Diazoresin Research Articles

Chiral resolution of ketoprofen by modified polymethyl methacrylate microspheres

AbstractDue to unique structural characteristics and chiral environment, β‐cyclodextrin (β‐CD) has a strong chiral separation ability. 4‐Chlorophenyl isocyanate (4CPI) also plays an important role in separating chiral drugs. In this paper, a chiral stationary phase: 4‐CPI‐β‐CD stationary phase (4CPI‐β‐CD@PMMA) was designed and prepared. Polymethyl methacrylate (PMMA) microspheres with uniform particle size and good monodispersity were prepared by modified seed polymerization and seed expansion methods. Using diazo resin as a coupling agent, PMMA microspheres were connected with 4CPI‐β‐CD to prepare a stationary phase with chiral recognition ability. PMMA microspheres and 4CPI‐β‐CD were also characterized. Compared with the traditional silica gel column, PMMA microspheres have higher preparation efficiency, better monodispersity, and better mechanical properties as chromatographic fillers. Finally, the chiral separation of ketoprofen was carried out by reversed‐phase high‐performance liquid chromatography, and the separation conditions were optimized. This paper is a good idea for the preparation of the chiral stationary phase.

Perfluorooctanoic acid used as a new covalently bonded electrophoretic coating to analyze proteins

Functionally modified coated capillary is essential for reducing the nonspecific interaction between samples and analytical instruments and improving detection sensitivity and analytical efficiency. Here, we used perfluorooctanoic acid and diazo resin as raw materials, and bonded them to the inner wall of the capillary through the electrostatic interaction of the coupling agent to construct a self-assembled coating tube with anti-fouling properties. The dynamic adsorption test of fluorescent protein confirmed that the coating had obvious anti-protein adsorption effect. The coating was used for capillary electrophoresis (CE) analysis of four mixed protein standard samples and egg white samples. The excellent protein separation spectrum confirmed the application value of the coating.

Isocyanate‐chitin modified microspheres for chiral drug separation in high performance liquid chromatography

AbstractIn this work, a two‐step activated swelling technique was effectively employed to successfully synthesize monodisperse porous poly(styrene‐divinylbenzene) (PS‐DVB) particles. Diazoresin (DR) transform an ionic bond into a covalent bond by photoreaction. Under ultraviolet irradiation, DR was used to covalently attach dichlorophenyl isocyanate to sulfonated PS‐DVB microspheres. The novel photo‐crosslinking reaction effectively overcomes the toxicity issues associated with conventional coupling agents and enables green production of chromatographic fillers. Modified PS‐DVB particles were indeed commonly used as filler material for the separation of chiral compounds by high performance liquid chromatography (HPLC). The porous modified microspheres designed effectively separate benzoone, DL‐mandelic acid, 2‐phenylcyclohexanone, ibuprofen, 2‐hydroxyl flavone, DL‐cysteine, chloraniline maleate, hesperidin, and other chiral compounds by 100 mm column. It is noteworthy that the isocyanate‐chitin modified microspheres are effective in separating chiral drugs (1000 μg/mL) within 5 min. Compared with ordinary microspheres, porous isocyanate‐chitin modified microspheres showed better separation efficiency under the same conditions. The enhancement is attributed to the increase in their specific surface area. Consequently, they are a better choice of chromatographic packing matrix.

Short bridging and partial derivatization synergistically modified β-cyclodextrin bonded chiral stationary phases for improved enantioseparation

β-Cyclodextrin (β-CD) and its derivatives have been widely employed in the field of chiral separation, but they are still faced the limitation of low enantioselectivity and complex processes. Derivatization with functional molecules or preparation as bridging dimers are the two main modifications for β-CD to obtain chiral recognition compounds. Herein, a partially derived bridged β-CD (CPI-EBCD) bonded chiral stationary phases was prepared to improve enantioseparation. The chiral recognition moiety was synthesized by a bridged β-cyclodextrin dimer using a short-chain bridging agent (ethylenediamine) and then modifying the bridged cyclodextrin with a 4-chlorophenylisocyanate (CPI) containing a benzene ring and polar group. Compared with natural β-CD, dual-chambered CPI-EBCDs have better encapsulation synergies and more recognition sites with the guest molecule, while the short flexible bridging groups make the double cavities closer and more easily recognizable as linear molecules. The introduction of derived groups CPI provided more recognition sites and more types of interactions, including π-π interaction force, hydrogen bonding effect, and dipole-dipole interaction, thus improving the enantiomer-specific chirality recognition effect. The chiral stationary phase CPI-EBCDP was obtained by connecting CPI-EDCB with mesoporous silica microspheres by simple photochemical reaction using a green non-toxic diazo resin as coupling agent, simplifying preparation process. In the reversed phase mode of liquid chromatography, CPI-EBCDP has excellent chiral recognition ability, and 12 chiral compounds are successfully isolated by optimizing mobile phase conditions, with good reproducibility and stability. The successful preparation of this new chiral stationary phase provides an important reference for the subsequent development of cyclodextrin-like chiral stationary phases.

Self-assembly of carbon nanomaterials onto carbon fiber to improve the interfacial properties of epoxy composites

The interfacial property of carbon fiber (CF) reinforced composites is crucial to facilitate the application of high-strength composites. Utilizing the electrostatic and hydrogen bond properties of diazo resin, carbon nanotubes (CNTs) and graphene oxide (GO) could be quickly grafted onto the surface of the CF via the layer-by-layer self-assembly technique. The results showed that CNTs and GO were uniformly coated onto the CF surface, and the chemical activity and roughness of the modified CF surface were improved significantly. The modified CF surface can significantly augment the interaction between the epoxy resin and the fiber. Remarkably, due to the good interfacial property, the impact performance of the composites reinforced with the nanomaterial-modified CF was improved obviously. In addition, the interface properties of the composites are studied in depth. This method is expected to achieve rapid surface modification of carbon fiber.

Preparation and chromatographic application of β‐cyclodextrin modified poly (styrene‐divinylbenzene) microspheres

AbstractIn order to better realize the separation of chiral enantiomers and prevent chiral compounds with toxic side effects from causing harm to human beings, porous microspheres were modified to improve their chromatographic separation performance. In this paper, in order to verify the chromatographic performance of porous polymer microspheres, the precise and controllable synthesis of poly (styrene‐divinylbenzene) (PS‐DVB) microspheres was realized based on the two‐step swelling method. Then, the porous PS‐DVB microspheres were sulfonated with concentrated sulfuric acid. The sulfonated microspheres were grafted with diazo resin (DR), and then the 3,5‐dichlorobenzene isocyanate modified β‐cyclodextrin (β‐CD‐DCIPI) was bonded to the sulfonated PS‐DVB microspheres by the DR. Finally, the bond inversion occurred after UV irradiation. We have successfully solved the toxic effect of traditional coupling agents by using the unique photo‐crosslinking reaction of DR. This novel and environmentally friendly chromatographic packing can be used to separate chiral compounds. The results showed that all of the eight compounds (chlorpheniramine; ibuprofen; benzoin; 2‐phenylcyclohexanone; trans‐stilbene oxide; Cobalt [III] acetylacetonate; Hesperetin; DL‐Mandelic acid) can be separated. It is worth noting that the modified microspheres can achieve good separation of chiral compounds with the concentration of 1 mg/ml in 3 min.

The Effect of the Topmost Layer and the Type of Bone Morphogenetic Protein-2 Immobilization on the Mesenchymal Stem Cell Response.

Recombinant human bone morphogenetic protein-2 (rhBMP-2) plays a key role in the stem cell response, not only via its influence on osteogenesis, but also on cellular adhesion, migration, and proliferation. However, when applied clinically, its supra-physiological levels cause many adverse effects. Therefore, there is a need to concomitantly retain the biological activity of BMP-2 and reduce its doses. Currently, the most promising strategies involve site-specific and site-directed immobilization of rhBMP-2. This work investigated the covalent and electrostatic binding of rhBMP-2 to ultrathin-multilayers with chondroitin sulfate (CS) or diazoresin (DR) as the topmost layer. Angle-resolved X-ray photoelectron spectroscopy was used to study the exposed chemical groups. The rhBMP-2 binding efficiency and protein state were studied with time-of-flight secondary ion mass spectrometry. Quartz crystal microbalance, atomic force microscopy, and enzyme-linked immunosorbent assay were used to analyze protein–substrate interactions. The effect of the topmost layer was tested on initial cell adhesion and short-term osteogenesis marker expression. The results show the highest expression of selected osteomarkers in cells cultured on the DR-ended layer, while the cellular flattening was rather poor compared to the CS-ended system. rhBMP-2 adhesion was observed only on negatively charged layers. Cell flattening became more prominent in the presence of the protein, even though the osteogenic gene expression decreased.

Synthesis of 3,5-dichlorobenzene isocyanate-derived β-cyclodextrin and 3,5-dimethyl phenyl isocyanate-derived β-cyclodextrin chiral stationary phases and their applications in the separation of chiral compounds

β-Cyclodextrin (β-CD) has a unique three-dimensional structure and chemical properties, and has a strong chiral separation ability. In this study, we linked 3,5-dichlorobenzene isocyanate to β-cyclodextrin and named this newly synthesized molecule β-CD-DCIPI. 3,5-Dimethylbenzene isocyanate was attached to β-cyclodextrin and named β-CD-DPIC. A modified polymerization-induced colloidal aggregation (PICA) method and self-made silica sol were used to synthesize mesoporous silica microspheres with a particle size of 2.38 μm-5.51 μm. A green non-toxic diazoresin (DR) is used as a coupling agent, which is connected to the surface of silica microspheres through electrostatic interaction. After ultraviolet light irradiation, ionic bonds are transformed into covalent bonds, and a new chiral stationary phase with chiral separation properties (β-CD-DCIPI@SiO2 and β-CD-DPIC@SiO2) is constructed. This article first characterizes the properties of mesoporous silica microspheres and β-CD-DCIPI@SiO2 and β-CD-DPIC@SiO2. Through reversed-phase high-performance liquid chromatography (RP-HPLC), the separation performance of two new chiral stationary phases in chiral compounds was explored and compared, and five chiral enantiomers were effectively separated.

Preparation and application of urea-based derivatized β-cyclodextrin chiral stationary phase based on diazotized silica microspheres

Recently, the design and development of efficient chiral stationary phases is still the core and goal of chiral chromatography. In order to quickly separate chiral drugs, we designed and prepared an environmentally friendly small particle chiral stationary phase: p-methylphenylurea-β-cyclodextrin chiral stationary phase (SiO2@PMPU-β-CD). Firstly, p-methylphenylurea-β-cyclodextrin (PMPU-β-CD) was connected to the surface of mesoporous silica microspheres by diazoresin (DR) to prepare a SiO2@PMPU-β-CD. In reverse elution mode, the column temperature was set at 25 °C, the flow rate was 0.2 mL/min, and ACNH2O (v/v = 70:30) was used as the elution condition of the mobile phase. The enantiomers of chlorpheniramine maleate, 2-phenylcyclohexanone, and promethazine were separated within 5 min. In addition, the addition of TEAA buffer to the mobile phase improved the enantiomer resolution of chlorpheniramine maleate from 1.03 to 5.69. The experimental results show that the SiO2@PMPU-β-CD column can be used for the separation of appellant chiral drugs with good repeatability, and the use of DR instead of silane coupling agent has the advantages of being non-toxic, environmentally protected, and easy to operate, which is of great significance for the development of chiral stationary phase.

Fabrication of Humidity-Resistant Optical Fiber Sensor for Ammonia Sensing Using Diazo Resin-Photocrosslinked Films with a Porphyrin-Polystyrene Binary Mixture.

Ammonia gas sensors were fabricated via layer-by-layer (LbL) deposition of diazo resin (DAR) and a binary mixture of tetrakis(4-sulfophenyl)porphine (TSPP) and poly(styrene sulfonate) (PSS) onto the core of a multimode U-bent optical fiber. The penetration of light transferred into the evanescent field was enhanced by stripping the polymer cladding and coating the fiber core. The electrostatic interaction between the diazonium ion in DAR and the sulfonate residues in TSPP and PSS was converted into covalent bonds using UV irradiation. The photoreaction between the layers was confirmed by UV-vis and Fourier transform infrared spectroscopy. The sensitivity of the optical fiber sensors to ammonia was linear when exposed to ammonia gases generated from aqueous ammonia solutions at a concentration of approximately 17 parts per million (ppm). This linearity extended up to 50 ppm when the exposure time (30 s) was shortened. The response and recovery times were reduced to 30 s with a 5-cycle DAR/TSPP+PSS (as a mixture of 1 mM TSPP and 0.025 wt% PSS in water) film sensor. The limit of detection (LOD) of the optimized sensor was estimated to be 0.31 ppm for ammonia in solution, corresponding to approximately 0.03 ppm of ammonia gas. It is hypothesized that the presence of the hydrophobic moiety of PSS in the matrix suppressed the effects of humidity on the sensor response. The sensor response was stable and reproducible over seven days. The PSS-containing U-bent fiber sensor also showed superior sensitivity to ammonia when examined alongside amine and non-amine analytes.

Synthesis and enantioseparation characteristics of a novel β-cyclodextrin chiral stationary phase based on diazotized silica in HPLC

A novel chiral selector polyacrylic acid-β-cyclodextrin (PAA-β-CD) was successfully prepared, then a facile synthesis of PAA-β-CD stationary phase based on diazotized silica was developed and characterized. Monodisperse silica microspheres were synthesized by a modified Stöber method. The obtained silica particles were functionalized by self-assembly positive charged photosensitive diazoresin (DR) and PAA-β-CD on the surface. The corresponding chiral stationary phase (CSP) was used in HPLC and the enantioseparation performance was investigated in both polar organic and reverse phase mode. Better separation abilities and excellent enantio-selectivities were obtained on PAA-β-CD CSP for antihistamine drugs in the acetonitrile and triethylammonium acetate buffer mobile phase. Abbreviations: AIBN: azodiisobutyronitrile; β-CD: b-cyclodextrin; β-CD-NH2: amino-β-CDcyclodextrin; β-CD-OTs: sulfonyl-b-cyclodextrin; CD: cyclodextrin; CSP: chiral stationary phase; DCC: dicyclohexyl carbimide; DR: diazoresin; MeOH: methanol; NMP: N-methyl pyrrolidone; PAA: polyacrylic acid; PAA-β-CD: polyacrylic acid-β-cyclodextrin; TEAA: triethylammonium acetate; TEOS: tetraethyl orthosilicate

Study on acidified carbon nanotubes modified polyacrylonitrile hollow fiber membrane

In this paper, the adsorption capacity of CNT modified polyacrylonitrile (PAN) film on copper ions under different conditions was studied by the adsorption experiment of the prepared multilayer diazo resin acidified carbon nanotubes/PAN composite film. The concentration of copper ion solution before and after adsorption was measured by inductively coupled plasma (ICP). The results show that the adsorption capacity of the pan film modified by CNT increases first and then reaches the adsorption equilibrium with the increase of the adsorption time of copper ion, and the adsorption capacity of the pan film modified by CNT increases with the increase of the initial concentration of copper ion and the external temperature With the increase of solution pH, the adsorption capacity of CNT modified polyacrylonitrile membrane to copper ion increases first and then decreases; after multiple desorption/adsorption of the modified membrane which has reached adsorption equilibrium, the membrane still has CNT adsorption capacity to copper ion, indicating that the membrane has excellent recycling performance.

Diazo Resin and Acidified Carbon Nanotube Modified Polyacrylonitrile Hollow Fiber Membrane

In this paper, multilayer diazo resin acidified nanotubes/polyacrylonitrile composite films were prepared by grafting diazo resin (DR) and acidified carbon nanotubes (CNT) onto the surface of commercial PAN hollow fiber films by layer by layer self-assembly method. Scanning electron microscopy (SEM), infrared spectroscopy, contact angle, thermogravimetry (TG), water flux and adsorption of heavy metals were used to study. The results showed that the diazo resin (DR) and acidified carbon nanotubes (CNT) were successfully grafted onto PAN Membrane by layer by layer self-assembly method, and carbonyl and carboxyl groups appeared on the surface of modified PAN Membrane; the layer by layer self-assembly did not damage the original morphology of PAN membrane; the hydrophilicity of modified PAN-(DR-CNT)3 membrane was improved, and the water flux was increased. The PAN membrane before and after modification has similar heat and weight loss, and the PAN membrane before and after modification has good thermal stability; the PAN membrane after modification can reach adsorption equilibrium in a relatively short time, and has good adsorption performance for heavy metal copper ions.

Thermally Responsive Anti‐Protein Adsorption Coated Capillary for Electrophoretic Analysis of Proteins

AbstractA thermal responsive and reusable capillary column coated with poly (ethylene glycol) diacrylate dithiothreitols (PEGDA‐DTT‐dithiols) was prepared using photosensitive diazo resin (DR) as a coupling agent. DR and PEGDA‐DTT‐dithiols film were self‐assembled on the inner surface of silica capillary with hydrogen bonding. Due to the photo‐sensitive effect of DR, the coating will be covalently cross‐linked under ultraviolet light irradiation, the application of photosensitive DR can provide a simple and environmentally friendly strategy for preparing covalently coated capillaries. PEGDA‐DTT‐dithiols coated column, which not only separates the baseline of the four mixed model proteins, but also has good separation effect on real samples, showing excellent anti‐protein adsorption performance. The thermal responsive capillary coating can be cleaned up and regenerated facilely with a heating treatment after the column was contaminated by proteins and reused without reducing efficiency. The thermal responsive PEGDA‐DTT‐dithiols coated capillary has the advantages of environmental friendliness and recycling.

Analysis of proteins by capillary electrophoresis with a novel diazoresin/β-Cyclodextrin covalent capillary coating method

In this paper, we report on a successful development and application of diazoresin (DR)/β-Cyclodextrin covalently linked capillary coatings using the layer by layer (LBL) self-assembly technique combined with photochemistry reactions. The modified capillary remarkably suppressed the protein adsorption on the inner surface of silica capillary and successfully separated lysozyme (Lys), myoglobin (Mb), bovine serum albumin (BSA) and ribonuclease A (RNase A). Furthermore, the DR/β-Cyclodextrin covalently linked capillary coatings showed good stability and repeatability. More importantly, this method is more environmentally friendly and simpler than traditional methods for the use of DR instead of highly toxic and moisture-sensitive silane coupling agent.

Study on Graphene Oxide-Modified Polyacrylonitrile Hollow Fiber Membrane

In this paper, a multilayer diazo resin-graphene oxide/polyacrylonitrile composite membrane was prepared by layer-by-layer self-assembly and UV-induced modification of commercial polyacrylonitrile (PAN) hollow fiber membranes grafted with diazo resin (DR) and graphene oxide (GO). Scanning electron microscopy (SEM), infrared spectroscopy, contact angle, thermogravimetric analysis (TG), water flux and adsorption properties of heavy metals were studied. The results showed that diazo resin (DR) and graphene oxide (GO) were successfully grafted onto PAN membranes by layer-by-layer self-assembly. Carbonyl and carboxyl groups appeared on the surface of the modified PAN membranes; layer-by-layer self-assembly modification did not destroy the original morphology of PAN membranes, resulting in smaller pore size and higher surface roughness; hydrophilicity of the modified PAN-(DR-GO)3 membranes. The contact angle of pure water decreases from 87.8 degrees to 55.5 degrees, and the water flux increases from 733.30 g.m−1.h−1 to 1250.48 g.m−1.h−1. The thermo gravimetric curves of PAN films before and after modification did not change significantly, and the PAN films before and after modification had good thermal stability. The modified PAN membrane can achieve adsorption equilibrium in a relatively short time, and has good adsorption performance for heavy copper ions, with the adsorption rate as high as 92%.

Chitosan composite hydrogels cross-linked by multifunctional diazo resin as antibacterial dressings for improved wound healing.

Skin lesions and injuries can increase the risk of pathogen infections. Developing efficacious wound dressings could effectively prevent bacterial infection and accelerate wound healing. Herein, we developed chitosan composite hydrogels cross-linked by multifunctional diazo resin (DR) as antibacterial dressings for improved wound healing. The composite hydrogels were in situ formed by electrostatic interactions, chelation interactions, and covalent bonds between carboxylated chitosan and DR under ultraviolet assisted without small photosensitizer. The resultant hydrogels (noted as DR-CCH) showed good stability at different DR concentrations in physiological buffers. The antibacterial assays showed the DR-CCH could inhibit and kill Escherichia coli and Staphylococcus aureus. What is more, our hydrogels could accelerate wound healing in vivo. The present study demonstrates this composite DR-CCH with trace zinc has potential for accelerated wound healing.

Preparation of porous sulfonated poly(styrene-divinylbenzene) microspheres and its application in hydrophilic and chiral separation

Monodisperse cross-linked poly (styrene-divinylbenzene) (P(S-DVB)) porous microspheres with a particle size of about 10 μm were obtained by using the improved two-step seed swelling polymerization method. The influence of different crosslinking degree on specific surface area of porous microparticles was carefully investigated. The surface morphology and pore structure of seed microspheres and porous microspheres were characterized by scanning electron microscopy (SEM), accelerated surface area and porosimetry analyzer. Porous P(S-DVB) microparticles were sulfonated and used as a hydrophilic column packing material for high performance liquid chromatography (HPLC). The separation of oxalic acid, formic acid, acetic acid and acrylic acid was achieved by using the sulfonated-P(S-DVB) particles as packing materials in HPLC. The back pressure of sulfonated-P(S-DVB) column could be maintained at especially low level even at high flow rates due to the excellent permeability of the fillers. Moreover, the separation of chiral drugs was successfully carried out by using the chitosan coated sulfonated-P(S-DVB) microspheres as a column packing material in HPLC. By using water soluble non-toxic photosensitive diazoresin (DR) as linker, a green and facile way to modify packing materials was developed.

A novel diazoresin/polystyrene-poly(ethylene oxide) covalent capillary coating for the analysis of proteins by capillary electrophoresis

A novel method for the preparation of covalently linked capillary coatings of polystyrene-poly (ethylene oxide) (PS-PEO) was demonstrated by using photosensitive diazoresin (DR) as coupling agents. Layer by layer (LBL) self-assembly membrane of DR and PS-PEO based on hydrogen bonding firstly was fabricated on the inner wall of capillary, then with the treatment of UV light through the unique photochemistry reaction of DR, the hydrogen bonding was converted into covalent bonding. The covalently bonded coatings have the ability of inhibiting protein adsorption on the inner surface of capillary, and thus a baseline separation of Lysozyme (Lys), cytochrome c (Cyt-c), bovine serum albumin (BSA), ribonuclease A (RNase A) and myoglobin (Mb) was achieved by using capillary electrophoresis (CE). Compared with bare capillary or non-covalently bonded DR/PS-PEO coatings, the covalently linked DR/PS-PEO capillary coatings improved the CE separation performance for proteins; what’s more, it exhibited good stability and repeatability. This method can provide a green and easy way to make the covalently coated capillaries for CE, replacing of the old way which using highly toxic and moisture sensitive silane coupling agent by DR in the covalent coating preparation.

Preparation of hydroxypropyl cellulose-poly (2-Methacryloyloxyethyl phosphorylcholine) coating for the analysis of proteins by capillary electrophoresis

We reported a new method for preparing coated capillaries in this paper. First, we combined hydroxypropyl cellulose (HPC) and 2-Methacryloyloxyethyl phosphorylcholine (MPC) to form hydroxypropyl cellulose-poly (2-Methacryloyloxyethyl phosphorylcholine) (HPC-PMPC) by atom transfer radical polymerization (ATRP). Then the photosensitive polymer diazoresin (DR) was used as a linker to the inner wall of the capillary, and finally exposed to ultraviolet light to form a stable covalent bond coating. Protein adsorption on the inner surface of capillary was effectively inhibited. The cytochrome c (Cyt-c), lysozyme (Lys), ribonuclease A (RNase A) and bovine serum albumin (BSA) were separated obviously using capillary electrophoresis (CE) within 15 minutes and showed good stability and repeatability.