A novel method for the analysis of calf thymus DNA based on CdTe quantum dots-Ru(bpy) 3 2+ photoinduced electron transfer system

Activatable QD-Based Near-Infrared Fluorescence Probe for Sensitive Detection and Imaging of DNA

Accurate detection of DNA is essential for the precise diagnosis of diseases. Here we report an activatable near-infrared (NIR) fluorescence nanoprobe (QD-Al-GFLX) composed of NIR quantum dots (QDs) and Al(III)-gatifloxacin (Al-GFLX) complexes for the sensitive detection of double-stranded DNA (dsDNA) both in aqueous solution and in living cells. We demonstrated that the initial strong NIR fluorescence of QDs in QD-Al-GFLX was quenched by the Al-GFLX complex via a photoinduced electron transfer (PET) mechanism. Upon interaction with dsDNA, the high binding affinity between dsDNA and Al-GFLX complex could trigger QD-Al-GFLX dissociation, which could eliminate the PET process, resulting in significant enhancement of NIR fluorescence. QD-Al-GFLX was sensitive and specific to detect dsDNA in aqueous solution, with a detection limit of 6.83 ng/mL. The subsequent fluorescence imaging revealed that QD-Al-GFLX holds a high ability to enter into live cells, generating strong NIR fluorescence capable of reporting on dsDNA levels. This study highlighted the potential of using QD-Al-GFLX nanoprobe for the real-time detection and imaging of dsDNA in living cells.

In vitro interaction investigation between three Ru(ii) arene complexes and human serum albumin: structural influences

In vitro interactions between three Ru(ii) arene complexes and human serum albumin were systematically investigated by multi-spectroscopic techniques.

Characterization of the interaction of a mono-6-thio-β-cyclodextrin-capped CdTe quantum dots-methylene blue/methylene green system with herring sperm DNA using a spectroscopic approach

Novel, water-soluble CdTe quantum dots (QDs) capped with β-cyclodextrin (β-CD) and ~ 4.0 nm in diameter were synthesized in aqueous solution, and characterized using transmission electron microscopy (TEM). A fluorescence-sensing system based on the photoinduced electron transfer (PET) of (mono-6-thio-β-CD)-CdTe QDs was then designed to measure the interaction of phenothiazine dyes [methylene blue (MB) and methylene green (MG)] with herring sperm DNA (hsDNA). This fluorescence-sensing system was based on a fluorescence "OFF-ON" mode. First, MB/MG adsorbed on the surface of (mono-6-thio-β-CD)-CdTe QDs effectively quenches the fluorescence of (mono-6-thio-β-CD)-CdTe QDs through PET. Then, addition of hsDNA restores the fluorescence intensity of (mono-6-thio-β-CD)-CdTe QDs, because hsDNA can bind with MB/MG and remove it from the as-prepared (mono-6-thio-β-CD)-CdTe QDs. In addition, detailed reaction mechanisms of the (mono-6-thio-β-CD)-CdTe QDs-MB/MG-hsDNA solution system were studied using optical methods, by comparison with the TGA-CdTe QDs-MB/MG-hsDNA solution system.

A sensitive quantum dots-based "OFF-ON" fluorescent sensor for ruthenium anticancer drugs and ctDNA

In this contribution, a simple and sensitive fluorescent sensor for the determination of both the three ruthenium anticancer drugs (1 to 3) and calf thymus DNA (ctDNA) was established based on the CdTe quantum dots (QDs) fluorescence "OFF-ON" mode. Under the experimental conditions, the fluorescence of CdTe QDs can be effectively quenched by ruthenium anticancer drugs because of the surface binding of these drugs on CdTe QDs and the subsequent photoinduced electron transfer (PET) process from CdTe QDs to ruthenium anticancer drugs, which render the system into fluorescence "OFF" status. The system can then be "ON" after the addition of ctDNA which brought the restoration of CdTe QDs fluorescence intensity, since ruthenium anticancer drugs broke away from the surface of CdTe QDs and inserted into double helix structure of ctDNA. The fluorescence quenching effect of the CdTe QDs-ruthenium anticancer drugs systems was mainly concentration dependent, which could be used to detect three ruthenium anticancer drugs. The limits of detection were 5.5 × 10(-8) M for ruthenium anticancer drug 1, 7.0 × 10(-8) M for ruthenium anticancer drug 2, and 7.9× 10(-8) M for ruthenium anticancer drug 3, respectively. The relative restored fluorescence intensity was directly proportional to the concentration of ctDNA in the range of 1.0 × 10(-8) M ∼ 3.0 × 10(-7) M, with a correlation coefficient (R) of 0.9983 and a limit of detection of 1.1 × 10(-9) M. The relative standard deviation (RSD) for 1.5 × 10(-7) M ctDNA was 1.5% (n = 5). There was almost no interference to some common chemical compounds, nucleotides, amino acids, and proteins. The proposed method was applied to the determination of ctDNA in three synthetic samples with satisfactory results. The possible reaction mechanism of CdTe QDs fluorescence "OFF-ON" was further investigated. This simple and sensitive approach possessed some potential applications in the investigation of interaction between drug molecules and DNA.

Detection of DNA using an “off-on” switch of a regenerating biosensor based on an electron transfer mechanism from glutathione-capped CdTe quantum dots to nile blue

A new DNA detection method, which relies on the “off-on” switch of a regenerated fluorescence biosensor based on an electron transfer mechanism from glutathione (GSH)-capped CdTe quantum dots (QDs) to nile blue (NB), is proposed.

"Turn-on-off-on" fluorescence switching of quantum dots-cationic porphyrin nanohybrid: a sensor for DNA

In this article, we describe a new platform for probing double stranded DNA (dsDNA) by tracing the "on-off-on" fluorescence signals of quantum dots-cationic porphyrin utilizing fluorescence and synchronous fluorescence measurements. Electrostatic interaction between the negatively charged thioglycolic acid capped CdTe quantum dots (CdTe-TGA QDs) and positively charged porphyrin surfaces leads to drastic quenching (turning off) of the donor by an effective electron transfer process. Interestingly, after the addition of calf thymus DNA (CtDNA), the porphyrins peel off from the quantum dot surface and bind to dsDNA, resulting in the restoration of fluorescence intensity of quantum dots (turning on). Consequently, this can be utilized for the selective sensing of dsDNA via optical responses. Experimental results show that the increase in fluorescence intensity is proportional to the concentration of CtDNA within the range of 6.5 × 10(-9) M to 29.6 × 10(-8) M under the optimized experimental conditions. Furthermore, the peel off mechanism was confirmed by atomic force measurement.