Misplaced Pages

#646353

78-599: Skin fibroblasts are vital in development and wound repair and they are affected by mechanical cues like tension, compression and shear pressure. Fibroblasts synthesize structural proteins, some of which are mechanosensitive and form integral part of the extracellular Matrix (ECM) e. g collagen types I, III, IV, V VI, elastin , lamin etc. In addition to the structural proteins, fibroblasts make Tumor-Necrosis-Factor - alpha (TNF-α), Transforming-Growth-Factor-beta (TGF-β) and matrix metalloproteases that plays in tissue in tissue maintenance and remodeling. Articular cartilage

156-662: A transplant material. The ability of an engineered biomaterial to induce a physiological response that is supportive of the biomaterial's function and performance is known as bioactivity. Most commonly, in bioactive glasses and bioactive ceramics this term refers to the ability of implanted materials to bond well with surrounding tissue in either osteo conductive or osseo productive roles. Bone implant materials are often designed to promote bone growth while dissolving into surrounding body fluid. Thus for many biomaterials good biocompatibility along with good strength and dissolution rates are desirable. Commonly, bioactivity of biomaterials

234-399: A biomaterial can be designed to include toxicity for an intended purpose. For example, application of toxic biomaterial is studied during in vivo and in vitro cancer immunotherapy testing. Toxic biomaterials offer an opportunity to manipulate and control cancer cells. One recent study states: "Advanced nanobiomaterials, including liposomes , polymers , and silica , play a vital role in

312-401: A biomaterial. biomaterials can be designed to replicate natural organisms, a process known as biomimetics . The structure of a biomaterial can be observed at different at different levels to better understand a materials properties and function. The arrangement of atoms and ions within a material is one of the most important structural properties of a biomaterial. The atomic structure of

390-431: A branched cytoplasm surrounding an elliptical, speckled nucleus having two or more nucleoli . Active fibroblasts can be recognized by their abundant rough endoplasmic reticulum (RER). Inactive fibroblasts, called ' fibrocytes ', are smaller, spindle-shaped, and have less RER. Although disjointed and scattered when covering large spaces, fibroblasts often locally align in parallel clusters when crowded together. Unlike

468-412: A function within the human body. The application of a specific biomaterial must combine the necessary composition, material properties, structure, and desired in vivo reaction in order to perform the desired function. Categorizations of different desired properties are defined in order to maximize functional results. Host response is defined as the "response of the host organism (local and systemic) to

546-474: A material can be viewed at different levels, the sub atomic level, atomic or molecular level, as well as the ultra-structure created by the atoms and molecules. Intermolecular forces between the atoms and molecules that compose the material will determine its material and chemical properties. The sub atomic level observes the electrical structure of an individual atom to define its interactions with other atoms and molecules. The molecular structure observes

624-406: A material may elicit little or no immune response in a given organism, and may or may not able to integrate with a particular cell type or tissue . Immuno-informed biomaterials that direct the immune response rather than attempting to circumvent the process is one approach that shows promise. The ambiguity of the term reflects the ongoing development of insights into "how biomaterials interact with

702-420: A more interactive functionality such as hydroxy-apatite coated hip implants . Biomaterials are also commonly used in dental applications, surgery, and drug delivery. For example, a construct with impregnated pharmaceutical products can be placed into the body, which permits the prolonged release of a drug over an extended period of time. A biomaterial may also be an autograft , allograft or xenograft used as

780-446: A new strategy in chemical synthesis and nanotechnology . Molecular crystals, liquid crystals, colloids, micelles, emulsions , phase-separated polymers, thin films and self-assembled monolayers all represent examples of the types of highly ordered structures, which are obtained using these techniques. The distinguishing feature of these methods is self-organization. Nearly all materials could be seen as hierarchically structured, since

858-485: A potential alternate word for biologically-produced materials such as bone, or fungal biocomposites. Additionally, care should be exercised in defining a biomaterial as biocompatible , since it is application-specific. A biomaterial that is biocompatible or suitable for one application may not be biocompatible in another. Material exploited in contact with living tissues, organisms, or microorganisms. Biomaterials can be derived either from nature or synthesized in

SECTION 10

#1733084865647

936-633: A process called epithelial-mesenchymal transition . Conversely, fibroblasts in some situations may give rise to epithelia by undergoing a mesenchymal to epithelial transition and organizing into a condensed, polarized, laterally connected true epithelial sheet. This process is seen in many developmental situations (e.g. nephron and notocord development), as well as in wound healing and tumorigenesis. Fibroblasts make collagen fibers, glycosaminoglycans , reticular and elastic fibers . The fibroblasts of growing individuals divide and synthesize ground substance. Tissue damage stimulates fibrocytes and induces

1014-599: A series of regulated tests that material must pass to be certified for use. These include the United States Pharmacopoeia IV (USP Class IV) Biological Reactivity Test and the International Standards Organization 10993 (ISO 10993) Biological Evaluation of Medical Devices. The main objective of biocompatibility tests is to quantify the acute and chronic toxicity of material and determine any potential adverse effects during use conditions, thus

1092-493: Is a hip replacement using ivory material which was first recorded in Germany 1891. Valuable criteria for viable natural biomaterials: Examples of natural biomaterials: Biopolymers are polymers produced by living organisms. Cellulose and starch , proteins and peptides , and DNA and RNA are all examples of biopolymers, in which the monomeric units, respectively, are sugars , amino acids , and nucleotides . Cellulose

1170-551: Is affected by the body's response to the foreign material. The body undergoes a cascade of processes defined under the foreign body response (FBR) in order to protect the host from the foreign material. The interactions between the device upon the host tissue/blood as well as the host tissue/blood upon the device must be understood in order to prevent complications and device failure. Tissue injury caused by device implantation causes inflammatory and healing responses during FBR. The inflammatory response occurs within two time periods:

1248-573: Is discovered, others in the same batch may be traced. Calcium sulfate (its α- and β-hemihydrates) is a well known biocompatible material that is widely used as a bone graft substitute in dentistry or as its binder. In the United States, 49% of the 250,000 valve replacement procedures performed annually involve a mechanical valve implant. The most widely used valve is a bileaflet disc heart valve or St. Jude valve. The mechanics involve two semicircular discs moving back and forth, with both allowing

1326-412: Is gauged by the surface biomineralization in which a native layer of hydroxyapatite is formed at the surface. These days, the development of clinically useful biomaterials is greatly enhanced by the advent of computational routines that can predict the molecular effects of biomaterials in a therapeutic setting based on limited in vitro experimentation. Self-assembly is the most common term in use in

1404-441: Is important. The material must be ductile for a similar reason that the tensile strength cannot be too high, ductility allows the material to bend without fracture and also prevents the concentration of stresses in the tissue when the temperature changes. The material property of toughness is also important for dental implants as well as any other rigid, load-bearing implant such as a replacement hip joint . Toughness describes

1482-399: Is in the spatial scale of the unit cell (lattice parameter) in each particular case. Molecular self assembly is found widely in biological systems and provides the basis of a wide variety of complex biological structures. This includes an emerging class of mechanically superior biomaterials based on microstructural features and designs found in nature. Thus, self-assembly is also emerging as

1560-472: Is made of a mineralized hard component (exhibits brittle fracture) and a softer organic component composed primarily of chitin . The brittle component is arranged in a helical pattern. Each of these mineral "rods" (1 μm diameter) contains chitin–protein fibrils with approximately 60 nm diameter. These fibrils are made of 3 nm diameter canals that link the interior and exterior of the shell. Biomaterials are used in: Biomaterials must be compatible with

1638-446: Is made up of porous ECM. The proteoglycans and interstitial fluids interact to give compressive force to the cartilage through negative electrostatic repulsive forces. The ion concentration difference between the extracellular and intracellular ions composition of chondrocytes result in hydrostatic pressure. During development, mechanical environment of joint determines surface and topology of the joint. In adult, moderate mechanical loading

SECTION 20

#1733084865647

1716-497: Is now known that mechanical  forces generated within cells and tissues provide regulatory signals. During the division of the fertilized oocyte , cells aggregate and the compactness between cells increases with the help of actomyosin-dependent cytoskeletal traction forces and their application to adhesive receptors in neighboring cells, thereby leading to formation of solid balls called Morula . The spindle positioning within symmetrically and asymmetrically dividing cells in

1794-454: Is required to maintain cartilage; immobilization of joint leads to loss of proteoglycans and cartilage atrophy while excess mechanical loading results in degeneration of joint. The nucleus is also responsive to mechanical signals which are relayed from the extracellular matrix through the cytoskeleton by the help of Linker of Nucleoskeleton and Cytoskeleton LINC-associated proteins like KASH and SUN. Examples of effect of mechanical responses in

1872-587: Is the Young's Modulus, E , which describes a material's elastic response to stresses . The Young's Moduli of the tissue and the device that is being coupled to it must closely match for optimal compatibility between device and body, whether the device is implanted or mounted externally. Matching the elastic modulus makes it possible to limit movement and delamination at the biointerface between implant and tissue as well as avoiding stress concentration that can lead to mechanical failure . Other important properties are

1950-403: Is the flexural rigidity, D . Flexural rigidity will determine how well the device surface can maintain conformal contact with the tissue surface, which is especially important for devices that are measuring tissue motion ( strain ), electrical signals ( impedance ), or are designed to stick to the skin without delaminating , as in epidermal electronics. Since flexural rigidity depends on

2028-458: Is the building block of the organic matrix , a triple helix with diameter of 1.5 nm. These tropocollagen molecules are intercalated with the mineral phase ( hydroxyapatite , calcium phosphate) forming fibrils that curl into helicoids of alternating directions. These " osteons " are the basic building blocks of bones, with the volume fraction distribution between organic and mineral phase being about 60/40. In another level of complexity,

2106-492: Is the connective tissue that protects bones of load-bearing joints like knee, shoulder by providing a lubricated surface. It deforms in response to compressive load, thereby reducing stress on bones. This mechanical responsiveness of articular cartilage is due to its biphasic nature; it contains both the solid and fluid phases. The fluid phase is made up of water -which contributes 80% of the wet weight – and inorganic ions e. g Sodium ion, Calcium ion and Potassium ion. The solid phase

2184-478: Is through the crystal lattice , which is a three-dimensional representation of the location of a repeating factor ( unit cell ) in the structure denoted with lattices . There are 14 different configurations of atom arrangement in a crystalline structure, and are all represented under Bravais lattices . During the formation of a crystalline structure, different impurities, irregularities, and other defects can form. These imperfections can form through deformation of

2262-503: The epigenome . Biomaterials A biomaterial is a substance that has been engineered to interact with biological systems for a medical purpose – either a therapeutic (treat, augment, repair, or replace a tissue function of the body) or a diagnostic one. The corresponding field of study, called biomaterials science or biomaterials engineering , is about fifty years old. It has experienced steady growth over its history, with many companies investing large amounts of money into

2340-439: The epithelial cells lining the body structures, fibroblasts do not form flat monolayers and are not restricted by a polarizing attachment to a basal lamina on one side, although they may contribute to basal lamina components in some situations (e.g. subepithelial myofibroblasts in intestine may secrete the α-2 chain-carrying component of the laminin , which is absent only in regions of follicle-associated epithelia which lack

2418-621: The ground substance and a variety of fibers . The composition of the ECM determines the physical properties of connective tissues. Like other cells of connective tissue, fibroblasts are derived from primitive mesenchyme . Hence, they express the intermediate filament protein vimentin , a feature used as a marker to distinguish their mesodermal origin. However, this test is not specific as epithelial cells cultured in vitro on adherent substratum may also express vimentin after some time. In certain situations, epithelial cells can give rise to fibroblasts,

Mechanobiology - Misplaced Pages Continue

2496-434: The human body " and eventually "how those interactions determine the clinical success of a medical device (such as pacemaker or hip replacement )". Modern medical devices and prostheses are often made of more than one material, so it might not always be sufficient to talk about the biocompatibility of a specific material. Surgical implantation of a biomaterial into the body triggers an organism-inflammatory reaction with

2574-427: The tensile and compressive strengths which quantify the maximum stresses a material can withstand before breaking and may be used to set stress limits that a device may be subject to within or external to the body. Depending on the application, it may be desirable for a biomaterial to have high strength so that it is resistant to failure when subjected to a load, however in other applications it may be beneficial for

2652-408: The ECM remodeling. ECM remodeling is described as changes in the ECM as a result of enzyme activity which can lead to degradation of the ECM. Immune regulation of tumors is largely determined by ECM remodeling because the ECM is responsible for regulating a variety of functions, such as proliferation, differentiation, and morphogenesis of vital organs. In many tumor types, especially those related to

2730-425: The acute phase, and the chronic phase. The acute phase occurs during the initial hours to days of implantation, and is identified by fluid and protein exudation along with a neutrophilic reaction. During the acute phase, the body attempts to clean and heal the wound by delivering excess blood, proteins, and monocytes are called to the site. Continued inflammation leads to the chronic phase, which can be categorized by

2808-420: The arrangement of atoms within the material. Finally the ultra-structure observes the 3-D structure created from the atomic and molecular structures of the material. The solid-state of a material is characterized by the intramolecular bonds between the atoms and molecules that comprise the material. Types of intramolecular bonds include: ionic bonds , covalent bonds , and metallic bonds . These bonds will dictate

2886-424: The associated healing of the damaged tissue. Depending upon the composition of the implanted material, the surface of the implant, the mechanism of fatigue, and chemical decomposition there are several other reactions possible. These can be local as well as systemic. These include immune response, foreign body reaction with the isolation of the implant with a vascular connective tissue, possible infection, and impact on

2964-437: The body express many genes that code for immune mediators and proteins. These mediators of immune response enable the cellular communication with hematopoietic immune cells. The immune activity of non-hematopoietic cells, such as fibroblasts, is referred to as “structural immunity”. In order to facilitate a fast response to immunological challenges, fibroblasts encode crucial aspects of the structural cell immune response in

3042-410: The body, and there are often issues of biocompatibility , which must be resolved before a product can be placed on the market and used in a clinical setting. Because of this, biomaterials are usually subjected to the same requirements as those undergone by new drug therapies. All manufacturing companies are also required to ensure traceability of all of their products, so that if a defective product

3120-405: The changes in spatial scale bring about different mechanisms of deformation and damage. However, in biological materials, this hierarchical organization is inherent to the microstructure. One of the first examples of this, in the history of structural biology, is the early X-ray scattering work on the hierarchical structure of hair and wool by Astbury and Woods. In bone, for example, collagen

3198-482: The codelivery of drugs and immunomodulators . These nanobiomaterial-based delivery systems could effectively promote antitumor immune responses and simultaneously reduce toxic adverse effects." This is a prime example of how the biocompatibility of a biomaterial can be altered to produce any desired function. Biodegradable biomaterials refers to materials that are degradable through natural enzymatic reactions . The application of biodegradable synthetic polymers began in

Mechanobiology - Misplaced Pages Continue

3276-516: The damage is so extreme that it is impossible to use the patient's own cells, artificial tissue cells are grown. The difficulty is in finding a scaffold that the cells can grow and organize on. The characteristics of the scaffold must be that it is biocompatible, cells can adhere to the scaffold, mechanically strong and biodegradable . One successful scaffold is a copolymer of lactic acid and glycolic acid . As discussed previously, biomaterials are used in medical devices to treat, assist, or replace

3354-485: The development of clinical-grade products. In view of the potential clinical applications of stem cell-derived tissues or primary epithelial cells, the use of human fibroblasts as an alternative to MEF feeders has been studied. Whereas the fibroblasts are usually used to maintain pluripotency of the stem cells, they can also be used to facilitate development of the stem cells into specific type of cells such as cardiomyocytes. Fibroblasts from different anatomical sites in

3432-407: The development of new products. Biomaterials science encompasses elements of medicine , biology , chemistry , tissue engineering and materials science . A biomaterial is different from a biological material, such as bone , that is produced by a biological system . However, "biomaterial" and "biological material" are often used interchangeably. Further, the word "bioterial" has been proposed as

3510-433: The early embryo is controlled by mechanical forces mediated by microtubules and actin microfilament system. Local variation in physical forces and mechanical cues such as stiffness of the ECM also control the expression of genes that give rise to the embryonic developmental process of blastulation . The loss of stiffness-controlled transcription factor Cdx leads to the ectopic expression of inner cell mass markers in

3588-543: The epithelial cells, ECM remodeling is common. Examples of TAF-derived ECM components include Tenascin and Thrombospondin-1 (TSP-1), which can be found in sites of chronic inflammation and carcinomas, respectively. Immune regulation of tumors can also occur through the TAF-derived modulators. Although these modulators may sound similar to the TAF-derived ECM components, they differ in the sense that they are responsible for

3666-422: The flow of blood as well as the ability to form a seal against backflow. The valve is coated with pyrolytic carbon and secured to the surrounding tissue with a mesh of woven fabric called Dacron (du Pont's trade name for polyethylene terephthalate ). The mesh allows for the body's tissue to grow, while incorporating the valve. Most of the time, artificial tissue is grown from the patient's own cells. However, when

3744-570: The hydroxyapatite crystals are mineral platelets that have a diameter of approximately 70 to 100 nm and thickness of 1 nm. They originally nucleate at the gaps between collagen fibrils. Similarly, the hierarchy of abalone shell begins at the nanolevel, with an organic layer having a thickness of 20 to 30 nm. This layer proceeds with single crystals of aragonite (a polymorph of CaCO 3 ) consisting of "bricks" with dimensions of 0.5 and finishing with layers approximately 0.3 mm (mesostructure). Crabs are arthropods, whose carapace

3822-409: The implanted material or device". Most materials will have a reaction when in contact with the human body. The success of a biomaterial relies on the host tissue's reaction with the foreign material. Specific reactions between the host tissue and the biomaterial can be generated through the biocompatibility of the material. The in vivo functionality and longevity of any implantable medical device

3900-424: The interactions of a biomaterial with the host living system. Important surface properties: In addition to a material being certified as biocompatible , biomaterials must be engineered specifically to their target application within a medical device . This is especially important in terms of mechanical properties which govern the way that a given biomaterial behaves. One of the most relevant material parameters

3978-514: The invasive microorganisms. Receptors on the surface of fibroblasts also allow regulation of hematopoietic cells and provide a pathway for immune cells to regulate fibroblasts. Fibroblasts, like tumor-associated host fibroblasts (TAF), play a crucial role in immune regulation through TAF-derived ECM components and modulators. TAF are known to be significant in the inflammatory response as well as immune suppression in tumors. TAF-derived ECM components cause alterations in ECM composition and initiate

SECTION 50

#1733084865647

4056-437: The laboratory using a variety of chemical approaches utilizing metallic components, polymers , ceramics or composite materials . They are often used and/or adapted for a medical application, and thus comprise the whole or part of a living structure or biomedical device which performs, augments, or replaces a natural function. Such functions may be relatively passive, like being used for a heart valve , or maybe bioactive with

4134-522: The later 1960s. Biodegradable materials have an advantage over other materials, as they have lower risk of harmful effects long term. In addition to ethical advancements using biodegradable materials, they also improve biocompatibility for materials used for implantation. Several properties including biocompatibility are important when considering different biodegradable biomaterials. Biodegradable biomaterials can be synthetic or natural depending on their source and type of extracellular matrix (ECM). Some of

4212-411: The lifespan of the implant. Graft-versus-host disease is an auto- and alloimmune disorder, exhibiting a variable clinical course. It can manifest in either acute or chronic form, affecting multiple organs and tissues and causing serious complications in clinical practice, both during transplantation and implementation of biocompatible materials. A biomaterial should perform its intended function within

4290-517: The living body without negatively affecting other bodily tissues and organs. In order to prevent unwanted organ and tissue interactions, biomaterials should be non-toxic . The toxicity of a biomaterial refers to the substances that are emitted from the biomaterial while in vivo . A biomaterial should not give off anything to its environment unless it is intended to do so. Nontoxicity means that biomaterial is: noncarcinogenic, nonpyrogenic , nonallergenic , blood compatible, and noninflammatory . However,

4368-417: The location and tissue context where they had previously resided, at least over a few generations. This remarkable behavior may lead to discomfort in the rare event that they stagnate there excessively. The main function of fibroblasts is to maintain the structural integrity of connective tissues by continuously secreting precursors of the extracellular matrix (ECM), providing all such components, primarily

4446-400: The macroscale to the nanoscale. Fibroblast A fibroblast is a type of biological cell typically with a spindle shape that synthesizes the extracellular matrix and collagen , produces the structural framework ( stroma ) for animal tissues , and plays a critical role in wound healing . Fibroblasts are the most common cells of connective tissue in animals. Fibroblasts have

4524-491: The macrostructure reveals properties such as cavities , porosity , gas bubbles, stratification , and fissures . The material's strength and elastic modulus are both independent of the macrostructure. Biomaterials can be constructed using only materials sourced from plants and animals in order to alter, replace, or repair human tissue/organs. Use of natural biomaterials were used as early as ancient Egypt, where indigenous people used animal skin as sutures. A more modern example

4602-419: The material to be low strength. There is a careful balance between strength and stiffness that determines how robust to failure the biomaterial device is. Typically, as the elasticity of the biomaterial increases, the ultimate tensile strength will decrease and vice versa. One application where a high-strength material is undesired is in neural probes ; if a high-strength material is used in these applications

4680-416: The material's ability to deform under applied stress without fracturing and having a high toughness allows biomaterial implants to last longer within the body, especially when subjected to large stress or cyclically loaded stresses , like the stresses applied to a hip joint during running. For medical devices that are implanted or attached to the skin, another important property requiring consideration

4758-719: The mechanical basis of tissue regulation may also lead to development of improved medical devices, biomaterials , and engineered tissues for tissue repair and reconstruction. Known contributors to cellular mechanotransduction are a growing list and include stretch-activated ion channels , caveolae , integrins , cadherins , growth factor receptors, myosin motors, cytoskeletal filaments, nuclei , extracellular matrix, and numerous other signaling molecules. Endogenous cell-generated traction forces also contribute significantly to these responses by modulating tensional prestress within cells, tissues, and organs that govern their mechanical stability, as well as mechanical signal transmission from

SECTION 60

#1733084865647

4836-511: The modern scientific community to describe the spontaneous aggregation of particles (atoms, molecules, colloids , micelles , etc.) without the influence of any external forces. Large groups of such particles are known to assemble themselves into thermodynamically stable, structurally well-defined arrays, quite reminiscent of one of the seven crystal systems found in metallurgy and mineralogy (e.g., face-centered cubic, body-centered cubic, etc.). The fundamental difference in equilibrium structure

4914-493: The most commonly-used biocompatible materials (or biomaterials) are polymers due to their inherent flexibility and tunable mechanical properties . Medical devices made of plastics are often made of a select few including: cyclic olefin copolymer (COC), polycarbonate (PC), polyetherimide (PEI), medical grade polyvinylchloride (PVC), polyethersulfone (PES), polyethylene (PE), polyetheretherketone (PEEK) and even polypropylene (PP). To ensure biocompatibility , there are

4992-403: The myofibroblast lining). Fibroblasts can also migrate slowly over substratum as individual cells, again in contrast to epithelial cells. While epithelial cells form the lining of body structures, fibroblasts and related connective tissues sculpt the "bulk" of an organism. The life span of a fibroblast, as measured in chick embryos, is 57 ± 3 days. Fibroblasts and fibrocytes are two states of

5070-468: The nucleus involve: The embryo is formed by self-assembly through which cells differentiate into tissues performing specialized functions. It was previously believed that only chemical signals give cues that control spatially oriented changes in cell growth, differentiation and fate switching that mediate morphogenetic controls. This is based on the ability of chemical signals to induce biochemical responses like tissue patterning in distant cells. However, it

5148-519: The physical and chemical properties of the material, as well as determine the type of material ( ceramic , metal , or polymer ). The microstructure of a material refers to the structure of an object, organism, or material as viewed at magnifications exceeding 25 times. It is composed of the different phases of form, size, and distribution of grains, pores, precipitates, etc. The majority of solid microstructures are crystalline , however some materials such as certain polymers will not crystallize when in

5226-451: The physiochemical properties of the tissue that the material is replacing. They are mechanical properties that are generated from a material's atomic and molecular construction. Important bulk properties: Surface properties refers to the chemical and topographical features on the surface of the biomaterial that will have direct interaction with the host blood/tissue. Surface engineering and modification allows clinicians to better control

5304-412: The presence of monocytes, macrophages, and lymphocytes. In addition, blood vessels and connective tissue form in order to heal the wounded area. Biocompatibility is related to the behavior of biomaterials in various environments under various chemical and physical conditions. The term may refer to specific properties of a material without specifying where or how the material is to be used. For example,

5382-418: The production of fibroblasts. Besides their commonly known role as structural components, fibroblasts play a critical role in an immune response to a tissue injury. They are early players in initiating inflammation in the presence of invading microorganisms. They induce chemokine synthesis through the presentation of receptors on their surface. Immune cells then respond and initiate a cascade of events to clear

5460-553: The same cells, the former being the activated state, the latter the less active state, concerned with maintenance and tissue metabolism. Currently, there is a tendency to call both forms fibroblasts. The suffix "-blast" is used in cellular biology to denote a stem cell or a cell in an activated state of metabolism . Fibroblasts are morphologically heterogeneous with diverse appearances depending on their location and activity. Though morphologically inconspicuous, ectopically transplanted fibroblasts can often retain positional memory of

5538-445: The solid state. Crystalline structure is the composition of ions, atoms, and molecules that are held together and ordered in a 3D shape. The main difference between a crystalline structure and an amorphous structure is the order of the components. Crystalline has the highest level of order possible in the material where amorphous structure consists of irregularities in the ordering pattern. One way to describe crystalline structures

5616-403: The solid, rapid cooling, or high energy radiation. Types of defects include point defects, line defects, as well as edge dislocation. Macrostructure refers to the overall geometric properties that will influence the force at failure, stiffness, bending, stress distribution, and the weight of the material. It requires little to no magnification to reveal the macrostructure of a material. Observing

5694-399: The tests required for a given material are dependent on its end-use (i.e. blood, central nervous system, etc.). Two properties that have a large effect on the functionality of a biomaterial is the surface and bulk properties . Bulk properties refers to the physical and chemical properties that compose the biomaterial for its entire lifetime. They can be specifically generated to mimic

5772-481: The thickness of the material, h , to the third power ( h ), it is very important that a biomaterial can be formed into thin layers in the previously mentioned applications where conformality is paramount. The molecular composition of a biomaterial determines the physical and chemical properties of a biomaterial. These compositions create complex structures that allow the biomaterial to function, and therefore are necessary to define and understand in order to develop

5850-421: The tidal volumes of mechanical ventilators reduces morbidity and death in patients with acute lung injury. Expandable stents physically prevent coronary artery constriction. Tissue expanders increase the skin area available for reconstructive surgery. Surgical tension application devices are used for bone fracture healing, orthodontics, cosmetic breast expansion and closure of non-healing wounds. Insights into

5928-546: The tissue will always fail before the device does (under applied load ) because the Young's Modulus of the dura mater and cerebral tissue is on the order of 500 Pa . When this happens, irreversible damage to the brain can occur, thus the biomaterial must have an elastic modulus less than or equal to brain tissue and a low tensile strength if an applied load is expected. For implanted biomaterials that may experience temperature fluctuations , e.g., dental implants , ductility

6006-482: The trophectoderm, and the pluripotent transcription factor, Oct-4 may be negatively expressed, thereby inducing lineage switching. This cell fate switching is regulated by the mechanosensitive hippo pathway The effectiveness of many of the mechanical therapies already in clinical use shows how important physical forces can be in physiological control. Several examples illustrate this point. Pulmonary surfactant promotes lung development in premature infants; modifying

6084-584: The variation and turnover of the ECM. Cleaved ECM molecules can play a critical role in immune regulation. Proteases like matrix metalloproteineases and the uPA system are known to cleave the ECM. These proteases are derived from fibroblasts. Mouse embryonic fibroblasts (MEFs) are often used as supportive "feeder cells" in research using human embryonic stem cells, induced pluripotent stem cells and primary epithelial cell culture. However, many researchers are trying to phase out MEFs in favor of culture media with precisely defined ingredients in order to facilitate

#646353