Civil Engineering Reference
In-Depth Information
Gelatin/BC nanocomposites have also been extensively investigated in the last
couple of years. Enzymatically modii ed gelatin was tested on the preparation of BC
nanocomposites with enhanced rehydration ability [134]. BC/gelatin nanocompos-
ites were obtained by immersion in a modii ed gelatin solution at 50ºC for 1 week. In
these conditions, gelatin entered the BC network and enveloped cellulose ribbons. h e
polar groups of gelatin (and its hydrolysates) represent the main factors contributing
to the increased rehydration aptitude. Gao
et al.
described the immobilization of gela-
tin onto BC nanoi bers via partial oxidation of BC with periodate to yield 2,3-dialde-
hyde BC, with an aldehyde content of around 60%, followed by reaction with gelatin
[135] or via crosslinking with procyanidin [136]. h e attachment and growth kinetics
and morphology of mice i broblast cells on these BC/gelatin nanocomposites demon-
strated their potentialities as scaf olds for tissue engineering. In a dif erent study, Chang
et al.
[137] investigated the assembly of alkaline-treated BC/gelatin nanocomposites
crosslinked with transglutaminase, genipin or 1-ethyl-3-(3-dimethylaminopropyl)car-
bodiimide (EDC) aiming to improve the mechanical strength and hydrophilic prop-
erties of BC nanocomposites. Crosslinking with carbodiimide promoted the most
ef ective improvements in the mechanical and hydrophilic properties of the nanocom-
posites probably because carbodiimide may form intramolecular crosslinking with gel-
atin polymeric chains or short-range intermolecular crosslinking between two adjacent
gelatin chains, facilitating integration of gelatin and BC and constructing a BC/gelatin
double network. BC/gelatin nanocomposites were also prepared by supplementing the
BC production culture medium with gelatin (1-10% w/v) [138]. h e nanocomposite
i lms showed dense and homogeneous morphologies and improved optical transpar-
ency and water absorption capacity. However, a signii cant drop of the mechanical
properties was observed for more than 3% of gelatin supplementation.
Choi
et al.
[139] fabricated BC/silk i broin nanocomposite plates with strength
(12.8-187.7 GPa) similar to that of human cortical bone, via an impregnation process.
h e BC nanoi bers acted as excellent reinforcement for the stress-transfer produced by
the interactions between the BC nanoi bers and the silk i broin matrix, as coni rmed by
Raman spectroscopy.
In a very creative fashion, Hu and Catchmark [140] developed bioabsorbable
cellulose nanocomposites by integration of cellulases into BC membranes (Figure 2.17).
Considering the harmless ef ect of the main product of the enzymatic degradation of
cellulose, glucose, these composites may be perfect for specii c wound care and tissue
engineering applications where the bioabsorbable character is crucial.
In a completely dif erent vein, Zhu
et al.
[141] evaluated the feasibility of BC/poly-
lysine nanocomposites, prepared by immersion of BC tubes in a polylysine solution, as
potential bacteriostatic food casings.
A novel biopolymeric nanocomposite i lm of BC and
Aloe vera
gel was developed by
means of adding
A. vera
gel in the culture medium in the course of biosynthesis in static
conditions [142]. With a 30% v/v
A. vera
gel supplementation, a nanocomposite i lm
with signii cantly improved mechanical strength, crystallinity, water absorption capac-
ity and water vapor permeability, in comparison with neat BC, was achieved. Taken
into account this properties and the intrinsic biocompatibility of both BC and
A. vera
gel, a wide range biomedical applications could be perceived for this material.
