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    Poly(Vinylamine) Derived N-Doped C-Dots with Antimicrobial and Antibiofilm Activities
    (MDPI (Multidisciplinary Digital Publishing Institute), 2021) Sutekin, Semiha Duygu; Şahiner, Mehtap; Suner, Selin Sağbaş; Demirci, Şahin; Güven, Olgun; Şahiner, Nurettin
    Nitrogen-doped carbon dots (N-doped C-dots) was synthesized by using poly(vinyl amine) (PVAm) as a nitrogen source and citric acid (CA) as a carbon source via the hydrothermal method. Various weight ratios of CA and PVAm (CA:PVAm) were used to synthesize N-doped C-dots. The N-doped C-dots revealed emission at 440 nm with excitation at 360 nm and were found to increase the fluorescence intensity with an increase in the amount of PVAm. The blood compatibility studies revealed no significant hemolysis for N-doped C-dots that were prepared at different ratios of CA:PVAm for up to 500 μg/mL concentration with the hemolysis ratio of 1.96% and the minimum blood clotting index of 88.9%. N-doped C-dots were found to be more effective against Gram-positive bacteria than Gram-negative bacteria, with the highest potency on Bacillus subtilis (B. subtilis). The increase in the weight ratio of PVAm in feed during C-dots preparation from 1 to 3 leads to a decrease of the minimum bactericidal concentration (MBC) value from 6.25 to 0.75 mg/mL for B. subtilis. Antibiofilm ability of N-doped C-dots prepared by 1:3 ratio of CA:PVAm was found to reduce %biofilm inhibition and eradication- by more than half, at 0.78 mg/mL for E. coli and B. subtilis generated biofilms and almost destroyed at 25 mg/mL concentrations.
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    Quercetin particles with lower inhibitory activity for ?-glucosidase and negligible effects on blood clotting
    (Turkish Chemical Society, 2021) Şahiner, Mehtap; Suner, Selin Sağbaş
    Poly(quercetin) (p(QR)) particles were synthesized by using poly (ethylene glycol) diglycidyl ether (PEGGE) crosslinker in a single step via a microemulsion system. The morphological, size, and functional analysis of the prepared particles were examined by optical microscope, scanning electron microscope (SEM), dynamic light scattering (DLS) measurements, and FT-IR spectroscopy. P(QR) particles were found to have spherical shape with 372±9 nm size range based on SEM images and DLS measurements. The zeta potential measurements, performed at different pH conditions, and potentiometric titration of p(QR) particles revealed that the isoelectric point and pKa values were around pH 2.5 and 2.3, respectively. Ferric reducing antioxidant power (FRAP) was determined for QR and p(QR) particles at pH 3.6 and found to be 9.4 and 0.43 µg of reduced Fe(II). The effects of QR and p(QR) particles on α-glucosidase enzyme activity were investigated at pH 6.9 and QR molecules and p(QR) particles can inhibit the α-glucosidase enzyme by 89.3% and 24.7%, respectively. The fluorescence spectroscopy of QR and p(QR) with fibrinogen showed that p(QR) particles do not induce clotting of blood.