Notes: This review gives a survey of the polarographic and voltammetric behavior of selected pharmaceuticals and substances of pharmaceutical relevance of various ring sizes (3-7, 14-membered rings, polyring drugs), besides macrocyclic compounds and their determination by polarography, voltammetry, and liquid chromatography-electrochemical detection (HPLC-EC) in the practical laboratory.

Notes: Various penems, structurally closely related carbapenems, and the intermediate 4-acetoxyazetidin-2-one were studied by direct current sampled dc, differential pulse polarography (DPP), cyclic voltammetry, and ac tensammetry. Optimum pH ranges for the determination of 4-acetoxyazetidin-2-one and the various penems are discussed. In Britton - Robinson buffer (BRP) penems exhibit (pH 3) one stable reduction wave, which can be exploited analytically. Carbapenems exhibit stability problems in BRP (pH 3). They can be determined after conversion by hydrolysis into a stable imine form. Useful linear concentration ranges are 10 to 140 μg/mL for 4-acetoxyazetidin-2-one and 20 to 170 and 0.5 to 70 μg/mL for penems using dc polarography and DPP, respectively. The precision of the proposed analytical methods is acceptable, with relative standard deviations around 2.5% for the assay of 4-acetoxyazetidin-2-one and 2.5 and 2-5% for the penem and carbapenem, respectively.

Notes: The state of the art of the electrochemistry of α-, β-, and γ-cyclodextrins (CDs) and cyclodextrin inclusion complexes and their polarographic and voltammetric assay are reviewed. The polarographic and voltammetric determination of physicochemical parameters of CD inclusion complexes are discussed. Practical applications of adsorption and inclusion effects for electroanalytical purposes are presented future prospects are discussed, and 95 references are given.

Notes: Slowly but inexorably the commodity materials that constitute over 95% of implantable devices are being withdrawn from the medical market. U.S. manufacturers operate on accumulated reserves and therefore are reluctant to say precisely when they will stop fabrication. Nonetheless, “thousands and perhaps millions of people [are] at risk of not being able to receive the most commonplace medical treatments1: vascular grafts, cardiac valves, hip joint prostheses, hydrocephalus shunts.”What is the problem? Companies that supply materials for, or components of, medical devices have stopped selling these essential ingredients to U.S. manufacturers of medical devices. Manufacturers, who typically have maintained large stocks since the unit cost of procuring raw materials is low compared to that of validating each new batch, are approaching the end of their reserves. The suppliers (typically multinational chemical companies one to three orders of magnitude larger than device manufacturers) have made the eminently rational decision to exit the U.S. market because they have been joined in expensive lawsuits related to allegedly defective products, such as temporomandibular joint (TMJ) prostheses and silicone breast implants. U.S. legal precedence allows an individual who has suffered bodily injury from a commercial product to sue all parties involved in the manufacturing of the product.2 In the case of medical devices, this doctrine has incriminated the suppliers of standard commodity materials, such as Dacron, Teflon, Delrin, and Silastic as well as standard engineering components used in the fabrication of medical devices.Suing DuPont or Dow Chemical for the failure of a prosthetic TMJ or a breast implant is a bit like suing U.S. Steel in the case of a car crash, or Texaco in the case of an automobile fire. Guilt by association. U.S. Steel supplied the raw metal from which the automobile was fashioned and Texaco the gasoline that fueled the fire. Similarly, Dacron yarn is essential for weaving or knitting large-diameter vascular grafts, Silastic is still the material for choice for constructing hydrocephalus shunts, and Teflon powder is critical to the manufacture of pacemaker batteries. None of these materials is the device. Because each implant contains only a few cents worth of any of these polymers, the sale of polymers to medical-device manufacturers represents an infinitesimal part of the market for polyethylene terephtalate, silicone elastomers, or polytetra-fluoroethylene. For example, the total sales of Teflon for TMJ implants were less than $2,000. In contrast, the annual cost to DuPont of defending itself against the lawsuits related to the TMJ (which it has won in all cases) has been hovering around $8 million!Therefore we have a perfectly understandable reason for American suppliers to refuse to deal any further with the U.S. medical-device industry, for overseas suppliers to adopt the same line of conduct, and for U.S. manufacturers to move fabrication abroad and de-emphasize innovation in the U.S. As a result, tens of thousands, and later perhaps millions, of U.S. citizens are at risk of not receiving some commonplace and effective medical treatments.3In 1994, 14 specialty societies concerned with the availability of materials for medical devices formed the “Biomaterials Availability Coalition” to investigate means to avoid the looming crisis. The coalition's objective was to assist in the formulation of legislative remedies, inform the scientific and clinical community, and be the advocate of patients. At its behest, a Biomaterials Availability Act was introduced in Congress in 1995, derailed, reintroduced in 1996 by Senators J. Lieberman (D-CT) and J. McCain (R-AZ), merged for convenience with the Product Liability Reform Act (HR 956), passed by both houses of Congress with comfortable majorities, then vetoed by President Clinton.

Notes: Current trends in blood oxygenator development favor devices which separate the blood phase from the gas phase by a thin film of plastic material. The additional barrier to diffusion presented by the plastic film is a low price to pay for the advantages of the “membrane oxygenator” over its cruder competitors of the “bubbler” or “filmer” type, namely, the absence of direct exposure of blood to gas (with the ensuing damage to the most fragile blood constituents) and the physical constraint of the extracorporeal blood volume to a fixed-size compartment (obviating the need for complex volume control systems). The first generation of membrane lungs relied on the plastic materials (“Teflon” and silicone rubber) and shapes (flat sheets and tubes) available for industrial uses. A new line of devices will be made possible by the development of new biomaterials and the development of production technologies for the specific purposes of artificial organ research.

Notes: A report on the Consensus Development Conference on “Clinical Applications of Biomaterial” held at the NIH, 1-3 November 1983 is presented. Included is the complete text of the Conference Statement.

Notes: The brain tissue reaction to permselective polymer capsules implanted in rats was evaluated for 1 to 54 weeks. The polymer capsules were well tolerated in all animals and no recognizable neurological or behavioral deficits were associated with the implants. Necrosis at the brain/polymer interface, as assessed with Nissl stain, was not observed. Foreign body giant cells were consistently absent. Immunocytochemically identified reactive neuroglial cells showed a remarkably low-grade tissue response to the synthetic material be yond the first 2 weeks of observation. Immunolabeled cortical neurons revealed conserved columnar arrays around the implants. Transmission electron microscopy showed a minimal degree of collagen deposition compared to implants in peripheral sites, and normal synapses within a few micrometers from the brain/polymer interface, supporting the prospect of biocompatible, immunoisolated xenografts in the central nervous system.