Plant Membrane-On-A-Chip: A Platform for Studying Plant Membrane Proteins and Lipids.

The cell plasma membrane is a two-dimensional, fluid mosaic material composed of lipids and proteins that create a semipermeable barrier defining the cell from its environment. Compared with soluble proteins, the methodologies for the structural and functional characterization of membrane proteins are challenging. An emerging tool for studies of membrane proteins in mammalian systems is a "plasma membrane on a chip," also known as a supported lipid bilayer. Here, we create the "plant-membrane-on-a-chip,″ a supported bilayer made from the plant plasma membranes of Arabidopsis thaliana, Nicotiana benthamiana, or Zea mays. Membrane vesicles from protoplasts containing transgenic membrane proteins and their native lipids were incorporated into supported membranes in a defined orientation. Membrane vesicles fuse and orient systematically, where the cytoplasmic side of the membrane proteins faces the chip surface and constituents maintain mobility within the membrane plane. We use plant-membrane-on-a-chip to perform fluorescent imaging to examine protein-protein interactions and determine the protein subunit stoichiometry of FLOTILLINs. We report here that like the mammalian FLOTILLINs, FLOTILLINs expressed in Arabidopsis form a tetrameric complex in the plasma membrane. This plant-membrane-on-a-chip approach opens avenues to studies of membrane properties of plants, transport phenomena, biophysical processes, and protein-protein and protein-lipid interactions in a convenient, cell-free platform.

Distinguishing cells using electro-acoustic spinning.

Many diseases, including cancer and covid, result in altered mechanical and electric properties of the affected cells. These changes were proposed as disease markers. Current methods to characterize such changes either provide very limited information on many cells or have extremely low throughput. We introduce electro-acoustic spinning (EAS). Cells were found to spin in combined non-rotating AC electric and acoustic fields. The rotation velocity in EAS depends critically on a cell's electrical and mechanical properties. In contrast to existing methods, the rotation is uniform in the field of view and hundreds of cells can be characterized simultaneously. We demonstrate that EAS can distinguish cells with only minor differences in electric and mechanical properties, including differences in age or the number of passages.

Interplay between biofilm microenvironment and pathogenicity of Pseudomonas aeruginosa in cystic fibrosis lung chronic infection.

Pseudomonas aeruginosa (PA) is a highly, if not the most, versatile microorganism capable of colonizing diverse environments. One of the niches in which PA is able to thrive is the lung of cystic fibrosis (CF) patients. Due to a genetic aberration, the lungs of CF-affected patients exhibit impaired functions, rendering them highly susceptible to bacterial colonization. Once PA attaches to the epithelial surface and transitions to a mucoid phenotype, the infection becomes chronic, and antibiotic treatments become inefficient. Due to the high number of affected people and the severity of this infection, CF-chronic infection is a well-documented disease. Still, numerous aspects of PA CF infection remain unclear. The scientific reports published over the last decades have stressed how PA can adapt to CF microenvironmental conditions and how its surrounding matrix of extracellular polymeric substances (EPS) plays a key role in its pathogenicity. In this context, it is of paramount interest to present the nature of the EPS together with the local CF-biofilm microenvironment. We review how the PA biofilm microenvironment interacts with drugs to contribute to the pathogenicity of CF-lung infection. Understanding why so many drugs are inefficient in treating CF chronic infection while effectively treating planktonic PA is essential to devising better therapeutic targets and drug formulations.

Cellulosic biofilm formation of Komagataeibacter in kombucha at oil-water interfaces.

Bacteria forming biofilms at oil-water interfaces have diverse metabolism, they use hydrocarbons as a carbon and energy source. Kombucha is a fermented drink obtained from a complex symbiotic culture of bacteria and yeast, where acetic acid bacteria present in kombucha use sugars as a carbon source to produce cellulosic biofilms. We hypothesize that Komagataeibacteraceae in kombucha can adsorb to and use hydrocarbons as the sole energy source to produce cellulosic biofilms. Hence we characterized a kombucha culture, studied bacterial adsorption and cellulosic biofilm formation of kombucha at the n-decane or mineral oil-kombucha suspension interface. The cellulosic biofilms were imaged using fluorescence microscopy and cryo-scanning electron microscopy, and their time-dependent rheology was measured. Komagataeibacter, the dominant bacterial genus in the kombucha culture, produced cellulosic biofilms with reduced cellulose biomass yield at the oil-kombucha suspension interfaces compared to at the air-kombucha suspension interface. The presence of biosurfactants in the supernatant secreted by the kombucha microbes led to a larger and faster decrease in the interfacial tension on both oil types, leading to the formation of stable and elastic biofilm membranes. The difference in interfacial tension reduction was insignificant already after 2 h of biofilm formation at the mineral oil-kombucha suspension interface compared to kombucha microbes resuspended without biosurfactants but persisted for longer than 24 h in contact with n-decane. We also demonstrate that Komagataeibacter in kombucha can produce elastic cellulosic biofilms using hydrocarbons from the oil interface as the sole source of carbon and energy. Thus Komagataeibacter and kombucha shows the potential of this system for producing valued bacterial cellulose through remediation of hydrocarbon waste.

Modifying superparamagnetic iron oxide and silica nanoparticles surfaces for efficient (MA)LDI-MS analyses of peptides and proteins.

RATIONALE: Surface functionalization is considered to be the foundation for developing nanomaterial applications in matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) analyses. However, the surface properties of nanostructures can influence their interaction with the analyte and consequently the mass data. In the present study, functionalized nanoparticles (NPs) were used for MALDI-MS and laser desorption/ionization mass spectrometry (LDI-MS) experiments in order to evaluate the effect of the surface properties of NPs on tailoring the intensity of mass signals. METHODS: Regarding the LDI-MS analyses, the surface of superparamagnetic iron oxide nanoparticles (SPIONs) was coated with nitrosonium tetrafluoroborate, citric acid, nitrodopamine, and gallic acid. Additionally, the SPIONs were applied as a matrix to analyze three small peptides. In the MALDI-MS analyses, silica NPs were selected as co-matrix and functionalized with cysteine, sulfobetaine, and amine alkoxysilanes. Then, the silica NPs were utilized as additives in the MALDI-MS samples of four proteins in a mass range between ~2000 and 60,000 Da. RESULTS: The results of LDI-MS analyses demonstrated more than one order enhancement in the signal intensity of analytes based on the amount of electrostatic interaction and laser energy absorption by the surface ligands. However, those of MALDI-MS experiments indicated a significant signal improvement when achieving the colloidal stability of silica NPs in the matrix solution. CONCLUSIONS: Based on the results, the surface properties of NPs affected the (MA)LDI-MS analyses indispensably. Finally, the functionalization of SPIONs represented a new model for the future development of NPs with both affinity and enhanced ionization abilities in mass spectrometry.

Cyclodextrin-Appended Superparamagnetic Iron Oxide Nanoparticles as Cholesterol-Mopping Agents.

Cholesterol plays a crucial role in major cardiovascular and neurodegenerative diseases, including Alzheimer's disease and rare genetic disorders showing altered cholesterol metabolism. Cyclodextrins (CDs) have shown promising therapeutic efficacy based on their capacity to sequester and mobilise cholesterol. However, the administration of monomeric CDs suffers from several drawbacks due to their lack of specificity and poor pharmacokinetics. We present core-shell superparamagnetic iron oxide nanoparticles (SPIONs) functionalised with CDs appended to poly (2-methyl-2-oxazoline) polymers grafted in a dense brush to the iron oxide core. The CD-decorated nanoparticles (CySPIONs) are designed so that the macrocycle is specifically cleaved off the nanoparticle's shell at a slightly acidic pH. In the intended use, free monomeric CDs will then mobilise cholesterol out of the lysosome to the cytosol and beyond through the formation of an inclusion complex. Hence, its suitability as a therapeutic platform to remove cholesterol in the lysosomal compartment. Synthesis and full characterization of the polymer as well as of the core-shell SPION are presented. Cholesterol-binding activity is shown through an enzymatic assay.

Biofilm formation at oil-water interfaces is not a simple function of bacterial hydrophobicity.

Bacterial adsorption to interfaces is the initial step in biofilm formation. The mechanism of biofilm formation at liquid-liquid interfaces differs from the process of biofilm formation on solid-liquid interfaces. Until now, the former is not well understood. We study the bacterial adsorption and biofilm formation of three different bacteria, P. aeruginosa, S. aureus, and S. epidermidis at the n-decane-water interface, with focus on the relationship between bacteria wettability, excretion of biosurfactants, and biofilm formation. The adhesion capacity of these bacteria to hydrocarbons was characterized using the bacterial adherence to hydrocarbons test. We monitored the interfacial rheology of bacterial adsorption and biofilm formation at the interface over time using a drop shape analyzer and imaged the formed biofilms by using fluorescence and scanning electron microscopy. P. aeruginosa showed high adhesion capacity to hydrocarbons, while the adhesion capacity of both staphylococci was negligible. P. aeruginosa also showed rapid adsorption to the n-decane-water interface as measured by the rapid decrease in interfacial tension for the pure bacteria suspension. However, S. epidermidis, with a negligible hydrophobicity value, showed the most substantial reduction in interfacial tension and the formation of the most elastic biofilms at the oil-water interface. S. epidermidis accomplishes this by the secretion of biosurfactants. S. aureus did not form biofilms at the n-decane-water interface, in contrast to P. aeruginosa and S. epidermidis. We conclude that bacterial adsorption and biofilm formation at oil-water interfaces, in general, are not simple functions of cell hydrophobicity. Biosurfactant modification and metabolism of the interface also play essential roles.

Minimal Reconstitution of Membranous Web Induced by a Vesicle-Peptide Sol-Gel Transition.

Positive strand RNA viruses replicate in specialized niches called membranous web within the cytoplasm of host cells. These virus replication organelles sequester viral proteins, RNA, and a variety of host factors within a fluid, amorphous matrix of clusters of endoplasmic reticulum (ER) derived vesicles. They are thought to form by the actions of a nonstructural viral protein NS4B, which remodels the ER and produces dense lipid-protein condensates. Here, we used in vitro reconstitution to identify the minimal components and elucidate physical mechanisms driving the web formation. We found that the N-terminal amphipathic domain of NS4B (peptide 4BAH2) and phospholipid vesicles (∼100-200 nm in diameter) were sufficient to produce a gel-like, viscoelastic condensate. This condensate coexists with the surrounding aqueous phase and affords rapid exchange of molecules. Together, it recapitulates the essential properties of the virus-induced membranous web. Our data support a novel phase separation mechanism in which phospholipid vesicles provide a supramolecular template spatially organizing multiple self-associating peptides thereby generating programmable multivalency de novo and inducing macroscopic phase separation.

Characterization of Biofilm Formation by Cronobacter spp. Isolates of Different Food Origin under Model Conditions.

Cronobacter spp. are opportunistic human pathogens that cause serious diseases in neonates and immunocompromised people. Owing to their biofilm formation on various surfaces, both their detection and their removal from production plants constitute a major challenge. In this study, food samples were randomly collected in Austria and examined for the presence of Cronobacter spp. Presumptive isolates were identified by a polyphasic approach. Five percent of the samples were positive for C. sakazakii and 2.4% for C. dublinensis. Individual growth of the isolates was characterized based on lag time, growth rate, and generation time. During an incubation period of 6 to 72 h, biofilm formation of 11 selected isolates was quantified under model conditions by a crystal violet staining assay with 96-well plates with different carbon sources (lactose, glucose, maltose, sucrose, and sodium acetate) and NaCl levels and under variable temperature and pH conditions. Biofilm formation was more pronounced at lactose concentrations between 0.25 and 3% compared with 5% lactose, which lead to thinner layers. C. sakazakii isolate C7, isolated from infant milk powder, was the strongest biofilm producer at 10 mM Mg2+ and 5 mM Mn2+, 0.5% sodium acetate, at pH levels between 7 and 9 at 37°C for 24 h. C. sakazakii strain C6 isolated from a plant air filter was identified as a moderate biofilm former and C. sakazakii strain DSM 4485, a clinical isolate, as a weak biofilm former. Based on PCR detection, genes bcsA, bcsB, and bcsG encoding for cellulose could be identified as markers for biofilm formation. Isolates carrying bcsA and bcsB showed significantly stronger biofilm formation than isolates without these genes ( P < 0.05), in strong correlation with the results obtained in the crystal violet assay. Further investigations using confocal laser scanning microscopy revealed that extracellular polymeric substances and glycocalyx secretions were the dominating components of the biofilms and that the viable fraction of bacteria in the biofilm decreased over time.

Biocompatible Glyconanoparticles by Grafting Sophorolipid Monolayers on Monodispersed Iron Oxide Nanoparticles.

This work presents the synthesis and characterization of sophorolipid-coated monodisperse iron oxide nanoparticles. Sophorolipids are biological glycosylated amphiphiles produced by the yeast S. bombicola. In their open acidic form, sophorolipids have been used as a surface stabilizing agent for metal and metal oxide nanoparticles but with a poor control over size and structural properties. In this work, the COOH function of sophorolipids (SL) was modified with nitrodopamine (NDA), a catechol known for its high affinity to iron ions. The resulting new form of sophorolipid-nitrodopamide (SL-NDA) was used as a surface ligand for monodisperse iron oxide nanoparticles. We show by a combination of thermogravimetric analysis and small-angle X-ray and neutron scattering that iron oxide nanoparticles (IONP) are stabilized by a single, high-density SL-NDA layer. This results in excellent colloidal stability under biologically relevant conditions, such as at high protein and salt concentrations. The IONP grafted with SL-NDA showed a negligible uptake by cells and no cytotoxicity, which was tested on two representative cell lines. Thus, they reveal the potential of sophorolipids as stable and nontoxic surface coatings for IONP-based biomedical and biotechnological applications.

Poly(ethylene glycol) Grafting of Nanoparticles Prevents Uptake by Cells and Transport Through Cell Barrier Layers Regardless of Shear Flow and Particle Size.

It has long been a central tenet of biomedical research that coating of nanoparticles with hydrated polymers can improve their performance in biomedical applications. However, the efficacy of the approach in vivo is still debated. In vitro model systems to test the performance of engineered nanoparticles for in vivo applications often use nonrepresentative cell lines and conditions for uptake and toxicity tests. We use our platform of monodisperse iron oxide nanoparticles densely grafted with nitrodopamide-poly(ethylene glycol) (PEG) to probe cell interactions with a set of cell types and culture conditions that are relevant for applications in which nanoparticles are injected into the bloodstream. In the past, these particles have proved to have excellent stability and negligible interaction with proteins and membranes under physiological conditions. We test the influence of flow on the uptake of nanoparticles. We also investigate the transport through endothelial barrier cell layers, as well as the effect that PEG-grafted iron oxide nanoparticles have on cell layers relevant for nanoparticles injected into the bloodstream. Our results show that the dense PEG brush and resulting lack of nonspecific protein and membrane interaction lead to negligible cell uptake, toxicity, and transport across barrier layers. These results contrast with far less well-defined polymer-coated nanoparticles that tend to aggregate and consequently strongly interact with cells, for example, by endocytosis.

COMPARATIVE PHYSIOCHEMICAL ANALYSIS OF HYDROPHOBINS PRODUCED IN ESCHERICHIA COLI AND PICHIA PASTORIS.

Hydrophobins (HFBs) are small surface-active proteins secreted by filamentous fungi. Being amphiphilic, they spontaneously form layers that convert surfaces from hydrophilic to hydrophobic and vice versa. We have compared properties of the class II HFB4 and HFB7 from Trichoderma virens as produced in Escherichia coli and Pichia pastoris. Since the production in E. coli required denaturation/renaturation steps because of inclusion bodies, this treatment was also applied to HFBs produced and secreted in yeast. The protein yields for both systems were similar. Both HFBs produced by E. coli proved less active on PET compared to HFBs produced in P. pastoris. HFBs produced in E. coli decreased the hydrophilicity of glass the most, which correlated with the adsorption of a more dense protein layer on glass compared to HFBs produced in P. pastoris. The hydrophobins produced in P. pastoris formed highly structured monolayers. Layers of hydrophobins produced in E. coli were less prone to self-organization. Our data suggests that irrespective of the production host, the HFBs could be used in various applications that are based on their surface activity. However, the production host and the subsequent purification procedure will influence the stability of HFB layers. In the area of high-value biomedical devices and nanomaterials, where the formation of highly ordered protein monolayers is essential, our results point to P. pastoris as the preferred production host. Furthermore, the choice of an appropriate hydrophobin for a given application appears to be equally important.

Controlled aggregation and cell uptake of thermoresponsive polyoxazoline-grafted superparamagnetic iron oxide nanoparticles.

Hydrophilic polymer-coated iron oxide nanoparticles are potential materials for a plethora of applications in the biotechnological field. Typical such polymers, e.g. dextran or poly(ethylene glycol), lack the ability to tailor the biological response to an environmental trigger, while common responsive polymers such as poly(N-isopropylacrylamide) or poly(acrylic acid) are not suitable for biomedical applications. We present the synthesis and characterization of superparamagnetic iron oxide nanoparticles with thermoresponsive polyoxazoline brushes grafted at unprecedented density using nitrodopamine anchor chemistry. Reversible aggregation/deaggregation is observed in water and biological medium, confirming control over the colloidal stability. Thermal switching of the solubility could only be achieved by global heating of the sample, while local magnetothermal heating did not produce a sufficiently strong temperature gradient through the brush. Varying the polymer composition allows for tuning of the lower critical solution temperature (LCST) as well as the average nanoparticle cluster size obtained upon heating. The LCST of polyoxazolines and the thermal colloidal stability are shown to be greatly affected by ion concentration, by polymer grafting density and also by the presence of serum protein; this shows that transition temperatures of free polymers in water can be very misleading for the design of polymer-coated nanomaterials for biomedical applications. Finally, the thermoresponsive SPION are shown to be non-cytotoxic and with a low cell uptake scaling with the hydration of the polymer brush, which is tuned by the polymer composition. Thus, we demonstrate that pozylated nanoparticles provide the advantages of PEG- and PNIPAM-grafted nanoparticles, but provide a tunable and more easily functionalizable platform for further development.

Interaction of Size-Tailored PEGylated Iron Oxide Nanoparticles with Lipid Membranes and Cells.

Targeted nanomedicine builds on the concept that nanoparticles can be directed to specific tissues while remaining inert to others organs. Many studies have been performed on the synthesis and cellular interactions of core-shell nanoparticles, in which a functional inorganic core is coated with a biocompatible polymer layer that should reduce nonspecific uptake and cytotoxicity. However, work is lacking that relates structural parameters of the core-shell structure and colloidal properties directly to interactions with cell membranes and further correlates these interactions to cell uptake. We have synthesized monodisperse (SD < 10%), single-crystalline, and superparamagnetic iron oxide nanoparticles (SPION) of different core size (3-8 nm) that are densely grafted with nitrodopamine-poly(ethylene glycol) (NDA-PEG(5 kDa)) brushes. We investigated the interactions of the PEGylated SPION with biomimetic membranes and cancer and kidney cells. It is shown that a dense homogeneous PEG shell suppresses membrane interactions and cell uptake but that nanoparticle curvature can influence membrane interactions for similarly grafted nanoparticles. Weak adsorption to anionic lipid membranes is shown to correlate with eukaryote cell uptake and is attributed to double-layer interactions without direct membrane penetration. This attraction is strongly suppressed during physiological conditions and leads to unprecedented low cell uptake and full cell viability when compared to those of traditional dextran-coated SPION. Less curved (larger core) PEGylated SPION show weaker membrane adsorption and lower cell uptake due to effectively denser shells. These results provide a better understanding of design criteria for core-shell nanoparticles in terms of avoiding nonspecific uptake by cells, reducing toxicity, and increasing circulation time.

Evaluation of High-Yield Purification Methods on Monodisperse PEG-Grafted Iron Oxide Nanoparticles.

Fundamental research on nanoparticle (NP) interactions and development of next-generation biomedical NP applications relies on synthesis of monodisperse, functional, core-shell nanoparticles free of residual dispersants with truly homogeneous and controlled physical properties. Still, synthesis and purification of e.g. such superparamagnetic iron oxide NPs remain a challenge. Comparing the success of different methods is marred by the sensitivity of analysis methods to the purity of the product. We synthesize monodisperse, oleic acid (OA)-capped, Fe3O4 NPs in the superparamagnetic size range (3-10 nm). Ligand exchange of OA for poly(ethylene glycol) (PEG) was performed with the PEG irreversibly grafted to the NP surface by a nitrodopamine (NDA) anchor. Four different methods were investigated to remove excess ligands and residual OA: membrane centrifugation, dialysis, size exclusion chromatography, and precipitation combined with magnetic decantation. Infrared spectroscopy and thermogravimetric analysis were used to determine the purity of samples after each purification step. Importantly, only magnetic decantation yielded pure NPs at high yields with sufficient grafting density for biomedical applications (∼1 NDA-PEG(5 kDa)/nm(2), irrespective of size). The purified NPs withstand challenging tests such as temperature cycling in serum and long-term storage in biological buffers. Dynamic light scattering, transmission electron microscopy, and small-angle X-ray scattering show stability over at least 4 months also in serum. The successful synthesis and purification route is compatible with any conceivable functionalization for biomedical or biomaterial applications of PEGylated Fe3O4 NPs.

Core-Shell Structure of Monodisperse Poly(ethylene glycol)-Grafted Iron Oxide Nanoparticles Studied by Small-Angle X-ray Scattering.

The promising applications of core-shell nanoparticles in the biological and medical field have been well investigated in recent years. One remaining challenge is the characterization of the structure of the hydrated polymer shell. Here we use small-angle X-ray scattering (SAXS) to investigate iron oxide core-poly(ethylene glycol) brush shell nanoparticles with extremely high polymer grafting density. It is shown that the shell density profile can be described by a scaling model that takes into account the locally very high grafting density near the core. A good fit to a constant density region followed by a star-polymer-like, monotonously decaying density profile is shown, which could help explain the unique colloidal properties of such densely grafted core-shell nanoparticles. SAXS experiments probing the thermally induced dehydration of the shell and the response to dilution confirmed that the observed features are associated with the brush and not attributed to structure factors from particle aggregates. We thereby demonstrate that the structure of monodisperse core-shell nanoparticles with dense solvated shells can be well studied with SAXS and that different density models can be distinguished from each other.

Synthesis and Magneto-Thermal Actuation of Iron Oxide Core-PNIPAM Shell Nanoparticles.

Superparamagnetic nanoparticles have been proposed for many applications in biotechnology and medicine. In this paper, it is demonstrated how the excellent colloidal stability and magnetic properties of monodisperse and individually densely grafted iron oxide nanoparticles can be used to manipulate reversibly the solubility of nanoparticles with a poly(N-isopropylacrylamide)nitrodopamine shell. "Grafting-to" and "grafting-from" methods for synthesis of an irreversibly anchored brush shell to monodisperse, oleic acid coated iron oxide cores are compared. Thereafter, it is shown that local heating by magnetic fields as well as global thermal heating can be used to efficiently and reversibly aggregate, magnetically extract nanoparticles from solution and spontaneously redisperse them. The coupling of magnetic and thermally responsive properties points to novel uses as smart materials, for example, in integrated devices for molecular separation and extraction.

Complete Exchange of the Hydrophobic Dispersant Shell on Monodisperse Superparamagnetic Iron Oxide Nanoparticles.

High-temperature synthesized monodisperse superparamagnetic iron oxide nanoparticles are obtained with a strongly bound ligand shell of oleic acid and its decomposition products. Most applications require a stable presentation of a defined surface chemistry; therefore, the native shell has to be completely exchanged for dispersants with irreversible affinity to the nanoparticle surface. We evaluate by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and thermogravimetric analysis/differential scanning calorimetry (TGA/DSC) the limitations of commonly used approaches. A mechanism and multiple exchange scheme that attains the goal of complete and irreversible ligand replacement on monodisperse nanoparticles of various sizes is presented. The obtained hydrophobic nanoparticles are ideally suited for magnetically controlled drug delivery and membrane applications and for the investigation of fundamental interfacial properties of ultrasmall core-shell architectures.

Lipogels: surface-adherent composite hydrogels assembled from poly(vinyl alcohol) and liposomes.

Drug-eluting engineered surface coatings are of paramount importance for many biomedical applications from implantable devices to tissue engineering. Herein, we present the assembly of lipogels, composite physical hydrogels assembled from poly(vinyl alcohol) and liposomes using thiol-disulfide exchange between end group modified PVA and thiocholesterol containing liposomes, and the response of adhering cells to these coatings. We demonstrate the controlled loading of liposomes into the polymer matrix and the preserved mechanical properties of the lipogels. Furthermore, the lipogels are successfully rendered cell adhesive by incorporation of poly(l-lysine) into the PVA polymer matrix or by poly(dopamine) coating of the lipogels. The successful lipid uptake from the lipogels by macrophages, hepatocytes, and myoblasts was monitored by flow cytometry. Finally, the delivery of active cargo, paclitaxel, to adherent myoblasts is shown, thus illustrating the potential of the lipogels as a drug eluting interface for biomedical applications.

Pleckstrin homology-phospholipase C-δ1 interaction with phosphatidylinositol 4,5-bisphosphate containing supported lipid bilayers monitored in situ with dual polarization interferometry.

We have determined the kinetics and affinity of binding of PH-PLCδ(1) to the PIP(2) headgroup lipids using an optical surface-sensitive technique in a time-resolved manner. The use of dual polarization interferometry to probe supported lipid bilayers (SLBs) of different compositions allowed determination of accurate affinity constants and a layer structure of the peptide binding to the model membrane platform. In addition, the platform enabled us to monitor the detailed adsorption kinetics characterized by a strong initial electrostatic attraction of the peptide to the SLB surface followed by rearrangement and loss of possibly clustered peptides upon specific binding to the phosphoinositide headgroup. These kinetics differed substantially from adsorption kinetics for nonspecific binding to similarly charged control SLBs.