Novel Method of Clickable Quantum Dot Construction for Bioorthogonal Labeling

ICP-MS and fluorescence dual-mode detection of ZIKV-RNA based on quantum dot labeling with hybridization chain reaction

The detection of Zika virus (ZIKV) is of great significance to human life and health. Herein, we presented an ICP-MS and fluorescent dual-mode sensor for quantitative analysis of Zika virus RNA fragments (ZIKV-RNA), which employed quantum dots (QDs) as signal tags and combined with hybridization chain reaction (HCR). The dual-mode sensor realized cross-checking of the analysis results and improved the assay accuracy. Firstly, the single-stranded DNA (ssDNA) was anchored on the surface of magnetic beads (MBs). Afterward, HCR was conducted with probe DNA-CdSe quantum dots conjugates (pDNA-QDs) and link DNA (lDNA), producing the MBs-ssDNA-[pDNA-QDs-lDNA]n conjugates. In the presence of target ZIKV-RNA, a strand displacement reaction occurred, leading to the dissociation of the [pDNA-QDs-lDNA]n labels from the conjugates into the solution. Finally, the signal intensity was detected using ICP-MS and fluorescence analysis, with achieved limits of detection of 131 pM and 152 pM, respectively. The inter-assay RSD values of fluorescence and ICP-MS were 3.94 % and 4.26 % at 10 nM level, respectively, showing that the method had good precision. This method showed high selectivity and was applied to the analysis of biological fluids. There was no significant difference between the results of ICP-MS modes and fluorescence mode. This method offers a new strategy for sensitivity analysis of ZIKV-RNA and exhibits promise in clinical applications for diagnosis.

Surface Functionalisation of Self-Assembled Quantum Dot Microlasers with a DNA Aptamer

The surface functionalisation of self-assembled colloidal quantum dot supraparticle lasers with a thrombin binding aptamer (TBA-15) has been demonstrated. The self-assembly of CdSSe/ZnS alloyed core/shell microsphere-shape CQD supraparticles emitting at 630 nm was carried out using an oil-in-water emulsion technique, yielding microspheres with an oleic acid surface and an average diameter of 7.3 ± 5.3 µm. Surface modification of the microspheres was achieved through a ligand exchange with mercaptopropionic acid and the subsequent attachment of TBA-15 using EDC/NHS coupling, confirmed by zeta potential and Fourier transform IR spectroscopy. Lasing functionality between 627 nm and 635 nm was retained post-functionalisation, with oleic acid- and TBA-coated microspheres exhibiting laser oscillation with thresholds as low as 4.10 ± 0.37 mJ·cm-2 and 7.23 ± 0.78 mJ·cm-2, respectively.

A novel and sensitive ratiometric fluorescent quantum dot-based biosensor for alkaline phosphatase detection in biological samples via the inner-filter effect

Alkaline phosphatase (ALP) is an important biomarker whose abnormal level in activity is associated with hepatobiliary, skeletal, and renal diseases as well as cancer. Herein, we synthesized ZnSe@ZnS quantum dots (ZnSe@ZnS QDs) and Mn-doped ZnS quantum dots (Mn:ZnS QDs) as fluorophores to establish the ratiometric fluorescent assay for ALP activity detection in biological samples. p-Nitrophenyl phosphate (PNPP) was used as a substrate for ALP, and the overlaps between absorption spectra of PNPP and excitation spectra of QDs resulted in sharp fluorescence quenching. Under the catalysis of ALP, PNPP was hydrolyzed into p-nitrophenol (PNP), which caused a red shift of absorption band of PNPP and fluorescence recovery of Mn:ZnS QDs (585 nm). However, the overlaps between absorption spectra of PNP and emission spectra of ZnSe@ZnS QDs led a further quenching of ZnSe@ZnS QDs (405 nm). Therefore, the ratiometric fluorescent signals (F ₅₈₅/F ₄₀₅) were associated with activity of ALP based on bidirectional responses of QDs to the concentration of PNPP. Under the optimum conditions, the method exhibited a good linear relationship from 4 to 96 U per L (R ² = 0.9969) with the detection limit of 0.57 U per L. Moreover, the method was successfully applied for detecting the ALP activity in a complex biological matrix (human serum and HepG2 cells) with impressive specificity. In particular, the complicated chemical modifications of QDs and pretreatments of biological samples were not required in the whole detection procedures. Therefore, it not only provided a sensitive, specific and simple approach to clinical ALP activity detection, but it also provided support for early diagnosis of diseases.

Synthesis of bio-templated clickable quantum dots and dual-emitting organic/inorganic complex for ratiometric fluorescence visual assay of blood glucose

With the prevalence of diabetes, rapid and simple blood glucose monitoring becomes more and more important. Here, we reported the synthesis of the bio-templated N3-CdZnTeS quantum dots (QDs), which was...

Detection of Mycobacterium Tuberculosis IS6110 gene fragment by fluorescent biosensor based on FRET between two-dimensional metal-organic framework and quantum dots-labeled DNA probe

Herein, a universal fluorescent biosensor was developed for detecting Mycobacterium Tuberculosis (MTB) specific insertion sequence IS6110 gene fragment based on Förster resonance energy transfer (FRET) strategy. CdTe quantum dots (QDs), with excellent luminous performance, were used to label single-stranded DNA (ssDNA) as fluorescence donor (QDs-DNA), in which the ssDNA was complementary to the IS6110 gene fragment. A new type of two-dimensional metal-organic framework (Cu-TCPP) was served as an acceptor. The Cu-TCPP exhibited a higher affinity towards ssDNA than double-stranded DNA (dsDNA). In the absence of targets, the fluorescence of QDs-DNA was quenched - due to the π-π stacking interactions between Cu-TCPP and ssDNA. Otherwise, QDs-DNA hybridized with the target to form a double helix and the fluorescence maintained in a target-concentration dependent manner. Excess QDs-DNA would be quenched and produced negligible background signal. The fluorescent sensor possessed a linear range from 0.05 nM to 1.0 nM with a low detection limit of 35 pM. Furthermore, we successfully applied this biosensing system to detect clinical sputum samples. This method displayed high sensitivity, specificity and great potentials in the early diagnosis of Tuberculosis.

Nanomaterial-Based Dual-Emission Ratiometric Fluorescent Sensors for Biosensing and Cell Imaging

Owing to the unique optophysical properties of nanomaterials and their self-calibration characteristics, nanomaterial-based (e.g., polymer dots (Pdots) quantum dots (QDs), silicon nanorods (SiNRs), and gold nanoparticle (AuNPs), etc.) ratiometric fluorescent sensors play an essential role in numerous biosensing and cell imaging applications. The dual-emission ratiometric fluorescence technique has the function of effective internal referencing, thereby avoiding the influence of various analyte-independent confounding factors. The sensitivity and precision of the detection can therefore be greatly improved. In this review, the recent progress in nanomaterial-based dual-emission ratiometric fluorescent biosensors is systematically summarized. First, we introduce two general design approaches for dual-emission ratiometric fluorescent sensors, involving ratiometric fluorescence with changes of one response signal and two reversible signals. Then, some recent typical examples of nanomaterial-based dual-emission ratiometric fluorescent biosensors are illustrated in detail. Finally, probable challenges and future outlooks for dual-emission ratiometric fluorescent nanosensors for biosensing and cell imaging are rationally discussed.