Polydopamine Nanostructures as Biomaterials for Medical Applications

Dexamethasone eluting polydopaminated polycaprolactone-poly (lactic-co-glycolic) acid for treatment of tracheal stenosis

Tracheal stenosis is commonly caused by injury, resulting in inflammation and fibrosis. Inhibiting inflammation and promoting epithelization can reduce recurrence after initial successful treatment of tracheal stenosis. Steroids play an important role in tracheal stenosis management. This study in vitro evaluated effectiveness of a polydopaminated polycaprolactone stent coated with dexamethasone-eluting poly(lactic-co-glycolic) acid microparticles (μPLGA) for tracheal stenosis management. Polydopamination was characterized by Raman spectroscopy and promoted epithelialization while dexamethasone delivery reduced macrophage activity, assessed by individual cell area measurements and immunofluorescent staining for inducible nitric oxide synthase (iNOS). Dexamethasone release was quantified by high-performance liquid chromatography over 30 days. Activation-related increase in cell area and iNOS production by RAW 264.7 were both reduced significantly (p < .05) through dexamethasone release. Epithelial cell spreading was higher on polydopaminated polycaprolactone (PCL) than PCL-alone (p < .05). Force required for stent migration was measured by pullout tests of PCL-μPLGA stents from cadaveric rabbit and porcine tracheas (0.425 ± 0.068 N and 1.082 ± 0.064 N, respectively) were above forces estimated to occur during forced respiration. Biomechanical support provided by stents to prevent airway collapse was assessed by comparing compressive circumferential stiffness, and stiffness of the stent was about 1/10th of the rabbit trachea (0.156 ± 0.023 N/mm vs. 1.420 ± 0.194 N/mm, respectively). A dexamethasone-loaded PCL-μPLGA stent platform can deliver dexamethasone and exhibits sufficient mechanical properties to anchor within the trachea and polydopamination of PCL is conducive to epithelial layer formation. Therefore, a polydopaminated PCL-μPLGA stent is a promising candidate for in vivo evaluation for treatment of tracheal restenosis.

Co-immobilization of Ciprofloxacin and Chlorhexidine as a Broad-Spectrum Antimicrobial Dual-Drug Coating for Poly(vinyl chloride) (PVC)-Based Endotracheal Tubes

The endotracheal tube (ETT) affords support for intubated patients, but the increasing incidence of ventilator-associated pneumonia (VAP) is jeopardizing its application. ETT surfaces promote (poly)microbial colonization and biofilm formation, with a heavy burden for VAP. Devising safe, broad-spectrum antimicrobial materials to tackle the ETT bioburden is needful. Herein, we immobilized ciprofloxacin (CIP) and/or chlorhexidine (CHX), through polydopamine (pDA)-based functionalization, onto poly(vinyl chloride) (PVC) surfaces. These surfaces were characterized regarding physicochemical properties and challenged with single and polymicrobial cultures of VAP-relevant bacteria (Pseudomonas aeruginosa, Acinetobacter baumannii, Klebsiella pneumoniae, Staphylococcus aureus, Staphylococcus epidermidis) and fungi (Candida albicans). The coatings imparted PVC surfaces with a homogeneous morphology, varied wettability, and low roughness. The antimicrobial immobilization via pDA chemistry was still evidenced by infrared spectroscopy. Coated surfaces exhibited sustained CIP/CHX release, retaining prolonged (10 days) activity. CIP/CHX-coated surfaces evidencing no A549 lung cell toxicity displayed better antibiofilm outcomes than CIP or CHX coatings, preventing bacterial attachment by 4.1-7.2 Log10 CFU/mL and modestly distressingC. albicans. Their antibiofilm effectiveness was endured toward polymicrobial consortia, substantially inhibiting the adhesion of the bacterial populations (up to 8 Log10 CFU/mL) within the consortia in dual- and even inP. aeruginosa/S. aureus/C. albicans triple-species biofilms while affecting fungal adhesion by 2.7 Log10 CFU/mL (dual consortia) and 1 Log10 CFU/mL (triple consortia). The potential of the dual-drug coating strategy in preventing triple-species adhesion and impairing bacterial viability was still strengthened by live/dead microscopy. The pDA-assisted CIP/CHX co-immobilization holds a safe and robust broad-spectrum antimicrobial coating strategy for PVC-ETTs, with the promise laying in reducing VAP incidence.

Polydopamine based photothermal/photodynamic synchronous coating modified intraocular lens for efficient and safer posterior capsule opacification prevention

Posterior capsule opacification (PCO), as one of the most common late complications after intraocular lens (IOL) implantation in cataract surgery, seriously affects patients' postoperative vision and surgical satisfaction, and can only be treated by laser incision of the posterior capsule. Although drug eluting coating modification have been proved to inhibit PCO effectively, the complicated coating methods and the potential toxicity of the antiproliferative drugs hinders its actual application. In this study, an indocyanine green (ICG) loaded polydopamine (PDA) coating modified IOL (IP-IOL) was designed to prevented PCO. In vitro and in vivo studies have shown that IP-IOL can effectively eliminate lens epithelial cells and significantly reduce the degree of PCO. At the same time, it still has good imaging quality and optical properties. Furthermore, both the near-infrared irradiation and ICG loaded PDA coating modified IOLs have proved to possess high biological safety to eyes. Thus, with easy preparation and safer near-infrared irradiated photothermal/photodynamic synchronous properties, such ICG loaded PDA coating provides an effective yet easier and safer PCO prevention after IOL implantation.

Synthesis of Taxifolin-Loaded Polydopamine for Chemo-Photothermal-Synergistic Therapy of Ovarian Cancer

Chemotherapy is a well-established method for treating cancer, but it has limited effectiveness due to its high dosage and harmful side effects. To address this issue, researchers have explored the use of photothermal agent nanoparticles as carriers for precise drug release in vivo. In this study, three different sizes of polydopamine nanoparticles (PDA-1, PDA-2, and PDA-3) were synthesized and evaluated. PDA-2 was selected for its optimal size, encapsulation rate, and drug loading rate. The release of the drug from PDA-2@TAX was tested at different pH and NIR laser irradiation levels. The results showed that PDA-2@TAX released more readily in an acidic environment and exhibited a high photothermal conversion efficiency when exposed to an 808 nm laser. In vitro experiments on ovarian cancer cells demonstrated that PDA-2@TAX effectively inhibited cell proliferation, highlighting its potential for synergistic chemotherapy-photothermal treatment.

Melanin/melanin-like nanoparticles: As a naturally active platform for imaging-guided disease therapy

The development of biocompatible and efficient nanoplatforms that combine diagnostic and therapeutic functions is of great importance for precise disease treatment. Melanin, an endogenous biopolymer present in living organisms, has attracted increasing attention as a versatile bioinspired functional platform owing to its unique physicochemical properties (e.g., high biocompatibility, strong chelation of metal ions, broadband light absorption, high drug binding properties) and inherent antioxidant, photoprotective, anti-inflammatory, and anti-tumor effects. In this review, the fundamental physicochemical properties and preparation methods of natural melanin and melanin-like nanoparticles were outlined. A systematical description of the recent progress of melanin and melanin-like nanoparticles in single, dual-, and tri-multimodal imaging-guided the visual administration and treatment of osteoarthritis, acute liver injury, acute kidney injury, acute lung injury, brain injury, periodontitis, iron overload, etc. Was then given. Finally, it concluded with a reasoned discussion of current challenges toward clinical translation and future striving directions. Therefore, this comprehensive review provides insight into the current status of melanin and melanin-like nanoparticles research and is expected to optimize the design of novel melanin-based therapeutic platforms and further clinical translation.

High-efficiency SERS platform based on 3D porous PPDA@Au NPs as a substrate for the detection of pesticides on vegetables

Nowadays, the presence of highly toxic and persistent residues of pesticides in water and food around the world is becoming a serious problem, and so their rapid and sensitive detection is critical to human health. In this work, a 3D composite nanoparticle of porous PDA (polydopamine) microspheres and Au NPs (PPDA@Au NPs) was proposed as a SERS substrate to detect pesticides. Porous PDA as a substrate was first synthesized with F127 (Pluronic F127), dopamine hydrochloride, and 1,3,5-TMB (1,3,5-trimethylbenzene) under weakly alkaline conditions by a one-step method. Then, HAuCl4 was in situ reduced in the pores of PPDA spheres and grew sequentially for effecting the reducibility of PPDA. As a result, uniform 3D PPDA@Au NPs with "hot spots" were successfully synthesized as SERS substrates, which could effectively avoid the agglomeration of gold nanoparticles to greatly improve the sensitivity and uniformity of the SERS platform. At the same time, methyl parathion, 4-chlorophenol, and 2,4-D as representatives of pesticides were detected with the proposed PPDA@Au NP-based SERS platform, with detection limits lower than 7.26, 7.52, and 11 ng mL-1, separately. The current work presents a simple preparation method to prepare sensitive and uniform SERS platform PPDA@Au NPs, which have potential for applications in actual pesticide and drug testing.

Aqueous green synthesis of organic/inorganic nanohybrids with an unprecedented synergistic mechanism for enhanced near-infrared photothermal performance

Silver sulfide (Ag2S) nanoparticles (NPs) represent one of the most popular inorganic reagents for near-infrared (NIR) photothermal therapy (PTT). However, the extensive biomedical applications of Ag2S NPs are greatly compromised by the hydrophobicity of the NPs prepared in organic solvents, their low photothermal conversion efficiency, certain surface modification-induced damage to their intrinsic properties and short circulation time. To develop a facile yet efficient green approach to overcome these shortcomings for improved properties and performance of Ag2S NPs, we report herein the construction of Ag2S@polydopamine (PDA) nanohybrids via a "one-pot" organic-inorganic hybridization strategy, which produces uniform Ag2S@PDA nanohybrids with well-modulated sizes in the range of 100-300 nm via the self-polymerization of dopamine (DA) and subsequent synergistic assembly of PDA with Ag2S NPs in a three-phase mixed medium containing water, ethanol and trimethylbenzene (TMB). Integration of dual photothermal moieties, i.e., Ag2S and PDA at a molecular level, endows Ag2S@PDA nanohybrids with synergistically enhanced NIR photothermal properties that are much better than those of either PDA or Ag2S NPs due to calculated combination indexes (CIs) of 0.3-0.7 between Ag2S NPs and PDA based on a modified Chou-Talalay method. Therefore, this study not only developed a facile "one-pot" green approach toward producing uniform Ag2S@PDA nanohybrids with well-modulated dimensions, but also revealed an unprecedented synergistic mechanism for organic/inorganic nanohybrids that is based on dual photothermal moieties providing enhanced near-infrared photothermal performance.

Temozolomide and chloroquine co-loaded mesoporous silica nanoparticles are effective against glioma

The past decades have witnessed great progress in nanoparticle-based cancer-targeting drug delivery systems, but their therapeutic potentials is yet to be fully exploited. In this research, temozolomide (TMZ) and chloroquine (CQ) were loaded into the mesoporous silica nanoparticles (MSNs), the surface was coated with polydopamine (PDA), and the complex was coupled with arginine-glycine-aspartic (RGD) to successfully prepare TMZ/CQ@MSN-RGD. RGD-MSNs accumulated more in the cell and tumor models than in unmodified MSNs in the in vitro and in vivo experiments and can directly induce apoptosis and autophagy in tumor cells. In addition, TMZ/CQ@MSN-RGD therapy enhanced the apoptosis effect of the RGD-MSNs in glioma. Therefore, the combination of autophagy inhibitor with chemotherapy drugs in nanocarriers may promote therapeutic efficacy in treating glioma.

Polydopamine nanoparticles coated with a metal-polyphenol network for enhanced photothermal/chemodynamic cancer combination therapy

Polydopamine nanoparticles (PDA NPs) are commonly used for photothermal therapy (PTT) of cancer because of their good biocompatibility and photothermal conversion capability. However, it is difficult to achieve a good tumor inhibition effect with a single PTT of PDA. Therefore, in this work, we prepared a combined anticancer nanosystem for enhanced chemodynamic therapy (CDT)/PTT by coating PDAs with an (-)-epigallocatechin gallate (EGCG)/iron (Fe) metal-polyphenol network (MPN). The MPN shell of this nanosystem named EGCG@PDA is degraded by the weakly acidic environment intracellular, releasing EGCG and Fe³⁺. EGCG inhibits the expression of heat shock proteins (HSPs) in cancer cells, thus eliminating their thermal protection against cancer cells for enhanced PTT. Meanwhile, the reductive EGCG can also reduce Fe³⁺ to Fe²⁺, to catalyze the decomposition of overexpressed hydrogen peroxide (H₂O₂) in cancer cells to generate strong oxidative hydroxyl radicals (OH), i.e., catalyzing the Fenton reaction, for CDT. After the Fenton reaction, the re-oxidized Fe ions can be reduced again by EGCG and reused to catalyze the Fenton reaction, which can achieve enhanced CDT. Both in vitro and in vivo studies have shown that EGCG@PDA has low dark toxicity and good anticancer effects. It is expected to be used for precision cancer therapy.

Simple bio-inspired coating of ureteral stent for protein and bacterial fouling and calcium encrustation control

Encrustation, caused by deposition of calcium and magnesium salts present in urine, is a common problem of indwelling urinary devices, such as ureteral stent. Encrustation was also found to be related to urinary tract infections; thus, it is necessary to prepare ureteral stents with antibacterial and antifouling surfaces to mitigate the occurrence of encrustation. In this study, commercial ureteral stent was coated with polydopamine (PDA), formed from self-polymerization of dopamine. The PDA coating was optimized in terms of dopamine concentration, pH, and coating time using response surface methodology. The chosen response parameters for optimization were calcium oxalate (CaC₂ O₄ ) encrustation and protein adsorption. Optimized PDA coating conditions were determined to be the following: pH 9.0, 2 mg/mL DA, and 3 days coating. The optimized PDA-coated ureteral stent exhibited outstanding resistance against CaC₂ O₄ encrustation, protein fouling, and bacterial adhesion due to its hydrophilic and functional coating layer. In comparison with the pristine ureteral stent, PDA coating was able to suppress approximately 97% and 87% of CaC₂ O₄ and protein adsorption, respectively. The PDA-coated ureteral stent was compared against those of commercially available ureteral stents and found to have superior encrustation and protein fouling mitigation performance. Finally, PDA coating was found to be highly stable for a storage period of 90 days, whether stored in wet or dry conditions.

Triple functional mild photothermal improves gene editing of PD-L1 for enhanced antitumor immunity

Traditional photothermal therapy ablates tumor cells by a high temperature (> 50 °C). Although it has shown good anti-tumor effect in animal models, the potential damages to healthy tissues and the unnecessary inflammatory reactions caused by the high temperature have hindered the clinical transitions of traditional photothermal therapy. In this study, we used polydopamine (PDA) as a mild photothermal material and control the maximum temperature below 45 °C, which not only avoided the side effects caused by a high temperature, but also ablated a fraction of tumor cells and produced tumor antigens. Meanwhile, the near-infrared (NIR) light also served as a "switch" to trigger the release of CRISPR/Cas9 RNP from Fe₃O₄ nanoparticles (Fe₃O₄ NPs) after their accumulation to tumor sites via magnetic targeting. The triple functional mild photothermal therapy achieved significant PD-L1 gene knockout efficiency in the tumor-bearing mice, reversed the condition of immunosuppression in the tumor microenvironment, led to a higher level of anti-tumor immune responses and effectively inhibited the growth of melanoma. We anticipate that this triple functional mild photothermal therapy would provide a potential new approach for the treatment of malignant tumors.

Modulation of Mitochondrial Bioenergetics by Polydopamine Nanoparticles in Human iPSC-Derived Cardiomyocytes

Myocardial infarction (MI) leads to the formation of an akinetic scar on the heart muscle causing impairment in cardiac contractility and conductance, leading to cardiac remodeling and heart failure (HF). The current pharmacological approaches for attenuating MI are limited and often come with long-term adverse effects. Therefore, there is an urgent need to develop novel multimodal therapeutics capable of modulating cardiac activity without causing any major adverse effects. In the current study, we have demonstrated the applicability of polydopamine nanoparticles (PDA-NPs) as a bioactive agent that can enhance the contractility and beat propagation of human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). Treatment of hiPSC-CMs with PDA-NPs demonstrated accumulation of the latter into mitochondria and significantly enhanced time-dependent adenosine triphosphate (ATP) production in these cells, indicating improved mitochondrial bioenergetics. Furthermore, the effect of PDA-NPs on hiPSC-CM activity was evaluated by measuring calcium transients. Treatment with PDA-NPs increased the calcium cycling in hiPSC-CMs in a temporal manner. Our results demonstrated a significant reduction in peak amplitude, transient duration, time to peak, and transient decay time in the PDA-NPs-treated hiPSC-CMs as compared to untreated hiPSC-CMs. Additionally, treatment of isolated perfused rat heart ex vivo with PDA-NPs demonstrated cardiotonic effects on the heart and significantly improved the hemodynamic function, suggesting its potential for enhancing whole heart contractility. Lastly, the gene expression analysis data revealed that PDA-NPs significantly upregulated cardiac-specific genes (ACADM, MYL2, MYC, HCN1, MYL7, GJA5, and PDHA1) demonstrating the ability to modulate genetic expression of cardiomyocytes. Taken together, these findings suggest PDA-NPs capability as a versatile nanomaterial with potential uses in next-generation cardiovascular applications.

Biopolymer coating for particle surface engineering and their biomedical applications

Surface engineering of particles based on a polymeric coating is of great interest in materials design and applications. Due to the disadvantages of non-biodegradability and undesirable biocompatibility, the application of petroleum-based synthetic polymers coating in the biomedical field has been greatly limited. In addition, there is lack of a universal surface modification method to functionalize particles of different compositions, sizes, shapes, and structures. Thus, it is imperative to develop a versatile biopolymeric coating with good biocompatibility and tunable biodegradability for the preparation of functional particle materials regardless of their surface chemical and physical structures. Recently, the natural polysaccharide polymers (e.g. chitosan and cellulose), polyphenol-based biopolymers (e.g. polydopamine and tannic acid), and proteins (e.g. amyloid-like aggregates) have been utilized in surface modification of particles, and applications of these modified particles in the field of biomedicine have been also intensively exploited. In this review, the preparation of the above three coatings on particles surface are summarized, and the applications of these materials in drug loading/release, biomineralization, cell immobilization/protection, enzyme immobilization/protection, and antibacterial/antiviral are exemplified. Finally, the challenges and the future research directions on biopolymer coating for particles surface engineering are prospected.

Fabrication of mechanically advanced polydopamine decorated hydroxyapatite/polyvinyl alcohol bio-composite for biomedical applications: In-vitro physicochemical and biological evaluation

In this study, polydopamine (PDA) coated hydroxyapatite (HA) reinforced polyvinyl alcohol (PVA) films were produced to be used in biomedical applications such as bone tissue regeneration. pDA is coated not only to prevent the agglomeration of HA when encountering interstitial fluids but also to strongly bind the PVA for the interaction between materials so that the mechanical performance becomes more stabilized. pDA was coated on the hydroxyapatite surface using a radical polymerization technique, and the reinforced PVA were produced with pDA-coated HA (pDA-HA/PVA) nanoparticles. Fundamental characteristic properties of pDA-HA/PVA nanocomposite films were examined by morphological/chemical (SEM-EDS), microstructural (XRD, Ft-IR, and Raman), thermodynamic (TGA and TM), mechanical performance (Vickers microhardness) and biological activity analysis (MTT, genotoxicity and antimicrobial efficacy investigations). Physicochemical analysis showed that all the samples studied exhibited homogeneous mineral distributions through the main structures. According to TGA, TMA and hardness tests, the new composite structure possessed higher mechanical properties than neat PVA. Further, pDA-HA/PVA nanocomposites exhibited high antibacterial capacities against Acinetobacter Baumannii (A.Baumannii), Staphylococcus aureus (S. aureus), and Streptococcus mutans (S.mutans). Moreover, the new nanocomposites were noted to present good biocompatibility for fibroblast (L929) cells and to support remarkably MCS cells. All in all, this comprehensive work shows that the thermo-mechanically improved pDA-HA/PVA films will increase the application fields of PVA in biomedical fields especially tooth-bone treatments for coating, filling, or occlusion purposes.

Lateral flow immunoassay based on polydopamine-coated metal-organic framework for the visual detection of enrofloxacin in milk

Herein, we report a new polydopamine (PDA)-coated metal-organic framework (MOF) as a label to improve the sensitivity of lateral flow immunoassay (LFIA). The MOF, UiO-66-NH₂, was synthesized via the hydrothermal method, and it exhibited the advantageous features of ordered pore structure, strong absorbance, and high specific surface area. Subsequently, UiO-66-NH₂ was coated with PDA to improve the antibody coupling effectivity and light absorption ability. The optical intensity and antibody coupling efficiency of UiO-66@PDA were superior to those of gold nanoparticles (AuNPs). Under the optimum condition, the limit of detection and cutoff value of UiO-66@PDA-LFIA in detecting enrofloxacin were 0.045 and 1.0 ng/mL, respectively, which were lower than those of AuNPs-LFIA (0.095 and 5 ng/mL). The recoveries of UiO-66@PDA-LFIA in low-fat milk and whole milk were 85.6-107.4% and 79.3-115.5%, respectively, with coefficients of variation of 2.91-9.59% and 3.91-11.8%, respectively, as further confirmed by liquid chromatography-tandem mass spectrometry. These results indicate that UiO-66@PDA can be used as a novel probe for LFIA development and applications. Graphical abstract.

Polydopamine-Mediated Protein Adsorption Alters the Epigenetic Status and Differentiation of Primary Human Adipose-Derived Stem Cells (hASCs)

Polydopamine (PDA) is a biocompatible cell-adhesive polymer with versatile applications in biomedical devices. Previous studies have shown that PDA coating could improve cell adhesion and differentiation of human mesenchymal stem cells (hMSCs). However, there is still a knowledge gap in the effect of PDA-mediated protein adsorption on the epigenetic status of MSCs. This work used gelatin-coated cell culture surfaces with and without PDA underlayer (Gel and PDA-Gel) to culture and differentiate primary human adipose-derived stem cells (hASCs). The properties of these two substrates were significantly different, which, in combination with a variation in extracellular matrix (ECM) protein bioactivity, regulated cell adhesion and migration. hASCs reduced focal adhesions by downregulating the expression of integrins such as αV, α1, α2, and β1 on the PDA-Gel compared to the Gel substrate. Interestingly, the ratio of H3K27me3 to H3K27me3+H3K4me3 was decreased, but this only occurred for upregulation of AGG and BMP4 genes during chondrogenic differentiation. This result implies that the PDA-Gel surface positively affects the chondrogenic, but not adipogenic and osteogenic, differentiation. In conclusion, for the first time, this study demonstrates the sequential effects of PDA coating on the biophysical property of adsorbed protein and then focal adhesions and differentiation of hMSCs through epigenetic regulation. This study sheds light on PDA-mediated mechanotransduction.

Quartz crystal microbalance-based biosensing of hepatitis B antigen using a molecularly imprinted polydopamine film

Quartz crystal microbalance (QCM)-based biosensors are highly attractive as rapid diagnostic devices for detecting infectious diseases. However, the fabrication of QCM-based biosensors often involves tedious processes due to the poor stability of the biological recognition elements. In this work, the simple self-polymerisation of dopamine was used to functionalise the QCM crystal surface with a molecularly imprinted polydopamine (MIPDA) sensing film for detecting the hepatitis B core antigen (HBcAg), a serological biomarker of hepatitis B. Recognition cavities that complemented the size and shape of HBcAg were observed on the QCM crystal surface after functionalisation with the MIPDA film. The MIPDA-QCM biosensor showed a selective affinity for HBcAg, recording frequency responses up to 7.8 folds larger towards HBcAg compared to human serum albumin at the same analyte concentrations. The biosensor response was enhanced by using the optimal concentrations of 10 mg mL^-1 of dopamine and 1 mg mL^-1 of template for MIPDA film formation, resulting in a low detection limit (0.88 μg mL^-1) that enables the detection of clinically relevant titres of HBcAg. The detection process could be completed within 10 min after sample loading without additional steps for signal amplification, highlighting the practical advantages of the MIPDA-QCM biosensor for point-of-care detection of hepatitis B.

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.

Glyconanoparticles with Activatable Near-Infrared Probes for Tumor-Cell Imaging and Targeted Drug Delivery

Background

Multifunctional nanocarriers based on tumor targeting and intracellular monitoring have received much attention and been a subject of intensive study by researchers in recent years. In this study, we report multifunctional glyconanoparticles with activatable near-infrared probes for tumor imaging and targeted drug delivery.

Methods

Disulfide-functionalized dicyanomethylene-4H-pyran (DCM-SS-NH₂) and amino-functionalized lactose were modified and loaded onto the surfaces of polydopamine nanoparticles (NPs) by Michael addition or Schiff-base reaction as GSH stimulation–responsive fluorescent probes and tumor-targeting moieties, respectively. Doxorubicin (DOX), a model anticancer drug, was loaded onto polydopamine through π–π interactions directly to prepare multifunctional PLDD (PDA@Lac/DCM/DOX) NPs.

Results

Experimental results showed that PLDD NPs had been successfully prepared. DCM, the fluorescence of which was quenched in PLDD NPs, was able to restore red fluorescence in a solution with a GSH concentration of 5 mM. The amount of DOX released from PLDD NPs was 44% over 72 hours in a weak-acid environment (pH 5). The results of CLSM and flow cytometry indicated that the PLDD NPs had good HepG2-targeting ability due to the special recognition between lactose derivative of NPs and overexpressed asialoglycoprotein receptors on HepG2 cell membrane. More importantly, the disulfide bond of DCM-SS-NH₂ was broken by the high concentration of GSH inside cancer cells, activating the near-infrared fluorescence probe DCM for cancer-cell imaging. MTT assays indicated that PLDD NPs exhibited higher anticancer efficiency for HepG2 cells and had reduced side effects on normal cells compared with free DOX.

Conclusion

The fluorescence of modified DCM loaded onto PLDD NPs is able to be restored in the high-concentration GSH environment within cancer cells, while improving the effectiveness of chemotherapy with reduced side effects. It provides a good example of integration of tumor imaging and targeted drug delivery.

Preparation and catalytic properties of polydopamine-modified polyacrylonitrile fibers functionalized with silver nanoparticles

Fiber-supported catalysts have attracted much attention due to their large specific surface area, high catalytic activity, and good recyclability. Functional polyacrylonitrile fibers were prepared by immersion of polyacrylonitrile fibers at room temperature in an alkaline dopamine (pH = 8.5) aqueous solution which can undergo self-polymerization and reduce silver ions to silver nanoparticles with mild reducibility and adsorption. The surface of the polyacrylonitrile fiber (PAN) was wrapped with a layer of polydopamine (PDA), and silver nanoparticles (Ag NPs) were adsorbed on the surface of PDA, forming an efficient fiber catalyst. The morphology and chemical composition of the catalyst material were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD) patterns, and Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS). The catalytic activity of the nanocomposite was evaluated for the reduction reaction of 4-nitrophenol using sodium borohydride (NaBH₄) at 35 °C with a material molar ratio of 1 : 10 and a fiber loaded catalysis dosage of 40 mg. The liquid phase yield can reach 98% in 30 minutes and can be reused after washing with ethanol. Moreover, the composite material exhibited a good stability up to 10 cycles without a significant loss of its catalytic activity. The results show that the catalyst is easy to recover from the reaction system and has maintained good stability and catalytic activity after many cycles.

Via the help of polydopamine, polyacrylonitrile fiber catalysts functionalized with silver nanoparticles were prepared and employed for the reduction reaction of 4-nitrophenol to 4-aminophenol, with a yield of 98% in 30 minutes, and can be reused for up to 10 cycles.

Facile fabrication and nanoscale assembly of polydopamine-functionalized, flexible chitosan films

Substrates that are simultaneously thin, strong, optically transparent, and biocompatible have diverse applications in a range of fundamental and applied fields. While nature-derived materials offer advantages of sustainability and inherent biocompatibility compared to synthetic polymers, their brittleness and swelling, as well as surface charge and chemical functionalization non-conducive to cell growth, can hinder widespread application. In this work, we discuss the fabrication and systematic characterization of polydopamine-coated chitosan thin films. Chitosan is a widely used, partially deacetylated form of chitin, derived from crustaceans and arthropods. Polydopamine (PDA) is derived from chemistries mimicking mussel foot adhesive proteins. A facile dip-coating process of thin and flexible, uncrosslinked chitosan films in aqueous dopamine solutions leads to dramatic changes in physical and chemical properties. We show how the PDA forms time-dependent assemblies on the film surfaces, affecting surface roughness, hydrophilicity, and mechanical strength. Coating the surface for even a few seconds provides functional changes to the films. Our results shows that the optimal coating time is on the order of few hours, whereby the films are optically transparent with excellent extensibility and Young’s modulus, while further coating reduces the benefits of this surface coating. These materials are biocompatible, serving as substrates for cell adhesion and growth while maintaining good viability. Overall, these findings give insight to the effects of PDA assembly on surfaces, and illustrate how a simple, quick, and robust bioinspired coating process can prime substrates for biomedical applications such as tissue engineering, biosensing, and wound healing.

Preparation, Characterization, and In Vitro/In Vivo Evaluation of 3-O-β-D-Galactosylated Resveratrol-Loaded Polydopamine Nanoparticles

3-O-β-D-galactosylated resveratrol (Gal-Res) was synthesized from resveratrol (Res) and 3-O-β-D-galactose (Gal) in our previous study. In order to improve the pH sensitivity and bioavailability of Gal-Res, Gal-Res nanoparticles (Gal-Res NPs) were prepared using polydopamine (PDA) as a drug carrier. The drug loading (DL %) and entrapment efficiency (EE %) of Gal-Res NPs were 46.80% and 88.06%. The average particle size, polydispersity index (PDI), and Zeta potential of Gal-Res NPs were 179.38 ± 2.83 nm, 0.129 ± 0.013, and - 28.05 ± 0.36 mV, respectively. The transmission electron microscope (TEM) showed that Gal-Res NPs had uniform spherical morphology. Compared with the fast release of raw Gal-Res, the in vitro release of Gal-Res NPs was slow and pH-sensitive. The results of the blood vessel irritation and hemolysis test demonstrated that Gal-Res NPs had good hemocompatibility. The pharmacokinetics study in rats showed that area under the curve of plasma drug concentration time (AUC_0→600) and half-life (t_1/2) of Gal-Res NPs were enhanced 1.82-fold and 2.19-fold higher than those of raw Gal-Res. The in vivo biodistribution results showed that Gal-Res NPs were more distributed in liver tissue than Gal-Res. Gal-Res NPs with high bioavailability and liver accumulation were hopeful drug delivery systems (DDS) to treat liver diseases.

Facile surface functional polyetheretherketone with antibacterial and immunoregulatory activities for enhanced regeneration toward bacterium-infected bone destruction

Existing biologically inert or unmodified implants to treat infectious bone defects or osteomyelitis still cannot effectively solve bacterial infection and osseointegration. In this work, a simple co-deposition strategy was developed to modify porous polyetheretherketone (PEEK) with improved antibacterial activity and controllable immunoregulatory ability. After PEEK was treated by H₂SO₄ to obtain porous PEEK (SPEEK), the self-polymerization of dopamine was operated on SPEEK in the solution of dopamine and gentamicin sulfate (GS) to prepare polydopamine (pDA) and GS layer-modified SPEEK (labeled as SPEEK–pDA–GS). The morphology, surface property, and molecular structure of SPEEK–pDA–GS were investigated. Besides the antibacterial property of SPEEK–pDA–GS ascribed to the successful immobilization of GS, SPEEK–pDA–GS exhibited promoted osseointegration through the results of mineralization, alkaline phosphatase (ALP) levels and osteogenic gene expression. Furthermore, the evaluation of the cell proliferation suggested that SPEEK–pDA–GS possessed the biocompatibility and the immunoregulatory ability that induced macrophages to anti-inflammatory M2 phenotype. Using rat as model, in vivo results containing X-ray, μ-CT, immunohistochemistry, and pathological analysis showed the excellent healing effect of SPEEK–pDA–GS on bone defect with infection with biological safety. This work illustrates a new insight into the simple and effective modification of PEEK and other implants with antibacterial, immunoregulatory, and osseointegration abilities for clinical requirement.

Recent Advances in Antioxidant Polymers: From Sustainable and Natural Monomers to Synthesis and Applications

Advances in technology have led to the production of sustainable antioxidants and natural monomers for food packaging and targeted drug delivery applications. Of particular importance is the synthesis of lignin polymers, and graft polymers, dopamine, and polydopamine, inulin, quercetin, limonene, and vitamins, due to their free radical scavenging ability, chemical potency, ideal functional groups for polymerization, abundance in the natural environment, ease of production, and activation of biological mechanisms such as the inhibition of the cellular activation of various signaling pathways, including NF-κB and MAPK. The radical oxygen species are responsible for oxidative damage and increased susceptibility to cancer, cardiovascular, degenerative musculoskeletal, and neurodegenerative conditions and diabetes; such biological mechanisms are inhibited by both synthetic and naturally occurring antioxidants. The orientation of macromolecules in the presence of the plasticizing agent increases the suitability of quercetin in food packaging, while the commercial viability of terpenes in the replacement of existing non-renewable polymers is reinforced by the recyclability of the precursors (thyme, cannabis, and lemon, orange, mandarin) and marginal ecological effect and antioxidant properties. Emerging antioxidant nanoparticle polymers have a broad range of applications in tumor-targeted drug delivery, food fortification, biodegradation of synthetic polymers, and antimicrobial treatment and corrosion inhibition. The aim of the review is to present state-of-the-art polymers with intrinsic antioxidant properties, including synthesis scavenging activity, potential applications, and future directions. This review is distinct from other works given that it integrates different advances in antioxidant polymer synthesis and applications such as inulin, quercetin polymers, their conjugates, antioxidant-graft-polysaccharides, and polymerization vitamins and essential oils. One of the most comprehensive reviews of antioxidant polymers was published by Cirillo and Iemma in 2012. Since then, significant progress has been made in improving the synthesis, techniques, properties, and applications. The review builds upon existing research by presenting new findings that were excluded from previous reviews.

Heteropore covalent organic framework-based composite membrane prepared by in situ growth on non-woven fabric for sample pretreatment of food non-targeted analysis

A heteropore covalent organic framework (COF)-based composite membrane material was prepared and proved to have a satisfactory effect on the pretreatment of vegetable samples. The composite membrane was fabricated by in situ growth of a dual-pore COF on the surface of polydopamine (PDA)-aminated non-woven (NW) fabric. Due to the difference in the strength of the interaction between the phytochromes/COF and the pesticides/COF, the removal of phytochromes and the recovery of pesticides can be achieved by adjusting the composition of the solution. Through a simple immersion or filtration operation, NW@PDA@COF composite membrane can quickly and almost completely remove interfering phytochromes in the samples. The recovery of pesticides was determined by HPLC-MS/MS, and the recovery efficiencies were 72.3~101.7% and 67.3~106.7% for immersion and filtration modes of five different vegetable samples, respectively; the RSD is between 1.1 and 19% (n = 3). The limits of detection and quantification for the 13 pesticides investigated were 0.08 μg·L^-1 and 0.23 μg·L^-1, respectively. A wide linear range of 1~1000 μg·L^-1 was observed with R² values from 0.9774 to 0.9998. The membrane can be repeatedly used for at least 10 times by using a facile elution treatment. Compared to other commonly used sample pretreatment materials, heteropore COF-based composite membrane is superior in terms of sorbent amount, treatment time, operation simplicity, and material reusability.

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.

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

Highly oriented, layered, and mechanically resilient films of polydopamine (PDA) have been synthesized from the air/water interface. The films show a unique layered structure, as shown by scanning and transmission electron studies (SEM/TEM) and X-ray diffraction analysis (XRD), which resemble that of 2D layered materials. The films exhibit a composition typical of PDA-based materials, as evidenced by X-ray photoelectron spectroscopy (XPS); moreover, the samples present the distinctive resonance modes of PDA-based nanomaterials in Raman and infrared spectroscopy (FTIR) experiments. The presence of highly ordinated 3-4 protomolecule stacking, taking place at the air/water interface, with a unique eumelanin-like supramolecular arrangement is presented. Moreover, the films show superior mechanical resilience with E = 13 ± 4 GPa and H = 0.21 ± 0.03 GPa, as revealed by nanoindentation experiments, making them highly resilient and easily transferable. Finally, the ordering induced by the interface opens many possibilities for further studies, including those regarding the supramolecular structure on PDA due to their similarity to 2D layered materials.

Surface Functionalization of Ti3C2Tx MXene Nanosheets with Catechols: Implication for Colloidal Processing

Precise tailoring of two-dimensional nanosheets with organic molecules is critical to passivate the surface and control the reactivity, which is essential for a wide range of applications. Herein, we introduce catechols to functionalize exfoliated MXenes (Ti₃C₂T_x) in a colloidal suspension. Catechols react spontaneously with Ti₃C₂T_x surfaces, where binding is initiated from a charge-transfer complex as confirmed by density functional theory (DFT) and UV-vis. Ti₃C₂T_x sheet interlayer spacing is increased by catechol functionalization, as confirmed by X-ray diffraction (XRD), while Raman and atomic force microscopy-infrared spectroscopy (AFM-IR) measurements indicate binding of catechols at the Ti₃C₂T_x surface occurs through metal-oxygen bonds, which is supported by DFT calculations. Finally, we demonstrate immobilization of a fluorescent dye on the surface of MXene. Our results establish a strategy for tailoring MXene surfaces via aqueous functionalization with catechols, whereby colloidal stability can be modified and further functionality can be introduced, which could provide excellent anchoring points to grow polymer brushes and tune specific properties.

Toward Designing of Anti-infective Hydrogels for Orthopedic Implants: From Lab to Clinic

An alarming increase in implant failure incidence due to microbial colonization on the administered orthopedic implants has become a horrifying threat to replacement surgeries and related health concerns. In essence, microbial adhesion and its subsequent biofilm formation, antibiotic resistance, and the host immune system's deficiency are the main culprits. An advanced class of biomaterials termed anti-infective hydrogel implant coatings are evolving to subdue these complications. On this account, this review provides an insight into the significance of anti-infective hydrogels for preventing orthopedic implant associated infections to improve the bone healing process. We briefly discuss the clinical course of implant failure, with a prime focus on orthopedic implants. We identify the different anti-infective coating strategies and hence several anti-infective agents which could be incorporated in the hydrogel matrix. The fundamental design criteria to be considered while fabricating anti-infective hydrogels for orthopedic implants will be discussed. We highlight the different hydrogel coatings based on the origin of the polymers involved in light of their antimicrobial efficacy. We summarize the relevant patents reported in the prevention of implant infections, including orthopedics. Finally, the challenges concerning the clinical translation of the aforesaid hydrogels are described, and considerable solutions for improved clinical practice and better future prospects are proposed.

Tailoring the immobilization and release of chlorhexidine using dopamine chemistry to fight infections associated to orthopedic devices

A crucial factor in the pathogenesis of orthopedics associated infections is that bacteria do not only colonize the implant surface but also the surrounding tissues. This study aimed to engineer an antimicrobial release coating for stainless steel (SS) surfaces, to impart them with the ability to prevent Staphylococci colonization. Chlorhexidine (CHX) was immobilized using two polydopamine (pDA)-based approaches: a one-pot synthesis, where CHX is dissolved together with dopamine before its polymerization; and a two-step methodology, comprising the deposition of a pDA layer to which CHX is immobilized. To modulate CHX release, an additional layer of pDA was also added for both strategies. Immobilization of CHX using a one-step approach yielded surfaces with a more homogenous coating and less roughness than the other strategies. The amount of released CHX was lower for the one-step approach, as opposed to the two-step approach yielding the higher release, which could be decreased by applying an outward layer of pDA. Both one and two-step approaches provided the surfaces with the ability to prevent bacterial colonization of the surface itself and kill most of bacteria in the bulk phase up to 10 days. This long-term antimicrobial performance alluded a stable and enduring immobilization of CHX. In terms of biocompatibility, the amount of CHX released from the one-step approach did not compromise the growth of mammalian cells, contrary to the two-step strategy. Additionally, the few bacteria that managed to adhere to surfaces modified with one-step approach did not show evidence of resistance towards CHX. Overall data underline that one-step immobilization of CHX holds great potential to be further applied in the fight against orthopedic devices associated infections.

In-line characterization of nanostructures produced by roll-to-roll nanoimprinting

We present an in-line metrology solution for dimensional characterization of roll-to-roll imprinted nanostructures. The solution is based on a scatterometric analysis of optical data from a hyperspectral camera deployed at a production facility, where nanostructures are produced at speeds of 10m/min. The system combines the ease of use of a real-space imaging system with the spectral information used in scatterometry. We present nanoscale dimensional measurements on one-dimensional line gratings with various periods and orientations. The depths of the produced structures are accurately characterized with uncertainties on the scale of a few nanometers. The hyperspectral imaging capabilities of the system can also be used to avoid vibrational effects.

Mesoporous Polydopamine Nanoparticles Attenuate Morphine Tolerance in Neuropathic Pain Rats by Inhibition of Oxidative Stress and Restoration of the Endogenous Antioxidant System

Oxidative stress resulting from reactive oxygen species (ROS) is known to play a key role in numerous neurological disorders, including neuropathic pain. Morphine is one of the commonly used opioids for pain management. However, long-term administration of morphine results in morphine antinociceptive tolerance (MAT) through elevation of ROS and suppression of natural antioxidant defense mechanisms. Recently, mesoporous polydopamine (MPDA) nanoparticles (NPS) have been known to possess strong antioxidant properties. We speculated that morphine delivery through an antioxidant nanocarrier might be a reasonable strategy to alleviate MAT. MPDAs showed a high drug loading efficiency of ∼50%, which was much higher than conventional NPS. Spectral and in vitro studies suggest a superior ROS scavenging ability of NPS. Results from a rat neuropathic pain model demonstrate that MPDA-loaded morphine (MPDA@Mor) is efficient in minimizing MAT with prolonged analgesic effect and suppression of pro-inflammatory cytokines. Additionally, serum levels of liver enzymes and levels of endogenous antioxidants were measured in the liver. Treatment with free morphine resulted in elevated levels of liver enzymes and significantly lowered the activities of endogenous antioxidant enzymes in comparison with the control and MPDA@Mor-treated group. Histopathological examination of the liver revealed that MPDA@Mor can significantly reduce the hepatotoxic effects of morphine. Taken together, our current work will provide an important insight into the development of safe and effective nano-antioxidant platforms for neuropathic pain management.

Polydopamine-based nanomaterials and their potentials in advanced drug delivery and therapy

Polydopamine (PDA) has shown great potentials in biomedical fields due largely to its unique physicochemical properties, including high photothermal transfer efficiency, excellent drug binding capacity, versatile adhesion ability, sensitive pH responsibility and great biocompatibility and biodegradability. These properties confer PDA-based nanoparticles the potentials either as the drug carriers for advanced drug delivery or as the bioactive agents for photothermal therapy, imaging and biosensing. This review aims to provide a comprehensive understanding of PDA, its polymerization mechanisms and the potentials of PDA-based nano-systems in treating various diseases, including cancer, diabetes, inflammation, bacterial infection and Parkinson's disease. In addition, the concerns of PDA in biomedical use are also discussed.

Laser-induced graphitization of polydopamine leads to enhanced mechanical performance while preserving multifunctionality

Polydopamine (PDA) is a simple and versatile conformal coating material that has been proposed for a variety of uses; however in practice its performance is often hindered by poor mechanical properties and high roughness. Here, we show that blue-diode laser annealing dramatically improves mechanical performance and reduces roughness of PDA coatings. Laser-annealed PDA (LAPDA) was shown to be >100-fold more scratch resistant than pristine PDA and even better than hard inorganic substrates, which we attribute to partial graphitization and covalent coupling between PDA subunits during annealing. Moreover, laser annealing provides these benefits while preserving other attractive properties of PDA, as demonstrated by the superior biofouling resistance of antifouling polymer-grafted LAPDA compared to PDA modified with the same polymer. Our work suggests that laser annealing may allow the use of PDA in mechanically demanding applications previously considered inaccessible, without sacrificing the functional versatility that is so characteristic of PDA.

Bioinspired Polydopamine Coating as an Adhesion Enhancer Between Paraffin Microcapsules and an Epoxy Matrix

Microencapsulated phase change materials (PCMs) are attracting increasing attention as functional fillers in polymer matrices, to produce smart thermoregulating composites for applications in thermal energy storage (TES) and thermal management. In a polymer composite, the filler-matrix interfacial adhesion plays a fundamental role in the thermomechanical properties. Hence, this work aims to modify the surface of commercial PCM microcapsules through the formation of a layer of polydopamine (PDA), a bioinspired polymer that is emerging as a powerful tool to functionalize chemically inert surfaces due to its versatility and great adhesive potential in many different materials. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) evidenced that after PDA coating, the surface roughness increased from 9 to 86 nm, which is beneficial, as it allows a further increase in the interfacial interaction by mechanical interlocking. Spectroscopic techniques allowed investigating the surface chemistry and identifying reactive functional groups of the PDA layer and highlighted that, unlike the uncoated microcapsules, the PDA layer is able to react with oxirane groups, thereby forming a covalent bond with the epoxy matrix. Hot-stage optical microscopy and differential scanning calorimetry (DSC) highlighted that the PDA modification does not hinder the melting/crystallization process of the paraffinic core. Finally, SEM micrographs of the cryofracture surface of epoxy composites containing neat or PDA-modified microcapsules clearly evidenced improved adhesion between the capsule shell and the epoxy matrix. These results showed that PDA is a suitable coating material with considerable potential for increasing the interfacial adhesion between an epoxy matrix and polymer microcapsules with low surface reactivity. This is remarkably important not only for this specific application but also for other classes of composite materials. Future studies will investigate how the deposition parameters affect the morphology, roughness, and thickness of the PDA layer and how the layer properties influence the capsule-matrix adhesion.

Surface-Mediated Intracellular Delivery by Physical Membrane Disruption

Effective and nondestructive intracellular delivery of exogenous molecules and other functional materials into living cells is of importance for diverse biological fundamental research and therapeutic applications, such as gene editing and cell-based therapies. However, for most exogenous molecules, the cell plasma membrane is effectively impermeable and thus remains the greatest barrier to intracellular delivery. In recent years, methods based on surface-mediated physical membrane disruption have attracted considerable attention. These methods exploit the physical properties of the surface to transiently increase the membrane permeability of cells come in contact thereto, thereby facilitating the efficient intracellular delivery of molecules regardless of molecule or target cell type. In this Review, we focus on recent progress, particularly over the past decade, on these surface-mediated membrane disruption-based delivery systems. According to the membrane disruption mechanism, three categories can be recognized: (i) mechanical penetration, (ii) electroporation, and (iii) photothermal poration. Each of these is discussed in turn and a brief perspective on future developments in this promising area is presented.

Spectroscopic Investigation and Nanoscale Characterization of Epinephrine Autooxidation under Alkaline Conditions

Melanins are intriguing biomaterials with unique physical and chemical properties. Due to the insoluble nature of the synthetic melanins prepared from different precursors, such as 3,4-dihydroxy-phenylalanine (DOPA) and dopamine (DA), it is still challenging to reveal the structure-property relationships. In this work, the autoxidation of epinephrine (EP) under basic conditions was investigated from the perspective of supramolecular chemistry, and the formed soluble epinephrine-melanin (EPM) was characterized on the nanoscale. The supramolecular aggregate nature of oxidation products has been identified on the basis of spectroscopic investigations. A two-dimensional sheet-like morphology with highly ordered in-plane stacking structures was observed for the first time, and the thickness of the nanosheet increased with increasing EPM concentration. More importantly, in contrast to the well-known monotonic absorption profiles of synthetic melanins, EPM shows featured and unusual pH-responsible absorption profiles in the near-ultraviolet region (UVA). The decrease in pH can induce the disappearance of the absorption in the lower-energy band and the reduction of aggregate size. The oxidative and aggregation kinetic processes of EP were investigated in three different alkaline systems by the combination of absorption and fluorescence spectroscopies. The oxidation process of EP shows concentration- and buffer-dependent behaviors. The unusual absorption properties of EPM were exploited for the fabrication of transparent UV-shielding chitosan biofilms and gelatin hydrogels. Extensive research on the molecular structures, supramolecular exciton coupling, and material-oriented property exploitation of EPM is highly anticipated.

Polydopamine-Lysophosphatidate-Functionalised Titanium: A Novel Hybrid Surface Finish for Bone Regenerative Applications

Aseptic loosening of total joint replacements (TJRs) continues to be the main cause of implant failures. The socioeconomic impact of surgical revisions is hugely significant; in the United Kingdom alone, it is estimated that £135m is spent annually on revision arthroplasties. Enhancing the longevity of titanium implants will help reduce the incidence and overall cost of failed devices. In realising the development of a superior titanium (Ti) technology, we took inspiration from the growing interest in reactive polydopamine thin films for biomaterial surface functionalisations. Adopting a "one-pot" approach, we exposed medical-grade titanium to a mildly alkaline solution of dopamine hydrochloride (DHC) supplemented with (3S)1-fluoro-3-hydroxy-4-(oleoyloxy)butyl-1-phosphonate (FHBP), a phosphatase-resistant analogue of lysophosphatidic acid (LPA). Importantly, LPA and selected LPA analogues like FHBP synergistically cooperate with calcitriol to promote human osteoblast formation and maturation. Herein, we provide evidence that simply immersing Ti in aqueous solutions of DHC-FHBP afforded a surface that was superior to FHBP-Ti at enhancing osteoblast maturation. The facile step we have taken to modify Ti and the biological performance of the final surface finish are appealing properties that may attract the attention of implant manufacturers in the future.

Pegylated Metal-Phenolic Networks for Antimicrobial and Antifouling Properties

Metal-phenolic networks (MPNs) have recently attracted great interest in material chemistry and biomaterials because of their biocompatible, versatile, and multifunctional properties. In this paper, we describe a facile method for preparation of a designable antifouling, antimicrobial, and substrate-independent coating assembled from the coordination of metal ions and catecholic groups. Hydrophilic and catecholic polymers were synthesized by copolymerization of dopamine methacrylamide (DMA) and poly(ethylene glycol)methyl methacrylate (PEGMA) to afford p(PEGMA- co-DMA). To investigate the assembly and formation of MPN films, two different metal ions, that is, ferrous (Fe^II) and ferric (Fe^III) ions, to react with p(PEGMA- co-DMA) were compared. The binding constants between iron ions and p(PEGMA- co-DMA) have been investigated by ultraviolet-visible spectroscopy (UV-vis). Measurements with atomic force microscopy, contact angle goniometer, and X-ray photoelectron spectroscopy (XPS) were carried out to quantitatively analyze the surface morphology, wettability, and interfacial elemental compositions of coatings, respectively. Moreover, ellipsometric measurements were performed to obtain the film thickness and grafting density. In addition, the pH-responsive property of the MPN films was investigated at different pH values, showing fast disassembly of the networks at low pH. The antifouling properties of the obtained coatings were analyzed by exposing them to bacteria of Escherichia coli and Staphylococcus epidermidis and NIH-3T3 fibroblasts under observation of fluorescence microscopy and cell imaging analysis. The findings suggest that the MPN from complexation of p(PEGMA- co-DMA) and metal ions provides excellent antifouling, pH-responsive, and biocompatible properties on a wide range of substrates. Furthermore, the released iron ions can effectively suppress the growth of bacteria. Accordingly, the new coating architecture offers a universal feature to control surface properties and functionalization for various applications.