Description
Medical-grade plastics refer to materials designed and intended for making medical products.
Most common plastics used in medical devices
| Name of Plastics | Outstanding Properties | Applications and Uses |
| Polyvinyl chloride (PVC) | Flexible and with reliable strength and durability, chemical resistance and stability | Blood and dialysis bags, IV bags and IV tubing, blister packaging, oxygen masks, oxygen tubing, surgical gloves and gowns, and catheters |
| Polyethylene (PE) | Resists impacts and corrosion and retains structural integrity even with repeated sterilizations. | Implants, PPE equipment, catheters |
| Polypropylene (PP) | High chemical resistance, resists stress, cracking, impact, fatigue | Disposable syringes, membranes for membrane oxygenators, connectors, non-absorbable sutures, finger-joint prostheses, reusable plastic containers, prescription bottles, surgical trays, implant caddies |
| Polystyrene (PS) | It does not conduct electricity, is tasteless and odorless, excellent gamma radiation resistance, excellent insulating properties | Culture trays, test tubes, Petri dishes, diagnostic components, housings for test kits and devices, implants |
| Polyethylene terephthalate (PE) | Resists attack by micro-organisms, high uniformity, resistance to chemicals and abrasion, good mechanical strength, and biostability | Extrusion of sutures, implantable textiles, and tubing for angioplasty balloons, sewing cuff of heart valves, vascular prostheses |
| Acrylonitrile butadiene styrene (ABS) | Rigid and rigidity, durable, resists chemicals and impacts, good dimensional stability, and insulating properties. | Medical masks, valves for ventilators, non-absorbable sutures, tendon prostheses, drug-delivery systems, and tracheal tubes. |
| Polycarbonate (PC) | Lightweight for easy handling, solid and tough to prevent breakage, transparent, resistant to sterilizations | Hemodialyzers, infusion systems, anesthesia containers, blood oxygenators, blood reservoirs, arterial filters, intravenous connectors, surgical instruments, and endoscopic appliances |
| Acetal | Excellent creep resistance, low water absorption, high wear characteristics, good electrical properties, resistance to hydrocarbons, chemicals, and solvents | Handheld diagnostic wands, sterilization trays, dental instruments, imaging equipment |
| Polysulfone (PSU) | Withstands repeated sterilizations, high-impact strength, good mechanical strength, chemical resistance. | The transparent portion of anesthesia masks, heart valve sizers, dialysis filtration cartridges, the outer shell of implantable catheter ports, surgical instrument cases and trays, dental instruments |
| Polyurethane (PUR) | Flexible, strong, durable, resistant to abrasions and chemicals, not absorbed by the body, non-allergenic | Implant devices, feeding tubes, dialysis devices, intra-aortic balloon pumps, surgical drains, pacemakers, artificial hearts, hospital beds, surgical tables |
Standardization and regulation
Production of medical-grade plastics needs to pass the requirements of the following medical certifications:
- ISO 10993
- ISO 13485:2016
- FDA registration
Testing protocols
Approving plastic for medical use requires that it hurdles some biocompatibility tests. The required tests vary from one product to another. In our company, the products undergo the following tests: hemolysis test, in-vitro cytotoxicity test, acute systemic toxicity test, irritation test, pyrogenicity test, and intradermal reaction test. A discussion of these biocompatibility tests follows hereunder.
Hemolysis test
Pyrogenicity test
The test involves the measurement of the rise in temperature of the experimental animal after intravenous administration of test article extract.
In-vitro cytotoxicity testing
Cytotoxicity testing determines if the material under examination can potentially damage the cell. The test involves exposing a cell culture to a sample of the material in question, followed by incubating both. After some specified time, medical examiners look at the cells and determine if lysis or malformations have occurred. The presence of changes in the cell structures means a cytotoxic effect.
Sensitization testing (intradermal reaction test)
Sensitization testing determines if the plastic material provokes an immunological or allergic reaction from the subject. This test applies extracts from the material under investigation to the test recipient. Then possible responses and reactions will be monitored and followed up. Responses, such as the formation of rashes and itchiness, may indicate sensitization to the material under examination.
Irritation testing
Irritation testing finds out the irritant potential of the material under examination. Medical examiners look at the reactions from the skin or the mucosal membranes of the subject. To test the effect of implantable materials, investigators deposit material extracts in the subject’s skin (intracutaneous injection) and look for possible reactions, such as redness or swelling in the skin. The presence of positive reactions indicates that the material could irritate the subject.
Acute systemic toxicity testing
Acute systemic toxicity testing determines the effects of the material extracts on the systems of the subject—immediately and after extended exposure. In the previous tests, investigators apply the material extracts locally. In this test, the medical examiners inject the material extracts into the subject. Immediately, they look for some adverse reactions. They repeat checking possible responses several times before the test concludes. Vital signs of the test recipients, such as the blood pressure and respiratory rates, will be monitored to ensure the presence or absence of reactions.
Genotoxicity testing
Genotoxicity testing finds out the damaging effect of the material extracts on the genes. It determines if the material incurs permanent genetic damage to the subject. In this test, medical investigators use salmonella bacteria because they are sensitive to mutagens. After exposure to the materials, only the mutated salmonella will survive. Researchers could determine the prevalence of mutations among the bacteria based on this.
Implantation testing
Implantation testing determines the reactions of the tissue to the implantable device or material. Hence, investigators implant the material or part of it into a particular tissue of an animal subject. After some time, the medical examiners remove some tissue samples around the implant and examine them microscopically for signs of disease.
Advantages of using plastics in medical equipment and devices
Medical devices have plastic components for the following reasons:
One-time use stops the spread of possible infections
Suppose a medical device has plastic components, such as a syringe barrel, syringe plunger, needle hub, and surgical tools. Medical practitioners can throw them away after one use. This action prevents the spread of possible infections.
A practical choice for manufacturing
Lightweight hand ergonomics
Medical surgeons experience hand fatigue when performing long surgery. Hence, they prefer surgical tools with plastic components. The use of plastics in surgical tools lightens the weight of the medical device. Reducing the weight of hand-held medical devices increases mobility in using the instrument.
Economical
Manufacturing with plastic resins entails lesser costs compared to using metals. This consequence holds at high or low volume production. Using plastics also entails cheaper storage and shipping fees because of their lightweight. With lesser production costs, manufacturers can cite affordability as one of the benefits of using their product.
Compatibility
Plastic materials offer superior compatibility with imaging and X-ray machines compared to metals. Metals prevent the normal functioning of the MRI’s magnetism and create interference with equipment featuring WiFi and Bluetooth. Medical devices using plastic materials produce more accurate images.
Recyclability
Some plastic medical applications allow recyclabilities, such as polypropylene sterilization wraps, irrigation bottles, basins, pitchers, and trays. Recycling lowers production expenditures and carbon footprints.
