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<p>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&#xa0;nm at the excitation wavelengths of 300–350&#xa0;nm. While a negatively zeta potential value of − 9.8 ± 2.6&#xa0;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&#xa0;mg/mL minimum inhibition concentration (MIC) against a Gram-negative bacterium, <i>Klebsiella pneumoniae</i>. The Phe CDs commenced the highest antibacterial effect against <i>Bacillus subtilis</i> (ATCC 6633) Gram-positive bacteria, but the lowest MIC value of 1.25&#xa0;mg/mL was determined for Tyr CDs against <i>Candida albicans</i> (ATCC 10231) fungus. Furthermore, a UV light exposure, 30&#xa0;min treatment of UV-A light with a 6.88&#xa0;mW/cm<sup>2</sup> irradiance value on amino acids CD exhibited improved photodynamic activity. The natural amino acid-derived CDs show great biocompatibility on L929 fibroblast cells with &gt; 86% cell viability, for all formulations except Tyr CDs, retaining 78 ± 3% viability even at 1000&#xa0;μg/mL concentration, and blood compatibility at 500&#xa0;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.</p>

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Antipathogenic carbon dots synthesized from fluorescent amino acids and their photodynamic activity

  • 期刊论文

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  • 发表日期：

    2026年5月3日

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  • Selin S. Suner,
  • Mehtap Sahiner,
  • Jorge H. Torres,
  • Nurettin Sahiner

摘要

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.