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Self-crosslinking of Tannic acid (TA) was accomplished to obtain poly(tannic acid) (p(TA)) particles in single step, surfactant free media using sodium periodate (NaIO4) as an oxidizing agent. Almost monodisperse p(TA) particles with 981 ± 76 nm sizes and −22 ± 4 mV zeta potential value with ellipsoidal shape was obtained. Only slight degradation of p(TA) particles with 6.8 ± 0.2% was observed at pH 7.4 in PBS up to 15 days because of the irreversible covalent formation between TA units, suggesting that hydrolytic degradation is independent from the used amounts of oxidation agents. p(TA) particles were found to be non-hemolytic up to 0.5 mg/mL concentration and found not to affect blood clotting mechanism up to 2 mg/mL concentration. Antioxidant activity of p(TA) particles was investigated by total phenol content (TPC), ferric reducing antioxidant potential (FRAP), trolox equivalent antioxidant capacity (TEAC), total flavanoid content (TFC), and Fe (II) chelating activity. p(TA) particles showed strong antioxidant capability in comparison to TA molecules, except FRAP assay. The antibacterial activity of p(TA) particles was investigated by micro-dilution technique on E. coli as Gram‑negative and S. aureus as Gram-positive bacteria and found that p(TA) particles are more effective on S. aureus with over 50% inhibition at 20 mg/mL concentration attained.

The prevalence of cardiovascular disease, oxidative stress-related complications, and chronic age-related illnesses is gradually increasing worldwide. Several causes include the ineffectiveness of medicinal treatment therapies, their toxicity, their inability to provide radical solutions in some diseases, and the necessity of multiple drug therapy in certain chronic diseases. It is therefore necessary for alternative treatment methods to be sought. In this review, polyphenols were identified and classified according to their chemical structure, and the sources of these polyphenol molecules are indicated. The cardioprotective, ROS scavenging, anti-aging, anticancer properties of polyphenolic compounds have been demonstrated by the results of many studies, and these natural antioxidant molecules are potential alternative therapeutic agents.

Tannic acid (TA) was employed as a novel colorimetric iron ion sensor. TA showed highly selective recognition for only Fe2+ and Fe3+ among a range of tested metal ions such as Cr3+, Mn2+, Co2+, Ni2+, Cu2+, Zn2+, Hg2+, and Pb2+. In the presence of these metal cation solutions, only Fe2+ and Fe3+ solutions underwent impressive color change detectable with the naked eye from colorless to purple and gray, respectively. Surprisingly, TA behaves as a highly selective sensor upon chemical oxidation of iron (Fe2+ and Fe3+) cations. In addition, various sensor applications of TA were performed. For this, TA-impregnated silica gel, alumina oxide sheet, and filter paper were used. Each test strip showed very high selectivity for iron ions. The detection limit of the sensor for Fe2+ and Fe3+ was found to be 1.0 × 10−6 M, and the association constant Ka was determined as 4.05 × 104 M−1 and 1.80 × 107 M−1. The order of ion binding power was determined to be Fe3+ > Fe2+ by UV-Vis spectroscopy. These discernable color changes due to the complexion of TA with Fe2+ and Fe3+ demonstrated the utilization of TA to selectively detect these metal cations.The use of tannic acid as a complexing agent that can detect Fe (II) and Fe (III) metal ions in environmental waters by colorimetry and spectrophotometry.

Nanostructured fluorescent particles derived from natural molecules were prepared by a green synthesis technique employing a microwave method. The precursors citric acid (CA) and cysteine (Cys) were used in the preparation of S- and N-doped Cys carbon dots (Cys CDs). Synthesis was completed in 3 min. The graphitic structure revealed by XRD analysis of Cys CDs dots had good water dispersity, with diameters in the range of 2–20 nm determined by TEM analysis. The isoelectric point of the S, N-doped CDs was pH value for 5.2. The prepared Cys CDs displayed excellent fluorescence intensity with a high quantum yield of 75.6 ± 2.1%. Strong antimicrobial capability of Cys CDs was observed with 12.5 mg/mL minimum bactericidal concentration (MBC) against gram-positive and gram-negative bacteria with the highest antimicrobial activity obtained against Staphylococcus aureus. Furthermore, Cys CDs provided total biofilm eradication and inhibition abilities against Pseudomonas aeruginosa at 25 mg/mL concentration. Cys CDs are promising antioxidant materials with 1.3 ± 0.1 μmol Trolox equivalent/g antioxidant capacity. Finally, Cys CDs were also shown to inhibit the acetylcholinesterase (AChE) enzyme, which is used in the treatment of Alzheimer’s disease, even at the low concentration of 100 μg/mL.

Micrometer-size poly(vinyl phosphonic acid) (p(VPA)) hydrogel was synthesized by employing UV irradiation of an emulsion containing vinyl phosphonic acid (VPA) and crosslinker, prepared using lecithin as surfactant and gasoline as solvent. The p(VPA) microgels were employed in absorption of UO₂ ²⁺ ions from aqueous environments and have very high and fast absorption capacity. In about 20 min, 670 mg UO₂ ²⁺ ions were absorbed per gram of p(VPA) microgel from the prepared UO₂ ²⁺ ion solution, and the absorption capacity increased up to 900 mg at pH 6. Various parameters affecting UO₂ ²⁺ absorption characteristics of p(VPA) were investigated. It was found that the Langmuir isotherm fitted the absorption characteristics of p(VPA) better than the Freundlich isotherm. Moreover, magnetic ferrite can be prepared within p(VPA) and used as a magnetically responsive p(VPA) microgel composite for externally controlled absorption of UO₂ ²⁺ ions with little decrease in the absorption capacity of the p(VPA) microgel.

Background/Objectives: Tannic acid (TA), a known natural polyphenolic acid with many bioactivities including antioxidants, antibacterial, and antiviral, can be combined with a natural essential amino acid L-lysine (LYS) in nanogel formulations to produce p(TA-co-LYS) (p(TA-co-LYS)) nanogels. Methods: A 1:1 mole ratio of TA:LYS was used to prepare corresponding spherical nanogels employing formaldehyde as a linker via the Mannich reaction. Results: The attained p(TA-co-LYS) particles were in 283 ± 57 nm size ranges (via SEM analysis) and possessed smooth surfaces. The zeta potential measurements of p(TA-co-LYS) nanogels suspension at different solution pHs revealed the isoelectric point (IEP) of pH 4.9, suggesting that the particles are negatively charged at the physiological pH range (e.g., at 7.4). In addition to the antioxidant efficacy of nanogels confirmed by three different tests, p(TA-co-LYS) particles showed significant Fe(II) ion chelating capacity at 350 µg/mL concentrations compared to bare TA, which is 21%, whereas the LYS molecule had a chelating capacity of 100% at the same concentrations. Moreover, it was found that p(TA-co-LYS) nanogels inhibited the Acetylcholinesterase enzyme (AChE) at a concentration-dependent profile, e.g., at 333 µg/mL concentration of p(TA-co-LYS), 57.2% of the enzyme AChE activity was inhibited. Furthermore, the minimum inhibition concentrations of p(TA-co-LYS) nanogels of Gram-negative Escherichia coli (ATCC 8739) and Gram-positive Staphylococcus aureus (ATCC 6538) were determined as 12.5 mg/mL. Conclusions: As cytotoxicity studies of p(TA-co-LYS) nanogels on L929 fibroblast cells also ascertained that these particles can be safely used in many biomedical applications, including antioxidant materials, drug delivery devices, and enzyme inhibitors.

This study reports the effect of polyethyleneimine’s molecular weight (PEI, Mn: 1200, 10,000, and 60,000 g/mol, denoted as PEI1.2, PEI10, and PEI60) on the physical, chemical, and biological characteristics of carbon dots (Cdots) derived from chitosan (Chi) and PEI (Chi-PEI Cdots). The size of Chi Cdots was 41.5 ± 6.1 nm, which increased to 50.9 ± 5.9, 71.4 ± 4.2, and 93.3 ± 7.4 nm with the preparation of Chi-PEI1.2, Chi-PEI10 and Chi-PEI60 Cdots. The fluorescence properties and quantum yield% values of the Cdots prepared from Chi, PEI1.2, PEI10, and PEI60 and their corresponding biopolymeric Chi-PEI Cdots were compared. A higher quantum yield of 26 ± 1.6% was observed for Chi-PEI1.2. This decreased with the increasing molecular weight of PEI and was calculated to be 15 ± 1.9% for Chi-PEI60. All the prepared bare Chi, bare PEI and corresponding bipolymeric Chi-PEI Cdots were observed to be nonhemolytic up to a 1 mg/mL concentration. Lower cytotoxic properties were observed for Chi-PEI Cdots on L929 fibroblast cells compared to their corresponding bare forms. Higher cell viability was observed for Chi-PEI1.2 Cdots with 95% viability in the presence of a 1000 µg/mL concentration. The antibacterial activity of the prepared Cdots against pathogens such as E. coli, K. pneumoniae, S. aureus, B. subtilis, and C. albicans was investigated and compared. Lower MIC and MBC values were determined for Chi-PEI10 against C. albicans with values of 12.5 and 50 mg/mL, respectively. Although the antibacterial properties of Chi-PEI Cdots were less strong than those of bare Cdots derived from individual Chi and PEI molecules, their light-induced antibacterial activities were found to be better.

Recently, major attention has been devoted to exploring and increase biomedical applications of catechins by directly employing them as constituents of nano-vehicles. Here, (+)-catechin (CAT) was integrated with another benign biomolecule, L-Lysine (LYS) using formaldehyde (FA) via single-step Mannich condensation reaction and self-assembled supramolecular CAT-LYS networks were synthesized. By using various molar feed ratios of CAT, LYS, and FA (CAT:LYS:FA), different formulations of CAT-LYS particles were obtained as CAT-LYS-1(1:1:1), CAT-LYS-2(2:1:1), CAT-LYS-3(1:2:1), and CAT-LYS-4(1:1:2) particles. The CAT-LYS-4 particles with the highest gravimetric yield of 68.9 ± 6.0% and 783.6 ± 56.6 nm hydrodynamic diameter was chosen for bioactivity studies. The CAT-LYS-4 particles exhibited 190.4 ± 1.3 µg/mL CAT-equivalent antioxidant capacity at 1000 µg/mL concentration with TEAC value of 0.24 ± 0.01 µmole Trolox-equivalent/g antioxidant activity. They showed 16.81 ± 3.47% Fe(II) chelation capacity at 350 µg/mL and 185.8 ± 22.8 µmole Fe(III) reducing power at 500 µg/mL concentration. Moreover, the CAT-LYS-4 particles retained more than half of the α-glucosidase inhibition activity of CAT in particulate form. Besides, a 50-fold improvement was achieved on the hemolytic blood compatibility of CAT-LYS-4 particles upon integration of LYS into CAT backbone (4.7 ± 1.2% at 250 µg/mL) compared to hemolysis ratio of native CAT molecules. They did not show coagulation effects up to 500 µg/mL concentration with > 94% clotting indices. Hence, the CAT-LYS particles with enhanced blood compatibilities and well-retained inherent bioactivities of their precursors in 3D colloidal particulate structures can serve as natural biocolloids for drug/active molecule transport applications in biomedicine.

Anionic hydrogels of poly(2-acrylamido-2-methyl-1-propansulfonic acid) (p(AMPS)) were prepared with a different amount of cross-linker extent and used for in situ preparation of magnetic and metal particles. The metal particles with various sizes were obtained inside the three-dimensional polymer matrixes by absorption of the corresponding metal ions from their aqueous solutions followed by the reduction in the presence of strong reducing agent. In addition to iron particles, cobalt, nickel, copper nanoparticles, and CdS, quantum dot has been prepared by utilizing hydrogel matrix as a template for inorganic/organic composite synthesis. It was observed that the amount of cross-linkers (0.5%, 0.75%, and 1% with respect to monomer mole ratio) used in this study for bare p(AMPS) has not significantly influenced the morphology of the hydrogels or the size of the iron particles while having great effect on swelling of p(AMPS) hydrogels in water. Copolymeric hydrogels of AMPS with acrylamide in different composition were also prepared. Thermogravimetric analysis and transmission electron microscopy results showed that the AMPS content of the copolymeric hydrogel has great impact on both the metal ion loading capacity and the size of the resultant metal particles.[PUBLICATION ABSTRACT]

Nitrogen-doped carbon dots (CDs) were prepared from essential fluorescent amino acids, such as lysine (Lys), phenylalanine (Phe), tyrosine (Tyr), and tryptophan (Trp) by two routes, microwave and teflon-lined autoclave. The fluorescent properties of these amino acids were significantly improved in their corresponding CD forms, especially for those prepared via the hydrothermal process. A significantly high fluorescent intensity was measured in the emission range of 420–470 nm at the excitation wavelengths of 300–350 nm. While a negatively zeta potential value of − 9.8 ± 2.6 mV was obtained for Lys CDs suspension, the CDs of Phe, Tyr, and Trp afforded strong positive zeta potentials, + 24.0 ± 2.4, + 12.5 ± 3.1, and + 31.9 ± 3.8 mV, respectively. The Lys CDs were found not to be antimicrobial even at a 10 mg/mL concentration, which is likely due to their negative surface charge that weakens electrostatic interactions with negatively charged microbial membranes. Whereas the Phe, Tyr, and Trp CDs had a 2.5 mg/mL minimum inhibition concentration (MIC) against a Gram-negative bacterium, Klebsiella pneumoniae. The Phe CDs commenced the highest antibacterial effect against Bacillus subtilis (ATCC 6633) Gram-positive bacteria, but the lowest MIC value of 1.25 mg/mL was determined for Tyr CDs against Candida albicans (ATCC 10231) fungus. Furthermore, a UV light exposure, 30 min treatment of UV-A light with a 6.88 mW/cm2 irradiance value on amino acids CD exhibited improved photodynamic activity. The natural amino acid-derived CDs show great biocompatibility on L929 fibroblast cells with > 86% cell viability, for all formulations except Tyr CDs, retaining 78 ± 3% viability even at 1000 μg/mL concentration, and blood compatibility at 500 μg/mL concentration. Therefore, these CDs derived from fluorescent amino acids are photoactivated and are of excellent nanosized materials in a variety of biomedical in vitro and in vivo uses, including diagnostic, sensor, and therapeutic applications.