Sonotrode
Disclosed are a sonotrode and its use for transdermal delivery of therapeutic or cosmetic compounds. The sonotrode 10 comprises a tubular neck 14 attached at a proximal end to a solid head 12 and ending at a distal end in a flared foot 16 . When coupled to an ultrasonic transducer and applied to skin of a human or animal, the sonotrode enhances the delivery of compounds into the skin.
1. A sonotrode for transmitting acoustic energy from an ultrasound generator to a substrate, for use in transdermal delivery of therapeutic or cosmetic compounds, the sonotrode comprising a proximal portion to be coupled in use to the ultrasound generator and a neck portion coupled at one end directly to the proximal portion and terminating at a distal end in a flared foot portion,
acoustic energy from the ultrasound generator being applied in use to the substrate by transmission of ultrasound through the proximal portion, the neck and the foot portion,
wherein a total effective length of the sonotrode is substantially equal to one third of a wavelength of the acoustic energy applied to the sonotrode from the ultrasound generator,
whereby a maximum amplitude of an acoustic energy wave is focused below a surface of the skin,
the neck portion has a smaller cross sectional area than both the foot portion and the proximal portion, and
the distal end of the sonotrode is formed with a blind bore that opens into the flared foot portion and extends straight into the neck portion where the bore terminates.
2. The sonotrode as claimed in claim 1 , wherein both the proximal portion and the neck portion are cylindrical with a constant outer diameter and the bore is a cylindrical bore with parallel sides and extends over substantially a whole length of the neck portion.
3. The sonotrode as claimed in claim 1 , wherein a length of the proximal portion is substantially equal to combined lengths of the neck and foot portions.
4. The sonotrode as claimed in claim 1 , wherein a diameter of the proximal portion is between about two and three times an external diameter of the neck portion.
5. The sonotrode as claimed in claim 1 , wherein a ratio between an internal diameter and an outer diameter of the neck portion is between about 1:4 and 1:2.
6. The sonotrode as claimed in claim 5 , wherein the internal diameter is between 50% and 80% of the outer diameter of the neck portion.
7. The sonotrode as claimed in claim 1 , wherein the neck portion and the bore in the neck portion are of circular cross section.
8. The sonotrode as claimed in claim 1 , wherein a ratio between a diameter of the foot portion and an outer diameter of the neck portion is at least about 3:2.
9. The sonotrode as claimed in claim 1 , wherein the sonotrode is made of aluminium or an aluminium alloy.
10. An apparatus for transdermal delivery of a therapeutic or cosmetic compound, comprising an ultrasound generator, a sonotrode as claimed in claim 1 connected to the ultrasound generator, and a perforator configured to form a series of perforation passageways in the substrate into which the compound is to be delivered either prior to or during application of ultrasound.
11. The apparatus as claimed in claim 10 , in which the perforator is is configured to form the series of perforation passageways by application of electromagnetic radiation to the substrate.
12. The apparatus as claimed in claim 11 , in which the electromagnetic radiation is laser light or radio frequency radiation.
13. A method for transdermal delivery of one or more therapeutic or cosmetic compounds to a human or animal body, the method comprising dermal application of the compound followed by dermal application of ultrasound, wherein the ultrasound is applied via a sonotrode as claimed in claim 1 when coupled to an ultrasound transducer.
14. The method according to claim 13 , wherein a frequency of the ultrasound is matched to a material and dimensions of the sonotrode such that a maximum intensity is reached between 0.3 mm and 2.0 mm below an outer surface of the skin of the human or animal body.
15. The method of claim 13 , wherein the sonotrode is used in combination with iontophoresis, electroporation, magnetic force fields, electromagnetic energy, mechanical pressure fields or electrical fields.