Critical point drying of hydrogels in analyte sensors

• US 9,963,556 B2
• Filed: 09/18/2014
• Issued: 05/08/2018
• Est. Priority Date: 09/18/2013
• Status: Active Grant

• Current Assignee: Senseonics, Incorporated (Senseonics Holdings, Inc.)
• Original Assignee: Senseonics, Incorporated (Senseonics Holdings, Inc.)
• Inventors: Huffstetler, Philip, Modzelewska, Aneta
• Primary Examiner(s): Jarrett, Lore R
• Application Number:
  US14/489,728
• Publication Number:
  US 20150079669A1
• Time in Patent Office: 1,328 Days
• CPC Class Codes: A61B 5/0071 by measuring fluorescence emission
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: A61B 5/1459 invasive, e.g. introduced into the body by a catheter A61B5/1464 takes precedence
• CPC Class Codes: A61B 5/6861 Capsules, e.g. for swallowing or implanting
• CPC Class Codes: C08J 3/00 Processes of treating or compounding macromolecular substances
• CPC Class Codes: F26B 21/14 using gases or vapours other than air or steam , e.g. inert gases
• CPC Class Codes: G01N 21/6428 Measuring fluorescence of fluorescent products of reactions or of fluorochrome labelled reactive substances, e.g. measuring quenching effects, using measuring "optrodes" in vivo A61B5/00; immunoassay G01N33/53

Abstract

A hydrogel is dried by a critical point drying technique. The hydrogel may include indicator molecules embedded therein and may be part of a hydrogel-based device, such as, for example, an analyte sensor.

Claims

1. A method of preparing a hydrogel for a hydrogel-based analyte sensor configured for sensing the presence of an analyte in contact with the analyte sensor, the method comprising:

applying the hydrogel to all or part of a surface of a sensor housing of the analyte sensor, wherein the hydrogel comprises indicator molecules that are configured to emit a detectable signal or a change in a detectable signal indicating the presence of the analyte;

applying a protective catalyst to the hydrogel, wherein applying the protective catalyst to the hydrogel comprises sputtering the protective catalyst on the hydrogel; and

drying the hydrogel, which (i) comprises the indicator molecules, (ii) has been applied to all or part of the surface of the sensor housing, and (iii) to which the protective catalyst has been applied, by a critical point drying technique that comprises;

replacing water within the hydrogel with an intermediate fluid that is miscible with water and CO₂;

replacing the intermediate fluid within the hydrogel with CO₂;

manipulating temperature and pressure to achieve super critical CO₂; and

removing the supercritical CO₂ from the hydrogel.

2. The method of claim 1, wherein the temperature for achieving super critical CO₂ is about 30-35°

C., and the pressure for achieving supercritical CO₂ is about 1000-1200 psi.

3. The method of claim 1, further comprising storing the hydrogel-based analyte sensor at room temperature after the critical point drying step.

4. The method of claim 1, further comprising implanting the critical point dried hydrogel-based analyte sensor into a living being without pre-hydrating the hydrogel-based analyte sensor prior to implanting.

5. The method of claim 1, wherein the protective catalyst is platinum.