Polydopamine Coatings Research Articles

High-flux polyamide nanofiltration membranes tuning by polydopamine-modified boron nitride nanosheets: Accelerating Mg2+/Li+ separation

As a promising technology for lithium extraction from salt lakes, nanofiltration membranes still face challenges in balancing between permeability and selectivity. In this paper, highly dispersed functionalized boron nitride nanosheets (BNNSs-NH2) were prepared by modifying exfoliated boron nitride nanosheets (BNNSs) with polydopamine, which were incorporated into a polyamide (PA) layer by aqueous phase conditioning to prepare positively charged polyamide nanofiltration membranes. Scanning electron microscopy (SEM) showed that the PDA nanoclusters on the surface of the BNNSs can disrupt the regular stacking parallel to the membrane surface. Energy spectrum (EDS) of SEM and X-ray photoelectron spectroscopy (XPS) etching further revealed that BNNSs-NH2 were dispersed within PA layer, creating transmembrane channels for molecular diffusion. The results showed a pure water permeance of 8.55 ± 0.24 L/m2 h bar, indicating that the stabilized intercalation of BNNSs-NH2 in the PA layer synergistically improved the water permeability. Meanwhile, the retention rate of MgCl2 remained at 94 %, which was attributed to the enhanced compatibility between BNNSs-NH2 and polyamide matrix by the polydopamine coating (PDA) on the surface, as well as the Dornan effect repulsion by the enhanced positive charge on the membrane surface. After the three-stage nanofiltration of membrane, the Mg2+/Li+ ratio decreased from 50 to 0.12. Overall, this method balances permeability and selectivity by adjusting pore size and positive charge, potentially offering new ideas and insights for the preparation and development of nanofiltration membranes for Mg2+/Li+ separation.

Cellulose acetate-based electrospun nanocomposites improved by mussel-inspired polydopamine coatings and copper iodide-decorated graphene oxide: A self-disinfecting nanofibrous membrane with potential biomedical applications

Personal protective equipment and fabrics have proven their efficient use in the SARS-CoV-2 pandemic, but because germs and viruses may survive on them, they can also operate as a source of disease transmission. Self-disinfecting textiles with the potential to kill different pathogens can be used as a substitute and prevent infections. In this research, copper iodide (CuI) decorated graphene oxide nanocomposite was synthesized through a green water-based procedure, and a novel nanofibrous membrane with improved antibacterial and antiviral characteristics was prepared by a mussel-inspired method, in which polydopamine (DOPA) and CuI-decorated graphene oxide (GO-CuI) nanocomposite were coated on cellulose acetate electrospun nanofibers (CA-DOPA-GOCuI). CA-DOPA-GOCuI NFM displayed extremely good antibacterial/antiviral properties with biofilm inhibition of 50 %, and very good cell viability and proliferation even though the virus was introduced to the cell culture. Furthermore, because it accelerated the healing process, this NFM showed great promise for use as a wound dressing. This may be because it inhibits infection and has an extremely high ROS scavenging capability of 80 %. Additionally, it was shown that CA-DOPA-GOCuI NFM was non-toxic to cells and blood compatible, with cell viability that was even higher than that of the control group of untreated cells. One possible explanation for this could be the inclusion of GO, a highly biocompatible member of the graphene family, which, when combined with CuI, reduced its toxicity to normal cells. Thus, the safety of CA-DOPA-GOCuI to normal cells, favorable cell proliferation and viability, and its high toxicity to bacteria and viruses indicate its great potential to be used in a wide range of biomedical applications, specifically, self-disinfecting fabrics and wound dressings.

Molecular Investigation of the Self-Assembly Mechanism Underlying Polydopamine Coatings: The Synergistic Effect of Typical Building Blocks Acting on Interfacial Adhesion.

Polydopamine (PDA) is well known as a mussel-inspired adhesive material composed of oligomeric heteropolymers. However, the conventional eumelanin-like structural assumption of PDA seems deficient in explaining its interfacial adhesion. To determine the decisive mechanism of PDA coating formation, experiments and simulations were performed in this study. 5,6-Dihydroxyindole (DHI), the signature building block of eumelanin, was introduced as the control group. Various typical building blocks in PDA were quantified by physicochemical characterizations, and the polar-group-dominated interfacial interaction was evaluated by classic molecular dynamics and metadynamics methods. Aminoethyl has been proven to be the key functional group inducing the adsorption of PDA on the hydroxylated silica substrates, while DHI shows limited adhesion to the substrate due to the absence of aminoethyl as the catechol-indole structure of DHI exhibits poor affinity to the silica surface. Pyrrole carboxylic acid, as an oxidative product detected from PDA/DHI, is unfavorable for its adhesion to silica substrates. Overall, the coating formation and self-aggregating precipitation of PDA are two competitive aminoethyl-consuming paths; thus, the in situ oxidative coupling of dopamine is indispensable for the PDA coating preparation. The collected PDA precipitates can no longer present satisfactory coating forming behavior, resulting from a shortage of aminoethyl moieties.

Ionic liquid-triggered charge regulation of polydopamine-based surface for antibacterial nanofiltration

The charged surfaces with desirable performance are of high concern in membrane separation but there exist challenges to tailor them over a task-specific range. Herein, we propose an ionic liquid (IL)-triggered charge regulation strategy for polydopamine (PDA)-based surfaces by tuning the number and position of amino groups of ILs. By strategically manipulating the location of amino groups in either the anion, cation, or both, we realize a complete inversion in the surface charge nature of PDA coatings from highly negative to negative and even highly positive (zeta potential: −25 mV to +25 mV). This charge inversion triggered by IL is attributed to both the number of protonable groups and shielding effect provided by counter ions. Such charge flip enhances Donna effect when the PDA/IL coatings serve as the skin layer of nanofiltration membranes, thereby enabling high rejection to both negative and positive target molecules (i.e., chlorogenic acids at various pH). Despite charge regulation, ILs with dual amino groups cross link the PDA aggregates, largely narrowing the pore size distribution of the skin layer. The IL cross-linked PDA skin layer with uniform pores thus shows a nearly 100 % rejection to the target solutes. Meanwhile, the IL synchronously endow the PDA coatings with tunable charge characteristics, imidazolium functional groups and exceptional superoleophobicity, compensating for the originally inferior antibacterial activity of membranes in a wide pH range.

Nucleation of Bioactive Hydroxyapatite on Polydopamine Coating Three-Dimensional Printed Poly (Lactic Acid) Macro-Porous Scaffold for Bone Grafting Application

Nucleation of Bioactive Hydroxyapatite on Polydopamine Coating Three-Dimensional Printed Poly (Lactic Acid) Macro-Porous Scaffold for Bone Grafting Application

Polydopamine-assisted smart bacteria-responsive hydrogel: Switchable antimicrobial and antifouling capabilities for accelerated wound healing

IntroductionWound infections and formation of biofilms caused by multidrug-resistant bacteria have constituted a series of wound deteriorated and life-threatening problems. The in situ resisting bacterial adhesion, killing multidrug-resistance bacteria, and releasing dead bacteria is strongly required to supply a gap of existing sterilization strategies. ObjectivesThis study aims to present a facile approach to construct a bacteria-responsive hydrogel with switchable antimicrobial-antifouling properties through a “resisting-killing-releasing” method. MethodsThe smart bacteria-responsive hydrogel was constructed by two-step immersion strategy: a simple immersion-coating process to construct Polydopamine (pDA) coatings on the surface of a gelatin-chitosan composite hydrogel and followed by grafting of bactericidal quaternary ammonium chitosan (QCS) as well as pH-responsive PMAA to this pDA coating. The in vitro antimicrobial activity, biocompatibility and the in vivo wound healing effects in a mouse MRSA-infected full-thickness defect model of the hydrogel were further evaluated. ResultsAssisted by polydopamine coating, the pH-responsive PMAA and bactericidal QCS are successfully grafted onto a gelatin-chitosan composite hydrogel surface and hydrogels maintain the adequate mechanical properties. At physiological conditions, the PMAA hydration layer endows the hydrogel with resistance to initial bacterial attachment. Once bacteria colonize and acidize local environment, the swelling PMAA chains tend to collapse then expose the bactericidal QCS, realizing the on-demand kill bacteria. Moreover, the dead bacteria can be released and the hydrogel will resume the resistance due to hydrophilicity of PMAA at increased pH, endowing the surface renewable ability. In vitro and in vivo studies demonstrate the favorable biocompatibility and wound healing capacity of hydrogels that can inhibit infection and further facilitate granulation tissue, angiogenesis, and collagen synthesis. ConclusionThis strategy provides a novel methodology for the development and design of smart wound dressing to combat multidrug-resistant bacteria infections.

Bioinspired multifunctional MXene-decorated textile for thermal management, durable self-cleaning, bio-protection and wearable strain sensor

Textile-based wearable electronic devices have gained significant attention due to their promising applications in personal thermal management, human healthcare monitoring, and human motion detection. Herein, a multifunctional MXene-decorated textile has been fabricated as a promising wearable electronic textile for thermal management, durable self-cleaning, bio-protection and wearable strain sensor. In this study, Ti3C2Tx MXene nanosheets, which are followed by surface engineering with mussel-inspired polydopamine coatings and hydrophobic octadecyl trimethoxysilane, are chosen as active materials for constructing multifunctional MXene-decorated textile. Thus, the multifunctional MXene-decorated textile (Cotton@ODMX) is fabricated by spray-coating the hydrophobic MXene-based composites (ODMX) onto the surface of the cotton textile. Such a Cotton@ODMX epitomizes a highly innovative electronic textile that not only retains the flexibility of the original textile, but also possesses remarkable superhydrophobic properties, outstanding photothermal conversion performance, photothermal self-healing capabilities, environmental stability and exceptional photothermal sterilization capabilities. More importantly, Cotton@ODMX is demonstrated to serve as a wearable strain sensor to monitor fundamental human movements, thus highlighting its impressive sensing capabilities. This work offers valuable insights for the development of multifunctional, flexible and wearable electronic devices with promising potential in personal thermal management, human healthcare monitoring, and human motion detection.

Polydopamine-Modified Liposomes: Preparation and Recent Applications in the Biomedical Field.

Polydopamine (PDA) is a bioinspired polymer that has unique and desirable properties for emerging applications in the biomedical field, such as extraordinary adhesiveness, extreme ease of functionalization, great biocompatibility, large drug loading capacity, good mucopenetrability, strong photothermal capacity, and pH-responsive behavior. Liposomes are consolidated and attractive biomimetic nanocarriers widely used in the field of drug delivery for their biocompatibility and biodegradability, as well as for their ability to encapsulate hydrophobic, hydrophilic, and amphiphilic compounds, even simultaneously. In addition, liposomes can be decorated with appropriate functionalities for targeted delivery purposes. Thus, combining the interesting properties of PDA with those of liposomes allows us to obtain multifunctional nanocarriers with enhanced stability, biocompatibility, and functionality. In this review, a focus on the most recent developments of liposomes modified with PDA, either in the form of polymer layers trapping multiple vesicles or in the form of PDA-coated nanovesicles, is proposed. These innovative PDA coatings extend the application range of liposomes into the field of biomedical applications, thereby allowing for easier functionalization with targeting ligands, which endows them with active release capabilities and photothermal activity and generally improves their interaction with biological fluids. Therefore, hybrid liposome/PDA systems are proposed for surface-mediated drug delivery and for the development of nanocarriers intended for systemic and oral drug delivery, as well as for multifunctional nanocarriers for cancer therapy. The main synthetic strategies for the preparation of PDA-modified liposomes are also illustrated. Finally, future prospects for PDA-coated liposomes are discussed, including the suggestion of potential new applications, deeper evaluation of side effects, and better personalization of medical treatments.

Polydopamine Coating of Graphitic Carbon Nitride, g-C3N4, Improves Biomedical Application.

Graphitic carbon nitride (g-C3N4) is an intriguing nanomaterial that exhibits photoconductive fluorescence properties under UV-visible light. Dopamine (DA) coating of g-C3N4 prepared from melamine was accomplished via self-polymerization of DA as polydopamine (PDA). The g-C3N4 was coated with PDA 1, 3, and 5 times repeatedly as (PDA@g-C3N4) in tris buffer at pH 8.5. As the number of PDA coatings was increased on g-C3N4, the peak intensity at 1512 cm-1 for N-H bending increased. In addition, the increased weight loss values of PDA@g-C3N4 structures at 600 °C from TGA thermograms confirmed that the coating was accomplished. The band gap of g-C3N4, 2.72 eV, was reduced to 0.87 eV after five coatings with PDA. A pristine g-C3N4 was found to have an isoelectric point (IEP) of 4.0, whereas the isoelectric points of 1PDA@g-C3N4 and 3PDA@g-C3N4 are close to each other at 3.94 and 3.91, respectively. On the other hand, the IEP of 5PDA@g-C3N4 was determined at pH 5.75 assuming complete coating with g-C3N4. The biocompatibility of g-C3N4 and PDA@g-C3N4 against L929 fibroblast cell lines revealed that all PDA@g-C3N4 coatings were found to be biocompatible up to a 1000 mg/mL concentration, establishing that PDA coatings did not adversely affect the biocompatibility of the composite materials. In addition, PDA@g-C3N4 was screened for antioxidant potential via total phenol content (TPC) and total flavonoid content assays and it was found that PDA@g-C3N4 has recognizable TPC values and increased linearly with an increased number of PDA coatings. Furthermore, blood compatibility of pristine g-C3N4 is enhanced considerably upon PDA coating, affirmed by hemolysis and the blood clotting index%. Additionally, α-glucosidase inhibitory properties of PDA@g-C3N4 structures revealed that 67.6 + 9.8% of this enzyme was evenly inhibited by 3PDA@g-C3N4 structure.

In situ green immobilization of palladium nanoparticles onto polydopamine-modified eggshell membrane for catalytic reduction of nitrophenols

4-Nitrophenol (4-NP) poses significant threats to both ecosystems and human health, making it essential and highly beneficial to take effective measures to mitigate its impact. Herein, eggshell membrane (ESM) with mussel-inspired polydopamine coatings (ESM-PDA) was constructed and utilized as a template for the immobilization of Pd NPs, resulting in ESM-PDA-Pd formation. The catalyst ESM-PDA-Pd exhibits exceptional performance in reducing 4-NP, and the TOF (turnover frequency) for ESM-PDA-Pd was determined to be 3.3 × 10−5 mmol·mg−1·min−1. Moreover, ESM-PDA-Pd demonstrates excellent catalytic activity in reducing other nitrophenols, including 2-nitrophenol (0.2196 min−1) and 2,4,6-nitrophenol (0.1177 min−1). Notably, the catalyst demonstrated brilliant recyclability, removing 92.4 % of 4-NP within 20 min after undergoing five consecutive runs. This underscores its potential for sustained and effective use in multiple cycles of nitrophenol reduction reactions. Furthermore, the measured Kapp in various water samples is as follows: ultrapure water (0.135 min−1) > tap water (0.109 min−1) > river water (0.083 min−1), indicating its significant potential for industrial applications.

Bioinspired Fabrication of an Insensitive Ammonium Perchlorate Core-Shell Composite with Polydopamine Coating.

In this research, an ammonium perchlorate/polydopamine (AP/PDA) core-shell composite was prepared in a non-aqueous solution to reduce the mechanical sensitivity of ammonium perchlorate (AP). The result showed that the AP/PDA core-shell composite could be successfully constructed in ethyl acetate solution with an AP recovery rate that reached 86%. The mechanical sensitivity of the obtained AP/PDA core-shell composite was significantly reduced with a PDA content of only 0.76%. The DSC and TG also indicated that the coating of PDA showed catalytic activity in the thermal decomposition of AP with a lower decomposition temperature and a decreased Ea value of AP. Thus, this study proposed a simple strategy for achieving a good balanced between harnessing the energy and ensuring the safety of ammonium perchlorate by significantly reducing its mechanical sensitivity by using a very low polydopamine coating layer content, and this shows great potential for the design and fabrication of insensitive energetic composites for use in propellants.

Superhydrophilic conformal polydopamine coating on nanostructured surface formed by capillary-induced solution infusion

As a material-independent adhesive coating agent with excellent functionality on interfaces of materials, polydopamine (PDA) has been widely applicable in bioengineering, environment, and energy fields. Conventional coating methods using dopamine (DA) solutions suffer from slow deposition rates, hindering the attainment of adequate thickness and durability. This work introduces a technique involving rapid capillary-induced solution infusion and in-air polymerization to overcome these limitations. By immersing nanostructured surfaces for just 10 s into the solution, the DA solution is uniformly infused onto the surface, and distributed evenly over the nanostructured surfaces. Polymerization is facilitated by oxygen diffusion from the air, resulting in the formation of a conformal coating up to a micrometer thick. These PDA coatings exhibit persistent superhydrophilicity with water contact angle below 10° and maintain resistance to abrasion, sonication, and oil fouling. Additionally, when applied to microfiber textiles, the PDA coating leads to excellent underwater oil repellency. Our method holds promise for compatibility with various wet-based coating techniques such as drop casting, spraying, spin coating, or ink-jet printing, opening avenues for versatile applications in diverse fields.

Microenvironment-regulated dual-hydrophilic coatings for glaucoma valve surface engineering

Glaucoma valves (GVs) play an essential role in treating glaucoma. However, fibrosis after implantation has limited their long-term success in clinical applications. In this study, we aimed to develop a comprehensive surface-engineering strategy to improve the biocompatibility of GVs by constructing a microenvironment-regulated and dual-hydrophilic antifouling coating on a GV material (silicone rubber, SR). The coating was based on a superhydrophilic polydopamine (SPD) coating with good short-range superhydrophilicity and antifouling abilities. In addition, SPD coatings contain many phenolic hydroxyl groups that can effectively resist oxidative stress and the inflammatory microenvironment. Furthermore, based on its in situ photocatalytic free-radical polymerization properties, the SPD coating polymerized poly 2-methylacryloxyethylphosphocholine, providing an additional long-range hydrophilic and antifouling effect. The in vitro test results showed that the microenvironment-regulated and dual-hydrophilic coatings had anti-protein contamination, anti-oxidation, anti-inflammation, and anti-fiber proliferation capabilities. The in vivo test results indicated that this coating substantially reduced the fiber encapsulation formation of the SR material by inhibiting inflammation and fibrosis. This design strategy for dual hydrophilic coatings with microenvironmental regulation can provide a valuable reference for the surface engineering design of novel medical implantable devices. Statement of significanceSuperhydrophilic polydopamine (SPD) coatings were prepared on silicone rubber (SR) by a two-electron oxidation method. Introduction of pMPC to SPD surface using photocatalytic radical polymerization to obtain a dual-hydrophilic coating. The dual-hydrophilic coating effectively modulates the oxidative and inflammatory microenvironment. This coating significantly reduced protein contamination and adhesion of inflammatory cells and fibroblasts in vitro. The coating-modified SR inhibits inflammatory and fibrosis responses in vivo, promising to serve the glaucoma valves.

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.

Polydopamine films: Versatile but interface-dependent coatings

Abstract Polydopamine coatings have been shown to allow to coat almost all materials with conformal films having a tunable thickness from a few up to more than 100 nm (and even more in some specific cases). These films are able to reduce metal cations, to be modified with many chemical moieties and advent hence as a “Holy Grail” in surface chemistry with an impressive amount of applicative papers published since 2007. However, the broad application field and ease of deposition from aqueous solutions hidden the complexity of the deposition mechanism(s). The discovery that polydopamine (PDA) films also form at air/water interfaces (in the absence of stirring or in stirring dependent manner) to yield membranes with physicochemical properties different than PDA films deposited at solid/water interfaces highlighted for the first time that the nature of the interfaces plays a major role in the PDA film growth mechanism and in the film properties. More recent research allowed to show that the surface chemistry of the used solid substrate modifies the composition of the thin deposited PDA film during the early stages of the deposition process with further deposition yielding to an almost substrate-independent PDA film. It is the aim of this review to describe complex surface effects occurring in PDA deposition and hence to complement other reviews which described the complexity of the chemistry yielding to PDA coatings.

Surface Modification of Polyetheretherketone (PEEK) Intervertebral Fusion Implant Using Polydopamine Coating for Improved Bioactivity.

The occurrence of bone diseases has been increasing rapidly, in line with the aging population. A representative spinal fusion material, polyetheretherketone (PEEK), is advantageous in this regard as it can work in close proximity to the elastic modulus of cancellous bone. However, if it is used without surface modification, the initial osseointegration will be low due to lack of bioactivity, resulting in limitations in surgical treatment. In this study, we aimed to modify the surface of PEEK cages to a hydrophilic surface by coating with polyethylene glycol (PEG), hyaluronic acid (HA), and polydopamine (PDA), and to analyze whether the coated surface exhibits improved bioactivity and changes in mechanical properties for orthopedic applications. Material properties of coated samples were characterized and compared with various PEEK groups, including PEEK, PEEK-PEG, PEEK-HA, and PEEK-PDA. In an in vitro study, cell proliferation was found to be enhanced on PDA-coated PEEK; it was approximately twice as high compared to the control group. In addition, mechanical properties, including static and torsion, were not affected by the presence of the coating. Thus, the results suggest that PEEK-PDA may have the potential for clinical application in fusion surgery for spinal diseases, as it may improve the rate of osseointegration.

Size effect of dynamic bioactive magnetic particles on regulated isolation of tumor cells

Circulating tumor cells (CTCs) are critical biomarkers in cancer metastasis, yet their isolation from the bloodstream remains a challenging task due to their low abundance. This study introduces a method for the efficient isolation of CTCs, utilizing dynamic biointerface-based magnetic particles (DBMPs), with a particular emphasis on the role of particle size. We have developed three distinct sizes DBMPs specifically tailored for effective CTCs interaction, leveraging the unique properties of polydopamine (PDA) coatings and phenylboronic acid (PBA)-modified capture peptides through reversible catechol-boronate interactions. Comparative analysis of DBMPs of varying sizes was assessed under uniform experimental conditions for their capture and release efficiencies. The findings reveal a clear distinction: smaller particles (DBMP1 and DBMP2) achieved greater efficiency in capturing CTCs, whereas the larger particles (DBMP3) were more effective in releasing them. This difference is ascribed to the varied interaction dynamics between the particles and CTCs. Furthermore, we have fine-tuned DBMP3 to optimize CTC capture while still maintaining a high efficiency in cell release. The integration of these DBMPs into a magnetic isolation framework is poised to significantly enhance CTCs isolation methods, marking a pivotal advancement in cancer diagnostics and management.

Standardized cycle life assessment of batteries using extremely lean electrolytic testing conditions

Despite the proposal of numerous advanced materials for batteries, there remains a notable lack of comprehensive assessment protocols that facilitate direct comparisons between laboratory-scale research and industrial trials. Here, we introduce a standardized method coined as extremely lean electrolytic testing (ELET), designed as a uniform framework for evaluating the performance across different battery systems. This approach replicates the cycling behaviour of larger pouch cells within the more manageable format of coin cells under ELET conditions. Employing ELET, we develop quantitative models to create contour maps that standardize cell performance metrics. To demonstrate the ELET efficacy, we explore the mitigation of electrolyte decomposition in lithium-ion batteries through applying polydopamine coatings on silicon/carbon composite anodes, achieving a 150% decrease in electrolyte decomposition compared to uncoated ones. Additionally, we employ the ELET method to compare the performance of various post-secondary and commercial batteries, demonstrating its full utility in battery evaluation.

Mg2+-promoted high-efficiency DNA conjugation on polydopamine surfaces for aptamer-based ochratoxin A detection

BackgroundSurface immobilization of DNA is the foundation of a broad range of applications in biosensing and specific DNA extraction. Polydopamine (PDA) coatings can serve as intermediate layers to immobilize amino- or thiol-labelled molecules, including DNA, onto various materials through Michael addition and/or Schiff base reactions. However, the conjugation efficiency is limited by electrostatic repulsion between negatively charged DNA and PDA. Recently, it has been reported that polyvalent metal ions (such as Mg2+ and Ca2+) can mediate the adsorption of DNA on PDA surfaces. Inspired by this, in this work we aimed to exploit polyvalent metal ions to facilitate the conjugation of DNA on PDA. ResultsMg2+ was used to promote the conjugation of amino-terminated DNA complementary to ochratoxin A (OTA) aptamer (cDNA-NH2) on PDA-coated magnetic nanoparticles (Fe3O4@PDA). After the reaction, the unlinked cDNA-NH2 adsorbed on Fe3O4@PDA mediated by Mg2+ was removed with EDTA. In the presence of 20 mM Mg2+, the amount of covalently linked cDNA-NH2 increased approximately 11-fold compared to that in the absence of Mg2+. The resulting Fe3O4@PDA@cDNA conjugates exhibited superior hybridization capacity towards OTA aptamers, minimal nonspecific adsorption, and excellent chemical stability. The conjugates combined with fluorophore-labelled aptamers were employed for OTA detection, achieving a limit of detection (LOD) of 2.77 ng mL−1. To demonstrate versatility, this conjugation method was extended to Ca2+-promoted conjugation of cDNA-NH2 on Fe3O4@PDA nanoparticles and Mg2+-promoted conjugation of cDNA-NH2 on PDA-coated 96-well plates. SignificanceThe conjugation efficiency of DNA on PDA was significantly improved with the assistance of polyvalent metal ions (Mg2+ and Ca2+), providing a facile and efficient method for DNA immobilization. Due to the substrate-independent adhesion property of PDA, this method demonstrates versatility in DNA surface modification and holds great potential for applications in target extraction, biosensing, and other fields.

Dendrite‐Free Lithium Metal Batteries Enabled by Coordination Chemistry in Polymer‐Ceramic Modified Separators

AbstractIssues with lithium dendrite growth and dead lithium formation limit the practical application of lithium metal batteries, especially under high current conditions where uneven temperature distribution leads to serious safety concerns. Herein, In situ assembly of polydopamine (PDA) and aluminum nitride (AlN) coatings on polypropylene (PP) separator is introduced to address these challenges. The AlN particles are encapsulated by PDA, and the functional groups in PDA form Al‐O coordination bonds with Al3+, which promote uniform Li+ flux and reduce the migration barrier of Li+, thereby enabling dendrite‐free lithium deposition. In addition, the designed PDA@AlN@PP separator exhibits excellent electrolyte wettability, enhanced mechanical performance, and stable thermal resistance, providing a uniform thermal distribution and serving as a robust barrier against dendrite penetration. As a result, symmetric Li||Li cells (over 1800 h at 1 mA cm−2 and 1 mAh cm−2) and Li||Cu cells (over 600 cycles at 0.5 mA cm−2 and 0.5 mAh cm−2, coulombic efficiency over 98%) demonstrate outstanding long cycle performance and high coulombic efficiency. Moreover, the corresponding Li||LiFePO4 cells exhibit a high specific capacity of 91.3 mAh g−1 at 5 C. This work provides a new approach for designing functionalized separators for high‐performance lithium metal batteries.