Dual Recognition Strategy for Specific and Sensitive Detection of Bacteria Using Aptamer-Coated Magnetic Beads and Antibiotic-Capped Gold Nanoclusters.

Food poisoning and infectious diseases caused by pathogenic bacteria such as Staphylococcus aureus (SA) are serious public health concerns. A method of specific, sensitive, and rapid detection of such bacteria is essential and important. This study presents a strategy that combines aptamer and antibiotic-based dual recognition units with magnetic enrichment and fluorescent detection to achieve specific and sensitive quantification of SA in authentic specimens and in the presence of much higher concentrations of other bacteria. Aptamer-coated magnetic beads (Apt-MB) were employed for specific capture of SA. Vancomycin-stabilized fluorescent gold nanoclusters (AuNCs@Van) were prepared by a simple one-step process and used for sensitive quantification of SA in the range of 32-10(8) cfu/mL with the detection limit of 16 cfu/mL via a fluorescence intensity measurement. And using this strategy, about 70 cfu/mL of SA in complex samples (containing 3 × 10(8) cfu/mL of other different contaminated bacteria) could be successfully detected. In comparison to prior studies, the developed strategy here not only simplifies the preparation procedure of the fluorescent probes (AuNCs@Van) to a great extent but also could sensitively quantify SA in the presence of much higher concentrations of other bacteria directly with good accuracy. Moreover, the aptamer and antibiotic used in this strategy are much less expensive and widely available compared to common-used antibodies, making it cost-effective. This general aptamer- and antibiotic-based dual recognition strategy, combined with magnetic enrichment and fluorescent detection of trace bacteria, shows great potential application in monitoring bacterial food contamination and infectious diseases.

Magnetically encoded luminescent composite nanoparticles through layer-by-layer self-assembly.

Sensitive and rapid detection of multiple analytes and the collection of components from complex samples are important in fields ranging from bioassays/chemical assays, clinical diagnosis, to environmental monitoring. A convenient strategy for creating magnetically encoded luminescent CdTe@SiO2 @n Fe3 O4 composite nanoparticles, by using a layer-by-layer self-assembly approach based on electrostatic interactions, is described. Silica-coated CdTe quantum dots (CdTe@SiO2 ) serve as core templates for the deposition of alternating layers of Fe3 O4 magnetic nanoparticles and poly(dimethyldiallyl ammonium chloride), to construct CdTe@SiO2 @n Fe3 O4 (n=1, 2, 3, …︁) composite nanoparticles with a defined number (n) of Fe3 O4 layers. Composite nanoparticles were characterized by zeta-potential analysis, fluorescence spectroscopy, vibrating sample magnetometry, and transmission electron microscopy, which showed that the CdTe@SiO2 @n Fe3 O4 composite nanoparticles exhibited excellent luminescence properties coupled with well-defined magnetic responses. To demonstrate the utility of these magnetically encoded nanoparticles for near-simultaneous detection and separation of multiple components from complex samples, three different fluorescently labeled IgG proteins, as model targets, were identified and collected from a mixture by using the CdTe@SiO2 @n Fe3 O4 nanoparticles.

Magnetic-encoded fluorescent multifunctional nanospheres for simultaneous multicomponent analysis.

In this study, magnetic-encoded fluorescent (CdTe/Fe3O4)@SiO2 multifunctional nanospheres were constructed by adjusting the initial concentration of Fe3O4 in a fabrication process based on reverse microemulsion. The resultant multifunctional nanospheres were characterized by transmission electron microscopy, X-ray diffraction measurements, fluorescence spectrophotometry, and vibrating sample magnetometry. They showed good fluorescence properties, gradient magnetic susceptibility (weak, moderate, and strong), and easy biofunctionalization for biomolecules, such as immunoglobulin G (IgG), protein, and antibody. Then the capture efficiency of the (CdTe/Fe3O4)@SiO2 nanospheres were investigated by using the fluorophore-labeled IgG-conjugated nanospheres as a model. Further studies demonstrated the ability of these (CdTe/Fe3O4)@SiO2 multifunctional nanospheres to accomplish sequentially magnetic separation, capture, and fluorescent detection for each corresponding antigen of CA125, AFP, and CEA with a detection limit of 20 KU/L, 10 ng/mL, and 5 ng/mL, respectively, from a mixed sample under a certain external magnetic field within a few minutes. The strategy of combining magnetic-encoding-based separation and fluorescence-based detection proposed in this study shows great potential to achieve easy, rapid, economical, and near-simultaneous multicomponent separation and analysis for a variety of targets such as drugs, biomarkers, pathogens, and so on.

One-step facile synthesis of hyaluronic acid functionalized fluorescent gold nanoprobes sensitive to hyaluronidase in urine specimen from bladder cancer patients.

Gold nanoparticles (AuNPs) have been widely used to develop fluorescence resonance energy transfer (FRET) sensors to detect biological substances, environmental pollutants, and disease markers due to their superior quenching capacity to fluorescence signals. In this study, we report the one-step facile synthesis of fluorescein isothiocyanate-labeled hyaluronic acid (FITC-HA) functionalized fluorescent AuNPs based FRET nanoprobes (FITC-HA-AuNPs) via chemical reduction of HAuCl4 by using FITC-HA as both a reducing and stabilizing agent. Then the FITC-HA-AuNPs FRET nanoprobes were used to detect hyaluronidase (HAase), a new type of disease marker, based on the specific enzymatic degradation of HAase to HA. Compared with similar work, the FITC-HA-AuNPs nanoprobes were much easier to prepare and the detection sensitivity was also high for HAase to reach a detection limit of 0.63 U mL(-1). More importantly, they also allowed for rapid HAase detection (within 3h) even in complex biological specimens (urine specimens from patients with bladder cancer) with satisfactory accuracy (recovery efficiency in the range of 92.8-106.9% with RSD ≤ 4.85%). Our studies suggested that such a novel design of FITC-HA-AuNPs FRET nanoprobes developed for sensitive, rapid and accurate detection of HAase had exciting potentials for clinical diagnosis of HAase-related diseases, such as bladder cancer.

Hyaluronic acid-decorated graphene oxide nanohybrids as nanocarriers for targeted and pH-responsive anticancer drug delivery.

A novel nanohybrid of hyaluronic acid (HA)-decorated graphene oxide (GO) was fabricated as a targeted and pH-responsive drug delivery system for controlling the release of anticancer drug doxorubicin (DOX) for tumor therapy. For the preparation, DOX was first loaded onto GO nanocarriers via π-π stacking and hydrogen-bonding interactions, and then it was decorated with HA to produce HA-GO-DOX nanohybrids via H-bonding interactions. In this strategy, HA served as both a targeting moiety and a hydrophilic group, making the as-prepared nanohybrids targeting, stable, and disperse. A high loading efficiency (42.9%) of DOX on the nanohybrids was also obtained. Cumulative DOX release from HA-GO-DOX was faster in pH 5.3 phosphate-buffered saline solution than that in pH 7.4, providing the basis for pH-response DOX release in the slightly acidic environment of tumor cells, while the much-slower DOX release from HA-GO-DOX than DOX showed the sustained drug-release capability of the nanohybrids. Fluorescent images of cellular uptake and cell viability analysis studies illustrated that these HA-GO-DOX nanohybrids significantly enhanced DOX accumulation in HA-targeted HepG2 cancer cells compared to HA-nontargeted RBMEC cells and subsequently induced selective cytotoxicity to HepG2 cells. In vivo antitumor efficiency of HA-GO-DOX nanohybrids showed obviously enhanced tumor inhibition rate for H22 hepatic cancer cell-bearing mice compared with free DOX and the GO-DOX formulation. These studies suggest that the HA-GO-DOX nanohybrids have potential clinical applications for anticancer drug delivery.