Plasmid DNA preparation services, compared on scale and grade

Advertised prices, verified

How a plasmid prep is quoted

1. Scale, in milligrams of DNA. Quotes start from the yield you need, not from the culture volume. A few hundred micrograms for cloning and transfection screening is a different product from tens of milligrams for a transfection campaign, and vendors publish separate price bands rather than a linear rate.
2. Grade: research, transfection or GMP. Research grade is standard column-purified DNA. Transfection grade adds endotoxin removal, which matters because endotoxin kills primary cells and skews every downstream readout. GMP grade adds a documented quality system and is priced in a different bracket entirely.
3. Endotoxin specification. Where endotoxin is specified, it is specified as a limit in endotoxin units per milligram, and the tighter the limit the higher the price. This is the single line that most often explains why two quotes for 'the same' prep differ by several multiples.
4. QC included, and QC you have to ask for. Most preps include concentration, purity ratios and a restriction digest check as standard. Full-plasmid sequencing confirmation is increasingly cheap and is worth adding explicitly, because a prep of the wrong construct is the failure mode that costs the most downstream time.

When outsourcing beats a maxiprep on the bench

For a single construct at modest scale, a kit on your own bench is usually cheaper in cash and faster in wall-clock time than shipping to a vendor and waiting. Outsourcing wins on volume, on grade, and on the weeks where the bench time is worth more than the reagent cost.

The clear case for outsourcing is endotoxin-controlled DNA for primary cells or in vivo work. Achieving and, more importantly, verifying a tight endotoxin specification in-house needs equipment and assays most labs do not run routinely, and the vendor price includes the verification.

What to specify so quotes are comparable

State the construct size, the yield in milligrams, the grade, the endotoxin limit if you need one, the buffer and concentration you want it delivered in, and whether you are supplying the plasmid or the vendor is making it. Those seven items are the whole quote.

If you are supplying material, say what you are sending: a glycerol stock, a transformed strain, or purified DNA. Vendors price the transformation and culture step differently depending on what arrives, and it is a common source of quote-to-quote variation that has nothing to do with their prep pricing.

Common questions

What does a plasmid prep service cost?

It is banded by yield and grade rather than quoted per milligram. The vendors in this index that publish a figure are shown above with the quote and date; a research-grade prep at modest scale and an endotoxin-specified transfection-grade prep at high scale sit in different brackets entirely.

Do I need transfection-grade or research-grade DNA?

Research grade is fine for cloning, bacterial work and robust immortalised cell lines. Transfection grade with endotoxin removal is worth the uplift for primary cells, stem cells, immune cells and anything going into an animal, where endotoxin measurably changes the result.

What endotoxin limit should I ask for?

Ask for the limit your downstream assay tolerates, and require it as a specification on the certificate rather than as a description. A vendor that will state a numeric limit per milligram is committing to it; one that describes DNA as 'low endotoxin' without a number is not.

Should I pay for sequencing confirmation?

Usually yes. Whole-plasmid sequencing has fallen to a small fraction of the prep cost, and it is the only check that catches a rearrangement or a wrong clone before the DNA reaches an experiment. It is cheap insurance against the most expensive failure mode.

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