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GELS STRUCTURE

CROSSLINKS. GELS STRUCTURE. LIQUID PHASE. POLYMERIC CHAINS. MATRICES ARE COHERENT SYSTEMS MADE UP BY A POLYMERIC NETWORK TRAPPING A CONTINUOUS LIQUID PHASE. THEY SHOW MECHANICAL PROPERTIES IN BETWEEN THOSE OF SOLIDS AND LIQUIDS. 20 m m. 0.2 m m.

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GELS STRUCTURE

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  1. CROSSLINKS GELS STRUCTURE LIQUID PHASE POLYMERIC CHAINS MATRICES ARE COHERENT SYSTEMS MADE UP BY A POLYMERIC NETWORK TRAPPING A CONTINUOUS LIQUIDPHASE. THEY SHOW MECHANICAL PROPERTIES IN BETWEEN THOSE OF SOLIDS AND LIQUIDS

  2. 20 mm 0.2 mm Schneider et al. J. American Chemical Society, 2002. (a) Laser scanning confocal microscopy. Green regions are fluorescently stained self-assembled peptide, and black regions are water-filled pores and channels. (b) CryoTEM. Dark structures are selfassembled peptide scaffold, while lighter gray areas are composed of vitrified water.

  3. PHYSICAL CROSSLINKS (weak) ENTANGLEMENTS (TOPOLOGICAL CONSTRAINS) CONNECTING DISORDERED ZONES Van der Walls, dipole-dipole, hydrogen bonding, Coulombic hydrophobic interactions ORDERED ZONES POLYSACCARIDES (GLUCANS, XANTHAN)

  4. PHYSICAL CROSSLINKS (strong) Ca++ Ca++ Ca++ Ca++ Ca++ Ca++ Ca++ EGGS BOX STRUCTURE INTERACTION BETWEEN THE BIVALENT ION AND GULURONIC UNIT ALGINATES

  5. CHEMICAL CROSSLINKS (strong: covalent bond) SCLEROGLUCAN CROSSLINKED WITH BORAX T. Coviello et al., Int. J. Biol. Macromolecules, 32 (2003) 83

  6. POROUS GELS: Cellulose – Acrylic Acid Crosslinking irradiation intensity Cellulose mass fraction Acrylic acid mass fraction

  7. Surface picture (406035) (ESEM)

  8. Cross-section picture (406035) (ESEM)

  9. Surface picture (208035) (ESEM)

  10. Cross-section picture (208035) (ESEM)

  11. GEL SUPERPOROSI

  12. a) Monomer dilution e) Oxidant b) Neutralization f) Reductant c) Crosslinker g) Bicarbonate d) Foaming aid and stabilizer SPH a) Monomer dilution e) Oxidant thermal initiator b) Neutralization f) Reductant c) Crosslinker d) Foaming aid g) Bicarbonate SAP Figure 6.2. Schematic representation of steps involved in the production of Super porous hydrogels (SPH) and Super absorbent polymers (SPA) (with permission from ref.[46]).

  13. POROSITA’ 2*RD RP FARMACO CATENE POLIMERICHE RD/RP 0.01 0.1 MEZZO CONTINUO MEZZO POROSO Il moto del farmaco avviene tra le maglie del reticolo polimerico contenenti anche le molecole del fluido di rilascio Il moto del farmaco avviene nel fluido di rilascio che riempe i canali le cui pareti sono costituite dal polimero ZONA INTERMEDIA

  14. DIFFUSIONE R = 0 DRUG R = Rp TORTUOSITA’ Lc/Rp POROSITA’ Vv/VT De=Dw*e/t

  15. IMPRINTED GELS I I I COMPLEX FORMATION I I CROSSLINKING I I = initiator WASHING = template = functional monomers = crosslinking monomers MOLECULAR IMPRINTING

  16. IMPRINTED POLYMERIC GELS: CHARACTERISTICS Binding affinity: a measure of how well the template molecule is attracted to the binding site Selectivity : the ability to differentiate between the template and other molecules Binding capacity : the maximum amount of template bound per mass or volume of polymer

  17. BINDING AFFINITY Forward reaction (binding) Backward reaction (un-binding) Association constant Macromolecular sites concentration Template concentration

  18. SELECTIVITY a = Ka1/Ka2 1 ≤ a≤ 8

  19. A A A A A A A A A A A A A A A A A A A A A P P P P P P P P P A A A A = PROTEIN = DRUG NETWORK SWELLING: DRUG CAN BE RELEASED A =ANALYTE EXAMPLE : SWELLING CONTROL

  20. EXAMPLE 2: TARGETED DELIVERY TISSUES OR CELLULAR LINING HYDROGEL DRUG CELLULAR RECEPTOR IMPRINTED FILM R R

  21. BIBLIOGRAFIA • Lapasin R, Pricl S, Rheology of Industrial Polysaccharides; Theory and Applications, Chapman and Hall, London, 1995. • Coviello T, Grassi M, Rambone G, Santucci E, a Carafa M , Murtas E, Riccieri F M, Franco Alhaique F. Novel hydrogel system from scleroglucan: synthesis and characterization J. Contr. Rel. 60, 367–378, 1999. • A. Kydonieus (Ed.), Treatise on Controlled Drug Delivery, Marcel Dekker, New York, 1992, pp. 54-55. • Colombo, P. 1993. Swelling-controlled release in hydrogel matrices for oral route. Adv. Drug. Dev. Rev., 11, 37 – 57 • Grassi M, Colombo I, Lapasin R. Drug release from an ensemble of swellablecrosslinked polymer particles. J. Contr. Rel. 68, 97-113, 2000.

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