Better tests for better health:
Best practices to transform assay development

Clinical diagnostic tools provide important information for clinicians, enabling them to deliver a definitive diagnosis and appropriate treatment and/or management plan to a patient. An accurate and timely diagnosis is essential for the delivery of optimal patient care and health outcomes. Since a diagnosis is the basis of all treatment plans, access to a reliable diagnostic test is vital. Technological breakthroughs have enabled cutting-edge diagnostic tests to be developed and routinely used in clinical practice. Designed to detect infectious diseases, pathological conditions, and metabolic states, these tests allow clinicians to treat patients with greater accuracy and speed than ever before.

One of these many diagnostic tests is the lateral flow test strip. Within the wide range of current applications, these easy-to-use diagnostic devices are used to confirm ovulation and pregnancy in women, detect viral and bacterial infections in humans and animals, quantify biomarkers in human body fluids, determine the presence of pathogens in foodstuffs, and screen for contaminants in environmental samples. Lateral flow tests became much more familiar to the general public during the COVID-19 pandemic, even though they were routinely used long before the COVID-19 outbreak. These immunoassays will continue to be regularly used for rapid testing across a range of industries – from environmental analysis and food testing to pharma and diagnostics.

Shawn Gaskell, Head of Diagnostic Manufacturing Materials and Dr. Michael Mansfield, Applications Development Scientist, MilliporeSigma, give an insight into the challenges associated with manufacturing within lateral flow diagnostics, in this article >>

In vitro diagnostics​

Healthcare providers rely on a variety of diagnostic tools to help them accurately diagnose and monitor conditions, which, in turn, helps to better guide treatment and management decisions. Among the most used diagnostic tools are in vitro diagnostics (IVD). IVDs are clinical tests performed on samples taken from the body, such as blood or tissue. These tests are vital for accurate disease detection and prevention, along with monitoring a person’s overall health. The term in vitro simply means ‘in glass’, which signifies that this test is conducted in a test tube, as opposed to in vivo tests, which are executed within the body.

IVDs can be performed via a range of different tools, from handheld devices to more complex, large, and sophisticated laboratory instruments. For instance – handheld and mobile diagnostic devices can be particularly valuable for healthcare facilities that reside in low- to middle-income countries, where laboratory access is limited, and healthcare can be compromised. One of the most valuable of these many tests is the lateral flow test, which became apparent during the COVID-19 pandemic and created a surge in their demand. As more demand is created for these types of tests, IVD manufacturers are challenged with an ever-changing regulatory landscape. It is important that the correct raw materials are chosen to best support their needs.

In the resources below, we explore IVD manufacturing and reveal how to best ensure you are audit-ready in an evolving regulatory landscape. We also explain why it is imperative to select high-quality raw materials when building a dependable IVD assay.


High demand for IVD testing was developed during the COVID-19 pandemic, including the global need for lateral flow tests, which quickly entered mainstream use. “Widespread availability of these simple tests allowed many of us to self-diagnose our COVID-19 status, without the need to travel to a clinic. Demonstration of their usefulness during the COVID pandemic is likely to support the expansion of lateral flow tests into additional aspects of personalized medicine.”

Although implementation of validated lateral flow tests in point-of-care testing is straightforward, development of a lateral flow test can be complex and challenging. Even though the tests appear simple and are conveniently concealed in a small plastic cassette for ease of use, it is a very different matter when we explore their interior. The inner workings of the lateral flow test comprise a sophisticated combination of materials, chemistries, and antibodies that are designed to recognise and capture target molecules of interest.

For more information on the link between COVID-19 and lateral flow tests, explore the resources below to find out how lateral flow tests empowered the fight against COVID-19, and learn how these modest tests were able to detect both symptomatic and asymptomatic infections.

Supporting the first line of defense in a pandemic

Read article

COVID-19 testing using lateral flow assays: sensitive, rapid, easy to use and point-of-care

Read article

Scientific partnerships bringing big results

In 2021, Merck KGaA Darmstadt, Germany, was awarded a €121 million contract from the United States government for the construction of a lateral flow membrane production facility to support the surge in demand experienced by its IVD customers. Merck KGaA is a leading science and technology company that has gained a positive worldwide reputation for its range of high-quality diagnostic solutions.  Read press release here.

Complete solutions

Making the jump from concept to clinic

Developing robust and sustainable diagnostic tools can be a long, expensive, and complex process. To allow for innovative diagnostic tools to move effectively from concept to clinic, it is essential that manufacturers collaborate with trusted partners who understand the complexities of the diagnostic market. The experts at Merck KGaA offer more than state-of-the-art product lines and reagents for COVID-19 detection. They also work closely with their customers on regulatory compliance, raw material sourcing, quality control, manufacturing, and production, to help them deliver consistent results. Within this immersive article, we will highlight the solutions Merck KGaA offer that help manufacturers streamline their transition from concept to clinical practice.

Membranes and pad materials

Lateral flow membranes are a key component in rapid diagnostic test kits. For over 30 years, the experts at Merck KGaA have developed the Hi-Flow™ Plus Lateral Flow Membranes. Available in different formats, such as rolls and cards, these membranes are widely recognized for their consistency.

Hi-Flow™ Plus Membrane Cards provide an easy-to-use subassembly – which means there is no need for the user to allocate time and resources to mounting membranes on an adhesive backing. They are manufactured with the membrane in a precise location to ensure consistency of performance in finished test strips. As a subassembly, they allow the user to simplify the manufacturing process and reduce production time, which reduces the time to market. For higher volume production on reel-to-reel equipment, membrane rolls are slit to the user’s desired width when ordered with the consistency that customers expect.

To help support users further, Merck KGaA has also created the SureWick® Conjugate, Sample, and Absorbent Pads to provide a complete solution for lateral flow test strip manufacture, which ensures that consistency of performance is achieved with each test strip. These materials are available in strip, sheet, and roll formats to suit different manufacturing processes.

In the materials and graphic below, learn how to simplify assay development, and accelerate the time to get to market with fit-for-use products to meet your IVD development and manufacturing needs.


Estapor® microspheres are small organic or inorganic spherical particles with a diameter of around 1 μm to 1000 μm. These modest particles encompass a significantly large surface area, which helps to generate faster kinetics and lower detection limits. Interestingly, their surfaces can be modified with different surface chemistries for specialized applications, such as to be used within diagnostic assays, flow cytometry, labeling, and much more. Microspheres can be used in many different applications such as CLIA, LTIA, and lateral flow.

Microsphere-based assays deliver valuable quantitative and qualitative information to clinicians, and Estapor® microspheres are used in a variety of applications, from diagnostic screening and immunoassay development to targeted drug delivery. In the case of lateral flow development, these particles improve assay sensitivity through fluorescence detection, make assays easier to read, and allow for signal quantification. However, there needs to be a balance between sensitivity and assay run time, which should be considered when selecting the right microspheres to meet your needs. For instance, larger microspheres increase assay sensitivity in exchange for a longer assay run time. To help get the balance right, Estapor® microspheres have been one of the top choices for many lateral flow diagnostic test manufacturers. These microspheres have been developed to be easily characterized and designed with key features to meet your needs. The diagram below represents the different stages of the assay development process.

Explore the resources below for protocols on covalent coupling of proteins to Estapor® Microspheres and their utilization and optimization in lateral flow tests.

Discover the technology for all your lateral flow needs

SureWick® Sample and Absorbent Pads

Made of 100% pure cellulose fibers, these materials can be used as sample or absorbent pads.  Their high bed volume allows them to absorb the sample when running tests.

C083 Cellulose Absorbent Sample Pads - Strips

C083 Cellulose Absorbent Sample Pads - Sheets

C083 Cellulose Absorbent Sample Pads - Rolls

SureWick® Glass Fiber Diagnostic Pads

These glass fiber substrates provide uniform surfaces, low extractables, and excellent consistency at a low price.  These pads interact minimally with the biomolecules in the test.

GFDX Glass Fiber Diagnostic Pads - Strips

GFDX Glass Fiber Diagnostic Pads - Sheets

GFDX Glass Fiber Diagnostic Pads - Rolls

Estapor® Europium Fluorescent Functionalized Microspheres

Main applications include quantitative lateral flow assays.

Estapor® Microspheres - F1-Eu-010

Estapor® Microspheres - F1-Eu-030

Estapor® Microspheres - F1-Eu-050

Hi-Flow™ Plus Membranes - Sample Sheet Packs

Sample packs containing five sheets of Hi-Flow™ Plus membrane. Ideal for early phase lateral flow test development.

Hi-Flow™ Plus HF75

Hi-Flow™ Plus HF90

Hi-Flow™ Plus HF120

Hi-Flow™ Plus HF135

Hi-Flow™ Plus HF180

Hi-Flow™ Plus Membranes - Sample Rolls

Individual rolls 2.5 cm wide x 100 m length. Ideal for reel-to-reel process development and low volume strip manufacture.

Hi-Flow™ Plus HF75

Hi-Flow™ Plus HF90

Hi-Flow™ Plus HF120

Hi-Flow™ Plus HF135

Hi-Flow™ Plus HF180

Hi-Flow™ Plus Membranes - Membrane Cards

Adhesive cards with the membrane pre-mounted so that you only need to add the pad materials. Ideal for early phase test strip development and low volume test strip manufacture.

Hi-Flow™ Plus HF75

Hi-Flow™ Plus HF90

Hi-Flow™ Plus HF120

Hi-Flow™ Plus HF135

Hi-Flow™ Plus HF180

Quality resources in lateral flow testing​

Technological advances have allowed for rapid diagnostic tools to take testing away from the laboratory and move it closer to the patient, whilst also delivering an accurate and timely result. Since we are bringing the test to the patient, it is critical to ensure consistent, robust, and high-quality materials are used for lateral flow assay development. Researchers must ensure they select the most suitable reagents, membranes, and antibodies to optimize their tests.

Assay development services are now available

Merck KGaA offers a new assay development service that works with you to optimize your lateral flow assay project.  As a raw materials supplier, Merck KGaA understands the importance of getting the components right the first time, and aims to be a valued partner for successful test to market. With laboratories and expertise in both the US and Europe, Merck KGaA has consultants who are ready to help you optimize your project and expedite your time to market.

Benefits of working with a lateral flow membrane expert:

To find out more about this expert service, hear from Eileen Hannigan and Sarah Nadin at Merck, as they share the benefits of working with a raw material supplier who also supports lateral flow assay development.

Learn how to optimize lateral flow assays for success

For those looking to learn more about manufacturing lateral flow tests, a new Rapid-Point-Of-Care Test Development course has been created.  This exciting adaptive learning program guides your in-depth journey through the development and manufacture of a lateral flow test.  Along the way, you will learn about technologies, regulatory issues and market trends from industry leaders.

View Rapid Point Of Care Test Development course

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