Ultra sonic release of DNA or RNA
Method and apparatus for sonication in connection with preparing a cellular sample containing DNA or RNA for performance of polymerase chain reaction (PCR) or for other reasons where it is important to break down the cell walls and other cellular structures to release cellular contents including DNA. The same methods and apparatus may be used to release DNA or RNA from virus for PCR or other uses. A novel apparatus which is capable of releasing cellular contents or releasing the DNA or RNA of virus without the aid of beads or chemicals is described herein. The apparatus is designed to deliver high levels of sonic energy through optimizing the geometry the apparatus and optimizing the force created by a piezoelectric transducer. The apparatus is capable of processing samples which are contained within fluid in a short amount of time between 30 seconds and two and one half minutes. The apparatus is small and can be field deployable or used in a standard molecular biology laboratory.
1. An apparatus for preparing biological samples, said apparatus comprising:
a transducer assembly having a first natural frequency for vibration in an range of ultrasonic frequencies, said transducer assembly including:
a piezoelectric transducer having a disc shape with a first center hole formed therein, said piezoelectric transducer being configured to vibrate within a range of ultrasonic frequencies; and
a holding ring having a disc shape with a second center hole formed therein, said holding ring being coupled to said piezoelectric transducer with said second center hole aligned with said first center hole, said second center hole being smaller than said first center hole;
a vial having a sidewall surrounding a chamber configured to receive and hold a biological sample therein, said sidewall being sized and shaped for insertion within said second center hole and to be coupled with said holding ring with an interference fit; and
an oscillator driver in electrical communication with said piezoelectric transducer, said oscillator driver being configured to cause said piezoelectric transducer to vibrate at an excitation frequency proximate said first natural frequency.
2. The apparatus of claim 1 , wherein said vial is substantially cylindrical.
3. The apparatus of claim 1 , wherein said vial includes a first end and a second end spaced from said first end, with said sidewall of said vial having a tapered portion between said first end and said second end.
4. The apparatus of claim 1 , wherein said second center hole includes a tapered portion.
5. The apparatus of claim 1 , wherein said first natural frequency is about 23 kHz.
6. The apparatus of claim 1 , wherein said first natural frequency includes a substantially radial vibration component causing said sidewall of said vial to deflect inwardly into said chamber.
7. The apparatus of claim 1 , wherein said oscillator driver is configured to sweep said excitation frequency through a range of excitation frequencies surrounding said first natural frequency.
8. The apparatus of claim 1 , wherein said oscillator driver is configured to sweep said excitation frequency between about 20.5 kHz and about 25.5 kHz.
9. The apparatus of claim 1 , wherein said holding ring is made from a metallic material.
10. The apparatus of claim 9 , wherein said vial is made from a material softer than said metallic material.
11. The apparatus of claim 9 , wherein said vial is made from a polypropylene material.
12. The apparatus of claim 1 , further comprising:
a structural casing; and
at least one acoustic insulator configured to support said transducer assembly within said structural casing.
13. The apparatus of claim 1 , wherein said chamber of said vial is configured to be filled with a fluid for immersing said biological sample.