Silica Nanoparticles: nano-glass!SiO2 nanoparticles

20 nm 70 nm 300 nm

SiO2

SiO2 nanoparticles

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

Silica nanoparticles since ever?

SiO2 nanoparticles

Silica nanoparticles everywhere?

SiO2 nanoparticles

Silica nanoparticles everywhere?

…

5

Silica nanoparticles: inorganic polymers

CH3 SiCH3

OCH3CH3

CH3 SiCH3

OHCH3

Cat.CH3 Si

CH3O

CH3

SiCH3

CH3

CH3

CH3 SiCH3

OHCH3

CH3 SiCH3

OHCH3

Cat.CH3 Si

CH3O

CH3

SiCH3

CH3

CH3

CH3 SiCH3

OCH3CH3

H2OCH3 Si

CH3OH

CH3Cat.

Hydrolysis

Reactions of ethoxysilanes and silanols

Condensation

H3CO SiOCH3

OCH3

OCH3

H2O

Cat.? Polymerization

Condensation

Nanobiotecnologie

6

O SiO

OO

Cat.O Si

OOH

O

O Si

O

OO

O SiO

OO

Si OO

O Cat.O Si

OO

OHSi OO

O

O SiO

OO

? ?

Since silicon is less electronewithdrawing than carbon, oligomer silanols are better nucleophiles than hydrolyzed monomer silanols: growth prevails over nucleation in base catalysis conditions.

Silica nanoparticles: synthesisBase-catalyzed polymerization

Nanobiotecnologie

7

Oligomers condensation stops when the total charge is high enough to grant colloidal stability to theparticles. 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 reactionmedium: ammonia generates salts that increase the ionic stenght of the medium and as a consequencedecreases the colloidal stability of the particles.

OH

OHO

HO

O

O

Oligomer

OH

OHO

HO

O

O

Oligomer

OOH

OOHO

O

HOO

HO SiO

OH

OHO

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.

SiO

O

OO

OH SiO

HO

OHO Si

O

OH

OHO Si

O

HO

OO Si O

HO

OSi

O

OH

OHO

k1 k2

OH

OHO

HO

O

O

Oligomer

Silica nanoparticles: synthesisBase-catalyzed polymerization

Nanobiotecnologie

Silica nanoparticles: preparationSiO2 nanoparticles

SiOH

HO

HOHO Si

OH

OH

HOHO

ion exchange resinO

OH

OOHO

O

HOO

HOM+

M+

M+ M+

M+

SiO

O

OO

OOH

OOHO

O

HOO

HOM+

M+

M+ M+

M+

a) NH3, H2O, EtOH

b) NH3, H2O, AOTn-ottano

SiO

OO

OOH

OOHO

O

HOO

HOM+

M+

M+ M+

M+

NH3, AOT, H2O

water

H2OH2O

HOO O O OH

O

M

M

M pKa ~ 3

~ 4.5 OH / nm2

10-30% Si (T3)

Silica nanoparticlesElectrostatically stabilized nanoparticles

Nanobiotecnologie

SiO2 nanoparticles

Interesting for nanomedicine?

Polymer Metal/Inorganic

Lipid Silica

11

70 nm

OHOH

HO O

O

OH

OO

HO

HO

O

O

O

HOHO

HO

HO

O OH OH OOH

OH

OH

OH

O

O

OH

O

SiOO

OO

Si O

SiO

O

Si

SiOO

SiOH

OOH

SiO

SurfaceBulk

Pores• La superficie può essere funzionalizzata con derivati organosilani.• Le pareti dei pori possono essere funzionalizzati con organosilani.• Nei pori e nella matrice possono essere intrappolate molecoleorganiche, specie inorganiche e persino altre nanoparticelle.

• Se si effettuano successive aggiunte di precursori, le particellepossono essere cresciute a stadi.

Silica nanoparticlesPlatforms for multifunctional systems

Nanobiotecnologie

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Etanolo

Si(OEt)4

E’ necessario usare derivati organosilani, ma nelle sintesi con tensioattivi si può ottenere anche intrappolamento sterico.

N

NH N

HNNH

NHO

(EtO)3Si

NH3/H2O

Stober, 1956; van Blaaderen, 1991

Silica nanoparticlesCovalent doping with alkoxysilanes

Nanobiotecnologie

HOO O O OH

O

M

M

M

OHHO

O O O OO

OO O O O

O

SiOR

RO ORF

SiSi

OH

OH

FF

Silica nanoparticlesSurface functionalization

Nanobiotecnologie

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Le nanoparticelle di silice sono trasparenti alla luce epossono essere drogate con molecole organiche. E’quindi semplice produrre nanoparticelle di silicefluorescenti:

• Il fluoroforo protetto dal solvente: maggior resaquantica.

• Il fluoroforo è protetto dall’ossigeno: fotobleachingridotto.

• La particella contiene decine di fluorescenti: maggiorluminosità (brightness)

NBD

Silica nanoparticlesFluorescent nanoparticles

Nanobiotecnologie

DNA microarrays

Fluorescent silica nanoparticlesNanoparticle-enhances assays

Nanobiotecnologie

Sandwich fluorescence immunoassays (FIA)

TEM micrograph of 70 nm silica particles dopedwith FTIC-APTES and surface functionalized withTAT peptide

Fluorescence microscope images of human lungadenocarcinoma cells after incubation withnanoparticles with (left) and without TAT peptide W. Tan et al., Chem. Commun., 2004, 2810-2811

PO32-

PO32-

PO32-

PO32-

PO32-

PO32-

PO32-

PO32-

PO32-

PO32-

PO32-

= GRKKRRQRRR (TAT)

=

O

COOH

HNHN

S

Si(OEt)3

OHHO

FTIC-APTES

Fluorescent silica nanoparticlesFluorescence imaging

Nanobiotecnologie

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microelettrodo Nano-sonda

pH

Fluorescent silica nanoparticlesFluorescence probes

Nanobiotecnologie

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1995: approvazione della FDA per l’applicazione oncologica

Terapia antitumorale che si avvale dell’utilizzo di:

- fotosensibilizzatore

- luce

- ossigeno molecolare

1PS

1PS*

3PS*

3O2

1O2*h IMAGING

CITOTOSSICITA’

Fluorescent silica nanoparticlesFluorescence probes

Nanobiotecnologie

VTES

Tween/H2O+

m-THPC

Dialisis

Singlet oxygen production Cells viability after irradiation

P.N. Prasad et al., Nano Lett, 2007, 7, 2835-2842

Fluorescent silica nanoparticlesPDT agents

Nanobiotecnologie

850 nm

Singlet oxygen

P.N. Prasad et al., JACS, 2007, 129, 2269-2275

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

Fluorescent silica nanoparticlesPDT agents

Nanobiotecnologie

Nanoparticles@nanoparticlesSilica encapsulation

Nanobiotecnologie

OH

OHO

HO

O

O

Oligomer

OH

OHO

HO

O

O

Oligomer

OOH

OOHO

O

HOO

HO SiO

OH

OHO

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.

D.-M. Huang et al., Nano Letters, 2007, 7, 149-154

FTIC

SiO2Fe3O4Schematic structure (up) and TEM micrograph of FTIC-APTES doped 50 nmsilica particles entrapping 10-nm Fe3O4 nanoparticles

A) Fluorescence microscope imagesof human mesenchymal stem cells(hMSCs) after incubation withnanoparticles (green) and alysosomes probe

B) MRI images of a nude mouse withinjected SiO2@Fe3O4nanoparticles

A

B

Iron oxide@silicaMultimodal imaging

Nanobiotecnologie

W. Tan et al., Anal. Chem. 2007, 79, 3075-3082

Iron oxide@silicaIn vitro cell detection and separation

Nanobiotecnologie

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C. Riviere, S. Roux et al., JACS, 2007, 129, 5076-5084

FTIC

SiO2Gd2O3

PEG

MRI images of a nude mouse withinjected SiO2@Gd2O3 nanoparticles B

AFluorescence reflectance images of a nude mouseafter injection of SiO2@Gd2O3 nanoparticles

Gadolinium oxide@silicaMultimodal imaging

Nanobiotecnologie

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

Latex@silica@layer-by-layer polymerControlled drug release

Nanobiotecnologie

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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

Mesoporous silicaSurfactant aggregates templated synthesis

Nanobiotecnologie

Mesoporous silicaSurfactant aggregates templated synthesis

Nanobiotecnologie

• 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

Mesoporous silicaSurfactant aggregates templated synthesis

Nanobiotecnologie

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.

Mesoporous silicaGatekeeping delivery

Nanobiotecnologie

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 

Mesoporous silicaGatekeeping delivery

Nanobiotecnologie

TEM images of MSN (a), iron oxide particles (b), capped MSN (c)

HeLa cells incubated with fluorescein loaded MSN 

Lin S-J et al., JACS, 2004, 126, 13216-13217

TEM

TEM

Confocal microscpe

Mesoporous silicaGatekeeping delivery

Nanobiotecnologie

Mesoporous silicaNanimpellers/nanovalves

Nanobiotecnologie

Apoptosis of PANC-1 incubated with MSNP induced by releasing CPT after irradiating for increasing times

Mesoporous silicaNanimpellers/nanovalves

Nanobiotecnologie

KB-31 cancer cells endocytosed doxorubicin-loaded fluorescein-labeled MSNPs within 3 h.This action is followed by doxorubicin releaseto the nucleus, induction of cytotoxicity, and theappearance of apoptotic bodies after 60 h(indicated by arrows), followed by nuclearfragmentation after 80 h.

Mesoporous silicaNanimpellers/nanovalves

NanobiotecnologieBefore magnetic field activation(viability 100%)

MPN loaded with Fl+ magnetic field(viability 84%)

MPN loaded with Dox+ magnetic field(viability 63%)

apoptotic bodies

Nanoparicles@Mesoporous silicaNanobiotecnologie

• 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

Nanoparicles@Mesoporous silicaTheranostic agents

Nanobiotecnologie

Fe3O4@mSiO2

Nanoparicles@Mesoporous silicaTheranostic agents

Nanobiotecnologie

HMn@mSiO2

mSiO2@Fe3O4