Polydopamine Films with 2D-like Layered Structure and High Mechanical Resilience

A stable dual-functional monomer imprinted polymer platform for electrochemical sensitive detection of PFAS

Electrochemical molecular imprinting technology (e-MIT) has gained significant attention for detecting emerging micropollutants like per- and polyfluoroalkyl substances (PFAS). However, designing efficient and reliable PFAS sensors based on e-MIT remains challenging. In this study, we explored a mechanism for synergistic adsorption recognition of dual-functional monomers (DM), based on which a molecularly imprinted electrochemical sensor with high sensitivity and stability was developed for PFOA detection. DFT simulations demonstrated that the synergistic interaction between DMs enhances both molecular adsorption capacity and structural stability. Response surface methodology was employed to optimize the MIP composition, revealing a strong correlation between the DM ratio and sensor performance. The optimized MIP-modified electrode exhibited a higher Langmuir adsorption coefficient (Kₐ = 8.92 × 10⁸ cm3 mol-1) and improved stability (RSD < 2 %) compared to single-functional monomer electrodes. Additionally, Al/Co-MOFs/rGO complexes are coupled as the sensor basement. The sensor displayed a wide linear detection range (10 pM to 100 nM), low detection limit (5 pM), and excellent recoveries (94 %-107 %) in river samples, demonstrating its robustness and reliability in real-world applications. This study highlights the potential of DM-based electrochemical sensors for sensitive and reliable detection of emerging micropollutants in complex water environments, paving the way for future monitoring and environmental protection.

A comparative study of polydopamine vs. glass ionomer cement for adhesion mechanisms on enamel and dentin using SEM and shear bond strength evaluation

Polydopamine (PD), inspired by the wet adhesion mechanism of mussel foot proteins, has emerged as a promising adhesive material with wide-ranging applications. This study aimed to compare the adhesive properties of PD and Glass Ionomer Cement (GIC) on enamel and dentin substrates, evaluating PD's potential as an alternative adhesive in dental practice. A total of 120 human premolars were prepared, with 80 teeth allocated for Scanning Electron Microscopy (SEM) analysis and 40 teeth reserved for shear bond strength testing. The 80 teeth for SEM were divided into four groups (n = 20 per group) based on the adhesive used (PD or GIC) and the substrate (enamel or dentin). The bond interfaces were analysed under SEM following adhesive self-polymerization. Statistical analysis using the Mann-Whitney U test (p < 0.05) revealed that GIC and PD showed more microcracks when bonded to dentin compared to enamel, with the PD-enamel group showing the fewest microcracks. For shear bond strength testing, the 40 remaining teeth were divided into four groups (n = 10 per group) according to the same adhesive-substrate combinations. The results analysed using the Kruskal-Wallis test (p < 0.001), indicated that PD bonded to enamel exhibited the highest bond strength, followed by PD-dentin, GIC-enamel, and GIC-dentin. These findings were consistent with the SEM analysis, demonstrating that PD provides superior bonding to enamel and outperforms GIC in both bond strength and interface quality. This study suggests that PD is a viable alternative to GIC, particularly for enamel bonding, and further research is recommended to assess its long-term clinical performance.

Preparation and characterization of mussel-inspired chitosan/polydopamine films and their feasibility for oral mucosa application

Oral mucosal lesions (OML), which represent a major public health issue worldwide, include any pathological changes in the oral mucosa, such as ulcers, pigmentation, and swelling. Due to its humid and dynamic complex environment, designing oral mucosal preparations poses significant challenges. Drawing inspiration from mussels, this study employed an eco-friendly one-pot strategy for the preparation of chitosan/polydopamine (CS/PDA) films. We demonstrated that CS-induced polymerization of dopamine monomers under acidic conditions, which might be attributed to the large number of hydrogen bonding sites of CS chains. PDA markedly enhances properties of the CS film and exhibits concentration dependence. At the concentration of 1 wt% PDA, the lap-shear strength and tensile strength of CS/PDA films reached 5.01 ± 0.24 kpa and 4.20 ± 0.78 kpa, respectively, indicating that the mucosal adhesion ability was significantly improved. In comparison with the single CS film, the swelling rate of CS/PDA film decreased by about 30 %. Rheological results also showed that the storage modulus returned to 93 % after cyclic large strain, while the single CS film only recovered to 73 %. Moreover, these films demonstrated good biocompatibility and enhanced oral ulcer healing in rats, providing a new and practical option for the local treatment of OML.

A biocompatible polydopamine platform for targeted delivery of nicotinamide mononucleotide and boosting NAD+ levels in the brain

Nicotinamide mononucleotide (NMN), a precursor of the coenzyme nicotinamide adenine dinucleotide (NAD+), has gained wide attention as an anti-aging agent, which plays a significant role in intracellular redox reactions. However, its effectiveness is limited by easy metabolism in the liver and subsequent excretion as nicotinamide, resulting in low bioavailability, particularly in the brain. Additionally, the blood-brain barrier (BBB) further hinders NMN supply to the brain, compromising its potential anti-aging effects. Herein, we developed a biocompatible polydopamine (PDA) platform to deliver NMN for boosting NAD+ levels in the brain for the first time. The lactoferrin (Lf) ligand was covalently attached to the PDA spheres to improve BBB transport efficiency. The resultant PDA-based system, referred to as PDA-Lf-NMN, not only exhibited superior BBB penetration ability but also improved the utilization rate of brain NMN in elevating NAD+ levels compared to NMN alone for both young (3 months) and old (21 months) mice. Moreover, after the old mice were treated with low-dose PDA-Lf-NMN (8 mg kg-1 day-1), they exhibited improved spatial cognition. Importantly, these nanomedicines did not induce any cellular necrosis or apoptosis. It provides a promising avenue for delivering NMN specifically to the brain, boosting NAD+ levels for promoting longevity and treating brain aging-related diseases.

The synthesis of polydopamine nano- and microspheres in microdroplets

Here we developed a microdroplet-based strategy for the rapid synthesis of uniform polydopamine nano- and microspheres. Polydopamine spheres with controllable sizes were generated within hundreds of microseconds by simply spraying water solutions of dopamine into microdroplets. Mass spectrometry revealed that dopamine was primarily oxidized into aminochrome, acting as the major building block for polydopamine. We anticipate that microdroplet chemistry will be rich in opportunities for the synthesis of functional nano- and micromaterials.

MXene-Polydopamine-antiCEACAM1 Antibody Complex as a Strategy for Targeted Ablation of Melanoma

Photothermal therapy (PTT) is a method for eradicating tumor tissues through the use of photothermal materials and photosensitizing agents that absorb light energy from laser sources and convert it into heat, which selectively targets and destroys cancer cells while sparing healthy tissue. MXenes have been intensively investigated as photosensitizing agents for PTT. However, achieving the selectivity of MXenes to the tumor cells remains a challenge. Specific antibodies (Ab) against tumor antigens can achieve homing of the photosensitizing agents toward tumor cells, but their immobilization on MXene received little attention. Here, we offer a strategy for the selective ablation of melanoma cells using MXene-polydopamine-antiCEACAM1 Ab complexes. We coated Ti3C2Tx MXene with polydopamine (PDA), a natural compound that attaches Ab to the MXene surface, followed by conjugation with an anti-CEACAM1 Ab. Our experiments confirm the biocompatibility of the Ti3C2Tx-PDA and Ti3C2Tx-PDA-antiCEACAM1 Ab complexes across various cell types. We also established a protocol for the selective ablation of CEACAM1-positive melanoma cells using near-infrared irradiation. The obtained complexes exhibit high selectivity and efficiency in targeting and eliminating CEACAM1-positive melanoma cells while sparing CEACAM1-negative cells. These results demonstrate the potential of MXene-PDA-Ab complexes for cancer therapy. They underline the critical role of targeted therapies in oncology, offering a promising avenue for the precise and safe treatment of melanoma and possibly other cancers characterized by specific biomarkers. Future research will aim to refine these complexes for clinical use, paving the way for new strategies for cancer treatment.

Capture and Storage of Cell-Free DNA via Bio-Informational Hydrogel Microspheres

Excessive cell-free DNA (cfDNA) can induce chronic inflammation by activating intracellular nucleic acid sensors. Intervention in cfDNA-mediated "pro-inflammatory signaling transduction" could be a potential alleviating strategy for chronic inflammation, such as in diabetic wounds. However, effectively and specifically downgrading cfDNA concentration in the pathological microenvironment remains a challenge. Therefore, this work prepares free-standing polydopamine nanosheets through DNA-guided assembly and loaded them into microfluidic hydrogel microspheres. The π─π stacking/hydrogen bonding interactions between polydopamine nanosheets and the π-rich bases of cfDNA, along with the cage-like spatial confinement created by the hydrogel polymer network, achieved cfDNA capture and storage, respectively. Catechol in polydopamine nanosheets can also assist in reducing reactive oxygen species (ROS) levels. Efficient cfDNA binding independent of serum proteins, specific interdiction of abnormal activation of cfDNA-associated toll-like receptor 9, as well as down-regulation of inflammatory cytokines and ROS levels are shown in this system. The chronic inflammation alleviating and the pro-healing effects on the mice model with diabetic wounds are also investigated. This work presents a new strategy for capturing and storing cfDNA to intervene in cell signaling transduction. It also offers new insights into the regulatory mechanisms between inflammatory mediators and biomaterials in inflammation-related diseases.

Ion and Molecular Sieving With Ultrathin Polydopamine Nanomembranes

In contrast to biological cell membranes, it is still a major challenge for synthetic membranes to efficiently separate ions and small molecules due to their similar sizes in the sub-nanometer range. Inspired by biological ion channels with their unique channel wall chemistry that facilitates ion sieving by ion-channel interactions, the first free-standing, ultrathin (10-17 nm) nanomembranes composed entirely of polydopamine (PDA) are reported here as ion and molecular sieves. These nanomembranes are obtained via an easily scalable electropolymerization strategy and provide nanochannels with various amine and phenolic hydroxyl groups that offer a favorable chemical environment for ion-channel electrostatic and hydrogen bond interactions. They exhibit remarkable selectivity for monovalent ions over multivalent ions and larger species with K+/Mg2+ of ≈4.2, K+/[Fe(CN)6]3- of ≈10.3, and K+/Rhodamine B of ≈273.0 in a pressure-driven process, as well as cyclic reversible pH-responsive gating properties. Infrared spectra reveal hydrogen bond formation between hydrated multivalent ions and PDA, which prevents the transport of multivalent ions and facilitates high selectivity. Chemically rich, free-standing, and pH-responsive PDA nanomembranes with specific interaction sites are proposed as customizable high-performance sieves for a wide range of challenging separation requirements.

Assessment of sealing efficacy, radiopacity, and surface topography of a bioinspired polymer for perforation repair

Background

Root perforation repair presents a significant challenge in dentistry due to inherent limitations of existing materials. This study explored the potential of a novel polydopamine-based composite as a root repair material by evaluating its sealing efficacy, radiopacity, and surface topography.

Methods

Confocal microscopy assessed sealing ability, comparing the polydopamine-based composite to the gold standard, mineral trioxide aggregate (MTA). Radiopacity was evaluated using the aluminium step wedge technique conforming to ISO standards. Surface roughness analysis utilized atomic force microscopy (AFM), while field emission scanning electron microscopy (FESEM) visualized morphology.

Results

The polydopamine-based composite exhibited significantly superior sealing efficacy compared to MTA (P < 0.001). Radiopacity reached 3 mm aluminium equivalent, exceeding minimum clinical requirements. AFM analysis revealed a smooth surface topography, and FESEM confirmed successful composite synthesis.

Conclusion

This study demonstrates promising properties of the polydopamine-based composite for root perforation repair, including superior sealing efficacy, clinically relevant radiopacity, and smooth surface topography. Further investigation is warranted to assess its clinical viability and potential translation to endodontic practice.

Rapid Deposition of the Biomimetic Hydroxyapatite-Polydopamine-Amino Acid Composite Layers onto the Natural Enamel

In this work, we developed a technology that enables rapid deposition of biomimetic composite films onto natural enamel slices (known as biotemplates). These films are composed of polydopamine (PDA) and nanocrystalline carbonate-substituted hydroxyapatite (nano-cHAp) that have been functionalized with amino acid l-Arginine. We utilized atomic force microscopy (AFM) and scattering scanning near-field optical microscopy (s-SNOM) combined with infrared (IR) synchrotron to achieve nanoscale spatial resolution for both IR absorption and topography analyses. This combined analytical modality allowed us to understand how morphology connects to local changes in the chemical environment on the biotemplate surface during the deposition of the bioinspired coating. Our findings revealed that when using the proposed technology and after the deposition of the first PDA layer, the film formed on the enamel surface nearly covers the entire surface of the specimen whose thickness is larger on the surface of the emerging enamel prisms. Calculation of the crystallinity index for the biomimetic layer showed a multiple increase compared with natural enamel. This indicates regular and dense aggregation of nano-cHAp into larger crystals, imitating the morphology of natural enamel rods. The microhardness of the formed PDA-based biomimetic layer mineralized with nano-cHAp functionalized with amino acid l-Arginine deposited on natural enamel was practically the same as that of natural enamel. The characterization of nano-cHAp-amino acid-PDA layers using IR and Raman microspectroscopy showed that l-arginine acts as a conjunction agent in the formation of mineralized biomimetic composite coatings. The uniformity of the mechanisms of PDA layer formation under different deposition conditions and substrate types allows for the formation of coatings regardless of the macro- and micromorphology of the template. Therefore, the results obtained in this work have a high potential for future clinical applications in dental practice.

Point-of-care dengue detection: polydopamine-modified electrode for rapid NS1 protein testing for clinical samples

Early diagnosis of dengue infection by detecting the dengue virus non-structural protein 1 (DENV-NS1) is important to the patients to initiate speedy treatment. Enzyme-linked immunosorbent assay (ELISA)-based NS1 detection and RT-PCR are time-consuming and too complex to be employed in remote areas of dengue-endemic countries. Meanwhile, those of NS1 rapid test by lateral flow assay suffer from low detection limit. Electrochemical-based biosensors using screen-printed gold electrodes (SPGEs) have become a reliable detection method to convey both ELISA's high sensitivity and rapid test portability. In this research, we developed an electrochemical biosensor for DENV-NS1 detection by employing polydopamine (PDA)-modified SPGE. The electrodeposition of PDA on the surface of SPGE serves as a bioconjugation avenue for anti-NS1 antibody through a simple and low-cost immobilization procedure. The biosensor performance was evaluated to detect DENV-NS1 protein in PBS and human serum through a differential pulse voltammetric (DPV) technique. The developed sensing platform displayed a low limit of detection (LOD) of 1.63 pg mL-1 and a wide linear range of 10 pg mL-1 to 1 ng mL-1 (R2 ∼ 0.969). The sensing platform also detected DEV-NS1 from four different serotypes in the clinical samples collected from dengue patients in India and Indonesia, with acceptable sensitivity, specificity, and accuracy values of 90.00%, 80.95%, and 87.65%, respectively. This result showcased the facile and versatile method of PDA coating onto the surface of screen-printed gold electrodes for a miniaturized point-of-care (PoC) detection device.

TiO2/PDA Multilayer Nanocomposites with Exceptionally Sharp Large-Scale Interfaces and Nitrogen Doping Gradient

The evolving field of photocatalysis requires the development of new functional materials, particularly those suitable for large-scale commercial systems. One particularly promising approach is the creation of hybrid organic/inorganic materials. Despite being extensively studied, materials such as polydopamine (PDA) and titanium oxide continue to show significant promise for use in such applications. Nitrogen-doped titanium oxide and free-standing PDA films obtained at the air/water interface are particularly interesting. This study introduces a straightforward and reproducible approach for synthesizing a novel class of large-scale multilayer nanocomposites. The method involves the alternate layering of high-quality materials at the air/water interface combined with precise atomic layer deposition techniques, resulting in a gradient nitrogen doping of titanium oxide layers with exceptionally sharp oxide/polymer interfaces. The analysis confirmed the presence of nitrogen in the interstitial and substitutional sites of the TiO2 lattice while maintaining the 2D-like structure of the PDA films. These chemical and structural characteristics translate into a reduction of the band gap by over 0.63 eV and an increase in the photogenerated current by over 60% compared with pure amorphous TiO2. Furthermore, the nanocomposites demonstrate excellent stability during the 1 h continuous photocurrent generation test.

Braided scaffolds with polypyrrole/polydopamine/hydroxyapatite coatings with electrical conductivity and osteogenic properties for bone tissue engineering

When impaired bones are grafted with bone scaffolds, the behaviors of osteoblast are dependent on the implant materials and surface morphology. To this end, we modulated the surface morphology of scaffolds that promote cell growth. In this study, ice-template and spraying method methods are employed to coat different proportions of PDA and PPy over the PLA/PVA weaving scaffolds, after which HA is Coated over via the electrochemical deposition, forming weaving scaffolds with electrically conductive PDA/PPy/HA coating. The test results indicate that with a PPy/PDA concentration ratio is 30, the PPy particles are more uniformly distributed on the fiber surface. The scaffolds are wrapped in a HA coating layer with a high purity, and calcium and phosphorus elements are evenly dispersed with a Ca/P ratio being 1.69. Owing to the synergistic effect between PDA and PPy coating, the scaffolds demonstrate excellent electrochemical stability and electrochemical activity. The biological activity of the scaffold increased to 274.66% under electrical stimulation. The new thinking proposed by this study extends the worth of applying textile structure to the medical field, the application of which highly increases the prospect of bone tissue engineering.

In Vitro/In Vivo Preparation and Evaluation of cRGDyK Peptide-Modified Polydopamine-Bridged Paclitaxel-Loaded Nanoparticles

Cancer remains a disease with one of the highest mortality rates worldwide. The poor water solubility and tissue selectivity of commonly used chemotherapeutic agents contribute to their poor efficacy and serious adverse effects. This study proposes an alternative to the traditional physicochemically combined modifications used to develop targeted drug delivery systems, involving a simpler surface modification strategy. cRGDyK peptide (RGD)-modified PLGA nanoparticles (NPs) loaded with paclitaxel were constructed by coating the NP surfaces with polydopamine (PD). The average particle size of the produced NPs was 137.6 ± 2.9 nm, with an encapsulation rate of over 80%. In vitro release tests showed that the NPs had pH-responsive drug release properties. Cellular uptake experiments showed that the uptake of modified NPs by tumor cells was significantly better than that of unmodified NPs. A tumor cytotoxicity assay demonstrated that the modified NPs had a lower IC50 and greater cytotoxicity than those of unmodified NPs and commercially available paclitaxel formulations. An in vitro cytotoxicity study indicated good biosafety. A tumor model in female BALB/c rats was established using murine-derived breast cancer 4T1 cells. RGD-modified NPs had the highest tumor-weight suppression rate, which was higher than that of the commercially available formulation. PTX-PD-RGD-NPs can overcome the limitations of antitumor drugs, reduce drug toxicity, and increase efficacy, showing promising potential in cancer therapy.

Fabrication and Characterization of a Polydopamine-Modified Bacterial Cellulose and Sugarcane Filter Cake-Derived Hydroxyapatite Composite Scaffold

The search for environmentally friendly and sustainable sources of raw materials has been ongoing for quite a while, and currently, the utilization and applications of agro-industrial biomass residues in biomedicine are being researched. In this study, a polydopamine (PDA)-modified bacterial cellulose (BC) and hydroxyapatite (HA) composite scaffold was fabricated using the freeze-drying method. The as-prepared hydroxyapatite was synthesized via the chemical precipitation method using sugarcane filter cake as a calcium source, as reported in a previous study. X-ray diffraction analysis revealed a carbonated phase of the prepared hydroxyapatite, similar to that of the natural bone mineral. Wide-angle X-ray scattering analysis revealed the successful fabrication of BC/HA composite scaffolds, while X-ray photoelectron spectroscopy suggested that PDA was deposited on the surface of the BC/HA composite scaffolds. In vitro cell viability assays indicated that BC/HA and PDA-modified composite scaffolds did not induce cytotoxicity and were biocompatible with MC3T3-E1 preosteoblasts. PDA-modified composite scaffolds showed enhanced protein adsorption capacity in vitro compared to the unmodified scaffolds. On a concluding note, these results demonstrate that agro-industrial biomass residues have the potential to be used in biomedical applications and that PDA-modified BC/HA composite scaffolds are a promising biomaterial for bone tissue engineering.

Laser-Induced Graphitization of Polydopamine on Titania Nanotubes

Since the discovery of laser-induced graphite/graphene, there has been a notable surge of scientific interest in advancing diverse methodologies for their synthesis and applications. This study focuses on the utilization of a pulsed Nd:YAG laser to achieve graphitization of polydopamine (PDA) deposited on the surface of titania nanotubes. The partial graphitization is corroborated through Raman and XPS spectroscopies and supported by water contact angle, nanomechanical, and electrochemical measurements. Reactive molecular dynamics simulations confirm the possibility of graphitization in the nanosecond time scale with the evolution of NH3, H2O, and CO2 gases. A thorough exploration of the lasing parameter space (wavelength, pulse energy, and number of pulses) was conducted with the aim of improving either electrochemical activity or photocurrent generation. Whereas the 532 nm laser pulses interacted mostly with the PDA coating, the 365 nm pulses were absorbed by both PDA and the substrate nanotubes, leading to a higher graphitization degree. The majority of the photocurrent and quantum efficiency enhancement is observed in the visible light between 400 and 550 nm. The proposed composite is applied as a photoelectrochemical (PEC) sensor of serotonin in nanomolar concentrations. Because of the suppressed recombination and facilitated charge transfer caused by the laser graphitization, the proposed composite exhibits significantly enhanced PEC performance. In the sensing application, it showed superior sensitivity and a limit of detection competitive with nonprecious metal materials.

Experimental Methods to Get Polydopamine Films: A Comparative Review on the Synthesis Methods, the Films' Composition and Properties

In 2007, polydopamine (PDA) films were shown to be formed spontaneously on the surface of all known classes of materials by simply dipping those substrates in an aerated dopamine solution at pH = 8.5 in the presence of Tris(hydroxymethyl) amino methane buffer. This universal deposition method has raised a burst of interest in surface science, owing not only to the universality of this water based one pot deposition method but also to the ease of secondary modifications. Since then, PDA films and particles are shown to have applications in energy conversion, water remediation systems, and last but not least in bioscience. The deposition of PDA films from aerated dopamine solutions is however a slow and inefficient process at ambient temperature with most of the formed material being lost as a precipitate. This incited to explore the possibility to get PDA and related films based on other catecholamines, using other oxidants than dissolved oxygen and other deposition methods. Those alternatives to get PDA and related films are reviewed and compared in this paper. It will appear that many more investigations are required to get better insights in the relationships between the preparation method of PDA and the properties of the obtained coatings.

A Study of the Peculiarities of the Formation of a Hybrid Interface Based on Polydopamine between Dental Tissues and Dental Composites, Using IR and Raman Microspectroscopy, at the Submicron Level

The creation of buffer (hybrid) layers that provide improved adhesion to two heterogeneous materials is a promising and high-priority research area in the field of dental materials science. In our work, using FTIR and Raman microspectroscopy at the submicron level in a system of dental composites/intact dental enamel, we assessed the molecular features of formation and chemically visualized the hybrid interface formed on the basis of a nature-like adhesive, polydopamine (PDA). It is shown that a homogeneous bioinspired PDA-hybrid interface with an increased content of O-Ca-O bonds can be created using traditional methods of dental tissue pretreatment (diamond micro drilling, acid etching), as well as the subsequent alkalinization procedure and the developed synthesis technology. The development of the proposed technology for accelerated deposition of PDA-hybrid layers, as well as the creation of self-assembled biomimetic nanocomposites with antibacterial properties, may in the future find clinical application for minimally invasive dental restoration procedures.

Recent progress and future perspectives of polydopamine nanofilms toward functional electrochemical sensors

Since its discovery in 2007, polydopamine nanofilms have been widely used in many areas for surface functionalization. The simple and low-cost preparation method of the nanofilms with tunable thickness can incorporate amine and oxygen-rich chemical groups in virtually any interface. The remarkable advantages of this route have been successfully used in the field of electrochemical sensors. The self-adhesive properties of polydopamine are used to attach nanomaterials onto the electrode's surface and add chemical groups that can be explored to immobilize recognizing species for the development of biosensors. Thus, the combination of 2D materials, nanoparticles, and other materials with polydopamine has been successfully demonstrated to improve the selectivity and sensitivity of electrochemical sensors. In this review, we highlight some interesting properties of polydopamine and some applications where polydopamine plays an important role in the field of electrochemical sensors.

The Convenience of Polydopamine in Designing SERS Biosensors with a Sustainable Prospect for Medical Application

Polydopamine (PDA) is a multifunctional biomimetic material that is friendly to biological organisms and the environment, and surface-enhanced Raman scattering (SERS) sensors have the potential to be reused. Inspired by these two factors, this review summarizes examples of PDA-modified materials at the micron or nanoscale to provide suggestions for designing intelligent and sustainable SERS biosensors that can quickly and accurately monitor disease progression. Undoubtedly, PDA is a kind of double-sided adhesive, introducing various desired metals, Raman signal molecules, recognition components, and diverse sensing platforms to enhance the sensitivity, specificity, repeatability, and practicality of SERS sensors. Particularly, core-shell and chain-like structures could be constructed by PDA facilely, and then combined with microfluidic chips, microarrays, and lateral flow assays to provide excellent references. In addition, PDA membranes with special patterns, and hydrophobic and strong mechanical properties can be used as independent platforms to carry SERS substances. As an organic semiconductor material capable of facilitating charge transfer, PDA may possess the potential for chemical enhancement in SERS. In-depth research on the properties of PDA will be helpful for the development of multi-mode sensing and the integration of diagnosis and treatment.

Ternary nanocomposite-based smart sensor: Reduced graphene oxide/polydopamine/alanine nanocomposite for simultaneous electrochemical detection of Cd2+, Pb2+, Fe2+, and Cu2+ ions

Heavy metal ion (HMI) sensors are the most sought commercial devices for environmental monitoring and food analysis research due to serious health concerns associated with HMI overdosage. Herein, we developed an effective electrochemical sensor for simultaneous detection of four HMI (Cd²⁺, Pb²⁺, Fe²⁺, and Cu²⁺) using a ternary nanocomposite of reduced graphene oxide functionalized with polydopamine and alanine (ALA/pDA/rGO). Comprehensive spectroscopic and microscopic characterizations were performed to ensure the formation of the ternary nanocomposite. The developed nanocomposite on glassy carbon electrode (GCE) yields >2-fold higher current than GO/GCE electrode with excellent electrochemical stability and charge transfer rate. Using DPV, various chemical and electrochemical parameters, such as supporting electrolyte, buffer pH, metal deposition time, and potential, were optimized to achieve highly sensitive detection of targeted HMI. For Cd²⁺, Pb²⁺, Fe²⁺, and Cu²⁺ sensing devised sensor exhibited detection limits of 1.46, 2.86, 50.23, and 17.95 ppb and sensitivity of 0.0929, 0.0744, 0.0051, and 0.0394 μA/ppb, respectively, with <6% interference. The sensor worked similarly well for real water samples with HMI. This study demonstrates a novel strategy for concurrently detecting and quantifying multiple HMI in water and soil using a smart ternary nanocomposite-based electrochemical sensor, which can also detect HMI in food samples.

Kinetic study of polydopamine sphere synthesis using TRIS: relationship between synthesis conditions and final properties

The synthesis and characterization of polydopamine (PDA) using dopamine (DA) as the monomer and (hydroxymethyl)aminomethane (TRIS) as the oxidant is studied. The effect of temperature and TRIS concentration on the kinetics of dopamine polymerization is evaluated, and the kinetic parameters are also calculated. Three TRIS concentrations are used to assess their effect on DA polymerization kinetics. The reaction at 1.5 mmol of TRIS shows a sustained increase of the rate constant with temperature from 2.38 × 10^-4 to 5.10 × 10^-4 when the temperature is increased from 25 to 55 °C; however, not all reactions follow an Arrhenius law. In addition, the correlation between the synthesis parameters and morphological, structural, and thermal properties of polydopamine is established. The morphology of the PDA particles is evaluated by Scanning Electron Microscopy (SEM), the relationships between the diameter, distribution size, and the rate constant. Thermal characterization by Differential Scanning Calorimetry (DSC) shows an endothermic transition around 130 °C associated with the melting of PDA's regular structure. It is supported by structural studies, such as infrared and Raman spectroscopy and X-ray Diffraction (XRD), by observing a broad peak at 23.1° (2θ) that fits with a graphitic-like structure of PDA.

Mitigation of biofouling with co-deposition of polydopamine and curcumin on the surface of a thin-film composite membrane

Reverse osmosis (RO) membrane has been widely used in various water treatment fields as an efficient desalination technology, but serious biofouling problem arises in the actual application process. Curcumin is known as a natural compound that can reduce biofouling by inhibiting the growth of microorganisms based on quorum sensing. Dopamine, a molecule with excellent adhesion and functionalization on the material's surface, has high research value for applying a curcumin coating to the membrane surface. Curcumin degrades under alkaline conditions, whereas dopamine must polymerize under alkaline conditions. Simultaneously, a coating may adversely affect curcumin. Therefore, a two-step coating process was considered by self-polymerizing dopamine on the thin-film composite membrane surface and then dip-coating curcumin attached to the polydopamine layer. Furthermore, the effect of time and concentration on the surface modification before and after membrane modification was investigated. The highest permeability of 1.39 L/m²/hr/bar was achieved with the modified membranes. The number of gram-positive bacteria decreased from 6.71 × 10⁶ to 9.67 × 10⁵ CFU/mL. This result is meaningful for antifouling through modification of the membrane surface. Use of curcumin can be applied to reduce biofouling and extend the lifetime of the membrane without pretreatment or membrane cleaning.

A two-step strategy to deposit a hydroxyapatite coating on polydopamine-coated polymer fibers

As the main inorganic component of human bones and teeth, hydroxyapatite (HA), with excellent bioactivity and biocompatibility, shows great potential in the bone tissue engineering field. Marine mussel-inspired polydopamine (PDA) possesses unique functional groups and thus can absorb the calcium ions from extracellular fluid, thereby triggering the precipitation of HA. This study is based on a two-step strategy. Using the chemical activity of PDA, polyvinyl alcohol/polylactic acid (PVA/PLA) braids were coated with a PDA layer that served as a template for the electrochemical deposition of a HA layer. The test results indicate that the resulting HA crystals were assembled on the polymer fibers in an urchin-like mannerwith a stratified structure. Subsequently, the HA/PDA-PVA/PLA braided bone scaffolds were immersed in simulated body fluid for ten days, after which the bone scaffolds were found to be completely coated with HA, indicating a good biomineralization capability. Cell activity of HA/PDA-PVA/PLA scaffolded by dopamine-assisted electrodeposition was 178.8% than that of PVA/PLA braids. This HA coating layer inspired by biochemical strategies may be useful in the field of bone tissue engineering.

MOF-derived CuO@ZnO modified titanium implant for synergistic antibacterial ability, osteogenesis and angiogenesis

Surface modification of titanium implants with antibacterial, osteogenic and even angiogenic capabilities are essential to enhance their clinical applicability. Herein, metal-organic framework (MOF) derived CuO@ZnO composite was grafted onto the polydopamine (PDA) modified titanium alloy to achieve vascularized bone regeneration. The CuO@ZnO-coated titanium effectively inhibits the formation of bacterial biofilms and the sterilization rate of Staphylococcus aureus (S. aureus) reaches 99%. Benefitting from the intrinsic porous architecture of MOFs, the Zn2+ and Cu2+ could be controllably released to facilitate the production of excess intracellular reactive oxygen species (ROS) inside the bacteria, which ensures the excellent antibacterial performance of the composite coating. The CuO@ZnO-coated titanium also exhibits good cytocompatibility, effectively promotes the adhesion and proliferation of the human bone marrow mesenchymal stem cells (hBMSCs) and reduces the level of the cell apoptosis. The up-regulated expression of the osteogenesis-related genes and the superior extracellular matrix mineralization reveals that the CuO@ZnO coating possesses fantastic osteoinductive properties. In addition, the transwell and tube formation assays of the human umbilical vein endothelial cells (HUVECs) suggest the superior angiogenesis ability of the CuO@ZnO-coated titanium. The released Cu2+ stimulated the angiogenesis of the HUVECs in vitro by up-regulating the expression of the vascular endothelial growth factor (VEGF). These findings will provide new insight into the development of multifunctional titanium implants for clinical applications.

Polydopamine at biological interfaces

In the last years coating of surfaces in the presence of dopamine or other catecholamines in oxidative conditions to yield "polydopamine" films has become a popular, easy and versatile coating methodology. Polydopamine(s) offer(s) also a rich chemistry allowing to post-functionalize the obtained coatings with metal nanoparticles with polymers and proteins. However, the interactions either of covalent or non-covalent nature between polydopamine and biomolecules has only been explored more recently. They allow polydopamine to become a material, in the form of nanoparticles, membranes and other assemblies, in its own right not just as a coating. It is the aim of this review to describe the most recent advances in the design of composites between polydopamine and related eumelanin like materials with biomolecules like proteins, nucleotides, oligosaccharides and lipid assemblies. Furthermore, the interactions between polydopamine and living cells will be also reported.

Fast Light-Driven Motion of Polydopamine Nanomembranes

The actuation of micro- and nanostructures controlled by external stimuli remains one of the exciting challenges in nanotechnology due to the wealth of fundamental questions and potential applications in energy harvesting, robotics, sensing, biomedicine, and tunable metamaterials. Photoactuation utilizes the conversion of light into motion through reversible chemical and physical processes and enables remote and spatiotemporal control of the actuation. Here, we report a fast light-to-motion conversion in few-nanometer thick bare polydopamine (PDA) membranes stimulated by visible light. Light-induced heating of PDA leads to desorption of water molecules and contraction of membranes in less than 140 μs. Switching off the light leads to a spontaneous expansion in less than 20 ms due to heat dissipation and water adsorption. Our findings demonstrate that pristine PDA membranes are multiresponsive materials that can be harnessed as robust building blocks for soft, micro-, and nanoscale actuators stimulated by light, temperature, and moisture level.

Replacing amine by azide: Dopamine azide polymerization triggered by sodium periodate

Polydopamine (PDA) have been widely described for a range of biomedical and surface engineering applications. However the structure of PDA remains elusive due to the insoluble nature of the polymer....

Facile Fabrication of a Functional Filter Tip for Highly Efficient Reduction of Nicotine Content in Mainstream Smoke

The nicotine addiction problem is of great concern, particularly in adolescents. Notably, nicotine addiction drives humans to continue smoking. Notably, several diseases and disorders are caused by smoking. To date, various adsorbents have been proposed to develop a functionalization filter tip for reducing nicotine content in mainstream smoke. However, the nicotine adsorption efficiencies of most of the reported functionalization filter tips were not satisfactory, and their preparation process was complex and time-consuming. Herein, we demonstrate a highly active and adsorbing filter tip for cigarettes, fabricated by decorating polydopamine (PDA) on the surface of a commercial filter tip in situ. The PDA coating on the filter tip was obtained by the self-polymerization of dopamine (DA) within 16 h, which was quicker and easier than the preparation processes of other reported functionalized filter tips. Significantly, the PDA-decorated filter tip had a nicotine adsorption efficiency as high as ∼95%, which was much higher than most of the commercial filter tips.