BIOSILICIFICATION: Formation of BIOSILICIFICATION: Formation of AmorphousAmorphousSilicaSilica Complex Structures in Biological Systems Complex Structures in Biological Systems

DIATOMS: Living in a Constructal Environment, p. 143

Silica Silica BiomineralsBiominerals

Diatom shellDiatom shell Radiolarian Radiolarian microskeletonmicroskeleton

Physicochemical Characterization of Physicochemical Characterization of BiosilicaBiosilica

SheetSheet--likelike globularglobular fibrilarfibrilar

Plant Plant BiosilicaBiosilica

BIOSILICIFICATION: Ornate Silica BIOSILICIFICATION: Ornate Silica ““SuperSuper--structuresstructures”” Not Reproduced by Man Not Reproduced by Man

Gross Biogenic Silica Production: ~ 240 Gross Biogenic Silica Production: ~ 240 ±± 40 40 TmolTmol ““SiSi””/annum/annumSilicon Processing: 6.7 Giga tons/annumSilicon Processing: 6.7 Giga tons/annum

THE DIATOM: An Ideal THE DIATOM: An Ideal ProtistProtistSystem for the Study of System for the Study of

BiosilicificationBiosilicification

M. Sumper, Science 2002, 295, 2430.

SILICA FORMATION: Condensation PolymerizationSILICA FORMATION: Condensation PolymerizationOf Of SilicicSilicic Acid at pH ~ 7 Acid at pH ~ 7

T. Coradin, P. Jean Lopez, ChemBioChem 2003, 4, 251.

BIOSILICA FORMATION: Inside the SilicaBIOSILICA FORMATION: Inside the SilicaDeposition Vesicle (SDV) Deposition Vesicle (SDV)

THE CATALYTIC ROLE OF BIOMOLECULES THE CATALYTIC ROLE OF BIOMOLECULES ON SILICA FORMATION: ON SILICA FORMATION: SilaffinsSilaffins

H2N S S K K S G S G S Y S K G S K COOH

O-HO3P O

-HO3PO

-HO3P O-HO3P

O-HO3P

O-HO3P

O-HO3P

NH

NH3C

N

H3C

CH3

NCH3

H3C N+

CH3

H3C

H3C

O-HO3P

HN

NCH3

NCH3H3C

x = 4-9 y = 4-9

N. Kröger, S. Lorenz, E. Brunner, M. Sumper, Science 2002, 298, 585

SILICA BIOTRANSPORT: How is SILICA BIOTRANSPORT: How is ““SiliconSilicon””Transported Inside the SDV? Transported Inside the SDV?

Transport of “soluble” silicate into the SDV

Increase of silicate concentration

Supersaturation in the SDV

Silica formation “at will” and “when needed”

Role of Silica Transport Vesicle (STV)

Role of biomolecules for silicon transport

GOAL: To identify macromolecules that extendGOAL: To identify macromolecules that extendor delay silica formation from soluble silicate or delay silica formation from soluble silicate B

IOIN

SPIR

ED A

PPR

OA

CH

BIO

INSP

IRED

APP

RO

AC

H Study silicification “in vitro” at pH ~ 7 in the absence of any “additives”

Identify macromolecules that may have a “delay” effect on silicification

Study the inhibitory effect of these macromolecules “in vitro” and compare to “control”

Long-term (3 days) and short-term (8 h) experiments

Monitor “soluble silica”

Study silica formed (if any) by several techniques

Identify mechanisms, structure/function relationships

Ways to improve inhibitory activity

ATTRIBUTES OF MACROMOLECULES THATATTRIBUTES OF MACROMOLECULES THATAFFECT SILICATE CONDENSATION AFFECT SILICATE CONDENSATION

Charged polyelectrolytes, water-soluble

Usually Cationic or Partially Cationic

“Proper” extent of Cationic Charge

What Kind of Cationic Groups?

Zwitter-Ions?

What about “neutral” polymers?

CLASSES OF MACROMOLECULES STUDIEDCLASSES OF MACROMOLECULES STUDIED

Cationic Dendrimers (-NH3+ end-groups)

Cationic, Amine-Containing Polymers (-NH3+, -NH2R+,

-NHR2+ groups)

Purely Cationic, Ammonium-Containing Polymers

(-NR3+ groups)

Copolymers (neutral + cationic groups)

Zwitter-Ions (-NH2R+, -NHR2+ and –PO3H- Groups)

Cationic, Phosphonium-Based oligomers

Neutral Polymers (polyvinylpyrrolidone)

FUNCTIONALITY OF DENDRIMERS FUNCTIONALITY OF DENDRIMERS ASASSiOSiO22 INHIBITORSINHIBITORS ((““δέντρονδέντρον”” + + ““µέροςµέρος””))

Tomalia, D. A., et al. Angew. Chem. Int. Ed. Engl. 1990, 29, 138.

N

N

O

NH

NH2O

NH2

N

O NH

O

NH

N

O NH

NH2

NH

O NH2

O

ONH

N

O NH

NH2

O

NH2

NH

HN

N

O

ONHNH2

HN

NH2 NH

PAMAM generation 1 (8 -NH2 terminal groups)

PAMAM = polyaminoamide

Biodegradable by virtue of theirBiodegradable by virtue of theiramide bondsamide bonds

VARIOUS GENERATIONS OF DENDRIMERSVARIOUS GENERATIONS OF DENDRIMERS

G = 1G = 12.2 nm2.2 nm

G = 2G = 22.9 nm2.9 nm

EFFECT OF DENDRIMERS ON EFFECT OF DENDRIMERS ON SiOSiO22 FORMATION FORMATION

Neofotistou, E.; Demadis, K.D. Coll. & Surf. A: Physicochem. Eng. Asp. 2004, 242, 213.

0 240 480 720 960 1200 1440100

150

200

250

300

350

400

450

500

solu

ble

SiO

2 (pp

m)

time (min)

CONTROL PAMAM 0.5 (40ppm) PAMAM 1.0 (40ppm) PAMAM 1.5 (40ppm) PAMAM 2.0 (40ppm) PAMAM 2.5 (40ppm)

pH = 7.0(minimum SiO2solubility)

DISPERSION OFDISPERSION OF SiOSiO2 2 –– PAMAMPAMAM--1 PRECIPITATES1 PRECIPITATESUSING ANIONIC POLYMERS USING ANIONIC POLYMERS

Demadis, K.D.; Neofotistou, E. Chem. Mater. 2007, 19, 581.

0 240 480 720 960 1200 1440 1680100

150

200

250

300

350

400

450

500

∆ιαλυτό

SiO

2 (pp

m)

χρόνος (min)

CONTROL PAMAM 1.0 (40ppm) PAMAM 1.0 (40ppm) - PAMCOAA (40ppm) PAMAM 1.0 (40ppm) - PAA(LOW MW) (40ppm) PAMAM 1.0 (40ppm) - PAA(HIGH MW) (40ppm) PAMAM 1.0 (40ppm) - CMI (40ppm)

time (min)

solu

ble

SiO

2(p

pm)

**

O

n

OH

*

O

n

OH

**

m

NH2O

PAA

PAM-co-AA

O

O

CH2OH

OH

OHOH

O

HOCH2

O

CH2

-O

O

O

CH2

HO

CH2

O

O

CH2

-O

OOH

CH2OH

n

CMI

Mavredaki, E.; Neofotistou, E.; Demadis, K.D. Ind. Eng. Chem. Res. 2005, 44, 7019.

DISPERSION OFDISPERSION OF SiOSiO2 2 –– PAMAMPAMAM--2 PRECIPITATES2 PRECIPITATESUSING USING GREENGREEN ANIONIC POLYMERS ANIONIC POLYMERS

0 240 480 720 960 1200 1440 1680100

150

200

250

300

350

400

450

500

∆ιαλυτό

SiO

2 (pp

m)

χρόνος (min)

CONTROL PAMAM 2.0 (40ppm) PAMAM 2.0 (40ppm) - PAMCOAA (40ppm) PAMAM 2.0 (40ppm) - PAA(LOW MW) (40ppm) PAMAM 2.0 (40ppm) - PAA(HIGH MW) (40ppm) PAMAM 2.0 (40ppm) - CMI (40ppm)

time (min)

solu

ble

SiO

2(p

pm)

**

O

n

OH

*

O

n

OH

**

m

NH2O

PAA

PAM-co-AAO

O

CH2OH

OH

OHOH

O

HOCH2

O

CH2

-O

O

O

CH2

HO

CH2

O

O

CH2

-O

OOH

CH2OH

n

CMI

Demadis, K.D.; Neofotistou, E. Chem. Mater. 2007, 19, 581.Mavredaki, E.; Neofotistou, E.; Demadis, K.D. Ind. Eng. Chem. Res. 2005, 44, 7019.

STABLE DISPERSIONS OFSTABLE DISPERSIONS OF SiOSiO2 2 –– PAMAM PAMAM PRECIPITATES WITH PRECIPITATES WITH GREENGREEN ANIONIC POLYMERS ANIONIC POLYMERS

PAMAM

PAMAM + PAM-co-AA

PAMAM + CMI

Mavredaki, E.; Neofotistou, E.; Demadis, K.D. Ind. Eng. Chem. Res. 2005, 44, 7019.

*

O

n

OH

**

m

NH2O

PAM-co-AA

O

O

CH2OH

OH

OHOH

O

HOCH2

O

CH2

-O

O

O

CH2

HO

CH2

O

O

CH2

-O

OOH

CH2OH

n

CMI

AMORPHOUS SiO2-PAMAM COMPOSITES

0

200

400

600

800

1000

1200

1400

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0

2θ

Si

0

10

20

30

40

50

60

4001400240 03400

wavenumbers (cm-1)

Tran

smitt

ance

(%)

ν(C=O)

1635

1096

788

464

ν(Si

-O-S

i)3432

ν(O

-H) -ΝΗ3

+

ν(Si-O-Si)

CATIONIC CATIONIC BIOBIO--POLYMERS FOR SiOPOLYMERS FOR SiO2 2 INHIBITIONINHIBITION

inulin(neutral)

Inulin(cationic)

chicory roots chicory roots (Renewable (Renewable

feedstock for feedstock for nonnon--food food

applications)applications)

biopolymer

3 cationic inulins:

CATIN-220 (DS = 0.22)CATIN-860 (DS = 0.86)CATIN-1280 (DS = 1.28)

DS = degree of substitution)

InulinInulin content: content: 14.9 14.9 -- 18.3 %18.3 %

EFFECT OF CATINEFFECT OF CATIN--1280 1280 BIOBIO--POLYMER POLYMER ON SiOON SiO2 2 INHIBITIONINHIBITION

0.0

100.0

200.0

300.0

400.0

500.0

control 100 ppm 150 ppm 200 ppm

24h

48h

72h

CATIN-1280 dosage

solu

ble

silic

ate

(ppm

)

0

100

200

300

400

500

0 1 2 3 4 5 6 7 8hours

solu

ble

silic

ate

(ppm

)

control

80 ppm CATIN-1280

Demadis, K.D.; Ketsetzi, A. Desalination 2008, 223, 487

SYNERGY BETWEEN CATINSYNERGY BETWEEN CATIN--1280 AND CMI1280 AND CMI

0,0

100,0

200,0

300,0

400,0

500,0

control

control+100ppmC

atin860+0ppmC

MI

control+100ppmC

atin860+50ppmC

MI

control+100ppmC

atin860+100ppmC

MI

control+100ppmC

atin860+150ppmC

MI

24h

48h

72h

additive dosage (ppm)

solu

ble

silic

a (p

pm)

~ 200 ppm silicicacid enhancement

Demadis, K.D.; Ketsetzi, A. Desalination 2008, 223, 487

SYNERGISTIC EFFECTS IN SiOSYNERGISTIC EFFECTS IN SiO2 2 INHIBITION:INHIBITION:CATIN + PASPCATIN + PASP

PASP = PASP = polyaspartatepolyaspartate

050

100150200250300350400450500

0 2 4 6 8 10polymerization time (h)

solu

ble

silic

ate

(ppm

as

SiO

2)

control

100 ppm CATIN + 100 ppm PASP

40 ppm CATIN + 60 ppm PASP

100 ppm CATIN

EFFECTS OF ZWITTEREFFECTS OF ZWITTER--IONIC POLYMERS IONIC POLYMERS ON SiOON SiO2 2 INHIBITION: INHIBITION: PhosphonomethylchitosanPhosphonomethylchitosan

O

OHHN

OH

CH2OHO

HN

OH

CH2OHO OH

HN

OH

CH2OH

O O

nO

CH3

O

CH3

O

CH3

CHT

O

OHNH3

+

OH

CH2OHO

NH3+

OH

CH2OHO OH

NH3+

OH

CH2OH

O O

n

O

HN

OH

CH2OH

O

mO

CH3 CHS

O

OHNH3

+

OH

CH2OHO

OH

CH2OHO OH

NH3+

OH

CH2OH

O O

q

O

HN

OH

CH2OH

O

mO

CH3 NH+

P PO O

-O O-HOOH

O

NH3+

OH

CH2OH

O

n

O

OH

CH2OH

O

p+H2N

P

O

O-HO

(m = 0.16, n = 0.37, p = 0.24, q = 0.14)

PCH

0

50

100

150

200

250

300

350

400

450

500

0 1 2 3 4 5 6 7 8

time (h)

solu

ble

silic

ate

(ppm

as

SiO

2)

control

150 ppm

200 ppm40 ppm

Effect of Effect of PhosphonomethylchitosanPhosphonomethylchitosan (PCH)(PCH)On Silica FormationOn Silica Formation

150

ppm

silic

icac

id

addi

tiona

l sta

biliz

atio

n

Demadis, K.D.; Ketsetzi, K. Pachis; A. Ramos, V.M. Biomacromolecules 2008, 9, 3288.

2

4

6

8

10

12

14

16

150016001700

wavenumber (cm-1)

tran

smitt

ance

(%)

silica

silica-PCH composite

PCH

6

8

10

12

14

16

18

20

22

400500600700800900100011001200130014001500

PCHsilica-PCH composite

silica

PhosphonomethylchitosanPhosphonomethylchitosan (PCH)(PCH)Entrapment in the Silica MatrixEntrapment in the Silica Matrix

Demadis, K.D.; Ketsetzi, K. Pachis; A. Ramos, V.M. Biomacromolecules 2008, 9, 3288.

Conclusions

Biosilicification is a very complex process (in vitro silicification, too!)

Nature uses silica biominerals for different purposes

Biosilica is not simple inorganic system

Biosilica is a composite materialThere are many potential applications

of silica