Micro and nano technology platforms: From cell viability monitoring to FET based biosensing

Nanotechnology is a multidisciplinary field that combines science and engineering to design, synthesize, characterize and explore applications for materials and devices whose smallest functional organization in at least one dimension is on the nanometer scale. Nanotechnology is undergoing an explosive development and the extent of potential application is vast and widely diverse. In the field of human health care, nanotechnology is helping to develop novel materials and structures, which have made it possible to miniaturize many of the tools used in conventional assays. Smart biochips constructed out of these novel materials and structures are now capable of performing limited in vitro diagnostic tests involved in immunoassays. In this work, we report two devices that make use of micro scale and/or nano scale structures to contribute to the ever-expanding use of biochips in human health care. The first device is a Patch-Clamp microchip that is capable of monitoring cell viability in real-time. It is critical to monitor the health of cells in biological life science and medical research. Researchers must know if a new drug is capable of killing cancer cells or in other cases to determine the toxic effects of a drug or a pesticide on healthy cells. Conventional cell viability monitoring techniques that use flow cytometer or fluorescent dyes in conjunction with fluorescence microscope are time consuming and require sample labeling. Alternatively, we have designed a patch-clamp microchip, which allows one to measure the ion-channel currents in real-time. This microchip provides a faster and label-free platform to monitor the health of the cell. Simultaneously, viability tests were performed on four different types of cancer cells (MB231, MB231-BR-vector, MB231-BR-HER 2, and MB231-BR) using the conventional fluorescent dye technique and using the patch-clamp microchip technique. For the patch-clamp technique, the seal resistance of the device decreased from ∼22 MΩ, (living cell) to ∼4 MΩ (dead cell) over a period of 120 minutes. Comparing the seal resistance to the intensity of the fluorescence images over the 120 minute period confirms a correlation between the health of the cell and the ion-channel current, validating our claim that the patch-clamp microchip can be used as an alternate technical platform to the conventional techniques that use fluorescent dyes or a flow cytometer. The second device is a Field-Effect Transistor (FET) based biosensor used for the detection of biomolecules. The conventional technique, ELISA, is still the gold standard for immunoassays. Most of the modern biosensors have exploited the semi conductive nature of CNT to design a label-free FET based immunosensor (biosensor that exclusively monitors the antibody-antigen interaction). Even though biosensors made out of a single CNT are ideally capable of detecting a single molecule, the fabrication of such devices is challenging. To avoid the fabrication complexity involved with a single CNT based immunosensor, we have developed an FET based biosensor, in which the channel is made out of Carbon Nanotube Thin Film (CNTF). The CNTF channel between the source and drain electrodes is assembled using electrostatic layer-by-layer (LBL) self-assembly. The bio-affinity interaction between Protein A and rabbit IgG is used to model the antibody-antigen interaction, and our initial results show the device is capable of detecting IgG concentrations as low as 1 pg/mL

All-carbon multi-electrode array for real-time in vitro measurements of oxidizable neurotransmitters

We report on the ion beam fabrication of all-carbon multi electrode arrays (MEAs) based on 16 graphitic micro-channels embedded in single-crystal diamond (SCD) substrates. The fabricated SCD-MEAs are systematically employed for the in vitro simultaneous amperometric detection of the secretory activity from populations of chromaffin cells, demonstrating a new sensing approach with respect to standard techniques. The biochemical stability and biocompatibility of the SCD-based device combined with the parallel recording of multi-electrodes array allow: i) a significant time saving in data collection during drug screening and/or pharmacological tests over a large number of cells, ii) the possibility of comparing altered cell functionality among cell populations, and iii) the repeatition of acquisition runs over many cycles with a fully non-toxic and chemically robust bio-sensitive substrate.Comment: 24 pages, 5 figure

Multifunctional nanostructures for intracellular delivery and sensing in electrogenic cells

In electrophysiology, multielectrode array devices (MEA) are the gold standard for the study of large ensambles of electrogenic cells. In the last decades, thanks to the adoption of nanotechnologies, the study of physiological and pathological conditions of electro-active cells in culture have becomes increasingly accurate. In parallel, studies exploited the integration of nanostructures with delivering capabilities with single-cell specificity and high throughput in biosensing platforms. Delivery and recording have independently led to great advances in neurobiology, however, their integration on a single chip would give complete insights into pathologies development and fundamental advancements in drug screening methods. In this work, we demonstrate how a microfluidic-MEA technology may be used to record both spontaneous and chemically induced activity in vitro. We propose a device that can deliver molecules to only a few chosen cells and detecting the response in cellular activity at multiple sites simultaneously. In addition, will be discussed how the adoption of nanoporous metamaterial in place of nanostructures might lower costs and speed up production. Furthermore, this same material, will be identified for the first time in this work as photoelectrical modulating material for eliciting electrogenic cells firing activity. Specifically, by converting NIR laser pulses into stimulatory currents, plasmonic metamaterials may be employed to induce action potentials. This method enables remote access to optical pacing with precise spatiotemporal control, allowing to be used as a valid alternative of the traditional genetic-based optical stimulation techniques. Therefore, in addition to pharmaceutical applications, these final characteristics may pave the way for a new generation of minimally invasive, cellular type-independent all-optical plasmonic pacemakers and muscle actuators

Multifunctional nanostructures for intracellular delivery and sensing in electrogenic cells

Biological studies on in vitro cell cultures are of fundamental importance for investigating cell response to external stimuli, such drugs for specific treatments, or for studying communication between cells. In the electrophysiology field, multielectrode array devices (MEA) are the gold standard for the study of large ensambles of electrogenic cells. Thus, their improvement is a central topic nowadays in neuroscience and cardiology [1]. In the last decades, thanks to the adoption of nanotechnologies, the study of physiological and pathological conditions of electro-active cells in culture have becomes increasingly accurate[2], allowing for monitoring action potentials from many cells simultaneously. In fact, nanoscale biomaterials were able to overcome the limitations of previous technologies, paving the way to the development of platforms for interfacing the electrogenic cells at unprecedented spatiotemporal scales. These devices, together with microfluidics, are starting to be used for drug screening and pharmaceutical drug development since they represent a powerful tool for monitoring cell response when cultures are stimulated by target compounds. Many pharmaceutical agents, however, including various large molecules (enzymes, proteins, antibodies) and even drug-loaded pharmaceutical nanocarriers, need to be delivered intracellularly to exercise their therapeutic action inside the cytoplasm[3]. Nanoscale electrodes offer individual cell access and non-destructive poration of the cellular membrane enabling high capability in the delivery of biomolecules. Among all the techniques, electroporation have proven encouraging potential as alternative to the carrier mediated methods for molecular delivery into cultured cells[4]. In this regard, different groups [5][6][7] exploited the integration of nanostructures with delivering capabilities with single-cell specificity and high throughput in biosensing platforms. These efforts provided powerful tools for advancing applications in therapeutics, diagnostics, and drug discovery, in order to reach an efficient and localized delivery on a chip. Despite these new tactics, there is still a critical need for the development of a functional approach that combines recording capabilities of nanostructured biosensors with intracellular delivery. The device should provide for tight contact between cells and electrode so as to enable highly localized delivery and optimal recording of action potentials in order to attain a high degree of prediction for the disease modeling and drug discovery. This \u201con-chip\u201d approach will help to gain deeper insight in several bio-related studies and analyses, providing a comprehensive knowledge of the entire cellular dynamics when selectively stimulated by the desired bio-molecules. In the first part of this dissertation, a solution will be proposed in order to fill this gap and respond to this need in the biology field. In the first chapter, I will describe briefly the principles of action potentials and how neurons and cardiomyocyte are composed, together with the development of electrophysiology and the advent of multielectrode arrays. In the second chapter, more details about fabrication and cell-electrode system modelling will be explained. In the same chapter, I will explore the development of multielectrode arrays up to the present days, along with the advent of nanotechnologies and the related techniques for improving the previous platforms. The different cell poration techniques will be described in order to reach the best recording capabilities without damaging cells. Electroporation, optoporation and spontaneous poration will be presented and the chosen technique for our application (electroporation) will be reviewed more in detail. In the third chapter, different methodologies for intracellular delivery will be explained, focusing also on the electroporation technique. A small paragraph about the integration of these techniques on chip will be inserted to illustrate the state of the art of these devices. The fourth chapter will explicate in details the Microfluidic multielectrode array idea, the approach used in order to fabricate this novel platform from scratch, the experiments carried out to verify its capabilities and the associated results. In the last paragraph, I will discuss how the proposed platform could became suitable for the day to day uses in research activity by employing nanoporous materials. In fact, big efforts are carried out in order to find appropriate metamaterials as substitutes of the 3D counterparts so as to decrease the cost of device manufacturing that makes them unfitting with research activity. As a novel electrode material, nanoporous metals possess unique properties, such as a low fabrication cost, high plasmonic enhancement and large surface-volume ratio[8]. Nanoporous gold behaves like a metamaterial whose effective dielectric response can be tuned accordingly to the wanted use. These properties make the material suitable for multiple biosensing application, from a high-performance and reliable SERS (surface enhanced raman scattering) substrate [9] to an electrode in CMOS MEAs capable of intracellular recordings[10]. All these properties were explored in the last years, but it could be interesting to further study if the characteristics of this material could make it a good photoelectrical modulating material for eliciting electrogenic cells firing activity. In this way, this technology could be in principle easily implemented on commercial CMOS devices, consenting stimulation and recording at single cell level with high-resolution sensors, opening the way to new methodologies for studying electrogenic cells and tissues. Electrical stimulation of excitable cells is the basis for many implantable devices in cardiac treatment and in neurological studies for treating debilitating neurological syndromes. In order to make the technique less invasive, optical stimulation was widely investigated [11]. The non-genetic photostimulation is starting to make its way in the field since it allows to avoid changing the biological framework by using transient thermal or electrochemical outputs from synthetic materials attached to the target cells[12]. If stimulated with impinging light these materials could inject free charges into the solution resulting in an ionic current at the interface able to eliciting of neurons[13] or cardiomyocyte action potentials. Plasmonic porous materials have all the suitable properties to be considered as an appealing tools for charge injection and consequently for stimulation of electrically active cells [14]. Thus, the second part of this dissertation will exploit the capabilities of these plasmonic metamaterials, placing particular emphasis on the possibility of photoelectrochemical modulation. In particular, in the fifth and last chapter I will describe all the properties and application of the porous material and the mechanism of photoemission. In the experimental paragraphs, the free charge photoemission properties of porous gold will be explored together with plasmonic non-genetic photostimulation of the cardiac cells on commercial CMOS MEAs

Development of a Novel Platform for in vitro Electrophysiological Recording

The accurate monitoring of cell electrical activity is of fundamental importance for pharmaceutical research and pre-clinical trials that impose to check the cardiotoxicity of all new drugs. Traditional methods for preclinical evaluation of drug cardiotoxicity exploit animal models, which tend to be expensive, low throughput, and exhibit species-specific differences in cardiac physiology (Mercola, Colas and Willems, 2013). Alternative approaches use heterologous expression of cardiac ion channels in non-cardiac cells transfected with genetic material. However, the use of these constructs and the inhibition of specific ionic currents alone is not predictive of cardiotoxicity. Drug toxicity evaluation based on the human ether-\ue0-go-go-related gene (hERG) channel, for example, leads to a high rate of false-positive cardiotoxic compounds, increasing drug attrition at the preclinical stage. Consequently, from 2013, the Comprehensive in Vitro Proarrhythmia Assay (CiPA) initiative focused on experimental methods that identify cardiotoxic drugs and to improve upon prior models that have largely used alterations in the hERG potassium ion channel. The most predictive models for drug cardiotoxicity must recapitulate the complex spatial distribution of the physiologically distinct myocytes of the intact adult human heart. However, intact human heart preparations are inherently too costly, difficult to maintain, and, hence, too low throughput to be implemented early in the drug development pipeline. For these reasons the optimization of methodologies to differentiate human induced Pluripotent Stem Cells (hiPSCs) into cardiomyocytes (CMs) enabled human CMs to be mass-produced in vitro for cardiovascular disease modeling and drug screening (Sharma, Wu and Wu, 2013). These hiPSC-CMs functionally express most of the ion channels and sarcomeric proteins found in adult human CMs and can spontaneously contract. Recent results from the CiPA initiative have confirmed that, if utilized appropriately, the hiPSC-CM platform can serve as a reliable alternative to existing hERG assays for evaluating arrhythmogenic compounds and can sensitively detect the action potential repolarization effects associated with ion channel\u2013blocking drugs (Millard et al., 2018). Data on drug-induced toxicity in hiPSC-CMs have already been successfully collected by using several functional readouts, such as field potential traces using multi-electrode array (MEA) technology (Clements, 2016), action potentials via voltage-sensitive dyes (VSD) (Blinova et al., 2017) and cellular impedance (Scott et al., 2014). Despite still under discussion, scientists reached a consensus on the value of using electrophysiological data from hiPSC-CM for predicting cardiotoxicity and how it\u2019s possible to further optimize hiPSC-CM-based in vitro assays for acute and chronic cardiotoxicity assessment. In line with CiPA, therefore, the use of hiPSC coupled with MEA technology has been selected as promising readout for these kind of experiments. These platforms are used as an experimental model for studying the cardiac Action Potentials (APs) dynamics and for understanding some fundamental principles about the APs propagation and synchronization in healthy heart tissue. MEA technology utilizes recordings from an array of electrodes embedded in the culture surface of a well. When cardiomyocytes are grown on these surfaces, spontaneous action potentials from a cluster of cardiomyocytes, the so called functional syncytium, can be detected as fluctuations in the extracellular field potential (FP). MEA measures the change in FP as the action potential propagates through the cell monolayer relative to the recording electrode, neverthless FP in the MEA do not allows to recapitualte properly the action potential features. It is clear, therefore, that a MEA technology itself is not enough to implement cardiotoxicity assays on hIPSCs-CMs. Under this issue, researchers spread in the world started to think about solutions to achieve a platform able to works both at the same time as a standard MEA and as a patch clamp, allowing the recording of extracellular signals as usual, with the opportunity to switch to intracellular-like signals from the cytosol. This strong interest stimulated the development of methods for intracellular recording of action potentials. Currently, the most promising results are represented by multi-electrode arrays (MEA) decorated with 3D nanostructures that were introduced in pioneering papers (Robinson et al., 2012; Xie et al., 2012), culminating with the recent work from the group of H. Park (Abbott et al., 2017) and of F. De Angelis (Dipalo et al., 2017). In these articles, they show intracellular recordings on electrodes refined with 3D nanopillars after electroporation and laser optoporation from different kind of cells. However, the requirement of 3D nanostructures set strong limitations to the practical spreading of these techniques. Thus, despite pioneering results have been obtained exploiting laser optoporation, these technologies neither been applied to practical cases nor reached the commercial phase. This PhD thesis introduces the concept of meta-electrodes coupled with laser optoporation for high quality intracellular signals from hiPSCs-CM. These signals can be recorded on high-density commercial CMOS-MEAs from 3Brain characterized by thousands of electrode covered by a thin film of porous Platinum without any rework of the devices, 3D nanostructures or circuitry for electroporation7. Subsequently, I attempted to translate these unique features of low invasiveness and reliability to other commercial MEA platforms, in order to develop a new tool for cardiac electrophysiological accurate recordings. The whole thesis is organized in three main sections: a first single chapters that will go deeper in the scientific and technological background, including an explanation of the cell biology of hiPSCs-CM followed by a full overview of MEA technology and devices. Then, I will move on state-of-the-art approaches of intracellular recording, discussing many works from the scientific literature. A second chapter will describe the main objectives of the whole work, and a last chapter with the main results of the activity. A final chapter will resume and recapitulate the conclusion of the work

Investigating computational properties of a neurorobotic closed loop system

This work arises as an attempt to increase and deepen the knowledge of the encoding method of the information by the nervous system. In particular, this study focuses on computational properties of neuronal cultures grown in vitro. Through a neuro-robotic close-loop system composed of either cortical or hippocampal cultures (plated on micro-electrode arrays) on one side and of a robot controlled by the cultures on the other side, it has been possible to analyze experimental dataopenEmbargo per motivi di segretezza e/o di proprietà dei risultati e/o informazioni sensibil

Organic electrochemical transistors based on PEDOT:PSS for the sensing of cellular signals from confluent cell layers down to single cells

Einleitung: Organisch elektrochemische Transistoren basierend auf dem Polymer poly(3,4- ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) sind Biosensoren, welche p-Typ Transistor Charakteristika zeigen basierend aus der Bewegung von Kationen in und aus der Polymerschicht. Die Sensorkonfiguration besteht aus drei Kontakten: der Source, dem Drain und der Gate-Elektrode, wobei die Polymerschicht durch einen Elektrolyten von der Gate-Elektrode getrennt ist. Die Kationen aus dem Elektrolyten werden durch die angelegte Spannung in das PEDOT:PSS geleitet, wo sie die offenen Sulfonat-Anionen des PSS kompensieren. Dies wiederum erhöht die Dichte der Löcher im PEDOT, was zu einem Abfall des Drain-Stroms führt. Dieser Stromabfall resultiert in der Ausschaltung des Sensors. Dieses Sensorverhalten kann für die unterschiedlichsten biologischen Messungen verwendet werden. Die OECTs können für die Detektion von elektrisch aktiven Zellen genutzt werden und erlauben gleichzeitig auch die Messung der Zelladhäsion. Die Nutzung dieser Sensoren für die Messung von Daten aus konfluenten Zellschichten bis zu Einzelzellmessungen in Kombination mit einer mathematischen Beschreibung der Ergebnisse wurde bisher noch nicht gezeigt. Ergebnisse: Um universal einsetzbare, hoch-sensitive und transparente Sensoren zu produzieren, wurden etablierte Reinraumprozesse in neuer und vereinfachter Weise genutzt. Faktoren die während der Sensorherstellung zu Schädigungen der Polymerschicht führen könnten, wie z.B. Ultraviolettstrahlung, wurden komplett eliminiert. Die Sensoren wurden bezüglich ihrer elektrischen Fähigkeiten und ihrer Stabilität in nassen sowie trockenen Umständen getestet. Das Testverfahren ermöglichte die Festsetzung der optimalen Parameter für die Herstellung der organisch elektrochemische Transistoren. Als wichtigster Faktor für das Sensorverhalten wurde das Volumen der Polymerschicht bestimmt. Das Volumen des PEDOT:PSS bestimmt die elektrischen Eigenschaften der Sensoren. Bleibt das Volumen der Polymerschicht für die Sensoren konstant, so wird die gleiche Transkonduktanz gemessen, eine Änderung in der Schichtdicke führt jedoch zu einem andern Verhalten bezüglich der Grenzfrequenz. Dünnere Schichten zeigen eine Erhöhung der Grenzfrequenz, wobei dickere Schichten einen gegenteiligen Effekt zeigen. Aus diesem Grund musste ein optimiertes Design erstellt werden, um die richtige Funktion der Sensoren für die geplanten Experimente zu gewährleisten. Unterschiedliche Zelltypen wurden genutzt, um ein breites Spektrum an Anwendungen für die fabrizierten Sensoren zu testen. Herzzellen wurden für die Messung von extrazellulären Aktionspotenzialen eingesetzt. Die getesteten Sensoren zeigten ein sehr gutes Signal-Rausch-Verhältnis mit schnellen Messzeiten, was sie zu idealen Sensoren für Aktionspotenzialmessungen macht. Zur selben Zeit wurden Transistor-Transferfunktionsmessungen durchgeführt, um die Fähigkeiten der Sensoren im Bereich der Impedanzmessungen zu ergründen. Diese Art von Messungen wurde bisher noch nicht publiziert. Durch die Verwendung von dicht wachsenden Madin-Darbey Kidney Zellen konnte die Änderung der Zellimpedanz durch Änderungen in den Zellverbindungen gemessen werden. Im Gegensatz zu den Madin-Darbey Kidney Zellen wachsen Human Embryo Kidney Zellen ohne Zellverbindungen. Da die Messung von dichten Zellkulturen nur Aussagen über die Population von Zellen als Ganzes erlaubt, wurden neue Protokolle entwickelt, um auf Einzelzelllevel zu messen. Die organisch elektrochemische Transistoren zeigten die Fähigkeit, Aktionspotenziale von Zellen sowie deren Adhäsion mit hoher Reproduzierbarkeit und Präzision zu messen. Organisch elektrochemische Transistoren, die die Transistor-Transferfunktion bis hinunter auf Einzelzellebene nutzen wurden bisher noch nicht gezeigt. Zusätzlich wurde ein mathematisches Modell entwickelt, um die Zellparameter aus den gewonnenen Daten zu ermitteln. Das mathematische Modell dient dabei der Verbesserung des Verständnisses bezüglich der Interaktion von Zellen und den Sensoren. Die Kombination aus den gezeigten Biosensoren mit optischer Transparenz und der Möglichkeit des mathematischen Fittens der Daten erlauben die Möglichkeit für unzählige Experimente. Ausblick: Die gezeigten Sensoren bieten eine exzellente Plattform für die Biosensorik mit der Möglichkeit für viele zukünftige Anwendungen. Die Sensoren sind dabei nicht auf die gezeigten Anwendungen limitiert, sondern können mit einfachen Mitteln für die unterschiedlichsten Zwecke angepasst werden.Summary: Organic electrochemical transistors based on the polymer poly(3,4- ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) are biosensors which use the movement of cations into and out of the polymer layer to generate a behavior that mimics p-type transistors. The device configuration has a source contact, a drain contact, and a gate electrode, which is separated from the polymer layer by an electrolyte. The cations of the electrolyte enter the PEDOT:PSS and compensate the pendant sulfonate anions on the PSS which increases the hole density in PEDOT. This results in a decrease of the drain current and a switching of the device into the off state. Using this device behavior, several biological signals can be detected. The OECTs can be used for the detection of action potentials of electrogenic cells, but also enable the measurement of the adhesion of cells to the device. The utilization of these devices for the measurement of confluent cell layers down to single cells in combination with a mathematical description was not shown so far. Results: In order to achieve versatile, highly sensitive, and transparent sensors, the fabrication of the devices with standard cleanroom processes was established in a unique and simplified way. Deteriorating factors such as exposure to ultraviolet radiation and contact with water were eliminated from the fabrication process. The sensors were characterized in regards to their electrical performance and stability in dry and wet conditions. The gathered results were used to generate a protocol for the best performing chips. Based on the generated data protocols for the fabrication, chemical post-treatment, as well as device operation, were established. Different sensing areas of the polymer layer were tested to determine their advantages for biosensing. The crucial factor for the devices was based on the volume of the deposited polymer layer. By keeping the volume of the PEDOT:PSS constant the transconductance remains the same, however thicker PEDOT:PSS layers resulted in devices with a comparatively lower cutoff frequency while thinner polymer layers resulted in a comparatively higher cutoff frequency. Therefore, an optimized chip layout had to be made to guarantee the functionality of the devices for their applications. Different cell types were used to test the devices towards their cell-sensing capabilities. Cardiomyocytes were used to establish the sensors for action potential measurements, and it was found that the sensors inherit a high signal-to-noise ratio making these devices ideal candidates for action potential measurements. At the same time, the impedimetric capabilities of the devices were investigated according to transistor-transfer function measurements which were not shown before with PEDOT:PSS based organic electrochemical transistors. By using densely growing cells, such as the Madin-Darby canine kidney cells, the change in impedance spectra towards changes in gap junction resistance could be proven. Human embryo kidney cells were used to investigate the behavior of dense cell cultures when no gap junctions are present. Since the observation of dense cellular cultures only allows for experiments on an arbitrary amount of cells, a protocol was established, and the devices were tested for measurements on a single cell level. The devices showed the capability for measurements of action potentials with the additional impedimetric data in high precision and reproducibility. Devices utilizing transistor-transfer function measurements with organic electrochemical transistors down to single cell level have not been shown so far. In addition, a new mathematical model was developed in order to calculate the cell-related parameters which demonstrate the distance between the cell and the polymer, offering a closer insight into the cellular attachment and detachment behavior. In combination with the fitting, the present platform was established with several possible applications ranging from confluent cells down to single cells while also offering the possibility of optically controlling the cell behavior due to the transparency of the devices. Outlook: The established devices offer an excellent biosensing platform which can be used in several future applications. The devices are not limited to the shown applications and can be altered to fit the desired use

Methods for immobilizing receptors in microfluidic devices: A review

In this review article, we discuss state-of-the-art methods for immobilizing functional receptors in microfluidic devices. Strategies used to immobilize receptors in such devices are essential for the development of specific, sensitive (bio)chemical assays that can be used for a wide range of applications. In the first section, we review the principles and the chemistry of immobilization techniques that are the most commonly used in microfluidics. We afterward describe immobilization methods on static surfaces from microchannel surfaces to electrode surfaces with a particular attention to opportunities offered by hydrogel surfaces. Finally, we discuss immobilization methods on mobile surfaces with an emphasis on both magnetic and non-magnetic microbeads, and finally, we highlight recent developments of new types of mobile supports

Development of experimental setups for the characterization of the mechanoelectrical coupling of cells in vitro

The field of mechanobiology emerged from the many evidences that mechanical forces acting on cells have a central role in their development and physiology. Cells, in fact, convert such forces into biochemical activities and gene expression in a process referred as mechanotransduction. In vitro models that mimic cell environment also from the mechanical point of view represent therefore a key tool for modelling cell behaviour and would find many applications, e.g. in drug development and tissue engineering. In this work I introduce novel tools for the study of mechanotransduction. In particular, I present a system for the evaluation of the complex response of electrically active cells, such as neurons and cardiomyocytes. This system integrates atomic force microscopy, extracellular electrophysiological recording, and optical microscopy in order to investigate cell activity in response to mechanical stimuli. I also present cell scaffolds for the in vitro study of cancer. Obtained results, although preliminary, show the potential of the proposed systems and methods to develop accurate in vitro models for mechanobiology studies