Preparation methods and apparatus adapted to filter small nucleic acids from biological samples

A kit adapted to preparation of a biological sample for further diagnostic processing, the kit comprising:

• a lysis agent configured to lyse the biological sample;
• a first binding buffer comprising one or more chaotropic agents, a salt compound, and a surfactant;
• a second binding buffer comprising:
• an alcohol comprising isopropanol, ethanol, or a combination thereof, and
• a salt compound comprising sodium chloride, potassium chloride, sodium phosphate, potassium phosphate, or a combination thereof;
• magnetic particles operable as binding supports;
• a first wash buffer comprising a chaotropic agent, a salt compound, and an alcohol;
• a second wash buffer comprising a salt compound and an alcohol;
• and
• an elution buffer comprising Tris-HCL.

A sample preparation system adapted to prepare a biological sample for molecular processing, comprising:

• a kit comprising a lysis agent, a first binding buffer comprising one or more chaotropic agents, a salt compound, and a surfactant, a second binding buffer comprising:
• an alcohol comprising isopropanol, ethanol, or a combination thereof, and a salt compound comprising sodium chloride, potassium chloride, sodium phosphate, potassium phosphate, or a combination thereof, magnetic particles operable as binding supports, a first wash buffer comprising a chaotropic agent, a salt compound, and an alcohol, a second wash buffer comprising a salt compound and an alcohol, and an elution buffer comprising TRIS-HCL;
• a first vessel positioned to receive a sample portion of the biological sample containing nucleic acid and the lysis agent;
• a heater element operable to heat the sample portion and the lysis agent and form a lysed sample;
• a pipette coupled to an aspiration and dispensing apparatus configured and operable to aspirate and dispense first magnetic particles and the first binding buffer into the lysed sample and form a first bindable mixture, which upon a first incubation binds a first nucleic acid portion having lengths greater than or equal to 500 bp to the first magnetic particles and leaves a first supernatant;
• a first magnet operable to separate the first magnetic particles with bound first nucleic acid portion from the first supernatant;
• a second vessel receiving the first supernatant, second magnetic particles, and the second binding buffer, which upon a second incubation binds a second nucleic acid portion having lengths less than 500 bp to the second magnetic particles and leaves a second supernatant;
• a second magnet separating the second magnetic particles with the second nucleic acid portion bound thereto from the second supernatant;
• a wash station configured to carry out first and second wash phases of the second magnetic particles with bound second nucleic acid portion, after separation from the second supernatant, wherein the first wash phase comprises immersing the second magnetic particles with a first wash buffer and the second wash phase comprises immersing the second magnetic particles with a second wash buffer;
• and
• an elution stage wherein the elution buffer is added to the second magnetic particles after the first and second wash phases and incubated in a third incubation to release the second nucleic acid portion and form a final eluate.