Abstract
Aerogels prepared from aqueous dispersions of anionic and
cationic cellulose nanofibrils (CNFs) were investigated
as solid supports for enzymes and silver nanoparticles
and to elicit a sustained antibacterial effect. The
imparted stabilization in dry conditions was studied with
aerogels that were cast after mixing the enzymes with
CNFs followed by dehydration (freeze-drying). The
activity of lysozyme immobilized in the given CNF system
was analyzed upon storage in liquid and air media. In
contrast with aqueous solutions of free, unbound enzyme,
which lost activity after the first day, the enzyme
immobilized physically in unmodified and cationic CNF
presented better stability (activity for a longer time).
However, the enzyme activity was reduced in the case of
anionic CNF, which was prepared by TEMPO-mediated
oxidation (TO-CNF). Both humidity and temperature reduced
the stability of the enzyme immobilized in the respective
CNF aerogel. The antibacterial activity of CNF aerogels
carrying lysozyme was also tested against gram-negative
and gram-positive bacteria. The results were compared
with those obtained from CNF systems loaded with silver
nanoparticles (AgNP) after in situ synthesis via UV
reduction. Storage in cold or dry conditions preserved
the activity and antibacterial performance of
enzyme-loaded CNF aerogels. As expected, the
lysozyme-containing aerogels showed lower inhibition than
the AgNP-containing aerogel. In this latter case, the
antibacterial activity depended on the concentration and
size of the nanoparticles. Compared to unmodified CNF and
TO-CNF, the aerogels prepared with cationic CNF, loaded
with either lysozyme or AgNPs, showed remarkably better
antibacterial activity. Similar experiments were
conducted with horseradish peroxidase, which confirmed,
to different degrees, the observations derived from the
lysozyme systems. Overall, the results indicate that
non-toxic and biodegradable CNF is a suitable support for
bio-active materials and is effective in protecting and
retaining enzymatic and antibacterial activities.
Original language | English |
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Pages (from-to) | 2837-2848 |
Journal | Cellulose |
Volume | 24 |
Issue number | 7 |
DOIs | |
Publication status | Published - 1 Jul 2017 |
MoE publication type | A1 Journal article-refereed |
Keywords
- antibacterial aerogel
- cellulose nanofibrils (CNF)
- enzyme stability
- lysozyme
- silver nanoparticles