Ana Milivojević

Titanium dioxide (TiO₂) is a widely studied semiconductor whose interfacial redox properties strongly influence its photocatalytic and biological performance. In this work, TiO₂ nanomaterials were surface-functionalized with green tea waste extract (GT) and subsequently impregnated with silver to obtain redox-active nanocomposites with tunable optical and biological properties. HPLC, FTIR, diffuse reflectance spectroscopy (DRS), and density functional theory (DFT) analyses demonstrated the formation of an organic–inorganic interface through adsorption of green tea-derived ligands. DFT calculations revealed complementary interfacial roles of the adsorbed constituents, with epigallocatechin gallate (EGCG) inducing interfacial charge-transfer (ICT) states that enable visible-light absorption, as reflected by the decrease in the apparent optical bandgap from ~3.48 eV for pristine TiO₂ to ~1.83 eV for TiO₂/EGCG. ICP-OES analysis further quantified the Ag loading in TiO₂/GT/Ag at 5.1 wt%. Electron paramagnetic resonance (EPR) experiments demonstrated that GT functionalization shifts the interfacial redox balance toward radical scavenging by suppressing excessive radical generation, whereas silver incorporation partially restores oxidative pathways, particularly under irradiation. These differences in interfacial redox behavior directly translate into distinct biological responses. TiO₂/GT/Ag showed the strongest antimicrobial activity, with visible-light enhancement observed predominantly against Staphylococcus aureus, while TiO₂/GT/Ag reduced H₂O₂-induced oxidative stress in non-malignant cells and promoted intracellular reactive oxygen species generation in cancer cells. These findings demonstrate that engineering the organic–inorganic interface through plant-derived ligands and silver incorporation provides an effective strategy for tuning the interfacial redox properties and light-responsive biological performance of TiO₂-based nanomaterials, thereby expanding their potential for antimicrobial and biomedical applications.

This study addresses the need for sustainable approaches in textile wastewater treatment by investigating laccase production with the white-rot fungus Schizophyllum commune TMF3 using agro-industrial waste as a substrate. Laccase was produced via solid-state fermentation on brewery spent grain under optimized conditions (1.75 g malt extract, 75% moisture, 7 days, 25 °C), reaching a maximum activity of 21.06 IU/g dry substrate. The crude enzyme was applied for the decolorization of azo and triphenylmethane dyes (50 mg/L). Decolorization efficiencies above 80% were achieved within 60 min without redox mediators, while chemical oxygen demand (COD) was reduced by more than 50% for all tested dyes. HPLC analysis showed parent dye peaks decreasing and the transformation products’ appearance. Antimicrobial activity testing showed no increase in inhibitory effects against Escherichia coli, Lactobacillus rhamnosus, Candida albicans, and Saccharomyces cerevisiae, while slight growth stimulation was observed in selected cases. Phytotoxicity assays using Triticum aestivum showed no inhibitory effects, with germination index values of 77–124%. Cytotoxicity assessment showed no effects for azo dyes, while cytotoxicity of the triphenylmethane dye decreased by 30% after treatment. These findings support the potential of agro-industrial laccase production as an effective approach for dye removal in sustainable wastewater strategies.

This study explored, for the first time, the simultaneous dyeing and functionalization of textiles using enzymatically synthesized mixtures of phloridzin and esculin oligomers. Initial screening using multifiber fabric containing diacetate, cotton, polyamide, polyester, polyacrylonitrile, silk, viscose, and wool revealed that the oligomers successfully imparted color and high antioxidant activity to cotton, polyamide, and viscose. These three materials were therefore selected for determination of key process parameters’ influence, including temperature (35 °C and 75 °C), reaction time (6 h and 19 h), and oligomers’ concentration (1.5 and 3.0 mg/mL). Treated fabrics were evaluated for color strength (K/S), antioxidant activity, and prebiotic capacity (in vitro stratum corneum model), with all properties assessed before and after washing. The results showed that several functionalized fabrics retained coloration and functionality after washing, while fabrics functionalized with esculin oligomers’ mixture showed strong prebiotic capacity. Overall, the polyamide that functionalized with 3.0 mg/mL esculin oligomers for 19 h at 35 °C was identified as a promising candidate for reusable colored textiles, including dermatology-oriented garments for sensitive or atopic skin, sportswear, protective workwear, and daily use functional items such as hygienic pads or cloth liners. These findings demonstrate the feasibility of developing textiles with targeted prebiotic functionality.

Background/Objectives: Numerous intrinsic and extrinsic stressors can disrupt the balance of the skin microbiome, leading to the development of various skin diseases. It has been proven that coagulase-negative staphylococci (CoNS) are important commensals for maintaining skin microbiome homeostasis and fighting cutaneous pathogens such as Staphylococcus aureus (S. aureus). Here, we examined the influence of polyphenol-rich enzymatic blackcurrant extract (EBCE) on pathogenic coagulase-positive S. aureus strains and beneficial CoNS, like Staphylococcus epidermidis (S. epidermidis), to explore its potential for rebalancing the skin microbiota. Methods: The polyphenol profile of EBCE was determined by ultra-high-pressure liquid chromatography–tandem mass spectrometry. Microwell plate assays were employed to study the effect of EBCE on five S. aureus strains isolated from the skin of atopic dermatitis patients. An in vitro human stratum corneum model was used to test its effect on mixed bacterial cultures. Results: EBCE inhibited the growth of all tested S. aureus strains by 80–100% at the highest tested concentration after 7 h. No microbial growth was observed at the highest tested EBCE concentration using the stratum corneum model inoculated with one selected pathogen (S. aureus SA-DUS-017) and one commensal laboratory strain (S. epidermidis DSM 20044). The lowest tested concentration did not interfere with S. aureus growth but strongly stimulated the growth of S. epidermidis (~300-fold colony forming unit increase). In addition, low EBCE concentrations strongly stimulated CoNS growth in microbiome samples taken from the armpits of healthy volunteers that were spiked with S. aureus SA-DUS-017. Conclusions: These preclinical data support further testing of EBCE-enriched topical preparations as potential cutaneous prebiotics in human studies.

Enzymatic oligomerization of flavonoids enables the synthesis of biomolecules with different structures and improved physicochemical and biological properties and can therefore broaden their application in industry. In this study, the influence of the key reaction parameters temperature, solvent, substrate, and enzyme concentrations on the synthesis of esculin oligomers was investigated. The reaction was optimized using response surface methodology (RSM) in order to obtain the highest products’ concentration and specific products’ yield (per mass of enzyme). Mass spectrometry revealed that oligomers with a degree of polymerization of up to 4 were synthesized in which dimers were the most abundant, while the NMR analysis of the esculin dimer product showed that C8-C8 link between two esculin units was formed. Maximum products’ concentration was obtained at 60 °C, in 14% (v/v) methanol, 7 mg/mL of esculin, and 54.6 U/L of laccase after 7 h, while the optimal conditions for specific products’ yield differed in the aspect of optimal laccase concentration which was 19 U/L for this output. Synthesized esculin oligomers exhibited higher iron chelating and cupric reducing antioxidant capacities and similar or even superior free radical scavenging activity compared to monomeric esculin. Moreover, the mixture of synthesized esculin oligomers has shown a promising potential to be used as a skin prebiotics, suggesting novel applications in skincare industries.

Due to their broad spectrum of biological activities and attractive pharmacological properties, flavonoids are very promising molecules for application in skin care products. In this study, phloridzin and naringin medium- and long-chain fatty acid esters were enzymatically synthesized in reaction with natural oils (coconut and linseed oil) and in vitro transdermal delivery of synthesized esters through artificial Strat-M (R) membrane was investigated. Experimental results were succesfully fitted using Peppas and Sahlin model which includes the lag phase. Release kinetics of all examined flavonoid esters from gel emulsions through the membrane depended on both diffusion and polymer relaxation effect (0.5<n < 1). The estimated effective diffusion coefficients ranged from 0.16810(-8) to 6.14910(-8) cm(2) s(-1) for phloridzin esters and from 0.11610(-8) to 4.21010(-8) cm(2) s(-1) for naringin esters. The effective diffusion coefficients decreased with the increase in ester molecular weight indicating the size-dependent diffusion. All formulation showed good stability, excellent hydration effect, and excellent dermatological compatibility without irritating effect. It can be concluded that gel emulsions with a mixture of flavonoid esters enzymatically synthesized in reaction with vegetable oils can be effectively topically applied as a skin care products.

Blackcurrant pomace is a widely available waste stream derived from the industrial production of juice rich in pectin and unextracted polyphenols. Since pectin, an emerging class of gastrointestinal prebiotics, is also a common cosmetic ingredient, the aim of this work was to evaluate blackcurrant pomace as a source of pectin-rich fractions suitable for application in prebiotic cosmetics. Hereby, this raw material was valorised by sequential extraction of acid-soluble (by citric acid, CAP) and Ca-bound (by ammonium oxalate, AOPP) pectic polysaccharides. Both fractions had favourable physicochemical features and a similar degree of methyl-esterification between low- and high-methoxyl pectin (approx. 50%), but CAP had significantly higher galacturonic acid content (72.3%), branching, and purity. Regardless of that, both had very high oil (18.96 mL/g for CAP and 19.32 mL/g for AOPP) and water (9.97 mL/g for CAP and 7.32 mL/g for AOPP)-holding capacities and excellent emulsifying properties, making them promising cosmetic ingredients. The polyphenol content was 10 times higher in CAP, while corresponding antioxidant activity was 3-fold higher. Finally, the influence of varying CAP and AOPP concentrations on common skin pathogen, Staphylococcus aureus, and beneficial skin bacteria, Staphylococcus epidermidis, was examined. The results show significant prebiotic potential of two pectic fractions since they were capable of selectively stimulating S. epidermidis, while S. aureus growth was inhibited, whereas CAP demonstrated a particularly high capacity of up to 2.2, even with methicillin-resistant S. aureus.

Blackcurrant is an anthocyanin-rich berry with proven antioxidant and photoprotective activity and emerging prebiotic potential, widely applied in cosmetic products. Hereby, highly efficient enzyme-assisted extraction of blackcurrant polyphenols was performed, giving extract with very high antioxidant activity. Obtained extract was characterized in terms of anthocyanin composition, incorporated into three different cosmetic formulations and subjected to Franz cell diffusion study. Experimental values obtained using cellulose acetate membrane for all four dominant anthocyanins (delphinidin 3-glucoside, delphinidin 3-rutinoside, cyanidin 3-glucoside and cyanidin 3-rutinoside) were successfully fitted with the Korsmeyer–Peppas diffusion model. Calculated effective diffusion coefficients were higher for hydrogel compared to oil-in-water cream gel and oil-in-water emulsion, whereas the highest value was determined for cyanidin 3-rutinoside. On the other hand, after a 72 h long experiment with transdermal skin diffusion model (Strat-M^® membrane), no anthocyanins were detected in the receptor fluid, and only 0.5% of the initial quantity from the donor compartment was extracted from the membrane itself after experiment with hydrogel. Present study revealed that hydrogel is a suitable carrier system for the topical delivery of blackcurrant anthocyanins, while dermal and transdermal delivery of these molecules is very limited, which implies its applicability for treatments targeting skin surface (i.e., prebiotic, photoprotective).

Current topical formulations containing vitamin C face limitations in therapeutic effectiveness due to the skin's selective properties that impede drug deposition. Consequently, the widespread use of toxic and irritating chemical permeation enhancers is common. Hereby, we investigated enzymatically derived fatty acid ascorbyl esters (FAAEs) obtained using natural oils for their skin permeation properties using the Strat‐M® skin model in a Franz cell diffusion study. By evaluating various cosmetic formulations without added enhancers, we found that emulgel is most suitable for enhancing the cutaneous and transdermal delivery of FAAEs. Furthermore, medium‐chain coconut oil‐derived FAAEs exhibited faster diffusion rates compared to sunflower oil‐based FAAEs with long‐side acyl residues, including the commonly applied ascorbyl palmitate. Experimental data were successfully fitted using the Peppas and Sahlin model, which accounted for a lag phase and the combined effect of Fickian diffusion and polymer relaxation. In the case of long‐chain esters, the lag phase was prolonged, and the calculated effective diffusion coefficients (D_eff) were lower compared to medium‐chain FAAEs. Accordingly, the highest D_eff value was observed for ascorbyl caprylate, being even 60 times higher than for ascorbyl palmitate. These results suggest the emerging potential of emulgel with incorporated coconut oil‐derived FAAEs for efficiently delivering vitamin C into the skin.