Implanted devices

Aliphatic isocyanates have a small but growing market application in thermoplastic polyurethanes (TPU). Medical appflcafions include wound dressings, catheters, implant devices, and blood bags. A security glass system using light-stable TPU as an inner layer is under evaluation for shatterproof automotive windshield appflcafions. 

The first implantable pacemaker, introduced in 1960, provided a permanent solution to a chronic bradyarrhythmia condition. This invention had a profound impact on the future of medical devices. The pacemaker was the first implantable device which became intrinsic to the body, enabling the patient to lead a normal life. 

Devices for the 1990s. The 1990s may turn out to be the decade of active arrhythmia-control devices. Implantable devices to pace, cardiovert, and defibrillate the heart without the need for open-heart surgery should become widely accepted before the year 2000. Dramatic developments and... 

Polybutadienes, polycaprolactones, polycarbonates, and amine-terminated polyethers (ATPEs) are shown in Scheme 4.4 as examples of other commercially available polyols. They are all specialty materials, used in situations where specific property profiles are required. For example, ATPEs are utilized in spray-applied elastomers where fast-reacting, high-molecular-weight polyamines give quick gel times and rapid viscosity buildup. Polycarbonates are used for implantation devices because polyuredtanes based on them perform best in this very demanding environment. Polycaprolactones and polybutadienes may be chosen for applications which require exceptional light stability, hydrolysis resistance, and/or low-temperature flexibility. 

All implantable devices and long-term surgically invasive devices are in Class lib unless they are intended ... 

Other IFNs that can be used in the treatment of viral infections include IFN-P, IFN-m, a molecule that is more potent than its nonglycosylated form, which itself has activity comparable to that of IFN-a (Buckwold et al. 2007), and that will be delivered continuously by an implantable device, IFN-y and 1FN-A,1, a pegylated form of which will soon be available. 

IFN-co (Intarcia Therapeutics, Emeryville, California) has been reported to be well tolerated and safe, in patients infected with various HCV genotypes, at doses of 15-120pg three times weekly for 12 weeks, with dose-dependent virological and biochemical responses (Plauth et al. 2002). At a dose of 25 pg daily, IFN-co induced a 2-log HCV RNA dechne at week 12 in two-thirds of 74 patients infected with HCV genotype 1 (Gorbakov et al. 2005). In a recent trial, SVR was achieved in 6% and 36% of patients receiving the same dose of IFN-O) without and with ribavirin, respectively (Novozhenov et al. 2007). A new trial of IFN-m, delivered continuously by an implantable device, will start soon. 

The third topic in polyphosphazene biomaterials that will be described in this article concerns surface implications. One of the major problems in the utilization of polyphosphazenes in solid state is their exploitation in the construction of implantable devices, for which good physical properties, minimum biological response, and good resistance to fungal or bacterial colonization may be required. 

Subcutaneous in vivo testing of these polymers (13,14) has shown minimal tissue response—similar, in fact, to the response to poly-(tetrafluoroethylene). These materials are candidates for use in heart valves, heart pumps, blood vessel prostheses, or as coating materials for pacemakers or other implantable devices. 

Surini S, Akiyama H, Morishita M, Nagai T, Takayama K. Release phenomena of insulin from an implantable device composed of a polyion complex of chitosan and sodium hyaluronate. J Controlled Release 2003 90 291-301. 

A major challenge in providing electrical power for implantable devices is the isolation of toxic or bio-incompatible materials. As the size of the device decreases to a centimeter or millimeter scale, the parts responsible for isolation, such as canisters and seals, begin to determine the size of the device. An alternative is to design an electrochemical system that is compatible with the physiological environment and can take advantage of chemical species available in that environment, specifically the... 

S. epidermidis is implicated in many medical implant infections. Mechanical heart valves, shunts, catheters and orthopedic devices are examples of implanted devices... 

Some implantation devices have extended well beyond the classic diffusional systems and have included not only bioerodible devices, but also implantable therapeutic systems that can be activated. There are devices activated by change in osmotic pressure to deliver insulin [225], morphine release trigger by vapor pressure [226], and pellets activated by magnetism... 

Insulin aggregation and precipitation was an impediment to the development of implantable devices for insulin delivery as noted by several investigators working with conventional insulin infusion devices [51-54]. The potential causes of the observed aggregation and precipitation are thermal effects, mechanical stress, the nature of the materials in contact with the insulin solution, formulation factors, and the purity of the insulin preparation. 

Most of the recent attention has been given to the development of subcutaneously implantable needle-type electrodes [14, 15, 34, 38], Such devices track blood glucose levels by measuring the glucose concentration in the interstitial fluid of the subcutaneous tissue (assuming the ratio of the blood/tissue levels is constant). Subcutaneously implantable devices are commonly designed to operate for a few days and be replaced by the patient. Success in this direction has reached the level of short-term human implantation ... 

M. Schlosser and M. Ziegler, Biocompatibility of active implantable devices, in Biosensors in the Body Continuous In Vivo Monitoring (D.M. Fraser, ed.), pp. 139-170. John Wiley, NY (1997). 

A remaining crucial technological milestone to pass for an implanted device remains the stability of the biocatalytic fuel cell, which should be expressed in months or years rather than days or weeks. Recent reports on the use of BOD biocatalytic electrodes in serum have, for example, highlighted instabilities associated with the presence of 02, urate or metal ions [99, 100], and enzyme deactivation in its oxidized state [101]. Strategies to be considered include the use of new biocatalysts with improved thermal properties, or stability towards interferences and inhibitors, the use of nanostructured electrode surfaces and chemical coupling of films to such surfaces, to improve film stability, and the design of redox mediator libraries tailored towards both mediation and immobilization. 

Effects on blood pressure, heart rate, lead II ECG, core body temperature, and locomotor activity can be explored using DataSciences telemetry implanted devices in rats, guinea-pigs, dogs, or primates. Effects on behavior can be captured on video using CCTV for dog and primate studies. Repeated administration and interaction studies can be performed. 

The Safe Medical Devices Act requires reporting of medical devices that probably caused the death, serious filness, or injury of a patient. Postmarket surveillance on permanently implanted devices required with methods for tracing and locating patients depending on such devices. FDA is authorized to recall device product. 

Other delivery systems are transdermal patches, metered dose inhalers, nasal sprays, implantable devices, and needle-free injections. A description of needleless injection is given in Exhibit 5.16. 

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