Recent developments in polydopamine: an emerging soft matter for surface modification and biomedical applications

PDA-Based Drug Delivery Nanosystems: A Potential Approach for Glioma Treatment

Glioma is characterized by high mortality and low postoperative survival. Despite the availability of various therapeutic approaches and molecular typing, the treatment failure rate and the recurrence rate of glioma remain high. Given the limitations of existing therapeutic tools, nanotechnology has emerged as an alternative treatment option. Nanoparticles, such as polydopamine (PDA)-based nanoparticles, are embodied with reliable biodegradability, efficient drug loading rate, relatively low toxicity, considerable biocompatibility, excellent adhesion properties, precisely targeted delivery, and strong photothermal conversion properties. Therefore, they can further enhance the therapeutic effects in patients with glioma. Moreover, polydopamine contains pyrocatechol, amino and carboxyl groups, active double bonds, catechol, and other reactive groups that can react with biofunctional molecules containing amino, aldehyde, or sulfhydryl groups (main including, self-polymerization, non-covalent self-assembly, π-π stacking, electrostatic attraction interaction, chelation, coating and covalent co-assembly), which form a reversible dynamic covalent Schiff base bond that is extremely sensitive to pH values. Meanwhile, PDA has excellent adhesion capability that can be further functionally modified. Consequently, the aim of this review is to summarize the application of PDA-based NPs in glioma and to acquire insight into the therapeutic effect of the drug-loaded PDA-based nanocarriers (PDA NPs). A wealthy understanding and argument of these sides is anticipated to afford a better approach to develop more reasonable and valid PDA-based cancer nano-drug delivery systems. Finally, we discuss the expectation for the prospective application of PDA in this sphere and some individual viewpoints.

Bioinspired, Ultra-fast Polymerization of Dopamine Under Mild Conditions

Spontaneous oxidative polymerization of dopamine (DA) has been widely exploited as a facile and versatile method for surface modification. However, the reaction is very slow and only occurs in alkaline solutions, which severely limit its applications. Herein we report that the reaction can be dramatically accelerated by using Fe²⁺ as catalyst. While it takes hours and days using conventional method, the Fe²⁺ -catalyzed reaction finishes almost immediately at pH 7.0. In addition, under the catalysis of Fe²⁺ , the reaction can occur at a pH down to 4.0. The fast Fe²⁺ -catalyzed polymerization of DA leads to fast deposition of polydopamine (PDA) coating, thus allowing fast surface modification and textile dyeing. The Fe²⁺ -catalyzed reaction also allows spatial control over the PDA deposition. The fast, simple and mild surface modification method developed here will find applications in numerous fields. This article is protected by copyright. All rights reserved.

Mussel-Inspired Ligand Clicking and Ion Coordination on 2D Black Phosphorus for Cancer Multimodal Imaging and Therapy

As a promising 2D nanocarrier, the biggest challenge of bare black phosphorus nanosheets (BP NSs) lies in the inherent instability, while it can be improved by surface modification strategies to a great extent. Considering the existing infirm BP NSs surface modification strategies, A mussels-inspired strong adhesive biomimetic peptide with azide groups for surface modification to increase the stability of BP NSs is synthesized. The azide groups on the peptide can quickly and precisely bind to the targeting ligand through click chemistry, solving the problem of nonspecificity of secondary modification of other mussel-mimicking materials. Besides, a catechol-Gd³⁺ coordination network is further constructed for magnetic resonance imaging (MRI) and inducing intracellular endo/lysosome escape. The fabricated BP-DOX@Gd/(DOPA)₄ -PEG-TL nanoplatform exhibits enhanced antitumor abilities through synergetic chemo/photothermal effects both in vitro and in vivo.

An ultrasensitive immunosensor based on cellulose nanofibrils/polydopamine/Cu-Ag nanocomposite for the detection of AFP

In this work, an ultrasensitive immunosensor for amperometric determination of alpha-fetoprotein (AFP) was developed utilizing Ag and Cu nanoparticles on polydopamine (PDA) functionalized cellulose nanofibrils (CNFs) composite (CNFs/PDA/Cu-Ag) as signal amplifier. PDA was first prepared by self-polymerizing of dopamine, and then was adsorbed on CNFs. The obtained CNFs/PDA was applied as substrate to electrolessly deposit Cu-Ag nanoparticles, using NaBH₄ as reducing agent. The structure and morphology of the synthesized CNFs/PDA/Cu-Ag nanocomposite were analyzed through Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray powder diffraction, scanning electron microscopy, particle size analyzer and transmission electron microscopy. The CNFs/PDA/Cu-Ag modified glassy carbon electrode can fix AFP antibody (Ab), and further capture AFP specifically. Electrochemical impedance spectroscopy and cyclic voltammetry were used to characterize the assembly process of immunosensor. The immunoreaction was amplified by electrocatalytical reduction of H₂O₂ on Cu-Ag nanoparticles, through which AFP was quantitatively detected. The developed sensor exhibits wide linear range of 0.01-100 ng mL^-1 (R² = 0.9963) with low detection limit of 4.27 pg mL^-1 (S/N = 3). In addition, it has been used for the detection of AFP in human serum, manifesting its preeminent application prospect in early liver cancer diagnosis.

Electrochemical deposition of lithium coating on titanium implant with enhanced early stage osseointegration

Recently, a large number of studies have reported that lithium (Li) displayed a positive effect on osteogenesis. However, only a few studies have investigated the Li-incorporated surfaces through electrochemical deposition. In this study, electrochemical deposition was conducted on a CHI600E electrochemical workstation. The characterization of electrochemical deposition (ECD) and ECD-Li surfaces were detected by field-emission scanning electron microscopy with energy-dispersive spectrometer. rBMSCs were cultured on two surfaces for subsequent adhesion, proliferation and live/dead assay. To evaluate the effects of Li-incorporated implants by electrochemical deposition on osseointegration in vivo, teeth extraction of two premolars and one first molar in bilateral mandible were performed on six male beagle dogs. After 3 months, ZDI and ZDI-Li implants were inserted into the bilateral mandible of each beagle dog. Micro Computed Tomography (Micro-CT) and hard tissue sectioning analysis were carried out to evaluate the osseointegration at 4- and 8-weeks post-implantation. Results showed that ECD-Li surface promoted adhesion and proliferation of BMSCs in the early stage. More importantly, through micro-CT analysis, the values of bone volume/total volume (BV/TV) (0.374 ± 0.015), bone-implant contact (BIC) (0.831 ± 0.025), and Tb.Th (0.412 ± 0.007) in ZDI-Li group was significantly higher than those of ZDI group (0.302 ± 0.009, 0.700 ± 0.023, 0.353 ± 0.001, p < .01) at 4 weeks. Similarly, ZDI-Li group manifested more bone contact with the implant surfaces at 4 weeks based on hard tissue sectioning analysis, whereas no significant difference was detected between two groups at 8 weeks. Therefore, incorporating Li into implant surface through ECD could enhance early osseointegration in vivo.

Metal Ion-Directed Functional Metal-Phenolic Materials

Metal ions are ubiquitous in nature and play significant roles in assembling functional materials in fields spanning chemistry, biology, and materials science. Metal-phenolic materials are assembled from phenolic components in the presence of metal ions through the formation of metal-organic complexes. Alkali, alkali-earth, transition, and noble metal ions as well as metalloids interacting with phenolic building blocks have been widely exploited to generate diverse hybrid materials. Despite extensive studies on the synthesis of metal-phenolic materials, a comprehensive summary of how metal ions guide the assembly of phenolic compounds is lacking. A fundamental understanding of the roles of metal ions in metal-phenolic materials engineering will facilitate the assembly of materials with specific and functional properties. In this review, we focus on the diversity and function of metal ions in metal-phenolic material engineering and emerging applications. Specifically, we discuss the range of underlying interactions, including (i) cation-π, (ii) coordination, (iii) redox, and (iv) dynamic covalent interactions, and highlight the wide range of material properties resulting from these interactions. Applications (e.g., biological, catalytic, and environmental) and perspectives of metal-phenolic materials are also highlighted.

Polycatechol-Derived Mesoporous Polydopamine Nanoparticles for Combined ROS Scavenging and Gene Interference Therapy in Inflammatory Bowel Disease

Benefiting from the evolution of nanotechnology, the combination therapy by gene interference and reactive oxygen species (ROS) scavenging are expected, which holds great potential in inflammatory bowel disease (IBD) therapy. However, the functional integration of different therapeutic modules through interface modification of gene vectors for safe and efficient treatment is urgently needed. Herein, we present a catechol chemistry-mediated core-shell nanoplatform for ROS scavenging-mediated oxidative stress alleviation and siRNA-mediated gene interference in a dextran sulfate sodium (DSS)-induced colitis model. The nanoplatform is constructed by employing mesoporous polydopamine nanoparticles (MPDA NPs) with surface modification of amines as the porous core for TNF-α-siRNA loading (31 wt %) and exerts an antioxidant function, while PDA-induced biomineralization of the calcium phosphate (CaP) coating is used as the pH-sensitive protective shell to prevent siRNA from premature release. The CaP layer degraded under weakly acidic subcellular conditions (lysosomes); thus, the synergistic integration of catechol and cation moieties on the exposed surface of MPDA resulted in an efficient lysosomal escape. Subsequently, effective ROS scavenging caused by the electron-donating ability of MPDA and efficient knocking down (40.5%) of tumor necrosis factor-α (TNF-α) via sufficient cytosolic gene delivery resulted in a synergistic anti-inflammation therapeutic effect both in vitro and in vivo. This work establishes the first paradigm of synergistic therapy in IBD by ROS scavenging and gene interference.

Polydopamine modified acellular dermal matrix sponge scaffold loaded with a-FGF: Promoting wound healing of autologous skin grafts

Despite increasing potentials as a skin regeneration template (DRT) to guide tissue healing, acellular dermal matrix (ADM) is still challenged by issues (like dense architecture, low cellular adhesion and poor vascularization), contributing to necrosis and shedding of upper transplanted skins. Modified with polydopamine (PDA), a novel and porous DRT capable of drug delivery was designed using porcine-derived ADM (PADMS) gels, termed PDA-PADMS. However, it was unclear whether it could efficiently deliver human acidic fibroblast growth factor (a-FGF) and regenerate skin defects. Herein, after being fabricated and optimized with PADMS gels in different ratios (1:6, 1:7, 1:8), PDA-PADMS loading a-FGF (PDA-PADMS-FGF) was evaluated by the morphology, physical& chemical properties, drug release and in-vitro biological evaluations, followed by full-thickness skin defects implanted with PDA-PADMS-FGF covered by transplanted skins. Apart from containing abundant collagen and elastin, porous PADMS (with a loose and uniform structure) was demonstrated to possess controlled release of a-FGF and biocompatibility attributed to PDA coating. Consistent with augmented cellular migration and proliferation in vitro, PDA-PADMS-FGF also accelerated wound healing and reduced scarring, improving collagen arrangement and neovascularization. In conclusion, PDA-PADMS-FGF has a good potential and application prospect as a matrix material for wound repair.

Colloidal Polydopamine Beads: A Photothermally Active Support for Noble Metal Nanocatalysts

Polydopamine (PDA) is a unique bioinspired synthetic polymer that integrates broadband light absorption, efficient photothermal transduction, and versatile surface-adhesion functions in a single material entity. Here, we utilize colloidal PDA beads in the submicron particle size regime as an easily processable and photothermally active support for sub-10 nm Pd nanocatalysts to construct a multifunctional material system that allows us to kinetically boost thermal catalytic reactions through visible and near-infrared light illuminations. Choosing the Pd-catalyzed nitrophenol reduction by ammonium formate as a model transfer hydrogenation reaction exhibiting temperature-dependent reaction rates, we demonstrate that interfacial molecule-transforming processes on metal nanocatalyst surfaces can be kinetically modulated by harnessing the thermal energy produced through photothermal transduction in the PDA supports.

Polyacrylic Acid Nanoplatforms: Antimicrobial, Tissue Engineering, and Cancer Theranostic Applications

Polyacrylic acid (PAA) is a non-toxic, biocompatible, and biodegradable polymer that gained lots of interest in recent years. PAA nano-derivatives can be obtained by chemical modification of carboxyl groups with superior chemical properties in comparison to unmodified PAA. For example, nano-particles produced from PAA derivatives can be used to deliver drugs due to their stability and biocompatibility. PAA and its nanoconjugates could also be regarded as stimuli-responsive platforms that make them ideal for drug delivery and antimicrobial applications. These properties make PAA a good candidate for conventional and novel drug carrier systems. Here, we started with synthesis approaches, structure characteristics, and other architectures of PAA nanoplatforms. Then, different conjugations of PAA/nanostructures and their potential in various fields of nanomedicine such as antimicrobial, anticancer, imaging, biosensor, and tissue engineering were discussed. Finally, biocompatibility and challenges of PAA nanoplatforms were highlighted. This review will provide fundamental knowledge and current information connected to the PAA nanoplatforms and their applications in biological fields for a broad audience of researchers, engineers, and newcomers. In this light, PAA nanoplatforms could have great potential for the research and development of new nano vaccines and nano drugs in the future.

Recent Development of MOF-Based Photothermal Agent for Tumor Ablation

Metal-organic frameworks (MOFs) are 3D-architecture compounds of metal ions and organic molecules with sufficient and permanent porosity, showing great potential as a versatile platform to load various functional moieties to endow the hybrid materials with specific applications. Currently, a variety of photothermal nanometals have been embedded into organic ligands for integrating the unique photothermal effects with the merits of MOFs to improve their performances for cancer therapy. In this review, we have summarized a series of novel MOF-based photothermal materials for this unique therapeutic modality against tumors from three main aspects according to their chemical compositions and structures, i) metal-doped MOF, ii) organic-doped MOF, and iii) polymer-coated MOF. In addition, we have summarized the latest developments and characteristics of MOF-based photothermal agents, such as good biocompatibility, low toxicity, and responsive photothermal conversion without destroying the structure of hybrid photothermal agent. At last, we addressed the future perspectives of MOF-based photothermal agent in the field of phototherapy.

Novel dopamine-modified cellulose acetate ultrafiltration membranes with improved separation and antifouling performances

Cellulose acetate (CA) is widely used in the preparation of ultrafiltration membranes due to its many excellent characteristics, especially chemical activity and biodegradability. To improve the inherent hydrophobic and antifouling properties of CA membrane, in this work, CA was successfully modified with dopamine (CA-2,3-DA) through selective oxidation and Schiff base reactions, which was confirmed by FTIR and ¹H NMR measurements. Then, CA-2,3-DA membrane with high water permeability and excellent antifouling property was prepared by the phase inversion method. Compared with the original CA membrane, the CA-2,3-DA membrane maintained a higher rejection ratio for BSA (92.5%) with a greatly increased pure water flux (167.3 L m^-2 h^-1), which could overcome the trade-off between permeability and selectivity of the traditional CA membrane to a certain extent. According to static protein adsorption and three-cycle dynamic ultrafiltration experiments, the CA-2,3-DA membrane showed good antifouling performance and superior long-term performance stability, as supported by the experimental results, including flux recovery ratio, flux decline ratio, and filtration resistance. It is expected that this approach can greatly expand the high-value utilization of modified natural organic polysaccharides in separation engineering.

Rational integration of defense and repair synergy on PEEK osteoimplants via biomimetic peptide clicking strategy

Polyetheretherketone (PEEK) has been widely used as orthopedic and dental materials due to excellent mechanical and physicochemical tolerance. However, its biological inertness, poor osteoinduction, and weak antibacterial activity make the clinical applications in a dilemma. Inspired by the mussel adhesion mechanism, here we reported a biomimetic surface strategy for rational integration and optimization of anti-infectivity and osteo-inductivity onto PEEK surfaces using a mussel foot proteins (Mfps)-mimic peptide with clickable azido terminal. The peptide enables mussel-like adhesion on PEEK biomaterial surfaces, leaving azido groups for the further steps of biofunctionalizations. In this study, antimicrobial peptide (AMP) and osteogenic growth peptide (OGP) were bioorthogonally clicked on the azido-modified PEEK biomaterials to obtain a dual-effect of host defense and tissue repair. Since bioorthogonal clicking allows precise collocation between AMP and OGP through changing their feeding molar ratios, an optimal PEEK surface was finally obtained in this research, which could long-term inhibit bacterial growth, stabilize bone homeostasis and facilitate interfacial bone regeneration. In a word, this upgraded mussel surface strategy proposed in this study is promising for the surface bioengineering of inert medical implants, in particular, achieving rational integration of multiple biofunctions to match clinical requirements.

Direct grafting of cellulose nanocrystals with poly(ionic liquids) via Gamma-ray irradiation and their utilization for adsorptive removal of CR

In this work, a simple but effective method based on Gamma-ray initiated polymerization was reported for the first time through direct irradiation of CNCs and ionic liquid monomer to obtain poly (ionic liquids) functionalized CNCs (IL@CNCs). The adsorptive removal of Congo red (CR) from aqueous solution by IL@CNCs was also examined and the influence of contact time, pH values, initial concentrations and temperature on adsorption behavior was investigated in detail. Under the same adsorption conditions, the adsorption capacity was increased from 59.72 mg/g (CNCs) to 195.83 mg/g (IL@CNCs). The results of the adsorption isotherm and adsorption kinetics showed that the experimental data were more suitable to be described by the Freundlich isotherm adsorption model and the pseudo-second-order model. The adsorption process of CR on the surface of the adsorbent was endothermic and spontaneous. When the aqueous solution was acidic, it was more conducive to the adsorption of CR. At 100% breakthrough, the value of adsorption capacity is 199.95 mg/g and the value of partition coefficient is 9.64. Moreover, the adsorption capacity is expected to be further improved through adjustment of polymerization parameters and this method can also be used for preparation other poly (ionic liquids) modified composites.

PDA-coated CPT@MIL-53 (Fe) based Theranostic Nanoplatform for pH-Responsive and MRI-Guided Chemotherapy

Theranostic nanoplatform for multimodal diagnosis and treatment of tumors is a currently research hotspot in the field of nanomedicine. MOF-based theranostic nanoplatforms of integrating drug delivery with magnetic resonance imaging...

Polydopamine-drug conjugate nanocomposites based on ZIF-8 for targeted cancer photothermal-chemotherapy

Stimuli-responsive prodrug-based nanoplatform with synergistic antitumor activity is of central importance to the development of promising nanomedicines for cancer therapy. Here, we describe a polydopamine-drug conjugate nanocomposite (ZP-PDA-DOX) with targeted cancer photothermal-chemotherapy (PTT-CT), which constructed by a gradual copolymerization of dopamine (DA) and pH-sensitive dopamine-derived prodrug (DA-DOX) into the porous channels of zeolite imidazolate frameworks-8 (ZIF-8), followed by PEGylation with amino-terminated folic acid-polyethylene glycol (NH₂ -PEG-FA) to acquire the high biocompatibility, specificity, and excellent tumor-targeting property. The incorporation of polydopamine strengthened the stability and dispersion of ZIF-8, and also conferred photothermal conversion effect. In the tumor acidic microenvironment, the acid-labile hydrazone linker of DA-DOX and ZIF-8 promptly degraded to release activated DOX. Moreover, the generated hyperthermia due to the high photothermal conversion efficiency of PDA component could accelerate drug release, and simultaneously thermally ablate tumor tissue to maximize the DOX-induced CT, which could also assist PTT to eradicate tumor cells. This study provides a promising strategy for targeted cancer PTT-CT with synergistic anti-tumor effect.

Easy Preparation of Liposome@PDA Microspheres for Fast and Highly Efficient Removal of Methylene Blue from Water

Mussel-inspired chemistry was usefully exploited here with the aim of developing a high-efficiency, environmentally friendly material for water remediation. A micro-structured material based on polydopamine (PDA) was obtained by using liposomes as templating agents and was used for the first time as an adsorbent material for the removal of methylene blue (MB) dye from aqueous solutions. Phospholipid liposomes were made by extrusion and coated with PDA by self-polymerization of dopamine under simple and mild conditions. The obtained Liposome@PDA microspheres were characterized by DLS and Zeta potential analysis, TEM microscopy, and FTIR spectroscopy. The effects of pH, temperature, MB concentration, amount of Liposome@PDA, and contact time on the adsorption process were investigated. Results showed that the highest adsorption capacity was obtained in weakly alkaline conditions (pH = 8.0) and that it could reach up to 395.4 mg g⁻¹ at 298 K. In addition, adsorption kinetics showed that the adsorption behavior fits a pseudo-second-order kinetic model well. The equilibrium adsorption data, instead, were well described by Langmuir isotherm. Thermodynamic analysis demonstrated that the adsorption process was endothermic and spontaneous (ΔG⁰ = −12.55 kJ mol⁻¹, ΔH⁰ = 13.37 kJ mol⁻¹) in the investigated experimental conditions. Finally, the applicability of Liposome@PDA microspheres to model wastewater and the excellent reusability after regeneration by removing MB were demonstrated.

Fabrication of Dexamethasone-Loaded Dual-Metal-Organic Frameworks on Polyetheretherketone Implants with Bacteriostasis and Angiogenesis Properties for Promoting Bone Regeneration

Polyetheretherketone (PEEK) is a biocompatible polymer, but its clinical application is largely limited due to its inert surface. To solve this problem, a multifunctional PEEK implant is urgently fabricated. In this work, a dual-metal-organic framework (Zn-Mg-MOF74) coating is bonded to PEEK using a mussel-inspired polydopamine interlayer to prepare the coating, and then, dexamethasone (DEX) is loaded on the coating surface. The PEEK surface with the multifunctional coating provides superior hydrophilicity and favorable stability and forms an alkaline microenvironment when Mg²⁺, Zn²⁺, 2,5-dihydroxyterephthalic acid, and DEX are released due to the coating degradation. In vitro results showed that the multifunctional coating has strong antibacterial ability against both Escherichia coli and Staphylococcus aureus; it also improves human umbilical vein endothelial cell angiogenic ability and enhances rat bone marrow mesenchymal stem cell osteogenic differentiation activity. Furthermore, the in vivo rat subcutaneous infection model, chicken chorioallantoic membrane model, and rat femoral drilling model verify that the PEEK implant coated with the multifunctional coating has strong antibacterial and angiogenic ability and promotes the formation of new bone around the implant with a stronger bone-implant interface. Our findings indicate that DEX loaded on the Zn-Mg-MOF74 coating-modified PEEK implant with bacteriostasis, angiogenesis, and osteogenesis properties has great clinical application potential as bone graft materials.

Polydopamine-Coated Poly(l-lactide) Nanofibers with Controlled Release of VEGF and BMP-2 as a Regenerative Periosteum

The periosteum plays an important role in vascularization and ossification during bone repair. However, in most studies, an artificial periosteum cannot restore both functions of the periosteum concurrently. In this study, a novel nanofiber that can sustain the release of vascular endothelial growth factor (VEGF) and bone morphogenetic protein-2 (BMP-2) was fabricated to enhance the durability of angiogenesis and osteogenesis during bone regeneration. A cell-free tissue engineered periosteum based on an electrospinning poly-l-lactic acid (PLLA) nanofiber was fabricated, on which VEGF and BMP-2 were immobilized through a polydopamine (PDA) coating conveniently and safely (BVP@PLLA membrane). The results indicated a significantly improved loading rate as well as a slow and sustained release of VEGF and BMP-2 with the help of the PDA coating. BMP-2 immobilized on nanofibers successfully induced the osteogenic differentiation of human bone marrow mesenchymal stem cells (BMSCs) in vitro with high expression of runt-related transcription factor 2 (Runx2), osteopontin (OPN), and alkaline phosphatase (ALP). Similarly, angiogenic differentiation of BMSCs with the expression of fetal liver kinase-1 (Flk-1) and vascular endothelial cadherin (VE-cadherin) was observed under the environment of VEGF sustained release. Moreover, an in vivo study revealed that the BVP@PLLA membrane could enhance vascular formation and new bone formation, which accelerates bone regeneration in rat femoral defects along with a massive periosteum defect. Therefore, our study suggests that the novel artificial periosteum with dual growth factor controlled release is a promising system to improve bone regeneration in bone defects along with a massive periosteum defect.

Horseradish peroxidase-catalyzed formation of polydopamine for ultra-sensitive magnetic relaxation sensing of aflatoxin B1

Aflatoxin B₁ as one of the most toxic mycotoxins poses a major health risk to humans and animals. Highly sensitive detection methods of aflatoxin B₁ are urgently required because of its low abundance in biological samples. In this work, we developed a magnetic relaxation sensing strategy using enzyme-catalyzed formation of polydopamine for signal amplification. Horseradish peroxidase can catalyze the reaction to generate polydopamine that assembles magnetic nanoparticles for magnetic relaxation sensing with a high signal-to-noise ratio. Combined with the specific antigen-antibody interaction, this magnetic sensor enables fast and ultra-sensitive detection of aflatoxin B₁ by using transverse relaxation time (T₂) as a readout. Under optimized conditions, the linear range of this magnetic sensor for detecting aflatoxin B₁ is from 10 pg/mL to 10 ng/mL, and the limit of detection is 0.35 pg/mL. This sensor has been challenged for the quantitative analysis of aflatoxin B₁ in animal feed samples that is promising for real-world applications.

Role of Free Catecholamine in Thiol-Ene Crosslinking for Hyaluronic Acid Hydrogels with High Loading Efficiency of Anticancer Drugs

BACKGROUND

Hyaluronic acid (HA) is a widely used polysaccharide in biomedical field because of its excellent biocompatibility. Its chemical structure can be modified with various functional groups. Recently, dopamine has been tethered onto the polymeric backbone to ensure long-term stability and tissue adhesiveness of HA hydrogel. However, the radical scavenging effect of dopamine on typical photo-induced crosslinking for hydrogels has not been specifically studied.

METHODS

Photo-crosslinkable norbornene-modified HA (NorHA) was synthesized and crosslinked by dithiothreitol containing dopamine at different concentrations. During in situ ultraviolet light-triggered crosslinking, storage moduli were monitored using an oscillatory rheometer. Additionally, the amount of thiol utilized for HA crosslinking was investigated under the presence and absence of dopamine. Finally, doxorubicin was encapsulated in the hydrogels, and the drug loading efficiency and release kinetics were measured.

RESULTS

Adding dopamine into the NorHA pre-gel solution delayed the gelation time, yet the final storage modulus of the hydrogel remained constant. That is, dopamine might partially consume the energy required for thiol-ene reaction to generate semiquinone radicals. Furthermore, the residual thiols which were not involved in the crosslinking decreased when the hydrogel was formed at a high concentration of dopamine, indicating the formation of Michael adducts of semiquinone and thiols. Interestingly, the presence of dopamine in the hydrogel increased the loading efficiency of the hydrophobic drugs due to π-π stacking and hydrogen bonding between dopamine and drugs.

CONCLUSION

The presence of free catecholamines in a photo-crosslinkable polymer can delay the gelation time but improve the drug loading efficiency.

Preparation of CNTs Coated with Polydopamine-Ni Complexes and Their Catalytic Effects on the Decomposition of CL-20

To improve the condensed-phase reaction rate of ε-CL-20, polydopamine (PDA)-nickel complex-coated multiwalled carbon nanotubes (CNTs) have been prepared and used as combustion catalysts. The PDA-Ni complex has been prepared and in situ coprecipitated with ε-CL-20 by an antisolvent crystallization process in its dimethyl sulfoxide (DMSO) solution. It has been shown that crystalline CL-20 composites included with PDA-Ni complexes are polygon-shaped with a smooth surface and an average diameter of 10-15 μm, whereas it is 140 μm for raw ε-CL-20 crystals. The catalytic reactivity of the complex on thermolysis of CL-20 has been investigated using the differential scanning calorimetry (DSC) and thermogravimetry (TG)-coupled Fourier transform infrared (FT-IR) spectroscopy technique. It has been found that CNT@PDA-Ni complexes have catalytic effects on the decomposition of ε-CL-20 by decreasing/shifting of the exothermic peak from T _p = 240.1 to 238.7 °C. The FT-IR spectra of CL-20 decomposition products under the effect of the catalyst predominantly show peaks at 1274, 1644 and 1596, 1912, 2265, and 1956-1800 cm^-1, indicating the presence of fragments with N₂O, NO₂, NO, HNCO, and NO/CO, respectively. The change in the ε-CL-20 decomposition mechanism should be attributed to the catalytic action of CNT, decreasing the formation of NO₂. Also, under the effect of the carbon-based catalyst, the HNCO formation was detected at another temperature in comparison with raw CL-20, with peak absorption at 224.1 vs 232.3 °C and the evolution was completed at 250.8 vs 246.2 °C, respectively.

3D printed hydrogel/PCL core/shell fiber scaffolds with NIR-triggered drug release for cancer therapy and wound healing

Hydrogel based scaffolds with the ability of on-demand drug delivery gained increasing interests for localized cancer therapy and tissue engineering application. However, most drug-loaded hydrogels are generally not suitable for long-term drug delivery, because of the uncontrolled diffusion of drugs from the swollen hydrogels. Therefore, in this study, a core/shell fiber scaffold was fabricated by coating a homogeneous layer of polycaprolactone (PCL) on the 3D printed alginate-gelatin hydrogel scaffolds. The PCL coatings could reduce the free diffusion of drugs from the core gels. Subsequently, polydopamine (PDA) was coated on the Gel/PCL core/shell scaffolds, endowing the scaffolds with great photothermal effects. Thus, near-infrared (NIR) laser triggered on-demand drug release was realized in this system due to the thermally induced sol-gel transition of the core gels. The released drugs (doxorubicin) and photothermal therapy could effectively prohibit or ablate tumor in vitro and in vivo. Additionally, the Gel/PCL/PDA core/shell scaffold could serve as platform for promoting wound healing. Therefore, the reported Gel/PCL/PDA core/shell scaffolds have the potential for application in localized cancer therapy and tissue regeneration. Especially for those cancer patients suffering surgical resection, the scaffolds could be implanted in the resection site to kill the residual or recurrent cancer cells, as well as to repair the tissue defects caused by surgery. STATEMENT OF SIGNIFICANCE: This paper reported a facile strategy to realize stimuli-triggered on demand drug release in vitro and in vivo. Polycaprolactone (PCL) and polydopamine were sequentially deposited on the surface of 3D printed drug-loaded alginate/gelatin scaffold. PCL encapsulation could effectively reduce the free diffusion of drugs from the core hydrogel, achieving sustained drug release. Polydopamine with good photothermal effects endowed the scaffold with stimuli-triggered drug release in response to near-infrared (NIR) laser irradiation. This scaffold could be applied for localized cancer therapy and tissue regeneration. Especially for those cancer patients suffering surgical resection, the scaffolds could be implanted in the resection site to kill the residual or recurrent cancer cells, as well as to repair the tissue defects caused by surgery.

Polydopamine nanofilms for high-performance paper-based electrochemical devices

Since the discovery of polydopamine (PDA), there has been a lot of progress on using this substance to functionalize many different surfaces. However, little attention has been given to prepare functionalized surfaces for the preparation of flexible electrochemical paper-based devices. After fabricating the electrodes on paper substrates, we formed PDA on the surface of the working electrode using a chemical polymerization route. PDA nanofilms on carbon were characterized by contact angle (CA) experiments, X-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy (topography and electrical measurements) and electrochemical techniques. We observed that PDA introduces chemical functionalities (RNH₂ and RC═O) that decrease the CA of the electrode. Moreover, PDA nanofilms did not block the heterogeneous electron transfer. In fact, we observed one of the highest standard heterogeneous rate constants (k_s ) for electrochemical paper-based electrodes (2.5 ± 0.1) × 10^-3  cm s^-1 , which is an essential parameter to obtain larger currents. In addition, our results suggest that carbonyl functionalities are ascribed for the redox activity of the nanofilms. As a proof-of-concept, the electrooxidation of nicotinamide adenine dinucleotide showed remarkable features, such as, lower oxidation potential, electrocatalytic peak currents more than 30 times higher when compared to unmodified paper-based electrodes and electrocatalytic rate constant (k_obs ) of (8.2 ± 0.6) × 10²  L mol^-1  s^-1 .

Phase-Change Composites Composed of Silicone Rubber and Pa@SiO2@PDA Double-Shelled Microcapsules with Low Leakage Rate and Improved Mechanical Strength

A kind of silicone rubber (SR)/paraffin (Pa)@silicon dioxide (SiO₂)@polydopamine (PDA) phase-change composite was prepared in this work. The double-shelled Pa@SiO₂@PDA phase-change microcapsules were constructed by oxidative self-polymerization of dopamine (DA) in Tris-HCl buffer solution. The effect of the DA content on the properties of Pa@SiO₂@PDA microcapsules and SR/Pa@SiO₂@PDA composites was researched. Due to the protective effect of SiO₂, PDA layer, and SR matrix, the SR/Pa@SiO₂@PDA composites have good leak-proofing performance, and the leakage rate of SR/Pa@SiO₂@PDA-2 is as low as 0.45%. Phase-change enthalpies of the Pa@SiO₂@PDA microcapsules and SR/Pa@SiO₂@PDA composites are reduced slightly with increasing DA content. Meanwhile, the composites displayed improved mechanical strength. The tensile strength of SR/Pa@SiO₂@PDA-2 can be up to 0.560 MPa, which is 1.85 times higher than the tensile strength of pure SR/Pa@SiO₂ because the interface compatibility between Pa@SiO₂ microcapsules and SR is improved through hydrogen bonding between the abundant groups on the PDA surface and the matrix. Moreover, the rough surface of the PDA-modified microcapsules also enhances the interface interaction through physical "interlocking". The new kind of SR/Pa@SiO₂@PDA composite can be used for thermal management.

[In vivo study of liposome-modified polyetheretherketone implant on bacteriostasis and osseointegration]

OBJECTIVE

To develop dexamethasone plus minocycline-loaded liposomes (Dex/Mino liposomes) and apply them to improve bioinert polyetheretherketone (PEEK) surface, which could prevent post-operative bacterial contamination, enhance ossification for physiologic osseointegration, and finally reduce implant failure rates.

METHODS

Dex/Mino liposomes were covalently grafted onto the PEEK surface using polydopamine (pDA) coating as a medium. Confocal laser scanning microscopy was used to confirm the binding of fluorescently labeled liposomes onto the PEEK substrate, and a microplate reader was used to semiquantitatively measure the average fluorescence intensity of fluorescently labeled liposome-decorated PEEK surfaces. Moreover, the mouse subcutaneous infection model and the beagle femur implantation model were respectively conducted to verify the bioactivity of Dex/Mino liposome-modified PEEK in vivo, by means of micro computed tomography (micro-CT) and hematoxylin and eosin (HE) staining analysis.

RESULTS

The qualitative and quantitative results of fluorescently labeled liposomes showed that, the red fluorescence intensity of the PEEK-pDA-lipo group was stronger than that of the PEEK-NF-lipo group (P < 0.05); the liposomes were successfully and uniformly decorated on the PEEK surfaces due to the pDA coating. After mouse subcutaneous implantation of PEEKs for 24 hours, HE staining results showed that the number of inflammatory cells in the PEEK-Dex/Mino lipo group were lower than that in the inert PEEK group (P < 0.05), indicating a lower degree of infection in the test group. These results suggested that the Mino released from the liposome-functionalized surface provided an effective bacteriostasis in vivo. After beagle femoral implantation of PEEK for 8 weeks, micro-CT results showed that the PEEK-Dex/Mino lipo group newly formed more continuous bone when compared with the inert PEEK group; HE staining results showed that more new bones were formed in the PEEK-Dex/Mino lipo group than in the inert PEEK group, which were firmly bonded to the functionalized PEEK surface and extended along the PEEK interface. These results suggested that the Dex released from the liposome-functionalized surface induced effective bone regeneration in vivo.

CONCLUSION

Dex/Mino liposome modification enhanced the bioactivity of inert PEEK, the functionalized PEEK with enhanced antibacterial and osseointegrative capacity has great potential as an orthopedic/dental implant material for clinical application.

SERS characterization of dopamine and in situ dopamine polymerization on silver nanoparticles

Dopamine (DA) regulates several functions in the central nervous system and its depletion is responsible for psychological disorders like Parkinson's disease. Several analytical approaches have been presented for DA detection in pathological diagnosis. SERS spectroscopy is a highly promising technique for the sensitive detection of DA. However, an improvement in its detection in aqueous solution is highly desirable for reliable quantification in biological fluids. In this work, we explored a label-free SERS approach for DA detection, employing two conventional methods to synthesize Ag colloids: reduction via citrates (c-AgNPs) and reduction via hydroxylamine (h-AgNPs), and SERS measurements were performed with a laser at 488 nm wavelength. Under these conditions, DA was identified through reproducible SERS spectra in the c-AgNP medium; however, the SERS spectra of DA in h-AgNP solution showed a completely different SERS profile. SERS band analysis revealed that DA in h-AgNPs was oxidized and converted into polydopamine (PDA), which was triggered after exposure to laser radiation. DA oxidation and PDA formation were followed over time through the SERS band profile at pH 7, 9 and 12. We found that in situ PDA formation started after 50 min of laser irradiation of DA at pH 7, while DA was quickly oxidized at pH 9 and 12. Here, we present a detailed SERS band analysis of PDA, which sheds light on the molecular steps in the pathway formation of the PDA structure. Spectroscopic analysis and characterization revealed that a long laser exposure time led to the formation of stable PDA complexes with AgNPs, which allowed us to propose a novel approach for synthesis of AgNP-PDA composites. In conclusion, to detect DA through a label-free SERS approach, c-AgNPs must be employed, while stable AgNP-PDA materials can be achieved with h-AgNPs and 488 nm laser excitation.

Foldable Glistening-Free Acrylic Intraocular Lens Biomaterials with Dual-Side Heterogeneous Surface Modification for Postoperative Endophthalmitis and Posterior Capsule Opacification Prophylaxis

Hydrophobic acrylic intraocular lenses (IOLs) are widely used in cataract treatment for posterior capsule opacification (PCO) prophylaxis. However, undesired glistening and postoperative endophthalmitis are two major potential risks. Hence, a series of poly(2-phenoxyethyl methacrylate-co-2-phenoxyethyl acrylate-co-2-ethylhexyl methacrylate) (PPPE) acrylic IOL materials were synthesized for "glistening-free" optimization. The selected PPPE with 2% 2-ethylhexyl methacrylate showed excellent optical, foldable, and thermomechanical properties. The anterior surface of PPPE was coated with polydopamine followed by gentamycin conjugation (PDA/GS). It inhibited bacterial adhesion by 74% and decreased the biofilm thickness by 87%. In inflammatory mimicking conditions, bacterial proliferation was restrained, with acidic-dependent GS release behavior. The surface of PPPE toward the posterior capsule remained hydrophobic. It was conducive to human lens epithelial cell adhesion, collagen IV and fibronectin adsorption, and the following "sealed sandwich structure" formation. In summary, the PPPE with a dual-side heterogeneous surface displayed good application prospects in postoperative endophthalmitis and PCO prevention.

State-of-art review on preparation, surface functionalization and biomedical applications of cellulose nanocrystals-based materials

Cellulose nanocrystals (CNCs) are a class of sustainable nanomaterials that are obtained from plants and microorganisms. These naturally derived nanomaterials are of abundant hydroxyl groups, well biocompatibility, low cost and biodegradable potential, making them suitable and promising candidates for various applications, especially in biomedical fields. In this review, the recent advances and development on the preparation, surface functionalization and biomedical applications of CNCs-based materials have been summarized and outlined. The main context of this paper could be divided into the following three parts. In the first part, the preparation strategies based on physical, chemical, enzymatic and combination techniques for preparation of CNCs have been summarized. The surface functionalization methods for synthesis CNCs-based materials with designed properties and functions were outlined in the following section. Finally, the current state about applications of CNCs-based materials for tissue engineering, medical hydrogels, biosensors, fluorescent imaging and intracellular delivery of biological agents have been highlighted. Moreover, current issues and future directions about the above aspects have also pointed out and discussed. We believe this review will attract great research attention of scientists from materials, chemistry, biomedicine and other disciplines. It will also provide some important insights on the future development of CNCs-based materials especially in biomedical fields.

Polydopamine antibacterial materials

Recently, the development of polydopamine (PDA) has demonstrated numerous excellent performances in free radical scavenging, UV shielding, photothermal conversion, and biocompatibility. These unique properties enable PDA to be widely used as efficient antibacterial materials for various applications. Accordingly, PDA antibacterial materials mainly include free-standing PDA materials and PDA-based composite materials. In this review, an overview of PDA antibacterial materials is provided to summarize these two types of antibacterial materials in detail, including the fabrication strategies and antibacterial mechanisms. The future development and challenges of PDA in this field are also presented. It is hoped that this review will provide an insight into the future development of antibacterial functional materials based on PDA.

Intervention of Polydopamine Assembly and Adhesion on Nanoscale Interfaces: State-of-the-Art Designs and Biomedical Applications

The translation of mussel-inspired wet adhesion to biomedical engineering fields have catalyzed the emergence of polydopamine (PDA)-based nanomaterials with privileged features and properties of conducting multiple interfacial interactions. Recent concerns and progress on the understanding of PDA's hierarchical structure and progressive assembly are inspiring approaches toward novel nanostructures with property and function advantages over simple nanoparticle architectures. Major breakthroughs in this field demonstrated the essential role of π-π stacking and π-cation interactions in the rational intervention of PDA self-assembly. In this review, the recently emerging concepts in the preparation and application of PDA nanomaterials, including 3D mesostructures, low-dimensional nanostructures, micelle/nanoemulsion based nanoclusters, as well as other multicomponent nanohybrids by the segregation and organization of PDA building blocks on nanoscale interfaces are outlined. The contribution of π-electron interactions on the interfacial loading/release of π electron-rich molecules (nucleic acids, drugs, photosensitizers) and the exogenous coupling of optical energy, as well as the impact of wet-adhesion interactions on the nano-bio interface interplay, are highlighted by discussing the structure-property relationships in their featured applications including fluorescent biosensing, gene therapy, drug delivery, phototherapy, combined therapy, etc. The limitations of current explorations, and future research directions are also discussed.

Hyaluronic acid functionalized biodegradable mesoporous silica nanocomposites for efficient photothermal and chemotherapy in breast cancer

Chemotherapy is one of conventional treatment methods for breast cancer, but drug toxicity and side effects have severely limited its clinical applications. Photothermal therapy has emerged as a promising method that, upon combination with chemotherapy, can better treat breast cancer. In this context, a biodegradable mesoporous silica nanoparticle (bMSN NPs) system was developed for loading doxorubicin (DOX) and IR780, to be potentially applied in the treatment of breast cancer. IR780 is encapsulated in the pores of bMSN NPs by hydrophobic adsorption, while DOX is adsorbed on the surface of the bMSN NPs by hyaluronic acid electrostatically, to form the bMID NPs. Transmission electron microscopy, fluorescence spectrum and UV absorption spectrum are used to prove the successful encapsulation of IR780 and the loading of DOX. In vitro experiments have shown bMID NPs present an excellent therapeutic effect on breast cancer cells. In vivo fluorescence imaging results have indicated that bMID NPs can accumulate in tumor sites gradually and achieve in vivo long-term circulation and continuous drug release. Furthermore, bMID NPs have provided obvious antitumor effects in breast cancer mouse models, thus evolving as an efficient platform for breast cancer therapy.

Effect of Anode Material on Electrochemical Oxidation of Low Molecular Weight Alcohols-A Review

The growing climate crisis inspires one of the greatest challenges of the 21st century-developing novel power sources. One of the concepts that offer clean, non-fossil electricity production is fuel cells, especially when the role of fuel is played by simple organic molecules, such as low molecular weight alcohols. The greatest drawback of this technology is the lack of electrocatalytic materials that would enhance reaction kinetics and good stability under process conditions. Currently, electrodes for direct alcohol fuel cells (DAFCs) are mainly based on platinum, which not only provides a poor reaction rate but also readily deactivates because of poisoning by reaction products. Because of these disadvantages, many researchers have focused on developing novel electrode materials with electrocatalytic properties towards the oxidation of simple alcohols, such as methanol, ethanol, ethylene glycol or propanol. This paper presents the development of electrode materials and addresses future challenges that still need to be overcome before direct alcohol fuel cells can be commercialized.

Surface bioengineering of diverse orthopaedic implants with optional functions via bioinspired molecular adhesion and bioorthogonal conjugations

In this work, we reported an upgraded mussel-inspired strategy for surface bioengineering of osteoimplants by combination of mussel adhesion and bioorthogonal click chemistry. The main idea of this strategy is a mussel-inspired synthetic peptide containing multiple 3,4-dihydroxy-L-phenylalanine (DOPA) units and a dibenzocyclooctyne (DBCO) terminal (DOPA-DBCO). According to the mussel adhesion mechanism, the DOPA-DBCO peptide could stably adhere onto a variety of material surface, leaving the residual DBCO groups on the surface. Then, the DBCO residues could be employed for a second-step bioorthogonal conjugation with azide-capping biomolecules through bioorthogonal click chemistry, finally leading to the biomodified surfaces. To demonstrate the generality of our strategy for surface biomodification of diversified orthopaedic materials including metallic and polymeric substrates, we here conceptually conjugated some typical azide-capping biomolecules on both metal and polymeric surfaces. The results definitely verified the feasibility for engineering of functional surfaces with some essential requirements of osteoimplants, for example, the ability to facilitate cell adhesion, suppress bacterial infection, and promote osteogenesis. In a word, this study indicated that our novel surface strategy would show broad applicability for diverse osteoimplants and in different biological scenarios. We can also image that the molecular specificity of bioorthogonal conjugation and the universality of mussel adhesion mechanism may jointly provide a versatile surface bioengineering method for a wider range of biomedical implants.

A durable superwetting clusters-inlayed mesh with high efficiency and flux for emulsion separation

How to rapidly and efficiently separate surfactant-stabilized emulsions has been a great challenge for oil/water separation materials. In this work, a durable superwetting copper mesh with high efficiency and flux for gravity-driven emulsion separation was fabricated by subtly inlaying polydopamine/polyethyleneimine@aminated carbon nanotubes (PDA/PEI@CNTs-NH₂) clusters in the mesh pores. The porous clusters with abundant cationic groups render the mesh with superwettability, submicron permeation channels and positive charges, so as to achieve strong demulsification ability. Based on the superwettability and the strong demulsification ability, the PDA/PEI@CNTs-NH₂ clusters-inlayed copper mesh (PPC-CM) exhibited high separation efficiency of over 99.5% for various anionic surfactant-stabilized oil-in-water emulsions. Meanwhile, the permeation flux of PPC-CM solely driven by gravity is as high as 3946.3 L m^-2 h^-1. The strong demulsification ability and high permeation flux of the superwetting mesh are due to the synergistic action of charge-screening effect of -NH³⁺ and size-sieving effect of optimized pore size. Furthermore, the resultant mesh exhibited excellent durability that it could resist serious physical abrasion and chemical corrosion. Especially the mesh after repeated separation can recover its positive charge by a simple acid treatment. These excellent performances highlight the superwetting mesh a promising potential for sustainable separation of highly stabilized oil/water emulsions.

Nano-catalytic behavior of highly efficient and regenerable mussel-inspired Fe3O4@CFR@GO and Fe3O4@CFR@TiO2 magnetic nanospheres in the reduction of Evans blue dye

Fe₃O₄@catechol formaldehyde resin coated @Graphene Oxide nanocomposite (Fe₃O₄@CFR@GO) and Fe₃O₄@catechol formaldehyde resin coated @TiO₂ (Fe₃O₄@CFR@TiO₂) nanocomposite were fabricated by hydrothermal method. Particularly, catechol bunches on the highest layer of nanospheres to play a mussel-inspired chemistry to assist combined with graphene oxide (GO) to wrap the Fe₃O₄@ coated nanosphere. The prepared catalyst was proven to be very efficient with less than a minute and vey less dosage (15–17 mg) in the adsorptive degradation of Evans blue dye. The adsorptive degradation of Evans blue dye with Fe₃O₄@CFR@GO and Fe₃O₄@CFR@TiO₂ nanocomposites are studied by several variables like the dye concentration, dosage, pH, contact time and temperature. It shows maximum adsorption capacity of 0.1435 mg/g (Fe₃O₄@CFR@GO) and 9.345 mg/g (Fe₃O₄@CFR@TiO₂) nanocomposites. The equilibrium concentration and the adsorption capacity were evaluated using three different isothermal models. The kinetic study determined that Evans blue dye adsorption was in good analogy with the pseudo-first-order kinetic model.

Polydopamine-carbon dots functionalized hollow carbon nanoplatform for fluorescence-imaging and photothermal-enhanced thermochemotherapy

The low power photothermal therapy can reduce the tissue damage caused by laser irradiation, thus the near-infrared (NIR) absorbing vehicles with high photothermal conversion efficiency are demanded in the low power treatment. Herein, the NIR-absorbing agent polydopamine (PDA) and carbon dots (CDs) were gated on the openings of hollow mesoporous carbon (HMC) to construct a photothermal enhanced multi-functional system (HMC-SS-PDA@CDs). Interestingly, the fluorescence emission wavelength of HMC-SS-PDA@CDs was red-shifted by FRET effect between PDA and CDs, which solved the dilemma of fluorescence quenching of carbon-based materials and was more conducive to cell imaging. The modification of PDA@CDs not only acts as the gatekeepers to realize multi-responsive release of pH, GSH and NIR, but also endows the HMC vehicle with excellent photothermal generation capacity, the possibility for bio-imaging as well as the enhanced stability. Naturally, both the cytological level and the multicellular tumor sphere level demonstrate that the delivery system has good low-power synergistic therapeutic with combination index (CI) of 0.348 and imaging effects. Meanwhile, the combined treatment group showed the highest tumor inhibition rate of 92.6% at 0.75 W/cm². Therefore, DOX/HMC-SS-PDA@CDs nano-platform had broad application prospects in low power therapy and convenient imaging of carbon-based materials.

Progress in polydopamine-based melanin mimetic materials for structural color generation

Structural color is a color derived from optical interaction between light and a microstructure and is often seen in nature. Natural melanin plays an important role in bright structural coloration. For example, the vivid colors of peacock feathers are due to structural colors. The periodic arrangement of melanin granules inside the feathers leads to light interference, and the black granules absorb scattered light well, resulting in bright structural color. In recent years, polydopamine (PDA) has attracted attention as a melanin mimetic material. This review article summarizes recent research on structural coloration using PDA-based artificial melanin materials. It also outlines possible applications using bright structural colors realized by artificial melanin materials and future perspectives.