A facile and versatile approach for controlling electroosmotic flow in capillary electrophoresis via mussel inspired polydopamine/polyethyleneimine co-deposition

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.

MOFs and PDA-supported immobilization of BSA in open tubular affinity capillary electrochromatography: Prediction and study on drug-protein interactions

Owing to the satisfactory properties such as high specific surface area, finely tunable chemical composition, large yet adjustable pore sizes, and diverse architecture, metal-organic frameworks (MOFs) have the potential to be used as a stable, efficient, reusable and protective biomacromolecule immobilization carrier in capillary electrophoresis. Herein, a novel immobilized receptor open-tubular affinity capillary electrochromatography (OT-ACEC) strategy was developed for the first time to rapidly investigate the interactions between a set of drugs and bovine serum albumin (BSA). To further increase the amount of immobilized BSA and maintain the bioactivity of BSA, BSA was immobilized on the inner capillary surface by using polydopamine (PDA) as the adhesion layer and surface functionalization agent, a MOF namely dresden university of technology-5 (DUT-5) as supporting platform and biomacromolecule immobilization carrier, respectively. The amount of immobilized BSA on the capillary surface of the BSA@capillary and the PDA/MOFs/BSA@capillary column are separately calculated as 0.00756 nmol and 0.01812 nmol. Besides, the PDA/MOFs/BSA@capillary column was applied to investigate the interactions between BSA and flavonoids, fluoroquinolones. Under the optimal interaction conditions, three flavonoids and three fluoroquinolones are able to achieve baseline separation in the PDA/MOFs/BSA@capillary column (with resolution values of three flavonoids, 5.78 and 4.13; three fluoroquinolones, 1.72 and 1.68). The PDA/MOFs/BSA@capillary column shows good stability and reproducibility over 100 runs (relative standard deviation (RSD)＜5%). In addition, the normalized capacity factor (K_RCE) in this method replaced the binding constant and was used as an evaluation index to fast predict the activities of 20 drugs, some of which have not yet been reported for their interactions with BSA. Spectroscopy and molecular docking further illuminated the binding mechanism.

Polydopamine-Assisted Rapid One-Step Immobilization of L-Arginine in Capillary as Immobilized Chiral Ligands for Enantioseparation of Dansyl Amino Acids by Chiral Ligand Exchange Capillary Electrochromatography

Herein, a novel L-arginine (L-Arg)-modified polydopamine (PDA)-coated capillary (PDA/L-Arg@capillary) was firstly fabricated via the basic amino-acid-induced PDA co-deposition strategy and employed to constitute a new chiral ligand exchange capillary electrochromatography (CLE-CEC) method for the high-performance enantioseparation of D,L-amino acids (D,L-AAs) with L-Arg as the immobilized chiral ligand coordinating with the central metal ion Zn(II) as running buffer. Assisted by hydrothermal treatment, the robust immobilization of L-Arg on the capillary inner wall could be facilely achieved within 1 h, prominently improving the synthesis efficiency and simplifying the preparation procedure. The successful preparation of PDA/L-Arg coatings in the capillary was systematically characterized and confirmed using several methods. In comparison with bare and PDA-functionalized capillaries, the enantioseparation capability of the presented CLE-CEC system was significantly enhanced. Eight D,L-AAs were completely separated and three pairs were partially separated under the optimal conditions. The prepared PDA/L-Arg@capillary showed good repeatability and stability. The potential mechanism of the greatly enhanced enantioseparation performance obtained by PDA/L-Arg@capillary was also explored. Moreover, the proposed method was further utilized for studying the enzyme kinetics of L-glutamic dehydrogenase, exhibiting its promising prospects in enzyme assays and other related applications.

Bioinspired Dopamine/Mucin Coatings Provide Lubricity, Wear Protection, and Cell-Repellent Properties for Medical Applications

Even though medical devices have improved a lot over the past decades, there are still issues regarding their anti-biofouling properties and tribological performance, and both aspects contribute to the short- and long-term failure of these devices. Coating these devices with a biocompatible layer that reduces friction, wear, and biofouling at the same time would be a promising strategy to address these issues. Inspired by the adhesion mechanism employed by mussels, here, dopamine is made use of to immobilize lubricious mucin macromolecules onto both manufactured commercial materials and real medical devices. It is shown that purified mucins successfully adsorb onto a dopamine pre-coated substrate, and that this double-layer is stable toward mechanical challenges and storage in aqueous solutions. Moreover, the results indicate that the dopamine/mucin double-layer decreases friction (especially in the boundary lubrication regime), reduces wear damage, and provides anti-biofouling properties. The results obtained in this study show that such dopamine/mucin double-layer coatings can be powerful candidates for improving the surface properties of medical devices such as catheters, stents, and blood vessel substitutes.

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.

Glycine-Induced Electrodeposition of Nanostructured Cobalt Hydroxide: A Bifunctional Catalyst for Overall Water Splitting

Herein, an interconnected α-Co(OH)₂ structure with a network-like architecture was used as a bifunctional electrocatalyst for the overall water splitting reaction in alkaline medium. The complexing ability of glycine with a transition metal was exploited to form [Co(gly)₃ ]^- dispersion at pH 10, which was used for the electrodeposition. High-resolution TEM, UV/Vis-diffuse reflectance spectroscopy, and X-ray photoelectron spectroscopy were used to confirm that the as-synthesized materials had an α-Co(OH)₂ phase. The electrocatalytic oxygen and hydrogen evolution activity of the glycine-coordinated α-Co(OH)₂ was found to be approximately 320 and 145 mV, respectively, at 10 mA cm^-2 . The material required approximately 1.60 V (vs. reversible hydrogen electrode; RHE) to achieve the benchmark of 10 mA cm^-2 for overall water splitting with a mass activity of approximately 63.7 A g^-1 at 1.60 V (vs. RHE). The chronoamperometric response was measured to evidence the stability of the material for overall water splitting for up to 24 h. Characterization of the catalyst after the oxygen and hydrogen evolution reactions was performed by XPS and showed the presence of a Co^II /Co^III oxidation state.

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%.

Interfacial engineered gadolinium oxide nanoparticles for magnetic resonance imaging guided microenvironment-mediated synergetic chemodynamic/photothermal therapy

Engineering interfacial structure of biomaterials have drawn much attention due to it can improve the diagnostic accuracy and therapy efficacy of nanomedicine, even introducing new moiety to construct theranostic agents. Nanosized magnetic resonance imaging contrast agent holds great promise for the clinical diagnosis of disease, especially tumor and brain disease. Thus, engineering its interfacial structure can form new theranostic platform to achieve effective disease diagnosis and therapy. In this study, we engineered the interfacial structure of typical MRI contrast agent, Gd₂O₃, to form a new theranostic agent with improved relaxivity for MRI guided synergetic chemodynamic/photothermal therapy. The synthesized Mn doped gadolinium oxide nanoplate exhibit improved T₁ contrast ability due to large amount of efficient paramagnetic metal ions and synergistic enhancement caused by the exposed Mn and Gd cluster. Besides, the introduced Mn element endow this nanomedicine with the Fenton-like ability to generate OH from excess H₂O₂ in tumor site to achieve chemodynamic therapy (CDT). Furthermore, polydopamine engineered surface allow this nanomedicine with effective photothermal conversion ability to rise local temperature and accelerate the intratumoral Fenton process to achieve synergetic CDT/photothermal therapy (PTT). This work provides new guidance for designing magnetic resonance imaging guided synergetic CDT/PTT to achieve tumor detection and therapy.

Modulation of electroosmotic flow in capillary electrophoresis by plant polyphenol-inspired gallic acid/polyethyleneimine coatings: Analysis of small molecules

Plant polyphenols can form functional coatings on various materials through self-polymerization. In this paper, a series of modified capillary columns, which possess diversity of charge characteristics for modulating electroosmotic flow (EOF), were prepared by one-step co-deposition of gallic acid (GA), a plant-derived polyphenol monomer, and branched polyethyleneimine (PEI). The physicochemical properties of the prepared columns were characterized by Fourier transform infrared spectroscopy (FT-IR), UV-Vis spectroscopy and scanning electron microscopy (SEM). The magnitude and direction of EOF of GA/PEI co-deposited columns were modulated by changing a series of coating parameters, such as post-incubation of FeCl₃, co-deposition time, and deposited amounts of GA and PEI with different relative molecular mass (PEI-600, PEI-1800, PEI-10000, and PEI-70000). Furthermore, the separation efficiencies of the prepared GA/PEI co-deposited columns were evaluated by separations of small molecules, including organic acids, polar nucleotides, phenols, nucleic acid bases and nucleosides. Results indicated that modulating of EOF plays an important role in enhancing the separation performance and reversing the elution order of the analytes. Finally, the developed method was successfully applied to quantitative analysis of acidic compounds in four real samples. The recoveries were in the range of 73.5%-85.8% for citric acid, benzoic acid, sorbic acid, salicylic acid and ascorbic acid in beverage and fruit samples, 101.6%-104.9% for cinnamic acid, vanillic acid, and ferulic acid in Angelica sinensis sample, while 84.6%-97.8% for guanosine-5'-monophosphate, uridine-5'-monophosphate, cytosine-5'- monophosphate and adenosine-5'-monophosphate in Cordyceps samples. These results indicated that the co-deposition of plant polyphenol-inspired GA/PEI coatings can provide new opportunities for EOF modulation of capillary electrophoresis.

Hybrid mesoporous nanorods with deeply grooved lateral faces toward cytosolic drug delivery

Hybrid mesoporous nanorods with six twisted sharp edges can induce effective penetration of intracellular barriers and cytosolic delivery of membrane-impermeable drugs through curvature effects.

Melanin-mimetic multicolor and low-toxicity hair dye

Most commercial permanent hair dyeing technologies are based on the oxidative process of p-phenylenediamine and its derivative materials. However, concerns about their toxicological issues have been raised throughout the years. Herein, we report an innovative surface coloration strategy for fabricating melanin-mimetic multicolor and low-toxicity hair dyes through sodium periodate-induced rapid deposition of eumelanin-like polydopamine (PDA) and pheomelanin-like PDA/cysteine co-deposited coatings on the hair surface. The color and morphology of the resulting hair were characterized in detail by several spectroscopy methods and the possible mechanism for the multi-coloring effects and structural differences of the melanin-mimetic coating was proposed. Our strategy eliminates the use of toxic dye precursors or organic solvents, and the favorable safety of the PDA-based formulations is demonstrated. The fabricated dyes can be applied to hair simply by combing, resulting in uniform multi-coloring effects within a short time. Furthermore, the melanin-mimetic hair dyes have excellent durability and ultraviolet protection performance. This work provides a facile and versatile methodology to develop the next generation of safe, sustainable and multicolor hair dyes and pave new avenues for advancing the field of surface coloration, nanoreactors, nanogenerators, energy storage materials and biomimetic sensing devices.

This study developed novel approaches for melanin-mimetic multicolor and low-toxicity hair dye through rapid deposition of PDA-based coatings on hair.

Redox modulation of polydopamine surface chemistry: a facile strategy to enhance the intrinsic fluorescence of polydopamine nanoparticles for sensitive and selective detection of Fe3

In recent years, polydopamine (PDA) nanoparticles have attracted considerable attention in different research fields because of their many fascinating physicochemical properties. However, as an analogue of naturally occurring melanin, PDA nanoparticles (PDANPs) typically exhibit weak fluorescence properties. Herein, we report a facile one-pot method for synthesizing bright blue luminescent PDANPs through the redox modulation of PDA surface chemistry. The composition and morphology of the resultant NPs were systematically characterized by transmission electron microscopy and several spectroscopy methods, which verified the successful fabrication of PDANPs. More importantly, comparative chemical analysis of dopamine polymerization revealed the significant impacts of synthesis conditions and PDA surface chemistry on the luminescence properties of PDANPs. Remarkably, in addition to their excellent water-solubility, salt-tolerance and high photostability under extreme pH conditions, the as-prepared PDANPs possess the highest quantum yield (5.1%) among all the reported intrinsic fluorescent PDANPs. Moreover, based on the coordination interaction between phenolic hydroxyl groups of PDANPs and ferric ions (Fe3+), the synthesized PDANPs were successfully utilized as a turn-off sensing platform for sensitive and selective detection of Fe3+ without using any additional targeting molecules. Upon increasing the Fe3+ concentration in the range from 0.5 to 20 μM, the fluorescence intensity of PDANPs decreased linearly. The detection limit of Fe3+ was 0.15 μM. Finally, this fluorescent sensor was successfully used to determine Fe3+ in natural water samples, showing good prospects for practical applications and may pave the way for the development of new rational methodologies for further enhancing the intrinsic fluorescence of PDA and fabricating other novel fluorescent organic nanoparticles.

Dopamine-assisted co-deposition: An emerging and promising strategy for surface modification

Mussel-inspired chemistry based on polydopamine (PDA) deposition has been developed as a facile and universal method for the surface modification of various materials. However, the inherent shortcomings of PDA coatings still impede their practical applications in the development of functional materials. In this review, we introduce the recent progress in the emerging dopamine-assisted co-deposition as a one-step strategy for functionalizing PDA-based coatings, and improving them in the aspects of deposition rate, morphology uniformity, surface wettability and chemical stability. The co-deposition mechanisms are categorized and discussed according to the interactions of dopamine or PDA with the introduced co-component. We also emphasize the influence of these interactions on the properties of the resultant PDA-based coatings. Meanwhile, we conclude the representative potential applications of those dopamine-assisted co-deposited coatings in material science, especially including separation membranes and biomaterials. Finally, some important issues and perspectives for theoretical study and applications are briefly discussed.

Robust Coatings via Catechol-Amine Codeposition: Mechanism, Kinetics, and Application

Bioinspired polyphenol/polyamine codeposition has been demonstrated by the competence for surface modification; however, the reaction processes including mechanism and kinetics remain superficially understood. In this work, the catechol (CA)-amine reaction has been thoroughly investigated by using CA and two amines m-phenylenediamine and piperazine. We verify that both primary and secondary amines are prone to link with CA through Michael addition to form polyphenol/polyamine oligomers under aerobic and mild-alkaline conditions. Molecular simulations indicate that the Michael addition products are dominant for both aromatic and aliphatic amines with CA, which supports the durable chem- and phystability of the codeposited coatings. The aggregation kinetics of polyphenol/polyamine is provided for the first time, and the formed aggregates show high-adhesive properties, which can be deposited as the skin layers for high-performance nanofiltration membranes.

Polydopamine-Coated Manganese Carbonate Nanoparticles for Amplified Magnetic Resonance Imaging-Guided Photothermal Therapy

This study reports a multifunctional nanoparticle (NP) that can be used for amplified magnetic resonance image (MRI)-guided photothermal therapy (PTT) due to its surface coating with a polydopamine (PDA) shell. Importantly, by means of introducing the surface coating of PDA, large quantities of water can be trapped around the NPs allowing more efficient water exchange, leading to greatly improved MR contrast signals compared with those from NPs without the PDA coating. Further, a distinct photothermal effect can be obtained arising from the strong absorption of PDA in the near-infrared (NIR) region. By synthesizing multifunctional MnCO₃@PDA NPs, for example, we found that the longitudinal relaxivity (r₁) of MnCO₃ NPs can improve from 5.7 to 8.3 mM^-1 s^-1. Subsequently, in vitro MRI and PTT results verified that MnCO₃@PDA could serve as an excellent MRI/PTT theranostic agent. Furthermore, the MnCO₃@PDA NPs were applied as an MRI/PTT theranostic agent for in vivo MRI-guided photothermal ablation of tumors by intratumoral injection in 4T1 tumor-bearing mice. The MR imaging result shows a significantly bright MR image in the tumor site. The MnCO₃@PDA-mediated PTT result shows high therapeutic efficiency as a result of high photothermal conversion efficiency. The present strategy of amplified MRI-guided PTT based on PDA coating of NPs will be widely applicable to other multifunctional NPs.

In Vivo Selective Capture and Rapid Identification of Luteolin and Its Metabolites in Rat Livers by Molecularly Imprinted Solid-Phase Microextraction

A method based on molecularly imprinted solid-phase microextraction (MIP-SPME) coupled with liquid chromatography-quadrupole time-of-flight tandem mass spectrometry (QTOF-MS/MS) was developed for the detection of luteolin and its metabolites in vivo. The MIP-SPME fibers were first fabricated by dopamine and silane, and then luteolin MIPs-coated fibers were successfully prepared using luteolin, acrylamide (AM), and ethylene glycol dimethacrylate (EGDMA) as the template, functional monomer and cross-linker, respectively. The characterizations of polymers were analyzed by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and the Brunauer-Emmett-Teller method (BET). The properties involving adsorption and selective experiments were evaluated, and these results revealed that MIP fibers presented high adsorption capacity and selectivity to luteolin. Furthermore, the developed MIP-SPME coupled with the LC-QTOF-MS/MS method was adopted to capture and identify luteolin and its metabolites in rat livers in vivo, and eventually, apigenin, chrysoeriol, and diosmetin were rapidly identified as metabolites.