Andrographis paniculata-Mediated Synthesis of Silver Nanoparticles (AgNPs) and Their Antimicrobial Activity Against the Oral Clinical Pathogen Streptococcus mutans.
Main Article Content
Abstract
Objective
The aim of this study was to evaluate the antimicrobial activity of silver nanoparticles synthesised through an eco‑friendly, plant‑based approach using Andrographis paniculata extract, specifically against Streptococcus mutans, which is the primary bacterium responsible for dental caries.
Materials and Methods
The green synthesis of silver nanoparticles was performed using an aqueous extract of Andrographis paniculata, which served both as a reducing agent to convert silver ions into nanoparticles and as a stabilising agent to prevent aggregation. Institutional ethical clearance was obtained prior to the commencement of the study at Saveetha Dental College. The biosynthesised nanoparticles were characterised using several analytical techniques: Ultraviolet‑Visible spectroscopy to confirm nanoparticle formation, Fourier‑Transform Infrared spectroscopy to identify functional groups involved in capping, Scanning Electron Microscopy to examine surface morphology, and Energy‑Dispersive X‑ray analysis to determine elemental composition. The antimicrobial activity against clinical isolates of S. mutans was assessed using the agar well diffusion method..
Results
The formation of silver nanoparticles was confirmed by the appearance of a characteristic surface plasmon resonance peak in the UV‑Vis spectrum. EDX analysis revealed a highly pure metallic phase with an elemental silver content of 69.5 wt%, indicating successful synthesis with minimal impurities. FTIR spectroscopy identified key phenolic and organic functional groups that were responsible for capping the nanoparticles and maintaining their stability in suspension. SEM micrographs showed well‑dispersed, predominantly spherical nanoparticles with an average size range of 200–450 nm. The synthesised silver nanoparticles exhibited prominent, concentration‑dependent antimicrobial activity against S. mutans, as well as antioxidant and anti‑cancer activities when compared to control groups.
Conclusion
This study demonstrates that silver nanoparticles synthesised using Andrographis paniculata extract possess strong inhibitory activity against Streptococcus mutans. The green synthesis approach described here offers a biocompatible and effective alternative for developing novel preventive dental therapeutics, with potential applications in the management of dental caries and other oral infections.
Article Details
References
Ahmed, S., Ahmad, M., Swami, B. L., & Ikram, S. (2016). A review on plants extract mediated synthesis of silver nanoparticles for antimicrobial applications: A green synthetic approach. Journal of Advanced Research, 7(1), 17-28.
Philip, D. (2010). Green synthesis of size and shape-controlled silver nanoparticles using Aloe vera plant extract. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 77(1), 287-291.
Rai, M., Yadav, A., & Gade, A. (2009). Silver nanoparticles as a new generation of antimicrobials. Biotechnology Advances, 27(1), 76-83.
Allaker, R. P. (2010). The use of nanoparticles in antimicrobial materials or their applications in dentistry. International Journal of Antimicrobial Agents, 36(4), 309-317.
Alexander, J. W. (2009). History of the medical use of silver. Surgical Infections, 10(3), 289-292.
Morones, J. R., Elechiguerra, J. L., Camacho, A., Holt, K., Kouri, J. B., Ramírez, J. T., & Yacaman, M. J. (2005). The bactericidal effect of silver nanoparticles. Nanotechnology, 16(10), 2346-2353.
Pelgrift, R. Y., & Friedman, A. J. (2013). Nanotechnology as a therapeutic tool to combat microbial resistance. Advanced Drug Delivery Reviews, 65(13), 1803-1815.
Pal, S., Tak, Y. K., & Mitra, J. M. (2007). Does the shape of silver nanoparticles influence their antimicrobial activity? New insights into the mechanism of action of silver nanoparticles. Applied and Environmental Microbiology, 73(6), 1712-1720.
Hossain, M. S., Urbi, Z., Sule, A., & Rahman, K. M. (2014). Andrographis paniculata (Burm. f.) Wall. ex Nees: A review of ethnobotany, phytochemistry, and pharmacology. The Scientific World Journal, 2014, 1-28.
Mishra, S. K., Sangwan, N. S., & Sangwan, R. S. (2007). Andrographis paniculata (Kalmegh): A review of its phytochemistry and pharmacology. Medicinal and Aromatic Plant Science and Biotechnology, 1(1), 92-108.
Subramanian, R., Asmawi, M. Z., & Sadikun, A. (2012). In vitro alpha-glucosidase and alpha-amylase enzyme inhibitory effects of Andrographis paniculata extract and andrographolide. Acta Biochimica Polonica, 59(3), 321-328.
Akbar, S. (2011). Andrographis paniculata: A review of pharmacological activities and clinical effects. Alternative Medicine Review, 16(1), 66-77.
Jiao, J., Li, Z. G., Gai, Q. Y., Lou, Y. J., Wei, F.Y., Fu, Y. J., & Ma, W. (2013). Microwave-assisted aqueous extraction of total flavonoids from Andrographis paniculata leaves. Industrial Crops and Products, 49, 147-155.
Loesche, W. J. (1986). Role of Streptococcus mutans in human dental decay. Microbiological Reviews, 50(4), 353-380.
Cornejo, O. E., Lefébure, T., Bitar, P. D., Lang, P., Richards, V. P., Stanhope, M. J., & Burne, R. A. (2013). Evolutionary and population genomics of the cavity-causing bacterium Streptococcus mutans. Proceedings of the National Academy of Sciences, 110(3), 986-991.
Berkowitz, R. J. (2003). Acquisition and transmission of Streptococcus mutans. Journal of the California Dental Association, 31(2), 135-138.
Goldstein, J., Newbury, D. E., Joy, D. C., Echlin, P., Lifshin, E., McLish, L., & Sawyer, L. (2012). Scanning Electron Microscopy and X-ray Microanalysis. Springer Science & Business Media.
Valgas, C., Souza, S. M. D., Smânia, E. F., & Smânia, A. (2007). Screening methods to determine antibacterial activity of natural products. Brazilian Journal of Microbiology, 38(2), 369-380.