Biomedical Engineering Reference
In-Depth Information
attached to a conducting polymer chain. We synthesized a number of different copolymers
for phycobiliprotein surface immobilization using the biotin-streptavidin interaction
(3,15). In the case of immobilization onto an LB polymer film, the film was first formed by
compressing an amphiphilic polymer, B-PUMT, synthesized as presented in Figure 1.1b
by the copolymerization of 3-undecylthiophene with 3-thiophenemethanol followed by
biotin derivatization. As shown in Figure 1.6, during its compression to a monolayer, the
B-PUMT copolymer exhibited a series of different complex micron-scale phase patterns in
the presence of different proteins at varying LB trough pressures and incubation times
(16). Upon injection of Str-PE or various protein controls into the subphase, then picking
up the film onto a glass substrate for optical measurement, phycoerythrin immobilization
was demonstrated to depend upon the presence of both the biotin derivatization of the
copolymer and the streptavidin derivatization of the phycoerythrin, as was the case in
the biotinylated B-DPPE LB monolayer film discussed previously.
Using the same copolymer, B-PUMT, we demonstrated that the Str-PE immobilization
could be carried out on the surface of optical fibers by a self-assembly technique much sim-
pler than the LB film experiment described above (17). As described in Figure 1.7, the fibers
were first declad to expose the optical surface, which was then silanized with chlorodi-
methyloctadecylsilane. Then, the B-PUMT was bound to the optical fiber surface through
hydrophobic interactions between its pendant undecyl chains and the octadecyl chains of
the silanizing agent. Biotin ligands on the copolymer, pendant in aqueous
solution, bound added streptavidin in the Str-PE complexes. The native fluorescence
22
µ
m
(a)
(b)
(c)
(d)
FIGURE 1.6
Fluorescence microscopic images of LB-monolayer films obtained in situ on the LB trough surface during film
assembly from: (a) the thiophene polymer B-PUMT (see Figure 1.1) expanded monolayer (
2 mN/m); (b) B-
PUMT compressed monolayer (15 mN/m); (c) expanded B-PUMT monolayer within 2 h after subphase injection
of Str-PE; (d) expanded B-PUMT monolayer 24 hr after subphase injection of Str-PE. Reprinted from Samuelson,
L.A., Kaplan, D.L., Lim, J.O., Kamath, M., Marx, K.A., Tripathy, S.K. (1994). Molecular Recognition Between a
Biotinylated Polythiophene Copolymer and Phycoerythrin Utilizing the Biotin-Streptavidin Interaction.
Thin
Solid Films
242:50-55. With permission from Elsevier Publishing.
