Whether an extra, subtle high-free-volume interphase in glassy polymers containing spherical nanoparticles really exists remains an open question, posing fundamental challenges for accurately predicting and intentionally tailoring the macroscopic transport behavior of these nanocomposites, which is crucial for a broad spectrum of industrial applications. Herein, we report new evidence supporting this controversial interphase by computational simulation and offer a generic framework for understanding how the interphase is shaped, based on a comparative strategy. This framework, validated by our previous experimental data, may provide guidance for rationally designing interfacial architectures in these nanocomposites that enable bottom-up tuning of their transport properties for specific applications.

Potential ecological risks of chromium(III) contaminates in tannery effluents have evoked considerable discussion and re-examination over the future role of chrome tannage, which has been long considered as the foundation of the modern leather industry. Despite previous magnetite-supported adsorbents for chromium removal, few of them were specifically engineered to address trivalent chromium, as well as the composition complexity in tannery effluents. Herein, gallic acid, a natural triphenolic compound capable of coordination to chromium(III), was covalently conjugated onto engineered magnetite nanoparticles via 1-ethyl-3-(3-dimethylaminepropyl) carbodiimide hydrochloride/N-hydroxysuccinimide (EDC/NHS) chemistry, in an effort to design a magnetically separable nanoadsorbent applicable for remediating chromium(III)-contaminated tannery effluents. The structure of the nanoadsorbent was systematically characterized by multiple techniques, and the influence of pH value, adsorbent dose, temperature, and leather-related co-existing substances on its chromium(III) removal potency was investigated, respectively. Also, kinetics, equilibrium, and thermodynamics studies were conducted to decipher the mechanism by which chromium(III) cations were adsorbed. Finally, the feasibility of treating real tannery effluents that also contained high concentrations of sulfides, chlorides, ammonium nitrogen, total suspended solids, chemical oxygen demand (CODCr), and biochemical oxygen demand (BOD) by using the nanoadsorbent designed herein was explored. It was found that the chromium(III) removal percentage was approximately 95.2 ± 1.6%, and the exhausted nanoadsorbent could be conveniently separated from the effluents via a simple magnetic process. By chemical desorption, the nanoadsorbent was regenerable, and reusable for multiple cycles without a significantly compromised adsorption potency. According to these results, we aim at providing an efficient solution that may be a great addition to the ongoing fight against chromium(III) contamination in tannery effluents.

Toxic Pb(II) contaminants in water pose a significant threat to the environment and public health, and thus technologies for Pb(II) remediation are attracting increasing industrial interests. In the present work, polyacrylic acid, offering abundant carboxyl groups capable of coordination with Pb(II) cations, was grafted from the magnetite nanoparticle surface via the bridging function of silane coupling agent for remediation of Pb(II)-contained water. Multiple techniques were employed to characterize the structure of the nanocomposite, and the effects of nanoadsorbent dose, pH value, and temperature on Pb(II) removal capability of the nanocomposite were investigated, respectively. Furthermore, adsorption kinetics and isotherms studies were performed for better understanding the mechanism by which Pb(II) cations were adsorbed. Finally, the feasibility of regenerating the exhausted nanoadsorbent by simply changing pH value was explored. According to these results, we intend to offer an efficient, separable, and reusable magnetic nanoadsorbent that may be a potential candidate for remediating Pb(II) contamination in water.

Widespread concern over antimicrobial toxicity and resistance development necessitates the thorough recovery of antimicrobial compounds from decontaminated collagen. Herein, ciprofloxacin molecules were acryloylated by reaction of the secondary amine in 7-piperazinyl substituent with acryloyl chloride, and then covalently immobilized, for the first time, on the vinyl-functionalized Fe3O4 nanoparticle surface via graft copolymerization with acrylic acid, in an effort to design a magnetically-recoverable nanocomposite potentially applicable for microbial decontamination of collagen solution. Unlike previous magnetite-supported antimicrobials invariably involving the release of antimicrobially-active component, these immobilized ciprofloxacin moieties proved non-leachable, in whole or in part, from the magnetite core, exerting antimicrobial activity as free ciprofloxacin, and thus could be thoroughly recovered from decontaminated collagen solution under magnetic fields. Also, it was found that the unique triple-helical conformation and, hence, bioactive properties of tropocollagens remained intact after decontamination using such recoverable antimicrobials. This proof-of-principle study aims to shed light on a long-standing dilemma in the collagen community: how to decontaminate collagen using antimicrobial compounds without being subject to antimicrobial residues?

Microbial deterioration of polyurethane (PU) leather coating continues to represent a significant challenge in maintaining the durability and hygiene of leather products. In the present study, model biocide sulfanilamide (SA) was covalently conjugated into PU backbone as chain extender, yielding a novel PU with enzymatically-switchable antimicrobial capability as leather-finishing material. The anticipated structure of the conjugate was evidenced by ultraviolet spectroscopy, high-performance liquid chromatography, Fourier transform infrared spectroscopy, 1H nuclear magnetic resonance spectroscopy and differential scanning calorimetry, respectively. In the presence of urease, a representative hydrolase derived from one microbial species prevalent on leather coating, such SA-conjugated PU coating was found to release free SA by urease-catalyzed cleavage of urea linkages. These regenerated SA molecules still exhibited bacteriostatic efficiency as pristine ones, against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Micrococcus luteus. When incubated without urease however, the coating displayed such substantially high resistance against hydrolysis that it maintained structural integrity throughout the incubation period. Furthermore, cell culture assay revealed that the SA-conjugated PU coating supported attachment and proliferation of normal human dermal fibroblasts, indicating a dermis-friendly feature. According to these results, the enzymatically-responsive PU designed in this study has great potential as an ideal leather-finishing material, which is capable of providing efficient protection against microbial deterioration while minimizing undesirable side effects associated with biocide abuse.Highlights► Sulfanilamide (SA) was conjugated into polyurethane for antimicrobial coating. ► In response to urease, the coating released SA that remained antimicrobial. ► The coating was dermis-friendly as functional leather-finishing material.

By combining solvent evaporation with wet phase inversion technique, an asymmetric polyurethane membrane (ASPU) was constructed from a sulfanilamide-conjugated PU, as a potential candidate for wound dressing application. As a result of the combined membrane-formation method, the ASPU membrane was constituted by an integral and dense skin layer supported by a porous sublayer. The skin layer was found impermeable to pathogenic organisms, while the sublayer was intended for draining excessive exudates. Compared with typical PU membrane dressings commercially available, the ASPU membrane exhibited a reasonable moisture vapor transmission rate, as well as significantly improved gas circulation and exudate absorption capabilities, which synergistically optimized the wound microenvironment for proper healing. Furthermore, the sulfanilamide-conjugated PU constituting ASPU membrane was designed as susceptible to urease, a representative hydrolase derived from inflammation-causing pathogens. In the presence of urease, urea linkages adjacent to sulfanilamide monomeric units were found catalytically cleaved, enabling release of free antibiotic sulfanilamide that held pharmacological activity from ASPU membrane. When incubated without urease, those cleavage sites exhibited substantially high resistance against hydrolysis so that no sulfanilamide release was detected throughout the incubation period. In this inflammation-responsive manner, the anti-inflammatory efficiency of antibiotics was significantly enhanced, while undesirable side effects associated with antibiotic abuse was minimized. Cell culture assay further revealed that the ASPU membrane displayed no cytotoxicity toward normal human dermis fibroblasts, suggesting a biocompatible potential. Based on these results, the multifunctional ASPU membrane designed in this study might be clinically suitable as an ideal biomedical dressing for wound care.