Antimicrobial Prosthetic Liner

Abstract

An antimicrobial prosthetic liner having an exterior fabric layer and an inner layer comprising a thermoplastic and further incorporating evenly distributed nanoparticles of certain metal oxide nanoparticles in an amount ranging from 2%-6% weight per weight and ranging in size from between 5 nanometers and 100 nanometers in diameter, most preferably 20 nanometers in diameter. Preferably, the metal oxide nanoparticles used are titanium dioxide and zinc oxide. Copper oxide, magnesium oxide, aluminum hydroxide as well as metal nanoparticles such as gold nanoparticles and silver nanoparticles may also be used to provide antimicrobial effects.

Claims

1. An antimicrobial prosthetic liner comprising: an open upper end; a closed distal end; and sidewalls between the closed distal end and the open upper end; and an inner layer of a thermoplastic material wherein the thermoplastic material is infused with metal oxide particles which are distributed evenly throughout the thermoplastic material in an amount between 2-10% by weight.

2. The antimicrobial prosthetic liner of claim 1 wherein the metal oxide is selected from the group consisting of silver nanoparticles, copper(I) oxide, copper(II) oxide, magnesium oxide, titanium dioxide, and zinc oxide.

3. The antimicrobial prosthetic liner of claim 2 wherein the metal oxide into the thermoplastic material is a mixture of metal oxide particles.

4. The antimicrobial prosthetic liner of claim 1 wherein the sidewalls have a thickness between 1-9 millimeters.

5. The antimicrobial prosthetic liner of claim 1 wherein the metal oxide particles have a diameter between 5-100 nanometers.

6. An antimicrobial prosthetic liner comprising: an open upper end; a closed distal end; and sidewalls between the closed distal end and the open upper end and having a thickness between 1-9 millimeters; and an inner layer of a thermoplastic material wherein the thermoplastic material is infused with metal oxide particles having a diameter between 5-100 nanometers selected from the group consisting of silver nanoparticles, copper(I) oxide, copper(II) oxide, magnesium oxide, titanium dioxide, and zinc oxide which are distributed evenly throughout the thermoplastic material in an amount between 2-10% by weight.

7. An antimicrobial prosthetic liner comprising: an open upper end; a closed distal end; and sidewalls between the closed distal end and the open upper end; and an inner layer of a thermoplastic material wherein the thermoplastic material is infused with metal oxide particles in an amount effective to cause oxidative stress on bacteria when donned on a residual limb.

8. The antimicrobial prosthetic liner of claim 7 wherein the metal oxide is selected from the group consisting of silver nanoparticles, copper(I) oxide, copper(II) oxide, magnesium oxide, titanium dioxide, and zinc oxide.

9. The antimicrobial prosthetic liner of claim 8 wherein the metal oxide into the thermoplastic material is a mixture of metal oxide particles.

10. The antimicrobial prosthetic liner of claim 7 wherein the sidewalls have a thickness between 1-9 millimeters.

11. The antimicrobial prosthetic liner of claim 7 wherein the metal oxide particles have a diameter between 5-100 nanometers.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] For a more complete understanding of the present disclosure and its advantages, reference is now made to the following descriptions, taken in conjunction with the accompanying drawings, in which:

[0020] FIG. 1 is a prior art graph showing the bactericidal properties of various metal oxides against Escherichia coli;

[0021] FIG. 2 is a prior art graph showing the bactericidal properties of various metal oxides against Staphylococcus aureus;

[0022] FIG. 3 is a prior art graph showing the bactericidal properties of titanium dioxide against Candida albicans;

[0023] FIG. 4 is a prior art table showing reduction in Candida albicans over time after on silicone elastomer containing various percentages of titanium dioxide;

[0024] FIG. 5 is a prior art table providing various mechanical properties of thermoplastic elastomers containing various metal oxides;

[0025] FIG. 6 is a front perspective view of the antimicrobial prosthetic liner; and

[0026] FIG. 7 is a cross-sectional view of the antimicrobial prosthetic liner.

[0027] Similar reference numerals refer to similar parts throughout the several views of the drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0028] The following description is of the best mode presently contemplated for carrying out the invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of describing one or more preferred embodiments of the invention. The scope of the invention should be determined with reference to the claims.

[0029] The present invention relates to a liner 100 for use with prosthetic devices. As shown in FIG. 6, the liner 100 for use with a prosthetic assembly comprises an open upper end 12 for receiving a residual limb, not shown, a closed distal end 14, and sidewalls 16 of predetermined thickness. The liner is airtight when donned over a residual limb. The preferred thickness of the sidewalls 16 is between 1-9 millimeters. The sidewalls 16 have an inner layer 18 of thermoplastic which may be silicone, styrene triblock copolymer gels, or urethane. The sidewalls 16 can be fabric or another layer of more durable and higher friction silicone.

[0030] The inner layer 18 is preferably infused with metal oxide particles 20 distributed evenly throughout its mass. This metal oxide is chosen from the group comprising of: silver nanoparticles, copper(I) oxide, copper(II) oxide, magnesium oxide, titanium dioxide, and zinc oxide. This list is not limiting and should be construed to encompass nanoparticles of metals and metal oxides suitable for antimicrobial liners now known or to be developed.

[0031] The metal oxides used in the present invention are used because they cause oxidative stress on the cell wall of the bacteria and other microbes that form over time when using prosthetic liners. Silver nanoparticles have bactericidal properties due to disassociation of silver ions and have long been used in treatment of infections, wounds, and burns. Silver nanoparticles having a diameter of less than 20 nanometers gain their bactericidal properties by attaching to sulfur-containing proteins in bacterial cell membranes which then induces a change in the membrane's permeability causing pores in the cell walls which then allow silver ions to infiltrate the cells causing damage as it attempts to pump the silver nanoparticles out eventually causing destruction of the cell membrane. Copper(I) oxide and copper(II) both have potent antibacterial activity due to reactive oxygen species (ROS) production after they attach to the bacterial cell walls which then causes oxidative stress and eventually destruction. Magnesium oxide may be more attractive than some of the other metal oxide options because it can be degraded and metabolized efficiently in the human body so long as renal function in the subject is normal. Titanium oxide demonstrates excellent antifungal and antibacterial properties against a broad range of Gram-positive and Gram-negative bacteria and is chemically stable, non-toxic, inexpensive, and is considered a Generally Recognized as Safe (GRAS) substance. Titanium oxide is also photocatalytic which means that the bactericidal properties of titanium oxide are accelerated in the presence of light energy by participating in redox reactions (which eventually destroy the bacterial cell wall) through the creation of electron donor and electron acceptor particles.

[0032] Zinc oxide is of particular importance for the present invention as it is a bio-safe material that possesses photo-oxidizing and photocatalytic properties. Zinc oxide has been shown to generate ROS including hydrogen peroxide, hydroxyl radicals, and peroxide. As described above, ROS is a major factor in mechanisms for cell wall damage in bacteria and, in this case, specifically with zinc oxide-localized interactions creating enhanced membrane permeability, loss of proton motive force, and uptake of dissolved zinc ions toxic to the cell. These mechanisms lead to mitochondria weakness, intracellular outflow, and release in gene expression of oxidative stress which causes eventual cell growth inhibition and cell death. In some cases, enhanced antibacterial activity can be attributed to surface defects due to the abrasive cell surface texture created by zinc oxide. Zinc oxide is non-toxic to and biocompatible with human cells.

[0033] The present invention infuses these metal oxide particles 20 into the inner layer 18 of the prosthetic liner 100, with the metal oxide particles 20 having a size range from 5 nanometers to 100 nanometers in diameter, preferably between 10 nanometers and 40 nanometers. The most preferred nanoparticles diameter is 20 nanometers. The amount of metal oxide particles 20 present in the inner layer 18 should range from 2% to 6% w/w and may be a single metal or metal oxide nanoparticle or a blend of those described herein.

[0034] In addition, other formulations that do not incorporate metal oxides may also be effective. For example, triclosan, chlorinated diphenyl ether, and isothiazolinone are all effective antifungal and antibacterial organic chemicals that could be incorporated into the thermoplastic inner layer 18. These organic chemicals may be included as a blend or present individually but overall should be present in a range between 0.0001% to 3% w/w in relation to the thermoplastic inner layer.

[0035] The present disclosure includes that contained in the appended claims, as well as that of the foregoing description. Although this invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention.

[0036] Now that the invention has been described,