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
Modulation of Silica Nanoparticle Uptake into Human Osteoblast Cells by Variation of the Ratio of Amino and Sulfonate Surface Groups: Effects of Serum
To
study the importance of the surface charge for cellular uptake of
silica nanoparticles (NPs), we synthesized five different single-
or multifunctionalized fluorescent silica NPs (FFSNPs) by introducing
various ratios of amino and sulfonate groups into their surface. The
zeta potential values of these FFSNPs were customized from highly
positive to highly negative, while other physicochemical properties
remained almost constant. Irrespective of the original surface charge, serum proteins adsorbed
onto the surface, neutralized the zeta potential values, and prevented
the aggregation of the tailor-made FFSNPs. Depending on the surface
charge and on the absence or presence of serum, two opposite trends
were found concerning the cellular uptake of FFSNPs. In the absence
of serum, positively charged NPs were more strongly accumulated by
human osteoblast (HOB) cells than negatively charged NPs. In contrast,
in serum-containing medium, anionic FFSNPs were internalized by HOB
cells more strongly, despite the similar size and surface charge of
all types of protein-covered FFSNPs. Thus, at physiological condition,
when the presence of proteins is inevitable, sulfonate-functionalized
silica NPs are the favorite choice to achieve a desired high rate
of NP internalization
Effective Bacterial Inactivation and Removal of Copper by Porous Ceramics with High Surface Area
In this study, we present porous ceramics combining the
antibacterial
effect of copper with an integrated copper removal adsorbent. After
preparing and characterizing the antibacterial copper-doped microbeads
and monoliths (CuBs and CuMs), their antibacterial efficiency is probed
against different nonpathogenic and pathogenic bacteria (<i>Bacillus
subtilis</i>,<i> Escherichia coli</i>,<i> Staphylococcus
aureus</i>, and <i>Pseudomonas aeruginosa</i>). An
antibacterial efficiency of 100% is reached within 15 min to 3 h for
all tested strains under static conditions. Dynamic tests with <i>B. subtilis</i> and <i>E. coli</i> showed high antibacterial
efficiency up to 99.93% even at continuous flux. To avoid any adverse
effects on the environment, continuous removal of released copper-ions
is accomplished with porous, high surface area monolithic adsorbents
(MAds). MAds are prepared similarly to the CuMs but without adding
copper during the manufacturing process. MAds reduce the amount of
copper released from the CuMs ≥ 99% during the first 15 min,
≥90% up to 2 h, and after 22 h of continuous filtration up
to 56% of the released copper is removed
Anchoring of Iron Oxyhydroxide Clusters at H and L Ferritin Subunits
Ferritin (Fn) proteins or their isolated
subunits can be used as
biomolecular templates for the selectively heterogeneous nucleation
and growth of nanoparticles, in particular of iron oxyhydroxides.
To shed light on the atomistic mechanisms of ferritin-promoted mineralization,
in this study we perform molecular dynamics simulations to investigate
the anchoring sites for Fe(III) clusters on Fn subunit assemblies
using models of goethite and ferrihydrite nanoparticles. For this
aim, we develop and parametrize a classical force field for Fe(III)
oxyhydroxides based on reference density functional theory calculations.
We then reveal that stable Fn–nanoparticle contacts are formed
not only via negatively charged amino acid residues (glutamic and
aspartic acid) but also, in a similar amount, via positively charged
(lysine and arginine) and neutral (histidine) residues. A large majority
of the anchoring sites are situated at the inner side of protein cages,
consistent with the natural iron storage function of ferritin in many
organisms. A slightly different distribution of anchoring sites is
observed on heavy (H) and light (L) Fn subunits, with the former offering
a larger amount of negative and neutral sites than the latter. This
finding is exploited to develop a Fn mineralization protocol in which
immobilized Fn subunits are first loaded with Fe<sup>2+</sup> ions
in a long “activation” step before starting their oxidation
to Fe<sup>3+</sup>. This leads to the formation of very dense and
uniform iron oxide films, especially when H subunits are employed
Interaction of the Physiological Tripeptide Glutathione with Colloidal Alumina Particles
Understanding of the molecular interactions of alumina
particles
with biomolecules is fundamental for a variety of biotechnological
processes. To study the interactions of polypeptides with alumina
particles, we have investigated the adsorption and desorption behavior
of the physiologically relevant tripeptide glutathione (GSH, γ-glutamylcysteinylglycine)
onto colloidal α-alumina particles (CPs). The adsorption of
GSH to positively charged alumina particles was rapid, increased proportionally
to the concentration of CPs, and shifted the isoelectric point of
the CP to a less alcaline pH. Desorption of particle-bound GSH was
achieved by increasing the ionic strength after adding salt to the
suspension, suggesting that adsorption of GSH to alumina is governed
by electrostatic interactions. The presence of negatively charged
and GSH-structurally related molecules such as glutamate, γ-glutamylcysteine,
γ-glutamylglutamate, or methyl-S-GSH prevented the binding of
GSH to the positively charged alumina surface in a concentration dependent
manner, while positively charged and net-uncharged molecules and GSH
esters did not affect GSH adsorption to alumina CPs. These data suggest
that exclusively electrostatic interaction via the carboxylate groups
of GSH governs its binding to alumina particles
Enhancing Cellular Uptake and Doxorubicin Delivery of Mesoporous Silica Nanoparticles via Surface Functionalization: Effects of Serum
In this study, we demonstrate how
functional groups on the surface of mesoporous silica nanoparticles
(MSNPs) can influence the encapsulation and release of the anticancer
drug doxorubicin, as well as cancer cell response in the absence or
presence of serum proteins. To this end, we synthesized four differently
functionalized MSNPs with amine, sulfonate, polyethylene glycol, or
polyethylene imine functional surface groups, as well as one type
of antibody-conjugated MSNP for specific cellular targeting, and we
characterized these MSNPs regarding their physicochemical properties,
colloidal stability in physiological media, and uptake and release
of doxorubicin <i>in vitro</i>. Then, the MSNPs were investigated
for their cytotoxic potential on cancer cells. Cationic MSNPs could
not be loaded with doxorubicin and did therefore not show any cytotoxic
and antiproliferative potential on osteosarcoma cells, although they
were efficiently taken up into the cells in the presence or absence
of serum. In contrast, substantial amounts of doxorubicin were loaded
into negatively charged and unfunctionalized MSNPs. Especially, sulfonate-functionalized
doxorubicin-loaded MSNPs were efficiently taken up into the cells
in the presence of serum and showed an accelerated toxic and antiproliferative
potential compared to unfunctionalized MSNPs, antibody-conjugated
MSNPs, and even free doxorubicin. These findings stress the high importance
of the surface charge as well as of the protein corona for designing
and applying nanoparticles for targeted drug delivery
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