NaOH treatment on phase, purity and particle size of rice husk nanosilica were investigated employing alkaline-extraction-acid-precipitation method. Mild reaction at lower NaOH (1.5 N) revealed small and fine particles (600 nm) due to moderate reaction rate. Morphology of human breast cancer cell line (3T3) revealed that suggestive cell distress effects were more pronounced at 500 μg/ml silica dosages which are in agreement with cell viability decrease (~50 %). Among different silica dosages, 10 μg/ml was found to have highest cell viability (∼70 ± 2 %) capable of increasing dissolved oxygen level while viability was almost decreased to 27 ± 5 % due to toxic effect caused at higher SiO2 dosage and could be a potential candidate best suited for biomedical applications through development of sustainable materials. © 2014 Springer Science+Business Media New York.