Nanoflares as Probes for Cancer Diagnostics

Abstract

Patients whose cancer is detected early are much more likely to have a positive prognosis and outcome. Nanoflares hold promise as a practical diagnostic platform for the early detection of cancer markers in living cells. These probes are based on spherical nucleic acid (SNAs) and are typically composed of gold nanoparticle cores and densely packed and highly oriented oligonucleotide shells; these sequences are complementary to specific mRNA targets and are hybridized to fluorophore-labeled reporter strands. Nanoflares take advantage of the highly efficient fluorescence quenching properties of gold, the rapid cellular uptake of SNAs that occurs without the use of transfection agents, and the enzymatic stability of such constructs to report a highly sensitive and specific signal in the presence of intracellular target mRNA. In this chapter, we will focus on the synthesis, characterization, and diagnostic applications of nanoflares as they relate to cancer markers.

Nanostructured luminescently labeled nucleic acids

“…A nanoflare comprises a gold nanoparticle (e.g. 13 nm diameter) densely coated with capture probe to which is hybridized a displaceable Cy5‐labeled reporter probe . In this so‐called ‘spherical nucleic acid’, the fluorescence signal of the Cy5 dye is quenched by the gold nanoparticle.…”

Tuning DNA–nanoparticle conjugate properties allows modulation of nuclease activity

“…6 For instance, SNAs show higher binding constants and sharper melting transitions with their complements than free oligonucleotides, 7,8 and they readily enter cells without the need for transfection agents. 6,9,10 SNAs are highly tunable, as various sizes of nanoparticles (typically between 10 and 100 nm), lengths of DNA or RNA (typically up to 50 bases), spacer lengths/compositions and oligonucleotide modifications can serve as tunable modular units. 6,11 Herein, we use the term SNA to refer exclusively to oligonucleotide-gold nanoparticle (AuNP) conjugates.…”

Relationships between Poly(ethylene glycol) Modifications on RNA–Spherical Nucleic Acid Conjugates and Cellular Uptake and Circulation Time

“…In contrast with their linear counterparts, SNAs are actively internalized by cells without the need for cytotoxic transfection reagents. − This process is often mediated by class A scavenger receptors , that have high affinities for SNAs but not the particle-free sequences. These structure-dependent properties have made SNAs promising single-entity agents for probing and regulating cellular processes. ,− For example, RNA–SNAs are attractive agents for gene regulation applications, in which the design of the nucleic acid sequence of a SNA may be tailored to effect the knock-down of a genetic target . Indeed, small interfering RNA (siRNA) SNAs have been shown to penetrate the skin, , when topically applied to mice, and cross the blood–brain barrier, when systemically administered.…”