Monitoring Molecular Assembly of Biofilms Using Quartz Crystal Microbalance with Dissipation (QCM-D)

The structure and the functionality of biofilm proteins, the main components of the extracellular matrix, can be tuned by protein engineering. The use of binding kinetics data has been demonstrated in the characterization of recombinantly produced biofilm proteins to control their behavior on certain surfaces or under certain conditions. Quartz crystal microbalance with dissipation monitoring (QCM-D) allows measuring the change in resonance frequency and the energy loss and distribution upon the interaction of molecules with the surface. The characterization of the molecular assembly of curli biofilm proteins on different surfaces using QCM-D is presented here as a detailed protocol. The experimental procedure detailed in this chapter can be applied and modified for other biofilm proteins or subunits to determine their surface adsorption and kinetic binding characteristics.

Customized peptidoglycan surfaces to investigate innate immune recognition via surface plasmon resonance

Glycan-protein interactions facilitate some of the most important biomolecular processes in and between cells. They are involved in different cellular pathways, cell-cell interactions and associated with many diseases, making these interactions of great interest. However, their structural and functional diversity poses great challenges in studying them at the molecular level. Surface plasmon resonance (SPR) technology presents great advantages to study glycan-protein interactions due to its superior sensitivity, ability to monitor real-time interactions, relatively simple data interpretation, and most importantly, direct measurement of binding without a need for fluorescent labeling. Here, another dimensionality of SPR in studying glycan-protein interactions is demonstrated via examples of binding between human innate immune receptors and their bacterial peptidoglycan ligands. In order to best resemble interactions in solution, a novel strategy of tethering the carbohydrate at different positions to the biosensor surface is applied to represent the potential displays of the carbohydrate ligand to the receptor. Subsequent kinetic analysis provides insights into the optimized configuration of peptidoglycan fragments for binding with its receptors. The manuscript contains a "how-to guide" to help with the implementation of these methods in other glycan-protein binding systems.

Environmental Surveillance for SARS-CoV-2 in Two Restaurants from a Mid-scale City that Followed U.S. CDC Reopening Guidance

Since mask use and physical distancing are difficult to maintain when people dine indoors, restaurants are perceived as high risk for acquiring COVID-19. The air and environmental surfaces in two restaurants in a mid-scale city located in north central Florida that followed the Centers for Disease Control and Prevention (CDC) reopening guidance were sampled three times from July 2020 to February 2021. Sixteen air samples were collected for 2 hours using air samplers, and 20 surface samples by using moistened swabs. The samples were analyzed by real-time reverse transcriptase-polymerase chain reaction (RT-PCR) for the presence of SARS-CoV-2 genomic RNA. A total of ~550 patrons dined in the restaurants during our samplings. SARS-CoV-2 genomic RNA was not detected in any of the air samples. One of the 20 surface samples (5%) was positive. That sample had been collected from a plastic tablecloth immediately after guests left the restaurant. Virus was not isolated in cell cultures inoculated with aliquots of the RT-PCR-positive sample. The likelihood that patrons and staff acquire SARS-CoV-2 infections may be low in restaurants in a mid-scale city that adopt CDC restaurant reopening guidelines, such as operation at 50% capacity so that tables can be spaced at least 6 feet apart, establishment of adequate mechanical ventilation, use of a face covering except while eating or drinking, and implementation of disinfection measures.

Surface modification of glass fiber-reinforced composite posts to enhance their bond strength to resin-matrix cements: an integrative review

BACKGROUND

Endodontically treated teeth usually can reveal an extensive loss of dental structure and require the use of intraradicular posts to provide adequate support and retention. Retention of the post depends on the surface treatment of the endodontic post itself and on the root canal dentin as well as on the type of resin-matrix cement.

PURPOSE

The main aim of this study was to conduct an integrative review on the influence of different surface treatment methods of glass fiber-reinfored resin composite (GFRC) posts on their push-out bond strength to resin-matrix cements in endodontically treated teeth rehabiliation.

METHOD

A literature search was performed on PubMed (via National Library of Medicine) regarding articles published within the last 10 years, using the following combination of search terms: "intracanal post" OR "endodontic post" OR "root canal post" OR "intraradicular post" OR "glass fiber" AND "resin cement" AND "adhesion" OR "bond strength" OR "shear bond strength" OR "push out".

RESULTS

Results from the selected studies recorded the highest push-out bond strength around 22.5 MPa) on GFRC posts to resin-matrix cements when the surfaces were pre-treated by grit-blasting with silicate followed by silane conditioning. However, high values of push-out bond strength (21.5 MPa) were also noticed for GFRC posts after etching with hydrogen peroxide followed by silance conditioning. Thus, the highest values of bond strength of endodontic posts to the resin-matrix cements were recorded when a combined physico-chemical approach was assessed. Non-treated surfaces showed the lowest bond strength values between 5 to and 9 MPa. Surface analyses of GFRC posts showed an increased roughness after grit-blasting or etching that promoted a mechanical interlocking of the adhesive and resin-matrix cements.

CONCLUSION

The combined treatment of glass fiber-reinforced resin composite post surfaces by physical and chemical methods can promote the increase in roughness and chemical functionalization of the surfaces prior to cementation., That results in a high mechanical interlocking of the resin-matrix cements and a stable retention of the teeth root intracanal posts.

CLINICAL RELEVANCE

Combining chemical and physical modification methods of surfaces can provide the most promising adhesion-enhancing pathways of GFRC posts to resin-matrix cements, that can decrease the risk of clinical failures by fracture and detachment of endodontic posts.

The role of stimulus-based cues and conceptual information in processing facial expressions of emotion

Face shape and surface textures are two important cues that aid in the perception of facial expressions of emotion. Additionally, this perception is also influenced by high-level emotion concepts. Across two studies, we use representational similarity analysis to investigate the relative roles of shape, surface, and conceptual information in the perception, categorisation, and neural representation of facial expressions. In Study 1, 50 participants completed a perceptual task designed to measure the perceptual similarity of expression pairs, and a categorical task designed to measure the confusability between expression pairs when assigning emotion labels to a face. We used representational similarity analysis and constructed three models of the similarities between emotions using distinct information. Two models were based on stimulus-based cues (face shapes and surface textures) and one model was based on emotion concepts. Using multiple linear regression, we found that behaviour during both tasks was related with the similarity of emotion concepts. The model based on face shapes was more related with behaviour in the perceptual task than in the categorical, and the model based on surface textures was more related with behaviour in the categorical than the perceptual task. In Study 2, 30 participants viewed facial expressions while undergoing fMRI, allowing for the measurement of brain representational geometries of facial expressions of emotion in three core face-responsive regions (the Fusiform Face Area, Occipital Face Area, and Superior Temporal Sulcus), and a region involved in theory of mind (Medial Prefrontal Cortex). Across all four regions, the representational distances between facial expression pairs were related to the similarities of emotion concepts, but not to either of the stimulus-based cues. Together, these results highlight the important top-down influence of high-level emotion concepts both in behavioural tasks and in the neural representation of facial expressions.

A novel multi-structural reinforced treatment on Ti implant utilizing a combination of alkali solution and bioactive glass sol

OBJECTIVE

Alkali treatment and bioactive glass (BG) sol dip-coating are well-known individual methods for titanium (Ti) surface modification. In this study, a unique combination of alkali treatment and bioactive glass sol dip coating was applied to the Ti substrate, then the mechanical properties and cell responses were investigated.

METHODS

Based on the methods introduced above, the Ti substrate was treated by 6 mL of an NaOH 5 M aqueous solution for 24 h at 60 ̊C; this was followed by adding 1.2 mL of a BG 58S sol to form a novel combined nanostructure network covered by a thin BG layer. For the assessment of the formed coating layer, the morphology, elemental analysis, phase structure, adhesion property and the cell response of the untreated and treated surfaces were investigated.

RESULTS

The BG coating layer was reinforced by the nanostructure, fabricated through the alkali treatment. The results obtained by applying the combined modification method confirmed that the mechanical and biological properties of the fabricated surface demonstrated the highest performance compared to that of the unmodified and individually modified surfaces.

SIGNIFICANCE

The achieved upgrades for this method could be gained from the demanded porous nanostructure and the apatite transformation ability of the alkali treatment. Therefore, the hybridized application of the alkali-BG treatment could be introduced as a promising surface modification strategy for hard-tissue replacement applications.

Response mechanisms of snails to the pulling force and its potential application in vacuum suction

Snails offer successful attachment and locomotion on horizontal and vertical surfaces, and have inspired extensive research to develop artificial adhesives. Here, we experimentally investigate the response mechanisms of snails to mechanical signals (pull-off force and crawling angle), then propose a way to design a bioinspired sucker, and theoretically analysis its application in vacuum suction. The experimental results indicate that the pull-off force is 7 N, about 22 times of its weight, and relatively invariant across the angles of the substrate. The flexible body increases work consumption by stretching and deformation during pulling, and a cavity with negative pressure differential can exist at the interface to help resist the pulling. We extract the flexible body and formation of a negative pressure cavity at the contact interface as two key elements of the bioinspired sucker, and the analysis shows that it can be adaptable to an extend range of products compared with conventional vacuum suction, which illustrates the potential for industrial or robotic manipulation.

Rapid inactivation of SARS-CoV-2 by titanium dioxide surface coating

Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission occurs via airborne droplets and surface contamination. Titanium dioxide (TiO 2) coating of surfaces is a promising infection control measure, though to date has not been tested against SARS-CoV-2. Methods: Virus stability was evaluated on TiO 2- and TiO 2-Ag (Ti:Ag atomic ratio 1:0.04)-coated 45 x 45 mm ceramic tiles. After coating the tiles were stored for 2-4 months before use. We tested the stability of both SARS-CoV-2 Spike pseudotyped virions based on a lentiviral system, as well as fully infectious SARS-CoV-2 virus. For the former, tile surfaces were inoculated with SARS-CoV-2 spike pseudotyped HIV-1 luciferase virus. At intervals virus was recovered from surfaces and target cells infected. For live virus,  after illuminating tiles for 0-300 min virus was recovered from surfaces followed by infection of Vero E6 cells. % of infected cells was determined by flow cytometry detecting SARS-CoV-2 nucleocapsid protein 24 h post-infection. Results: After 1 h illumination the pseudotyped viral titre was decreased by four orders of magnitude. There was no significant difference between the TiO 2 and TiO 2-Ag coatings. Light alone had no significant effect on viral viability. For live SARS-CoV-2, virus was already significantly inactivated on the TiO 2 surfaces after 20 min illumination. After 5 h no detectable active virus remained. Significantly, SARS-CoV-2 on the untreated surface was still fully infectious at 5 h post-addition of virus. Overall, tiles coated with TiO 2 120 days previously were able to inactivate SARS-CoV-2 under ambient indoor lighting with 87% reduction in titres at 1h and complete loss by 5h exposure. Conclusions: In the context of emerging viral variants with increased transmissibility, TiO 2 coatings could be an important tool in containing SARS-CoV-2, particularly in health care facilities where nosocomial infection rates are high.

Adhesion of Norovirus to Surfaces: Contribution of Thermodynamic and Molecular Properties Using Virus-Like Particles

The aim of the study was to assess human norovirus and feline calicivirus (FCV) surface free energy, hydrophobicity, and ability to interact with fresh foods and food-contact surfaces. Virus-like particles (VLPs) of human norovirus (GI.1 and GII.4) and FCV were produced, purified, and analyzed for their surface free energy, hydrophobicity, and the total interfacial free energy of interaction [Formula: see text] with lettuce, strawberry, polyethylene, and stainless steel. GII.4 VLPs were further tested for adhesion at different pH, ionic strengths, and temperature. All the VLPs and the test materials showed low surface energies, as well as hydrophobic characters except for GI.1. Nearly all [Formula: see text] values were propitious for spontaneous adhesion. GII.4 VLPs adsorbed almost indifferently to stainless steel, polyethylene, and lettuce. Isoelectric point and high temperature generally promoted adhesion while ionic strength effect was surface-dependant. According to this study, all the materials assessed are of low-energy and hydrophobic nature except GI.1 VLPs. Interfacial free energies of interaction were favorable for spontaneous adhesion ([Formula: see text] < 0) of all VLPs to the test materials, except for GI.1 VLPs to both stainless steel and straweberry. It is also found that norovirus adhesion is more sensitive to physicochemical conditions than to surface character itself.

Protein-protein interactions at a glance: Protocols for the visualization of biomolecular interactions

Protein-protein interactions (PPIs) play a key role in many biological processes and are intriguing targets for drug discovery campaigns. Advancements in experimental and computational techniques are leading to a growth of data accessibility, and, with it, an increased need for the analysis of PPIs. In this respect, visualization tools are essential instruments to represent and analyze biomolecular interactions. In this chapter, we reviewed some of the available tools, highlighting their features, and describing their functions with practical information on their usage.

Influence of the second phase on protein adsorption on biodegradable Mg alloys' surfaces: Comparative experimental and molecular dynamics simulation studies

The effect of the second phase on the mechanical properties and corrosion resistance of Mg alloys has been systematically studied. However, there is limited information on the effect of the second phase on protein adsorption behavior. In the present study, the effect of the second phase on protein adsorption on the surfaces of biodegradable Mg alloys was investigated using experimental methods and molecular dynamics (MD) simulations. The experimental results showed that the effect of the second phase on fibrinogen adsorption was type-dependent. Fibrinogen preferentially adsorbed on Y-, Ce-, or Nd-involved second phases, while the second phase containing Zn inhibited its adsorption. MD simulations revealed the mechanism of the second phase that influenced protein adsorption in terms of charge distribution, surface-protein interaction energy, and water molecule distribution. Our studies proposed a deep understanding of the design of Mg-based biomaterials with superior biocompatibility. STATEMENT OF SIGNIFICANCE: Mechanical properties, uniform degradation, and biocompatibility must be considered while designing biomedical Mg alloys. To improve the mechanical properties and corrosion resistance of Mg alloys, the second phase is usually required. However, the effects of the second phase on biocompatibility of Mg alloys have been rarely reported. Here, the influence of the second phase on protein adsorption was experimentally studied by designing Mg alloys with different types of second phase. The first principle calculation and MD simulation were used to reveal the mechanism by which the second phase influences protein adsorption. This work could be used to better elucidate the protein adsorption mechanisms and design principles to improve the biocompatibility of Mg alloys.

The viability of SARS-CoV-2 on solid surfaces

The COVID-19 pandemic had a major impact on life in 2020 and 2021. One method of transmission occurs when the causative virus, SARS-CoV-2, contaminates solids. Understanding and controlling the interaction with solids is thus potentially important for limiting the spread of the disease. We review work that describes the prevalence of the virus on common objects, the longevity of the virus on solids, and surface coatings that are designed to inactivate the virus. Engineered coatings have already succeeded in producing a large reduction in viral infectivity from surfaces. We also review work describing inactivation on facemasks and clothing and discuss probable mechanisms of inactivation of the virus at surfaces.

Diurnal variation in the human skin microbiome affects accuracy of forensic microbiome matching

BACKGROUND

The human skin microbiome has been recently investigated as a potential forensic tool, as people leave traces of their potentially unique microbiomes on objects and surfaces with which they interact. In this metagenomic study of four people in Hong Kong, their homes, and public surfaces in their neighbourhoods, we investigated the stability and identifiability of these microbiota traces on a timescale of hours to days.

RESULTS

Using a Canberra distance-based method of comparing skin and surface microbiomes, we found that a person could be accurately matched to their household in 84% of tests and to their neighbourhood in 50% of tests, and that matching accuracy did not decay for household surfaces over the 10-day study period, although it did for public surfaces. The time of day at which a skin or surface sample was taken affected matching accuracy, and 160 species across all sites were found to have a significant variation in abundance between morning and evening samples. We hypothesised that daily routines drive a rhythm of daytime dispersal from the pooled public surface microbiome followed by normalisation of a person's microbiome by contact with their household microbial reservoir, and Dynamic Bayesian Networks (DBNs) supported dispersal from public surfaces to skin as the major dispersal route among all sites studied.

CONCLUSIONS

These results suggest that in addition to considering the decay of microbiota traces with time, diurnal patterns in microbiome exposure that contribute to the human skin microbiome assemblage must also be considered in developing this as a potential forensic method. Video Abstract.

Evaluating quality of soils formed on basement complex rocks in Kaduna State, northern Guinea savanna of Nigeria

A few investigations have been done regarding the soil quality index (SQI) for various locations, soil types, and states. Still, little has been reported regarding SQI for both surface and control sections, especially for the Northern Guinea Savanna of Nigeria. Due to the subsurface property pedogenic influence on soil function, it is crucial to assess SQI using surface and subsurface properties as both properties influence soil productivity. We investigated the potentials of choosing a minimum data set for soil quality indicators and assess soil quality (SQ), using both surface and entire soil pedon data for the soils on the basement complexes. Both additive and weighted soil quality indices and different scoring methods (linear and non-linear) were used in evaluating SQ. Out of the twenty-three soil properties subjected to PCA, eight indicators (TEB, clay, silt, K, EA, EC, BD, and Fe) were selected as the minimum data set (MDS). There was not much difference in the calculated soil quality using the non-linear additive (SQI-NLA), linear additive (SQI-LA), linear weighted (SQI-LW), and non-linear weighted (SQI-NLW) for the soils as they were all rated low (SQI < 0.55). The estimated SQI for the control section had relatively higher values than the surface soil, thus suggesting the need to incorporate both surface and entire soil profile properties in assessing SQ as both are important in integrating the relationship between soil properties and management goals which eventually provides complete information that affects the production of crops.

Efficient development of silk fibroin membranes on liquid surface for potential use in biomedical materials

Silk fibroin (SF) protein is versatile for the application of biomaterials due to its excellent mechanical properties, biocompatibility and biodegradability. However, the efficient way to fabricate SF membranes with special structure is still challenging. Here, we develop an efficient and simple way to create SF membranes on the liquid (i.e. subphase) surface. It is essential to prepare highly concentrated SF solution with low surface tension by dissolving the degummed SF powders in 6% (w/v) LiBr/methanol solution by one step. 95 wt% polyethylene glycol (PEG) 200 and 30 wt% (NH₄)₂SO₄ are the subphases, on which the SF solution spreads quickly, generating nonporous and microporous SF membranes (SFM-1 and SFM-2), respectively. PEG 200 causes more ordered molecular packing (β-sheets) in SFM-1. While Fast diffusion and denaturation of SF on (NH₄)₂SO₄ solution lead to the formation of microporous, water-unstable membrane SFM-2. Both membranes have good transparency, hydrophilicty, and mechanical properties. To fabricate antibacterial biomaterials, we design a composite membrane by SFM-1 and SFM-2 sandwiching a layer of hydroxypropyl trimethylammonium chloride chitosan (HACC) to provide antibacterial functions. The sandwich membrane has good cell viability and antibacterial properties, showing potential use for biomedical materials.

Multifunctional superhydrophobic surfaces

Surface wetting has a significant influence on the performance and applications of the materials. The superhydrophobic surfaces have water repellency due to low surface energy chemistry and micro/nanostructure roughness. The amazing applications of superhydrophobic surfaces (SHSs) lead to increase attention to superhydrophobicity in recent decades. The SHSs have been fabricated through chemical and physical methods. The further properties of SHSs as functions such as self-healing, anti-bacterial, anti-fouling, and stimuli-responsiveness are considered as the functions of the SHSs. The Multifunctional SHSs (MSHSs) that contained superhydrophobicity and at least two other properties as the next generation of the SHSs are swiftly developed in recent years. The multiple applications of the MSHSs are originated from specific morphology and functional groups of the MSHSs. The functions (properties) of the MSHSs are categorized into three groups including self-cleaning properties, restrictive properties, and smart properties. Designing and keeping surface structure plays a significant role in fabricating durable MSHSs. However, there is a big challenge to design and also scale up mechanochemical durable MSHSs. Based on state-of-the-art investigations, establishing a self-healing function can improve the durability of SHSs. The durable self-healing MSHSs can enhance the performance of the other functions and lifespan of the surface. In this review, all surface structures and superhydrophobic agents in MSHSs are investigated. The perspective of the MSHSs determined the next generation of the MSHSs have several significant parameters including durability, stability, more functions, more responsiveness, and environmentally friendly features for fabricating the large-scale MSHSs and enhancing their applications.

The salivary pellicle on dental biomaterials

The salivary pellicle, an adlayer formed by adsorption of salivary components on teeth and dental biomaterials, has direct consequences on basic outcomes of dentistry. Here, we provide an overview of salivary pellicle formation processes with a critical focus on dental biomaterials. We describe and critique the array of salivary pellicle measurement techniques. We also discuss factors that may affect salivary pellicle formation and the heterogeneity of the published literature describing salivary pellicle formation on dental biomaterials. Finally, we survey the many effects salivary pellicles have on dental biomaterials and highlight its implications on design criteria for dental biomaterials. Future investigations may lead to rationally designed dental biomaterials to control the salivary pellicle and enhance material function and patient outcomes.

Rapid inactivation of SARS-CoV-2 by titanium dioxide surface coating

Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission occurs via airborne droplets and surface contamination. Titanium dioxide (TiO 2) coating of surfaces is a promising infection control measure, though to date has not been tested against SARS-CoV-2. Methods: Virus stability was evaluated on TiO 2- and TiO 2-Ag (Ti:Ag atomic ratio 1:0.04)-coated 45 x 45 mm ceramic tiles. After coating the tiles were stored for 2-4 months before use. We tested the stability of both SARS-CoV-2 Spike pseudotyped virions based on a lentiviral system, as well as fully infectious SARS-CoV-2 virus. For the former, tile surfaces were inoculated with SARS-CoV-2 spike pseudotyped HIV-1 luciferase virus. At intervals virus was recovered from surfaces and target cells infected. For live virus,  after illuminating tiles for 0-300 min virus was recovered from surfaces followed by infection of Vero E6 cells. % of infected cells was determined by flow cytometry detecting SARS-CoV-2 nucleocapsid protein 24 h post-infection. Results: After 1 h illumination the pseudotyped viral titre was decreased by four orders of magnitude. There was no significant difference between the TiO 2 and TiO 2-Ag coatings. Light alone had no significant effect on viral viability. For live SARS-CoV-2, virus was already significantly inactivated on the TiO 2 surfaces after 20 min illumination. After 5 h no detectable active virus remained. Significantly, SARS-CoV-2 on the untreated surface was still fully infectious at 5 h post-addition of virus. Overall, tiles coated with TiO 2 120 days previously were able to inactivate SARS-CoV-2 under ambient indoor lighting with 87% reduction in titres at 1h and complete loss by 5h exposure. Conclusions: In the context of emerging viral variants with increased transmissibility, TiO 2 coatings could be an important tool in containing SARS-CoV-2, particularly in health care facilities where nosocomial infection rates are high.

Highly hydrophobic polytetrafluoroethylene particle immobilization via polydopamine anchor layer on nitric oxide releasing polymer for biomedical applications

Biomedical surface-associated infections and thrombus formation are two major clinical issues that challenge patient safety and patient the fate of a medical device in the body . Single platform multifunctional surfaces are critical to address both these indwelling medical device-related problems. In this work, bio-inspired approaches are employed to fabricate a polymer composite with a versatile surface that can reduce bacterial infections and platelet adhesion in vitro. In the first bio-inspired approach, the functionality of nitric oxide (NO) produced by endothelial cell lining of blood vessels is mimicked through incorporation of S-nitroso-N-acetylpenicillamine (SNAP) within a CarboSil-2080A™ (CarboSil) polymer composite matrix. The second approach involves utilizing mussel adhesive chemistry, via polydopamine (PDA) to immobilize polytetrafluoroethylene (PTFE) particles on the polymer composite surface. The PTFE coating facilitates a decrease in wettability by making the polymer composite surface highly hydrophobic (contact angle ca. 120°). The surface of the fabricated polymer composite , CarboSil SNAP-PTFE, had a cobblestone-like structured appearance as characterized through scanning electron microscopy (SEM). Water contact angle (WCA) and surface tension measurements indicated no significant coating losses after 24 h under physiological conditions. NO surface flux was measured and analyzed for 5 days using a chemiluminescence-based nitric oxide analyzer and was found to be within the physiological range. CarboSil SNAP-PTFE reduced adhered bacteria (99.3 ± 0.5% for Gram-positive S. aureus and 99.1 ± 0.4% for Gram-negative E. coli) in a 24 h in vitro study. SEM analysis showed the absence of biofilm formation on CarboSil SNAP-PTFE polymer composites, while present on CarboSil in 24 h exposure to S. aureus. Platelet adhesion was reduced by 83.3 ± 4.5%. Overall, the results of this study suggest that a combination of NO-releasing CarboSil with PTFE coating can drastically reduce infection and platelet adhesion.

Surface roughness of enamel and root surface after scaling, root planning and polishing procedures: An in-vitro study

Objectives

The aim of this study was to evaluate enamel and root surface roughness on exracted human teeth by using different tecniques (ultrasonic scaler, hand instruments, polishing paste, pumice and air powder system).

Materials and methods

A total of 200 samples were divided into two groups (enamel and root) randomly with 100 samples for each enamel and root groups. The groups were divided into 5 subgroups: Group I: ultrasonic scaler, group II: hand instruments, group III: polishing paste, group IV: pumice, group V: air-powder. Surface roughness (Ra) was assessed with Mitutoyo SJ-410 device. The one-way analysis of variance (ANOVA) test along with the Tukey test was used for statistical analysis. P values less than 0.05 were considered statistically significant.

Results

The use of ultrasonic scalers caused the highest roughness increase on the enamel surface (0.935 ​± ​0.010), whereas the use of pumice was the least (0.896 ​± ​0.018) (p ​< ​0.05). There was a significant difference between ultrasonic scalers and all the groups (hand instruments, polishing paste, pumice and air powder system) on enamel surface (p ​< ​0.05). Maximum surface roughness increase was observed in the ultrasonic scalers on root surface. There was a significant difference between ultrasonic scalers and polishing paste, pumice and air powder on root surface, respectively (p ​< ​0.05).

Conclusion

The use of ultrasonic scalers cause more rough enamel and root surfaces than hand instrumentation and polishing tecniques.

Clinical relevance

Uneven surfaces adversely affect the intended periodontal healing by creating a retention area of microbial dental plaque.

A PCR method to identify ochratoxin A-producing Aspergillus westerdijkiae strains on dried and aged foods

Ochratoxins are a group of mycotoxins that frequently occur as contaminants in agricultural commodities and foods, including dry-cured meats and cheeses. The fungus Aspergillus westerdijkiae is frequently isolated from aged foods and can produce ochratoxin A (OTA). However, individual strains of the fungus can have one of two OTA production phenotypes (chemotypes): OTA production and OTA nonproduction. Monitoring and early detection of OTA-producing fungi in food are the most effective strategies to manage OTA contamination. Therefore, we examined genome sequence data from five A. westerdijkiae strains isolated from the surface of cheese from southern Italy to identify genetic markers indicative of the twoOTA chemotypes. This analysis revealed a naturally occurring deletion of the OTA regulatory gene, otaR, in an OTA-nonproducing isolate.We used this information to design a polymerase chain reaction (PCR) method that could identify A. westerdijkiae and distinguish between the two OTA chemotypes. In this method, the PCR primers were complementary to conserved sequences flanking otaR and yielded different-sized amplicons from strains with the different chemotypes. The primers did not yield ota-region-specific amplicons from other OTA-producing species. Because the method is specific to A. westerdijkiae and can distinguish between the two OTA chemotypes, it has potential to significantly improve OTA monitoring programs.

Why does SARS-CoV-2 survive longer on plastic than on paper?

The Covid-19 coronavirus, SARS-CoV-2, is inactivated much faster on paper (3 h) than on plastic (7 d). By classifying materials according to virus stability on their surface, the following list is obtained (from long to short stability): polypropylene (mask), plastic, glass, stainless steel, pig skin, cardboard, banknote, cotton, wood, paper, tissue, copper. These observations and other studies suggest that SARS-CoV-2 may be inactivated by dryness on water absorbent porous materials but sheltered by long-persisting micro-droplets of water on waterproof surfaces. If such physical phenomenons were confirmed by direct evidence, the persistence of the virus on any surface could be predicted, and new porous objects could be designed to eliminate the virus faster.

Surface-Plasmon Holography

Holography was originally invented for the purpose of magnifying electron microscopic images without spherical aberration and has been applied to photography for recording and reconstructing three-dimensional objects. Although it has been attracting scientists and ordinary people in the world, it is still a technology in science fiction movies. In this review, we discuss a new version of holography that uses surface plasmons on thin metal film. We discuss conventional holography and its drawbacks, such as overlapping of ghost and background due to the contribution of unnecessary diffraction and monochromacy for avoiding the unwanted diffraction components of different colors. Surface-plasmon holography is a version of near-field holography to overcome drawbacks of conventional holography. Comparison with conventional and volume holography for color reconstruction is discussed in reciprocal lattice space. Localized mode of surface plasmons and meta-surface holography are also reviewed, and feature perspectives and issues are discussed.

Detection and infectivity potential of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) environmental contamination in isolation units and quarantine facilities

OBJECTIVES

Environmental surfaces have been suggested as likely contributors in the transmission of COVID-19. This study assessed the infectivity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) contaminating surfaces and objects in two hospital isolation units and a quarantine hotel.

METHODS

SARS-CoV-2 virus stability and infectivity on non-porous surfaces was tested under controlled laboratory conditions. Surface and air sampling were conducted at two COVID-19 isolation units and in a quarantine hotel. Viral RNA was detected by RT-PCR and infectivity was assessed by VERO E6 CPE test.

RESULTS

In laboratory-controlled conditions, SARS-CoV-2 gradually lost its infectivity completely by day 4 at ambient temperature, and the decay rate of viral viability on surfaces directly correlated with increase in temperature. Viral RNA was detected in 29/55 surface samples (52.7%) and 16/42 surface samples (38%) from the surroundings of symptomatic COVID-19 patients in isolation units of two hospitals and in a quarantine hotel for asymptomatic and very mild COVID-19 patients. None of the surface and air samples from the three sites (0/97) were found to contain infectious titres of SARS-Cov-2 on tissue culture assay.

CONCLUSIONS

Despite prolonged viability of SARS-CoV-2 under laboratory-controlled conditions, uncultivable viral contamination of inanimate surfaces might suggest low feasibility for indirect fomite transmission.

Synthesis and cytotoxic analysis of thiolated xylose derivatives decorated on gold nanoparticles

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Nanoparticles covered with carbohydrates constitute a good bio-mimetic model.

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D-xylose gold nanoparticles with linkages of alkyl or polyethylene glycol synthesized via D-xylosethiols.

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Forming self-assembled monolayers on gold nanoparticles.

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The potential use of intact or thiolated xylose derivatives decorated on AuNPs.

The rapid development of metal nanoparticles capped by an organic monolayer offers the possibility to create a whole new variety of products with novel characteristic, functions and applications. Among these, nanoparticles covered with carbohydrates (glyconanoparticles) constitute a good bio-mimetic model of carbohydrate presentation at the cell surface and are currently centered on many glycobiological and biomedical applications. In this study, a series of novel D-xylose gold nanoparticles (AuNPs) with linkages of alkyl or polyethylene glycol have been synthesized via D-xylosethiols, forming self-assembled monolayers on gold nanoparticles. The nano-gold solution, two carbohydrate derivatives and modified nano-gold solution were tested for cytotoxicity to check the biocompatibility. The MTT assay on NIH 3T3 cell lines confirmed that all the test materials showed no toxicity with the more than 90 % of cell viability in both low concentration (1 μM) and high concentration (100 μM), compared with the control.