DNA aptamer functionalized nanomaterials for intracellular analysis, cancer cell imaging and drug delivery.

The advance in studying inter- and intra-cellular biochemical processes has made important contributions to our understanding of biology in the past several decades. Such fundamental advancement also has significant impact on cell imaging and drug delivery. Technologies such as fluorescent resonant energy transfer (FRET), single molecular imaging, and gene regulation have allowed unparalleled insights into cellular functions and mechanisms in drug delivery. An exciting development in this area is the combination of unique optical or magnetic properties of nanomaterials with high selectivity of DNA/RNA aptamers. Together these aptamer-functionalized nanomaterials have enabled novel analytical techniques that advance our understanding and treatment of disease, aging, and cancer [1–3]. This review highlights recent work on using DNA aptamer-nanomaterial hybrid platforms for the applications in cellular analysis, imaging and targeted drug delivery (Figure 1). Figure 1 A general illustration of the three cellular analysis and therapeutic applications of aptamer-functionalized nanoparticles. 2. Overview of Nanomaterials and Aptamers 2.1 Nanomaterials for Cellular Applications Metal nanoparticles have been used widely for the studies of cellular uptake and analysis due to their simple synthesis, easy modifications, and biocompatibility. For applications in cellular analysis, gold and silver nanoparticles have been especially common owing to their excellent plasmonic properties, which have enabled significant advances in localized surface plasmon resonance (LSPR) for applications such as surface enhanced Raman spectroscopy [4]. When in close proximity to the surface of a plasmonic metal, the Raman signal can achieve 1014 enhancements, due to electromagnetic enhancements from plasmonic “hot spots”. Nanoparticles [5], nanoshells [6], nanoflowers [7], nanorods [8], and many other nanostructures [9] have all been recently been explored for their plasmonic properties in cell imaging, uptake mechanisms, and detection of various analytes [10]. The reader is directed to other recent reviews that focus on SERS/plasmonic applications of nanoparticles for cellular analysis [11*]. Other types of nanomaterials such as silica nanoparticles, quantum dots (QDs), and carbon based nanomaterials have also been applied in cellular applications [12–14]. Nanosized silica is widely known for excellent compatibility and has been used extensively in cellular studies [15]. More recently, mesoporous structures dramatically increased the surface area of silica nanoparticles and enabled high loading of cargo for cellular imaging and delivery [16]. Another material of interests is semiconducting QDs. Because of their fluorescence stability, board absorption and narrow emission band, they are uniquely suited for high resolution [17] and multiplex imaging of cells [18*]. Carbon based nanomaterials such as carbon nanotubes, fullerenes, and most recently graphene and graphene oxide are also promising nanomaterials for cellular applications, including the use of stabilized graphene oxide in cellular imaging and drug delivery [19–21].