Bio-inspired Surface Modification Research Articles

Probing Lead Ion Contamination in Aqueous Solution Through Bio-Inspired Surface Modification of Gold Nanoparticles on D-Shaped Fiber

A key challenge for detection circuits is the capability of rapidly quantifying target molecules with lower level of limit of detection. An additional obstacle in this direction is also the ease of fabrication of sensing probes. In such cases, D-shaped optical fiber probe can be utilized to shrink the footprint as well as provide ample scope of surface modification of the sensing surface. The detection of D-shaped fiber probe functionalized by chitosan modified gold nanoparticle is comprehensively and procedurally investigated and demonstrated toward detection of lead ions. Through adoption of a very inexpensive intensity interrogation approach, the scheme renders limit of detection of 2 ppb, with a remarkable linearity of ∼0.98 within a range 1–20 ppb. Even in presence of interfering ions, the scheme provides brilliant selectivity toward lead, suggesting the potential for this scheme in integrated photonic architectures.

Bio-inspired Polydopamine Surface Modification of Nanodiamonds and Its Reduction of Silver Nanoparticles.

Surface functionalization of nanodiamonds (NDs) is still challenging due to the diversity of functional groups on the ND surfaces. Here, we demonstrate a simple protocol for the multifunctional surface modification of NDs by using mussel-inspired polydopamine (PDA) coating. In addition, the functional layer of PDA on NDs could serve as a reducing agent to synthesize and stabilize metal nanoparticles. Dopamine (DA) can self-polymerize and spontaneously form PDA layers on ND surfaces if the NDs and dopamine are simply mixed together. The thickness of a PDA layer is controlled by varying the concentration of DA. A typical result shows that a thickness of ~5 to ~15 nm of the PDA layer can be reached by adding 50 to 100 µg/mL of DA to 100 nm ND suspensions. Furthermore, the PDA-NDs are used as a substrate to reduce metal ions, such as Ag[(NH3)2]+, to silver nanoparticles (AgNPs). The sizes of the AgNPs rely on the initial concentrations of Ag[(NH3)2]+. Along with an increase in the concentration of Ag[(NH3)2]+, the number of NPs increases, as well as the diameters of the NPs. In summary, this study not only presents a facile method for modifying the surfaces of NDs with PDA, but also demonstrates the enhanced functionality of NDs by anchoring various species of interest (such as AgNPs) for advanced applications.

Bio-inspired Polydopamine Surface Modification of Nanodiamonds and Its Reduction of Silver Nanoparticles

Bio-inspired Polydopamine Surface Modification of Nanodiamonds and Its Reduction of Silver Nanoparticles

Surface Modification of Calcium Silicate via Mussel-Inspired Polydopamine and Effective Adsorption of Extracellular Matrix to Promote Osteogenesis Differentiation for Bone Tissue Engineering.

Calcium silicate-based cement has garnered huge interest in recent years, due to its versatility and potential in mass fabrication of a variety of bioceramics. For this study, the main objective was to fabricate functionalized calcium silicate (CS) powder integrated with a simple bio-inspired surface modification using polydopamine (PDA), to regulate cellular behaviors such as cellular adhesion, and subsequently cell differentiation and proliferation. For this study, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) techniques were used to analyze the chemical compositions and observe the surface characteristics of our PDA coated CS cements. Such modifications were found to enhance Wharton Jelly’s mesenchymal stem cells (WJMSC) in various ways. Firstly, PDA-coated CS cements were found to significantly enhance cell adhesion with higher expressions of cell adhesion markers, such as focal adhesion kinase and integrins. This was further supported by morphology analysis of the cells. This enhanced cell adhesion, in turn, led to significantly higher secretion of extracellular matrix (ECM) proteins, such as collagen I and fibronectin, which directly promoted cell attachments and proliferation. In our osteogenesis assays, it was found that secretion and expression of osteogenesis related genes and proteins were significantly higher and were dependent on the PDA content. Therefore, these results demonstrated that such simple bio-inspired modification techniques of synthetic degradable CS cements can be applied as a future modification, to modify and convert inert surfaces of synthetic bone grafts to enhance and modulate the cell behaviors of WJMSCs. This in turn can be used as a potential alternative for further bioengineering research.

Polydopamine induced natural fiber surface functionalization: a way towards flame retardancy of flax/poly(lactic acid) biocomposites

Aiming to improve flame retardancy of natural fiber reinforced poly (lactic acid) (PLA) composites, a bio-inspired fiber surface modification approach was investigated in this study. Raw flax fiber was firstly coated with a thin adhesive polydopamine (PDA) film in an aqueous solution of dopamine, followed by in situ growth of iron phosphonate on the fiber surface. The modified flax fiber was added into PLA to prepare flame retardant biocomposite. Compared with raw flax reinforced PLA with a limiting oxygen index (LOI) of 19.1% and no rating in vertical burning test (UL-94), the modified PLA composite possessed a high LOI of 26.1% and V-2 rating. Meanwhile, the fiber surface modification resulted in suppression on both peak heat release rate (decreased by 16%) and total smoke production (decreased by 21%) in cone calorimeter test (CCT). Moreover, tensile modulus of the flame retardant composite was remarkably enhanced, accompanied with a slightly decreased tensile strength compared to raw PLA. The polydopamine assisted surface modification proved to be a feasible approach to improve the flame retardancy of fiber reinforced composites.

Bioinspired Modification of Poly(L-lactic acid)/Nano-Sized β-Tricalcium Phosphate Composites with Gelatin/Hydroxyapatite Coating for Enhanced Osteointegration and Osteogenesis.

Compared to pure poly(L-lactic acid) (PLLA), PLLA/nano-sized β-tricalcium phosphate (PLLA/nβ-TCP) composites show both superior interfacial compatibility and osteoinductive, and consequently hold great potential for bone defect repair applications. However, their dismal osteointegration limits their further development in bone regeneration, adding the need for tailored modification. In this study, a bioinspired modification approach was proposed to construct gelatinhydroxyapatite (GEL/HAP) coating onto PLLA/nβ-TCP composites by combining chemical grafting with in situ reaction methods. The incorporation of the biomimetic GEL/HAP coating substantially improved MC3T3-E1 cell adhesion, proliferation and osteogenic differentiation, as demonstrated by morphological observation. Cell Counting Kit-8 (CCK-8) assay, alkaline phosphate activity test (ALP), and quantitative real-time polymerase chain reaction (qRT-PCR) analysis. Furthermore, GEL/HAP-PLLA/nβ-TCP composites and their control counterparts (i.e., bare PLLA/nβ-TCP) were synchronously implanted into femoral condylar defects of an identical rabbit. Characterizations including microcomputed tomography (micro-CT), histological analysis and the push-out test revealed that the biomimetic coating not only improved osteointegration but also significantly promoted bone regeneration. Overall, for the first time, bioinspired surface modification of the PLLA/nβ-TCP composite with GEL/HAP coating was demonstrated to be an efficient strategy for enhancing the osteointegration and osteogenesis functions of bone implants.

Mimicking elephant mud bathing to produce wettable polyester

Bio-inspired and biomimetic surface modifications are identified as one of the fascinating areas of research. In this study, nature’s way of cooling elephants’ body temperature using mud bathing was mimicked to create a superior wettable polyester fabric with improved comfortability. For that, bentonite nanoclay was covalently grafted on polyester fabric using (3-aminopropyl) triethoxysilane as a coupling agent. FTIR spectroscopy and SEM were used to characterize bentonite grafted polyester while the wettability was proved by standard protocols. This fabric coating strongly withstands more than 50 cycles of laundry. It is expected that this bio-inspired wettable polyester fabric may break the barrier of using polyester in various hydrophilic textile applications.

Catechol grafted silica particles for enhanced adhesion to metal by coordinate bond

Catechol-functionalized materials have been widely studied due to improved adhesion and metal-catechol coordination properties. In this study, silica particles, which are the base material in a multitude of applications, were modified with catechol groups based on a surface grafting reaction via amine- and carboxylic acid-functionalized silica particles. The chemical compositions of the modified particles were analyzed using Fourier transform infrared (FT-IR) and thermal gravimetric analysis (TGA). The surface properties of each particle were investigated using zeta potential, contact angle, and Brunauer–Emmett–Teller (BET) analysis. A series of characterizations verified successful modification with individual catecholic monomers of dopamine onto the silica surface. On the basis of the bioinspired surface modification, catechol-functionalized silica particles (SiO2CA) exhibited outstanding adhesion properties with metals. The SiO2CA showed enhanced Fe3+-capturing capacity that was five times that of bare silica particles. Furthermore, SiO2CA exhibits outstanding adhesion on the TiO2-coated layer. The improved adhesion properties of SiO2CA were due to high affinity and strong binding as a result of the metal-catechol coordination.

Biofouling behavior and performance of forward osmosis membranes with bioinspired surface modification in osmotic membrane bioreactor

Forward osmosis (FO) has received considerable interest for water and energy related applications in recent years. Biofouling behavior and performance of cellulose triacetate (CTA) forward osmosis membranes with bioinspired surface modification via polydopamine (PD) coating and poly (ethylene glycol) (PEG) grafting (PD-g-PEG) in a submerged osmotic membrane bioreactor (OMBR) were investigated in this work. The modified membranes exhibited lower flux decline than the pristine one in OMBR, confirming that the bioinspired surface modification improved the antifouling ability of the CTA FO membrane. The result showed that the decline of membrane flux related to the increase of the salinity and MLSS concentration of the mixed liquid. It was concluded that the antifouling ability of modified membranes ascribed to the change of surface morphology in addition to the improvement of membrane hydrophilicity. The bioinspired surface modifications might improve the anti-adhesion for the biopolymers and biocake.

Enhancing antimicrobial activity of TiO2/Ti by torularhodin bioinspired surface modification

Implant-associated infections are a major cause of morbidity and mortality. This study was performed using titanium samples coated by anodization with a titanium dioxide (TiO2) shielded nanotube layer. TiO2/Ti surface was modified by simple immersion in torularhodin solution and by using a mussel-inspired method based on polydopamine as bio adhesive for torularhodin immobilization. SEM analysis revealed tubular microstructures of torularhodin and the PDA ability to function as a catchy anchor between torularhodin and TiO2 surface.Corrosion resistance was associated with TiO2 barrier oxide layer and nano-organized oxide layer and the torularhodin surface modification does not bring significant changes in resistance of the oxide layer.Our results demonstrated that the torularhodin modified TiO2/Ti surface could effectively prevent adhesion and proliferation of Escherichia coli, Staphylococcus aureus, Enterococcus faecalis, Bacillus subtilis, and Pseudomonas aeruginosa. The new modified titanium surface showed good biocompatibility and well-behaved haemocompatibility.This biomaterial with enhanced antimicrobial activity holds great potential for future biomedical applications.

Superhydro-oleophobic bio-inspired polydimethylsiloxane micropillared surface via FDTS coating/blending approaches

In this work we render superhydro-oleophobic properties to the surface of polydimethylsiloxane (PDMS) elastomer through bio-inspired micropillar surface and chemical modification with a fluorosilane polymer, trichloro(1H,1H,2H,2H-perfluorooctyl)silane (FDTS). Two different chemical modification approaches were applied on both flat and micropillar PDMS: (1) vapor deposition of FDTS on cured PDMS surface, and (2) blending FDTS with the liquid PDMS precursor before curing. Comparative studies of the water and oil contact angles on the neat and FDTS-modified PDMS (both flat and micropillar) indicated that superhydro-oleophobicity was delivered by a combination of FDTS chemistry and micropillar geometry. FDTS-blended PDMS micropillar displayed better oleophobicity with an oil contact angle of ∼141° than FDTS-coated PDMS micropillar (∼115°). In contrast to the smooth surface of FDTS-blended PDMS micropillar, rough surface with some structure defects were found on the FDTS-coated micropillar surface caused by the vapor deposition process; the surface defects might be responsible for the observed low oleophobicity of FDTS-coated PDMS micropillar. Superhydrophobicity of FDTS-blended PDMS micropillar in terms of water contact angles was found to be independent of the quantity of FDTS. However, the oleophobicity of FDTS-blended PDMS micropillar was found to be dependent of the quantity of FDTS; with the increased weight concentration of FDTS in PDMS, the oils contact angle first increased and then leveled out at a finite concentration. FTIR and XPS were applied to analyze surface chemistry information suggesting the blended FDTS segregated from bulk PDMS and enriched at the surface to reduce surface tension so as to make surface super-oleophobic.

Experimental Evidence of Rapid Water Transport through Carbon Nanotubes Embedded in Polymeric Desalination Membranes

As water molecules permeate ultrafast through carbon nanotubes (CNTs), many studies have prepared CNTs-based membranes for water purification as well as desalination, particularly focusing on high flux membranes. Among them, vertically aligned CNTs membranes with ultrahigh water flux have been successfully demonstrated for fundamental studies, but they lack scalability for bulk production and sufficiently high salt rejection. CNTs embedded in polymeric desalination membranes, i.e., polyamide thin-film composite (TFC) membranes, can improve water flux without any loss of salt rejection. This improved flux is achieved by enhancing the dispersion properties of CNTs in diamine aqueous solution and also by using cap-opened CNTs. Hydrophilic CNTs were prepared by wrapping CNT walls via bio-inspired surface modification using dopamine solution. Cap-opening of pristine CNTs is performed by using a thermo-oxidative process. As a result, hydrophilic, cap-opened CNTs-embedded polyamide TFC membranes are successfully prepared, which show much higher water flux than pristine polyamide TFC membrane. On the other hand, less-disperse, less cap-opened CNTs-embedded TFC membranes do not show any flux improvement and rather lead to lower salt rejection properties.

Bioinspired surface modification of poly(2-hydroxyethyl methacrylate) based microbeads via oxidative polymerization of dopamine

Surface modification of support materials is crucial for improving their selectivities and biocompatibilities in bioaffinity applications. However, conventional modification techniques including chemical or physical conjugations mostly suffer from limitations of their multistep and complicated procedures, surface denaturations, batch-to-batch inconsistencies, and insufficient surface conjugations. In this study, we demonstrate a simple yet effective bioinspired approach for the surface modification of poly(2-hydroxyethyl methacrylate) [PHEMA] based bioaffinity adsorbents through oxidative polymerization of dopamine. The magnetic (mPHEMA) and non-magnetic (PHEMA) polymeric microbeads were fabricated by suspension polymerization technique. Surface modification of obtained microbeads was then carried out by using dopamine molecules under alkaline conditions. The polydopamine (PDOPA) coated microbeads were further employed as a bioaffinity absorbent targeted for immunoglobulin G (IgG) molecules. The effects of pH, temperature, protein concentration and ionic strength on the IgG adsorption process have been investigated. We found that PDOPA coated microbeads display dramatically higher IgG adsorption capacities when compared with their un-modified forms. Adsorption capacities also increased with increasing temperature. Monolayer Langmuir adsorption model can be thought more applicable for these adsorbent systems.

Enhanced osteoblastic cell response on zirconia by bio-inspired surface modification

Excellent esthetic properties and limited plaque adhesion make zirconia ceramics an ideal material for implants in the fields of dentistry and orthopedics. Unfortunately, the physicochemical stability of zirconia makes it difficult to improve biocompatibility through surface modification. The dopamine-derived residue, 3,4-dihydroxy-l-phenylalanine (l-DOPA), has been identified as an important molecule secreted by marine mussels for the formation of adhesive pads. This study coated zirconia with l-DOPA to improve the biocompatibility of ZrO2. As confirmed by contact angle and X-ray photoelectron spectroscopy (XPS), the formation of l-DOPA film can be controlled by varying the process temperature. Results from scanning electron microscopy (SEM) and atomic force microscopy (AFM) show that the topography of the zirconia substrate was preserved after being coated with a film of l-DOPA. Specifically, the thickness of the coating and initial cell spreading ability were both enhanced by preparing samples at higher temperatures. l-DOPA coated zirconia demonstrated better cyto-compatibility than uncoated specimens, as indicated by cell responses such as cell spreading and proliferation. These preliminary results suggest that l-DOPA film could be used to improve the cyto-compatibility of zirconia and further has the potential to immobilize other biofunctional molecules in biomedical applications.

A bioinspired fouling-resistant surface modification for water purification membranes

Abstract Surface deposition of polydopamine, PD, using facile aqueous-based chemistry at mild reaction conditions, was accomplished on reverse osmosis, nanofiltration, ultrafiltration, and microfiltration membranes. This surface treatment not only retained much of the membranes’ intrinsic pure water permeability, but also improved the fouling resistance of polypropylene microfiltration (MF), poly(tetrafluoroethylene) MF, poly(vinylidene fluoride) MF, poly(arylene ether sulfone) ultrafiltration (UF), polysulfone UF, polyamide (PA) nanofiltration, and PA reverse osmosis membranes, as measured using oil/water emulsion filtration. To demonstrate scalability of this approach, PD was applied to, and improved the fouling resistance of, membrane modules. Following PD deposition, membranes could be further modified by grafting fouling-resistant macromolecules, such as poly(ethylene glycol), to further improve fouling resistance of MF membranes.

Lift, Drag, and Cavitation Onset On Rudders With Leading-edge Tubercles

This paper presents the experimental measurement of lift and drag as well as the determination of the onset of cavitation on rudders with leading-edge protuberances (tubercles) that are operating at low to moderate Reynolds Numbers in water. The leading-edge shape used for the rudders in this study is derived from our earlier work concerning the analysis of the leading-edge morphology found on the pectoral flippers of humpback whales. While humpback whales do not swim at speeds that induce cavitation, engineered control surfaces based on this bio-inspired control surface modification might operate in cavitation conditions. This point motivates our present work to investigate the onset of cavitation on small aspect ratio rudders with tubercles. Our findings are that (i) the presence of leading-edge tubercles accelerates the onset of cavitation, (ii) the tubercles can modify the location of the onset of cavitation, (iii) the tubercle geometry has an influence on the rudder's hydrodynamic performance, (iv) for the lower Reynolds Numbers considered in this paper, the tubercles decrease lift and increase drag for angles of attack between 15 and 22 deg, (v) for angles above 22 deg, rudders with tubercles generate more lift than smooth rudders, and (vi) for the higher Reynolds Numbers investigated, the difference in performance between the smooth and tubercled rudders diminishes, suggesting the existence of a critical Reynolds Number for a given tubercle geometry beyond which tubercles have no significant effect on hydrodynamic performance.

Controlled gene-eluting metal stent fabricated by bio-inspired surface modification with hyaluronic acid and deposition of DNA/PEI polyplexes

A metal stent that could elute plasmid DNA (pDNA) in a controlled manner for substrate-mediated gene transfection was fabricated by first coating with hyaluronic acid (HA) and subsequent deposition of pDNA. To create robust HA coating layer on stainless steel (SS316L) surface, HA was derivatized with dopamine which is a well-known adsorptive molecule involving mussel adhesion process. The HA-coated surface was verified by various analytical techniques and proved to be very hydrophilic and stable, also showing superior biocompatibility in terms of suppressed plasma protein adsorption. For surface loading of pDNA, cationic pDNA/polyethylenimine (PEI) polyplexes were prepared and ionically adsorbed onto the HA-coated SS316L surface. The adsorbed surface exhibited evenly distributed nano-granular topography while the polyplexes maintained the nano-particular morphology. The pDNA was released out in a controlled manner for a period of 10 days with maintaining structural integrity. The dual coated substrate with HA and pDNA/PEI polyplexes exhibited greatly enhanced gene transfection efficiency, when compared to both bare substrate adsorbed with the polyplexes and PEI/pDNA polyelectrolyte multilayers. Dually functionalized stent with HA and pDNA exhibited effective biocompatibility and gene transfection.

Bio-inspired dual surface modification to improve tribological properties at small-scale

In miniaturized devices like micro/nano-electro-mechanical systems (MEMS/NEMS), the critical forces, namely adhesion and friction restrict the smooth operation of the elements that are in relative motion. MEMS/NEMS are traditionally made of silicon, whose tribological properties are not good. In this paper, we present an investigation on the approach of dual surface modification of silicon surfaces and their tribological properties at micro-scale. The dual surface modification is a combination of topographical and chemical modifications. As the topographical modification, micro-patterns with varying shapes of pillars and channels were fabricated on Si(1 0 0) wafer surfaces using photolithography method. Chemical modification included the coating of micro-patterns with diamond-like carbon (DLC) and Z-DOL (perfluoropolyether, PFPE) thin films. The surfaces with combined modification were evaluated for their micro-friction behavior in comparison with those of bare Si(1 0 0) flat surfaces and the topographically/chemically modified silicon surfaces. Results showed that the surfaces with dual modification exhibited superior tribological properties. These results indicate that a combination of topographical and chemical modification is very effective in enhancing tribological properties at small-scale. The combined surface treatments such as the ones investigated in the current work could be useful for tribological applications in small-scale devices such as MEMS/NEMS. The motivation for undertaking the dual modification approach comes from an earlier observation made on the significant influence of the surface characteristics of lotus leaf on its micro-friction behavior.