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A novel strategy for the fabrication of a colorimetric aptasensor using label free gold nanoparticles (AuNPs) is proposed in this work, and the strategy has been employed for the assay of adenosine deaminase (ADA) activity. The aptasensor consists of adenosine (AD) aptamer, AD and AuNPs. The design of the biosensor takes advantage of the special optical properties of AuNPs and the interaction between AuNPs and single-strand DNA. In the absence of ADA, the AuNPs are aggregated and are blue in color under appropriate salt concentration because of the grid structure of an AD aptamer when binding to AD, while in the presence of the analyte, AuNPs remain dispersed with red color under the same concentration of salt owing to ADA converting AD into inosine which has no affinity with the AD aptamer, thus allowing quantitative investigation of ADA activity. The present strategy is simple, cost-effective, selective and sensitive for ADA with a detection limit of 1.526 U L(-1), which is about one order of magnitude lower than that previously reported. In addition, a very low concentration of the inhibitor erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA) could generate a distinguishable response. Therefore, the AuNP-based colorimetric biosensor has great potential in the diagnosis of ADA-relevant diseases and drug screening.

We report the development of Hadamard transform fluorescence spectral imaging microscopy by using a movable one-dimensional Hadamard mask to encode the image signals and a linear charge-coupled device (CCD) to detect the encoded spectral image signal. The technique has the ability of multi-spectral imaging and images with four dimensions: location coordinate (X and Y), fluorescence intensity (Z) and wavelength (lambda) (or time (t)) can be obtained. The results show that the system has high spectral resolving power (0.3 nm) and imaging capability, where image resolution up to 511 x 512 can be easily obtained for analysis of tiny samples. Multicolor imaging of acridine orange/ethidium bromide double-stained fibroblast treated with glyoxal shows that 1.5 mM glyoxal obviously causes apoptosis, thus demonstrating that identification of apoptotic cells can be realized using the Hadamard system not only through morphologic changes but also by the spectral evidences of the fluorescently stained cells. In addition, based on immunostaining with quantum dots (QDs) emitting at 550 and 610 nm to tag and trace two breast cancer biomarkers human epidermal growth factor receptor 2 (HER-2) and estrogen receptor (ER) in human breast cancer tissue with in situ dual-color fluorescence imaging, sensitive spectra and images were obtained and show that the system can be applied to visualize and quantitatively measure the subcellular proteins inside the tumor tissues, especially when a single laser line is used as the illuminating source for multi-components with different emission peaks. The preliminary biomedical applications indicate the great potential of the Hadamard imaging system as a useful tool in biomedicine.

We report an indirect method for cancer cell recognition using photostable fluorescent silica nanoprobes as biological labels. The dye-doped fluorescent silica nanoparticles were synthesized using the water-in-oil (W/O) reverse microemulsion method. The silica matrix was produced by the controlled hydrolysis of tetraethylorthosilicate (TEOS) in water nanodroplets with the initiation of ammonia (NH3·H2O). Fluorescein isothiocyanate (FITC) or rhodamine B isothiocyanate conjugated with dextran (RBITC-Dextran) was doped in silica nanoparticles (NPs) with a size of 60 ± 5 nm as a fluorescent signal element by covalent bonding and steric hindrance, respectively. The secondary antibody, goat anti-rabbit IgG, was conjugated on the surface of the PEG-terminated modified FITC-doped or RBITC-Dextran-doped silica nanoparticles (PFSiNPs or PBSiNPs) by covalent binding to the PEG linkers using the cyanogen bromide method. The concentrations of goat anti-rabbit IgG covering the nanoprobes were quantified via the Bradford method. In the proof-of-concept experiment, an epithelial cell adhesion molecule (EpCAM) on the human breast cancer SK-Br-3 cell surface was used as the tumor marker, and the nanoparticle functionalized with rabbit anti-EpCAM antibody was employed as the nanoprobe for cancer cell recognition. Compared with fluorescent dye labeled IgG (FITC-IgG and RBITC-IgG), the designed nanoprobes display dramatically increased stability of fluorescence as well as photostability under continuous irradiation.

We present a low background, highly selective and amplified fluorescent sensor for potassium ions using graphene oxide (GO) and a cationic conjugated polymer (CCP). This method takes advantage of the phenomenon that the addition of CCP cannot release the dye labeled guanine-rich DNA from the GO surface, and the conformational switch of the guanine-rich DNA from random coil to G-quadruplex induced by the target.