Plaque-Forming Titer Assays

Creative Biolabs has always led to the development of biotechnology with superior service quality. To meet the needs of our customers, we have introduced plaque-forming titer assays to control or guarantee the quality of viral vectors. The plaque assays can be used to purify viral clonal populations or to detect viral titers as plaque-forming units per ml (pfu/ml), which can help you more precisely control the amount of virus used to infect cells in subsequent experiments.

Introduction of Plaque-Forming Titer Assays

Detecting the concentration of the virus in the sample (the virus titer) is one of the most important steps in virologic experiments. The plaque assays are a relatively common method for detecting the number of infected viruses. This technique was originally used to calculate the titer of phage. Later, it has been continuously improved to determine the titer of many different viruses in animal virology, especially in the purification and titer determination of adenoviral vectors.

To perform the plaque assay, it is necessary to prepare a diluted virus stock solution to be inoculated into a susceptible cell monolayer. After the incubation period, the cell monolayer is covered with an agar medium that can form a gel to attach the virus to the cells. When incubated with a culture plate, the initially infected cells release viral progeny, and the new virus is spatially limited by gelation to infect adjacent cells. Therefore, each infectious virus particle produces a circular shape infected cell area called plaque. Eventually, the plaque will grow to a size visible to the naked eye. Live cell dyes are often used in experiments to stain live cells to make them more distinct from infected cells. This method is generally used to determine a virus that causes significant damage to infected cells.

Figure 1. Plaque-forming titer assays.

Plaque Assay Service Protocol

1. The customer determines the number of plates used in the experiment and the dilution requirements for each plate.
2. The corresponding host cells required for viral infection are inoculated on the plates and cultured until the confluency of the cells reaches 70%.
3. Prepare the agarose solution, we will prepare the corresponding volume of agarose solution according to the customer's needs, and strictly control the process to avoid pollution.
4. Prepare virus dilutions corresponding to the plate settings required by the customer.
5. Inoculate monolayer cells with 1 ml of the appropriate virus dilution, incubate for 1-2 hours to allow the virus to adsorb.
6. Monolayer cells are covered with agarose gel and incubated for 5-10 days to observe cell infection. If dyeing is required, we will add the corresponding dye to the prepared agarose.
7. The well-isolated plaques on the plate are counted to determine the titer of the virus.

Plaque-Forming Titer Assays for Adenovirus Vector

Designing and constructing adenoviral vectors for the delivery and expression of foreign genes according to the needs of customers has always been a superior service project of Creative Biolabs. In order to help customers more accurately control the amount of virus in the experiment, we provide customers with plaque-forming titer assay, as well as virus plaque purification, plaque virus amplification and other services established on this basis. If you have any questions or have any difficulties, you can contact us by email or send us an inquiry to find a complete solution.