Porvair Sciences is a leading manufacturer of high quality polypropylene deep-well microplates for applications including compound storage, fraction collection, sample mixing and preparation. Using only virgin extractable-free grades of polymer in the production process ensures that you get reliable reproducible results free from contamination each time. This guide will suggest the best deep-well plate options for your particular area of research.

Polypropylene is a naturally-opaque white polymer which in its raw untreated state is intrinsically hydrophobic and offers a medium-low bind surface for proteins and peptides. In addition, it also acts as a low-attachment surface for adherent cells. These properties can be modified, or enhanced, by further treatment, for example, coating with very low binding compounds.

Polypropylene can be sterilised using gamma radiation, by treatment with ethylene oxide or by autoclaving at 121ºC. However, as the melting point of pure homopolymer is 171ºC, and the commercially available grades 160 – 166ºC, autoclaving of polypropylene deep-well plates is not recommended. This is because some softening of the polymer will be observed and this can lead to distortion of the plate structure and consequent deviation from the strict ANSI/SLAS microplate dimensions. Ethylene oxide sterilisation can also be problematic due to the oxidative nature of the process which can transform the natural hydrophobic surface into a strongly hydrophilic surface.

Deep-well plates can have various geometries depending on the shape of the well and also the profile of the well bottom. The most common geometries are square-well plate with pyramid, or Vshape, bottoms and round-well plates with round bottoms. The advantage of the square V-well is very high recovery of compounds from these low-dead volume plates. Whilst round-well plates exhibit higher dead volumes, they do allow for excellent mixing and are useful in bead-beating applications where beads might otherwise get stuck in the tight bottom of a V-well.

The height of a deep-well plate will normally determine the maximum volume, but in recent years space has been saved through the use of ‘common wall’ designs in round-well format that use larger diameter wells to reduce height and maximise volume. These designs can also allow more plates to be fitted into equipment such as HPLC autosamplers, incubators and the like.

When selecting round-well plates, it is important to consider whether sealing will be accomplished by an adhesive seal, a friction seal (or cap mat) or through thermal sealing with a welded foil. In the case of adhesive seals, rimless plates with a completely smooth top surface are preferable. For friction seals, either rimmed or rimless work best, whereas for heat weld sealing, a raised rim is essential. This does not really apply to square-well plates as the divisions between wells act like rims anyway.