Biomedical Engineering Reference
In-Depth Information
The highest resolutions can be realized via SLA (70-250 lm). However, SLA
requires appropriate liquid photopolymers that are still limited in availability,
whereas 3D printing is a rather fast process but characterized by weak bonding
between powder particles [ 122 ].
Surface patterning of novel polyesters to be used in bone tissue engineering is
realized via the 3D printing process [ 123 ]. Novel biocompatible polyacrylate-
based photopolymers have been synthesized for scaffold fabrication via stereoli-
thography [ 148 ]. Whitesides and co-workers first described the patterning of
proteins and cells using so-called soft lithography [ 149 , 150 ]. Patterning via
electrospinning was used to study the role of nanostructured mesoporous silicon in
discriminating invitro calcification for electrospun scaffold composites [ 118 ].
Electrospun scaffold composites consisting of PCL/gelatine nanofiber have been
produced and micropatterned by femtosecond laser ablation for tissue engineering
applications [ 116 ].
The geometry and size of ECM structures do have significant effects on various
cell properties including attachment/adhesion, migration, and proliferation.
Differences in the height of nanotopographic features influence cell behavior through
secondary effects, such as alterations in the effective substrate stiffness [ 151 ].
Gerecht and co-workers could demonstrate that nanotopographic-structured
ECM alters the morphology and proliferation of human ESCs through cytoskel-
etal-mediated mechanisms. Poly(dimethylsiloxane) gratings with 600-nm features
and spacing have been designed that are able to induce ESC alignment and
elongation [ 152 ]. In addition, they could also show that nanotopographic features
altered the organization of various cytoskeletal components such as F-actin,
vimentin, c-tubulin, and a-tubulin. Changes in proliferation and morphology were
abolished by the effect of actin-disrupting agents. Furthermore, the influence of
nanotopographic features may be mediated through secondary effects such as
alterations in the effective stiffness perceived by the cell or differences in protein
adsorption caused by ECM nanotopographics.
Surface patterning via self-assembled composites. In addition to functionali-
zation via chemical reactions, solid substrates (scaffolds) can be covered by
ultrathin films, single monolayers or multilayers using different methods: (a) self-
assembling methods, (b) the co-called layer-by-layer (LbL) method, or (c) the
Langmuir-Blodgett (LB) technique. Both surface chemistry and topography can
be varied in a very controlled manner via film-coating [ 153 , 154 ]. Whitesides and
colleagues have reviewed the application of so-called soft lithography in biology
and biochemistry using self-assembling processes [ 150 ].
Chen and co-workers studied a hybrid system consisting of a self-assembled
composite matrix in a hierarchical 3D scaffold to be used for bone tissue engi-
neering. The effects of the PCL-based hybrid scaffold on hMSC seeding efficiency,
proliferation, distribution, and differentiation were investigated. Porous PCL
meshes prepared by FDM were embedded in a matrix of hyaluronic acid, methylated
collagen, and terpolymer via polyelectrolyte complex coacervation. Studies showed
clearly that embedded scaffolds provided a higher cell seeding efficiency, a more
homogeneous cell distribution, and more osteogenically differentiated cells, verified
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