Biomedical Engineering Reference
In-Depth Information
via atomic transfer radical polymerization from mica preinitiated with an
adsorbed random copolymer, and (c) a LB monolayer of the phospholipid
1,2-dipalmitoylphosphatidylcholine (DPPC). The different film properties and
morphologies gave distinct optical patterns in the measurements and analy-
ses. By fitting the obtained reflectivity curves with the standard Parratt algo-
rithm (Parratt 1954) they were able to extract the structural information of
the nanofilms on thickness and apparent roughness.
For biofuel cells and biosensors, bioelectrodes require more complex designs
than what LB films can offer. The seminal work by Decher and his coworkers
(Lvov et al. 1993; Schmitt et al. 1993; Decher 1997) opened a new possi-
bility of multilayer architecture and LBL fabrication for bioelectrodes. They
show that multilayer structures can be tailored with careful control of poly-
meric or macromolecular assemblies in the architecture to fabricate bioelec-
trodes with unique properties. This approach has been widely adopted by
many (e.g., Sun et al. 1999) to fabricate bioelectrodes for various applications.
XRR, sometimes in combination with neutron reflectometry (NR), have been
demonstrated to be quite useful in understanding the internal structure in the
LBL adsorbed polyelectrolyte films (Schmitt et al. 1993; Lvov et al. 1993).
Hollmann et al. used XRR in combination with NR and total internal reflec-
tion fluorescence (TIRF) to study the structure and protein bovine serum
albumin (BSA) binding capacity on a planar polyacrylic acid (PAA) brush
(Hollmann et al. 2007), which is an example illustrating a delicate control and
optimization of protein immobilization for biological functions.
Another interesting approach is the design and synthesis of inorganic poly-
mer hybrid materials and structures, most in thin films, that posses periodi-
cally organized nanoporosity in this class of so-called “periodically organized
mesoporous materials and thin films” (POMMs and POMTFs). Sanchez and
his coworkers recently presented an excellent review (Sanchez et al. 2008) on
this class of materials and characterization techniques used to understand
their formations and resulting properties. The tuning of the interface between
the inorganic template and the polymerizing phase and the control over chem-
ical and processing conditions are the key to producing tailor-made POMTFs
with a high degree of reproducibility. XRR has been used with other mod-
ern analytical tools, including two-dimensional grazing incidence small-angle
x-ray scattering (GISAXS), ellipsoporosimetry, high-resolution transmission
electron microscopy (HRTEM), WAXS, time-resolved infrared spectroscopy,
SAW, and optically polarized xenon NMR; to provide temporal and spatial
resolutions to help researchers understand the film formation processes and
the mesostructural properties. This class of materials utilizes the intrinsic
physical and chemical properties of the inorganic or hybrid matrices in com-
bination with a highly defined nanoporous network of a tunable pore size and
connectivity, high surface area and accessibility, and a specific orientation with
respect to the substrate. Therefore, POMMs and POMTFs are a promising
class of advanced materials for a variety of future applications as biomaterials,
bioelectrodes, and for biomicrofluidics, among others.
Search WWH ::
Custom Search