Droplet-based microfluidic synthesis of silver nanoparticles stabilized by PVA and PVP: applications in anticancer and antimicrobial activities

Droplet-based microfluidic reactors are promising platforms for the synthesis of nanoparticles having several potential applications. This study reports the synthesis of long-term stable silver nanoparticles (AgNPs) using a segmented flow polymethyl methacrylate (PMMA)-based microfluidic platform for the first time. The polymeric stabilizers, polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP), were used to stabilize the AgNPs suspensions over a long period of time at room temperature. These particles were characterized using ultraviolet–visible (UV–Vis) spectroscopy, field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray (EDX) and X-ray diffraction (XRD) analysis. The stability analysis of colloidal suspensions of AgNPs was accessed using UV–Vis spectroscopy for a period of 6 months. PVA was found to be comparatively the more effective stabilizer for AgNPs. The average size distribution of AgNPs stabilized with PVA was found to be 16.8 ± 1.8 nm using scanning electron microscopy. These suspensions were then stored for a period of 36 months and observed to remain stable with an increase in the size up to 41.7 ± 7 nm. PVA-stabilized AgNPs were assessed against 4T1 breast cancer cells and were observed to hinder the growth of breast cancer cells at a very low dose of 20 µg/mL with 87% (p = 0.0042) efficacy. These AgNPs showed significant antibacterial activity against Neisseria gonorrhoeae, Staphylococcus aureus and Micrococci luteus. The maximum zone of inhibition obtained was 18 mm against Staphylococcus aureus at a very low concentration of 20 µg/mL. These outcomes indicate that the proposed microfluidic reactor provides a robust approach for the preparation of highly stable AgNPs in combination with PVA as stabilizer which has also shown great potential in antibacterial and anticancer treatments.