Oxidative Self-polymerization Of Dopamine Research Articles

Investigation of the oxidative self- polymerization of dopamine under alkaline conditions on wool fabrics

Most studies about polydopamine in the textile field have been related to cotton fibers. There are not many studies about the use of polydopamine on wool fibers. A limited number of studies have focused on the coloring of wool, whereas wool is the fiber with the highest variety of intermolecular attraction forces among all natural and man-made fibers. Polydopamine contains high amounts of catechol and amine functional groups due to its structure. In this study, different from the literature, oxidative self-polymerization of dopamine was achieved on wool fabric for different periods of time, and the coated fabrics were examined with characterization tests and spectrophotometrically. In this study, lower values were obtained than lightness (L*) values reported for other fibers in previous studies, and it was concluded that the wool-PDA interaction is superior to other fibers. Scanning electron microscopy and energy-dispersive X-ray spectroscopy results showed that the polymerization and nano-coating formed successfully and continued to remain on the surface after washing. The lowest lightness value was obtained in the 32 h coating. However, the lowest color change after washing was in the 16 h coating (0.44%). This result showed that the coating was completed within 16–32 hours and there was only accumulation on the surface in the later times.

A low-friction and high-stability hydrophilic PVP/PEG coated TPU for interventional catheter applications

Vascular interventional catheters are generally made of hydrophobic polymers, which may lead to vascular injury, poor lubrication and other consequences due to friction with vascular wall or stent in the process of intervention. In this study, the PDA-PVP/PEG composite coating was prepared based on common TPU catheter material to improve its hydrophilic lubrication behavior. Firstly, the oxidative self-polymerization of dopamine (PDA) was initiated and deposited on the surface of TPU in a weak alkali environment, and then the PVP/PEG coating was prepared by UV curing with PDA as the intermediate adhesion layer. The composite coating was optimized step by step by lubricating material system, process parameters, molecular weight, and concentration. Compared with the blank control group, the water contact angle decreased from 91.3° to about 28.3°, and the friction coefficient decreased from 0.4 to about 0.03, and the composite coating was not damaged after 30 min of reciprocating sliding. The results of cytotoxicity grade Level 1 and hemolysis rate less than 5 % also proved that the composite coating showed good cytotoxicity and blood compatibility. In summary, the PDA-PVP/PEG hydrophilic lubricating composite coating revealed excellent comprehensive properties.

Preparation of dopamine/L-cysteine modified PVDF composite membrane and its application in the removal of mercury ions from water

Polyvinylidene fluoride (PVDF), embodying a stabilization under thermal environment and capability to resist chemical corrosion, is widely used as a membrane-forming material. However, its inherent hydrophobicity and lack of active functional groups in the structure limit its suitability for adsorption applications. In this study, PVDF-based membranes were first prepared by the non-solvent phase inversion method, and then, polydopamine (PDA) was coated on these membranes by the oxidative self-polymerization of dopamine (DA). Then, L-cysteine (LCys) was grafted by self-assembly to obtain a highly hydrophilic PVDF composite (PVDF@PDA-LCys) membrane with excellent ability for Hg(II) ion capture. The membrane has the following characteristics: excellent hydrophilicity, with a water contact angle (WCA) that drops to 0° within 3 s, which is far superior to the 89.22° WCA of the PVDF-based membrane. Given an 10 mg·L−1 initial concentration of Hg(II), adsorption experiences 120 min, the removal efficiency reaches 95.14%. The fitted maximum adsorption capacity is 97.98 mg·g−1. Additionally, the composite membrane exhibits good acid resistance. When the solution pH is as low as 1.5, the Hg(II) ion removal efficiency is still close to 70%. The performance of the composite membrane remains stable after repeated use. This study demonstrates an environmentally friendly and practical method for preparing PVDF-based composite membranes with potential applications in wastewater treatment.

Abstract 5736: Sonochemical preparation of SP94 peptide-decorated pH-responsive biodegradable biopolyester nanoparticles for targeted therapy in hepatocellular carcinoma

Abstract Stimulation in response to nanoparticles responding to endogenous stimuli in the tumor microenvironment has been extensively studied for the release of chemotherapeutic drug. Therefore, we aimed to develop a biocompatible delivery of taxol (TAX) delivery vector system for the treatment of hepatocellular carcinoma (HCC). A basic backbone, TAX loaded poly (3-hydroxybutyrate-co-3-hydroxyvalerate) PHBV nanoparticle (PHBV-TAX-NPs), were designed and prepared via sonochemical method. The pH-responsive shell of PHBV-TAX-NPs was formed by oxidative self-polymerization of dopamine (PDA) in an alkaline environment. The HCC-targeted peptide SP94 binds to PDA-coated nanoparticles (NPs) through the Michael reaction. Moreover, the nanoparticle surface-grafted SP94 peptide serve as a specific ligand for targeting HCC. The chemical structures and properties of these nanoparticles were characterized by transmission electron microscope, dynamic light scattering-autosizer, differential scanning calorimetry, fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and thermogravimetry. As expected, excellent targeting of these SP94-PDA-PHBV-TAX-NPs was demonstrated by cellular uptake and cytotoxicity experiments in HCC cells. Compared with that of free TAX, the SP94-PDA-PHBV-TAX-NPs showed more superior antitumor efficacy in the xenograft mouse model. Notably, the SP94-PDA-PHBV-TAX-NPs were except for their potent anticancer activity, it was less toxic in vitro and in vivo compared to TAX in mice. These studies suggest the potential beneficial use of SP94-PDA-PHBV-TAX-NPs in future HCC-targeted therapy with drug-loaded nanocarriers. Citation Format: Mingfang Wu, Qi Wang, Zhengran Gong, Zixuan Liu, Haodong Zheng, Xinjie Chen, Chen Zhong. Sonochemical preparation of SP94 peptide-decorated pH-responsive biodegradable biopolyester nanoparticles for targeted therapy in hepatocellular carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5736.

Functionalization of PCL-based nanofibers loaded with hirudin as blood contact materials

Blood-contacting materials with good mechanical property, excellent anticoagulant function and promoting effect on endothelialization are in great demand for clinical application such as vascular grafts in treating cardiovascular diseases. In this study, electrospinning nanofiber scaffolds of polycaprolactone (PCL) were functionalized by oxidative self-polymerization of dopamine (PDA) on the surface followed by the modification of anticoagulant recombinant hirudin (rH) molecules. The morphology, structure, mechanical property, degradation behavior, cellular compatibility and blood compatibility of the multifunctional PCL/PDA/rH nanofiber scaffolds were evaluated. The diameter of the nanofibers was between 270–1030 nm. The ultimate tensile strength of the scaffolds was around 4 MPa and the elastic modulus increased with the amount of rH. The degradation tests in vitro indicated that the nanofiber scaffolds began to crack on the 7th day, but still maintained the nanoscale architecture within a month. The cumulative release of rH from the nanofiber scaffold was up to 95.9 % at 30th day. The functionalized scaffolds promoted the adhesion and proliferation of endothelial cells, while resisting platelet adhesion and enhancing anticoagulation effects. The hemolysis ratios of all scaffolds were <2 %. The nanofiber scaffolds are promising candidates for vascular tissue engineering.

A catalytic membrane based on dopamine directional deposition biomimetically induced by immobilized enzyme for dye degradation

Dopamine-assisted deposition technology is widely used in functional modification of polymer membranes due to the advantages such as simple operation, mild reaction, and strong adhesion to materials. Limited by the major defects of spontaneous polymerization in an alkaline environment and non-selective adhesion, it is still challenging to achieve directional deposition, stability, and fast deposition rate at the same time. Herein, inspired by tyrosinase-induced melanin directional deposition on the skin, we present a biomimetic catalysis strategy for the directional deposition of dopamine on the target surface. By immobilizing laccase on the target surface, the oxidative self-polymerization of dopamine can be inhibited, and the biomimetic induced directional deposition on membrane can be achieved. The biomimetic catalytic membrane covered with a uniform and stable laccase-dopamine coating can be used for the degradation of azo printing and dyeing wastewater. Moreover, the degradation efficiency of the catalytic membrane for methyl orange can reach 19.8 μg/min, and the relative activity can still be maintained at about 81% after 6 cycles, showing high catalytic activity and stability.

In Situ Grown Nanohydroxyapatite Hybridized Graphene Oxide: Enhancing the Strength and Bioactivity of Polymer Scaffolds.

Graphene oxide (GO) and nanohydroxyapatite (nHA) are usually used for improving the strength and bioactivity of polymer scaffolds. However, due to the nano-aggregation effect, these applications often face the problems of uneven dispersion and poor interface bonding. In this work, their hybrids (GO@nHA) were constructed by combining chemical modification and in situ growth methods, realizing the perfect combination of nHA and GO. First, the functionalization of GO was realized through oxidative self-polymerization of dopamine (DA), and the product was denoted GO@DA. Furthermore, the in situ growth of nHA on GO@DA was induced by hydrothermal reactions to prepare GO@nHA hybrids. Then, the obtained hybrid was added to the polymer matrix, and a composite scaffold was prepared through a selective laser sintering process. The results demonstrated that with the addition of GO@DA and GO@nHA, the ultimate strength was increased to 16.8 and 18.6 MPa, respectively, which is 66 and 84% higher than the 10.1 MPa of the polylactic acid (PLA) scaffold. In addition, composite scaffolds exhibited good biomineralization ability in vitro and also promoted the adhesion and proliferation of MG63 cells.

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.

Integrin αvβ3-targeted polydopamine-coated gold nanostars for photothermal ablation therapy of hepatocellular carcinoma.

Photothermal therapy (PTT) has emerged as a promising cancer therapeutic method. In this study, Arg-Gly-Asp (RGD) peptide-conjugated polydopamine-coated gold nanostars (Au@PDA-RGD NPs) were prepared for targeting PTT of hepatocellular carcinoma (HCC). A polydopamine (PDA) shell was coated on the surface of gold nanostars by the oxidative self-polymerization of dopamine (termed as Au@PDA NPs). Au@PDA NPs were further functionalized with polyethylene glycol and RGD peptide to improve biocompatibility as well as selectivity toward the HCC cells. Au@PDA-RGD NPs showed an intense absorption at 822 nm, which makes them suitable for near-infrared-excited PTT. Our results indicated that the Au@PDA-RGD NPs were effective for the PTT therapy of the αVβ3 integrin receptor-overexpressed HepG2 cells in vitro. Further antitumor mechanism studies showed that the Au@PDA-RGD NPs-based PTT induced human liver cancer cells death via the mitochondrial–lysosomal and autophagy pathways. In vivo experiments showed that Au@PDA-RGD NPs had excellent tumor treatment efficiency and negligible side effects. Thus, our study showed that Au@PDA-RGD NPs could offer an excellent nanoplatform for PTT of HCC.

Synthesis of surface imprinted polymers based on wrinkled flower-like magnetic graphene microspheres with favorable recognition ability for BSA

Nowadays, the employing of molecular imprinting technique in the analysis and separation of proteins from complex biological samples has been widely favored by researchers. To enrich the types of surface protein imprinted materials and expand the application fields of graphene materials, novel surface molecular imprinted polymers (MIPs) based on magnetic graphene microspheres Fe3O4@rGO@MIPs are first synthesized in this paper. Fe3O4@rGO@MIPs are prepared by oxidative self-polymerization of dopamine on the surface of magnetic graphene (Fe3O4@rGO) composite microspheres. Bovine serum albumin (BSA) is selected as protein template. Fe3O4@rGO microspheres with wrinkled flower-like structure are obtained by compounding Fe3O4 and graphene oxide in an appropriate ratio via the method of high-temperature reduction self-assembly. The microspheres exhibit promising dispersibility, high external surface area, rich pore structure, and sufficient magnetic properties. These advantages not only prevent the agglomeration of imprinted microspheres in the aqueous phase, which is conducive to contact and static adsorption, but also increase the amount of protein imprinting. Additionally, sufficient magnetic properties ensure fast and effective separation of the adsorbents. While the adsorption capacity is increased, the separation procedure becomes simple. The binding capacity of Fe3O4@rGO@MIPs for BSA can reach 317.58 mg/g within 60 min, and the imprinting factor (IF) is 4.24. More importantly, Fe3O4@rGO@MIPs can specifically recognize the target BSA from the mixed proteins and the actual sample. There is no significant decrease in the adsorption amount, IF, and magnetic properties after eight runs. It is promising to be used in the separation of proteins from the actual biological samples.

Electroless deposition of silver nanoparticles on cellulose nanofibrils for electromagnetic interference shielding films

High-efficient electromagnetic interference (EMI) shielding films were successfully fabricated by electroless deposition of silver nanoparticles (AgNPs) on polydopamine (PDA) functionalized cellulose nanofibrils (CNFs) as building blocks according to a pressured-extrusion film-forming process. PDA was first functionalized on CNFs by oxidative self-polymerization of dopamine (DA) to synthesize CNFs@PDA, on which AgNPs were electrolessly deposited. The obtained CNFs@PDA@AgNPs composite films served as tightly-connected conductive network, so as to significantly improve the whole electrical conductivity of the EMI shielding films. Utilizing CNFs as green and soft matrix, the fabricated CNFs@PDA@AgNPs EMI films show an outstanding mechanical enduring performance. The CNFs@PDA@AgNPs films with weight ratios of CNFs:AgNO3 = 1:24 exhibited superb electrical conductivity of 1,000,000 S m−1 and remarkable EMI shielding effectiveness of 93.8 dB at 8.2 GHz in X band. This work provides a simple methodology to achieve surface metallization of insulating fibers to supersede traditional metals for highly efficient EMI shielding applications.

Lateral Flow Immunoassay Based on Polydopamine-Coated Gold Nanoparticles for the Sensitive Detection of Zearalenone in Maize.

In this work, polydopamine-coated gold nanoparticles (Au@PDAs)weresynthesized by the oxidative self-polymerization of dopamine (DA) on the surface of AuNPs and applied for the first time as a signal-amplification label in lateral flow immunoassays (LFIAs) for the sensitive detection of zearalenone (ZEN) in maize. The PDA layer functioned as a linker between AuNPs and anti-ZEN monoclonal antibody (mAb) to form a probe (Au@PDA-mAb). Compared with AuNPs, Au@PDA had excellent color intensity, colloidal stability, and mAb coupling efficiency. The limit of detection of the Au@PDA-based LFIA (Au@PDA-LFIA) was 7.4 pg/mL, which was 10-fold lower than that of the traditional AuNP-based LFIA (AuNP-LFIA) (76.1 pg/mL). The recoveries of Au@PDA-LFIA were 93.80-111.82%, with the coefficient of variation of 1.08-9.04%. In addition, the reliability of Au@PDA-LFIA was further confirmed by the high-performance liquid chromatography method. Overall, our study showed that PDA coating can chemically modify the surface of AuNPs through a simple method and can thus significantly improve the detection sensitivity of LFIA.

Improved performance of thin-film nanocomposite nanofiltration membranes as induced by embedded polydopamine-coated silica nanoparticles

We modified thin-film nanofiltration membranes by embedding in them silica nanoparticles (SiNPs) coated with polydopamine (PDA), which is well-known to mimic the adhesive characteristics of mussels. The coating process was triggered by the oxidative self-polymerization of dopamine on the surface of SiNPs, and the membranes were fabricated through interfacial polymerization (reaction between piperazine and trimesoyl chloride, TMC). Thin-film nanofiltration membranes embedded with PDA-SiNPs (TFNPDA-SiNPs) were compared with pristine polyamide membrane, as well as with polyamide membrane embedded with uncoated SiNPs. Energy-dispersive X-ray spectroscopy confirmed that TFNPDA-SiNPs contained more nanoparticles than the polyamide membrane with uncoated SiNPs. Accordingly, the hydrophilicity of TFNPDA-SiNPs was higher. TFNPDA-SiNPs fabricated from using a concentration of 0.35 g PDA-SiNPs/g TMC delivered the highest pure water flux of 80.0 ± 4.6 L⋅m−2⋅h−1 at 6 bar; salt rejections were as follows: RNa2SO4 = 97%; RMgSO4 = 94%; RMgCl2 = 68%; RNaCl = 35%. The TFNPDA-SiNPs also demonstrated the greatest antifouling ability, as its flux was the highest at the end of three cycles of antifouling tests, where bovine serum albumin was used as model protein foulant.

Nanoencapsulated phase change material with polydopamine-SiO2 hybrid shell for tough thermo-regulating rigid polyurethane foam

Novel nanoencapsulated phase change materials (NePCMs) with polydopamine (PDA)-SiO2 hybrid shell material were prepared, and the thickness of PDA layer was highly tunable. The PDA layer was fabricated through oxidative self-polymerization of dopamine in Tris−HCl buffer solution, on preformed NePCMs with SiO2 shell. When Tris−HCl concentration is fixed at 50 mM and dopamine concentration is increased from 2 to 8 g/L, the shell thickness of the obtained NePCMs increases gradually from 27 to 37 nm. Phase change enthalpies of the NePCMs with PDA-SiO2 hybrid shell are reduced slightly with increasing PDA layer thickness. Thermal stability of the as-prepared NePCMs is improved obviously, compared with that of unencapsulated n-octadecane. It is further demonstrated that the NePCMs with PDA-SiO2 hybrid shell can be incorporated into thermo-regulating rigid polyurethane foams with high mechanical performance, due to improved interfacial compatibility and interaction between PDA layer and polyurethane matrix.

Antibacterial polymer scaffold based on mesoporous bioactive glass loaded with in situ grown silver

An antibacterial scaffold is highly desirable to prevent bacterial infection in orthopedic treatment. In this work, silver was in situ grown in mesoporous bioactive glass (MBG) to endow a polymer scaffold with sustained antibacterial activity. In detail, MBG was firstly modified by the oxidative self-polymerization of dopamine (denoted as pMBG). Then, pMBG was used to capture silver ions into the mesoporous channel via coordination reaction and further in situ reduce silver ions to metallic silver by the redox reaction of the catechol groups. Finally, the Ag loaded pMBG (Ag@pMBG) was introduced into polymer matrices to construct composite scaffold by additive manufacturing technology. The antibacterial tests showed that the composite scaffold exhibited robust antibacterial activity with an inhibition ring of 24.2 mm and bacterial inhibition rate more than 99% against Escherichia coli. Moreover, ion release behavior demonstrated that the composite scaffold could continually release Ag over 28 days. Besides, the composite scaffold also showed good cytocompatibility in facilitating osteoblast adhesion and proliferation.

A fast self-healing and conductive nanocomposite hydrogel as soft strain sensor

Remarkable progress achieved for conductive hydrogels has been witnessed in recent years. However, hydrogels are easily damaged during the course of use, which limits their applications as soft conductors. Here, the nanocomposite hydrogels with fast self-healing property, conductive capability and strain-sensitive performance are successfully obtained via simple synthesis routes. Dynamic diol-borate eater bonds built from polyvinyl alcohol (PVA) and borax mainly allow nanocomposite hydrogels to display decent self-healing behaviors in mechanical (restore 92.89% of original tensile strength within 60 s), electrical (restore 96.7 ± 2% of original resistance within 4.2 s) and rheological recovery experiments without any external stimuli. Meanwhile, hydrogen bonds in prepared networks can endow hydrogels with self-healing property to a certain extent. Graphene oxide (GO) is partially reduced under the oxidative self-polymerization of dopamine (DA), providing conductivity for nanocomposite hydrogels (2.7 mS cm−1). Besides, the mechanical property and conductivity of nanocomposite hydrogels are controlled by the reduction degree of GO. Due to physical interactions formed among oxygen functional groups, the nanocomposite hydrogels show greater behaviors in mechanical, rheological and swelling tests verse pure PVA hydrogels. Furthermore, the acquired hydrogels demonstrate strain sensitivity in the designed LED bulb circuit. In view of no apparent anaphylaxis of nanocomposite hydrogels to human skins, the soft stain sensor prepared by designed hydrogel can be fabricated to detect human activities, such as bending and sitting. Our work offers an effective approach to synthesize a fast self-healing, conductive and strain-sensitive hydrogel applied as soft strain sensor for human movement monitoring.

Nano polydopamine crosslinked thiol-functionalized hyaluronic acid hydrogel for angiogenic drug delivery.

Crosslinking of polymeric network using nanoparticles by physical or chemical method to obtain hydrogel is an emerging approach. Herein, we synthesized Polydopamine (PDA) nanoparticles via oxidative self-polymerization of dopamine in water-ethanol mixture. Thiol-functionalized hyaluronic acid was developed using cysteamine and hyaluronic acid (HA-Cys) via 1-Ethyl-3-(3-Dimethylaminopropyl) Carbodiimide - N-hydroxysuccinimide (EDC-NHS) crosslinking chemistry. Developed HA-Cys conjugate was cross-linked using PDA nanoparticles via Michael-type addition reaction. Synthesized nanoparticles were monodisperse with size of 124 ± 8 nm and had spherical morphology. FTIR characterization confirmed successful synthesis of HA-Cys conjugate and subsequent crosslinking with PDA nanoparticles. Rheological characterization revealed that hydrogels were injectable in nature with good mechanical stability. Dimethyloxalylglycine (DMOG) loaded PDA nanoparticle showed sustained drug release for period of 7 days from composite hydrogel. Hydrogel microenvironment facilitated enhanced endothelial cell migration, proliferation and attachment. Furthermore, in response to release of DMOG from developed hydrogel, cells showed enhanced capillary tube formation in vitro. Overall, these results demonstrate that PDA cross-linked thiol-functionalized hydrogel was developed in a facile manner under physiological conditions. These developed hydrogels could be potentially used in tissue engineering and drug delivery.

Preparation of Robust Superhydrophobic Halloysite Clay Nanotubes via Mussel-Inspired Surface Modification

In this study, a novel and convenient bio-inspired modification strategy was used to create stable superhydrophobic structures on halloysite clay nanotubes (HNTs) surfaces. The polydopamine (PDA) nanoparticles can firmly adhere on HNTs surfaces in a mail environment of pH 8.5 via the oxidative self-polymerization of dopamine and synthesize a rough nano-layer assisted with vitamin M, which provides a catechol functional platform for the secondary reaction to graft hydrophobic long-chain alkylamine for preparation of hierarchical micro/nano structures with superhydrophobic properties. The micromorphology, crystal structure, and surface chemical composition of the resultant superhydrophobic HNTs were characterized by field emission scanning electron (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The as-formed surfaces exhibited outstanding superhydrophobicity with a water contact angle (CA) of 156.3 ± 2.3°, while having little effect on the crystal structures of HNTs. Meanwhile, the resultant HNTs also showed robust stability that can conquer various harsh conditions including strong acidic/alkaline solutions, organic solvents, water boiling, ultrasonic cleaning, and outdoor solar radiation. In addition, the novel HNTs exhibited excellent packaged capabilities of phase change materials (PCMs) for practical application in thermal energy storage, which improved the mass fractions by 22.94% for stearic acid and showed good recyclability. These HNTs also exhibited good oil/water separation ability. Consequently, due to the superior merits of high efficiency, easy operation, and non-toxicity, this bionic surface modification approach may make HNTs have great potentials for extensive applications.

Mussel-inspired nanostructured coatings assembled using polydopamine nanoparticles and hydroxyapatite nanorods for biomedical applications

Abstract Producing hierarchical nanostructured coatings with a biomimetic composition is an effective surface modification strategy to improve the bioactivity of biomaterials. In this study, mussel-inspired polydopamine nanoparticles (PDA-NPs) and hydroxyapatite (HA) nanorods were used to modify Ti surfaces. Firstly, the PDA-NPs were prepared via oxidative self-polymerization of dopamine. Secondly, the HA nanorods were decorated with a PDA nanolayer in order to improve the adhesion of the HA nanorods. Thirdly, the PDA-NPs and PDA-decorated HA nanorods were alternately assembled to form a porous and hierarchical micro/nanostructured {PDA/HA} composite coating on the Ti surfaces. Finally, Bone ​morphogenetic protein-2 (BMP-2) was immobilized on the {PDA/HA} composite coating using the functional groups of PDA. The BMP-2-loaded {PDA/HA} composite coating exhibited excellent biocompatibility and promoted the adhesion, proliferation, and differentiation of bone marrow stromal cells. The animal implantation tests indicated that the BMP-2-loaded {PDA/HA} composite coating promoted the formation of new bone tissue.

Innovative method of metal coating of microcapsules containing phase change materials

Microencapsulation of phase change materials (PCMs) is needed to prevent PCM leaking during melting. However, the low thermal conductivity of the microcapsules shell limits their applications. To enhance thermal conductivity of PCM microcapsules, a new method was developed for coating them with a metal using dopamine surface activation followed by electroless plating. The oxidative self-polymerization of dopamine (PDA) on the shell of the polymeric PCM microcapsules makes the surface active by providing chemisorption sites for metal deposition. Scanning electron microscope (SEM) images of the metal coated microcapsules without PDA pre-treatment did not show evidence of Ag metal on the surface of microcapsules. However, PCM microcapsules were completely covered with Ag metal when they were pre-treated with PDA as indicated by SEM and EDX tests. The enhancement in the thermal conductivity of silver coated PCM microcapsules of different size and for different silver coating coverage was investigated and discussed. This was confirmed by the enhancement in the performance of these silver-coated microcapsules using thermal cycling tests.