Publications by authors named "Ester Segal"

52 Publications

Highly-Tunable Polymer/Carbon Nanotubes Systems: Preserving Dispersion Architecture in Solid Composites via Rapid Microfiltration.

ACS Macro Lett 2012 Jul 19;1(7):848-852. Epub 2012 Jun 19.

Elbit Systems Electro-Optics-Elop Ltd., Advanced Technology Park, Rehovot 76111, Israel.

This research presents a new fabrication method for tailoring polymer/carbon nanotube (CNT) nanostructures with controlled architecture and composition. The CNTs are finely dispersed in polymeric latex, that is, polyacrylate, via ultrasonication, followed by a microfiltration process. The latter step allows preserving the homogeneous dispersion structure in the resulting solid nanocomposite. The combination of microfiltration and proper choice of the polymer latex, particle size, and composition allows the design of complex nanostructures with tunable properties, for example, porosity and mechanical properties. An important attribute of this methodology is the ability to tailor any desired composition of polymer-CNT systems, that is, nanotube content can practically vary anywhere between 0 to 100 wt %. Thus, for the first time, a given polymer/CNT system is studied over the entire CNTs composition, resembling two-phase polymer blends. The polyacrylate in these systems exhibits a structural transition from a continuous matrix (nanocomposite) to segregated domains dispersed within a porous CNTs network. An analogy of this structural transition to phase inversion phenomena in two-phase polymer blends is suggested. The resulting polyacrylate/CNT layers exhibit a percolation threshold as low as 0.04 wt %. Additionally, these nanomaterials show low total reflectance values throughout the visible, NIR and SWIR spectrum at a CNT content as low as 1 wt %, demonstrating their potential applicability for optical devices.
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http://dx.doi.org/10.1021/mz300145aDOI Listing
July 2012

Aptasensors versus immunosensors-Which will prevail?

Eng Life Sci 2022 Mar 13;22(3-4):319-333. Epub 2022 Jan 13.

Faculty of Biotechnology and Food Engineering Technion - Israel Institute of Technology Haifa Israel.

Since the invention of the first biosensors 70 years ago, they have turned into valuable and versatile tools for various applications, ranging from disease diagnosis to environmental monitoring. Traditionally, antibodies have been employed as the capture probes in most biosensors, owing to their innate ability to bind their target with high affinity and specificity, and are still considered as the gold standard. Yet, the resulting immunosensors often suffer from considerable limitations, which are mainly ascribed to the antibody size, conjugation chemistry, stability, and costs. Over the past decade, aptamers have emerged as promising alternative capture probes presenting some advantages over existing constraints of immunosensors, as well as new biosensing concepts. Herein, we review the employment of antibodies and aptamers as capture probes in biosensing platforms, addressing the main aspects of biosensor design and mechanism. We also aim to compare both capture probe classes from theoretical and experimental perspectives. Yet, we highlight that such comparisons are not straightforward, and these two families of capture probes should not be necessarily perceived as competing but rather as complementary. We, thus, elaborate on their combined use in hybrid biosensing schemes benefiting from the advantages of each biorecognition element.
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http://dx.doi.org/10.1002/elsc.202100148DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8961048PMC
March 2022

Paving the Way to Overcome Antifungal Drug Resistance: Current Practices and Novel Developments for Rapid and Reliable Antifungal Susceptibility Testing.

Small Methods 2021 11 23;5(11):e2100713. Epub 2021 Sep 23.

Department of Biotechnology and Food Engineering, Technion-Israel Institute of Technology, Haifa, 320003, Israel.

The past year has established the link between the COVID-19 pandemic and the global spread of severe fungal infections; thus, underscoring the critical need for rapid and realizable fungal disease diagnostics. While in recent years, health authorities, such as the Centers for Disease Control and Prevention, have reported the alarming emergence and spread of drug-resistant pathogenic fungi and warned against the devastating consequences, progress in the diagnosis and treatment of fungal infections is limited. Early diagnosis and patient-tailored therapy are established to be key in reducing morbidity and mortality associated with fungal (and cofungal) infections. As such, antifungal susceptibility testing (AFST) is crucial in revealing susceptibility or resistance of these pathogens and initiating correct antifungal therapy. Today, gold standard AFST methods require several days for completion, and thus this much delayed time for answer limits their clinical application. This review focuses on the advancements made in developing novel AFST techniques and discusses their implications in the context of the practiced clinical workflow. The aim of this work is to highlight the advantages and drawbacks of currently available methods and identify the main gaps hindering their progress toward clinical application.
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http://dx.doi.org/10.1002/smtd.202100713DOI Listing
November 2021

Design considerations of aptasensors for continuous monitoring of biomarkers in digestive tract fluids.

Talanta 2022 Mar 4;239:123124. Epub 2021 Dec 4.

Faculty of Biotechnology and Food Engineering, Technion- Israel Institute of Technology, Haifa, 3200003, Israel. Electronic address:

We present a porous Si (PSi)-based label-free optical biosensor for sensitive and continuous detection of a model target protein biomarker in gastrointestinal (GI) tract fluids. The biosensing platform is designed to continuously monitor its target protein within the complex GI fluids without sample preparation and washing steps. An oxidized PSi Fabry-Pérot thin films are functionalized with aptamers, which are used as the capture probes. The optical response of the aptamer-conjugated PSi is studied upon exposure to unprocessed GI fluids, originated from domestic pigs, spiked with the target protein. We investigate biological and chemical surface passivation methods to stabilize the surface and reduce non-specific adsorption of interfering proteins and molecules within the GI fluids. For the passivated PSi aptasensor we simulate continuous in vivo biosensing conditions, demonstrating that the aptasensor could successfully detect the target in a continuous manner without any need for surface washing after the target protein binding events, at a clinically relevant range. Furthermore, we simulate biosensing conditions within a smart capsule, in which the aptasensor is occasionally exposed to GI fluids in flow or via repeated cycles of injection and static incubation events. Such biosensor can be implemented within ingestible capsule devices and used for in situ biomarker detection in the GI tract.
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http://dx.doi.org/10.1016/j.talanta.2021.123124DOI Listing
March 2022

Porous Silicon-Based Aptasensors: Toward Cancer Protein Biomarker Detection.

ACS Meas Sci Au 2021 Oct 25;1(2):82-94. Epub 2021 Aug 25.

Department of Biotechnology and Food Engineering, Technion-Israel Institute of Technology, Haifa 3200003, Israel.

The anterior gradient homologue-2 (AGR2) protein is an attractive biomarker for various types of cancer. In pancreatic cancer, it is secreted to the pancreatic juice by premalignant lesions, which would be an ideal stage for diagnosis. Thus, designing assays for the sensitive detection of AGR2 would be highly valuable for the potential early diagnosis of pancreatic and other types of cancer. Herein, we present a biosensor for label-free AGR2 detection and investigate approaches for enhancing the aptasensor sensitivity by accelerating the target mass transfer rate and reducing the system noise. The biosensor is based on a nanostructured porous silicon thin film that is decorated with anti-AGR2 aptamers, where real-time monitoring of the reflectance changes enables the detection and quantification of AGR2, as well as the study of the diffusion and target-aptamer binding kinetics. The aptasensor is highly selective for AGR2 and can detect the protein in simulated pancreatic juice, where its concentration is outnumbered by orders of magnitude by numerous proteins. The aptasensor's analytical performance is characterized with a linear detection range of 0.05-2 mg mL, an apparent dissociation constant of 21 ± 1 μM, and a limit of detection of 9.2 μg mL (0.2 μM), which is attributed to mass transfer limitations. To improve the latter, we applied different strategies to increase the diffusion flux to and within the nanostructure, such as the application of isotachophoresis for the preconcentration of AGR2 on the aptasensor, mixing, or integration with microchannels. By combining these approaches with a new signal processing technique that employs Morlet wavelet filtering and phase analysis, we achieve a limit of detection of 15 nM without compromising the biosensor's selectivity and specificity.
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http://dx.doi.org/10.1021/acsmeasuresciau.1c00019DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8532149PMC
October 2021

Morlet Wavelet Filtering and Phase Analysis to Reduce the Limit of Detection for Thin Film Optical Biosensors.

ACS Sens 2021 08 13;6(8):2967-2978. Epub 2021 Aug 13.

Department of Electrical Engineering and Computer Science, Vanderbilt University, Nashville, Tennessee 37235, United States.

The ultimate detection limit of optical biosensors is often limited by various noise sources, including those introduced by the optical measurement setup. While sophisticated modifications to instrumentation may reduce noise, a simpler approach that can benefit all sensor platforms is the application of signal processing to minimize the deleterious effects of noise. In this work, we show that applying complex Morlet wavelet convolution to Fabry-Pérot interference fringes characteristic of thin film reflectometric biosensors effectively filters out white noise and low-frequency reflectance variations. Subsequent calculation of the average difference in extracted phase between the filtered analyte and reference signals enables a significant reduction in the limit of detection (LOD). This method is applied on experimental data sets of thin film porous silicon sensors (PSi) in buffered solution and complex media obtained from two different laboratories. The demonstrated improvement in the LOD achieved using wavelet convolution and average phase difference paves the way for PSi optical biosensors to operate with clinically relevant detection limits for medical diagnostics, environmental monitoring, and food safety.
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http://dx.doi.org/10.1021/acssensors.1c00787DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8403169PMC
August 2021

Antibody-Functionalized Halloysite Nanotubes for Targeting Bacterial Cells.

ACS Appl Bio Mater 2021 05 11;4(5):4094-4104. Epub 2021 Apr 11.

Department of Biotechnology and Food Engineering, Technion-Israel Institute of Technology, Technion City, Haifa 3200003, Israel.

Halloysite nanotubes (HNTs) are naturally occurring tubular clay particles which have emerged in recent years as a promising nanomaterial for numerous applications. Specifically, HNTs' large pore volume and high specific surface area in combination with their biocompatibility make them ideal nanocarriers for bioactive compounds. This research aims to design and synthesize functionalized HNTs, which could selectively bind to target bacterial cells in suspension. Such a system can allow us to treat target cells within a challenging heterogeneous population, such as contaminated ecosystems or gut flora. HNTs functionalization is achieved by immobilizing specific antibodies onto the nanotube surface. The synthetic route is realized by the following subsequent steps: acidic etching of the HNTs, silanization of reactive surface hydroxyls, conjugation of protein A, and oriented immobilization of the antibody. HNT functionalization is studied by a set of analytical techniques including attenuated total reflectance Fourier-transform infrared spectroscopy, zeta potential measurements, thermal gravimetric analysis, scanning and transmission electron microscopy, as well as fluorescence microscopy. The selective binding of the functionalized HNTs to their target bacteria is observed upon incubation with live homogenous and heterogeneous cultures using fluorescence microscopy and high-throughput flow cytometry. Plate count and live/dead staining experiments demonstrate the biocompatibility of the antibody-HNT hybrid with its target bacteria. The suggested HNT-based smart carrier constitutes a generic platform for targeted delivery that could be selectively tailored against any microorganism by facile antibody adjustment.
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http://dx.doi.org/10.1021/acsabm.0c01332DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8161669PMC
May 2021

3D-printed microfluidics integrated with optical nanostructured porous aptasensors for protein detection.

Mikrochim Acta 2021 02 4;188(3):67. Epub 2021 Feb 4.

Department of Biotechnology and Food Engineering, Technion - Israel Institute of Technology, Haifa, Israel.

Microfluidic integration of biosensors enables improved biosensing performance and sophisticated lab-on-a-chip platform design for numerous applications. While soft lithography and polydimethylsiloxane (PDMS)-based microfluidics are still considered the gold standard, 3D-printing has emerged as a promising fabrication alternative for microfluidic systems. Herein, a 3D-printed polyacrylate-based microfluidic platform is integrated for the first time with a label-free porous silicon (PSi)-based optical aptasensor via a facile bonding method. The latter utilizes a UV-curable adhesive as an intermediate layer, while preserving the delicate nanostructure of the porous regions within the microchannels. As a proof-of-concept, a generic model aptasensor for label-free detection of his-tagged proteins is constructed, characterized, and compared to non-microfluidic and PDMS-based microfluidic setups. Detection of the target protein is carried out by real-time monitoring reflectivity changes of the PSi, induced by the target binding to the immobilized aptamers within the porous nanostructure. The microfluidic integrated aptasensor has been successfully used for detection of a model target protein, in the range 0.25 to 18 μM, with a good selectivity and an improved limit of detection, when compared to a non-microfluidic biosensing platform (0.04 μM vs. 2.7 μM, respectively). Furthermore, a superior performance of the 3D-printed microfluidic aptasensor is obtained, compared to a conventional PDMS-based microfluidic platform with similar dimensions.
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http://dx.doi.org/10.1007/s00604-021-04725-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7862519PMC
February 2021

Halloysite nanotubes - the nano-bio interface.

Nanoscale 2020 Dec;12(46):23444-23460

Department of Biotechnology and Food Engineering, Technion - Israel Institute of Technology, Technion City, 3200003 Haifa, Israel.

The numerous biological applications of nanoparticles in general and nano-clays in particular are rooted in understanding and harnessing their dynamic nano-bio interface. Among clays, the intrinsically-mesoporous halloysite nanotubes (HNTs) have emerged in recent years as promising nanomaterials. The diverse interactions of these nanotubes with living cells, encompassing electrostatic, van der Waals, and ion exchange, along with cellular response, are crucial in determining the behaviour of HNTs in biological systems. Thus, rational engineering of the nanotube properties allows for vast applications ranging from bacteria encapsulation for bioremediation, through algae flocculation for aquaculture, to intracellular drug delivery. This review summarizes the many aspects of the nano-bio interface of HNTs with different cell types (bacteria, algae and fungi, and mammalian cells), highlighting biocompatibility/bio-adverse properties, interaction mechanisms, and the latest cutting-edge technologies.
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http://dx.doi.org/10.1039/d0nr06820aDOI Listing
December 2020

Antifungal Susceptibility Testing of on Silicon Microwells by Intensity-Based Reflectometric Interference Spectroscopy.

ACS Infect Dis 2020 10 21;6(10):2560-2566. Epub 2020 Sep 21.

Institute of Technical Chemistry, Leibniz University Hannover, 30167 Hannover, Germany.

There is a demonstrated and paramount need for rapid, reliable infectious disease diagnostics, particularly those for invasive fungal infections. Current clinical determinations for an appropriate antifungal therapy can take up to 3 days using current antifungal susceptibility testing methods, a time-to-readout that can prove detrimental for immunocompromised patients and promote the spread of antifungal resistant pathogens. Herein, we demonstrate the application of intensity-based reflectometric interference spectroscopic measurements (termed iPRISM) on microstructured silicon sensors for use as a rapid, phenotypic antifungal susceptibility test. This diagnostic platform optically tracks morphological changes of fungi corresponding to conidia growth and hyphal colonization at a solid-liquid interface in real time. Using as a model fungal pathogen, we can determine the minimal inhibitory concentration of clinically relevant antifungals within 12 h. This assay allows for expedited detection of fungal growth and provides a label-free alternative to broth microdilution and agar diffusion methods, with the potential to be used for point-of-care diagnostics.
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http://dx.doi.org/10.1021/acsinfecdis.0c00234DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7584364PMC
October 2020

Mass Transfer Limitations of Porous Silicon-Based Biosensors for Protein Detection.

ACS Sens 2020 10 21;5(10):3058-3069. Epub 2020 Sep 21.

Department of Biotechnology and Food Engineering, Technion-Israel Institute of Technology, Haifa 3200003, Israel.

Porous silicon (PSi) thin films have been widely studied for biosensing applications, enabling label-free optical detection of numerous targets. The large surface area of these biosensors has been commonly recognized as one of the main advantages of the PSi nanostructure. However, in practice, without application of signal amplification strategies, PSi-based biosensors suffer from limited sensitivity, compared to planar counterparts. Using a theoretical model, which describes the complex mass transport phenomena and reaction kinetics in these porous nanomaterials, we reveal that the interrelated effect of bulk and hindered diffusion is the main limiting factor of PSi-based biosensors. Thus, without significantly accelerating the mass transport to and within the nanostructure, the target capture performance of these biosensors would be comparable, regardless of the nature of the capture probe-target pair. We use our model to investigate the effect of various structural and biosensor characteristics on the capture performance of such biosensors and suggest rules of thumb for their optimization.
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http://dx.doi.org/10.1021/acssensors.0c00670DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7589614PMC
October 2020

Aptasensors for Point-of-Care Detection of Small Molecules.

Biosensors (Basel) 2020 Aug 26;10(9). Epub 2020 Aug 26.

Institute of Technical Chemistry, Leibniz Universität Hannover, Callinstr. 5, 30167 Hannover, Germany.

Aptamers, a group of nucleic acids which can specifically bind to a target molecule, have drawn extensive interest over the past few decades. For analytics, aptamers represent a viable alternative to gold-standard antibodies due to their oligonucleic nature combined with advantageous properties, including higher stability in harsh environments and longer shelf-life. Indeed, over the last decade, aptamers have been used in numerous bioanalytical assays and in various point-of-care testing (POCT) platforms. The latter allows for rapid on-site testing and can be performed outside a laboratory by unskilled labor. Aptamer technology for POCT is not limited just to medical diagnostics; it can be used for a range of applications, including environmental monitoring and quality control. In this review, we critically examine the use of aptamers in POCT with an emphasis on their advantages and limitations. We also examine the recent success of aptasensor technology and how these findings pave the way for the analysis of small molecules in POCT and other health-related applications. Finally, the current major limitations of aptamers are discussed, and possible approaches for overcoming these challenges are presented.
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http://dx.doi.org/10.3390/bios10090108DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7559136PMC
August 2020

Aptamers vs. antibodies as capture probes in optical porous silicon biosensors.

Analyst 2020 Jul 10;145(14):4991-5003. Epub 2020 Jun 10.

Institute of Technical Chemistry, Leibniz University of Hannover, Callinstr. 5, 30167 Hannover, Germany.

Over the past decade aptamers have emerged as a promising class of bioreceptors for biosensing applications with significant advantages over conventional antibodies. However, experimental studies comparing aptasensors and immunosensors, under equivalent conditions, are limited and the results are inconclusive, in terms of benefits and limitations of each bioreceptor type. In the present work, the performance of aptamer and antibody bioreceptors for the detection of a his-tagged protein, used as a model target, is compared. The bioreceptors are immobilized onto a nanostructured porous silicon (PSi) thin film, used as the optical transducer, and the target protein is detected in a real-time and label-free format by reflective interferometric Fourier transform spectroscopy. For the antibodies, random-oriented immobilization onto the PSi nanostructure results in a poor biosensing performance. Contrary, Fc-oriented immobilization of the antibodies shows a similar biosensing performance to that exhibited by the aptamer-based biosensor, in terms of binding rate, dynamic detection range, limit of detection and selectivity. The aptasensor outperforms in terms of its reusability and storability, while the immunosensor could not be regenerated for subsequent experiments.
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http://dx.doi.org/10.1039/d0an00178cDOI Listing
July 2020

Lab-on-a-Chip Devices for Point-of-Care Medical Diagnostics.

Adv Biochem Eng Biotechnol 2020 May 21. Epub 2020 May 21.

Department of Biotechnology and Food Engineering, Technion - Israel Institute of Technology, Haifa, Israel.

The recent coronavirus (COVID-19) pandemic has underscored the need to move from traditional lab-centralized diagnostics to point-of-care (PoC) settings. Lab-on-a-chip (LoC) platforms facilitate the translation to PoC settings via the miniaturization, portability, integration, and automation of multiple assay functions onto a single chip. For this purpose, paper-based assays and microfluidic platforms are currently being extensively studied, and much focus is being directed towards simplifying their design while simultaneously improving multiplexing and automation capabilities. Signal amplification strategies are being applied to improve the performance of assays with respect to both sensitivity and selectivity, while smartphones are being integrated to expand the analytical power of the technology and promote its accessibility. In this chapter, we review the main technologies in the field of LoC platforms for PoC medical diagnostics and survey recent approaches for improving these assays.
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http://dx.doi.org/10.1007/10_2020_127DOI Listing
May 2020

Bone Morphogenic Protein 2-Loaded Porous Silicon Carriers for Osteoinductive Implants.

Pharmaceutics 2019 Nov 12;11(11). Epub 2019 Nov 12.

Department of Biotechnology and Food Engineering, Technion-Israel Institute of Technology, Haifa 3200003, Israel.

Bone morphogenetic proteins (BMPs) are probably the most important growth factors in bone formation and healing. However, the utilization of BMPs in clinical applications is mainly limited due to the protein poor solubility at physiological pH, rapid clearance and relatively short biological half-life. Herein, we develop degradable porous silicon (PSi)-based carriers for sustained delivery of BMP-2. Two different loading approaches are examined, physical adsorption and covalent conjugation, and their effect on the protein loading and release rate is thoroughly studied. The entrapment of the protein within the PSi nanostructures preserved its bioactivity for inducing osteogenic differentiation of rabbit bone marrow mesenchymal stems cells (BM-MSCs). BM-MSCs cultured with the BMP-2 loaded PSi carriers exhibit a relatively high alkaline phosphatase (ALP) activity. We also demonstrate that exposure of MSCs to empty PSi (no protein) carriers generates some extent of differentiation due to the ability of the carrier's degradation products to induce osteoblast differentiation. Finally, we demonstrate the integration of these promising BMP-2 carriers within a 3D-printed patient-specific implant, constructed of poly(caprolactone) (PCL), as a potential bone graft for critical size bone defects.
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http://dx.doi.org/10.3390/pharmaceutics11110602DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6920899PMC
November 2019

Increased surface area of halloysite nanotubes due to surface modification predicts lung inflammation and acute phase response after pulmonary exposure in mice.

Environ Toxicol Pharmacol 2020 Jan 1;73:103266. Epub 2019 Oct 1.

National Research Centre for the Working Environment, Lersø Parkallé 105, Copenhagen, DK-2100, Denmark; DTU Health Tech, Technical University of Denmark, Kgs. Lyngby, DK-2800, Denmark. Electronic address:

The toxicological potential of halloysite nanotubes (HNTs) and variants after functional alterations to surface area are not clear. We assessed the toxicological response to HNTs (NaturalNano (NN)) before and after surface etching (NN-etched). Potential cytotoxicity of the two HNTs was screened in vitro in MutaTMMouse lung epithelial cells. Lung inflammation, acute phase response and genotoxicity were assessed 1, 3, and 28 days after a single intratracheal instillation of adult female C57BL/6 J BomTac mice. The doses were 6, 18 or 54 μg of HNTs, compared to vehicle controls and the Carbon black NP (Printex 90) of 162 μg/mouse. The cellular composition of bronchoalveolar lavage (BAL) fluid was determined as a measure of lung inflammation. The pulmonary and hepatic acute phase responses were assessed by Serumamyloida mRNA levels in lung and liver tissue by real-time quantitative PCR. Pulmonary and systemic genotoxicity were analyzed by the alkaline comet assay as DNA strand breaks in BAL cells, lung and liver tissue. The etched HNT (NN-etched) had 4-5 times larger BET surface area than the unmodified HNT (NN). Instillation of NN-etched at the highest dose induced influx of neutrophils into the lungs at all time points and increased Saa3 mRNA levels in lung tissue on day 1 and 3 after exposure. No genotoxicity was observed at any time point. In conclusion, functionalization by etching increased BET surface area of the studied NN and enhanced pulmonary inflammatory toxicity in mice.
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http://dx.doi.org/10.1016/j.etap.2019.103266DOI Listing
January 2020

Neuroprotective Effect of Nerve Growth Factor Loaded in Porous Silicon Nanostructures in an Alzheimer's Disease Model and Potential Delivery to the Brain.

Small 2019 11 4;15(45):e1904203. Epub 2019 Sep 4.

Faculty of Engineering, Bar-Ilan University, Ramat-Gan, 5290002, Israel.

Nerve growth factor (NGF) plays a vital role in reducing the loss of cholinergic neurons in Alzheimer's disease (AD). However, its delivery to the brain remains a challenge. Herein, NGF is loaded into degradable oxidized porous silicon (PSiO ) carriers, which are designed to carry and continuously release the protein over a 1 month period. The released NGF exhibits a substantial neuroprotective effect in differentiated rat pheochromocytoma PC12 cells against amyloid-beta (Aβ)-induced cytotoxicity, which is associated with Alzheimer's disease. Next, two potential localized administration routes of the porous carriers into murine brain are investigated: implantation of PSiO chips above the dura mater, and biolistic bombardment of PSiO microparticles through an opening in the skull using a pneumatic gene gun. The PSiO -implanted mice are monitored for a period of 8 weeks and no inflammation or adverse effects are observed. Subsequently, a successful biolistic delivery of these highly porous microparticles into a live-mouse brain is demonstrated for the first time. The bombarded microparticles are observed to penetrate the brain and reach a depth of 150 µm. These results pave the way for using degradable PSiO carriers as potential localized delivery systems for NGF to the brain.
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http://dx.doi.org/10.1002/smll.201904203DOI Listing
November 2019

Antimicrobial LDPE/EVOH Layered Films Containing Carvacrol Fabricated by Multiplication Extrusion.

Polymers (Basel) 2018 Aug 4;10(8). Epub 2018 Aug 4.

Department of Biotechnology and Food Engineering, Technion-Israel Institute of Technology, Haifa 3200003, Israel.

This work describes the fabrication of antimicrobial multilayered polymeric films containing carvacrol (used as a model essential oil) by co-extrusion and multiplication technique. The microlayering process was utilized to produce films, with up to 65 alternating layers, of carvacrol-containing low-density polyethylene (LDPE) and ethylene vinyl alcohol copolymer (EVOH). Carvacrol was melt compounded with LDPE or loaded into halloysite nanotubes (HNTs) in a pre-compounding step prior film production. The detailed nanostructure and composition (in terms of carvacrol content) of the films were characterized and correlated to their barrier properties, carvacrol release rate, and antibacterial and antifungal activity. The resulting films exhibit high carvacrol content despite the harsh processing conditions (temperature of 200 °C and long processing time), regardless of the number of layers or the presence of HNTs. The multilayered films exhibit superior oxygen transmission rates and carvacrol diffusivity values that are more than two orders of magnitude lower in comparison to single-layered carvacrol-containing films (i.e., LDPE/carvacrol and LDPE/(HNTs/carvacrol)) produced by conventional cast extrusion. The (LDPE/carvacrol)/EVOH and (LDPE/[HNTs/carvacrol])/EVOH films demonstrated excellent antimicrobial efficacy against and in micro-atmosphere assays and against and in cherry tomatoes, used as the food model. The results presented here suggest that sensitive essential oils, such as carvacrol, can be incorporated into plastic polymers constructed of tailored multiple layers, without losing their antimicrobial efficacy.
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http://dx.doi.org/10.3390/polym10080864DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6403741PMC
August 2018

Designing Bacterial Chemotactic Receptors Guided by Photonic Femtoliter Well Arrays for Quantifiable, Label-Free Measurement of Bacterial Chemotaxis.

ACS Biomater Sci Eng 2019 Feb 17;5(2):603-612. Epub 2019 Jan 17.

Whole cell bioreporters, such as bacterial cells, can be used for environmental and clinical sensing of specific analytes. However, the current methods implemented to observe such bioreporters in the form of chemotactic responses heavily rely on microscope analysis, fluorescent labels, and hard-to-scale microfluidic devices. Herein, we demonstrate that chemotaxis can be detected within minutes using intrinsic optical measurements of silicon femtoliter well arrays (FMAs). This is done via phase-shift reflectometric interference spectroscopic measurements (PRISM) of the wells, which act as silicon diffraction gratings, enabling label-free, real-time quantification of the number of trapped bacteria cells in the optical readout. By generating unsteady chemical gradients over the wells, we first demonstrate that chemotaxis toward attractants and away from repellents can be easily differentiated based on the signal response of PRISM. The lowest concentration of chemorepellent to elicit an observed bacterial response was 50 mM, whereas the lowest concentration of chemoattractant to elicit a response was 10 mM. Second, we employed PRISM, in combination with a computational approach, to rapidly scan for and identify a novel synthetic histamine chemoreceptor strain. Consequently, we show that by using a combined computational design approach, together with a quantitative, real-time, and label-free detection method, it is possible to manufacture and characterize novel synthetic chemoreceptors in ().
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http://dx.doi.org/10.1021/acsbiomaterials.8b01429DOI Listing
February 2019

Designing Porous Silicon Films as Carriers of Nerve Growth Factor.

J Vis Exp 2019 01 25(143). Epub 2019 Jan 25.

Department of Biotechnology and Food Engineering, Technion - Israel Institute of Technology; Russell Berrie Nanotechnology Institute, Technion - Israel Institute of Technology;

Despite the great potential of NGF for treating neurodegenerative diseases, its therapeutic administration represents a significant challenge as the protein does not cross the blood-brain barrier, owing to its chemical properties, and thus requires long-term delivery to the brain to have a biological effect. This work describes fabrication of nanostructured PSi films as degradable carriers of NGF for sustained delivery of this sensitive protein. The PSi carriers are specifically tailored to obtain high loading efficacy and continuous release of NGF for a period of four weeks, while preserving its biological activity. The behavior of the NGF-PSi carriers as a NGF delivery system is investigated in vitro by examining their capability to induce neuronal differentiation and outgrowth of PC12 cells and dissociated DRG neurons. Cell viability in the presence of neat and NGF-loaded PSi carriers is evaluated. The bioactivity of NGF released from the PSi carriers is compared to the conventional treatment of repetitive free NGF administrations. PC12 cell differentiation is analyzed and characterized by the measurement of three different morphological parameters of differentiated cells; (i) the number of neurites extracting from the soma (ii) the total neurites' length and (iii) the number of branching points. PC12 cells treated with the NGF-PSi carriers demonstrate a profound differentiation throughout the release period. Furthermore, DRG neuronal cells cultured with the NGF-PSi carriers show an extensive neurite initiation, similar to neurons treated with repetitive free NGF administrations. The studied tunable carriers demonstrate the long-term implants for NGF release with a therapeutic potential for neurodegenerative diseases.
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http://dx.doi.org/10.3791/58982DOI Listing
January 2019

Porous Silicon Bragg Reflector/Carbon Dot Hybrids: Synthesis, Nanostructure, and Optical Properties.

Front Chem 2018 23;6:574. Epub 2018 Nov 23.

Department of Biotechnology and Food Engineering, Technion-Israel Institute of Technology, Haifa, Israel.

Carbon dots (C-dots) exhibit unique fluorescence properties, mostly depending upon their physical environments. Here we investigate the optical properties and nanostructure of Carbon dots (C-dots) which are synthesized within different porous Silicon (PSi) Bragg reflectors. The resulting hybrids were characterized by photoluminescence, X-ray photoelectron, and Fourier Transform Infrared spectroscopies, as well as by confocal and transmission electron microscopy. We show that by tailoring the location of the PSi Bragg reflector photonic bandgap and its oxidation level, the C-dots emission spectral features can be tuned. Notably, their fluorescence emission can be significantly enhanced when the high reflection band of the PSi host overlaps with the confined C-dots' peak wavelength, and the PSi matrix is thermally oxidized at mild conditions. These phenomena are observed for multiple compositions of PSi Bragg reflectors/C-dots hybrids.
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http://dx.doi.org/10.3389/fchem.2018.00574DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6265313PMC
November 2018

Porous Silicon-Based Photonic Biosensors: Current Status and Emerging Applications.

Anal Chem 2019 01 30;91(1):441-467. Epub 2018 Nov 30.

Department of Electrical Engineering and Computer Science , Vanderbilt University , Nashville , Tennessee 37235 , United States.

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http://dx.doi.org/10.1021/acs.analchem.8b05028DOI Listing
January 2019

Recent Advances in the Race to Design a Rapid Diagnostic Test for Antimicrobial Resistance.

ACS Sens 2018 11 2;3(11):2202-2217. Epub 2018 Nov 2.

Department of Biotechnology and Food Engineering , Technion - Israel Institute of Technology , Haifa , Israel 3200003.

Even with advances in antibiotic therapies, bacterial infections persistently plague society and have amounted to one of the most prevalent issues in healthcare today. Moreover, the improper and excessive administration of antibiotics has led to resistance of many pathogens to prescribed therapies, rendering such antibiotics ineffective against infections. While the identification and detection of bacteria in a patient's sample is critical for point-of-care diagnostics and in a clinical setting, the consequent determination of the correct antibiotic for a patient-tailored therapy is equally crucial. As a result, many recent research efforts have been focused on the development of sensors and systems that correctly guide a physician to the best antibiotic to prescribe for an infection, which can in turn, significantly reduce the instances of antibiotic resistance and the evolution of bacteria "superbugs." This review details the advantages and shortcomings of the recent advances (focusing from 2016 and onward) made in the developments of antimicrobial susceptibility testing (AST) measurements. Detection of antibiotic resistance by genomic AST techniques relies on the prediction of antibiotic resistance via extracted bacterial DNA content, while phenotypic determinations typically track physiological changes in cells and/or populations exposed to antibiotics. Regardless of the method used for AST, factors such as cost, scalability, and assay time need to be weighed into their design. With all of the expansive innovation in the field, which technology and sensing systems demonstrate the potential to detect antimicrobial resistance in a clinical setting?
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http://dx.doi.org/10.1021/acssensors.8b00900DOI Listing
November 2018

Antimicrobial Carvacrol-Containing Polypropylene Films: Composition, Structure and Function.

Polymers (Basel) 2018 Jan 16;10(1). Epub 2018 Jan 16.

Department of Biotechnology and Food Engineering, Technion-Israel Institute of Technology, Haifa 3200003, Israel.

Significant research has been directed toward the incorporation of bioactive plant extracts or essential oils (EOs) into polymers to endow the latter with antimicrobial functionality. EOs offer a unique combination of having broad antimicrobial activity from a natural source, generally recognized as safe (GRAS) recognition in the US, and a volatile nature. However, their volatility also presents a major challenge in their incorporation into polymers by conventional high-temperature-processing techniques. Herein, antimicrobial polypropylene (PP) cast films were produced by incorporating carvacrol (a model EO) or carvacrol, loaded into halloysite nanotubes (HNTs), via melt compounding. We studied the composition-structure-property relationships in these systems, focusing on the effect of carvacrol on the composition of the films, the PP crystalline phase and its morphology and the films' mechanical and antimicrobial properties. For the first time, molecular dynamics simulations were applied to reveal the complex interactions between the components of these carvacrol-containing systems. We show that strong molecular interactions between PP and carvacrol minimize the loss of this highly-volatile EO during high-temperature polymer processing, enabling semi-industrial scale production. The resulting films exhibit outstanding antimicrobial properties against model microorganisms ( and ). The PP/(HNTs-carvacrol) nanocomposite films, containing the carvacrol-loaded HNTs, display a higher level of crystalline order, superior mechanical properties and prolonged release of carvacrol, in comparison to PP/carvacrol blends. These properties are ascribed to the role of HNTs in these nanocomposites and their effect on the PP matrix and retained carvacrol content.
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http://dx.doi.org/10.3390/polym10010079DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6415180PMC
January 2018

On Chip Protein Pre-Concentration for Enhancing the Sensitivity of Porous Silicon Biosensors.

ACS Sens 2017 12 27;2(12):1767-1773. Epub 2017 Nov 27.

Institute of Technical Chemistry, Leibniz Universität Hannover , Callinstr. 5, 30167 Hanover, Germany.

Porous silicon (PSi) nanomaterials have been widely studied as label-free optical biosensors for protein detection. However, these biosensors' performance, specifically in terms of their sensitivity (which is typically in the micromolar range), is insufficient for many applications. Herein, we present a proof-of-concept application of the electrokinetic isotachophoresis (ITP) technique for real-time preconcentration of a target protein on a PSi biosensor. With ITP, a highly concentrated target zone is delivered to the sensing area, where the protein target is captured by immobilized aptamers. The detection of the binding events is conducted in a label-free manner by reflective interferometric Fourier transformation spectroscopy (RIFTS). Up to 1000-fold enhancement in local concentration of the protein target and the biosensor's sensitivity are achieved, with a measured limit of detection of 7.5 nM. Furthermore, the assay is successfully performed in complex media, such as bacteria lysate samples, while the selectivity of the biosensor is retained. The presented assay could be further utilized for other protein targets, and to promote the development of clinically useful PSi biosensors.
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http://dx.doi.org/10.1021/acssensors.7b00692DOI Listing
December 2017

Aptamer-based detection of adenosine triphosphate via qPCR.

Talanta 2017 Sep 18;172:199-205. Epub 2017 May 18.

Institute of Technical Chemistry, Leibniz University of Hannover, Callinstr. 5, Hannover 30167, Germany.

Sensitive and specific detection and quantification of small molecules often remain challenging. We developed a novel magnetic bead-based aptamer-assisted real-time PCR (Apta-qPCR) assay to provide a versatile platform for quantification of small molecules. The assay has been realized for the detection of ATP as a model system. The assay relies on a combination of qPCR with the target-induced dissociation (TID) of ATP aptamer from an oligonucleotide, complementary to the ATP binding site of the aptamer. The complementary oligonucleotide was immobilized on deoxythymidine (dT)-modified magnetic beads (dT-beads) and hybridized with the aptamer. The presence of ATP resulted in dissociation of the aptamer from the dT-beads and the dissociated aptamer was quantified using qPCR. The Apta-qPCR assay was able to detect 17nM ATP with a broad dynamic range from 50nM to 5mM. The assay is label-free, and real-time PCR-based detection of aptamer facilitates high sensitivity. The presented method is highly versatile and can be applied to various aptamer-target pairs to allow detection of a broad range of target analytes.
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http://dx.doi.org/10.1016/j.talanta.2017.05.037DOI Listing
September 2017

Unraveling Antimicrobial Susceptibility of Bacterial Networks on Micropillar Architectures Using Intrinsic Phase-Shift Spectroscopy.

ACS Nano 2017 06 16;11(6):6167-6177. Epub 2017 May 16.

Department of Biotechnology and Food Engineering, ‡Department of Urology, Bnai Zion Medical Center, Faculty of Medicine, and §The Russell Berrie Nanotechnology Institute, Technion-Israel Institute of Technology , Haifa 3200003, Israel.

With global antimicrobial resistance becoming increasingly detrimental to society, improving current clinical antimicrobial susceptibility testing (AST) is crucial to allow physicians to initiate appropriate antibiotic treatment as early as possible, reducing not only mortality rates but also the emergence of resistant pathogens. In this work, we tackle the main bottlenecks in clinical AST by designing biofunctionalized silicon micropillar arrays to provide both a preferable solid-liquid interface for bacteria networking and a simultaneous transducing element that monitors the response of bacteria when exposed to chosen antibiotics in real time. We harness the intrinsic ability of the micropillar architectures to relay optical phase-shift reflectometric interference spectroscopic measurements (referred to as PRISM) and employ it as a platform for culture-free, label-free phenotypic AST. The responses of E. coli to various concentrations of five clinically relevant antibiotics are optically tracked by PRISM, allowing for the minimum inhibitory concentration (MIC) values to be determined and compared to both standard broth microdilution testing and clinic-based automated AST system readouts. Capture of bacteria within these microtopologies, followed by incubation of the cells with the appropriate antibiotic solution, yields rapid determinations of antibiotic susceptibility. This platform not only provides accurate MIC determinations in a rapid manner (total assay time of 2-3 h versus 8 h with automated AST systems) but can also be employed as an advantageous method to differentiate bacteriostatic and bactericidal antibiotics.
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http://dx.doi.org/10.1021/acsnano.7b02217DOI Listing
June 2017

Rapid and label-free detection of protein a by aptamer-tethered porous silicon nanostructures.

J Biotechnol 2017 Sep 25;257:171-177. Epub 2017 Jan 25.

Institute of Technical Chemistry, Leibniz Universität Hannover, Callinstr. 5, 30167 Hanover, Germany. Electronic address:

Protein A, which is secreted by and displayed on the cell membrane of Staphylococcus aureus is an important biomarker for S. aureus. Thus, its rapid and specific detection may facilitate the pathogen identification and initiation of proper treatment. Herein, we present a simple, label-free and rapid optical biosensor enabling specific detection of protein A. Protein A-binding aptamer serves as the capture probe and is immobilized onto a nanostructured porous silicon thin film, which serves as the optical transducer element. We demonstrate high sensitivity of the biosensor with a linear detection range between 8 and 23μM. The apparent dissociation constant was determined as 13.98μM and the LoD is 3.17μM. Harnessing the affinity between protein A and antibodies, a sandwich assay format was developed to amplify the optical signal associated with protein A capture by the aptamer. Using this approach, we increase the sensitivity of the biosensor, resulting in a three times lower LoD.
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http://dx.doi.org/10.1016/j.jbiotec.2017.01.005DOI Listing
September 2017

Prolonged controlled delivery of nerve growth factor using porous silicon nanostructures.

J Control Release 2017 07 14;257:51-59. Epub 2016 Dec 14.

Department of Biotechnology and Food Engineering, Technion - Israel Institute of Technology, Haifa 32000, Israel; Russell Berrie Nanotechnology Institute, Technion - Israel Institute of Technology, Haifa 32000, Israel. Electronic address:

Although nerve growth factor (NGF) is beneficial for the treatment of numerous neurological and non-neurological diseases, its therapeutic administration represents a significant challenge, due to the difficulty to locally deliver relevant doses in a safe and non-invasive manner. In this work, we employ degradable nanostructured porous silicon (PSi) films as carriers for NGF, allowing its continuous and prolonged release, while retaining its bioactivity. The PSi carriers exhibit high loading efficacy (up to 90%) of NGF and a continuous release, with no burst, over a period of>26days. The released NGF bioactivity is compared to that of free NGF in both PC12 cells and dissociated dorsal root ganglion (DRG) neurons. We show that the NGF has retained its bioactivity and induces neurite outgrowth and profound differentiation (of >50% for PC12 cells) throughout the period of release within a single administration. Thus, this proof-of-concept study demonstrates the immense therapeutic potential of these tunable carriers as long-term implants of NGF reservoirs and paves the way for new localized treatment strategies of neurodegenerative diseases.
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http://dx.doi.org/10.1016/j.jconrel.2016.12.008DOI Listing
July 2017

Porous Silicon-Based Biosensors: Towards Real-Time Optical Detection of Target Bacteria in the Food Industry.

Sci Rep 2016 11 30;6:38099. Epub 2016 Nov 30.

Department of Biotechnology and Food Engineering, Technion - Israel Institute of Technology, Haifa 3200003, Israel.

Rapid detection of target bacteria is crucial to provide a safe food supply and to prevent foodborne diseases. Herein, we present an optical biosensor for identification and quantification of Escherichia coli (E. coli, used as a model indicator bacteria species) in complex food industry process water. The biosensor is based on a nanostructured, oxidized porous silicon (PSi) thin film which is functionalized with specific antibodies against E. coli. The biosensors were exposed to water samples collected directly from process lines of fresh-cut produce and their reflectivity spectra were collected in real time. Process water were characterized by complex natural micro-flora (microbial load of >10 cell/mL), in addition to soil particles and plant cell debris. We show that process water spiked with culture-grown E. coli, induces robust and predictable changes in the thin-film optical interference spectrum of the biosensor. The latter is ascribed to highly specific capture of the target cells onto the biosensor surface, as confirmed by real-time polymerase chain reaction (PCR). The biosensors were capable of selectively identifying and quantifying the target cells, while the target cell concentration is orders of magnitude lower than that of other bacterial species, without any pre-enrichment or prior processing steps.
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http://dx.doi.org/10.1038/srep38099DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5128872PMC
November 2016
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