Assessment of nanoparticle immersion depth at liquid interfaces from chemically equivalent macroscopic surfaces.

HYPOTHESIS: We test whether the wettability of nanoparticles (NPs) straddling at an air/water surface or oil/water interface can be extrapolated from sessile drop-derived macroscopic contact angles (mCAs) on planar substrates, assuming that both the nanoparticles and the macroscopic substrates are chemically equivalent and feature the same electrokinetic potential. EXPERIMENTS: Pure silica (SiO2) and amino-terminated silica (APTES-SiO2) NPs are compared to macroscopic surfaces with extremely low roughness (root mean square [RMS] roughness ≤ 2 nm) or a roughness determined by a close-packed layer of NPs (RMS roughness âˆ¼ 35 nm). Equivalence of the surface chemistry is assessed by comparing the electrokinetic potentials of the NPs via electrophoretic light scattering and of the macroscopic substrates via streaming current analysis. The wettability of the macroscopic substrates is obtained from advancing (ACAs) and receding contact angles (RCAs) and in situ synchrotron X-ray reflectivity (XRR) provided by the NP wettability at the liquid interfaces. FINDINGS: Generally, the RCA on smooth surfaces provides a good estimate of NP wetting properties. However, mCAs alone cannot predict adsorption barriers that prevent NP segregation to the interface, as is the case with the pure SiO2 nanoparticles. This strategy greatly facilitates assessing the wetting properties of NPs for applications such as emulsion formulation, flotation, or water remediation.

Genipin-crosslinked chitosan/alginate/alumina nanocomposite gels for 3D bioprinting.

Immobilizing microorganisms inside 3D printed semi-permeable substrates can be desirable for biotechnological processes since it simplifies product separation and purification, reducing costs, and processing time. To this end, we developed a strategy for synthesizing a feedstock suitable for 3D bioprinting of mechanically rigid and insoluble materials with embedded living bacteria. The processing route is based on a highly particle-filled alumina/chitosan nanocomposite gel which is reinforced by (a) electrostatic interactions with alginate and (b) covalent binding between the chitosan molecules with the mild gelation agent genipin. To analyze network formation and material properties, we characterized the rheological properties and printability of the feedstock gel. Stability measurements showed that the genipin-crosslinked chitosan/alginate/alumina gels did not dissolve in PBS, NaOH, or HCl after 60 days of incubation. Alginate-containing gels also showed less swelling in water than gels without alginate. Furthermore, E. coli bacteria were embedded in the nanocomposites and we analyzed the influence of the individual bioink components as well as of the printing process on bacterial viability. Here, the addition of alginate was necessary to maintain the effective viability of the embedded bacteria, while samples without alginate showed no bacterial viability. The experimental results demonstrate the potential of this approach for producing macroscopic bioactive materials with complex 3D geometries as a platform for novel applications in bioprocessing.

Arsenic and sulfur nanoparticle synthesis mimicking environmental conditions of submarine shallow-water hydrothermal vents.

Arsenic and sulfur mineralization is a natural phenomenon occurring in hydrothermal systems where parameters like temperature and organic matter (OM) can influence the mobilization of the toxic metalloid in marine environments. In the present study we analyze the influence of temperature and OM (particularly sulfur-containing additives) on As and S precipitation based on the recent discovery of As-rich nanoparticles in the hydrothermal system near the coast of the Greek island Milos. To this end, we experimentally recreate the formation of amorphous colloidal particles rich in As and S via acidification (pH 3-4) of aqueous precursors at various temperatures. At higher temperatures, we observe the formation of monodisperse particles within the first 24 h of the experiment, generating colloidal particles with diameters close to 160 nm. The S:As ratio and particle size of the synthetized particles closely correlates with values for AsxSy particles detected in the hydrothermal system off Milos. Furthermore, organic sulfur containing additives (cysteine and glutathione, GSH) are a key factor in the process of nucleation and growth of amorphous colloidal AsxSy particles and, together with the temperature gradient present in shallow hydrothermal vents, dictate the stabilization of As-bearing nanomaterials in the environment. Based on these findings, we present a simple model that summarizes our new insights into the formation and mobility of colloidal As in aquatic ecosystems. In this context, amorphous AsxSy particles can present harmful effects to micro- and macro-biota not foreseen in bulk As material.

A versatile ceramic capillary membrane reactor system for continuous enzyme-catalyzed hydrolysis.

As an alternative to classical batch processes, enzyme-catalyzed hydrolysis can also be carried out continuously. To facilitate this, a continuous ceramic capillary membrane reactor system (CCCMRS) was developed which can be operated with various proteolytic enzymes immobilized on the porous ceramic capillary membranes. This system has several advantages over common batch processes regarding stability, reproducibility and controllability and can easily be adapted to optimal reaction conditions and individual preferences. Two exemplary applications utilizing the CCCMRS were carried out and investigated in long-term stability studies. In the first application the continuous enzymatic cleavage of human IgG into the antibody fragments Fab and Fc by immobilized papain was performed. A total volume of 22 mL of 1 mg mL-1 IgG-solution was enzymatically cleaved over a period of 33.3 h. The antibody cleavage products could be detected in an SEC-HPLC over the whole process time thus indicating long-term stability of the continuous hydrolysis process. The second application investigated the continuous digestion of pea and almond protein isolates by immobilized Alcalase resulting in the generation of a large variety of different peptides. This peptide fingerprint remains constant over a long period of time enabling fractionation and thus making the peptides accessible for further bioactivity studies in sufficient quantities. The constant peptide fingerprint could be shown in the RP-HPLC analysis for all 30 samples with a total volume of 29.7 mL collected over a period of 45 h.

Synergistic and Competitive Adsorption of Hydrophilic Nanoparticles and Oil-Soluble Surfactants at the Oil-Water Interface.

Fundamental insights into the interplay and self-assembly of nanoparticles and surface-active agents at the liquid-liquid interface play a pivotal role in understanding the ubiquitous colloidal systems present in our natural surroundings, including foods and aquatic life, and in the industry for emulsion stabilization, drug delivery, or enhanced oil recovery. Moreover, well-controlled model systems for mixed interfacial adsorption of nanoparticles and surfactants allow unprecedented insights into nonideal or contaminated particle-stabilized emulsions. Here, we investigate such a model system composed of hydrophilic, negatively, and positively charged silica nanoparticles and the oil-soluble cationic lipid octadecyl amine with in situ synchrotron-based X-ray reflectometry, which is analyzed and discussed jointly with dynamic interfacial tensiometry. Our results indicate that negatively charged silica nanoparticles only adsorb if the oil-water interface is covered with the positively charged lipid, indicating synergistic adsorption. Conversely, the positively charged nanoparticles readily adsorb on their own, but compete with octadecyl amine and reversibly desorb with increasing concentrations of the lipid. These results further indicate that with competitive adsorption, an electrostatic exclusion zone exists around the adsorbed particles. This prevents the adsorption of lipid molecules in this area, leading to a decreased surface excess concentration of surfactants and unexpectedly high interfacial tension.

Janus nanoparticles designed for extended cell surface attachment.

In this study, we present Janus nanoparticles that are designed for attaching to a eukaryotic cell surface with minimal cell uptake. This contrasts the rapid uptake via various endocytosis pathways that non-passivated isotropic particles usually encounter. Firmly attaching nanoparticles onto cell surfaces for extended periods of time can be a powerful new strategy to employ functional properties of nanoparticles for non-invasive interrogation and manipulation of biological systems. To this end, we synthesized rhodamine-doped silica (SiO2) nanoparticles functionalized with 1,2-distearoyl-sn-glycero-3-phosphoethanolamine (DSPE) on one hemisphere of the nanoparticle surface and high-molecular-weight long-chain poly(ethylene glycol) on the other one using the wax-Pickering emulsion technique. Nanoparticle localization was studied with NIH 3T3 rat fibroblasts in vitro. In these studies, the Janus nanoparticles adhered to the cell surface and, in contrast to isotropic control particles, only negligible uptake into the cells was observed, even after 24 h of incubation. In order to characterize the potential endocytosis pathway involved in the uptake of the Janus nanoparticles in more detail, fibroblasts and nanoparticles were incubated in the presence or absence of different endocytosis inhibitors. Our findings indicate that the Janus particles are not affected by caveolae- and receptor-mediated endocytosis and the prolonged attachment of the Janus nanoparticles is most likely the result of an incomplete macropinocytosis process. Consequently, by design, these Janus nanoparticles have the potential to firmly anchor onto cell surfaces for extended periods of time and might be utilized in various biotechnological and biomedical applications like cell surface tagging, magnetic manipulation of the cell membrane or non-invasive drug and gene delivery.

Wet-spinning of magneto-responsive helical chitosan microfibers.

Helical structures can be found in nature at various length scales ranging from the molecular level to the macroscale. Due to their ability to store mechanical energy and to optimize the accessible surface area, helical shapes contribute particularly to motion-driven processes and structural reinforcement. Due to these special features, helical fibers have become highly attractive for biotechnological and tissue engineering applications. However, there are only a few methods available for the production of biocompatible helical microfibers. Given that, we present here a simple technique for the fabrication of helical chitosan microfibers with embedded magnetic nanoparticles. Composite fibers were prepared by wet-spinning and coagulation in an ethanol bath. Thereby, no toxic components were introduced into the wet-spun chitosan fibers. After drying, the helical fibers had a diameter of approximately 130 µm. Scanning electron microscopy analysis of wet-spun helices revealed that the magnetic nanoparticles agglomerated into clusters inside the fiber matrix. The helical constructs exhibited a diameter of approximately 500 µm with one to two windings per millimeter. Due to their ferromagnetic properties they are easily attracted to a permanent magnet. The results from the tensile testing show that the helical chitosan microfibers exhibited an average Young's modulus of 14 MPa. By taking advantage of the magnetic properties of the feedstock solution, the production of the helical fibers could be automated. The fabrication of the helical fibers was achieved by utilizing the magnetic properties of the feedstock solution and winding the emerging fiber around a rotating magnetic collector needle upon coagulation. In summary, our helical chitosan microfibers are very attractive for future use in magnetic tissue engineering or for the development of biocompatible actuator systems.

Reversible Adsorption of Nanoparticles at Surfactant-Laden Liquid-Liquid Interfaces.

In this study, we show that hydrophilic nanoparticles can readily desorb from liquid-liquid interfaces in the presence of surfactants that do not change the wettability of the particles. Our observations are based on a simple theoretical approach to assess the number of adsorbed particles at the surfactant-laden liquid-liquid interface. We test this approach by studying the interfacial self-assembly of equally charged particles and lipids dissolved in separate immiscible phases. Hence, we investigate the interfacial adsorption of aminated silica particles (80 nm) and octadecylamine to the decane/water interface by interfacial tension measurements, which are supplemented by interfacial rheology of the adsorbed interfacial films, scanning electron microscopy images of Langmuir-Blodgett films, and measurements of the three-phase contact angle of the particle surface in the presence of surfactants. The measurements show that particles adsorb at the surfactant-laden interface at all investigated surfactant concentrations and compete with the surfactants for interfacial coverage. Additionally, the wettability of the hydrophilic particles does not change in the presence of the lipids, except for the highest investigated lipid concentration. Comparing the adsorption energies of one particle and of the lipids as a function of the particle contact angle provides an estimate of the tendency for interfacial adsorption of particles from which the particle coverage can be assessed. Based on these findings, equally charged particles and lipids show a competitive behavior at the interface determined by the bulk surfactant concentration and the attachment energies of the particles at the interface. This leads to a simple mechanistic model demonstrating that particles can readily desorb from the interface due to direct displacement by surfactants, which are loosely adsorbed at the oil-facing particle side. This mechanism critically lowers the otherwise high interfacial energy barrier against particle desorption, which otherwise would lead to virtually irreversible particle attachment at the interface.

Embedding live bacteria in porous hydrogel/ceramic nanocomposites for bioprocessing applications.

In this work, we present a biocompatible one-pot processing route for ceramic/hydrogel nanocomposites in which we embed live bacteria. In our approach, we fabricate a highly stable alginate hydrogel with minimal shrinkage, highly increased structural and mechanical stability, as well as excellent biocompatibility. The hydrogel was produced by ionotropic gelation and reinforced with alumina nanoparticles to form a porous 3D network. In these composite gels, the bacteria Escherichia coli and Bacillus subtilis were embedded. The immobilized bacteria showed high viability and similar metabolic activity as non-embedded cells. Even after repeated glucose consumption cycles, the material maintained high structural stability with stable metabolic activity of the immobilized bacteria. Storing the bionanocomposite for up to 60 days resulted in only minor loss of activity. Accordingly, this approach shows great potential for producing macroscopic bioactive materials for biotechnological processes.

Selective, Agglomerate-Free Separation of Bacteria Using Biofunctionalized, Magnetic Janus Nanoparticles.

This study presents a scalable method for designing magnetic Janus nanoparticles, which are capable of performing bacterial capture, while preventing agglomeration between bacterial cells. To this end, we prepared silica-coated magnetite Janus nanoparticles functionalized with a bacteria-specific antibody on one side and polyethylene glycol chains on the other, using the established wax-in-water emulsion strategy. These magnetic Janus nanoparticles specifically interact with one type of bacteria from a mixture of bacteria via specific antigen-antibody interactions. Contrarily to bacterial capture with isotropically functionalized particles, the bacterial suspensions remain free from cell-nanoparticle-cell agglomerates, owing to the passivation coating with polyethylene glycol chains attached to the half of the magnetic nanoparticles pointing away from the bacterial surface after capture. The selective magnetic capture of Escherichia coli cells was achieved from a mixture with Staphylococcus simulans without compromising bacterial viability and with an efficiency over 80%. This approach is a promising method for rapid and agglomeration-free separation of live bacteria for identification, enrichment, and cell counting of bacteria from biological samples.

Intracapillary immune complexes recruit and activate slan-expressing CD16+ monocytes in human lupus nephritis.

Lupus nephritis is a major cause of morbidity in patients with systemic lupus erythematosus. Among the different types of lupus nephritis, intracapillary immune complex (IC) deposition and accumulation of monocytes are hallmarks of lupus nephritis class III and IV. The relevance of intracapillary ICs in terms of monocyte recruitment and activation, as well as the nature and function of these monocytes are not well understood. For the early focal form of lupus nephritis (class III) we demonstrate a selective accumulation of the proinflammatory population of 6-sulfo LacNAc+ (slan) monocytes (slanMo), which locally expressed TNF-α. Immobilized ICs induced a direct recruitment of slanMo from the microcirculation via interaction with Fc γ receptor IIIA (CD16). Interestingly, intravenous immunoglobulins blocked CD16 and prevented cell recruitment. Engagement of immobilized ICs by slanMo induced the production of neutrophil-attracting chemokine CXCL2 as well as TNF-α, which in a forward feedback loop stimulated endothelial cells to produce the slanMo-recruiting chemokine CX3CL1 (fractalkine). In conclusion, we observed that expression of CD16 equips slanMo with a unique capacity to orchestrate early IC-induced inflammatory responses in glomeruli and identified slanMo as a pathogenic proinflammatory cell type in lupus nephritis.

Flow rate dependent continuous hydrolysis of protein isolates.

Food protein hydrolysates are often produced in unspecific industrial batch processes. The hydrolysates composition underlies process-related fluctuations and therefore the obtained peptide fingerprint and bioactive properties may vary. To overcome this obstacle and enable the production of specific hydrolysates with selected peptides, a ceramic capillary system was developed and characterized for the continuous production of a consistent peptide composition. Therefore, the protease Alcalase was immobilized on the surface of aminosilane modified yttria stabilized zirconia capillaries with a pore size of 1.5 µm. The loading capacity was 0.3 µg enzyme per mg of capillary with a residual enzyme activity of 43%. The enzyme specific peptide fingerprint produced with this proteolytic capillary reactor system correlated with the degree of hydrolysis, which can be controlled over the residence time by adjusting the flow rate. Common food proteins like casein, sunflower and lupin protein isolates were tested for continuous hydrolysis in the developed reactor system. The peptide formation was investigated by high-performance liquid chromatography. Various trends were found for the occurrence of specific peptides. Some are just intermediately occurring, while others cumulate by time. Thus, the developed continuous reactor system enables the production of specific peptides with desired bioactive properties.

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 Fe2+ ions in a long "activation" step before starting their oxidation to Fe3+. This leads to the formation of very dense and uniform iron oxide films, especially when H subunits are employed.

Borosilicate Glass Fiber-Optic Biosensor for the Detection of Escherichia coli.

Polyclonal antibodies against Escherichia coli and fluorescent, secondary, antibodies were immobilized on borosilicate glass fibers pre-treated with 3-glycidyloxypropyl trimethoxysilane (GPS). Light with an average wavelength of 627 nm, emitted by a diode placed at one end of the glass fiber, was detected by an ultrasensitive photodiode with peak sensitivity at 640 nm. Changes in fluorescence, caused by binding of E. coli to the antibodies, changed the net refractive index of the glass fiber and thus the internal reflection of light. These evanescent changes in photon energy were recorded by an ultrasensitive photodiode. Signals were amplified and changes in voltage recorded with a digital multimeter. A linear increase in voltage readings was recorded over 2 h when 3.0 × 107 CFU/ml and 2.77 × 109 CFU/ml E. coli were adhered to the antibodies. Voltage readings were recorded with E. coli cell numbers from 2 × 103 CFU/ml to 2 × 106 CFU/ml, but readings remained unchanged for 2 h, indicating that the limit of detection is 3.0 × 107 CFU/ml. This simple technology may be used to develop a low-cost, portable, fiber-optic biosensor to detect E. coli in infections and may have applications in the medical field. Research is in progress to optimize the sensitivity of the fiber-optic biosensor and determine its specificity.

Controlling the pro-inflammatory function of 6-sulfo LacNAc (slan) dendritic cells with dimethylfumarate.

BACKROUND: The fumaric acid ester (FAE) dimethylfumarate (DMF) is a small molecule immunomodulator successfully used for the treatment of psoriasis and multiple sclerosis (MS). DMF is thought to inhibit pathogenic immune responses with Th17/Th1T cells, and IL-23/IL-12 producing dendritic cells (DCs). 6-sulfo LacNAc expressing dendritic cells (slanDCs) are a human pro-inflammatory cell type found frequently among the infiltrating leukocytes in skin lesions of psoriasis and brain lesions of MS. OBJECTIVE: To explore the influence of DMF on functional properties and cell signaling pathways of slanDCs. METHODS: In the context of slanDCs we studied the role of DMF in modulating cell migration, phenotypic maturation, cytokine production, cell signaling and T cell stimulation. RESULTS: Initially, we observed the reduction of slanDCs numbers in psoriasis skin lesions of FAE treated patients. Studying whether DMF controls the migratory capacity of slanDCs to chemotactic factors expressed in psoriasis we observed an inhibition of the CX3CL1 and C5a depedent cell migration. DMF also attenuated the rapid spontaneous phenotypic maturation of slanDCs, as judged by a reduced CD80, CD86, CD83 and HLA-DR expression. In addition, we observed a DMF-dependent decrease of IL-23, IL-12, TNF-α and IL-10 secretion, and noticed a reduced capacity to stimulate Th17/Th1 responses. DMF targeted in slanDCs different intracellular cell signaling pathways including NFκB, STAT1 and HO-1. CONCLUSIONS: With this study we identify a frequent pro-inflammatory cell type found in psoriasis and MS as a relevant target for the therapeutic immunomodulatory effects of DMF.

Electrostatic assembly of zwitterionic and amphiphilic supraparticles.

We demonstrate the electrostatic assembly of oppositely charged silica particles into an ensemble of well-defined core-satellite supraparticles, which are a type of patchy particle. To achieve controlled heteroaggregation, we used oppositely charged silica particles with different sizes ranging from 5nm to 150nm at several concentrations. The assembly works best with larger particles, resulting in a fairly low polydispersity and a low amount of bridging between the individual clusters. Using smaller particles produces high polydispersity, large clusters and uncontrolled aggregation and bridging. Furthermore, even with controlled aggregation into well-defined clusters in the case of bigger particles, we observe an uneven covering of the central particles with around 1-6 satellite particles adsorbed to the central particle. This behavior is not predicted by simple pairwise DLVO potentials which would anticipate an even spacing of the satellite particles on the core. We explain these observations by taking into account the interactions of the adsorbing particles within the ionic cloud of the central particle. We hypothesize that when the adsorbing satellite particles are small compared to the diameter of the ion cloud of the core particle, they aggregate within the ion cloud and therefore do not create a well-defined monolayer on the surface of the core particle, instead forming small agglomerates during adsorption. Finally, both the assembled zwitterionic clusters and clusters that were partially hydrophobized were tested for their capabilities as Pickering emulsifiers. The zwitterionic clusters showed a strongly increased surface activity compared to the individual particles, while the hydrophobized particles changed the emulsion type from w/o to o/w. Interfacial dilatational rheological tests supported the observations from the emulsion tests. With this, we demonstrate that a relatively unordered ensemble of supraparticles is able to show well-defined functionality at a higher hierarchical level as Pickering emulsifiers.

Colloidal capsules: nano- and microcapsules with colloidal particle shells.

Utilizing colloidal particles for the assembly of the shell of nano- and microcapsules holds great promise for the tailor-made design of new functional materials. Increasing research efforts are devoted to the synthesis of such colloidal capsules, by which the integration of modular building blocks with distinct physical, chemical, or morphological characteristics in a capsule's shell can result in novel properties, not present in previous encapsulation structures. This review will provide a comprehensive overview of the synthesis strategies and the progress made so far of bringing nano- and microcapsules with shells of densely packed colloidal particles closer to application in fields such as chemical engineering, materials science, or pharmaceutical and life science. The synthesis routes are categorized into the four major themes for colloidal capsule formation, i.e. the Pickering-emulsion based formation of colloidal capsules, the colloidal particle deposition on (sacrificial) templates, the amphiphilicity driven self-assembly of nanoparticle vesicles from polymer-grafted colloids, and the closely related field of nanoparticle membrane-loading of liposomes and polymersomes. The varying fields of colloidal capsule research are then further categorized and discussed for micro- and nano-scaled structures. Finally, a special section is dedicated to colloidal capsules for biological applications, as a diverse range of reports from this field aim at pharmaceutical agent encapsulation, targeted drug-delivery, and theranostics.

Enhanced cell adhesion on bioinert ceramics mediated by the osteogenic cell membrane enzyme alkaline phosphatase.

Functional bone and dental implant materials are required to guide cell response, offering cues that provide specific instructions to cells at the implant/tissue interface while maintaining full biocompatibility as well as the desired structural requirements and functions. In this work we investigate the influence of covalently immobilized alkaline phosphatase (ALP), an enzyme involved in bone mineralization, on the first contact and initial cell adhesion. To this end, ALP is covalently immobilized by carbodiimide-mediated chemoligation on two highly bioinert ceramics, alpha-alumina (Al2O3) and yttria-stabilized zirconia (Y-TZP) that are well-established for load-bearing applications. The physicochemical surface properties are evaluated by profilometry, zeta potential and water contact angle measurements. The initial cell adhesion of human osteoblasts (HOBs), human osteoblast-like cells (MG-63) and mesenchymal stromal cells (hMSCs) was investigated. Cell adhesion was assessed at serum free condition via quantification of percentage of adherent cells, adhesion area and staining of the focal adhesion protein vinculin. Our findings show that after ALP immobilization, the Al2O3 and Y-TZP surfaces gained a negative charge and their hydrophilicity was increased. In the presence of surface-immobilized ALP, a higher cell adhesion, more pronounced cell spreading and a higher number of focal contact points were found. Thereby, this work gives evidence that surface functionalization with ALP can be utilized to modify inert materials for biological conversion and faster bone regeneration on inert and potentially load-bearing implant materials.

Carbon Nanomaterials as Antibacterial Colloids.

Carbon nanomaterials like graphene, carbon nanotubes, fullerenes and the various forms of diamond have attracted great attention for their vast potential regarding applications in electrical engineering and as biomaterials. The study of the antibacterial properties of carbon nanomaterials provides fundamental information on the possible toxicity and environmental impact of these materials. Furthermore, as a result of the increasing prevalence of resistant bacteria strains, the development of novel antibacterial materials is of great importance. This article reviews current research efforts on characterizing the antibacterial activity of carbon nanomaterials from the perspective of colloid and interface science. Building on these fundamental findings, recent functionalization strategies for enhancing the antibacterial effect of carbon nanomaterials are described. The review concludes with a comprehensive outlook that summarizes the most important discoveries and trends regarding antibacterial carbon nanomaterials.

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 in vitro. 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.