DSM Non-Biofouling Coatings: A Stealth Approach to Fighting Biofilms BioInterface 18 th October 2009 Atlanta, GA.

Transcription

1 Reliable Diagnosis & Discovery DSM : A Stealth Approach to Fighting Biofilms BioInterface 18 th October 2009 Atlanta, GA. Jens Thies PhD, Jun Qiu PhD, Ron de Rijk and Ellis Derikx

2 Content Introduction DSM anti-microbial coatings Non-biofouling surfaces Protein adsorption Microbial adhesion Microbial adhesion on scratched surfaces Conclusions

3 Introduction Biofouling: The undesired accumulation of biological materials on surfaces (Proteins, DNA and cells). Causes problems in: Pre-analytics Diagnostics (e.g. sensors) Storage Medical devices (e.g.implants)

4 DSM Silver based antimicrobial Coating Concept: Lubricious coating + colloidal silver Reduced damage mucosal lining Reduced bacterial adhesion Benefits: Low friction High wear resistance Inner lumen coating On various substrates, such as silicon Excellent activity against a wide variety of bacteria such as E. Coli, Pseudomonas aeruginosa, Enterococcus faecalis in dynamic and static antimicrobial tests Less encrustration Ag + living bacteria dead bacteria Foley catheter

5 DSM Hemocompatible Antimicrobial coatings Concept: Hemocompatible anti-microbial coating Potential Benefits: Antimicrobial activity: Demonstrated activity against E. Coli and S. Aureus (gram - and gram +) Hemocompatibility: Positive results in Hemocompatibility and Thrombogenicity tests Excellent lubricity and superior durability: Reduces stiction and friction. Manufacturing benefits: UV cured coating technology. Status: First concept ready to be tested by customers high thrombogenicity See poster by Alessio Piermattei PhD No thrombogenicity

6 How to prevent bio-fouling Brush structure prevents protein adsorption to the surface If protein adsorption is suppressed, then so is cellular adhesion Application normally by self assembly to form monolayer Protein Protein PEO brush Substrate

7 How is it done today? Adsorption of simple polymeric surfactants. Hydrophilic side chains Hydrophobic backbone Surface adsorption desorption Surface No permanent chemical link with surface or each other High extractables and no mechanical durability

8 VitroStealth TM system 8 Colloidal silica (15nm) functionalised with acrylates (step1) & PEO (step 2). Coating is applied to surface, solvent evaporation and UV curing (step3) Advantages 1 2 Easy to apply Many substrates possible Mechanically robust 3 Easy to make thicker (micron) coatings

9 Surface wetting Static contact angle as a function of time

10 Measuring protein adsorption: Reflectometry Protein adsorption on surface causes a change in reflection of parallel and perpendicular polarized laser light Example curve: lysozyme on bare silica Adsorbed mass (mg m -2 ) Time (sec) J. Coll. Interf. Sci., 1996; 178:

11 VitroStealth TM effective to a wide range of proteins Protein adsorption (mg m 2 ) Effect charge variation Adsorption Buffer silica coating silica coating silica coating silica coating Lysozyme ++ Ribonuclease + Myoglobin +/- _-lactalbumin - Protein adsorption (mg m 2 ) Effect protein size variation Adsorption Buffer silica coating silica coating silica coating silica coating Insulin 5.8 kda _-lactalbumin 14 kda BSA 69 kda Fibrinogen 340 kda Stability >20 months in ambient storage condition, based on the Lysozym adsorption (< 0.1 mg/m 2 ) testing by Reflectometry

12 Blood proteins on coating Fibrinogen on bare silica Fibrinogen adsorption on coating BSA adsorption on bare silica BSA adorption on coating 2.25 Adsorbed protein (mg m-2) Time (sec) More adsorption of larger fibrinogen as expected Adsorption of BSA and Fibrinogen on VitroStealth TM both below detection limit

13 Adsorption human blood plasma Blood plasma bare silica Blood plasma coating 2.00 Adsorbed proteins (mg m -2 ) Time (sec) 100 x diluted with PBS

14 Cellular (Bacterial) Adhesion Parallel plate flow system Busscher et al, Clin. Microbiol. Rev, 2006;19:

15 Early bacterial adhesion Results (2006) Micrograph of S. Epidermidis HBH 276 adhering after (a) 4 h and (b) the subsequent passage of an air bubble (Sheer force ~ 10-7 N) glass (left) and coating I (right). The images are 98 x 98 um. Thies et al, JBMR Part A, vol. 91A, issue 3, pg824, 2009

16 Adhesion Staphylococcus epidermidis (2009) 2.5E+07 Bare glass 2.0E+07 Coated glass from 30 % MeOH Bacterial adhesion ( #/cm 2 ) 1.5E E E+06 Glass VitroStealth TM 0.0E Time (sec) Very strong decrease of bacterial adhesion by the coating on glass (detection limit >>99.9 % )

17 Bacterial adhesion on coated polymer films Number of bacteria (10 6 cm -2 ) Coated PP (2%) bare 2% 3:7 MeOH:water bare 2% MeOH 10% MeOH 10% IPA bare Glass PET PS PP 2% MeOH 10% MeOH 10% IPA bare 2% MeOH 10% MeOH 10% IPA Coated PP (10%) Bare PET Coated PET Bare PS Coated PS

18 Mechanical durability 4nm PEG brush layer scratched with glass J Biomed Mat Res B 2005;73B: um PEG particle layer Scratched with steel wool through to the substrate 5um PEG particle layer Scratched with steel wool If scratches do not expose the underlying substrate then non-adhering feature is maintained! Pencil hardness = F-H Steel wool 250g, 5 double rubs = no visible scratches Hardness (nano-indentation) = GPa E r = GPa

19 Conclusions and Discussion DSM non-biofouling coatings dramatically reduce protein adsorption and microbial adhesion. Anti-microbial applications of non-fouling surfaces should be carefully selected depending on the clinical setting. S. epidermidis persists in peri-implant tissue rather than on the implanted biomaterial itself. (Boelens et al., J Infect Dis 2000;181: ; Broekhuizen et al.,infect Immun 2007;75: ). DSM Biomedical believes that a tool box of anti-microbial approaches is required to fight biofilm formation in a broad range of medical device application (no panacea) Long term biomaterial implants should facilitate intimate tissue connectivity

20 Features of the VitroStealth TM Features: Cross-linkable non-biofouling coating reduces unspecific accumulation of biological species such as proteins, nucleic acids and cells on surfaces. Hemo-compatible and non-cytotoxic (Iso & Iso ) Excellent optical properties low extractables (ppm-ppb level) Good mechanical durability (adhesion and cohesion) Sterilizable (Gamma, ETO) Long-term shelf-life for both formulations and coated parts Broad IP protection Iso13485 quality systems cgmp manufacturing of all coating components Coating process development: On request

21 VitroStealth TM coated Reliable Diagnosis & Discovery Acknowledgments: Dr. Paul Holmes, Dr. Edwin Currie, Dr. Astrid Roosjen, Harm Langermans. (DSM Research) Prof. H. C. van der Mei & Prof. H. J. Busscher (University of Groningen) Prof. W. Norde (Wageningen University) Many thanks. Thies et al, JBMR Part A, vol. 91A, issue 3, pg824, 2009 Uncoated glass Contact: Jens Thies Business Development Manager