Reneta Toshkova

Background: The use of biodegradable polymeric implants for localised drug delivery is a strategy for improving cancer treatment, as it maintains high local drug concentrations while minimising systemic toxicity. Erufosine, a third-generation alkylphosphocholine, is active against a wide range of malignant cells, but its clinical application is limited due to the lack of suitable sustained-release formulations. Methods: Biodegradable polymer blends based on poly(ε-caprolactone) (PCL)/polyethylene glycol (PEG) and poly(D,L-lactide-co-glycolide) (PLGL)/PEG were developed as local drug delivery systems for erufosine. The polymer composition was optimised using doxorubicin as a model compound. Erufosine release was quantified by HPLC–MS/MS over 14 days. The therapeutic efficacy of the implants was evaluated in Graffi myeloid tumor bearing hamsters using two implantation strategies: primary implantation at the time of tumor inoculation and postoperative implantation following tumor resection (using primary and postoperative implantation). Histopathological examination was performed to assess tissue response and tumor morphology. Results: Incorporation of PEG significantly enhanced drug release from the biodegradable matrices, with the PCL/PEG (2:1, w/w) and PLGL/PEG (2:1, w/w) formulations showing the most favourable release profile. HPLC-MS/MS analysis showed an initial burst release followed by sustained erufosine release for up to 14 days. Local implantation of erufosine-loaded carriers significantly prolonged survival and decreased mortality of Graffi tumour-bearing hamsters with postoperatively drug-loaded implants. Histopathological analysis revealed extensive tumor cell degeneration and necrosis, confirming the biological activity of locally released erufosine. In PLGL/PEG-treated animals, the formation of a fibrovascular capsule around the implant suggested that host tissue response might partially restrict drug diffusion despite favourable in vitro release kinetics. Conclusions: Biodegradable PCL/PEG and PLGL/PEG implants provide sustained local erufosine delivery and moderate antitumor activity in vivo. The findings demonstrate that therapeutic efficacy depends not only on polymer-controlled drug release but also on the response of host tissues to the implanted biomaterial

Exopolysaccharides (EPS) from microalgae have emerged as promising natural anticancer agents owing to their selective cytotoxicity toward tumor cells and low toxicity to healthy tissues. However, the molecular mechanisms and targets underlying their anticancer activity remain poorly understood. In the present study, EPS isolated from Coelastrella sp. BGV was evaluated for cytotoxicity and antiproliferative activity against a panel of human cancer cell lines (HepG2, HCT116, A549, and MDA-MB-231). The effects of EPS on mitochondrial function, cell cycle progression, apoptosis, and autophagy were investigated using flow cytometry and fluorescence microscopy. To gain mechanistic insight, molecular docking of a representative EPS disaccharide, α-L-Fucp-(1→6)-β-D-Galp, was performed against DC-SIGN and galectin-3 using the CB-Dock2 platform with the AutoDock Vina engine. The EPS exhibited minimal cytotoxicity toward non-tumor cells, and induced significant concentration-dependent antiproliferative activity in all tested cancer cell lines. MDA-MB-231 breast cancer cells were the most sensitive, with an IC₅₀ value of 57.5 ± 10 µg/mL and a selectivity index of 5.2 relative to non-tumor cells. Mechanistically, EPS treatment induced mitochondrial membrane depolarization, S-phase cell cycle arrest, autophagy, and apoptosis, as demonstrated by nuclear fragmentation, chromatin condensation, and increased Annexin V positivity. Molecular docking identified DC-SIGN and galectin-3 as plausible molecular targets, suggesting potential anticancer activity of Coelastrella sp. BGV EPS that may involve both direct pro-apoptotic effects and modulation of carbohydrate-mediated signaling pathways. Collectively, these findings provide new mechanistic insight into the anticancer activity of Coelastrella sp. BGV EPS and support its further investigation as a promising natural candidate for adjunctive cancer therapy.

Spatially separated dual-bioactive delivery platform from electrospun polyhydroxybutyrate/poly(ethylene oxide) fibers loaded with rutin (PHB/PEO/RUT) and decorated with zein/Melissa officinalis particles (zein/MO) were obtained by simultaneous electrospinning/electrospraying. The morphology of the materials, their thermal properties and chemical composition were systematically studied by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and attenuated total reflectance Fourier transform infrared spectroscopy (ATR–FTIR). The incorporation of PEO into the fabricated fibrous materials enhanced their wettability. It was demonstrated that the newly developed materials had high encapsulation efficiency (99.8 ± 0.1%) of RUT and/or MO. The architecture of the materials affected the in vitro release profile of the bioactive agents. RUT exerted its DPPH^• scavenging capacity upon incorporation into the fibers. An increase in antioxidant activity was observed in the fibrous mats loaded with both RUT and MO. Moreover, the developed materials decreased the viability of SH-4 melanoma cells to a greater extent than that of non-cancerous HaCaT keratinocytes. The combined rapid release and sustained release of bioactive agents and the antioxidant and anticancer activity of the newly developed materials render them promising candidates as platforms for local drug delivery.

In this study, novel electrospun polymer mats based on biocompatible poly(lactic acid) (PLA) and hydrophilic poly(ethylene glycol) (PEG) were successfully fabricated for the co-delivery of two natural polyphenols, quercetin (QUE) and rosmarinic acid (RA). Scanning electron microscopy (SEM) revealed the formation of defect-free, continuous nanofibers with high interconnected porosity. By mimicking the structural features of the native extracellular matrix, these nanofibrous platforms facilitate pronounced combined antioxidant and anticancer action. X-ray diffraction (XRD) analysis confirmed that the rapid solvent evaporation during electrospinning induced a physical state transformation, converting both QUE and RA from their native crystalline structures into an amorphous dispersion within the polymer fibrous materials, thereby optimizing their potential bioavailability. The obtained hybrid fibrous materials possessed good mechanical properties. Moreover, the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay demonstrated that the incorporation of PEG enhanced matrix hydrophilicity, allowing the four-component PLA/PEG/QUE/RA mats to achieve the highest antioxidant efficiency (98.1%), suggesting an enhanced, complementary radical-neutralization pathway. Furthermore, in vitro biological assessments against human cervical carcinoma cell line (HeLa) and normal murine embryo fibroblasts BALB/3T3 demonstrated prominent anticancer activity, while noncancerous cells were significantly less affected. The dual-loaded PLA/PEG/QUE/RA fibrous mats induced significant cell shrinkage, chromatin condensation, and apoptotic cell death in HeLa cells, while normal BALB/3T3 fibroblasts retained cell membrane integrity and displayed higher resistance. Modeled after the native extracellular matrix, these bioinspired materials demonstrate significant antioxidant and anticancer activity, highlighting their potential for applications in localized cancer therapy, wound management, and tissue engineering.

Natural polyphenols, particularly quercetin (QUE) and rosmarinic Acid (RA), possess significant synergistic therapeutic potential as potent antioxidants and anti-inflammatories. However, their poor stability, low water solubility, and resulting limited bioavailability severely hinder their effective clinical translation. This study addresses these fundamental limitations by designing a novel advanced drug delivery platform utilizing electrospinning. We have fabricated composite high-molecular-weight poly(L-Lactic Acid) (PLA)/polyethylene glycol (PEG) nanofibers for the simultaneous co-delivery of both QUE and RA, optimizing compound stability and release kinetics. PLA provided mechanical integrity and sustained release properties, while the incorporation of PEG strategically enhanced the mat’s wettability, enabling precise control over initial drug dissolution. Comprehensive characterization confirmed uniform, bead-free morphology and high entrapment efficiency for both polyphenols. Crucially, the PLA/PEG blend successfully achieved a biphasic release profile, featuring an initial burst release mediated by PEG followed by a sustained release phase governed by the PLA matrix. Furthermore, the performed in vitro investigations using SH-4 melanoma cells and HaCaT normal keratinocytes revealed that the prepared novel materials containing the polyphenols possessed high anticancer activity to the used cancer cell line. However, the toxicity to the normal cell line is much lower. Therefore, this novel electrospun composite scaffold offers an effective strategy to enhance the stability, control the delivery, and maximize the synergistic therapeutic benefits of quercetin and rosmarinic Acid for applications in areas such as advanced wound care, tissue regeneration, and antitumor therapies.

The rising incidence of cancer and the limitations of current therapeutic strategies underscore the urgent need to identify novel bioactive compounds for antitumor drug development. Cyanobacteria are widespread Gram-negative, photoautotrophic prokaryotes that have been recognized as an important source of biologically active secondary metabolites with vast potential for application in the fields of pharmaceutics. The aim of the present study was to analyze the phytochemical composition, antioxidant, and antitumor activities of low-temperature (LT) and high-temperature (HT) aqueous extracts of the cyanobacterium Chroococcus sp. R-10. Extracts were prepared and analyzed for phytochemical composition using UPLC-DAD, and antioxidant activity was tested via multiple assays. Antiproliferative effects were evaluated on human tumor cell lines, and the effects on cell cycle progression studied using flow cytometry. Fluorescence microscopy was employed to examine extract-induced cytomorphological changes in the treated cancer cells. UPLC-DAD analyses showed very similar chromatographic profiles of the extracts and identified glycogen as their main constituent. Both extracts displayed concentration-dependent antioxidant activity, with notable radical scavenging and ferric-reducing capacity. LT extract demonstrated higher phenolic content and antioxidant capacity. Both extracts reduced cell viability, particularly in MCF-7 and MDA-MB-231 breast carcinoma cell lines. Flow cytometry and fluorescent microscopy analyses revealed that the suppressed proliferative activity of the cancer cells was associated with a retardation of cell cycle progression and apoptosis induction. This study identifies Chroococcus sp. R-10 as a promising source of phytochemical compounds with pharmaceutical relevance and provides a rationale for further investigations to identify the primary bioactive constituents and elucidate their mechanisms of anticancer action.

Quercetin (QUE) is a bioactive flavonoid that is naturally present in various fruits and possesses many pharmacological activities. Despite its health benefits, the bioavailability of quercetin is relatively low due to its crystalline form and hydrophobic structure. An approach to overcoming these drawbacks is its incorporation into amorphous polymer matrices. PLA and PLA/PEG fibrous materials loaded with QUE were obtained by electrospinning. The XRD analysis revealed a visible decrease in the crystallinity of QUE after its incorporation into PLA and PLA/PEG fibers. The obtained fibrous materials and, especially, the PLA/PEG mat loaded with the flavonoid exhibited high antioxidant activity due to the better wettability and higher release rate of the bioactive compound. Moreover, the PLA/QUE and PLA/PEG/QUE mats possessed antibacterial properties against Staphylococcus aureus and Pseudomonas aeruginosa. Furthermore, the antitumor activity of the prepared mats was tested against SH-4 cancer cells and HaCaT keratinocytes. The obtained results reveal that the QUE-loaded fibrous mats exhibited high anticancer activity against cancer cells but lower toxicity to normal keratinocytes. The combined antioxidant, antibacterial and in vitro antitumor activities render these novel PLA-based materials loaded with QUE promising candidates for wound dressing applications and for application in local tumor treatment.

Background: The plant extract of quercetin possesses valuable pharmacological properties. However, its high instability, poor water solubility, and low cell bioavailability has limited its medical applications. An innovative approach used to overcome these limitations is the QUE incorporation in suitable polymer carriers. Methods: In the present study, fibrous materials based on PLA or PLA/PEG loaded with the flavonoid quercetin (QUE) were obtained by the electrospinning technique. Diverse morphological, spectroscopic, physico-mechanical, and spectrophotometric methods were used to characterize the prepared electrospun mats. Results: The addition of hydrophilic PEG to the polymer matrix improved its wettability and assisted the more rapid release of QUE from the PLA/PEG fibrous mat than from the PLA one. The obtained fibrous mats possess good mechanical properties. Moreover, QUE-loaded electrospun mats exhibited high anticancer activity against HeLa cervical cancer cells, but lower toxicity to normal cells. Conclusions: The obtained perspective results revealed the potential of the obtained QUE-loaded materials to find applications for wound healing and cancer treatment.

Exopolysaccharides (EPS) isolated from the cyanobacteria Arthronema africanum were examined for antiproliferative activity. The effects of EPS on the human cancer cell lines of lung (A549), cervical (HeLa), colon (HCT), hepatocellular (HepG-2), and mammary (MDA-MB-231) carcinoma were determined using NRU-test. Non-tumour cell line HaCaT was used as control to assess the selectivity towards the cancer cells. EPS influence on the distribution of cells in different phases of the cell cycle was analyzed using flow cytometry. Acridine orange/ethidium bromide and DAPI staining were carried out to determine the ability of EPS to induce apoptosis. EPS-treatment caused decrease in cell viability of all types of cancer cells, with the strong inhibition against HeLa cells. The significantly lower cytotoxicity in non-tumour HaCaT cells demonstrated the selectivity of the cytotoxicity effects. EPS did not induce any changes in the cell cycle distribution. The fluorescence microscopy analysis revealed cytomorphological changes associated with the induction of apoptotic cell death after EPS treatment. The presented results show significant antiproliferative activity of the studied EPS and demonstrate that Arthronema africanum is a promising source of bioactive compounds with potential for use in cancer therapy.

Green algae of the genus Coelastrella have attracted the attention of scientists due to their rich biochemical composition and potential for application in phytomedicine. The present study investigated the influence of light on the bioactive capacity of extracts from the Bulgarian strain of the green microalgae Coelastrella sp. BGV. Three LED lights were examined—red/blue (C1), blue (C2), and control white light (C3). The respective ethanol extracts were analyzed for the total content of phenolic antioxidants. The antimicrobial activity was tested using the disk-diffusion method against 10 microorganisms. The antiproliferative and cytotoxic effects on cervical carcinoma HeLa and hepatocellular carcinoma HepG2 cell lines, as well as non-tumorigenic embryonal fibroblasts BALB/3T3 control, were evaluated using a cell viability assay. The overall results highlighted blue light as a factor enhancing the antioxidant, antibacterial, and cytotoxic activities of the C2 microalgal extract. Additionally, the investigated mechanism of the antitumor activity revealed a proapoptotic effect. In contrast, the C1 extract exhibited weaker activity and selectivity, while the C3 extract was the least active but demonstrated high cytotoxic selectivity. This study could contribute to expanding knowledge about the high biological potential of green microalgae and the development of biotechnological approaches for its regulation.