Page 299 - Advances in Textile Biotechnology

280 Advances in textile biotechnology

Table 11.1 Examples of molecular probes and their targets of importance in
biological applications

Probe Target
Small molecule (e.g. biotin*) Protein (e.g. streptavidin*)
Carbohydrate Protein
Protein (e.g. RGD peptides*) Protein (e.g. cell surface integrins*)
Enzyme (e.g. alkaline phosphatase*) Substrate (e.g. indolyl phosphates)
Substrate Enzyme
Oligonucleotide (DNA or RNA) Oligonucleotide (DNA or RNA)
Chelator Inorganics

* See text.

approach is conceptually identical to the surface activation described above,
although here activation allows for the elaboration of complex polyvalent
molecular architectures.

In a first demonstration of the potential of XG-immobilized polymeriza-
tion initiators, we successfully attached an atom-transfer radical polymer-
ization (ATRP) initiator, the 2-bromopropionyl group, onto cellulose via
the XG conjugate XG–INI ATRP . Subsequently, methylmethacrylate and

styrene were independently polymerized from filter paper sheets to create
highly hydrophobic surfaces (Zhou et al., 2005). A particular advantage of
controlled polymerization techniques, such as ATRP, is that polymer chains
grow at the same rate, which results in low polydispersity and well-defi ned
molecular properties (Matyjaszewski and Xia, 2001). Furthermore, the
‘living’ nature of ATRP facilitates the production of complex polymer block
structures (Carlmark and Malmström, 2003), whereas the combination of
graft polymerization with subsequent chemical modification opens a mul-

titude of possibilities to further tailor cellulosic material properties (Golas
and Matyjaszewski, 2007; Nyström et al., 2006).
Attachment of the ring-opening polymerization (ROP) initiator
2,2-bis(methylol)propionic acid (bis-MPA) onto cellulose via the XG–
INI ROP conjugate has been used to extend the grafting-from-XG concept to
so-called biodegradable polymers. Both poly(ε-caprolactone) (PCL) and
poly(l-lactic acid) (PLLA) polyesters have been successfully grafted from
XG–INI ROP -modifi ed fi lter paper to yield hydrophobic surfaces (Lönnberg
et al., 2006). Notably, initiation from XG–INI ROP produced papers that con-
tained less polymer and were slightly less hydrophobic, for all polymers and
graft lengths studied, than those resulting from direct esterification of the

initiator onto cellulose. However, whereas the esterified and grafted cellu-
lose paper surfaces were completely resistant to cellulase enzyme attack,
papers onto which PCL and PLLA were grafted from XG–INI ROP could be

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