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Formaldehyde (FA) is widely used in industry and also common in daily life. Finding an efficient method to determine FA is quite an industrial challenge. Herein, a novel method based on a resonance light scattering (RLS) technique was developed for the detection of FA with high sensitivity. Carbon dots (CDs) were used as RLS probes. CDs were obtained via one-pot solvothermal treatment from o-phenylenediamine. CDs showed yellow fluorescence with a quantum yield of 0.41. Due to the multiple amino groups on the surface of CDs, FA can be captured easily by formation of a covalent C = N bond based on the Schiff-base reaction. Owing to the covalent crosslinking, CD nanoparticles aggregated, and even formed precipitate. The aggregation of CDs induced RLS enhancement, where the RLS increment was linearly related to the concentration of FA ranging from 4 nM to 1.6 mM, with a limit of detection (LOD) of 1.6 nM. In comparison with many previous reports, the present RLS method showed a wider linear range and lower LOD. Furthermore, the RLS system was successfully used to detect FA in real food samples. The proposed system has prospective applicability in the detection of FA in food fields.

This work describes the facile designing of three conjugated microporous polymers incorporated based on the ferrocene (FC) unit with 1,4-bis(4,6-diamino-s-triazin-2-yl)benzene (PDAT), tris(4-aminophenyl)amine (TPA-NH2), and tetrakis(4-aminophenyl)ethane (TPE-NH2) to form PDAT-FC, TPA-FC, and TPE-FC CMPs from Schiff base reaction of 1,1′-diacetylferrocene monomer with these three aryl amines, respectively, for efficient supercapacitor electrodes. PDAT-FC and TPA-FC CMPs samples featured higher surface area values of approximately 502 and 701 m2 g−1, in addition to their possession of both micropores and mesopores. In particular, the TPA-FC CMP electrode achieved more extended discharge time compared with the other two FC CMPs, demonstrating good capacitive performance with a specific capacitance of 129 F g−1 and capacitance retention value of 96% next 5000 cycles. This feature of TPA-FC CMP is attributed to the presence of redox-active triphenylamine and ferrocene units in its backbone, in addition to a high surface area and good porosity that facilitates the redox process and provides rapid kinetics. [ABSTRACT FROM AUTHOR]

As the food processing by-products, hericium erinaceus residues (HER) and pineapple peel (PP) are good sources of cellulose and chitosan that can be prepared into hydrogels for structuring a drug delivery system. Hydrogel is one new type biomaterial for drug delivery with excellent absorbent ability applied in wound dressing. In this research, one composite self-healing hydrogel with pH sensitivity for drug delivery system based on the Schiff-base reaction was fabricated. Therein aldehyde group of oxidized microcrystalline cellulose (OMCC) from PP were crosslinked with amino group of carboxymethyl chitosan (CMCS) from HER via Schiff-base reaction for structuring hydrogels. The structures of the prepared hydrogels were characterized. Meanwhile, its blood clotting activity and physical properties were investigated. The hydrogels show some favorable performances with suitable gel time (54 s of minimum), distinguish swelling rate (about 31.18 g/g), good mechanical, self-healing characteristic and well coagulation effect. The cumulative release of the rutin-loaded hydrogel OMCM-54 reached about 80 % within 6 h, suggesting the well-controlled release of rutin by crosslinking degree between the modified OMCC and CMCS based on Schiff-base reaction. The novel biomaterial based on hericium erinaceus residues and pineapple peel shows its potential use as wound dressing. [Display omitted] • Pineapple peel and hericium erinaceus residues were modified as hydrogel materials. • Modified cellulose/chitosan hydrogels were synthesized via Schiff base reaction. • The hydrogel shows comparable modulus with human skin and fast self-healing effect. • The prepared hydrogel exhibited good blood clotting property as wound dressing. [ABSTRACT FROM AUTHOR]

Extracted from Platycodon grandiflorum , platycodon grandiflorum polysaccharides (PGPs) with diverse biological functions have been extensively employed for modification and fabrication of hydrogels for biomedical applications, such as wound dressings. However, since the lack of effective structural design, the reported polysaccharide-based hydrogel dressings are still suffered from structural failures and limited bio-functionality. Herein, we demonstrate a facile and general strategy to fabricate a supramolecular hydrogel composed of PGP-based polymer brush as building blocks combined with a Ca2+-mediated self-assembly process. The specific polymer brush with high branch functionality was achieved with polyacrylamide arms evenly grown on the PGP (grafting efficiency as high as 80 %) with series of chemical modifications. With above structural merits, the resulting hydrogel with densely crosslinked polymer brush featured enhanced mechanical strength as well as self-healing, and shear-thinning behaviors. Further biocompatible investigation indicated the as-prepared hydrogels with admirable performances in self-adhesion (adhesive strength of 16.7–79.5 kPa), a pH-responsive swelling ratio as high as 44 at pH 5.4, and pH-responsive degradation. They also showed antioxidant capacity by scavenging DPPH activity of nearly 80 % in 20 min, hemocompatibility, cell viability and cell migration. Impressively, the PGP-based polymer brush hydrogel served as a wound dressing revealed significant acceleration on wound closure. [ABSTRACT FROM AUTHOR]

The aim of this study is to prepare nanocomposite hydrogel based on gelatin/oxidized alginate, and evaluate its reinforcement by incorporation of nanohydroxyapatite (nHA) for use in bone tissue engineering applications. We used Schiff-base reaction as a click chemistry to prepare nanocomposite hydrogels. Additionally, the nHA was modified using sodium alendronate as a bisphosphonate through formation of coordinate bonds (chelate formation) to prepare bisphosphonate-modified hydroxyapatite (nHABP). The presence of bisphosphonate in the network can improve the cytocompatibility of the scaffolds and suppress the nanoparticles aggregation by inducing steric repulsion. Improved mechanical and rheological properties in the samples containing nHABP is due to the enhanced dispersion of modified nanoparticles as a result of the additional interaction between amine groups in the nHABP and aldehyde groups in the polymeric matrix. We demonstrated how the presence of bisphosphonate ligand in the oxidized alginate-gelatin network can improve nanoparticles dispersion via Schiff-base reaction.

In order to better showcase the freshness of fresh meat, merchants usually place absorbent pads under tray packaging for preservation. However, the current absorbent pads can only absorb a small amount of blood water and cannot effectively inhibit the growth and reproduction of microorganisms in tray packaging. Herein, a super absorbent aerogel pad for preserving fresh meat was prepared through the Schiff base reaction. Benefiting from the superhydrophilicity and porous structure of aerogels, the prepared G3D1BC0.5 (Gelatin: Dialdehyde starch = 3:1, Bacterial cellulose: 0.5%) aerogel not only possessed excellent adsorption performance but also rapidly regain their shape under 70% compression strain. The G3D1BC0.5 aerogel incorporating curcumin (Cur) showed the good antibacterial ability where the survival rate of Listeria monocytogenes , Staphylococcus aureus , Escherichia coli and Salmonella typhimurium significantly decreased to lower than 45% with the increase of Cur content (P < 0.05). Furthermore, the prepared aerogels had the excellent preservation effect on fresh meat during storage. The G3D1BC0.5-Cur0.7 aerogels can extend the shelf-life of fresh pork to 12 days by inhibiting microbial growth, protein oxidation, and lipid oxidation. Therefore, the prepared aerogel in the present study had great potential for preservation of fresh pork. [Display omitted] • Development of superabsorbent aerogel is based on Schiff base reaction. • Bacterial cellulose significantly improves the performance of aerogel. • The prepared superabsorbent aerogel can release curcumin to inhibit bacteria. • Superabsorbent antibacterial aerogel extends the shelf life of fresh pork to 12 d. [ABSTRACT FROM AUTHOR]

• Two novel tetrabenzonaphthalene-linked conjugated microporous polymers (TBN-pH CMPs) were constructed. • These CMPs had large surface areas and outstanding thermal stability. • The TBN-TPA CMP–based electrode had high specific capacitances of 251 F g–1 at 0.5 A g–1. • TBN-TPA CMP material appears promising for charge and energy storage applications. Conjugated microporous polymers (CMPs) have been applied widely in several energy storage applications. Triphenylamine derivatives are good electrode materials that can be processed into SC devices because of their high charge mobilities, unique electronic properties, and high redox activity. We prepared two novel tetrabenzonaphthalene-linked conjugated microporous polymers (TBN-pH CMPs) through [4 + 2] and [4 + 3] Schiff-base condensations of 2,7,10,15-tetra(4-formylphenyl)tetrabenzonaphthalene (TBN-PhCHO) with tetrakis(4-aminophenyl)ethene (TPE-4NH 2) and tris(4-aminophenyl)amine (TPA-3NH 2), respectively. Fourier transform infrared, and solid-state 13C NMR spectroscopy investigated the structures of the as-prepared CMPs. These CMPs, had large surface areas and outstanding thermal stability at temperatures of up to 400 °C, making them suitable for use as electrodes in supercapacitor (SC) systems. Indeed, the TBN-TPA CMP–based electrode had high specific capacitances (251 F g − 1 measured at 0.5 A g–1) and capacity retentions (94%, measured after 5000 cycles at 10 A g–1) when tested in three-electrode systems. We attribute the remarkable electrochemical activity and conductivity of the TBN-TPA CMP electrode to its large specific surface area (230 m2 g–1) and chemical structure featuring stacking of the benzene rings of its redox-active triphenylamine moieties. [ABSTRACT FROM AUTHOR]

In this study, a cellulose membrane (CM)-based enzymatic colorimetric biosensor with high storage, long-term stability, and rapid screening was constructed. CM was oxidized by sodium periodate (OCM), and the C2-C3 position hydroxyl group (–OH) on the CMs was oxidized to the aldehyde group (–CHO). The amino group (–NH 2) of α-glu and the –CHO on OCM immobilized α-glu reacted through a simple Schiff base reaction to obtain Schiff-based CM (SCM), which could screen AGIs rapidly within only 80 sec. The screening mechanism was that 4-Nitrophenyl α-D-glucopyranoside (PNPG) is a kind of α-glu chromogenic substrate, under the catalysis of α-glu, it produces yellow 4-Nitrophenyl (PNP), which through physical absorption immobilized on SCM immediately render the SCM colorless to yellow. Acarbose was chosen as a representative inhibitor. When acarbose was added, it was competitively bound to the active site of α-glu so that α-glu could not catalyze PNPG to produce PNP, thereby reducing the color intensity of SCM. SCM inherited CM's unique highly loose interpenetrating porous morphology was exhibited by FESEM results, providing many channels and sites for immobilizing α-glu. EDS, FT-IR, and XPS characterized SCM's preparation and sensing mechanisms. These results indicated that the N, O bidentate ligands were successfully introduced on the CM via the Schiff base bond (-C=N-). The VLOD of SCM is 5 × 10–4 mM in the linear range of acarbose from 0 to 0.6 mM, and the IC50 was 16.77 μM. Application experiments such as response time, sensitivity, selectivity, and long-term stability proved that the biosensor could detect AGI rapidly within 80 sec and possessed high selectivity and long-term storage stability. After 120 days of storage at 4 °C, the color intensity was lost by less than 10%. [Display omitted] • The biosensor was obtained using CM as carriers for α-glucosidase immobilization. • The rapid qualitative detection of AGI was achieved within 80 sec by the biosensor. • The VLOD and IC 50 of the detection acarbose were 5 × 10-4 mM and 16.77 μM. • The high stability was proved through long-term storage investigated within 120 days. • The mechanism was that α-glu catalyzed PNPG to produce PNP was immobilized on SCM. This study constructed a cellulose membrane (CM)-based enzymatic colorimetric biosensor with high storage, long-term stability, and rapid screening. CM was oxidized by sodium periodate (OCM), and the C2-C3 position hydroxyl group (–OH) on the CMs was oxidized to the aldehyde group (–CHO). The amino group (–NH 2) of α-glu and the –CHO on OCM immobilized α-glu reacted through a simple Schiff base reaction to obtain Schiff-based CM (SCM), which could screen AGIs rapidly within only 80 sec. The screening mechanism was that 4-Nitrophenyl α-D-glucopyranoside (PNPG) under the catalysis of α-glu produces yellow 4-Nitrophenyl (PNP), which through physical absorption immobilized on SCM immediately renders the SCM colorless to yellow. When acarbose was added, it was competitively bound to the active site of α-glu so that α-glu could not catalyze PNPG to produce PNP, thereby reducing the color intensity of SCM. SCM inherited CM's highly loose interpenetrating porous morphology was exhibited by FESEM results, providing many channels and sites for immobilizing α-glu. The VLOD of SCM is 5 × 10−4 mM in the linear range of acarbose from 0 to 0.6 mM, and the IC 50 was 16.77 μM. After 120 days of storage at 4 °C, the color intensity was lost less than 10 %. [ABSTRACT FROM AUTHOR]

By skillfully replacing one nitrogen among the triazine of g-C 3 N 4 with carbon atom, the as-prepared CNU 0.075 sample not only increases π-electron availability and narrows the bandgap of g-C 3 N 4 , but also absorb more solar light up to 750 nm. As a result, the photocatalytic hydrogen evolution rate of the optimal C self-doped g-C 3 N 4 is almost as high as 20 times that of bare g-C 3 N 4 under the blue light illumination. • Carbon self-doping in the specific site of the network of g-C 3 N 4 was obtained. • Photoactivity has been increased to about 20 times that of bare g-C 3 N 4 under the blue light. • The CNU 0.075 can effectively cover more sufficient photo flux (λ = 750 nm). • Direct incorporation C 4 N 2 ring into network of g-C 3 N 4 contributes to the enhanced photogenerated carrier dissociation. Nowadays, the C-substitution for N in g-C 3 N 4 can promote π-electron availability and thus considerably increase its photocatalytic properties. However, the replacement of N in triazine ring of g-C 3 N 4 by carbon atom represents a huge challenge on account of the higher electronegativity of N over C. Herein, we firstly report a simple and effective strategy for skillfully replacing one nitrogen with carbon atom by copolymerizing π-electrons-rich uracil with dicyandiamide via a facile Schiff-base reaction. The results show that direct incorporation C 4 N 2 ring into the framework not only maintains the structural features of g-C 3 N 4 and narrows its bandgap from 2.75 to 2.58 eV, but also effectively boosts the dissociation of photogenerated excitons. Consequently, C-incorporated g-C 3 N 4 could harvest more solar light (λ = 750 nm). As expected, the photocatalytic hydrogen evolution rate of the optimal C self-doped g-C 3 N 4 is almost as high as 13 and 20 times that of bare g-C 3 N 4 under the visible-light exposure and the blue light illumination, respectively. Most importantly, the optimal sample also shows excellent performance under the green (λ = 500 nm) and yellow (λ = 550 nm) light illumination (94.07 and 28.47 μmol g−1 h−1, respectively). This work sheds light on a subtle molecular-tailored protocol for controlling carbon self-doping site of the g-C 3 N 4 to optimize the intrinsic electronic properties and photoactivity. [ABSTRACT FROM AUTHOR]

• A coating with anti-adhesive and bactericidal properties was prepared. • Tobramycin works as a bactericidal agent and a cross-linker in polyimide networks. • The coating can be obtained via a facile one-step Schiff-base reaction. Herein, we report an effective bacterial anti-adhesive and bactericidal coating based on a Schiff-base reaction. The hydrophilic polyoxyethylene-bis-amine (PEG-bis-amine) is introduced in the system to endow the coating with valid bacterial anti-adhesive performance, while the tobramycin (Tob) with multi-amines serves as both a bactericidal agent and one of the cross-linkers for the construction of polyimide networks. The coating is obtained via a facile solvent-annealing method. This type of dual-functional antibacterial coating may provide as an excellent antibacterial platform for broad applications in bactericidal surfaces. [ABSTRACT FROM AUTHOR]

In this study, we used polyaldehyde gum Arabic (OGA) and carboxymethyl chitosan (CMCS) as a gel matrix to form an injectable self-healing hydrogel by Schiff-base bonding. Further, graphene oxide (GO) was loaded with doxorubicin (DOX) to the hydrogel, which resulted in a CMCS-OGA/GO@DOX hydrogel. We achieved a DOX drug loading capacity of 43.80 ± 1.13 %. Rheological studies showed that GO hydrogels have improved mechanical properties. The in vitro release profile showed pH responsiveness with 88.21 % DOX release at pH 5.5. Biocompatibility studies showed that the hydrogel composition had good cytocompatibility with L929 cells. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay showed a cell survival rate of 93.88 % within 48 h. The DOX-loaded hydrogel exhibited higher cell mortality in breast cancer cells (4 T1), with an inhibition rate of 79.4 % at 48 h. Acridine orange/ethidium bromide staining experiments on 4 T1 cells showed that when loaded with the same DOX concentration, the hydrogel significantly reduced the toxic effects on normal cells, whereas it had significant cytotoxic effects on cancer cells. This result indicates that the prepared GO hydrogel drug delivery system can serve as a novel approach for localized breast cancer treatment. Carboxymethyl chitosan (CMCS) and oxidised Arabic gum (OGA) were modified to form a water-soluble CMCS and a green, non-toxic aldehyde Arabic gum through strong oxidation with sodium periodate. The aldehyde groups in CMCS and OGA were crosslinked through the Schiff base reaction to form the CMCS-OGA hydrogel. Graphene oxide loaded with doxorubicin (GO@DOX) was directly incorporated into the hydrogel to prepare the injectable self-healing CMCS-OGA/GO@DOX hydrogel for localized breast cancer therapy. In the acidic tumour environment, the self-healing ability of the Schiff base bonds decreased, causing the structure of the hydrogel to collapse and allowing the GO@DOX to leak out through the swollen and enlarged pores, resulting in localized release of DOX in the tumour tissue for anti-tumour effects. [Display omitted] [ABSTRACT FROM AUTHOR]

Cinnamaldehyde exhibits excellent anti-mold properties that can preserve bamboo. However, establishing a stable bonding linkage (C N) requires cinnamaldehyde modification, which can be used to manipulate cell wall characteristics and improve bamboo durability. In this study, cinnamaldehyde's chemical fixation into bamboo through the Mannich reaction was successfully achieved, resulting in enhanced anti-mold capacity and dimensional stability. The modified bamboo exhibited remarkable anti-mold properties, with a 40.0% increase in resistance to swelling caused by moisture fluctuations. Nanoindentation analysis also revealed that the internal bamboo cell wall's mechanical properties improved following modification, including a significant improvement in surface hydrophobicity from 13.9° to 67.3°. Concerning the impact of the modification on bamboo cells, the sclerenchyma cell of bamboo was determined to be the focus. We used guaiacol as a lignin model compound to elucidate the potential mechanism of cinnamaldehyde modification, specifically Schiff base formation, using nuclear magnetic resonance spectra. This study shows a viable dual preservative strategy to extend bamboo lifespan. [Display omitted] • A novel approach to facilitating bamboo dual preservative strategy. • The Mannich reaction was successfully achieved, resulting in enhanced durability of bamboo. • The sclerenchyma cell of bamboo was determined to be the focus in the modification. [ABSTRACT FROM AUTHOR]

Polydimethylsiloxane (PDMS) is a biocompatible polymer that has been applied in many fields. However, the surface hydrophobicity of PDMS can limit successful implementation, and this must be reduced by surface modification to improve biocompatibility. In this study, we modified the PDMS surface with a hydrogel and investigated the effect of this on hydrophilicity, bacterial adhesion, cell viability, immune response, and biocompatibility of PDMS. Hydrogels were created from hyaluronic acid and gelatin using a Schiff-base reaction. The PDMS surface and hydrogel were characterized using nuclear magnetic resonance, X-ray photoelectron spectroscopy, attenuated total reflection Fourier-transform infrared spectroscopy, and scanning electron microscopy. The hydrophilicity of the surface was confirmed via a decrease in the water contact angle. Bacterial anti-adhesion was demonstrated for Pseudomonas aeruginosa, Ralstonia pickettii, and Staphylococcus epidermidis, and viability and improved distribution of human-derived adipose stem cells were also confirmed. Decreased capsular tissue responses were observed in vivo with looser collagen distribution and reduced cytokine expression on the hydrogel-coated surface. Hydrogel coating on treated PDMS is a promising method to improve the surface hydrophilicity and biocompatibility for surface modification of biomedical applications.

A new class of injectable, biocompatible and biodegradable hydrogel is reported. This hydrogel is derived from N-succinyl chitosan (SCS) mixed with water-soluble dialdehyde starch (DAS) without using a conventional chemical crosslinker. The hybrid hydrogel is formed owing to the Schiff’s base reaction between amine groups of SCS and dialdehyde groups of DAS to form CHN group. SCS, DAS, and SCS–DAS hybrid hydrogels were synthesized and then characterized by FTIR analysis spectroscopy. The influence of SCS:DAS ratio in hybrid polymers solution on physicochemical properties of resultant hydrogels (e.g. gelation time, gel fraction (%) and equilibrium swelling ratio), surface morphology, in vitro weight loss (%), and mechanical stability was examined. The results demonstrated that SCS content has a profound role for forming tighter crosslinked hybrid hydrogels, where the increase of SCS content reduces the time for hydrogel forming. Also, the water uptake and hydrolytic weight loss decrease. Meanwhile, the DAS content increases, and mechanical properties of SCS–DAS hybrid hydrogels decrease. Curcumin release profile and adhered HGF cells on hydrogel surface sharply influenced the SCS portion in hybrid hydrogel composition. The SCS–DAS hybrid hydrogel properties afforded a possible opportunity to be used as a covalent in situ forming hybrid hydrogels in biomedical applications such as, tissue engineering and cartilage repair.

A new hydrazone bond covalent organic polymer (BTH-PD-COP) was well designed and successfully synthesized based on the principle of Schiff-base reaction and the concept of reticular chemistry with 1,3,5-Benzenetricarbohydrazide (BTH) and 1,4-phthalaldehyde (PD) as organic monomers. The structure and properties of BTH-PD-COP materials were characterized by Fourier transform infrared spectroscopy (FT-IR), 13C solid state NMR, scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and thermogravimetric analysis (TGA). The results show that the BTH-PD-COP material has excellent physical and chemical properties. [ABSTRACT FROM AUTHOR]

To obtain a safe and biodegradable material for food packaging, this study developed a facile and green process of anchoring nisin onto oxidized cellulose through a simple Schiff base reaction for long-term antimicrobial active food packaging. To the best of our knowledge, this is the first report of such a packaging. The grafting reaction between the amino groups of nisin and the aldehyde groups of oxidized cellulose films was successfully established to obtained a nisin anchored cellulose films (NC) membrane; the structure was characterized with Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis. The NCs membrane had an outstanding transparent property of above 90% transmittance through 300 nm to 800 nm; while, the barrier properties against oxygen remain excellent. The thermal stability of the NCs membrane remained excellent and enabled an easier degradation than the original cellulose membrane. The NCs membrane displayed good antimicrobial activity against Alicyclobacillus acidoterrestris DSM 3922T in a long-term way, thus demonstrating good potential as food packaging material. The obtained results are promising and confirm the development of NCs membranes as green materials for food packaging. [ABSTRACT FROM AUTHOR]

In this study, pH-sensitive in situ gelling hydrogels based on oxidized alginate and gelatin-containing doxorubicin (DOX) loaded chitosan/gold nanoparticles (CS/AuNPs) nanogels were fabricated via Schiff-base bond formation. The obtained CS/AuNPs nanogels indicated a size distribution of about 209 nm with a zeta potential of +19.2 mV and an encapsulation efficiency of around 72.6 % for DOX. The study of the rheological properties of hydrogels showed that the value of G' is higher than G″ for all hydrogels, which confirms the elastic behavior of hydrogels in the applied frequency range. The rheological and texture analysis demonstrated the higher mechanical properties of hydrogels containing β-GP and CS/AuNPs nanogels. The release profile of DOX after 48 h indicates the 99 % and 73 % release amount at pH = 5.8 and pH = 7.4, respectively. MTT cytotoxicity study showed that the prepared hydrogels are cytocompatible on MCF-7 cells. By the Live/Dead assay, it was demonstrated that the cultured cells on DOX-free hydrogels were almost alive in the presence of CS/AuNPs nanogels. However, the hydrogel-containing drug and free DOX in the same concentration caused high death of MCF-7 cells as expected, which showed the potential of the developed hydrogels for application in the local treatment of breast cancer. [Display omitted] [ABSTRACT FROM AUTHOR]

• A hydrophobic NH 2 -UiO-66@H COF hybrid was successfully fabricated and explored as a promising SPE sorbent. • The NH 2 -UiO-66@H COF hybrid exhibited better extraction performance than NH 2 -UiO-66 and H COF via synergistic effects. • A sensitive detection method was established for analysis of flavonoids in food samples. Metal-organic framework (MOF) and covalent organic framework (COF) exhibit excellent extraction performance in sample pretreatment, but their wider application is hindered by some inherent drawbacks. Herein, we successfully synthesized a novel MOF@COF hybrid material with large specific surface area, good chemical stability and reusability, which is suitable as a solid phase extraction (SPE) sorbent for the efficient extraction of flavonoids. Importantly, due to the synergistic effect, the obtained MOF@COF hybrid material showing a higher extraction efficiency than individual MOF and COF. This is mainly due to the obtained MOF@COF hybrid material combines the high specific surface area of MOF and multiple interactions (hydrophobic interaction, hydrogen bonding and π-π stacking interaction) with flavonoids conferred by the COF structure. Then, a sensitive analytical method for flavonoids with ideal linear range (1–500 ng mL−1), low detection limit (0.15–0.41 ng mL−1) and good repeatability (2.64–6.20%) was developed under optimized conditions. In addition, the MOF@COF hybrid sorbent has better selectivity for hydrophobic targets containing multiple hydrogen bond acceptors/donors. Finally, the established method was applied to the determination of flavonoids in different food samples, and satisfactory recoveries (81.4–102.1%) were obtained, which initially confirmed its applicability. [ABSTRACT FROM AUTHOR]

A new class of injectable, biocompatible and biodegradable hydrogel is reported. This hydrogel is derived from N-succinyl chitosan (SCS) mixed with water-soluble dialdehyde starch (DAS) without using a conventional chemical crosslinker. The hybrid hydrogel is formed owing to the Schiff’s base reaction between amine groups of SCS and dialdehyde groups of DAS to form CH N group. SCS, DAS, and SCS–DAS hybrid hydrogels were synthesized and then characterized by FTIR analysis spectroscopy. The influence of SCS:DAS ratio in hybrid polymers solution on physicochemical properties of resultant hydrogels ( e.g. gelation time, gel fraction (%) and equilibrium swelling ratio), surface morphology, in vitro weight loss (%), and mechanical stability was examined. The results demonstrated that SCS content has a profound role for forming tighter crosslinked hybrid hydrogels, where the increase of SCS content reduces the time for hydrogel forming. Also, the water uptake and hydrolytic weight loss decrease. Meanwhile, the DAS content increases, and mechanical properties of SCS–DAS hybrid hydrogels decrease. Curcumin release profile and adhered HGF cells on hydrogel surface sharply influenced the SCS portion in hybrid hydrogel composition. The SCS–DAS hybrid hydrogel properties afforded a possible opportunity to be used as a covalent in situ forming hybrid hydrogels in biomedical applications such as, tissue engineering and cartilage repair. [ABSTRACT FROM AUTHOR]

[Display omitted] • An ultra-small hydrazone-linked covalent organic polymer (UHCOP) was synthesized. • UHCOP presented good stability and strong fluorescence in aqueous solution. • UHCOP is promising as fluorescent sensor for Fe3+detection in aqueous solution. A novel ultra-small hydrazone-linked covalent organic polymer (UHCOP) was synthesized based on the Schiff-base reaction between 2,4,6-trihydroxy-1,3,5-benzenetricarbaldehyde and 1,4-benzenedicarbohydrazide at room temperature and utilized as a sensitive fluorescent sensor for rapid (<2 min) and selective detection of Fe3+ in aqueous solution. The prepared UHCOP displayed ultra-small size with the diameter of 7.98 ± 0.97 nm and gave a stable fluorescent emission at 510 nm. UHCOP exhibited good sensitivity and highly selectivity towards Fe3+. The coordination interaction between UHCOP and Fe3+ resulted in the obviously aggregation-caused quenching response of UHCOP. The linear range was from 5.0 μM to 1.4 mM (R2 = 0.999) with the detection limit of 2.5 μM. Finally, UHCOP has been successfully applied in the detection of Fe3+ in real water samples, proving the fabricated UHCOP is promising as a sensitive fluorescent sensor for selective detection of Fe3+ in aqueous solution. [ABSTRACT FROM AUTHOR]

Bigels were formed by using glycerol monolaurate, MCT and cinnamaldehyde as the oil phase and chitosan as the aqueous phase. Oil and aqueous phase was gelled by the self-assembly of glycerol monolaurate, and cross-linking of cinnamaldehyde droplets with chitosan, respectively. [Display omitted] • Bigels were produced using plant-based ingredients and dual gelling method. • Chitosan crosslinking by cinnamaldehyde contributed to gel formation. • Covalent crosslinks modulated the structure and properties of bigels. • Cream was simulated with good texture and speadability. In this study, chitosan-based bigels were fabricated, where glycerol monolaurate was added in MCT oil to produce a gelled lipid phase and cinnamaldehyde was included in the lipid phase in order to act as a crosslinking agent. The synergistic effect of pH on chemical crosslinking effects was investigated. The potential of using these bigels as an alternative to cream was also investigated. The pH of the aqueous phase played an important role in controlling the extent of the Schiff-base reaction promoted by cinnamaldehyde. At pH 3.8, the bigels formed were homogenous but at pH 5.0 and 5.5 they exhibited phase separation, which highlighted the importance of chemical crosslinking. To better mimic the properties of real cream, span 80 was added to create a more homogeneous and smoother structure of the bigels. These bigels might provide a healthy and more sustainable alterative to food products that contain plastic fats, like cream. [ABSTRACT FROM AUTHOR]

Two covalent organic frameworks (COFs), as the supports of transition metal catalysts, were prepared and coordinated with nickel to synthesize two precatalysts for ethylene oligomerization. The chemical structure of sub-constructing unit had a significant influence on the specific surface area and the catalytic performance of covalent organic frameworks supported nickel(Ⅱ) catalysts. Two COFs were stacked in lamellae, and the specific surface area and the pore volume of COF with p -phthalaldehyde as sub-constructing unit were far larger than those of COF with butanedione as sub-constructing unit. The catalyst with a larger specific surface area had a higher catalytic activity and a higher selectivity of low carbon olefins in ethylene oligomerization because of a higher specific surface areas and larger pore structure for ethylene diffusion and mass transfer. Two catalysts can be reused at least three times without considerable loss in the catalytic activity and the selectivity toward short-chain α-olefins. Two covalent organic frameworks, as the supports of transition metal catalysts, were prepared and coordinated with nickel to synthesize two precatalysts for ethylene oligomerization in the presence of methylaluminoxane (MAO). The chemical structure of the sub-constructing unit had a significant influence on the specific surface area and the catalytic performance of covalent organic frameworks supported Ni(Ⅱ) catalysts. The main oligomers of the two catalysts were C 4 –C 6 α-olefins in cyclohexane and the catalytic properties of Ni@MAPA-COF were superior to Ni@MABD-COF because of the higher nickel content and the larger specific surface area. [Display omitted] • Two COFs were prepared and further coordinated with nickel(Ⅱ) to synthesize precatalysts for ethylene oligomerization. • Sub-constructing unit would affect the textural properties of catalysts for specific surface area and coordination mode. • Catalyst with larger specific surface area exhibited the predominant selectivity toward C 4 –C 6 (1-C 4 /C 6 , >82%). • Two catalysts can be reused three times without considerable loss in ethylene oligomerization. • Postulated catalytic cycle for ethylene oligomerization catalyzed by Ni@MABD/MAPA-COF was proposed. [ABSTRACT FROM AUTHOR]

Supramolecular self-assembly, an important strategy in nanotechnology, has been widely studied in the past two decades. In this review, we have introduced the recent progress on construction of two-dimensional (2D) nanostructures by host-guest supramolecular chemistry at solid-liquid interface, and the interactions between the host assembly and the guest molecules are the major concerns. At first, the hydrogen bonds connected hybrid structures are discussed. And then we have paid a close attention on the surface-confined condensation reactions that has flourished recently in direct preparing novel nanostructures with increasing structural complexity. In the end, the cavity confinement of the 2D supramolecular host-guest architectures has been studied. On the basis of the above-mentioned interactions, a group of functional hybrid structures have been prepared. Notably, scanning tunneling microscopy (STM), a unique technique to probe the surface morphology and information at the single molecule level, has been used to probe the formed structures on highly oriented pyrolytic graphite (HOPG) surface. [ABSTRACT FROM AUTHOR]

Abstract: The fast, sensitive detection for 6 aromatic amines and direct observation of intermediates of Schiff-base reactions were achieved through reactive desorption electrospray ionization mass spectrometry (reactive DESI-MS). Pure acetone was electrosprayed to impact the aromatic amines on the paper, allowing two reactions, a proton-transfer reaction and a Schiff-base reaction, to occur in these experiments. The former was used to detect the aromatic amines, and the protonated analytes generated were selected for the qualitative and quantitative analysis. The false-positive signals were excluded by tandem mass spectrometry. For the 6 analytes, linear signal responses were obtained, and each had a dynamic range of 5 orders of magnitude. The relative standard deviation (RSD) and limit of detection (LOD) for all the measurements were in 1.5–5.3% and 0.03–0.2pg/mm2 range, respectively. The latter is a nucleophilic addition reaction that occurred between the aromatic amines and the acetone. The carbinolamine intermediates of these reactions were directly detected and identified by reactive DESI-MS. The data show that reactive DESI-MS is not only a reliable, sensitive tool for chemical analysis, but also a valid and promising method for studying organic reactions simultaneously, especially for heterogeneous reactions that occurred at a solution/solid interface. [Copyright &y& Elsevier]

To overcome the efficiency-cytotoxicity dilemma of native PEI and incorporate the advantages of alginate, we designed a novel gene vector by grafting PEI 2000 onto alginate, an anionic polysaccharide with excellent biocompatibility. The alginate-graft-PEI (Alg-g-PEI) was successfully synthesized and then characterized by elemental analysis, 1H-NMR and 13C-NMR. The Mw of Alg-g-PEI is ca. 17 000. Acid-base titration confirmed that Alg-g-PEI retained the buffering capacity of native PEI. The DNA binding ability of the polymer was confirmed by gel retardation assay. DSL analysis showed that Alg-g-PEI had a particle size and zeta-potential similar to PEI 25K. AFM detected a clear and well-shaped morphology of the complexes. Additionally, Alg-g-PEI exhibited lower cytotoxicity than PEI 25K in BEL7402, MSC and RVMSC cells. Compared with PEI 25K, Alg-g-PEI had comparable or even higher transfection efficiency. Similarly, Alg-g-PEI-mediated VEGF expression was significantly higher compared with PEI 25K-mediated VEGF expression. All together, our results suggest that Alg-g-PEI has a potential to be a safe and efficient agent for gene therapy. [ABSTRACT FROM AUTHOR]

[Display omitted] • - A novel PEI-functionalized microcapsules were fabricated. • - The simple heating process creates thermal-induced microcracks at the shell. • - PMs exhibit high adsorption capacity for Cu2+, Cd2+, and Zn2+. • - Reusability of PMs was maintained at a high level of 80% after 5 cycles. • - PMs can be readily recovered by external magnetic-field after adsorption. Herein, amino-functionalized monodisperse polymeric microcapsules were prepared via Schiff-base reaction between polyethyleneimine (PEI) and glutaraldehyde (GA) using a microfluidic approach. The GA encapsulated in the microcapsules leaked through thermal-induced microcracks at the shell of the microcapsules, and then the leaked GA caused crosslinking of the PEI molecules onto the shell without any further treatments. The success of amino-functionalization and the surface morphology of the microcapsules were demonstrated by Fourier transform infrared spectroscopy, scanning electron microscopy, and optical microscopy. Due to the presence of abundant amine groups in the PEI molecules on the shell, the amino-functionalized microcapsules serve as an effective adsorbent for heavy metal ions (HMI). The as-prepared microcapsules were evaluated as adsorbents to remove Cu2+, Cd2+, and Zn2+ ions from the aqueous solution under varying process parameters such as pH, contact time, and metal ion concentration. The adsorption capacity of the microcapsules for Cu2+, Cd2+, and Zn2+ was measured and fitted using the Sips isotherm model. After completion of HMI adsorption, the microcapsules were readily separated from the aqueous suspension by an external magnetic field. In addition, the cyclic adsorption–desorption efficiency of the amino-functionalized microcapsules was almost maintained for five times. [ABSTRACT FROM AUTHOR]

In this work, a polymer precursor was first synthesized using p -terphenyl (TP) and terephthaloyl chloride (TC) as monomers. Then, cross-linking was realized by means of a Schiff base reaction with melamine (MA) as a modifier to obtain an amine-functionalized porous organic polymer TP-TC-MA. The synthesized polymers were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), and point of zero charge (pH pzc ) measurements, as well as on the basis of nitrogen adsorption-desorption isotherms. Adsorption experiments were carried out to evaluate the adsorption properties of TP-TC-MA for methyl orange (MO), a typical anionic azo dye that has widespread industrial application. The amount of MO adsorbed on TP-TC-MA was evaluated by ultraviolet-visible (UV-Vis) spectroscopy at a wavelength of 463 nm. Microscopic analysis revealed that the as-synthesized polymer had an aggregated particle-shaped structure. XRD spectra confirmed that TP-TC-MA was an amorphous polymer, consistent with the results of high-resolution TEM experiments. The Brunauer-Emmett-Teller (BET) specific surface area and total pore volume of TP-TC-MA were determined as 708.5 m 2 /g and 0.556 cm 3 /g, respectively. The measured pH pzc of TP-TC-MA was 4.0, probably because of the abundant nitrogen-containing groups provided by MA. The factors affecting adsorption, such as pH, adsorbent dosage, contact time, initial pollutant concentration, and ionic strength, were investigated. Because of the protonation of the N-atom in TP-TC-MA, the pH had a strong impact on the adsorption of MO. The removal efficiency could be maximized at the optimized pH of 3.0. The adsorption equilibrium isotherm, measured at 25 ℃ and a concentration of 50-500 mg/L, showed that the MO adsorption over TP-TC-MA followed the Langmuir isotherm, with a maximum adsorption capacity of 156.3 mg/g. The modeling of the experimental adsorption data was consistent with the pseudo-second-order kinetic model, which indicated fast adsorption and chemisorption as the dominant mechanism. With increasing ionic strength, the adsorption of MO slightly decreased, suggesting a partial antagonistic ion effect. Results of the selectivity study revealed that TP-TC-MA was more selective toward MO than methylene blue (MB), which indicated that electrostatic interactions played a significant role during the adsorption progress. Five adsorption-desorption cycles showed that TP-TC-MA could be regenerated without significant deterioration of its adsorption efficiency, indicating that it has good stability and reusability. The observed adsorption performance indicated that this MA-modified porous organic polymer offers prospects for further research and application in the treatment of dye-containing wastewaters.

Polydimethylsiloxane (PDMS) is a biocompatible polymer that has been applied in many fields. However, the surface hydrophobicity of PDMS can limit successful implementation, and this must be reduced by surface modification to improve biocompatibility. In this study, we modified the PDMS surface with a hydrogel and investigated the effect of this on hydrophilicity, bacterial adhesion, cell viability, immune response, and biocompatibility of PDMS. Hydrogels were created from hyaluronic acid and gelatin using a Schiff-base reaction. The PDMS surface and hydrogel were characterized using nuclear magnetic resonance, X-ray photoelectron spectroscopy, attenuated total reflection Fourier-transform infrared spectroscopy, and scanning electron microscopy. The hydrophilicity of the surface was confirmed via a decrease in the water contact angle. Bacterial anti-adhesion was demonstrated for Pseudomonas aeruginosa, Ralstonia pickettii, and Staphylococcus epidermidis, and viability and improved distribution of human-derived adipose stem cells were also confirmed. Decreased capsular tissue responses were observed in vivo with looser collagen distribution and reduced cytokine expression on the hydrogel-coated surface. Hydrogel coating on treated PDMS is a promising method to improve the surface hydrophilicity and biocompatibility for surface modification of biomedical applications. [ABSTRACT FROM AUTHOR]

• Injectable AP-OC hydrogel was in-situ crosslinked without any chemical crosslinker. • Both of modified natural-polysaccharides were soluble in neutral solution. • Swelling and degradation property of AP-OC hydrogel can be tuned by its composition. • Amino site content in the hydrogel was crucial for good biocompatibility. • Hydrogel had desired gelation time and good biocompatibility for skin wound healing. Hydrogel can provide a favorable moisture environment for skin wound healing. In this study, a novel in-situ crosslinked injectable hydrogel was prepared using the water-soluble amidated pectin (AP) and oxidized chitosan (OC) through Schiff-base reaction without any chemical crosslinker. The influence of AP content on the properties of the hydrogel was systemically investigated. It showed that gelation time, pore structure, swelling capability and degradability of the hydrogel can be tuned by varying the content of amine and aldehyde groups from AP and OC. All the porous hydrogels with various AP contents (65%, 70%, and 80%) presented desirable gelation time, swelling property, high hemocompatibility and biocompatibility. Particularly, AP-OC-65 hydrogel presented superior swelling capability and better hemo- and bio-compatibility, owing to more residual amine sites in the hydrogel. Therefore, the injectable AP-OC-65 hydrogel has a greater potential for application to wound dressing or skin substitute. [ABSTRACT FROM AUTHOR]

• The porous organic polymer, 4AS-MBP, was prepared via a simple Schiff-base reaction. • The absorbent, 4AS-MBP, has excellent tolerance to harsh acidic and basic conditions. • 4AS-MBP displayed similar adsorption capacities over a wide pH range. • The relative selectivity coefficients of 4AS-MBP for Hg(II)/Metal(II) were in a range of 54.3–823. An efficient porous organic polymer (POP)-based adsorbent (4AS-MBP), synthesized from melamine, 4-allyloxy benzaldehyde and ethanedithiol (EDT) via a Schiff-base reaction and thiol–ene addition in a straightforward strategy, was prepared to remove Hg(II) ions from water. The chemical structure and morphology of 4AS-MBP were investigated by FT-IR, solid-state 13C NMR, EA, SEM, TEM and BET analysis. Adsorption experiments were conducted by varying the Hg(II) concentration, contact time and pH to study the adsorption kinetics and equilibrium. Mesoporous 4AS-MBP exhibited a maximum adsorption capacity of 312 mg g−1. The results indicated that Hg(II) adsorbed onto the adsorbent through monolayer chemisorption. Interestingly, 4AS-MBP was highly stable, even in the presence of 2 M NaOH or HCl, and displayed similar adsorption capacities over a wide pH range. Furthermore, the adsorbents could be reused at least five times without a loss of adsorption capacity. More importantly, the relative selectivity coefficients of 4AS-MBP for Hg()/Pb(II), Hg(II)/Cd(II), Hg(II)/Cu(II), Hg(II)/Zn(II) and Hg(II)/Mg(II) were 54.3, 221, 243, 468 and 823, respectively. [ABSTRACT FROM AUTHOR]

Transparent and flexible alginate-based membranes containing antibacterial drugs were prepared by a casting/solvent evaporation method from alginate solution mixed with chitosan floccule (CSF) and oxidized sodium alginate (OAlg). To improve the properties of the membranes, CSF and OAlg were added to the alginate solution in different ratios. The mechanism of membrane formation is attributed to two aspects: Schiff-base cross-linking between CSF and OAlg; ion cross-linking between sodium alginate and CaCl 2. The results showed that the incorporation of CSF and OAlg had a significant effect on the properties of the alginate membrane. With the change in the ratio between CSF and OAlg, the tensile strength, swelling rate, water vapor permeability, wettability and degradation stability of the membranes were significantly changed. In order to enhance the anti-bacterial properties, clindamycin (DA) and silver sulfadiazine (AgSD), which represent water-soluble and water-insoluble drug models, were integrated into the membrane, respectively. The results of controlled release effects and inhibition zones indicate that the alginate membranes containing drugs have a promising future in treatment of bacterial infection as wound dressing. Image 1 • A transparent and flexible alginate-based membrane was prepared. • Chitosan floccule improved the alginate membrane dressing. • Drugs enhanced the anti-bacterial properties of membrane dressing. [ABSTRACT FROM AUTHOR]

Paper chromatography (PC) is a highly flexible, fast, and efficient separation method. In this study, a chromatographic paper with a chiral separation function was investigated and a paper chromatographic method for chiral separation was developed. Single-factor experiments and orthogonal tests were used to determine the optimal oxidation conditions for filter paper. The optimal conditions were that sodium periodate 4% (mass percentage), pH 2 buffer solution, reaction temperature 45℃, and reaction time 4 h. Under the optimal conditions, the aldehyde group content of a dialdehyde-based filter paper was 57.93% (amount of substance percentage). A paper-based chiral separation material was synthesized by a microwave-assisted Schiff-base reaction of the oxidized filter paper with L-glutamic acid. The developing solvent for separating racemic tartaric acid using this chiral filter paper consisted of 100 mL of n -butanol, 50 mL of 50%(v/v) acetic acid, and 0.1000 g of bromophenol blue. The rate of flow ( R f ) values of L-tartaric acid and D-tartaric acid were 0.52 and 0.40, respectively. This method does not require large-scale equipment to perform the chiral separation and it is therefore suitable for general teaching, research, and industrial applications.