BIOSILICIFICATION: Formation of Amorphous Silica Complex ...

BIOSILICIFICATION: Formation of AmorphousSilica Complex Structures in Biological SystemsDIATOMS: Living in a Constructal Environment, p. 143

Silica BiomineralsDiatom shellRadiolarian microskeleton

Physicochemical Characterization of Biosilica

Plant BiosilicaSheet-likeglobularfibrilar

BIOSILICIFICATION: Ornate Silica“Super-structures” Not Reproduced by ManGross Biogenic Silica Production: ~ 240 ± 40 Tmol “Si”/annumSilicon Processing: 6.7 Giga tons/annum

THE DIATOM: An Ideal ProtistSystem for the Study ofBiosilicificationM. Sumper, Science 2002, 295, 2430.

SILICA FORMATION: Condensation PolymerizationOf Silicic Acid at pH ~ 7T. Coradin, P. Jean Lopez, ChemBioChem 2003, 4, 251.

BIOSILICA FORMATION: Inside the SilicaDeposition Vesicle (SDV)

THE CATALYTIC ROLE OF BIOMOLECULESON SILICA FORMATION: Silaffins- HO 3 P- HO 3 PO O- HO 3 P- HO 3 PO- HO 3 PO- HO 3 POO- HO 3 POH 2 N S S K K S G S G S Y S K G S K COOH- HO 3 PONHH 3 CNH 3 CHNN + CH 3CH 3H 3 CH 3 CNx = 4-9y = 4-9NCH3H 3 CNCH 3H 3 CNCH 3N. Kröger, S. Lorenz, E. Brunner, M. Sumper, Science 2002, 298, 585

SILICA BIOTRANSPORT: How is “Silicon”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 extendor delay silica formation from soluble silicateBIOINSPIRED APPROACH‣ Study silicification “in vitro” at pH ~ 7 in theabsence of any “additives”‣ Identify macromolecules that may have a “delay” effecton silicification‣ Study the inhibitory effect of these macromolecules “invitro” 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 THATAFFECT 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 STUDIED‣ Cationic Dendrimers (-NH 3+ end-groups)‣ Cationic, Amine-Containing Polymers (-NH 3+ , -NH 2 R + ,-NHR 2+ groups)‣ Purely Cationic, Ammonium-Containing Polymers(-NR 3+ groups)‣ Copolymers (neutral + cationic groups)‣ Zwitter-Ions (-NH 2 R + , -NHR 2+ and –PO 3 H - Groups)‣ Cationic, Phosphonium-Based oligomers‣ Neutral Polymers (polyvinylpyrrolidone)

FUNCTIONALITY OF DENDRIMERS ASSiO 2 INHIBITORS (“δέντρον” + “µέρος”)N H 2ON H 2NHONH 2N H 2HNNHOONHNONHNOONNNHONHNNHONH 2O NHPAMAM = polyaminoamideN H 2NHNONHONHNH 2Biodegradable by virtue of theiramide bondsNH 2PAMAM generation 1(8 -NH 2terminal groups)Tomalia, D. A., et al. Angew. Chem. Int. Ed. Engl. 1990, 29, 138.

VARIOUS GENERATIONS OF DENDRIMERSG = 12.2 nmG = 22.9 nm

EFFECT OF DENDRIMERS ON SiO 2 FORMATIONsoluble SiO 2(ppm)500450400350300250200150CONTROLPAMAM 0.5 (40ppm)PAMAM 1.0 (40ppm)PAMAM 1.5 (40ppm)PAMAM 2.0 (40ppm)PAMAM 2.5 (40ppm)1000 240 480 720 960 1200 1440time (min)pH = 7.0(minimum SiO 2solubility)Neofotistou, E.; Demadis, K.D. Coll. & Surf. A: Physicochem. Eng. Asp. 2004, 242, 213.

DISPERSION OF SiO 2 – PAMAM-1 1 PRECIPITATESUSING ANIONIC POLYMERS*O- O*OOPAAnOHn**OHPAM-co-AAO- OCH 2OHHOCH 2OCH 2CH 2HOOCH 2OHOOOHOHOOO*mCH 2ONH 2OHnCH 2OHCMIsoluble ∆ιαλυτό SiO 2(ppm) 2(ppm)500450400350300250200150CONTROLPAMAM 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)1000 240 480 720 960 1200 1440 1680χρόνος time (min)Mavredaki, E.; Neofotistou, E.; Demadis, K.D. Ind. Eng. Chem. Res. 2005, 44, 7019.Demadis, K.D.; Neofotistou, E. Chem. Mater. 2007, 19, 581.

DISPERSION OF SiO 2 – PAMAM-2 2 PRECIPITATESUSING GREEN ANIONIC POLYMERS*O- O*OOPAAnOHn**OHPAM-co-AAO- OCH 2OHHOCH 2OCH 2CH 2HOOCH 2 OHOOOH OOHOOCH 2OOH*mNH 2nCH 2 OHCMIsoluble SiO 2(ppm)∆ιαλυτό SiO 2(ppm)500450400350300250200150CONTROLPAMAM 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)1000 240 480 720 960 1200 1440 1680χρόνος (min)time (min)Mavredaki, E.; Neofotistou, E.; Demadis, K.D. Ind. Eng. Chem. Res. 2005, 44, 7019.Demadis, K.D.; Neofotistou, E. Chem. Mater. 2007, 19, 581.

STABLE DISPERSIONS OF SiO 2 – PAMAMPRECIPITATES WITH GREEN ANIONIC POLYMERSOHCH 2 OHO*n**mOHOHOOOOHONH 2OHOCH 2OCH 2PAM-co-AAO- OOCH 2CH 2OOnCH 2 OH- OCH 2HOOHCMIPAMAMPAMAM + CMIPAMAM + PAM-co-AAMavredaki, E.; Neofotistou, E.; Demadis, K.D. Ind. Eng. Chem. Res. 2005, 44, 7019.

AMORPHOUS SiO 2 -PAMAM COMPOSITES60Transmittance (%)50403020103432ν(O-H)-ΝΗ 3+ν(C=O)1635ν(Si-O-Si)1096788ν(Si-O-Si)46414001200100080060040020000.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.003400240014004002θwavenumbers (cm -1 )Si

CATIONIC BIO-POLYMERS FOR SiO 2 INHIBITIONbiopolymerinulin(neutral)Inulin(cationic)chicory roots(Renewablefeedstock fornon-foodapplications)Inulin content:14.9 - 18.3 %3 cationic inulins:CATIN-220 (DS = 0.22)CATIN-860 (DS = 0.86)CATIN-1280 (DS = 1.28)DS = degree of substitution)

EFFECT OF CATIN-1280BIO-POLYMERON SiO 2 INHIBITION500.0500400.024h400soluble silicate (ppm)300.0200.0100.048h72hsoluble silicate (ppm)30020010080 ppm CATIN-1280control0.0control 100 ppm 150 ppm 200 ppmCATIN-1280 dosage00 1 2 3 4 5 6 7 8hoursDemadis, K.D.; Ketsetzi, A. Desalination 2008, 223, 487

SYNERGY BETWEEN CATIN-1280 AND CMI500,024h400,048h300,072h~ 200 ppm silicicacid enhancement200,0100,0soluble silica (ppm)0,0control+100ppmCatin860+150ppmCMIcontrol+100ppmCatin860+100ppmCMIcontrol+100ppmCatin860+50ppmCMIcontrol+100ppmCatin860+0ppmCMIcontroladditive dosage (ppm)Demadis, K.D.; Ketsetzi, A. Desalination 2008, 223, 487

SYNERGISTIC EFFECTS IN SiO 2 INHIBITION:CATIN + PASPsoluble silicate (ppm as SiO 2)500450400350300250200150100500100 ppm CATIN + 100 ppm PASP40 ppm CATIN + 60 ppm PASP100 ppm CATINcontrol0 2 4 6 8 10polymerization time (h)PASP = polyaspartate

EFFECTS OF ZWITTER-IONIC IONIC POLYMERSON SiO 2 INHIBITION: PhosphonomethylchitosanOHCH 2 OHOOHHNOCH 3CH 2 OHOOHHNCH 3OCH 2 OHOOHHNOHCH 3CHTOOnOOHCH 2 OHOOHNH 3+OCH 2 OHOOHHNCH 3OCH 2 OHOOHNH 3+OCH 2 OHO OHOHNH 3+CHSOmnOHCH 2 OHOOH+ NH 3OCH 2 OHOOHHNOCH 2 OHCH 2 OHCH 2 OHOOOOHO OHO OHONH 3+CH 3 + H 2 NNmH+npOqCH 2 OHO OHOH+ NH 3PCHHOPOO -- O P OH HO P O -OO(m = 0.16, n = 0.37, p = 0.24, q = 0.14)

Effect of Phosphonomethylchitosan (PCH)On Silica Formation50045040 ppm200 ppmsoluble silicate (ppm as SiO2)400350300250200150100150 ppmcontrol150 ppm silicic acidadditional stabilization5000 1 2 3 4 5 6 7 8time (h)Demadis, K.D.; Ketsetzi, K. Pachis; A. Ramos, V.M. Biomacromolecules 2008, 9, 3288.

Phosphonomethylchitosan (PCH)Entrapment in the Silica Matrix1614silica2220silica-PCH compositePCHtransmittance (%)121086silica-PCH compositePCH1816141210silica4821700160015006150014001300120011001000900800700600500400wavenumber (cm -1 )Demadis, K.D.; Ketsetzi, K. Pachis; A. Ramos, V.M. Biomacromolecules 2008, 9, 3288.

Conclusions Biosilicification is a very complexprocess (in vitro silicification, too!) Nature uses silica biominerals fordifferent purposes Biosilica is not simple inorganicsystem Biosilica is a composite material There are many potential applicationsof silica