Binding a target substance

Abstract

Magnetic particles capable of binding a target substance, which comprise a magnetic material and a matrix material, wherein the magnetic material is remanent upon exposure to a magnetic field and the matrix material has a surface comprising functional groups which promote disaggregation of the particles in the presence of a liquid phase.

Description

FIELD OF THE INVENTION[0001]The present invention relates to magnetic particles capable of binding a target substance such as nucleic acid, a process for making such magnetic particles, and a process for isolating a target substance from a target substance-containing sample.BACKGROUND TO THE INVENTION[0002]Procedures involving nucleic acids such as DNA and RNA continue to play a crucial role in biotechnology. Nucleic acid detection and manipulation including hybridisation, amplification, sequencing and other processes generally require nucleic acid to have been isolated from contaminating material. Where a nucleic acid-containing sample is a biological sample, contaminating material may include proteins, carbohydrates, lipids and polyphenols. Accordingly, a variety of approaches have hitherto been used in the isolation of DNA or RNA.[0003]Early methods of isolating nucleic acid involved a series of extractions with organic solvents, involving ethanol precipitation and dialysis of th...

AI Technical Summary

Benefits of technology

[0013]It has surprisingly been found that remanent magnetic particles can be extremely effective in separation or isolation of target substances from a sample. Remanent magnetic particles according to the present invention may form aggregates when suspended in a liquid phase but are readily dispersible upon application of a force to disrupt the aggregates. Advantageously, the matrix material of the magnetic particles has a surface comprising functional groups which promote this disaggregation of the particles in the presence of the liquid phase.

[0014]Because the magnetic particles are remanent, they are highly responsive to magnetic fields. The particles can be made smaller than conventional magnetic particles and yet respond quickly to a magnetic field. This has an advantage that the smaller the particle, generally the higher the binding capacity. Accordingly, the invention allows the use of high capacity, small particles which are still capable of obtaining a fast separation, as compared with larger conventional particles. Particles according to the invention are superior to paramagnetic and superparamagnetic particles of the same size in terms of velocity in a magnetic field. This is an enormous advantage regarding isolation. In automatic systems it becomes possible to increase the number of samples to be analysed dramatically.

[0018]The length or diameter of the magnetic particles is typically in the range 0.1 to 5,000 μm, preferably in the range 0.1 to 1,000 μm, more preferably in the range 0.1 to 500 μm, most preferably in the range 0.1 to 100 μm. It is found that smaller particles can be separated quickly in a magnetic field and will have high binding capacity. It is preferred that the magnetic particles are substantially spherical because particles of this shape disaggregate more easily.

[0036]A step of separating the magnetic particles with the nucleic acid bound thereto from the liquid phase is generally required in order to remove contaminants in the liquid phase. Further washing steps may be applied to the solid phase at this point. Any conventional separation step for separating solid phase from liquid phase is applicable, including centrifugation and decanting of the liquid phase from the pelleted solid phase or using a column in which the solid phase is packed and the liquid phase passed through. Where the magnetic solid phase is used, this facilitates separation, which can be carried out in the presence of a magnetic field.

[0059]The step of dispersing the sample with the magnetic particles preferably comprises subjecting the magnetic particles to disruption to disaggregate the particles. The disruption may comprise mechanical, acoustic or UV disruption. Mechanical disruption includes pipetting, stirring, vortexing and / or shaking so as to disaggregate the particles. Acoustic disruption includes ultra sonication and UV disruption. It is important that the sample is dispersed as fully as possible with the magnetic particles so as to maximise binding of the target substance thereto.

Problems solved by technology

These early methods are relatively laborious and time-consuming and may result in low yield.

It has hitherto been thought that particles which are themselves magnetic in the absence of a magnetic field (and which are known as remanent particles) are undesirable because they disadvantageously form aggregates because of their remanence.