Activities & Competences

The goal for our activities is development of medical devices for disinfection, which utilizes ultra-violet C light emitting diode technology (UVC LED). The result of our research, developments and prototyping are solutions which can be connected to existing medical devices close to the patient. Together with our collaborators we have worked with the UVC LED technology since its appearance. The UVC LEDs have been integrated into prototyped light sources and tested on medical tubing in various contaminated settings.

During the work and research we have acquired specific knowledge about the optical design and how to interface between the UVC LED light sources and the narrow and small enclosures and medical tubing. Sampling from small enclosures and microbiological testing is an important step to consider in the overall performance tests of developed prototypes. The available materials with applicable optical properties for use in the UVC spectral range (240 – 280 nm) are very limited.  This is a challenge in the design of the UVC disinfection devices. Below you will find references to our earlier scientific work.   

References

A UVC Device for Intra-luminal Disinfection of Catheters: In Vitro Tests on Soft Polymer Tubes Contaminated with Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli and Candida albicans

Photochemistry and Photobiology — 2011, Volume 87, Issue 5, pp. 1123-1128

Bak, Jimmy Technical University of Denmark • Department of Photonics Engineering
Begovic, Tanja Technical University of Denmark • Department of Photonics Engineering
Bjarnsholt, Thomas (University of Copenhagen • Department of International Health, Immunology and Microbiology, Faculty of Health Sciences Nielsen, Anne (University of Copenhagen • Department of International Health, Immunology and Microbiology, Faculty of Health Sciences

Corresponding author Jimmy Bak: contact@uvclinical.com

Potential In Vivo UVC Disinfection of Catheter Lumens: Estimation of the Doses Received by the Blood Flow Outside the Catheter Tip Hole

Photochemistry and Photobiology — 2011, Volume 87, Issue 2, pp. 350-356

Bak, Jimmy • Technical University of Denmark • Department of Photonics Engineering
Jørgensen, Thomas Martini Technical University of Denmark • Department of Photonics Engineering Helfmann, Jurgen Laser- und Medizin-Technologie GmbH (LMTB), Berlin
Gravemann, Ute Blood Center of the German Red Cross (NSTOB), Springe, Germany
Vorontsova, Inessa Universidad Popular Autónoma del Estado de Puebla

Corresponding author Jimmy Bak: contact@uvclinical.com

Disinfection of Pseudomonas aeruginosa biofilm contaminated tube lumens with ultraviolet C light emitting diodes

Biofouling — 2010, Volume 26, Issue 1, pp. 31-38

Bak, Jimmy • Technical University of Denmark • Department of Photonics Engineering Ladefoged, S.D.Tvede, M. Gregersen, A. Copenhagen University Hospital • Nephrological Clinic Begovic, Tanja • Technical University of Denmark • Department of Photonics Engineering

Corresponding author Jimmy Bak: contact@uvclinical.com

ABSTRACT

Bacterial biofilms on long-term catheters are a major source of infection. Exposure to ultraviolet C (UVC – 265 nm) light was shown in an earlier study to reduce the number of bacteria substantially on ex vivo treated urinary patient catheters. Very large doses (long treatment times) should, however, be applied to obtain 99.9% disinfection rates. The major reason was that besides cells the mature biofilm contained absorbing and scattering particulates, which made the biofilm opaque. The potential of UVC light emitting diodes (LED) for disinfection purposes in catheter-like tubes contaminated with biofilm was investigated. It was shown that UVC light propagation was possible through both Teflon and catheter tubes (silicone). The disinfection efficiency of the diodes was demonstrated on tubes contaminated artificially with a Pseudomonas aeruginosa biofilm. The tubes were connected to a flow system and biofilms were produced during a 3 day period. Tubes in lengths of 10 (Teflon, silicone) and 20 cm (Teflon) were contaminated. Tubes for control and for UVC treatment were contaminated in parallel. Biofilms were sampled from the total inner surface of the tubes. Colony counts on the control samples were in the range of 5 6 105–1.3 6 109 CFU ml71, with disinfection rates in the range 96– 100%. The applied UVC doses corresponded to treatment times between 15 and 300 min. Disinfection (100%) was obtained in 10 cm Teflon tubes exposed for 30 min (detection limit 55 CFU ml71). The same result was obtained for a 20 cm Teflon tube exposed for 300 min. The disinfection rate was 96% for the 20 cm tube if the dose was reduced to 30 min. A disinfection rate of 99.99% was observed for a 10 cm peritoneal dialysis catheter tube (silicone) exposed for 300 min. Differences between the tubes were dependent on the differences in length and the type of the material. The UVC light was transmitted six times more efficiently in Teflon than in silicone tubes of equal length (10 cm). The germicidal effect to obtain a 99.99% killing rate for the biofilm (*78 J m72) is comparable to that for the planktonic bacterium. It is concluded that there is potential for LED UVC light sources if they are used for disinfection of thin biofilms.
Keywords: biofilm; UVC; ultraviolet light; light emitting diodes; LED; disinfection; sterilization; Pseudomonas aeruginosa; tubes; catheters; peritoneal dialysis catheter; catheter lumen; liquid light guide; light propagation in tubes; refractive index of NaCl solution; UVC transmittance in polymer tubes; FEP Teflon tubes; silicone tubes

Photographs showing the evenly distributed illumination of the inner surface of a Teflon tube filled with a 20% NaCl solution (left) and the more uneven distribution of light in tubes filled with pure water with a lower refractive index (right). The visualization experiments were carried using blue laser light at 442 nm.

UVC fluencies for preventative treatment of pseudomonas aeruginosa contaminated polymer tubes

Biofouling — 2010, Volume 26, Issue 7, pp. 821 – 828

Bak, Jimmy • Technical University of Denmark • Department of Photonics Engineering Ladefoged, Søren D Copenhagen University Hospital • Nephrological Clinic
Begovic, Tanja • Technical University of Denmark • Department of Photonics Engineering Winding, Anne, DMU Århus Universitet.

Corresponding author Jimmy Bak: contact@uvclinical.com

ABSTRACT

Exposing Pseudomonas aeruginosa biofilm grown on the inner surface of Teflon and silicone tubes to UVC light (265 nm) from light emitting diodes (LED) has previously been shown to substantially reduce biofilm growth. Smaller UVC fluencies were required to disinfect Teflon tubes compared to silicone tubes. Light propagation enhancement in tubes can be obtained if the refractive index of the intra-luminal saline solution is higher than that of the polymer. This condition is achieved by using Teflon tubes with a low refractive index (1.34) instead of the polymers with a high refractive index (1.40–1.50) normally used for tubing in catheter production. Determining whether or not UVC light exposure can disinfect and maintain the intra-luminal number of colony forming units (CFUs) at an exceedingly low level and thus avoid the growth and establishment of biofilm is of interest. The use of UVC diodes is demonstrated to be a preventative disinfection treatment on tubes made of Teflon, which enhances the UVC light propagation, and on tubes made of a softer material, ethylene vinyl acetate (EVA), which is suitable for catheters but much less suitable for UVC light propagation. Simulating an aseptic breach (*103–104 CFU ml71), the UVC disinfection set-up was demonstrated using tubes contaminated with planktonic P. aeruginosa. After the tubes (10–20 cm) were inoculated with the bacterial solution for 3 h, they were emptied and filled with saline solutions (0.9–20%). Next UVC fluencies (0–21 mJ cm72) were applied to the tubes 3 h after inoculation. Colony counts were carried out on liquid samples drawn from the tubes the first day after UVC treatment and liquid and surface samples were collected and analyzed 3–4 days later. A fluence of approximately 1.0 mJ cm72 was noted as being sufficient for no growth for a period of 3–4 days for the Teflon tubes. Determining the fluence threshold for the EVA tubes was not possible. Almost all of the UVC-treated EVA tubes were disinfected simply by filling the tubes with a saline solution. Direct UVC treatment of the contaminated EVA tubes revealed, however, that a fluence of 21 mJ cm72 killed the bacteria present in the tubes and kept them disinfected for a period of 3–4 days.
Keywords: biofilm; UVC; light emitting diodes; disinfection; sterilization; Pseudomonas aeruginosa; tubes; catheters; catheter sepsis; catheter bacteremia; catheter lumen; liquid light guide; refractive index; sodium chloride; fluoroethylene propylene; Teflon; ethylene vinyl acetate; UV transmittance in tubes.

Dose requirements for UVC disinfection of catheter biofilms

Biofouling — 2009, Volume 25, Issue 4, pp. 289-296

Bak, Jimmy • Technical University of Denmark • Department of Photonics Engineering Ladefoged, Søren D. Copenhagen University Hospital • Nephrological Clinic
Tvede, Michael Copenhagen University Hospital • Department of Clinical Microbiology Begovic, Tanja • Technical University of Denmark • Department of Photonics Engineering Gregersen, Annette Copenhagen University Hospital • Department of Clinical Microbiology

Corresponding author Jimmy Bak: contact@uvclinical.com

ABSTRACT

Bacterial biofilms on permanent catheters are the major sources of infection. Exposure to ultraviolet-C (UVC) light has been proposed as a method for disinfecting the inner surface of catheters. Specification of a UVC-based device for in vivo disinfection is based on the knowledge of the required doses to kill catheter biofilm. Given these doses and the power of available UVC light sources, calculation of the necessary treatment times is then possible. To determine the required doses, contaminated urinary catheters were used as test samples and UVC treated in vitro. Patient catheters (n 1⁄4 67) were collected and cut into segments of equal size and treated with various UVC doses. After treatment, the biofilm was removed by scraping and quantified by counting colony forming units. Percentage killing rates were determined by calculating ratios between UVC-treated samples and controls (no UVC treatment). Mean killing rates were 89.6% (0.5 min), 98% (2 min), and 99% (60 min). Approximately 99% killing was obtained with a UVC dose of 15 kJ m72. This dose, which is about 100 to 1000 times greater than the lethal dose for planktonic cells, is expected to be the maximum dose required to maintain newly inserted catheters free of contamination. The combination of high doses required to kill mature biofilm and the limited effect of current UVC light sources result in a relative long treatment time (*60 min). If a UVC-based method is to be of practical use for disinfection of catheters in the clinic, repeated preventive treatments should be carried out on newly inserted catheters.
Keywords: biofilm; UVC radiation; catheters; contamination; disinfection

Disinfection of Biofilms in Tubes with Ultraviolet Light

IUVA — World Congress of the International UltraViolet Association, 2009

Bak, Jimmy • Technical University of Denmark • Department of Photonics Engineering

Begovic, Tanja • Technical University of Denmark • Department of Photonics Engineering

Corresponding author Jimmy Bak: contact@uvclinical.com

Intraluminal Disinfection with Ultraviolet-C Light

Poster displayed at WoCoVa conference in Amsterdam 2012

Jimmy Bak (U-vivo ApS& DTU Fotonik) and Tanja Begovic (DTU Fotonik)

Download poster: sdkdlaskaæs

Corresponding author Jimmy Bak: contact@uvclinical.com

ABSTRACT

UVC light has been since 1913 for disinfection of drinking water. Its disinfection properties are based on the photoinduced dimerization of the double bonds in the bacterial DNA base pairs, which leaves the bacterial cell in a state in which it cannot multiply. We have demonstrated earlier in several reports that UVC light can be launched into polymer tubes and disinfect tubes contaminated with Pseudomonas aeruginosa biofilm and various planktonic bacteria. We present a UVC prototype device for intra-luminal disinfection of catheter hubs and tubes. The LED and other optical and electric parts are an integrated part of the device, which via a disposable unit is joined to a Luer connector. In addition, we demonstrate a newly designed single—lumen catheter, which allows UVC light to propagate and disinfect the entire lumen.

Disinfection of catheter tubes with ultraviolet-C light

Poster displayed at the GaveCelt conference in Torino 2013

Jimmy Bak and Tanja Begovic, Department of Photonics, DTU Denmark

Thomas Bjarnsholt and Anne Nielsen, Faculty of Health Sciences, KU Denmark

Corresponding author Jimmy Bak: contact@uvclinical.com

ABSTRACT

UVC light can be launched into polymer tubes and disinfect tubes contaminated with biofilm and planktonic bacteria. UVC kills bacteria by modifying their DNA and has been used for more than a century for disinfection.
New light sources show promise for the development of small handheld device for clinical use. A UVC device for intra-luminal disinfection of catheter hubs and tubes is presented. The device consists of optical and electric parts, which via a disposable unit is joined to the Luer connector. We also demonstrate a prototype catheter, which allows UVC light to propagate and disinfect the entire lumen. The efficiency in tubes coated with human plasma is demonstrated as well.

Intra-luminal disinfection with ultraviolet-C light

Poster displayed at the AVA conference in San Antonio 2012

Jimmy Bak and Tanja Begovic, Department of Photonics, DTU Denmark

Corresponding author Jimmy Bak: contact@uvclinical.com

INTRODUCTION

UVC light has been used since 1913 for disinfection of drinking water. In 1990 it was suggested for intraluminal disinfection of catheters. Its germicidal properties are based on the photo induced dimerization of the double bonds in the bacterial DNA base-pairs, which leaves the bacterial cell in a state in which it cannot multiply. The dose is dependent on the UVC intensity and exposure time:

Dose (Fluence) = Intensity Exposure Time

Typically doses for 99.9 % kill of planktonic bacteria are a few mJ/cm2: E. coli and S. aureus ~ 6.6 mJ/cm2, P.aeruginosa ~ 10.5 mJ/cm2 Doubling the dose gives approximately 1 log reduction.