Biomimetic Coatings Research Articles

Principles of Biofouling Protection in Marine Sponges: A Model for the Design of Novel Biomimetic and Bio-inspired Coatings in the Marine Environment?

The process of biofouling of marine structures and substrates, such as platforms or ship hulls, proceeds in multiple steps. Soon after the formation of an initial conditioning film, formed via the adsorption of organic particles to natural or man-made substrates, a population of different bacterial taxa associates under the formation of a biofilm. These microorganisms communicate through a complex quorum sensing network. Macro-foulers, e.g., barnacles, then settle and form a fouling layer on the marine surfaces, a process that globally has severe impacts both on the economy and on the environment. Since the ban of tributyltin, an efficient replacement of this antifouling compound by next-generation antifouling coatings that are environmentally more acceptable and also showing longer half-lives has not yet been developed. The sponges, as sessile filter-feeder animals, have evolved antifouling strategies to protect themselves against micro- and subsequent macro-biofouling processes. Experimental data are summarized and suggest that coating of the sponge surface with bio-silica contributes to the inhibition of the formation of a conditioning film. A direct adsorption of the surfaces by microorganisms can be impaired through poisoning the organisms with direct-acting secondary metabolites or toxic peptides. In addition, first, compounds from sponges have been identified that interfere with the anti-quorum sensing network. Sponge secondary metabolites acting selectively on diatom colonization have not yet been identified. Finally, it is outlined that direct-acting secondary metabolites inhibiting the growth of macro-fouling animals and those that poison the multidrug resistance pump are available. It is concluded that rational screening programs for inhibitors of the complex and dynamic problem of biofilm production, based on multidisciplinary studies and using sponges as a model, are required in the future.

Spectroscopic investigation on the structural modifications induced by radical stress on oligopeptides for tissue engineering

EAK16 (AEAEAKAKAEAEAKAK) and seven alternating polar/hydrophobic oligopeptides (derived from EAK16 by primary structure modifications) were tested for their resistance to free radical attack, in view of their possible use as biomimetic coatings of biomedical devices; in fact, oxidative radical stress, mainly due to hydroxyl radicals (•OH), is a common physiological condition occurring under acute or chronic inflammatory response. •OH radicals, mimicking an endogenous radical stress, were generated by gamma‐radiolysis of water solutions. IR and Raman spectroscopies were used to investigate the damages induced by free radicals on the oligopeptides, in particular on their folding and inter‐chain interactions.Some oligopeptides, i.e. EAK16 (pept1), pept3 (obtained by K → O substitution), pept5 (A → Abu substitution), pept7 (insertion at the N‐terminus of the RGD sequence), and pept8 (RGD insertion and “scrambling” of the sequence) were not severely affected by the treatment and retained their prevalent structure (i.e. α‐helix for pept8 and β‐sheet for the others). The other peptides, i.e. pept2 (obtained by E → D substitution), pept4 (E → D and K → O substitutions) and pept6 (A → Y substitution), showed significant conformational changes (i.e. increase in the α‐helix content) upon irradiation. In pept2 and pept4, modifications in hydrophobic and ionic interactions were observed; the latter were mainly ascribed to the decarboxylation of acidic amino acids. In pept6, the main target of the •OH attack was Tyr, as deduced by the strong variations observed in Tyr bands both in IR and Raman spectra.This study may contribute to gain insight into the different biological performances of the EAK16‐derived peptides and to identify the most adequate materials usable for bone regeneration. Copyright © 2013 John Wiley & Sons, Ltd.

The design and features of apatite-coated chitosan microspheres as injectable scaffold for bone tissue engineering

In this paper we developed two types of chitosan-based microspheres with and without biomimetic apatite coatings and compared their potential as injectable scaffolds for bone regeneration. The microspheres were obtained by emulsion cross-linking (E0) and coacervate precipitation (C0), respectively. They were then biomimetically coated with apatite to become E1 and C1 microspheres. The physicochemical properties and biocompatibility of the microspheres were characterized. Both E0 and C0 microspheres presented favorable ranges of diameter, density and Rockwell hardness. However, there were differences in the degree of cross-linking, shape, morphology, degradation rate, swelling rate, pH value after PBS immersion and the biocompatibility between E0 and C0. The apatite coating was successfully prepared for both C0 and E0, which enhanced the attachment, proliferation and differentiation of MC3T3-E1 cells. In conclusion, our results suggest the feasibility of using chitosan microspheres as a potential injectable scaffold. Both the preparation method and the biomimetic apatite coating contribute to their biological properties.

Self-cleaning antimicrobial surfaces by bio-enabled growth of SnO2 coatings on glass

Conventional vapor-deposition techniques for coatings require sophisticated equipment and/or high-temperature resistant substrates. Therefore bio-inspired techniques for the fabrication of inorganic coatings have been developed in recent years. Inspired by the biology behind the formation of the intricate skeletons of diatoms orchestrated by a class of cationic polyamines (silaffins) we have used surface-bound spermine, a naturally occurring polyamine, to promote the fast deposition of homogeneous, thin and transparent biomimetic SnO2 coatings on glass surfaces. The bio-enabled SnO2 film is highly photoactive, i.e. it generates superoxide radicals (O2˙(-)) upon sunlight exposure resulting in a strong degradation of organic contaminants and a strong antimicrobial activity. Upon illumination the biomimetic SnO2 coating exhibits a switchable amphiphilic behavior, which - in combination with its photoactivity - creates a self-cleaning surface. The intrinsic self-cleaning properties could lead to the development of new protective, antifouling coatings on various substrates.

Nanocoatings containing sulfated polysaccharides prepared by layer-by-layer assembly as models to study cell-material interactions.

The understanding of both cell-extracellular matrix (ECM) and cell-material interactions is crucial for the success of implantable biomaterials including tissue engineering devices. ECM is rich in sulfated and aminated glycosaminoglycans and proteoglycans. The development of synthetic models containing those chemical groups is thus of major interest. Thin coatings of polysaccharides with controlled sulfur and nitrogen contents were developed by layer-by-layer assembly. In particular, the multilayers were prepared by assembling chitosan with κ-, ι- and λ-carrageenan (increasing sulfur content). The nanostructured multilayers were characterized by quartz crystal microbalance with dissipation (QCM-D), atomic force microscopy (AFM), scanning electron microscopy (SEM), water contact angle, X-ray photoelectron spectroscopy (XPS) and used as models to study the effect of the sulfate groups over the behavior of osteoblast-like cells. The biomimetic coatings increased the alkaline phosphatase (ALP) activity and proliferation compared with unmodified polycaprolactone surfaces. Biomineralization increase with the presence of the coatings is significantly higher on ι-carrageenan coatings, suggesting that the sulfate groups may interact positively with molecules involved in the osteoblastic activity as it occurs in the natural ECM. The developed nanocoatings can constitute an interesting model to understand the biological influence of the sulfate and amine groups existing on the surface of biomaterials.

Phosophorylcholine-based Biomimetic Coatings for Nanomedical Applications

Phosophorylcholine-based Biomimetic Coatings for Nanomedical Applications

Evaluation of Biological Properties of Electron Beam Melted Ti6Al4V Implant with Biomimetic Coating In Vitro and In Vivo

BackgroundHigh strength porous titanium implants are widely used for the reconstruction of craniofacial defects because of their similar mechanical properties to those of bone. The recent introduction of electron beam melting (EBM) technique allows a direct digitally enabled fabrication of patient specific porous titanium implants, whereas both their in vitro and in vivo biological performance need further investigation.MethodsIn the present study, we fabricated porous Ti6Al4V implants with controlled porous structure by EBM process, analyzed their mechanical properties, and conducted the surface modification with biomimetic approach. The bioactivities of EBM porous titanium in vitro and in vivo were evaluated between implants with and without biomimetic apatite coating.ResultsThe physical property of the porous implants, containing the compressive strength being 163 - 286 MPa and the Young’s modulus being 14.5–38.5 GPa, is similar to cortical bone. The in vitro culture of osteoblasts on the porous Ti6Al4V implants has shown a favorable circumstance for cell attachment and proliferation as well as cell morphology and spreading, which were comparable with the implants coating with bone-like apatite. In vivo, histological analysis has obtained a rapid ingrowth of bone tissue from calvarial margins toward the center of bone defect in 12 weeks. We observed similar increasing rate of bone ingrowth and percentage of bone formation within coated and uncoated implants, all of which achieved a successful bridging of the defect in 12 weeks after the implantation.ConclusionsThis study demonstrated that the EBM porous Ti6Al4V implant not only reduced the stress-shielding but also exerted appropriate osteoconductive properties, as well as the apatite coated group. The results opened up the possibility of using purely porous titanium alloy scaffolds to reconstruct specific bone defects in the maxillofacial and orthopedic fields.

Erratum to: Comparison of mesenchymal stem cell proliferation and differentiation between biomimetic and electrochemical coatings on different topographic surfaces

Erratum to: Comparison of mesenchymal stem cell proliferation and differentiation between biomimetic and electrochemical coatings on different topographic surfaces

Comparison of mesenchymal stem cell proliferation and differentiation between biomimetic and electrochemical coatings on different topographic surfaces

The hypothesis for this study was that there is no difference in mesenchymal stem cells (MSCs) proliferation and osteogenic differentiation between calcium-phosphate (CaP) coatings with different crystal size deposited on different topographic surfaces of metal discs. Polished (P) and sand-blasted (SB) tantalum and TiAl6V4 discs were CaP coated by three methods-biomimetic (BioM), electrochemical at 20 mA/cm(2) and at 6.5 mA/cm(2)-and cultured with MSCs. At days 4, 7 and 14, cell proliferation-alamarBlue(®) activity and DNA quantification-and differentiation down the osteogenic lineage-ALP activity normalised per amount of DNA and SEM (morphology)-were analysed. Results showed that MSCs proliferated more when cultured on the nano-sized BioM coatings compared to uncoated and electrochemically coated discs. MSCs also proliferated more on P surfaces than on SB and or electrochemical coatings. All the coatings induced osteogenic differentiation, which was greater on electrochemical coatings and SB discs.

Improving in vitro corrosion resistance of biomimetic calcium phosphate coatings for Mg substrates using calcium hydroxide layer

Biomimetic calcium phosphate coatings have been studied to improve the corrosion resistance of biodegradable magnesium alloys. The corrosion resistance of these coatings is often limited by defects during creation. A method for improving the corrosion response of these coatings is therefore needed if biomimetic coatings are to be used for corrosion protection. In this study, a calcium hydroxide underlayer was applied to improve the properties of these biomimetic coatings. The in vitro corrosion response was studied using hydrogen evolution and electrochemical techniques. It was found that the calcium hydroxide layer increased the corrosion resistance of the coatings. The coatings created had fewer defects than the unmodified biomimetic coatings. Over time, the calcium hydroxide layer also prevented the defects in the coating from growing, leading to longer lasting protection. The results of this study suggest that calcium hydroxide coatings can significantly improve the corrosion protection of a biomimetic coating.

Biomimetic Mineralization of Calcium Phosphate on a Functionalized Porous Silicon Carbide Biomaterial

AbstractPorous biomorphic silicon carbide (bioSiC) is a structurally realistic, high‐strength, and biocompatible material which is promising for application in load‐bearing implants. The deposition of an osteoconductive coating is essential for further improvement of its integration with the surrounding tissue. A new strategy towards biomimetic calcium phosphate coatings on bioSiC is described. X‐ray photoelectron spectroscopy (XPS) analysis shows that using 10‐undecenoic acid methyl ester a covalently bound monolayer can be synthesized on the surface of the bioSiC. After hydrolysis it exposes carboxylic acid groups that promote the selective nucleation and growth of a very well‐defined crystalline layer of calcium phosphate. The resulting calcium phosphate coating is characterized by X‐ray diffraction and electron microscopy techniques. Further, ion beam imaging is employed to quantify the mineral deposition meanwhile, three‐dimensional dual‐beam imaging (FIB/SEM) is used to visualize the bioSiC/mineral interface. The monolayer is show to actively induce the nucleation of a well‐defined and highly crystalline mixed octacalcium phosphate/hydroxyapatite (OCP/HAP) coating on implantable bioSiC substrates with complex geometry. The mild biomimetic procedure, in principle, allows for the inclusion of bioactive compounds that aid in tissue regeneration. Moreover, the mixed OCP/HAP phase will have a higher solubility compared to HAP, which, in combination with its porous structure, is expected to render the coating more reabsorbable than standard HAP coatings.

Enhancement in broadband and quasi-omnidirectional antireflection of nanopillar arrays by ion milling

A new technique is developed to fabricate biomimetic antireflection coatings (ARCs). This technique combines a bottom-up fabrication approach (glancing angle deposition, or GLAD) with a top-down engineering process (ion milling). The GLAD technique is first utilized to produce nanopillar arrays (NPAs) with broadened structures, which are subsequently transformed into biomimetic tapered geometries by means of post-deposition ion milling. This structure transformation, due to milling-induced mass redistribution, remarkably decreases reflection over a wide wavelength range (300–1700 nm) and field of view (angle of incidence < 60° with respect to the substrate normal). The milling-induced antireflection enhancement has been demonstrated in the NPAs made of Si, SiOx and TiO2, illustrating that this integrated technique is readily adapted to a wide variety of materials. Good agreement between simulation and experiment indicates that the enhanced antireflection performance is ascribed to a smoother refractive index transition from the substrate to the air, which improves the impedance match and reduces reflection losses. Additionally, ion bombardment tends to alter the stoichiometry and diminish the crystallographic structure of the NPA materials. The broadband and quasi-omnidirectional antireflection observed establishes the strong competitiveness of this technique with the methods previously reported.

Comparison study of biomimetic strontium-doped calcium phosphate coatings by electrochemical deposition and air plasma spray: morphology, composition and bioactive performance

In this study, strontium-doped calcium phosphate coatings were deposited by electrochemical deposition and plasma spray under different process parameters to achieve various coating morphologies. The coating composition was investigated by energy dispersive X-ray spectroscopy and X-ray diffraction. The surface morphologies of the coatings were studied through scanning electron microscopy while the cytocompatibility and bioactivity of the strontium-doped calcium phosphate coatings were evaluated using bone cell culture using MC3T3-E1 osteoblast-like cells. The addition of strontium leads to enhanced proliferation suggesting the possible benefits of strontium incorporation in calcium phosphate coatings. The morphology and composition of deposited coatings showed a strong influence on the growth of cells.

Multilayer Roll-Bonded Sandwich: Processing, Mechanical Performance, and Bioactive Behavior

Multifunctionality and improving the properties of materials make it necessary to use hybrid systems such as combinations of metals with polymers. Their applications can be found in all areas where light weight and improved and adapted mechanical properties as well as high functionality are needed. Moreover, tailored types of hybrids can be interesting for biomedical applications, as under specific conditions they show, e.g., good strength combined with high elasticity. Herein, we present preliminary tests on the biomimetic behavior of AISI SS316L/polypropylene copolymer/AISI SS316L sandwich. Biomimetic coatings were produced by inducing a calcium phosphate layer in a way similar to the process of natural bone formation. Knowledge of the formability of three-layered sandwich sheets and their biomimetic behavior is presented.

Effect of Biomimetic Nanocrystalline Apatite Surface on Bone Ingrowth

The Success of Hydroxyapatite-Coated Acetabular Components Has Not Been Consistent. Plasma-Sprayed Hydroxyapatite Coatings Work Well on Nonporous Substrates but Do Not Coat the Inner Surfaces of Open-Porous Substrates. Solution Deposition Can Generate Consistent Bioceramic Coats on Porous Surfaces that More Closely Mimic the Trabecular Pattern and Biochemistry at the Bone Interface. we Compared Bone Response to the Following Implants: Porous-Coated Ti6al4v Cylinders with 1 of 3 Treatments: Plasma Sprayed with Hydroxyapatite (HA), Coated with a Solution-Deposited Biomimetic Apatite Coating (BA), and Untreated (Control). Bilateral Femurs in 36 Rabbits Were Implanted with One of the above Implants. Bone Ingrowth for HA and BA Surfaces Was Significantly Higher than that for Control Surfaces. No Fragmentation or Debris Production Was Evident in the Apatite Coat of the BA Group. A Biomimetic Coat of Solution-Deposited Apatite May Be Resistant to Coating Delamination and Particle Generation.

Surface properties of Al2O3-YSZ ceramic composites modified by a combination of biomimetic coatings and electric polarization

Alumina-containing yttria-stabilized zirconia composite (Al-YSZ) has a higher flexural strength than YSZ, although Al-YSZ cannot directly bond with bone tissues. To expand the biomedical applications of Al-YSZ, new surface modifications were investigated to improve the bioactivity in the present study. The combination of a biomimetic coatings method using an alternate soaking technique and electric polarization treatment was performed on Al-YSZ. The crystalline phases of the starting Al-YSZ sintered disks were assigned to tetragonal ZrO2 and α-Al2O3 phases. The analyses of the electrical properties were carried out using complex impedance and thermally stimulated depolarized current measurements for polarization treatments. Our results indicate that the stored charges in Al-YSZ via polarization decreased in YSZ, because of the added alumina, while the calcium phosphate film deposited by the biomimetic coatings method on polarized Al-YSZ was observed to be thicker than the non-polarized film. The coating method would be suitable for the complex geometry of biomaterials. As a result, polarized Al-YSZ fabricated using an alternate soaking process is expected to be useful as a biomaterial under load-bearing conditions.

Emulsion route in fabrication of micro and nanocontainers for biomimetic self-healing and self-protecting functional coatings

Designing of novel self-healing materials possessing an active feedback on various destructive factors is one of most quickly developing areas in contemporary material engineering. Self-healing and self-protecting coatings represent one of particular classes of these materials that able on damage to recover their anticorrosive or antifouling function. Most established approach to impart to the coating this ability is nowadays the use of container-based structures when the protective agent trapped in containers is embedded in the coating matrix. There are different ways to produce containers for the further incorporation into coating but the role of emulsion route in the containers preparation is probably predominant. Herein, the contemporary achievements in the field of emulsion encapsulation are reviewed. Several types of containers for biomimetic functional coatings synthesized via emulsion as an initial system are presented based mainly on the earlier published and very recently obtained results of our research group. An overview is given of some interfacial physical and chemical methods utilized for the transformation of emulsion droplets into nano- or microscaled containers showing their specific advantages and drawbacks. Successful incorporation of containers in the diverse types of coatings showed is promising for novel materials production in many application fields.

Gelatin-Modified Biomimetic Apatite Coatings

Biomimetic coatings constituted of gelatin and nanocrystalline apatite were deposited on titanium substrates from a slightly supersaturated calcium phosphate (CaP) solution enriched with different amounts of gelatin. Although the biopolymer inhibits the crystallization of the inorganic phase, as shown by the reduction of the mean dimensions of the spherical aggregates and of the degree of crystallinity of the apatitic phase on increasing gelatin concentration, the deposition of a uniform layer of nanocrystalline apatite takes place in a few hours. Gelatin incorporation into the precipitate increases on increasing its concentration in solution, up to about 20 wt%. Osteoblast-like MG63 cells cultured on the coatings display good proliferation and increased values of the differentiation parameters with respect to the control. The presence of gelatin improves significantly the biological response to the biomimetic coatings, as shown by the higher values of proliferation, collagen type I and osteocalcin production, as well as alkaline phosphatase activity stimulation.

Nanostructured ZnO as biomimetic anti-reflective coatings on textured silicon using a continuous solution process

A novel table-top, microreactor-assisted nanomaterial deposition (MAND™) process, which combines the merits of microreaction technology with solution-phase nanomaterial synthesis and film deposition, was used to grow a nanostructured ZnO anti-reflective coating on a textured silicon substrate from aqueous solution. The subwavelength, anti-reflective nanostructures mimicked the structure and performance of the surface of the eye from a night-flying moth. Solution-processed Ag nanoparticles were applied as a seed layer on the textured silicon surface leading to preferred heterogeneous nucleation and good area coverage. Preferential growth of the nanostructured ZnO was controlled by changing residence time, reaction temperature, and concentration of precursor solution without the use of a buffer reagent (e.g. HMTA). Well-aligned ZnO nanorod arrays were fabricated by MAND at a very high deposition rate (i.e. 125 nm min−1) compared to batch hydrothermal method. The surface reflection of the polished silicon was suppressed from an average of 30.8% between wavelengths of 400 and 900 nm to 10.6% after micro-scale pyramidal surface texturing to 3.4% after application of the ZnO nanostructure on the textured silicon. The results provide a potential economical path to broadband anti-reflection (AR) for silicon wafers and solar cell substrates.

Bioactive Surface Structure and Bio-Absorption of Human Dentin Granules Designed by the Supersonic Demineralization and Biomimetic Coating Technique

Bioactive Surface Structure and Bio-Absorption of Human Dentin Granules Designed by the Supersonic Demineralization and Biomimetic Coating Technique