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Frequently Asked Questions

We have collected the most frequently asked questions here for you. If you cannot find your answer, don’t hesitate to send your question to us at 

General Questions

Do SIRION Biotech manufacture in the US? Where is your manufacturing site located?

Our manufacturing laboratories are located in Graefelfing, near Munich in Germany.

Do US customers have to be involved in the customs and delivery process?

No, SIRION Biotech International takes care of that for you.

You also have sites in Boston and Paris. What do they do for SIRION?

The Boston and Paris offices are dedicated to business development in North America and South and Western Europe respectively. Our Boston office also looks after customs and shipping for US clients.

Where can you deliver?

We can deliver to most countries where there is no trade embargo with Europe. Since import requirements are different for most countries outside the EU, please consult with your Account Manager for detailed information.

Viral Vector Questions

What are the timelines for AAV, LV and AV production?

You can find the timelines for production here for AAV, LV, and AV

What production scales (AAV, LV and AV) are possible?

You can find the production scales here for AAV, LV, and AV.

What are the available Quality controls for late preclinical batches?

You can find a full list of available QC and Analytics here

How are viral titers measured? What is the concentration of viral vector batches?

Viral titers can be determined in three different ways:

The total particle titer (Viral Particles (VP)/ml):
A physical titer which measures all viral particles in a virus stock irrespective whether they contain a functional vector genome or not. Standard methods to determine total particle titers are ELISA, UV/VIS spectrometry, analytical ultracentrifugation and electron microscopy.

The vector genome titer (Genomic copies (GC)/ml or Vector genomes (VG/ml)
A physical titer which provides information on the total number of vector genome containing viral particles of a viral stock. The vector genome titer is determined by qPCR, qRTPCR or ddPCR.

The functional Titer (Infectious units (IU)/ml or Transducin units(TU)/ml):
Measures the number of functional particles which express the gene of interest or therapeutic payload encoded on the vector genome in a target cell or tissue. The expression levels can be either measured on mRNA by qRT-PCR or on protein by FACS or Western Blot.

What is the concentration of viral vector batches?

Standard concentration ranges as provided by Sirion Biotech are as follows:

AAV: 1.0E12 VG/ml – 5E13 VG/ml

AV: 1.0E9 IU/ml – 1.0E11 IU/ml

LV: 1.0E6 IU/ml – 1.0 E9 IU/ml or 1.0E7 TU/ml – 1.0 E10 TU/ml

What are the gene size limitations for viral vector construction?

Adenovirus: 7.5 kb

Lentivirus: 5 kb constitutive/ 4 kb inducible

AAV: 4,5 kb

These are the total capacity limitations. Promotor and reporter-systems are not included in these numbers. Please contact a SIRION Biotech representative to discuss the details of your project

What production cell lines and purification methods do you use for AAV?

You can find detailed information about our upstream and downstream processes for AAV here.

How should viral vectors be stored?

Freeze-thaw cycles can dramatically reduce viral titer. We recommend immediately aliquoting vectors upon receipt, and storing at -80⁰C.

Can customer send their own viral vector expression plasmid for production?


Does SIRION also ship the pAAV plasmids together with the viral particles?


Do you perform gene synthesis on site?

No, we externalize the sequence synthesis to different partners according to the project needs.

Can SIRION perform cloning of the plasmids necessary for the viral vector production ?

Yes, SIRION has a dedicated molecular biology lab staffed with an experienced team. 

Can SIRION take care of the plasmid production?

Yes, to up to 20mg

How can SIRION help me on the conversion of my project from in silico design to viral vector particles I could use in my lab?

SIRION has extensive experience in developing viral vector projects with clients, with over 4000 viral constructs developed so far, and over 8000 virus vectors manufactured. Your Account Manager will work with you to determine your needs and develop a project plan. Once the design is shared, the molecular biology team will validate the feasibility of the cloning, and the Account Manager will develop a quotation based on your needs.

What does SIRION base its recommendation around client projects on?

SIRION has over 15 years of experience in viral vector projects and their use in many different contexts in target validation and Gene & Cell therapy applications. We bring all this knowledge and experience together in our Viral Vector Know-How Hub. If there is something we have not done before SIRION’s scientific team will investigate to give the most reliable recommendation.

Which reporter genes can you propose for my projects?

The choice of a reporter gene is heavily dependent on the read out of the experiment. We recommend reporter genes that we know work in the planned context. We are happy to clone or synthesize any chosen reporter gene that we do not need a license for, or that the customer has the rights to use.

How do I go about placing an order?

You can find an example of the Project Process here. The ordering process is simple and will be fully explained to you by your SIRION Biotech representative. You can contact us using the form here.


At which concentration should I use LentiBOOST?

LentiBOOST is provided at 100 mg/ml in an aqueous solution and is suggested to be used in the range of 0.1 mg/ml to 5 mg/ml final concentration. The optimal concentration should be tested for each individual setting and cell system.

For which cell types can LentiBOOST be used?

In general, LentiBOOST is not restricted to any specific cell type. In primary cells it has been shown to increase transduction of CD34+ HSC, neuronal stem cells, MSCs, T cells, hard-to-transduce murine T cells, NK cells, and fibroblasts (Masiuk 2019, Hauber 2018, Simon 2019, Delville 2018 and customer data).

Is LentiBOOST toxic for my cells?

LentiBOOST does not show any cytotoxic effects in a standardized test system up to 20 mg/ml final concentration. Furthermore, no cytotoxicity was observed when used with primary CD34+ HSC and T-Cells (Masiuk 2019, Hauber 2018, Simon 2019, Delville 2018).

How is LentiBOOST used?

LentiBOOST is used as a lentiviral transduction enhancer and only intended to be used in vitro.

What is the composition of LentiBOOST?

LentiBOOST is an aqueous solution of a chemically synthesized polymer. It does not contain any material of animal or human origin.

How stable is LentiBOOST?

Due to its composition LentiBOOST is very stable and can be stored at -20°C for 3 years. After thawing it is stable at 4-8°C for 3 months. Also, exposure to room temperature (20-25°C) for 3 months does not affect its stability*.
* These data are based on an internal, standardized assay; thus results may differ in customer specific cell types and should be tested in customer specific cell culture settings.

Over how many freeze-thaw cycles is LentiBOOST stable?

No loss of functionality was observed after 5 freeze-thaw cycles*.
* These data are based on an internal, standardized assay; thus results may differ in customer specific cell types and should be tested in customer specific cell culture settings.

Is there a protocol for optimal usage of LentiBOOST?

We offer a manual that contains our experiences as well as aggregated customer feedback on how to use LentiBOOST optimally. You can find the manual here