Antimicrobial articles produced by additive manufacturing

Abstract

An antibiotic-eluting article for implantation into a mammalian subject, produced by an additive manufacturing process wherein a polymeric material is concurrently deposited with a selected antibiotic. The additive manufacturing process is a fused deposition modeling process. The antibiotic-eluting article may be temporary or permanent orthopaedic skeletal component, an orthopaedic articulating joint replacement component, and/or an external hard-shell casing for an implantable device. One or more bone-growth-promoting compositions may be concurrently deposited with the polymeric material. The implantable device may be a cardiac pacemaker, a spinal cord stimulator, a neurostimulation system, an intrathecal drug pump for delivery of medicants into the spinal fluid, and infusion pump for delivery of chemotherapeutics and or anti-spasmodics, an insulin pump, an osmotic pump, and a heparin pump.

Claims

1. An antibiotic-eluting article comprising an antibiotic-containing polymeric mono-filament consisting of: a dry blend of: a polymer and at least one antibiotic; wherein the amount of the at least one antibiotic is between about 0.1 weight percent and about 20.0 weight percent relative to the total weight of the antibiotic-containing polymeric mono-filament; wherein the polymer is selected from the group consisting of: polylactic acid, polycaprolactone, polyamide, and polyethylene; wherein the diameter of the antibiotic-containing polymeric mono-filament is in the range of about 0.89 millimeters to about 3.0 millimeters, wherein the polymer and the at least one antibiotic are homogenously distributed throughout the antibiotic-containing polymeric mono-filament, wherein the dry blend has been extruded through an extrusion die to produce the antibiotic-containing polymeric mono-filament, and wherein the antibiotic-containing polymeric mono-filament is extrudable through a fused deposition modelling machine to produce the antibiotic-eluting article having the at least one antibiotic homogenously distributed throughout and elutable from the antibiotic-eluting article.

2. The antibiotic-eluting article of claim 1, wherein the antibiotic is selected from the group consisting of an aminoglycoside, an azole, a β-lactam antibiotic, a β-lactamase inhibitor, a cephalosporin, chloramphenicol, clindamycin, fusidic acid, a glycopeptide, a macrolide, metronidazole, mupirocin, a penicillin, a polyene, a quinolone, a rifamycin, a sulfonamide, tetracycline, trimethoprim, and combinations thereof.

3. The antibiotic-eluting article of claim 1, wherein the amount of the at least one antibiotic is between about 0.5 weight percent and about 10.0 weight percent relative to the total weight of the antibiotic-containing polymeric mono-filament.

4. The antibiotic-eluting article of claim 1, wherein the amount of the at least one antibiotic is between about 0.75 weight percent and about 5.0 weight percent relative to the total weight of the antibiotic-containing polymeric mono-filament.

5. An antibiotic-eluting article comprising an antibiotic-containing polymeric mono-filament consisting of: a dry blend of: a polymer, at least one antibiotic, and a bone-growth-promoting composition; wherein the amount of the at least one antibiotic is between about 0.1 weight percent and about 20.0 weight percent relative to the total weight of the antibiotic-containing polymeric mono-filament; wherein the polymer is selected from the group consisting of: polylactic acid, polycaprolactone, polyamide, and polyethylene; wherein the diameter of the antibiotic-containing polymeric mono-filament is in the range of about 0.89 millimeters to about 3.0 millimeters, wherein the polymer and the at least one antibiotic are homogenously distributed throughout the antibiotic-containing polymeric mono-filament, wherein the dry blend has been extruded through an extrusion die to produce the antibiotic-containing polymeric mono-filament, and wherein the antibiotic-containing polymeric mono-filament is extrudable through a fused deposition modelling machine to produce the antibiotic-eluting article having the at least one antibiotic homogenously distributed throughout and elutable from the antibiotic-eluting article.

6. The antibiotic-eluting article of claim 5, wherein the bone-growth-promoting composition is selected from the group consisting of: hyaluronic acid, β-(tricalcium phosphate), SOST (sclerostin), an antagonist that modulates the Wnt signaling pathway, (3-((4(4-tert-butyl-benzyl)-(pyridine-3-sulfonyl)-amino)-methyl)-phenoxy-)-acetic-acid and its analogs, 7-[(4-butyl-benzyl)-methanesulfonyl-amino]heptanoic acid and its analogs, 7-{[2-(3,5-dichloro-phenoxyl)-ethyl]-methanesulfonyl-amino}-heptanoic acid and its analogs, and 3-benzothiepin derivatives.

7. The antibiotic-eluting article of claim 1, wherein the antibiotic composition is selected from the group consisting of tobramycin, gentamicin, vancomycin, and combinations thereof.

8. The antibiotic-eluting article of claim 1, wherein the antibiotic-eluting article is provided with an outer coat comprising a biocidal composition.

9. The antibiotic-eluting article of claim 8, wherein the outer coat comprises one or more of silver nanoparticles, zinc pyrithione, and cationic polymeric biocides.

10. The antibiotic-eluting article of claim 1, wherein the article is an orthopaedic skeletal component.

11. The antibiotic-eluting article of claim 1, wherein the article is an orthopaedic articulating joint replacement component.

12. The antibiotic-eluting article of claim 1, wherein the article is an external casing for an implantable device.

13. The antibiotic-eluting article of claim 1, wherein the article is selected from the group consisting of a cardiac pacemaker, a spinal cord stimulator, a neurostimulation system, an intrathecal drug pump for delivery of medicants into the spinal fluid, an infusion pump for delivery of chemotherapeutics and/or anti-spasmodics, an insulin pump, an osmotic pump, and a heparin pump.

14. The antibiotic-eluting article of claim 1, wherein the article is an implantable dental prosthesis or a replacement tooth component.

15. The antibiotic-eluting article of claim 1, wherein the article is a transcutaneous skin surface treatment device.

16. The antibiotic-eluting article of claim 1, wherein the article is a wound treatment device.

Description

EXAMPLES

Example 1

(1) Plastic filaments comprising 1% of the antibiotic tobramycin were prepared with a two-step process as follows. First step: a master batch comprising 10% tobramycin was prepared by dry-mixing together 1 kg of the antibiotic (sourced from Prinova Canada, Scarborough, ON, CA) with 9 kg of PLA granules sourced from Nature Works LLC (Blair, Neb., USA). The 10% master batch was fed into the feed throat of a LEISTRITZ® lab twin-screw extruder (LEISTRITZ is a registered trademark of Leistritz Aktiengesellschaft Stock Corp., Nürnberg, Fed. Rep. Germany), after which, the extruded strands were pelletized. Second step: 1 kg of the 10% tobramycin/PLA pellets were dry-mixed together with 9 kg of PLA granules after which, the dry blend mixture was fed into the feed throat of a DAVIS-STANDARD® single screw extruder (DAVIS-STANDARD is a registered trademark of Davis-Standard LLC, Pawcatuck, Conn., USA), and extruding a mono-filament with a nominal diameter of 0.051 inches+/−0.002 inches. The mono-filament was air cooled after leaving the extruder die to prevent internal filament porosity, characterized using a laser gauging system for diameter and ovality, and then wound onto a High-impact Polystyrene (HIPS) spool with a 6-inch diameter hub. A control filament was prepared by extruding PLA granules into a mono-filament that was cooled and then wound onto a HIPS spool with a 6-inch diameter hub.

(2) The 1% tobramycin PLA filament was supplied to the extrusion nozzle of a STRATASYS® MOJO® FDM® 3D printer (STRATASYS and MOJO are registered trademarks of Stratasys Inc., Eden Prairie, Minn., USA) to print replicate test coupons with an extrusion temperature of 205° C. Each test coupon had a diameter of 25 mm and a thickness of 2.5 mm, and one surface with a “shiny” appearance and the other surface having a “matte” appearance. Control coupons having the same physical dimensions and appearance as the test coupons, were printed with the STRATASYS® MOJO® FDM® 3D primer by feeding the control PLA filament through the extrusion nozzle at an extrusion temperature of 205° C.

(3) Aliquots of a culture of Staphylococcus aureus grown in Tryptic soy broth (TSB) were plated onto the surface of Tryptic soy agar (TSA) contained within Petri plates. Two test coupons were placed onto the plated S. aureus culture in a Petri plate with one shiny side down and one matte side down. Two control coupons were placed onto the plated S. aureus culture in a Petri plate with one shiny side down and one matte side down. Triplicate plates were prepared with test coupon and with control coupons. The Petri plates were incubated for 72 h at 37° C. after which, the plates were examined for the occurrence of zones of inhibition around the coupons. No inhibition of the growth of S. aureus in the Petri plates receiving the control coupons. However, significant zones of inhibition in the growth of S. aureus were observed around the shiny surfaces (37.7 mm) and the matte surfaces (36.3 mm) of the test coupons thereby confirming that tobramycin was eluted from the 3D-printed articles comprising 1% of this antibiotic in PLA.

Example 2

(4) Four different types of antibiotic-containing plastic filaments were prepared with three different concentrations (1% w/w; 2% w/w; 5% w/w) of three antibiotics, i.e., tobramycin, and gentamicin, vancomycin, for use in 3D printing by FDM® machines. The four plastics tested were: (i) polylactic acid (PLA), (ii) polycaprolactone (PCL), (iii) high-density polyethylene (HDPE), and (v) nylon 12 (N12). Those skilled in these arts will know that articles produced with PLA and PCL are resorbable, i.e., they are materials that are broken down and assimilated by a mammalian body over an extended time-period. The skilled person will also know that articles produced with HDPE and N12 are non-resorbable, i.e., they are materials that will not break down and be assimilated by a mammalian body over extended time periods. The different combinations of antibiotics and polymers produced for this example are shown in Table 1.

(5) Tobramycin was sourced from Prinova Canada. Gentamicin and vancomycin were sourced from Gold Biotechnology Inc. (St. Louis, Mo. USA). PLA granules were sourced from NatureWorks LLC. PCL granules were sourced from Perstorp Plastics Systems Inc. (Lakewood, Wash., USA). HDPE granules were sourced from A. Schulman Americas (Akron, Ohio, USA). Nylon 12 granules were sourced from EMS-Chemie (North America) Inc. (Sumter, S.C., USA). A 10% master batch of each antibiotic polymer mixture was prepared as outlined in Example 1. Subsequently, the 1%, 2%, and 5% antibiotic polymer mixtures were prepared as outlined in Example 1 with the appropriate quantities of the 10% antibiotic master blend mixed with pure polymer granules to arrive at the target mixtures after which, each target mixture was fed into the feed throat of a DAVIS-STANDARD® single screw extruder for extrusion of a mono-filament. The individual mono-filaments were air cooled after leaving the extruder die to prevent internal filament porosity, characterized using a laser gauging system for diameter and ovality, and then wound onto High-impact Polystyrene (HIPS) spools with 6-inch diameter hubs.

(6) TABLE-US-00001 TABLE 1 Antibiotic-containing plastic filaments produced for 3D printing Antibiotic AB %.sup.1 PLA.sup.2 PCL.sup.3 HDPE.sup.4 N12.sup.5 Tobramycin 0 Yes .sup. —.sup.6 Yes — 1 Yes — Yes — 2 Yes — Yes — 5 Yes — Yes — Gentamicin 0 Yes Yes — Yes 1 Yes Yes — Yes 2 Yes Yes — Yes 5 Yes Yes — Yes Vancomycin 0 Yes Yes — Yes 1 Yes Yes — Yes 2 Yes Yes — Yes 5 Yes Yes — Yes .sup.1AB % = % antibiotic in plastic filament w/w .sup.2PLA = polylactic acid .sup.3PCL = polycaprolactone .sup.4HDPE = high-density polyethylene .sup.5N12 = nylon 12 .sup.6— = not done

(7) Selected physical properties of the antibiotic-containing plastic filaments were determined following the test methods set out in ASTM D636 document titled “Standard Test Method for Tensile Properties of Plastics” published by ASTM International and publicly available from their website: http://www.astm.org/Standards/D638.htm. The physical properties of the antibiotic-containing plastic filaments are listed in Tables 2-9.

(8) TABLE-US-00002 TABLE 2 Physical properties of PLA filaments containing tobramycin Tobramycin content in PLA filaments* Physical parameter 0 1% 2% 5% Diameter (inches) 0.071 0.035 0.05 0.05 Peak load (lbf) 13.4 ± 0.2  8.4 ± 0.6 11.5 ± 0.4  5.1 ± 1.5 Peak stress (lbf/in.sup.2) 3393.9 ± 61.1  8731.5 ± 655.8 5853.1 ± 191.2  2579.6 ± 758.7  Strain at break (%)  1.68 ± 0.05  1.34 ± 0.06 0.91 ± 0.14 0.48 ± 0.25 Modulus (lbf/in.sup.2) 419148.4 ± 42180.8 611923.6 ± 33989.1 628082.5 ± 194179.6 635066.5 ± 214856.0 *data are means of three replicates ± SD

(9) TABLE-US-00003 TABLE 3 Physical properties of PLA filaments containing gentamicin Gentamicin content in PLA filaments* Physical parameter 0 1% 2% 5% Diameter (inches) 0.071 0.05 0.05 0.05 Peak load (lbf) 13.4 ± 0.2 10.9 ± 0.5 11.4 ± 0.2 11.4 ± 0.2 Peak stress (lbf/in.sup.2) 3393.9 ± 61.1  5531.1 ± 269.5 5778.6 ± 113.5 6336.1 ± 102.3 Strain at break (%)  1.68 ± 0.05  1.06 ± 0.22  1.09 ± 0.06  1.17 ± 0.06 Modulus (lbf/in.sup.2) 419148.4 ± 42180.8   604840 ± 244516.8 450303.6 ± 38473.7 546278.1 ± 50610.4 *data are means of three replicates ± SD

(10) TABLE-US-00004 TABLE 4 Physical properties of PLA filaments containing vancomycin Vancomycin content in PLA filaments* Physical parameter 0 1% 2% 5% Diameter (inches) 0.071 0.05 0.05 0.05 Peak load (lbf) 13.4 ± 0.2 13.0 ± 0.7  12.4 ± 1.8 13.1 ± 0.8 Peak stress (lbf/in.sup.2) 3393.9 ± 61.1  6609.7 ± 332.2  6290.1 ± 908.2 6653.3 ± 391.2 Strain at break (%)  1.68 ± 0.05 0.98 ± 0.11  1.19 ± 0.65  1.41 ± 0.27 Modulus (lbf/in.sup.2) 419148.4 ± 42180.8 671627.6 ± 145252.7 1038602.0 ± 395613.8 522213.5 ± 35208.2 *data are means of three replicates ± SD

(11) TABLE-US-00005 TABLE 5 Physical properties of PCL filaments containing gentamicin Gentamicin content in PCL filaments* Physical parameter 0 1% 2% 5% Diameter (inches) 0.05 0.05 0.05 0.05 Peak load (lbf)  3.7 ± 0.2 3.7 ± 0.2.sup.   3.8 ± 0.2  3.7 ± 0.2 Peak stress (lbf/in.sup.2) 1912.5 ± 49.8  1879.2 ± 99.7    2113.1 ± 102.9 1861.3 ± 69.1 Modulus (lbf/in.sup.2) 55555.9 ± 1517.8 604840 ± 244516.8 58610.4 ± 2657.2 57471.36 ± 2302.3 *data are means of three replicates ± SD

(12) TABLE-US-00006 TABLE 6 Physical properties of PCL filaments containing vancomycin Vancomycin content in PCL filaments* Physical parameter 0 1% 2% 5% Diameter (inches) 0.05 0.05 0.05 0.05 Peak load (lbf)  3.7 ± 0.2  3.7 ± 0.2   3.6 ± 0.02  3.5 ± 0.1 Peak stress (lbf/in.sup.2) 1912.5 ± 49.8  1937.3 ± 47.5   1825,8 ± 108.7 1789.2 ± 53.0  Modulus (lbf/in.sup.2) 55555.9 ± 1517.8 51031.2 ± 1086.2 50216.9 ± 424.2 51517.0 ± 3950.4 *data are means of three replicates ± SD

(13) TABLE-US-00007 TABLE 7 Physical properties of HDPE filaments containing tobramycin Tobramycin content in HDPE filaments* Physical parameter 0 1% 2% 5% Diameter (inches) 0.05 0.05 0.05 0.05 Peak load (lbf)  3.8 ± 0.1  4.1 ± 0.1  4.2 ± 0.1  4.1 ± 0.1 Peak stress (lbf/in.sup.2) 1938.6 ± 38.1 2098.6 ± 45.3  2160.3 ± 32.3  2051.4 ± 28.2.sup.  Modulus (lbf/in.sup.2) 77164.13 ± 2407.7 88987.4 ± 3410.3 90373.6 ± 1156.1 99006.4 ± 7086+2 *data are means of three replicates ± SD

(14) TABLE-US-00008 TABLE 8 Physical properties of N12 filaments containing gentamicin Gentamicin content in N12 filaments* Physical parameter 0 1% 2% 5% Diameter (inches) 0.05 0.05 0.05 0.05 Peak load (lbf)  10.9 ± 0.2  10.9 ± 0.1  10.6 ± 0.1 10.8 ± 0.8 Peak stress (lbf/in.sup.2) 5543.5 ± 83.3 5552.6 ± 65.9 5383.7+54.4 5500.5 ± 396.1 Modulus (lbf/in.sup.2) 191838.5 ± 6330.7 197138.9 ± 1785.7 198748.8 ± 8950.8 207710.2 ± 7946.3  *data are means of three replicates ± SD

(15) TABLE-US-00009 TABLE 9 Physical properties of N12 filaments containing vancomycin Vancomycin content in N12 filaments* Physical parameter 0 1% 2% 5% Diameter (inches) 0.05 0.05 0.05 0.05 Peak load (lbf)  10.9 ± 0.2  10.9 ± 0.1 10.3 ± 0.5  10.7 ± 0.1 Peak stress (lbf/in.sup.2) 5543.5 ± 83.3 5344.4 ± 66.8 5246.3 ± 262.2 5443.5 ± 61.3 Modulus (lbf/in.sup.2) 191838.5 ± 6330.7 195980.7 ± 5111.5 201682.2 ± 1576.0  212733.5 ± 7729.7 *data are means of three replicates ± SD

(16) Each antibiotic-containing filament was separately supplied to the extrusion nozzle of a STRATASYS® MOJO® FDM® 3D printer to print replicate test coupons, each coupon having the physical dimensions of a diameter of 25 mm and a thickness of 2.5 mm, with one surface having a “shiny” appearance and the other surface having a “matte” appearance. Control coupons having the same physical dimensions and appearance as the test coupons, were printed with the STRATASYS® MOJO® printer by feeding the control filaments through the extrusion nozzle. The 2% and 5% tobramycin/PLA test coupons were printed with an extrusion temperature of 170° C., while the PLA control coupons and the 1% tobramycin PLA test coupons were printed with an extrusion temperature of 205° C. The N12 control coupons, the 1%, 2% and 5% gentamicin/N12 coupons, and the 1%, 2%, and 5% vancomycin/N12 coupons were printed at an extrusion temperature of 195° C. The remaining control coupons and test coupons were printed with an extrusion temperature of 170° C.

Example 3

(17) The elution of antibiotics from the test coupons produced in Example 2 was assessed by the inhibition of the growth of S. aureus on the surfaces of Meuller Hinton agar contained within Petri dishes onto which test coupons placed. S. aureus cultures were grown on TSA amended with 5% sheep blood. A sufficient amount of S. aureus culture was transferred from the TSA culture plates to a 0.85% sterile saline solution to provide a uniform suspension that fell within a 0.5-2.0 McFarland turbidity standard. Aliquots of the S. aureus culture were plated onto Meuller Hinton agar in Petri dishes after which, two test coupons/dish (or alternatively, control coupons) were placed on the agar; one with its shiny side up and the other with its matte side up. The Meuller Hinton agar-containing Petri dishes were then incubated for about 72 hrs at temperatures in the range of about 35° C. to about 37° C. The zones of inhibition around each coupon were then measured and recorded (in mm). A clear zone around a test coupon indicates the inhibition of growth of S. aureus. The diameter of a control coupon is 25 mm and is considered the “0” point. If no inhibition occurred, then the value “25” was recorded and indicates that no inhibition of microbial growth occurred. The data shown in Tables 10, 11, and 12 confirm that all three antibiotics tested, i.e., tobramycin, gentamicin, and vancomycin, were eluted from articles printed with extruded antibiotic-containing polymers as evidenced by zones of inhibition of S. aureus cultures by articles comprising PLA polymer (Table 10), inhibition of S. aureus cultures by articles comprising PCL polymer (Table 11), and inhibition of S. aureus cultures by articles comprising HPDE polymer (Table 12).

(18) TABLE-US-00010 TABLE 10 Elution of antibiotics from 3D-printed articles comprising PLA Antibiotic concentration Antibiotic Control 1% 2% 5% Tobramycin 25 37.7 27.5 28 Gentamicin 25 34.0 26.5 37.5

(19) TABLE-US-00011 TABLE 12 Elution of antibiotics from 3D-printed articles comprising HDPE polymer Antibiotic concentration Antibiotic Control 1% 2% 5% Tobramycin 25 27.0 28.5 37.5

(20) TABLE-US-00012 TABLE 11 Elution of antibiotics from 3D-printed articles comprising PCL polymer Antibiotic concentration Antibiotic Control 1% 2% 5% Gentamicin 25 32.0 38.5 41.0 Vancomycin 25 28.5 25 28.5

Example 4

(21) A study was done to assess the 3D printing performance of a polymer loaded with a combination of three antibiotics (tobramycin, gentamicin, vancomycin) and the elution of the antibiotics from 3D printed articles comprising the antibiotic-loaded polymer. A 10% master batch of each antibiotic dry-mixed with PLA was prepared, then extruded with a LEISTRITZ® lab twin-screw extruder after which, the extruded strands were pelletized. Then, 1 kg of each master batch was dry-mixed with 7 kg of PLA granules after which, the dry blend mixture was fed into the feed throat of a DAVIS-STANDARD® single screw extruder from which was extruded a mono-filament that comprised 3% antibiotics (i.e., 1% tobramycin+1% gentamicin+1% vancomycin). The mono-filament was air-cooled after leaving the extruder die to prevent internal filament porosity, characterized using a laser gauging system for diameter and ovality, and then wound onto a High-impact Polystyrene (HIPS) spool with a 6-inch diameter hub. A control filament was prepared by extruding PLA granules into a mono-filament that was cooled and then wound onto a HIPS with a 6-inch diameter hub.

(22) Selected physical properties of the three antibiotic-containing plastic mono-filaments were determined following the test methods as described in Example 2. The physical properties of the three antibiotic-containing plastic mono-filaments are listed in Table 13.

(23) TABLE-US-00013 TABLE 13 Antibiotic concentration Physical parameter 0 3% Diameter (inches) 0.07 0.05 Peak load (lbf) 13.4 ± 0.2 11.7 ± 0.4  Peak stress (lbf/in.sup.2) 3393.9 ± 61.1  5948.2 ± 0.4   Strain at break (%)  1.68 ± 0.05 1.03 ± 0.08 Modulus (lbf/in.sup.2) 419148.4 ± 42180.8 550481.3 ± 45529.63

(24) The three-antibiotic-containing filament was supplied to the extrusion nozzle of a STRATASYS® MOJO® FDM® 3D printer to print replicate test coupons at an extrusion temperature of 170° C., each coupon having the physical dimensions of a diameter of 25 mm and a thickness of 2.5 mm, with one surface having a “shiny” appearance and the other surface having a “matte” appearance. The control coupons for this study were taken from the batch of control coupons produced in Example 1.

(25) The elution of antibiotics from the test coupons comprising 3% of the combined three antibiotics in PLA, was assessed by the inhibition of the growth of S. aureus on the surfaces of Meuller Hinton agar as described in Example 3. The data shown in Table 14 confirm that the three antibiotics were eluted from articles printed with extruded polymers comprising the three antibiotics.

(26) TABLE-US-00014 TABLE 14 Antibiotic concentration Antibiotic 0 3% 1% tobramycin + 25 36.5 1% gentamicin + 1% vancomycin