Hydrophilic Chains Research Articles

(Invited) Fullerenes for Bio-Applications: The Way of Water

Nano-materials are emerging as important components for a series of bio-applications. In this context, carbon nanostructures such as graphene, carbon nanotubes and fullerenes have unique chemical and physical properties that make them attractive for such applications. Carbon nanomaterials have been used in tissue engineering, biosensing and drug delivery. They have also shown anti-microbial activity. They can be loaded with drugs for controlled local delivery. More importantly, the surface of carbon nanomaterials can be functionalised to enhance their biocompatibility by increasing their water-solubility.In this talk, I will present an update on our work in using fullerenes and their derivatives for developing bio-nanomaterials. I shall focus on the combination of carbon nanostructures and polymeric materials which can result in supramolecular hydrogels with interesting properties. Hydrogels are emerging as important materials in applications such as cellular scaffoldings in regenerative medicine/tissue engineering, tissue replacements, wound dressings, etc.I will present the synthesis of supramolecular hydrogels made from fullerenes of different sizes (C60, C84 and C90–92) that have been hydroxylated and functionalised with hydrophilic oligoethylene glycol chains. To the best of our knowledge, there have been no attempts made at incorporating higher fullerenes and their derivatives into such extended supramolecular structures, before now.I will also show possibilities for extending our approach to endohedral fullerenes such as N@C60. I will show how we can use advanced techniques including AFM to characterise the elasticity of the hydrogels formed. The ability to incorporate endohedral fullerenes in hydrogels may be important in extending the possibility for using these materials as sensors in vitro or even in vivo, exploiting the quantum properties of such molecular systems such as their extended electron and nuclear spin lifetimes.

Enhancing Impregnability in Reinforced Composite Membrane Using Greener Dispersion

Perfluorosulfonic acid (PFSA) polymer commonly offer high ionic conductivity, chemical and physical properties, and rapid response, making them widely used in energy conversion technologies like fuel cell and water electrolysis. Industrial commercialization of the polymer electrolyte membranes for water electrolysis depends not only on sufficient electrochemical performance but also requires gas barrier properties and high dimensional stability. To improve the properties of these polymer electrolyte membranes selection of an appropriate dispersion solvent and optimization of its composition ratio are very important. However, PFSA polymer limits the types of dispersion solvents due to its unique structure, which consist of combining a hydrophilic perfluorovinyl ether side chain with sulfonate groups onto a hydrophobic tetrafluoroethylene backbone.Here, we have introduced a new greener mixture system for the fabrication of PFSA-reinforced composite membranes for water electrolysis and compared it with conventional solvent systems. Our solvent system not only produced a more densely packed support layer but also relaxed the anisotropy of the reinforced composite membrane. As a result, the compressive strength and tensile strain increased, making it possible to compensate for the shortcomings caused by the support. Also, this increased impregnability resulted in relatively low gas permeability and high ionic conductivity. The water electrolysis performance was comparable with those prepared using an NMP-based solvent. These results demonstrate a method for preparing PFSA dispersions for reinforced composite membrane and their potential to replace hazardous solvents used in fabrication processes.

Antiscaling Pickering Emulsions Enabled by Amphiphilic Hairy Cellulose Nanocrystals.

Nucleation and growth of sparingly soluble salts, referred to as scaling, has posed substantial challenges in industrial processes that deal with multiphase flows, including enhanced oil recovery (EOR). During crude oil extraction/recovery, seawater is injected into oil reservoirs and yields water-in-oil (W/O) emulsions that may undergo calcium carbonate (CaCO3) scaling. Common antiscaling macromolecules and nanoparticles have adverse environmental impacts and/or are limited to functioning only in single-phase aqueous media. Here, we develop a novel antiscaling cellulose-based nanoparticle that enables scale-resistant Pickering emulsions. Cellulose fibrils are rationally nanoengineered to yield amphiphilic hairy cellulose nanocrystals (AmHCNC), bearing hydrophilic dicarboxylate groups and hydrophobic alkyl chains on disordered cellulose chains (hairs) protruding from nanocrystal ends. The unique chemical and structural properties of AmHCNC render them the first dual functional antiscaling and emulsion stabilizing nanoparticle. AmHCNC stabilize W/O Pickering emulsions at a concentration of 1.00 wt % for 1 week while inhibiting CaCO3 scale formation up to 70% by mass at a supersaturation degree of ∼101 compared with the synthetic surfactant Span 80. To the best of our knowledge, this study presents the first biopolymer-based solution for the long-lasting scaling challenge in multiphase media, which may set the stage for developing sustainable scale-resistant multiphase flows in a broad spectrum of industrial sectors.

One-Pot Preparation of Ratiometric Fluorescent Molecularly Imprinted Polymer Nanosensor for Sensitive and Selective Detection of 2,4-Dichlorophenoxyacetic Acid.

The development of fluorescent molecular imprinting sensors for direct, rapid, and sensitive detection of small organic molecules in aqueous systems has always presented a significant challenge in the field of detection. In this study, we successfully prepared a hydrophilic colloidal molecular imprinted polymer (MIP) with 2,4-dichlorophenoxyacetic acid (2,4-D) using a one-pot approach that incorporated polyglycerol methacrylate (PGMMA-TTC), a hydrophilic macromolecular chain transfer agent, to mediate reversible addition-fragmentation chain transfer precipitation polymerization (RAFTPP). To simplify the polymerization process while achieving ratiometric fluorescence detection, red fluorescent CdTe quantum dots (QDs) and green fluorescent nitrobenzodiazole (NBD) were introduced as fluorophores (with NBD serving as an enhancer to the template and QDs being inert). This strategy effectively eliminated background noise and significantly improved detection accuracy. Uniform-sized MIP microspheres with high surface hydrophilicity and incorporated ratiometric fluorescent labels were successfully synthesized. In aqueous systems, the hydrophilic ratio fluorescent MIP exhibited a linear response range from 0 to 25 μM for the template molecule 2,4-D with a detection limit of 0.13 μM. These results demonstrate that the ratiometric fluorescent MIP possesses excellent recognition characteristics and selectivity towards 2,4-D, thus, making it suitable for selective detection of trace amounts of pesticide 2,4-D in aqueous systems.

Symmetry, aggregation and counterion role in tuning NIR absorbance of a Cu(I) coordination complex

A homoleptic Cu(I) coordination complex bearing N^N-bischelating functionalised biquinoline (BQCOOTEG) ligand and weakly coordinating counterions, BF4 or ClO4 respectively, was designed, synthesized and characterized. Hydrophilic tetraethyleneglycol chains functionalizing the ligands help water solubility of these compounds, that show aggregation in water with increasing concentration. Self-assembly behaviour in water was investigated by accurate 1H NMR and UV–Vis-NIR absorption studies, supported by computational studies, highlighting the influence of counterion-metal distance in tuning NIR absorbance of the complex.

Synthesis and Structure Optimization of Star Copolymers as Tunable Macromolecular Carriers for Minimal Immunogen Vaccine Delivery.

Minimal immunogen vaccines are being developed to focus antibody responses against otherwise challenging targets, including human immunodeficiency virus (HIV), but multimerization of the minimal peptide immunogen on a carrier platform is required for activity. Star copolymers comprising multiple hydrophilic polymer chains ("arms") radiating from a central dendrimer unit ("core") were recently reported to be an effective platform for arraying minimal immunogens for inducing antibody responses in mice and primates. However, the impact of different parameters of the star copolymer (e.g., minimal immunogen density and hydrodynamic size) on antibody responses and the optimal synthetic route for controlling those parameters remains to be fully explored. We synthesized a library of star copolymers composed of poly[N-(2-hydroxypropyl)methacrylamide] hydrophilic arms extending from poly(amidoamine) dendrimer cores with the aim of identifying the optimal composition for use as minimal immunogen vaccines. Our results show that the length of the polymer arms has a crucial impact on the star copolymer hydrodynamic size and is precisely tunable over a range of 20-50 nm diameter, while the dendrimer generation affects the maximum number of arms (and therefore minimal immunogens) that can be attached to the surface of the dendrimer. In addition, high-resolution images of selected star copolymer taken by a custom-modified environmental scanning electron microscope enabled the acquisition of high-resolution images, providing new insights into the star copolymer structure. Finally, in vivo studies assessing a star copolymer vaccine comprising an HIV minimal immunogen showed the criticality of polymer arm length in promoting antibody responses and highlighting the importance of composition tunability to yield the desired biological effect.

Polypeptoid Monomer Sequence and Chemical Composition as Independent Controls of Interfacial Tension and Elasticity at Air/Fluid Interfaces.

We use sequence-specific polypeptoids to characterize the impact of the monomer sequence on the adsorption of surface-active polymers at fluid/fluid interfaces. Sets of 36 repeat unit polypeptoids with identical chemical composition, but different sequences of hydrophobic moieties along the oligomer chain (taper, inverse taper, blocky, and evenly distributed), are designed and characterized at air/water interfaces. Polypeptoids are driven to the interfaces by decreasing the solvent quality of the aqueous solution. In situ processing of the adsorbed layers causes a collapse of polypeptoids and the formation of irreversibly adsorbed, solvent-avoiding layers at interfaces. Differences in thermodynamic properties, driven by solubility, between the collapsed structures at interfaces are studied with measurements of interfacial tension. The dilatational modulus of polypeptoid-coated interfaces is used as a proxy to probe the extent of the coil-globule collapse at the interface. The role of hydrophobicity is investigated by comparing four sequences of polypeptoids with an increased size of the hydrophilic side chains. In each set of polypeptoids, the composition of molecules, not the sequence, controls the surface concentration. The molecules are described in terms of the distribution of the hydrophobic monomers on the backbone of the polymer. Inverse taper (IT) and blocky (B) sequences of hydrophobic moieties favor the formation of highly elastic interfaces after processing, while taper (T) and distributed (D) showed lower elasticity after processing, which is achieved by replacing good solvent with poor solvent and then nonsolvent. These structures allow for the study of the impact of the chemical composition and sequence of monomers on the properties of polymer-coated interfaces.

Unveiling the transformation of organics in leachate during the composite anode-supported electro-hybrid ozonation-coagulation (CA-E-HOC) treatment: Significance of synergy among chlorine, coagulant, and ozone

Ozone and its advanced oxidation processes are commonly used to remove organics from leachate because of their high efficiency in eliminating toxic and resistant compounds. However, the mechanisms underlying the transformations of these organic compounds remain unclear. This study aimed to investigate the organic transformation during the composite anode (CA)-supported electro-hybrid ozonation-coagulation (CA-E-HOC) treatment of leachate, where chlorine and coagulants were coproduced on CA for ozone activation, to gain a deeper understanding of the synergistic effects when chlorine, coagulant, and ozone are simultaneously present within a single unit for leachate treatment. Reactive oxygen species and reactive chlorine species in the CA-E-HOC facilitated the degradation of unsaturated and aromatic compounds into hydrophilic organic chains or mineralisation to CO2/H2O. The aromatic carbon (C=C) and long-chain aliphatic carbon (C-C) are converted to carbonyl carbon (O-C=O), which is easily degraded by microorganisms during the subsequent treatment process. The reactive chlorine species and ozone molecules transform CHOS into CHO through −S and −SH2, whereas •OH converts CHNOS into CHNO. The enriched CHO substances were further converted into saturated fatty acids and carbohydrates through oxidation reactions (+O), making them more susceptible to conversion into CO2 and H2O by interacting with •OH and Cl•/ClO•, ultimately resulting in organic mineralisation. This study contributes to a better understanding of molecular changes in organics during leachate treatment using the CA-E-HOC process, with potential implications for practical applications.

High Antifouling Performance of Weakly Hydrophilic Polymer Brushes: A Molecular Dynamics Study.

The antifouling performance of polymer brushes usually improves with increasing hydrophilicity of the grafted polymer. However, in some cases, less hydrophilic polymers show comparable or better antifouling performance than do more hydrophilic polymers. We investigate the mechanism of this anomalous behavior using molecular dynamics (MD) simulations of coarse-grained (CG) models of weakly and strongly hydrophilic polymers. The antifouling performance is evaluated from the potential of mean force of a model protein. The strongly hydrophilic polymer exhibits a better antifouling performance than the weakly hydrophilic polymer when the substrate of the polymer brush is repulsive. However, when the substrate is sufficiently attractive, the weakly hydrophilic polymer brush becomes more effective than the strongly hydrophilic brush in a certain range of grafting density. This is because the weakly hydrophilic polymer chains form a tightly packed layer that prevents the adsorbate molecule from contacting the substrate. We also perform all-atom (AA) MD simulations for several standard polymers to examine the correspondence with the CG polymer models. The weakly hydrophilic CG polymer is found to be similar to poly[N-(2-hydroxypropyl)methacrylamide] and poly(2-hydroxyethyl methacrylate), both of which have a hydroxyl group in a monomer unit. The strongly hydrophilic CG polymer resembles zwitterionic poly(carboxybetaine methacrylate). A discussion referring to the adsorption free energies of proteins on surfaces calculated in previous AA MD studies suggests that the higher antifouling performance of less hydrophilic polymer brushes can be realized for various combinations of protein and surface.

Salt-Screened Transition toward Bulk-Like Water Dynamics near Polymeric Zwitterions.

The superior antifouling performance of zwitterionic materials is commonly linked to their hydration structure, in which tight surface binding of water molecules inhibits solute adsorption. However, there is comparatively little direct experimental data on the hydration water structure and dynamics around zwitterionic moieties, including the longer-range behavior of the hydration shell that modulates the approach of solutes to the polymer surface. This work experimentally probes the dynamics of the diffusing hydration water molecules around a series of zwitterion chemistries using Overhauser dynamic nuclear polarization relaxometry. Surprisingly, water dynamics measured within ∼1 nm of the zwitterions were minimally inhibited compared to those near uncharged hydrophilic or cationic side chains. Specific dissolved ions further enhance the water diffusivity near the zwitterions, rendering the hydration shell bulk water-like. These results that the hydration of a zwitterion surface is nearly indistinguishable from bulk water suggest that these surfaces are "invisible" to biological constituents in a manner tunable by the ionic environment and the chemical design of the zwitterionic surface.

Engineering shrinkage resistance of nano-structured hydrogels in seawater for fast uranium capture

Synthetic hydrogels, which are 3D networks composed of crosslinked hydrophilic polymer chains, have been created using various crosslinked ways for uranium capture due to full exposure of chelate functional groups. However, the conventional honeycomb-like hydrogels exhibit non-connected micropore structure, which locks abundant water molecules and hence is unfavorable for mass transfer. Herein, we demonstrate a simple synthesis of the nano-structured hydrogel with activated nanogels as nano-crosslinkers (denoted as PGP hydrogel), and probe into the relationship between hydrogel structural parameters and uranium adsorption kinetics. It is found that the PGP hydrogel with a low crosslinking density of ∼0.02 mol/m3 possesses interconnected micropores, thereby facilitating diffusion of uranyl ions (UO22+) in 3D polymeric networks. Furthermore, a freeze-assisted soaking strategy is proposed to endow PGP hydrogel (denoted as target hydrogel) with strong shrinkage resistance in natural seawater, resulting in a ∼40 % increase in water permeance to reach 369 Lm−2h−1MPa−1. Correspondingly, the adsorption equilibrium time is shortened to ∼11 days. Although the uranium uptake capacity of PGP hydrogels with and without freeze-assisted soaking treatment remain basically unchanged (∼9.73 mg-U/g-Ads), a high uranium adsorption rate of 0.88 mg/g/d for the target hydrogel surpasses most currently available polymer adsorbents. The presented strategy is generalizable to a broader range of applications involving the adsorption of economically valuable ions in seawater or brine lake.

Pyrobacteriopheophorbide-a derivatives possessing various hydrophilic esterifying groups at the C17-propionate residues for photodynamic therapy.

Aiming at the application to photodynamic therapy, natural bacteriochlorophyll-a was converted to chemically stable free-base derivatives possessing different kinds of hydrophilic C17-propionate residues. These semi-synthetic bacteriochlorins were found to have self-assembling ability in an aqueous environment and formed stable J-type aggregates in a cell culture medium containing 0.2% DMSO. The electronic absorption spectra of all the sensitizers showed Qy absorption maxima at 754 nm in DMSO as their monomeric states, while a drastic shift of the red-most bands to ca. 880 nm was observed in the aqueous medium. The circular dichroism spectra in the medium showed much intense signals compared to those measured in DMSO, supporting the formation of well-ordered supramolecular structures. By introducing hydrophilic side chains, the bacteriochlorin sensitizers could be dispersed in the aqueous medium as their J-aggregates without the use of any surfactants. Cellular uptake efficiencies as well as photodynamic activities were evaluated using human cervical adenocarcinoma HeLa cells. Among the 11 photosensitizers investigated, the best result was obtained for a charged derivative possessing trimethylammonium terminal (17-CH2CH2COOCH2CH2N+(CH3)3I-) and photocytotoxicity of EC50 = 0.09 μM was achieved by far-red light illumination of 35 J/cm2 from an LED panel (730 nm).

Study of Interfacial Properties of Anionic–Nonionic Surfactants Based on Succinic Acid Derivatives via Molecular Dynamics Simulations and the IGMH Method

Surfactants are widely used in fields such as oil recovery and flotation. The properties and mechanisms of surfactants can be effectively studied using molecular dynamics (MD) simulations. Herein, the aggregation behavior of surfactants was studied at the oil–water interface by MD simulation, and the micro-morphology of surfactants was analyzed under a low concentration and saturated state at the oil–water interface, respectively. The visualization results of the MD simulation showed that DTOA was saturated at the oil–water interface at 120 surfactant molecules, whereas 160 surfactant molecules were required for BEMA. In addition, the effect of surfactant concentration on the interfacial thickness and hydrogen bond distribution was studied, with the inflection point of hydrogen bond distribution identified as a characteristic parameter for surfactant saturation at the oil–water interface. The aggregation behavior of their hydrophobic and hydrophilic chains at the oil–water interface was qualitatively assessed using order parameters. Finally, the aggregation state of surfactants in salt-containing systems was studied, and it was found that the surfactants could effectively adsorb magnesium ions and calcium ions at the oil–water interface. However, the curve of the number of hydrogen bonds varies greatly, with a possible reason being that BEMA has a different coordination manner with diverse metal ions. This study provides some original insights into both the theoretical study and practical application of anionic and nonionic surfactants.

Conductive NR/PMMA-RAFT-CNT-rGO composites and their morphological, mechanical, and electrical properties

This study reports the synthesis of poly(methyl methacrylate) (PMMA)-carbon nanotube (CNT)-reduced graphene oxide (rGO) emulsions via reversible addition-fragmentation chain-transfer (RAFT)-mediated surfactant-free emulsion polymerization using a hydrophilic chain transfer agent. The rGO was prepared by the modified Hummers method and reduced with L-ascorbic acid. The effects of the CNT:rGO ratios and CNT and rGO contents on the conversion and stability of emulsion were investigated. Increasing the CNT and rGO contents from 1 to 4 wt% decreased the monomer conversion, while all the samples remained as colloidal dispersions. The morphology of PMMA-CNT-rGO composites showed the incorporated arrangement of a linear CNT portion connected with the rGO sheet dependent on the CNT:rGO ratio. Various PMMA-CNT-rGO filled natural rubber (NR) cast films were prepared. The NR/PMMA-CNT-rGO composite film with a 1 wt% filler loading at a CNT:rGO ratio of 1:1 presented a quite high modulus value (3.08 MPa) and sufficient intrinsic electrical conductivity (1.36 S/m) due to its strong filler-matrix interaction. Thus, the PMMA-RAFT-CNT-rGO composites at a very low filler content can be used as an effective reinforcement to enhance the mechanical and electrical properties of NR films with a high compatibility between the fillers and NR matrix.

Preparation of mussel-inspired adhesion nanocapsules and their application on cotton fabrics

In this study, a hyperbranched polymer (HBP) with a hydrophobic backbone and hydrophilic adhesive catechol side chains was synthesized through the Michael addition reaction between multi-vinyl monomers with dopamine. Underwater adhesion experiments demonstrated that HBP had rapidly strong adhesion. Using HBP as the wall material and lavender essential oil (LO) as the core material, catechol-hyperbranched nanocapsules (CHNPs) with good adhesion and acidic responsive properties were prepared by solvent evaporation method. Subsequently, ACFs with good wash resistance were prepared by impregnation and further introduction of Fe3+. After 25 washing cycles, the retention rate of LO in CF treated solely with CHNPs solution (CHNPs@CF) was only 9.7 %, whereas the retention rate increased to 17.8 % for CHNPs@CF treated with FeCl3 solution (Fe3+/CHNPs@CF). The persistent adhesion of CHNPs on cotton fabrics (CF) is achieved by hydrogen bonding and Fe3+-catechol coordination bonding. These results confirm the significant potential of CHNPs in aromatic textile applications and it is expected to promote the diversified development of functional textiles.

High conductivity and dimensional stability brominated poly (aryl piperidinium) anion exchange membranes: Synergistic interaction of hydrophilic and superhydrophobic fluorinated side chains

Anion-exchange membrane fuel cells (AEMFCs) is a promising renewable energy device for hydrogen production. Anion exchange membranes (AEMs), the key component of AEMFCs, is generally needed for excellent dimensional stability and conductivity. Here, we synthesised a variety of AEMs with different number of C–F bonds to enhance the hydrophilic/hydrophobic micro-phase separation structure while maintaining dimensional stability. At 80 °C, the QPBTTP-PEG-10-F9 shows high OH− conductivity (∼179.02 mS cm−1), excellent dimensional stability (swelling ratio <19 %), and mechanical properties (elongation at break: 37 %, tensile strength: 71 MPa). In addition, QPBTTP-PEG-10-F9 shows good alkaline stability (conductivity remaining of 92.52 %) in 3 M NaOH solution for 1800 h. The peak power density (PPD) of a single cell assembled with QPBTTP-PEG-10-F9 can reach 534.79 mW cm−2 with a current density of 951 mA cm−2.

Quantitative Comparison of the Hydration Capacity of Surface-Bound Dextran and Polyethylene Glycol.

We have quantified and compared the hydration capacity (i.e., capability to incorporate water molecules) of the two surface-bound hydrophilic polymer chains, dextran (dex) and poly(ethylene glycol) (PEG), in the form of poly(l-lysine)-graft-dextran (PLL-g-dex) and poly(l-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG), respectively. The copolymers were attached to a negatively charged silica-titania surface through the electrostatic interaction between the PLL backbone and the surface in neutral aqueous media. While the molecular weights of PLL and PEG were fixed, that of dex and the grafting density of PEG or dex on the PLL were varied. The hydration capacity of the polymer chains was quantified through the combined experimental approach of optical waveguide lightmode spectroscopy (OWLS) and quartz crystal microbalance with dissipation monitoring (QCM-D) to yield a value for areal solvation (Ψ), i.e., mass of associated solvent molecules within the polymer chains per unit substrate area. For the two series of copolymers with comparable stretched chain lengths of hydrophilic polymers, namely, PLL(20)-g-PEG(5) and PLL(20)-g-dex(10), the Ψ values gradually increased as the initial grafting density on the PLL backbone increased or as g decreased. However, the rate of increase in Ψ was higher for PEG than dextran chains, which was attributed to higher stiffness of the dextran chains. More importantly, the number of water molecules per hydrophilic group was clearly higher for PEG chains. Given that the -CH2CH2O- units that make up the PEG chains form a cage-like structure with 2-3 water molecules, these "strongly bound" water molecules can account for the slightly more favorable behavior of PEG compared to dextran in both aqueous lubrication and antifouling behavior of the copolymers.

Chitosan-Type-A-Gelatin Hydrogels Used as Potential Platforms in Tissue Engineering for Drug Delivery.

Hydrogels are materials made of crosslinked 3D networks of hydrophilic polymer chains that can absorb and retain significant amounts of water due to their hydrophilic structure without being dissolved. In relation to alternative biomaterials, hydrogels offer increased biocompatibility and biodegradability, giving them distinct advantages. Thus, hydrogel platforms are considered to have the potential for the development of biomedical applications. In this study, the main objective was the development of hybrid hydrogels to act as a drug delivery platform. These hydrogels were made from chitosan (CH) and type A gelatin (G), two natural polymers that provide a supportive environment for cellular attachment, viability, and growth, thanks to their unique properties. Particularly, the use of gelatins for drug delivery systems provides biodegradability, biocompatibility, and non-toxicity, which are excellent properties to be used in the human body. However, gelatins have some limitations, such as thermal instability and poor mechanical properties. In order to improve those properties, the aim of this work was the development and characterization of hybrid hydrogels with different ratios of CH-G (100-0, 75-25, 50-50, 25-75, 0-100). Hydrogels were characterized through multiple techniques, including Fourier transform infrared (FTIR) spectroscopy, rheological and microstructural studies, among others. Moreover, a model hydrophilic drug molecule (tetracycline) was incorporated to evaluate the feasibility of this platform to sustain the release of hydrophilic drugs, by being tested in a solution of Phosphate Buffer Solution at a pH of 7.2 and at 37 °C. The results revealed that the synergy between chitosan and type A gelatin improved the mechanical properties as well as the thermal stability of it, revealing that the best ratios of the biopolymers are 50-50 CH-G and 75-25 CH-G. Thereby, these systems were evaluated in a controlled release of tetracycline, showing a controlled drug delivery of 6 h and highlighting their promising application as a platform for controlled drug release.

Tailored Metal-Porphyrin Based Molecular Electrocatalysts for Enhanced Artificial Nitrogen Fixation to Green Ammonia.

Electrochemical nitrogen reduction (E-NRR) is one of the most promising approaches to generate green NH3. However, scarce ammonia yields and Faradaic efficiencies (FE) still limit their use on a large scale. Thus, efforts are focusing on different E-NRR catalyst structures and formulations. Among present strategies, molecular electrocatalysts such as metal-porphyrins emerge as an encouraging option due to their planar structures which favor the interaction involving the metal center, responsible for adsorption and activation of nitrogen. Nevertheless, the high hydrophobicity of porphyrins limits the aqueous electrolyte-catalyst interaction lowering yields. This work introduces a new class of metal-porphyrin based catalysts, bearing hydrophilic tris(ethyleneglycol) monomethyl ether chains (metal = Cu(II) and CoII)). Experimental results show that the presence of hydrophilic chains significantly increases ammonia yields and FE, supporting the relevance of fruitful catalyst-electrolyte interactions. This study also investigates the use of hydrophobic branched alkyl chains for comparison, resulting in similar performances with respect to the unsubstituted metal-porphyrin, taken as a reference, further confirming that the appropriate design of electrocatalysts carrying peripheral hydrophilic substituents is able to improve device performances in the generation of green ammonia.

Surface Reconstruction of Silicone-Based Amphiphilic Polymers for Mitigating Marine Biofouling.

Poly(dimethylsiloxane) (PDMS) coatings are considered to be environmentally friendly antifouling coatings. However, the presence of hydrophobic surfaces can enhance the adhesion rate of proteins, bacteria and microalgae, posing a challenge for biofouling removal. In this study, hydrophilic polymer chains were synthesised from methyl methacrylate (MMA), Poly(ethylene glycol) methyl ether methacrylate (PEG-MA) and 3-(trimethoxysilyl) propyl methacrylate (TPMA). The crosslinking reaction between TPMA and PDMS results in the formation of a silicone-based amphiphilic co-network with surface reconstruction properties. The hydrophilic and hydrophobic domains are covalently bonded by condensation reactions, while the hydrophilic polymers migrate under water to induce surface reconstruction and form hydrogen bonds with water molecules to form a dense hydrated layer. This design effectively mitigates the adhesion of proteins, bacteria, algae and other marine organisms to the coating. The antifouling performance of the coatings was evaluated by assessing their adhesion rates to proteins (BSA-FITC), bacteria (B. subtilis and P. ruthenica) and algae (P. tricornutum). The results show that the amphiphilic co-network coating (e.g., P-AM-15) exhibits excellent antifouling properties against protein, bacterial and microalgal fouling. Furthermore, an overall assessment of its antifouling performance and stability was conducted in the East China Sea from 16 May to 12 September 2023, which showed that this silicon-based amphiphilic co-network coating remained intact with almost no marine organisms adhering to it. This study provides a novel approach for the development of high-performance silicone-based antifouling coatings.