Biomedical Engineering Reference
In-Depth Information
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FIGURE 8.2 Schematic diagrams illustrating the fabrication process of surface-modifi ed neural micro-
electrodes with nanotubular PEDOT: (a) electrospinning of biodegradable polymer (PLGA) fi bers with well-
defi ned surface texture (1) onto the probe tip, (b) electrochemical polymerization of conducting polymers
(PEDOT) (2) around the electrospun PLGA fi bers, and (c) dissolving the electrospun core PLGA fi bers to
create nanotubular conducting polymers (3). Optical micrograph of (e) the gold electrode site, (f) the electrode
site after electrospinning showing the coverage of the PLGA electrospun nanoscale fi bers, (g) the electrode
after electrochemical deposition of conducting PEDOT on the gold site and around the electrospun fi bers, and
(h) the electrode after removal of the core PLGA fi ber templates. (Reprinted from Abidian, M.R., Kim, D.H.,
and Martin, D.C., Adv. Mater. , 18, 405, 2006.)
nanomaterials can be tailored toward more sophisticated systems for effi cient control of drug deliv-
ery. Silicon-based porous nanomaterials include silicon nanowires, porous silica, 46,47 biomimetic
siliceous nanocapsules, 48,49 and porous silicon. 50
8.2.2.1
Mobil Composition of Matter-41 Porous Silica
After the discovery of M41S family at Mobil Corp. in 1992, 51 extensive research interest has been
directed at these fi rst synthesized well-ordered mesoporous solids, especially the Mobil Composi-
tion of Matter-41 (MCM-41), showing hexagonal arrays of cylindrical mesopores, is prepared by the
self-assembly of silica. Surfactant micelles are used as the structuring agent in this process. 52-58 Pos-
itively charged surfactants function as templates forming an ordered organic-inorganic composite
with the negatively charged silicate species based on the electrostatic interactions. Through cal-
cinations, the surfactant is removed and the porous silicate network is left (Figure 8.5). 59 These
materials exhibit well-defi ned, ordered porosity with a large specifi c surface area (up to 1000 m 2 /g),
a large mesoporous volume, and thermal stability. The pore sizes can be controlled during the syn-
thesis and typically range from 15 to 100 Å (Figure 8.6).
In addition to their potential catalytic application, MCM-41 mesoporous materials are used in
the drug delivery systems. 60 The silanol-terminated pore walls can be functionalized using conve-
nient chemistry to provide specifi city for drug absorption and release schemes. 47,61 Different drug
release profi les were obtained depending on the pore size and the interaction between the host
matrix and the guest drug molecules. A more complicated gated drug delivery system based on the
 
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