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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. - PowerPoint PPT Presentation
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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 THOSE OF SOLIDS AND LIQUIDS
CROSSLINKS POLYMERIC CHAINS
LIQUID PHASE
(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.
PHYSICAL CROSSLINKS (weak)
ENTANGLEMENTS (TOPOLOGICAL CONSTRAINS)
ORDERED ZONES
CONNECTING DISORDERED
ZONES
Van der Walls, dipole-dipole,
hydrogen bonding, Coulombic
hydrophobic interactions
POLYSACCARIDES (GLUCANS, XANTHAN)
PHYSICAL CROSSLINKS (strong)
Ca++ Ca++Ca++ Ca++ Ca++Ca++
EGGS BOX STRUCTURE
OO O
OH
OH
OHOH
OH
O
O OH
O
OCa 2+Ca++
INTERACTION BETWEEN THE BIVALENT ION AND
GULURONIC UNIT
ALGINATES
CHEMICAL CROSSLINKS (strong: covalent bond)
SCLEROGLUCAN CROSSLINKED WITH
BORAX
T. Coviello et al., Int. J. Biol. Macromolecules, 32 (2003) 83
POROUS GELS: Cellulose – Acrylic Acid
Acrylic acid mass fraction
Cellulose mass fraction
Crosslinking irradiation intensity
Surface picture (406035) (ESEM)
Cross-section picture (406035) (ESEM)
Surface picture (208035) (ESEM)
Cross-section picture (208035) (ESEM)
GEL SUPERPOROSI
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
POROSITA’
RD/RP0.01 0.1ZONA
INTERMEDIAMEZZO 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*RD RP
Il moto del farmaco avviene tra le maglie del reticolo polimerico contenenti anche le molecole del fluido di rilascio
DIFFUSIONE
R = 0
R = Rp
DRUG
De = Dw */TORTUOSITA’
Lc/Rp
POROSITA’ Vv/VT
IMPRINTED GELSMOLECULAR IMPRINTINGMOLECULAR IMPRINTING
I
I
I
I
I
I
I = initiator= template
= functional monomers
= crosslinking
monomers
COMPLEX FORMATION
CROSSLINKING
WASHING
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
BINDING AFFINITY
MTTMk
k
f
rMacromolecular sites concentration
Template concentration
TMkR ff Forward reaction (binding)
MTkR rr Backward reaction (un-binding)
TMMT
Kkk
K dr
fa
1Association
constant
SELECTIVITY
= Ka1/Ka2
1 ≤ ≤ 8
APA A P
AA
PA
A PA
A
A
A
AA
A
A
A
A
NETWORK SWELLING:DRUG CAN BE RELEASED
EXAMPLE : SWELLING CONTROL
PA
A
PA
APA A
PA
A
= DRUGA =ANALYTE
P = PROTEIN
IMPRINTED FILM
DRUG
HYDROGEL
EXAMPLE 2: TARGETED DELIVERY
R CELLULAR RECEPTOR
TISSUES OR CELLULAR LINING
R
BIBLIOGRAFIA1) 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.