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Osteoarthritis is a prevalent degenerative joint disease characterized by progressive articular cartilage loss and destruction. The resultant increase in friction causes severe pain. The collagen I matrix (COL I) has been used clinically for cartilage repair; however, how COL I acts at cartilage surfaces is unclear. Here, we studied adsorption and lubrication of synovial fluid components, albumin, γ-globulin, and the phospholipid DPPC, on COL I under physiological conditions using surface plasmon resonance and an in situ sensing surface force apparatus. Our results revealed COL I had poor lubrication ability, a fairly high coefficient of friction (COF, μ = 0.651 ± 0.013), and surface damage under a 7 mN load. DPPC formed an improved lubricating layer on COL I (μ = 0.072 ± 0.016). In sharp contrast, albumin and γ-globulin exhibited poor lubrication with an order of magnitude higher COF but still provided benefits by protecting COL I from wear. Hence, DPPC on COL I may help optimize COL I implantation design.

Chloroform is an harmful chlorinated hydrocarbon which is hardly degraded using actual dechlorination methods. Alternatively, carboxymethyl cellulose/zero-valent iron appears promising to degrade chlorinated hydrocarbons in water, yet actually carboxymethyl cellulose cannot inhibit the oxidation and sedimentation of iron ions under alkaline condition. Here, polyethylene glycol, a green and low-cost non-ionic polymer, was used as a stabilizer to synthesize polyethylene glycol-stabilized Fe/Ni nanoparticles (PEG-Fe/Ni) for removing chloroform from water in a wide range of pH, from 3 to 11. PEG-Fe/Ni was prepared by a stepwise liquid-phase chemical reduction, then added into groundwater to remove chloroform. Results show that polyethylene glycol can both reduce the particle size from 106.9 to 79.6 nm and prevent the oxidation and sedimentation of iron ions under alkaline condition. The removal efficiency of chloroform increased from 86.3 to 100% at pH 6 in the presence of polyethylene glycol, and slightly decreased to 95.4% at pH 11. The calculated rate constant (k) indicates that chloroform removal follows pseudo-first-order kinetics. Furthermore, the PEG-Fe/Ni also removed chloroform from real groundwater at pH 8 with an efficiency of 90.1% in 4 h, which is higher than that for Fe/Ni nanoparticles, of 41.7%.

The treatment of multicontaminant wastewater has attracted extensive attention in recent years. Herein, we synthesized a porous and hydrophobic composite (Zr-MOF-SH/MF) via the in situ growth of mercapto-functionalized Zr-metal–organic frameworks (MOFs) (Zr-MOF-SH) on the surface of a melamine formaldehyde (MF) sponge. The successful growth of hydrophobic Zr-MOF-SH, as confirmed by SEM, XRD, and XPS analysis, made the MF sponge become hydrophobic with a water contact angle of 125°. The adsorption capacity of the Zr-MOF-SH/MF composite for dichloromethane can reach up to 113 g/g. Moreover, the composite can efficiently and selectively remove Hg2+ ions from water. Especially, PCN-224-MAA/MF had an adsorption capacity of 412.5 mg/g for Hg2+ ions. The removal efficiency of Hg2+ ions increased as the oil content in the oil–water mixture increased. In addition, PCN-224-MAA/MF can be recovered and reused five times with only a slight decrease in adsorption capacity. This study provides a promising strategy for the synthesis of a dual-functional composite that exhibits excellent performance in removing oil and heavy metal ions simultaneously from water.

Pollution of waters by chlorinated organic pollutants is difficult to clean using actual remediation methods because these pollutants are highly stable. For instance, chloroform (CHCl3) is poorly reactive with common oxidants such as iron-activated persulfate, ozone and Fenton’s reagents. Therefore, there is a need to develop new oxidants. Here, we designed a new dechlorination system, in which tannic acid and NaOH work synergistically to activate persulfate. We tested the effect of temperature and concentrations of persulfate, NaOH and tannic acid, on chloroform removal from water. Free radical-quenching experiments were performed to identify active species. Results show that chloroform removal increased from 42.5 to 97.6 wt.% after the addition of 300 mg/L tannic acid in 0.4 M NaOH. Superoxide radicals (O 2 ·− ) was primarily responsible for the degradation of chloroform in the persulfate/NaOH/tannic acid system, in which tannic acid reacts with persulfate to produce hydroperoxide. Hydroperoxide then reduces persulfate to generate sulfate radicals (SO4·−), and produces O 2 ·− . NaOH-activated persulfate produces hydroxyl radicals (HO·), which can oxidize chloroform. This dechlorination system showed excellent degradation efficiency for recalcitrant halogenated compounds, making it a very promising candidate for practical applications.

Expansin has nonhydrolytic disruptive activity and synergistically acts with cellulases to enhance the hydrolysis of cellulose. The adsorption-desorption of expansin on noncellulosic lignin can greatly affect the action of expansin on lignocellulose. In this study, three lignins with different sources (kraft lignin (KL), sodium lignin sulfonate (SLS), and enzymatic hydrolysis lignin (EHL)) were selected as the substrates. The real-time adsorption-desorption of Bacillus subtilis expansin (BsEXLX1) on lignins was monitored using quartz crystal microgravimetry with dissipation (QCM-D). The effects of temperature and Tween 80 on the adsorption-desorption behaviors were also investigated. The results show that BsEXLX1 exhibited high binding ability on lignin and achieved maximum adsorption of 283.2, 273.8, and 266.9 ng cm-2 at 25 °C on KL, SLS, and EHL, respectively. The maximum adsorption decreased to 148.2-192.8 ng cm-2 when the temperature increased from 25 to 45 °C. Moreover, Tween 80 competitively bound to lignin and significantly prevented expansin adsorption. After irreversible adsorption of Tween 80, the maximum adsorption of BsEXLX1 greatly decreased to 33.3, 37.2, and 10.3 ng cm-2 at 25 °C on KL, SLS, and EHL, respectively. Finally, a kinetic model was developed to analyze the adsorption-desorption process of BsEXLX1. BsEXLX1 has a higher adsorption rate constant (kA) and a lower desorption rate constant (kD) on KL than on SLS and EHL. The findings of this study provide useful insights into the adsorption-desorption of expansin on lignin.

A convenient and efficient approach for the surface modification of antifouling materials is highly desirable in numerous applications like affinity-based biosensors. Herein, we fabricated a hybrid antifouling coating on Au surfaces, with thiolated hyaluronic acid (HA) being chemically adsorbed to Au surfaces by the "graft to" approach, followed by a self-assembly of a smaller zwitterionic peptide named p-EK to obtain HA/p-EK-modified surfaces. The real-time sensorgrams of surface plasmon resonance biosensor manifested the successful modification of HA and p-EK on Au surfaces, indicating that there were some bare Au substrates on the HA-modified surfaces for peptide binding. The obtained HA/p-EK surfaces exhibited high hydrophilicity with a water contact angle of 9°. Quartz crystal microbalance and surface plasmon resonance experiments verified that further grafting the zwitterionic p-EK peptide on HA-modified surfaces could enhance the antifouling performance by one time. The improved protein resistance could be mainly contributed by the modification of the zwitterionic peptide that shields the exposed Au substrates from interacting with protein foulings. This strategy by grafting a smaller zwitterionic peptide might provide a novel way to achieve an enhanced protein-resistant performance of the macromolecular coating obtained by the "graft to" surface modification approach.

Biological pretreatment is a safe and environmentally friendly method for disrupting recalcitrant lignocellulose structures. Expansin and expansin-like proteins are used to open up the cellulose structure and display significant synergism when mixed with cellulases that catalyze the breakdown of (hemi)cellulose into sugars. However, the adsorption behavior of expansin in the presence of sugar products is yet unknown. In this work, we monitored the effects of various sugars on the real-time adsorption of Bacillus subtilis expansin (BsEXLX1) onto cellulose films using a quartz crystal microbalance with dissipation. Cellobiose and xylose at low concentrations enhanced BsEXLX1 adsorption, whereas they disrupted adsorption at higher concentrations. Arabinose and mannose continuously inhibited expansin adsorption with increasing concentration. No obvious influence of glucose and galactose on BsEXLX1 adsorption was found. Contact angle measurements and atomic force microscopy of cellulose upon BsEXLX1 adsorption in the presence of sugars showed that both hydrophilicity and roughness increased with BsEXLX1 treatment. These results give us the ability to modulate and control expansin adsorption and provide insights into effective expansin use during enzymatic hydrolysis of lignocellulose in biorefineries.

A superhydrophobic and superoleophilic porous composite was successfully prepared via a polydopamine-assisted surface coating of MIL-53(Fe) and 1-dodecanethiol (DDT) on a melamine formaldehyde (MF) sponge. The as-prepared sponge composite (MIL-DDT@MF) has a high water contact angle (WCA) of 151.8°, which is probably attributed to both the rough surface derived from in situ growth of MIL-53 nanocrystals and the low surface energy due to grafting of hydrophobic 1-dodecanethiol. The MIL-DDT@MF sponge can effectively absorb oil or organic solvent with an absorption capacity of up to 54.1 (for petroleum) to 120.2 (for chloroform) times its own weight. In addition, the MIL-DDT@MF sponge retained a high absorption capacity and maintained approximately 78% of its original value after 50 cycles of reuse. Moreover, the MIL-DDT@MF sponge can selectively absorb the oil/organic solvent from water and achieve continuous oil-water separation. The separation efficiency of n-hexane, dichloromethane, and crude oil from water or seawater can reach above 95%. The superhydrophobic and superoleophilic MIL-DDT@MF sponge has potential as a promising absorbent for treatment of oily wastewater.

Nanozymes, defined as nanomaterials with enzyme-like activity, have attracted extensive interest in both fundamental and applied research. Laccases are members of the multi-copper oxidases, which are utilized as green catalysts in the environmental catalysis and biochemical industry. In this paper, we report a facile strategy for the preparation of a new class of nanozyme (denoted as CH-Cu) with laccase-like activity inspired by the structure of the active site and the electron transfer pathway of laccase via the coordination of Cu+/Cu2+ with a cysteine (Cys)-histidine (His) dipeptide. The CH-Cu nanozymes exhibit excellent catalytic activity, recyclability and substrate universality and have a similar Km (Michaelis constant) and a higher vmax (maximum rate) than laccase at the same mass concentration. They are robust under a variety of conditions, such as extreme pH, high temperature, long-term storage and high salinity, which can cause severe loss in the catalytic activity of laccase. Higher efficacy of the CH-Cu nanozymes compared with laccase in the degradation of chlorophenols and bisphenols is also demonstrated in a batch reaction. Furthermore, a method for the quantitative detection of epinephrine by a smart phone is established based on the CH-Cu nanozymes. We believe that this nanozyme has promising applications in environmental catalysis and rapid detection and expect that combining key peptides as metal ligands with metal ions to mimic the structure of the catalytic center of a natural enzyme will be a general and important strategy for the design and synthesis of a new type of nanozyme that can be used in various applications.

Challenges associated with nonspecific adsorption of proteins on sensor surfaces have steered the development of novel antifouling materials and strategies. Inspired by human synovial fluid composition and structure, we designed synergistic antifouling coatings with mixtures of hyaluronic acid (HA) and a zwitterionic bottlebrush polymer (BB). Using a fast and convenient online surface modification method, the polymers were immobilized on the Au surface, significantly increasing its hydrophilicity. Using surface plasmon resonance (SPR), a 10:1 ratio of HA to BB was found optimal to provide the best antifouling performance. Bovine serum albumin (BSA) adsorption on HA-BB coated surfaces was 0.2 ng/cm2, which was 60 times lower than BB or HA alone and 25 times lower than the commonly accepted ultralow adsorption limit (

To analyze multiple analytes in trace samples, low-dosage and high efficiency are crucial in many common cases. Herein, we developed a facile method using a single-channel surface plasmon resonance (SPR)-based biosensor for the simultaneous detection of gentamicin (GEN) and melamine (MEL) in milk and serum with only one sample injection. Based on a sandwich immunoassay, non-interfering antibodies against GEN from mouse (AbGEN) and against MEL from rabbit (AbMEL) were chosen to capture the analytes. Secondary antibodies against mouse (AbM) and rabbit (AbR) were used to bind with AbGEN and AbMEL to determine the concentrations of GEN and MEL on a single channel of an SPR sensor. All of the detection process could be done in 10 min with 50 μL of sample injection. According to the response shifts of AbM and AbR, two standard curves for GEN and MEL were obtained successively, with the limit of detection (LOD) values at 4.4 ng mL-1 and 1.3 ng mL-1, respectively. Moreover, the feasibility was determined by spiking milk and serum samples with GEN and MEL, with recoveries in the range of 81.6%-118.0%. Importantly, the analytes can be substituted by others for much more applications. This method is also expected to multiply the detection efficiency of multi-channel SPR biosensors with low-dosage samples in the future.

2,5-Diformylfuran (2,5-DFF) is an important furan-based chemical with broad application potential. To address the difficulties in isolating/purifying the product and recycling the 2,2,6,6- tetramethylpiperidine-1-oxy (TEMPO)-based catalysts, we employed a solvent with a low boiling point in which TEMPO has a low solubility to investigate the effects of TEMPO and its analogs on catalyzing the oxidation of 5-hydroxymethylfurfural (5-HMF). The results indicated that in ethyl acetate with the substitution of one H of TEMPO at the C4 position with either an acetamido ( NH-Ac), methoxy ( OCH3), hydroxy ( OH) or isothiocyanato ( N C S) group, the resulting compound had a product selectivity similar to that of TEMPO (>86%), except for the 4-isothiocyanato-TEMPO-catalyzed reaction. However, after two Hs were substituted with an oxo group ( O), the catalytic efficiency significantly decreased (product yield 16%, selectivity 52%). Based on both the catalytic efficiency and catalyst solubility, a highly efficient method for preparing 2,5-DFF was established using ethyl acetate as the solvent, 4-acetamido-TEMPO as the catalyst and Fe(NO3)3 and NaCl as cocatalysts. At 40 °C with a substrate concentration of 0.125 mol/L, 5-HMF was completely converted in 2 h, and the yield of 2,5-DFF was 89%. Moreover, when the substrate concentration increased to 0.25 mol/L, the yield of 2,5-DFF was 87%. When 4-acetamido-TEMPO was recovered by centrifugation, the product yield remained as high as 86% after three cycles, demonstrating good recyclability.

Effective binding between cellulases and cellulose is essential for enzymatic hydrolysis of lignocellulose. Expansin can loosen the cellulose structure and can enhance the efficiency of cellulase. However, possible synergy between cellulases and expansin is not clear. In this work, the real-time adsorption of exoglucanases (Cel7A) or endoglucanases (Cel7B) with Bacillus subtilis expansin (BsEXLX1) and the enzymatic hydrolysis of cellulose were followed using quartz crystal microbalance with dissipation (QCM-D). Initial adsorption rate, adsorption capacity, and pseudo-steady-state rate of cellulose hydrolysis by Cel7A/Cel7B increased in the presence of BsEXLX1. When injecting Cel7A or Cel7B together with BsEXLX1 at a mass ratio of 1:1, the hydrolysis rate was almost 5 times the rate for Cel7A or Cel7B alone at 25 °C. These results increase our understanding of the real-time synergism between cellulases and expansin on cellulose, as well as the impact of their synergy on the enzymatic hydrolysis of cellulose. ispartof: CARBOHYDRATE POLYMERS vol:253 ispartof: location:England status: published

In this study, we proposed a bioinspired approach for the deposition and zwitteration of hyaluronic acid (HA) with a reduced glutathione (GSH) to form a composite layer that functions as a low fouling coating. A polyanion of the HA–dopamine conjugate (HADA) possessing catechol groups was synthesized by carbodiimide chemistry between HA and dopamine. Then, the dopamine conjugated biofunctional polymers (HADA) were grafted onto Au substrates via the transformation of catechol into a quinone group under mild oxidative conditions followed by a reaction with GSH to avoid undesired adhesion and also to shield the exposed Au substrate. Analysis of XPS spectra and wettability indicated that HADA and GSH were successfully grafted onto Au substrates. Surface plasmon resonance analysis showed that both HADA and further GSH modified surfaces exhibited reduced nonspecific adsorption. The attachment of GSH to HADA modified surfaces (HADA-G) resulted in better antifouling performance, with a low or ultralow protein adsorption of 0–7.51 ng cm−2 when exposed to single protein solutions, and a reduction in nonspecific adsorption from cow's milk to 10% compared to that of bare gold. The enhanced antifouling performance of HADA-G modified surfaces was likely due to the zwitterionic structure in GSH, which can induce stronger surface hydration through electrostatic interactions as well as the hydrogen bonding induced by HADA. Our results provide a facile and universal approach to surface modification and demonstrate the benefits of using a composite layer for the design of low fouling surfaces.

Enzyme-responsive supramolecular hydrogels are a new class of smart materials and have enormous potential to be used in biology and medicine. In this study, α-chymotrypsin was proposed to promote the self-assembly of amino acid derivatives for the preparation of such supramolecular hydrogels. It is found that α-chymotrypsin significantly shortens the gelation time from 8 days (or no gelation occurred within 2 weeks) to 10 min–4 h depending on the structure of amino acid derivatives. The chemical compositions and microstructures of the hydrogels were further investigated by LC-MS, microscopy and spectroscopy techniques. The results show that the transparent hydrogels consist of long nanofibers with approximately 20 nm in diameter. These nanofibers are composed of Fmoc-amino acid and amino acid, which were formed from the hydrolysis of amino acid ester, with a molar ratio of 4.346 : 1 (Fmoc-F/F) and 0.548 : 1 (Fmoc-F/Y), respectively. Furthermore, the molecular simulation was performed to investigate the specific recognition of α-chymotrypsin to amino acid derivatives. The results indicate that the enzyme–substrate interactions are responsible for promoting the supramolecular self-assembly of these amino acid derivatives into fibrous hydrogels. In addition to being the first example of enzyme–substrate interaction-promoted supramolecular self-assembly, this novel concept opens up the possibility of making use of various enzymes and their substrates (or analogues) in the discovery of new supramolecular materials with enzyme responsiveness.

Amyloid fibrillation of proteins is likely a key factor leading to the development of amyloidosis-associated diseases. Inhibiting amyloid fibrillation has become a crucial therapeutic strategy. Water-soluble, fluorescent silicon nanoparticles (SiNPs) have great potential in biomedicine for various therapeutic and diagnostic purposes; however, it is unclear whether SiNPs have the ability to inhibit amyloid fibrillation. Herein, insulin was chosen as a protein model, and SiNPs of varying sizes were synthesized upon UV irradiation. The influence of size and concentration of the SiNPs on insulin fibrillation was investigated, and it has been observed that these variables were crucial in regulating insulin fibrillation. Using an average particle size of 6.6 nm and increasing the concentration of the SiNPs to 5.0 μg mL−1, the Thioflavin T (ThT) fluorescence intensity decreased significantly by 90%, with an increased lag time of 76.8 h, compared to that of the control. Insulin aggregates were short, thin fibrils or clusters when incubated with SiNPs, compared to the long, thick fibrils formed for insulin alone. Additionally, we found that the SiNPs prevent the conformational transition of insulin from its initial structure to β-sheets, and thus inhibit nucleation, which is necessary for the formation of large fibrils. The inhibitory activity is attributed to the interactions between the SiNPs and insulin during the nucleation period. Our results demonstrate that the SiNPs disrupt insulin amyloid fibrillation, and thus, may play a useful role in new therapeutic and diagnostic strategies for amyloid-related disorders.

The increasing demand for long lasting antifouling surfaces has steered the development of accessible, novel, biocompatible and environmentally-friendly materials. Inspired by lubricin (LUB), a component of mammalian synovial fluid with excellent antifouling properties, we designed three block polymers with bottle-brush structures and outstanding stability, efficacy, and ease of use. By a simple drop casting or online exposure, the polymers strongly adsorbed on silica surfaces in less than 10 min and were found to be stable in extremely high-salinity solutions and under an unprecedented wide range of pH. The polymers antifouling properties against proteins and bacteria were evaluated using different techniques, demonstrating ultralow fouling properties. With serum albumin and lysozyme adsorption < 0.2 ng/cm2, the polymers were found to be 50 and 25 times more effective than LUB and the known ultralow fouling coatings. The antifouling properties were also successfully tested under MPa compression pressures by direct force measurements using the surface forces apparatus (SFA). The findings of this study suggest that these polymers are amongst the most robust and efficient antifouling agents known today.

Nanoscale zero valent iron (nZVI) and bimetallic nZVI has been widely applied to remove various contaminants from water and soil, but their activities can be greatly reduced due to the precipitation of the generated Fe ions. Here we adopted tannic acid (TA) as stabilizer to synthesize high activity Fe-Pd nanoparticles (NPs) and scavenger of the generated Fe ions to keep the rapid dechlorination of two organochlorides. Inductively coupled plasma optical emission spectrometry and UV–vis spectroscopy measurements indicated the generated Fe ions were harvested by TA and formed bis- and tris-TA-iron complexes in the dechlorination solution. TA promoted 40-fold and 10-fold increase in dechlorination efficiency of p-chlorophenol and florfenicol attributing to the complexation of Fe ion by TA. This strategy may inspire novel ways to deal with the passivation of nZVI caused by the precipitation of Fe ions and benefits for the developing of longevity and high-efficient nZVI materials.

Effective regulation of cellulase adsorption is key to improving the efficiencies of the two major bottlenecks of lignocellulose hydrolysis and cellulase recovery. In this work, we investigated the effect of inhibitors, pH, and temperature on the adsorption of exo- and endoglucanases (Cel7A and Cel7B, respectively) on cellulose using quartz crystal microgravimetry with dissipation. The addition of glucose and cellobiose can both inhibit the hydrolysis activity of Cel7A, whereas only cellobiose can inhibit that of Cel7B. Notably, the adsorption was favored by acidic conditions (pH ≤ 4.8) and low temperature, whereas alkaline conditions (pH 9 and 10) facilitated enzyme desorption, which is useful to guide the process of cellulase recovery. The adsorption and hydrolysis activity of Cel7A and Cel7B were both higher at 45 °C than at 25 °C. These findings pave the way to effective regulation of cellulase adsorption and thus improve lignocellulose conversion and cellulase recovery. ispartof: LANGMUIR vol:34 issue:45 pages:13514-13522 ispartof: location:United States status: published

We report the spontaneous formation of lyotropic liquid crystals from the self-assembly of a series of minimalistic peptides. The highly charged peptides could self-assemble into rigid helical nanofilaments in water and spontaneously order into hexagonal liquid-crystalline phases with interfilament separations of ≤240 A. The formation of liquid crystals from the self-assembly of such simple peptides is dictated not only by the concentration and pH but also by the amino acid sequence of the peptides. Peptides containing the rigid Phe-Phe (FF) segment showed much higher propensities to form a liquid-crystalline phase with long-range order. Moreover, because of the intrinsic chirality of the peptides, the self-assembled birefringent liquid crystals could serve as sensing elements for the visual discrimination of chiral species and as templates for the biomimetic synthesis of mesoporous silica with ordered cavities. The results offer new opportunities for the design of peptide liquid crystals that are potenti...

Black phosphorus quantum dots (BPQDs) as novel nanomaterials have many potential applications in biomedicine. However, the interaction of BPQDs with proteins and their biological effects and potential risks are still unclear. Here, mucin, which serves biologically as a physical barrier against foreign substances entering tissues, was chosen as a model substrate for studying the adsorption–desorption behavior of BPQDs using surface plasmon resonance sensing and a quartz crystal microbalance with dissipation monitoring. We found that the surface modification of BPQDs with poly(ethylene glycol)-amine (PEG-NH2) reduces the adsorption rate of the quantum dots but increases their adsorbed amount on the mucin surface. The pH value, ionic strength, and ionic valence also had significant effects on the adsorption behavior of BPQDs. Upon increasing the pH from 2 to 7, the amount of BPQD adsorption decreased from 14.1 to 3.2 ng/cm2. A high ionic strength and ionic valence (e.g., Mg2+, Al3+) also inhibit the surface ...

Polyvinylidene fluoride (PVDF) membranes are limited in the field of oil-in-water emulsion treatment because the intrinsic hydrophobicity of PVDF can cause serious membrane fouling. Here, a superhydrophilic PVDF membrane (PVDF@PDA-GSH) was fabricated using a facile, versatile, mussel-inspired method. The pristine PVDF membrane was coated with dopamine under mild alkaline conditions by a dip-coating method, followed by addition of glutathione (GSH) via a simple reaction. GSH was successfully coated onto the membrane surface and confirmed by X-ray photoelectron spectroscopy and energy dispersive X-ray spectrometry. Hierarchical surface structure and superhydrophilicity were examined by scanning electron microscopy and contact angle, respectively, giving the PVDF@PDA-GSH membrane excellent wettability and antifouling ability. The water flux of PVDF@PDA-GSH was several-fold higher than conventional filtration membranes, and the oil rejection ratio was nearly 99%. The PVDF@PDA-GSH membrane also showed favorable reusability because the flux recovery ratio (FRR) remained above 90% after five cycles. In general, these results indicated that this modification might provide a good method for the fabrication of superhydrophilic PVDF membranes with good prospects for water filtration applications.

4-Nitrophenol (4-NP) is a priority pollutant in water and is both carcinogenic and genotoxic to humans and wildlife even at very low concentrations. Thus, we herein fabricated a novel molecularly imprinted core-shell nanohybrid as a ratiometric fluorescent sensor for the highly sensitive and selective detection of 4-NP. This sensor was functioned by the transfer of fluorescence resonance energy between photoluminescent carbon dots (CDs) and 4-NP. This sensor was synthesized by linking organosilane-functionalized CDs to silica-coated CdSe quantum dots (CdSe@SiO2) via Si–O bonds. The nanohybrids were further modified by anchoring a molecularly imprinted polymer (MIP) layer on the ratiometric fluorescent sensor through a facile sol–gel polymerization method. The morphology, chemical structure, and optical properties of the resulting molecularly imprinted dual-emission fluorescent probe were characterized by transmission electron microscopy and spectroscopic analysis. The probe was then applied in the detection of 4-NP and exhibited good linearity between 0.051 and 13.7 μg/mL, in addition to a low detection limit of 0.026 μg/mL. Furthermore, the simplicity, reliability, high selectivity, and high sensitivity of the developed sensor demonstrate that the combination of MIPs and ratiometric fluorescence allows the preparation of excellent fluorescent sensors for the detection of trace or ultra-trace analytes. Electronic supplementary material The online version of this article (10.1186/s11671-018-2440-6) contains supplementary material, which is available to authorized users.

The separation of oil-water emulsions has attracted considerable attention in recent years. The main challenge is to find new cost-effective ways to develop a separation technology that has the potential for scaling up treatment. In this study, benefitting from the idea in traditional chemical engineering processes, we report on three-dimensionally printed superhydrophobic poly(lactic acid) (PLA) packings for oil-in-water emulsion separation. Superhydrophobicity was achieved through a bioinspired modification process including selective solvent etching and nanoparticle decoration. The obtained superhydrophobic PLA packing has an air-water contact angle of 150° and a water adhesion force of 22 μN. A maximum separation efficiency of 95% was achieved while retaining a relatively high flux of 7.5 kL m

Preventing the unwanted adsorption of proteins and cells at articular cartilage surfaces plays a critical role in maintaining healthy joints and avoiding degenerative diseases such as osteoarthritis. Immobilized at the surface of healthy articular cartilage is a thin, interfacial layer of macromolecules consisting mainly of hyaluronic acid (HA) and lubricin (LUB; a.k.a. PRG4) that is believed to form a co-adsorbed, composite film now known to exhibit synergistic tribological properties. Bioinspired by the composition of cartilage surfaces, composite layers of HA and LUB were grafted to Au surfaces and the antiadhesive properties were assessed using surface plasmon resonance and quartz crystal microbalance. A clear synergistic enhancement in antiadhesive properties was observed in the composite films relative to grafted HA and LUB layers alone. Atomic force microscopy (AFM) normal force measurements provide insight into the architecture of the HA/LUB composite layer and implicate a strong contribution of hydrophobic interactions in the binding of LUB end-domains directly to HA chains. These AFM force measurements indicate that the adhesion of LUB to HA is strong and indicate that the hydrophobic coupling of LUB to HA shields the hydrophobic domains in these molecules from interactions with other proteins or molecules.

Nanoscale zero-valent iron has been widely applied in environmental remediation and toxic waste treatment, especially for the degradation of persistent organic pollutants (POPs). However, the dechlorination activity of Fe nanoparticles (Fe NPs) can be suppressed by the precipitation of iron oxides generated from the corrosion of Fe-Pd NPs under alkaline conditions, leading to a decreased dechlorination efficiency. Faced with this challenge, we report a highly effective dechlorination system that functions over a broad pH range and especially well under alkaline conditions in this work. Procyanidin (PROC), a natural polyphenol, was utilized as a stabilizer to manipulate the size distribution of Fe-Pd NPs and, more importantly, as a scavenger of Fe ions to prevent iron oxide precipitation. Experiments and theoretical calculations reveal that the generated Fe ions was mainly present in the form of bis- and tris-PROC-Fe complexes in the reaction solution. Compared with pristine Fe-Pd NPs, the PROC-modified Fe-Pd NPs had a dechlorination efficiency that was increased 20-fold (pH 9.0). Notably, a normalized rate constant was enhanced by more than 2 orders of magnitude compared to the previously reported dechlorination systems. The PROC-modified Fe-Pd NPs showed excellent dechlorination efficiency over a wide pH range (2.3–13.0). Nanyang Technological University This work was supported by the National Natural Science Foundation of China (21621004, 51473115, 21776212), Tianjin Municipal Science and Technology Bureau, China (16JCZDJC37900, 18YFHBZC00010, 18YFZCSF00590), and the Ministry of Education (grant No. NCET-11-0372). JY thanks to a start-up grant of NTU, M4082049.070.

The treatment of oil spill and the separation of oil-water mixture have been widely concerned in recent years. In this work, a one-pot synthesis strategy is developed to prepare fluorine functionalized zirconium-based metal organic framework (Zr-MOFs) (denoted as UiO-66-1F) by using 4-fluorobenzoic acid as modulator and modifier and p-phthalic acid (PTA) as ligand. 4-fluorobenzoic acid can participate in the formation of frameworks structure and cause structural defects, causing larger surface area and hierarchically porous structure. The hydrophobicity of UiO-66-1F increases with increasing of the ratio of 4-fluorobenzoic acid to zirconium chloride and when the ratio is 10, the synthesized UiO-66-1F(10) shows high hydrophobicity with a water contact angle (WCA) of 122° while the WCA of original UiO-66 is only 21°. UiO-66-1F(10) also has good chemical stability over a wide pH range (pH 1∼11) and good hydrothermal stability. In addition, a superhydrophobic sponge (UiO-66-1F(10)@PDA@sponge) with a WCA of 150° was prepared via in situ growth of UiO-66-1F(10) on a polydopamine modified sponge (PDA@sponge). The resulting composite shows high absorption capacities for various oils and organic solvents ranging from 50.5 g/g (n-hexane)– 107.8 g/g (dichloromethane) and good recyclability.

We investigated the effects of ultrasound treatment on cellulase adsorption and lignocellulose hydrolysis. The activity of cellulase remained constant upon low-power ultrasound treatment ( 280 W). Oscillating cellulase adsorption occurred upon ultrasound treatment with any intensity. The maxima for desorption and adsorption were 41.9 and 83.1%, respectively, during 1 h of 90 W ultrasound treatment at 50 °C. A comparison between the short-time with long-time ultrasound experiments indicated that ultrasound treatment tended to desorb cellulase from substrate. However, ultrasound treatment also led to further surface erosion of biomass, which increased cellulase accessibility. These joint actions of ultrasound treatment induced the oscillating adsorption of cellulase. The increase in cellulase accessibility caused by ultrasound treatment led to a significant enhancement in lignocellulose hydrolysis.

Bionanomaterials synthesized by bioinspired templating methods have emerged as a novel class of composite materials with varied applications in catalysis, detection, drug delivery, and biomedicine. In this study, two kinds of cross-linked lysozyme crystals (CLLCs) with different sizes were applied for the in situ growth of Au nanoparticles (AuNPs). The resulting composite materials were characterized by light microscopy, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy. The catalytic properties of the prepared materials were examined in the catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). It was found that the size of the AuNPs increased with an increase in Au loading for both small and large crystals. In addition, small crystals favored homogeneous adsorption and distribution of the metal precursors. And the size of the AuNPs within small crystals could be maintained below 2.5 nm by managing the HAuCl4/lys...

A catalytic membrane reactor, which contains a membrane matrix and a catalytic film of alloy nanoparticle-loaded β-lactoglobulin fibrils (NPs@β-LGF), was developed for the continuous-flow reduction of 4-nitrophenol (4-NP). The Cu–Ag and Cu–Ag–Au alloy NPs were synthesized using β-LGF as a scaffold and stabilizing agent. In this process, the Cu nanoclusters were formed in the initial stage and were able to promote the synthesis of Ag0, which acts as a reducing agent for the rapid formation of Au0. Furthermore, a catalytic membrane reactor was constructed by depositing the NPs@β-LGFs on a membrane matrix. The catalytic activity of the Cu–Ag–Au alloy NPs was higher than that of the Cu–Ag alloy NPs, using the reduction of 4-NP to 4-AP as a model reaction. The observed rate constant in the continuous-flow system is also higher than that in the batch system. In addition, these catalytic membrane reactors had good operating stability and antibacterial activity.

Functionalized silica nanoparticles with strong acidity and different hydrophobicity were successfully synthesized by an alkali co-condensation method. The structure of the hydrophobic solid acids were characterized, and the catalytic properties were investigated in fructose dehydration to 5-hydroxymethylfurfural (5-HMF). Experiment results indicated that catalyst hydrophobicity has a positive influence on both 5-HMF yield and selectivity. The highest yield of 5-HMF (87%) with full conversion of fructose was obtained when the most hydrophobic solid acid (SiNP-SO3H-C16) was used as the catalyst. The reason can be interpreted as the hydrophobic groups in the silica nanoparticles can effectively isolate SO3H groups with water molecules in the reaction system, and thus hinder the rehydration of 5-HMF, which is the main side-reaction in 5-HMF formation. Other important reaction parameters such as reaction medium, temperature, time and catalyst loading were also studied for fructose dehydration. Recycling and control experiments demonstrated the good reusability and stability of the functionalized silica nanoparticles. Furthermore, inulin was also used as a feedstock for 5-HMF production and gave a high 5-HMF yield of 65% in the catalysis of a moderate hydrophobic silica nanoparticle.

It is broadly observed that graphene oxide (GO) films appear transparent with a thickness of about several nanometers, whereas they appear dark brown or almost black with thickness of more than 1 μm. The basic color mechanism of GO film on a sub-micrometer scale, however, is not well understood. This study reports on GO pseudo-1D photonic crystals (p1D-PhCs) exhibiting tunable structural colors in the visible wavelength range owing to its 1D Bragg nanostructures. Striking structural colors of GO p1D-PhCs could be tuned by simply changing either the volume or concentration of the aqueous GO dispersion during vacuum filtration. Moreover, the quantitative relationship between thickness and reflection wavelength of GO p1D-PhCs has been revealed, thereby providing a theoretical basis to rationally design structural colors of GO p1D-PhCs. The spectral response of GO p1D-PhCs to humidity is also obtained clearly showing the wavelength shift of GO p1D-PhCs at differently relative humidity values and thus encouraging the integration of structural color printing and the humidity-responsive property of GO p1D-PhCs to develop a visible and fast-responsive anti-counterfeiting label. The results pave the way for a variety of potential applications of GO in optics, structural color printing, sensing, and anti-counterfeiting.

This study presents a facile, rapid and effective method for the fabrication of optical fiber surface plasmon resonance (SPR) sensors via polydopamine (PDA)-accelerated electroless plating (ELP). The bioinspired PDA coating formed through the facile self-polymerization of dopamine (DA) was utilized as a versatile material for optic-fiber functionalization. Gold seeds were then rapidly and firmly adsorbed onto the PDA functional layer by amino and imino intermediates generated during the polymerization, and a gold film sensor was fabricated after metal deposition. The fabrication time of the sensor was decreased by 6–12 times, and the fabricated sensor exhibited higher sensitivity, better reproducibility and adhesion stability compared with those fabricated by the traditional ELP. Some key experimental parameters, including DA polymerization temperature, DA polymerization time, and plating time, were investigated in detail. The optimized sample exhibited high sensitivity ranging from 1391 nm per RIU to 5346 nm per RIU in the refractive index range of 1.328 to 1.386. Scanning electron microscopy images indicated that the sensor surface consisted of gold nanoparticles with a uniform particle size and an orderly arrangement, and the film thickness was approximately 60 nm. Another PDA layer was formed on the gold film for facile immobilization of antibodies. The sensor exhibited effective antibody immobilization ability and high sensitivity for human IgG detection over a wide range of concentrations from 0.5 to 40 μg mL−1, which indicate the potential applications of the fabricated sensor in immunoassays.

We herein report a novel strategy for the removal of heavy metals and the subsequent preparation of a metal ceramic for immobilizing enzymes. To demonstrate this concept, Ni2+ ions were removed from an aqueous solution via entrapment by chitosan nanoparticles, and the resulting Ni(II)-containing precipitate was mixed with the ceramic matrix to give the Ni-doped ceramic (Ni-CP), which was subsequently applied in lipase immobilization. Under optimized conditions, Ni2+ removal reached 99.4%, and the Ni-CP showed significant chelation towards lipase following immobilization. In addition, a lipase activity yield of 164% was obtained under optimal conditions. Furthermore, the thermal and storage stabilities of Ni-CP-lipase exhibited a wider applied range, and the Ni-CP reusability was maintained at 97.5% following 20 cycles, suggesting high stability and excellent recyclability. Hence, the entrapped Ni2+ exhibited improved stability, thus reducing leakage into the environment. Furthermore, the chelation between Ni2+ and lipase improved enzyme activity and stability, and thus, may be suitable for application in large-scale production. It is therefore expected that this novel approach for enzyme immobilization has the potential to serve as an important technique in the field of biocatalysis.

Herein, we design and synthesize a novel hydrolase model by integrating the supramolecular self-assembly of an amphiphilic short peptide (Fmoc-FFH) and electrostatic complexation (with PEI) at an aqueous liquid–liquid interface to synthesize stable peptide–polymer Fmoc-FFH/PEI hybrid capsules (FPCs). After treatment with glutaraldehyde as a crosslinking agent, we can obtain novel Fmoc-FFH/PEI/GA hybrid capsules (FPGCs). The FPGCs with imidazolyl groups as the catalytic centers exhibit high catalytic activity for the hydrolysis of p-nitrophenyl acetate (PNPA). The resulting hydrolase model (FPCs or FPGCs) shows kinetics behavior typical of natural enzymes, and the catalytic activity is higher than that of a Fmoc-FFH hydrogel. The enhanced catalytic activity may be attributed to the high density of catalytic sites on the inner surface of the hybrid capsule. Additionally, the FPGCs retained 93% of their productivity after fifteen cycles, suggesting high stability and excellent recyclability. This novel hybrid capsule is expected to be applied as a substitute for natural hydrolases in industrial production applications.

A universal strategy is developed to construct a superhydrophobic and superoleophilic metal-organic framework (MOF) by an amidation reaction between amino group and acid chloride of octadecanoyl chloride. The introduction of long alkyl chain reduced the surface free energy, yielding a superhydrophobic Zr-MOF (UiO-66-NH-C18) with a high water contact angle (WCA) of 151.7°. The adsorbed amount of water on the UiO-66-NH-C18 was only 5.59 mmol/g, which was just 28 % of that on the UiO-66-NH2. More importantly, the hydrophobic modification improved the stability of Zr-MOFs under strong alkaline conditions (e.g., pH = 13). Furthermore, the UiO-66-NH-C18 can selectively absorb organic solvent from water and achieve continuous oil-water separation. The oil-water separation efficiency could reach up to 99.9 %. In addition, the UiO-66-NH-C18@sponge was also prepared through dip-coating of UiO-66-NH-C18 on the melamine sponge in the presence of PDMS solution. The resulting composite shows high adsorption capacities for various oils and organic solvents ranging from 32.3–66.1 g/g. The superhydrophobic UiO-66-NH-C18@sponge has potential as a promising absorbent for treatment of oily wastewater.

Summary Amyloid are protein aggregates formed by cross β structures assemblies. Inhibiting amyloid aggregation or facilitating its disassembly are considered to be two major effective therapeutic strategies in diseases involving peptide or protein fibrillation such Alzheimer's disease or diabetes. Using thioflavin-T fluorescence, far-UV circular dichroism spectroscopy, and atomic force microscopy, we found nontoxic and biocompatible black phosphorus quantum dots (BPQDs) appear to have an exceptional capacity to inhibit insulin aggregation and to disassemble formed mature fibrils, even at an ultralow concentration (100 ng/mL). The inhibition of fibrillation persists at all stages of insulin aggregation and increases PC12 cells survival when exposed to amyloid fibrils. Molecular dynamics simulations suggest that BPQDs are able to stabilize the α-helix structure of insulin and obliterate the β-sheet structure to promote the fibril formation. These characteristics make BPQDs be promising candidate in preventing amyloidosis, disease treatment, as well as in the storage and processing of insulin., Graphical Abstract, Highlights • BPQDs inhibit insulin amyloid fibrillation at an ultralow concentration • BPQDs can depolymerize protofibrils and even mature fibers • BPQDs inhibit aggregation mainly by van der Waals' force and hydrophobic interaction • BPQDs are biocompatible and can reduce insulin fibrils-induced cytotoxicity, Drugs; Cell Biology

ZnO is widely used as a photocatalyst in industry, however, it is still a challenge to degrade refractory antibiotics in water. In this study, a novel surface-functionalized N,S-doped carbon quantum dot (N,S-CQD) was synthesized and embedded into ZnO for the formation of a new ZnO/N,S-CQDs hybrid nanoflower via one-pot hydrothermal process. The as-prepared ZnO/N,S-CQDs showed significantly enhanced photocatalytic activity under visible and near-infrared (NIR) light irradiation, in which 72.8% of MG was decomposed after 180 min under NIR light. In addition, approximately 92.9% and 85.8% of ciprofloxacin (CIP) were degraded by ZnO/N,S-CQDs under simulated sunlight for 20 min and natural sunlight for 50 min, respectively. Furthermore, the mechanism was investigated and the results show that the surface functionalization, electron transfer, up-converted luminescence properties of N,S-CQDs, together with the highly reactive facets of ZnO nanoflowers, made great contributions to the enhanced photocatalytic activity of ZnO/N,S-CQDs. Additionally, the results of active species trapping experiments indicated that the hydroxide free radicals, holes and superoxide radical anions all played certain roles in the photocatalytic reaction. Finally, ZnO/N,S-CQDs was employed for photodegradation of antibiotics in actual water, the degradation efficiency of antibiotics still remained above 60% after 120 min. We believe that the ZnO/N,S-CQDs nanoflower is a promising photocatalyst for the degradation of refractory antibiotics under sunlight irradiation. The relatively low cost and excellent photocatalytic performance of ZnO/N,S-CQDs is beneficial for industrial applications.

Ultrathin 2-dimensional transition metal dichalcogenides (TMDs) have become a class of high-potential materials in biomedicine due to their intriguing properties. They have been applied to solve biomedical challenges, such as biosensing, bioimaging, drug delivery, and cancer therapy. However, studies of the interactions between these materials and biomolecules are insufficient. Mucous tissue serves as a barrier to foreign hazardous substances and a gel layer for substance exchange. The main organic matter of mucous tissue is mucin, so it was selected as a model biomolecule to study its interactions with six different TMD nanosheets (NSs), including single-layered (SL), few-layered (FL), and small few-layered (SFL) MoS2 and WS2 NSs, using quartz crystal microbalance (QCM) with a dissipation monitor (QCM-D) and surface plasmon resonance (SPR). Additionally, UV absorption, fluorescence, and circular dichroism (CD) spectroscopy were applied to investigate the mechanism of the interactions and to study the conformational change of mucin. We found that the TMD NSs could adsorb on the mucin layer and affect its viscoelasticity. The results indicated that the SL WS2 NSs exhibited the highest initial absorption rate and the maximum absorption amount, while the SL MoS2 NSs exhibited the highest initial desorption rate. During the adsorption, the viscoelasticity variations of the mucin layer caused by the WS2 nanosheets were weaker than those caused by the MoS2 nanosheets. Furthermore, the conformational changes of mucin caused by the SL MoS2, SL WS2, and SFL MoS2 NSs were higher than those resulting from other TMD NSs. These findings provide important information on the interactions between TMD NSs and mucin and provide useful insights into the interfacial behavior of TMD NSs before they enter tissues.

Fly ash particles can contribute to haze and adverse health outcomes. In this study, two mucins, one from bovine submaxillary glands (bovine submaxillary mucin, BSM) and one from porcine stomach (porcine gastric mucin), as well as bovine serum albumin (BSA), which served as the physical barriers against foreign substances entering the tissues and the blood protein, respectively, were chosen as models for the investigations of the interactions between the proteins and the fly ash particles. Their adsorption behaviors were studied using spectroscopy and a quartz crystal microbalance with a dissipation monitor (QCM-D). The results indicated that the fly ash particles can induce the loosening of mucins and BSA, probably via the formation of complexes. Further, the secondary structure of proteins changed in the presence of fly ash particles. The α-helix content decreased with an increasing fly ash particle concentration. The addition of fly ash particles into protein solutions led to fluorescence quenching, which suggested that there were interactions between these particles and the mucins and BSA. The association constants ( K

We report a new kind of peptide-polysaccharide aerogel which was formed by the coassembly of the fluorenylmethyloxycarbonyl-diphenylalanine (Fmoc-FF) peptide and the polysaccharide konjac glucomannan (KGM). The porosity and hydrophobicity of the hybrid aerogels could be facilely tailored by modifying the mass ratio of Fmoc-FF and KGM. The aerogels with tunable architecture showed good performance for the separation of a wide variety of oil-water mixtures. The results provide an opportunity for the design of peptide materials as a new class of biocompatible absorbents with potential applications in biomedicine and separation.

Nanoscale zero-valent iron (nZVI) has shown considerable promise in the treatment of chlorinated organic compounds, but rapid aggregation and inactivation hinder its application. In this study, palladium-doped zero-valent iron nanoparticles involving poly (γ-glutamic acid) (Fe-Pd@PGA NPs) were synthesized. The nanoparticles were small (~100 nm), uniformly distributed, and highly stable. The dechlorination performance of Fe-Pd@PGA NPs was evaluated using p-CP as a model. The results demonstrated that Fe-Pd@PGA NPs show high activity even in weakly alkaline conditions. The maximum rate constant reached 0.331 min− 1 at pH 9.0 with a Fe to p-CP ratio of 100. Additionally, the dechlorination activity of Fe-Pd@PGA NPs is more than ten times higher than that of the bare Fe-Pd NPs, demonstrating the crucial role of PGA in this system. Furthermore, we investigated the dechlorination performance in the presence of different anions. The results indicated that Fe-Pd@PGA NPs can maintain high activity in the presence of Cl−, H2PO4−, and humic acid, while HPO42−and HCO3− ions slightly reduce the dechlorination activity. We believed that PGA is a promising stabilizer and promoter for Fe-Pd NPs and the Fe-Pd@PGA NPs have the potential for practical applications. Electronic supplementary material The online version of this article (10.1186/s11671-018-2634-y) contains supplementary material, which is available to authorized users.

Ochratoxin A (OTA) is a type of mycotoxin generated from the metabolism of Aspergillus and Penicillium, and is extremely toxic to humans, livestock, and poultry. However, traditional assays for the detection of OTA are expensive and complicated. Other than OTA aptamer, OTA itself at high concentration can also adsorb on the surface of gold nanoparticles (AuNPs), and further inhibit AuNPs salt aggregation. We herein report a new OTA assay by applying the localized surface plasmon resonance effect of AuNPs and their aggregates. The result obtained from only one single linear calibration curve is not reliable, and so we developed a “double calibration curve” method to address this issue and widen the OTA detection range. A number of other analytes were also examined, and the structural properties of analytes that bind with the AuNPs were further discussed. We found that various considerations must be taken into account in the detection of these analytes when applying AuNP aggregation-based methods due to their different binding strengths.

Enzyme-loaded water-in-oil Pickering emulsion is a promising system for biphasic catalytic reactions. In this paper, we report on oriented enzyme immobilization at the oil/water interface in a Pickering emulsion, in which CHO-Janus silica nanoparticles (CHO-JNPs) are utilized as a stabilizer of the emulsion and support for the enzyme to enhance both catalytic activity and recyclability. The catalytic performance of this immobilized enzyme (lipase from Candida sp.) was evaluated by esterification of hexanoic acid and 1-hexanol in a water/heptane biphasic medium. The results show that the specific catalytic activity of the immobilized enzyme (33.2 U mL-1) was 6.5 and 1.4 times higher than that of free enzyme (5.1 U mL-1) and encapsulated enzyme in the liquid core (23.3 U mL-1), respectively. Moreover, the immobilized enzyme demonstrated good stability and recyclability, retaining 75% of its activity after 9 cycles. We expect that oriented enzyme immobilization at the oil/water interface will be an important strategy for enhancing catalytic performance in Pickering emulsions.

The structural colors produced by pseudo-1D photonic crystals of graphene oxide originate from the regularly layered structure of GO films, which have been previously reported. For the same observation regarding the tunable color reflection obtained from the dried GO films, Hong et al. suggest a different mechanism to the previously published model.

For the analysis of massive samples containing multiple analytes, the enhancement of detection efficiency is crucial. In this study, a facile method was developed for sequential detection of chloramphenicol (CAP) and gentamicin (GEN) in complex samples, e.g. milk, using a surface plasmon resonance (SPR)-based biosensor. Based on the immune inhibition format, two conjugates of antigen and bovine serum albumin (BSA)-denoted as CAP-BSA and GEN-BSA-were grafted on the same channel of the SPR sensor chip. Two standard curves for CAP and GEN were separately obtained by first mixing a single antibody with different concentrations of the relevant antigen. Moreover, different regeneration solutions were screened for sequential analysis. An alkaline solution was found to completely remove the antibody against GEN (AbGEN) from the chip, but it exhibited limited ability to dissociate the antibody against CAP (AbCAP). Therefore, alkaline solution and Gly-HCl solutions are successively applied to elute AbGEN and AbCAP, respectively. By gradual elutions, CAP and GEN concentrations were simultaneously calculated with limit of detection values of 5.28ng/mL and 2.26ng/mL, respectively. Furthermore, the spiking milk samples with CAP and GEN validated the assay with recoveries of 77.6-101.1%. Therefore, this method is expected to improve the detection efficiency of SPR biosensors.

We report a new approach to constructing a peptide–polysaccharide hybrid hydrogel via the calcium-ion-triggered co-assembly of fluorenylmethyloxycarbonyl-diphenylalanine (Fmoc-FF) peptide and alginate. Calcium ions triggered the self-assembly of Fmoc-FF peptide into nanofibers with diameter of about 30 nm. Meanwhile, alginate was rapidly crosslinked by the calcium ions, leading to the formation of stable hybrid hydrogel beads. Compared to alginate or Fmoc-FF hydrogel alone, the hybrid Fmoc-FF/alginate hydrogel had much better stability in both water and a phosphate-buffered solution (PBS), probably because of the synergistic effect of noncovalent and ionic interactions. Furthermore, docetaxel was chosen as a drug model, and it was encapsulated by hydrogel beads to study the in vitro release behavior. The sustained and controlled docetaxel release was obtained by varying the concentration ratio between Fmoc-FF peptide and alginate.

Surface plasmon resonance (SPR) biosensors have many possible applications, but are limited by sensor chip surface fouling, which blocks immobilization and specific binding by the recognizer elements. Therefore, there is a pressing need for the development of antifouling surfaces. In this paper, the mechanisms of antifouling materials were firstly discussed, including both theories (hydration and steric hindrance) and factors influencing antifouling effects (molecular structures and self-assembled monolayer (SAM) architectures, surface charges, molecular hydrophilicity, and grafting thickness and density). Then, the most recent advances in antifouling materials applied on SPR biosensors were systematically reviewed, together with the grafting strategies, antifouling capacity, as well as their merits and demerits. These materials included, but not limited to, zwitterionic compounds, polyethylene glycol-based, and polysaccharide-based materials. Finally, the prospective research directions in the development of SPR antifouling materials were discussed. Statement of Significance Surface plasmon resonance (SPR) is a powerful tool in monitoring biomolecular interactions. The principle of SPR biosensors is the conversion of refractive index change caused by molecular binding into resonant spectral shifts. However, the fouling on the surface of SPR gold chips is ubiquitous and troublesome. It limits the application of SPR biosensors by blocking recognition element immobilization and specific binding. Hence, we write this paper to review the antifouling mechanisms and the recent advances of the design of antifouling materials that can improve the accuracy and sensitivity of SPR biosensors. To our knowledge, this is the first review focusing on the antifouling materials that were applied or had potential to be applied on SPR biosensors.

Self-assembly of chiral nanostructures is of considerable interest, since the ability to control the chirality of these structures has direct ramifications in biology and materials science. A new approach to design chiral nanostructures from self-assembly of N-(9-fluorenylmethoxycarbonyl)-protected phenylalanine-tryptophan-lysine tripeptides is reported. The terminal charges can induce helical twisting of the assembled β-sheets, enabling the formation of well-defined chiral nanostructures. The degree and direction of twisting in the β-sheets can be precisely tailored through in situ pH and temperature modulations. This enables the assembly of reconfigurable chiral nanomaterials with easily adjustable size and handedness. These results offer new insight into the mechanism of helical twist formation, which may enable the precise assembly of highly dynamical materials with potential applications in biomedicine, chiroptics, and chiral sensing.