Pathogens that cause healthcare associated infections (HAIs) pose an ongoing and increasing challenge to health care facilities, both in the clinical treatment of patients and in preventing cross-transmission of problematic pathogens. The frequency of pathogens in HAIs was highlighted in a study conducted by the National Healthcare Safety Network (NHSN)1The ten most common pathogens account for 84% of HAIs.

        

HAIs result in more deaths than AIDS, auto accidents and breast cancer combined in the United States2. As a result, manufacturers are looking to antimicrobial coatings that are biocompatible, biostable, inert, non-toxic and can meet FDA compliance guidelines. This has led to an increased interest in antimicrobial protection for devices in continuous contact with patients (catheters and other medical devices)3.    

Why an Alternative is Needed

Silver has been the foremost antimicrobial in use because it has a high efficacy against a wide range of potentially disease-causing microorganisms. Generally, silver ions work by concentrating on the surface of the product where they can act against contaminating bacteria. The silver ions essentially bind with the bacteria and microbes, damaging their cells, which in turn disrupts the bacteria’s normal function, stopping them from reproducing and causing the bacteria to die.

While silver ion technology has been generally accepted in the industry, medical device manufacturers have expressed concerns. One problem is that the technology wears down in strength over time. While damaged pathogens cannot come back to life, new pathogens may be introduced. Also, high exposure or ingestion of highly concentrated forms of ionic silver may cause “Argyria or argyrosis,” a permanent discoloration of skin.

Antibiotics containing antimicrobial solutions are also available and have shown effectiveness in some applications. However, there are some disadvantages that have been observed in their use. The local and fast release of antibiotics can reduce the effectiveness for long-term use of catheters and other applications as their concentration drops below the minimal inhibitory concentration. Additionally, the use of high doses of antibiotics can result in antibiotic resistance, and may have limited effectiveness against a wide range of microorganisms.4,5,6

microRESIST Antimicrobial technology offers an alternative. This significant breakthrough combines the benefits of naturally biocompatible Parylene with antimicrobial properties to effectively eliminate harmful microorganisms on coated medical devices. microRESIST completely encapsulates the surface of a device, regardless of size or complexity, with a pinhole-free, micron level coating that has both antimicrobial and biocompatible properties.

Understanding microRESIST  

To understand microRESIST, you first must understand Parylene, which is an ultra-thin and pinhole-free coating applied by a gas deposition process where the coating actually grows onto any surface that needs protection. The molecular “growth” of Parylene coatings ensures a uniform, conformal coating at the thickness specified by the manufacturer and, because it is vapor phase deposition process, it also penetrates into every crevice, regardless of how seemingly inaccessible. Parylenes N, C and Parylene HT have been widely used in medical applications for decades, providing excellent barrier properties against body fluids as well as moisture, chemicals and common gases. The coating also possess excellent dry-film lubricity characteristics, making it a common choice for devices that must be protected and yet still have surface properties that let them slide easily within the body. 

Parylenes N, C and Parylene HT comply with the biological testing requirements of ISO-10993 and are certified to comply with the biological testing requirements for USP Class VI Plastics.microRESIST adds a new level of protection to Parylene by incorporating an organic compound into the basic Parylene formulation, adding advanced antimicrobial properties.

Testing and Results

Samples coated with microRESIST antimicrobial Parylene technology were tested for antimicrobial activity according to JIS Z 28018. To determine the microbial log reduction, films containing SCS microRESIST were inoculated with microorganisms, and then incubated for 24 hours. All samples protected with SCS microRESIST demonstrated greater than 5 Log reduction after 24 hours.

Sets of microRESIST coated samples were immersed in Phosphate Buffered Saline (PBS) at 37°C for 7 days and 15 days, respectively, then inoculated with E. coli and tested per JIS Z 2801 to determine the microbial reduction. A non-PBS immersed sample (0 days) was used as a control. All SCS microRESIST coated samples achieved greater than 5 Log reduction.Samples protected with SCS microRESIST antimicrobial Parylene technology were also subjected to cytotoxicity testing per ISO 10993, part 5. The test sample met the ISO 10993 requirements.

Along with the antimicrobial properties being tested, microRESIST treated samples were also tested for the ability to withstand the most common sterilization processes. Two sets of SCS microRESIST treated samples were sterilized; one set using gamma radiation, dose range between 10-15kGy (1.0 to 1.5 Mrad), the other using Ethylene Oxide (EtO). Samples were then tested for effectiveness against E. coli according to JIS Z 2801. SCS microRESIST(post sterilization) achieved greater than 4 Log reduction against E. coli bacteria.

The coefficient of friction (COF) of Parylene coated surfaces (without antimicrobial properties) and SCS microRESIST coated surfaces were also tested, in accordance with ASTM D 1894-08 at room temperature. Results indicate there is no statistical difference between the samples.

Expanding the Antimicrobial Reach

microRESIST technology fills both the gap of antimicrobial attributes for Parylene itself and also offers an alternative to the limited reach of standard silver ion technology. Any devices that come in contact with, or are placed into the body, can be protected against a variety of microorganisms. microRESIST applications may include:

·         Electronic circuit boards

·         Dermal drug delivery devices

·         Sensors & transducers

·         Cochlear devices

·         MEMS, biochips

·         Pulse generators: ICDs, pacemakers, neurostimulators

·         RFID devices

·         Radiation dosimeters

·         Electrosurgical devices

·         Hearing aids

·         Ocular devices

·         Ventilators

·         Seals, O-rings, tubing

·         Brain probes

·         Stents

·         Catheters and guide wires

·         Needles

·         Molds

·         Urological tools

As HAIs continue to pose a challenge to hospitals and healthcare facilities, microRESIST adds an alternative to purchasing silver ion-embedded tubing or surfaces. This gives medical manufacturers an antimicrobial technology that effectively eliminates and protects against microorganisms.

Footnotes

1Hidon et al. Antimicrobial-Resistant Pathogens Associated with Healthcare Associates Infections: Annual Summary of Data Reported to the National Healthcare Safety Network at the Center for Disease Control and Prevention, 2006-2007. Infection Control and Hospital Epidemiology. November 2008. Vol. 29, Mo.11).

2Safe Care Campaign. Infection facts you need to know. http://www.safecarecampaign.org/facts.html (Accessed June 10, 2013)

3PR Newswire, Antimicrobial Coatings Market Is Expected To Reach USD 3.3 Billion Globally by 2018: Transparency Market Research. http://www.prnewswire.com/news-releases/antimicrobial-coatings-market-is-expected-to-reach-usd-33-billion-globally-by-2018-transparency-market-research-186912691.html (accessed January 22, 2013)

4Walder, B.; Pittet, D.; Tramer, M.R. Prevention of bloodstream infections with central venous catheters treated with anti-infective agents depends on catheter type and insertion time: Evidence from a meta-analysis. Infect. Control Hosp. Epidemiol. 2002, 23, 748-756.

5Kälicke, T.; Schierholz, J.; Schlegel, U.; Frangen, T.M.; Köller, M.; Printzen, G.; Seybold, D.; Klöckner, S.; Muhr, G.; Arens, S. Effect on infection resistance of a local antiseptic and antibiotic coating on osteosynthesis implants: An in vitro and in vivo study. J. Orthop. Res. 2006, 24, 1622-1640.

6Harris, L.G.; Mead, L.; Müller-Oberländer, E.; Richards, R.G. Bacteria and cell cytocompatibility studies on coated medical grade titanium surfaces. J. Biomed. Mater. Res. 2006, 78A, 50-58.

7Certificates of Compliance, USP Biological Tests, NAMSA, Incorporated, Northwood, OH.

8 JIS Z 2801: 2010. Antibacterial products – Test for antibacterial activity and efficacy.

Author Contact information

Rakesh Kumar, Ph.D.

Vice President of Technology

Specialty Coating Systems

7645 Woodland Drive

Indianapolis, Indiana 46278 USA

317.244.1200

rkumar@scscoatings.com

www.scscoatings.com