Polydopamine-based permanent coating capillary electrochromatography for auxin determination

Sulfonic Functionalized Polydopamine Coatings with pH-Independent Surface Charge for Optimizing Capillary Electrophoretic Separations

Enhancing the pH-independence and controlling the magnitude of electroosmotic flow (EOF) are critical for highly efficient and reproducible capillary electrophoresis (CE) separations. Herein, we present a novel capillary modification method utilizing sulfonated periodate-induced polydopamine (SPD) coating to achieve pH-independent and highly reproducible cathodic EOF in CE. The SPD-coated capillaries were obtained through post-sulfonation treatment of periodate-induced PDA (PDA-SP) coatings adhered on the capillary inner surface. The successful immobilization of the SPD coating and the substantial grafting of sulfonic acid groups were confirmed by a series of characterization techniques. The excellent capability of PDA-SP@capillary in masking silanol groups and maintaining a highly robust EOF mobility was verified. Additionally, the parameters of sulfonation affecting the EOF mobilities were thoroughly examined. The obtained optimum SPD-coated column offered the anticipated highly pH-independent and high-strength cathodic EOF, which is essential for enhancing the CE separation performance and improving analysis efficiency. Consequently, the developed SPD-coated capillaries enabled successful high-efficiency separation of aromatic acids and nucleosides and rapid cyclodextrin-based chiral analysis of racemic drugs. Moreover, the SPD-coated columns exhibited a long lifetime and demonstrated good intra-day, inter-day, and column-to-column repeatability.

Preparation of covalently bonded liposome capillary column and its application in evaluation of drug membrane permeability

Two liposomes, including 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) + 1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine (PE) + cholesterol (Chol) (DSPC/PE/Chol liposomes) and soybean lecithin (SPC) + PE + Chol (SPC/PE/Chol liposomes), were prepared and fixed on the inner wall of capillary column by using the adhesion of polydopamine (PDA) membrane and the cross-linking property of glutaraldehyde (GA). The immobilized liposome capillary column (ILCC) has good repeatability and stability based on the electrophoretic mobility of analyte. A CE method based on the immobilized liposome capillary column chromatography (ILCCC) was successfully developed to study the retention behavior of drugs on ILCC, and the logarithm of retention factor (log k) of neutral and ionic drugs were determined. The results show that the log k measured by the ILCCC based on two liposomes have a good linear fitting (R² = 0.86). Moreover, the linear relationship between ILCCC system and other related research systems (octanol-water system and immobilized artificial membrane (IAM)) was analyzed, and the results indicate that SPC/PE/Chol ILCCC, DSPC/PE/Chol ILCCC and IAM systems have good fitting results, R² values are 0.86 and 0.78, respectively. In addition, the normalization coefficients of ILCCC and IAM systems obtained by the linear free energy relationship (LFER) analysis are close and the d value is small. In short, the ILCCC is a simple and feasible method for studying drug membrane permeability.

Preparation of a polydopamine/β-cyclodextrin coated open tubular capillary electrochromatography column and application for enantioseparation of five proton pump inhibitors

An open tubular capillary electrochromatography column was prepared by immobilizing β-cyclodextrin on the inner wall of pretreated capillary via noncovalent adsorption of polydopamine. The resulting coating layer on the capillary was characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. Electroosmotic flow was studied to evaluate the variation of the immobilized columns. The prepared columns showed good chiral separation performance toward five proton pump inhibitors including lansoprazole, pantoprazole, tenatoprazole, rabeprazole, and omeprazole. The influences of β-cyclodextrin concentration, coating time, buffer pH, buffer concentration, and applied voltage on separation were investigated. In the optimum conditions, the enantiomers of five analytes were fully resolved within 15 min with high resolutions of 4.57 to 8.13. The method was extensively validated in terms of accuracy, precision, and linearity and proved to be robust. The relative standard deviation values for migration times and peak areas of the analytes representing intraday and interday were less than 1.9 and 3.6%, respectively. Further, the polydopamine/β-cyclodextrin coated capillary column could be successively used over 100 runs without showing significant decrease in the separation efficiency.

Simultaneous Preconcentration and Spectrophotometric Determination of Two Colorants (E110 and E133) in Some Foodstuffs Using a New Mussel-Inspired Adsorbent

BACKGROUND

A naturally occurring material, namely sporopollenin (SP), was subjected to an easy physical surface modification process called a polydopamine coating. The treatment changed the acid-base properties of the surface, so that in the new form the SP surface gained a very attractive character for anionic dyes.

OBJECTIVE

The aim of the study was to develop preconcentration and subsequent spectrophotometric determination methods for two anionic colorants, brilliant blue (BB) and sunset yellow (SY), using polydopamine-coated (PDC) SP.

METHOD

The experiments were carried out in a column system, and the effects of experimental parameters were studied to determine optimal conditions for the quantitative, simultaneous spectrophotometric determination of the dyes.

RESULTS

The dyes could be detected at µg/L levels in their binary mixtures, so the detection limits were found to be 1.5 and 4.3 µg/L in the linear dynamic ranges of 0.0-3.5 and 0-8 µg/mL for BB and SY, respectively. The proposed material and procedure led to quantitative recoveries of between 95 and 100% for the dyes.

CONCLUSIONS

The procedure was applied to real food samples containing BB and SY and both dyes were successfully determined in liquid and solid foodstuffs. The mussel-inspired surface modification is proposed as a useful process to modify the surface of SP.

HIGHLIGHTS

The mussel-inspired polydopamine dip-coating method was adopted to modify the surface of SP for the first time. The PDCSP was successfully used to create a new adsorptive preconcentration method for simultaneous spectrophotometric determination of BB and SY in foodstuffs.

Solvothermal-assisted in situ rapid growth of octadecylamine functionalized polydopamine-based permanent coating as stationary phase for open-tubular capillary electrochromatography

In recent years, mussel-inspired polydopamine (PDA) based materials have been widely used as stationary phases for open-tubular capillary electrochromatography (OT-CEC) because of their various excellent properties. Nevertheless, the traditional synthesis routes of functionalized PDA-based capillary columns usually are time-consuming and limited in aqueous solutions. Herein, we report a facile and rapid route to prepare octadecylamine (ODA) functionalized PDA coated OT-CEC columns in organic solvents via a novel one-step in situ solvothermal-assisted coating strategy. Through this developed solvothermal-assisted approach, the growth rate of ODA/PDA coating was significantly speeded up and their hybrid coating process on the capillary inner surface could be rapidly completed in 60 min. The successful preparation of the solvothermal-assisted ODA/PDA hybrid coating were systematically characterized and confirmed by several methods. The influence of the preparation parameters on the formation of hybrid coating and the separation ability of the ODA/PDA modified columns were systematically explored. Consequently, the high-efficiency baseline separation of four kinds of neutral, acidic and basic analytes were achieved based on the ODA/PDA modified columns. The repeatability of the solvothermal-assisted ODA/PDA coated column was also studied, and the relative standard deviations for intra-day, inter-day and column-to-column were all less than 5%. Additionally, the solvothermal-assisted ODA/PDA modified column exhibited good stability and long lifetime.

Biopolymer-Inspired N-Doped Nanocarbon Using Carbonized Polydopamine: A High-Performance Electrocatalyst for Hydrogen-Evolution Reaction

Hydrogen-evolution reaction (HER) is a promising technology for renewable energy conversion and storage. Electrochemical HER can provide a cost-effective method for the clean production of hydrogen. In this study, a biomimetic eco-friendly approach to fabricate nitrogen-doped carbon nanosheets, exhibiting a high HER performance, and using a carbonized polydopamine (C-PDA), is described. As a biopolymer, polydopamine (PDA) exhibits high biocompatibility and can be easily obtained by an environmentally benign green synthesis with dopamine. Inspired by the polymerization of dopamine, we have devised the facile synthesis of nitrogen-doped nanocarbons using a carbonized polydopamine for the HER in acidic media. The N-doped nanocarbons exhibit excellent performance for H2 generation. The required overpotential at 5 mA/cm2 is 130 mV, and the Tafel slope is 45 mV/decade. Experimental characterizations confirm that the excellent performance of the N-doped nanocarbons can be attributed to the multisite nitrogen doping, while theoretical computations indicate the promotion effect of tertiary/aromatic nitrogen doping in enhancing the spin density of the doped samples and consequently in forming highly electroactive sites for HER applications.

In situ one-pot synthesis of polydopamine/octadecylamine co-deposited coating in capillary for open-tubular capillary electrochromatography

Mussel-inspired polydopamine (PDA) based materials are attractive as stationary phase for open-tubular capillary electrochromatography (OT-CEC) due to their many fascinating properties. However, all of the existing strategies for fabricating PDA based OT-CEC columns are limited in aqueous solutions. Consequently, it is a challenge work to directly immobilize the hydrophobic functional materials onto the inner wall of PDA modified capillary. Herein, by using the organic amine-inducing co-deposition strategy, a novel preparative method was developed for in situ one-pot synthesis of PDA/octadecylamine (ODA) co-deposited coating inside capillary as OT-CEC stationary phase. The formation and morphology of the PDA/ODA co-deposited coating were characterized by field emission scanning electron microscopy, atomic force microscope, attenuated total reflectance Fourier transform infrared spectroscopy and contact angle measurements. The separation performance of the fabricated PDA/ODA modified columns was validated by the separation of alkylbenzenes and steroids, which could achieve baseline separation with high separation efficiency. Their separation was found to follow the reversed phase chromatographic retention mechanism. The co-deposited column showed good stability and long lifetime. The repeatability of the PDA/ODA co-deposited column was also evaluated, with the relative standard deviations for intra-day and inter-day runs less than 5% and column-to-column runs less than 6%.

Preparation and evaluation of a polydopamine-modified capillary silica monolith for capillary electrochromatography

A novel capillary silica monolith (CSM) with surface modification was prepared for capillary electrochromatography (CEC) by using polydopamine (PDA) as a functional coating.

Chondroitin sulfate-polydopamine modified polyethylene terephthalate with extracellular matrix-mimetic immunoregulatory functions for osseointegration

Optimal integration between the polyethylene terephthalate (PET) graft and host bone is a prerequisite to obtain a satisfactory outcome after graft implantation for ligament reconstruction.

A chemiluminescence resonance energy transfer for the determination of indolyl acetic acid using luminescent nitrogen-doped carbon dots as acceptors

A CRET method was fabricated for the determination of IAA using Ce(iv)–Na₂SO₃ as the donor and N-CDs as the acceptor.

A Simple and Selective Fluorescent Sensor Chip for Indole-3-Butyric Acid in Mung Bean Sprouts Based on Molecularly Imprinted Polymer Coatings

In this paper, we report the preparation of molecularly imprinted polymer coatings on quartz chips for selective solid-phase microextraction and fluorescence sensing of the auxin, indole-3-butyric acid. The multiple copolymerization method was used to prepare polymer coatings on silylated quartz chips. The polymer preparation conditions (e.g., the solvent, monomer, and cross-linker) were investigated systemically to enhance the binding performance of the imprinted coatings. Direct solid-phase fluorescence measurements on the chips facilitated monitoring changes in coating performance. The average binding capacity of an imprinted polymer coated chip was approximately 152.9 µg, which was higher than that of a non-imprinted polymer coated chip (60.8 µg); the imprinted coatings showed the highest binding to IBA among the structural analogues, indicating that the coatings possess high selectivity toward the template molecule. The developed method was used for the determination of the auxin in mung bean extraction, and the recovery was found to be in the range of 91.5% to 97.5%, with an RSD (n = 3) of less than 7.4%. Thus, the present study provides a simple method for fabricating a fluorescent sensor chip for selective analysis.

Polydopamine-mediated preparation of an enzyme-immobilized microreactor for the rapid production of wax ester

In our study, a polytetrafluoroethylene (PTFE) open-tubular enzyme-immobilized microreactor has been successfully prepared using dopamine polymerization and multi-layer deposition.

Open tubular-capillary electrochromatography: Developments and applications from 2013 to 2015

Open tubular CEC (OT-CEC) separates analyte mixtures by a combination of electrophoretic, electro-osmotic, and/or chromatographic effects. OT-CEC research is an active and growing field, with studies encompassing a wide range of investigations related to new strategies for chemical modification of the inner surface of the capillary, leading to the introduction of novel stationary phase coatings. This review has examined the literature on OT-CEC from 2013 to August 2015 and highlights the developments in the fabrication of highly selective stationary phases, based on materials that include cyclodextrin chiral selectors, graphene and graphene oxide, metal-organic frameworks, molecularly imprinted polymers, nanoparticles, nanolatex particles, nanocomposites, in situ generated polymers, block polymers, tentacle-type polymers, polyelectrolyte multilayers, polysaccharides, phospholipids, and proteins. This review, while considering the development of novel OT-CEC coating materials, specifically examines different immobilization or coating methodologies and approaches and also discusses the separation mechanisms that occur with these new materials. These OT-CEC coatings are intended mainly to separate low molecular weight molecules relevant to the pharmaceutical, agricultural, and food industries as well as for use in environmental monitoring.

Functionalization of Polydopamine via the Aza-Michael Reaction for Antimicrobial Interfaces

Polydopamine (pDA) coatings afford tremendous versatility due to their capabilities to provide substrate-independent functionalization with a wide range of amine- and thiol-containing molecules. In this work, we developed a new and facile conjugation approach to the formation of β-amino carbonyl linkages between pDA and acrylate/acrylamide molecules via the aza-Michael reaction. Sulfobetaine acrylamide (SBAA), sulfobetaine methacrylate (SBMA), and poly(ethylene glycol) methacrylate (PEGMA) were employed to graft onto pDA films, giving rise to formation of antifouling coatings. Because of the universal adhesive property of pDA, the coating strategy was applied to different substrates, including TiO2, gold, SiO2, Nitinol alloy, polystyrene, and poly(dimethylsiloxane). The variation of surface chemistry and surface wettability upon pDA modification and subsequent conjugation was monitored with X-ray photoelectron spectroscopy (XPS) and water contact angle measurements. Antifouling properties of coatings were challenged by three common Gram-negative and Gram-positive bacteria. Cytocompatibility of the coatings with NIH-3T3 fibroblasts was accessed using MTT assay. The results showed that pDA coatings grafted with SBAA exhibited superhydrophilicity and excellent fouling resistance likely due to the high chemical reactivity of acrylamide, leading to high grafting density. In addition, dual functional coatings containing passive and active antibacterial components were constructed through the in situ deposition of antimicrobial agent, silver nanoparticles, in pDA, followed by the grafting of SBAA for bacterial repellence. The composite coatings allowed reducing adsorption of E. coli by >95%, while killing attached bacteria by up to 98% upon the releasing of Ag(+) ions as measured by inductively coupled plasma mass spectrometry. Consequently, this work paves a new avenue to the grafting strategy to engineer pDA and to the functional bioinspired antifouling interfaces in a substrate-independent fashion.

Nucleus-staining with biomolecule-mimicking nitrogen-doped carbon dots prepared by a fast neutralization heat strategy

Biomolecule-mimicking nitrogen-doped carbon dots (N-Cdots) were synthesized from dopamine by a neutralization heat strategy. Fluorescence imaging of various cells validated their nucleus-staining efficiency. The dopamine-mimicking N-Cdots "trick" nuclear membranes to achieve nuclear localization and imaging.

Layer-by-layer self-assembly of polydopamine/gold nanoparticle/thiol coating as the stationary phase for open tubular capillary electrochromatography

Much attention has been paid to utilizing polydopamine (PDA) as the stationary phase in open-tubular capillary electrochromatography (OT-CEC) owing to its diverse properties, such as strong adhesion to various surfaces, latent reactivity toward amine and thiol groups and metal ion chelating/redox activities. In this study, a novel open-tubular capillary column coated with polydopamine/gold nanoparticles/thiols (PDA/Au NPs/thiols) has been fabricated based on the multiple properties of PDA for the first time. The capillary inner surface was firstly functionalized with a layer of PDA/Au NPs using the strong adhesive and metal ion redox properties of PDA. Thiols were then introduced and covalently reacted with the hybrid coating based on the Michael addition reaction of PDA and thiols and also Au-S bonds. Moreover, benefitting from the porosity of PDA, layer-by-layer (LBL) self-assembly was further applied to increase the amounts of stationary phase (Au NPs and thiols), which can significantly enhance the separation effectiveness and stability of the coated column. The formation of the PDA/Au NP/thiol coating in the capillary was confirmed and characterized by scanning electron microscopy (SEM), Energy Dispersive Spectrometry (EDS) and AFM (Atomic Force Microscopy). Then the separation effectiveness of the PDA/Au NP/thiol@capillary was verified by the separation of alkylbenzenes, which can achieve baseline separation easily with high column efficiency. In addition, the column showed long lifetime and good stability. The relative standard deviations (RSDs) for intra-day and inter-day repeatability of the PDA/Au NP/thiol@capillary were lower than 5%. Therefore, the layer-by-layer self-assembly of PDA/Au NPs/thiols on the capillary inner-surface could be an effective capillary modification strategy.

Chromatographic selectivity of graphene capillary column pretreated with bio-inspired polydopamine polymer

Column fabrication by integration of graphene sheets on a polydopamine layer achieved improved column efficiency and chromatographic performance in capillary gas chromatographic separations.

Enantiomer separation of propranolol and tryptophan using bovine serum albumin functionalized silica nanoparticles as adsorbents

The immobilization of popular chiral selectors on the surface of nanomaterials to prepare new chiral adsorbents for preparative chiral separation is a research hotspot in separation science nowadays.

Mussel-inspired dopamine- and plant-based cardanol-containing polymer coatings for multifunctional filtration membranes

A series of copolymers [PCD#s, where # is the weight percentage of dopamine methacrylamide (DMA) in polymers] containing mussel-inspired hydrophilic dopamine and plant-based hydrophobic cardanol moieties was prepared via radical polymerization using DMA and 2-hydroxy-3-cardanylpropyl methacrylate (HCPM) as the monomers. PCD#s were used as coating materials to prevent flux decline of the membranes caused by the adhesion of biofoulants and oil-foulants. Polysulfone (PSf) ultrafiltration membranes coated with PCD#s showed higher biofouling resistance than the bare PSf membrane, and the bactericidal properties of the membranes increased upon increasing the content of HCPM units in the PCD#s. Serendipitously, the PSf membranes coated with the more or less amphiphilic PCD54 and PCD74, having the optimum amount of both hydrophilic DMA and hydrophobic HCPM moieties, showed noticeably higher oil-fouling resistance than the more hydrophilic PCD91-coated membrane, the more hydrophobic PCD0-coated membrane, and the bare PSf membrane. Therefore, multifunctional coating materials having biofouling- and oil-fouling-resistant and bactericidal properties could be prepared from the monomers containing mussel-inspired dopamine and plant-based cardanol groups.

Development of a rapid LC-DAD/FLD method for the simultaneous determination of auxins and abscisic acid in plant extracts

Plant hormones play a crucial role in controlling plant growth and development. These groups of naturally occurring substances trigger physiological processes at very low concentrations, which mandate sensitive techniques for their quantitation. This paper describes a method to quantify endogenous (±)-2-cis-4-trans-abscisic acid, indole-3-acetic acid, indole-3-propionic acid, and indole-3-butyric acid. The method combines high-performance liquid chromatography (HPLC) with diode array and fluorescence detection in a single run. Hybrid tea rose 'Monferrato' matrices (leaves, petals, roots, seeds, androecium, gynoecium, and pollen) were used as references. Rose samples were separated and suspended in extracting methanol, after which (±)-2-cis-4-trans-abscisic acid and auxins were extracted by solvent extraction. Sample solutions were added first to cation solid phase extraction (SPE) cartridges and the eluates to anion SPE cartridges. The acidic hormones were bound to the last column and eluted with 5% phosphoric acid in methanol. Experimental results showed that this approach can be successfully applied to real samples and that sample preparation and total time for routine analysis can be greatly reduced.

Metal deposition by electroless plating on polydopamine functionalized micro- and nanoparticles

A novel approach for the fabrication of metal coated micro- and nanoparticles by functionalization with a thin polydopamine layer followed by electroless plating is reported. The particles are initially coated with polydopamine via self-polymerization. The resulting polydopamine coated particles have a surface rich in catechols and amino groups, resulting in a high affinity toward metal ions. Thus, they provide an effective platform for selective electroless metal deposition without further activation and sensitization steps. The combination of a polydopamine-based functionalization with electroless plating ensures a simple, scalable, and cost-effective metal coating strategy. Silver-plated tungsten carbide microparticles, copper-plated tungsten carbide microparticles, and copper-plated alumina nanoparticles were successfully fabricated, showing also the high versatility of the method, since the polymerization of dopamine leads to the formation of an adherent polydopamine layer on the surface of particles of any material and size. The metal coated particles produced with this process are particularly well suited for the production of metal matrix composites, since the metal coating increases the wettability of the particles by the metal, promoting their integration within the matrix. Such composite materials are used in a variety of applications including electrical contacts, components for the automotive industries, magnets, and electromagnetic interference shielding.

A versatile polydopamine platform for facile preparation of protein stationary phase for chip-based open tubular capillary electrochromatography enantioseparation

A novel, simple, and economical method for the preparation of chiral stationary phases for chip-based enantioselective open tubular capillary electrochromatography (OT-CEC) using polydopamine (PDA) coating as an adhesive layer was reported for the first time. After the poly(dimethylsiloxane) (PDMS) microfluidic chip was filled with dopamine (DA) solution, PDA film was gradually formed and deposited on the inner wall of microchannel as permanent coating via the oxidation of DA by the oxygen dissolved in the solution. Due to possessing plentiful catechol and amine functional groups, PDA coating can serve as a versatile multifunctional platform for further secondary reactions, leading to tailoring of the coatings for protein bioconjugation by the thiols and amines via Michael addition or Schiff base reactions. Bovine serum albumin (BSA), acting as a target protein, was then stably and homogeneously immobilized in the PDA-coated PDMS microchannel to fabricate a novel protein stationary phase. Compared with the native PDMS microchannels, the modified surfaces exhibited much better wettability, more stable and enhanced electroosmotic mobility, and less nonspecific adsorption. The water contact angle and electroosmotic flow of PDA/BSA-coated PDMS substrate were measured to be 44° and 2.83×10(-4)cm(2)V(-1)s(-1), compared to those of 112° and 2.10×10(-4)cm(2)V(-1)s(-1) from the untreated one, respectively. Under a mild condition, d- and l-tryptophan were efficiently separated with a resolution of 1.68 within 130s utilizing a separation length of 37mm coupled with in-column amperometric detection on the PDA/BSA-coated PDMS microchips. This present versatile platform, facile conjugation of biomolecules onto microchip surfaces via mussel adhesive protein inspired coatings, may offer new processing strategies to prepare a biomimetic surface design on microfluidic chips, which is promising in high-throughput and complex biological analysis.