Interaction of Multiwalled Carbon Nanotubes with Model Cell Membranes: A QCM-D Study

Transcription

1 Interaction of Multiwalled Carbon Nanotubes with Model Cell Membranes: A QCM-D Study PENG YI and Kai Loon Chen (PI) Department of Geography and Environmental Engineering Johns Hopkins University 1

2 Overview Background and objective Preparation and characterization of multiwalled carbon nanotubes (MWNTs) Deposition kinetics of MWNTs on SLBs Reversibility of MWNT deposition on SLBs Attachment of MWNTs to phospholipid vesicles Conclusions 2

3 Carbon Nanotubes (CNTs) mrbarlow.wordpress.com Single-walled carbon nanotubes (SWNTs) Multiwalled carbon nanotubes (MWNTs) 3

4 Applications of Carbon Nanotubes Electronic properties: semiconducting or metallic Cao et al., Nature, 2008, phys.org Mechanical properties: high strength; light weight 4

5 Potential Release of Carbon Nanotubes Potential Routes of Release Consumer products which contain CNTs Factories producing CNTs and CNT-based products Waste disposal facilities, e.g., incinerators and landfills CNTs can be oxidized in natural and engineered environments OH =O COOH 5

6 Toxicity of Carbon Nanotubes Cause respiratory toxicity in rats Muller et al., Toxicology and Applied Pharmacology 2005, mg MWNTs/rat granulomas Inactivate microorganisms Kang et al., Langmuir 2007,

7 Toxicity of Carbon Nanotubes Induce apoptosis of human epidermal keratinocytes Shvedova et al., Journal of Toxicology & Environmental Health, Part A, 2003, Monteiro-Riviere et al., Toxicology Letters, 2005,

8 Interaction of CNTs with Cell Membranes Sylvia S. Mader, Biology, 9 th ed., 2007, McGraw-Hill Companies, Inc. 8

9 Recent Research on Adsorption of Nanoparticles on Model Cell Membranes C 60 fullerol ph 3 ph 5 ph 7.4 ph 4 ph 5 ph 7.4 Hou et al., Langmuir, 2011,

10 Objective To investigate the influence of solution chemistry on deposition and remobilization of MWNTs on model cell membranes 10

11 Oxidization and Characterization of MWNTs Expose pristine MWNTs to a 3:1 acid mixture of 98% H 2 SO 4 and 69% HNO 3 The distribution of oxygen-containing functional groups was quantified by X-ray photoelectron spectroscopy in conjunction with vapor phase chemical derivatization OH =O COOH Atomic Percentage of Oxygen (%) Yi and Chen, Langmuir 2011, 27, O (Total) O(C-OH) O(COOH) O(C=O) O(Others) Oxygen-Containing Functional Groups 11

12 Preparation of MWNT Stock Suspensions Sonication 20 hours Centrifugation Supernatant 5 mins, 1400 RCF 12

13 Electrokinetic Properties of MWNTs in NaCl and CaCl 2 Solutions EPM (10-8 m 2 /Vs) CaCl 2 NaCl 37 C ph Electrolyte Concentration (mm) Electrophoretic mobility (EPM) Brookhaven ZetaPALS At ph 7.3, most carboxyl groups are expected to be deprotonated 13

14 Quartz Crystal Microbalance with Dissipation Monitoring (QCM-D) Laminar flow at 0.6 ml/min [MWNT] = ca. 0.5 mg/l T = 37 ºC, ph = 7.3 or

15 Principle of QCM-D Frequency and Dissipation Amplitude A(t)=A 0 exp(-t/ ) sin(2 ft+ ) D=1/ f Time From qsense Generally, the frequency decreases as the deposited mass on the crystal increases The dissipation increases as the softness of the deposited layer increases 15

16 Preparation of Vesicle Suspensions DOPC: (1,2-dioleoyl-sn-glycero-3- phosphocholine) HEPES buffer (10 mm HEPES, 150 mm NaCl, ph 7.4) Chloroform Dry under vacuum Extrusion through 50-nm membrane 90 nm in diameter From Avanti Polar Lipids, Inc. com/ 16

17 Preparation of Vesicle Suspensions From Avanti Polar Lipids, Inc. 17

18 Electrophoretic Mobilities of DOPC Vesicles EPM (10-8 m 2 /Vs) CaCl 2 NaCl 37 C ph Electrolyte Concentration (mm) The surface charge of vesicles approaches neutral at high NaCl concentrations The surface charge of vesicles is reversed when CaCl 2 concentration is above 0.5 mm 18

19 Formation of SLBs on Silica-coated QCM-D Crystals Frequency Shift, f (5) (Hz) DOPC liposomes DI water HEPES buffer (formation of SLB) HEPES buffer T = 37 ºC 6 ph = Frequency 0 Dissipation Time (min) Cartoons are from qsense 19 Dissipation Shift, D (5) (10-6 )

20 Formation of SLBs on Silica Wafer Richter et al., Biophysical Journal, 2003,

21 Deposition of MWNTs on SLBs Frequency Shift, f (5) (Hz) mm CaCl 2 MWNT deposition on SLBs at 3 mm CaCl 2 df ( 5 ) dt The decrease of frequency is proportional to the mass of deposited MWNTs Time (min) 21

22 Deposition Rates of MWNTs on DOPC SLBs in the presence of CaCl 2 at ph d f (5) /dt (Hz/min) CaCl 2 Concentration (mm) SLB ( ) Silica ( ) 22

23 Deposition Rates of MWNTs on PLL-modified Surfaces in CaCl 2 at ph d f (5) /dt (Hz/min) CaCl 2 Concentration (mm) PLL (+) Silica ( ) 23

24 Deposition Kinetics of MWNTs on SLBs in the presence of CaCl 2 Attachment Efficiency CaCl 2 Concentration (mm) Attachment Efficiency: df (5) dt df dt (5) / fav / α is the fraction of collision between CNTs and membrane surfaces that will result in permanent attachment. 24

25 Deposition Kinetics of MWNTs on SLBs in the presence of CaCl 2 Attachment Efficiency 1 Unfavorable Favorable critical deposition concentration = 0.46 mm CaCl 2 Concentration (mm) EDL and van der Waals interactions Attachment Efficiency: df (5) dt df dt (5) / fav Charge reversal of SLBs when CaCl 2 concentration is higher than CDC 25 /

26 Deposition Kinetics of MWNTs on SLBs in the presence of NaCl Attachment Efficiency NaCl Concentration (mm) Attachment Efficiency: df (5) dt df dt (5) / fav The EPM of DOPC vesicles at 70 mm NaCl was close to zero. Thus, electrostatic repulsion was not the dominant interaction Headgroups of DOPC lipids are strongly hydrophilic. Water can strongly bind to the exposed headgroups of the DOPC SLBs and result in repulsive hydration forces / 26

27 Effect of ph on Deposition Kinetics of MWNTs on DOPC SLBs Frequency Shift, f (5) (Hz) mm NaCl, ph mm NaCl, ph Time (min) 27

28 Effect of ph on Deposition Kinetics of MWNTs on DOPC SLBs Frequency Shift, f (5) (Hz) mm NaCl, ph mm NaCl, ph Time (min) EPM (10-8 m 2 /Vs) mm NaCl DOPC vesicles MWNTs ph 2.0 ph 7.3 Deposition of MWNTs is favorable at ph 2.0 because MWNTs and SLBs are oppositely charged 28

29 Independence of Attachment Efficiency on Electrolyte Concentration at ph 2.0 Attachment Efficiency mm NaCl 150 mm NaCl NaCl Concentration Deposition of MWNTs is favorable at ph 2.0 because MWNTs and SLBs are oppositely charged 29

30 Reversibility of MWNT Deposition on DOPC SLBs at Decreased Electrolyte Concentration Frequency Shift, f (5) (Hz) CNT deposition 1 mm on SLBs at 1 mm CaCl CaCl 2 1 mm CaCl M CaCl 2 12% DI water (ph 7.3) Time (min) 25% SLBs became negatively charged when CaCl 2 concentration decreased from 1 mm to 1μM Electrostatic attraction became electrostatic repulsion which resulted in the release of MWNTs The incomplete release may be due to the surfacecharge heterogeneity of MWNTs 30

31 Reversibility of MWNT Deposition on DOPC SLBs at Increased ph Frequency Shift, f (5) (Hz) mm NaCl (ph 2) CNT deposition on SLBs at 1 mm NaCl (ph 2) 1 mm NaCl (ph 2) 1 mm NaCl (ph 7.3) Time (min) 19% SLBs became negatively charged when ph increased from 2.0 to 7.3 The electrostatic repulsion between both negatively charged MWNTs and SLBs lead to the release of MWNTs The deposited MWNTs were only partially released due to surface-charge heterogeneity of MWNTs 31

32 Attachment of MWNTs on Supported Vesicular Layer Frequency Shift, f (5) (Hz) HEPES buffer Deposition of DOPC vesicles on gold surface HEPES buffer Time (min) 1 mm CaCl 2 MWNT deposition ph 7.3 at 1 mm CaCl 2, ph 7.3 Gold-coated crystal Dissipation Shift, D (5) (10-6 ) 32

33 Cryogenic TEM Imaging of MWNT-Vesicle Suspensions 200 nm (a) MWNTs had aggregated with DOPC vesicles in a 1 mm CaCl 2 and ph 7.3 solution for ca. 20 min before cryo-tem images were taken Deformation of vesicles was observed upon attachment on MWNTs 50 nm (b) 33

34 Concluding Remarks Deposition kinetics of MWNTs on DOPC SLBs in the presence of CaCl 2 are governed by EDL and van der Waals forces In the presence of NaCl, hydration force seems to play an important role in controlling the deposition kinetics of MWNTs on DOPC SLBs The MWNTs deposited on SLBs are mostly irreversible when rinsed with a low-ionic-strength and ph 7.3 solution Interactions between MWNTs and supported vesicles resulted in no significant damage to vesicular integrity Further studies will be conducted on CMP nanoparticles, namely, ceria, silica, and alumina nanoparticles 34

35 Acknowledgements Prof. Howard Fairbrother and Drs. Billy Smith and Kevin Wepasnick from Department of Chemistry, JHU Semiconductor Research Corporation (Grant number: ) Contact information: 35