Chemically Modulating Ceria-Based Artificial Haloperoxidase for Enhanced Antibacterial Activity and Biofilm Inhibition.

Ceria (CeO2) nanoparticles with haloperoxidase (HPO)-like activity have gained attention as a biologically benign antifoulant. 3,4-Dihydroxy-l-phenylalanine (DOPA), a main composition in mussel foot proteins, plays a crucial role in the biofouling process. However, the impact on the HPO-like activity and antifouling performance of CeO2 nanoparticles when DOPA molecules adsorb on them remains unexplored. This interesting question warrants investigation, particularly considering that it may occur in an actual marine environment. Herein, the interaction between DOPA and CeO2 is explored. Despite the higher Ce3+ fractions and the lower band gap energies due to the electron transfer from DOPA to the CeO2 surface, DOPA still had a slightly negative effect on the HPO-like activity of CeO2 since they decreased the exposed Ce3+ sites. The DOPA-CeO2 nanocomposites with HPO-like activities could kill bacteria and trigger quorum-sensing signaling quenching, achieving a biofilm inhibition performance. Amazingly, 0.1% DOPA-CeO2 nanocomposite exhibited higher antibacterial activity and better biofilm suppression activities due to its HPO-like activity and positive zeta potential. The remarkable results demonstrated that DOPA, as a participant in the biofouling process, could enhance the antibacterial activity and antifouling performance of CeO2 nanoparticles at an appropriate concentration.

Facet-dependent haloperoxidase-like activities of CeO2 nanoparticles contribute to their excellent biofilm formation suppression abilities.

Biofilms adhering to different surfaces have significant negative impacts in various fields. Cerium oxide nanoparticles can serve as mimics of haloperoxidase for biological biofilm inhibition applications. The regulation of the exposed facet of CeO2 nanoparticles influences their efficiency in various catalytic processes. However, there is still a lack of systematic studies on the facet-dependent haloperoxidase-like activity of CeO2. In the present study, the facet-dependent haloperoxidase activities and antibiofilm performance of CeO2 nanoparticles were elucidated through experiment analysis and density function theory calculation. The as-prepared CeO2 nanoparticles inhibited bacterial survival and catalyzed the oxidative bromination of quorum sensing signaling molecules, achieving biofilm inhibition performance. The antibacterial and biofilm formation suppression abilities were consistent with their haloperoxidase activities. The {111}- and {110}-facet CeO2 nanopolyhedra, as well as the {110}- and {100}-facet CeO2 nanorods, which had higher haloperoxidase activity showed better antibiofilm performance than the {100}-facet CeO2 cubes. The present findings provide a comprehensive understanding of the facet-dependent haloperoxidase-like activity of CeO2. Furthermore, engineering CeO2 morphologies with different crystal facets may represent a novel method for significantly adjusting their haloperoxidase-like activity.

Antifouling applications and fabrications of biomimetic micro-structured surfaces: A review.

BACKGROUND: Since the inception of the term "Biomimetics" in 1991, the concept of utilizing natural solutions or deriving inspiration from nature to address contemporary engineering challenges has gained significant attention within the scientific community. Organisms, in order to thrive in harsh environments, have evolved a wide range of micro/nanostructured surfaces, which serve as a rich source of inspiration for the development of artificial micro/nano-structured surfaces. These natural adaptations provide valuable insights and novel pathways for fabricating such surfaces. AIM: To conclude recent advances in micro/nano-structured surfaces from four aspects: biomimetic micro-structured surfaces of plants and animals, properties and applications of biomimetic surfaces, methods of preparations, and their limitation. KEY SCIENTIFIC CONCEPTS: Artificial micro/nano-structured surfaces inspired by animals and plants are classified and demonstrated according to their living environment. The performances, principles and preparation techniques of natural superhydrophobic surfaces, slippery liquid-infused porous surfaces (SLIPS), anisotropic surfaces, etc. are described in detail. Moreover, the pros and cons of each preparation measures are compared and the challenges developing large-scale, cost-effective surface microstructure preparation processes are pointed out. In the end, the development trends of artificial micro/nano-structured surface are forecasted.

Novel Wood-Based Functional Material with Vibration and Noise Reduction.

As a kind of typical green material, natural materials tend to exhibit excellent performance in the engineering field because of their structure and special functions. The homogeneous vessels of red willow (RW) are potentially unique structures to store lubricants or reinforcing agents to present special functions for engineering applications. A series of novel red willow wood-based composites, which were infused with nano-MoS2 and then reinforced by the epoxy, were developed. Their self-lubricating, mechanical vibration and noise reduction performances were investigated, and the friction, vibration, and noise reduction mechanisms were disclosed. The infusion MoS2 treatment was very beneficial for improving the tribological properties of MoS2-curing epoxy/red willow (MCW), and the coefficient of friction (COF) was reduced by 65.8% under water-lubricated friction after infusing 24 times. Meanwhile, the mechanical performances of MCW were obviously enhanced through the curing treatment of the epoxy. The synergistic effects of the infusion and curing treatments significantly decreased the wear phenomena on the friction surfaces of MCW and weakened the COF and its fluctuation amplitudes, which resulted in the presented excellent vibration and noise reduction performance. The knowledge gained herein could not only develop a novel wood-based composite with low COF and good vibration reduction properties in the engineering field but also provide a new methodology for the design of artificial porous materials with stable and smooth friction processes.

Comparison of intelligibility measures for children with velopharyngeal insufficiency: visual analog scale ratings, interval scales, and orthographic transcription (OT)-based measures.

Regardless of the underlying cause for speech impairment in speakers with cleft palate, a universal consequence of cleft palate is reduced speech intelligibility. Still, there is no standardised approach for measuring intelligibility for speakers with cleft speech. The current study aimed to determine the relationship between orthographic transcription (OT)-based measures, interval-scale ratings, and visual analog scale (VAS) ratings for perceptual judgements of intelligibility in speakers with cleft palate as judged by speech-language pathologists (SLPs). The speaker participants were six speakers with velopharyngeal insufficiency secondary to cleft palate. Four sets of sentences from the Hearing in Noise Test were recorded from each speaker. A total of 14 SLPs provided their intelligibility judgement on these speaker's recordings by word-by-word orthographic transcriptions, a visual analog scale (0-100), and a 5-point interval rating scale. A Spearman rank correlation test indicated a negative, strong correlation between OT-based measurements and VAS scores (r = -.94; p = 0.01) and between OT-based measurements and interval rating scores (r = -.77, p = 0.01). A strong, positive correlation was found between scores obtained from VAS and interval rating scales (r = .83, p = 0.05). The strong relationship between the objective measure of intelligibility (i.e. OT-based measure) and a subjective measure of intelligibility (i.e. VAS and interval scale) supports using a less time-consuming VAS as a substitute for orthographic transcription in measuring intelligibility in cleft palate speech.

Effects of multitasker babble noise on speech intelligibility in children with velopharyngeal insufficiency (VPI).

BACKGROUND: Intelligibility measurement is influenced by the characteristics of a speaker, listener and contextual factors. This study addresses the clinical problem of measuring speech intelligibility in children with velopharyngeal insufficiency (VPI) in real-world conditions. AIMS: The purpose of the study was to investigate the effects of background noise on speech intelligibility in speakers with velopharyngeal insufficiency (VPI) compared to typical speech. The study further determined the contribution of nasalance and articulation accuracy in judgments of intelligibility. METHODS & PROCEDURES: Fifteen speakers diagnosed with VPI and their typical peers provided audio recordings of 20 sentences from the Hearing in Noise Test. Speech samples were presented over quiet and noise (+5 dB signal-to-noise ratio) conditions to 70 naïve listeners. Intelligibility scores from naïve listeners' orthographic transcriptions were obtained as the percentage of correctly identified words. OUTCOMES & RESULTS: A repeated-measures analysis of variance showed diagnosis of VPI (F(1, 28) = 13.44, p = 0.001, and presence of noise (F(1, 28) = 39.18, p < 0.001) significantly affected the intelligibility scores. There was no interaction between the diagnosis of VPI and noise (F(1, 28) = 0.06, p = 0.80). The multivariate regression analysis indicated that nasalance and articulation accuracy explain a significant amount of variance in the intelligibility scores of VPI speakers in quiet (F(2, 12) = 7.11, p < 0.05, R2   = 0.55, R2 Adjusted   = 0.47) and noise (F(2, 12) = 6.32, p < 0.05, R2   = 0.51, R2 Adjusted   = 0.43), but the significance mainly came from the effect of percentage of consonants correct (ß = 0.97, t(12) = 2.90, p = 0.01). Percentage of consonants correct significantly increased the speech intelligibility in either with or without noise conditions. CONCLUSIONS & IMPLICATIONS: The current work suggests that background noise will significantly affect reductions in intelligibility in both groups; the effect is more prominent in VPI speech. It was also further noted that articulation accuracy significantly affected intelligibility in quiet and noise rather than nasalance scores. WHAT THIS PAPER ADDS: What is already known on the subject Intelligibility measurement is influenced by the characteristics of a speaker, listener and contextual factors. Accordingly, it is essential to determine the degree to which speech assessments in the clinic can predict communication difficulties in the presence of background noise in real life. Background noise can adversely cause speech intelligibility degradation in individuals with speech disorders. What this study adds The study examined the effects of background noise on speech intelligibility in speakers with velopharyngeal insufficiency (VPI) secondary to cleft palate compared to typical speech. The study results suggested that the presence of background noise will significantly affect reductions in intelligibility in both groups; however, the effect is more prominent in VPI speech. What are the clinical implications of this work? We found out that the intelligibility of VPI speech is lower in the presence of background noise, and therefore, assessments of speech intelligibility in clinical settings should take this into account. To ensure effective communication in noisy environments, recommended strategies include selecting quiet locations, eliminating potential distractions and supplementing communication with nonverbal cues. It is important to recognize that the effectiveness of these strategies may vary depending on the individual and the specific communication context.

Research Progress on New Environmentally Friendly Antifouling Coatings in Marine Settings: A Review.

Any equipment submerged in the ocean will have its surface attacked by fouling organisms, which can cause serious damage. Traditional antifouling coatings contain heavy metal ions, which also have a detrimental effect on the marine ecological environment and cannot fulfill the needs of practical applications. As the awareness of environmental protection is increasing, new environmentally friendly and broad-spectrum antifouling coatings have become the current research hotspot in the field of marine antifouling. This review briefly outlines the formation process of biofouling and the fouling mechanism. Then, it describes the research progress of new environmentally friendly antifouling coatings in recent years, including fouling release antifouling coatings, photocatalytic antifouling coatings and natural antifouling agents derived from biomimetic strategies, micro/nanostructured antifouling materials and hydrogel antifouling coatings. Highlights include the mechanism of action of antimicrobial peptides and the means of preparation of modified surfaces. This category of antifouling materials has broad-spectrum antimicrobial activity and environmental friendliness and is expected to be a new type of marine antifouling coating with desirable antifouling functions. Finally, the future research directions of antifouling coatings are prospected, which are intended to provide a reference for the development of efficient, broad-spectrum and green marine antifouling coatings.

Enhanced antifouling properties of marine antimicrobial peptides by PEGylation.

Covalent immobilisation of antimicrobial peptides (AMPs) on underwater surfaces to combat marine biofouling is of great interest as it is an efficient, broad-spectrum and environmentally friendly strategy. Similar to post-translational modifications of natural proteins, artificial modifications of antimicrobial peptides can introduce important impacts on their properties and functions. The present work revealed the enhanced effect of PEGylation on the antifouling properties of marine antimicrobial peptides (LWFYTMWH) through grafting the modified peptides on aluminium surfaces. PEG was coupled to the peptide by solid-phase peptide synthesis, and the PEGylated peptides were bioconjugated to the aluminium surfaces which was pre-treated by aryldiazonium salts to introduce carboxyl groups. The carboxy group has been activated through the reaction with 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide. The successful modification was confirmed via FT-IR and XPS. Interestingly, the PEGylated peptides modified surfaces could kill 90.0% Escherichia coli (Gram-negative) and 76.1% Bacillus sp. (Gram-positive), and showed better antifouling performance than the original peptides modified surfaces. Furthermore, molecular dynamics simulations showed PEGylation could enhance the ability of peptides to destroy membrane. The PEGylated peptides inserted into the membrane and induced the change in local curvature of membrane, leading to the rupture of membrane. The presence of PEG changed the antimicrobial peptides into more flexible conformations and the high hydrophilicity of PEG hindered the settlement of bacteria. These might be the two main working mechanisms for the increased antifouling efficiency of PEGylated peptides modified surface. This study provided a feasible modification strategy of antimicrobial peptides to enhance their antifouling properties.

The Reduction in the Deformation of HDPE Composites Using Self-Lubricating Fillers in an Aqueous Environment.

Reducing the deformation of polymer matrix materials can decrease the fluctuation of coefficient of friction (COF), and friction-induced vibration and its amplitudes. HDPE composites with T-ZnOw as a fixed strengthening filler were modified with the addition of Si3N4 particles at different concentrations. The COFs, wear rates, micro-morphologies, and friction-induced vibrations were obtained by conducting sliding tests against carbon steel balls in an aqueous environment at a low velocity and high load. The mechanism of the reduction in frictional fluctuation due to the addition of Si3N4 particles was revealed through the frictional responses. The results demonstrated that 4 wt% addition of Si3N4 in HDPE can enhance the strain-stress property and improve the lubrication by forming a lubricating film. Therefore, the surface deformation and the fluctuations of COFs and its vibrations were reduced. The aggregation phenomenon and reduced strain-stress response at a high concentration of Si3N4 disrupted the positive fluctuating reduction, and resulted in a rough surface with severe tearing and cracking deformations. Additionally, it led to fluctuating wear behaviors with high COF and vibrations. The results obtained in this study can elucidate the effects of adding Si3N4 particles to enhance lubrication in polymer composites. Additionally, the results provide a new research method for designing and manufacturing polymer-based composites with low friction-induced fluctuations.

Antibacterial properties of Magainin II peptide onto 304 stainless steel surfaces: A comparison study of two dopamine modification methods.

Marine biofouling is perplexing the development of marine industry, and the traditional antifouling methods are restricted by the requirements of marine environmental friendliness. Marine bacteria attachment is the initial stage of marine fouling and it can be effectively reduced by reducing bacterial attachment. In this study, two modification methods were reported to synthesize antibacterial surfaces based on the different order of Magainin Ⅱ (MAG Ⅱ) modification. The preparation of SS-DA-M was generated by modifying the 304 stainless steel (304 SS) surface with dopamine firstly and then grafting the MAG Ⅱ onto the dopamine modified surface; SS-M-DA was obtained by modifying 304 SS surface using MAG Ⅱ derivative which synthesized by MAG Ⅱ and dopamine under weak acid condition. XPS, contact angle, film thickness and surface topography analysis showed that both methods grafted MAG Ⅱ onto the 304 SS surface successfully, changing the morphology and wettability of the substrates. Antibacterial results demonstrated that the two modified surfaces possessed strong resistance against V. natriegens, and the antibacterial efficiency of SS-DA-M and SS-M-DA reached 98.07 % and 99.79 %, respectively. Robustness results illustrated that the modified surface could keep strong antibacterial capacity in seawater for a long time. The phy-chemical properties and antibacterial properties of SS-M-DA surface were superior to SS-DA-M surface because more MAG Ⅱ were grafted onto 304 SS surface and the distribution was more uniform than the SS-DA-M surface. The investigation may offer a new and promising strategy to tackle surface fouling of hull, aquaculture cage and other marine facilities.

Role of trapped air and lubricant in the interactions between fouling and SiO2 nanoparticle surfaces.

Both biomimetic superhydrophobic surfaces and biomimetic slippery liquid-infused porous surfaces (SLIPSs) have been developed as potential alternatives for solving the problem of biofouling. Herein, a facile method was used to construct superhydrophobic surfaces and liquid infused porous surfaces on stainless steels for antifouling applications. The nano-structures were formed by electrostatic attraction between polycations and negatively charged SiO2 nanoparticles, providing a structural basis for superhydrophobic surfaces and liquid infused surfaces. Biofouling testing suggested excellent antifouling performances of the liquid infused porous surfaces by decreasing the adhesion of Chlorella pyrenoidosa by 93% and of Phaeodactylum tricornutum by 71%. The thermodynamic interpretation further indicated that the air layer captured by the superhydrophobic surfaces and the lubricant layer entrapped by the liquid infused porous surfaces played the dominant role in their antifouling performances. The inspiring results might show great potential for liquid infused porous surfaces in antifouling applications.

Rippled Polymer Surface Generated by Stick-Slip Friction.

Textured surfaces with varied functionalities are generally fabricated by etching, cutting, or printing. In this study, different from the usual generation of grooves along the sliding direction in friction, regular parallel ripples that are perpendicular to the sliding direction were generated on a polymer surface by the stick-slip friction of polymer/metal friction pairs lubricated with water. Ripple height was proportional to the peak friction force in the sticking process. Ripple wavelength decreased as the sliding velocity increased. The generation of ripples was ascribed to the adhesion and plastic deformation during stick-slip motion. The achieved rippled surface effectively improved the lubrication property of the two surfaces. These findings demonstrate a new method of in situ manufacturing ripples on a soft material surface through a controlled traditional sliding friction and also provide a new insight into the stick-slip friction behavior of materials.

Coupling mechanism between wear and oxidation processes of 304 stainless steel in hydrogen peroxide environments.

Stainless steel is widely used in strongly oxidizing hydrogen peroxide (H2O2) environments. It is crucial to study its wear behaviour and failure mode. The tribological properties and oxidation of 304 stainless steel were investigated using a MMW-1 tribo-tester with a three-electrode setup in H2O2 solutions with different concentrations. Corrosion current densities (CCDs), coefficients of frictions (COFs), wear mass losses, wear surface topographies, and metal oxide films were analysed and compared. The results show that the wear process and oxidation process interacted significantly with each other. Increasing the concentration of H2O2 or the oxidation time was useful to form a layer of integrated, homogeneous, compact and thick metal oxide film. The dense metal oxide films with higher mechanical strengths improved the wear process and also reduced the oxidation reaction. The wear process removed the metal oxide films to increase the oxidation reaction. Theoretical data is provided for the rational design and application of friction pairs in oxidation corrosion conditions.

Tribological Properties of Water-lubricated Rubber Materials after Modification by MoS2 Nanoparticles.

Frictional vibration and noise caused by water-lubricated rubber stern tube bearings, which are generated under extreme conditions, severely threaten underwater vehicles' survivability and concealment performance. This study investigates the effect of flaky and spherical MoS2 nanoparticles on tribological properties and damping capacity of water-lubricated rubber materials, with the aim of decreasing frictional noise. A CBZ-1 tribo-tester was used to conduct the sliding tests between rubber ring-discs and ZCuSn10Zn2 ring-discs with water lubrication. These materials' typical mechanical properties were analysed and compared. Coefficients of friction (COFs), wear rates, and surface morphologies were evaluated. Frictional noise and critical velocities of generating friction vibration were examined to corroborate above analysis. Results showed that spherical MoS2 nanoparticles enhanced rubber material's mechanical and tribological properties and, in turn, reduced the friction noise and critical velocity. Flaky MoS2 nanoparticles reduced COF but did not enhance their mechanical properties, i.e., the damping capacity, wear resistance property; thus, these nanoparticles did not reduce the critical velocity obviously, even though increased the frictional noise at high load. The knowledge gained in the present work will be useful for optimizing friction pairs under extreme conditions to decrease frictional noise of water-lubricated rubber stern tube bearings.

[Clinical analysis of retinoic acid syndrome developed in 11 patients with acute promyelocytic leukemia].

To explore the clinical features, risk factors an d treatment of retinoic acid syndrome (RAS) in patients with acute promyelocytic leukemia (APL) treated with retinoic acid, the clinical and laboratory data of 11 APL patients with RAS were retrospectively analysed. The results showed that earlier and more common symptoms of RAS were successively dyspnea (11/11), fever (10/11) and hydrothorax (6/11). Higher WBC count (> or = 15.0 x 10(9)/L) in the course of treatment of all-trans retinoic acid susceptible to develop RAS (9/11). The RAS patients were treated with dexamethasone without discontinuing the treatment of retinoic acid, complete remission was achieved in 10 cases and one patient died from disseminated intravascular coagulation. It is concluded that the identification and dexamethasone treatment of RAS in earlier period are extremely important for obtaining better clinical curative effect, and it does not influence therapeutic effect of continuing application of retinoic acid.