1. GELS STRUCTURE
LIQUID PHASE
CROSSLINKS
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

2. Schneider et al. J. American Chemical Society, 2002.
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)
ORDERED ZONES
CONNECTING DISORDERED ZONES
Van der Walls,
dipole-dipole,
hydrogen bonding, Coulombic
hydrophobic interactions
POLYSACCARIDES (GLUCANS, XANTHAN)

4. INTERACTION BETWEEN THE BIVALENT ION AND GULURONIC UNIT
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
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. SPH SAP a) Monomer dilution c) Crosslinker b) Neutralization
d) Foaming aid
and stabilizer
e) Oxidant
f) Reductant
g) Bicarbonate
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’ RD/RP 0.01 0.1 MEZZO CONTINUO MEZZO POROSO ZONA INTERMEDIA
Il moto del farmaco avviene tra le maglie del reticolo polimerico contenenti anche le molecole del fluido di rilascio
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
RD/RP
0.01
0.1
ZONA INTERMEDIA

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

15. = crosslinking monomers
IMPRINTED GELS
MOLECULAR IMPRINTING
COMPLEX FORMATION I
I = initiator
= template
= functional monomers
= crosslinking monomers
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
a = Ka1/Ka2
1 ≤ a ≤ 8

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

20. EXAMPLE 2: TARGETED DELIVERY
CELLULAR RECEPTOR
TISSUES OR CELLULAR LINING
IMPRINTED FILM
DRUG
HYDROGEL 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
Colombo, P 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 swellable crosslinked polymer particles. J. Contr. Rel. 68, , 2000.