Targeted Quantum Dot Conjugates for siRNA Delivery

Abstract

Treatment of human diseases such as cancer generally involves the sequential use of diagnostic tools and therapeutic modalities. Multifunctional platforms combining therapeutic and diagnostic imaging functions in a single vehicle promise to change this paradigm. in particular, nanoparticle-based multifunctional platforms offer the potential to improve the pharmacokinetics of drug formulations, while providing attachment sites for diagnostic imaging and disease targeting features. We have applied these principles to the delivery of small interfering RNA (siRNA) therapeutics, where systemic delivery is hampered by rapid excretion and nontargeted tissue distribution. Using a PEGlyated quantum dot (QD) core as a scaffold, siRNA and tumor-homing peptides (F3) were conjugated to functional groups on the particle's surface. We found that the homing peptide was required for targeted internalization by tumor cells, and that siRNA cargo could be coattached without affecting the function of the peptide. Using an EGFP model system, the role of conjugation chemistry was investigated, with siRNA attached to the particle by disulfide cross-linkers showing greater silencing efficiency than when attached by a nonreducible thioether linkage. Since each particle contains a limited number of attachment sites, we further explored the tradeoff between number of F3 peptides and the number of siRNA per particle, leading to an optimized formulation. Delivery of these F3/siRNA-QDs to EGFP-transfected HeLa cells and release from their endosomal entrapment led to significant knockdown of EGFP signal. By designing the siRNA sequence against a therapeutic target (e.g., oncogene) instead of EGFP, this technology may be ultimately adapted to simultaneously treat and image metastatic cancer.

15 years on siRNA delivery: Beyond the State-of-the-Art on inorganic nanoparticles for RNAi therapeutics

“…After this study, siRNA-QDs as light-emitting nanoparticles [67] have been extensively used for gene silencing approaches [21,[68][69][70]. One of the most promising features of siRNA-QDs is the proton-sponge effect.…”

“…Encapsulation of these QDs into polymers may be the key to solving some issues related to acute toxicity but may decrease their intrinsic potential as vehicles for delivery. 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 REVIEW NANO TODAY 21 Although nontoxic QDs for imaging and siRNA delivery in vitro have been developed recently [68,72], a meticulous analysis of their long-term cytotoxicity is necessary before they can be used in vitro and especially in vivo biomedical applications.…”

“…However, all these strategies have in common the use of thiolated siRNA, generally synthesized as disulphide and reduced with dithiothreitol (DTT) [21,118] or tris(2-carboxyethyl)phosphine (TCEP) [73] prior to the attachment.…”

“…nanosized structures made by an inorganic material (e.g. silica, gold, iron oxide, quantum dots, carbon nanotubes, calcium phosphate), coated by polymeric layers and conjugated to siRNA through specific approaches including covalent binding, electrostatic absorption and encapsulation, depending on the material [17][18][19][20][21][22]. Compared to conventional transfection agents, nanoparticle-conjugated siRNAs have been shown to be less susceptible to degradation by nuclease activity, exhibit greater cellular uptake and higher siRNA effective concentration; which has accelerated siRNA delivery in this direction over the past few years.…”

Nanodentistry: Combining Nanostructured Materials and Stem Cells for Dental Tissue Regeneration

“…n Targeting therapy: gene, protein & drug intracellular delivery One of the most attractive concepts in manipulating the fate of stem cells and directing their differentiation into specific cell populations is the use of nanomaterials for intracellular gene delivery (e.g., RNAi and DNA) [91,92]. Generally, viral (e.g., adenoviruses, lentiviruses and retroviruses) and nonviral vectors (e.g., lipids and polymers) can be used for cellular transfection and/or nucleofection, thus offering durable gene expression within stem cells [93][94][95][96].…”