Removal of stratum corneum by means of light

• US 6,245,060 B1
• Filed: 12/27/1999
• Issued: 06/12/2001
• Est. Priority Date: 03/25/1997
• Status: Expired due to Term

• Current Assignee: Abbott Laboratories Incorporated
• Original Assignee: Abbott Laboratories Incorporated
• Inventors: Muetterties, Andrew J., Henning, Timothy P., Loomis, Neil W., Pope, Mark R., Bojan, Peter M.
• Primary Examiner(s): Dvorak, Linda C. M.
• Assistant Examiner(s): GIBSON, ROY DEAN
• Application Number:
  US09/472,695
• Time in Patent Office: 533 Days
• Field of Search: 609/2-3, 609/9-12, 607/89
• US Class Current: 606/9
• CPC Class Codes: A61B 18/20 using laser
• CPC Class Codes: A61B 2017/00765 Decreasing the barrier function of skin tissue by radiated energy, e.g. using ultrasound, using laser for skin perforation
• CPC Class Codes: A61B 2018/00636 Sensing and controlling the application of energy
• CPC Class Codes: A61B 2018/1807 using light other than laser radiation
• CPC Class Codes: A61B 5/14514 using means for aiding extraction of interstitial fluid, e.g. microneedles or suction
• CPC Class Codes: A61B 5/150022 for capillary blood or interstitial fluid
• CPC Class Codes: A61B 5/15136 by use of radiation, e.g. laser
• CPC Class Codes: A61M 2037/0007 having means for enhancing the permeation of substances through the epidermis, e.g. using suction or depression, electric or magnetic fields, sound waves or chemical agents

Abstract

A method for increasing the permeability of the stratum corneum by means of a source of light, preferably a laser, more preferably a pulsed laser. By increasing the permeability of the stratum corneum, access to the interstitial fluid is achieved, thereby enabling measurement of analytes in the interstitial fluid. In one aspect, the method comprises the steps of:

(a) providing a source of light having a wavelength of from about 930 nm to about 1040 nm; and

(b) exposing a region of the stratum corneum of the patient to said source of light for a period of time sufficient to form an opening in the stratum corneum.

Preferably, exposure of the region of the stratum corneum to the source of light is ceased when an amount of interstitial fluid fills the opening in the stratum corneum, which amount is sufficient to cause the scatter intensity of the light reflected from the surface of the interstitial fluid occupying the opening in the stratum corneum to differ from the scatter intensity of the light reflected from a region of the stratum corneum that is substantially free of interstitial fluid. The invention also involves an apparatus for carrying out the foregoing method.

Claims

1. Apparatus for forming an opening in a region of the stratum corneum of a patient comprising:

(a) a source of light for providing energy to form an opening in the stratum corneum;

(b) a lens assembly for collimating and focusing light from the source of light onto the surface of the stratum corneum;

(c) a broadband detector for detecting a signal related to the intensity of light reflected from the surface of the stratum corneum and from interstitial fluid that fills the opening formed in the stratum corneum by the collimated, focused light from the source of light;

(d) an amplifier for increasing the signal detected by the broadband detector;

(e) a sample and hold circuit for holding the first incremental signal received from said amplifier;

(f) a threshold comparator for comparing an incremental signal received from said amplifier subsequent to the first incremental signal received from said amplifier;

(g) a signal generator and power control circuit for generating a signal to cause a driver circuit to drive current needed to operate said source of light at a desired power level;

(h) a means for commanding said signal generator to generate a signal;

(i) a means for commanding said sample and hold circuit to hold the first incremental signal received from said amplifier;

(j) a means for commanding said threshold comparator to compare (1) an incremental signal received from said amplifier subsequent to the first incremental signal with (2) the first incremental signal received from said amplifier; and

(k) a means for resetting said threshold comparator.

2. The apparatus of claim 1, wherein said source of light is a laser.

3. The apparatus of claim 1, wherein said source of light is a pulsed laser.

4. The apparatus of claim 1, wherein said source of light is a pulsed source of light.

5. The apparatus of claim 4, wherein said first incremental signal is produced by a first pulse generated by said pulsed source of light.

6. The apparatus of claim 5, wherein said threshold comparator compares the incremental signal after a given pulse is generated by said pulsed source of light with the incremental signal measured after said first pulse is generated by said pulsed source of light.

7. The apparatus of claim 6, wherein said threshold comparator is set to be triggered when a scatter intensity of a given pulse of light differs from a scatter intensity of said first pulse of light by at least about 5%.

8. The apparatus of claim 6, wherein said threshold comparator is set to be triggered when a scatter intensity of a given pulse of light differs from a scatter intensity of said first pulse of light by at least about 10%.

9. The apparatus of claim 1, wherein at least one of said means for commanding the signal generator to generate a signal, said means for commanding the sample and hold circuit to hold the first incremental signal received from said amplifier, said means for commanding the threshold comparator to compare (1) an incremental signal received from said amplifier subsequent to the first incremental signal with (2) the first incremental signal received from said amplifier, or said means for resetting said threshold comparator is a microcontroller.

10. The apparatus of claim 1 wherein said broadband detector has a bandwidth ranging from about 800 nm to about 1700 nm.

11. The apparatus of claim 1, wherein said signal generator is a pulse generator.