Noscapinoids bearing silver nanocrystals augmented drug delivery, cytotoxicity, apoptosis and cellular uptake in B16F1, mouse melanoma skin cancer cells

Abstract

Purpose: Noscapine (Nos) and reduced brominated analogue of noscapine (Red-Br-Nos) prevent cellular proliferation and induce apoptosis in cancer cells either alone or in combination with other chemotherapeutic drugs. However, owing to poor physicochemical properties, Nos and Red-Br-Nos have demonstrated their anticancer activity at higher and multiple doses. Therefore, in present investigation, silver nanocrystals of noscapinoids (Nos-Ag²⁺ nanocrystals and Red-Br-Nos-Ag²⁺ nanocrystals) were customized to augment drug delivery, cytotoxicity, apoptosis and cellular uptake in B16F1 mouse melanoma cancer cells.

Methods and results: Nos-Ag²⁺ nanocrystals and Red-Br-Nos-Ag²⁺ nanocrystals were prepared separately by precipitation method. The mean particle size of Nos-Ag²⁺ nanocrystals was measured to be 25.33±3.52nm, insignificantly (P>0.05) different from 27.43±4.51nm of Red-Br-Nos-Ag²⁺ nanocrystals. Furthermore, zeta-potential of Nos-Ag²⁺ nanocrystals was determined to be -25.3±3.11mV significantly (P<0.05) different from -15.2±3.33mV of Red-Br-Nos-Ag²⁺ nanocrystals. The shape of tailored nanocrystals was slightly spherical and or irregular in shape. The architecture of Nos-Ag²⁺ nanocrystals and Red-Br-Nos-Ag²⁺ nanocrystals was crystalline in nature. FT-IR spectroscopy evinced the successful interaction of Ag²⁺ nanocrystals with Nos and Red-Br-Nos, respectively. The superior therapeutic efficacy of tailored nanocrystals was measured in terms of enhanced cytotoxicity, apoptosis and cellular uptake. The Nos-Ag²⁺ nanocrystals and Red-Br-Nos-Ag²⁺ nanocrystals exhibited an IC₅₀ of 16.6μM and 6.5μM, significantly (P<0.05) lower than 38.5μM of Nos and 10.3μM of Red-Br-Nos, respectively. Finally, cellular morphological alterations in B16F1 cells upon internalization of Nos-Ag²⁺ nanocrystals and Red-Br-Nos-Ag²⁺ nanocrystals provided the evidences for accumulation within membrane-bound cytoplasmic vacuoles and in enlarged lysosomes and thus triggered mitochondria mediated apoptosis via caspase activation.

Conclusion: Preliminary investigations substantiated that Nos-Ag²⁺ nanocrystals and Red-Br-Nos-Ag²⁺ nanocrystals must be further explored and utilized for the delivery of noscapinoids to melanoma cancer cells.

Keywords: Apoptosis; Cellular uptake; Cytotoxicity; Melanoma; Noscapinoids; Silver nanocrystals.