Laboratory processes involving nucleic acid sequences are nowadays very common and often performed as a matter of routine. Such processes include inter alia hybridizing and enzymatic reactions.
A common type of such processes is amplification reactions, such as the polymerase chain reaction, or abbreviated PCR. As is well-known, the PCR technique provides for the highly specific amplification of unique DNA segments defined by two surrounding primer sequences. PCR thereby offers a convenient way of obtaining sufficient quantities of DNA for inter alia nucleotide sequencing purposes. One major application of PCR is for diagnostic purposes. For a description of PCR it may, for example, be referred to White, T. et al., Trends in Genetics, 5, 179 (1989).
Extensively used solid supports in the context of molecular-genetic reactions have so far been paramagnetic beads due to the large total area provided thereby and their simplified handling and processing. Thus, for example, such magnetic beads having streptavidin immobilized thereto are commercially available.
However, the simultaneous processing of large sets of samples through sequential reaction steps using e.g. magnetic beads as a solid phase is technically demanding and involves a substantial risk of contamination between reactions. This is, of course, particularly undesired in amplification contexts, such as PCR, where the multiplication of contaminating sequences may result.
DD-A-279 506 discloses the use of a multipronged device for DNA-sequencing on a solid phase by chemical degradation (Maxam-Gilbert method). The device has a set of rods, each with immobilization primers attached, which rods are designed to fit into a set of reaction vessels. The labelled DNA fragments to be sequenced are immobilized to the rods by dipping them into respective vessels containing the DNA fragments. The further processing of the immobilized DNA fragments is conducted by dipping the rods into vessels containing corresponding reagents and solution, and the contents of the respective vessels containing DNA fragments degraded by the respective base specific reagents are lyophilized and then subjected to gel electrophoresis.
It is readily seen that the use of a multipronged device as suggested by Rosentahl et al., supra, obviates several of the problems related to the use of separate solid phase elements, like paramagnetic beads or microtiter wells, for example. A problem of this "patrix-matrix" type approach, however, which is likely to have limited its application, has been to provide for sufficient binding capacities on the individual prongs.
It may be mentioned in this context that a similar "patrix-matrix" strategy, permitting sets of solid supports (patrices) to be coordinately moved between corresponding sets of reaction wells (matrices), has previously been applied in peptide synthesis. Also, a type of multipronged solid support permitting the simultaneous processing of multiple samples is commercially available for immunoassay applications.
Thus, while a nucleic acid sample procedure using a multipronged device as described above may simplify the procedure significantly and reduce the risk of mix-up and contamination to a substantial degree, there still remains, however, the relatively cumbersome step of releasing the reaction products from the solid support and transferring them to the analyzer apparatus in question.