Other Plastics:
Beside these various specialized plastic products can also be seen in the market such as polycarbonate, polymethylmethacrylate, Nylon, polyester, Glass fiber reinforced plastics, ABS copolymers, Teflon, blends and multilayered combinations.
A medical device that is adequately designed for its intended use should be safe for that use. The device should not release any harmful substances into the patient that can lead to adverse effects. Some manufacturers believe that biocompatibility is sufficiently indicated if their devices are made of medical grade material or materials approved by FDA as direct or indirect additives. The term medical grade does not have an accepted legal or regulatory definition and can be misleading without biocompatibility testing. There is no universally accepted definition for biomaterial and biocompatibility, yet the manufacturer who ultimately markets a device were required by FDA to demonstrate biocompatibility of the product as part of the assurance of its safety and effectiveness. The manufacturer is responsible for understanding biocompatibility tests and selecting methods that best demonstrate the following:
1. The lack of adverse biological response from the biomaterial.
2. The absence of adverse effects on patients.
3. The diversity of the materials used, types of medical devices, intended uses, exposures, and potential harms present an enormous challenge to design and conduct well-defined biocompatibility testing programs.
The experience gained in one application area is not necessarily transferable to another application. The same applies to different or sometimes slightly different (variable) materials. Biocompatibility describes the state of a biomaterial within a physiological environment without the material adversely affecting the tissue or the tissue adversely affecting the material. Biocompatibility is a chemical and physical interaction between the material and the tissue and the biological response to these reactions. Biocompatibility assays are used to predict and prevent adverse reactions and establish the absence of any harmful effects of the material. Such assays help to determine the potential risk that the material may pose to the patient.
The proper use of biocompatibility tests can reject potentially harmful materials while permitting safe materials to be used for manufacturing the device.‖
These factors include the type of device, intended use, liability, degree of patient contact, nature of the components, and potential of the device to cause harm. There are no universal tests to satisfy all situations, and there is no single test that can predict biological performance of the material or device and reliably predict the safety of the device. The types and intended uses of medical devices determine the types and number of tests required to establish biocompatibility. Biological tests should be performed under conditions that simulate the actual use of the product or material as closely as possible and should demonstrate the biocompatibility of a material or device for a specific intended use. These tests were more extensive for a new material than for those materials that have an established history of long and safe uses.
All materials used in the manufacture of a medical device should be considered for an evaluation of their suitability forintended use. Consideration should always be given to the possibility of the release of toxic substances from the base materials, as well as any contaminants that might remain after the manufacturing process or sterilization.
Biocompatibility is generally demonstrated by tests utilizing toxicological principles that provide information on the potential toxicity of materials in the clinical application. Biocompatibility should not be defined by a single test. It is highly unlikely that a single parameter were able to ensure biocompatibility; therefore it is necessary to test as many biocompatibility parameters as appropriate. It is also important to test as many samples as possible, therefore suitable positive and negative controls should produce a standard response index for repeated tests.
Biocompatibility testing should be designed to assess the potential adverse effects under actual use conditions or specific conditions close to the actual use conditions. The physical and biological data obtained from biocompatibility tests should be correlated to the device and its use.
Accuracy, reproducibility, and interpretability of tests depend on the method and equipment used and the investigator‘s skill and experience.
Toxicity may come from leachable components of the material due to differences in formulation and manufacturing procedures. Products are frequently composed of components; however simple examples are a disposable syringe (needle, barrel, plunger, lubricant, and stopper etc.). Changing a component can significantly alter the biocompatibility of a product, and certain components, by the nature of both their composition and exposure to patients, are more likely to present biocompatibility problems. An example is the common disposable plastic syringe, of which billions are used each year. For the syringe, the most likely problem component is the stopper—the flexible piece at the end of the plunger.
The stopper is most commonly made of natural rubber, and has direct contact with fluids entering the body (and frequently a fluid path).
Plastics used in medical device applications must meet stringent performance requirements through production, packaging, shipping, end use, and disposal. Many devices and device kits are sterilized before they are shipped for use. During manufacturing and during end use they also come in contact with various chemicals, solvents, bodily fluids, skin, organs, and tissues. The materials used in medical devices must be resistant to the sterilization methods, chemicals, and fluids that they encounter, be compatible with bodily fluids, skin and tissues and still maintain their safety, effectiveness, and functionality.
Requirements for plastics use in medical device include the following:
Material characterization
Sterilization resistance
Chemical and lipid resistance
Extractables and leachables characterization
Biocompatibility and haemocompatibility
Shelf life and stability
Many devices need to be packaged and sterilized either before distribution or before use. Examples of such device are exam and surgical gloves, clean room garments, specimen cups, wound care products, sutures, needles, syringes, catheters, drain bags, IV bags, fluid delivery systems, dialysis equipments, implants, surgical instruments, dental instruments, surgery supplies, and combination products.
