Drug Delivery Cannula with Continuous Glucose Monitoring Capability
By combining analyte concentration monitoring electrodes and infusion functions into a single subcutaneous element, the described sensing cannulae having a rectangular cross-section avoids the need for two separate devices for insulin delivery and glucose concentration determination. The substantially flat, thus planar, surface of the sensing cannula provides a substrate for deposition of one or more sensing electrodes, preferably through a lithographic-type process. The inner lumen of the sensing cannula serves as a conduit for drug delivery and is formed in a manner that is compatible with lithographic-type electrode formation. The rectangular cross-section of the sensing cannula also allows face and side ports establishing fluid communication between the inner lumen and tissue that preferably reduces the incidence of occlusion of the inner lumen of the sensing cannula.
1 . An A sensing cannula for delivering a drug and determining glucose concentration when subcutaneously implanted, the sensing cannula comprising:
a proximal end and a distal end;
a planar top face comprising an electrode;
a planar bottom face; and
a thickness between the planar top face and the planer bottom face comprising an inner lumen,
where the planar top face, the planar bottom face, and the thickness in combination provide a rectangular cross-section to the sensing cannula, and
where the inner lumen provides fluid communication from the proximal end to the distal end of the cannula.
2 . The cannula of claim 1 where the electrode of the planar top face is a working electrode and the planar bottom face comprises a pseudo-reference electrode.
3 . The cannula of claim 1 where the electrode of the planar top face is a working electrode and the planar bottom face comprises a counter electrode and a reference electrode.
4 . The cannula of claim 1 where the electrode of the planar top face comprises a working electrode and a pseudo-reference electrode.
5 . The cannula of claim 1 where the electrode of the planar top face comprises a working electrode, a counter electrode, and a reference electrode.
6 . The cannula of claim 1 , where a width of the planar top face and the planar bottom face is from 0.2 mm to 1.0 mm.
7 . The cannula of claim 6 where a length of the cannula defined by the inner lumen is seven to thirty times the width.
8 . The cannula of claim 1 where the inner lumen is in fluid communication with a source of a drug, the source of the drug chosen from a drug delivery pump, a syringe, and a gravity-fed source.
9 . The cannula of claim 1 where a distal end of the inner lumen constitutes from 50% to 90% of a cross-sectional area of the distal end of the cannula.
10 . The cannula of claim 1 where the inner lumen is formed from a polymeric tube.
11 . The cannula of claim 10 where the polymeric tube comprises a polymer chosen from polytetrafluoroethylene, polyurethane, polyolefin, polyimide, polyether ether ketone, silicone, epoxy, urea formaldehyde, phenolics, unsaturated polyester resins, and combinations thereof.
12 . The cannula of claim 10 where the polymeric tube has a melting temperature that is higher than the glass transition temperature of surrounding polymer, where the surrounding polymer contacts the polymeric tube and contributes to the thickness between the planar top face and the planer bottom face of the cannula.
13 . The cannula of claim 12 where the surrounding polymer is a thermoplastic polymer chosen from poly-ether imide, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polybenzimidazole, acrylic, nylon, fluoropolymers, and combinations thereof.
14 . The cannula of claim 12 where the surrounding polymer comprises fibers chosen from carbon fiber, glass fiber, and combinations thereof.
15 . The cannula of claim 1 further comprising an electrical contact on the planar top face at the proximal end, where the electrical contact is in electrical communication with the electrode.
16 . The cannula of claim 1 further comprising a thin permselective membrane on the electrode, where the thin permselective membrane contacts an enzyme and a redox mediator.
17 . The cannula of claim 1 where the electrode has a surface area that is not more than 20% to 25% of the surface area of a pseudo-reference electrode.
18 . The cannula of claim 1 further comprising at least one port establishing fluid communication between the inner lumen and at least one of the planar top face, the planar bottom face, and the thickness.
19 . The cannula of claim 18 where the inner lumen lacks fluid communication with the distal end.
20 . The cannula of claim 1 further comprising a trocar contacting at least one of the planar top face and the planar bottom face.
21 . The cannula of claim 1 where the distal end is tapered to a point.
22 . The cannula of claim 1 where a distal end of the inner lumen is in fluid communication with a metal tube extending beyond the distal end of the cannula.
23 . A method of making multiple planar top and planar bottom face sensing cannula from a sheet assembly array, the method comprising:
forming a sheet assembly array on a metal stencil, the metal stencil including slots cut through the metal stencil and alignment features,
where the sheet assembly array is formed on the metal stencil by bonding polymer sheets comprising conductive layers, and
where the metal stencil comprises multiple inner lumen formers tensioned by the alignment features in the metal stencil; and
singularizing the sheet assembly array to form the multiple planar top and planar bottom face sensing cannula.
24 .- 35 . (canceled)