Evangelia A. Pavlatou

N. Lagopati, K. Evangelou, P. Falaras, E.-Ph.C.Tsilibary, P. V.S.Vasileiou, S. Havaki, A. Angelopoulou, E.A. Pavlatou, V.G.Gorgoulis

Pharmacology & Therapeutics (2021), 222, 107795

The multivariate condition of cancer disease has been approached in various ways, by the scientific community. Recent studies focus on individualized treatments, minimizing the undesirable consequences of the conventional methods, but the development of an alternative effective therapeutic scheme remains to be held. Nanomedicine could provide a solution, filling this gap, exploiting the unique properties of innovative nanostructured materials. Nanostructured titanium dioxide (TiO₂) has a variety of applications of daily routine and of advanced technology. Due to its biocompatibility, it has also a great number of biomedical applications. It is now clear that photo-excited TiO₂ nanoparticles, induce generation of pairs of electrons and holes which react with water and oxygen to yield reactive oxygen species (ROS) that have been proven to damage cancer cells, triggering controlled cellular processes. The aim of this review is to provide insights into the field of nanomedicine and particularly into the wide context of TiO₂-NP-mediated anticancer effect, shedding light on the achievements of nanotechnology and proposing this nanostructured material as a promising anticancer photosensitizer.

doi: 10.1016/j.pharmthera.2020.107795

N. Lagopati, M.-A. Gatou, D.S. Tsoukleris, E.A. Pavlatou

Nanomedicine & Nanotechnology (2020), 5 (1), 1-12

The transmission of a wide range of diseases, related to the infection by pathogenic microorganisms is a major public health problem that daily endangers the safety of human population. Silver has been thoroughly studied and used against bacteria due to its antimicrobial properties. Nanostructured silver gathers all the advantages of the silver itself, as well as the advanced performance of the nanomaterials. Thus, currently, silver nanoparticles constitute the most widely used kind of nanoparticles in biomedicine, due to their attractive antimicrobial properties. A variety of physical and chemical methods are employed for the AgNPs synthesis. However, many of them include the use of toxic reagents or require large amounts of energy, during the synthesis process. For this reason, many eco-friendly methods are proposed in order to synthesize AgNPs. Hence, biogenic synthesis of AgNPs, utilizing biological resources opens a novel route for the development of alternative production processes. These methods seem to have significant dvantages, as the extracts contribute positively to the formation and enhancement of the antimicrobial activity of AgNPs, also acting as protective agents of the produced particles. In this review an integrated approach of AgNPs bio-synthetic methods using microorganisms, such as bacteria and fungi, plants and plant extracts, as well as several templates, like DNA and viruses is discussed, shedding light on the comparative advantages of them.

doi:10.23880/nnoa-16000185

E. Rosolymou, S. Spanou, C. Zanella, D.S. Tsoukleris, S. Köhler, P. Leisner, E.A. Pavlatou

Coatings (2020), 10 (8), 775

Direct current electrodeposited Sn-Ni/TiO₂ nanostructured coatings were produced by embedding two different doped types of TiO₂ particles within the alloy matrix, a commercially available doped carbon-based and doped N,S-TiO₂ particles. The structural characteristics of the composite coatings have been correlated with the effect of loading, type of particles in the electrolytic bath, and the applied current density. Regardless of the type of doped particles TiO₂, increasing values of applied current density resulted in a reduction of the co-deposition percentage of TiO₂ particles and an increase of Tin content into the alloy matrix. The application of low current density values accompanied by a high load of particles in the bath led to the highest codeposition percentage (~3.25 wt.%) achieved in the case of embedding N,S-TiO₂ particles. X-ray diffraction data demonstrated that in composite coatings the incorporation of the different types of TiO₂ particles in the alloy metal matrix modified significantly the nano-crystalline structure in comparison with the pure coatings. The best photocatalytic behavior under visible irradiation was revealed for the composite coatings with the highest co-deposition percentage of doped N,S-TiO₂ particles, that also exhibited enhanced wear resistance and slightly reduced microhardness compared to pure ones.

doi: 10.3390/coatings10080775

N. Lagopati, E.A. Pavlatou

American Journal of Biomedical Science & Research (2020), 9 (1), 47-53

Alginic acid, also known as algin or alginate, is a natural carbohydrate, which is derived from marine brown algae, as well as some microorganisms. It can be used in various applications. In particular, alginate has shown great potential in the areas of wound healing, drug delivery, in vitro cell culture, and tissue engineering, allowing the categorization of it as a promising biomaterial, or a basic component of other biomaterials. The unique characteristics of alginic acid, such as the biocompatibility, the mild required gelation conditions, the low toxicity, the relative low cost and the simple modifications, allow the development of alginate hydrogels, and alginate derivatives with enhanced properties. The aim of this review, is to present an overview of the properties of alginate, shedding light on the current and potential applications and suggesting new perspectives for future studies.

doi: 10.34297/AJBSR.2020.09.001350

D. Koukouzelis, A. Rozaria, N. Pontillo, S. Koutsoukos, E.A. Pavlatou, A. Detsi

M.-A. Gatou, N. Lagopati, D. Tsoukleris, E.A. Pavlatou

Biomedical Journal of Science & Technology Research (2020), 25 (5), 19426-19436

The global use of crude oil for energy applications has increased during the last decades, leading to an extensive release of oil into the environment as well. Thus, contamination deriving from oil spills and industrial wastewater has been recognized as one of the major environmental issues, imposing a serious threat to both human and marine ecosystem health. Treatment of contamination and pollution caused by crude oil constitutes a quite challenging and elaborate process. Among the conventional technologies applied for oil-water separation, oil absorption process has been widely examined in recent years. Commercial sponges, such as melamine and polyurethane sponges, have attracted great attention in the field of crude oil removal both from seawater and industrial wastewater, due to their low cost, high porous three-dimensional (3D) structure, low density, excellent mechanical properties and remarkable reusability. However, the amphipathic nature of commercial sponges limits their application for oil absorption treatment processes. In order to improve their oil absorption performance, several modification methods have been utilized. In the current manuscript, an overview of various methods used for the superhydrophobic/Superoleophilicity modification of commercially available sponges for oil-water separation, is provided, in order to highlight the potential use of these sponges as a novel, highly efficient, low-cost, recyclable and environmental friendly absorbent for the recovery of spilled crude oil both from seawater and industrial wastewater.

doi: 10.26717/BJSTR.2020.25.004251

K. Dalacosta, E.A. Pavlatou

Computer Applications in Engineering Education (2019), 28 (1), 5–16

This paper presents an educational digital material on "solid crystal structures", in which cartoons agents direct undergraduate students on a learning cycle of understanding concepts from the submicroscopic level and correlate with the corresponding macroscopic‐related properties. Specifically, undergraduate students are given the opportunity to study basic crystal structures starting from structural units, composing the unit cells in a three‐dimensional (3D) pattern that are characterized and related with intermolecular forces within them, and finally leading to basic crystalline solids associated with the macroscopic behavior of solid materials expressed by physical and mechanical properties such as hardness, electrical conductivity, etc. The design of the digital material was focused on the cognitive benefits that students gained after viewing 3D visualizations for which students were able to manipulate the rotation or size of them, to enhance their conceptual understanding addressed to chemistry and engineering, accompanied by cartoons agents. Digital material was constructed to be accessible from and compatible with any web browser without any third‐party plugin. A research using a properly designed questionnaire was conducted in the School of Chemical Engineering in Greece where the evaluation indicated that students preferred using this web material due to its simplicity and their active involvement by self‐controlling the pace and the way of learning.

doi: 10.1002/cae.22169

E. Galata, E.A. Georgakopoulou, M.E. Kassalia, N. Papadopoulou-Fermeli, E.A. Pavlatou

Materials (2019), 12 (16), 2589

In this study, the synthesis of smart, polymerically embedded titanium dioxide (TiO₂) nanoparticles aimed to exhibit photo-induced anticancer properties under visible light irradiation is investigated. The TiO₂ nanoparticles were prepared by utilizing the sol gel method with different dopants, including nitrogen (N-doped), iron (Fe-doped), and nitrogen and iron (Fe,N-doped). The dopants were embedded in an interpenetrating (IP) network microgel synthesized by stimuli responsive poly (N-Isopropylacrylamide-co-polyacrylicacid)–pNipam-co-PAA forming composite particles. All the types of produced particles were characterized by X-ray powder diffraction, micro-Raman, Fourier-transform infrared, X-ray photoelectron, ultra-violet-visible spectroscopy, Field Emission Scanning Electron, Transmission Electron microscopy, and Dynamic Light Scattering techniques. The experimental findings indicate that the doped TiO₂ nanoparticles were successfully embedded in the microgel. The N-doped TiO₂ nano-powders and composite particles exhibit the best photocatalytic degradation of the pollutant methylene blue under visible light irradiation. Similarly, the highly malignant MDA-MB-231 breast cancer epithelial cells were susceptible to the inhibition of cell proliferation at visible light, especially in the presence of N-doped powders and composites, compared to the non-metastatic MCF-7 cells, which were not affected.

doi: 10.3390/ma12162589

N. Chronopoulou, E. Siranidi, A.M. Routsi, H. Zhao, J. Bai, A. Karantonis, E.A. Pavlatou

Surface and Coatings Technology (2018), 350, 672-685

Composite nickel coatings, were produced under direct (DC) and pulse current (PC) from a Watt's type bath, containing 0.5 g/L hybrid MWCNTs-Al₂O₃ , in presence and absence of additive Sodium Dodecyl Sulfate-SDS. Surface morphology, crystallographic orientation, wear resistance and corrosion resistance were studied. Micro-Raman measurements revealed that MWCNTs-Al₂O₃ is distributed at the whole depth of the cross-section profile analysis. The application of pulse current, favored a random crystallographic orientation of Ni crystallites with reduced grain sizes in comparison with pure Ni. The evaluation of the tribological data demonstrated that the composite coatings produced under pulse conditions in presence of additive, exhibited lower coefficient of friction, higher resistance to dry sliding accompanied by the presence of increased amounts of nickel oxide in wear tracks compared to pure Ni coatings. The behavior of pure and composite coatings in corrosive environment was evaluated by electrochemical impedance spectroscopy. It was found that composite coatings attained their corrosion resistance characteristics for 60 h in 0.6 M NaCl solution. Differences between pure nickel and composite coatings were attributed mainly to morphological differences rather than differences on corrosion performance.

doi: 10.1016/j.surfcoat.2018.07.034

K. Dalacosta, E.A. Pavlatou

New Trends and Issues Proceedings on Humanities and Social Sciences (2018), 5 (4), 83–89

In chemical engineering, undergraduate students often have to face the highly demanding process of understanding concepts from the microscopic level (e.g., ionic crystals such as zinc sulphide or covalent lattice crystals diamond, graphite, graphene etc.) and then explain with certain physical–chemical properties their macroscopic behaviour. Therefore, the main idea was to construct a specifically designed educational material that focusses on the benefits of viewing visualisations to enhance students’ conceptual understanding of solids and crystal structures augmented by cartoons, and evaluate its usability. The interactive ‘cartoons’ agents were developed from scratch, giving them freedom of movement and realism at the same time. A research was conducted in the School of Chemical Engineering in Greece (National Technical University of Athens), evaluated the usability of the digital material and the contribution of the 3-D visualisations and the cartoons agents in the understanding of such high-cognitive load concepts.Keywords: Cartoons, 3-D visualisations, crystal structures, chemical engineering.

doi: 10.18844/prosoc.v5i4.3707

N. Chronopoulou, D. Vozios, P. Schinas, E.A. Pavlatou

Materials Today: Proceedings (2018), 5 (14), 27653-27661

Pure nickel and composite nickel coatings were produced by using a Watts bath containing 0.1g/L Graphene platelets-GnPs in presence or absence of the surfactant Sodium Dodecyl Sulfate under both direct current-DC and pulse current-PC conditions. The surface morphology, crystallographic orientation, and micro-hardness as well as the wear mechanism of the produced coatings under dry sliding conditions were investigated. The results have shown that the presence of additive in the electrolytic bath led to a more uniform distribution of Graphene platelets in the nickel metal matrix. The simultaneous presence of additive in combination with the imposition of high pulse current frequency is accompanied by the predominance of a mixed Ni crystalline orientation [110 + 111], while for all composites an enhancement of the crystalline orientation through (111) axis was revealed. The presence of Graphene platelets increases the micro-hardness values of the coatings and enhances the wear resistance compared to pure nickel coatings produced under the same electrolytic conditions.

doi: 10.1016/j.matpr.2018.09.086

A.Kamtsikakis, E. Kavetsou, K. Chronaki, E. Kiosidou, E.A. Pavlatou, A. Karana, C. Papaspyrides, A. Detsi, A. Karantonis, S. Vouyiouka

Bioengineering (2017), 4 (4), 81, 2017

The scope of the current research was to assess the feasibility of encapsulating three commercial antifouling compounds, Irgarol 1051, Econea and Zinc pyrithione, in biodegradable poly(lactic acid) (PLA) nanoparticles. The emulsification–solvent evaporation technique was herein utilized to manufacture nanoparticles with a biocide:polymer ratio of 40%. The loaded nanoparticles were analyzed for their size and size distribution, zeta potential, encapsulation efficiency and thermal properties, while the relevant physicochemical characteristics were correlated to biocide–polymer system. In addition, the encapsulation process was scaled up and the prepared nanoparticles were dispersed in a water-based antifouling paint in order to examine the viability of incorporating nanoparticles in such coatings. Metallic specimens were coated with the nanoparticles-containing paint and examined regarding surface morphology.

doi: 10.3390/bioengineering4040081

A.G.Thanos, E. Katsou, S. Malamis, V. Drakopoulos, P. Paschalakis, E.A. Pavlatou, K. J. Haralambous

Applied Clay Science (2017), 147, 54-62

This work investigated the removal of Cr(VI) from aqueous solutions by employing Pb-modified zeolite, vermiculite and perlite as adsorbents. Natural zeolite and vermiculite exhibited high Pb²⁺ adsorption (~80% of the total Pb²⁺ concentration in solution), while perlite resulted in low lead adsorption (21%). Subsequently, the Pb-modified zeolite and vermiculite exhibited high Cr(VI) adsorption. The maximum Cr(VI) adsorption capacity as predicted by the Langmuir isotherm was 18.9 mgg⁻¹ for zeolite and 23.0 mgg⁻¹ for vermiculite. Langmuir was the isotherm equation that best fitted the experimental data. In terms of kinetics the Elovich equation represented the best fit to Cr(VI) adsorption on the studied modified minerals. The lowest mineral concentration that was tested (10 gL⁻¹) resulted in the highest solid phase equilibrium concentration. Desorption experiments were not effective since the desorption percent achieved with NaCl solution was very low (4–6%). Cr(VI) removal using Pb-modified minerals can be applied in the successive treatment of industrial wastewater first for lead and then for Cr(VI) removal.

doi: 10.1016/j.clay.2017.05.040

A.G. Thanos, A. Sotiropoulos, S. Malamis, E. Katsou, E.A. Pavlatou, K.J. Haralambous

Desalination and Water Treatment (2016), 57, 27869-27878

Surfactant-modified minerals have been widely used for the sorption of anionic and non-polar organic contaminants. This paper investigates the regeneration of various hexadecyltrimethylammonium bromide (HDTMA)-modified natural minerals saturated with chromate anions using different solutions for the extraction of chromates that has been sorbed at optimum conditions. The examined minerals include HDTMA-modified zeolite (clinoptilolite), exfoliated vermiculite, bentonite and attapulgite (palygorskite). Deionized water and sodium chloride, potassium chloride and sodium cyanide solutions at different concentrations (0.1–3M) were employed as chromate desorption solutions. The HDTMA/Cr(VI)-mineral type, the desorbing solution type and its concentration and the mineral–solution contact time are key parameters that affect the process. From our results it was deduced that regeneration and reuse of HDTMA-modified minerals saturated with chromate is feasible. Bentonite exhibited greater stability than the other minerals studied in adsorption/desorption processes, maintaining 73% of its initial adsorption capacity after 14 successive regeneration cycles. The regeneration performance of the examined minerals follows the order: Bentonite>Attapulgite>Zeolite>Vermiculite. Kinetic study revealed that desorption was faster than adsorption, while the pseudo-second-order equation simulated better the experimental data.

doi: 10.1080/19443994.2016.1186395

K. Ellinas, K. Tsougeni, P. S. Petrou, G. Boulousis, D. Tsoukleris, E.A. Pavlatou, A. Tserepi, S. E. Kakabakos, E. Gogolides

Chemical Engineering Journal (2016), 300, 394–403

Cyclo-olefin polymer (COP) surfaces are micro-nanotextured using O₂ plasma chemistry in one-step process. These surfaces subsequently display multiple functionality, (A) they are stable in time (i.e. non ageing), functional, high surface area, substrates suitable for biomolecule binding, after thermal annealing in order to induce accelerated hydrophobic recovery while preserving the chemical functionality created by the plasma. (B) Alternatively, they are robust and environmentally stable superhydrophobic and superoleophobic surfaces, after mechanical stabilization via wetting-drying and gas-phase coating with a perfluoroctyltrichlorosilane monolayer (PFOTS) or plasma deposited Teflon-like polymer layer. The plasma treated, micro-nanotextured surfaces used for biomolecule binding exhibit remarkable retention of the initially immobilized biomolecule compared to untreated COP surfaces (up to 75%), after washing with aggressive washing solutions (sodium dodecyl sulfate), while showing excellent intensity, uniformity and sensitivity. The superoleophobic COP material surfaces exhibit very high static contact angles (SCA>150°) and very low hysteresis (CAH<10°), for a wide range of liquids from water (surface tension: 72.8 mN/m) to hexadecane (surface tension: 27 mN/m). In addition, these superhydrophobic and superoleophobic surfaces exhibit excellent stability against environmental ageing after 60 continuous cycles of exposure to various harsh environmental conditions (heat, moisture, UV irradiation) in a controlled environment. Finally, the two presented functionalities are combined for the first time on the same COP substrate, creating localized rough hydrophilic and antifouling patterns that exhibit spatially selective biomolecule immobilization inside a microfluidic device.

doi: 10.1016/j.cej.2016.04.137

F. Giannopoulos, N. Chronopoulou, J. Bai, H. Zhao, D.I. Pantelis, E.A. Pavlatou, A. Karantonis

Electrochimica Acta (2016), 207, 76–86

In this work, composite coatings were fabricated by electrolytic co-deposition of hybrid MWCNT-Al₂O₃ particles with Ni matrix from a Watts type bath, with and without the use of the sodium dodecyl sulfate additive, under both direct and pulse current conditions. The surface morphology and structural characteristics of the coatings were investigated for the different types of applied current mode, in the absence and presence of the additive. The mechanism of electrochemical co-deposition of Ni and hybrid particles was investigated by linear sweep voltammetry, electrochemical impedance spectroscopy and quartz crystal microbalance measurements in order to elucidate some aspects of the co-deposition mechanism. It was found that the presence of hybrid MWCNT-Al₂O₃ particles promotes direct proton discharge as well as hydrogen coverage, thus decreasing the deposition efficiency.

doi: 10.1016/j.electacta.2016.04.162

N. Lagopati, E. Tsilibary, P. Falaras, P. Papazafiri, E.A Pavlatou, E. Kotsopoulou, P. Kitsiou

International Journal of Nanomedicine (2014), 9 (1), 3219-3230

The use of nanoparticles has seen exponential growth in the area of health care, due to the unique physicochemical properties of nanomaterials that make them desirable for medical applications. The aim of this study was to examine the effects of crystal phase-nanostructured titanium dioxide particles on bioactivity/cytotoxicity in breast cancer epithelial cells. Cultured Michigan Cancer Foundation (MCF)-7 and human breast adenocarcinoma (MDA-MB-468) breast cancer epithelial cells were exposed to ultraviolet A light (wavelength 350nm) for 20 minutes in the presence of aqueous dispersions of two different nanostructured titanium dioxide (TiO₂) crystal phases: anatase and an anatase–rutile mixture. Detailed characterization of each titanium dispersion was performed by dynamic light scattering. A 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide (MTT) colorimetric assay was employed to estimate the percentage of viable cells after each treatment. Western blot analysis of protein expression and characterization, as well as a deoxyribonucleic acid (DNA)-laddering assay, were used to detect cell apoptosis. Our results documented that 100% anatase TiO₂ nanoparticles (110–130nm) exhibited significantly higher cytotoxicity in the highly malignant MDA-MB-468 cancer cells than anatase–rutile mixtures (75%/25%) with the same size. On the contrary, MCF-7 cells (characterized by low invasive properties) were not considerably affected. Exposure of MDA-MB-468 cells to pure anatase nanoparticles or anatase–rutile mixtures for 48 hours resulted in increased proapoptotic Bax expression, caspase-mediated poly(adenosine diphosphate ribose) polymerase (PARP) cleavage, DNA fragmentation, and programmed cell death/apoptosis. The obtained results indicated that pure anatase TiO₂ nanoparticles exhibit superior cytotoxic effects compared to anatase–rutile mixtures of the same size. The molecular mechanism of TiO₂ nanoparticle cytotoxicity involved increased Bax expression and caspase-mediated PARP inactivation, thus resulting in DNA fragmentation and cell apoptosis.

doi: 10.2147/IJN.S62972

Α. Tzani, A. Douka, A. Papadopoulos, E.A. Pavlatou, E. Voutsas, A. Detsi

ACS Sustainable Chemistry and Engineering (2013), 1 (9), 1180-1185

In the frame of research that examines the use of task-specific ionic liquids (ILs) for developing green methodologies toward novel bioactive compounds, ethanolamine-derived ILs were synthesized and used as solvents and catalysts in a domino Knoevenagel–Michael reaction. After extended optimization studies regarding the most important reaction parameters such as reaction time, temperature, and molar ratio of reactants, it was ascertained that the reaction between 4-hydroxy-coumarin and various benzaldehydes in the synthesized ILs proceeded smoothly at 40°C in 3h, providing the desired biscoumarins in very satisfactory yields (up to 97%) and high purity after simple workup. The task-specific ILs were recycled and reused three times without a noticeable decrease in their catalytic activity. Moreover, the biodegradability potential of the synthesized ILs has been investigated by applying the biological oxygen demand (BOD-5) closed bottle test. The results indicated that organic carbon was biodegraded up to 59% within five days.

doi: 10.1021/sc4001093

A.V. Katsanaki, A.G., Kontos, T.Maggos, M. Pelaez, V .Likodimos, E.A. Pavlatou, D.D. Dionysiou, P. Falaras

Applied Catalysis B: Environmental (2013), 140-141, 619-625

Visible light activated nanostructured TiO2 with nitrogen and fluorine co-dopants were prepared by the surfactant assisted sol–gel method and immobilized on glass substrates by dip coating. The films were inserted inside a continuous flow photoreactor and examined for the photocatalytic oxidation of NO air pollutant with initial concentration of 200–800 ppbv. The modified catalysts exhibited significant photocatalytic activity under daylight illumination, with maximum percentage of NO removal equal to 24.2% and photooxidation rate up to 0.66 μgm⁻²s⁻¹. The reaction rates increased proportionally to the incident light intensity whereas for the strongly absorbed UV light a deviation from linearity was observed. Mass balance during photooxidation was confirmed by determining the amount of NO₃⁻ product residues onto the photocatalyst surface.

doi: 10.1016/j.apcatb.2013.04.070

N. Kalogeropoulos, J. Tzigounakis, E.A. Pavlatou, A. Boudouvis

Computer Applications in Engineering Education (2013), 21, 671-683

In this study, the score equivalence of computer‐based assessment (CBA) and paper‐and‐pencil testing (PPT) in an undergraduate course of introductory computer programing at the National Technical University of Athens' School of Chemical Engineering, was examined. The research was carried out with 211 students participating, and was realized by a specially constructed CBA platform as well as the classical PPT. Both types of assessment included the same questions of multiple‐choice type, completing and correcting code in Fortran, as well as writing Fortran code from scratch. The results showed that, in general, students performed better and received higher scores under CBA compared to PPT. In particular, the very good students benefited from the advantages that the computer compiler offers in debugging code and completing code exercises and, thus, received relatively higher scores in these parts of the test. Moreover, switching answers and devoting more time‐on‐task was found to be beneficial for the students' performance. Overall, the findings of this study revealed that the actual programing abilities of the students are better evaluated using such CBA tests.

doi: 10.1002/cae.20512