Nanotopography

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Nanotopography refers to specific surface features which form or are generated at the nanoscopic scale. While the term can be used to describe a broad range of applications ranging from integrated circuits to microfluidics, in practice it typically applied to sub-micron textured surfaces as used in biomaterials research.

Contents

In nature

Several functional nanotopographies have been identified in nature. Certain surfaces like that of the lotus leaf have been understood to apply nanoscale textures for abiotic processes such as self-cleaning. [1] Bio-mimetic applications of this discovery have since arrived in consumer products. In 2012, it was recognized that nanotopographies in nature are also used for antibiotic purposes. The wing of the cicada, the surface of which is covered in nanoscale pillars, induces lysis of bacteria. While the nano-pillars were not observed to prevent cell adhesion, they acted mechanistically to stretch microbial membranes to breakage. In vitro testing of the cicada wing demonstrated its efficacy against a variety of bacterial strains. [2]

Manufacturing

Numerous technologies are available for the production of nanotopography. High-throughput techniques include plasma functionalization, abrasive blasting, and etching. Though low cost, these processes are limited in the control and replicability of feature size and geometry. [3] Techniques enabling greater feature precision exist, among them electron beam lithography and particle deposition, but are slower and more resource intensive by comparison. Alternatively, processes such as molecular self-assembly can be utilized which provide an enhanced level of production speed and feature control.

Applications to medicine

Though the effects of nanotopography on cell behavior have only been recognized since 1964, some of the first practical applications of the technology are being realized in the field of medicine. [4] Among the few clinical applications is the functionalization of titanium implant surfaces with nanotopography, generated with submersion etching and sand blasting. This technology has been the focal point of a diverse body of research aimed at improving post-operative integration of certain implant components. The determinant of integration varies, but as most titanium implants are orthopedics-oriented, osseointegration is the dominant aim of the field.

Applications to cell engineering

Nanotopography is readily applied to cell culture and has been shown to have a significant impact on cell behavior across different lineages. [4] Substrate features in the nanoscale regime down to the order of 9 nm are able to retain some effect. Subjected solely to topographical cues, a wide variety of cells demonstrate responses including changes in cell growth and gene expression. [5] Certain patterns are able to induce stem cells to differentiate down specific pathways. [6] Notable results include osteogenic induction in the absence of media components [7] as well as near-total cell alignment as seen in smooth muscle. [8] The potential of topographical cues to fulfill roles otherwise requiring xeno-based media components offers high translatability to clinical applications, as regulation and cost related to animal-derived products constitutes a major roadblock in a number of cell-related technologies.

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Tissue engineering Biomedical engineering discipline

Tissue engineering is a biomedical engineering discipline that uses a combination of cells, engineering, materials methods, and suitable biochemical and physicochemical factors to restore, maintain, improve, or replace different types of biological tissues. Tissue engineering often involves the use of cells placed on tissue scaffolds in the formation of new viable tissue for a medical purpose but is not limited to applications involving cells and tissue scaffolds. While it was once categorized as a sub-field of biomaterials, having grown in scope and importance it can be considered as a field of its own.

Dental implant Surgical component that interfaces with the bone of the jaw

A dental implant is a prosthesis that interfaces with the bone of the jaw or skull to support a dental prosthesis such as a crown, bridge, denture, or facial prosthesis or to act as an orthodontic anchor. The basis for modern dental implants is a biologic process called osseointegration, in which materials such as titanium or zirconia form an intimate bond to bone. The implant fixture is first placed so that it is likely to osseointegrate, then a dental prosthetic is added. A variable amount of healing time is required for osseointegration before either the dental prosthetic is attached to the implant or an abutment is placed which will hold a dental prosthetic/crown.

Osseointegration is the direct structural and functional connection between living bone and the surface of a load-bearing artificial implant. A more recent definition defines osseointegration as "functional ankylosis ", where new bone is laid down directly on the implant surface and the implant exhibits mechanical stability. Osseointegration has enhanced the science of medical bone and joint replacement techniques as well as dental implants and improving prosthetics for amputees.

Bioglass 45S5

Bioglass 45S5 or calcium sodium phosphosilicate, is a bioactive glass specifically composed of 45 wt% SiO2, 24.5 wt% CaO, 24.5 wt% Na2O, and 6.0 wt% P2O5. Typical applications of Bioglass 45S5 include: bone grafting biomaterials, repair of periodontal defects, cranial and maxillofacial repair, wound care, blood loss control, stimulation of vascular regeneration, and nerve repair.

Plasma cleaning

Plasma cleaning is the removal of impurities and contaminants from surfaces through the use of an energetic plasma or dielectric barrier discharge (DBD) plasma created from gaseous species. Gases such as argon and oxygen, as well as mixtures such as air and hydrogen/nitrogen are used. The plasma is created by using high frequency voltages to ionise the low pressure gas, although atmospheric pressure plasmas are now also common.

Cardiomyoplasty is a surgical procedure in which healthy muscle from another part of the body is wrapped around the heart to provide support for the failing heart. Most often the latissimus dorsi muscle is used for this purpose. A special pacemaker is implanted to make the skeletal muscle contract. If cardiomyoplasty is successful and increased cardiac output is achieved, it usually acts as a bridging therapy, giving time for damaged myocardium to be treated in other ways, such as remodeling by cellular therapies.

Foreign body reaction Medical condition

A foreign body reaction (FBR) is a typical tissue response to a foreign body within biological tissue. It usually includes the formation of a foreign body granuloma. Tissue-encapsulation of an implant is an example, as is inflammation around a splinter. Foreign body granuloma formation consists of protein adsorption, macrophages, multinucleated foreign body giant cells, fibroblasts, and angiogenesis. It has also been proposed that the mechanical property of the interface between an implant and its surrounding tissues is critical for the host response.

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.

Sp7 transcription factor Protein-coding gene in the species Homo sapiens

Transcription factor Sp7, also called osterix (Osx), is a protein that in humans is encoded by the SP7 gene. It is a member of the Sp family of zinc-finger transcription factors It is highly conserved among bone-forming vertebrate species It plays a major role, along with Runx2 and Dlx5 in driving the differentiation of mesenchymal precursor cells into osteoblasts and eventually osteocytes. Sp7 also plays a regulatory role by inhibiting chondrocyte differentiation maintaining the balance between differentiation of mesenchymal precursor cells into ossified bone or cartilage. Mutations of this gene have been associated with multiple dysfunctional bone phenotypes in vertebrates. During development, a mouse embryo model with Sp7 expression knocked out had no formation of bone tissue. Through the use of GWAS studies, the Sp7 locus in humans has been strongly associated with bone mass density. In addition there is significant genetic evidence for its role in diseases such as Osteogenesis imperfecta (OI).

Per-Ingvar Brånemark

Per-Ingvar Brånemark was a Swedish physician and research professor, acknowledged as the "father of modern dental implantology". The Brånemark Osseointegration Center (BOC), named after its founder, was founded in 1989 in Gothenburg, Sweden.

Nano-scaffolding 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.

Bioceramic

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.

Arginylglycylaspartic acid 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.

Surface modification of biomaterials with proteins

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.

Titanium biocompatibility

Titanium was first introduced into surgeries in the 1950s after having been used in dentistry for a decade prior. It is now the metal of choice for prosthetics, internal fixation, inner body devices, and instrumentation. Titanium is used from head to toe in biomedical implants. One can find titanium in neurosurgery, bone conduction hearing aids, false eye implants, spinal fusion cages, pacemakers, toe implants, and shoulder/elbow/hip/knee replacements along with many more. The main reason why titanium is often used in the body is due to titanium's biocompatibility and, with surface modifications, bioactive surface. The surface characteristics that affect biocompatibility are surface texture, steric hindrance, binding sites, and hydrophobicity (wetting). These characteristics are optimized to create an ideal cellular response. Some medical implants, as well as parts of surgical instruments are coated with titanium nitride (TiN).

A simulated body fluid (SBF) is a solution with an ion concentration close to that of human blood plasma, kept under mild conditions of pH and identical physiological temperature. SBF was first introduced by Kokubo et al. in order to evaluate the changes on a surface of a bioactive glass ceramic. Later, cell culture media, in combination with some methodologies adopted in cell culture, were proposed as an alternative to conventional SBF in assessing the bioactivity of materials.

Treena Livingston Arinzeh is Professor of Biomedical Engineering at New Jersey Institute of Technology in Newark, New Jersey. She is known for her research on adult stem-cell therapy. Arinzeh takes part in the American Chemical Society's Project Seeds program, opening up her lab for high school students from economically disadvantaged backgrounds for summer internships.

Matthew John Dalby FRSE is Professor of Cell Engineering at the University of Glasgow. His research is focused on mesenchymal stem cell interactions with nanotopography, with particular focus on the use of metabolomics, to study mechanotransduction.

Titanium foams exhibit high specific strength, high energy absorption, excellent corrosion resistance and biocompatibility. These materials are ideally suited for applications within the aerospace industry. An inherent resistance to corrosion allows the foam to be a desirable candidate for various filtering applications. Further, titanium's physiological inertness makes its porous form a promising candidate for biomedical implantation devices. The largest advantage in fabricating titanium foams is that the mechanical and functional properties can be adjusted through manufacturing manipulations that vary porosity and cell morphology. The high appeal of titanium foams is directly correlated to a multi-industry demand for advancement in this technology.

A root-analog dental implant (RAI) – also known as a truly anatomic dental implant, or an anatomical/custom implant – is a medical device to replace one or more roots of a single tooth immediately after extraction. In contrast to common titanium screw type implants, these implants are custom-made to exactly match the extraction socket of the specific patient. Thus there is usually no need for surgery.

References

  1. ↑ Feng, L; et al. (2002). "Super-Hydrophobic Surfaces: From Natural to Artificial". Advanced Materials. 14 (24): 1857–1860. doi:10.1002/adma.200290020. S2CID   137276048.
  2. ↑ Ivanova, Elena P.; Hasan, Jafar; Webb, Hayden K.; Truong, Vi Khanh; Watson, Gregory S.; Watson, Jolanta A.; Baulin, Vladimir A.; Pogodin, Sergey; Wang, James Y.; Tobin, Mark J.; Löbbe, Christian; Crawford, Russell J. (2012). "Natural Bactericidal Surfaces: Mechanical Rupture of Pseudomonas aeruginosa Cells by Cicada Wings". Small. 8 (16): 2489–2494. doi:10.1002/smll.201200528. ISSN   1613-6810. PMID   22674670.
  3. ↑ Stevens, B; et al. (2008). "A review of materials, fabrication methods, and strategies used to enhance bone regeneration in engineered bone tissues". Journal of Biomedical Materials Research Part B: Applied Biomaterials. 85 (2): 573–582. doi:10.1002/jbm.b.30962. PMID   17937408.
  4. 1 2 Curtis, A.S.G.; Varde M (1964). "Control of cell behavior: topological factors". Journal of the National Cancer Institute. 33 (1): 15–26. doi:10.1093/jnci/33.1.15. PMID   14202300.
  5. ↑ Le Guehennec, L; et al. (2007). "Surface treatments of titanium dental implants for rapid osseointegration". Dental Materials. 23 (7): 844–854. doi:10.1016/j.dental.2006.06.025. PMID   16904738.
  6. ↑ McNamara, L. E.; McMurray, R. J.; Biggs, M. J. P.; Kantawong, F.; Oreffo, R. O. C.; Dalby, M. J. (2010). "Nanotopographical Control of Stem Cell Differentiation". Journal of Tissue Engineering. 1 (1): 120623. doi:10.4061/2010/120623. ISSN   2041-7314. PMC   3042612 . PMID   21350640.
  7. ↑ Dalby, Matthew J.; Gadegaard, Nikolaj; Tare, Rahul; Andar, Abhay; Riehle, Mathis O.; Herzyk, Pawel; Wilkinson, Chris D. W.; Oreffo, Richard O. C. (2007). "The control of human mesenchymal cell differentiation using nanoscale symmetry and disorder". Nature Materials. 6 (12): 997–1003. Bibcode:2007NatMa...6..997D. doi:10.1038/nmat2013. ISSN   1476-1122. PMID   17891143.
  8. ↑ Yim, Evelyn K.F.; Darling, Eric M.; Kulangara, Karina; Guilak, Farshid; Leong, Kam W. (2010). "Nanotopography-induced changes in focal adhesions, cytoskeletal organization, and mechanical properties of human mesenchymal stem cells". Biomaterials. 31 (6): 1299–1306. doi:10.1016/j.biomaterials.2009.10.037. ISSN   0142-9612. PMC   2813896 . PMID   19879643.
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