In the quest for innovative and effective antimicrobial solutions, this study explores the successful encapsulation of thymol within chitosan nanoparticles (CNP-T), aiming to enhance its stability and broaden its application potential across various industries. Thymol, a natural compound known for its potent antimicrobial properties, often faces limitations due to its volatility and poor water solubility. Encapsulating it within chitosan nanoparticles offers a promising avenue to overcome these challenges, creating a more stable and efficient delivery system.

The research meticulously details the two-stage ionic emulsion method employed for producing CNP-T, investigating various chitosan-to-thymol ratios: 1:0, 1:0.25, 1:0.5, 1:0.75, and 1:1. This systematic approach allowed for the optimization of the encapsulation process to achieve the most desirable characteristics. A comprehensive battery of tests was then performed to characterize the resulting CNP-T, including analyses of diameter, stability, loading capacity, chemical interactions, thermal stability, morphology, and antibacterial properties.

Crucially, the study identified the 1:0.5 chitosan-to-thymol ratio as optimal, yielding CNP-T with the smallest diameter (10 nm) and exceptional stability. This small particle size is vital for enhanced bioavailability and penetration in various applications. At this optimal ratio, the CNP-T demonstrated impressive encapsulation efficiency of 57.53% and a loading capacity of 41.52%. These figures highlight the significant amount of thymol successfully incorporated into the nanoparticles, indicating an efficient encapsulation process.

Further characterization using Fourier-transform infrared spectroscopy (FTIR) provided strong evidence of successful thymol encapsulation. The FTIR spectrum of the 1:0.5 CNP-T exhibited additional characteristic peaks at 2961 cm⁻¹ and 2872 cm⁻¹, which are directly related to the C-H stretching vibrations of thymol. This unequivocally confirms the chemical interaction and successful entrapment of thymol within the chitosan matrix. Beyond structural confirmation, the thermal stability of the encapsulated thymol was significantly enhanced. While free thymol decomposed at 236.27°C, the encapsulated thymol in 1:0.5 CNP-T showed remarkable resilience, decomposing at a much higher temperature of 384.75°C. This substantial increase in thermal stability is a critical advantage, suggesting that CNP-T can withstand harsher processing conditions and maintain its integrity for longer periods.

The practical efficacy of CNP-T was rigorously tested against common bacterial pathogens, namely Staphylococcus aureus (S. aureus) and Salmonella typhimurium (S. typhimurium). The results conclusively demonstrated that CNP-T effectively inhibited the growth of both bacteria, thereby confirming its potent antibacterial properties. This finding underscores the potential of CNP-T as a powerful antimicrobial agent. The stable and diminutive size of the CNP-T developed in this research, coupled with its proven antibacterial efficacy and enhanced thermal stability, makes it a highly promising material for diverse applications. Its utility spans across critical sectors such as agriculture (e.g., as natural pesticides or plant disease control agents), the food industry (e.g., as a food preservative or in active packaging to extend shelf life and ensure food safety), and medical industries (e.g., as a component in antimicrobial wound dressings or drug delivery systems). This research paves the way for the development of safer, more effective, and sustainable solutions in these vital fields.

Figure 1: Effect of Chitosan-Thymol Ratio on the Encapsulation of Thymol in Chitosan Nanoparticle (CNP-T)

Figure 2: Schematic diagram of antibacterial mechanism of CNP, 1:0.5 CNP-T, and 1:1 CNP-T

Figure 3: TEM micrographs (magnification x25k, inset images at magnification x50k) and respective particle size distribution histograms of CNP-T produced with chitosan-thymol ratios of (a) 1:0.5 and (b) 1:1.

Source:

Ruzanna Ahmad Shapi’i, Siti Hajar Othman, Mohd Nazli Naim, Intan Syafinaz Mohamed Amin Tawakkal

(https://www.sciencedirect.com/science/article/pii/S0927775725011045#fig0015)

Date of Input: 18/07/2025 | Updated: 18/07/2025 | roslina_ar