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    Biofilm inhibition and bacterial eradication by C-dots derived from polyethyleneimine-citric acid
    (Elsevier B.V., 2022) Abraham, Wakeem L.; Demirci, Şahin; Wypyski, Madison S.; Ayyala, Ramesh S.; Bhethanabotla, Venkat R.; Lawson, Louise B.; Şahiner, Nurettin
    Protonable polyethyleneimine (PEI) and citric acid (CA) based C-dots were prepared via a hydrothermal process, yielding particles with a hydrodynamic diameter of ~100 and ~80 nm, and zeta potential of ? 2.3 ± 0.1 and + 23.4 ± 0.2 mV for PEI-CA C-dots and their protonated form, respectively. Treating Staphylococcus aureus with these C-dots resulted in a statistically significant reduction in bacterial growth, specifically growth in the planktonic phase as well as in the development of bacterial biofilm when compared to untreated (p < 0.05). When 24 h matured S. aureus biofilms were treated with C-dots, a significant disruption and dispersion of bacteria from the existing biofilms was noted as compared to untreated (p < 0.05). Other Gram-positive microorganisms (B. cereus, S. epidermidis, S. pyogenes) and Gram-negative (P. mirabilis, E. coli, and P. aeruginosa) were also susceptible to the antimicrobial activity of the PEI-CA C-dots with significant inhibition of bacterial growth noted for all organisms after C-dot treatment. Only for B. cereus, S. epidermidis, and P. aeruginosa was this reduction in total growth reflected in decreased planktonic growth. However, biofilm formation by all organisms was reduced significantly upon treatment with the C-dots, including those for which planktonic growth was not impacted. © 2022 Elsevier B.V.
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    Synthesis and characterization of nitrogen-doped carbon dots as fluorescent nanoprobes with antimicrobial properties and skin permeability
    (Elsevier, 2020) Demirci, Şahin; McNally, Alexandra B.; Ayyala, Ramesh S.; Lawson, Louise B.; Şahiner, Nurettin
    Nitrogen doped carbon dots (N-doped C-dots) were prepared using polyethyleneimine (PEI) and citric acid (CA) as precursors via the hydrothermal method. Various weight ratios of PEI and CA, 1:0.5, 1:1, and 1:2, were used in the synthesis of N-doped C-dots. The N-doping of prepared C-dots was confirmed with an FT-IR peak that was observed at 1652 cm(-1) assigned to N-H bending. The hydrodynamic diameters of prepared N-doped C-dots were 70.2 +/- 6.9, 32.2 +/- 4.7, and 11.5 +/- 3.1 nm by DLS measurements, and surface charges values were 1.32 +/- 0.8, 0.14 +/- 0.2, and -1.57 +/- 0.7 mV, for 1:0.5, 1:1, and 1:2 wt ratio based on PEI of CA, respectively. A high quantum yield 53 +/- 4.8% according to quinine sulfate standard was determined for 1:1 C-dot prepared from 1:1 wt ratio of PEI:CA. The C-dots were found to inhibit growth of both Gram-negative and Gram-positive bacteria with no noted toxicity to mammalian cells in vitro. Skin permeation studies indicate that the particles permeate into and through the dermis within hours, indicating their potential use for topical administration.