The objective of the present work was to prepare lipid nanoparti-
cles encapsulated with Thuja oil with an objective to improve its stability 
and oral bioavailability. The results of preformulation study are identical 
to the specification reported for Thuja oil revealing yellow liquid with 
characteristic odor, a boiling point of 115°C and solubility in methanol 
and ethanol. All the prominent stretching and bending vibrations of Thuja 
oil were present in the physical mixture indicating a compatibility be-
tween the both the components. The preparation of the T-SLNs was 
achieved using probe-sonication method. Total eight formulations of T-
SLNs were prepared by varying the concentration of the lipid, concentra-
tion of the surfactant and time of sonication. These formulations were 
assessed for particle size and encapsulation efficiency. The particle size of 
the formulations ranged between 111 ± 2.88 to 126 ± 168.56 nm. The 
encapsulation efficiency of the SLNs ranged between 71.23 ± 0.17 to 
87.75 ± 0.30%.The particle size and zeta potential of the formulation T-
SLN3 were 125 ± 2.64 nm and -21.7 ± 2.61 mV respectively. The stability 
of T-SLN3 was studied by storing at 4 ± 1 °C for 30 days. The particle size 
remained stable at the end of the study with drug entrapment of 81.3%. 
This suggests that the SLNs prepared are stable on storage. The T-SLN3 
was evaluated for antibacterial action against E. coli and S. aureus. The 
SLN was able to exhibit significant antibacterial action against S. aureus 
whereas activity against E. coli was poor. 

Thuja oil, Lipid nanoparticles, stearic acid, Probe sonication,  Antimicrobial 

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