Metal nanoparticles are being extensively used in various biomedical applications due to their small size to volume ratio and extensive thermal stability. Gold nanoparticles (GNPs) are an obvious choice due to their amenability of synthesis and functionalization, less toxicity and ease of detection. The present review focuses on various methods of functionalization of GNPs and their applications in biomedical research. Functionalization facilitates targeted delivery of these nanoparticles to various cell types, bioimaging, gene delivery, drug delivery and other therapeutic and diagnostic applications. This review is an amalgamation of recent advances in the field of functionalization of gold nanoparticles and their potential applications in the field of medicine and biology.

Significance: Nanoparticle-mediated delivery of siRNA to hepatocytes has treated disease in humans. However, systemically delivering RNA drugs to nonliver tissues remains an important challenge. To increase the number of nanoparticles that could be studied in vivo, we designed a high-throughput method to measure how >100 nanoparticles delivered mRNA that was translated into functional protein in vivo. We quantified how >250 lipid nanoparticles (LNPs) delivered mRNA in vivo, identifying two LNPs that deliver mRNA to endothelial cells. One of the LNPs codelivered Cas9 mRNA and single-guide RNA in vivo, leading to endothelial cell gene editing. This approach can identify nanoparticles that target new cells.

Peer reviewed article authored by (Vardharajula S, Ali SZ, Tiwari PM, Eroğlu E, Vig K, Dennis VA, Singh SR). Read article or submit your manuscript for publishing.

The lung is a critical prophylaxis target for clinically important infectious agents, including human respiratory syncytial virus (RSV) and influenza. Here, we develop a modular, synthetic mRNA-based approach to express neutralizing antibodies directly in the lung via aerosol, to prevent RSV infections. First, we express palivizumab, which reduces RSV F copies by 90.8%. Second, we express engineered, membrane-anchored palivizumab, which prevents detectable infection in transfected cells, reducing in vitro titer and in vivo RSV F copies by 99.7% and 89.6%, respectively. Finally, we express an anchored or secreted high-affinity, anti-RSV F, camelid antibody (RSV aVHH and sVHH). We demonstrate that RSV aVHH, but not RSV sVHH, significantly inhibits RSV 7 days post transfection, and we show that RSV aVHH is present in the lung for at least 28 days. Overall, our data suggests that expressing membrane-anchored broadly neutralizing antibodies in the lungs could potentially be a promising pulmonary prophylaxis approach.

Reduced toxicity and ease of modification make gold nanoparticles (GNPs) suitable for targeted delivery, bioimaging and theranostics by conjugating cell-penetrating peptides (CPPs). This study presents the biodistribution and enhanced intracellular uptake of GNPs functionalized with VG-21, a CPP derived from vesicular stomatitis virus glycoprotein (G). Cell penetrating efficiency of VG-21 was demonstrated using CellPPD web server, conjugated to GNPs and were characterized using, UV-visible and FTIR spectroscopy, transmission electron microscopy, dynamic light scattering and zeta potential. Uptake of VG-21 functionalized GNPs (fGNPs) was tested in eukaryotic cell lines, HEp-2, HeLa, Vero and Cos-7, using flow cytometry, fluorescence and transmission electron microscopy (TEM), and inductively coupled plasmon optical emission spectroscopy (ICP-OES). The effects of nanoparticles on stress and toxicity related genes were studied in HEp-2 cells. Cytokine response to fGNPs was studied in vitro and in vivo. Biodistribution of nanoparticles was studied in BALB/c mice using TEM and ICP-OES. VG-21, GNPs and fGNPs had little to no effect on cell viability. Upon exposure to fGNPs, HEp-2 cells revealed minimal down regulation of stress response genes. fGNPs displayed higher uptake than GNPs in all cell lines with highest internalization by HEp-2, HeLa and Cos-7 cells, in endocytotic vesicles and nuclei. Cytokine ELISA showed that mouse J774 cells exposed to fGNPs produced less IL-6 than did GNP-treated macrophage cells, whereas TNF-α levels were low in both treatment groups. Biodistribution studies in BALB/c mice revealed higher accumulation of fGNPs than GNPs in the liver and spleen. Histopathological analyses showed that fGNP-treated mice accumulated 35 ng/mg tissue and 20 ng/mg tissue gold in spleen and liver respectively, without any adverse effects. Likewise, serum cytokines were low in both GNP- and fGNP-treated mice. Thus, VG-21-conjugated GNPs have enhanced cellular internalization and are suitable for various biomedical applications as nano-conjugates.