Oligonucleotide manufacturing: scale, purity and release

What changes with scale

1. Coupling efficiency compounds, so length is the cost driver. Each addition is a chemical step at slightly less than complete efficiency, and the full length yield falls geometrically with length. That is why a long oligonucleotide costs disproportionately more and why purification matters more the longer it gets.
2. Purification, not synthesis, sets the cost at scale. Desalted material is cheap; cartridge, high performance liquid chromatography and gel purification each add a step and a yield loss. Specify the purification the application actually needs, because buying gel purity for a screening primer is a large recurring waste.
3. Modifications multiply everything. Every dye, quencher, phosphorothioate linkage or modified base is a separate reagent with its own coupling behaviour and its own cost, and some combinations constrain the purification route. List every modification when asking for a quotation.
4. Fix the release testing in the specification. Mass spectrometry confirming identity, a purity measurement by a stated method, and concentration by absorbance are the usual release package. A certificate that reports concentration alone is a shipping note rather than a release.
5. Write change control into the supply agreement. A supplier changing a synthesis site, a reagent source or a purification route can shift impurity profiles in ways an assay will feel. Notification with lead time, and lot reservation, are the terms worth more than a small price difference.

Impurities, and which ones matter

Truncated sequences from incomplete coupling, depurinated material, and residues of protecting groups and reagents are the usual impurity classes. Which matter depends on the application: a truncation that is invisible in a polymerase chain reaction can ruin an antisense experiment.

Ask what the impurity profile looks like for your purification grade, and whether the supplier measures it routinely or on request. The answer tells you a good deal about the operation.

Formats and delivery from oligonucleotide manufacturers

Plates, tubes, dried or in solution, normalised to concentration or supplied at yield. For anything automated, the plate format and the normalisation are what decide how much handling arrives with the order.

Normalised plates cost more and remove a quantification and dilution step from every user. At volume that is usually the cheaper arrangement.

Storage and stability

Dried at low temperature is the stable form; in solution the rate depends on the buffer and on whether it is nuclease free. Aliquot on arrival and record the date, because a stock diluted and refrozen repeatedly degrades measurably.

For modified oligonucleotides, follow the supplier's storage instruction rather than the general rule. Dyes and some modifications are considerably less stable than the backbone.

gmp oligos, and where the grade begins

gmp oligos start earlier in the process than the name suggests. The synthesis chemistry is much the same; what the grade adds is qualified raw materials, a documented purification, identity and purity testing against a written specification, and a batch record, which is what an oligonucleotide used as a drug substance or as a critical reagent in a licensed kit requires. Scale and grade are priced separately, so a milligram at GMP can cost more than a gram of research grade, and the lead time is set by the release testing rather than the coupling.

oligosynthesis, and the cycle behind the price

Oligosynthesis is phosphoramidite chemistry run as a four step cycle on a solid support: detritylation, coupling, capping and oxidation, once per base, with an average yield per cycle that compounds. That compounding is the whole economics of the product. A stepwise yield a fraction of a per cent lower is barely visible on a twenty base oligo and dominates a hundred base one, which is why long sequences cost more per base and why purification moves from a cartridge to HPLC as length grows. Scale, length, modifications and purification are the four things a price is built from.

A galnac oligonucleotide, and what the conjugation adds

Attaching a triantennary N-acetylgalactosamine ligand to a strand turns delivery into receptor-mediated uptake by hepatocytes, which is why the approved liver-targeted silencing drugs are built this way. For synthesis it adds a conjugation step and a purification burden, since the conjugate and the unconjugated strand have to be separated and the ligand's own purity characterised. Quotes are per milligram of purified conjugate and are dominated by that step rather than by the oligonucleotide's length.

An oligonucleotide properties calculator, and what to check

A properties calculator reports length, molecular weight, GC content, melting temperature and extinction coefficient, and the number people misuse is the melting temperature, since it depends on the salt and oligonucleotide concentrations the calculator assumed and on the thermodynamic model it used. For a primer pair the useful comparison is between the two primers under the same assumptions. Check the extinction coefficient too, because concentration from absorbance depends on it and a modified base changes it.

An oligonucleotide mass calculator, and what it is for

A mass calculator returns the molecular weight of a sequence, which is what a mass spectrometry check is read against, and the number depends on the modifications and on whether the strand is a free acid or a salt, which is the commonest source of a mismatch between the calculated and observed mass. For concentration work the extinction coefficient rather than the mass is the number that matters. Where a modification is unusual, ask the supplier for the expected mass rather than trusting a generic calculator.

Common questions

Why does a longer oligonucleotide cost so much more?

Because coupling efficiency compounds. Each addition is slightly less than complete, so the proportion of full length product falls geometrically with length, and more material must be made and purified to deliver the same amount.

What purification do I actually need?

Desalted for routine primers, cartridge or chromatographic purification for probes and anything where truncated sequences interfere, and the highest grades for therapeutic or diagnostic applications. Buying above the need is a large recurring cost.

What should oligonucleotide analysis on a certificate show?

Identity by mass spectrometry against the expected mass, purity by a named method with the value, and concentration with the method used. Those three make the material traceable; a concentration alone does not.

How do I secure supply from an oligonucleotide manufacturer?

A supply agreement with change notification, lot reservation, an agreed specification and a stated lead time, plus a qualified second source where the volume justifies the second validation.

Browse by service class

• Compare Gene synthesis on advertised prices