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GELS STRUCTURE MATRICES ARE COHERENT SYSTEMS MADE UP BY A POLYMERIC NETWORK TRAPPING A CONTINUOUS LIQUID PHASE. THEY SHOW MECHANICAL PROPERTIES IN BETWEEN.

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Presentation on theme: "GELS STRUCTURE MATRICES ARE COHERENT SYSTEMS MADE UP BY A POLYMERIC NETWORK TRAPPING A CONTINUOUS LIQUID PHASE. THEY SHOW MECHANICAL PROPERTIES IN BETWEEN."— Presentation transcript:

1 GELS STRUCTURE 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 CROSSLINKS POLYMERIC CHAINS LIQUID PHASE

2 (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. 20 m 0.2 m Schneider et al. J. American Chemical Society, 2002.

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

4 PHYSICAL CROSSLINKS (strong) Ca ++ EGGS BOX STRUCTURE Ca ++ 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 Acrylic acid mass fraction Cellulose mass fraction Crosslinking irradiation intensity

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 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]). a) Monomer dilution c) Crosslinker b) Neutralization d) Foaming aid and stabilizer e) Oxidant f) Reductant g) Bicarbonate SPH a) Monomer dilution c) Crosslinker b) Neutralization d) Foaming aid e) Oxidant thermal initiator f) Reductant g) Bicarbonate SAP

13 POROSITA R D /R P 0.010.1 ZONA INTERMEDIA MEZZO POROSO CATENE POLIMERICHE FARMACO Il moto del farmaco avviene nel fluido di rilascio che riempe i canali le cui pareti sono costituite dal polimero MEZZO CONTINUO 2*R D RPRP Il moto del farmaco avviene tra le maglie del reticolo polimerico contenenti anche le molecole del fluido di rilascio

14 DIFFUSIONE R = 0 R = R p DRUG D e = D w * / TORTUOSITA L c /R p POROSITA V v /V T

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

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 Macromolecular sites concentration Template concentration Forward reaction (binding)Backward reaction (un-binding) Association constant

18 SELECTIVITY = K a1 / K a2 1 8

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

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

21 BIBLIOGRAFIA 1)Lapasin R, Pricl S, Rheology of Industrial Polysaccharides; Theory and Applications, Chapman and Hall, London, 1995. 2)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. 3)A. Kydonieus (Ed.), Treatise on Controlled Drug Delivery, Marcel Dekker, New York, 1992, pp. 54-55. 4)Colombo, P. 1993. Swelling-controlled release in hydrogel matrices for oral route. Adv. Drug. Dev. Rev., 11, 37 – 57 5)Grassi M, Colombo I, Lapasin R. Drug release from an ensemble of swellable crosslinked polymer particles. J. Contr. Rel. 68, 97-113, 2000.


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