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Hydration of ultra-thin surface films and its role in enhancement of biocompatibility of medical devices Mike Thompson Department of Chemistry and Institute.

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Presentation on theme: "Hydration of ultra-thin surface films and its role in enhancement of biocompatibility of medical devices Mike Thompson Department of Chemistry and Institute."— Presentation transcript:

1 Hydration of ultra-thin surface films and its role in enhancement of biocompatibility of medical devices Mike Thompson Department of Chemistry and Institute for Biomaterials and Biomedical Engineering, University of Toronto 9 th Annual Conference on the Physics, Chemistry and Biology of Water Pamporovo, Bulgaria, October, 2014

2 Topics The core of our research – theranostics – combined therapy and detection Fouling and the sensor–biological fluid interface Link between fouling and biocompatibility Anti-thrombotic surface chemistry Role of surface hydration Neutron reflectometry of ultra – thin film water Anti-fouling / anti-thrombogenetic effect - concerted mechanism involving structured water Questions

3 The Challenges of Critical Care Sick Patients Coagulopathy Inflammation Organ Failure Shock

4 In-line theranostics and medical bypass circuitry

5 Electromagnetic acoustic wave sensor

6 Fouling of Quartz by Serum Sheikh, S.; Yang, D. Y.; Blaszykowski, C.; Thompson, M. Chem. Commun. 2012, 48, 1305 undiluted goat serum 12

7 Surface Modifier Structure Anchoring function Head function Backbone Substrate Quartz (piezoelectric), gold (electrical), stainless steel (implant), plastics (flexible),... Trichlorosilyl (Cl 3 Si), trialkoxysilyl ((RO) 3 Si), thiol (–SH),... Alkyl: –(CH 2 ) n – Oligoethylene glycol (OEG): –(O–CH 2 –CH 2 ) n – Perfluoroalkyl: –(CF 2 ) n – Functionalizable for subsequent biomolecule immobilization X Y Linkers for biosensors 5

8 Systematic Structural Modification Sheikh, S.; Yang, D. Y.; Blaszykowski, C.; Thompson, M. Chem. Commun. 2012, 48, 1305 1/1 (v/v) H 2 O/MeOH room temp., overnight 13

9 Antifouling Behaviour Sheikh, S.; Yang, D. Y.; Blaszykowski, C.; Thompson, M. Chem. Commun. 2012, 48, 1305 Through the use of structurally simple surface modifiers, the frequency shift due to the adsorption of goat serum was substantially reduced from ~ -31 kHz for bare quartz to less than -3 kHz for MEG-OH films 14

10 BLOOD CONTACTING MEDICAL DEVICES Blood Contacting Medical Devices Vascular Graft Hemo- dialyzer P Pacemaker Stents Extracor poreal Circuits Econous Inc. July 2012

11 Blood interaction and bypass circuitry Cardiopulmonary bypass (CPB) surgery is a common operation with Over 1 million yearly worldwide 1 Has several undesired consequences including blood coagulation After surgery complications can occur for 20% for low risk patients with 12% result in multi organ dysfunction syndrome 2 Multi organ dysfunction syndrome has a mortality rate of 40% 3 1. Sphere medical statistics 2. Grover FL:. Ann Thorac Surg 1999;68:367-373; discussion 374-376. 3. Kollef MH, Wragge T, Pasque C:. Chest 1995;107:1395-1401. Biosensors Group IBBME

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13 Collagen Coated Polycarbonate surfaces

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15 MEG-OH coated Surfaces

16 To investigate the hydration of ultra-thin films and gain insight into its anti – fouling mechanism. 1)Probe water density of water at MEG-OH and OTS-OH adlayers (normal to the surface) ‒Examine interfacial water 2)Determine the effect of the internal ether oxygen atom on behaviour of water with adlayer Bulk water Water density profile MEG-OH OTS-OH How? Neutron reflectometry

17 CNBC’s National Research Universal (NRU) Reactor Neutrons produced via fission of 235 U (D 2 O moderator) Largest global producer of medical isotopes ( 60 Co, 99 Mo, 131 I) > 85% neutron time to users (universities, research facilities) Applications: Structural chemistry, soft materials, thin films/interfaces (examples) Greetings from Chalk River! D3 Neutron Reflectometer 6 Beam lines!!! Ontario Neutron Reflectometry (NR) A neutron diffraction technique probing the specular reflectivity of surfaces and buried interfaces in layered systems Functions and Features Structural and compositional information (e.g. oxide growth) Atomic distribution (depth profiles) High penetration depth Film thickness (up to 200 nm) Sensitive to 1 H and 2 H Manipulation of contrast between media

18 Addition of layer (film) N+1 interfaces d Cr Air Si Kiessig fringes: Oscillations originate from constructive/destructive interference of reflected neutron waves Frequency depends on thickness of the layer Δq= 2π/d Amplitude depends on contrast between adjacent media (ΔSLD) - Enhanced sensitivity with increasing contrast Period of oscillation 1/α layer thickness (d) Kiessig fringes Amplitude α ΔSLD 9.42 x 10 -6 Å -2 3.00 x 10 -6 Å -2 2.07 x 10 -6 Å -2 9.42 x 10 -6 Å -2 3.00 x 10 -6 Å -2 2.07 x 10 -6 Å -2 Dampened oscillations z σjσj j koko ksks θoθo θoθo x Surface Roughness Diffuse scattering of neutrons ↓ R

19 MEG-OH OTS-OH Si/SiO 2 Fringes on MEG-OH, OTS-OH reflectivity curves confirm presence of a ‘layer’ between SiO 2 and CMW (interference of reflected neutron wave) MEG-OH: dampened oscillations (low amplitude) OTS-OH : sharper minima, oscillations with higher amplitude FIT REFLECTIVITY DATA WITH MODEL

20 SLD Profile: 2-Phase Fit SiO 2 Interfacial waterBulk Film Reflectivity + Fits Sample SLD SiO2 (x 10 -6 Å -2 ) σ SiO2 (Å) d1 (Å) SLD 1 (x 10 -6 Å -2 ) SLD B (x 10 -6 Å -2 ) σ B (Å) MEG-OH3.6714.321.72.973.6616.5 OTS-OH3.569.718.70.903.531.6 Low SLD (organic coating)

21 “Water Barrier”? quartz 17 MEG-OH quartz OTS-OH 6 Å 22 Å BULK BULK 5 Å 4 Å - - - - - - - - - - - - - not to scale INTERFACIALWATER

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23 Some questions What is the origin of the myth that high quality SAMs reduce adsorption + fouling? What is the precise role of the distal –OH in MEG-OH? Why is the chemistry so “robust” in terms of antifouling / antithrombogenesis? Can the surface chemistry lead to a quantum changes in medical device technology? Does hydration play a role in biochemical interactive selectivity – e.g. cell signaling?

24 Mike Thompson Research Group, October, 2014 Jack Sheng Jenise Chen Dr. Sonia Sheikh Niall Crawley Brian De La Franier Edmund Chan Elaine Chak Ellie Wong Kiril Fedorov Tairan Wang Pat Benvenuto Rohan Ravindranath Dr. Chris Blaszykowski Ruben Machado Dr. Larisa Cheran Miguel Neves Victor Crivianu-Gaita

25 THANKS FOR LISTENING! mikethom@chem.utoronto.ca


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