(M1230-03-15) Fabrication of Eco-Benign Isoniazid-Loaded-Silver Nanoparticles: A Novel Approach against Multidrug-Resistant Tuberculosis

Purpose: Eco-benign synthesis is a synthesis process that utilises non-toxic and biocompatible raw materials that cause no harm to the environment. As such, it prioritises reducing the environmental impact of chemical synthesis, which is a promising strategy for developing infectious disease drugs. Tuberculosis (TB) is a major global health burden exacerbated by drug resistance and toxicity issues, especially with first-line TB drugs such as isoniazid (ISO). Metallic nanoparticles, specifically silver nanoparticles (AgNPs), have shown the potential to increase drug efficacy and reduce toxicity. Plant-mediated synthesis is an eco-benign process that avoids toxic chemicals and utilises natural reducing and stabilising plant phytochemicals for AgNP synthesis. This study aimed to establish an eco-benign approach to the functionalisation of AgNPs with ISO, using Spinacia Oleracea leaf extract (SLE) as the reducing and capping agent and polyvinylpyrrolidone (PVP) for enhanced stabilisation.

Methods: AgNPs were synthesised using Silver nitrate and 10% (v/v) Spinacia Oleracea leaf extract (SLE), then, functionalised with ISO (AgNP+ISO), and further stabilised with PVP. PVP is known to provide stability through particle coating. Two different drug loading approaches were explored to observe this stabilisation effect. ISO was added either before or after PVP, i.e., PVP 1 (AgNP + ISO + PVP1) and PVP 2 (AgNP + PVP2 + ISO). PVP concentration of 0.005g/ml was used for both loading methods. The synthesised AgNPs, AgNP + ISO, AgNP + ISO + PVP1 and AgNP + PVP2 + ISO were characterised spectrophotometrically using ultraviolent-visible spectroscopy (UV-VIS), morphology, size and elemental characterisations were conducted using scanning electron microscopy (SEM), dynamic light scattering (DLS) and Transmission Electron Microscopy (TEM) – Energy Dispersive Xray (TEM-EDX).

Results: Analytical studies confirmed the successful eco-benign synthesis of AgNPs loaded with ISO. UV-Vis spectroscopy confirmed the presence of AgNPs, and ISO through strong absorbance curves with peaks at 450nm (AgNPs), 430nm (AgNP + ISO), 460nm (AgNP + ISO + PVP1) and 435nm (AgNP + PVP2 + ISO). Size analysis using DLS confirmed nanoparticle sizes ranging from 76 – 150 nm, with AgNP + ISO + PVP1 being the smallest and AgNP + PVP2 + ISO, resulting in the largest particle size. All PDI values were below 0.35. Based on the higher UV-Vis absorbance and smaller nanoparticle size observed with the AgNP + ISO + PVP1 method, it was selected as the ideal loading method. Furthermore, SEM analysis showed that the eco benign method generated spherical nanoparticles in the AgNP only samples, and this shape was maintained in all the drug loaded samples. Also, the TEM-EDX elemental composition of the PVP 1 method, as shown in Figure 2, revealed the presence of both the plant extract related elements and silver in the nanoparticles. Assessment of the drug loading efficiency of the AgNPs, established over 90% loading capacity in all the samples, AgNP + ISO (90%), AgNP + ISO + PVP1 (93.3%), AgNP + PVP2 + ISO (92.8%). Hence, the AgNP + ISO + PVP1 method had a slightly higher loading capacity compared to AgNP + PVP2 + ISO.

Conclusion: Overall, the eco-benign fabrication approach used in this study produced nanosized ISO-loaded AgNPs with over 90% loading capacity. The AgNP + ISO + PVP1 conjugation method particularly exhibited superior performance, facilitating optimum drug loading efficiency of ~93%. These results validate the potential of using eco-benign synthesis to develop novel nanotherapeutics against TB. Further investigations will be conducted on the antituberculosis effects of ISO-AgNPs, which could have positive implications for the treatment of drug-resistant TB.

Acknowledgements: This project is funded by the Niger Delta Development Commission (NDDC). Special thanks to my supervisors and thesis committee for their advice and feedback.

Figure 1: UV-Vis absorption spectrum of the synthesised AgNPs showing the presence of drug (ISO) in all drug loaded samples, represented by strong absorbance peaks at 279 nm for ISO and 420 nm for AgNP

Figure 2: SEM images of generated silver nanoparticles (AgNPs) and TEM EDX analysis of PVP 1 samples showing the presence of SLE related elements (coper CU, Magnesium Mg) and silver.