(M-503) Pulp-Dentin Regeneration Using Nitric Oxide Releasing Biomimetic Nanomatrix Gel

Background: Dental pulp tissue exposed to mechanical trauma or cariogenic processes can result in root canals and/or periapical infections, which can be treated with root canal treatment. Recently developed nitric oxide (NO) releasing biomimetic nanomatrix gel can be applied to the regenerative endodontics; antibiotic molecules can be encapsulated within the self-assembled biomimetic nanomatrix gel to be released in controlled manner inside root canal; unique viscoelastic property of the nanomatrix gel enables direct injection into the infected root canal space.

Hypothesis: Antibiotics and NO releasing nanomatrix gel will demonstrate an efficient antibacterial effect and recruit endogenous stem cells to induce pulp-dentin revitalization, while providing a favorable pulp-dentin tissue mimicking extracellular matrix environment.

Object:
o To evaluate anti-bacterial effects of antibiotics and NO releasing biomimetic nanomatrix gel on clinical samples
o To evaluate the cellular effects of antibiotics and NO releasing biomimetic nanomatrix gel on dental pulp stem cells (DPSCs)
o To develop an in vivo infected tooth model and evaluate the revitalization capacity of antibiotics and NO releasing biomimetic nanomatrix gel

Materials and Methods:
The NO releasing nanomatrix gel was synthesized using self-assembled peptide amphiphiles with Fmoc chemistry. Antibiotics, Ciprofloxacin and Metronidazole were encapsulated within the NO gel to evaluate antimicrobial activity. NO releasing biomimetic nanomatrix gel was evaluated on DPSCs' cellular behavior. Experiments were performed with four conditions: 1) Basal media without NO nanomatrix gel (B-N), 2) Basal media with NO nanomatrix gel (B+N), 3) Induced media without NO nanomatrix gel (I-N), and 4) Induced media with NO nanomatrix gel (I+N) at 4,7,14, and 21 days. DPSCs’ proliferation, and differentiation, were evaluated using CyQuant®, Alkaline Phosphatase (ALP) assay, Alizarin red staining, and Real Time Quantitative Reverse Transcription Polymerase Chain Reaction (qRT-PCR). The migration testing was performed by using a microchannel system. Pilot in vivo model was developed to test the application of NO releasing nanomatrix gel.

Results, Conclusions, and Discussions:
o PA-YK-NO successfully encapsulated with antibiotics and demonstrates antibacterial effect with and without antibiotics. NO does not interfere with the antibacterial effect of the antibiotics and NO may be effective for the antibacterial activity and it may reduce unnecessary antibiotic usage from the pulp treatment regimen.
o PA-YK-NO is biocompatible to DPSCs’ viability, proliferation, differentiation, and migration. NO provides a bio-inducible extracellular matrix-mimicking microenvironment.
o PA-YK-NO demonstrates pulp-dentin healing capacity by formation of root dentin, closing root apices, and reducing periapical lesion from the pilot in vivo data. The results will be confirmed further using a rat infection model.

Acknowledgements (Optional):
This project was supported by the grant of National Institute of Health, 1K08DE027401 for KC, ad 1R01HL125391 for HWJ

References (Optional):
o Shah D, Lynd T, Ho D, Chen J, Vines J, Jung HD, Kim JH, Zhang P, Wu H, Jun HW, Cheon K. Pulp- Dentin Tissue Healing Response: A Discussion of Current Biomedical Approaches. J Clin Med. Feb 5;9(2) 434, 2020
o Nam OH, Cheon K, Kim MS, Lee HS, Choi SC. Evaluation of the periodontal and pulpal healing of replanted rat molars with doxycycline root conditioning. J Periodontal Implant Sci. Jun;49(3):148-157, 2019
o Moon CY, Nam OH, Kim M, Lee HS, Kaushik SN, Cruz Walma DA, Jun HW, Cheon K, Choi SC. Effects of the nitric oxide releasing biomimetic nanomatrix gel on pulp-dentin regeneration: Pilot study. PLoS One. 13(10): e0205534, 2018