First paragraph of the article:
One of the critical challenges in medical diagnosis and therapy using nanotechnology is the assembly of multiple components in a multifunctional delivery system. This includes functionalities that can be structurally and chemically tailored in a nanocarrier for multi-modality imaging, cell targeting, drug storage, and controlled drug release. Development of these complex systems primarily utilizes existing basic nanosystems, such as carbon nanotubes, graphene, iron oxides, silica, quantum dots, and polymeric nanomaterials. Extensive attempts have been made to design, synthesize, and assemble some of these major components described above, for diagnostic and therapeutic delivery systems. Most of the approaches center on surface functionalization with drugs, biotechnology-derived molecules, including DNA, RNA, peptides, and antibodies, and imaging agents such as quantum dots. One of the major limitations of this approach is the single surface structure of the nanosystem. To date, nanoparticles represent the most widely used carrier system for multifunctional drug delivery applications. These structures normally assume a symmetrical, spherical or tubular geometry with limited surface available for attachment of multiple components. Frequently, multifunctional conjugates on a single carrier interact with each other leading to undesired adverse effects. The design and assembly of a symmetrical, single surface carrier is further complicated by unfavorable structural and chemical arrangements of these functional components. It is, therefore, critical to develop multi-surface nanostructures for assembly of a variety of components using a clinically acceptable drug delivery platform that can best utilize the intrinsic properties of the nanomaterials.