Nanobio I-surface tension-15
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Nano+bio NanoBio I (14/09/15): NanoBio II (16/09/15): NanoBio III (5/10/15): Surface forces- Examples in nature Applications Cells and cell components Proteins, AB, applications, optical microscopy Applications (lab on a chip, Nanoparticle and Nanowire bio- applications) Questions etc… 30/09
Transcript of Nanobio I-surface tension-15
Nano+bio NanoBio I (14/09/15):
NanoBio II (16/09/15):
NanoBio III (5/10/15):
Surface forces- Examples in nature Applications
Cells and cell components Proteins, AB, applications, optical microscopy
Applications (lab on a chip, Nanoparticle and Nanowire bio-applications)
Questions etc… 30/09
γ =Nm
= Force / unit length = Energy / unit surface
Crea9ng surfaces costs energy
Interfacial tension Surface energy
Energy cost for crea9ng the surface: E= 2 A γ
A
Surface created: 2 A
Spheres are the shape with the smallest surface for a given volume
hDp://www.123rf.com
Crea9ng surfaces costs energy
γwater/air= 72 mN/m γwater/oil= 50 mN/m γmercury/air= 490 mN/m
hDp://www.kidsdiscover.com
INTERFACES: liquid-‐liquid gas-‐liquid solid-‐solid solid-‐liquid : WETTING
Wikipedia
θc : contact angle
θc < 90°: weUng θc > 90°: non weUng
WeUng
Terminology:
When the liquid is water
Hydrophilic surface: likes water
Hydrophobic surface: does not like water
Rough surfaces Micro/nanostructured surfaces Progress in M
aterialsScience 56 (2011) 1–108
Rf = surface roughness factor = Surface area solid-‐liquid/ flat projected area
Wikipedia
Rough surfaces Micro/nanostructured surfaces
Wenzel state Cassie or Cassie-‐Baxter state Predic9ve model:
Contact line density Λ: total perimeter of asperi9es over a given unit area
If Λ>Λc: Cassie-‐Baxter state If Λ<Λc : Wenzel state
Λ=4x/y2
Example:
Hydrophobic micro/nanostructured surfaces
Lotus leaf
Progress in Materials
Science 56 (2011) 1–108
Rose petal
Langmuir, 2008, 24 (8), pp 4114–4119
hDp://blogs.nature.com
/from_the_lab_bench/
Langmuir, 2008, 24 (8), pp 4114–4119
Hydrophobic micro/nanostructured surfaces
Superhydrophobic surfaces: Contact angle >150° and roll-‐off angle <10° Self cleaning effect
www.youtube.com
Lotus leaf
Inspired research on: -‐ new genera9on of fabrics -‐ coa9ngs, windows etc…
How to make interfaces more stable?
How to make interfaces more stable?
Surfactants (=acAng on surfaces) Molecules that lower the interfacial energy
Head that likes water
Tail that likes oil/air ≈ 1-‐5 nm
= Polar head, hydrophilic head
= Apolar tail, hydrophobic tail
Surfactants (=acAng on surfaces) Molecules that lower the interfacial energy
air
water
γ = 72 mN/m
air
water
γ ≈ 25 mN/m
Surfactant applica9ons
Emulsion defini9on: mixture of 2 non miscible liquids One liquid is dispersed into the other
Emulsion stabiliza9on
hDp://sparror.cubecinema.com/
Dispersed Phase Con9nuous phase
A B
C D
E F G
H
Which of the following object contains surfactant?
A B
C D
E F G
H
Which of the following object contains surfactant?
Anethole: soluble in ethanol-‐not in water
Milk proteins Egg yolk (phospholipids) No surfactants Lots of surfactants!
Lots of surfactants! Surfactants to prevent lung collapse
No surfactants
Ouzo effect: Surfactant–free stable emulsion!
Anethole: soluble in ethanol-‐not in water
You need 3 liquids: Liquid 1 : water Liquid 2 : ethanol – soluble in water Liquid 3 : anethole (organic flavoring substance ≈ oil)-‐ Soluble in ethanol, but not in water.
Before pouring the water, the anethole is in ethanol, both liquids are miscible, the solu9on is transparent. Aper adding water, the anethol forms small droplets (≈ 1µm)surrounded by ethanol and suspended in water. The droplets are stable.
anethole
ethanol
water
Lung surfactants
Laplace Law: P=2γ/r: pressure needed to maintain an air in water spherical bubble (the alveoli can be approximated by a air-‐in-‐water bubbles with an interfacial energy γ) When the air is expelled: r becomes very small. If there are no surfactants, the pressure needed to prevent lung collape (=to maintain the small air bubble is very big). If there are surfactants at the interface, the interfacial tension become smaller (γ) and the pressure needed to prevent lung collapse is smaller.
The surfactant prevent lung collapse upon air expulsion
r
Surfactants
Neutral
Anionic
Ca9onic
zwiDerionic
Surfactants
Sodium stearate (soap)
Phospholipids: example Phospha9dylcholine (component of cell membrane) Found in egg yolk, soy…
Surfactants
Water layer Air
Air
Surfactants Micelles
hDp://w
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ension.com
hDp://www.piercen
et.com
Air
Water
Cri9cal micellar concentra9on: Surfactant concentra9on above which micelles form.
Surfactant applica9ons Laundry detergent, soap etc….
Water
Fabric with fat stain
Surfactant applica9ons
Examples: VinaigreDe (Unstable) , Mayonnaise (stabilized by egg yolk) Cosme9cs, lo9ons (stabilized by polymers etc…)
Emulsion stabiliza9on
Surfactants Liposomes (ar9ficial vesicles): Plenty of possibili9es for drug delivery
-‐ Can be loaded with molecules / drugs
-‐ Protect the drug from in vivo condi9ons (stomach, blood, immune cells) -‐ Surface can be func9onalized (target cells)
-‐ Some can deliver drug inside cells by membrane fusion (difficult for hydrophilic drugs to cross the cell membrane) -‐ some release their cargo on specific condi9ons (pH, pressure, temperature….)
hDp://w
ww.britannica.com
10 nm-‐10 µm
Surfactants Liposome applica9ons
www.nature.com/nnano/journal/v7/n8/pdf/nnano.2012.84.pdf
Local delivery of vasodilators for trea9ng atherosclerosis (University of Geneva, 2012) Atherosclerosis: -‐ no specific biomarkers iden9fied -‐ high shear stress due to the narrowing of the blood vessel
Vesicles break and release their content at high shear stress
Dendrimers
wikipedia
Synthe9c nanomaterials that are approximately 5-‐10 nanometres in diameter
Dendrimers
Catherine A. Brummond , 2004
Hydroxycamptothecin (cancer drug) encapsulated in a biodegradable polyether dendrimer
