Doctor

UNIVERSIDAD DE GUADALAJARA
CENTRO UNIVERSITARIO DE CIENCIAS EXACTAS E INGENIERIAS DEPARTAMENTO DE MADERA, CELULOSA Y PAPEL

Curso "Introducción a la ciencia de los biomateriales y sus propiedades nanoestructurales"

Tema 5. Hidrogeles
Instructor: Dr. Ezequiel Delgado Fornué
Centro de Investigación en Biomateriales Departamento de Madera, Celulosa y Papel ezedelfor@gmail.com

Septiembre2008

Advanced Drug Delivery Reviews 43 (2002) 3–12 www.elsevier.com / locate / drugdeliv

Hydrogels for biomedical applications
Allan S. Hoffman*
Bioengineering Department, Box 352255, University of Washington, Seattle, WA 98195, USA Received 26 July 2001; accepted 29 August 2001

Abstract

The information contained in this presentation (including all figures andpermeation ofhas Thisarticle reviews the composition and synthesis of hydrogels, the character of their absorbed water, and tables) solutes within their swollen matrices. The most important properties of hydrogels relevant to their biomedical applications been taken from Hoffman´s review (2002). are also identified, especially for use of hydrogels as drug and cell carriers, and as tissue engineering matrices. ! 2002Elsevier Science B.V. All rights and Additional illustrations reserved.chemical structures have been taken from Wikipedia.
Keywords: Hydrogels; Drug delivery; Water; Pores; Tissue engineering
Dr. Ezequiel Delgado Fornué, Centro de Investigación en Biomateriales, Universidad de Guadalajara, México, Sept. 8-19, 2008

Contents

2

What is a gel?
A gel (from the lat. Gelu-freezing, cold, ice orGelatus-frozen, immobile) is an apparently solid, jelly-like material formed from a colloidal solution. By weight, gels are mostly liquid, yet they behave like solids due to the addition of a gelling agent.

Illustrations from Wikipedia the Free Encyclopedia
Dr. Ezequiel Delgado Fornué, Centro de Investigación en Biomateriales, Universidad de Guadalajara, México, Sept. 8-19, 2008

3

•Hydrogels
based
on
both
natural
and
synthetic
polymers
are
of
interest
for
 encapsulation
of
cells. • Most
recently
have
become
especially
attractive
to
the
new
field
of
tissue
 engineering
as
matrices
for
repairing
and
regenerating
a
wide
variety
of
 tissues
and
organs. • Hydrogels
are
hydrophilic
polymer
networks
which
may
absorb
from
10–20%
(an
arbitrary
lower
limit)
up
to
thousands
of
times
their
dry
weight
 in
water. • Hydrogels
may
be
chemically
stable
or
they
may
degrade
and
eventually
 disintegrate
and
dissolve.

Dr. Ezequiel Delgado Fornué, Centro de Investigación en Biomateriales, Universidad de Guadalajara, México, Sept. 8-19, 2008

4

Two
types
of
gels: 
 ★
Reversible
or
physical
gels ★
Chemical
gels

Dr. Ezequiel Delgado Fornué, Centro de Investigación en Biomateriales, Universidad deGuadalajara, México, Sept. 8-19, 2008

5

•They
are
called
‘reversible’,
or
‘physical’
gels
when
the
networks
are
held
 together
by
molecular
entanglements,
and/or
secondary
forces
including
ionic,
 H‐bonding
or
hydrophobic
forces. •Physical
hydrogels
are
not
homogeneous,
since
clusters
of
molecular
 entanglements,
or
hydropho‐bically‐or
ionically‐associated
domains,
can
 create
inhomogeneities.•Free
chain
ends
or
chain
loops
also
represent
transient
network
defects
in
 physical
gels. •When
a
polyelectrolyte
is
combined
with
a
multi‐valent
ion
of
the
opposite
 charge,
it
may
form
a
physical
hydrogel
known
as
an
‘ionotropic’
hydrogel. •They
may
gel
or
precipitate
depending
on
their
concentrations,
the
ionic
 strength,
and
pH
of
the
solution.
The
products
of
such
ion‐crosslinked
systems
are
known
as
complex
coacervates,
polyion
complexes,
or
polyelectrolyte
 complexes.
Dr. Ezequiel Delgado Fornué, Centro de Investigación en Biomateriales, Universidad de Guadalajara, México, Sept. 8-19, 2008

6

2.4 HYDROGELS

61

Ratner & Hoffman 1996
FIG. 1. (A) Ideal macromolecular network of a hydrogel. (B) Network with multifunctional junctions. (C) Physical...