Silvija Šafranko

Bio: Silvija Šafranko is an academic researcher from Josip Juraj Strossmayer University of Osijek. The author has contributed to research in topics: Calcium oxalate & Hesperidin. The author has an hindex of 5, co-authored 16 publications receiving 85 citations.

Antimicrobial Activity of Chamomile Essential Oil: Effect of Different Formulations.

Abstract: Essential oils (EOs) are highly lipophilic, which makes the measurement of their biological action difficult in an aqueous environment. We formulated a Pickering nanoemulsion of chamomile EO (CPe). Surface-modified Stober silica nanoparticles (20 nm) were prepared and used as a stabilizing agent of CPe. The antimicrobial activity of CPe was compared with that of emulsion stabilized with Tween 80 (CT80) and ethanolic solution (CEt). The antimicrobial effects were assessed by their minimum inhibitory concentration (MIC90) and minimum effective (MEC10) concentrations. Besides growth inhibition (CFU/mL), the metabolic activity and viability of Gram-positive and Gram-negative bacteria as well as Candida species, in addition to the generation of oxygen free radical species (ROS), were studied. We followed the killing activity of CPe and analyzed the efficiency of the EO delivery for examined formulations by using unilamellar liposomes as a cellular model. CPe showed significantly higher antibacterial and antifungal activities than CT80 and CEt. Chamomile EOs generated superoxide anion and peroxide related oxidative stress which might be the major mode of action of Ch essential oil. We could also demonstrate that CPe was the most effective in donation of the active EO components when compared with CT80 and CEt. Our data suggest that CPe formulation is useful in the fight against microbial infections.

Green Extraction Techniques for Obtaining Bioactive Compounds from Mandarin Peel ( Citrus unshiu var. Kuno ): Phytochemical Analysis and Process Optimization.

Abstract: In this study, an efficient utilization and valorization of mandarin peel (Citrus unshiu Marc. var. Kuno) was investigated using innovative and green extraction techniques. The first step of this study included the extraction and analysis of the volatile compounds by performing a supercritical CO2 (SC-CO2) extraction under different operating pressure conditions (100 and 300 bar). The analysis of volatile compounds of the obtained extracts was conducted by gas chromatography-mass spectrometry (GC-MS), and limonene was found to be the dominant volatile component (13.16% at 100 bar; 30.65% at 300 bar). After SC-CO2 treatment, the exhausted citrus peel waste enriched with bioactive compounds was subjected to subcritical water extraction (SWE) in a wide temperature range (130-220 °C) using different solvent-solid ratio (10-30 mL/g) in time periods from 5 to 15 min, in order to obtain bioflavonoids. Identification and quantification of present bioflavonoids was conducted by high-performance liquid chromatography with a with a diode array detector (HPLC), and hesperidin (0.16-15.07 mg/g) was determined as the most abundant flavanon in mandarin peel with other polyphenolic compounds that were possible by-products of thermal degradation. At higher temperatures, the presence of 5-hydroxymethylfurfural (5-HMF) and chlorogenic acid were detected. Antiradical activity and total phenolic content in the extracts were determined using spectrophotometric methods, while the process optimization was performed by response surface methodology (RSM).

An Overview of the Recent Developments in Carbon Quantum Dots—Promising Nanomaterials for Metal Ion Detection and (Bio)Molecule Sensing

Abstract: The fluorescent carbon quantum dots (CQDs) represent an emerging subset of carbonaceous nanomaterials, recently becoming a powerful tool for biosensing, bioimaging, and drug and gene delivery. In general, carbon dots are defined as zero-dimensional (0D), spherical-like nanoparticles with <10 nm in size. Their unique chemical, optical, and electronic properties make CQDs versatile materials for a wide spectrum of applications, mainly for the sensing and biomedical purposes. Due to their good biocompatibility, water solubility, and relatively facile modification, these novel materials have attracted tremendous interest in recent years, which is especially important for nanotechnology and nanoscience expertise. The preparation of the biomass-derived CQDs has attracted growing interest recently due to their low-cost, renewable, and green biomass resources, presenting also the variability of possible modification for the enhancement of CQDs’ properties. This review is primarily focused on the recent developments in carbon dots and their application in the sensing of different chemical species within the last five years. Furthermore, special emphasis has been made regarding the green approaches for obtaining CQDs and nanomaterial characterization toward better understanding the mechanisms of photoluminescent behavior and sensing performance. In addition, some of the challenges and future outlooks in CQDs research have been briefly outlined.

Separation of selected bioactive compounds from orange peel using the sequence of supercritical CO2 extraction and ultrasound solvent extraction: optimization of limonene and hesperidin content

Abstract: The orange peel (Citrus sinensis L.) from the variety Washington Navel was extracted by supercritical CO2 (SC-CO2) at different parameters. The extracts were analyzed by gas chromatography-mass spe...

Smart Textile Triboelectric Nanogenerators: Prospective Strategies for Improving Electricity Output Performance

Abstract: By seamlessly integrating the wearing comfortability of textiles with the biomechanical energy harvesting function of a triboelectric nanogenerator (TENG), an emerging and advanced intelligent textile, i.e., smart textile TENG, is developed with remarkable abilities of autonomous power supply and self-powered sensing, which has great development prospects in the next-generation human-oriented wearable electronics. However, due to inadequate interface contact, insufficient electrification of materials, unavoidable air breakdown effect, output capacitance feature, and special textile structure, there are still several bottlenecks in the road towards the practical application of textile TENGs, including low output, high impedance, low integration, poor working durability, and so on. In this review, on the basis of mastering the existing theory of electricity generation mechanism of TENGs, some prospective strategies for improving the mechanical-to-electrical conversion performance of textile TENGs are systematically summarized and comprehensively discussed, including surface/interface physical treatments, atomic-scale chemical modification, structural optimization design, work environmental control, and integrated energy management. The advantages and disadvantages of each approach in output enhancement are further compared at the end of this review. It is hoped that this review can not only provide useful guidance for the research of textile TENGs to select optimization methods but also accelerate their large-scale practical process.

At-Home Colorimetric and Absorbance-Based Analyses: An Opportunity for Inquiry-Based, Laboratory-Style Learning

Abstract: In light of COVID-19 in spring 2020, we developed a simple and versatile inquiry-based, laboratory-style active learning colorimetry experiment amenable to at-home quantitative analysis. In this ex...

Review of Student-Built Spectroscopy Instrumentation Projects.

Abstract: One challenge of teaching chemical analysis is the proliferation of sophisticated, but often impenetrable, instrumentation in the modern laboratory. Complex instruments, and the software that runs them, distance students from the physical and chemical processes that generate the analytical signal. A solution to this challenge is the introduction of a student-driven instrument-building project. Visible absorbance spectroscopy is well-suited to such a project due to its relative simplicity and the ubiquity of absorbance measurements. This Article reviews simple instructor- and student-built instruments for spectroscopy, providing an overview of common designs, components, and applications. This comprehensive summary includes options that are suitable for in-person or remote learning with K–12 students and undergraduates in general chemistry, analytical chemistry, instrumental analysis, and electronics courses.

Antibacterial Efficiency of Carbon dots Against Gram-Positive and Gram-Negative Bacteria: A Review

Abstract: The nontoxic characteristics and inherent antibacterial potency of Carbon dots (CDs) have earned immense attention in the last few years. As the increasing antibiotic resistance of bacterial strains create critical health risks, replacement of conventional antibiotics with alternative antibacterial agents is highly encouraged. The light-driven antibacterial action CDs is a safe process with minimal side effects. Direct interaction of CDs with bacterial cells also contribute to the overall antibacterial activity. Unique and complex mechanisms of antibacterial activity of CDs involve ROS generation, degeneration of cell structure, and leakage of the cytoplasm because of DNA binding and modulation of gene expression. This review provides a systematic overview of the antibacterial potency of CDs to eradicate Gram-positive and Gram-negative bacteria. Various mechanisms of antibacterial activity and factors that contribute to antibacterial action of CDs also discussed. It also highlights the synergistic effects on the antibacterial performance of modified CDs and significant future research concerns.