11 research outputs found
Molecular Beacon Modified Sensor Chips for Oligonucleotide Detection with Optical Readout
Three different surface bound molecular
beacons (MBs) were investigated
using surface plasmon fluorescence spectroscopy (SPFS) as an optical
readout technique. While MB1 and MB2, both consisting of 36 bases,
differed only in the length of the linker for surface attachment,
the significantly longer MB3, consisting of 56 bases, comprised an
entirely different sequence. For sensor chip preparation, the MBs
were chemisorbed on gold via thiol anchors together with different
thiol spacers. The influence of important parameters, such as the
length of the MBs, the length of the linker between the MBs and the
gold surface, the length and nature of the thiol spacers, and the
ratio between the MBs and the thiol spacers was studied. After hybridization
with the target, the fluorophore of the longer MB3 was oriented close
to the surface, and the shorter MBs were standing more or less upright,
leading to a larger increase in fluorescence intensity. Fluorescence
microscopy revealed a homogeneous distribution of the MBs on the surface.
The sensor chips could be used for simple and fast detection of target
molecules with a limit of detection in the larger picomolar range.
The response time was between 5 and 20 min. Furthermore, it was possible
to distinguish between fully complementary and singly mismatched targets.
While rinsing with buffer solution after hybridization with target
did not result in any signal decrease, complete dehybridization could
be carried out by intense rinsing with pure water. The MB modified
sensor chips could be prepared in a repeatable manner and reused many
times without significant decrease in performance
The Effect of Size and Geometry of Poly(acrylamide) Brush-Based Micropatterns on the Behavior of Cells
In
this study, the fabrication, detailed characterization, and application
of long-term stable micropatterned bio-interfaces of passivating polyÂ(acrylamide)
(PAAm) brushes on transparent gold for application in the study of
cell-surface interactions is reported. The micropatterns were fabricated
by microcontact printing of an initiator for surface-initiated atom
transfer radical polymerization (SI-ATRP), SI-ATRP of acrylamide,
and subsequently backfilling of the unfunctionalized areas of 400–2500
μm<sup>2</sup> size and systematically altered number of corners
with octadecanethiol. As verified by surface plasmon resonance spectroscopy,
the physisorption of fibronectin (FN) was restricted to the adhesive
areas. Exploiting this platform, the effect of micropattern geometry
and size of cell-adhesive FN areas surrounded by passivating PAAm
brushes on transparent gold substrates on the attachment of cells
and cytoskeleton alignment was investigated at the single-cell level.
Exceptional long-term stability of the patterned PAAm brushes and
arrays of adhesive areas, in which human pancreatic tumor cells (Patu
8988T) and fibroblast cells (NIH 3T3) were confined for more than
one week, was observed. Adhesive areas of 1600 μm<sup>2</sup> or less constrained the cell shape and caused focal adhesions to
accumulate in the corners of the pattern. These changes were most
obvious for the PatuT cells in adhesive areas of ∼900 μm<sup>2</sup>, in which the actin filaments were aligned, following the
boundary of the pattern, and merged in the focal adhesions concentrated
in the corners of the pattern. NIH 3T3 cells possessed a larger cell
area, which led to an optimal cytoskeleton alignment in adhesive patterns
of ∼1600 μm<sup>2</sup>. The alignment of the cytoskeleton
was found to be less pronounced in cells on larger adhesive areas,
where the PatuT cells spread similarly to cells on unpatterned substrates.
By contrast, the NIH 3T3 cells were found to stretch even on larger
adhesive areas, spanning from one corner to the other. The long-term
stability under cell culture conditions of the patterns introduced
here will also be useful for long-term studies of single and multiple
cells, cell motility in toxicity assays, and stem cell differentiation
The Effect of Size and Geometry of Poly(acrylamide) Brush-Based Micropatterns on the Behavior of Cells
In
this study, the fabrication, detailed characterization, and application
of long-term stable micropatterned bio-interfaces of passivating polyÂ(acrylamide)
(PAAm) brushes on transparent gold for application in the study of
cell-surface interactions is reported. The micropatterns were fabricated
by microcontact printing of an initiator for surface-initiated atom
transfer radical polymerization (SI-ATRP), SI-ATRP of acrylamide,
and subsequently backfilling of the unfunctionalized areas of 400–2500
μm<sup>2</sup> size and systematically altered number of corners
with octadecanethiol. As verified by surface plasmon resonance spectroscopy,
the physisorption of fibronectin (FN) was restricted to the adhesive
areas. Exploiting this platform, the effect of micropattern geometry
and size of cell-adhesive FN areas surrounded by passivating PAAm
brushes on transparent gold substrates on the attachment of cells
and cytoskeleton alignment was investigated at the single-cell level.
Exceptional long-term stability of the patterned PAAm brushes and
arrays of adhesive areas, in which human pancreatic tumor cells (Patu
8988T) and fibroblast cells (NIH 3T3) were confined for more than
one week, was observed. Adhesive areas of 1600 μm<sup>2</sup> or less constrained the cell shape and caused focal adhesions to
accumulate in the corners of the pattern. These changes were most
obvious for the PatuT cells in adhesive areas of ∼900 μm<sup>2</sup>, in which the actin filaments were aligned, following the
boundary of the pattern, and merged in the focal adhesions concentrated
in the corners of the pattern. NIH 3T3 cells possessed a larger cell
area, which led to an optimal cytoskeleton alignment in adhesive patterns
of ∼1600 μm<sup>2</sup>. The alignment of the cytoskeleton
was found to be less pronounced in cells on larger adhesive areas,
where the PatuT cells spread similarly to cells on unpatterned substrates.
By contrast, the NIH 3T3 cells were found to stretch even on larger
adhesive areas, spanning from one corner to the other. The long-term
stability under cell culture conditions of the patterns introduced
here will also be useful for long-term studies of single and multiple
cells, cell motility in toxicity assays, and stem cell differentiation
Surface Nanobubbles Studied by Time-Resolved Fluorescence Microscopy Methods Combined with AFM: The Impact of Surface Treatment on Nanobubble Nucleation
The impact of surface treatment and
modification on surface nanobubble
nucleation in water has been addressed by a new combination of fluorescence
lifetime imaging microscopy (FLIM) and atomic force microscopy (AFM).
In this study, rhodamine 6G (Rh6G)-labeled surface nanobubbles nucleated
by the ethanol–water exchange were studied on differently cleaned
borosilicate glass, silanized glass as well as self-assembled monolayers
on transparent gold by combined AFM-FLIM. While the AFM data confirmed
earlier reports on surface nanobubble nucleation, size, and apparent
contact angles in dependence of the underlying substrate, the colocalization
of these elevated features with highly fluorescent features observed
in confocal intensity images added new information. By analyzing the
characteristic contributions to the excited state lifetime of Rh6G
in decay curves obtained from time-correlated single photon counting
(TCSPC) experiments, the characteristic short-lived (<600 ps) component
of could be associated with an emission at the gas–water interface.
Its colocalization with nanobubble-like features in the AFM height
images provides evidence for the observation of gas-filled surface
nanobubbles. While piranha-cleaned glass supported nanobubbles, milder
UV-ozone or oxygen plasma treatment afforded glass–water interfaces,
where no nanobubbles were observed by combined AFM-FLIM. Finally,
the number density of nanobubbles scaled inversely with increasing
surface hydrophobicity
Detailed Study of BSA Adsorption on Micro- and Nanocrystalline Diamond/β-SiC Composite Gradient Films by Time-Resolved Fluorescence Microscopy
The adsorption of
bovine serum albumin (BSA) on micro- and nanocrystalline
diamond/β-SiC composite films synthesized using the hot filament
chemical vapor deposition (HFCVD) technique has been investigated
by confocal fluorescence lifetime imaging microscopy. BSA labeled
with fluorescein isothiocyanate (FITC) was employed as a probe. The
BSA<sup>FITC</sup> conjugate was found to preferentially adsorb on
both O-/OH-terminated microcrystalline and nanocrystalline diamond
compared to the OH-terminated β-SiC, resulting in an increasing
amount of BSA adsorbed to the gradient surfaces with an increasing
diamond/β-SiC ratio. The different strength of adsorption (>30
times for diamond with a grain size of 570 nm) coincides with different
surface energy parameters and differing conformational changes upon
adsorption. Fluorescence data of the adsorbed BSA<sup>FITC</sup> on
the gradient film with different diamond coverage show a four-exponential
decay with decay times of 3.71, 2.54, 0.66, and 0.13 ns for a grain
size of 570 nm. The different decay times are attributed to the fluorescence
of thiourea fluorescein residuals of linked FITC distributed in BSA
with different dye–dye and dye–surface distances. The
longest decay time was found to correlate linearly with the diamond
grain size. The fluorescence of BSA<sup>FITC</sup> undergoes external
dynamic fluorescence quenching on the diamond surface by H- and/or
sp<sup>2</sup>-defects and/or by amorphous carbon or graphite phases.
An acceleration of the internal fluorescence concentration quenching
in BSA<sup>FITC</sup> because of structural changes of albumin due
to adsorption, is concluded to be a secondary contributor. These results
suggest that the micro- and nanocrystalline diamond/β-SiC composite
gradient films can be utilized to spatially control protein adsorption
and diamond crystallite size, which facilitates systematic studies
at these interesting (bio)Âinterfaces
Microfluidic-Based Cell-Embedded Microgels Using Nonfluorinated Oil as a Model for the Gastrointestinal Niche
Microfluidic-based
cell encapsulation has promising potential in therapeutic applications.
It also provides a unique approach for studying cellular dynamics
and interactions, though this concept has not yet been fully explored.
No in vitro model currently exists that allows us to study the interaction
between crypt cells and Peyer’s patch immune cells because
of the difficulty in recreating, with sufficient control, the two
different microenvironments in the intestine in which these cell types
belong. However, we demonstrate that a microfluidic technique is able
to provide such precise control and that these cells can proliferate
inside microgels. Current microfluidic-based cell microencapsulation
techniques primarily use fluorinated oils. Herein, we study the feasibility
and biocompatibility of different nonfluorinated oils for application
in gastrointestinal cell encapsulation and further introduce a model
for studying intercellular chemical interactions with this approach.
Our results demonstrate that cell viability is more affected by the
solidification and purification processes that occur after droplet
formation rather than the oil type used for the carrier phase. Specifically,
a shorter polymer cross-linking time and consequently lower cell exposure
to the harsh environment (e.g., acidic pH) results in a high cell
viability of over 90% within the protected microgels. Using nonfluorinated
oils, we propose a model system demonstrating the interplay between
crypt and Peyer’s patch cells using this microfluidic approach
to separately encapsulate the cells inside distinct alginate/gelatin
microgels, which allow for intercellular chemical communication. We
observed that the coculture of crypt cells alongside Peyer’s
patch immune cells improves the growth of healthy organoids inside
these microgels, which contain both differentiated and undifferentiated
cells over 21 days of coculture. These results indicate the possibility
of using droplet-based microfluidics for culturing organoids to expand
their applicability in clinical research
Microfluidic-Based Cell-Embedded Microgels Using Nonfluorinated Oil as a Model for the Gastrointestinal Niche
Microfluidic-based
cell encapsulation has promising potential in therapeutic applications.
It also provides a unique approach for studying cellular dynamics
and interactions, though this concept has not yet been fully explored.
No in vitro model currently exists that allows us to study the interaction
between crypt cells and Peyer’s patch immune cells because
of the difficulty in recreating, with sufficient control, the two
different microenvironments in the intestine in which these cell types
belong. However, we demonstrate that a microfluidic technique is able
to provide such precise control and that these cells can proliferate
inside microgels. Current microfluidic-based cell microencapsulation
techniques primarily use fluorinated oils. Herein, we study the feasibility
and biocompatibility of different nonfluorinated oils for application
in gastrointestinal cell encapsulation and further introduce a model
for studying intercellular chemical interactions with this approach.
Our results demonstrate that cell viability is more affected by the
solidification and purification processes that occur after droplet
formation rather than the oil type used for the carrier phase. Specifically,
a shorter polymer cross-linking time and consequently lower cell exposure
to the harsh environment (e.g., acidic pH) results in a high cell
viability of over 90% within the protected microgels. Using nonfluorinated
oils, we propose a model system demonstrating the interplay between
crypt and Peyer’s patch cells using this microfluidic approach
to separately encapsulate the cells inside distinct alginate/gelatin
microgels, which allow for intercellular chemical communication. We
observed that the coculture of crypt cells alongside Peyer’s
patch immune cells improves the growth of healthy organoids inside
these microgels, which contain both differentiated and undifferentiated
cells over 21 days of coculture. These results indicate the possibility
of using droplet-based microfluidics for culturing organoids to expand
their applicability in clinical research
Microfluidic-Based Cell-Embedded Microgels Using Nonfluorinated Oil as a Model for the Gastrointestinal Niche
Microfluidic-based
cell encapsulation has promising potential in therapeutic applications.
It also provides a unique approach for studying cellular dynamics
and interactions, though this concept has not yet been fully explored.
No in vitro model currently exists that allows us to study the interaction
between crypt cells and Peyer’s patch immune cells because
of the difficulty in recreating, with sufficient control, the two
different microenvironments in the intestine in which these cell types
belong. However, we demonstrate that a microfluidic technique is able
to provide such precise control and that these cells can proliferate
inside microgels. Current microfluidic-based cell microencapsulation
techniques primarily use fluorinated oils. Herein, we study the feasibility
and biocompatibility of different nonfluorinated oils for application
in gastrointestinal cell encapsulation and further introduce a model
for studying intercellular chemical interactions with this approach.
Our results demonstrate that cell viability is more affected by the
solidification and purification processes that occur after droplet
formation rather than the oil type used for the carrier phase. Specifically,
a shorter polymer cross-linking time and consequently lower cell exposure
to the harsh environment (e.g., acidic pH) results in a high cell
viability of over 90% within the protected microgels. Using nonfluorinated
oils, we propose a model system demonstrating the interplay between
crypt and Peyer’s patch cells using this microfluidic approach
to separately encapsulate the cells inside distinct alginate/gelatin
microgels, which allow for intercellular chemical communication. We
observed that the coculture of crypt cells alongside Peyer’s
patch immune cells improves the growth of healthy organoids inside
these microgels, which contain both differentiated and undifferentiated
cells over 21 days of coculture. These results indicate the possibility
of using droplet-based microfluidics for culturing organoids to expand
their applicability in clinical research
Microfluidic-Based Cell-Embedded Microgels Using Nonfluorinated Oil as a Model for the Gastrointestinal Niche
Microfluidic-based
cell encapsulation has promising potential in therapeutic applications.
It also provides a unique approach for studying cellular dynamics
and interactions, though this concept has not yet been fully explored.
No in vitro model currently exists that allows us to study the interaction
between crypt cells and Peyer’s patch immune cells because
of the difficulty in recreating, with sufficient control, the two
different microenvironments in the intestine in which these cell types
belong. However, we demonstrate that a microfluidic technique is able
to provide such precise control and that these cells can proliferate
inside microgels. Current microfluidic-based cell microencapsulation
techniques primarily use fluorinated oils. Herein, we study the feasibility
and biocompatibility of different nonfluorinated oils for application
in gastrointestinal cell encapsulation and further introduce a model
for studying intercellular chemical interactions with this approach.
Our results demonstrate that cell viability is more affected by the
solidification and purification processes that occur after droplet
formation rather than the oil type used for the carrier phase. Specifically,
a shorter polymer cross-linking time and consequently lower cell exposure
to the harsh environment (e.g., acidic pH) results in a high cell
viability of over 90% within the protected microgels. Using nonfluorinated
oils, we propose a model system demonstrating the interplay between
crypt and Peyer’s patch cells using this microfluidic approach
to separately encapsulate the cells inside distinct alginate/gelatin
microgels, which allow for intercellular chemical communication. We
observed that the coculture of crypt cells alongside Peyer’s
patch immune cells improves the growth of healthy organoids inside
these microgels, which contain both differentiated and undifferentiated
cells over 21 days of coculture. These results indicate the possibility
of using droplet-based microfluidics for culturing organoids to expand
their applicability in clinical research
Microfluidic-Based Cell-Embedded Microgels Using Nonfluorinated Oil as a Model for the Gastrointestinal Niche
Microfluidic-based
cell encapsulation has promising potential in therapeutic applications.
It also provides a unique approach for studying cellular dynamics
and interactions, though this concept has not yet been fully explored.
No in vitro model currently exists that allows us to study the interaction
between crypt cells and Peyer’s patch immune cells because
of the difficulty in recreating, with sufficient control, the two
different microenvironments in the intestine in which these cell types
belong. However, we demonstrate that a microfluidic technique is able
to provide such precise control and that these cells can proliferate
inside microgels. Current microfluidic-based cell microencapsulation
techniques primarily use fluorinated oils. Herein, we study the feasibility
and biocompatibility of different nonfluorinated oils for application
in gastrointestinal cell encapsulation and further introduce a model
for studying intercellular chemical interactions with this approach.
Our results demonstrate that cell viability is more affected by the
solidification and purification processes that occur after droplet
formation rather than the oil type used for the carrier phase. Specifically,
a shorter polymer cross-linking time and consequently lower cell exposure
to the harsh environment (e.g., acidic pH) results in a high cell
viability of over 90% within the protected microgels. Using nonfluorinated
oils, we propose a model system demonstrating the interplay between
crypt and Peyer’s patch cells using this microfluidic approach
to separately encapsulate the cells inside distinct alginate/gelatin
microgels, which allow for intercellular chemical communication. We
observed that the coculture of crypt cells alongside Peyer’s
patch immune cells improves the growth of healthy organoids inside
these microgels, which contain both differentiated and undifferentiated
cells over 21 days of coculture. These results indicate the possibility
of using droplet-based microfluidics for culturing organoids to expand
their applicability in clinical research