7 research outputs found
Controlling Mixed-Protein Adsorption Layers on Colloidal Alumina Particles by Tailoring Carboxyl and Hydroxyl Surface Group Densities
We
show that different ratios of bovine serum albumin (BSA) and
lysozyme (LSZ) can be achieved in a mixed protein adsorption layer
by tailoring the amounts of carboxyl (−COOH) and aluminum hydroxyl
(AlOH) groups on colloidal alumina particles (<i>d</i><sub>50</sub> ≈ 180 nm). The particles are surface-functionalized
with −COOH groups, and the resultant surface chemistry, including
the remaining AlOH groups, is characterized and quantified using elemental
analysis, ζ potential measurements, acid–base titration,
IR spectroscopy, electron microscopy, nitrogen adsorption, and dynamic
light scattering. BSA and LSZ are subsequently added to the particle
suspensions, and protein adsorption is monitored by in situ ζ
potential measurements while being quantified by UV spectroscopy and
gel electrophoresis. A comparison of single-component and sequential
protein adsorption reveals that BSA and LSZ have specific adsorption
sites: BSA adsorbs primarily via AlOH groups, whereas LSZ adsorbs
only via −COOH groups (1–2 −COOH groups on the
particle surface is enough to bind one LSZ molecule). Tailoring such
groups on the particle surface allows control of the composition of
a mixed BSA and LSZ adsorption layer. The results provide further
insight into how particle surface chemistry affects the composition
of protein adsorption layers on colloidal particles and is valuable
for the design of such particles for biotechnological and biomedical
applications
Ordered Surface Structuring of Spherical Colloids with Binary Nanoparticle Superlattices
Surface-patterning
colloidal matter in the sub-10 nm regime generates
exceptional functionality in biology and photonic and electronic materials.
Techniques of artificially generating functional patterns in the small
nanoscale advanced in a fascinating manner in the last several years.
However, they remain often restricted to planar and noncolloidal substrates.
Patterning colloidal matter in solution via bottom-up assembly of
smaller subunits on larger core particles is highly challenging because
it is necessary to force the subunits onto randomly moving objects.
Consequently, the non-equilibrium conditions present during nanoparticle
self-assembly are difficult to control to eventually achieve the desired
material structures. Here, we describe the formation of surface patterns
with intrinsic periodic repeats of 8.9 ± 0.9 nm and less on hard,
amorphous colloidal core particles by assembling binary nanoparticle
superlattices on the curved particle surface. The colloidal environment
is preserved during the entire bottom-up crystallization of variable
building blocks (here, monodispersed 5 nm Au and 2.4 nm Pd nanoparticles
(NPs) and 230 nm SiO<sub>2</sub> core particles) into AB<sub>13</sub>-like, binary, and isotropic superlattice domains on the amorphous
cores. The three-dimensional, bottom-up assembly technique is a new
tool for patterning colloidal matter in the sub-10 nm surface regime
for gaining access to multicomponent metamaterials for bionanoscience,
photonics, and electronics
Ordered Surface Structuring of Spherical Colloids with Binary Nanoparticle Superlattices
Surface-patterning
colloidal matter in the sub-10 nm regime generates
exceptional functionality in biology and photonic and electronic materials.
Techniques of artificially generating functional patterns in the small
nanoscale advanced in a fascinating manner in the last several years.
However, they remain often restricted to planar and noncolloidal substrates.
Patterning colloidal matter in solution via bottom-up assembly of
smaller subunits on larger core particles is highly challenging because
it is necessary to force the subunits onto randomly moving objects.
Consequently, the non-equilibrium conditions present during nanoparticle
self-assembly are difficult to control to eventually achieve the desired
material structures. Here, we describe the formation of surface patterns
with intrinsic periodic repeats of 8.9 ± 0.9 nm and less on hard,
amorphous colloidal core particles by assembling binary nanoparticle
superlattices on the curved particle surface. The colloidal environment
is preserved during the entire bottom-up crystallization of variable
building blocks (here, monodispersed 5 nm Au and 2.4 nm Pd nanoparticles
(NPs) and 230 nm SiO<sub>2</sub> core particles) into AB<sub>13</sub>-like, binary, and isotropic superlattice domains on the amorphous
cores. The three-dimensional, bottom-up assembly technique is a new
tool for patterning colloidal matter in the sub-10 nm surface regime
for gaining access to multicomponent metamaterials for bionanoscience,
photonics, and electronics
Ordered Surface Structuring of Spherical Colloids with Binary Nanoparticle Superlattices
Surface-patterning
colloidal matter in the sub-10 nm regime generates
exceptional functionality in biology and photonic and electronic materials.
Techniques of artificially generating functional patterns in the small
nanoscale advanced in a fascinating manner in the last several years.
However, they remain often restricted to planar and noncolloidal substrates.
Patterning colloidal matter in solution via bottom-up assembly of
smaller subunits on larger core particles is highly challenging because
it is necessary to force the subunits onto randomly moving objects.
Consequently, the non-equilibrium conditions present during nanoparticle
self-assembly are difficult to control to eventually achieve the desired
material structures. Here, we describe the formation of surface patterns
with intrinsic periodic repeats of 8.9 ± 0.9 nm and less on hard,
amorphous colloidal core particles by assembling binary nanoparticle
superlattices on the curved particle surface. The colloidal environment
is preserved during the entire bottom-up crystallization of variable
building blocks (here, monodispersed 5 nm Au and 2.4 nm Pd nanoparticles
(NPs) and 230 nm SiO<sub>2</sub> core particles) into AB<sub>13</sub>-like, binary, and isotropic superlattice domains on the amorphous
cores. The three-dimensional, bottom-up assembly technique is a new
tool for patterning colloidal matter in the sub-10 nm surface regime
for gaining access to multicomponent metamaterials for bionanoscience,
photonics, and electronics
Ordered Surface Structuring of Spherical Colloids with Binary Nanoparticle Superlattices
Surface-patterning
colloidal matter in the sub-10 nm regime generates
exceptional functionality in biology and photonic and electronic materials.
Techniques of artificially generating functional patterns in the small
nanoscale advanced in a fascinating manner in the last several years.
However, they remain often restricted to planar and noncolloidal substrates.
Patterning colloidal matter in solution via bottom-up assembly of
smaller subunits on larger core particles is highly challenging because
it is necessary to force the subunits onto randomly moving objects.
Consequently, the non-equilibrium conditions present during nanoparticle
self-assembly are difficult to control to eventually achieve the desired
material structures. Here, we describe the formation of surface patterns
with intrinsic periodic repeats of 8.9 ± 0.9 nm and less on hard,
amorphous colloidal core particles by assembling binary nanoparticle
superlattices on the curved particle surface. The colloidal environment
is preserved during the entire bottom-up crystallization of variable
building blocks (here, monodispersed 5 nm Au and 2.4 nm Pd nanoparticles
(NPs) and 230 nm SiO<sub>2</sub> core particles) into AB<sub>13</sub>-like, binary, and isotropic superlattice domains on the amorphous
cores. The three-dimensional, bottom-up assembly technique is a new
tool for patterning colloidal matter in the sub-10 nm surface regime
for gaining access to multicomponent metamaterials for bionanoscience,
photonics, and electronics
Virus Removal in Ceramic Depth Filters Based on Diatomaceous Earth
Ceramic filter candles, based on the natural material
diatomaceous
earth, are widely used to purify water at the point-of-use. Although
such depth filters are known to improve drinking water quality by
removing human pathogenic protozoa and bacteria, their removal regarding
viruses has rarely been investigated. These filters have relatively
large pore diameters compared to the physical dimension of viruses.
However, viruses may be retained by adsorption mechanisms due to intermolecular
and surface forces. Here, we use three types of bacteriophages to
investigate their removal during filtration and batch experiments
conducted at different pH values and ionic strengths. Theoretical
models based on DLVO-theory are applied in order to verify experimental
results and assess surface forces involved in the adsorptive process.
This was done by calculation of interaction energies between the filter
surface and the viruses. For two small spherically shaped viruses
(MS2 and PhiX174), these filters showed no significant removal. In
the case of phage PhiX174, where attractive interactions were expected,
due to electrostatic attraction of oppositely charged surfaces, only
little adsorption was reported in the presence of divalent ions. Thus,
we postulate the existence of an additional repulsive force between
PhiX174 and the filter surface. It is hypothesized that such an additional
energy barrier originates from either the phage’s specific
knobs that protrude from the viral capsid, enabling steric interactions,
or hydration forces between the two hydrophilic interfaces of virus
and filter. However, a larger-sized, tailed bacteriophage of the family <i>Siphoviridae</i> was removed by log 2 to 3, which is explained
by postulating hydrophobic interactions
Adsorption and Orientation of the Physiological Extracellular Peptide Glutathione Disulfide on Surface Functionalized Colloidal Alumina Particles
Understanding the
interrelation between surface chemistry of colloidal
particles and surface adsorption of biomolecules is a crucial prerequisite
for the design of materials for biotechnological and nanomedical applications.
Here, we elucidate how tailoring the surface chemistry of colloidal
alumina particles (<i>d</i><sub>50</sub> = 180 nm) with
amino (−NH<sub>2</sub>), carboxylate (−COOH), phosphate
(−PO<sub>3</sub>H<sub>2</sub>) or sulfonate (−SO<sub>3</sub>H) groups affects adsorption and orientation of the model
peptide glutathione disulfide (GSSG). GSSG adsorbed on native, −NH<sub>2</sub>-functionalized, and −SO<sub>3</sub>H-functionalized
alumina but not on −COOH- and −PO<sub>3</sub>H<sub>2</sub>-functionalized particles. When adsorption occurred, the process
was rapid (≤5 min), reversible by application of salts, and
followed a Langmuir adsorption isotherm dependent on the particle
surface functionalization and ζ potential. The orientation of
particle bound GSSG was assessed by the release of glutathione after
reducing the GSSG disulfide bond and by ζ potential measurements.
GSSG is likely to bind via the carboxylate groups of one of its two
glutathionyl (GS) moieties onto native and −NH<sub>2</sub>-modified
alumina, whereas GSSG is suggested to bind to −SO<sub>3</sub>H-modified alumina via the primary amino groups of both GS moieties.
Thus, GSSG adsorption and orientation can be tailored by varying the
molecular composition of the particle surface, demonstrating a step
toward guiding interactions of biomolecules with colloidal particles