Chemistry: molecular biology and microbiology – Measuring or testing process involving enzymes or... – Involving nucleic acid
Patent
1996-05-10
1998-05-19
Weber, Jon P.
Chemistry: molecular biology and microbiology
Measuring or testing process involving enzymes or...
Involving nucleic acid
435 21, 435188, 436 94, C12N 168, C12N 996, G01N 33567, G01N 3300
Patent
active
057534438
DESCRIPTION:
BRIEF SUMMARY
This application is the U.S. National Phase of international application No. PCT/EP94/03217, filed Sep. 24, 1994, and designating the Unites States.
The present invention relates to a process for the production of a preparation for staining nuclear DNA to be used in flow cytometry, the preparation obtained by such a process, and a kit for its use.
It is well known that cytofluorometric analysis took a fundamental role in diagnostics and its use is steadily increasing, together with the development of new and more sophisticated analysis techniques and apparatus.
More particularly, the determination of cellular DNA contents through flow cytometry is fundamental in the oncologic field as well as in determining the cellular ploidy by cytofluorometric analysis.
Up to now the working solution containing the specific dye and a thermolabile enzyme, was prepared in an extemporaneous way at the time of using it, because of the well known stability problems of the proteins in the anhydrous condition, but such a process is not at all satisfactory because it is also well known that extemporaneous preparations depend too much from the present situation and the operator's skill, thus they do not warrant reproducible results.
Indeed, as proteins in the anhydrous condition generally show stability problems and their rehydration is rather long, difficult and sometimes incomplete, it was hitherto considered impossible to make a preparation for staining nuclear DNA to be stored in the anhydrous condition and to be reconstructed at the time of use.
It was now surprisingly found that this problem is brilliantly solved by mixing the protein with a surfactant, so as to cause the formation of a water envelope around the molecule, obtain a better stability with time and a more complete hydration at the moment of use.
In other words, not a true lyophilization but instead a crystallization of the preparation is carried out, so that it may be perfectly stored for a long time.
The ingredients to be used in the production of the preparation according to the present invention must be chosen obviously in a proper way. As enzyme a specific ribonuclease is used, for instance type A bovine ribonuclease; as a dye, a fluorescent halide binding specifically to nucleic acids, preferably propidium iodide, but other fluorescent halides are suitable as well; as a surfactant, it is necessary to use a non ionic surfactant such as NONIDET P 40 (BDH Laboratory Supplies Ltd., Poole, Dorset, Great Britain). NONIDET P40 is (octylphenoxyl)polyethoxyethanol.
Once the working solution is prepared, it is delivered in vials in such amount as to allow an analytic determination for each vial, which is therefore single dose, and the solution water is evaporated under vacuum.
It is known that DNA staining may take place either in a hypotonic medium, if it is desired to stain only isolated nuclei, or in an isotonic medium, if it desired to keep intact the cell structure for possible morphologic studies or checking proliferation markers.
Two different diluents are therefore prepared for reconstituting the working solution, consisting of salts with a different concentration according to either diluent.
Consequently, three different single dose kits may be supplied to users, namely the vial containing the preparation, accompanied by a bottle containing either the isotonic or the hypotonic diluent, or two vials each with one of the diluents.
The production of the preparation according to the present invention will be now illustrated in detail in the following practical example of preparation, which however should not be construed as limiting in any way the scope of the invention.
EXAMPLE
The chosen dye is propidium iodide, that links specifically by intercalation to the nucleic acids in their double strand structure; it is therefore necessary to remove the cell RNA by enzymatic digestion, using a specific ribonuclease, so as to avoid an overestimation (moreover the RNA contents of a cell is not constant, but it may vary with the state of activity).
Access of the dye
REFERENCES:
patent: 4087328 (1978-05-01), Swaisgood
patent: 4668618 (1987-05-01), Thornthwaite
Barbesti et al. "DNA Flow Cytometry Performed By Stablized Propidium Iodide Staining," European Journal of Histochemistry, vol. 37, 1993, p. 68.
Brown et al. "Propellant-driven aerosols of functional proteins as potential therapeutic agents in the respiratory tract," Immunopharmacology, vol. 28, No. 3, Oct. 1994, pp. 241-257.
Luisi et al. "Reverse micelles as hosts for proteins and small molecules", Biochimica & Biophysica Acia 947 (1988) pp. 209-246.
1996 Biochemcals Catalog. (Boehringer Mannheim: Indianapolis, IN) p. 495, 1996.
van der Engh et al. Cytometry (1984) vol. 5, pp. 108-117 1984.
BIO-RAD Laboratories S.r.l.
Hanley Susan
Weber Jon P.
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