Biology Reference
In-Depth Information
The American Society of Testing Materials (ASTM F04 division IV) is
making efforts to establish standard guidelines for tissue engineered medical
products (
ASTM, 2001
). The F2103 guide covers the evaluation of chitosan
salts suitable for use in medical applications. Moreover,
chitosan hydrochloride
(a derivative of chitosan) has been included in the European Pharmacopeia
in 2002 (
Pharmacopeia, 2002
).
In order to be approved as a biomedical material, sterility is an important
issue to resolve. Chitosan products intended for parenteral administration
and those in contact with serous fluids, for example, wounds, have to be ster-
ilized before use. Common methods for the sterilization include exposure to
dry heat, saturated steam, ethylene oxide, or
g
radiation. Before using any of
these methods for chitosan product sterilization, their effects on polymer
properties and end performance have to be tested, as they can cause irrevers-
ible damage to the morphological, physical, mechanical, and biological
characteristics. Dry heat sterilization method resulted in lower aqueous
solubility for chitosan and in insolubility in acidic aqueous media (
Lim,
Khor, & Ling, 1999
). Saturated steam and
g
irradiation caused an accelera-
tion in the rate and extent of chitosan chain scission events, respectively.
The use of 70% ethanol, as a sterilizing agent, is a suitable method as it
did not alter chitosan-membrane characteristic; however, it is limited to
small-scale applications. Ethylene oxide is a simple technique to be used
for sterilization of industrially produced chitosan membrane, preserving
chitosan-membrane morphology, percentage of strain at break, and
in vitro
cytotoxicity to Vero cells. Moreover, this method can be used for
industrial sterilization of chitosan membrane (
Marreco, da Luz Moreira,
Genari, & Moraes, 2004
). The long-term storage may have effects and
implications on the integrity of chitin and chitosan materials (
Kam,
Khor, & Lim, 1999
), and further investigation is needed to optimize steril-
ization and storage method conditions.
It has been shown that chitosan is capable of forming large phospholipid
aggregates by inducing the fusion of small dipalmitoyl phosphatidylcholine
bilayers, which are a major component of the plasma membrane (
Pavinatto
et al., 2007; Zuo et al., 2006
). Thus, the use of chitosan as a “fusogen” might
be more advantageous as a potential clinical tool relative to nonionic poly-
mers (e.g., PEG or P188).
Due to its highbiodegradability and biocompatibility, togetherwith its spe-
cific interactions with components of the extracellular matrix (ECM) and
growth factors, chitosan employment is growing in a variety of applications,
including implantable and injectable orthopedic and periodontal systems, drug
