Xiaoqun Gong

Quantum dot-based immunochromatography test strip for rapid, quantitative and sensitive detection of alpha fetoprotein.

Rapid, quantitative detection of tumor markers with high sensitivity and specificity is critical to clinical diagnosis and treatment of cancer. We describe here a novel portable fluorescent biosensor that integrates quantum dot (QD) with an immunochromatography test strip (ICTS) and a home-made test strip reader for detection of tumor markers in human serum. Alpha fetoprotein (AFP), which is valuable for diagnosis of primary hepatic carcinoma, is used as a model tumor marker to demonstrate the performance of the proposed immunosensor. The principle of this sensor is on the basis of a sandwich immunoreaction that was performed on an ICTS. The fluorescence intensity of captured QD labels on the test line and control line served as signals was determined by the home-made test strip reader. The strong luminescence and robust photostability of QDs combined with the promising advantages of an ICTS and sensitive detection with the test strip reader result in good performance. Under optimal conditions, this biosensor is capable of detecting as low as 1 ng/mL AFP standard analyte in 10 min with only 50 μL sample volume. Furthermore, 1000 clinical human serum samples were tested by both the QD-based ICTS and a commercial electrochemiluminescence immunoassay AFP kit simultaneously to estimate the sensitivity, specificity and concordance of the assays. Results showed high consistency except for 24 false positive cases (false positive rate 3.92%) and 17 false negative cases (false negative rate 4.38%); the error rate was 4.10% in all. This demonstrates that the QD-based ICTS is capable of rapid, sensitive, and quantitative detection of AFP and shows a great promise for point-of-care testing of other tumor markers.

Size-Tuning Ionization To Optimize Gold Nanoparticles for Simultaneous Enhanced CT Imaging and Radiotherapy

Computed tomography (CT) contrast and radiosensitization usually increase with particle sizes of gold nanoparticles (AuNPs), but there is a huge challenge to improve both by adjusting sizes under the requirements of in vivo application. Here, we report that AuNPs have great size-dependent enhancements on CT imaging as well as radiotherapy (RT) in the size range of 3-50 nm. It is demonstrated that AuNPs with a size of ∼13 nm could simultaneously possess superior CT contrast ability and significant radioactive disruption. The Monte Carlo method is further used to evaluate this phenomenon and indicates that the inhomogeneity of gold atom distributions caused by sizes may influence secondary ionization in whole X-ray interactions. In vivo studies further indicate that this optimally sized AuNP improves real-time CT imaging and radiotherapeutic inhibition of tumors in living mice by effective accumulation at tumors with prolonged in vivo circulation times compared to clinically used small-molecule agents. These results suggest that ∼13 nm AuNPs may serve as multifunctional adjuvants for clinical X-ray theranostic application.

Rapid and Quantitative Detection of Prostate Specific Antigen with a Quantum Dot Nanobeads-Based Immunochromatography Test Strip

Convenient and fast testing using an immunochromatography test strip (ICTS) enables rapid yes/no decisions regarding a disease to be made. However, the fundamental limitations of an ICTS, such as a lack of quantitative and sensitive analysis, severely hampers its application in reliable medical testing for the early detection of cancer. Herein, we overcame these limitations by integrating an ICTS with quantum dot nanobeads (QD nanobeads), which were fabricated by encapsulating QDs within modified poly(tert-butyl acrylate-co-ethyl acrylate-co-methacrylic acid) and served as a robust signal-generating reagent for the ICTS. Prostate specific antigen (PSA) was used as a model analyte to demonstrate the performance of the QD nanobeads-based ICTS platform. Under optimized conditions, the concentration of PSA could be determined within 15 min with high sensitivity and specificity using only 40 μL of sample. The detection limit was enhanced by ∼12-fold compared with that of an ICTS that used QDs encapsulated by commercial 11-mercaptoundecanoic acid (QDs@MUA) as the signal-generating reagent. At the same time, the possible clinical utility of this approach was demonstrated by measurements recorded from PSA-positive patient specimens. Our data suggest that the QD nanobeads-based ICTS platform is not only rapid and low-cost but also highly sensitive and specific for use in quantitative point-of-care diagnostics; thus, it holds promise for becoming a part of routine medical testing for the early cancer of detection.

Construction of a novel cationic polymeric liposomes formed from PEGylated octadecyl-quaternized lysine modified chitosan/cholesterol for enhancing storage stability and cellular uptake efficiency

The design and construction of delivery vectors with high stability and effective cellular uptake efficiency is very important. In this study, a novel polymeric liposomes (PLs) formed from PEGylated octadecyl‐quaternized lysine modified chitosan (OQLCS) and cholesterol with higher size stability and cellular uptake efficiency has been synthesized successfully. Compared to conventional liposomes (CLs; phosphatidyl choline/cholesterol), the calcein‐loaded PLs exhibited a multi‐lamellar structure with homogenous size diameter (200 nm) and high calcein encapsulation efficiency (about 92%). PLs could be stored at different temperature (25, 4, and −20°C) and different medium (deionized water, phosphate‐buffered saline, and human plasma solution) for up to 4 weeks without significant size change. The spectrophotometer fluorometry analysis and the flow cytometry analysis indicated that in comparison with CL, PLs with positive zeta potential facilitates the uptake of calcein by MCF‐7 tumor cells. The data suggests that PLs may provide a new method to overcome the stability and enhance the uptake efficiency of CLs. Biotechnol. Bioeng. 2010;106: 952–962.

Structural design and preparation of high-performance QD-encoded polymer beads for suspension arrays

Fluorescence-encoded polymer bead-based suspension arrays are widely used in biomolecular screening and diagnostic applications. The interior structure of polymer beads, especially the pore size, plays an important role in the preparation of fluorescent beads with a large encoding capacity and stability. Here, highly cross-linked carboxylated poly(styrene-co-ethylene glycol dimethacrylate-co-methacrylic acid) beads (PSEMBs) with optimum pore sizes were designed, fabricated, and further employed in the preparation of high-performance QD-encoded microbeads via a gradual solvent evaporation method. The PSEMBs and QD-encoded PSEMBs were characterized by scanning electron microscopy (SEM), laser scanning confocal microscopy, and spectrofluorometry. The SEM images and flow cytometry results of PSEMBs demonstrate the good sphericity and uniform particle size distribution. Confocal microscope images illustrate that highly uniform, bright fluorescent beads are obtained and the quantum dots (QDs) have filtrated into the entire microspheres, with the required pore size achieved by adjusting the content of porogen. Furthermore, QD-encoded PSEMBs were found to be photostable without leakage of QDs, and to retain their bright fluorescence for at least 20 days. Immunoassay performances for human IgG detections indicate that carboxyl groups on the fluorescent microsphere surface facilitate efficient attachment of biomacromolecules, and therefore enable high detection sensitivity (0.01 ng mL−1) in sandwich immunoreactions. These results indicate that designed optical encoding microcarriers can be successfully applied to high-throughput and multiplexed biomolecular assays. Moreover, the new porous PSEMBs designed and fabricated in this report can efficiently load other nanoparticles (e.g. magnetic nanoparticles, Au and Ag nanoparticles) for a wide range of applications.

MC540 and upconverting nanocrystal coloaded polymeric liposome for near-infrared light-triggered photodynamic therapy and cell fluorescent imaging.

In clinic, the application of photodynamic therapy (PDT) in deep tissue is severely constrained by the limited penetration depth of visible light needed for activating the photosensitizer (PS). In this Article, a merocyanine 540 (MC540) and upconverting nanoparticle (UCN) coloaded functional polymeric liposome nanocarrier, (MC540 + UCN)/FPL, was designed and constructed successfully for solving this problem in PDT. Compared with the conventional approaches using UCNs absorbing PSs directly, the combination of UCN and polymeric liposome has unique advantages. The UCN core as a transducer can convert deep-penetrating near-infrared light to visible light for activating MC540. The functional polymeric liposome shell decorated with folate as a nanoshield can keep the UCN and MC540 stable, protect them from being attacked, and help them get into cells. The results show that (MC540 + UCN)/FPL is an individual nanosphere with an average size of 26 nm. MC540 can be activated to produce singlet oxygen successfully by upconverting fluorescence emitted from UCNs. After (MC540 + UCN)/FPL was modified with folate, the cell uptake efficiency increased obviously. More interestingly, in the PDT effect test, the (MC540 + UCN)/FPL nanocarrier further improved the inhibition effect on tumor cells by anchoring targeting folate and transactivating transduction peptide. Our data suggest that the (MC540 + UCN)/FPL nanocarrier may be a useful nanoplatform for future PDT treatment in deep-cancer therapy based on upconversion mechanism.

Quantum dots/particle-based immunofluorescence assay: synthesis, characterization and application.

Recently, it has been proved that quantum dots (QDs) hold the potential to be used in the bioanalysis as fluorescent probes for their many unique optical properties. In this paper, immunofluorescence assay, an integration of particle-based immunoassays and fluorescent QD-probes, was constructed. Firstly, high quality CdSe/ZnS QDs were prepared. Then after being water-solubilized by amphiphilic polymer based on self-assembling, the QDs were labeled by immunoglobulin G (IgG) antibody. At the same time, both carboxyl-polystyrene (PS) and magnetic carboxyl-PS microspheres were prepared and coated by antigens. The antigen sensitized PS microspheres were specifically captured by the QD-IgG bioconjugates based on the antibody-antigen reaction, which was confirmed by the immunofluorescence test in vitro. The sensitivity of current assay was tested by sandwich immunofluorescence assay using human alpha fetoprotein (AFP) as antigen model. The detection limit of AFP antigen is 4.9 ng/mL.

A novel method to enhance quantum yield of silica-coated quantum dots for biodetection

In this paper, based on selecting the appropriate type of quantum dots (QDs), a novel method is developed to enhance the quantum yield (QY) of silica-coated QD nanoparticles (SQDNPs). The effect of varying types of QDs on the QY after silica encapsulation is systematically studied. The results show that QDs with appropriate structure and composition of shells can much better retain the initial QY after silanization. The seven-layered shell/core QDs with QY of 47.8% nearly completely retain the original QY and is the best type among six types of QDs for silica modification. In the aspect of shell composition, the CdS plays an important role for QY retention since the lattice mismatch between CdSe and CdS is lower than that of CdSe and ZnS. After the appropriate type of QDs is chosen for silica coating, the highly fluorescent SQDNPs are chemically modified with amine, thiol and carboxyl groups, and then labeled by antibodies for particle-based immunofluorescence assay. The results indicate that the SQDNPs-antibody bioconjugates are alternative fluorescent probes useful for biodetection.

Facile fabrication of multi-colors high fluorescent/superparamagnetic nanoparticles

We developed a novel method to prepare multi-colors high fluorescent/superparamagnetic nanoparticles (FMNPs) employing hydrophobic multi-color quantum dots (QDs) and hydrophobic Fe(3)O(4) (MNPs) via ultrasonic emulsification method. This structural procedure was simple, one-off, and timesaving. Different-sizes FMNPs with encoding single/multi-color QDs and MNPs were achieved. Analysis with transmission electron microscopy (TEM) and particle size analyzer demonstrated that the as-prepared samples were spherical, uniform in size distribution; Ultraviolet-visible (UV-vis) absorption spectroscopy and photoluminescence (PL) measurement showed the FMNPs had good optical properties, lacking of fluorescence resonance energy transfer (FRET) inside FMNPs; vibrating sample magnetometer (VSM) indicated that FMNPs were superparamagnetic. These results indicate that the as-prepared FMNPs have potential of serving as a hybrid of QDs and MNPs in bioanalysis communities.

Facile Synthesis of Gd-Cu-In-S/ZnS Bimodal Quantum Dots with Optimized Properties for Tumor Targeted Fluorescence/MR In Vivo Imaging.

Dual-modal imaging techniques have gained intense attention for their potential role in the dawning era of tumor early accurate diagnosis. Chelate-free robust dual-modal imaging nanoprobes with high efficiency and low toxicity are of essential importance for tumor targeted dual-modal in vivo imaging. It is still a crucial issue to endow Cd-free dual-modal nanoprobes with bright fluorescence as well as high relaxivity. Herein, a facile synthetic strategy was developed to prepare Gd-doped CuInS/ZnS bimodal quantum dots (GCIS/ZnS, BQDs) with optimized properties. The fluorescent properties of the GCIS/ZnS BQDs can be thoroughly optimized by varying reaction temperature, aging time, and ZnS coating. The amount of Gd precursor can be well-controlled to realize the optimized balance between the MR relaxivity and optical properties. The obtained hydrophobic GCIS/ZnS BQDs were surface engineered into aqueous phase with PEGylated dextran-stearyl acid polymeric lipid vesicles (PEG-DS PLVs). Upon the phase transfer, the hydrophilic GCIS/ZnS@PLVs exhibited pronounced near-infrared fluorescence as well as high longitudinal relaxivity (r1 = 9.45 mM(-1) S(-1)) in water with good colloidal stability. In vivo tumor-bearing animal experiments further verified GCIS/ZnS@PLVs could achieve tumor-targeted MR/fluorescence dual-modal imaging. No toxicity was observed in the in vivo and ex vivo experiments. The GCIS/ZnS@PLVs present great potential as bimodal imaging contrast agents for tumor diagnosis.