Biomimetic material

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Biomimetic materials are materials developed using inspiration from nature. This may be useful in the design of composite materials. Natural structures have inspired and innovated human creations. [1] Notable examples of these natural structures include: honeycomb structure of the beehive, strength of spider silks, bird flight mechanics, and shark skin water repellency. [2] The etymological roots of the neologism "biomimetic" derive from Greek, since bios means "life" and mimetikos means "imitative".[ citation needed ]

Contents

Tissue engineering

Biomimetic materials in tissue engineering are materials that have been designed such that they elicit specified cellular responses mediated by interactions with scaffold-tethered peptides from extracellular matrix (ECM) proteins; essentially, the incorporation of cell-binding peptides into biomaterials via chemical or physical modification. [3] Amino acids located within the peptides are used as building blocks by other biological structures. These peptides are often referred to as "self-assembling peptides", since they can be modified to contain biologically active motifs. This allows them to replicate information derived from tissue and to reproduce the same information independently. Thus, these peptides act as building blocks capable of conducting multiple biochemical activities, including tissue engineering. [4] Tissue engineering research currently being performed on both short chain and long chain peptides is still in early stages.

Such peptides include both native long chains of ECM proteins as well as short peptide sequences derived from intact ECM proteins. The idea is that the biomimetic material will mimic some of the roles that an ECM plays in neural tissue. In addition to promoting cellular growth and mobilization, the incorporated peptides could also mediate by specific protease enzymes or initiate cellular responses not present in a local native tissue. [3]

In the beginning, long chains of ECM proteins including fibronectin (FN), vitronectin (VN), and laminin (LN) were used, but more recently the advantages of using short peptides have been discovered. Short peptides are more advantageous because, unlike the long chains that fold randomly upon adsorption causing the active protein domains to be sterically unavailable, short peptides remain stable and do not hide the receptor binding domains when adsorbed. Another advantage to short peptides is that they can be replicated more economically due to the smaller size. A bi-functional cross-linker with a long spacer arm is used to tether peptides to the substrate surface. If a functional group is not available for attaching the cross-linker, photochemical immobilization may be used. [3]

In addition to modifying the surface, biomaterials can be modified in bulk, meaning that the cell signaling peptides and recognition sites are present not just on the surface but also throughout the bulk of the material. The strength of cell attachment, cell migration rate, and extent of cytoskeletal organization formation is determined by the receptor binding to the ligand bound to the material; thus, receptor-ligand affinity, the density of the ligand, and the spatial distribution of the ligand must be carefully considered when designing a biomimetic material. [3]

Biomimetic mineralization

Proteins of the developing enamel extracellular matrix (such as amelogenin) control initial mineral deposition (nucleation) and subsequent crystal growth, ultimately determining the physico-mechanical properties of the mature mineralized tissue. Nucleators bring together mineral ions from the surrounding fluids (such as saliva) into the form of a crystal lattice structure, by stabilizing small nuclei to permit crystal growth, forming mineral tissue. [5] Mutations in enamel ECM proteins result in enamel defects such as amelogenesis imperfecta. Type-I collagen is thought to have a similar role for the formation of dentin and bone. [6] [7]

Dental enamel mineral (as well as dentin and bone) is made of hydroxylapatite with foreign ions incorporated in the structure. Carbonate, fluoride, and magnesium are the most common heteroionic substituents. [8]

In a biomimetic mineralization strategy based on normal enamel histogenesis, a three-dimensional scaffold is formed to attract and arrange calcium and/or phosphate ions to induce de novo precipitation of hydroxylapatite. [9]

Two general strategies have been applied. One is using fragments known to support natural mineralization proteins, such as Amelogenin, Collagen, or Dentin Phosphophoryn as the basis. [10] Alternatively, de novo macromolecular structures have been designed to support mineralization, not based on natural molecules, but on rational design. One example is oligopeptide P11-4. [11]

In dental orthopedics and implants, a more traditional strategy to improve the density of the underlying jaw bone is via the in situ application of calcium phosphate materials. Commonly used materials include hydroxylapatite, tricalcium phosphate, and calcium phosphate cement. [12] Newer bioactive glasses follow this line of strategy, where the added silicone provides an important bonus to the local absorption of calcium. [13]

Extracellular matrix proteins

Many studies utilize laminin-1 when designing a biomimetic material. Laminin is a component of the extracellular matrix that is able to promote neuron attachment and differentiation, in addition to axon growth guidance. Its primary functional site for bioactivity is its core protein domain isoleucine-lysine-valine-alanine-valine (IKVAV), which is located in the α-1 chain of laminin. [14]

A recent study by Wu, Zheng et al., synthesized a self-assembled IKVAV peptide nanofiber and tested its effect on the adhesion of neuron-like pc12 cells. Early cell adhesion is very important for preventing cell degeneration; the longer cells are suspended in culture, the more likely they are to degenerate. The purpose was to develop a biomaterial with good cell adherence and bioactivity with IKVAV, which is able to inhibit differentiation and adhesion of glial cells in addition to promoting neuronal cell adhesion and differentiation. [14] The IKVAV peptide domain is on the surface of the nanofibers so that it is exposed and accessible for promoting cell contact interactions. The IKVAV nanofibers promoted stronger cell adherence than the electrostatic attraction induced by poly-L-lysine, and cell adherence increased with increasing density of IKVAV until the saturation point was reached. IKVAV does not exhibit time dependent effects because the adherence was shown to be the same at 1 hour and at 3 hours. [14]

Laminin is known to stimulate neurite outgrowth and it plays a role in the developing nervous system. It is known that gradients are critical for the guidance of growth cones to their target tissues in the developing nervous system. There has been much research done on soluble gradients; however, little emphasis has been placed on gradients of substratum bound substances of the extracellular matrix such as laminin. [15] Dodla and Bellamkonda, fabricated an anisotropic 3D agarose gel with gradients of coupled laminin-1 (LN-1). Concentration gradients of LN-1 were shown to promote faster neurite extension than the highest neurite growth rate observed with isotropic LN-1 concentrations. Neurites grew both up and down the gradients, but growth was faster at less steep gradients and was faster up the gradients than down the gradients. [15]

Biomimetic artificial muscles

Electroactive polymers (EAPs) are also known as artificial muscles. EAPs are polymeric materials and they are able to produce large deformation when applied in an electric field. This provides large potential in applications in biotechnology and robotics, sensors, and actuators. [16]

Biomimetic photonic structures

The production of structural colours concerns a large array of organisms. From bacteria (Flavobacterium strain IR1) [17] to multicellular organisms, ( Hibiscus trionum , [18] Doryteuthis pealeii (squid), [19] or Chrysochroa fulgidissima (beetle) [20] ), manipulation of light is not limited to rare and exotic life forms. Different organisms evolved different mechanisms to produce structural colours: multilayered cuticle in some insects [20] and plants, [21] grating like surface in plants, [18] geometrically organised cells in bacteria... all of theme stand for a source of inspiration towards the development of structurally coloured materials. Study of the firefly abdomen revealed the presence of a 3-layer system comprising the cuticle, the Photogenic layer and then a reflector layer. Microscopy of the reflector layer revealed a granulate structure. Directly inspired from the fire fly Reflector layer, an artificial granulate film composed of hollow silica beads of about 1.05 μm was correlated with a high reflection index and could be used to improve light emission in chemiluminescent systems. [22]

Artificial enzyme

Artificial enzymes are synthetic materials that can mimic (partial) function of a natural enzyme without necessarily being a protein. Among them, some nanomaterials have been used to mimic natural enzymes. These nanomaterials are termed nanozymes. Nanozymes as well as other artificial enzymes have found wide applications, from biosensing and immunoassays, to stem cell growth and pollutant removal. [23]

Biomimetic composite

Biomimetic composites are being made by mimicking natural design strategies. The designs or structures found in animals and plants have been studied and these biological structures are applied to manufacture composite structure. Advanced manufacturing techniques like 3d printing are being used by the researcher to fabricate them. [24]

Related Research Articles

<span class="mw-page-title-main">Extracellular matrix</span> Network of proteins and molecules outside cells that provides structural support for cells

In biology, the extracellular matrix (ECM), is a network consisting of extracellular macromolecules and minerals, such as collagen, enzymes, glycoproteins and hydroxyapatite that provide structural and biochemical support to surrounding cells. Because multicellularity evolved independently in different multicellular lineages, the composition of ECM varies between multicellular structures; however, cell adhesion, cell-to-cell communication and differentiation are common functions of the ECM.

<span class="mw-page-title-main">Tooth enamel</span> Major tissue that makes up part of the tooth in humans and many animals

Tooth enamel is one of the four major tissues that make up the tooth in humans and many animals, including some species of fish. It makes up the normally visible part of the tooth, covering the crown. The other major tissues are dentin, cementum, and dental pulp. It is a very hard, white to off-white, highly mineralised substance that acts as a barrier to protect the tooth but can become susceptible to degradation, especially by acids from food and drink. In rare circumstances enamel fails to form, leaving the underlying dentin exposed on the surface.

<span class="mw-page-title-main">Ultrastructure</span>

Ultrastructure is the architecture of cells and biomaterials that is visible at higher magnifications than found on a standard optical light microscope. This traditionally meant the resolution and magnification range of a conventional transmission electron microscope (TEM) when viewing biological specimens such as cells, tissue, or organs. Ultrastructure can also be viewed with scanning electron microscopy and super-resolution microscopy, although TEM is a standard histology technique for viewing ultrastructure. Such cellular structures as organelles, which allow the cell to function properly within its specified environment, can be examined at the ultrastructural level.

<span class="mw-page-title-main">Dentin</span> Calcified tissue of the body; one of the four major components of teeth

Dentin or dentine is a calcified tissue of the body and, along with enamel, cementum, and pulp, is one of the four major components of teeth. It is usually covered by enamel on the crown and cementum on the root and surrounds the entire pulp. By volume, 45% of dentin consists of the mineral hydroxyapatite, 33% is organic material, and 22% is water. Yellow in appearance, it greatly affects the color of a tooth due to the translucency of enamel. Dentin, which is less mineralized and less brittle than enamel, is necessary for the support of enamel. Dentin rates approximately 3 on the Mohs scale of mineral hardness. There are two main characteristics which distinguish dentin from enamel: firstly, dentin forms throughout life; secondly, dentin is sensitive and can become hypersensitive to changes in temperature due to the sensory function of odontoblasts, especially when enamel recedes and dentin channels become exposed.

<span class="mw-page-title-main">Ameloblastin</span> Protein-coding gene in the species Homo sapiens

Ameloblastin is an enamel matrix protein that in humans is encoded by the AMBN gene.

<span class="mw-page-title-main">Hydroxyapatite</span> Naturally occurring mineral form of calcium apatite

Hydroxyapatite is a naturally occurring mineral form of calcium apatite with the formula Ca5(PO4)3(OH), often written Ca10(PO4)6(OH)2 to denote that the crystal unit cell comprises two entities. It is the hydroxyl endmember of the complex apatite group. The OH ion can be replaced by fluoride or chloride, producing fluorapatite or chlorapatite. It crystallizes in the hexagonal crystal system. Pure hydroxyapatite powder is white. Naturally occurring apatites can, however, also have brown, yellow, or green colorations, comparable to the discolorations of dental fluorosis.

<span class="mw-page-title-main">Nanofiber</span>

Nanofibers are fibers with diameters in the nanometer range. Nanofibers can be generated from different polymers and hence have different physical properties and application potentials. Examples of natural polymers include collagen, cellulose, silk fibroin, keratin, gelatin and polysaccharides such as chitosan and alginate. Examples of synthetic polymers include poly(lactic acid) (PLA), polycaprolactone (PCL), polyurethane (PU), poly(lactic-co-glycolic acid) (PLGA), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), and poly(ethylene-co-vinylacetate) (PEVA). Polymer chains are connected via covalent bonds. The diameters of nanofibers depend on the type of polymer used and the method of production. All polymer nanofibers are unique for their large surface area-to-volume ratio, high porosity, appreciable mechanical strength, and flexibility in functionalization compared to their microfiber counterparts.

<span class="mw-page-title-main">Biomaterial</span> Any substance that has been engineered to interact with biological systems for a medical purpose

A biomaterial is a substance that has been engineered to interact with biological systems for a medical purpose, either a therapeutic or a diagnostic one. The corresponding field of study, called biomaterials science or biomaterials engineering, is about fifty years old. It has experienced steady and strong growth over its history, with many companies investing large amounts of money into the development of new products. Biomaterials science encompasses elements of medicine, biology, chemistry, tissue engineering and materials science.

<span class="mw-page-title-main">AMELX</span> Protein-coding gene in humans

Amelogenin, X isoform is a protein that in humans is encoded by the AMELX gene. AMELX is located on the X chromosome and encodes a set of isoforms of amelogenin by alternative splicing. Amelogenin is an extracellular matrix protein involved in the process of amelogenesis, the formation of enamel on teeth.

A nerve guidance conduit is an artificial means of guiding axonal regrowth to facilitate nerve regeneration and is one of several clinical treatments for nerve injuries. When direct suturing of the two stumps of a severed nerve cannot be accomplished without tension, the standard clinical treatment for peripheral nerve injuries is autologous nerve grafting. Due to the limited availability of donor tissue and functional recovery in autologous nerve grafting, neural tissue engineering research has focused on the development of bioartificial nerve guidance conduits as an alternative treatment, especially for large defects. Similar techniques are also being explored for nerve repair in the spinal cord but nerve regeneration in the central nervous system poses a greater challenge because its axons do not regenerate appreciably in their native environment.

<span class="mw-page-title-main">Remineralisation of teeth</span>

Tooth remineralization is the natural repair process for non-cavitated tooth lesions, in which calcium, phosphate and sometimes fluoride ions are deposited into crystal voids in demineralised enamel. Remineralization can contribute towards restoring strength and function within tooth structure.

Nano-scaffolding or nanoscaffolding is a medical process used to regrow tissue and bone, including limbs and organs. The nano-scaffold is a three-dimensional structure composed of polymer fibers very small that are scaled from a Nanometer scale. Developed by the American military, the medical technology uses a microscopic apparatus made of fine polymer fibers called a scaffold. Damaged cells grip to the scaffold and begin to rebuild missing bone and tissue through tiny holes in the scaffold. As tissue grows, the scaffold is absorbed into the body and disappears completely.

<span class="mw-page-title-main">Bioceramic</span>

Bioceramics and bioglasses are ceramic materials that are biocompatible. Bioceramics are an important subset of biomaterials. Bioceramics range in biocompatibility from the ceramic oxides, which are inert in the body, to the other extreme of resorbable materials, which are eventually replaced by the body after they have assisted repair. Bioceramics are used in many types of medical procedures. Bioceramics are typically used as rigid materials in surgical implants, though some bioceramics are flexible. The ceramic materials used are not the same as porcelain type ceramic materials. Rather, bioceramics are closely related to either the body's own materials or are extremely durable metal oxides.

A fibrin scaffold is a network of protein that holds together and supports a variety of living tissues. It is produced naturally by the body after injury, but also can be engineered as a tissue substitute to speed healing. The scaffold consists of naturally occurring biomaterials composed of a cross-linked fibrin network and has a broad use in biomedical applications.

<span class="mw-page-title-main">Arginylglycylaspartic acid</span> Chemical compound

Arginylglycylaspartic acid (RGD) is the most common peptide motif responsible for cell adhesion to the extracellular matrix (ECM), found in species ranging from Drosophila to humans. Cell adhesion proteins called integrins recognize and bind to this sequence, which is found within many matrix proteins, including fibronectin, fibrinogen, vitronectin, osteopontin, and several other adhesive extracellular matrix proteins. The discovery of RGD and elucidation of how RGD binds to integrins has led to the development of a number of drugs and diagnostics, while the peptide itself is used ubiquitously in bioengineering. Depending on the application and the integrin targeted, RGD can be chemically modified or replaced by a similar peptide which promotes cell adhesion.

<span class="mw-page-title-main">Mineralized tissues</span> Biological tissues incorporating minerals

Mineralized tissues are biological tissues that incorporate minerals into soft matrices. Typically these tissues form a protective shield or structural support. Bone, mollusc shells, deep sea sponge Euplectella species, radiolarians, diatoms, antler bone, tendon, cartilage, tooth enamel and dentin are some examples of mineralized tissues.

<span class="mw-page-title-main">Peptide amphiphile</span>

Peptide amphiphiles (PAs) are peptide-based molecules that self-assemble into supramolecular nanostructures including; spherical micelles, twisted ribbons, and high-aspect-ratio nanofibers. A peptide amphiphile typically comprises a hydrophilic peptide sequence attached to a lipid tail, i.e. a hydrophobic alkyl chain with 10 to 16 carbons. Therefore, they can be considered a type of lipopeptide. A special type of PA, is constituted by alternating charged and neutral residues, in a repeated pattern, such as RADA16-I. The PAs were developed in the 1990s and the early 2000s and could be used in various medical areas including: nanocarriers, nanodrugs, and imaging agents. However, perhaps their main potential is in regenerative medicine to culture and deliver cells and growth factors.

<span class="mw-page-title-main">Surface modification of biomaterials with proteins</span>

Biomaterials are materials that are used in contact with biological systems. Biocompatibility and applicability of surface modification with current uses of metallic, polymeric and ceramic biomaterials allow alteration of properties to enhance performance in a biological environment while retaining bulk properties of the desired device.

<span class="mw-page-title-main">Decellularization</span>

Decellularization is the process used in biomedical engineering to isolate the extracellular matrix (ECM) of a tissue from its inhabiting cells, leaving an ECM scaffold of the original tissue, which can be used in artificial organ and tissue regeneration. Organ and tissue transplantation treat a variety of medical problems, ranging from end organ failure to cosmetic surgery. One of the greatest limitations to organ transplantation derives from organ rejection caused by antibodies of the transplant recipient reacting to donor antigens on cell surfaces within the donor organ. Because of unfavorable immune responses, transplant patients suffer a lifetime taking immunosuppressing medication. Stephen F. Badylak pioneered the process of decellularization at the McGowan Institute for Regenerative Medicine at the University of Pittsburgh. This process creates a natural biomaterial to act as a scaffold for cell growth, differentiation and tissue development. By recellularizing an ECM scaffold with a patient’s own cells, the adverse immune response is eliminated. Nowadays, commercially available ECM scaffolds are available for a wide variety of tissue engineering. Using peracetic acid to decellularize ECM scaffolds have been found to be false and only disinfects the tissue.

Growing teeth is a bioengineering technology with the ultimate goal to create new full molars in a person or an animal.

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