Icing and Adhesion Behaviors on Surfaces with Varied Lattice Constants.

Investigating droplet wetting and icing behavior is crucial for comprehending the principles of surface icing and the design of anti-icing surfaces. In this study, we present the evidence from molecular dynamics (MD) simulations that reveal a hitherto unreported behavior of droplet wetting and icing adhesion on surfaces with lattice constants from 2.7 to 4.5 Å. Here, we observe that the contact angles (CA) of droplets on a face-centered cubic (FCC) lattice surface consistently correlate positively with the lattice constant. Further examination of droplet behavior on an idealized crystal surface reveals that hydrophilic surfaces (e.g., CA = 85°) inhibit freezing more effectively than hydrophobic surfaces (e.g., CA = 97°). This finding contradicts the conventional explanation that hydrophobic surfaces reduce heterogeneous nucleation, thereby delaying icing. This study introduces a mechanistic explanation for the promotion of water icing by hydrophobic surfaces and offers a novel design concept for the development of anti-ice surfaces in future applications.

Biomimetic Slippery Surface with Exclusive Liquid-Repellent and Self-Cleaning Properties for Antifouling.

The nature always offers amazing inspiration, where it is highly desirable to endow coatings on marine equipment with powerful functions. An excellent example is slippery zone of Nepenthes pitcher, which possesses novel liquid-repellent and self-cleaning performance. Therefore, this study presents an efficient fabrication method to prepare a novel coating. The coatings were fabricated by designing biomimetic textures extracted from the lunate bodies of slippery zone on polydimethylsiloxane (PDMS) and then grafting Dictyophora indusiata polysaccharide (DIP) modifier. The as-prepared slippery coatings exhibited outstanding antifouling properties against kinds of daily life pollutants such as Chlorella and coffee. This synergistic strategy was proposed combined with environmentally friendly modifier grafting and heterogeneous microstructure on the surface to broaden new probabilities for manufacturing slippery coatings with incredible protective functionality.

Pressure-Activatable Liquid Metal Composites Flexible Sensor with Antifouling and Drag Reduction Functional Surface.

Flexible sensors produced through three-dimensional (3D) printing have exhibited promising results in the context of underwater sensing detection (for applications in navigational vehicles and human activities). However, underwater vehicles and activities such as swimming and diving are highly susceptible to drag, which can cause negative impacts such as reduced speed and increased energy consumption. Additionally, microbial adhesion can shorten the service life of these vehicles. However, natural organisms are able to circumvent such problems, with shark skin offering excellent barrier properties and ruffled papillae providing effective protection against fouling. Here, we show that a sandwich system consisting of a spraying layer, conductive elastomer composite, and encapsulation layer can be printed for multifunctional integrated underwater sensors. The modulated viscoelastic properties of liquid metal form the foundation for printing features, while its pressure-activated properties offer the potential for switchable sensors. An integrated drag reduction and antifouling layer were created by combining the shark skin surface shield scale structure with the lotus leaf surface papillae structure. A 3D-printed flexible sensor was designed using our approach to monitor attitude changes and strain in underwater environments, showcasing its capabilities. Our printed sensors can reduce biological attachment density by more than 50% and reduce underwater drag by 8.6-10.3%.

Effect of molecular helical structure on self-growing and damping of single network κ-carrageenan hydrogel.

Molecular helical is ubiquitous in molecular structures, however, the impact of the structure on mechanical properties has yet to be extensively studied. In this study, we synthesized a single network κ-carrageenan (KC) hydrogel with the molecular double helix structure, and elucidated its unique self-enhancing and damping properties from a molecular structural perspective. During cycle tensile tests, the helical structure was stretched and entangled to form a directional arrangement, increasing the elastic modulus and achieving 'self-reinforcement'. Meanwhile, the molecular helices have a spring-like damping effect, allowing the hydrogel to dampen low-frequency noise while transmitting high-frequency signals. By utilizing the hydrogel to create electrodes for electrocardiogram (ECG) detection, we were able to effectively filter out noise generated by movements while retaining necessary signals. Our work thus presents a potential pathway bridging from microscopic molecular structure to macroscopic mechanical properties of materials.

Optomechanically-induced nonreciprocal conversion between microwave and optical photons.

We theoretically propose a scheme of the nonreciprocal conversion device between photons of two arbitrary frequencies in a hybrid cavity optomechanical system, where two optical cavities and two microwave cavities are coupled to two different mechanical resonators via radiation pressure. Two mechanical resonators are coupled together via the Coulomb interaction. We study the nonreciprocal conversions between both the same and different types of frequency photons. The device is based on multichannel quantum interference to break the time-reversal symmetry. Our results show the perfect nonreciprocity conditions. By adjusting the Coulomb interaction and the phase differences, we find that the nonreciprocity can be modulated and even transformed into reciprocity. These results provide new insight into the design of nonreciprocal devices, including isolators, circulators, and routers in quantum information processing and quantum networks.

Dendritic Nanogels Directed Dual-Encapsulation Topical Delivery System of Antimicrobial Peptides Targeting Skin Infections.

Antimicrobial peptides (AMPs) are promising antibacterial agents in the fight against multidrug resistant pathogens. However, their application to skin infections is limited by the absence of a realizable topical delivery strategy. Herein, a hybrid hierarchical delivery system for topical delivery of AMPs is accomplished through the incorporation of AMPs into dendritic nanogels (DNGs) and their subsequent embedding into poloxamer gel. The high level of control over the crosslink density and the number of chosen functionalities makes DNGs ideal capsules with tunable loading capacity for DPK-060, a human kininogen-derived AMP. Once embedded into the poloxamer gel, DPK-060 encapsulated in DNGs displays a slower release rate compared to those entrapped directly in the gels. In vitro EpiDerm Skin Irritation Tests show good biocompatibility, while MIC and time-kill curves reveal the potency of the peptide toward Staphylococcus aureus. Anti-infection tests on ex vivo pig skin and in vivo mouse infection models demonstrate that formulations with 0.5% and 1% AMPs significantly inhibit the growth of S. aureus. Similar outcomes are observed for an in vivo mouse surgical site infection model. Importantly, when normalizing the bacteria inhibition to released/free DPK-060 at the wound site, all formulations display superior efficacy compared to DPK-060 in solution.

Responses and tolerance mechanisms of microalgae to heavy metal stress: A review.

Microalgae, the primary producers in water ecosystems, are the main food of fish and shrimp. Microalgae have a great capacity to absorb heavy metals, and low concentrations of heavy metals can promote the growth of them. But high concentrations have a strong influence on the physiological and biochemical processes in algae, such as growth, photosynthesis, cell ultrastructure, protein content and fatty acid composition. Heavy metals may also induce the formation of reactive oxygen species (ROS), which causes the oxidation damage of protein, lipid and thiol peptides, and activates the antioxidant system. Heavy metals can be removed or converted into another state by biosorption of cell surface, accumulation in cells, combining with antioxidant enzymes and so on. This review summarized the responses of microalgae to heavy metals and comprehensively described the removal and tolerance mechanisms by extracellular adsorption and intracellular accumulation, which are helpful to treat pollution and improve the culture of microalgae.

Dendritic Hydrogels Induce Immune Modulation in Human Keratinocytes and Effectively Eradicate Bacterial Pathogens.

Infections caused by antibiotic-resistant bacteria are globally a major threat, leading to high mortality rates and increased economic burden. Novel treatment strategies are therefore urgently needed by healthcare providers to protect people. Biomaterials that have inherent antibacterial properties and do not require the use of antibiotics present an attractive and feasible avenue to achieve this goal. Herein, we demonstrate the effect of a new class of cationic hydrogels based on amino-functional hyperbranched dendritic-linear-dendritic copolymers (HBDLDs) exhibiting excellent antimicrobial activity toward a wide range of clinical Gram-positive and Gram-negative bacteria, including drug-resistant strains isolated from wounds. Intriguingly, the hydrogels can induce the expression of the antimicrobial peptides RNase 7 and psoriasin, promoting host-mediated bacterial killing in human keratinocytes (HaCaT). Moreover, treatment with the hydrogels decreased the proinflammatory cytokine IL-1ß, reactive nitrogen species (NO), and mitochondrial reactive oxygen species (ROS) in S. aureus-infected HaCaT cells, conjunctively resulting in reduced inflammation.

Economic Friendly ZnO-Based UV Sensors Using Hydrothermal Growth: A Review.

Ultraviolet (UV) sensors offer significant advantages in human health protection and environmental pollution monitoring. Amongst various materials for UV sensors, the zinc oxide (ZnO) nanostructure is considered as one of the most promising candidates due to its incredible electrical, optical, biomedical, energetic and preparing properties. Compared to other fabricating techniques, hydrothermal synthesis has been proven to show special advantages such as economic cost, low-temperature process and excellent and high-yield production. Here, we summarize the latest progress in research about the hydrothermal synthesis of ZnO nanostructures for UV sensing. We particularly focus on the selective hydrothermal processes and reveal the effect of key factors/parameters on ZnO architectures, such as the laser power source, temperature, growth time, precursor, seeding solution and bases. Furthermore, ZnO hydrothermal nanostructures for UV applications as well as their mechanisms are also summarized. This review will therefore enlighten future ideas of low-temperature and low-cost ZnO-based UV sensors.

Novel Therapeutic Platform of Micelles and Nanogels from Dopa-Functionalized Triblock Copolymers.

Multi-drug delivery systems constructed from a basic polymeric scaffold, and which have the ability to target a variety of biomedical applications, can streamline the development of nanomedicine to provide both environmental and economical relief. Herein, amphiphilic ABA-triblock copolymers are synthesized and assembled sequentially into micelles and nanogels as drug delivery systems following a thorough evaluation on advanced in vitro models to explore their potential for the treatment of cancer and bacterial infections. Short blocks of 5-methyl-5-allyloxycarbonyl-1,3-dioxan-2-one (MAC) are oligomerized from PEG6k and thereafter functionalized with dihydroxyphenylalanine (dopa)-functional thiols using thiol-ene coupling (TEC) click chemistry. The copolymers self-assemble into well-defined micelles in aqueous solution and are further formulated into nanogels via UV-induced TEC. The resulting spherical micelles and nanogels are stable nanoparticles, with sizes ranging between 100 and 200 nm. The nanogels are found to be non-toxic to a panel of cell lines and mask the toxicity of the potent drugs until their release. The nanogels would be superior to micelles for the elimination of cancer cells supported by both 2D cell culture and a 3D spheroid model. The opposite conclusion could be drawn for bacteria inhibition.

Extracellular adsorption, intracellular accumulation and tolerance mechanisms of Cyclotella sp. to Cr(VI) stress.

Heavy metals have caused widespread concern due to their adverse effects on aquatic organisms. However, there are few studies on their tolerance mechanism. In this study, the tolerance mechanisms of Cyclotella sp. to Cr(VI) were explored. The increase of antioxidant enzymes activity acting as a defense mechanism could help Cyclotella sp. to reduce the oxidative damage caused by the heavy metal Cr(VI). Cr(VI) was also combined with the functional groups on the cell surface to detoxify and was transported into the cell by binding to the carrier protein. In addition, it is worth noting that the molecular docking simulation showed that Cr(VI) combined with macromolecular compounds in cells through hydrogen and ionic bonds, which can reduce the toxicity of chromium. The determination of chromium content in cells showed that chromium was accumulated in cells. Furthermore, the low concentration of Cr(VI) had a growth stimulation on Cyclotella sp., while the growth of Cyclotella sp. microalgae was obvious inhibited when Cr(VI) concentration was over 0.5 mg/L. The content of Chlorophyll a (Chl-a) and soluble protein both had a dramatic change under the stress of Cr(VI). Cell ultrastructure analysis showed that plasmolysis phenomenon and dissolution of organelle structures when Cyclotella sp. was exposed to Cr(VI). The series of changes in Cyclotella sp. allow it to be an indicator of Cr(VI) pollution in water. Meanwhile, these findings were helpful to further understand the tolerance mechanism of Cr(VI) on microalgae and provide new insights to assess Cr(VI) toxicity to the microalgae.

Physiological and morphological responses and tolerance mechanisms of Isochrysis galbana to Cr(VI) stress.

The effects of the initial concentrations of Cr(VI) on chlorophyll-a (Chl-a), soluble protein and ultrastructure were investigated. Results showed that <0.5 and >1.0 mg L-1 Cr(VI) stimulated and inhibited the growth of Isochrysis galbana, respectively. The tolerance mechanisms of I. galbana to Cr(VI) included the following: (1) increased activities of superoxide dismutase (SOD) and peroxidase (POX) for peroxidative damage resistance, (2) accumulation of Cr(VI) on the cell surface and inside the cell for detoxification and (3) conversion of intracellular Cr(VI) to less toxic Cr(III) as indicated by X-ray photoelectron spectroscopy (XPS) results. Cr(VI) enrichment by I. galbana may cause damage to marine ecology and human bodies through the food chain. The tolerance mechanisms of I. galbana to Cr(VI) may be potentially used to treat low-concentration Cr(VI) wastewater. Therefore, the responses and tolerance mechanisms of I. galbana to Cr(VI) must be further studied.

Polydopamine-Assisted Immobilization of Chitosan Brushes on a Textured CoCrMo Alloy to Improve its Tribology and Biocompatibility.

Due to their bioinert and reliable tribological performance, cobalt chromium molybdenum (CoCrMo) alloys have been widely used for articular joint implant applications. However, friction and wear issues are still the main reasons for the failure of implants. As a result, the improvement of the tribological properties and biocompatibility of these alloys is still needed. Thus, surface modification is of great interest for implant manufacturers and for clinical applications. In this study, a strategy combining laser surface texturing and chitosan grafting (mussel inspired) was used to improve the tribological and biocompatible behaviors of CoCrMo. The microstructure and chemical composition were investigated by atomic force microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy, respectively. The tribological properties were discussed to determine their synergistic effects. To evaluate their biocompatibility, osteoblast cells were cocultured with the modified surface. The results show that there is a distinct synergistic effect between laser surface texturing and polymer brushes for improving tribological behaviors and biocompatibility. The prepared chitosan brushes on a textured surface are a strong mechanism for reducing friction force. The dimples took part in the hydrodynamic lubrication and acted as the container for replenishing the consumed lubricants. These brushes also promote the formation of a local lubricating film. The wear resistance of the chitosan brushes was immensely improved. Further, the worn process was observed, and the mechanism of destruction was demonstrated. Co-culturing with osteoblast cells showed that the texture and grafting have potential applications in enhancing the differentiation and orientation of osteoblast cells.

Constructing a Dual-Function Surface by Microcasting and Nanospraying for Efficient Drag Reduction and Potential Antifouling Capabilities.

To improve the drag-reducing and antifouling performance of marine equipment, it is indispensable to learn from structures and materials that are found in nature. This is due to their excellent properties, such as intelligence, microminiaturization, hierarchical assembly, and adaptability. Considerable interest has arisen in fabricating surfaces with various types of biomimetic structures, which exhibit promising and synergistic performances similar to living organisms. In this study, a dual bio-inspired shark-skin and lotus-structure (BSLS) surface was developed for fabrication on commercial polyurethane (PU) polymer. Firstly, the shark-skin pattern was transferred on the PU by microcasting. Secondly, hierarchical micro- and nanostructures were introduced by spraying mesoporous silica nanospheres (MSNs). The dual biomimetic substrates were characterized by scanning electron microscopy, water contact angle characterization, antifouling, self-cleaning, and water flow impacting experiments. The results revealed that the BSLS surface exhibited dual biomimetic features. The micro- and nano-lotus-like structures were localized on a replicated shark dermal denticle. A contact angle of 147° was observed on the dual-treated surface and the contact angle hysteresis was decreased by 20% compared with that of the nontreated surface. Fluid drag was determined with shear stress measurements and a drag reduction of 36.7% was found for the biomimetic surface. With continuous impacting of high-speed water for up to 10 h, the biomimetic surface stayed superhydrophobic. Material properties such as inhibition of protein adsorption, mechanical robustness, and self-cleaning performances were evaluated, and the data indicated these behaviors were significantly improved. The mechanisms of drag reduction and self-cleaning are discussed. Our results indicate that this method is a potential strategy for efficient drag reduction and antifouling capabilities.

Fabricating hierarchical micro and nano structures on implantable Co-Cr-Mo alloy for tissue engineering by one-step laser ablation.

Surface texturing is one of the effective strategies to improve bioactivity of implantable materials. In this study, hierarchical micro and nano structure (HMN) were fabricated on Co-Cr-Mo alloy substrate by a movable picosecond laser irradiation. Respectively, microgrooves with nano ripples and islands were produced on Co-Cr-Mo alloy by low and high laser power density. X-ray diffraction apparatus (XRD) phase analysis illustrated that substrate was in the phase of γ- face-centered cubic structure (FCC) before laser treatment, while it was in ε-hexagonal closest packing structure (HCP) phase dominant after laser treatment. Cell adhesion and proliferation studies showed that the HMN surface exhibits enhanced adhesion of MC3TC-E1 osteoblast and promoted cell activity. Analyzing of the morphology of osteoblast cells indicated cells were in high ratio of elongation on the HMN surface, while they mainly kept in round shape on the polished surface. Results indicated the formation of hierarchical structure on Co-Cr-Mo alloy was able to improve biological performances, suggesting the potential application in cobalt based orthopedic implants.

Preparation and bioactive properties of chitosan and casein phosphopeptides composite coatings for orthopedic implants.

Using the layer-by-layer deposition method, functional chitosan/casein phospopeptides (CS/CPP) composite coatings were produced on Co-Cr-Mo alloy. The CS/CPP composite coatings had the dendritic topography, and were quite hydrophilic. Zeta potential measurements showed the composite coatings were negative charged at neural pH. XPS results indicated that the CS/CPP composite coatings were covalently bond to the substrate. When MC3T3-E1 cells were seeded on the CS/CPP composite coatings, no cytotoxicity was observed. The bone morphogenetic protein-2 (BMP-2) mRNA expression was significantly up-regulated in MC3T3-E1 cells cultured on the composite coatings and it was twice as much as that of cells cultured on the bare substrate. The expression of osteoprotegerin (OPG) mRNA and the ratio of OPG/receptor activator of nuclear factor-κB ligand (RNAKL) mRNA were increased 5-fold and 55-fold, respectively. These results suggested the CS/CPP composite coatings may have potential application in cobalt matrix orthopaedic implants.

In vivo synthesis of calcium oxalate whiskers on CoCrMo alloy surfaces via biomineralization.

Surface treatments using bio-technology are valuable and fascinating in the sense that such treatments are natural and yield good biocompatibility. Calcium oxalate whiskers for biomedical applications were successfully synthesized on the CoCrMo alloy surfaces implanted in Aloe leaves which consist of many active bio-chemical elements. The effect of surface wettability and surface morphology on the formation of whiskers was investigated using four differently treated CoCrMo surfaces: (i) smoothly polished surface, (ii) electrochemical etched surface, (ii) textured surface with dimples, and (iv) parallel orientated-grooved surface. Results showed that the formed whiskers had a length ranging between 100 µm and 600 µm, and a diameter in the range of 2 µm to 5 µm. Electrochemically etched surfaces had better wettability and were favorably for growing whiskers. Surface morphology with (i) dimple textures or (ii) parallel grooves facilitated the effective control of the size and amount of the grown whiskers.

Sulfated modification and immunomodulatory activity of water-soluble polysaccharides derived from fresh Chinese persimmon fruit.

In this study, three kinds of chemically sulfated polysaccharides (PFP-S) were derived from a water-soluble polysaccharide of persimmon fruit with chlorosulfonic acid-pyridine method. Relationship between the degree of substitution and immunomodulatory activity of PFP-S was examined with the splenocytes experiment. The results showed that the splenocytes-activating activity was significantly enhanced by PFP-S in all the groups compared with control group (P<0.01). PFP-SII exhibited the most potent splenocytes-activating activity by increased cytokine production and NO release. It also suggested that the sulfate groups and molecular weight of polysaccharides are key factors to regulate the immunomodulatory activities.