Impact of reaction variables and PEI/l-cysteine ratio on the optical properties and cytocompatibility of cationic Ag₂S quantum dots as NIR bio-imaging probes

Abstract

Near-infrared emitting semiconductor quantum dots (NIRQDs) are popular fluorescent probes due to better penetration depth and elimination of tissue autofluorescence.

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

“…Photoluminescence lifetime measurements conducted with QD3 indicated a multiexponential luminescence decay with an average lifetime (T average ) of 55.03 ns ( Figure 2C). This is somewhat similar to lifetime values reported for other Ag 2 S QDs with different coatings in the literature [23,50]. The faster component (T1) which arises from non-radiative events such as surface dangling bonds or electron-hole traps, which are considered as defects, was determined as 8.40 Nanomedicine 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 The IR spectrum of NAC-Ag 2 S QDs (QD3) were recorded between 4000-650 cm -1 and compared with the free NAC.…”

“…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.…”

One-Step Aqueous Synthesis of Anionic and Cationic AgInS2 Quantum Dots and Their Utility in Improving the Efficacy of ALA-Based Photodynamic Therapy

“…The emission intensity of both QDs increased with time, similar to Ag 2 S-2MPA, which was reported before ( Figure 3 a,e). 27 To better understand the time dependence of PL intensity, the kinetics of the photogenerated charge carriers were studied using the time-resolved PL spectra of these QDs.…”

“…Polymeric coating molecules provide colloidal stability due to multidentate binding to the nanocrystal surface but produce poor luminescence due to the lack of effective surface passivation and surface defects. 24 , 27 , 28 However, if they are mixed with small, thiolated molecules that can reach the surface, bind strongly, and reduce defects, both good stability and strong luminescence may be achieved. 24 , 28 Likewise, the advantage of 2MPA over 3MPA in enhancing the luminescence intensity and colloidal stability due to the stability of 2MPA and energetically favorable bidentate surface binding compared to 3MPA has been demonstrated on CdS QDs, and this approach was successfully utilized in Ag 2 S QDs by our group, as well.…”

Recent Advances of Low Biological Toxicity Ag2S QDs for Biomedical Application

“…In this work, Ag 2 S achieved in situ coating with MPEG‐SH and the luminescent in the medical window between 775 and 930 nm with QY 2–65% by changing the reaction variables such as PEG molecular weight, pH, and precursor ratios. Acar et al use one pot aqueous method prepared Ag 2 S NIR QDs. The prepared Ag 2 S NIR QDs can be used for in vitro fluorescence labeling and in vivo optical imaging agents by coating composed of branched polyethyleneimine (PEI)–25 kDa and l‐cysteine (Cys).…”