Adhesive polydopamine-based photothermal hybrid hydrogel for on-demand lidocaine delivery, effective anti-bacteria, and prolonged local long-lasting analgesia

Considering the astonishing prevalence of localized pain affecting billions of patients worldwide, the development of advanced analgesic formulations or delivery systems to achieve clinical applicability is of great significance. In this study, an integrated PDA-based LiH@PDA@Ag@PAA@Gelatin system was designed for sustained delivery of lidocaine hydrochloride (LiH). By optimizing the preparation process and formulation of the hydrogel, the hydrogel exhibited superior mechanical properties, reversibility, adhesion strength, and self-healing attributes. Moreover, PDA@Ag nanoparticles were evenly dispersed within the hydrogel, and the optimized PDA@Ag@PAA@Gelatin showed a higher photothermal conversion efficiency than that of pure PDA. Importantly, LiH@PDA@Ag@PAA@Gelatin could effectively capture and eradicate bacteria through the synergistic interaction between near-infrared (NIR), PDA, Ag and LiH. In vitro and in vivo tests demonstrated that LiH@PDA@Ag@PAA@Gelatin exhibited higher drug delivery efficiency compared to commercial lidocaine patches. By evaluating the mechanical pain withdrawal threshold of the spared nerve injury (SNI) model in rats, it was proven that LiH@PDA@Ag@PAA@Gelatin enhanced and prolonged the analgesic effect of LiH. Furthermore, LiH@PDA@Ag@PAA@Gelatin induced by NIR possessed excellent on-demand photothermal analgesic ability. Therefore, this study develops a convenient method for preparing localized analgesic hydrogel patches, providing an important step towards advancing PDA-based on-demand pain relief applications.

Mechanism of Self-Oxidative Copolymerization and its Application with Polydopamine-pyrrole Nano-copolymers

Currently, the copolymer of dopamine (DA) and pyrrole (PY) via chemical and electrochemical oxidation usually requires additional oxidants, and lacks flexibility in regulating the size and morphology, thereby limiting the broad applications of DA-PY copolymer in biomedicine. Herein, the semiquinone radicals produced by the self-oxidation of DA is ingeniously utilized as the oxidant to initiate the following copolymerization with PY, and a series of quinone-rich polydopamine-pyrrole copolymers (PDAm -nPY) with significantly enhanced absorption in near-infrared (NIR) region without any additional oxidant assistance is obtained. Moreover, the morphology and size of PDAm -nPY can be regulated by changing the concentration of DA and PY, thereby optimizing nanoscale PDA0.05 -0.15PY particles (≈ 150 nm) with excellent NIR absorption and surface modification activity are successfully synthesized. Such PDA0.05 -0.15PY particles show effective photoacoustic (PA) imaging and photothermal therapy (PTT) against 4T1 tumors in vivo. Furthermore, other catechol derivatives can also copolymerize with PY under the same conditions. This work by fully utilizing the semiquinone radical active intermediates produced through the self-oxidation of DA reduces the dependence on external oxidants in the synthesis of composite materials and predigests the preparation procedure, which provides a novel, simple, and green strategy for the synthesis of other newly catechol-based functional copolymers.

Rapidly Inhibiting the Inflammatory Cytokine Storms and Restoring Cellular Homeostasis to Alleviate Sepsis by Blocking Pyroptosis and Mitochondrial Apoptosis Pathways

Pyroptosis, systemic inflammation, and mitochondrial apoptosis are the three primary contributors to sepsis's multiple organ failure, the ultimate cause of high clinical mortality. Currently, the drugs under development only target a single pathogenesis, which is obviously insufficient. In this study, an acid-responsive hollow mesoporous polydopamine (HMPDA) nanocarrier that is highly capable of carrying both the hydrophilic drug NAD⁺ and the hydrophobic drug BAPTA-AM, with its outer layer being sealed by the inflammatory targeting peptide PEG-LSA, is developed. Once targeted to the region of inflammation, HMPDA begins depolymerization, releasing the drugs NAD⁺ and BAPTA-AM. Depletion of polydopamine on excessive reactive oxygen species production, promotion of ATP production and anti-inflammation by NAD⁺ replenishment, and chelation of BAPTA (generated by BA-AM hydrolysis) on overloaded Ca²⁺ can comprehensively block the three stages of sepsis, i.e., precisely inhibit the activation of pyroptosis pathway (NF-κB-NLRP3-ASC-Casp-1), inflammation pathway (IL-1β, IL-6, and TNF-α), and mitochondrial apoptosis pathway (Bcl-2/Bax-Cyt-C-Casp-9-Casp-3), thereby restoring intracellular homeostasis, saving the cells in a state of "critical survival," further reducing LPS-induced systemic inflammation, finally restoring the organ functions. In conclusion, the synthesis of this agent provides a simple and effective synergistic drug delivery nanosystem, which demonstrates significant therapeutic potential in a model of LPS-induced sepsis.

Ga2O3 Quantum Dots with N-Doped Amorphous Carbon Fixed for Efficient Storage and Transfer of Lithium Ions by Introduction of Dopamine Hydrochloride

The Ga₂O₃ anode has great potential due to its self-healing and high theoretical capacity in lithium-ion batteries. Like anodes with other transition metal oxides, the Ga₂O₃ anode has the problems of structural change and low electrical conductivity. The electrochemical performance of the Ga₂O₃ anode still needs to be improved. In this work, we synthesized a Ga₂O₃ quantum dots@N-doped carbon (Ga₂O₃-QD@NC) composite by hydrothermal reaction with a carbon source of dopamine hydrochloride, in which Ga₂O₃ quantum dots were dispersed in the interior of the amorphous carbon. Such a special structure is conducive to the high-speed migration of lithium ions and electrons and effectively inhibits volume expansion and agglomeration. Smaller and more uniform quantum dots facilitate efficient repair of the structure. Due to these advantages, the Ga₂O₃-QD@NC electrode has great electrochemical performance. The Ga₂O₃-QD@NC electrode has an initial discharge capacity of 1580 mAh g^-1 with a high first Coulombic efficiency of 62.8% and a cycling capacity of 953 mAh g^-1 under 0.1 A g^-1. It even has a capacity of 460 mAh g^-1 at 1 A g^-1 after 300 cycles. This strategy can provide a new direction for the Ga₂O₃ anode in lithium-ion batteries with high capacity.

Structural elucidation of polydopamine facilitated by ionic liquid solvation

Minimal understanding of the formation mechanism and structure of polydopamine (pDA) and its natural analogue, eumelanin, impedes the practical application of these versatile polymers and limits our knowledge of the origin of melanoma. The lack of conclusive structural evidence stems from the insolubility of these materials, which has spawned significantly diverse suggestions of pDA's structure in the literature. We discovered that pDA is soluble in certain ionic liquids. Using these ionic liquids (ILs) as solvents, we present an experimental methodology to solvate pDA, enabling us to identify pDA's chemical structure. The resolved pDA structure consists of self-assembled supramolecular aggregates that contribute to the increasing complexity of the polymer. The underlying molecular energetics of pDA solvation and a macroscopic picture of the disruption of the aggregates using IL solvents have been investigated, along with studies of the aggregation mechanism in water.

Mussel-Inspired Two-Dimensional Halide Perovskite Facilitated Dopamine Polymerization and Self-Adhesive Photoelectric Coating

Polydopamine (PDA) is a good adhesion agent for lots of gels inspired by the mussel, whereas hybrid organic-inorganic perovskites (HOIPs) usually exhibit extraordinary optoelectronic performance. Herein, mussel-inspired chemistry has been integrated with two-dimensional HOIPs first, leading to the preparation of new crystal (HDA)₂PbBr₄ (1) (DA = dopamine). The organic cation dopamine can be introduced into PDA resulting in a thin film of (HPDA)₂PbBr₄ (PDA-1). The dissolved inorganic components of layered perovskite in DMF solution together with H₂O₂ addition can facilitate DA polymerization greatly. More importantly, PDA-1 can inherit an excellent semiconductor property of HOIPs and robust adhesion of the PDA hydrogel resulting in a self-adhesive photoelectric coating on various interfaces.

Size Regulation of Polydopamine Nanoparticles by Boronic Acid and Lewis Base

Size regulation of polydopamine nanoparticles (PDA NPs) is vital to melanin-inspired materials. The general strategy usually focuses on tuning of the reaction parameters which could affect the dopamine (DA) monomer polymerization process, such as pH, temperature, monomer concentration, etc. The reaction between boronic acids and catechols to form boronic esters has been widely applied in many fields, but little attention has been paid in the size regulation of PDA NPs. Here, it is speculated that the fine size regulation of PDA NPs can be directly achieved by using boronic acids and Lewis base molecules. It is found that these issues could indeed significantly affect the stability of the boronic esters formed by boronic acids and DA, which may further inhibit the monomer polymerization kinetics and tune the particle size of the resulting PDA NPs. It is also found that the several intrinsic properties of PDA NPs such as the free radical scavenging ability, UV spectral absorption, photothermal behavior, and structural color all change with the particle size. It is believed that this work can provide new opportunities for fabricating melanin-inspired PDA NPs with well controlled size and properties.

Structure and properties of flexible starch-based double network composite films induced by dopamine self-polymerization

Starch-based packaging materials are being developed to alleviate environmental pollution and greenhouse gas emissions associated with plastic-based ones. However, the high hydrophilicity and poor mechanical properties of pure-starch films limit their widespread application. In this study, dopamine self-polymerization was used as a strategy to improve the performance of starch-based films. Spectroscopy analysis showed that strong hydrogen bonding occurred between polydopamine (PDA) and starch molecules within the composite films, which significantly altered their internal and surface microstructures. The composite films had a greater water contact angle (> 90°), which indicated that the incorporation of PDA reduced their hydrophilicity. Additionally, the elongation at break of the composite films was 11-fold higher than pure-starch films, indicating that PDA improved film flexibility, while the tensile strength decreased to some extent. The composite films also exhibited excellent UV-shielding performance. These high-performance films may have practical applications in food and other industries as biodegradable packaging materials.

High-Precision Micropatterning of Polydopamine by Multiphoton Lithography

Mussel-inspired polydopamine (PDA) initiates a multifunctional modification route that leads to the generation of novel advanced materials and their applications. However, existing PDA deposition techniques still exhibit poor spatial control, have a very limited capability of micropatterning, and do not allow local tuning of the PDA topography. Herein, PDA deposition based on multiphoton lithography (MPL) is demonstrated, which enables full spatial and temporal control with nearly total freedom of patterning design. Using MPL, 2D microstructures of complex design are achieved with pattern precision of 0.8 µm without the need of a photomask or stamp. Moreover, this approach permits adjusting the morphology and thickness of the fabricated microstructure within one deposition step, resulting in a unique tunability of material properties. The chemical composition of PDA is confirmed and its ability for protein enzyme immobilization is demonstrated. This work presents a new methodology for high-precision and complete control of PDA deposition, enabling PDA incorporation in applications where fine and precise local surface functionalization is required. Possible applications include multicomponent functional elements and devices in microfluidics or lab-on-a-chip systems.

Novel and Sustainable Colorants Developed via Incorporating Azo Chromophores into Dopamine Molecules

Inspired by the application of dopamine as an "anchor" and UV absorber, novel sustainable colorants with biscatecholic structure were synthesized through a simple incorporation of simple azo chromophores with dopamine. Their structures were confirmed using MS and NMR analyses, and their application on textile materials was investigated. Compared to the simple azo chromophores with almost no coloring ability on fabrics, the biscatecholic colorants could color different fabrics effectively, mainly through self-polymerization only in the presence of a trace amount of organic base at room temperature, which is environmentally friendly in terms of saving resources and alleviating chemical pollution. Meanwhile, the UV resistance of colored fabrics was enhanced significantly, showing the advantage of protecting wearers from UV damage.

In Situ, One-Pot Method to Prepare Robust Superamphiphobic Cotton Fabrics for High Buoyancy and Good Antifouling

Multifunctional superamphiphobic cotton fabrics are in high demand. However, preparation of such fabrics is often difficult or complicated. Herein, a novel superamphiphobic fabric is constructed by a simple one-pot method with an in situ growth process. Under suitable alkaline conditions, dopamine (DA) can be oxidized to benzoquinone. Meanwhile, 3-aminopropyltriethoxysilane (APTES), 1H,1H,2H,2H-perfluorodecyltriethoxysilane (FAS-17) molecules undergo the hydrolysis reaction and bond together. Besides, benzoquinone can react with APTES by Schiff base and hollow nanoclusters can be finally obtained because of the steric hindrance effect of benzene ring and long alkyl chain. Such nanoclusters are formed on the surface of fabric, which endows the fabric with extreme liquid repellence. The effects of pH value and DA concentration on the surface morphology and lyophobic properties of the fabric are systematically studied. The water and pump oil contact angles of the superamphiphobic fabric obtained under the optimal reaction conditions can reach 160 and 151°, respectively. The lyophobicity of the fabric is maintained even after undergoing various harsh tests, showing significant durability and stability. In addition, the superamphiphobic fabric exhibits good antifouling and strong buoyancy ability. The superamphiphobic fabric can load 35 and 27.4 times its own weight in water and oil, respectively, which shows great potential in the field of functional textiles such as swimming suits, protective clothing, and life jackets in the future.

Molecularly Imprinted Synthetic Antibodies: From Chemical Design to Biomedical Applications

Billions of dollars are invested into the monoclonal antibody market every year to meet the increasing demand in clinical diagnosis and therapy. However, natural antibodies still suffer from poor stability and high cost, as well as ethical issues in animal experiments. Thus, developing antibody substitutes or mimics is a long-term goal for scientists. The molecular imprinting technique presents one of the most promising strategies for antibody mimicking. The molecularly imprinted polymers (MIPs) are also called "molecularly imprinted synthetic antibodies" (MISAs). The breakthroughs of key technologies and innovations in chemistry and material science in the last decades have led to the rapid development of MISAs, and their molecular affinity has become comparable to that of natural antibodies. Currently, MISAs are undergoing a revolutionary transformation of their applications, from initial adsorption and separation to the rising fields of biomedicine. Herein, the fundamental chemical design of MISAs is examined, and then current progress in biomedical applications is the focus. Meanwhile, the potential of MISAs as qualified substitutes or even to transcend the performance of natural antibodies is discussed from the perspective of frontier needs in biomedicines, to facilitate the rapid development of synthetic artificial antibodies.

Stacked hexagonal prism of Ag@Ni-MOF-1 as functionalized SERS platform through rational integration of catalytic synthesis of dopamine-quinone at physiological pH with a biomimetic route

Herein, a novel stacked hexagonal prism, Ag@Ni-MOF-1, was designed and developed as an integrated SERS platform not only for successfully catalyzing the in situ synthesis of DA-quinone under physiological pH, but also for establishing an approach for specific determination of Cys, an important species in the brain related to Alzheimer's disease (AD).

Facile synthesis of polydivinylbenzene coated magnetic polydopamine coupled with pressurized liquid extraction for the extraction and cleanup of polycyclic aromatic hydrocarbons in soils

Due to the trace levels of polycyclic aromatic hydrocarbons (PAHs) in soil and the complexity of soil matrices, effective sample pretreatment methods are of great significance to obtain accurate analytical results. In this paper, polydopamine (PDA) encapsulated Fe₃O₄ particles were used as seeds for in situ polymerization of divinylbenzene (DVB) to derive magnetic hybrid material Fe₃O₄@PDA@PDVB. Coupled with pressurized liquid extraction, Fe₃O₄@PDA@PDVB was investigated as a selective adsorbent for the extraction and cleanup of PAHs in soil. The prepared magnetic material was characterized and demonstrated to possess strong hydrophobicity and superparamagnetism. Under optimal conditions, Fe₃O₄@PDA@PDVB can effectively extract 15 PAHs from a 30% methanol solution within 2 min, and it is more selective for PAHs than for n-alkane in soil extracts. The matrix effect significantly decreased after extraction by the prepared material, which showed superiority to a silica gel column method (EPA 3630C Method). The developed method was linear (5-1000 ng g^-1) with coefficient of determination (R²) ranging from 0.9986-0.9998, and the limits of detection were 0.13-0.54 ng g^-1. Additionally, repetitive experiments indicated that the prepared material was reproducible and reusable with relative standard deviations below 8.4% and 8.6%, respectively. Finally, the new method was successfully employed to determine the concentrations of PAHs in genuine soil and standard reference material, and the results were comparable to those of widely utilized EPA methodology.

Silica-polydopamine hybrids as light-induced oxidase mimics for colorimetric detection of pyrophosphate

In this study, silica-polydopamine hybrids (SPDA) were fabricated by a facile and one-step heating method using dopamine and (3-aminopropyl)triethoxysilane (APTES) as the reaction reagents. It was firstly found that light illuminated-SPDA could oxidize colorless 3,3',5,5'-tetramethylbenzidine (TMB) to produce blue ox-TMB. The coloration process was quenched very efficiently via the addition of Cu2+. The presence of pyrophosphate ion (PPi) in the solution of light-illuminated SPDA-Cu2+-TMB induced the recovery of the coloration process. The recovery occurred because PPi coordinated with Cu2+, effectively sequestering the ion from SPDA. A calibration curve was developed that is related to the extent of absorption recovery to [PPi], making the SPDA-Cu2+-TMB system a sensitive and selective turn-on sensor for PPi detection. The limit-of-detection (LOD) for PPi was 0.06 μmol L-1 (S/N = 3) with a linear dynamic range of 0.1-30 μmol L-1 and the calibration curve of linear equation is given as: y = 0.00146x + 0.05096 (r = 0.9974). The proposed method has been successfully applied to the detection of PPi in human serum with satisfactory recovery. The simplicity, low cost, high sensitivity, good reproducibility and excellent selectivity of the PPi detection platform based on the light-induced oxidase mimicking property of SPDA makes it promising for further applications of SPDA in chemo/biosensing.

The molecular mechanisms underlying mussel adhesion

Marine mussels are able to firmly affix on various wet surfaces by the overproduction of special mussel foot proteins (mfps). Abundant fundamental studies have been conducted to understand the molecular basis of mussel adhesion, where the catecholic amino acid, l-3,4-dihydroxyphenylalanine (DOPA) has been found to play the major role. These studies continue to inspire the engineering of novel adhesives and coatings with improved underwater performances. Despite the fact that the recent advances of adhesives and coatings inspired by mussel adhesive proteins have been intensively reviewed in literature, the fundamental biochemical and biophysical studies on the origin of the strong and versatile wet adhesion have not been fully covered. In this review, we show how the force measurements at the molecular level by surface force apparatus (SFA) and single molecule atomic force microscopy (AFM) can be used to reveal the direct link between DOPA and the wet adhesion strength of mussel proteins. We highlight a few important technical details that are critical to the successful experimental design. We also summarize many new insights going beyond DOPA adhesion, such as the surface environment and protein sequence dependent synergistic and cooperative binding. We also provide a perspective on a few uncharted but outstanding questions for future studies. A comprehensive understanding on mussel adhesion will be beneficial to the design of novel synthetic wet adhesives for various biomedical applications.

A nickel foam modified with electrodeposited cobalt and phosphor for amperometric determination of dopamine

Considering the importance of dopamine (DA) detection for neuroscience and disease diagnosis, herein, an electrochemical sensor for dopamine is described. It is based on the use of a Ni-Co-P nanostructure fabricated on nickel foam via electrode position from cobalt chloride and ammonium phosphate for 10 min. Time-dependent experiments show the transformation of Ni-Co-P nanoparticles to spheres. The resulting electrode display excellent electrochemical response to DA. Figures of merit include (a) a working potential of 0.55 V (vs. Ag/AgCl); (b) an electrochemical sensitivity of 5262 μA mM^-1 cm^-2; (c) a wide linear range (from 0.5 to 2350 μM), and (d) a 1 μM detection limit. The outstanding electrochemical performance is explained by the synergistic effects of large surface area, improved electron transfer, presence of free binders, and the presence of three active components (nickel, cobalt and phosphonium ion). Graphical abstract A Ni-Co-P nanostructure was electrodeposited on nickel foam to obtain an electrochemical sensor for amperometric determination of dopamine with outstanding performance.

Direct Evidence for the Critical Role of 5,6-Dihydroxyindole in Polydopamine Deposition and Aggregation

The definitive role of the intermediate 5,6-dihydroxyindole (DHI) in the formation of polydopamine (PDA) coatings from aqueous dopamine (DA) has not been clearly elucidated and remains highly controversial. Our foray into this debate as reported in this study agrees with some reported assertions that DHI-based coatings are not synonymous with PDA coatings. Our conclusion arises from a systematic comparison of the components and properties of DHI-based coatings and PDA coatings. In addition, through careful copolymerization studies of DA and DHI, our studies reported herein unequivocally suggest that both DA and DHI are partial building blocks for PDA formation. Our results also provide additional evidence of the critical role of DHI in controlling the thickness of PDA coatings, through competitive events between PDA aggregation in solutions and deposition onto substrates. These findings highlight the complex interplay between both DHI and uncyclized DA moieties in the formation of adhesive catechol/amine materials.

Micro-Structured Polydopamine Films via Pulsed Electrochemical Deposition

Polydopamine (PDA) films are interesting as smart functional materials, and their controlled structured formation plays a significant role in a wide range of applications ranging from cell adhesion to sensing and catalysis. A pulsed deposition technique is reported for micro-structuring polydopamine films using scanning electrochemical microscopy (SECM) in direct mode. Thereby, precise and reproducible film thicknesses of the deposited spots could be achieved ranging from 5.9 +/- 0.48 nm (1 pulse cycle) to 75.4 nm +/- 2.5 nm for 90 pulse cycles. The obtained morphology is different in comparison to films deposited via cyclic voltammetry or films formed by autooxidation showing a cracked blister-like structure for high pulse cycle numbers. The obtained polydopamine spots were investigated in respect to their electrochemical properties using SECM approach curves. Quantitative kinetic data in dependence of the film thickness, the substrate potential, and the used redox species were obtained.

Unravelling the polydopamine mystery: is the end in sight?

Mass spectroscopic studies using deuterium-labeling reveal a novel structure for polydopamine, deriving from dopaminochrome and uncyclized dopamine.

Size control synthesis of melanin-like polydopamine nanoparticles by tuning radicals

We report the first effort to control the size of polydopamine nanoparticles via adding either strong free radical scavengers (i.e. edaravone) or stable free radicals (i.e. PTIO˙) during the polymerization.

Polydopamine Induced in-Situ Formation of Metallic Nanoparticles in Confined Microchannels of Porous Membrane as Flexible Catalytic Reactor

Oxidant-regulated polymerization of dopamine was exploited, for the first time, for effective surface engineering of the well-defined cylindrical pores of nuclear track-etched membranes (NTEMs) to develop novel catalytic membrane reactor. First, in the presence of a strong oxidant, controlled synthesis of polydopamine (PDA) with tunable particle size was achieved, allowing a homogeneous deposition to the confined pore channels of NTEMs. The PDA interfaces rich in catechol and amine groups provided enhanced hydrophilicity to promote mass transport across the membrane and abundant nucleation sites for formation and stabilization of metallic nanoparticles (NPs). In-situ reductive growth of multiple metallic NPs, including Pd, Ag, and Au, was then achieved inside the cylindrical pores of NTEMs. Using the functionalized membrane as a catalytic reactor, efficient reduction of 4-nitrophenol (4-NP) was demonstrated in a flow-through mode. Moreover, after dissolution removal of the NTEMs, self-sustained one-dimensional (1D) PDA/M (M = Pd, Ag, or Au) hybrid nanotubes (NTs), with determined aspect ratio and a length reaching up to 10 μm, were obtained for catalysis of 4-NP in a batch reaction mode. This study established a facile and versatile method, by rational tuning of the polymerization behavior of dopamine, for effective modification of confined microscale/nanoscale cavities with different surface characteristics. The integration of PDA chemistry with NTEMs would provide more opportunities for development of novel catalytic membrane reactors as well as for the tailored synthesis of functional 1D nanotubes for broadened applications.

Polydopamine Surface Chemistry: A Decade of Discovery

Polydopamine is one of the simplest and most versatile approaches to functionalizing material surfaces, having been inspired by the adhesive nature of catechols and amines in mussel adhesive proteins. Since its first report in 2007, a decade of studies on polydopamine molecular structure, deposition conditions, and physicochemical properties have ensued. During this time, potential uses of polydopamine coatings have expanded in many unforeseen directions, seemingly only limited by the creativity of researchers seeking simple solutions to manipulating surface chemistry. In this review, we describe the current state of the art in polydopamine coating methods, describe efforts underway to uncover and tailor the complex structure and chemical properties of polydopamine, and identify emerging trends and needs in polydopamine research, including the use of dopamine analogs, nitrogen-free polyphenolic precursors, and improvement of coating mechanical properties.