Papers

I.-A. Vagena, M.-A. Gatou, G. Theocharous, P. Pantelis, M. Gazouli, N. Pippa, V.G. Gorgoulis, E.A. Pavlatou, N. Lagopati

Nanomaterials 2024, 14 (5), 397

The wide array of structures and characteristics found in ZnO-based nanostructures offers them a versatile range of uses. Over the past decade, significant attention has been drawn to the possible applications of these materials in the biomedical field, owing to their distinctive electronic, optical, catalytic, and antimicrobial attributes, alongside their exceptional biocompatibility and surface chemistry. With environmental degradation and an aging population contributing to escalating healthcare needs and costs, particularly in developing nations, there’s a growing demand for more effective and affordable biomedical devices with innovative functionalities. This review delves into particular essential facets of different synthetic approaches (chemical and green) that contribute to the production of effective multifunctional nano-ZnO particles for biomedical applications. Outlining the conjugation of ZnO nanoparticles highlights the enhancement of biomedical capacity while lowering toxicity. Additionally, recent progress in the study of ZnO-based nano-biomaterials tailored for biomedical purposes is explored, including biosensing, bioimaging, tissue regeneration, drug delivery, as well as vaccines and immunotherapy. The final section focuses on nano-ZnO particles’ toxicity mechanism with special emphasis to their neurotoxic potential, as well as the primary toxicity pathways, providing an overall review of the up-to-date development and future perspectives of nano-ZnO particles in the biomedicine field.

doi: 10.3390/nano14050397

 

A.G. Mitsopoulou, E.A. Pavlatou

Education Sciences 2024, 14 (2), 183

The present study’s objective constitutes the examination of the prognostic factors that influence the inclination of students in secondary school towards pursuing higher education. To achieve this goal, an existing questionnaire was utilized and appropriately altered to align with the Greek educational system. The survey involved the participation of 301 secondary school students from Piraeus, which comprises one of Greece’s major cities. The outcomes of the research yield substantial endorsement for the principles outlined in the social cognitive career theory. Specifically, the study highlights the significant role of family background, encompassing the educational levels of the parents, the students’ perceptions of the family’s financial situation, and the financial support provided by the family during the students’ academic journey, in shaping the students’ intent towards pursuing higher education. Moreover, the presence of a secure attachment bond between students and their parents suggests a favorable inclination towards higher education. Conversely, students deriving from low-income families are prone to exhibit hesitancy in pursuing higher education. The acquired data reveal a constructive relationship among outcome expectations, social support, as well as the process of students’ interest in developing a desire for higher education. Conversely, factors such as gender and age, as well as the presence of siblings studying in higher education, appear to have little influence in this regard.

doi: 10.3390/educsci14020183

M.-A. Gatou, A. Syrrakou, N. Lagopati, E.A. Pavlatou

Reactions 2024, 5 (1), 135-194

Contemporary technological and industrial advancements have led to increased reliance on chemicals for product innovation, leading to heightened contamination of water sources by traditional pollutants (organic dyes, heavy metals) and disease-causing microorganisms. Wastewater treatment processes now reveal “emerging pollutants”, including pharmaceuticals, endocrine disruptors, and agricultural chemicals. While some are benign, certain emerging pollutants can harm diverse organisms. Researchers seek cost-effective water purification methods that completely degrade pollutants without generating harmful by-products. Semiconductor-based photocatalytic degradation, particularly using titanium dioxide (TiO2), is popular for addressing water pollution. This study focuses on recent applications of TiO2 nanostructures in photocatalysis for eliminating various water pollutants. Structural modifications, like doping and nanocomposite formation, enhance photocatalyst performance. The study emphasizes photocatalytic elimination mechanisms and comprehensively discusses factors impacting both the mechanism and performance of nano-TiO2-based photocatalysts. Characteristics of TiO2, such as crystal structure and energy band-gap, along with its photocatalytic activity mechanism, are presented. The review covers the advantages and limitations of different TiO2 nanostructure production approaches and addresses potential toxicity to human health and the environment. In summary, this review provides a holistic perspective on applying nano-TiO2 materials to mitigate water pollution.

doi: 10.3390/reactions5010007

E. Rosolymou, A. Karantonis, E.A. Pavlatou

Materials 2024, 17 (2), 392

Sn–Ni alloy matrix coatings co-deposited with TiO2 nanoparticles (Evonik P25) were produced utilizing direct (DC) and pulse electrodeposition (PC) from a tin–nickel chloride-fluoride electrolyte with a loading of TiO2 nanoparticles equal to 20 g/L. The structural and morphological characteristics of the resultant composite coatings were correlated with the compositional modifications that occurred within the alloy matrix and expressed via a) TiO2 co-deposition rate and b) composition of the matrix; this was due to the application of different current types (DC or PC electrodeposition), and different current density values. The results demonstrated that under DC electrodeposition, the current density exhibited a more significant impact on the composition of the alloy matrix than on the incorporation rate of the TiO2 nanoparticles. Additionally, PC electrodeposition favored the incorporation rate of TiO2 nanoparticles only when applying a low peak current density (Jp = 1 Adm−2). All of the composite coatings exhibited the characteristic cauliflower-like structure, and were characterized as nano-crystalline. The composites’ surface roughness demonstrated a significant influence from the TiO2 incorporation rate. However, in terms of microhardness, higher co-deposition rates of embedded TiO2 nanoparticles within the alloy matrix were associated with decreased microhardness values. The best wear performance was achieved for the composite produced utilizing DC electrodeposition at J = 1 Adm−2, which also demonstrated the best photocatalytic behavior under UV irradiation. The corrosion study of the composite coatings revealed that they exhibit passivation, even at elevated anodic potentials.

doi: 10.3390/ma17020392

Ch. Kaliampakou, N. Lagopati, E.A. Pavlatou, C.A. Charitidis

Gels 2023, 9, 857

The generation of 3D structures comprises three interlinked phases: material development, the printing process, and post-printing treatment. Numerous factors control all three phases, making the optimization of the entire process a challenging task. Until now, the state of the art has mainly focused on optimizing material processability and calibration of the printing process. However, after the successful Direct Ink Writing (DIW) of a hydrogel scaffold, the post-printing stage holds equal importance, as this allows for the treatment of the structure to ensure the preservation of its structural integrity for a duration that is sufficient to enable successful cell attachment and proliferation before undergoing degradation. Despite this stage’s pivotal role, there is a lack of extensive literature covering its optimization. By studying the crosslinking factors and leveling the post-treatment settings of alginate–gelatin hydrogel, this study proposes a method to enhance scaffolds’ degradation without compromising the targeted swelling behavior. It introduces an experimental design implementing the Response Surface Methodology (RSM) Design of Experiments (DoE), which elucidated the key parameters influencing scaffold degradation and swelling, and established an alginate ratio of 8% and being immersed for 15 min in 0.248 M CaCl2 as the optimal level configuration that generates a solution of 0.964 desirability, reaching a degradation time of 19.654 days and the swelling ratio of 50.00%.

doi: 10.3390/gels9110857

M.-A. Gatou, K. Kontoliou, E. Volla, K. Karachalios, G. Raptopoulos, P. Paraskevopoulou, N. Lagopati, E.A. Pavlatou

Catalysts 2023, 13, 1367

Zinc oxide (ZnO) possesses exceptional potential to be utilized in water and wastewater treatment applications, either as a photocatalyst or in membrane incorporation. In the present study, ZnO nanoparticles were synthesized using the precipitation method. The Taguchi approach with the L32b orthogonal array was utilized in order to optimize the experimental conditions for the synthesis of the nanoparticles and to ensure that relatively smaller-sized particles were obtained. The design was characterized by ten factors, where nine of them possessed four levels, while one had two levels. This study’s design factors were the type of Zn precursor, the concentration of the Zn precursor, the type of precipitating agent, the precipitation agent’s concentration, the type of utilized solvent, the pH value of the solvent, the temperature used during the synthetic procedure, the calcination temperature, the time of stirring during synthesis, as well as the stirring speed. The influences of those factors on the selected response parameters (the average crystallite size, degree of crystallinity, energy band gap (Eg), and photodegradation constant (k)) were then evaluated. XRD analysis and the calculated Eg values indicated that the hexagonal wurtzite structure was the only crystalline phase present in the produced samples. The photocatalytic efficiency of all ZnO nanoparticles was examined in the degradation of rhodamine B under UV light irradiation. The optimal conditions were achieved using zinc acetate dihydrate as the Zn precursor at a concentration equal to 0.3 M, sodium hydroxide as the precipitating agent (1.5 M), methanol as the solvent (the pH value of the solvent was equal to 13), a temperature during the synthetic procedure of 70 °C, 600 °C as calcination temperature, a 90 min stirring time, and 700 rpm as the stirring speed. The optimized ZnO sample was synthesized based on the aforementioned conditions and thoroughly characterized. The acquired results confirmed the prediction of the Taguchi approach, and the most enhanced k-value was observed.

doi: 10.3390/catal13101367

N. Lagopati, N. Pippa, M.-A. Gatou, N. Papadopoulou-Fermeli, V.G. Gorgoulis, M. Gazouli, E.A. Pavlatou

Applied Sciences 2023, 13, 9172

Aquatic habitats cover almost 70 % of the Earth, containing several species contributing to marine biodiversity. Marine and aquatic organisms are rich in chemical compounds that can be widely used in biomedicine (dentistry, pharmacy, cosmetology, etc.) as alternative raw biomaterials or in food supplements. Their structural characteristics make them promising candidates for tissue engineering approaches in regenerative medicine. Thus, seaweeds, marine sponges, arthropods, cnidaria, mollusks, and the biomaterials provided by them, such as alginate, vitamins, laminarin, collagen, chitin, chitosan, gelatin, hydroxyapatite, biosilica, etc., are going to be discussed focusing on the biomedical applications of these marine-originated biomaterials. The ultimate goal is to highlight the sustainability of the use of these biomaterials instead of conventional ones, mainly due to the antimicrobial, anti-inflammatory, anti-aging and anticancer effect.

doi: 10.3390/app13169172

Μ.-Α. Gatou, Ι.-Α. Vagena, Ν. Pippa, Μ. Gazouli, Ε.Α. Pavlatou, Ν. Lagopati

Crystals 2023, 13, 1236

This review study aims to present, in a condensed manner, the significance of the use of crystalline carbon-based nanomaterials in biomedical applications. Crystalline carbon-based nanomaterials, encompassing graphene, graphene oxide, reduced graphene oxide, carbon nanotubes, and graphene quantum dots, have emerged as promising materials for the development of medical devices in various biomedical applications. These materials possess inorganic semiconducting attributes combined with organic π-π stacking features, allowing them to efficiently interact with biomolecules and present enhanced light responses. By harnessing these unique properties, carbon-based nanomaterials offer promising opportunities for future advancements in biomedicine. Recent studies have focused on the development of these nanomaterials for targeted drug delivery, cancer treatment, and biosensors. The conjugation and modification of carbon-based nanomaterials have led to significant advancements in a plethora of therapies and have addressed limitations in preclinical biomedical applications. Furthermore, the wide-ranging therapeutic advantages of carbon nanotubes have been thoroughly examined in the context of biomedical applications.

doi: 10.3390/cryst13081236

M.-A. Gatou, I.-A. Vagena, N. Lagopati, N. Pippa, M. Gazouli, E.A. Pavlatou

Nanomaterials 202313, 2224

Over the last ten years, there has been a growing interest in metal–organic frameworks (MOFs), which are a unique category of porous materials that combine organic and inorganic components. MOFs have garnered significant attention due to their highly favorable characteristics, such as environmentally friendly nature, enhanced surface area and pore volume, hierarchical arrangements, and adjustable properties, as well as their versatile applications in fields such as chemical engineering, materials science, and the environmental and biomedical sectors. This article centers on examining the advancements in using MOFs for environmental remediation purposes. Additionally, it discusses the latest developments in employing MOFs as potential tools for disease diagnosis and drug delivery across various ailments, including cancer, diabetes, neurological disorders, and ocular diseases. Firstly, a concise overview of MOF evolution and the synthetic techniques employed for creating MOFs are provided, presenting their advantages and limitations. Subsequently, the challenges, potential avenues, and perspectives for future advancements in the utilization of MOFs in the respective application domains are addressed. Lastly, a comprehensive comparison of the materials presently employed in these applications is conducted.

doi: 10.3390/nano13152224 

M.-A. Gatou, E. Fiorentis, N. Lagopati, E.A. Pavlatou

Water 2023, 15, 2773

Organic pollutants found in industrial effluents contribute to significant environmental risks. Degradation of these pollutants, particularly through photocatalysis, is a promising strategy ensuring water purification and supporting wastewater treatment. Thus, photodegradation of rhodamine B and phenol under visible-light irradiation using TiO2/SiO2 composite nanoparticles was within the main scopes of this study. The nanocomposite was synthesized through a wet impregnation method using TiO2 and SiO2 nanopowders previously prepared via a facile sol–gel approach and was fully characterized. The obtained results indicated a pure anatase phase, coupled with increased crystallinity (85.22 %) and a relative smaller crystallite size (1.82 nm) in relation to pure TiO2 and SiO2 and an enhanced specific surface area (50 m2/g) and a reduced energy band gap (3.18 eV). Photodegradation of rhodamine B upon visible-light irradiation was studied, showing that the TiO2/SiO2 composite reached total (100 %) degradation within 210 min compared to pure TiO2 and SiO2 analogues, which achieved a ≈45 % and ≈43 % degradation rate, respectively. Similarly, the composite catalyst presented enhanced photocatalytic performance under the same irradiation conditions towards the degradation of phenol, leading to 43.19 % degradation within 210 min and verifying the composite catalyst’s selectivity towards degradation of rhodamine B dye as well as its enhanced photocatalytic efficiency towards both organic compounds compared to pure TiO2 and SiO2. Additionally, based on the acquired experimental results, ●O2−, h+ and e were found to be the major reactive oxygen species involved in rhodamine B’s photocatalytic degradation, while ●OH radicals were pivotal in the photodegradation of phenol under visible irradiation. Finally, after the TiO2/SiO2 composite catalyst was reused five times, it indicated negligible photodegradation efficiency decrease towards both organic compounds.

doi: 10.3390/w15152773

E. Galata, C.M. Veziri, G.V. Theodorakopoulos, G.E. Romanos, E.A. Pavlatou

Membranes 202313, 627

The adhesion enhancement of a graphene oxide (GO) layer on porous ceramic substrates is a crucial step towards developing a high-performance membrane for many applications. In this work, we have achieved the chemical anchoring of GO layers on custom-made macroporous disks, fabricated in the lab by pressing α-Al2O3 powder. To this end, three different linkers, polydopamine (PDA), 3-Glycidoxypropyltrimethoxysilane (GPTMS) and (3-Aminopropyl) triethoxysilane (APTMS), were elaborated for their capacity to tightly bind the GO laminate on the ceramic membrane surface. The same procedure was replicated on cylindrical porous commercial ZrO2 substrates because of their potentiality for applications on a large scale. The gas permeance properties of the membranes were studied using helium at 25°C as a probe molecule and further scrutinized in conjunction with water permeance results. Measurements with helium at 25°C were chosen to avoid gas adsorption and surface diffusion mechanisms. This approach allowed us to draw conclusions on the deposition morphology of the GO sheets on the ceramic support, the mode of chemical bonding with the linker and the stability of the deposited GO laminate. Specifically, considering that He permeance is mostly affected by the pore structural characteristics, an estimation was initially made of the relative change in the pore size of the developed membranes compared to the bare substrate. This was achieved by interpreting the results via the Knudsen equation, which describes the gas permeance as being analogous to the third power of the pore radius. Subsequently, the calculated relative change in the pore size was inserted into the Hagen–Poiseuille equation to predict the respective water permeance ratio of the GO membranes to the bare substrate. The reason that the experimental water permeance values may deviate from the predicted ones is related to the different surface chemistry, i.e., the hydrophilicity or hydrophobicity that the composite membranes acquire after the chemical modification. Various characterization techniques were applied to study the morphological and physicochemical properties of the materials, like FESEM, XRD, DLS and Contact Angle.

doi: 10.3390/membranes13070627

E. Fiorentis, M.-A. Gatou, N. Lagopati, E.A. Pavlatou

Biomedical Journal of Scientific and Technical Research 2023, 15 (1), 42382

Silica nanoparticles (SiNPs) are widely utilized in various industries, such as food, synthetic processes, medical diagnosis and drug delivery, owing to their adjustable particle size, extensive surface area and excellent biocompatibility. Numerous studies have explored the biomedical applications of SiNPs, including the customization of their surfaces and structures to target different types of cancers and facilitate disease diagnosis. This mini review encompasses recent research on the biomedical applications of SiNPs, incorporating fundamental discoveries and ongoing exploratory advancements of their research, and particularly their implementation in drug delivery systems for the diagnosis and treatment of various diseases within the human body, holding potential for practical developments in the future.

doi: 10.26717/BJSTR.2023.51.008057

D.S. Tsoukleris, M.-A. Gatou, N. Lagopati, L. Sygellou, D.C. Christodouleas, P. Falaras, E.A. Pavlatou
 
Water 2023, 15 (11), 2052
 
Among key issues in municipal wastewater treatment plants (MWTP) is the existence of pathogenic bacteria in the discarded effluents. Conventional disinfectants (ozone, UV irradiation, chlorine) have been insufficient in providing safe water due to the development of undesirable and noxious by-products. TiO2 comprises an attractive alternative to conventional methods because of its versatility and recently explored biocidal efficiency. As a result, within the framework of this study, chemically modified, visible active nanocrystalline TiO2 powders (N-TiO2, N,S-TiO2, and Ag@N-TiO2) were prepared via a low-cost, feasible sol-gel method for the treatment of real municipal wastewater effluents. Wastewater samples were acquired from the outlet of the treatment of Antiparos (Cyclades, Greece) MWTP during the summer period in which a great number of seasonal habitants and tourists usually visit the island, resulting in at least a doubling of the population. All synthesized powders were thoroughly characterized using various morphological and spectroscopic techniques, such as FE-SEM, XRD, micro-Raman, FTIR, DLS, UV-DRS, and XPS. Photocatalytic evaluation experiments were initially conducted towards Rhodamine B degradation under visible light irradiation. Among all studied powders, Ag@N-TiO2 indicated the highest efficiency, reaching total degradation (100%) of RhB within 240 min due to its smaller crystallite size (1.80 nm), enhanced surface area (81 m2g−1), and reduced energy band gap (Eg = 2.79 eV). The effect of the produced powders on the disinfection as assessed in terms of fecal indicator microorganisms (E. coli and total coliforms) inactivation was also examined in a semi-pilot scale-up photocatalytic reactor. Ag@N-TiO2 nanopowder was also found substantially more active for both groups of bacteria, leading to complete inactivation in less than 35 min, probably due to the higher production of H2O2/•OH, as emerged from the photocatalytic mechanism study. In addition, Ag@N-TiO2 nanoparticles demonstrated excellent photocatalytic and disinfection stability even after five subsequent recycling trials (8.34% activity loss and complete inactivation, respectively). The results of the present study demonstrate the feasibility for Ag@N-TiO2 to be utilized as a viable, eco-friendly approach for the photocatalytic pathogenic bacteria inactivation as an alternative disinfection approach for municipal wastewater treatment plant effluents with intense seasonal fluctuations in volume.
 

N. Lagopati, Th.-F. Valamvanos, V. Proutsou, K. Karachalios, N. Pippa, M.-A. Gatou, I.-A. Vagena, S. Cela, E.A. Pavlatou, M. Gazouli, E. Efstathopoulos

Chemosensors 2023, 11(6), 317

Early-stage, precise disease diagnosis and treatment has been a crucial topic of scientific discussion since time immemorial. When these factors are combined with experience and scientific knowledge, they can benefit not only the patient, but also, by extension, the entire health system. The development of rapidly growing novel technologies allows for accurate diagnosis and treatment of disease. Nanomedicine can contribute to exhaled breath analysis (EBA) for disease diagnosis, providing nanomaterials and improving sensing performance and detection sensitivity. Through EBA, gas-based nano-sensors might be applied for the detection of various essential diseases, since some of their metabolic products are detectable and measurable in the exhaled breath. The design and development of innovative nanomaterial-based sensor devices for the detection of specific biomarkers in breath samples has emerged as a promising research field for the non-invasive accurate diagnosis of several diseases. EBA would be an inexpensive and widely available commercial tool that could also be used as a disease self-test kit. Thus, it could guide patients to the proper specialty, bypassing those expensive tests, resulting, hence, in earlier diagnosis, treatment, and thus a better quality of life. In this review, some of the most prevalent types of sensors used in breath-sample analysis are presented in parallel with the common diseases that might be diagnosed through EBA, highlighting the impact of incorporating new technological achievements in the clinical routine.

doi: 10.3390/chemosensors11060317

M.-E. Kassalia, N. Chorianopoulos, G.-J. Nychas, E.A. Pavlatou

Applied Sciences (2023), 13 (7), 4498

The aim of the present study was to investigate the photoinduced properties of nitrogen-doped titanium dioxide (N-TiO2) against the Salmonella ser. Typhimurium bacterial biofilm, under visible-light irradiation. The capability of N-TiO2 nanoparticles working as multipurpose materials with antimicrobial applications, as well as environmental ones, was therefore investigated. The sol–gel method was used to synthesize N-TiO2 particles, which were then characterized by Fourier-transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS), Brunauer–Emmett–Teller (BET) analysis of surface area, scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDS), and transmission electron microscopy (TEM). The results showed that the particles formed were nano-sized and had the expected Ti-O bonds and the presence of elemental N. The as-produced N-TiO2 nanoparticles (NPs) were tested for their antimicrobial activity. The antibacterial photocatalytic testing was performed under visible-light irradiation, on Salmonella Typhimurium biofilm. To form the biofilm, stainless steel (ss) coupons were incubated with three different strains of Salmonella Typhimurium bacteria for 48 h at 15°C in tryptone soy broth (TSB). After the biofilm’s formation, the coupons were placed on a horizontal, rectangular, batch, equipped with a vis-LED irradiation source reactor in the presence of N-TiO2 NPs. After 1, 2, and 3 h of irradiation, sampling of the bacterial population was assessed. The results showed an evident inhibition of proliferation under light irradiation when the N-TiO2 was present, compared to the non-irradiated NPs. It is noteworthy that, during the first 2 h, the TiO2 NPs specimens tended to attract more bacteria on their surface then the control specimens, due to their higher available surface area, which worked as a shelter. There were ~6% viable (remaining) Salmonella cells after the first hour of visible-light irradiation with N-TiO2 NPs.

doi: 10.3390/app13074498

P. Pantelis, G. Theocharous, N. Lagopati, D. Veroutis, D.-F. Thanos, G.-P. Lampoglou, N. Pippa, M.-A. Gatou, I. Tremi, A. Papaspyropoulos, E. Kyrodimos, E.A. Pavlatou, M. Gazouli, K. Evangelou, V.G. Gorgoulis

Antioxidants (2023), 12 (1), 169

The contemporary lifestyle of the last decade has undeniably caused a tremendous increase in oxidative-stress-inducing environmental sources. This phenomenon is not only connected with the rise of ROS levels in multiple tissues but is also associated with the induction of senescence in different cell types. Several signaling pathways that are associated with the reduction in ROS levels and the regulation of the cell cycle are being activated, so that the organism can battle deleterious effects. Within this context, autophagy plays a significant role. Through autophagy, cells can maintain their homeostasis, as if it were a self-degradation process, which removes the “wounded” molecules from the cells and uses their materials as a substrate for the creation of new useful cell particles. However, the role of autophagy in senescence has both a “dark” and a “bright” side. This review is an attempt to reveal the mechanistic aspects of this dual role. Nanomedicine can play a significant role, providing materials that are able to act by either preventing ROS generation or controllably inducing it, thus functioning as potential therapeutic agents regulating the activation or inhibition of autophagy.

doi: 10.3390/antiox12010169

M.-E. Kassalia, Z. Nikolaou, Ε.A. Pavlatou

Applied Sciences (2023), 13 (2), 774

The primary objective of this research is to propose and compile a specific protocol for photocatalytic measurements of modified TiO2 particles under visible-light irradiation. Nitrogen-modified titanium dioxide (N-TiO2) powder was synthesized by the sol–gel method and characterized by X-ray Diffraction Analysis (XRD), Field Emission Scanning Electron Microscopy (FESEM), Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS), Raman Spectroscopy (micro-Raman), and Ultraviolet–visible Spectroscopy (UV-Vis). Photocatalytic tests were performed on a specially designed photocatalytic batch reactor to test the ability of the powder to degrade hazardous toxic compounds. Via the Taguchi method, nine experiments (L9) were compiled to examine the factors that affect the photocatalytic activity of the nano-sized powder. The N-TiO2 particles were characterized by the dominance of the crystalline anatase phase, exhibiting crystals in the nano-scale. The Taguchi method was designed to control four selected parameters (pollutant selection among azo dyes, amount of catalyst to pollutant, distance of the photocatalytic cell from the radiation source, and time protocol) with three levels/options each. Conclusions were drawn regarding the way each parameter affects the final degradation of the pollutant. The parameter that proved to affect the degradation of the pollutant to a greater extent was the choice of pollutant, followed by the amount of catalyst. The other two factors almost slightly affect the process, with a similar percentage. Taking into account the abovementioned results, a photocatalytic protocol for testing TiO2 nano-powder activity under visible light irradiation is proposed by using a batch, horizontal, rectangular, vis-LED equipped reactor with reflective walls.

doi: 10.3390/app13020774

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

Biomedical Journal of Scientific & Technical Research, 47 (2), 38305-38308 

Carbon quantum dots are a new class of zero-dimensional carbon nanomaterials that due to their low toxicity, high water dispersibility and fluorescent properties, have attracted a lot of attention for biomedical applications. They can be synthesized with many different methods through both bottom-up and top-down approaches. In this mini review we summarize the existing literature regarding the electrochemical exfoliation of pure graphite that produces nanostructures of diameter smaller than 10 nm. We focus on the electrolytes that are used and the voltage applied, as the main factors that contribute on the size, structure, composition and yield of the carbon quantum dots. In order to explain the findings of the literature, we briefly analyze the mechanism of the graphite exfoliation from the ions, under applied voltage. Furthermore, we report on the many advantages that the electrochemical approach has over competing methodologies, that make it an attractive method for mass production of carbon quantum dots, with the intention to be used in biomedical applications.

doi: 10.26717/BJSTR.2022.47.007479

N. Papadopoulou-Fermeli, N. Lagopati, N. Pippa, E. Sakellis, N. Boukos, V.G. Gorgoulis, M. Gazouli, E.A. Pavlatou

Pharmaceutics (2023), 15 (1), 135

The synthesis of titania-based composite materials with anticancer potential under visible-light irradiation is the aim of this study. In specific, titanium dioxide (TiO2) nanoparticles (NPs) chemically modified with silver were embedded in a stimuli-responsive microgel (a crosslinked interpenetrating network (IP) network that was synthesized by poly (N-Isopropylacrylamide) and linear chains of polyacrylic acid sodium salt, forming composite particles. The ultimate goal of this research, and for our future plans, is to develop a drug-delivery system that uses optical fibers that could efficiently photoactivate NPs, targeting cancer cells. The produced Ag-TiO2 NPs, the microgel and the composite materials were characterized through X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), micro-Raman spectroscopy, ultraviolet-visible spectroscopy (UV-Vis), dynamic light scattering (DLS) and transmission electron microscopy (TEM). Our results indicated that Ag-TiO2 NPs were successfully embedded within the thermoresponsive microgel. Either Ag-TiO2 NPs or the composite materials exhibited high photocatalytic degradation efficiency on the pollutant rhodamine B and significant anticancer potential under visible-light irradiation.

doi: 10.3390/pharmaceutics15010135

M.-A. Gatou, N. Lagopati, I.-A. Vagena, M. Gazouli, E.A. Pavlatou

Nanomaterials (2023), 13 (1), 122

Semiconductor photocatalysts, particularly ZnO nanoparticles, were synthesized via the precipitation method using four different precursors (zinc acetate/zinc nitrate/zinc sulfate/zinc chloride) and compared, according to their optical, structural, photocatalytic, and anticancer properties. The materials were characterized via X-ray Diffraction method (XRD), micro-Raman, Fourier Transform Infrared Spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET), Dynamic Light Scattering (DLS), and Field Emission Scanning Electron Microscope (FESEM) analysis. Photocatalysis was conducted under UV and visible light irradiation, using Rhodamine B as the organic pollutant. It was observed that the highest photocatalysis efficiency was obtained by the nanoparticles synthesized from the zinc acetate used as precursor material. A cell-dependent anticancer efficiency of the tested ZnO nanoparticles was also observed, that was also attributed to the different precursors and the synthesis method, revealing that the nanoparticles that were synthesized from zinc acetate were more bioactive among the four tested precursors. Overall, the data revealed that both the enhanced photocatalytic and biological activity of ZnO nanoparticles derived from zinc acetate precursor could be attributed to the reduced crystalline size, increased surface area, as well as the observed hexagonal crystalline morphology.

doi: 10.3390/nano13010122

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