Material standards for medical manufacturing

Medical manufacturing involves instruments, implants and equipment used for diagnostics, therapeutics and monitoring. This includes hip and knee replacements and other reconstructive devices, along with implantable monitors, such as those used for cardiac care.

What makes a material medical grade?

Manufacturing properties of materials used in medical environments, specifically that have patient contact, should be medical grade. There are no standards in place for what exactly “medical grade” means. What is agreed is that patient-contact materials must be biocompatible. This involves assessing the compatibility of resulting medical devices with a biological system.

Medical materials on the device that come into contact with the human body will be tested for biocompatibility and safety. This will include testing for toxicity, degradation, and skin sensitivity.

The testing should be carried out by following the relevant ISO standards, which are recognized the world over. The U.S. uses USP testing for polymers, but also recognizes ISO. You can learn more about USP testing here.

The ISO standard for biocompatibility is ISO 10993. Testing your device’s biocompatibility involves collecting qualitative and quantitative data on the materials in the context of biological safety. Meeting ISO 10993 requirements designates the device’s material as medical grade. The ISO is the International Organization for Standardization. Specifically, your material will need to meet the relevant standard in order to achieve ISO 10993 certification. The primary ones are:

Standard	Title	What it involves
ISO 10993-1	Evaluation and testing within a risk management process	Detailed guidance on assessing potential biological hazards associated with all types of medical devices, including active, nonactive, implantable and non-implantable
ISO 10993-18	Chemical characterisation of medical-device materials within a risk-management process	Involves three possible approaches: compositional evaluation, extractables evaluation and leachables evaluation
ISO 10993-17	Establishment of allowable limits of leachable substances	Identifies the leachable substances, quantifying the associated risks and limiting exposure within tolerable levels
ISO 10993-5	Tests for in vitro cytotoxicity	Specifies the incubation of cultured cells in contact with a device and/or extracts of a device either directly or through diffusion

Achieving ISO 10993 certification will also help you meet U.S. FDA or EU (MDR) regulations, which will allow you to market and sell your medical device in the relevant region.

It’s also worth noting that when looking for a manufacturer, choose one who’s certified ISO 13485. This ensures that the manufacturer’s quality management systems meet ISO standards specific to medical devices.

 

Standards for medical materials

The manufacturing process can alter how materials react, so it makes sense that standards apply to the devices, not materials. If the device as a whole meets FDA or EU (MDR) regulations, there’s no need to prove that the material itself is suitable. So in other words, there are no EU (MDR) or FDA-approved materials for medical devices, nor is there any ISO standard for medical device materials. It’s never possible to say Material A is acceptable for all medical devices. There are just too many variables involved, from material formulations to quality management systems.

Materials used in medical devices

Medical-device materials are evolving to find biological solutions and introduce design flexibility and harness technological advancements. For now, common materials used for medical devices include the following:

 

Overview

Metals	Ceramics	Polymers
Solid, non-organic materials used in 80% of all medical devices Due to corrosion-resistance properties, stainless steel is typically used for metal medical devices Highly ductile and malleable Good compressive, tension and shear strength High electrical and thermal conductivity Metals combined with other materials allows properties to be modified through creation of alloys	Do not degrade in body: ideal as implants Good insulators: can be moulded in small sizes Aluminium oxide typically used in ceramic medical devices, but zirconium dioxide gaining in popularity Mechanically hard and brittle; low plasticity High compressive strength Low tension and shear strength Low electrical conductivity: some act as semiconductors and at extreme temps, a few act as superconductors Chemically nonreactive	Include different forms of plastics and rubber Must be sterilisable, contamination resistant, and have acceptably low levels of toxicity Can be moulded to precise tolerances Unlike metals, do not interfere with MRIs Lightweight, can have outstanding flexibility Typically inexpensive Can be made bioabsorbable: suitable for temporary uses Can achieve desired qualities via processing Used in 3D printing for customising and prototyping devices
Composites
Combination of two materials from above Enables device to contain desired characteristics of one material while compensating for unwanted properties Two materials usually combined at the macroscopic layer Skin, bones, muscles and teeth are examples of tissue made of natural composite materials; synthesised composites are sometimes suitable to replicate or reinforce the function of such tissues

Note: Raw material for medicine manufacturing can be obtained from specialist life-science companies.

 

Biomaterials

Biomaterials are subsets within the above material classifications. These can be synthetic or natural materials that interact with biological systems within the body. It’s worth noting that traditionally,

common materials used in medical devices have been inert in design on purpose. This prevents the material from being absorbed by tissue or degrading the device via contact. Scientists are exploring materials that can be absorbed or naturally eliminated by design, enabling implants to perform their function until no longer needed. This prevents the patient from having to undergo further surgery. They’re also designing materials to become part of the body.

A word about metals

Why is platinum used in surgical instruments? Platinum has outstanding resistance to corrosion. It’s also inert, so when the instrument touches organs or tissues, there won’t be any problems. This is also why stainless steel in medical devices is so popular, particularly grade 304. It chemically will not react with bodily tissue. Titanium in medical applications is well known for its use in hip replacements and joints. It’s used for implants and surgical devices because it encourages osseointegration (ingrowth with bones and tissue).

International standards for medical devices

The ISO is recognized the world over. U.S. medical instruments and devices adhere to ISO as well. These standards are denoted with three parts. First is “ISO,” second is a number, followed by the year of issue. ISO guidelines for medical devices include standards for quality management systems. Note: Medical-device testing certification is awarded or refused by the product tester you use.

What are the ISO standards for hospital equipment?

These are some examples of standards you’ll need to follow, which are available for purchase.

ISO Standards	ISO medical devices
ISO 10282:2014	Single-use sterile rubber surgical gloves
ISO/DIS 10282	Single-use sterile rubber surgical gloves
ISO 11193-1:2020	Single-use medical examination gloves — Part 1: Specification for gloves made from rubber latex or rubber solution
ISO 11193-2:2006	Single-use medical examination gloves — Part 2: Specification for gloves made from poly(vinyl chloride)
ISO 21171:2006	Medical gloves — Determination of removable surface powder
ISO 22609:2004	Clothing for protection against infectious agents — Medical face masks — Test method for resistance against penetration by synthetic blood (fixed volume, horizontally projected)
ISO 22610:2018	Surgical drapes, gowns and clean air suits, used as medical devices, for patients, clinical staff and equipment — Test method to determine the resistance to wet bacterial penetration
ISO 22882:2016	Castors and wheels — Requirements for castors for hospital beds

 

ANSI

ANSI is the ISO representative in the U.S. and is also composed of other American organizations, such as the Association for the Advancement of Medical Instrumentation (AAMI) and the American Society for Quality (ASQ).

When ANSI adopts a standard, the organizations involved appear as a prefix. So U.S. example standards show up as:

Standard	Description
ANSI/AAMI/ISO 13485:2003 (R2009)	Medical devices — Quality management systems: Requirements for regulatory purposes
ANSI/AAMI/ISO 14971:2007 (R2010)	Medical devices — Application of risk management to medical devices

A note of caution: standards are always being revised, withdrawn, or added. Always check with the relevant organization to ensure you’re using the most up-to-date standards.

An example of this is ANSI, whose policy includes regular reviews of standards.

 

IEC

The International Electrotechnical Commission (IEC) sets international standards for the basic safety and essential performance of medical electrical equipment. Labelling is considered a critical component by regulatory bodies, so ensure the correct standard is followed. IEC standards have to be purchased, but include these examples:

IEC 60601-2-52:2009	Medical electrical equipment — Part 2-52: Particular requirements for the basic safety and essential performance of medical beds
IEC/TR 60601-4-1:2017	Medical electrical equipment — Part 4-1: Guidance and interpretation — Medical electrical equipment and medical electrical systems employing a degree of autonomy
IEC 60601-2-52:2009/AMD 1:2015	Medical electrical equipment — Part 2-52: Particular requirements for the basic safety and essential performance of medical beds — Amendment 1
IEC 60601-2-52:2009/COR 1:2010	Medical electrical equipment — Part 2-52: Particular requirements for the basic safety and essential performance of medical beds — Technical Corrigendum 1
IEC 60601-2-31:2020	Medical electrical equipment — Part 2-31: Particular requirements for the basic safety and essential performance of external cardiac pacemakers with internal power source

 

Processes used to manufacture medical devices

We’ve already mentioned that 3D printing is used not just for prototyping medical devices, but also for customizing devices themselves. You can 3D print plastics and metal. The most common processes used are CNC machining, additive manufacturing and injection molding. The process you use will depend on a number of factors, of course. The table below is a good first step in making your decision.

Process	CNC Machining	Additive manufacturing	Injection moulding
Unique/low volume		X
High volume	X		X
Using metal	X	X
Proof of concept		X
Complex geometry	X	X	X
Alter material properties		X	X
High dimensional accuracy	X		X
Shortest production time			X

 

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