Biomimetic Composite Structural T-joints

Biological structural fixed joints exhibit unique attributes,including highly optimized fiber paths which minimize stress concentrations.In addition,since the joints consist of continuous,uncut fiber architectures,the joints enable the organism to transport information and chemicals from one part of the body to the other.To the contrary,sections of man-made composite material structures are often joined using bolted or bonded joints,which involve low strength and high stress concentrations.These methods are also expensive to achieve.Additional functions such as fluid transport,electrical signal delivery,and thermal conductivity across the joints typically require parasitic tubes,wires,and attachment clips.By using the biomimetic methods,we seek to overcome the limitations which are present in the conventional methods.In the present work,biomimetic co-cured composite sandwich T-joints were constructed using unidirectional glass fiber,epoxy resin,and structural foam.The joints were fabricated using the wet lay-up vacuum bag resin infusion method.Foam sandwich T-joints with multiple continuous fiber architectures and sandwich foam thickness were prepared.The designs were tested in quasi-static bending using a mechanical load frame.The significantweight savings using the biomimetic approaches is discussed,as well as a comparison of failure modes versus architecture is described.     

Biomimetic asymmetric hydrogenation.

Enzymes and synthetic organometallic catalysts utilize different approaches for the creation of chiral centers in prochiral substrates. While chiral organometallic catalysts realize the transfer of chirality mainly by repulsive interactions, several enzymes use preferentially stereodiscriminating hydrogen bonding. To investigate if hydrogen bonding within the catalyst-substrate assembly can also have a benefit on the rhodium diphosphine-catalyzed asymmetric hydrogenation, some model metal complexes and substrates were investigated. As 'biomimetically acting' functionalities, hydroxy groups were incorporated in the chiral ligand. Three secondary interactions could be identified by different analytical methods which influence rate and enantioselectivity of the catalytic reaction: 1) HO/Rh-interactions, 2) HO/HO-interactions within the backbone of the ligand, and 3) hydrogen bonding between HO-groups of the ligand and functional groups of an appropriate substrate. Due to the effect of the additional hydroxy groups, enantioselectivities by up to 99% ee could be induced in the hydrogenation product even with water as solvent.     

Biomimetic vibrissal sensing for robots

Active vibrissal touch can be used to replace or to supplement sensory systems such as computer vision and, therefore, improve the sensory capacity of mobile robots. This paper describes how arrays of whisker-like touch sensors have been incorporated onto mobile robot platforms taking inspiration from biology for their morphology and control. There were two motivations for this work: first, to build a physical platform on which to model, and therefore test, recent neuroethological hypotheses about vibrissal touch; second, to exploit the control strategies and morphology observed in the biological analogue to maximize the quality and quantity of tactile sensory information derived from the artificial whisker array. We describe the design of a new whiskered robot, Shrewbot, endowed with a biomimetic array of individually controlled whiskers and a neuroethologically inspired whisking pattern generation mechanism. We then present results showing how the morphology of the whisker array shapes the sensory surface surrounding the robot's head, and demonstrate the impact of active touch control on the sensory information that can be acquired by the robot. We show that adopting bio-inspired, low latency motor control of the rhythmic motion of the whiskers in response to contact-induced stimuli usefully constrains the sensory range, while also maximizing the number of whisker contacts. The robot experiments also demonstrate that the sensory consequences of active touch control can be usefully investigated in biomimetic robots.     

Development of Biomimetic Squid-Inspired Suckers

Biomechanical properties of squid suckers were studied to provide inspiration for the development of sucker artefacts for a robotic octopus.Mechanical support of the rings found inside squid suckers was studied by bending tests.Tensile tests were carried out to study the maximum possible sucking force produced by squid suckers based on the strength of sucker stalks,normalized by the sucking areas.The squid suckers were also directly tested to obtain sucking forces by a special testing arrangement.Inspired by the squid suckers,three types of sucker artefacts were developed for the arm skin of an octopus inspired robot.The first sucker artefact made of knitted nylon sheet reinforced silicone rubber has the same shape as the squid suckers.Like real squid suckers,this type of artefact also has a stalk that is connected to the arm skin and a ring to give radial support.The second design is a straight cylindrical structure with uniform wall thickness made of silicone rubber.One end of the cylinder is directly connected to the arm skin and the other end is open.The final design of the sucker has a cylindrical base and a concave meniscus top.The meniscus was formed naturally using the surface tension of silicone gel,which leads to a higher level of the liquid around the edge of a container.The wall thickness decreases towards the tip of the sucker opening.Sucking forces of all three types of sucker artefacts were measured.Advantages and disadvantages of each sucker type were discussed.The final design of suckers has been implemented to the arm skin prototypes.     

Biomimetic approaches to tendon repair

The linear organization of collagen fibers in tendons results in optimal stiffness and strength at low strains under tensile load. However, this organization makes repairing ruptured or lacerated tendons extremely difficult. Current suturing techniques to join split ends of tendons, while providing sufficient mechanical strength to prevent gapping, are inadequate to carry normal loads. Immobilization protocols necessary to restore tendon congruity result in scar formation at the repair site and peripheral adhesions that limit excursion. These problems are reviewed to emphasize the need for novel approaches to tendon repair, one of which is the development of biomimetic tendons. The objective of the empirical work described here was to produce biologically-based, biocompatible tendon replacements with appropriate mechanical properties to enable immediate mobilization following surgical repair. Nor-dihydroguaiaretic acid (NDGA), a di-catechol from creosote bush, caused a dose dependent increase in the material properties of reconstituted collagen fibers, achieving a 100-fold increase in strength and stiffness over untreated fibers. The maximum tensile strength of the optimized NDGA treated fibers averaged 90 MPa; the elastic modulus of these fibers averaged 580 MPa. These properties were independent of strain rates ranging from 0.60 to 600 mm/min. Fatigue tests established that neither strength nor stiffness were affected after 80 k cycles at 5% strain. Treated fibers were not cytotoxic to tendon fibroblasts. Fibroblasts attached and proliferated on NDGA treated collagen normally. NDGA-fibers did not elicit a foreign body response nor did they stimulate an immune reaction during six weeks in vivo. The fibers survived 6 weeks with little evidence of fragmentation or degradation. The polymerization scheme described here produces a fiber-reinforced NDGA-polymer with mechanical properties approaching an elastic solid. The strength, stiffness and fatigue properties of the NDGA-treated fibers are comparable to those of tendon. These fibers are biocompatible with tendon fibroblasts and elicit little rejection or antigenic response in vivo. These results indicate that NDGA polymerization may provide a viable approach for producing collagenous materials that can be used to bridge gaps in ruptured or lacerated tendons. The tendon-like properties of the NDGA-fiber would allow early mobilization after surgical repair. We predict that timely loading of parted tendons joined by this novel biomaterial will enhance mechanically driven production of neo-tendon by the colonizing fibroblasts and result in superior repair and rapid return to normal properties.     

Biomimetic design of nanopatterned membranes

The biomimetic approach copying the supramolecular building principle of many archaeal cell envelopes (i.e., a plasma membrane with associated S-layer proteins) has resulted in stable lipid membranes with excellent reconstitution properties for transmembrane proteins. This is a particular challenge as one-third of all proteins in an organism are membrane proteins like pores, ion channels, or receptors. At S-layer supported lipid membranes, spatial well-defined domains on the S-layer protein interact noncovalently with lipid head groups within the lipid membrane resulting in a nanopatterning of a few anchored and scores of diffusional free-lipid molecules. In addition, no impact on the hydrophobic core region and on the function of reconstituted integral proteins has been determined. Among others, particularly S-layer stabilized membranes can be used for structure-function studies on reconstituted integral proteins and also in the membrane protein-based molecular nanotechnology, e.g., in the design of biosensing devices (e.g., lipid chip or lab-on-a-chip), or for receptor or ion channel-based high-throughput screening.     

Biomimetic Materials to Characterize Bacteria-host Interactions

Bacterial attachment to host cells is one of the earliest events during bacterial colonization of host tissues and thus a key step during infection. The biochemical and functional characterization of adhesins mediating these initial bacteria-host interactions is often compromised by the presence of other bacterial factors, such as cell wall components or secreted molecules, which interfere with the analysis. This protocol describes the production and use of biomimetic materials, consisting of pure recombinant adhesins chemically coupled to commercially available, functionalized polystyrene beads, which have been used successfully to dissect the biochemical and functional interactions between individual bacterial adhesins and host cell receptors. Protocols for different coupling chemistries, allowing directional immobilization of recombinant adhesins on polymer scaffolds, and for assessment of the coupling efficiency of the resulting “bacteriomimetic” materials are also discussed. We further describe how these materials can be used as a tool to inhibit pathogen mediated cytotoxicity and discuss scope, limitations and further applications of this approach in studying bacterial - host interactions.     

The Top of the Biomimetic Triangle

There is increasing observational evidence indicating that crystalline interfacial water layers play a central role in evolution and biology. For instance in cellular recognition processes, in particular during first contact events, where cells decide upon survival or entering apoptosis. Understanding water layers is thus crucial in biomedical engineering, specifically in the design of biomaterials inspired by biomimetic principles. Whereas there is ample experimental evidence for crystalline interfacial water layers on surfaces in air, their subaquatic presence could not be verified directly, so far. Analysing a polarity dependent asym- metry in the surface conductivity on hydrogenated nanocrystalline diamond, we show that crystalline interfacial water layers persist subaquatically. Nanoscopic interfacial water layers with an order different from that of bulk water have been identified at room temperature on both hydrophilic and hydrophobic model surfaces - in air and subaquatically. Their generalization and systematic inclusion into the catalogue of physical and chemical determinants of biocompatibility complete the biomimetic triangle.     

Biomimetic polyene cyclizations: A review

It has been shown that certain polyenic substances, having trans olefinic bonds in the 1,5 relationship, can be induced to undergo stereospecific, nonenzymic, cationic cyclization to give polycyclic products with the all trans (“natural”) configuration. These transformations appear to mimic in principle the biogenetic conversion of squalene into polycyclic triterpenoids, e.g., lanosterol. Acetal as well as allylic alcohol functions have proved to be effective initiators for such cyclizations, many of which proceed to a remarkable degree of completion giving mainly totally cyclized products. Thus, it has been possible to convert, in a single step, an open chain tetraenic acetal having no chiral centers, into a tetracyclic product having seven such centers. The process is highly stereoselective giving only two of 64 possible racemates.Methylacetylenic and also styryl end groups are particularly useful cyclization terminators as they provide a means of realizing five-membered ring formation. Systems with these terminators have been developed for effecting the total synthesis of the steroid nucleus in a single step starting from a substrate containing only one ring.The mechanism of these biomimetic as well as of the enzymic cyclizations is open to question, but the balance of the evidence is somewhat in favor of a synchronous process.     

Biomimetic nanosystems and novel composite nanobiomaterials

Biophysicochemical approaches to the solution of nanotechnology problems associated with the design of functional biomimetic nanosystems, hybrid and composite nanobiomaterials and study of their structure-function relationships. The results of studies concerned with physicochemical mechanisms of the formation of organized biomimetic nanostructures and bioinorganic nanomaterials in systems involving a bulky liquid phase and the interface (gas-liquid, solid-liquid, liquid-liquid)during the synthesis and structure formation with the participation of the components of colloid systems, inorganic nanoparticles of various composition and clusters of metals, surfactants, polyelectrolytes and their complexes are discussed. In the development of the methods for the formation of composite bioinorganic nanosystems containing inorganic nanocomponents, two major approaches were used: adsorption and incorporation into the biomolecular matrix or colloid system of presynthesized inorganic nanoparticles, as well as the synthesis of the inorganic nanophase immediately in the biomolecular system. The methods of obtaining biomaterials and nanosystems are based on the principles of biomimetics, biomineralization, self-assembly and self-organization, combination and integration of a number of synthetic and physicochemical methods (physical and chemical adsorption, Langmuir technique, the formation of polycomplexes, chemical linking, competitive interactions, and substitution of ligands in supramolecular and coordination complexes) and nanocomponents of different nature. In particular, a novel approach to the preparation of highly organized nanofilm materials was developed, which is based on the effect of self-assembly and self-organization of colloid nanoparticles during the formation of their complexes with polyfunctional biogenic ligands in the volume of the liquid phase in the absence of any surfaces and interfaces. The physical and chemical factors responsible for the formation of structurally ordered biomolecular and composite nanosystems including nano-sized components of different nature and the possibilities to control the composition, structure, and properties of resulting nanomaterials and nanosystems are discussed. The experimental methods and approaches developed may be useful in studies of structure-property relationships and basic mechanisms of structural organization and transformation at the nanoscales level in biological, artificial, and hybrid nanosystems. The problems of practical application of the synthetic methods and the corresponding nanomaterials are discussed.     

Biomimetic asymmetric oxidative coupling of phenols

This paper describes the first examples of asymmetric induction in the oxidative coupling of phenols using chiral oxidants. When chiral cupric-amine complexes were used as oxidants, low asymmetric induction was achieved in the coupling of naphthols. The formation of optically active d-dehydrogriseofulvin and l-Licarin A using the cupric-l-a-phenylethylamine complex perhaps mimics the action of copper-containing enzymes known to catalyze phenol coupling.     

Biomimetic mineralization of noble metal nanoclusters

A number of biological systems have developed highly orchestrated detoxification mechanisms toward the bioreduction and mineralization of noble metals. These systems incorporate small peptides and proteins as nucleation sites for metal binding and nanocluster stabilization. Herein, we present the use of biologically relevant ligands ranging from single amino acids (histidine, imidazole, and cysteine) to linear peptides (glutathione and a histidine rich peptide) in the stabilization of a variety of noble metal surfaces (Au(0), Ag(0), Pt(0), and Cu(0)). As a result, the different nanocluster/ligand combinations offered a broad range of sizes and stabilitites. The peptide coat also affords a unique functional handle for the formation of larger assemblies. Using Ni chelation and immunomolecular approaches, strategies for the assembly of nanocluster heterostructures were investigated.     

Biomimetic systems for studying actin-based motility

Actin polymerization provides a major driving force for eukaryotic cell motility. Successive intercalation of monomeric actin subunits between the plasma membrane and the filamentous actin network results in protrusions of the membrane enabling the cell to move or to change shape. One of the challenges in understanding eukaryotic cell motility is to dissect the elementary biochemical and biophysical steps that link actin polymerization to mechanical force generation. Recently, significant progress was made using biomimetic, in vitro systems that are inspired by the actin-based motility of bacterial pathogens such as Listeria monocytogenes. Polystyrene microspheres and synthetic phospholipid vesicles coated with proteins that initiate actin polymerization display motile behavior similar to Listeria, mimicking the leading edge of lamellipodia and filopodia. A major advantage of these biomimetic systems is that both biochemical and physical parameters can be controlled precisely. These systems provide a test bed for validating theoretical models on force generation and polarity establishment resulting from actin polymerization. In this review, we discuss recent experimental progress using biomimetic systems propelled by actin polymerization and discuss these results in the light of recent theoretical models on actin-based motility.     

Biomimetic approach to cardiac tissue engineering

Here, we review an approach to tissue engineering of functional myocardium that is biomimetic in nature, as it involves the use of culture systems designed to recapitulate some aspects of the actual in vivo environment. To mimic the capillary network, subpopulations of neonatal rat heart cells were cultured on a highly porous elastomer scaffold with a parallel array of channels perfused with culture medium. To mimic oxygen supply by haemoglobin, the culture medium was supplemented with a perfluorocarbon (PFC) emulsion. Constructs cultivated in the presence of PFC contained higher amounts of DNA and cardiac markers and had significantly better contractile properties than control constructs cultured without PFC. To induce synchronous contractions of cultured constructs, electrical signals mimicking those in native heart were applied. Over only 8 days of cultivation, electrical stimulation induced cell alignment and coupling, markedly increased the amplitude of synchronous construct contractions and resulted in a remarkable level of ultrastructural organization. The biomimetic approach is discussed in the overall context of cardiac tissue engineering, and the possibility to engineer functional human cardiac grafts based on human stem cells.     

Biomimetic platforms for human stem cell research

Stem cells are central to developing new treatment options for tissue regeneration and constructing controllable models for biological research. Bioengineered cell culture environments that combine microenvironmental control with tissue-specific transport and signaling are critical tools in our efforts to study tissue development, regeneration, and disease under conditions that predict the human in vivo context. We propose that experimentation at the interfaces of biology, engineering, and medical sciences is critical for unlocking the full potential of stem cells. Here, we focus on the design and utilization of in vitro platforms that recapitulate the environments associated with tissue development, disease, and regeneration.     

Piezoelectrically Actuated Biomimetic Self-Contained Quadruped Bounding Robot

This paper presents the development of a mesoscale self-contained quadruped mobile robot that employs two pieces ofpiezocomposite actuators for the bounding locomotion.The design of the robot leg is inspired by legged insects and animals,and the biomimetic concept is implemented in the robot in a simplified form,such that each leg of the robot has only one degreeof freedom.The lack of degree of freedom is compensated by a slope of the robot frame relative to the horizontal plane.For theimplementation of the self-contained mobile robot,a small power supply circuit is designed and installed on the robot.Experimentalresults show that the robot can locomote at about 50 mm·s^-1with the circuit on board,which can be considered as asignificant step toward the goal of building an autonomous legged robot actuated by piezoelectric actuators.     

Biomimetic monolayer films of digalactosyldiacylglycerol incorporating plastoquinone

The photosynthesis is the process used by plants and bacteria cells to convert inorganic matter in organic thanks to the light energy. This process consist on several steps, being one of them the electronic transport from the photosystem II to the cytochrome thanks to plastoquinone-9 (PQ). Here we prepare membranes that mimic the characteristics and composition of natural photosynthetic cell membranes and we characterize them in order to obtain the PQ molecules position in the membrane and their electrochemical behaviour. The selected galactolipid is digalactosyldiacylglycerol (DGDG) that represents the 30% of the thylakoid membrane lipid content. The results obtained are worthful for several science fields due to the relevance of galactolipids as anti-algal, anti-viral, anti-tumor and anti-inflammatory agents and the antioxidant and free radical scavenger properties of prenylquinones.Both pure components (DGDG and PQ) and the DGDG:PQ mixtures have been studied using surface pressure–area isotherms. These isotherms give information about the film stability and indicate the thermodynamic behaviour of the mixture and their physical state. The Langmuir–Blodgett (LB) film has been transferred forming a monolayer that mimics the bottom layer of the biological membranes. This monolayer on mica has been topographically characterized using AFM and both the height and the physical state that they present have been obtained. Moreover, these monolayers have been transferred onto ITO that is a hydrophilic substrate with good optical and electrical features, so that, it is suitable for studying the electrochemical behaviour of these systems and it is a good candidate for energy producing devices.     

Biomimetic particles in drug and vaccine delivery

Over the last two decades, lipid supramolecular association to particles has been systematically studied on latex, silica or drug particles over a range of experimental conditions in order to achieve optimal bilayer deposition onto particles. The difficult step of vesicle disruption, especially for bilayers in the rigid gel state, was circumvented by using previously disrupted charged vesicles, namely, charged bilayer fragments or disks. Thereby, under appropriate conditions of the intervening medium, bilayer fragments coalesced around particles. In this mini-review, some applications of biomimetic particles in drug and vaccine delivery are discussed such as: encapsulation of hydrophobic drug particles, isolation and reconstitution of cell receptor function, presentation of antigens to the immunological system or highly effective antimicrobial action of positively charged bilayer disks by themselves or upon coverage of hydrophobic antimicrobial drug particles with the cationic bilayer fragments. In summary, a myriad of novel applications for spherical or discoidal biomimetic particles can be anticipated from the proofs-of-concept discussed in this work.     

ENDOXY - Development of a Biomimetic Oxygenator-Test-Device

Objective

This study focusses on the development of a biomimetic oxygenator test device. Due to limited biocompatibility, current oxygenators do not allow mid- to long-term therapy. Tissue engineering uses autologous cell sources to overcome the immunogenic barriers of biomaterials. Surface coating with endothelial cells might improve hemocompatibility and thus prevent immunogenic reactions of the body. In this study this concept is applied to endothelialise a gas-permeable membrane to develop a biomimetic oxygenator test-device (ENDOXY).

Methods

ENDOXY—a multifunctional test-system was developed to endothelialise a gas-permeable membrane suitable for cell culture and to test the cell retention under shear stress and to measure gas transfer through it.

Results

Successful endothelialisation of the membrane was achieved and cells showed characteristic endothelial morphologies. They stained positive for endothelial markers. The number of cells aligned with shear stress and cell retention after blood perfusing experiments was high. Gas transfer is observed via uncoated and endothelialised membranes.

Conclusion

The study showed promising results with regard to system design, endothelialisation, and cell retention under shear stress conditions. It strongly encourages further research into the system by testing different membrane materials to design a biomimetic membrane surface and pave way for a fully hemocompatible oxygenator.