8 research outputs found
A miniaturized bioreactor system for the evaluation of cell interaction with designed substrates in perfusion culture
In tissue engineering, the chemical and topographical cues within three-dimensional (3D) scaffolds
are normally tested using static cell cultures but applied directly to tissue cultures in perfusion
bioreactors. As human cells are very sensitive to the changes of culture environment, it is essential to
evaluate the performance of any chemical, and topographical cues in a perfused environment before
they are applied to tissue engineering. Thus the aim of this research was to bridge the gap between
static and perfusion cultures by addressing the effect of perfusion on cell cultures within 3D
scaffolds. For this we developed a scale down bioreactor system, which allows to evaluate the
effectiveness of various chemical and topographical cues incorporated into our previously developed
tubular ε-polycaprolactone scaffold under perfused conditions. Investigation of two exemplary cell
types (fibroblasts and cortical astrocytes) using the miniaturized bioreactor indicated that: (1) quick
and firm cell adhesion in 3D scaffold was critical for cell survival in perfusion culture compared
with static culture, thus cell seeding procedures for static cultures might not be applicable. Therefore
it was necessary to re-evaluate cell attachment on different surfaces under perfused conditions before
a 3D scaffold was applied for tissue cultures, (2) continuous medium perfusion adversely influenced
cell spread and survival, which could be balanced by intermittent perfusion, (3) micro-grooves still
maintained its influences on cell alignment under perfused conditions, while medium perfusion
demonstrated additional influence on fibroblast alignment but not on astrocyte alignment on grooved
substrates. This research demonstrated that the mini-bioreactor system is crucial for the development of functional scaffolds with suitable chemical and topographical cues by bridging the gap between
static culture and perfusion culture
Additional file 1: of Step-and-Repeat Nanoimprint-, Photo- and Laser Lithography from One Customised CNC Machine
Increased technical details and exemplary material. (DOCX 2.02Ă‚Â mb
The Development of a É›-Polycaprolactone Scaffold for Central Nervous System Repair
Potential treatment strategies for the repair of spinal cord injury (SCI)
currently favor a combinatorial approach incorporating several factors,
including exogenous cell transplantation and biocompatible scaffolds.
The use of scaffolds for bridging the gap at the injury site is very
appealing although there has been little investigation into the central
nervous system neural cell interaction and survival on such scaffolds
before implantation. Previously, we demonstrated that aligned
microgrooves 12.5-25 μm wide on ε-polycaprolactone (PCL) promoted
aligned neurite orientation and supported myelination. In this study, we
identify the appropriate substrate and its topographical features required
for the design of a three-dimensional scaffold intended for
transplantation in SCI. Using an established myelinating culture system
of dissociated spinal cord cells, recapitulating many of the features of
the intact spinal cord, we demonstrate that astrocytes plated on the
topography secrete soluble factors(s) that delay oligodendrocyte
differentiation, but do not prevent myelination. However, as myelination
does occur after a further 10-12 days in culture, this does not prevent
the use of PCL as a scaffold material as part of a combined strategy for
the repair of SCI
Label-Free Segmentation of Co-cultured Cells on a Nanotopographical Gradient
The function and fate of cells is influenced by many
different
factors, one of which is surface topography of the support culture
substrate. Systematic studies of nanotopography and cell response
have typically been limited to single cell types and a small set of
topographical variations. Here, we show a radical expansion of experimental
throughput using automated detection, measurement, and classification
of co-cultured cells on a nanopillar array where feature height changes
continuously from planar to 250 nm over 9 mm. Individual cells are
identified and characterized by more than 200 descriptors, which are
used to construct a set of rules for label-free segmentation into
individual cell types. Using this approach we can achieve label-free
segmentation with 84% confidence across large image data sets and
suggest optimized surface parameters for nanostructuring of implant
devices such as vascular stents
Controlling Metamaterial Transparency with Superchiral Fields
The
advent of metamaterials has heralded a period of unprecedented control
of light. The optical responses of metamaterials are determined by
the properties of constituent nanostructures. The current design philosophy
for tailoring metamaterial functionality is to use geometry to control
the nearfield coupling of the elements of the nanostructures. A drawback
of this geometry-focused strategy is that the functionality of a metamaterial
is predetermined and cannot be manipulated easily postfabrication.
Here we present a new design paradigm for metamaterials, in which
the coupling between chiral elements of a nanostructure is controlled
by the chiral asymmetries of the nearfield, which can be externally
manipulated. We call this mechanism dichroic coupling. This phenomenon
is used to control the electromagnetic induced transparency displayed
by a chiral metamaterial by tuning the chirality of the near fields.
This “non-geometric” paradigm for controlling optical
properties offers the opportunity to optimally design chiral metamaterials
for applications in the polarization state control and for ultrasensitive
analysis of biomaterials and soft matter
Induced Chirality through Electromagnetic Coupling between Chiral Molecular Layers and Plasmonic Nanostructures
We report a new approach for creating chiral plasmonic
nanomaterials.
A previously unconsidered, far-field mechanism is utilized which enables
chirality to be conveyed from a surrounding chiral molecular material
to a plasmonic resonance of an achiral metallic nanostructure. Our
observations break a currently held preconception that optical properties
of plasmonic particles can most effectively be manipulated by molecular
materials through near-field effects. We show that far-field electromagnetic
coupling between a localized plasmon of a nonchiral nanostructure
and a surrounding chiral molecular layer can induce plasmonic chirality
much more effectively (by a factor of 10<sup>3</sup>) than previously
reported near-field phenomena. We gain insight into the mechanism
by comparing our experimental results to a simple electromagnetic
model which incorporates a plasmonic object coupled with a chiral
molecular medium. Our work offers a new direction for the creation
of hybrid molecular plasmonic nanomaterials that display significant
chiroptical properties in the visible spectral region
Chiral Plasmonic Fields Probe Structural Order of Biointerfaces
The
structural order of biopolymers, such as proteins, at interfaces
defines the physical and chemical interactions of biological systems
with their surroundings and is hence a critical parameter in a range
of biological problems. Known spectroscopic methods for routine rapid
monitoring of structural order in biolayers are generally only applied
to model single-component systems that possess a spectral fingerprint
which is highly sensitive to orientation. This spectroscopic behavior
is not a generic property and may require the addition of a label.
Importantly, such techniques cannot readily be applied to real multicomponent
biolayers, have ill-defined or unknown compositions, and have complex
spectroscopic signatures with many overlapping bands. Here, we demonstrate
the sensitivity of plasmonic fields with enhanced chirality, a property
referred to as superchirality, to global orientational order within
both simple model and “real” complex protein layers.
The sensitivity to structural order is derived from the capability
of superchiral fields to detect the anisotropic nature of electric
dipole–magnetic dipole response of the layer; this is validated
by numerical simulations. As a model study, the evolution of orientational
order with increasing surface density in layers of the antibody immunoglobulin
G was monitored. As an exemplar of greater complexity, superchiral
fields are demonstrated, without knowledge of exact composition, to
be able to monitor how qualitative changes in composition alter the
structural order of protein layers formed from blood serum, thereby
establishing the efficacy of the phenomenon as a tool for studying
complex biological interfaces
Superchiral Plasmonic Phase Sensitivity for Fingerprinting of Protein Interface Structure
The
structure adopted by biomaterials, such as proteins, at interfaces
is a crucial parameter in a range of important biological problems.
It is a critical property in defining the functionality of cell/bacterial
membranes and biofilms (<i>i.e.</i>, in antibiotic-resistant
infections) and the exploitation of immobilized enzymes in biocatalysis.
The intrinsically small quantities of materials at interfaces precludes
the application of conventional spectroscopic phenomena routinely
used for (bio)Âstructural analysis due to a lack of sensitivity. We
show that the interaction of proteins with superchiral fields induces
asymmetric changes in retardation phase effects of excited bright
and dark modes of a chiral plasmonic nanostructure. Phase retardations
are obtained by a simple procedure, which involves fitting the line
shape of resonances in the reflectance spectra. These interference
effects provide fingerprints that are an incisive probe of the structure
of interfacial biomolecules. Using these fingerprints, layers composed
of structurally related proteins with differing geometries can be
discriminated. Thus, we demonstrate a powerful tool for the bioanalytical
toolbox