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Interaction of Gold Nanoparticles with Cells

Presentation of Seminar Conducted by Prof. Mathias Brus

Noha Abu El Magd

on 19 November 2012

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Transcript of Interaction of Gold Nanoparticles with Cells

Prof. Mathias Brust

University of Liverpool

10/10/2012 Interaction of Gold Nanoparticles with Cells Professor of Chemistry at the University of Liverpool
Member of the applied physical chemistry research group at the university of Liverpool
Author of over 40 scientific publications

Editorial Roles:
Chemistry World (Editorial Board Member 2006- )
Nanotechnology, Diagnostics and Therapeutics (Editorial Board Member 2006 - )
Analytical Chemistry (Member of A-Page International Advisory Board 2004 - )
Journal of Materials Chemistry (Editorial Board Member 2003 - 2006)
Professional awards :
Industrially Sponsored Award (Corus Group) for the Chemistry of the Noble Metals (Royal Society of Chemistry 2004)
EPSRC Advanced Research Fellowship (EPSRC 1998) Mathias Brust
Cellular uptake mechanisms of gold nano-particles, using HeLa Cells.
Intracellular fate of incorporated gold nano-particles.
The electrochemical model of the cell-membrane. (Organisation of ligand cells and changing properties)
Surprising electro-catalytic properties of gold nano-particles, using a dropping Hg electrode as a probe.
Nanoparticle membrane model interaction with a dropping Hg electrode.
Mechanisms employed to attempt the prevention of nanoparticle excision from the cell (endosomal pathway). Outline They do not occur in nature, and therefore are not biologically active.
It is difficult to maintain their nanoscale sizes
How sure can we be that they are even safe for us to use? Why Gold Nanoparticles? Gold Nanoparticles can be easily chemically modified.
They can carry specific recognition functions and can carry and deliver cargo.
They possess unique optical properties.

These properties make Gold nanoparticles ideal potential candidates for drug and delivery agents, and their optical properties enable their employment as intracellular probes for diagnostic analysis, as well as targets for intracellular damage through photochemical or hydrothermal effects , i.e. Cancer treatment Why not? How can we get the nanoparticles into the cell?
Keep them in there?
How do we get them to do what we want? The question is... Figure (1 ) Scematic diagram of peptide modified Gold Nanoparticles (Z.Krepetic et. Al 2011) Investigate this phenomena using peptide-modified gold nanoparticles, (synthesised by a modified Tukevich- Frens method) , and how they are incorporated into HeLa cells. Most of the nanoparticles are taken up through an endocytotic route.
The Endocytotic vesicles fuse with the cell membrane and enter the cell.
They form late endosomes, lysosomes and multi-vescular bodies.
Endocytosis: Calveolin mediated, Clatherin Mediated, and Calveolin and Clatherin mediated Endocytosis.
(P.Nativo, I.Prior and M.Brust 2008) Getting them in Figure (2): Uptake of PEG modified gold nanoparticles through liposomes (A) Caveolae ( B) Clathirin, mediated encocytosis (P.Nativo, I.Prior and M.Brust 2008) Clathirin and Calveolin Mediated Endocytosis Figure( 3) Intracellular gold content as a function of time as dtermined by AES for different functionalised Gold nanoparticles (Z. Zrepetic et. Al 2011) Nano-particles are usually confined to endocytotic vesicles and are unable to participate in metabolic events that take place in the cytoplasm, and are eventually exocytosed. Once inside the cell.. Have the nano-particles exit the endocytotic vesicle, by penetrating the vesicle membrane or rupturing it to expel the contents of the endosome.
A photochemical process creates radicals which destroy the endosomal membrane to get particles out of the cell
Microinjection of the particles so that they are not confined to endocytotic vesicles.
Cell penetrating particles may used to modify the properties of the surface, enabling them to enter the cytosol and other organelles, such as the nucleus and mitochondria, to some extent.

(P.Nativo, I.Prior and M.Brust 2008), (Z. Zrepetic et. Al 2011) How do we avoid this fate? Figure ( 4 )TEM images of TAT modified nanoparticles incorporated into HeLa cells. Figure 6.0: a hypothetical scheme of the experimental (Z. Zrepetic et. Al 2011) Figure 5.0: Stereological analysis of the TEM images show the gold nanoparticle area density as a function of time in different intracellular organelles. (Z.Krepetic et.al 2011)
  However, as the incubation time increases, the vesicles formed eventually become exocytotic and particles are excreted from the cell. Q. Does modulating the membrane potential have an effect on the uptake of nanoparticles?
K⁺/Na⁺ channels controlling membrane potential.
The Isotonic medium of high [K⁺], stops uptake completely.
Does this imply that the gold nanoparticles are electro-chemically active? The electrochemical model of the cell-membrane. Membrane on an electrode surface is used to pull the nanoparticles in to look at the effect of potential on the nanoparticles.

Phospholipid (DOPC) monolayer on a hanging Hg drop electrode;
Hydrophobic part attaches to Hg,
Hydrophilic part attaches to water,

A micelle similar to half of a bi-layer membrane is formed.
(M.Brust and G.Gordillo 2012) Nanoparticle membrane model interaction with a dropping Hg electrode Cyclic voltammetry using a Hanging Mercury Drop electrode, can be used to investigate the electocatalytic properties of Gold nanoparticles.

Mercury drop electrode serves as the working electrode, polarised with respect to Ag|AgCl as a reference electrode a platinum wire as a counter electrode.

Investigating the unique proton redox chemistry that takes place at the surface.

(M.Brust and G.Gordillo 2012) Surprising electro-catalytic properties of gold nano-particles, using a dropping Hg electrode as a probe. Figure (7): The cyclic voltametric response of 1-3nm gold particle dispersion at a hanging mercury drop electode in acetic acetate buffer solution, with a potential sweep rate of 1V/s. (M.Brust and G.Gordillo 2012) Cyclic Voltammogram The reaction taking place at the surface is the reversible electrocatalytic reduction of H+ from adsorbed Hydrogen species.
The proton adorbed is reduced, a second proton is reduced at the same site, the two are immediately combined, releasing molecular hydrogen. This corresponds to the reductive curve
Ultimately: 2H⁺ + 2e⁻  H₂(adsorbed)
The reverse sweep oxidation curve corresponds to the re-oxidation of the adsorbed hydrogen species.

(M.Brust and G.Gordillo 2012) Reactions at the surface Gold nanoparticles can be transported into the cell either via liposomes, which fuse with the cell membrane or using surface modifying peptides, the mechanism of which is unclear.
Once inside the cell, the nanoparticles must find a way to escape the vesicles, and enter other organelles in the lysosome.
Eventually all nanoparticles are exocytosed from the cell
Changing the membrane potential affects the uptake of gold nanoparticles by the cell.
Gold nanoparticles exhibit unique electro chemical catalytic properties, as shown. In Conclusion Thank you Mathias Brust Picture :
RSCPublishing ChemComm, Mathias Brust [online], 2012, [ 17/11/2012], available from: http://www.rsc.org/Publishing/Journals/cc/News/ChemCommAuthorsScoreTop10Hit.asp
Information about Mathias Brust:
University of Liverpool, University home, Chemistry, Staff, Mathias Brust,Prof, 2012 [17/11/2012], available from: http://www.liv.ac.uk/chemistry/staff/mathias-brust/
NATIVO,P,I, PRIOR, M, BRUST, 2008, Uptake and Intracellular Fate of Surface-Modified Gold Nanoparticles, ACSNano, Volume 2, (8), 1639-1644
BRUST, M, G, GORDILLO, 2012, Electrocatalytic Hydrogen Redox Chemistry on Gold Nanoparticles, Journal of the American Chemical Society, 134, 3318-3321
KRPETIC, Z, S, SALEEMI, I, PRIOR, V, SEE, R, QURESHI, M, BRUST, 2011,Negotiation os Intracellular Membrane Barriers by TAT-Modified Gold Nanoparticles, ASCNano, Volume 5 (6), 5195-5201 References
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