Magnetic-silica particles (MAGSi) have been widely used for rapid and large-scale nucleic acid extraction. However, the

synthesis procedure normally involves washing steps, which will produce chemical waste and are time-consuming. In this

study, we synthesized magnetic-silica fi ne particles by eliminating the washing step in magnetic nanoparticle production,

thereby improving environmental sustainability and reducing synthesis time. First, magnetic nanoparticles (MNP) with sizes

averaging around 100 nm (based on dynamic light scattering (DLS) data) were synthesized via co-precipitation continued

with silica coating by the Stöber method, without washing the Fe 3 O 4 nanoparticles. Compared to the washed MNP, the

unwashed MNP exhibited similar magnetization, with 47.85 emu/g for the unwashed and 47.10 emu/g for the washed MNP.

The unwashed MNP was also successfully coated with silica, which resulted in a decrease in magnetization (5.00 emu/g)

with a Fe 3 O 4 :SiO 2 mass ratio of 1:8. Compared to MAGSi synthesized by washed MNP, the unwashed MNP produced

MAGSi with a larger size (~ 1700 nm compared to 320 nm based on the DLS data), more pronounced SiO 2 FTIR peaks, and

lower magnetization due to a thicker SiO 2 layer. The MAGSi synthesized using the unwashed MNP is still eff ectively able

to extract RNA and DNA from viral (SARS-CoV-2 and Canine Distemper Virus) and bacterial (Leptospira spp.) samples, as

validated through PCR and qRT-PCR. This work introduces a practical and sustainable approach for synthesizing MAGSi,

demonstrating their utility in nucleic acid extraction without compromising performance.