Custom DNA Oligos

  • Custom DNA oligo synthesis from 2 to 300 bases
  • Your choice of plate, strip or tube for optimal flexibility
  • Standard DNA oligos are shipped within 24 hours
  • Purified & modified oligos within 4 business days
  • Over 300 modifications available

Custom oligos quality standards

DNA synthesis has been our core product for over 20 years. All custom oligos are manufactured under ISO 9001 and ISO 13485 quality standards. These quality standards reflect good reliable and safe products as a result of stringent production and manufacturing procedures.

Custom DNA oligos can be ordered in our webshop by entering your DNA sequences (up to 300 bases!) or by email. Login to our webshop and order your oligo's!

For medium and high-throughput applications oligos can be ordered in plates. No additional charge for orders containing more than 48 oligos per plate. More information about DNA synthesis in plates.

Order your primes and/or probes delivered in any format according to your specifications. All fluorophore -quencher combinations possible, ideal for Real-Time PCR applications.

With our oligo prepaid service we make oligo ordering easy. Credit can be easily transferred to your account. Oligos can then be ordered immediately, eliminating possible delays due to purchase authorization. Please contact Biolegio for more information.

Oligonucleotides up to 300 bases are achieved with our B-pure Oligonucleotide Synthesis protocol. This  protocol enables high quality long oligo synthesis at an affordable price. By using the B-pure protocol we can achieve a coupling efficiency >99,5%. 
>More about long oligos and coupling efficiency

Oligonucleotides longer than 80 bases are synthesized automatically on this protocol. Additional quality control is performed on our state-of-the-art LC-MS system to guarantee highest quality and optimized functionality of the oligonucleotides.

Oligo scale and length

Biolegio offers four different synthesis scales for DNA oligos: 10 nmol, 40 nmol, 200 nmol and 1000 nmol. For each synthesis scale there is a restriction regarding the length of the oligo. 

10 nmol scale:      40 bases max. length
40 nmol scale:      150 bases max. length
200 nmol scale:    225 bases max. length
1000 nmol scale:  300 bases max. length

Guaranteed yield standard oligos

For non-labeled, non-HPLC/PAGE purified standard DNA oligos up to 30 bases we guarantee a minimum yield. However in many cases you will receive more than the guaranteed minimum!

10 nmol scale:     10 nmol min. yield
40 nmol scale:     20 nmol min. yield
200 nmol scale:   95 nmol min. yield
1000 nmol scale: 400 nmol min. yield


Biolegio has two synthesis protocols:  'High Purity' and 'B-pure'. The used protocol depends on the length of the oligo. This means that the protocols have been optimized for certain oligo lengths. 

  • High purity protocol is used for oligos between 1 and 79 bases. 
  • All DNA oligos longer than 80 bases are synthesized on our B-pure synthesis protocol.

Each protocol delivers the highest possible coupling efficiency for the specified range. 

Your DNA oligo can be shipped dry or dissolved, annealed or mixed. Standard DNA oligos are delivered dissolved in a tube in a concentration of 100 pmol/μl.

Available buffers
  • H2O buffer
  • LoTE buffer
  • TE buffer

DNA oligos can be delivered in any format (plates, tubes, etc.), concentration or combination. Have a look at our oligo dispensing service for more information about this topic.

All DNA oligos are synthesized under low salt conditions. This avoids the need for purification for most basic molecular biology applications. Additional purification is available for more sensitive applications. Furthermore, we recommend purification for oligos longer than 40 bases. 

We offer three different forms of purification:

  • Reverse-Phase cartridge purification
  • HPLC
  • PAGE

>more about purification

Modifications can be incorporated either during (direct) or after (indirect) synthesis. You can choose from over 300 modifications. If your desired modification is not listed on our website, please contact us.

>view modifications


How can I add a modification to my oligo?

Select the modifications of your choice in our webshop or in our excel ordering sheet. In the webshop you can have instant insight in pricing. 

How can I add mixed bases to my oligo?

Use the standard code letters for mixed bases / wobbles

How can I order DNA/RNA hybrid oligos?

DNA/RNA hybrid oligos can be ordered in with some minor adjustments in the sequence. Mark the RNA bases by placing a lower case 'r' in front of them. For DNA bases place a lower case 'd' in front. For 'chemistry' choose DNA/RNA hybrid.

Unmodified oligos can be used for at least 12 months when stored at -20°C. Use nuclease-free, sterile water for working solutions. Oligonucleotides modified with fluorescent dyes should be kept away from light as much as possible. Avoid repeated freeze-thaw cycles as this process can lead to degradation of the oligo.

All your DNA oligos are delivered with a specification sheet including GC-content, molecular weight, melting temperature (Tm), OD value, sequence and quantity in μgram and nmol. 

A stringent quality control system ensures that you can expect the quality of our oligonucleotides to be of the highest standard. Before the synthesis, all chemicals are checked to meet our quality standards. During the fully automated oligo synthesis, all steps of the synthesis are monitored by multiple control functions on our DNA synthesizers. This way we can assure the coupling efficiency of the synthesis to meet our demands.

Synthesis is followed by further quality controls to guarantee the quality of the oligos. All oligos are routinely analyzed by optical density (OD) measurement. In addition, oligos are analyzed by gel electrophoresis and Liquid Chromatography Mass Spectrometry (LCMS). If oligos do not meet our requirement they are resynthesized. The result of our stringent QC process is a product of the highest standard. All oligos are delivered with our product specification sheet, which includes: % GC content, yield in nmol and μgram, OD, melting temperature and molecular weight (MW).


Biolegio uses optimized phosphoramidite chemistry and reagents of the highest quality. Order handling and oligo synthesis programs result in an average coupling efficiency above 99,5%. With this efficiency we are able to synthesize DNA oligos up to 300 bases. Synthesis is performed under low salt conditions, which avoids the need for additional purification for most basic molecular biology applications, such as PCR, sequencing, hybridization studies and antisense studies. Additional purification by HPLC, PAGE or cartridge is available for more sensitive applications.

Oligonucleotide synthesis is carried out by a step-wise addition of nucleotide residues to the 5’-terminus of the growing chain until the desired sequence is assembled. Each addition is referred to as a synthetic cycle (figure 1) and consists of four chemical reactions: deblocking, coupling, capping and oxidation. At the end of the synthesis the oligo is released from the solid support and is eluted from the column or well. As solid support we use polystyrene beads (PB).

Oligo synthesis cycle