Riboflavin-Conjugated Multivalent Dendrimer Platform for Cancer-Targeted Drug and Gene Delivery

Abstract

Riboflavin receptors (RFRs) are overexpressed in several malignant cells, and have been characterized as an emerging tumor surface biomarker. In this article, we discuss the design principles of a RFR-targeted nanoparticle system and illustrate its applications with studies performed in our laboratories. This system is based on a poly(amidoamine) (PAMAM) dendritic polymer which is modified on the surface by conjugation with riboflavin (RF) as the targeting ligand. First, we discuss the application of this system for targeted drug delivery by its conjugation with methotrexate as an antitumor payload. In cell-based experiments performed in vitro, this drug conjugate displayed RF-dependent, potent inhibition of cell growth in RFR(+) KB carcinoma cells. Second, the use of the RF-conjugated dendrimer for gene delivery applications through the formation of polyplexes with plasmid DNA is described. The ability of this targeted system to significantly enhance gene transfection in epithelial cells points to its potential as a promising new class of nonviral vectors. Third, the tunability of the functional properties of the dendrimer through modular integration is illustrated with an optically active gold nanoparticle (AuNP). The resultant dendrimer-coated AuNPs have a unique capability for tumor cell imaging via surface plasmon resonance scattering. Finally, we discuss the biophysical basis of the multivalent mechanism involved in the tight and specific binding of a RF-conjugated multivalent dendrimer to RFRs on the cell surface. The design principles and proof of concept studies presented here are strongly supportive of the promising potential of RF-conjugated nanoparticles for delivery and imaging applications in tumors.