Soft fluorescent nanomaterials for biological and biomedical imaging

Abstract

Soft fluorescent nanomaterials have attracted recent attention as imaging agents for biological applications, because they provide the advantages of good biocompatibility, high brightness, and easy biofunctionalization. Here, we provide a survey of recent developments in fluorescent soft nano-sized biological imaging agents. Various soft fluorescent nanoparticles (NPs) (including dye-doped polymer NPs, semiconducting polymer NPs, small-molecule organic NPs, nanogels, micelles, vesicles, and biomaterial-based NPs) are summarized from the perspectives of preparation method, structure, optical property, and surface functionalization. Based on both optical and functional properties of the nano-sized imaging agents, their applications are then reviewed in terms of in vitro imaging, in vivo imaging, and cellular-process imaging, by means of specific or nonspecific targeting.

Iridium-Based Dual-Functional Nanoparticles for Far-Red Imaging and Photodynamic Therapy

“…It can be seen that the spectra of iridium complexes in NPs are similar to that in THF. The three absorption bands at 283 nm, 381 nm and 480 nm are assigned to spin-allowed π-π* transition of DPQ ligand, spin-allowed 1 MLCT band and spin-forbidden 3 MLCT, respectively, and the far red emission at around 668 nm is from 3 MLCT [13].…”

“…Synthesis and characterization of phosphorescent Ir-NPs (DPQ) 2 Ir(acac)-doped biocompatible NPs (Ir-NPs) were prepared by previously reported encapsulationreprecipitation method [3]. Briefly, the hydrophobic species of PS, DTS and DPQ) 2 Ir(acac) aggregated into nanoparticles under hydrophobic interaction after being injected into water, which were subsequently encapsulated by a PLL shell.…”

“…Fluorescence imaging has become a highly sensitive and indispensable technique for noninvasive visualization of living specimens with subcellular resolution that cannot be achieved by ultrasound or magnetic resonance imaging [1][2][3]. In particular, fluorescence imaging with long wavelength ranged from far-red to near-infrared (NIR) (650-900 nm) is much desired for in vivo imaging and medical diagnosis because of the merits of minimal interference from tissue autofluorescence, reduced light scattering, and high tissue penetration [4][5][6].…”

“…In this work, a far-red phosphorescent hydrophobic iridium complex with emission wavelength at 668 nm was embedded into biocompatible NPs using a modified encapsulation-reprecipitation method [3,[29][30][31]. Phosphorescence of the complex was highly oxygen-sensitive in organic solvent, but became nearly independent of oxygen after being immobilized into particle matrix that was actually oxygen-permeable.…”

Silica passivated conjugated polymer nanoparticles for biological imaging applications

“…The nanoparticles are synthesised using two methods: mini-emulsion and nanoprecipitation. The mini-emulsion method involves dissolving the CP in an aprotic, water immiscible solvent then emulsifying the solution through sheer force in an aqueous solution that contains surfactant [23][24][25][26] . In contrast, the nano-precipitation method involves dissolving the CP into a water-miscible solvent such as THF and then injecting it into a non-solvent (such as water).…”