ABSTRACT [Download PDF] [View Full Text]
Objective To prepare aldolylated hyaluronic acid-modified antimicrobial carbon dots (AHA-CDs) eye drops and evaluate its antibacterial activity against Staphylococcus aureus in vitro and in vivo.
Methods AHA-CDs eye drops were synthesized by modifying small particle size positively charged carbon dots and introducing aldehyde-based hyaluronic acid.The AHA-CDs were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy.The antibacterial activity of AHA-CDs against Staphylococcus aureus was evaluated using the microdilution method, plate counting, and live-dead bacteria fluorescence staining in vitro.The mouse bacterial keratitis model was established by removing the corneal epithelium after ring drilling and inoculating Staphylococcus aureus.Eighteen conventional female C57BL/6 mice aged 6-8 weeks were selected and divided into a blank control group, an AHA-CDs-treated group and a tobramycin-treated group of 6 mice each using random number table method, and the mice were treated with phosphate buffer saline, 80 μg/ml AHA-CDs, and 80 μg/ml tobramycin eye drops three times daily for 5 consecutive days accordingly to assess antibacterial activity against Staphylococcus aureus in vivo.Another 12 mice were divided into an AHA-CDs group and a normal control group using the random number table method, with 6 mice in each group, which were treated with 80 μg/ml AHA-CDs and phosphate buffer saline for 7 days.The mice were then sacrificed.Their eyeballs were removed and stained with hematoxylin-eosin to observe and compare the morphology and integrity of the eyeballs between the two groups to evaluate the treatment’s biosafety.The use and care of the animals complied with the principles of the ARRIVE guidelines.The study protocol was approved by the Ethics Committee of the Experimental Animal Care of Henan Eye Hospital (No.HNEECA-2022-17).
Results The successful preparation of AHA-CDs was demonstrated by transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. In vitro studies showed that the minimum inhibitory concentration of AHA-CDs against Staphylococcus aureus was approximately 8 μg/ml, which effectively inhibited bacterial growth at a lower concentration.Plate counting results showed that only 20% of the bacteria survived after 10 minutes of treatment with AHA-CDs.Fluorescence staining of live/dead bacteria showed obvious red fluorescence signals after 4 hours of treatment with AHA-CDs and SP-CDs. In vivo studies showed that, after 5 days of treatment with AHA-CDs eye drops, the corneas of mice with bacterial keratitis were obviously transparent, and the corneal epithelium was basically repaired.In contrast, the tobramycin-treated group exhibited incomplete epithelial repair and mild corneal edema. In vivo safety evaluation revealed that the eye tissue morphology remained intact and no structural abnormalities were observed after AHA-CDs treatment.
Conclusions AHA-CDs eye drops have superior antibacterial effects in vivo and in vitro, and inactivate bacteria rapidly and effectively.