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In this work, we report the design and fabrication of a light-addressable, paper-based nanocomposite scaffold for optical pacing and read-out of in vitro grown cardiac tissue. The scaffold consists of paper cellulose microfibers functionalized with gold nanorods (GNRs) and semiconductor quantum dots (QDs), embedded in a cell-permissive collagen matrix. The GNRs enable cardiomyocyte activity modulation through local temperature gradients induced by modulated near-infrared (NIR) laser illumination, with the local temperature changes reported by temperature-dependent QD photoluminescence (PL). The micrometer-sized paper fibers promote the tubular organization of HL-1 cardiac muscle cells, while the NIR plasmonic stimulation modulates reversibly their activity. Given the nanoscale spatial resolution and facile fabrication, paper-based nanocomposite scaffolds with NIR modulation offer excellent alternatives to electrode-based or optogenetic methods for cell activity modulation, at the single cell level, and are compatible with 3D tissue constructs. Such paper-based optical platforms can provide new possibilities for the development of in vitro drug screening assays and heart disease modeling.

Studying brain diseases and developing therapies requires versatile in vitro systems for long-term neuronal cultures. SH-SY5Y neuroblastoma cells are ideal for modeling neurodegenerative diseases. Although SH-SY5Y cells are commonly used in 2D cultures, 3D systems offer more physiologically relevant models. Studies have shown 3D culturing up to 7 days, but a simple, reproducible, and tunable system has yet to be identified. Cellulose holds potential to fulfill these needs. Cellulose and its derivatives are sustainable, cytocompatible, and ideal for synthesizing biocompatible hydrogels. Its abundance and ease of chemical modification make it a highly attractive biomaterial. This study explored nanocellulose-based hydrogels for promoting neuronal growth and morphogenesis. To enhance cell adhesion, a small amount of collagen was added to the hydrogel, and the resulting cell morphologies were analyzed and compared with those cultured in collagen and Matrigel. By chemically oxidizing cellulose and adjusting the blend, we developed composites that maintained neuronal viability for over 14 days in 3D cultures. Our findings show that nanocellulose-collagen composites offer superior cytocompatibility, promoting neuronal viability and neurite outgrowth more effectively than Matrigel and collagen. These tunable biomaterials support long-term 3D neuronal cultures, making them valuable for creating standardized models for disease research and drug development., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Alkali and quaternary ammonium cations interact with negatively charged cellulose nanocrystals (CNCs) bearing sulfated or carboxylated functional groups. As these are some of the most commonly occurring cations CNC encounter in applications, the thermodynamic parameters of these CNC-counterion interactions were evaluated with isothermal titration calorimetry (ITC). Whereas the adsorption of monovalent counterions onto CNCs was thermodynamically favourable at all evaluated conditions as indicated by a negative Gibbs free energy, the enthalpic and entropic contributions to the CNC-ion interactions were found to be strongly dependent on the hydration characteristics of the counterion and could be correlated with the potential barrier to water exchange of the respective ions. The adsorption of chaotropic cations onto the surface was exothermic, while the interactions with kosmotropic cations were endothermic and completely entropy-driven. The interactions of CNCs with more bulky quaternary ammonium counterions were more complex, and the mechanism of interaction shifted from electrostatic interactions with surface charged groups of CNCs towards adsorption of alkyl chains onto the CNC hydrophobic planes when the alkyl chain length increased., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Different microscopy and scattering methods used in the literature to determine the dimensions of cellulose nanocrystals derived from cotton and bacterial cellulose were compared to investigate potential bias and discrepancies. Atomic force microscopy (AFM), small-angle X-ray scattering (SAXS), depolarized dynamic light scattering (DDLS), and static light scattering (SLS) were compared. The lengths, widths, and heights of the particles and their respective distributions were determined by AFM. In agreement with previous work, the CNCs were found to have a ribbon-like shape, regardless of the source of cellulose or the surface functional groups. Tip broadening and agglomeration of the particles during deposition cause AFM-derived lateral dimensions to be systematically larger those obtained from SAXS measurements. The radius of gyration determined by SLS showed a good correlation with the dimensions obtained by AFM. The hydrodynamic lateral dimensions determined by DDLS were found to have the same magnitude as either the width or height obtained from the other techniques; however, the precision of DDLS was limited due to the mismatch between the cylindrical model and the actual shape of the CNCs, and to constraints in the fitting procedure. Therefore, the combination of AFM and SAXS, or microscopy and small-angle scattering, is recommended for the most accurate determination of CNC dimensions.

The motion of self-propelling microswimmers is significantly affected by confinement, which can enhance or reduce their mobility and also steer the direction of their propulsion. While their interactions with solid boundaries have already received considerable attention, many aspects of the influence of liquid-liquid interfaces (LLI) on active particle propulsion still remain unexplored. In this work, we studied the adsorption and motion of bimetallic Janus sideways propelled rods dispersed at the interface between an aqueous solution of hydrogen peroxide and oil. The wetting properties of the bimetallic rods result in a wide distribution of their velocities at the LLI. While a fraction of rods remain immotile, we note a significant enhancement of motility for the rest of the particles with velocities of up to 8 times higher in comparison to those observed near a solid wall. Liquid-liquid interfaces, therefore, can provide a new way to regulate the propulsion of bimetallic particles.

Foreign body response (FBR), inflammation, and fibrotic encapsulation of neural implants remain major problems affecting the impedance of the electrode-tissue interface and altering the device performance. Adhesion of proteins and cells (e.g., pro-inflammatory macrophages, and fibroblasts) triggers the FBR cascade and can be diminished by applying antifouling coatings onto the implanted devices. In this paper, we report the deposition and characterization of a thin (±6 nm) sulfobetaine-based coating onto microfabricated platinum electrodes and cochlear implant (CI) electrode arrays. We found that this coating has stable cell and protein-repellent properties, for at least 31 days in vitro, not affected by electrical stimulation protocols. Additionally, its effect on the electrochemical properties relevant to stimulation (i.e., impedance, charge injection capacity) was negligible. When applied to clinical CI electrode arrays, the film was successful at inhibiting fibroblast adhesion on both the silicone packaging and the platinum/iridium electrodes. In vitro, in fibroblast cultures, coated CI electrode arrays maintained impedance values up to five times lower compared to non-coated devices. Our studies demonstrate that such thin sulfobetaine containing layers are stable and prevent protein and cell adhesion in vitro and are compatible for use on CI electrode arrays. Future in vivo studies should be conducted to investigate its ability to mitigate biofouling, fibrosis, and the resulting impedance changes upon long-term implantation in vivo., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Over recent years, nano-engineered materials have become an important component of artificial extracellular matrices. On one hand, these materials enable static enhancement of the bulk properties of cell scaffolds, for instance, they can alter mechanical properties or electrical conductivity, in order to better mimic the in vivo cell environment. Yet, many nanomaterials also exhibit dynamic, remotely tunable optical, electrical, magnetic, or acoustic properties, and therefore, can be used to non-invasively deliver localized, dynamic stimuli to cells cultured in artificial ECMs in three dimensions. Vice versa, the same, functional nanomaterials, can also report changing environmental conditions-whether or not, as a result of a dynamically applied stimulus-and as such provide means for wireless, long-term monitoring of the cell status inside the culture. In this review article, we present an overview of the technological advances regarding the incorporation of functional nanomaterials in artificial extracellular matrices, highlighting both passive and dynamically tunable nano-engineered components.

Disease research and drug screening platforms require in vitro model systems with cellular cues resembling those of natural tissues. Fibrillar alignment, occurring naturally in extracellular matrices, is one of the crucial attributes in tissue development. Obtaining fiber alignment in 3D, in vitro remains an important challenge due to non-linear material characteristics. Here, we report a cell-compatible, shear stress-based method allowing to obtain 3D homogeneously aligned fibrillar collagen hydrogels. Controlling the shear-stress during gelation results in low strain rates, with negligible effects on the viability of embedded SH-SY5Y cells. Our approach offers reproducibility and tunability through a paradigm shift: The shear-stress initiation moment, being the critical optimization parameter in the process, is related to the modulus of the developing gel, whereas state of the art methods often rely on a predefined time to initiate the alignment procedure. After curing, the induced 3D alignment is maintained after the release of stress, with a linear relation between the total acquired strain and the fiber alignment. This method is generally applicable to 3D fibrillar materials and stress/pressure-controlled setups, making it a valuable addition to the fast-growing field of tissue engineering. STATEMENT OF SIGNIFICANCE: Controlling fiber alignment in vitro 3D hydrogels is crucial for developing physiologically relevant model systems. However, it remains challenging due to the non-linear material characteristics of fibrillar hydrogels, limiting the scalability and repeatability. Our approach tackles these challenges by utilizing a stress-controlled rheometer allowing us to monitor structural changes in situ and determine the optimal moment for applying a shear-stress inducing alignment. By careful parameter control, we infer the relationship between time, induced strain, alignment and biocompatibility. This tunable and reproducible method is both scalable and generally applicable to any fibrillar hydrogel, therefore, we believe it is useful for research investigating the link between matrix anisotropy and cell behavior in 3D systems, organ-on-chip technologies and drug research., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

Despite the importance of cell characterization and identification for diagnostic and therapeutic applications, developing fast and label-free methods without (bio)-chemical markers or surface-engineered receptors remains challenging. Here, we exploit the natural cellular response to mild thermal stimuli and propose a label- and receptor-free method for fast and facile cell characterization. Cell suspensions in a dedicated sensor are exposed to a temperature gradient, which stimulates synchronized and spontaneous cell-detachment with sharply defined time-patterns, a phenomenon unknown from literature. These patterns depend on metabolic activity (controlled through temperature, nutrients, and drugs) and provide a library of cell-type-specific indicators, allowing to distinguish several yeast strains as well as cancer cells. Under specific conditions, synchronized glycolytic-type oscillations are observed during detachment of mammalian and yeast-cell ensembles, providing additional cell-specific signatures. These findings suggest potential applications for cell viability analysis and for assessing the collective response of cancer cells to drugs., (© 2022 The Authors. Advanced Science published by Wiley-VCH GmbH.)

Optical interrogation of cellular electrical activity has proven itself essential for understanding cellular function and communication in complex networks. Voltage-sensitive dyes are important tools for assessing excitability but these highly lipophilic sensors may affect cellular function. Label-free techniques offer a major advantage as they eliminate the need for these external probes. In this work, it is shown that endogenous second-harmonic generation (SHG) from live cells is highly sensitive to changes in transmembrane potential (TMP). Simultaneous electrophysiological control of a living human embryonic kidney (HEK293T) cell, through a whole-cell voltage-clamp reveals a linear relation between the SHG intensity and membrane voltage. The results suggest that due to the high ionic strengths and fast optical response of biofluids, membrane hydration is not the main contributor to the observed field sensitivity. A conceptual framework is further provided that indicates that the SHG voltage sensitivity reflects the electric field within the biological asymmetric lipid bilayer owing to a nonzero χ eff ( 2 ) tensor. Changing the TMP without surface modifications such as electrolyte screening offers high optical sensitivity to membrane voltage (≈40% per 100 mV), indicating the power of SHG for label-free read-out. These results hold promise for the design of a non-invasive label-free read-out tool for electrogenic cells., (© 2022 Wiley-VCH GmbH.)

Aggregation of amyloid β peptides is known to be one of the main processes responsible for Alzheimer's disease. The resulting dementia is believed to be due in part to the formation of potentially toxic oligomers. However, the study of such intermediates and the understanding of how they form are very challenging because they are heterogeneous and transient in nature. Unfortunately, few techniques can quantify, in real time, the proportion and the size of the different soluble species during the aggregation process. In a previous work (Deleanu et al . Anal. Chem. 2021, 93, 6523-6533), we showed the potential of Taylor dispersion analysis (TDA) in amyloid speciation during the aggregation process of Aβ (1-40) and Aβ (1-42). The current work aims at exploring in detail the aggregation of amyloid Aβ (1-40):Aβ (1-42) peptide mixtures with different proportions of each peptide (1:0, 3:1, 1:1, 1:3, and 0:1) using TDA and atomic force microscopy (AFM). TDA allowed for monitoring the kinetics of the amyloid assembly and quantifying the transient intermediates. Complementarily, AFM allowed the formation of insoluble fibrils to be visualized. Together, the two techniques enabled us to study the influence of the peptide ratios on the kinetics and the formation of potentially toxic oligomeric species.

Introduction: The inherent fluorescence properties of iron oxide nanoparticles (IONPs) were characterized, and their applicability for multiphoton imaging in cells was tested in combination with their magnetic resonance imaging (MRI) capabilities., Methods: Superparamagnetic iron oxide nanoparticles were synthesized and subsequently coated with polyethylene glycol to make them water-dispersible. Further characterization of the particles was performed using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), dynamic light scattering (DLS), superconducting quantum interference device (SQUID) and magnetic resonance relaxivity measurements. MRI and fluorescence properties of bare IONPs were first studied in solution and subsequently in A549-labeled cells., Results: The particles, with a core size of 11.3 ± 4.5 nm, showed a good negative MRI contrast in tissue-mimicking phantoms. In vitro studies in mammalian A549 cells demonstrate that these IONPs are biocompatible and can also produce significant T2/T2* contrast enhancement in IONPs-labeled cells. Furthermore, excitation-wavelength dependent photoluminescence was observed under one- and two-photon excitation., Discussion: The obtained results indicated that IONPs could be used for fluorescence label-free bioimaging at multiple wavelengths, which was proven by multiphoton imaging of IONPs internalization in A549 cancer cells., Competing Interests: The authors report no conflicts of interest in this work., (© 2021 Reynders et al.)

To overcome the problems of refractive index matching and increased disorder when working with traditional heterostructure colloidal photonic crystals (CPCs) with dual or multiple photonic bandgaps (PBGs) for fluorescence enhancement in water, we propose the use of a chemical heterostructure in hollow sphere CPCs (HSCPCs). A partial chemical modification of the HSCPC creates a large contrast in wettability to induce the heterostructure, while the hollow spheres increase the refractive index difference when used in aqueous environment. With the platform, fluorescence enhancement reaches around 160 times in solution, and 72 times (signal-to-background ratio ~7 times) in cells during proof-of-concept live cardiomyocyte contractility experiments. Such photonic platform can be further exploited for chemical sensing, bioassays, and environmental monitoring. Moreover, the introduction of chemical heterostructures provides new design principles for functionalized photonic devices., (Copyright © 2021 Elsevier B.V. All rights reserved.)

The application of antibodies in nanomedicine is now standard practice in research since it represents an innovative approach to deliver chemotherapy agents selectively to tumors. The variety of targets or markers that are overexpressed in different types of cancers results in a high demand for antibody conjugated-nanoparticles, which are versatile and easily customizable. Considering up-scaling, the synthesis of antibody-conjugated nanoparticles should be simple and highly reproducible. Here, we developed a facile coating strategy to produce antibody-conjugated nanoparticles using 'click chemistry' and further evaluated their selectivity towards cancer cells expressing different markers. Our approach was consistently repeated for the conjugation of antibodies against CD44 and EGFR, which are prominent cancer cell markers. The functionalized particles presented excellent cell specificity towards CD44 and EGFR overexpressing cells, respectively. Our results indicated that the developed coating method is reproducible, versatile, and non-toxic, and can be used for particle functionalization with different antibodies. This grafting strategy can be applied to a wide range of nanoparticles and will contribute to the development of future targeted drug delivery systems.

Flocculation is a widely used technology in industry including for wastewater treatment and microalgae harvesting. To increase the sustainability of wastewater treatment, and to avoid contamination of the harvested microalgal biomass, there is a need for bio-based flocculants to replace synthetic polymer flocculants or metal salt coagulants. We developed the first cellulose nanocrystalline flocculant with a grafted cationic point charge, i.e. glycine betaine ( i.e. N , N , N -trimethylglycine) grafted cellulose nanocrystals (CNCs) effective for the flocculation of kaolin (a model system for wastewater treatment), the freshwater microalgae Chlorella vulgaris , and the marine microalgae Nannochloropsis oculata . We successfully grafted glycine betaine onto CNCs using a one-pot reaction using a tosyl chloride activated esterification reaction with a degree of substitution ranging from 0.078 ± 0.003 to 0.152 ± 0.002. The degree of substitution is controlled by the reaction conditions. Flocculation of kaolin (0.5 g L -1 ) required a dose of 2 mg L -1 , a comparable dose to commercial polyacrylamide-based flocculants. Flocculation was also successful for freshwater as well as marine microalgae (biomass concentration about 300 mg L -1 dry matter), although the flocculation efficiency of the latter remained below 80%. The dose to induce flocculation (DS = 0.152 ± 0.002) was 20 mg L -1 for the freshwater Chlorella vulgaris and 46 mg L -1 for the marine Nannochloropsis oculata , comparable to other bio-based flocculants such as chitosan or TanFloc., Competing Interests: There are no conflicts of interest to declare., (This journal is © The Royal Society of Chemistry.)

Tailored hydrogels mimicking the native extracellular environment could help overcome the high variability in outcomes within regenerative endodontics. This study aimed to evaluate the effect of the chemokine-binding and antimicrobial polymer, chlorite-oxidized oxyamylose (COAM), on the microstructural properties of fibrin and self-assembling peptide (SAP) hydrogels. A further goal was to assess the influence of the microstructural differences between the hydrogels on the in vitro behavior of human dental pulp stem cells (hDPSCs). Structural and mechanical characterization of the hydrogels with and without COAM was performed by atomic force microscopy and scanning electron microscopy to characterize their microstructure (roughness and fiber length, diameter, straightness, and alignment) and by nanoindentation to measure their stiffness (elastic modulus). Then, hDPSCs were encapsulated in hydrogels with and without COAM. Cell viability and circularity were determined using confocal microscopy, and proliferation was determined using DNA quantification. Inclusion of COAM did not alter the microstructure of the fibrin hydrogels at the fiber level while affecting the SAP hydrogel microstructure (homogeneity), leading to fiber aggregation. The stiffness of the SAP hydrogels was sevenfold higher than the fibrin hydrogels. The viability and attachment of hDPSCs were significantly higher in fibrin hydrogels than in SAP hydrogels. The DNA content was significantly affected by the hydrogel type and the presence of COAM. The microstructural stability after COAM inclusion and the favorable hDPSCs' response observed in fibrin hydrogels suggest this system as a promising carrier for COAM and application in endodontic regeneration.

Understanding microbial adhesion and retention is crucial for controlling many processes, including biofilm formation, antimicrobial therapy as well as cell sorting and cell detection platforms. Cell detachment is inextricably linked to cell adhesion and retention and plays an important part in the mechanisms involved in these processes. Physico-chemical and biological forces play a crucial role in microbial adhesion interactions and altering the medium ionic strength offers a potential means for modulating these interactions. Real-time studies on the effect of ionic strength on microbial adhesion are often limited to short-term bacterial adhesion. Therefore, there is a need, not only for long-term bacterial adhesion studies, but also for similar studies focusing on eukaryotic microbes, such as yeast. Hereby, we monitored, in real-time, S. cerevisiae adhesion on gold and silica as examples of surfaces with different surface charge properties to disclose long-term adhesion, retention and detachment as a function of ionic strength using quartz crystal microbalance with dissipation monitoring. Our results show that short- and long-term cell adhesion levels in terms of mass-loading increase with increasing ionic strength, while cells dispersed in a medium of higher ionic strength experience longer retention and detachment times. The positive correlation between the cell zeta potential and ionic strength suggests that zeta potential plays a role on cell retention and detachment. These trends are similar for measurements on silica and gold, with shorter retention and detachment times for silica due to strong short-range repulsions originating from a high electron-donicity. Furthermore, the results are comparable with measurements in standard yeast culture medium, implying that the overall effect of ionic strength applies for cells in nutrient-rich and nutrient-deficient media., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Inc. All rights reserved.)

A simple and cost-effective method based on multi-photon microscopy is presented for the preliminary screening of the general morphology, size range and heterogeneity of Ir(iii) nano-aggregate formulations., Competing Interests: There are no conflicts of interest to declare., (This journal is © The Royal Society of Chemistry.)

Self-assembly of cellulose nanocrystals (CNCs) doped with anisotropic gold nanorods (AuNRs) was studied by small-angle neutron scattering. Correlation distances and structured domains were analysed to determine the influence of CNC and AuNR concentration on structuring. The transfer of the nematic structure of CNCs to AuNRs is explained in terms of an entropy-driven evolution from an isotropic to a cholesteric phase, with small nematic domains already present in the "isotropic" phase in equilibrium with the chiral nematic phase.

Poly(thiophene)s have an inherently large third-order nonlinear optical (TONO) response, but applications are not straightforward due to unoptimized materials. Therefore, several structure-property relationships (molar mass, branching, regioregularity) are investigated to unravel which structural modifications give the highest TONO response. Poly(3-hexylthiophene) with different molar masses, poly[3-(2-ethylhexyl)thiophene] with different molar masses, and random copolymers with different degrees of regioregularity are synthesized and measured by UV-vis spectroscopy and the third harmonic scattering technique. Every structural modification that leads to an increase in π-π interactions in poly(thiophene)s leads to an increase in the TONO response of the material. Therefore, a material with a high molar mass, an unbranched alkyl side chain, and a high regioregularity degree is preferably tested as a promising TONO material.

Hematopoietic stem/progenitor cells (HSPCs) are responsible for the generation of blood cells throughout life. It is believed that, in addition to soluble cytokines and niche cells, biophysical cues like elasticity and oxygen tension are responsible for the orchestration of stem cell fate. Although several studies have examined the effects of bone marrow (BM) niche elasticity on HSPC behavior, no study has yet investigated the effects of the elasticity of other niche sites like the fetal liver (FL), where HSPCs expand more extensively. In this study, we evaluated the effect of matrix stiffness values similar to those of the FL on BM-derived HSPC expansion. We first characterized the elastic modulus of murine FL tissue at embryonic day E14.5. Fibrin hydrogels with similar stiffness values as the FL (soft hydrogels) were compared with stiffer fibrin hydrogels (hard hydrogels) and with suspension culture. We evaluated the expansion of total nucleated cells (TNCs), Lin - /cKit + cells, HSPCs (Lin - /Sca + /cKit + (LSK) cells), and hematopoietic stem cells (HSCs: LSK- Signaling Lymphocyte Activated Molecule (LSK-SLAM) cells) when cultured in 5% O 2 (hypoxia) or in normoxia. After 10 days, there was a significant expansion of TNCs and LSK cells in all culture conditions at both levels of oxygen tension. LSK cells expanded more in suspension culture than in both fibrin hydrogels, whereas TNCs expanded more in suspension culture and in soft hydrogels than in hard hydrogels, particularly in normoxia. The number of LSK-SLAM cells was maintained in suspension culture and in the soft hydrogels but not in the hard hydrogels. Our results indicate that both suspension culture and fibrin hydrogels allow for the expansion of HSPCs and more differentiated progeny whereas stiff environments may compromise LSK-SLAM cell expansion. This suggests that further research using softer hydrogels with stiffness values closer to the FL niche is warranted.

Structured illumination microscopy (SIM) is a widely used super resolution imaging technique that can down-modulate a sample's high-frequency information into objective recordable frequencies to enhance the resolution below the diffraction limit. However, classical SIM image reconstruction methods often generate poor results under low illumination conditions, which are required for reducing photobleaching and phototoxicity in cell imaging experiments. Although denoising methods or auxiliary items improved SIM image reconstruction in low signal level situations, they still suffer from decreased reconstruction quality and significant background artifacts, inevitably limiting their practical applications. In order to improve the reconstruction quality, second-order optimized regularized SIM (sorSIM) is designed specifically for image reconstruction in low signal level situations. In sorSIM, a second-order regularization term is introduced to suppress noise effect, and the penalty factor in this term is selected to optimize the resolution enhancement and noise resistance. Compared to classical SIM image reconstruction algorithms as well as to those previously used in low illumination cases, the proposed sorSIM provides images with enhanced resolution and fewer background artifacts. Therefore, sorSIM can be a potential tool for high-quality and rapid super resolution imaging, especially for low signal images.

Cell-material interactions are crucial for many biomedical applications, including medical implants, tissue engineering, and biosensors. For implants, while the adhesion of eukaryotic host cells is desirable, bacterial adhesion often leads to infections. Surface free energy (SFE) is an important parameter that controls short- and long-term eukaryotic and prokaryotic cell adhesion. Understanding its effect at a fundamental level is essential for designing materials that minimize bacterial adhesion. Most cell adhesion studies for implants have focused on correlating surface wettability with mammalian cell adhesion and are restricted to short-term time scales. In this work, we used quartz crystal microbalance with dissipation monitoring (QCM-D) and electrical impedance analysis to characterize the adhesion and detachment of S. cerevisiae and E. coli , serving as model eukaryotic and prokaryotic cells within extended time scales. Measurements were performed on surfaces displaying different surface energies (Au, SiO 2 , and silanized SiO 2 ). Our results demonstrate that tuning the surface free energy of materials is a useful strategy for selectively promoting eukaryotic cell adhesion and preventing bacterial adhesion. Specifically, we show that under flow and steady-state conditions and within time scales up to ∼10 h, a high SFE, especially its polar component, enhances S. cerevisiae adhesion and hinders E. coli adhesion. In the long term, however, both cells tend to detach, but less detachment occurs on surfaces with a high dispersive SFE contribution. The conclusions on S. cerevisiae are also valid for a second eukaryotic cell type, being the human embryonic kidney (HEK) cells on which we performed the same analysis for comparison. Furthermore, each cell adhesion phase is associated with unique cytoskeletal viscoelastic states, which are cell-type-specific and surface free energy-dependent and provide insights into the underlying adhesion mechanisms.

Relative to the amount of knowledge concerning bacterial biofilms, little is known about the impact of physico-chemical properties of support material on fungal biofilm adhesion and physiology. In the field of industrial fermentation, large-scale production of low-cost fungal secondary product is a challenging area of research. In the present work, the effect of physico-chemical surface properties of five different materials (Teflon, glass, Viton™ rubber, silicon rubber, and stainless steel) on the production of class II hydrophobins (HFBI and HFBII) from Trichoderma reesei (HFB2a-2) and Trichoderma harzianum) was evaluated. Two culture systems (shake flask and drip flow reactor (DFR)) were used in this study to promote biomass growth and the production of hydrophobins. Furthermore, the effect of physico-chemical surface properties (hydrophobicity, surface energy) and surface texture (roughness) of support material on the initial colonization and attachment of the fungal biofilm was evaluated. Maximum biofilm productivity was obtained using Viton™ rubber for T. reesei and Viton™ rubber and stainless steel as support materials for T. harzianum. Scanning electron microscope (SEM) revealed that fungal biofilm adhesion was higher on the rough hydrophobic Viton rubber surface as compared to the smooth hydrophobic Teflon surface. Initial colonization initiated because of surface irregularities and holes in the material as hyphal filaments. Moreover, compared to traditional submerged fermentation, a significant increase in biofilm productivity for both strains (T. reesei, T. harzianum) in all five materials was obtained.

Gold nanoparticles (AuNPs) are regarded as promising building blocks in functional nanomaterials for sensing, drug delivery and catalysis. One remarkable property of these particles is the localized surface plasmon resonance (LSPR), which gives rise to augmented optical properties through local field enhancement. LSPR also influences the nonlinear optical properties of metal NPs (MNPs) making them potentially interesting candidates for fast, high resolution nonlinear optical imaging. In this work we characterize and discuss the wavelength dependence of the hyper-Rayleigh scattering (HRS) behavior of spherical gold nanoparticles (GNP) and gold nanorods (GNR) in solution, from 850 nm up to 1300 nm, covering the near-infrared (NIR) window relevant for deep tissue imaging. The high-resolution spectral data allows discriminating between HRS and two photon photoluminescence contributions. Upon particle aggregation, we measured very large enhancements (ca. 10 4 ) of the HRS intensity in the NIR, which is explained by considering aggregation-induced plasmon coupling effects and local field enhancement. These results indicate that purposely designed coupled nanostructures could prove advantageous for nonlinear optical imaging and biosensing applications., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We report on a novel biomimetic sensor that allows sensitive and specific detection of Escherichia coli (E. coli) bacteria in a broad concentration range from 10 2 up to 10 6  CFU/mL in both buffer fluids and relevant food samples (i.e. apple juice). The receptors are surface-imprinted polyurethane layers deposited on stainless-steel chips. Regarding the transducer principle, the sensor measures the increase in thermal resistance between the chip and the liquid due to the presence of bacteria captured on the receptor surface. The low noise level that enables the low detection limit originates from a planar meander element that serves as both a heater and a temperature sensor. Furthermore, the experiments show that the presence of bacteria in a liquid enhances the thermal conductivity of the liquid itself. Reference tests with a set of other representative species of Enterobacteriaceae, closely related to E. coli, indicate a very low cross-sensitivity with a sensor response at or below the noise level., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Building further upon the high spatial resolution offered by ultrasonic imaging and the high optical contrast yielded by laser excitation of photoacoustic imaging, and exploiting the temperature dependence of photoacoustic signal amplitudes, this paper addresses the question whether the rich information given by multispectral optoacoustic tomography (MSOT) allows to obtain 3D temperature images. Numerical simulations and experimental results are reported on agarose phantoms containing gold nanoparticles and the effects of shadowing, reconstruction flaws, etc. on the accuracy are determined.

Recent developments in nonlinear optical light scattering techniques have opened a window into morphological and structural characteristics for a variety of supramolecular systems. However, for the study of dynamic processes, the current way of measuring is often too slow. Here we present an alternative measurement scheme suitable for following dynamic processes. Fast acquisition times are achieved through Fourier imaging, allowing simultaneous detection at multiple scattering angles for different polarization combinations. This allows us to follow the crystal growth of the metal organic framework ZIF-8 in solution. The angle dependence of the signal provides insight into the growth mechanism by probing the evolution of size, shape and concentration, while polarization analysis yields structural information in terms of point group symmetry. Our findings highlight the potential of dynamic angle-resolved harmonic light scattering to probe crystal growth processes, assembly-disassembly of biological systems, adsorption, transport through membranes and myriad other applications.

Aluminum chlorohydrates (ACH) are used in numerous applications and commercial products on a global scale including water treatment, catalysis or antiperspirants. They are complex mixtures of water soluble aluminum polycations of different degrees of polymerization, that are difficult to separate and quantify due to their susceptibility to depolymerize in solution when placed out of equilibrium, which is inherent to any separation process. We recently achieved the first capillary electrophoresis separation and characterization of ACH oligomers using 4-morpholineethanesulfonic acid (MES) as background electrolyte counter-ion. MES stabilizes the separated ACH oligomers during the electrophoretic process leading to highly repeatable and fast separations. In this work, the separation of ACH oligomers was further studied and perfected by varying the ionic strength, MES concentration and pH of the background electrolyte. Complex electrophoretic behavior is reported for the separation of Al 13 , Al 30 and Na + ions according to these experimental parameters. The transformation of the electropherograms in effective mobility scale and the use of the slope-plot approach are used to better understand the observed changes in selectivity/resolution. Optimal conditions (700 mM MES at 25 mM ionic strength containing 0.1 mM didodecyldimethylammonium bromide for dynamic capillary coating, pH 4.8) obtained for the separation of ACH oligomers are used for the baseline separation of samples difficult to analyze with other methods, including different molecular, aggregated and colloidal forms of aluminum from the Al 13 , Al 30 and Na + mixture, validating the rationale of the approach., (Copyright © 2018. Published by Elsevier B.V.)

The stability of the Keggin polycation ε-Al 13 is monitored by 27 Al NMR and ferron colorimetric assay upon heating aluminum aqueous solutions containing different amino acids with overall positive, negative, or no charge at pH 4.2. A focus on the effect of the amino acids on the isomerization process from ε- to δ-Al 13 is made, compared and discussed as a function of the type of organic additive. Amino acids such as glycine and β-alanine, with only one functional group interacting relatively strongly with aluminum polycations, accelerate isomerization in a concentration-dependent manner. The effect of this class of amino acids is also found increasing with the pK a of their carboxylic acid moiety, from a low impact from proline up to more than a 15-fold increased rate from the stronger binders such as glycine or β-alanine. Amino acids with relatively low C-terminal pK a , but bearing additional potential binding moieties such as free alcohol (hydroxyl group) moiety of serine or the amide of glutamine, speed the isomerization comparatively and even more than glycine or β-alanine, glutamine leading to the fastest rates observed so far. With aspartic and glutamic acids, changes in aluminum speciation are faster and significant even at room temperature but rather related to the reorganization toward slow reacting complexed oligomers than to the Al 13 isomerization process. The linear relation between the apparent rate constant of isomerization and the additive concentration points to a first-order process with respect to the additives. Most likely, the dominant process is an accelerated ε-Al 13 dissociation, increasing the probability of δ isomer formation.

Objectives: Composites may undergo biodegradation in the oral cavity. The objective was to investigate the effect of single- and multi-species biofilms on the surface roughness and topography of two composites., Methods: Disk-shaped specimens of a paste-like, Bis-GMA-free (Gradia Direct Anterior, GC), and a flowable, Bis-GMA-based composite (Tetric EvoFlow, Ivoclar-Vivadent) were prepared. After ethylene-oxide sterilization (38°C), specimens (n=3) were incubated with Streptococcus mutans or mixed bacterial culture (Streptococcus mutans, Streptococcus sanguinis, Actinomyces naeslundii and Fusobacterium nucleatum). As negative controls, unexposed specimens and specimens exposed to sterile medium (BHI) were used. Specimens exposed to acidified BHI medium (pH=5) and enzymatic solution of cholesterol esterase served as positive control. Following 6-week incubation, the attached biofilms were collected for real-time PCR assessment, after which the surface roughness and topography of the specimens were analyzed with atomic force microscopy. Surface hydrophilicity/hydrophobicity was determined by contact angle measurements. Biofilm structure was analyzed with scanning electron microscopy., Results: Even though multi-species biofilms were thicker, with more cells attached, they did not significantly affect the surface roughness of the composites. On the other hand, S. mutans alone significantly increased the roughness of Tetric by 40.3%, while its effect on Gradia was lower (12%). The total amount of attached bacteria, however, did not differ between the composites., Conclusions: S. mutans can increase the surface roughness of composites, depending on their composition. This ability of S. mutans is, however, mitigated in co-culture with other species. In particular, bacterial esterases seem to be responsible for the increased composite surface roughness upon biofilms exposure., Clinical Significance: Cariogenic bacteria can degrade composites, thereby increasing the surface roughness. Increased roughness and subsequent improved bacterial accumulation may facilitate the development of secondary caries around composites, which is the most common reason for the restoration failure., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Hollow sphere colloidal photonic crystals (HSCPCs) exhibit the ability to maintain a high refractive index contrast after infiltration of water, leading to extremely high-quality photonic band gap effects, even in an aqueous (physiological) environment. Superhydrophilic pinning centers in a superhydrophobic environment can be used to strongly confine and concentrate water-soluble analytes. We report a strategy to realize real-time ultrasensitive fluorescence detection in patterned HSCPCs based on strongly enhanced fluorescence due to the photonic band-edge effect combined with wettability differentiation in the superhydrophobic/superhydrophilic pattern. The orthogonal nature of the two strategies allows for a multiplicative effect, resulting in an increase of two orders of magnitude in fluorescence.

Optical brain stimulation gained a lot of attention in neuroscience due to its superior cell-type specificity. In the design of illumination strategies, predicting the light propagation in a specific tissue is essential and requires knowledge of the optical properties of that tissue. We present the estimated absorption and reduced scattering in rodent brain tissue using non-destructive contact spatially resolved spectroscopy (cSRS). The obtained absorption and scattering in the cortex, hippocampus and striatum are similar, but lower than in the thalamus, leading to a less deep but broader light penetration profile in the thalamus. Next, the light distribution was investigated for different stimulation protocols relevant for fiber-optic based optogenetic experiments, using Monte Carlo simulation. A protocol specific analysis is proposed to evaluate the potential of thermally induced side effects., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Small soluble species of amyloid-beta (Aβ) formed during early peptide aggregation stages are responsible for several neurotoxic mechanisms relevant to the pathology of Alzheimer's disease (AD), although their interaction with the neuronal membrane is not completely understood. This study quantifies the changes in the neuronal membrane elasticity induced by treatment with the two most common Aβ isoforms found in AD brains: Aβ40 and Aβ42. Using quantitative atomic force microscopy (AFM), we measured for the first time the static elastic modulus of living primary hippocampal neurons treated with pre-aggregated Aβ40 and Aβ42 soluble species. Our AFM results demonstrate changes in the elasticity of young, mature and aged neurons treated for a short time with the two Aβ species pre-aggregated for 2 hours. Neurons aging under stress conditions, showing aging hallmarks, are the most susceptible to amyloid binding and show the largest decrease in membrane stiffness upon Aβ treatment. Membrane stiffness defines the way in which cells respond to mechanical forces in their environment and has been shown to be important for processes such as gene expression, ion-channel gating and neurotransmitter vesicle transport. Thus, one can expect that changes in neuronal membrane elasticity might directly induce functional changes related to neurodegeneration.

Gold nanoparticles functionalized with polyethylene glycol of different chain lengths are used to determine the influence of the capping layer thickness on the radiosensitizing effect of the particles. The size variations in organic coating, built up with polyethylene glycol polymers of molecular weight 1-20 kDa, allow an evaluation of the decrease in dose enhancement percentages caused by the gold nanoparticles at different radial distances from their surface. With localized eradication of malignant cells as a primary focus, radiosensitization is most effective after internalization in the nucleus. For this reason, we performed controlled radiation experiments, with doses up to 20 Gy and particle diameters in a range of 5-30 nm, and studied the relaxation pattern of supercoiled DNA. Subsequent gel electrophoresis of the suspensions was performed to evaluate the molecular damage and consecutively quantify the gold nanoparticle sensitization. In conclusion, on average up to 58.4% of the radiosensitizing efficiency was lost when the radial dimensions of the functionalizing layer were increased from 4.1 to 15.3 nm. These results serve as an experimental supplement for biophysical simulations and demonstrate the influence of an important parameter in the development of nanomaterials for targeted therapies in cancer radiotherapy.

Nanoparticles of different materials are already in use for many applications. In some applications, these nanoparticles need to be deposited on a substrate in a fast and reproducible way. We have developed a new direct liquid injection system for nanoparticle deposition by chemical vapor deposition using a liquid nanoparticle precursor. The system was designed to deposit nanoparticles in a controlled and reproducible way by using two direct liquid injectors to deliver nanoparticles to the system. The nanoparticle solution is first evaporated and then the nanoparticles flow onto a substrate inside the vacuum chamber. To allow injection and evaporation of the liquid, a direct liquid injection and vaporization system are mounted on top of the process chamber. The deposition of the nanoparticles is controlled by parameters such as deposition temperature, partial pressure of the gases, and flow rate of the nanoparticle suspension. The concentration of the deposited nanoparticles can be varied simply by changing the flow rate and deposition time. We demonstrate the capabilities of this system using gold nanoparticles. The selected suspension flow rates were varied between 0.25 and 1 g/min. AFM analysis of the deposited samples showed that the aggregation of gold nanoparticles is well controlled by the flow and deposition parameters.

Selective perturbation of the activity of specific cell types in the brain tissue is essential in understanding the function of neuronal circuits involved in cognition and behavior and might also provide therapeutic neuromodulation strategies. Such selective neuronal addressing can be achieved through the optical activation of light-sensitive proteins called opsins that are expressed in specific cell populations through genetic methods-hence the name "optogenetics." In optogenetic experiments, the electrical activity of the targeted cell populations is optically triggered and monitored using arrays of microelectrodes. In closed-loop studies, the optical stimulation parameters are adjusted based on the recorded activity, ideally in real time. Here we describe the basic tools and the protocols allowing closed-loop optogenic experiments in vivo.

Several questions about the role of the oxygen sensor prolyl-hydroxylase 2 (PHD2) in cancer have not been addressed. First, the role of PHD2 in metastasis has not been studied in a spontaneous tumor model. Here, we show that global PHD2 haplodeficiency reduced metastasis without affecting tumor growth. Second, it is unknown whether PHD2 regulates cancer by affecting cancer-associated fibroblasts (CAFs). We show that PHD2 haplodeficiency reduced metastasis via two mechanisms: (1) by decreasing CAF activation, matrix production, and contraction by CAFs, an effect that surprisingly relied on PHD2 deletion in cancer cells, but not in CAFs; and (2) by improving tumor vessel normalization. Third, the effect of concomitant PHD2 inhibition in malignant and stromal cells (mimicking PHD2 inhibitor treatment) is unknown. We show that global PHD2 haplodeficiency, induced not only before but also after tumor onset, impaired metastasis. These findings warrant investigation of PHD2's therapeutic potential., (Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.)

The photoluminescence (PL) of colloidal quantum dots (QDs) is known to be sensitive to the solution pH. In this work we investigate the role played by the organic coating in determining the pH-dependent PL. We compare two types of CdSe/ZnS QDs equipped with different organic coatings, namely dihydrolipoic acid (DHLA)-capped QDs and phospholipid micelle-encapsulated QDs. Both QD types have their PL intensity quenched at acidic pH values, but they differ in terms of the reversibility of the quenching process. For DHLA-capped QDs, the quenching is nearly irreversible, with a small reversible component visible only on short time scales. For phospholipid micelle-encapsulated QDs the quenching is notably almost fully reversible. We suggest that the surface passivation by the organic ligands is reversible for the micelle-encapsulated QDs. Additionally, both coatings display pH-dependent spectral shifts. These shifts can be explained by a combination of irreversible processes, such as photo-oxidation and acid etching, and reversible charging of the QD surface, leading to the quantum-confined Stark effect (QCSE), the extent of each effect being coating-dependent. At high ionic strengths, the aggregation of QDs also leads to a spectral (red) shift, which is attributable to the QCSE and/or electronic energy transfer.

Missense mutations in alanine 673 of the amyloid precursor protein (APP), which corresponds to the second alanine of the amyloid β (Aβ) sequence, have dramatic impact on the risk for Alzheimer disease; A2V is causative, and A2T is protective. Assuming a crucial role of amyloid-Aβ in neurodegeneration, we hypothesized that both A2V and A2T mutations cause distinct changes in Aβ properties that may at least partially explain these completely different phenotypes. Using human APP-overexpressing primary neurons, we observed significantly decreased Aβ production in the A2T mutant along with an enhanced Aβ generation in the A2V mutant confirming earlier data from non-neuronal cell lines. More importantly, thioflavin T fluorescence assays revealed that the mutations, while having little effect on Aβ42 peptide aggregation, dramatically change the properties of the Aβ40 pool with A2V accelerating and A2T delaying aggregation of the Aβ peptides. In line with the kinetic data, Aβ A2T demonstrated an increase in the solubility at equilibrium, an effect that was also observed in all mixtures of the A2T mutant with the wild type Aβ40. We propose that in addition to the reduced β-secretase cleavage of APP, the impaired propensity to aggregate may be part of the protective effect conferred by A2T substitution. The interpretation of the protective effect of this mutation is thus much more complicated than proposed previously., (© 2014 by The American Society for Biochemistry and Molecular Biology, Inc.)

Objective: Closed-loop operation of neuro-electronic systems is desirable for both scientific and clinical (neuroprosthesis) applications. Integrating optical stimulation with recording capability further enhances the selectivity of neural stimulation. We have developed a system enabling the local delivery of optical stimuli and the simultaneous electrical measuring of the neural activities in a closed-loop approach., Approach: The signal analysis is performed online through the implementation of a template matching algorithm. The system performance is demonstrated with the recorded data and in awake rats., Main Results: Specifically, the neural activities are simultaneously recorded, detected, classified online (through spike sorting) from 32 channels, and used to trigger a light emitting diode light source using generated TTL signals., Significance: A total processing time of 8 ms is achieved, suitable for optogenetic studies of brain mechanisms online.

The immobilization of proteins on flat substrates plays an important role for a wide spectrum of applications in the fields of biology, medicine, and biochemistry, among others. An essential prerequisite for the use of proteins (e.g., in biosensors) is the conservation of their biological activity. Losses in activity upon protein immobilization can largely be attributed to a random attachment of the proteins to the surface. In this study, we present an approach for the immobilization of proteins onto a chemically heterogeneous surface, namely a surface consisting of protein-permissive and protein-repellent areas, which allows for significant reduction of random protein attachment. As protein-permissive, i.e., as protein-binding sites, ultra pure metallic nanoparticles are deposited under vacuum onto a protein-repellent PEG-silane polymer layer. Using complementary surface characterization techniques (atomic force microscopy, quartz crystal microbalance, and X-ray photoelectron spectroscopy) we demonstrate that the Au nanoparticles remain accessible for protein attachment without compromising the protein-repellency of the PEG-silane background. Moreover, we show that the amount of immobilized protein can be controlled by tuning the Au nanoparticle coverage. This method shows potential for applications requiring the control of protein immobilization down to the single molecule level.

Guidance of neuronal extensions is a complex process essential for linking neurons into complex functional networks underlying the workings of the neural system. Decades of research have suggested the ability of neuronal growth cones to integrate multiple types of cues during the extension process, but also have raised numerous still unanswered questions about synergy or antagonism between the superimposed chemical and mechanical signaling inputs. In this study, using a novel microfabricated analysis platform, we investigate the response of primary mouse embryonic hippocampal neurons to superimposed topographic and soluble chemical cues. We find that an optimal spatial frequency of topographic cues exists, maximizing the precision of the neurite extension. This optimal frequency can help the extending neurites navigate a topographically complex environment, providing pronounced directional selectivity. We also demonstrate that this cue can synergistically enhance attractive and suppress repulsive guidance by the bi-functional soluble cue Netrin-1, and eliminate the repulsive guidance by a chemorepellent Semaphorin3A (Sema3A). These results suggest that topographic cues can provide optimal periodic input into the guidance signaling processes involved in growth cone chemoattraction and can synergistically interact with chemical gradients of soluble guidance cues, shedding light on complex events accompanying the development of the functional nervous system.

The establishment of neuronal connectivity depends on the correct initial polarization of the young neurons. In vivo, developing neurons sense a multitude of inputs and a great number of molecules are described that affect their outgrowth. In vitro, many studies have shown the possibility to influence neuronal morphology and growth by biophysical, i.e. topographic, signaling. In this work we have taken this approach one step further and investigated the impact of substrate topography in the very early differentiation stages of developing neurons, i.e. when the cell is still at the round stage and when the first neurite is forming. For this purpose we fabricated micron sized pillar structures with highly reproducible feature sizes, and analyzed neurons on the interface of flat and topographic surfaces. We found that topographic signaling was able to attract the polarization markers of mouse embryonic neurons -N-cadherin, Golgi-centrosome complex and the first bud were oriented towards topographic stimuli. Consecutively, the axon was also preferentially extending along the pillars. These events seemed to occur regardless of pillar dimensions in the range we examined. However, we found differences in neurite length that depended on pillar dimensions. This study is one of the first to describe in detail the very early response of hippocampal neurons to topographic stimuli.

Simultaneous electrical stimulation and recording are used to gain insights into the function of neuronal circuitry. However, artifacts produced by the electrical stimulation pulses prevent the recording of neural responses during, and a short period after, the stimulation duration. In this work, we describe a mixed-signal recording topology with template subtraction for removing the artifact during the stimulation pulse. Emulated artifacts generated from a lumped electrical circuit model and experimental artifacts in cardiac cell cultures are used to evaluate the topology. The simulations show that delays between the emulated artifact and its estimated compensation template represent the largest error source of the analog template subtraction. The quantization error appears like random noise and determines the threshold level for the action potential detection. Simulations show that removal of the artifacts is possible, allowing the detection of action potentials during the stimulation pulsing period, even for high-amplitude saturating artifacts. Measurement results with artifacts elicited in cardiac cell cultures show feasible applications of this topology. The proposed topology therefore promisingly opens up a previously unavailable detection window for improving the analysis of the neuronal activity.

Embryonic cells are very robust in surviving dissection and culturing protocols and easily adapt to their in vitro environment. Despite these advantages, research in the olfactory field on cultured embryonic olfactory neurons is sparse. In this study, two primary rat olfactory explant cultures of different embryonic d (E17 and E20) were established, comprising epithelium and bulb. The functionality of these neurons was tested by measuring intracellular calcium responses to cAMP-inducing agents forskolin (FSK) and 3-isobutyl-1-methylxanthine (IBMX) with fluorescence microscopy. For E17, the responsive cell fraction increased over time, from an initial 3% at the 1 d in vitro (DIV) to a maximum of 19% at 11 DIV. The response of E20 neurons fluctuated over time around a more or less stable 13%. A logistic regression analysis indicated a significant difference between both embryonic d in the response to FSK + IBMX. In addition, of these functional neurons, 23.3% of E17 and 54.3% of E20 cultures were responsive to the odorant isoamyl acetate.

The reliable integration of carbon nanotube (CNT) electrodes in future neural probes requires a proper embedding of the CNTs to prevent damage and toxic contamination during fabrication and also to preserve their mechanical integrity during implantation. Here we describe a novel bottom-up embedding approach where the CNT microelectrodes are encased in SiO(2) and Parylene C with lithographically defined electrode openings. Vertically aligned CNTs are grown on microelectrode arrays using low-temperature plasma-enhanced chemical vapor deposition compatible with wafer-scale CMOS processing. Electrodes with 5, 10, and 25 μm diameter are realized. The CNT electrodes are characterized by electrochemical impedance spectroscopy and cyclic voltammetry and compared against cofabricated Pt and TiN electrodes. The superior performance of the CNTs in terms of impedance (≤4.8 ± 0.3 kΩ at 1 kHz) and charge-storage capacity (≥513.9 ± 61.6 mC/cm(2)) is attributed to an increased wettability caused by the removal of the SiO(2) embedding in buffered hydrofluoric acid. Infrared spectroscopy reveals an unaltered chemical fingerprint of the CNTs after fabrication. Impedance monitoring during biphasic current pulsing with increasing amplitudes provides clear evidence of the onset of gas evolution at CNT electrodes. Stimulation is accordingly considered safe for charge densities ≤40.7 mC/cm(2). In addition, prolonged stimulation with 5000 biphasic current pulses at 8.1, 40.7, and 81.5 mC/cm(2) increases the CNT electrode impedance at 1 kHz only by 5.5, 1.2, and 12.1%, respectively. Finally, insertion of CNT electrodes with and without embedding into rat brains demonstrates that embedded CNTs are mechanically more stable than non-embedded CNTs.

To cope with the growing needs in research towards the understanding of cellular function and network dynamics, advanced micro-electrode arrays (MEAs) based on integrated complementary metal oxide semiconductor (CMOS) circuits have been increasingly reported. Although such arrays contain a large number of sensors for recording and/or stimulation, the size of the electrodes on these chips are often larger than a typical mammalian cell. Therefore, true single-cell recording and stimulation remains challenging. Single-cell resolution can be obtained by decreasing the size of the electrodes, which inherently increases the characteristic impedance and noise. Here, we present an array of 16,384 active sensors monolithically integrated on chip, realized in 0.18 μm CMOS technology for recording and stimulation of individual cells. Successful recording of electrical activity of cardiac cells with the chip, validated with intracellular whole-cell patch clamp recordings are presented, illustrating single-cell readout capability. Further, by applying a single-electrode stimulation protocol, we could pace individual cardiac cells, demonstrating single-cell addressability. This novel electrode array could help pave the way towards solving complex interactions of mammalian cellular networks., (This journal is © The Royal Society of Chemistry 2012)

Since a few decades, micro-fabricated neural probes are being used, together with microelectronic interfaces, to get more insight in the activity of neuronal networks. The need for higher temporal and spatial recording resolutions imposes new challenges on the design of integrated neural interfaces with respect to power consumption, data handling and versatility. In this paper, we present an integrated acquisition system for in vitro and in vivo recording of neural activity. The ASIC consists of 16 low-noise, fully-differential input channels with independent programmability of its amplification (from 100 to 6000 V/V) and filtering (1-6000 Hz range) capabilities. Each channel is AC-coupled and implements a fourth-order band-pass filter in order to steeply attenuate out-of-band noise and DC input offsets. The system achieves an input-referred noise density of 37 nV/√Hz, a NEF of 5.1, a CMRR > 60 dB, a THD < 1% and a sampling rate of 30 kS/s per channel, while consuming a maximum of 70 μA per channel from a single 3.3 V. The ASIC was implemented in a 0.35 μm CMOS technology and has a total area of 5.6 × 4.5 mm². The recording system was successfully validated in in vitro and in vivo experiments, achieving simultaneous multichannel recordings of cell activity with satisfactory signal-to-noise ratios.

The signal-to-noise ratio of in vivo extracellular neural recordings with microelectrodes is influenced by many factors including the impedance of the electrode-tissue interface, the noise of the recording equipment and biological background noise from distant neurons. In this work we study the different noise sources affecting the quality of neural signals. We propose a simplified noise model as an analytical tool to predict the noise of an electrode given its geometrical dimensions and impedance characteristics. With this tool we are able to quantify different noise sources, which is important to determine realistic noise specifications for the design of electronic neural recording interfaces.