces for several months and are resistant to most commonly used cleaning agents. Thus, effective decontamination of the environment is essential in preventing the transmission of C. difficile in health-care establishments. However, this emphasis on decontamination must also be extended to laboratories due to risk of exposure of staff to potentially virulent strains. Though few cases of laboratory-acquired infection have been reported, the threat of infection by C. difficile in the laboratory is real. Our aim was to test the efficacy of four disinfectants, Actichlor, MicroSol 3+, TriGene Advance and Virkon, and one laboratory decontaminant, Decon 90, against vegetative cells and spores of C. difficile. Five strains were selected for the study: the three most commonly encountered epidemic strains in Scotland, PCR ribotypes 106, 001 and 027, and control strains 630 and VPI 10463. MICs were determined by agar dilution and broth microdilution. All the agents tested inhibited the growth of vegetative cells of the selected strains at concentrations below the recommended working concentrations. Additionally, their effect on spores was determined by exposing the spores of these strains to different concentrations of the agents for different periods of time. For some of the agents, an exposure of 10 min was required for sporicidal activity. Further, only Actichlor was able to bring about a 3 log(10) reduction in spore numbers under clean and dirty conditions. It was also the only agent that decontaminated different hard, non-porous surfaces artificially contaminated with C. difficile spores. However, this too required an exposure time of more than 2 min and up to 10 min. In conclusion, only the chlorine-releasing agent Actichlor was found to be suitable for the elimination of C. difficile spores from the environment, making it the agent of choice for the decontamination of laboratory surfaces.

Evaluation of the sporicidal activity of different chemical disinfectants used in hospitals against Clostridium difficile

Decontamination of surfaces and medical equipment is integral to the control of Clostridium difficile transmission, and many products claim to inactivate this bacterium effectively. Thirty-two disinfectants were tested against spores of C. difficile in a suspension test based on European Standard BS EN 13704:2002, with contact times of 1 and 60 min in simulations of clean (0.3% albumin) and dirty (3% albumin) conditions. The addition of a 1-min contact time was chosen as a more realistic simulation of probable real-life exposures in the situation being modelled than the 60 min specified by the Standard. The manufacturer's lowest recommended concentrations for use were tested. Sixteen products achieved >10(3) reduction in viability after 60 min (the pass criterion for the Standard) under both clean and dirty conditions. However, only eight products achieved >10(3) reduction in viability within 1 min under dirty conditions. Three products failed to reduce the viability of the C. difficile spores by a factor of 10(3) in any of the test conditions. This study highlights that the application of disinfectants claiming to be sporicidal is not, in itself, a panacea in the environmental control of C. difficile, but that carefully chosen environmental disinfectants could form part of a wider raft of control measures that include a range of selected cleaning strategies.

Carrier Tests To Assess the Effective Sporicidal Concentration of a Liquid Chemical Disinfectant for a Sanitization Program

The aim of the present investigation was to evaluate the microbial efficacy against highly resistant bacterial spores on different substrates using the lowest effective concentration of a market liquid sporicide based on peracetic acid. The validation was carried out following modified European regulatory agencies procedures or test methods and USP guidelines, employing carriers of materials usually treated with the sporicidal solution and present in grade A cleanrooms and spores of four different microorganisms: Bacillus subtilis and Clostridium sporogenes, both from the ATCC collection, and Bacillus cereus and Bacillus sphaericus as environmental isolates. A statistical evaluation of data was made to estimate the variance for different study conditions. The experiments highlighted that 70% suitable dilution of the ready-to-use peracetic acid solution was effective in both clean and dirty conditions, showing at least 2 log spore reduction after treatment. To obtain effective sporicidal action on the surfaces in cleanrooms it is sufficient to use a sporicidal solution with a ready-to-use concentration of 70% while ensuring a contact time of 10 min. In any case, the reduction of sporicide concentration ensures a high degree of disinfection and provides a consumption savings. Wide-spectrum disinfectants are used in the pharmaceutical industry for the decontamination of work surfaces and equipment, but these products have some degree of toxicity for operators. This work arises from the needs of pharmaceutical companies to find the lowest effective concentration of sanitizers in order to reduce toxicity to personnel. The sanitizer used in the study was a market liquid sporicide based on peracetic acid. When we started our work no similar studies were reported in the literature, so we took European regulatory agencies and USP guidelines as a starting point, employing carriers of hard, non-porous materials usually treated with the sporicidal solution and present in sterile rooms and spores of four different microorganisms. The experiments highlighted that it is sufficient to use a 70% sporicidal solution concentration with a contact time of 10 min to reduce the number of spores to acceptable values for medicinal production. The reduction of sporicide concentration both ensures a high degree of disinfection and provides a safer working environment and consumption savings.

Lipofuscin Quantification as a Potential Tool for Age Estimation in Snow Crabs,Chionoecetes opilio (O. Fabricius, 1788) (Decapoda, Oregoniidae)

AbstractLipofuscin levels were investigated in snow crabs (Chionoecetes opilio) to assess the applicability of lipofuscin quantification as an age determining tool for this species. Localization and quantification of lipofuscin granules in the olfactory lobe cell mass (OLCM) of the brain were conducted by confocal microscopy and image analysis. The majority of immature crabs had no detectable lipofuscin. Crabs with a dirty carapace condition (an indication of greater age) had more lipofuscin (in terms of granule density, area fraction, and mean granule size) than crabs with a clean carapace condition; however, the amount of lipofuscin was much lower than that in more temperate species. Lipofuscin content was positively correlated with carapace size among crabs with a clean carapace but not among crabs with a dirty carapace. No correlation was observed between average lipofuscin granule fluorescent intensity and carapace width. OLCM neuron characteristics were also investigated. An inverse relationship was observed between neuron density and carapace width although it is unknown if this density reduction is due to a loss of neurons, an increase in size of the structures, or both. Furthermore, a positive relationship was observed between neuron size and carapace width. The range of neuron size also increased in larger crabs, suggesting the presence of mitotically active cells in the OLCM. Although lipofuscin levels were higher in dirty carapace condition (presumably older) crabs than in clean carapace crabs and increased with size (in mature, clean carapace snow crabs), the lack of detectable lipofuscin in most immature crabs, generally low levels of lipofuscin in mature crabs, and lack of increase with size in older (dirty carapace) crabs limits the applicability of this age estimation tool for this species.

Aerodynamics as troubleshooting of wet fading

The prevention of soiling of glass panes and brakes is an important safety issue. Studies conducted in the thermal wind tunnel of FKFS have shown that brake discs and brake pads at aerodynamically optimized vehicles have greater traction in wet an dirty conditions.

Ultrastructural features of the process of wound healing after tail and limb amputation in lizard

AbstractAlibardi, L. 2010. Ultrastructural features of the process of wound healing after tail and limb amputation in lizard.—Acta Zoologica (Stockholm) 91: 306–318Wound healing and re‐epitelization after amputation of tail and limb in lizard have been studied by electron microscopy to understand the cytological base of immunity to infection in this species. After 2 days post‐amputation in both limb and tail stumps, numerous granulocytes are accumulated over the stump, and participate to the formation of the scab. Bacteria remain confined to the scab or are engulfed by leukocytes and migrating keratinocytes located underneath the scab. Bacteria are degraded within lysosomes present in these cells and are not observed among mesenchymal cells or in blood vessels of the regenerative blastema. Granulocytes, migrating keratinocytes, and later macrophages form an effective barrier responsible for limiting microbe penetration. The innate immunity in lizard is very effective in natural (dirty) condition and impedes the spreading of infection to inner tissues. While the complete re‐epitelization of the tail stump underneath the scab requires 4–7 days, the same process in the limb requires 8–18 or more days post‐amputation, depending from the level of amputation and the persistence of a protruding humerus or femurs on the stump surface. This delay produces the permanence of inflammatory cells such as granulocytes and macrophages in the limb stump for a much longer period than in the tail stump, a process that stimulates scarring.

Do European Standard Disinfectant tests truly simulate in-use microbial and organic soiling conditions on food preparation surfaces?

The results from European standard disinfectant tests are used as one basis to approve the use of disinfectants in Europe. The design of these laboratory-based tests should thus simulate as closely as possible the practical conditions and challenges that the disinfectants would encounter in use. No evidence is available that the organic and microbial loading in these tests simulates actual levels in the food service sector. Total organic carbon (TOC) and total viable count (TVC) were determined on 17 visibly clean and 45 visibly dirty surfaces in two restaurants and the food preparation surfaces of a large retail store. These values were compared to reference values recovered from surfaces soiled with the organic and microbial loading, following the standard conditions of the European Surface Test for bactericidal efficacy, EN 13697. The TOC reference values for clean and dirty conditions were higher than the data from practice, but cannot be regarded as statistical outliers. This was considered as a conservative assessment; however, as additional nine TOC samples from visibly dirty surfaces were discarded from the analysis, as their loading made them impossible to process. Similarly, the recovery of test organisms from surfaces contaminated according to EN 13697 was higher than the TVC from visibly dirty surfaces in practice; though they could not be regarded as statistical outliers of the whole data field. No correlation was found between TVC and TOC in the sampled data, which re-emphasizes the potential presence of micro-organisms on visibly clean surfaces and thus the need for the same degree of disinfection as visibly dirty surfaces. The organic soil and the microbial burden used in EN disinfectant standards represent a realistic worst-case scenario for disinfectants used in the food service and food-processing areas.

Inactivation of murine norovirus by chemical biocides on stainless steel

BackgroundHuman norovirus (NoV) causes more than 80% of nonbacterial gastroenteritis in Europe and the United States. NoV transmission via contaminated surfaces may be significant for the spread of viruses. Therefore, measures for prevention and control, such as surface disinfection, are necessary to interrupt the dissemination of human NoV. Murine norovirus (MNV) as a surrogate for human NoV was used to study the efficacy of active ingredients of chemical disinfectants for virus inactivation on inanimate surfaces.MethodsThe inactivating properties of different chemical biocides were tested in a quantitative carrier test with stainless steel discs without mechanical action. Vacuum-dried MNV was exposed to different concentrations of alcohols, peracetic acid (PAA) or glutaraldehyde (GDA) for 5 minutes exposure time. Detection of residual virus was determined by endpoint-titration on RAW 264.7 cells.ResultsPAA [1000 ppm], GDA [2500 ppm], ethanol [50% (v/v)] and 1-propanol [30% (v/v)] were able to inactivate MNV under clean conditions (0.03% BSA) on the carriers by ≥ 4 log10 within 5 minutes exposure time, whereas 2-propanol showed a reduced effectiveness even at 60% (v/v). Furthermore, there were no significant differences in virus reduction whatever interfering substances were used. When testing with ethanol, 1- and 2-propanol, results under clean conditions were nearly the same as in the presence of dirty conditions (0.3% BSA plus 0.3% erythrocytes).ConclusionProducts based upon PAA, GDA, ethanol and 1-propanol should be used for NoV inactivation on inanimate surfaces. Our data provide valuable information for the development of strategies to control NoV transmission via surfaces.

Josephson tunnel junctions with a strong ferromagnetic interlayer

The dependence of the critical current density ${j}_{c}$ on the ferromagnetic interlayer thickness ${d}_{F}$ was determined for $\text{Nb}/{\text{Al}}_{2}{\text{O}}_{3}/\text{Cu}/\text{Ni}/\text{Nb}$ Josephson tunnel junctions with ferromagnetic Ni interlayer thicknesses from very thin films $(\ensuremath{\sim}1\text{ }\text{nm})$ upward and classified into $F$-layer thickness regimes showing a dead magnetic layer, exchange, $\text{exchange}+\text{anisotropy}$ and total suppression of ${j}_{c}$. The Josephson coupling changes from 0 to $\ensuremath{\pi}$ as function of ${d}_{F}$, and---very close to the crossover thickness---as function of temperature. The strong suppression of the supercurrent in comparison to nonmagnetic $\text{Nb}/{\text{Al}}_{2}{\text{O}}_{3}/\text{Cu}/\text{Nb}$ junctions indicated that the insertion of a $F$ layer leads to additional interface scattering. The transport inside the dead magnetic layer was in dirty limit. For the magnetically active regime fitting with both the clean and the dirty limit theories was carried out, indicating dirty limit condition, too. The results were discussed in the framework of literature.

Development of bactericidal and virucidal testing standards for aquaculture disinfectants

There is a need for standardised comparative data on the efficacy of aquaculture disinfectants to guide their use by farmers and health professionals, as well as Competent Authorities for authorisation or listing purposes. Towards this aim, two already available CEN (Comité Européen de Normalisation) quantitative suspension test standards for the evaluation of bactericidal and virucidal activity of disinfectants and antiseptics for use in the veterinary field were modified by using agents and testing conditions representative of aquaculture conditions. For evaluating bactericidal activity, BS EN1656:2000 was modified to test disinfectant activity against Aeromonas salmonicida subsp. salmonicida (ATCC 14174), Yersinia ruckeri (ATCC 29473), Carnobacterium piscicola (ATCC 35586) and Lactococcus garvieae (NCIMB 702927) for a contact time of 30 min and temperature of 4 °C. Interfering substance was used as described for dirty conditions in the standard (10 g l − 1 yeast extract plus 10 g l − 1 bovine serum albumin solution). The substituted organisms could be stored and readily resuscitated. They were not adversely affected by the assay conditions (except exposure to the disinfectant) and could be readily prepared as suspensions. Four example products, coded A–D, were tested using both methods (including a peroxygen system, a product containing a mixture of hydrogen peroxide and peracetic acid, an acidic iodophore and a Chloramine T containing product). The neutralisation-dilution method, preferred in the standard, was appropriate for all products. Although there was greater test-to-test variation at the higher end of effective dilutions, repeat testing gave reliable results for four products as bactericides. L. garvieae and C. piscicola were the most resistant bacterial pathogens tested, requiring concentrations between 0.1–0.5% of the four products tested to achieve 5 log 10 inactivation. For evaluating virucidal activity, BS EN 14675:2006 was modified to use infectious pancreatic necrosis virus (IPNV), Spjarup serotype, using the same products with testing conditions as for BS EN1656:2000. The acidic iodophore-containing product (C) gave rise to cell cytotoxicity problems with the recommended neutralisation dilution method for titration of remaining viral activity. The other three products were reliably tested for virucidal activity using the modified assay. A further assay modification for virus mixed with Product C involved membrane dialysis for 48 h following test exposure and neutralisation by dilution. This reduced cell cytotoxicity enough to allow titration of the remaining viable IPNV.

Gecko adhesion: evolutionary nanotechnology

If geckos had not evolved, it is possible that humans would never have invented adhesive nanostructures. Geckos use millions of adhesive setae on their toes to climb vertical surfaces at speeds of over 1ms-1. Climbing presents a significant challenge for an adhesive in requiring both strong attachment and easy rapid removal. Conventional pressure-sensitive adhesives (PSAs) are either strong and difficult to remove (e.g. duct tape) or weak and easy to remove (e.g. sticky notes). The gecko adhesive differs dramatically from conventional adhesives. Conventional PSAs are soft viscoelastic polymers that degrade, foul, self-adhere and attach accidentally to inappropriate surfaces. In contrast, gecko toes bear angled arrays of branched, hair-like setae formed from stiff, hydrophobic keratin that act as a bed of angled springs with similar effective elastic modulus to that of PSAs. Setae are self-cleaning and maintain function for months during repeated use in dirty conditions. Setae are an anisotropic 'frictional adhesive' in that adhesion requires maintenance of a proximally directed shear load, enabling either a tough bond or spontaneous detachment. Gecko-like synthetic adhesives may become the glue of the future-and perhaps the screw of the future as well.

Biocidal Effect of a Sanitizer/Disinfectant, Foodsafe, against Bacteria, Yeast, and Mycobacteria

Background: Sanitizers and disinfectants are essential for hygienic control to prevent food poisoning. We evaluated the biocidal activity of a chlorine-based sanitizer/disinfectant, Foodsafe (Neochemical, Paju, Korea), against bacteria, yeasts, and mycobacteria. Methods: Clinical isolates and reference ATCC strains were exposed to the sanitizer/disinfectant solution (HOCl 100 ppm) prepared with Safefood tablets for various periods (0.5, 1, 2, 5, 10, 30, and 60 min). After the exposure the mixture of microorganisms and Safefood solution was inoculated into tryptic soy broth and onto tryptic soy agar or Sabouraud dextrose agar and cultured at 35 o C. Results: All strains of bacteria, yeasts, mycobacteria, and vegetative form of Bacillus subtilis were killed within 2 min of an exposure to Foodsafe (100 ppm of HOCl) under both clean and dirty conditions. But, the spore form of B. subtilis was not killed even after 60 min. Conclusion: It may be recommended that Foodsafe can be used as an effective sanitizer/disinfectant for food hygienic control and an intermediate-level disinfectant for hospital infection control. (Korean J Clin Microbiol 2008;11:117-122)

Gecko Adhesion: Structure, Function, and Applications

AbstractGeckos attach and detach their adhesive toes in milliseconds while running with reckless abandon on nearly any surface. The adhesive on gecko toes differs dramatically from that of conventional adhesives. Conventional pressure-sensitive adhesives (PSAs) are soft viscoelastic polymers that degrade, foul, self-adhere, and attach accidentally to inappropriate surfaces. In contrast, gecko toes bear angled arrays of branched, hair-like fibers (setae) formed from stiff, hydrophobic keratin that act as a bed of angled springs with an effective stiffness similar to that of PSAs. Setae are selfcleaning and maintain function for months during repeated use in dirty conditions. Setae are an anisotropic “frictional adhesive” in that adhesion requires maintenance of a proximally directed shear load. Thus, gecko setae resist inappropriate bonding and are capable of easy and rapid attachment and detachment. Engineered adhesive nanostructures inspired by geckos may become the glue of the future—and perhaps the screw of the future as well.