Elaboration on “Tailor-made functional surfaces based on cellulose-derived
materials” a paper by Chao Wang, Richard A. Venditti, Kai Zhang - Appl Microbiol
Biotechnol (2015) 99:5791–5799
Cellulose:
Cellulose is a polysaccharide that consists of β (1-4) linked D-glucose units. It is one of the most
abundant materials on earth and is mainly used for the production of paper and cardboard. It has
several characteristics that make it a suitable candidate for the development of functional surfaces: It
is biocompatible and sustainable and its many hydroxyl groups can be functionalized.
Cellulose can be used to fabricate materials of diverse size scales. It can form micro sized cellulose
fibers, chrystalline nano- cellulose and also polymers on a molecular level. These different cellulose
based materials can then be used to prepare different types of functional surfaces, including
bioactive and non-adhesive surfaces.
General Methodology:
There are two general methods of processing cellulose: The post modification of existing cellulose
surfaces and the manufacturing of surfaces with functionalized cellulose derivatives. These surfaces
can be modified with bioactive molecules (enzymes, nucleic acids and antibodies), polymers and
nanoparticles (Figure 1).
Figure 1: Cellulose of different size scales (left panel) is used to create modified surfaces (middle panel) which are then
used to immobilize bioactive molecules or to create functional surfaces (right panel).
The surface modification methods can be categorized into three groups: Physical adsorption,
covalent interaction and biochemical coupling.
Modification by physical adsorption is often weak and reversible; however the adsorption of
carboxymethyl cellulose (CMC) is specific and irreversible. Therefore CMC is often used as an
anchoring layer on cellulose surfaces.
Covalent interaction modifications are can be done via the graft onto or the graft from
method. With the graft onto method, bioactive molecules are coupled to functional groups on
cellulose surfaces by azide-alkyne cycloaddition or thiol-ene coupling. The graft from approach uses
initiators that are immobilized on the cellulose surface and facilitate surface initiated polymerization
of monomers. Examples for this technique include atom transfer radical polymerization and ring
opening polymerization.
Biochemical coupling methods include the immobilization of molecules or nanoparticles onto
cellulose surfaces. This is achieved with the use of carbohydrate binding module containing
bifunctional fusion proteins, ligand receptor pairing (avidin-biotin interaction) or enzyme-mediated
ligation.
Specific functional surfaces:
Cellulose can be used as a basis or a variety of functional surfaces. The following section will give an
overview over the most promising ones.
Bioactive surfaces: Cellulose is a great support material for bioactive molecule immobilization as it is
renewable, biocompatible, has low cytotoxicity and is bioinert. Bioactive surfaces can be created by
several methods:
As described before CMC is a good linker molecule and it can be used for the covalent
conjugation of bioactive molecules onto cellulose surfaces. After CMC is added to cellulose, avidins
can be adsorbed or conjugated onto the carboxyl groups and biotinylated functionalities can be
coupled onto the avidins.
Functionalized nanofibrilated cellulose (NFC) is used to conjugate proteins onto the NFC. The
functionalization can be achieved with carboxylic acid, amines or epoxy groups. Functionalizations
with carboxylic acid or amines require multiple steps reactions, while the functionalization with
epoxy groups requires only a single step. The downside of epoxy group functionalization is that it has
the lowest efficiency.
Polyamidoamine (PAMAM) is a dendrimer with a branched structure that carries multifunctional surface amine groups. These amine groups can be used to attach bioactive molecules to
the cellulose surface with PAMAM acting as a linker molecule.
The sortase A-mediated approach utilizes the transpeptidase sortase A to ligate proteins with
genetically introduces recognition sequences onto functionalized cellulose surfaces. Sortase A
catalyzes the cleavage between threonine and glycine at the LPXTG motif. This creates an acylenzyme intermediate which is then transferred to the N-terminus of an oligoglycine motif. The
advantages of this approach are its high efficiency and selectivity; that it can be done at physiological
pH and temperature and the conjugation is site directed and regiospecific.
Non-adhesive surfaces:
Non adhesive surfaces have practical applications in water treatment and medical devices that come
into contact with blood. Therefore anti-fouling and antimicrobial surfaces have gained increasing
attention recently. Anti-fouling and anti-microbial properties can be introduces into cellulose
surfaces via the following methods: Zwitterionic macromolecules can be adsorbed onto cellulose to
reduce the adsorption of proteins. This is applied in blood purification and ultrafiltration.
Furthermore antibiotics, cell lytic enzymes and metal nanoparticles can be immobilized or blended
on or into the cellulose based materials. These could be used in antimicrobial wound dressings and in
food packaging
Summary & Conclusion:
Cellulose is a sustainable, biocompatible and bioinert resource that can be modified to suit different
size scales. There are many methods of creating bioactive and non-adhesive surfaces and many
possibilities of modification and application. Challenges include the precise introduction of
functionalities while maintaining the cellulose backbone and morphology. Further research will be
needed to compare and evaluate the existing methods and to develop new ones.
Sources:
•
Tailor-made functional surfaces based on cellulose-derived materials. Chao Wang & Richard
A. Venditti & Kai Zhang. Appl Microbiol Biotechnol (2015) 99:5791–5799 DOI
10.1007/s00253-015-6722-y
•
Rana D, Matsuura T (2010) Surface modifications for antifouling membranes. Chem Rev
110:2448–2471. doi:10.1021/cr800208y
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Koseoglu-Imer DY, Dizge N, Koyuncu I (2012) Enzymatic activation of cellulose acetate
membrane for reducing of protein fouling. Colloids Surf B 92:334–339.
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