2268-19 Conference on Nanotechnology for Biological and Biomedical Applications (Nano-Bio-Med) 10-14 October 2011 From Bio- to Nano-Interfaces Kislon VOITCHOVSKY Dept.of Materials Science & Eng. EPFL, STI-IMX-SUNMIL Batiment MXG, Station 12 1015 Lausanne SWITZERLAND
Supramolecular NanoMaterials and Interfaces Laboratory department of materials science and engineering Institute of materials - Institut de Matériaux SuNMIL स न मल ΣoυΝΜιΛ From Bio- to Nano-Interfaces Kislon Voitchovsky kislon.voitchovsky@epfl.ch سنمل ICTP-KFAS NanoBioMed Conference, Trieste, 11 October 2011
At the interface with biology In nature molecules protein ions lipid vesicles... biological process In nanomedicine drug molecules nanoparticles polymer aggregates... biological material (cell) How do synthetic nano-objects interact with their surrounding?
Interfaces at the nanoscale Trypsin + + How are interfaces at the nanoscale? Does the coexistence of hydrophobic and hydrophilic nanoscale domains (e.g. on proteins) provide surfaces with special properties?
Solid-Liquid interfaces Medium M γ M Medium M1 γ M1 Medium M2 γ M2 Energy cost: γ MM = γ M + γ M = 2γ M Interfacial energy: γ M1M2 = γ M1 + γ M2 W M1M2
Solid-liquid interfaces Thermodynamics at the interface: the work of adhesion Liquid γ L vacuum Solid Interfacial energy γ SL : γ SL = γ S + γ L W SL (Dupré equation) interfacial energy ~ work of adhesion Bulk liquid Solid Interfacial liquid
Interfaces at the molecular level
Solid-liquid interfaces Probing the solid-liquid interface with AFM < 2nm amplitude ~ interface size
A brief introduction to AM-AFM k c A nanoscale tip mounted on a flexible cantilever is used to probe a sample locally
A brief introduction to AM-AFM k c A vibrating tip Amplitude Α and phase φ The tip vibration is damped by as the cantilever approaches the surface (here in liquid)
AM-AFM Basics A feedback loop keeps the cantilever vibration amplitude A constant Detection: amplitude A and phase ϕ
AM-AFM Basics P in = Po + P tip m z γ z + ( k + k ) z = A0 k cos( ωt) TS c TS z( t) = Acos( ω t + ϕ) c Amplitude A Phase φ
AM-AFM Basics
Biointerfaces at the nanoscale
Biointerfaces at the nanoscale liquid substrate
Biointerfaces at the nanoscale
Biointerfaces at the nanoscale 30 mm 100 mm 300 mm 1000 mm Cytopl. Extrcell. 5 nm bar RMS extracell.: 0.15 nm / 0.15 nm / 0.15 nm / 0.13 nm RMS cytopl.: 0.15 nm / 0.25 nm / 0.25 nm / 0.26 nm Nanoscale (2010) 2, 222-29
Protein electrostatics Looking at specific ionic effects: Li +, K + and Cs + Purple Membrane cytoplasmic surface at 50mM salt concentration 50nm x 50nm Voitchovsky et al. 2007
Biointerfaces at the nanoscale Nanoscale (2010) 2, 222-29
Biointerfaces at the nanoscale + K + + Na + Alternation of hydrophobic/philic domains Specific ionic effects Controlled local flexibility...
Striped nanoparticles as synthetic proteins
Metal Nanoparticles Synthesis Metal Salt (AuHCl 4 ) + + Reducing Agent (NaBH 4 ) Direct mixed ligands reaction ** Ligand exchange reaction * 3 nm
Imaging Self Assembled Monolayers Scanning Tunneling Microscopy 3 nm OT
Mixed Self-Assembled Monolayers Au (111) OT MPA 5 nm
STM Images of Striped Nanoparticles b b a c c 2 nm 2 nm d 5 nm
A More Realistic Vision Cartoon Simulations Microscopy Images
Stripe Formation in Mixed Monolayers Entropy gain in stripe formation Unpublished data TEM, NMR, Noesy Gel Electrophor. AUC Size Unpublished data
Striped nanoparticles Diffusion Challenge of cellmembrane penetration Adapted from: Nature Reviews Drug Discovery (2005) 4 581-593
Effect of Nanoparticle Coating Protein Interactions
Cell Membrane Penetration 4 0 C Experiment A B C D The absence of endocytosis has been independently confirmed via TEM studies
Endocytosis Inhibitors Calcein Only PI Staining No sodium azide and 2-deoxyglucose Z-Stack Images CyQuant Calcein and Striped NPs sodium azide and 2-deoxyglucose Calcein and TriMethyl Ammonium NPs
The Tale of Two Supramolecular Systems Striped Nanoparticles Lipid Bilayers
At the more fundamental level. AFM images of supported bilayers and striped particles 70 nm
At the more fundamental level. AFM study of Nanoparticles-bilayer interactions 5 4 2 μm 3 2 0-2 nm 1 70 nm -4 0 0 1 2 μm 3 4 5 Poster: Maria RICCI
Towards an Understanding V, I V In collab. with Prof. Yann Astier, University of Lisbon, Portugal I t 1,2 diphytanoyl-snglycero phosphocholine lipid bilayer ph 8.1 Tris-HCl 0.1 M, KCl 2 M Reference Ag/AgCl electrodes t
Nanoparticle/Bilayer Interactions Blank All TMA/MUS MUS/brOT MUS OT 2:1 Blank T=30min 0.8 mg/ml T=1h 1.6 mg/ml T=1h30 2.0 mg/ml T=2h20 Carney, Stellacci, in preparation
Solubility of Rippled Nanoparticles OT MUA HT with N. Marzari, MIT; PNAS 9886, 2008 1 x 1 2 x 2
Striped nanoparticles
Interfacial Energy (IE) At the micron/nano scale W SL = γ LV (1 + cos θ CA ) γ L (1 + cos θ CA ) Cassie State: (cos θ CA ) obs = = f 1 (cos θ CA ) 1 + f 2 (cos θ CA ) 2 = = f 1 + f 2 (cos θ CA ) 2 Wenzel State: (cos θ CA ) obs = r (cos θ CA )
Interfacial Energy Microscopy
Interfacial AM-AFM Pressure to remove liquid near the sample and the tip surfaces: } α ~ β
Interfacial AM-AFM high-resolution phase φ E cycl, ext phase φ local wetting (work of adhesion)
High Resolution Images
Effect of structure on interfacial energy
Structure Effects on Surface Energy W sl = x A W A sl + x B W B sl x A = component A surface fraction x B = 1 - x A
Work of Adhesion Measurements
Structure Component to I.E. W SL AB = x A W SL A + x B W SL B Wsl = x A W A sl + x B W B sl + f(structure)
Structural Component in I.E. Cavitation From D. Chandler, Nature, 2005
Solid-liquid interfaces with structured surfaces Adding salt should decrease cavitation
Conclusions
Acknowledgements