Biomedical Engineering Reference
In-Depth Information
Roy
et al
. (2003) have studied the performance of biodegradable
composites for bone repair by the integration of b-tricalcium phosphate
(b-TCP) particles in the PLGA porous matrix, providing evidence for a
role of the ceramic phase in the degradation mechanisms of the polymer
matrix. the relatively low molecular weight of the 50:50 PLGa (only 50
kDa) promotes a fast hydrolytic degradation
in vivo
, with rapid mechanical
failure owing to loss of structure. During the PLGa degradation via bulk
erosion, the release of acidic degradation products leads to a local decrease
in pH, which rapidly causes local tissue damage, that is bone resorption and
fibrous tissue formation. The presence of reactive calcium phosphates such
as a- and b-TCP may enable the decay in pH to be buffered, influencing
the final polymer degradation. In this direction, several studies related to
in
vitro
degradation of PLa composites with various additive charges of tCP
particles have highlighted a pH drop at the most of up to 5, corresponding
to the approximate pH for activated macrophages, indicating the occurrence
of probable bone resorption (Holy
et al
., 1999; Lin
et al
., 1999).
9.6 References
Agrawal CM and Ray RB (2001), 'Biodegradable polymeric scaffolds for musculoskeletal
tissue engineering',
J Biomed Mater Res
,
55
, 141-50.
Aho AJ, Ekfors T, Dean PB, Aro HT, Ahonen A and Nikkanen V (1994), 'Incorporation
and clinical results of large allografts of the extremities and pelvis'.
Clin Orthop
Relat Res
, (
307
), 200-13.
Alexander H (1996),
Biomaterial Science
, Ratuer BD (ed.), Academic Press, San Diego,
94-105.
Akay M and Aslan N (1995), 'An estimation. of fatigue life for a carbon fibre/polyether
ether ketone hip joint prosthesis',
Proc Inst Mech Engrs
,
Part H
,
229
, 93-103.
Ambrosio L, Caprino G, Nicolais L, Nicodemo L, Huang SJ, Guida G and Ronca D
(1987),
Composite Structures
, Marshall IH (ed.), Elsevier Applied Science, London
and new york, Vol.
2
, 2.337-2.344.
Ambrosio L, Netti PA, Iannace S, Huang SJ and Nicolais L (1996), 'Composite hydrogels
for intervertebral disc prostheses',
J Mater Sci: Mater Med
,
7
, 251-4.
Ambrosio L, De Santis R and Nicolais L (1998a), 'Composite hydrogels for implants',
J Proc Instn Mech Engrs
,
212
(H), 93-9.
Ambrosio L, De Santis R, Iannace S, Netti PA and Nicolais L (1998b), 'Viscoelastic
behavior of composite ligament prostheses',
J Biomed Mater Res
,
42
, 1, 6-12.
Ambrosio L, Netti PA, Santaniello B and Nicolais L (2001), 'Composite materials as
scaffolds for tissue engineering',
Biomedical Polymers and Polymer therapeutics
,
Chiellini
et al
. (eds), Kluwer Academic/Plenum USA Part 1, 227-33.
Apicella A, Liguori A, Masi E and Nicolais L (1994),
Experimental techniques and design
in Composite Materials
, Found MS (ed.), Academic Press, Sheffield, 323-38.
Arends CB (1993),
Polymer toughening
,
Foundations of Materials Science and Engineering
.
Smith WF (ed.), 2nd edition, McGraw Hill, New York.
Arrington ED, Smith WJ, Chambers HG, Bucknell AL and Davino NA (1996), 'Complications
of iliac crest bone graft harvesting',
Clin Orthop Relat Res
,
329
, 300-9.
