Silica Nanoparticles: nano

SiO2 nanoparticles
Silica Nanoparticles: nano-glass!
SiO2
20 nm
70 nm
300 nm
SiO2 nanoparticles
Silica nanoparticles since ever?
1860: colloidal silica discovered by Thomas Graham (sol-gel)
1933: aqueous suspension of colloidal silica produced and commercialized by
IG Farben (Germany)
1956: Kolbe observe the formation of silica nanoparticles when
tetraethoxysilane (TEOS) is reacted with water in alcohols
1964: Stober and Fink report the controlled polymerization of TEOS in
ethanol/water/ammonia
1992: Van Blaadered demonstrates the possibility to include organosilanes in
silica nanoparticles.
1998: Arriagada and Osseo-Asare report the reversed emulsion synthesis
2003: Prasad reports the microemulsion synthesis of ORMOSIL nanoparticles
SiO2 nanoparticles
Silica nanoparticles everywhere?
SiO2 nanoparticles
Silica nanoparticles everywhere?
…
Nanobiotecnologie
Silica nanoparticles: inorganic polymers
Reactions of ethoxysilanes and silanols
CH3
CH3
Si OCH3
CH3
CH3
CH3
Si OCH3
CH3
CH3
CH3
Si OH
CH3
H2O
CH3
Cat.
CH3
CH3
OCH 3
H 3CO Si OCH 3
OCH 3
CH3
Si OH
CH3
CH3
Si OH
CH3
CH3
Si OH
CH3
H2 O
Cat.
Cat.
Cat.
?
Hydrolysis
CH3
CH3
CH3 CH3
Si O Si CH3
CH3 CH3
CH3 CH3
Si O Si CH3
CH3 CH3
Condensation
Condensation
Polymerization
5
Nanobiotecnologie
Silica nanoparticles: synthesis
Base-catalyzed polymerization
O
O
O Si O
O
Cat.
O
O Si OH
O Si O
O
O
O
O
O Si O Si O
O
O
O Si O Si O
O
O
?
Cat.
OH
O
?
O
O Si O
O
Since silicon is less electronewithdrawing than carbon, oligomer silanols are better
nucleophiles than hydrolyzed monomer silanols: growth prevails over nucleation in
base catalysis conditions.
6
Nanobiotecnologie
Silica nanoparticles: synthesis
Base-catalyzed polymerization
O
O
O Si
O
OH
O
O
Si
HO
OH
O
O
HO Si
HO
O
O
O
Si O
O Si
HO HO
k1
HO
O
O
Si
HO
OH
k2
O
OH
Oligomer
O
O
OH
Hydrolysis of precursor tretalkoxysilane is the rate-determining step. Polymer-monomer reaction is faster
than monomer-monomer reaction→ monodisperse particles growth.
However oligomers, once formed, are higlhy unstable and condese to form larger particles.
HO
O
OH
O
OH
O
OH
HO
Oligomer
Oligomer
O
HO
O
O
OH
HO O
O
O
OH
O
O
HO Si
OH
O
O OH
Oligomers condensation stops when the total charge is high enough to grant colloidal stability to the
particles. Starting from that moment the particles grow by furter monomer condensation on their surface.
Finale dimensions are essentially controlle by the amount of catalist (ammonia) present in the reaction
7
medium: ammonia generates salts that increase the ionic stenght of the medium and as a consequence
decreases the colloidal stability of the particles.
SiO2 nanoparticles
Silica nanoparticles: preparation
HO O M +
O
OH
HO
M+
HO
OH
Si
HO
HO
HO
OH
HO Si
OH
ion exchange resin
water
M+
O
O M+
O OH
M+
HO O M +
O
OH
HO
M+
O
O
O Si
O
a) NH3 , H 2O, EtOH
b) NH3 , H 2O, AOT
n-ottano
M+
O
O M+
O OH
M+
H2O
H 2O
HO O M +
O
OH
HO
M+
O Si
O
O
NH 3, AOT, H 2O
M+
O
O M+
O OH
M+
Nanobiotecnologie
Silica nanoparticles
Electrostatically stabilized nanoparticles
HO
O
pKa ~ 3
M
M
O
O
OH
M
O
~ 4.5 OH / nm2
10-30% Si (T3)
SiO2 nanoparticles
Interesting for nanomedicine?
Polymer
Lipid
Metal/Inorganic
Silica
Nanobiotecnologie
Silica nanoparticles
Platforms for multifunctional systems
Bulk
Surface
O
HO
O
OH
O
HO
HO
70 nm
O
HO
Si O
O
O
Si O
Si O
O Si O
OH
O Si O
O
O
Si
Si
OH
OH
O
OH
OH
OH
O
HO
OH
O
O
O
O
OH
HO
OH
HO
O
• La superficie può essere funzionalizzata con derivati organosilani.
O
OH OH
Pores
• Le pareti dei pori possono essere funzionalizzati con organosilani.
• Nei pori e nella matrice possono essere intrappolate molecole
organiche, specie inorganiche e persino altre nanoparticelle.
• Se si effettuano successive aggiunte di precursori, le particelle
possono essere cresciute a stadi.
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Nanobiotecnologie
Silica nanoparticles
Covalent doping with alkoxysilanes
Etanolo
Si(OEt)4
NH3/H2O
O
NH
N
NH
NH
N
HN
(EtO)3 Si
E’ necessario usare derivati
organosilani, ma nelle sintesi con
tensioattivi si può ottenere anche
intrappolamento sterico.
12
Stober, 1956; van Blaaderen, 1991
Nanobiotecnologie
Silica nanoparticles
Surface functionalization
HO
O
O
O
O
O
OH
M
M
HO
O
O
O
OH
M
O
F
Si
OR
F
F
RO OR
Si
O
OH
O
O
O
O
Si
O
OH
Nanobiotecnologie
Silica nanoparticles
Fluorescent nanoparticles
Le nanoparticelle di silice sono trasparenti alla luce e
possono essere drogate con molecole organiche. E’
quindi semplice produrre nanoparticelle di silice
fluorescenti:
• Il fluoroforo protetto dal solvente: maggior resa
quantica.
• Il fluoroforo è protetto dall’ossigeno: fotobleaching
ridotto.
• La particella contiene decine di fluorescenti: maggior
luminosità (brightness)
NBD
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Nanobiotecnologie
Fluorescent silica nanoparticles
Nanoparticle-enhances assays
Sandwich fluorescence immunoassays (FIA)
DNA microarrays
Nanobiotecnologie
Fluorescent silica nanoparticles
Fluorescence imaging
PO32-
PO32-
PO32-
PO32-
PO32-
PO32-
PO32PO32-
TEM micrograph of 70 nm silica particles doped
with FTIC-APTES and surface functionalized with
TAT peptide
PO32-
PO32-
PO3
2-
= GRKKRRQRRR (TAT)
HO
O
OH
COOH
=
H
N
HN
FTIC-APTES
Si(OEt)3
S
Fluorescence microscope images of human lung
adenocarcinoma cells after incubation with
nanoparticles with (left) and without TAT peptide
W. Tan et al., Chem. Commun., 2004, 2810-2811
Nanobiotecnologie
Fluorescent silica nanoparticles
Fluorescence probes
pH
microelettrodo
Nano-sonda
17
Nanobiotecnologie
Fluorescent silica nanoparticles
Fluorescence probes
1995: approvazione della FDA per l’applicazione oncologica
Terapia antitumorale che si
avvale dell’utilizzo di:
- fotosensibilizzatore
- luce
- ossigeno molecolare
CITOTOSSICITA’
1PS*
3PS*
h
1PS
IMAGING
18
1O *
2
3O
2
Nanobiotecnologie
Fluorescent silica nanoparticles
PDT agents
Tween/H2O
+
VTES
Dialisis
m-THPC
Singlet oxygen production
Cells viability after irradiation
P.N. Prasad et al., Nano Lett, 2007, 7, 2835-2842
Nanobiotecnologie
Fluorescent silica nanoparticles
PDT agents
850 nm
Singlet oxygen
Transmission images of HeLa cells treated with NP before (c)
and after (d) irradiation at 850 nm
Absorption and emission spectra of the two dyes
P.N. Prasad et al., JACS, 2007, 129, 2269-2275
Nanobiotecnologie
Nanoparticles@nanoparticles
Silica encapsulation
HO
O
OH
O
OH
O
OH
HO
Oligomer
Oligomer
O
HO
O
O
OH
HO O
O
O
OH
O
O
HO Si
OH
O
OH
O
Since polymer-monomer reaction is faster than monomer-monomer reaction,
monomers added to a basic solution of an appropriate template may lead to the
formation of a silica shell.
Nanobiotecnologie
Iron oxide@silica
Multimodal imaging
FTIC
Fe3O4
SiO2
Schematic structure (up) and TEM micrograph of FTIC-APTES doped 50 nm
silica particles entrapping 10-nm Fe3O4 nanoparticles
B
A
A) Fluorescence microscope images
of human mesenchymal stem cells
(hMSCs) after incubation with
nanoparticles (green) and a
lysosomes probe
B) MRI images of a nude mouse with
injected
SiO2@Fe3O4
nanoparticles
D.-M. Huang et al., Nano Letters, 2007, 7, 149-154
Nanobiotecnologie
Iron oxide@silica
In vitro cell detection and separation
W. Tan et al., Anal. Chem. 2007, 79, 3075-3082
Nanobiotecnologie
Gadolinium oxide@silica
Multimodal imaging
A
Fluorescence reflectance images of a nude mouse
after injection of SiO2@Gd2O3 nanoparticles
PEG
FTIC
Gd2O3
SiO2
MRI images of a nude mouse with
injected SiO2@Gd2O3 nanoparticles
B
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C. Riviere, S. Roux et al., JACS, 2007, 129, 5076-5084
Nanobiotecnologie
Latex@silica@layer-by-layer polymer
Controlled drug release
Drug relase modes
TEM micrograph of hollow
mesoporous silica nanoparticles
IBU release in simulated stomach (pH 1.4)
and intestinal (pH 8) fluids
J. Shi et al., Angew. Chem. Int. Ed., 2005, 44, 5083-5087
Nanobiotecnologie
Mesoporous silica
Surfactant aggregates templated synthesis
Alcuni tensioattivi in elevata concentrazione
formano strutture tubolari impaccate
Tali strutture funzionano come stampi per la
produzione di materiali mesoporosi
Sintesi di silice mesoporosa MCM-41
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Nanobiotecnologie
Mesoporous silica
Surfactant aggregates templated synthesis
• Surfactant: CTAB (cationic)
• Silica precursor: TEOS
• Catalyst: NaOH
• Solvent: water
• Co-precursor: organosilane (12%)
• Surfactant removal: calcination or HCl extraction
• The use of the co-precursor allows shape control
Nanobiotecnologie
Mesoporous silica
Surfactant aggregates templated synthesis
1. Tunable particle size. The particle size of MSN can be tuned from 50 to 300 nm allowing a facile
endocytosis by living animal and plant cells without any significant cytotoxicity.
2. Stable and rigid framework. Compared to other polymer-based drug carriers, MSN is more resistant to
heat, pH, mechanical stress, and hydrolysis-induced degradations.
3. Uniform and tunable pore size. The pore size distribution of MSN is very narrow and the pore diameter
can be tuned between 2 and 6 nm. These features allow one to adjust the loading of different drug
molecules and to study the kinetics of drug release with high precision.
4. High surface area and large pore volume. As mentioned previously, the total surface area (> 900 m2/g)
and pore volume (> 0.9 cm3/g) are very large, which allows high loadings of drug molecules.
5. Two functional surfaces. MSN have an internal surface (i.e., cylindrical pores) and an external surface (i.e.
exterior particle surface). This characteristic allows the selectively functionalization of the internal and/or
external surfaces of MSN with different moieties.
6. Unique porous structure. MSN is comprised of honeycomb-like, 2D hexagonal porous structure with
cylindrical pores running from one end of the sphere to the other. There is no interconnectivity between
individual porous channels.
Nanobiotecnologie
Mesoporous silica
Gatekeeping delivery
The DTT-induced release profiles of Vancomycin and ATP
from the CdS-capped MSN system upon DTT addition
Ca2+ efflux in astrocites upon incubation with ATP
loaded MSN after addition of mercaptoethanol Nanobiotecnologie
Mesoporous silica
Gatekeeping delivery
TEM images of MSN (a), iron oxide particles (b),
capped MSN (c)
HeLa cells incubated with fluorescein loaded MSN Nanobiotecnologie
Mesoporous silica
Gatekeeping delivery
TEM
TEM
Confocal
microscpe
Lin S-J et al., JACS, 2004, 126, 13216-13217
Nanobiotecnologie
Mesoporous silica
Nanimpellers/nanovalves
Apoptosis of PANC-1 incubated with MSNP induced
by releasing CPT after irradiating for increasing times
Nanobiotecnologie
Mesoporous silica
Nanimpellers/nanovalves
KB-31 cancer cells endocytosed doxorubicinloaded fluorescein-labeled MSNPs within 3 h.
This action is followed by doxorubicin release
to the nucleus, induction of cytotoxicity, and the
appearance of apoptotic bodies after 60 h
(indicated by arrows), followed by nuclear
fragmentation after 80 h.
Nanobiotecnologie
Mesoporous silica
Nanimpellers/nanovalves
Before magnetic
field activation
(viability 100%)
MPN loaded with Fl
+ magnetic field
(viability 84%)
apoptotic bodies
MPN loaded with Dox
+ magnetic field
(viability 63%)
Nanobiotecnologie
Nanoparicles@Mesoporous silica
• CTAB can act both as water solubilizing agent and
pore template.
• Different nanoparticles can be encapsulated by
retaining their properties.
a) Iron oxide np
b) Iron oxide nanowires
c) MnO np
d) Fe3O4 np and CdSe np
Nanobiotecnologie
Nanoparicles@Mesoporous silica
Theranostic agents
Fe3O4@mSiO2
Nanobiotecnologie
Nanoparicles@Mesoporous silica
Theranostic agents
HMn@mSiO2
mSiO2@Fe3O4