Artificial corneas

In order to achieve the firm fixation of the artificial cornea to host tissues, composites of collagen-immobilized poly(vinyl alcohol) hydrogel with hydroxyapatite were synthesized by a hydroxyapatite particles kneading method. The preparation method, characterization, and the results of corneal cell adhesion and proliferation on the composite material were studied. PVA-COL-HAp composites were successfully synthesized. A micro-porous structure of the PVA-COL-HAp could be introduced by hydrochloric acid treatment and the porosity could be controlled by the pH of the hydrochloric acid solution, the treatment time, and the crystallinity of the HAp particles. Chick embryonic keratocyto-like cells were well attached and proliferated on the PVA-COL-HAp composites. This material showed potential for keratoprosthesis application. Further study such as a long-term animal study is now required [241]. 

In the biomedical area, SPHs and SPH composites can be used to make various biomedical devices, such as artificial pancreas, artificial cornea, and artihcial skin, articular cartilage, soft tissue substitutes, cell growth substrates in tissue engineering, burn dressings, surgical augmentation of the female breast, or hemoperfusion in blood detoxification and in the treatment of uremia. 

Teflon was introduced to the public in 1960 when the first Teflon-coated muffin pans and frying pans were sold. Like many new materials, problems were encountered. Bonding to the surfaces was uncertain at first. Eventually the bonding problem was solved. Teflon is now used for many other applications including acting as a biomedical material in artificial corneas, substitute bones for nose, skull, hip, nose, and knees ear parts, heart valves, tendons, sutures, dentures, and artificial tracheas. It has also been used in the nose cones and heat shield for space vehicles and for their fuel tanks. 

Pino, M., Stingelin, N., and Tanner, K.E. (2008) Nucleation and growth of apatite on NaOH-treated PEEK, HDPE and UHMWPE for artificial cornea materials. Acta Biomater., 4 (6), 1827-1836. 

In the field of medicine, biomimetic solutions and products span the range from externally worn biomimetic devices that augment the function of sensory organs such as hearing aids and artificial corneas to implantable biomimetic devices. Implantable devices function as (i) simple physical replacements including silicone implants used in cosmetology, dentures and dental implants, and artificial... 

Other biomedical applications of polymers include sustained and controlled drug delivery formulations for implantation, transdermal and trans-cornealuses, intrauterine devices, etc. (6, 7). Major developments have been reported recently on the use of biomaterials for skin replacement (8), reconstruction of vocal cords (9), ophthalmic applications such as therapeutic contact lenses, artificial corneas, intraocular lenses, and vitreous implants (10), craniofacial, maxillofacial, and related replacements in reconstructive surgery (I), and neurostimulating and other electrical-stimulating electrodes (I). Orthopedic applications include artificial tendons (II), prostheses, long bone repair, and articular cartilage replacement (I). Finally, dental materials and implants (12,13) are also often considered as biomaterials. 

Contact lenses are the most common polymer product in ophthalmology. The basic requirements for this type of materials are (T)excellent optical properties with a refractive index similar to cornea good wettability and oxygen permeability ( ) biologically inert, degradation resistant and not chemically reactive to the transfer area ( ) with certain mechanical strength for intensive processing and stain and precipitation prevention. The common used contact lens material includes poly-P-hydroxy ethyl methacrylate, poly-P-hydroxy ethyl methacrylate-N-vinyl pyrrolidone, poly-P-hydroxy ethyl methacrylate, Poly-P-hydroxy ethyl methacrylate - methyl amyl acrylate and polymethyl methacrylate ester-N-vinyl pyrrolidone, etc. The artificial cornea can be prepared by silicon rubber, poly methyl... 

This is almost the same in the medical field. The current quahty of care could not be achieved without plastic to which no one pays attention blood bags, heart valves, prostheses, artificial corneas, capsule medication, etc. Once again, if plastics are the most effective materials, it is because they possess, unlike other materials, all the properties required in medicine exceptional sealing, perfect hygienic barrier, lightweight, flexibility, plasticity, durability, transparency, compatibility with other materials and low cost. 

Another ophthalmologic application of polymeric prostheses is the artificial cornea or keratoprosthesis. This device has been developed for more than a century, starting with the work of Heusser who was the first to implant artificial corneas in patients in 1859 [189], However, it was not until after World War II that researchers noticed that PMMA particles were well tolerated in patient eyes [190]. Ever since, other polymeric materials such as nylon, PU, and PTFE... 

I. J. Constable, G.J. Crawford, Interpenetrating polymer network (IPN) as a permanent joint between the elements of a new type of artificial cornea, J. Biomed. Mater. Res. 28 (1994) 745-753. 

J. Shimazaki, J. Tanaka, K. Tsubota, Amniotic membrane immobilized poly(vinyl alcohol) hybrid polymer as an artificial cornea scaffold that supports a stratified and differentiated corneal epithelium, J. Biomed. Mater. Res. B 81 (2007) 201-206. 

Y.X. Huang, Q.H. Li, An active artificial cornea with the function of inducing new corneal tissue generation in vivo—a new approach to corneal tissue engineering, Biomed. Mater. 2 (2007) S121-S125. 

Wang JH, Gao C, Zhang YS, Wan YZ (2010) Preparation and in vitro characterization of BC/PVA hydrogel composite for its potential use as artificial cornea biomaterial. Mater Sci Eng C Mater Biol Appl 30 214—218... 

These multifilaments are used for medical triplications like scular grafts, ligamoit and artificial cornea. The artificial cornea is presented in detail. 

The polymer material used for the artificial cornea was Solef 1008/0001 and for the cell tests 1006/0001 produced by Solvay-Solexis S.A., Tavaux, France. The melt spinning trials were performed at a bicomponent plant (Foumd Polymertechnik GbmH, Alfter-Impekoven, Germany, Figure 1). 

Production of flat fabrics and branched tubular structures with various geometries can be produced at the RWTH-ITA with the help of a special double-needle-bar Raschel Machine (Figure 3, Type DR 16 EEC/EAC Karl Mayer Textilmaschinenfabrik GmbH, Oberfaausen, Germany). Fields of application are e.g. keratoprosthesis (artificial cornea), vascular grafts, heart-valves, hernia-meshes and stents. 

In foe following two projects involving PVDF as material for medical qiplication are presented. These projects are in different stage of development The iBist jnoject is foe development of an artificial cornea (keratoprosthesis). This prosthesis was already in clinical trial and stated its functionality and therefore is ready to be launched. The second project is a basic study in early stage. Here the aim is a fundamental understanding of the influence of different PVDF fibre structures on cell adhesion. 

Figure 4 Artificial cornea made fiom PVDF fibres Clinical tried... 

PVDF is a suitable polymer for plication in medical textiles. At the Institut fitr Textiltechnik RWTH Aachen University PVDF can be processed from polymer to the final medical tactile. An artificial cornea (keratoprosthesis) out of PVDF was produced in close cooperation with the University Hospital of RWTH Aachen University (Universithtsklinikum Aachen) and other Institutes. This prosthesis was tested and saved die eyesight of a patient. 

Lin R, Mao X, Yu Q, Tan B. Preparation of bioactive nano-hydroxyapatite coating for artificial cornea. Curr Appl Phys 2007 7(l) E85-9. 

Plunkett s Teflon remained a military secret until after the war, when it became a modern miracle. It has been used to coat frying pans and seal plumbing joints. Teflon is one of the few artificial materials that the body tolerates, and it has been used for artificial corneas, bones, joints, tracheas, heart valves, tendons, bile ducts, and dentures. The United States is even said to have produced a Teflon President. 

A study conducted by Wang et al. employed the use of PVA-BC produced by freeze-thawing as a composite material for use as an artificial cornea replacement. 

Chirila T, Hicks C, Dalton P, Vijayasekaran S, Lou X, Hong Y, Qayton A, Ziegelaar B, Fitton J, Flatten S et al (1998) Artificial cornea. Prog Polym Sci 23 447-473... 

Keratoprostheses or artificial corneas have been developed for restoring minimal comeal function [104]. However, most of these devices are manufactured from synthetic materials that are not bioresorbable and are therefore outside the scope of this review. In addition, their use is reserved for end-stage disease. 

Fluorocarbons, In artificial cornea, blood vessels, heart-valve coatings, reconstructive surgery, bone substitution. 

Furthermore, the properties of BC, namely its favorable mechanical properties, biocompatibility, in situ moldability and porosity (that favors cell prohferation), gives BC excellent perspectives as scaffold for tissue engineering. Several works have focused on designing ideal biomedical devices from BC, such as artificial blood vessels [8, 71], artificial cornea [72], heart valve prosthesis [73], artificial bone [74] and artificial cartilage [70,75]. 

TGF-P2 PDMS Controlling the growth of corneal epithehal cells (artificial cornea) 288... 

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