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,...

Who writes standards

In the United States, voluntary consensus standards are developed by a number of organizations. In the medical electronics, sterilization, vascular prostheses, and cardiac valve areas, most standards are developed by committees within the Association for the Advancement of Medical Instrumentation (AAM1). In the implant materials and implants area, most standards are set by ASTM Committee F-4 on medical and surgical materials and devices. These documents may then be reviewed and accepted by the...

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....

Info

PMN, monocytes, B cells respiratory burst activity B cells, monocytes secre-tion of factor I, respiratory burst activity leads to a variety of responses, including chemotaxis of these cells into an inflammatory locus activation of the cells to release the contents of several types of secretory vesicles and produce reactive oxygen species that mediate cell killing increased expression of CR1, CR3, and LFA-1, resulting in cellular hyperadherence and the production of other mediators such as...

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...

Host Reactions To Biomaterials And Their Evaluation

Contents released htstam ine, etc. FIG. 3. Types of hypersensitivity reactions. FIG. 3. Types of hypersensitivity reactions. body are present in the circulation at the same time, forming immune complexes that can lodge in the walls of blood vessels. These reactions are unlikely for biomaterials applications except for slowly releasing drug delivery and biod gradation systems. Type IV hypersensitivity reactions do not involve the production of antibody, but...