Gergana Kirova

The presence of antibiotic residues in aquatic environments poses a significant risk to water quality and public health, creating a need for effective and sustainable treatment technologies. In this study, a chitosan-based nanocomposite containing silver, cobalt, and iron (CS-HNC) was synthesized under mild conditions without a calcination step and evaluated for the removal of tetracycline (TC) from aqueous solutions. Attention was given to TC removal at an initial concentration of 10 mg L⁻¹. Although this concentration exceeds those typically reported for natural surface waters, it is lower than the concentrations frequently employed in adsorption studies and therefore provides a useful basis for evaluating the performance of the developed adsorbent under controlled laboratory conditions. The material was characterized by field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and Fourier transform infrared spectroscopy (FTIR). The characterization results confirmed the successful formation of the nanocomposite and the incorporation of metal-containing phases within the chitosan matrix. The effects of key sorption parameters were investigated, showing that TC removal was only weakly influenced by pH and ionic strength. The maximum sorption capacity reached 45.7 mg g⁻¹, while removal efficiencies of 94.3% and 98.4% were achieved after 30 and 120 min, respectively, at an initial TC concentration of 10 mg L⁻¹. Sorption kinetics were best described by the pseudo-second-order model, whereas equilibrium data were better fitted by the Freundlich isotherm model. No detectable leaching of Ag, Co, or Fe was observed after soaking the material in deionized water and in a solution adjusted to pH 2 for 24 h, indicating good stability of the synthesized material under the investigated conditions. These findings suggest that the developed CS-HNC nanocomposite is a promising sorbent for the removal of TC.

Nutraceuticals are food-based products that provide health benefits beyond basic nutrition and play an increasingly important role in preventive healthcare. Ensuring their quality, safety, and efficacy is critical as the global market expands. A systematic literature search was conducted in Scopus, Web of Science, and PubMed using keywords such as ‘nutraceuticals,’ functional foods,’ and ‘quality control,’ with studies selected based on their focus on methods for standardization, characterization, and quality assessment. This review summarizes current analytical approaches, including spectroscopic, chromatographic, and techniques for elemental analysis, highlighting their applications in compound identification, quantification, detection of adulterants, and overall quality control. Emerging challenges and future trends, such as the integration of chemometrics and real-time analytical strategies, are also discussed, providing a comprehensive perspective on the evolving field of nutraceutical analysis.

This study explores the use of the waste-pretreated biomass of the macro-fungus Ganoderma resinaceum as a biosorbent for removing ciprofloxacin from aqueous solutions. Batch experiments were conducted to evaluate the biosorption performance of G. resinaceum under varying conditions. Key operational parameters—including pH, biosorbent dosage, contact time, and initial ciprofloxacin concentration—were systematically assessed. Equilibrium was reached within 120 min. Equilibrium data were fitted to both Freundlich and Langmuir isotherm models, with the Langmuir model providing a better fit. Under optimal conditions (initial pH of 7.0, 120-min contact time, 1 g/L biosorbent dosage, and ciprofloxacin concentrations ranging from 4 to 20 mg/L), the maximum biosorption capacity was determined to be 18.4 mg/g. Kinetic analysis revealed that the biosorption process followed a pseudo-second-order model. Furthermore, the biomass was characterized before and after biosorption using scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy. The FT-IR analysis of G. resinaceum biomass revealed the presence of hydroxyl, amino, and carbonyl functional groups, which play a crucial role in the binding and biosorption of ciprofloxacin molecules.

Background: Nutrition has been shown to significantly influence the biomarkers of both the multielement status and the lipid profile. However, there are some specific local environmental and genetic factors, that define the substantial variability of their levels in different populations. Several large studies in the last decade report that Bulgaria is among the first countries in the European Union in terms of premature death from cardiovascular diseases under the age of 65. This emphasizes the importance of the recommended annual screening of the lipid profile by adults. The essential role of the elements copper (Cu), zinc (Zn), selenium (Se), rubidium (Rb) and magnesium (Mg) for the antioxidant and immune defense of the body has been a subject of scientific interest in the last thirty years. However, there is scarce data on the influence of nutrition habits of Bulgarians on the serum levels of Mg, Cu, Zn, Se, and Rb. Aim: To determine the serum levels of Mg, Cu, Zn, Se, Rb, total cholesterol, LDL-, HDL-cholesterol, and triglycerides, and evaluate their relationship with nutrition. Methodology: A group of 107 directly selected healthy volunteers of Bulgarian nationality (50 males and 57 females, aged 18 to 65 years) were included in the study. Exclusion criteria were acute or chronic diseases, and intake of dietary supplements containing Se, Zn, Cu, Rb and Mg in the last 6 months. Venous blood serum levels of Cu, Zn, Se, Rb, and Mg were determined via collision cell inductively coupled plasma mass spectrometry (ICP-MS). Enzymatic methods were used to measure total cholesterol, LDL-cholesterol, HDL-cholesterol, and triglycerides. Results: In participants consuming fish less than once a week, we measured significantly lower Se levels (р < 0.0001) and lower LDL-cholesterol (p = 0.038). Significantly higher total cholesterol levels were found in the group consuming meat less than twice a week (p = 0.038). We observed suboptimal Se levels (less than 80 μg/L) in 42% of the participants. Dyslipidemia was found in more than 50% of the total group: total cholesterol > 5.2 mmol/L, 50.5%; LDL-cholesterol > 2.6 mmol/L, 74.8%; HDL-cholesterol < 1.68 mmol/L for women, and < 1.45 mmol/L for men, 49.5%. Conclusion: The established suboptimal serum levels of Se and lipid profile parameters in healthy individuals from the Bulgarian population emphasizes the importance of targeted monitoring of these laboratory indicators in patient groups at increased risk of cardiovascular and autoimmune diseases. Moreover, the influence of nutrition habits on multielement and lipid profile must be considered in assessing the need for lifestyle corrections, micro- and macronutrient supplementation in these pathological conditions.

Although dental implants appear to be an alternative for treatment of tooth loss, fixed prosthetic restorations are an irreplaceable part of oral rehabilitation. Regarding the EU directives concerning cobalt health risks, titanium alloys may be an alternative to cobalt–chromium and nickel–chromium for metal–ceramic dental restorations. The presented review briefly describes the specific properties of titanium, and the challenges met during production and use of titanium–ceramic fixed prosthetic restorations.

The removal of pharmaceuticals from aqueous environments has become a critical ecological challenge. Biosorption has emerged as a promising and cost-effective solution for pharmaceutical removal. This review examines the potential of microbial and algal-derived biosorbents, including fungi, bacteria, and algae, in the biosorption of pharmaceuticals from water. The removal efficiency of various types of biosorbents is discussed in relation to the chemical structure and functional groups presented on the biosorbent surfaces at various process parameters, such as pH, contact time, biosorbent dosage, and initial pharmaceutical concentration. Additionally, the benefits of chemical and physical modifications, immobilization techniques, and the reusability of biosorbents are highlighted. The major goal of the present review is not just to gather and discuss information about possible mechanisms of biosorption, which to some extent are still speculative, and to explain the effect of process parameters on the removal but also to highlight the advantages and disadvantages of various types of microbial/algal biosorbents and to ease the selection of proper biosorbents for pharmaceuticals removal. In this way, the review will benefit and induce more technological studies in the field of biosorption.

Background: Environmental and physiological factors influence human ionom, which requires the development of reliable region-specific reference intervals (RIs). This study aimed to establish population-based RIs of copper (Cu), zinc (Zn), selenium (Se), rubidium (Rb), and magnesium (Mg), in relation to age, sex, and physical activity. Methods: The RIs were established according to the CLSI EP28-A3c guidelines. A reference group of 120 directly selected healthy volunteers of Bulgarian nationality (60 males and 60 females, aged 18 to 65 years) were included in the study. The participants were separated into two groups: low (2 h/week, n=60) physical activity. Serum levels of Cu, Zn, Se, Rb, and Mg (sCu, sZn, sSe, sRb, sMg), were determined via collision cell inductively coupled plasma mass spectrometry (ICP-MS). Results: The RIs in this study are generally comparable to those in other countries. However, 43% of the participants had sSe lower than the threshold of 80 µg/L, correlating with the optimal expression of key selenoproteins. A significant sex-related difference was found for Cu (male vs female, p = 0.003), as well as an age-related significant difference for Cu between the groups of women below and above 30 years of age (p = 0.001). Conclusions: In this study, we verified the RIs of sCu, sZn, sSe, and sMg for the Bulgarian population with ICP-MS. A RI of sRb, missing up to the present was established, thus filling the gap. Specific sex-, age-, and physical activity-related associations of the elements were elucidated.

Four azo dyes known to form anionic complexes with V(V) were investigated as potential liquid–liquid extraction–spectrophotometric reagents for the antihistamine medication hydroxyzine hydrochloride (HZH). A stable ion-association complex suitable for analytical purposes was obtained with 6-hexyl-4-(2-thiazolylazo)resorcinol (HTAR). The molar absorption coefficient, limit of detection, linear working range, and relative standard deviation in the analysis of real pharmaceutical samples (tablets and syrup) were 3.50 × 10⁴ L mol⁻¹ cm⁻¹, 0.13 μg mL⁻¹, 0.43–12.2 μg mL⁻¹, and ≤2.7%, respectively. After elucidating the molar ratio in the extracted ion-association complex (HZH:V = 1:1), the ground-state equilibrium geometries of the two constituent ions—HZH⁺ and [VO₂(HTAR)]⁻—were optimized at the B3LYP level of theory using 6-311++G** basis functions. The cation and anion were then paired in four different ways to find the most likely structure of the extracted species. In the lowest-energy structure, the VO₂ group interacts predominantly with the heterochain of the cation. A hydrogen bond is present (V–O···H–O; 1.714 Å) involving the terminal oxygen of this chain.

Ginkgo biloba has been cultivated in Bulgaria since the end of the 19th century. Ividual specimens can be seen in almost every park. Females of the tree are considered contaminants of the landscape because their ripe seeds have a strong odor and are not utilized. We undertook this study to clarify whether ginkgo seeds of local origin can be converted from an unwanted and unused environmental pollutant into a source of beneficial compounds. Various analytical and chromatographic methods were used to quantify the major constituents and ten biologically active compounds in methanol seed extract. The results showed that the seeds are low in proteins (5%) and fats (1%); the seeds were also rich in unsaturated fatty acids and tocopherols. About 44% of nut starch was resistant to in vitro enzymatic hydrolysis. The amount of terpene trilactones in an aqueous-methanol seed extract was significantly higher than the number of flavonoids. Ginkgotoxin and ginkgolic acid were also found. The extract demonstrated weak antimicrobial activity against thirteen microorganisms. This study revealed that seeds of locally grown Ginkgo trees can be used as a source of biologically active substances. The chemical composition show similarity to those of seeds from other geographical areas.

Betonica bulgarica is an endemic species distributed in Bulgaria. The chemical composition of the essential oil analysed by GC–MS (Gas chromatography–mass spectrometry) and the content of trace elements analysed by ICP–MS (Inductively coupled plasma mass spectrometry) were determined. Additionally, a study on the types and distribution of trichomes was done using a microscope with a camera. The essential oil was characterized using a high concentration of sesquiterpene hydrocarbons, whose major compounds are β-caryophyllene (17.4%), germacrene D (9.9%), and β-bourbonene (6.7%). The contents of manganese (177.2 µg/g) and strontium (156.8 µg/g) were highest among the investigated micronutrients. Two types of trichomes were identified on the adaxial and abaxial epidermises of the leaves of B. bulgarica—covering and glandular. Peltate stacked glandular trichomes with a four-celled head of type B were observed on the leaf surface.