Additionally, functionalization of the NP’s surface with hydrophilic molecules, such as PEG, can also greatly increase their solubility, help evading macrophage-mediated uptake and, thus, avoid removal from the systemic circulation and protect their carriers from enzymatic degradation when used in vivo . For active targeting, NPs can be easily inhibitor functionalized with a wide variety of biological moieties, such as antibodies, peptides, and/or DNA/RNA to specifically target extracellular and intracellular receptors or pathways . The use of NPs functionalized with multiple peptides or antibodies, such as monoclonal antibodies, have been described
to successfully Inhibitors,research,lifescience,medical target specific cell surface proteins or receptors on cancer cells and further direct their antitumor action, leading to tumor cell death with minimal damage to collateral healthy cells [36, 39–41]. In dilution calculator nucleic-acid
functionalized NPs, DNA and RNA macromolecules can be used to simultaneously target specific Inhibitors,research,lifescience,medical sequences and exert their genetic-based therapy [42, 43]. To help tracking noble metal NPs in vivo and enhance the imaging properties of such moieties, leading to more efficient control of their therapeutic properties, they can also be functionalized with chemical moieties, such as Raman [44, 45] or fluorescent [46, 47] reporters. 2.2. Gene Silencing Antisense Inhibitors,research,lifescience,medical DNA [48, 49] and RNA interference (RNAi) via the use of small-interfering RNA [50–53] have emerged as a powerful and useful tools to block gene function and for sequence-specific Inhibitors,research,lifescience,medical posttranscriptional gene silencing, playing an important role in downregulation of specific gene expression in cancer cells. Small interfering RNAs (siRNAs) can be transfected into mammalian cells by a variety of methods that influence the strength and duration of the silencing response, which in turn is affected
by the amount of siRNA that is delivered and on the potential of each siRNA to suppress its Inhibitors,research,lifescience,medical target. Thus, one drawback of using naked siRNAs is that they show extremely short half-lives, weak protection against action by RNases, poor chemical stability, Cilengitide and common dissociation from vector . In fact, the major obstacle to clinical application is the uncertainty about how to deliver therapeutic RNAs (e.g., miRNA and/or siRNA) with maximal therapeutic impact. Nanotechnology offers an unprecedented opportunity to overcome these problems, as nanoscale devices, due to their small size, can readily interact with biomolecules on both the surface of cells and inside of cells for longer periods of time . Gold NPs (AuNPs) have shown potential as intracellular delivery vehicles for antisense oligonucleotides  and for therapeutic siRNA by providing protection against RNAses and ease of functionalization for selective targeting [42, 43].