Sample Surface Research Articles

P-356. Reduction of high-touch surface aerobic bacteria and fungi colony counts with the implementation of ActivePure continuous disinfection technology

Abstract Background As hospitals nationwide rebound from the effects of the COVID pandemic, reduced staffing and increased hospital-acquired infections (HAIs) are still challenges. Surface disinfection plays a pivotal role in the prevention of HAIs. To improve high-touch surface disinfection and remove the dependence on the human factor, ActivePure continuous disinfection technology devices were installed in the Medical Intensive Care Unit (MICU) HVAC system at Ochsner LSU Health Shreveport in October 2023. ActivePure is a novel technique that kills microbes in the environment by using an advanced photocatalytic oxidation particle. Methods A prospective study was conducted in the 19-bed MICU. Two weeks before device activation, 50 high-touch surface samples and 10 reservoir samples were collected by sterile sponge in situ and plated onto Nutritive (tryptic soy) agar for total aerobic microbial counts, Selective (Sabouraud dextrose) agar for total fungal counts, selective (MeReSa) agar for total MRSA counts, and CHROMagar selective for Carbapenem-Resistant Acinetobacter baumannii (CRAB). All agar plates were incubated at 30°C or 37°C (as applicable) for 48-96 hours. For evaluation, serial dilution plate counts were used to calculate the CFU per sponge for each media type. The detection limit was 10 CFU/sponge for each evaluation. After 4 weeks post-activation, 50 high-touch surface samples and 10 reservoir samples from the same pre-activation sample locations were collected and evaluated via the same methods, and the same was repeated at 9 weeks post-activation. Routine cleaning and disinfection protocols were unchanged during the entire study period. Figure 2 Results The mean aerobic bacterial and fungi surface CFUs were reduced over 99.78% (Fig 1). The mean MRSA surface CFUs were reduced by 99.99% and the mean CRAB surface CFUs were reduced by 99.75% (Fig 2). There was a 94% reduction in surfaces with greater than 500 CFUs/100cm2 of MRSA. There was a 100% reduction in reservoirs with greater than 500 CFUs/100cm2 of CRAB and 80% reduction in reservoirs with greater than 10 CFUs/100cm2 of CRAB. Conclusion The ActivePure continuous disinfection technology devices significantly reduced total aerobic bacteria, including MRSA, difficult-to-treat CRAB, and fungi surface colony counts on high-touch surfaces. Disclosures Kimberly Trosch, RN, BSN, ActivePure Technologies: Full time employee Daniel Marsh, n/a, ActivePure Medical: Advisor/Consultant

Alteration's Control on Frictional Behavior and the Depth of the Ductile Shear Zone in Geothermal Reservoirs in Volcanic Arcs

AbstractThe majority of geothermal energy is produced in tectonically active volcanic‐arc regions due to their high geothermal gradients. Reservoirs in these settings are often stratified with smectite/kaolinite‐, illite‐, and chlorite‐rich zones, in order of increasing depth and temperature. Eighteen andesitic core and surface samples were taken from five geothermal fields in the Lesser‐Antilles and Cascade volcanic arcs. The collected samples have experienced various degrees of alteration and can be considered, in their ensemble, to be representative of the previously mentioned alteration zones. The influence of the alteration was assessed through biaxial rate‐and‐state friction experiments on prepared gouge. The samples were each tested at 10, 30, and 50 MPa normal stress in both nominally dry and nominally wet conditions. While significant water‐induced frictional‐strength reduction was observed, phyllosilicate content dominates frictional behavior, with increased phyllosilicate content reducing frictional strength, promoting velocity‐strengthening behavior, and reducing frictional healing. Negative frictional healing is observed and likely related to the presence of expandable clays, leading to frictional weakness over long time periods. It is suggested that, by controlling frictional strength, phyllosilicate content influences the depth of onset of ductile shear zones, which often underlie these reservoirs and are critical for the horizontal advection and vertical sealing of geothermal fluid. Further, as these types of reservoirs are likely critically stressed, varying degrees of alteration within different reservoir zones can give rise to the formation of stress jumps. Overall, the frictional behavior depended to a first order on overall phyllosilicate content, potentially simplifying engineering studies.

Behavior of the dielectric and pyroelectric responses of ferroelectric fine‐grained ceramics

AbstractWe demonstrated the correlations between the specific temperature behavior of the colossal dielectric permittivity, unusual electro‐transport characteristics, and frequency dependences of the pyroelectric response of the fine‐grained ceramics prepared by the spark plasma sintering of the ferroelectric BaTiO3 nanoparticles. The temperature dependences of the electro‐resistivity indicate the frequency‐dependent transition in the electro‐transport mechanisms between the lower and higher conductivity states accompanied by the maximum in temperature dependence of the loss angle tangent. The pyroelectric thermal wave probing revealed the existence of the spatially inhomogeneous counter‐polarized ferroelectric states at the opposite surfaces of the ceramic sample. We described the temperature behavior of the colossal dielectric response and losses using the core−shell model for ceramic grains, effective medium approximation, and Maxwell−Wagner approach.

Physicochemical Properties and Bacterial Adhesion of Conventional and 3D Printed Complete Denture PMMA Materials: An In Vitro Study - Part I.

To evaluate and compare the surface morphology, wettability, roughness, and bacterial adhesion properties of polymethyl methacrylate (PMMA) materials fabricated by conventional methods and 3D printing for complete denture applications. Two PMMA materials were investigated: Conventionally processed (ProBase Hot) and 3D-printed (3DP) (V-Print Dentbase). Surface morphology (n = 3) was analyzed using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Surface roughness (n = 10) was measured using an optical profilometer. Wettability was assessed through contact angle measurements (n = 6) at 10, 30, and 60 seconds. Bacterial adhesion (n = 9) and biofilm formation (n = 3) were evaluated using Escherichia coli (E. coli) as a model organism, with quantitative bacterial counts and SEM analysis of bacterial morphology. Data were statistically analyzed. Scanning electron microscopy analysis revealed nanoparticles on the surface of 3DP samples, while EDX detected silicon in these samples, absent in conventional PMMA. 3D-printed surfaces exhibited significantly lower roughness (1.05 ± 0.32 µm) compared to conventional surfaces (20.46 ± 6.71 µm) (p < 0.001). Contact angle measurements showed that 3DP surfaces were more hydrophilic (64-68°) than conventional surfaces (100°) (p < 0.05). Bacterial adhesion studies demonstrated more adherent bacteria on 3DP surfaces (92.5 ± 30.8) compared to the conventional surfaces (57.6 ± 12.5), but biofilm formation was observed only on conventional surfaces. 3D-printed PMMA exhibited distinct surface characteristics compared to conventionally processed PMMA, including the presence of silicon nanoparticles, lower surface roughness, and higher hydrophilicity. While 3DP surfaces showed higher initial bacterial adherence, in contrast, they appeared to inhibit biofilm formation, which highlights the complex nature of bacterial interactions with these materials. Further clinical studies are needed to validate the results of this investigation and generate clinical translational data. How to cite this article: Khoury P, Kharouf N, Etienne O, et al. Physicochemical Properties and Bacterial Adhesion of Conventional and 3D Printed Complete Denture PMMA Materials: An In Vitro Study - Part I. J Contemp Dent Pract 2024;25(11):1001-1008.

The fabrication of conveyor rubber belt via bio‐oil obtained by rice husk pyrolysis

AbstractBio‐oil, also called pyrolysis oil, bio‐fuel oil, pyrolytic oil, or liquid wood, is produced through biomass pyrolysis at high‐temperature decomposition without added oxygen. In this study, the use of the liquid product (bio‐oil) obtained as a result of the pyrolysis of rice husk was investigated. The aim of the work was the employment of obtained bio‐oil instead of rubber process oil and binder resin in rubber dough mixtures used in the production of conveyor belts. The bio‐oil obtained from pyrolysis of rice husk was used instead of resin and aromatic oil at rates of 25%, 50%, 75%, and 100% in the rubber fabrication. The optimum curing time was initially determined by rheometer tests before the vulcanization process. Then, the adhesion strengths rubber‐cloth (rubber‐weave) and cloth‐cloth (weave‐weave) of belt samples were tested and compared. Furthermore, the appearance and distribution on the surface of rubber samples were analyzed by scanning electron microscope (SEM). It was found that the bio‐oil derived from rice husk pyrolysis can be effectively utilized in rubber products due to its ability to reduce curing time. Moreover, the torque values also increased as the amount of bio‐oil was increased.Highlights Bio‐oil was obtained by pyrolysis of rice husk. Bio‐oil was employed as rubber process oil and softener oil in rubber dough. The adhesion and rheometer tests of rubber belt samples were investigated. Rice husk‐derived bio‐oil decreased the curing time of rubber fabrication. The cross‐linking feature in the belt structure increased.

Microbial Level and Microbiota Change of Laver in Dried Laver Processing Line During Production Seasons

To understand better the high microbial load in dried laver (Porphyra yezoensis or nori), this study analyzed the aerobic plate count (APC), coliform count, temperature change, and microbiota of processing water, laver materials, and food contact surface (FCS) samples from three processing plants during the dried laver processing season from December 2023 to April 2024. The seawater used for the first washing had a low microbial load (APCs &lt; 1–2.85 log CFU/g; coliform &lt; 1 log CFU/g) and was dominated by Proteobacteria, Firmicutes, and Bacteroidota. The microbial load of fresh laver (4.21–4.76 log CFU/g) remained unchanged after seawater washing, but significantly increased after continuous shredding, sponge dehydration, first drying, and with the seasonal temperature rise. The microbiota of laver before drying was vulnerable between processing steps and seasons, but consistently shifted back to fresh laver microflora and was dominated by Flavobacteriaceae after drying. The FCSs (except for the curtain), which had a high microbial load (APCs 5.25–8.26 log CFU/g; coliform 1.52–4.84 log CFU/g) with similar microbiota to seawater, caused the secondary contamination of laver during processing. This study revealed the microbial proliferation of laver and seawater microflora in the continuous processing line with high nutrients and with the seasonal processing water temperature rise caused by the local weather, highlighting the need for routine cleaning and sanitizing, better washing of fresh laver, and low temperature control for future dried laver production.

Strategy for enhancing Cistanche deserticola drying efficiency and quality based on novel freeze-infrared hybrid drying: moisture transition points control.

Fresh Cistanche deserticola, a valuable medicinal and dietary ingredient with exceptional functional properties, exhibits a high moisture content and is susceptible to deterioration due to its high moisture content. Therefore, it is imperative to identify an appropriate dehydration method. This study primarily focuses on enhancing the efficiency and quality of dried C. deserticola, through a hybrid drying process that combines freeze-drying (FD) and infrared drying (IRD). The samples were first dehydrated by FD and then transferred to IRD until the end of drying, with different moisture transition points (based on FD durations of 5.5, 6.0, 6.5, and 7.0 h, and the corresponding groups are marked as FD5.5h-IR, FD6.0h-IR, FD6.5h-IR, and FD7.0h-IR). The FD6.5h-IR method proved to be 32.08% more energy efficient than the sole FD method. The microscopic examination revealed that the surfaces of samples treated using the FD6.5h-IR and FD7h-IR techniques were smoother and clearer with smaller and more uniform pores, similar to the microstructure of the solely FD sample. Furthermore, the FD6.5h-IR treatment has been demonstrated to be highly effective in maintaining the retention of active ingredients in products. Given the disadvantage of FD7h-IR treatment in terms of energy consumption, FD6.5h was identified as the best moisture transition point. This investigation offers a theoretical basis for enhancing quality control and refining the process during the FD-IRD processing of newly harvested C. deserticola slices. © 2025 Society of Chemical Industry.

Evaluation of Candida Species on Food and Non-Food Contact Surfaces among Students Residing in School Hostels in a Tertiary Institution, Ile Ife, Osun State, Nigeria

Candida species are significant opportunistic fungal pathogens that can cause various diseases, particularly among individuals with compromised immunity. While there is plenty of literature on Candida in clinical and public settings, incidence on surfaces within student residence halls is still not well understood. The distribution and frequency of Candida species were assessed on surfaces that come into contact with food and non-food items at the Obafemi Awolowo University residence halls in Ile-Ife, Nigeria. Seven out of nine residence halls of the university were studied using a cross-sectional investigation. Sterile swabs were used to collect surface samples from 50 rooms, which were subsequently processed on Hi Chrome Candida Differential Agar and Sabouraud Dextrose Agar. Data analysis was done using the Chi-square test with a significance level of p &lt; 0.05. It was found that Candida species were fairly common, with an occurrence rate of 86%. The contamination rate on non-food contact surfaces was 64% compared to 76% on food contact surfaces. Its dominating species was Candida glabrata, which comprised 28%, followed by Candida albicans 6%, and Candida tropicalis was also 6%. More pronounced co-infections were noticed at the postgraduate hall: food-contact surfaces between the Candida albicans and Candida glabrata comprised 28.6%. The Moremi Hall recorded the greatest percentage of total contamination at 26%. The results stress the need for improved hygienic practices, routine check-ups, and public health programs to avoid opportunistic infections among students, as well as the need to turn attention to the possible danger of fungal contamination in communal living facilities.

Electrochemical insights into the direct dissolution of impure sphalerites and their partial oxidation in an acidic environment

This study examined the electrodissolution mechanism of five impure sphalerite samples, which differ significantly in purity levels, along with their partially oxidized counterparts in a 0.5 M H2SO4. Partially oxidized samples were prepared through an incomplete leaching of sphalerite using H2SO4 with Fe2(SO4)3.H2O as an oxidizing agent. The original sphalerite samples and the partially oxidized samples were referred to as SP and POS samples, respectively. Analyses using XRD, SEM, Raman spectroscopy, and electrochemical techniques suggested presence of elemental sulfur and a metal-deficient layer on the surface of the POS samples. Cyclic voltammetry revealed that the sample with the highest iron content exhibited the highest electrochemical response, while the sphalerite with the highest lead concentration had the lowest activity. Electrochemical impedance spectroscopy (EIS) studies showed that impedance values were higher in the POS samples compared to the PS samples, indicating a correlation within the passivation phenomenon. In conclusion, these findings suggested that the sphalerite dissolution process is primarily controlled by charge transfer and kinetic polarization. This understanding can lead to the development of more selective and sustainable extraction methods and improving the overall economic viability of zinc hydrometallurgical operations.

Devulcanization of Waste Tire Rubber via Microwave and Biological Methods: A Review

This paper presents a thorough literature review on devulcanization methods applied to waste tire rubber: “microwave devulcanization” and “biological desulfurization”. To do so, 80 papers published from the year 1990 to 2024 in journals with subscription and open access status across 12 databases were reviewed. This paper compares the efficacy and reviews the basic concepts, advantages, processes, and variable parameters of these two methods. In microwave devulcanization, microwave energy breaks the sulfur crosslinks between polymer chains. The latter breakage is mainly enabled by the presence of carbon black in the tire, which is an excellent microwave absorbent. In biological desulfurization, bacteria or fungi convert the crosslinks to elemental sulfur substances or sulfate. In general, microwave devulcanization of rubber leads to a lower crosslink density and thus a higher degree of devulcanization. On the one hand, breaking the crosslinks requires a significantly shorter time than biological desulfurization. Crosslink scission occurs throughout the sample in microwave devulcanization but only on the sample surface in biological desulfurization. Microwave devulcanization is not sensitive to rubber additives and does not require detoxification before devulcanization. On the other hand, biological desulfurization requires detoxification before devulcanization since it involves living organisms that may not tolerate certain rubber additives.

Fabrication of Z-Scheme MIL-125/Ag/BiOBr Heterojunctions with Enhanced Photocatalytic Reduction of Cr6.

Herein, first, MIL-125 samples were synthesized via a hydrothermal method. Then, Ag species were doping on the surface of MIL-125 samples via the photolysis of silver nitrate. Finally, the Z-scheme MIL-125/Ag/BiOBr composite was synthesized via a directed liquid assembly method. The structure, morphology, and optical properties of the prepared samples were investigated via X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopic mapping, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, N2 adsorption-desorption analysis, ultraviolet-visible spectroscopy, photoluminescence spectroscopy, surface photovoltage analysis, transient photocurrent response analysis, electrochemical impedance spectroscopy, and electron spin resonance analysis. Photocatalytic experiments indicated that the photocatalytic Cr6+ reduction efficiency of MIL-125/Ag/BiOBr heterojunctions was 85.7% at pH = 6, which was approximately 5.5 and 2.2 times higher than that using BiOBr and MIL-125 alone, respectively. This performance was attributed to the intimate interfacial contact between MIL-125 and BiOBr and the doping of Ag species, which increased the transfer and separation of photogenerated carriers and inhibited the recombination of electrons and holes. Furthermore, the possible photocatalytic Cr6+ reduction mechanism of the Z-scheme MIL-125/Ag/BiOBr photocatalyst was proposed.

Preparation of Silicon Nanopillar Arrays Using Reactive Ion Etching with a Faraday Cage.

Faraday cages are extensively utilized in plasma-based etching and deposition processes to regulate ion behavior due to their shielding effect on electromagnetic fields. Herein, vertical silicon nanopillar arrays are fabricated through SF6 and O2 reactive ion etching. By incorporation of a Faraday cage in the plasma equipment, the impact of the Faraday cage on the morphology of the silicon nanopillars is analyzed; the Faraday cage blocks out the sputtered particles and eradicates the formation of silicon nanograss. Specifically, it regulates the value and dispersion of the etching rate by varying the mesh number and the distance from the grid wires to the sample surface. A "flattening belly" phenomenon of silicon nanopillars associated with the temperature is resolved using segmented multiple etching processes. This research contributes to an in-depth analysis of plasma etching using a Faraday cage as well as potential applications for silicon nanopillars.

Multi-cohort analysis identifying core ocular surface microbiome and bacterial alterations in eye diseases.

Inconsistency exists among reported studies on the composition of human ocular surface microbiome (OSM). The roles of OSM in ocular diseases remain uncertain. In this study, we aimed to determine the composition of OSM and to evaluate its potential roles and functions from multiple cohorts. Raw 16 s sequencing data were obtainable from publicly available repositories, sourced from 17 published studies. Employing a standardized method, we processed the data and conducted a cross-cohort analysis. Through bioinformatics pipelines QIIME2 and PICRUSt2, we processed a total of 1875 ocular surface samples. Core microbiome analyses, genera comparisons, and MetaCyc pathway analyses were performed within each cohort independently. The results were then combined to identify shared patterns across different datasets. The core OSM comprised seven genera: Corynebacterium, Staphylococcus, Acinetobacter, Streptococcus, Pseudomonas, Cutibacterium and Bacillus. Corynebacterium and Staphylococcus are the most abundant genera on ocular surface. Most ocular diseases showed OSM alterations and eight genera demonstrated a non-specific, shared response among two or more ocular diseases. Moreover, changes in various metabolic pathways were predicted following OSM alteration, indicating potential roles of OSM in biological processes. We refined the core OSM candidates combining multiple cohorts. The common pattern shared by different cohorts is worth further investigation. Changes in metabolic pathways based on bioinformatic analysis indicated a role of OSM on ocular diseases. Our results help extend the knowledge and encourage further investigations on the associations between OSM and ocular diseases.

Preparation of CuO–CeO2/CaO Composite Oxides and its Ablation Performances of CO/CO2

ABSTRACT CuO – CeO2/CaO composite oxide was prepared for mine special environment in this study through the solid-phase impregnation method using the traditional CuO – CeO2 and CaO as the CO catalyst and the modified additive, respectively, to address the CO poisoning in underground coal mines effectively. Influences of CaO mass on the ablation performances of CuO – CeO2/CaO were investigated under dynamic and static CO/CO2 heat capture experiments using the self-made activity testing device. Results demonstrated that adding CaO can realize in-situ adsorption of CO2, thus increasing utilization of oxygen and promoting CO catalysis of the prepared composite oxide. The performances of CuO – CeO2/0.15CaO was the best when the dosage of CaO was 15 wt%. The CO reaction capacity and CO2 adsorption capacity reached 1.17 and 0.56 mg·g−1, respectively. The thermodynamic properties and microstructural characteristics of the synthesized composite oxide were systematically investigated utilizing a simultaneous thermal analyzer, Fourier infrared spectrometer, XRD diffractometer, and scanning electron microscope. Adding CaO can also improve the thermostability of the composite oxide and increase active sites on the sample surface. The emergence of adsorption products Ca(OH)2 and CaCO3 proves that CuO – CeO2/CaO has relatively good moisture and CO2 adsorption. Analysis of the ablation performances of CO/CO2 after coal combustion with CuO – CeO2/CaO revealed that the prepared composite oxide not only effectively lowers CO concentration after coal combustion but also adsorbs CO2 during catalysis and decreases smoke risks. The released CO concentration from coal combustion after 240 s can be decreased to less than 0.0024% when the mass ratio of CuO – CeO2/0.15CaO and coal is 1:3. The ablation results confirm that, as a new type of composite material, the CuO – CeO2/0.15CaO composite oxide can provide a new technical means for CO control in coal mines.

An Artefact-Minimized Raman Probe for Analyzing Biological Tissues.

Availability of a suitable tool for carrying out non-invasive measurement of Raman signatures insitu, from biological tissues having low Raman cross section is a clinically unmet need faced with manifold challenges. A Raman probe can prove to be an invaluable component of clinical Raman diagnostic systems. We present development of a Raman probe capable of measuring artefact free Raman spectra of biological tissues insitu. The developed probe uses a single lens for simultaneous illumination and collection of the Raman signal backscattered from the sample surface. This configuration ensures not only maximum overlapping of the illumination and collection volumes, ultimately leading to optimal throughput but also reduces the fiber-induced artefacts. The results show a superior performance of the developed Raman probe in measuring the Raman signatures from biological samples having lower Raman cross-sections, compared to that of the two commercially available Raman probes.

Quantification of microplastics released from plastic food containers during rinsing and migration by pyrolysis-gas chromatography/mass spectrometry.

In this study, a pyrolysis-gas chromatography/mass spectrometry method was established to quantify microplastics (MPs) released from plastic food containers during rinsing and migration. The inner surface of actual samples was rinsed with deionized water, and the MPs in rinse water were collected through a glass fiber membrane with pore size of 1μm. Subsequently, thoroughly cleaned polypropylene (PP) food packaging containers were selected for migration tests under different simulants, migration temperatures, and migration times. It was found that MPs corresponding to the materials of product manufacture were detected in all collected containers during rinsing. By migration tests, the results showed that high-fat foods, high/low temperature (5°C), and long exposure periods can promote the release of MPs. It was also proved that the migration of MPs from plastic food containers was one of the important sources for human exposure to MPs. The obtained results can provide evidence for the safety risk assessment of plastic food containers.

A prospective self-controlled study on the alterations of the ocular surface and conjunctival transcriptomic profile associated with prolonged exposure to video display terminals.

To assess the impact of prolonged and intense exposure to video display terminals (VDTs) on ocular surface homeostasis. 30 subjects limited daily VDT usage to less than 3h for one week, then extended usage to more than 8h/day for the next three weeks. Ocular symptoms and signs were evaluated weekly using the Ocular Surface Disease Index (OSDI) questionnaire and clinical examinations. Eyelid margins and meibomian glands were examined, and ocular surface samples were collected for transcriptomic analysis. Average daily VDT time increased from 2.55±0.46h initially to 11.17±2.45, 11.75±2.63, and 10.89±2.41h over three weeks. The dry eye diagnosis rate rose from 6.67% to 51.67%. Total OSDI score (P=0.008), symptoms score (P=0.014), and visual function score (P=0.002) significantly increased. Mean fluorescein break-up time (FBUT) decreased from 6.46s to 3.08s. Corneal fluorescein staining (CFS) score (P<0.001) and lissamine green conjunctival staining (LCjs) score (P=0.036) worsened. Ocular redness index (RI) increased at 1 week and 3 weeks (P=0.007, P=0.001). Telangiectasia scores of both upper and lower eyelid margins increased at 3 weeks (P=0.002, P<0.001). Meibomian gland orifice blockage worsened (P=0.014, P=0.002). Transcriptomic analysis revealed dynamic alterations in ocular surface gene expression, including inflammatory and hormonal responses. MUC5AC and TFF1 genes showed negative correlations with OSDI and conjunctival staining score, respectively. Prolonged VDT exposure deteriorates ocular surface symptoms and signs, with significant inflammatory responses and hormonal activity indicating an imbalance in ocular surface homeostasis.

Indicators of the Microbial Corrosion of Steel Induced by Sulfate-Reducing Bacteria Under the Influence of Certain Drugs

Microorganisms cause microbiologically influenced corrosion, for the prevention of which bactericide inhibitors are used. The aim of the work was to study in vitro the sensitivity of SRB Desulfovibrio oryzae NUChC SRB1 to different concentrations of dimethyl sulfoxide (DMSO), and evaluate the indicators of the microbial corrosion of steel induced by this bacterium in the presence of the pharmaceutical drugs DMSO and paracetamol. The sensitivity of SRB D. oryzae to 1–100% DMSO (v/v) was studied via the dilution method in Postgate’s “C” liquid medium. The corrosion activity of D. oryzae against steel 3 was investigated under DMSO and paracetamol treatment at a final concentration of 45% (v/v) and 0.2% (w/v), respectively, according to the ability of bacteria to form a biofilm on the surface of the steel samples (via the crystal violet method) and the effect on the corrosion rate (via the gravimetric method). It was revealed that DMSO affected D. oryzae NUChC SRB1 and exhibited bactericidal properties (at a concentration range of 10–100%, v/v) and antibiofilm properties (at a concentration of 45%, v/v). Despite its antibiofilm properties confirmed by the reduction in bacterial biofilm mass, anticorrosion features were not observed in the model 35-day conditions of the microbial corrosion of steel in an anaerobic environment with bacterial sulfate reduction. Paracetamol (0.2%, w/v) did not affect biofilm formation by SRB under these conditions, and significantly contributed to an increase in the rate of the microbial corrosion of steel. The prospect of further research is to assess the effect of DMSO and paracetamol on the indicators of microbial corrosion induced by SRB under the influence of the concentrations of these compounds found in wastewater, to clarify the possible additional causes of damage to the equipment of treatment plants. Further research should also be directed at investigating the antimicrobial properties of complexes of compounds with DMSO, which should be considered as an ecological solution to the problem of microbiologically influenced corrosion prevention.

The effects of anodization and instrumentation on titanium abutment surface characteristics and biofilm formation.

To assess the impact of anodization and instrumentation on titanium abutment surface characteristics (surface roughness and wettability) and biofilm formation (viability and mass). Titanium discs were obtained from pre-milled abutment blanks made of titanium-6aluminum-7niobium alloy. Polished samples were divided into three groups: un-anodized, gold-anodized, and pink-anodized. Instrumentation methods included no-instrumentation, air polishing, and titanium scaling treatment. Surface roughness was measured using an optical profilometer, and wettability was determined by measuring the contact angles using the sessile drop method with an optical tensiometer. Biofilm formation by Streptococcus sanguinis was evaluated based on the biofilm viability and mass. The biofilm viability was evaluated through colony-forming unit counting (CFU/mL), and biofilm mass was assessed with crystal violet staining (mean absorbance measured at 490nm, in optical density values). Sample surfaces before and after biofilm formation were also examined by scanning electron microscope (SEM). Two-way ANOVA was performed to determine the group differences, and Spearman's correlation (ρ) was used to analyze the correlation among surface roughness, wettability, and CFU/mL (α=0.05). Pink anodization significantly increased surface roughness (0.38±0.07µm, p<0.001) compared to un-anodized samples (0.25±0.01µm), while gold anodization did not (0.24±0.03µm, p=0.301). Among pink-anodized groups, air polishing resulted in significantly lower surface roughness (0.33±0.08µm) compared to titanium scaling (0.51±0.11µm, p<0.001) and no instrument treatment (0.38±0.07µm, p=0.050). Anodization significantly increased wettability (p<0.001), while instrumentation with a titanium scaling decreased it (p<0.001). The combination of un-anodized samples and titanium scaling treatment showed the lowest wettability with the highest contact angle (70.72±2.63°). The biofilm viability, measured by CFU/mL, was significantly inhibited by anodization (p<0.001) and air polishing (p<0.001) while promoted by titanium scaling (p<0.001). Gold-anodized titanium discs subjected to air polishing exhibited the lowest CFU/mL (279,420±16,300), while un-anodized samples instrumented with a titanium scaler had the highest CFU/mL (945,580±13,580). Biofilm mass, quantified by optical density values, was significantly inhibited by anodization (p<0.001) as well as air polishing (p=0.001). A moderate negative correlation was observed between CFU and wettability (ρ=-0.55, p<0.001). Gold- and pink-anodized titanium surfaces were more hydrophilic, leading to less biofilm formation than un-anodized ones. Biofilm formation was inhibited by air polishing while promoted by titanium scaling. Gold anodization combined with air polishing had the least biofilm formation and can be considered the preferred abutment anodization/instrumentation combination.

Development of a novel laboratory approach for evaluating the adhesion strength of biofilms to human dentine.

Biofilms may show varying adherence strengths to dentine. This study quantified the shear force required for the detachment of multispecies biofilm from the dentine using fluid dynamic gauging (FDG) and computation fluid dynamics (CFD). To date this force has not been quantified. Multispecies biofilms were grown over 3, 7 and 14 days on 2 mm thick dentine sections of human molars (n = 8 per group). The FDG technique with different suction flow rates (100%, 80% and 40%) was used to assess biofilm removal. At maximum suction (100%), the flow rate was 500 mL/min. Digital images of each stained dentine sample were captured (10× magnification) before and after subjecting the samples to the various suction flow rates. The change in colour saturation versus control (△E) value was determined to assess removal of biofilm using digital softwares (Image J© and Colormine©). The imposed shear forces were then estimated using CFD and correlated with the △E values. FDG and CFD analysis showed that complete removal of biofilm by using water as the gauging liquid was not possible across any of the experimental groups. Three-day biofilms required significantly lower shear forces for removal than 7-day or 14-day biofilms. The maximum shear forces were seen in the 14-day biofilm group at all flow rates tested. When assessing for residual biofilm on the dentine, the △E value showed residual biofilms of approximately 40% at all time periods at a 100% flowrate. Complete removal of multispecies biofilm was not possible in any experimental group. This study for the first-time records forces needed to remove polymicrobial biofilms form the surface of a dentine sample. Within the limits of this study, mature biofilms require greater shear forces for removal. This is important when planning protocols for biofilm removal.