Research data and clinical studies
SSD Antimicrobial Coatings
Anti-Infective Coating for Medical Devices
Infection resistant coatings minimize the risk of device-associated infection and may provide long term benefits for implantable devices. A clinically relevant in-vitro biofilm test model was developed for analyzing bacterial adsorption and viability.
For urology applications, clinical isolates taken from urinary tract infections of the pathogens; E. coli, E, faecelis, C. albicans, P. aeruginosa, and S. aureus and grown to steady state in separate continuously stirred bioreactors. Inoculate suspensions of each pathogen were diluted to approximately 1.0 x 10 3 CFU/mL in artificial urine, and allowed to contact 100 mm 2 test coupons of the finished form of the anti-infective coating in a once pass over flow cell bioreactor. The test coupons were analyzed by; confocal laser scanning microscopy (CLSM) utilizing a viability stain, scrape and plate for overnight incubation on R2A agar, and quantitative PCR.
Source: http://www.bacterin.com
Results presented are for E.coli on an antimicrobial loaded catheter utilizing a dual loaded silver compound/antimicrobial peptide on a sustained release platform. The coating can be incorporated onto a variety of medical plastics and shows a 4 log reduction over a current anti-infective technology for
7 days.
Guy S. Cook, Bacterin Inc.A presentation to ASAIO 2001
Antithrombogenic Heparin Coatings
Anti-Xa Activity of Heparin-containing Surface Films
Summary
Two separate sections (~1-2 cm 2 each) of two distinct surface films (6-65B and 6-65D, respectively) were incubated in isotonic Anti-Xa buffer at 37 o C. At various times (e.g. 1 hr, 24 hr, 48 hr, 1 wk, 2 wk, etc.), the incubation buffer was removed from the surface film and assayed for heparin Anti-Xa activity by the USP Anti-Xa method. Fresh buffer solution was then used to replace the removed buffer and the incubation continued until the next assay point, where the procedure was repeated.
The results with the two films were quite distinct. The 6-65B films appeared to be quite hydrophobic, with the film “scrolling” into a small tube in the incubation buffer. Also, within 1 week of extraction, over 2 mg (~450-500 Units) of heparin was extracted from each of the duplicate, 6-65B films. After two weeks, the 6-65B films had released a quantity of heparin equivalent to ~12-13% of the original film mass (see Table 1, attached). Film 6-65D, on the other hand, only eluted or released heparin at a relatively slow rate, resulting in about ~2-3% of the original film mass being eluted as biologically active heparin in the first two weeks (see Table 1). The 6-65D film also did not change physical shape during the incubation in buffer, but appeared to be hydrophilic and retain its original shape and texture.
Experimental Design and Details
• Cut 5-6 separate pieces of each of the 6-65 films and placed these in tared 12 X 75 mm Falcon tubes.
• By weight, closely matched duplicate films for each of the two film types (4 samples total) were then treated with 1 ml each of USP Anti-Xa buffer for
1 hour at 37 o C.
• The incubation buffer was removed to a separate tube, and then assayed for Anti-Xa activity, after appropriate serial dilution with additonal
Anti-Xa buffer.
• After removal of the first 1 ml of buffer from each film, the buffer was replaced in each tube with 5 mls of buffer for continued incubation. For all subsequent assays and incubations (beyond the 1 hour point), 5 mls of incubation buffer was used in each case.
• Anti-Xa assay buffer consists of 0.05 M Tris, 0.0075 M EDTA, 0.175 M NaCl, and 0.1% PEG-8000, pH = 8.4
• Anti-Xa assays were perfomed according to the USP Heparin Sodium monograph procedure on a STA Compact hemostasis instrument
(Parsippany, NJ).
Conclusions:
Based upon the quantities of heparin released from each of the film types, the 6-65D appears to be retaining a significant portion of the starting heparin mass. If the remaining heparin is biologically active and accessible at the surface of the film, we will be able to measure this with the USP Anti-Xa method. This experiment is planned for the 1 month time period. If the latter experiment shows biologically active heparin on the film surface, this would appear to be an interesting, and stable anti-thrombotic film, as it appears that no further heparin is eluting from the 6-65D films at two weeks and that the remaining heparin is tightly bound.
By contrast, the 6-65B films appear to have “released” all of the starting heparin within the the first two weeks, leaving little chance that there remains biologically active heparin at the film surface. My suggestion is to not assay or incubate the 6-65B films any further.
Heparin release/retention in urethane 6-65D
Time |
Ave eluted, mg |
Ave cum % |
|
Surface |
|
|
|
eluted |
|
Active |
|
0 Hr |
0 |
0 |
|
by factor Xa |
|
1 Hr |
0.0349 |
3.43 |
|
|
|
1 Day |
0.1609 |
17.415 |
|
|
|
2 Day |
0.0081 |
18.215 |
|
|
|
3 Day |
0.0063 |
18.835 |
|
|
|
7 Day |
0.0068 |
19.5 |
|
|
|
14 Day |
0.0004 |
19.58 |
|
|
|
30 Day |
0.0007 |
19.64 |
|
2.2mU/cm2 |
|
60 Day |
0.00005 |
20.66 |
|
2.5mU/cm2 |
|
90 day |
below detection |
|
1.5 mU/cm2 |
|
6 month |
below detection |
|
2.0mU/cm2 |
|
Film load,mg |
1.02 |
100 |
|
|
|
Test Facility: Biocascade
Notes:
The films were tested for bioavailable heparin via an antifactor Xa test. Surface heparin can bind AT III and inhibit anti Xa. Functional testing is more relevant than other styles of reporting heparin activity.
Basic Drug Delivery
Transgene Delivery of Plasmid DNA to Smooth Muscle Cells and Macrophages from a Biostable Polymer-coated Stent
(31 page PDF file. 1.2M Download)