In Vitro Tests

Practice for extraction of medical plastics. A method for extraction of medical plastics in liquids that simulate body fluids. The extraction vehicle is then used for chemical or biological tests. Extraction fluids include saline, vegetable oil (sesame or cottonseed), and water. F813. Practice for direct contact cell culture evaluation of materials for medical devices. A cell culture test using ATCC L929 mouse connective tissue cells. This method or this type of cell culture method can be...

Process and Mechanism of Action

Below its boiling point of 11UC, EtO is a clear, colorless liquid. It is toxic and a suspected human carcinogen. Contact with the skin and eyes and inhalation of the vapors should be avoided. EtO is used in the pure form or mixed with N2, C02, or a non-ozone-depleting chlorofluorocarbon (GFC)-like compound (HCFCjHFC. Pure EtO and mixtures without a proven inexting compound are flammable and potentially explosive. Owing to the negative effects of CFC compounds (Freon) on the earth's ozone layer,...

Info

Acute inflammation is of relatively short duration, lasting from minutes to days, depending on the extent of injury. Its main characteristics are the exudation of fluid and plasma FIG. 2. cute inflammation with inf ammatory exudate and polymorphonu-ciear leukocytcs adjacent to the outer surface ot an ePTFE vascuiar grafe. Hcma-toxylin and eosin stain. x 140, FIG. 2. cute inflammation with inf ammatory exudate and polymorphonu-ciear leukocytcs adjacent to the outer surface ot an ePTFE vascuiar...

Lung substitutes and assist

The lungs are the body's interface with the air. They provide the means of getting oxygen into the blood and carbon dioxide out. The lungs perform their transport processes via a membrane that separates the air from the blood. As the blood cells deform to pass through the intricate and very fine capillary network, oxygen and carbon dioxide transport occur through the membrane. Failure of the lungs or their inability to carry out these functions requires artificial respiratory support in the...

Pmn

I nt ill u nosti rvc 111 an ce, Cytokine production A nil gen presentation Antibody production Antigen prese illation Cytokine production, Ail Li bod y response, mmu nosurvei 11 ance (Virus, Tumors) FIG. I. The functional elements of the immune iystem. Cells of the immune system ate produced from stem cells in the bone marrow. These cells (PMN, monocytes, etc. enter the blood and lymph, migrating to the various organs and tissues of the body where they perform their immunosurveillance function,...

Inflammation Wound Healing and the Foreign Body Response

Inflammation, wound healing, and foreign body response are generally considered as parts of the tissue or cellular host BiomatertaU Science Copyright 3 996 by Academic Press, Inc. All rights of reproduction in any form reserved. TABLE 1 Sequence of Local Events Following Implantation Acute inflammation Chronic inflammation Granulation tissue Foreign body reaction Fibrosis responses to injury. Table 1 lists the sequence of these events following injury. From a biomaterials perspective, placing a...

Noble Metals

The noble metals platinum, iridium, rhodium, gold, and palladium are generally preferred for electrical stimulation because of their low chemical reactivity and high resistance to corrosion. However, even these metals undergo dissolution during both in vitro and in vivo stimulation. In the saline environment, the metals may dissolve as ehloro-complexes such as PtCl6 2, PtCy4-, and AuO, 1', or they may form unstable surface films which will spall and leave metallic deposits in the tissue. The...

Short Term In Vivo Testing

Testing biomaterials in rabbits for primary skin irritation. A procedure to assess the irritancy of a biomaterial in contact with intact or abraded skin. This test would be indicated for surgical glove material, or skin dressings. F720. Practice for testing guinea pigs for contact allergens guinea pig maximization test. A two-stage induction procedure employing Freund's complete adjuvant and sodium lauryl sulfate, followed two weeks later by a challenge with the extract material. Ten...

Cells

Hypothesis for calcification of clinical bioprosthetic heart valves emphasizing relationships among host and implant factors, nucleation and growth of calcific nodules, and clinical failure of the device. (Reproduced with permission from F. J. Schoen et al Lab. Invest. 52 531, 1985.) Calcification on Contraceptive Intrauterine Devices Calcification of contraceptive intrauterine devices (IUD) has been suspected of causing dysfunction leading to either detachment of the device or...

Molecular Mechanisms Of Celltosurface Adhesion

Molecular mechanisms in cell-to-surface adhesion are suggested by generalizations from colloid chemistry, microbiology, biochemistry, and physics. Bacteria particles less than 1 im in size may be thought inrially to behave as in colloid systems. The following model, in the mam applicable to bacteria and in part to tissue cells, is derived from the suggestions of many authors. Microorganisms are exposed to the surface of a biomaterial, foreign body, or tissue substrata by direct contamination,...

Distance

Types of silicate glass interfaces with aqueous or physiological solutions. on top of the alkali-depleted Si02-rich film. When multivalent cations such as Al3+, Fe3+, and Ti4+ are present in the glass or solution, multiple layers form on the glass as the saturation of each cationic complex is exceeded, resulting in a type I11B surface (Fig. 6), which does not bond to tissue. A general equation describes the overall rate of change of glass surfaces and gives rise to the interfacial...

Electronic Theory

Electronic theory postulates that electronic transfer between adhesive and adherent may lead to electrostatic forces that result in high intrinsic adhesion. Such interactions may arise in certain specialized situations, but for typical adhesive-substrate interfaces, any electrical double layer generated does not contribute significantly to the observed adhesion (Kinlock 1987 Schub, and Nardin, 1994). The evidence available at present suggests that for most biological adhesives, adsorption...

Consuming vs Nonconsuming Sensors

There are at least two distinct ways in which a sensor can interact with its environment these can be called consuming and nonconsuming (Fig. 2). A nonconsuming or equilibrium sensor is one that can give a stable reading with no net transport of matter or energy between the sensor and its environment. For example, while a thermometer is approaching equilibrium it takes up or releases heat, but when it has reached its ultimate temperature it no longer directly affects the tempeature of Chemlcnl...

Adsorption Theory

This theory postulates that if intimate interfacial molecular contact is achieved, interatomic and intermolecular forces will establish a strong joint. Such forces include van der Waals and hydrogen bonds, donor acceptor bonds involving acid base interactions, and primary bond (ionic, covalent, metallic) formation (chemisorption). Numerous studies have suggested that secondary bonds (van der Waals and hydrogen bonds) alone are sufficient to establish strong bonding. However, where environmental...

Composition and characteristics of adhesive biomaterials

Most soft tissue adhesives are intended to be temporary, that is, they are removed or degrade when wound healing is sufficiently advanced for the tissue to maintain its integrity. Effective adhesion can be obtained on dry skin or wound surfaces by using wound dressing strips with acrylate-based adhesives. However, on wound surfaces that are wet with tissue fluid or blood, the adhesive must be able to be spread on such wet surfaces, provide adequate working time, develop and maintain adhesion,...

Applications Advantages and Disadvantages

Currently, the main use of this method for implants occurs in hospitals with the intraoperative steam sterilization of metallic devices. It is the method of choice for the sterilization of metallic surgical instruments and heat-resistant surgical supplies (linen drapes, dressings). A specialized form of steam sterilization is also used for many intravenous solutions. The advantages of steam sterilization are efficacy, speed, process simplicity, and lack of toxic residues. The high temperature...

Biofilms

Microorganisms in colonies on surfaces form layers two to hundreds of organisms thick composed of cellular material, extracellular polysaccharides, environmental adsorbates, and debris. This surface composite is called the biofilm or slime. In nature, biofilms accumulate to significant thicknesses and may impede flow in hydraulic systems. Most organisms within a mature microcolony are not attached to a two-dimensional surface but are fixed within the three-dimensional structure of the biofilm....

O3h Hnso3h

Represent areas that are demonstrably devoid of both epidermis and dermis, the outer and inner layers of skin, respectively. Such wounds normally close by contraction of wound edges and by synthesis of scar tissue. Previously, collagen and various glycosaminoglycans, each prepared in various forms such as powder and films, had been used to cover such deep wounds without observing a significant modification in the outcome of the wound healing process (compare the historical review of Schmitt,...

Perspectives and Possibilities in Biomaterials Science

The field of biomaterials is a young one, with perhaps 40 years of formal history. We have come from an earlier era in which research and development in biomaterials was driven by surgeon-visionary-entrepreneurs (the surgeon hero), to the 1990s where these development activities have largely been transferred to university and industrial laboratories. We are entering an era of exciting discoveries in molecular biology, cell biology, and materials science. The old-style, empirical research driven...

New Research Directions

The current interest in developing alternatives to animal testing has resulted in the development and refinement of a wide variety of in vitro assays. Cell cultures have been used for several decades for screening anticancer drugs and evaluating genotoxicity (irreversible interaction with the nucleic acids). Babich and Borenfreund (1987) have modified the elution assay for use with microtiter plates to evaluate the dose response cytotoxicity potential of alcohols, phenolic derivatives, and...

Peritoneal Dialysis

Peritoneal dialysis is carried out in the peritoneal cavity of the patient. The peritoneum is a thin membrane lining the abdominal cavity and covering the abdominal organs. It forms a closed sac. Through a cannula placed through the skin or a catheter permanently implanted, dialysate solution (about 2 liters in an adult) is infused, allowed to dwell for a designated time period, and drained. This process is repeated according to the needs of the patient. This semipermeable membrane permits...

Somf Background Concepts

Solid Organs Histology Stroma Parenchyma

FIG. 3 Photomicrographs oi histologic sections of the basic tissues. (A) Epithelium skill epidermis, cutrtilcoui surface it top . Maturation occurs by proliferation of basal cells (arrows) and their migration to the surface to eventually become nonliving keratin. H Full cross section of skin K, keratin epidermis-, and d. dermis. C) Connective tissue (boner. Vertebral trabecule (arrow) surrounded by bone marrow. (D) Muscle tissue (bean muscic), with cross-stria sons family apparent. 'Si Nerve,...

Soft Hydrogcl Contact Lenses

The soft hydrogcl contact lenses (SCL) are supple and fit snugly on the corneal surface. Because there is little tear exchange under these lenses, most of the oxygen that reaches the cornea must permeate through the lens. The oxygen permeability coefficient of hydrogel materials increases exponentially with the water content. The hydrogel lenses are made of slightly cross-linked hy-drophilic polymers and copolymers. The original hydrogel contact lens material was poly(2-hydroxyethyl...

Rigid Contact Lenses

The rigid contact lenses, as well as the FFP lenses, fit loosely on the cornea and move with the blink more or less freely over the tear film that separates the lens from the corneal surface. The mechanical properties of rigid and FFP contact lenses must be such that any flex on the lens provoked by the blink must recover instantaneously at the end of the blink. The first widely available contact lenses were made of poly-(methyl methacrylate), which is an excellent optical biomaterial in almost...

Testing Biomaterials

Lai.or, Steven M. Niemi, Sharon J. Northup, Buddy D. Ratner, Myron Spector, Brad H. Vale, and John E. Willson How can biomaterials be evaluated to determine if they are biocompatible and whether they function appropriately in the in vivo environment This section discusses testing procedures. A few general comments will clarify key themes and ideas that are common to biological testing of all biomaterials. Some biomaterials fulfill their intended function in seconds....

Hemofiltration

Hemofiltration refers to the removal of fluid from whole blood. Solute and water are removed strictly by convective flux. The standard hemodialysis membrane, however, is a poor reproduction of the filtration properties of the nephron's glomerulus. The standard hemodialysis membrane can separate from the blood solutes that are typically less than about 5,000 Da. In an effort to make the process more like that of the natural glomerulus and to duplicate the process in the natural kidney, membranes...

Extracorporeal Artificial Organs

Historically, the term extracorporeal artificial organs has been reserved for life support techniques requiring the on-line processing of blood outside the patient's body. The substitution, support, or replacement of organ functions is performed when the need is only temporary or intermittent support may be sufficient. The category of extracorporeal artificial organs does not include various other techniques which may justifiably be considered as such, such as infusion pumps or dermal patches...

Implant Sites

The primary criterion for selecting an implant site in an animal model is its similarity to the site to be employed in human use of the medical device. However, often there are limitations in the ability of certain tissues and organs in animal models to accommodate implants of a meaningful size. In assessing the appropriateness of a specific tissue as an implant site in any animal model, the healing and remodeling characteristics of the four basic types of tissue (connective tissue, muscle,...

Self Regulated

Self-regulated devices are capable of altering drug output in response to an external change and can be classified into substrate-specific and environment-specific devices. Two different types of devices are under development. In one type, the substrate modulates drug release from the device, while in the other type the substrate triggers drug release from a passive device. Modulated Devices The major driving force for developing such devices is a need to better control diabetes since it is now...

Degradative Effects of the Biological Environment on Metals and Ceramics

Williams The environment to which biomaterials are exposed during prolonged use i.e., the internal milieu of the body can be described as an aqueous medium containing various anions, cations, organic substances, and dissolved oxygen. The anions are mainly chloride, phosphate, and bicarbonate ions. The principal cations are Na , K , Ca2 , and Mg2 , but with smaller amounts of many others. The organic substances include low-molecular-weight species as well as...

Evaluation Of Tissue Reaction

The method used to evaluate the tissue reaction to any biomaterial should consider the intended use of the material and should be incorporated in the experimental design. Local responses to implanted materials can be assessed qualitatively and quantitatively by several methods, depending on the objective of the experiment. Systemic responses are also important in assessing in vivo compatibility, and are discussed elsewhere in this volume. The methods of evaluation addressed in this section are...