Bacterial Adhesion Rate Research Articles

Optimizing PEEK implant surfaces for improved stability and biocompatibility through sandblasting and the platinum coating approach

Polyether–ether–ketone (PEEK) is a commonly employed biomaterial for spinal, cranial, and dental implant applications due to its mechanical properties, bio-stability, and radiolucency, especially when compared to metal alloys. However, its biologically inert behavior poses a substantial challenge in osseointegration between host bone and PEEK implants, resulting in implant loosening. Previous studies identified PEEK surface modification methods that prove beneficial in enhancing implant stability and supporting cell growth, but simultaneously, those modifications have the potential to promote bacterial attachment. In this study, sandblasting and sputter coating are performed to address the aforementioned issues as preclinical work. The aim is to investigate the effects of surface roughness through alumina sandblasting and a platinum (Pt) sputtered coating on the surface friction, cell viability, and bacterial adhesion rates of PEEK material. This study reveals that a higher average surface roughness of the PEEK sample (the highest was 1.2 μm obtained after sandblasting) increases the coefficient of friction, which was 0.25 compared to the untreated PEEK of 0.14, indicating better stability performance but also increased bacterial adhesion. A novelty of this study is that the method of Pt coating after alumina sandblasting is seen to significantly reduce the bacterial adhesion by 67% when compared to the sandblasted PEEK sample after 24 h immersion, implying better biocompatibility without changing the cell viability performance.

Inhibitory and preventive effects of Arnebia euchroma (Royle) Johnst. root extract on Streptococcus mutans and dental caries in rats

BackgroundDental caries is one of the prevalent conditions that threaten oral health. Arnebia euchroma (Royle) Johnst. root (AR) extracts exhibit anti-inflammatory, anti-cancer, and antibacterial properties. This study was designed to investigate the antibacterial impact of AR extract on Streptococcus mutans (S. mutans) UA159 and the anti-caries effect on rats.MethodsThe antibacterial activity of AR extract against S. mutans and its biofilm was determined using the bacterial sensitivity test, the biofilm sensitivity test, and the live-dead staining technique. By fluorescently tagging bacteria, the influence of bacterial adhesion rate was determined. Using a rat caries model, the anti-caries efficacy and safety of AR extract were exhaustively investigated in vivo.ResultsAR extract inhibit not only the growth of S. mutans, but also the generation of S. mutans biofilm, hence destroying and eliminating the biofilm. Moreover, AR extract were able to inhibit S. mutans’ adherence to saliva-encapsulated hydroxyapatite (HAP). Further, in a rat model of caries, the AR extract is able to greatly reduce the incidence and severity of caries lesions on the smooth surface and pit and fissure of rat molars, while exhibiting excellent biosafety.ConclusionsAR extract exhibit strong antibacterial activity against S. mutans and can lower the incidence and severity of dental cavities in rats. These findings suggest that Arnebia euchroma (Royle) Johnst. could be utilized for the prevention and treatment of dental caries.

Transmittance of PDMS film on the fluorescent performance and synergistic antifouling effect of SWLAP/PDMS composite coatings

The film-forming substances in waterborne silicone coatings play a crucial role in the properties of coatings. A novel waterborne fluorescent antifouling coating inspired by fluorescent coral was reported in this paper. A series of sky-blue waterproof long afterglow phosphor (SWLAP)/polydimethylsiloxane (PDMS) composite coatings were prepared with different properties of hydroxy‑terminated silicone oil emulsion (HT-SOE). SWLAP is irradiated by sunlight during the day and emits fluorescence at night to interfere with the normal physiological activities of marine organisms. The high transmittance of PDMS films formed by HT-SOE contributes to the high fluorescence intensity of coatings. The adhesion behavior of marine bacteria and Navicula sp. on the coatings was studied under simulated alternative day-night, continuous light, and constant dark conditions. The results showed that the bacterial adhesion rate (BAR) and diatom removal rate (DRR) under simulated alternative day-night conditions of coatings was significantly decreased and increased, respectively. C-S20/5011 had the best static and dynamic antifouling performance. The BAR was only 2.46 % after 24 h and DRR reached 39.9 % after 48 h. Under continuous light or dark conditions, the antifouling abilities of coatings mainly depend on their surface performance and mechanical properties. The fluorescence effect played an important role in the synergistic antifouling mechanism. This study provides a new idea for environmentally friendly antifouling coatings and becomes an important step in the development of green and long-acting marine antifouling coatings.

Influence of Light Conditions on the Antibacterial Performance and Mechanism of Waterborne Fluorescent Coatings Based on Waterproof Long Afterglow Phosphors/PDMS Composites.

Marine microbial adhesion is the fundamental cause of large-scale biological fouling. Low surface energy coatings can prevent marine installations from biofouling; nevertheless, their static antifouling abilities are limited in the absence of shear forces produced by seawater. Novel waterborne antifouling coatings inspired by fluorescent coral were reported in this paper. Waterproof long afterglow phosphors (WLAP) were introduced into waterborne silicone elastomers by the physical blending method. The composite coatings store energy during the day, and the various colors of light emitted at night affect the regular physiological activities of marine bacteria. Due to the synergistic effect of fouling-release and fluorescence antifouling, the WLAP/polydimethylsiloxane (PDMS) composite coating showed excellent antifouling abilities. The antibacterial performance of coatings was tested under simulated day-night alternation, continuous light, and constant dark conditions, respectively. The results illustrated that the antibacterial performance of composite coatings under simulated day-night alternation conditions was significantly better than that under continuous light or darkness. The weak lights emitted by the coating can effectively inhibit the adhesion of bacteria. C-SB/PDMS showed the best antibacterial effect, with a bacterial adhesion rate (BAR) of only 3.7%. Constant strong light also affects the normal physiological behavior of bacteria, and the weak light of coatings was covered. The antibacterial ability of coatings primarily relied on their surface properties under continuous dark conditions. The fluorescent effect played a vital role in the synergetic antifouling mechanism. This study enhanced the static antifouling abilities of coatings and provided a new direction for environmentally friendly and long-acting marine antifouling coatings.

The Effect of Conductive Polyaniline on the Anti-Fouling and Electromagnetic Properties of Polydimethylsiloxane Coatings.

In this paper, four conductive polyaniline powders doped in hydrochloric acid, sulfuric acid, phosphoric acid, and sulfonic acid were selected and blended with polydimethylsiloxane to prepare coatings with an electromagnetic absorption effect and fouling desorption effect, respectively. A UV spectrophotometer was used to evaluate the settling rate of the powders. Fourier transform infrared spectrometry, laser confocal microscopy, and scanning electron microscopy were used to observe the morphology and structure of the powder and the coating. The interface properties of the coatings were characterized using a contact angle measurement, the mechanical properties of the coatings using a tensile test, and the electromagnetic properties of the powders and microwave absorption properties of the coatings using vector network analyzers. Meanwhile, the antifouling performance of the coatings was evaluated via the marine bacteria adhesion test and benthic diatom adhesion test, and the effect of conductive polyaniline on the antifouling performance of the coating was analyzed. The results show that adding polyaniline reduced the surface energy of the coating and increased the roughness, mechanical properties and anti-fouling properties of the coating. Moreover, adding appropriate polyaniline powder can enhance the electromagnetic wave loss of the coating. The followings values were recorded for a hydrochloric-acid-doped polyaniline coating: lowest surface energy of 17.17 mJ/m2, maximum fracture strength of 0.95 MPa, maximum elongation of 155%, maximum bandwidth of 3.81 GHz, and peak of reflection loss of -23.15 dB. The bacterial detachment rate of the polydimethylsiloxane (PDMS) samples was only 30.37%. The bacterial adhesion rates of the composite coating containing hydrochloric-acid-doped polyaniline were 4.95% and 2.72% after rinsing and washing, respectively, and the desorption rate was 45.35%. The chlorophyll concentration values were 0.0057 mg/L and 0.0028 mg/L, respectively, and the desorption rate was 54.62%.

Synergistic Antibacterial Surface with Liquid Repellency and Enhanced Photothermal Bactericidal Activity.

The presence of microorganisms on biomedical devices and food packaging surfaces poses an important threat to human health. Superhydrophobic surfaces, a powerful tool to combat pathogenic bacterial adhesion, are threatened by their poor robustness. As a supplement, photothermal bactericidal surfaces may be expected to kill adhered bacteria. Using copper mesh as a mask, we prepared a superhydrophobic surface with a homogeneous conical array. The surface shows synergistic antibacterial properties, including a superhydrophobic character against bacterial adhesion and photothermal bactericidal activity. As a result of the excellent liquid repellency, the surface could highly repel the adherence of bacteria after immersing in a bacterial suspension for 10 s (95%) and 1 h (57%). Photothermal graphene can easily eliminate most adhered bacteria during the subsequent treatment of near-infrared (NIR) radiation. After a self-cleaning wash, the deactivated bacteria were easily rinsed off the surface. Furthermore, this antibacterial surface exhibited an approximately 99.9% resisted bacterial adhesion rate regardless of planar and various uneven surfaces. The results offer promising advancement of an antibacterial surface combining both adhesion resistance and photothermal bactericidal activity in fighting microbial infections.

Experimental Study of MICP-Solidified Calcareous Sand Based on Ambient Temperature Variation in the South China Sea

With the continuous advancement of the construction of the Hainan Free Trade Port and Island Reef Project, deploying Microbial Induced Calcium Carbonate Precipitation (MICP technology) for related research on the temperature range in this area would be of great significance. MICP technology is an innovative and sustainable new soil reinforcement technology that uses the metabolic activity of specific bacteria to produce calcium carbonate precipitation (CaCO3) to connect loose soil. A few previous studies reporting on the applications of MICP technology in different temperature environments drew different conclusions. Therefore, this study involved MICP sand column reinforcement tests at ambient temperatures of 20 °C, room temperature, 30 °C, and 40 °C. The reinforcement effect was evaluated using indicators such as CaCO3 generation rate, Ca2+ conversion rate, bacterial adhesion rate, water absorption rate, and unconfined compressive strength, providing a reference basis for the future applications of MICP technology to island and reef engineering construction. The results showed that, with an increase of temperature from 20 °C to 40 °C, the CaCO3 production rate, Ca2+ conversion rate, and unconfined compressive strength showed a trend of first increasing and then decreasing; the UCS was 548 KPa at 20 °C and 2276.67 KPa at 30 °C; the water absorption rate at 20 °C was 25.32, which decreased continuously with increasing temperature, and reached 21.49 at 40 °C; and the bacterial adhesion rate also continued to rise in the range of 20 °C to 40 °C, from 10.91 to 28.44. The increase in temperature had an impact on the physiological state of bacterial cells. A scanning electron microscope test shows that CaCO3 crystal forms generated under different temperature environments were different, and the CaCO3 mineral deposits generated during MICP reinforcement at 30 °C were denser. Fewer gaps were present between adjacent sand particles, and the bond was tight, which served better as a bridge. The strength of the solidified sample was also higher. The annual average temperature of the South China Sea is about 30 °C. The findings of this experiment provide feasibility and sustainable development for MICP project reinforcement in the South China Sea.

Influence of Physical and Mechanical Parameters on Cavitation Erosion and Antifouling Behaviour of Multilayer Silica-Based Hybrid Sol–Gel Coatings on Aluminium Alloys

Sol–gel coatings can provide anti-fouling and erosion resistance while being safe to use in the marine environment. MAPTMS/ZPO multilayer coatings deposited on the AA2024-T3 aluminium surface using the dip-coating method at three different thicknesses (2, 4, and 6 µm) are investigated in this work. The coatings are characterised in terms of physical and mechanical properties, and these properties are investigated in comparison to previously obtained cavitation erosion resistance levels of the coatings. Additionally, the efficiency of the coatings against biofouling was assessed using Phaeodactylum tricornutum, a marine diatom. The influence of the formation of organic–inorganic hybrid materials (OIHMs) from the prepared sols on the physical and mechanical properties of the coatings were analysed. A variety of techniques, including attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR), water contact angle (WCA) measurements, pencil hardness testing, cross-cut adhesion testing, a roughness profilometer, and nano-indentation, were performed on the bare and coated substrates. The results indicated that the thickness, hydrophobicity, and adherence of the coatings are strongly affected by the roughness. The elastic strain failure (H/E) and resistance to plastic deformation (H3/E2) coefficients were higher than those of the bare substrate before and after the cavitation erosion test, indicating that the coating had a higher ability to withstand deformation in comparison to the substrate alone. Furthermore, the microscopic analysis of a marine diatom, Phaeodactylum tricornutum, revealed that coated surfaces exhibited a decreased rate of bacterial adhesion and biofilm formation. The data show that sol–gel formed coatings outperform uncoated AA2024-T3 in terms of hardness, elastic strain, plastic deformation, and biofouling resistance. These characteristics are attributed to the coatings’ mechanical and adhesive capabilities, as well as their tribological behaviour.

Surface grafting of cellulose triacetate hollow fiber membranes with Ag@ZnO-hyperbranched polyglycerols nanoparticles for constructing antifouling and antibacterial surfaces

In recent years, using novel nanomaterials to improve the antifouling and antibacterial performance of reverse osmosis membranes has received much attention. In this study, hydrophilic Ag@ZnO-hyperbranched polyglycerols nanoparticles were fabricated by ring-opening multibranched polymerization of glycidyl acid with the core-shell Ag@ZnO nanoparticles. The cellulose triacetate composite membranes were prepared by grafting Ag@ZnO-HPGs nanoparticles on the surface of cellulose triacetate membranes. The surface of the nanoparticles with active functional group –OH was confirmed by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Surface morphology, charge, and hydrophilicity of the composite membranes were characterized by scanning electron microscope, zeta potential, and contact angle analysis. The results showed that grafting the Ag@ZnO-HPGs nanoparticles onto the cellulose triacetate membrane surface improved the physical and chemical properties of the cellulose triacetate composite membranes. The water flux of cellulose triacetate composite membranes increased while the salt rejection rate to NaCl slightly decreased. Meanwhile, the cellulose triacetate composite membranes showed excellent antifouling properties of having a high flux recovery. The antibacterial performance of the cellulose triacetate composite membrane against E. coli and S. aureus was prominent that the antibacterial rates were 99.50% and 92.38%, and bacterial adhesion rates were as low as 19.12% and 21.35%, respectively.

Anti-fouling TiO2-Coated Polymeric Membrane Ion-Selective Electrodes with Photocatalytic Self-Cleaning Properties

Nowadays, using a polymeric membrane ion-selective electrode (ISE) to achieve reliable ion sensing in complex samples remains challenging because of electrode fouling. To address this challenge, we describe a polymeric membrane ISE with excellent anti-fouling and self-cleaning properties based on surface covalent modification of an anatase TiO2 coating. Under ultraviolet illumination, the reactive oxygen species produced by photocatalytic TiO2 can not only kill microorganisms but also degrade organic foulants into carbon dioxide and water, and a formed superhydrophilic film can effectively prevent the adsorption of foulants, thus inhibiting the occurrence of biofouling and organic fouling of the sensors. More importantly, residual foulants could be fully self-cleaned through the flow of water droplets. By using Ca2+-ISE as a model, an anti-fouling polymeric membrane potentiometric sensor has been developed. Compared to the unmodified electrode, the TiO2-coated Ca2+-ISE exhibits remarkably improved anti-biofouling properties with a low bacterial adhesion rate of 4.74% and a high inhibition rate of 96.62%. In addition, the proposed electrode displays unique properties of anti-organic dye fouling and a superior self-cleaning ability even after soaking in a concentrated bacterial suspension of 109 CFU mL-1 for 60 days. The present approach can be extended to improve the fouling resistance of other electrochemical or optical membrane sensors and is promising for the construction of contamination-free sensors.

Zwitterionic polymer coating on medical sponges via a silane coupling agent for inhibiting bacterial and fibroblast adhesion

Medical sponges are widely used in wound management, however the adhesion of bacterial or wound tissue to them may cause infection or secondary damage to patients. In this work, anti-bioadhesive polyvinyl alcohol-formaldehyde sponges with zwitterionic coating were prepared by the dip-coating process using the reactive zwitterionic phosphorylcholineated polyvinylamine (PVAm-PC) and commercial silane coupling agent KH560 at different mass ratios, and their structure, physicochemical, biocompatible and anti-bioadhesive properties were investigated. As compared to pristine sponges, the PVAm-PC-KH560 (PPK) modified sponges with the interconnected pore structure had almost unchanged water vapor transmission rate but decreased swelling degree to a certain extent possibly due to the formation of rigid Si–O–Si networks in the sponges. In vitro biological evaluation confirmed that PVAm-PC-KH560 modified sponges were not cytotoxic and had good resistance to bacteria adhesion with only ∼16% and ∼11% relative bacterial adhesion rate for E. coli and S. aureus respectively. And the optimized PPK-2 sponge showed the best comprehensive bacterial adhesion inhibition properties. Further adhesion assay of L929 fibroblasts showed that PPK-2 sponge could significantly reduce the adhesion of L929 fibroblasts. The results strongly suggested that dip-coating with zwitterionic PVAm-PC and KH560 may provide a promising and facile method to construct an anti-bioadhesive surface for biomedical applications.

Influence of surface properties on the adhesion of bacteria onto different casings

Bacteria adhere to the surfaces of sausage casing and form biofilms, which causes food spoilage and quality deterioration. However, bacterial adhesion to the casing surfaces has not received enough attention and has not been extensively studied. In this study, the effect of the physicochemical properties of casing surfaces on bacterial initial adhesion were investigated with Leuconostoc mesenteroides as model bacteria. The adhesion of Leuconostoc mesenteroides onto 5 types of casings were systematically investigated, including animal casings, collagen casings, cellulose casings, fiber casings, and nylon casings, which are the most frequently encountered casings in sausage processing. It was found that the number of viable cells on the casings following the trend as: animal casings > collagen casings > fiber casings > cellulose casings > nylon casings after 4 h of incubation time. This phenomenon might be due to the different physicochemical properties of the different casings. Therefore, physicochemical factors, including zeta potential, hydrophobicity and roughness of casings, zeta potential and hydrophobicity of Leuconostoc mesenteroides, were further characterized. In terms of hydrophobic interactions, the results showed that the number of bacteria attached to the casings did not conform to the trend of hydrophobic interaction. In terms of electrostatic interactions, the results showed that the number of bacteria attached to the casings did not conform to the trend of hydrophobic interaction. The casings with different surface roughnesses in a range of 1.67–20.83 μm, the variation of bacterial adhesion quantity was in good agreement with the variation trend of casing roughness, the result showed that the surface roughness was the key factor dominating the bacterial adhesion rate compared with the surface hydrophobicity and zeta potential. The results give new insights to explore the mechanism of bacterial adhesion on casings and prevent sausage spoilage.

Antioxidant and antibacterial PBAT/lignin-ZnO nanocomposite films for active food packaging

In present works, the lignin-zinc oxide (LZn) hybrid particles composed with lignin nanoparticles (LNP) and zinc oxide (ZnO) were prepared by a simple hydrothermal method under different pH conditions. Results from infrared spectra, thermogravimetric analysis, and elemental analysis evidenced the successful synthesis of LZn hybrids. The bacterial survival rate of LZn-9 (pH=9) against E. coli and S. aureus decreased to 9% and 49%, while the value of LNP was 69% and 80%, respectively. Then glyceryl methacrylate (GMA) was grafted on poly (butyleneadipate-co-terephthalate) (PBAT), following by the addition of LZn hybrid to prepare the master batches. Finally, the master batches were catalyzed by trimethylamine, and the PBAT-G-xLZn composite films were produced. The tensile modulus and yield strength of PBAT-G-3LZn increased by 35.2% and 28.6% compare with pure PBAT, respectively. The PBAT/LZn composite films were found to have obvious UV shielding, antioxidant and antibacterial activities. Composites belong to the contact type antibacterial, the bacterial adhesion rates of PBAT-G-xLZn were obviously reduced compare with pure PBAT. The transmittance at λ = 320 nm of PBAT-G-3LZn film was only 0.16%, and the radical scavenging activity (RSA) value was 11.6%. The Zn2+ migration concentration of PBAT-G-3LZn was only 3.3 μg/L. Therefore, the PBAT/LZn composite films were believed to be applied for active food packaging.

Rhamnolipids Application for the Removal of Vanadium from Contaminated Sediment.

The use of biosurfactants in bioremediation of hydrocarbons and in the removal of heavy metals in crude oils is considered an attractive subject. The vanadium pollution in soil and sediments had attracted research interest in exploring eco-friendly methods of remediation. The present study was conducted to evaluate the potential of a biosurfactant to remove vanadium from artificially contaminated sand. The biosurfactant producer's strain selection process was carried out from 23 strains in two steps. In the primary screening, four preliminary tests were carried out: the emulsification index (24 and 72h), the surface tension, and the rate of bacterial adhesion to hydrocarbons. In the secondary screening, the surface tension and rhamnolipids concentration were determined, also critical micellar concentration and dilution were calculated. The RNA 16s of selected strain was sequence and the strain was identified as Pseudomonas sp. By chromatographic and spectroscopic assays, the structure of the rhamnolipids was determined. The maximal vanadium removal efficiency (85.5%) was achieved with a rhamnolipids' concentration of 240mgl-1. The vanadium concentration was determined by spectroscopic technique. Rhamnolipids produced by this strain can potentially be used in the removal of vanadium.

Cold plasma assisted deposition of organosilicon coatings on stainless steel for prevention of adhesion of Salmonella enterica serovar Enteritidis

The persistence of Salmonella enterica on abiotic surfaces in hospitals and the agri-food industries leads to several infections worldwide. In this context, this work aimed to study the adhesion of S. Enteritidis on plasma-modified stainless steel to prevent biofilm-associated-infections. Surface modification was achieved by the elaboration of organosilicon coatings from the monomer 1,1,3,3-tetramethyldisiloxane, mixed with oxygen, using a flowing nitrogen microwave post-discharge plasma polymerization technique. The effect of cold plasma parameters on the properties of the coatings, the coated surface topography and S. Enteritidis cell adhesion was studied. The results showed that the surface topography influenced the bacterial adhesion rate. Indeed, rough surfaces did not repel S. Enteritidis since the number of attached cells on these coatings was between 30 ± 4 to 65 ± 4 bacteria per microscopic field. Otherwise, smoother surfaces demonstrated an anti-adhesive character since the number of attached cells was almost nil on these coatings.

Streptococcus mutans adherence to conventional and self-ligating brackets: an in vitro study.

ABSTRACTIntroduction: Although self-ligating brackets presumably provide better hygiene conditions, no consensus has been reached so far. Objective: Therefore, the objective of this study was to evaluate, in an in vitro experimental design, the adherence of Streptococcus mutans (SM) in self-ligating and conventional brackets of different manufacturers and ligature types. Methods: Four commercial brands of maxillary premolar metal brackets were tested (Abzil®; Morelli®; 3M Unitek®; and GAC®). Each one was subdivided into three groups, which varied according to the type of ligature and bracket model (metallic, elastic, and self-ligating), totalizing twelve groups, composed of six brackets each. Previously sterilized brackets were initially immersed in saliva for one hour, and subsequently washed and added in a bacterial suspension, maintained in aerobiosis for 72 hours. The adhered bacteria were then separated and quantified by colony forming units (CFU/mL) counting after 48 hours of growth. The groups were compared by Kruskal-Wallis and Dunn post-hoc tests (p< 0.05). Results: Regardless of the commercial brand, self-ligating brackets had significantly less CFU/mL. However, according to comparisons performed within each commercial brand, only Abzil® self-ligating brackets had significantly lower biofilm adhesion. Among all of the self-ligating models, GAC® brackets presented the highest bacterial adhesion rate. Conclusions: Self-ligating brackets are likely to present lower rates of biofilm adhesion. Particularly, Abzil® and GAC® self-ligating brackets are less likely to accumulate biofilm. Although such results are derived from an in vitro study, practitioners might acknowledge findings concerning bacterial adhesion as one of the relevant features to be considered during bracket selection.

Effect of size fractioned alginate-based transparent exopolymer particles on initial bacterial adhesion of forward osmosis membrane support layer

In the forward osmosis (FO) process, biofouling is well pronounced on the active side where wastewater and seawater are used as feed and draw solution, respectively. However, the biofouling tendencies within the support layer are not clear. Therefore, the objective of this study was to investigate the effect of TEP pre-conditioning on hydophobicity and initial bacterial attachment of FO membrane support layer. Two structurally distinct FO membranes from different manufacturers were pre­conditioned by soaking in artificial sea water filtrates containing size fractioned TEP. The conditioning solution pre-treated with a 0.4μm pore size filter, contributed to the highest bacterial adhesion rates during bacterial attachment testing in both steady state and cross-flow mode in a lab-scale FO system for both membrane types. CTA-ES support exhibited higher numbers of adhered bacteria when compared to PA-TFC support in a steady state. Conversely, in cross-flow lab-scale testing, a negative impact of fouling on PA-TFC was more apparent than the CTA-ES membrane. This was attributed to the higher porosity and surface roughness of the PA-TFC membrane. Overall, our findings reinforce the potential impact of hydrodynamics conditions and membrane properties on the fouling behavior of FO membrane support layer.

Bacterial adhesion rate on food grade ceramics and Teflon as kitchen worktop surfaces

Here we present a research of bacterial adhesion to two most often used materials in modern kitchens, namely food grade ceramics and Teflon. To test the bacterial adhesion on kitchen worktops Escherichia coli, Pseudomonas aeruginosa and Campylobacter jejuni were used as the most common foodborne contaminants. Contact angle, roughness and streaming potential measurements were used for surface characterization. Crystal violet staining and scanning electron microscopy were applied for bacterial adhesion analysis. We showed that the adhesion of tested bacteria strains was lower on the Teflon surface compared to the ceramics. The hydrophobicity of the surface substantially contributed to the bacterial adhesion rate. On the other hand, the surface roughness and charge did not play a crucial role in the adhesion process.

The Levels of Plastic-associated Heterotrophic Bacteria on Three Different Types of Plastics

Plastic pollution in marine ecosystems is one of the most important study topics in recent years. The toxicity, mobility and long-term persistence characteristics of plastics create risk in ecosystems, biota and human health. In this study, the levels of heterotrophic bacteria attached to the surfaces of commonly used plastic types; polyvinylchloride (PVC), polyethylene (PE), and polypropylene (PP) were tested in a mechanical experimental system prepared with seawater under controlled conditions in laboratory. The seawater, which was used in the experimental system, was taken under aseptic conditions from the Golden Horn Estuary, located in the Istanbul region of Turkey. Three different types of plastic (PVC, PE and PP), in two different (glass slide (76x26 cm) and virgin micro pellets (5mm diameter) size, were placed in the experiment setup filled with seawater and incubated for 28 days at ambient temperature. At the end of 28 days, the counts of heterotrophic bacteria were tested using the spread plate technique on Marine Agar (Difco), in both plastic surfaces and surrounding seawater. The levels of heterotrophic bacteria were recorded to be lower in the seawater surrounding the micropellets and lam-size plastic samples. The seawater sample bacterial levels were recorded as 12x109 CFU/ml, at the start of the experiment. At the end of the 28th days, it was recorded to be 83x109 CFU/ml. The highest levels of heterotrophic bacteria were recorded as 41x1010 CFU /cm-2 and 61x1010 CFU /cm-2 on the lam-size surfaces and the micropellet surface of the polypropylene samples, respectively. In the experiments, the PP plastic type has been recorded as a more preferred plastic derivative by heterotrophic bacteria according to the PVC and PE plastic types, but there has been no significant difference in the bacterial adhesion rates on the surfaces. The study contributed increasing knowledge on the bacterial approach to microplastics types. However, there is a need for long term studies related to the mechanism of bacteria attached to microplastics.

Preliminary study of microstructure, mechanical properties and corrosion resistance of antibacterial Ti-15Zr-xCu alloy for dental application

Ti-15Zr-xCu (3 ≤ x ≤ 7, wt.%) novel antibacterial and antibiofilm alloys with competitive mechanical properties, biological responses and corrosion resistance were designed and fabricated. Annealing heat treatment on Ti-15Zr-7Cu (TZC-7A), after holding for 2 h at slightly above their beta transus temperature (BTT) ensured their tensile strength (UTS), yield strength (YS) and hardness (HRV) were improved by 31.2%, 20% and 12.3% respectively compared to the control without Cu, Ti-15Zr (T-15ZA). Although the 3 wt.% Cu alloy displayed the highest elongation (26%), the TZC-7A alloy also possessed a good ductility. Presence of evenly dispersed Ti2Cu and Zr2Cu Cu-rich intermetallic phases formed as interwoven and alternating lamellae within the α + β matrix as a result of Cu addition, as revealed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). These greatly contributed to their strengthening and bactericidal properties. Over 98% antibacterial effect against E. coli and S. aureus have been imparted, coupled with excellent biofilm inhibition. Potentiodynamic polarization curves showed that the TZC-7A alloy possessed higher corrosion resistance than commercially pure titanium, cp-Ti; contact angle test revealed enhanced hydrophilicity; while confocal laser scanning microscopy (CLSM) and cell counting kit (CCK-8) assays also displayed drastically lowered bacterial adhesion rate with comparatively no cytotoxicity. Cell attachment on all alloys was similar but the best spread was obtained on TZC-7A after 24 h. The developed alloy has good potential as an antibacterial implant material with combination of optimized properties.