The development of simple, cost-effective, and advanced multifunctional technology is the need of the hour to combat cancer as well as bacterial infections. There have been reports of silver nanoparticles (AgNPs), silver salts, and Prussian blue (PB) being used for medicinal purposes which are clinically approved. In this context, in the present communication, we incorporated PB and silver salts (silver nitrate) to develop silver PB analogue nanoparticles (SPBANPs), a new nanomedicine formulation as a safer and effective mode of treatment strategy (2-in-1) for both cancer and bacterial infections. Considering all fundamental issues of nanomedicine, along with understanding of the biological impact of PB, we designed a simple, fast, efficient, cheap, and eco-friendly method for the synthesis of [poly­(N-vinyl-2-pyrrolidone)]-stabilized silver hexacyanoferrate nanoparticles (silver PB analogue: Ag3[Fe­(CN)6] abbreviated as SPBANPs). Various analytical tools were used to analyze and characterize the nanomaterials (SPBANPs). The SPBANPs were highly stable for several weeks in various phosphate buffers with a range of physiological pH conditions (pH = 6–8). The nanoparticles showed biocompatibility in vivo in C57BL6/J mice that encouraged us to screen the nanoparticles for various biomedical applications. The SPBANPs themselves exhibited remarkable inhibition of cancer cell proliferation (B16F10, A549, MCF-7, and SK-OV-3) in vitro. Substantial inhibition of melanoma tumor growth was observed in the C57BL6/J mouse model (aggressive murine melanoma model: B16F10) after intraperitoneal administration of the SPBANPs without any anticancer drug. Additionally, the SPBANPs exhibited excellent antibacterial activity in various Gram-negative (Escherichia coli, Klebsiella pneumonia, and Pseudomonas aeruginosa) and Gram-positive (Bacillus subtilis) bacteria. Interestingly, this nanoformulation itself works as a drug delivery vehicle, as well as an anticancer and antibacterial agent. The in vitro and in vivo results together demonstrate that this biocompatible nanoformulation (SPBANPs) without an anticancer drug or antibiotic could be explored to develop as a multifunctional therapeutic agent (2-in-1) for the treatment of cancer and bacterial infections in the near future.

Near infrared (NIR) fluorescence imaging is a striking imaging modality for biomedical and clinical applications due to its deep tissue penetration and low phototoxicity. The major issue with NIR dyes is their non-specific distribution and requirement of tagging with biomolecules for specific tissue localization. Till now, there have been no imaging agents available that can distribute into a specific organ without the need for targeted ligands, which remains as an unmet clinical need. In the present study, we demonstrate that the Zinnia elegans plant extract (abbreviated as ZE) assisted synthesis of highly biocompatible gold nanoparticles (AuZE), leading to their non-invasive bio-imaging applications in the NIR region (red at 820 nm emission: NIR region). AuZE and ZE both exhibited green fluorescence at 350 nm excitation and red fluorescence in the NIR region (710 nm). We verified the source of this fluorescence, which originates from the fluorescent molecules present in the ZE extract. After intraperitoneal administration in C57BL6 mice, very interestingly, AuZE is distributed into the brain of C57BL6 mice without the need for any targeted ligand and exhibited bright red fluorescence in the NIR region (710 nm excitation, 820 nm emission) as evidenced by non-invasive imaging as well as ICPOES techniques. We further explored the activity of ZE and AuZE as cell labeling agents (B16F10 cells were pre-incubated with AuZE and implanted into mice, and the fluorescence was monitored), which could be applicable for graft transplantation biology. To the best of our knowledge, this is the first report that demonstrates the versatile applications of green synthesized gold nanoparticles using a ZE extract. Considering these exciting results and fruitful outcomes, the ZE and AuZE NPs would stand as an alternative imaging agent to commercially available NIR dyes and change the conventional fluorescence-based bioimaging strategies. Therefore, the biosynthesized AuNPs open new directions for future research to explore these latest observations in the field of disease diagnosis and therapy.

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