Sandro Carrara - Academia.edu (original) (raw)

Papers by Sandro Carrara

Remote system for monitoring animal models with single-metabolite bio-nano-sensors

ABSTRACT A novel system for remote monitoring of metabolism in an animal model is proposed in thi... more ABSTRACT A novel system for remote monitoring of metabolism in an animal model is proposed in this paper. The system is obtained by integrating bio-nano-sensors to detect single-metabolites, an electrochemical front-end made with off-the-shelf components, a radio frequency communication sub-system, and an antenna of new design. The system has been calibrated and tested for continuous monitoring of four different metabolites: glucose, lactate, glutamate, and adenosine triphosphate. Tests using animal models (mice) have been conducted to investigate tissue inflammation induced by the implanted bio-nano-sensors. These tests confirm that our system is suitable and reliable for remote monitoring of single-metabolites in experiments with animal models.

Empowering Low-Cost CMOS Cameras by Image Processing to Reach Comparable Results with Costly CCDs

BioNanoScience, 2013

ABSTRACT Despite the huge research effort to improve the performance of the complementary metal o... more ABSTRACT Despite the huge research effort to improve the performance of the complementary metal oxide semiconductor (CMOS) image sensors, charge-coupled devices (CCDs) still dominate the cell biology-related conventional fluorescence microscopic imaging market where low or ultra-low noise imaging is required. A detailed comparison of the sensor specifications and performance is usually not provided by the manufacturers which leads the end users not to go out of the habitude and choose a CCD camera instead of a CMOS one. However, depending on the application, CMOS cameras, when empowered by image processing algorithms, can become cost-efficient solutions for conventional fluorescence microscopy. In this paper, we introduce an application-based comparative study between the default CCD camera of an inverted microscope (Nikon Ti-S Eclipse) and a custom-designed CMOS camera and apply efficient image processing algorithms to improve the performance of CMOS cameras. Quantum micro-bead samples (emitting fluorescence light at different intensity levels), breast cancer diagnostic tissue cell samples, and Caco-2 cell samples are imaged by both CMOS and CCD cameras. The results are provided to show the reliability of CMOS camera processed images and finally to be of assistance when scientists select their cameras for desired applications.

Superior sensing performance of MWCNT-based electrodes to detect unconjugated bilirubin

Thin Solid Films

Microdevices dedicated to monitor metabolite levels have recently enabled many applications in th... more Microdevices dedicated to monitor metabolite levels have recently enabled many applications in the field of cell analysis, to monitor cell growth and development of numerous cell lines. By combining the traditional technology used for electrochemical biosensors with nanoscale materials, it is possible to develop miniaturized metabolite biosensors with unique properties of sensitivity and detection limit. In particular, enzymes tend to adsorb onto carbon nanotubes and their optical or electrical activity can perturb the electronic properties. In the present work we propose multi-walled carbon nanotube-based biosensors to monitor a cell line highly sensitive to metabolic alterations, in order to evaluate lactate production and glucose uptake during different cell states. We achieve sensors for both lactate and glucose, with sensitivities of 40.1 A mM −1 cm −2 and 27.7 A mM −1 cm −2 , and detection limits of 28 M and 73 M, respectively. This nano-biosensing technology is used to provide new information on cell line metabolism during proliferation and differentiation, which are unprecedented in cell biology.

Design, development, and validation of an in-situ biosensor array for metabolite monitoring of cell cultures

Biosensors and Bioelectronics, 2014

Conventional pharmaceutical processes involving cell culture growth are generally taken under con... more Conventional pharmaceutical processes involving cell culture growth are generally taken under control with expensive and long laboratory tests performed by direct sampling to evaluate quality. This traditional and well-established approach is just partially adequate in providing information about cell state. Electrochemical enzyme-based biosensors offer several advantages towards this application. In particular, they lend themselves to miniaturization and integration with cheap electronics. In the present work we go through the design, the development, and the validation of a self-contained device for the on-line measurement of metabolites in cell culture media. We microfabricated a sensing platform by using thin film technologies. We exploited electrodeposition to precisely immobilize carbon nanotubes and enzymes on miniaturized working electrodes. We designed and realized the electronics to perform the electrochemical measurements and an Android application to display the measurements on smartphones and tablets. In cell culture media glucose biosensor shows a sensitivity of 4.7 ± 1.3 nA mM(-1)mm(-2) and a detection limit of 1.4mM (S/N = 3σ), while for lactate biosensor the sensitivity is 12.2 ± 3.8 nA mM(-1)mm(-2) and the detection limit is 0.3mM. The whole system was then validated by monitoring U937 cell line over 88 h. Metabolic trends were fully congruent with cell density and viability. This self-contained device is a promising tool to provide more detailed information on cell metabolism that are unprecedented in cell biology.

Cytometry, 2001

Background: This study investigated the relationship between chromatin compactness, which is dire... more Background: This study investigated the relationship between chromatin compactness, which is directly related to chromatin condensation, and DAPI uptake. Materials and Methods: For the structural characterization of in situ chromatin, we used fluorescence microscopy and differential scanning calorimetry on calf thymocytes. The compactness of nuclear chromatin was altered by permeabilizing native cells with NP40 detergent. A time-dependent analysis of detergent effects was performed by acquiring nuclear images at different time intervals after permeabilization. In order to compare nuclei of different sizes, we implemented a geometrical correction in the calculation of the integrated fluorescence intensity. For a quantitative evaluation of chromatin condensation we introduced two new parameters, "average chromatin packing ratio" and "average dye spatial density."

Hybrid Nanostructures: Organic Interconnections and Device Applications

2006 1st International Conference on Nano-Networks and Workshops, 2006

Silicon technology is rapidly progressing toward device sizes in the range of 10 nm. The evolutio... more Silicon technology is rapidly progressing toward device sizes in the range of 10 nm. The evolution rate of silicon technology in next decades will require the use of new materials and processes to develop revolutionary CMOS devices. Organic nanostructures onto semiconductors or metals may provide interesting solutions to address the technological issues of nanoscale devices. In particular, technologies and devices based on organic nanostructures such as carbon nanotubes, semiconductor or metallic nanoparticles, DNA-templated nanowires may supply solutions for on-chip interconnections. The aim of this work is to present recent results on hybrid nanostructures based on gold nanoparticles stabilized by organic coating. Particular emphasis is devoted to the problem of the interconnections at the nanoscale. The resulting hybrid devices are suitable to develop single electron transistors and memories

2010 Biomedical Circuits and Systems Conference (BioCAS), 2010

Robust and reliable measurements in electrochemical biosensing of molecules are crucial for perso... more Robust and reliable measurements in electrochemical biosensing of molecules are crucial for personalized medicine. Electrochemical sensors based on cytochrome P450 can detect the large majority of drugs commonly used in pharmacological treatments. The same cytochrome can detect different substrates; each of them changes the electrochemical response of the enzyme in a specific manner. Our system exploits the measure of electrical potential to identify the drug type, while current measurements decode the drug concentration. Since potential and current are affected by pH and temperature, and since variations occur in the patient samples, we propose a novel design for multiplexing biosensing with pH and temperature control, which ensures more precise measurements for drugs identification and their quantification.

2011 12th International Symposium on Quality Electronic Design, 2011

This paper describes an electrochemical biosensor for molecules for personalized medicine includi... more This paper describes an electrochemical biosensor for molecules for personalized medicine including pH and temperature shift monitoring system. Electrochemical sensors based on the cytochromes P450 detect the large majority of drugs commonly used in pharmacological treatments. The same cytochrome detects different drugs at different electrochemical interface potentials. Therefore, the potential encodes the drug type meanwhile current encodes drug concentration. However, potential and current depend on pH variations that might occur in the patient sample. This paper presents evidence of these variations and proposes a novel design for multiplexing the biosensing with a new pH and temperature control system.

2010 IEEE Sensors, 2010

A novel single-chip and multiplexed read-out circuit for multi-electrode electrochemical sensors,... more A novel single-chip and multiplexed read-out circuit for multi-electrode electrochemical sensors, in standard 0.18 μm UMC CMOS technology, is presented. The circuit is a part of a fully-integrated biochip (in design) for the detection of multiple metabolites. The proposed topology is based on the potentiostat approach, and it is devoted to detect currents within the range of 250 pA -650 nA for an electrode active area of 0.25 mm 2 . The need of multi-metabolites monitoring asks for a system with multi-working electrodes. In the proposed configuration, switches select one working electrode at each clock phase, while the others are short-circuited to the reference one, in order to nullify the injected current inside the counter. Low noise and low energy topology (50μW at 1.5V of voltage supply) is employed for the control amplifier. The linearity of the proposed read-out circuit allows accuracy better than 0.1%.

Cytometry, 1996

Two common fixatives-glutaraldehyde and eth-anoYacetic acid mixture-were studied to understand th... more Two common fixatives-glutaraldehyde and eth-anoYacetic acid mixture-were studied to understand their effects on DNA distribution inside the cell nucleus. Native calf thymocytes were analyzed by using a DNA selective fluorescent dye (DAPI) and computational optical sectioning microscopy on isolated cells before and after Exation. In order to estimate quantitatively the intranuclear DNA distribution, the stained calf thymocytes images were processed by removing the out-of-focus contributions present in each optical section. Although preliminary, the results show that within individual nuclei the frequency distribution of the fluorescence intensity appears significantly and differentially altered by the two Exatives. Namely with re-spect to the native unfixed preparation, the ethanol/ acetic acid causes the complete disappearance of the higher intensity pixels, whereas glutaraldehyde fixation can be associated with the appearance of new ones of an even higher intensity. The quantitative analysis of the processed images allowed us to reconstruct the topological distribution of DNA inside the nucleus and to correlate the data with the results obtained by differential scanning calorimetry on similar samples. o 1996 Wiley-Liss, I~C .

Materials Letters, 2006

The fabrication of single electron transistors and/or highly sensitive biosensors is still a chal... more The fabrication of single electron transistors and/or highly sensitive biosensors is still a challenging task on account of the tight control required to get proper shapes and size of the electrodes. The nanosized tips and the separation of a few nanometers between electrode pairs are critical features. Conventional lithography is not suited to obtain these features because of the resolution limits, so that previous alternative approaches have involved the use of electron beam lithography, focused ion beam lithography or scanning probe nanolithography. The novel approach presented in this letter is the exploitation of X-ray lithography in the Elettra synchrotron to fabricate arrays of nanocontacts spaced a few nanometers, devoted to the design of a new class of nanodevices based on nanoparticles and/or single molecules, including single electron transistors and highly sensitive biosensors. The method to fabricate such devices is illustrated and discussed. Experimental details of the fabrication process are given and preliminary results are presented through SEM and AFM images. It is worth noting that this paper presents a viable method to produce nanocontacts by using the X-ray lithography by synchrotron radiation source, that has not yet been reported together with experimental, though preliminary, data.

Proceedings of 2010 IEEE International Symposium on Circuits and Systems, 2010

with gate-all-around (GAA) configuration and Si nanowire (SiNW) channel. Similar behavior has als... more with gate-all-around (GAA) configuration and Si nanowire (SiNW) channel. Similar behavior has also been investigated for SBFETs with poly-Si nanowire (poly-SiNW) channel in back-gate configuration. The memristive devices presented here have the potential of a very high integration density, and they are suitable for hybrid CMOS co-fabrication with a CMOS-compatible process. We show that 2 different regimes are possible, making these devices suitable either for volatile ambipolar memory or resistive random access memory (RRAM) applications. In addition, frequency-and amplitude-dependence of the memristive behavior are reported.

2009 3rd International Workshop on Advances in sensors and Interfaces, 2009

Label-free DNA detection is of crucial role to when developing point-of-care biochips to be used ... more Label-free DNA detection is of crucial role to when developing point-of-care biochips to be used in personalized therapy. Capacitance detection is a promising technology for label-free DNA detection. However, data published in literature often show evident time drift, large standard deviation, scattered data points, and poor reproducibility. To solve these problems, alkanethiol molecules such as mercapto-hexanol are usually considered as blocking agents. The aim of the present paper is to investigate new blocking agents to further improve DNA probe surfaces. Data from AFM, SPR, florescence microscopy, and capacitance measurements are used to demonstrate the new lipoates molecules. Moreover precursor layers obtained by using Ethylene-glycol alkanethiols offer further improvements in terms of diminished detection errors. Film structure is investigated at the nano-scale to justify the detection improvements in terms of probe surface quality. This study demonstrates the superiority of lipoate and Ethylene-glycol molecules as blocking candidates when immobilizing molecular probes onto spot surfaces in labelfree DNA biochip.

Microelectronics Journal, 2010

Label-free DNA detection plays a crucial role in developing point-of-care biochips. Capacitance d... more Label-free DNA detection plays a crucial role in developing point-of-care biochips. Capacitance detection is a promising technology for label-free detection. However, data published in literature often show evident time drift, large standard deviation, scattered data points, and poor reproducibility. To address these problems, mercapto-hexanol or similar alkanethiols are usually considered as blocking agents. The aim of the present paper is to investigate new blocking agents to further improve DNA probe surfaces. Data from AFM, SPR, florescence microscopy, and capacitance measurements are used to investigate new lipoate and ethylene-glycol molecules. The new surfaces offer further improvements in terms of diminished detection errors. Film structures are investigated at the nano-scale to justify the detection improvements in terms of probe surface quality. This study demonstrates the superiority of lipoate and ethylene-glycol molecules as blocking candidates when immobilizing molecular probes onto spot surfaces in label-free DNA biochip.

Superior sensing performance of multi-walled carbon nanotube-based electrodes to detect unconjugated bilirubin

Thin Solid Films, 2013

ABSTRACT The direct electrochemical behaviour of bilirubin in the physio-pathological concentrati... more ABSTRACT The direct electrochemical behaviour of bilirubin in the physio-pathological concentration range and at physiological pH was investigated by cyclic voltammetry. Nanostructured electrodes with a thin film of multi-walled carbon nanotubes exhibited a higher sensing performance than bare electrodes. The detection limit obtained with nanostructured electrodes (4.2 +/- 0.1 mu M) allows the detection of both normal and pathological levels of bilirubin. Due to its sparse solubility in aqueous solvents, in human fluids bilirubin is found in the form of soluble complex with albumin. Therefore, the nanostructured-sensor response was studied in presence of different concentrations of this protein. A signal weakening was observed with increasing concentrations of albumin due to the decrease of free bilirubin. Finally, bilirubin detection was tested at concentrations typical of newborn jaundice (200-500 mu M) and in the presence of normal albumin levels. A detection limit of 9.4 +/- 0.3 mu M was identified. Since this value is below the minimum critical bilirubin concentration for newborns, our sensor, modified with a thin film of carbon nanotubes, could potentially be used for bilirubin detection in cases of newborn jaundice.

Thin Solid Films, 2010

Sensing systems based on electrochemical detection have generated great interest because electron... more Sensing systems based on electrochemical detection have generated great interest because electronic readout may replace conventional optical readout in microarray. Moreover, they offer the possibility to avoid labelling for target molecules. A typical electrochemical array consists of many sensing sites. An ideal microfabricated sensor-chip should have the same measured values for all the equivalent sensing sites (or spots). To achieve high reliability in electrochemical measurements, high quality in functionalization of the electrodes surface is essential. Molecular probes are often immobilized by using alkanethiols onto gold electrodes. Applying effective cleaning methods on the chip is a fundamental requirement for the formation of densely-packed and stable self-assembly monolayers. However, the available well-known techniques for chip cleaning may not be so reliable. Furthermore, it could be necessary to recycle the chip for reuse. Also in this case, an effective recycling technique is required to re-obtain well cleaned sensing surfaces on the chip. This paper presents experimental results on the efficacy and efficiency of the available techniques for initial cleaning and further recycling of micro-fabricated chips. Piranha, plasma, reductive and oxidative cleaning methods were applied and the obtained results were critically compared. Some interesting results were attained by using commonly considered cleaning methodologies. This study outlines oxidative electrochemical cleaning and recycling as the more efficient cleaning procedure for electrochemical based sensor arrays.

Thin Solid Films, 2004

A nanocomposite of multi-walled carbon nanotubes (MWNTs) embedded in poly(ortho-anisidine) (POAS)... more A nanocomposite of multi-walled carbon nanotubes (MWNTs) embedded in poly(ortho-anisidine) (POAS) and pure POAS were synthesised by oxidative polymerisation. Langmuir -Schaefer (LS) films were fabricated at air -liquid interface. The in situ doping process was performed during the film deposition itself by spreading chloroform solutions of the materials onto 1 M HCl. The specific conductivity of both the nanocomposite (POAS-MWNTs) and pure POAS was investigated to verify the effective enhancement provided by the insertion of MWNTs inside the polymeric matrix. The morphology of POAS-MWNTs nanocomposite films was investigated by atomic force microscopy. Evident relationship between the film morphology and its conducting properties was revealed. D

Thin Solid Films, 1996

(LB) films of fatty acid salts of bivalent metals to an atmosphere of H2S allows to form in them ... more (LB) films of fatty acid salts of bivalent metals to an atmosphere of H2S allows to form in them small particles of metal sulphides, such as CdS, PbS, CuS etc. Different investigation techniques allow one to estimate the sizes of the particles to lie within the nanometer range. The particle sizes are suitable for the formation ofjunctions displaying monoelectron phenoinena. Thejunctions were formed using scanning tunnelling microscopy (STM) , which allowed to localise the particle position on the graphite substrate. Then voltage-current (V-I) characteristics were measured using graphite as the first electrode and the STM tip as the second one. The shape of the V-l characteristic curves revealed monoelectron phenomena in such junctions at room temperature. The specific electronic properties of the particles, such as the bandgap, turned out to be non-critical for the origin of the phenomena.

Thin Solid Films, 1997

Langmuir-Blodgett (LB) films of poly(ortho-anisidine) (POAS) have been fabricated at pH 1 of the ... more Langmuir-Blodgett (LB) films of poly(ortho-anisidine) (POAS) have been fabricated at pH 1 of the subphase, where the doping during the monolayer formation is essential for high quality of the ultrathin films. POAS LB films have been systematically characterized using low-angle X-ray diffraction, UV-Vis and VI'IR spectroscopic, current-voltage and capacitance-frequency measurements, respectively. The effect of annealing on the physical properties of POAS LB films has been studied as a function of temperature (from 60 to 150 °C). It has been shown that annealing causes changes in structural, optical and electrical characteristics of POAS LB films. The decrease in thickness (from 24 to 18.1 ,~) of each monolayer of POAS film has been observed for annealing at 150 °C. The value of conductivity of POAS LB film has been shown to be varying from 0.4 to 10 s S cm-i as a function of annealing temperature. The continuous shift of the UV absorption bands from 840 to 590 nm with annealing temperature is arising due to the simultaneous change of charge defects in POAS LB films. Differential scanning calorimetry studies show a complete evaporation of dopant ions occurring at 180 'C in the powder form of POAS, whereas complete removal of dopants ions for LB films have been observed for annealing at 150 °C. The Cole-Cole plot obtained at 80 °C for POAS LB film shows a mark deviation from a semicircle which indicates the operation of complex behaviour in the POAS LB films. It also shows the typical behaviour of interfacial polarization caused by the contact effect of POAS LB films with chromium metal of interdigited electrodes for annealing at 150 °C. © 1997 Elsevier Science S.A.