Getting glued in the sea.

Inspired by ocean organisms, scientists have been developing adhesives for application in the marine environment. However, water and high salinity, which not only weaken the interfacial bonding by the hydration layer but also induce the deterioration of adhesives by erosion, swelling, hydrolysis, or plasticization, are detrimental to adhesion, resulting in specific challenges in the development of under-seawater adhesives. In this focus review, current adhesives that are capable of macroscopic adhesion in seawater were summarized. The design strategies and performance of these adhesives were reviewed based on their bonding methods. Finally, some future research directions and perspectives for under-seawater adhesives were discussed.

Cooperation of Zr(IV)-N and Zr(IV)-O coordinate bonds of Zr(IV)-amide ensures the transparent and tough polyacrylamide hydrogels.

Developing advanced soft machines and tissue engineering for load-bearing cartilage or tendons requires tough hydrogels. However, the construction of double or triple crosslinked networks for these tough hydrogels, i.e., a strong network crosslinked by covalent bonds and one or two sacrificial networks built by hydrogen bonds or coordinate bonds, generally asks for multiple steps. It remains a challenge to develop hydrogels with a combination of excellent toughness and a high content of water through the time-saving one-pot process. This study demonstrates that this puzzle could be solved through engineering zirconium(IV)-amide coordinate bonds. To be specific, the combination of strong Zr(IV)-O and moderate Zr(IV)-N coordinate bonds in Zr-polyacrylamide (Zr-PAAm) hydrogels has the advantage that they are usually generated through multiple cross-linked networks. Compared to chemical crosslinked PAAm hydrogels, the highly transparent Zr-PAAm hydrogels crosslinked by Zr(NO3)4 displayed a 26-times increase in fracture stress, 4-times in fracture strain, 6-times in elastic modulus, and over 250-times in toughness. Besides, the mechanical properties of Zr-PAAm hydrogels could be altered over a wide range via changing the anion species, showing a dependence on the Hofmeister effect. The co-existence of Zr(IV)-N and Zr(IV)-O has been confirmed through XPS and FTIR characterizations. In particular, the effect of Zr(IV)-N in Zr-PAAm hydrogels has been verified by comparing the property changes of Zr-PAAm hydrogels before and after swelling in water, in which the Zr(IV)-N in the as-prepared hydrogels was replaced by Zr(IV)-O in the swollen gels. With ultra-stretchability and high transparency, the colorless Zr-PAAm hydrogels displayed rich interference colors under stretching, which brought great potential in anti-counterfeiting materials.

Gluing blood into gel by electrostatic interaction using a water-soluble polymer as an embolic agent.

Liquid embolic agents are widely used for the endovascular embolization of vascular conditions. However, embolization based on phase transition is limited by the adhesion of the microcatheter to the embolic agent, use of an organic solvent, unintentional catheter retention, and other complications. By mimicking thrombus formation, a water-soluble polymer that rapidly glues blood into a gel without triggering coagulation was developed. The polymer, which consists of cationic and aromatic residues with adjacent sequences, shows electrostatic adhesion with negatively charged blood substances in a physiological environment, while common polycations cannot. Aqueous polymer solutions are injectable through clinical microcatheters and needles. The formed blood gel neither adhered to the catheter nor blocked the port. Postoperative computed tomography imaging showed that the polymer can block the rat femoral artery in vivo and remain at the injection site without nontarget embolization. This study provides an alternative for the development of waterborne embolic agents.

Exploring potential opportunities for the efficient development of the cobalt industry in China by quantitatively tracking cobalt flows during the entire life cycle from 2000 to 2021.

Owing to its key role in high-tech industry and clean energy technology, cobalt has been regarded as a critical material in many countries. In this paper, material flow analysis was used to quantitatively track cobalt material flows in China throughout the entire life cycle from 2000 to 2021. Based on data pertaining to cobalt commodity trade, cobalt loss during raw material processing, and recovered cobalt, we analysed the actual cobalt consumption in China. During the study period from 2000 to 2021, the main findings were as follows: (1) China's cobalt raw material imports accounted for 84.7% of the total raw materials acquired, while the export of cobalt-containing end products amounted to 32.6% of the total production. (2) China's cumulative net import of all cobalt commodities reached 561 kt, and battery products accounted for 73.3% of the total cobalt consumption. (3) China recovered 77 kt of cobalt from end-of-life products, while 327 kt of cobalt was not recovered. (4) The cumulative cobalt loss during raw material processing reached 288 kt, with the highest loss occurring in refining (51.0%), followed by manufacturing and fabrication (26.5%), beneficiation (12.3%), and ore mining (10.2%). The overall utilization efficiency of cobalt was 73.8% throughout the entire life cycle. (5) China's actual cobalt consumption reached 497 kt, accounting for 51.9% of the apparent cobalt consumption. Moreover, 61.1% of the cobalt products produced in China was consumed domestically, while 38.9% was exported. The massive export of cobalt commodities resulted in China bearing a disproportionate responsibility for carbon emission reduction. The research results can provide a scientific reference for the reasonable adjustment of the trade structure of cobalt commodities and realization of the economic and efficient utilization of cobalt resources in China.

Quantitative determination of cation-π interactions between metal ions and aromatic groups in aqueous media by a hydrogel Donnan potential method.

Cation-π interactions in aqueous media are known to play critical roles in various biological activities. However, quantitative experimental information, such as the binding ratio of metal ions to aromatic groups, is hardly available due to the lack of a suitable test system and method. Herein, we proposed a hydrogel Donnan potential method to determine the binding ratio of metal ions to aromatic groups on polymer networks in aqueous media. In this method, we adopted recently developed poly(cation-π) hydrogels with a rich adjacent sequence of the cationic group and the aromatic group on the polymer network. A microelectrode technique (MET) is used to measure the Donnan potential of the poly(cation-π) hydrogels. From the Donnan potential, the binding ratios of various metal ions to aromatic groups are quantitatively determined for the first time.

Bioinspired Underwater Adhesives.

Underwater adhesives are in high demand in both commercial and industrial sectors. Compared with adhesives used in dry (air) environments, adhesives used for wet or submerged surfaces in aqueous environments have specific challenges in development and performance. In this review, focus is on adhesives demonstrating macroscopic adhesion to wet/underwater substrates. The current strategies are first introduced for different types of underwater adhesives, and then an overview is provided of the development and performance of underwater adhesives based on different mechanisms and strategies. Finally, the possible research directions and prospects of underwater adhesives are discussed.

Effectiveness and Safety of Acupoint Application of Guan Xin Su He Pill () for Patients with Chronic Stable Angina Pectoris: A Multi-Center, Randomized Controlled Trial.

OBJECTIVE: To assess the clinical effectiveness of acupoint application (AP) of Guan Xin Su He Pill (, GXSHP) for patients with chronic stable angina pectoris (CSAP). METHODS: This study was carried out in 3 local hospitals in Chengdu, China. After baseline evaluation, eligible patients were randomly assigned to the placebo application for acupoints (PAA) group or the herbal application for acupoints (HAA) group. Patients in the HAA group underwent AP with herbal powder, which was mainly GXSHP, and patients in the PAA group underwent AP with sham drugs. For each treatment session, unilateral acupoints including Neiguan (PC 6), Danzhong (RN 17), Xinshu (BL 15) and Jueyinshu (BL 14), were stimulated for both groups. AP was performed 3 times a week with a 2-day interval for 4 weeks. The primary outcome was the frequency of angina pectoris attacks per week, while the secondary outcomes included angina pain intensity measured by the Visual Analogue Scale (VAS), dose of rescue oral drugs (nitroglycerin), scores on the Seattle Angina Questionnaire (SAQ), Self-Rating Anxiety Scale scores (SAS) and Self-Rating Depression Scale scores (SDS). Clinical outcomes were measured at week 0, 4 and 8. The safety of AP of GXSHP treatment for CSAP were assessed. RESULTS: A total of 121 patients were enrolled. Baseline characteristics were comparable across the 2 groups. After treatment, the angina attack numbers in the HAA group were significantly reduced from 11.00 to 4.81 (P<0.05). While, for PAA group, the angina frequency was not significantly improved (baseline 10.55; post-treatment 11.05). The HAA group had significantly fewer angina attacks than the PAA group (P<0.05). Pain intensity measured by VAS in HAA group was significantly reduced from 4.06 to 3.02 (P<0.05). While, for PAA group, the VAS was significantly increased (baseline 3.62; post-treatment 3.96; P<0.05). Clinical outcomes showed better improvement after treatment in the HAA group than in the PAA group in terms of oral administration of rescue drugs, SAS, SDS and SAQ scores (P<0.05). The adverse events were also reported. CONCLUSION: AP of GXSHP is a safe and effective treatment for CSAP patients (Registration No. NCT02029118).

Electromagnetic properties of crayfish and its responses of temperature and moisture under microwave field.

To reveal the application potential of microwave heating in the thermal processing of crayfish, this work explored the electromagnetic properties of different parts of crayfish and the patterns of temperature and moisture responses in crayfish during microwave heating. The results of electromagnetic analysis demonstrated that the electromagnetic properties of different parts of crayfish were different, and the tail had higher dielectric properties and reflective loss than other parts, but the maximum thickness of each part of crayfish was almost within their heating depth of microwave. The visual imaging and numerical simulation of temperature and moisture responses showed there were nonuniform temperature and moisture distributions in crayfish during microwave heating. The crayfish tail was selectively heated and rapidly cooked, but its moisture loss was far less than the mass loss of whole crayfish. Furthermore, the immobilized water in crayfish tail meat was continuously converted to free water, while the bound water was relatively stable during microwave heating. This work provided the theoretical references for the assumption that cooking the crayfish by microwave to overcome the shortcomings of boiling. PRACTICAL APPLICATION: In this work, we innovatively applied microwave heating to the heat processing of crayfish, and analyzed the electromagnetic properties of different parts in crayfish and explored its temperature and moisture responses under microwave field. Although this is a basic research, which provided some theoretical references for the assumption that microwave heating of crayfish (Procambarus clarkia) may be a clean and efficient means of overcoming the shortcomings associated with boiling. In particular, the simulation model of crayfish was established according to its real size and shape, which provided an option for the prediction of temperature response of crayfish in the microwave field.

Mussel byssus cuticle-inspired ultrastiff and stretchable triple-crosslinked hydrogels.

Applications in the harsh environment require hydrogels with ultra-stiffness, toughness, and stretchability. However, it remains a challenge to increase the elastic modulus without sacrificing the maximum elongation of hydrogels, because of the trade-off between stiffness and extensibility. Inspired by the crosslinking hierarchy of mussel byssus cuticle, here, we report a strategy to fabricate an ultra-stiff, tough and stretchable triple-crosslinked (TC) hydrogel. The polymer is crosslinked by chemical crosslinker at first, subsequently by introducing a polyphenolic compound, tannic acid (TA), and metal ions. The hydrogen-bond-based network between the polymer and TA works as an extensible and energy-dissipative network, mimicking the matrix of the cuticle, while the higher crosslinked domains formed by the coordinate bonds between TA and metal ions contribute to the stiffness. The triple-crosslinked hydrogel exhibits two orders of magnitude increase in stiffness (E = 58 MPa), but without sacrificing the maximum elongation (ε = 850%), compared with those of metal-free hydrogels (E = 0.18 MPa, and ε = 860%). The combination of ultra-stiffness, toughness, and stretchability in hydrogels is successfully achieved through leveraging the hierarchically cross-linked network based on hydrogen bonding and coordination bonding. Moreover, utilizing the wide distribution of bonding strength of coordination interaction, the mechanical properties of triple-crosslinked hydrogels can be manipulated by using different kinds of catechol-metal coordination.

Are oil spills an important source of heavy metal contamination in the Bohai Sea, China?

Accurate evaluation of the heavy metal contamination caused by oil spills is more urgent than that of organic pollution since heavy metals are toxic and persistent. This study applies bulk geochemical parameters and hydrocarbon compositions to explore heavy metal contamination caused by oil spills. The contents of six heavy metals (Cu, Pb, Zn, Cr, Ni, and Co), total organic carbon, aliphatic hydrocarbons, and grain size were measured in 50 subsurface sediment samples obtained from an area affected by oil spills in the Bohai Sea. The values of the contamination factor (CF), the geo-accumulation index (Igeo), and the enrichment factor (EF) indicate moderate contamination with the six investigated heavy metals at most of the sampling sites. Riverine inputs, oil spills, and airborne dust are the three main sources of the heavy metals, and oil spills are the significant source of heavy metal contamination in the areas. The distributions of the mean grain size (Mz) and the contents of unresolved complex mixture (UCM) and Cr suggest that crude oil migrates from deep hydrocarbon reservoirs through geological faults and seeps through coarse-grained sediments until it reaches fine-grained sediments. The spilled oil contributes appreciable amounts of heavy metals to the sediments at the oil-contaminated sites. At these sites, the heavy metals from oil spills overprinted on those contributed by terrigenous materials, which are the predominant source of metals in the subsurface sediments in the areas affected by oil spills.

Adjacent cationic-aromatic sequences yield strong electrostatic adhesion of hydrogels in seawater.

Electrostatic interaction is strong but usually diminishes in high ionic-strength environments. Biosystems can use this interaction through adjacent cationic-aromatic amino acids sequence of proteins even in a saline medium. Application of such specific sequence to the development of cationic polymer materials adhesive to negatively charged surfaces in saline environments is challenging due to the difficulty in controlling the copolymer sequences. Here, we discover that copolymers with adjacent cation-aromatic sequences can be synthesized through cation-π complex-aided free-radical polymerization. Sequence controlled hydrogels from diverse cation/aromatic monomers exhibit fast, strong but reversible adhesion to negatively charged surfaces in seawater. Aromatics on copolymers are found to enhance the electrostatic interactions of their adjacent cationic residues to the counter surfaces, even in a high ionic-strength medium that screens the electrostatic interaction for common polyelectrolytes. This work opens a pathway to develop adhesives using saline water.

Fabrication of Tough Hydrogel Composites from Photoresponsive Polymers to Show Double-Network Effect.

Inspired by the toughening mechanism of double-network (DN) gels, tough hydrogel composites with a sandwich structure were fabricated from photoresponsive polymers. By copolymerization of hydrophilic monomers, 2-ureidoethyl methacrylate (UM), and photoresponsive hydrophobic monomers, (2-nitrobenzyloxycarbonylaminoethyl methacrylate (NBOC)) at high concentrations, physical hydrogels that are soft and highly stretchable are formed due to the hydrophobic associations of NBOC, serving as dynamic crosslinkers. By UV irradiation, the physical crosslinking switches into chemical crosslinking, and the soft physical hydrogels transform into rigid and less stretchable chemical hydrogels. By UV curing the surface layers of the physical hydrogels, we prepared hydrogel composites having a sandwiched structure with two rigid outer layers and a soft inner layer. The molecular-level continuous interfaces and matched swelling ratios between the layers ensure the macroscale hydrogel composites' high strength and toughness with a DN gel effect. The outer layers fracture preferentially at deformation, playing a role like the first network of a DN gel, while the inner layer maintains the integrity, playing a role resembling the second network. The evolution of the fracture morphology of the rigid layers gives useful insight into the internal fracture process of DN gels.

Acupuncture as Adjunctive Therapy for Chronic Stable Angina: A Randomized Clinical Trial.

IMPORTANCE: The effects of acupuncture as adjunctive treatment to antianginal therapies for patients with chronic stable angina are uncertain. OBJECTIVE: To investigate the efficacy and safety of acupuncture as adjunctive therapy to antianginal therapies in reducing frequency of angina attacks in patients with chronic stable angina. DESIGN, SETTING, AND PARTICIPANTS: In this 20-week randomized clinical trial conducted in outpatient and inpatient settings at 5 clinical centers in China from October 10, 2012, to September 19, 2015, 404 participants were randomly assigned to receive acupuncture on the acupoints on the disease-affected meridian (DAM), receive acupuncture on the acupoints on the nonaffected meridian (NAM), receive sham acupuncture (SA), and receive no acupuncture (wait list [WL] group). Participants were 35 to 80 years of age with chronic stable angina based on the criteria of the American College of Cardiology and the American Heart Association, with angina occurring at least twice weekly. Statistical analysis was conducted from December 1, 2015, to July 30, 2016. INTERVENTIONS: All participants in the 4 groups received antianginal therapies as recommended by the guidelines. Participants in the DAM, NAM, and SA groups received acupuncture treatment 3 times weekly for 4 weeks for a total of 12 sessions. Participants in the WL group did not receive acupuncture during the 16-week study period. MAIN OUTCOMES AND MEASURES: Participants used diaries to record angina attacks. The primary outcome was the change in frequency of angina attacks every 4 weeks from baseline to week 16. RESULTS: A total of 398 participants (253 women and 145 men; mean [SD] age, 62.6 [9.7] years) were included in the intention-to-treat analyses. Baseline characteristics were comparable across the 4 groups. Mean changes in frequency of angina attacks differed significantly among the 4 groups at 16 weeks: a greater reduction of angina attacks was observed in the DAM group vs the NAM group (difference, 4.07; 95% CI, 2.43-5.71; P < .001), in the DAM group vs the SA group (difference, 5.18; 95% CI, 3.54-6.81; P < .001), and in the DAM group vs the WL group (difference, 5.63 attacks; 95% CI, 3.99-7.27; P < .001). CONCLUSIONS AND RELEVANCE: Compared with acupuncture on the NAM, SA, or no acupuncture (WL), acupuncture on the DAM as adjunctive treatment to antianginal therapy showed superior benefits in alleviating angina. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT01686230.

Polydopamine Generates Hydroxyl Free Radicals under Ultraviolet-Light Illumination.

Polydopamine (PDA) generally demonstrates as an efficient free-radical scavenger. However, its free-radical chemistry under illumination is unclear, which becomes important in view of growing studies of polydopamine applications in photoprotector and photothermal therapy. In this study, for the first time, we reported an experimental investigation of the generation of hydroxyl free radicals from ultraviolet (UV)-illuminated polydopamine in an aqueous environment. By using terephthalic acid as fluorescent probe, we measured hydroxyl radicals generated from UV-illuminated polydopamine with different shapes and sizes. The morphology of PDA shows significant influence on its productions of hydroxyl free radicals. Through characterizations of UV-vis absorption spectroscopy, fluorescence spectroscopy, X-ray photoelectron spectrometry, mass spectrometry, and thermogravimetric analysis, we demonstrated the change of PDA nanomaterials brought by UV-light illumination in composition and thermal stability. We proposed a tentative mechanism for interpreting the relationship between morphology and photostability of PDA nanomaterials. These results reveal underlying complexity of polydopamine chemistry under light illumination that will deepen our understanding and benefit its further application.

Tannic Acid-Based Multifunctional Hydrogels with Facile Adjustable Adhesion and Cohesion Contributed by Polyphenol Supramolecular Chemistry.

Adhesiveness of hydrogels depends on the balance and synergy of their cohesion and adhesion. However, it is a challenge to fabricate catechol-based hydrogels with high adhesiveness because the required condition for cohesion and adhesion of these hydrogels is in conflict with each other: strong cohesion (gelation) requires a weak basic condition, whereas strong adhesion requires an acidic condition. Here, we demonstrated that by utilizing polyphenol supramolecular chemistry, the coexistence of strong cohesion and adhesion can be achieved in a hydrogel via the one-pot method. Poly(dimethyl diallyl ammonium chloride)/tannic acid (PDDA/TA) hydrogel has been studied as a proof of concept. Compared with catechol moieties that covalently grafted on polymer chains, TA can bring high density of pyrogallol/catechol functional groups for polymers via a noncovalent pathway, as well as high acidity in the system. As a result, the cohesion of the hydrogel is enhanced significantly, the highest storage moduli can reach up to ca. 0.15 MPa; besides, the high acidity of the hydrogel prevents pyrogallol/catechol groups from oxidation and guarantees strong adhesion; thus, the hydrogel can adhere to diverse substrates steadily, including tissues, glass, metals, and plastic. Moreover, because of the adjustable adhesiveness via changing the pH, the PDDA/TA hydrogel becomes a unique system with patternable adhesiveness. In addition, the hydrogel has rapid self-healing and high ionic conductivity (∼4.3 S m-1). This study demonstrates that utilizing polyphenol chemistry in the construction of hydrogels opens a new path toward multifunctional hydrogels with improved properties.

Characterizations of the Formation of Polydopamine-Coated Halloysite Nanotubes in Various pH Environments.

Recent studies demonstrated that polydopamine (PDA) coating is universal to nearly all substrates, and it endows substrates with biocompatibility, postfunctionality, and other useful properties. Surface chemistry of PDA coating is important for its postmodifications and applications. However, there is less understanding of the formation mechanism and surface functional groups of PDA layers generated in different conditions. Halloysite is a kind of clay mineral with tubular nanostructure. Water-swellable halloysite has unique reactivity. In this study, we have investigated the reaction of dopamine in the presence of water-swellable halloysite. We have tracked the reaction progresses in different pH environments by using UV-vis spectroscopy and surface-enhanced Raman spectroscopy (SERS). The surface properties of PDA on halloysite were clarified by X-ray photoelectron spectroscopy (XPS), SERS, Fourier transform infrared (FTIR) characterizations, zeta potential, surface wettability, and morphological characterizations. We noticed that the interaction between halloysite surface and dopamine strongly influences the surface functionality of coated PDA. In addition, pH condition further modulates surface functional groups, resulting in less content of secondary/aromatic amine in PDA generated in weak acidic environment. This study demonstrates that the formation mechanism of polydopamine becomes complex in the presence of inorganic nanomaterials. Substrate property and reaction condition dominate the functionality of obtained PDA together.

[Strategy on the recruitment of free community medical-consultation in acupuncture clinical trials].

The difficulty in the participant recruitment is the common question in acupuncture clinical trial study. The existing recruitment of clinical trial is most applicable for the clinical trial of medicines. Because the intervention of acupuncture clinical trial is different from that of medicines, characterized as the specialties in "theory, principle, acupoints, technique", it is very necessary to develop the strategy on the participant recruitment in acupuncture clinical trial. The free community medical consultation is one of the important means of recruitment. In the paper, by taking the participant recruitment of acupuncture clinical trial on chronic stable angina pectoris as the example, the discussion is given on the strategy on the recruitment of free community medical consultation in the aspects of feasible investigation of recruitment approach, recruitment plan, participant screening, etc. The revisiting after the free community medical consultation is the important approach to the improvement of successful recruitment. This strategy on the recruitment of free community medical consultation is highly practical and improves the successful rate and compliance of the participant recruitment. Hence, this strategy deserves to be promoted.

Oxidative Self-Polymerization of Dopamine in an Acidic Environment.

A weak alkaline condition (pH > 8) is a general requirement for oxidative self-polymerization of dopamine. Here, we first demonstrated the generation of polydopamine in an acidic environment via a hydrothermal method. The pH scope of self-polymerization of dopamine is extended to pH ∼ 1 in a hydrothermal process. Polydopamine generated via a hydrothermal method shows similar chemical features and radical scavenging activity with that generated in a basic environment.

Hierarchical porous polycaprolactone microspheres generated via a simple pathway combining nanoprecipitation and hydrolysis.

We demonstrated a one-pot, soap-free fabrication of porous polycaprolactone microspheres by combining nanoprecipitation and hydrolysis. The obtained porous polycaprolactone microspheres show great advantages for application in drug delivery.

Folic acid-polydopamine nanofibers show enhanced ordered-stacking via π-π interactions.

Recent research has indicated that polydopamine and synthetic eumelanins are optoelectronic biomaterials in which one-dimensional aggregates composed of ordered-stacking oligomers have been proposed as unique organic semiconductors. However, improving the ordered-stacking of oligomers in polydopamine nanostructures is a big challenge. Herein, we first demonstrate how folic acid molecules influence the morphology and nanostructure of polydopamine via tuning the π-π interactions of oligomers. MALDI-TOF mass spectrometry reveals that porphyrin-like tetramers are characteristic of folic acid-polydopamine (FA-PDA) nanofibers. X-ray diffraction combined with simulation studies indicate that these oligomers favour aggregation into graphite-like ordered nanostructures via strong π-π interactions. High-resolution TEM characterization of carbonized FA-PDA hybrids show that in FA-PDA nanofibers the size of the graphite-like domains is over 100 nm. The addition of folic acid in polydopamine enhances the ordered stacking of oligomers in its nanostructure. Our study steps forward to discover the mystery of the structure-property relationship of FA-PDA hybrids. It paves a way to optimize the properties of PDA through the design and selection of oligomer structures.