To develop fluorescent labels for multicolor imaging, rare-earth-ion-doped ZrO 2 nanocrystals were prepared by a complex precursor method. Laser excitation of 976 nm induced single fluorescent bands of green and red upconversion ͑UC͒ in ZrO 2 :Er 3+ and ZrO 2 :Er 3+ +Yb 3+ nanocrystals, respectively. A suppression ratio ͑SR͒ parameter was introduced, defined as the UC intensity ratio of the main band to all the other detected impurity bands, and SR values in the order of 10-100 were experimentally obtained, demonstrating the excellent monochromaticity of the UC labels. Thus, the two-color UC labels obtained are potentially ideal to be used for biological multicolor imaging.

Toluidine blue-mediated photodynamic therapy could effectively treat periodontitis in vivo and has high potential in clinical application.

Room temperature bright white upconversion (UC) luminescence in Yb3+–Tm3+–Er3+ ions doped Y2O3 nanocrystals was obtained under single-wavelength diode laser excitation of 976nm. The white light consists of the blue, green, and red UC radiations which correspond to the transitions G41→H63 of Tm3+, H11∕22∕S3∕24→I15∕24, and F9∕24→I15∕24 of Er3+ ions, respectively. The UC mechanisms were proposed based on spectral, kinetic, and pump power dependence analyses. The calculated color coordinates display that white light can be achieved in a wide range of pumping powers, which promises their potential applications in the field of displays, lasers, photonics, and biomedicine.

Our previous in vitro study has shown that toluidine blue (TB)-mediated lethal photosensitization of periodontal pathogens (PPs) from periodontal patients is possible. The purpose of this study was to investigate whether TB-mediated photosensitization exerted damaging effects on periodontal tissues in mice. Twenty-four mice were randomly divided into four groups; the experimental photodynamic therapy (PDT) group was treated with 1 mg/ml TB and light irradiation (60 J/cm(2), 635 nm, 337 s). Those in control groups were subjected to 140 J/cm(2) laser irradiation alone or to 2.5 mg/ml TB alone or received neither TB nor light exposure. All the mice were killed 72 h after they had been subjected to PDT, and periodontal tissue samples were taken for histological examination. During the 72 h observation period, no mice showed any distress. No necrotic or inflammatory changes were found in the gingiva, dentin, dental pulp or alveolar bone of the mice in any of the groups in this study. The results suggest that TB-mediated PDT is a safe antimicrobial approach for the treatment of periodontopathy without damaging effects to adjacent normal tissues.

No abstract