Spectroscopic and Calorimetric Studies of Molecular Recognitions in a Dendrimer-Surfactant Complex

Cationic Dendrimers for siRNA Delivery: An Overview of Methods for In Vitro/In Vivo Characterization

This chapter reviews the different techniques for analyzing the chemical-physical properties, transfection efficiency, cytotoxicity, and stability of covalent cationic dendrimers (CCDs) and self-assembled cationic dendrons (ACDs) for siRNA delivery in the presence and absence of their nucleic cargos. On the basis of the reported examples, a standard essential set of techniques is described for each step of a siRNA/nanovector (NV) complex characterization process: (1) analysis of the basic chemical-physical properties of the NV per se; (2) characterization of the morphology, size, strength, and stability of the siRNA/NV ensemble; (3) characterization and quantification of the cellular uptake and release of the siRNA fragment; (4) in vitro and (5) in vivo experiments for the evaluation of the corresponding gene silencing activity; and (6) assessment of the intrinsic toxicity of the NV and the siRNA/NV complex.

Ground-State Heterogeneity along with Fluorescent Byproducts Causes Excitation-Dependent Fluorescence and Time-Dependent Spectral Migration in Citric Acid-Derived Carbon Dots

The integrity of fluorescent carbon dot (FCD) emission deserves its highest appreciation when sample purification is performed with extreme care. Several controversial phenomena of FCD fluorescence including excitation-dependent emission, spectral migration with time, and thereby violation of the Kasha-Vavilov rule, which sparked intense debate during recent reports, disappeared when we rigorously purified the as-synthesized FCD sample. Purification was performed by first visual silica column chromatography (observing the emissions under UV illumination) and subsequently prolonged membrane dialysis. Most of the surprising phenomena of FCD fluorescence reported earlier apparently arose from ground-state spectral heterogeneity of FCD sample containing a large amount of fluorescent impurities (mostly polymeric or oligomeric in nature). Observation of our ensemble spectroscopic measurements, albeit nicely matched with recent reports based on single-particle experiments, differed largely from that of other ensemble measurements. Our results reconciled a number of long-standing controversies on FCD emission mostly by emphasizing the urgency of sample purification with more scientific rigor.