October 21, 2020

Glass fiber filters for straightforward nucleic acid extraction

By Cytiva

Glass fiber filters offer a straightforward solution for nucleic acid extraction. Find out how this versatile material provides a high quality and flexible alternative to silica powder and magnetic beads when isolating nucleic acids.

The outbreak of the novel coronavirus (SARS‑CoV-2) and subsequent COVID-19 global pandemic triggered a sudden need for extraordinary scientific research and diagnostic development. The entire scientific community, from startups to multinational corporations, faced exponential challenges to understand a new, previously uncharacterized virus and its effects on the global population.

The pandemic highlights the need for accessible and high-quality nucleic acid extraction methods of all kinds for researchers, molecular diagnostics developers, and kit manufacturers.

The ability to efficiently isolate nucleic acids from samples is often a challenge, with a balance required between efficient DNA and/or RNA extraction and maintaining the integrity of these nucleic acids. What seems a basic step in the workflow can become a bottleneck.

Having high quality, flexible options for extraction methods is valuable to researchers and manufacturers, enabling them to adjust their protocols and ensure suitability to application, as well as laboratory setup and scale.

Approaches to nucleic acid extraction

There are many solution-based and solid-phase nucleic extraction methods. Phenol-Chloroform and alkaline extraction are two common lab-brewed approaches for extracting genomic DNA from eukaryotic cells and plasmids from E. coli respectively.

Commercial kits tend to employ solid-phase extraction, using materials such as silica, borosilicate glass, or specific surface chemistries by application.

Silica powder

Silica is commonly known for its ability to bind DNA and other nucleic acids with the use of chaotropic salts. After binding nucleic acids, silica powder is pelleted during the washing steps before eluting the nucleic acids with water or a suitable buffer.

The method is straightforward, but requires careful handling so as not to lose granules of silica during pipetting steps. Silica powder might therefore be better suited to applications where some variability in yield is acceptable.

Magnetic beads

Magnetic bead-based nucleic acid extraction has become a popular choice in recent years due to its flexibility and effectiveness in the isolation of biomolecules. With several surface chemistry options for a range of applications, magbeads are well suited for nucleic acid isolation and size selection for next-generation sequencing (NGS), as well as lab-based immunoassays and custom conjugations.

In contrast to column-based approaches, magnetic beads are more easily automated, making high throughput extraction possible at the same time as optimizing yield, purity, and reproducibility.

Find out more in our ‘Scientist’s guide to magnetic beads’

Glass fiber filters

As an alternative to both silica powder and magnetic beads, borosilicate glass fiber (GF) filters also offer nucleic acid extraction that is straightforward and high quality. Glass fiber is an incredibly versatile material, with numerous applications as a depth filter.

As the major component of glass fiber filters is silica, they are well suited for nucleic acid extraction using the same binding principles as traditional chaotropic salt-based systems. Glass fiber provides the additional benefits of being a robust, adaptable, and easy-to-handle material.

GF filters enable the use of a classical workflow in DNA or RNA extraction, which is familiar to many lab users. They are an easy, cost-effective, and flexible point of entry to nucleic acid extraction for start-ups developing molecular diagnostics and nucleic acid kits.

Discover a range of different glass fiber filters

Glass fiber filters for classical nucleic acid extraction

Nucleic acid extraction with glass fiber filters makes use of chaotropic salts to disrupt hydrogen bonds in DNA, and detergents to denature cellular proteins and increase their solubility. Chaotropic salts typically used are guanidinium thiocyanate (GuSCN) and guanidinium hydrochloride (GuHCl).

In this method, cell lysis releases cellular components including nucleic acids into a cell lysate. The lysate is then removed and the aqueous solution passed through a glass fiber filter where the nucleic acids are bound onto the silica in the filter.

A series of wash steps removes all the unwanted components, isolating and purifying the nucleic acids on the filter. An elution buffer then releases the nucleic acids from the filter, producing a purified sample ready for analysis (Fig 1).

Classical nucleic acid extraction method using glass fiber filters

Fig 1. Classical workflow for nucleic acid extraction using glass fiber filters via centrifugation (left) and vacuum manifold (right).

Why use glass fiber in nucleic acid extraction?

A cost-effective option

This straightforward method for nucleic acid extraction does not require any specialized laboratory equipment or consumables. Many researchers are familiar with handling and using glass fiber filters in research and diagnostic laboratories for wide range of applications. Sourcing glass fiber filters is simple and cost-effective, which are important considerations for small laboratories and start-ups.

Glass fiber filter can be found as a relatively inexpensive bulk material in sheet and reel format, as well as discs.

Convenient formats for assay design, development and manufacturing

For developers, the availability of glass filter material in sheet and reel formats provides a lot of options for assay design and optimization. Researchers can potentially “punch-and-go” discs in different diameters to fit equipment and test for process optimization. They can stack layers of glass fiber, or indeed different grades of glass fiber in different combinations to achieve optimum nucleic acid binding, loading capacity, and yield for their sample type and application.

Manufacturers can also take advantage of sheet and reel formats to punch glass filters to their own specifications for incorporation into assay components.

The cost-effectiveness and availability of glass fiber filters in a range of grades and formats makes it relatively easy to test consumables and workflow, create an optimized protocol or product, and incorporate into manufacturing at scale.

Delivering quality

High- quality glass fiber can deliver efficient and consistent nucleic acid extraction.

At Cytiva, the Whatman lab filtration range includes a variety of glass fiber filter materials suitable for use in extraction workflows, varying in particle retention size and thickness (Table 1). Each of these materials is manufactured to the same high standards and enables efficient nucleic acid isolation.

Table 1. Overview of Whatman glass fiber filter grades suitable for nucleic acid extraction

Whatman glass fiber filter grade

Typical particle retention (µm)1

Nominal thickness (µm)

Typical water flow rate (mL/min)2

GF/A 1.6 260 143
GF/B 1.0 675 81
GF/D 2.7 675 681
GF/F 0.7 420 41
GMF150 1.0 730

1In liquid at 98% efficiency. 2Normalized for 9 am diameter. Measured under gravity for comparative purposes.

Glass fiber prefilters

Traces of denatured proteins can sometimes remain in the supernatant during a centrifugation-based extraction protocol. In situations where this is a risk, a large pore, high thickness grade of glass fiber, such as Whatman GF/D, can act as an efficient prefilter.

Using a prefilter reduces the likelihood of clogging a stack of fine retention glass fiber layers and reducing the overall capacity. Whatman GMF150 is a multilayer graded density filter that is designed for this purpose, combining prefilter and fine retention filter into a self-contained filter stack.

Whatman filters can also be modified to create a customized product for specific application needs, simplifying process development and providing the option to source suitable materials rather than adapt applications.


Nucleic acid extraction has a vital role in the development of molecular diagnostics during the Covid-19 pandemic, but can be a bottleneck for academic and industry scientists alike. Having a dependable and well-understood option for this essential technique, ideally with no need for specialized equipment, can be crucial.

A variety of approaches exist for purifying DNA and RNA, each with advantages and disadvantages making them more suited or not to specific applications.

GF filters offer a cost-effective and straightforward option for laboratory researchers, start-ups, diagnostic developers, and kit manufacturers. Using the material for nucleic acid extraction is simple but rapid and, with the variety of available glass fiber grades and formats, the workflow can be readily optimized.

Starting with the raw material, scientists can assess the qualities and specifications of the different grades available and select or combine the most appropriate for their specific application.

Cytiva provides a broad portfolio of GF filters to support nucleic acid extraction for a variety of applications and available platforms. This flexibility is key for startups as well as larger laboratories, independent of stage in research and development or scale.

For support with any aspect of nucleic acid extraction or associated applications, contact your local Cytiva representative or the Scientific Support team to discuss your needs. Find out more about Whatman glass fiber filters for nucleic acid extraction and request a sample.

For samples or to contact a specialist