Highly luminescent and cytocompatible cationic Ag₂S NIR-emitting quantum dots for optical imaging and gene transfection

Abstract

The development of non-toxic theranostic nanoparticles capable of delivering a therapeutic cargo and providing a means for diagnosis is one of the most challenging tasks in nano-biotechnology. Gene therapy is a very important mode of therapy and polyethyleneimine (PEI) is one of the most successful vehicles for gene transfection, yet poses significant toxicity. Optical imaging utilizing quantum dots is one of the newer but fast growing diagnostic modalities, which requires non-toxic, highly luminescent materials, preferentially active in the near infrared region. Ag2S NIRQDs fit to this profile perfectly. Here, we demonstrate the aqueous synthesis of cationic Ag2S NIRQDs with a mixed coating of 2-mercaptopropionic acid (2MPA) and PEI (branched, 25 kDa), which are highly luminescent in the NIR-I window (λem = 810-840 nm) as new theranostic nanoparticles. Synergistic stabilization of the QD surface via the simultaneous use of a small molecule and a polymeric material provided the highest quantum yield, 150% (with respect to LDS 798 at pH 7.4), reported in the literature for Ag2S. These cationic particles show a dramatic improvement in cytocompatibility even without PEGylation, a strong optical signal easily detected by confocal laser microscopy and effective conjugation and transfection of the green fluorescence protein plasmid (pGFP) to HeLa and MCF-7 cell lines (40% efficiency). Overall, these Ag2S NIRQDs show great potential as new theranostics.

Ultra‐Sensitive Detection of Proteins Using Chemically Modified Nanoporous PVDF Membrane with Attenuated Near IR Autofluorescence

“…The characteristic peaks of α and β phases were noted for pristine PVDF at 1180–750 cm −1 and 1400–840 cm −1 respectively . The C=C bond formation during dehydrofluorination is observed at 1637 cm −1 . As shown in Figure (b), the alkali treatment on PVDF caused the formation of carbon−carbon double bonds due to dehydrofluorination reaction.…”

“…In PVDF, the regularity of the CH 2 ‐CF 2 groups is destroyed by dehydrofluorination once treated with alkali as indicated in Figure b. The component at 286.8 eV represents a contribution from the secondary shift experienced by the CH 2 groups that are adjacent to CF 2 , the formation of C=C structure . The CF 2 peak is slightly to lower binding energy suggests the occurrence of dehydrofluorination reaction.…”

Development of Near-Infrared Region Luminescent N-Acetyl-L-Cysteine-Coated Ag 2 S Quantum Dots with Differential Therapeutic Effect

“…Ag 2 S QDs emerged as a new class of QDs with emission in the NIR region and became very popular with the highly biocompatible, stable and strongly luminescent nature [13][14][15][16]. Very low solubility constant (K sp = 6.3 x 10 -50 ) inhibits the release of Ag + ions into the biological media and ensures high biocompatibility [17].…”

“…It does not only influence the QD-cell interaction, biodistribution and biocompatibility, but also it controls the particle growth, provide colloidal stability and surface functionality for the conjugation of desired ligands, peptides, drugs or oligonucleotides to QDs for specific action [18][19][20]. Ag 2 S QDs were synthesized with several functional coating materials in the literature such as 2-mercaptopropionic acid (2-MPA) [16], dimercaptosuccinic acid (DMSA) which is a heavy metal chelator [21], bovine serum albumin (BSA) [22], polyethylene glycol [14], ribonuclease-A (RNase A) [17] or with mixed coatings such as polyethyleneimine (PEI)/2-MPA [15] and F o r R e v i e w O n l y PEI/cysteine [23]. These studies demonstrate the impact of coating on particle size, emission wavelength and toxicity.…”

The design of hybrid materials based on magnetic Fe3O4 nanoparticles and luminescent CdS nanoparticles for cell visualization

“…The key advantages of such materials over organic luminescent dyes, which are traditionally used for this purpose, are sta bility in biological objects and stability against pho tobleaching [3]. By varying the nanoparticle size and chemical composition, it is possible to obtain lumines cent materials with an emission band in any spectral region, in particular, in the near IR range (e.g., QDs based on Ag 2 S) [4]. Currently, considerable interest has been expressed in hybrid nanoparticles combining magnetic and luminescent properties [5,6].…”