Our group has been actively involved in the synthesis of QDs and magnetic QDs (MQDs) [-]. We have successfully demonstrated the magnetic and fluorescent properties of Fe2O3-CdSe MQDs, silica -coated QDs or MQDs and their application in cell labeling (Figure ) . The silanization using aminopropyl triethoxysilane (APS) in a reverse microemulsion produced thin silica coating on bare CdSe QDs or Fe2O3-CdSe MQD with surface NH2 groups. The methoxy groups of APS were hydrolyzed and condensed with another APS, exposing surface amine groups on the silanized QDs (SiO2/QDs) for conjugation with oleyl-O-poly(ethyleneglycol)-succinyl-N-hydroxysuccinimidyl ester, denoted as bio-anchored membrane (BAM). The reaction between the amine group and NHS ester resulted in a covalent amide bond formation, leaving the exposed oleyl group for the effective targeting of cell membrane. The labeling of live cell membranes (HepG2 human liver cancer cells and NIH-3T3 mouse fibroblast cells) using confocal laser scanning microscopy (CLSM) indicated the successful conjugation of silica-coated QDs or MQDs with BAM.
The research on superparamagnetic iron oxide nanoparticles (SPIONs) has been growing exponentially over the last several years. The field continues to drive in the direction of biomedical applications, especially molecular therapeutics by exploiting the immense qualities of SPIONs . This includes the distinctive controllable properties such as size, shape, magnetism, crystallinity and flexibility in fabricating multifunctional SPIONs with fluorescence, targeting ligands, drugs etc, thanks to the advancements in the syntheses and functionalization techniques developed hitherto. There are some excellent synthetic methods in prior arts on the formation of superparamagnetic magnetite (Fe3O4) and maghemite (γ-Fe2O3) SPIONs, with size control, narrow distribution, water solubility and surface functionalization [-]. The co-precipitation method is a conventional synthetic paradigm where Fe(II) and Fe(III) salts are co-precipitated in a basic solution in the presence of coating materials such as polymer or dextran (or its derivatives). Although the resulted iron oxide nanoparticles (NPs) are larger in size (ca. 100 nm) and partially crystalline, the particles are readily water soluble where their surfaces are directly functionalized. Alternatively, thermal decomposition method using precursors such as Fe(CO)5, Fe(Stearate)2, with high boiling solvents (octadecene, benzyl ether) and surfactants/ligands (oleic acid, oleylamine) can be used to synthesize smaller sized hydrophobic SPIONs (5-10 nm). In order to impart the SPIONs with water solubility for biomedical applications, water-oil microemulsion method can be employed as a reaction medium for coating a hydrophilic ligand (e.g. silica, peptides) on the hydrophobic surface.
In the present study, new surface-modified iron oxide nanoparticles were synthesized for the separation of lung cancer cells by simple precipitation of Fe(II) and Fe(III) salts in an aqueous ammonia solution, followed by the addition of polyethylenimine (PEI).