During the past decades, numerous achievements concerning luminescent zinc oxide nanoparticles (ZnO NPs) have been reported due to their improved luminescence and good biocompatibility. The photoluminescence of ZnO NPs usually contains two parts, the exciton-related ultraviolet (UV) emission and the defect-related visible emission. With respect to the visible emission, many routes have been developed to synthesize and functionalize ZnO NPs for the applications in detecting metal ions and biomolecules, biological fluorescence imaging, nonlinear multiphoton imaging, and fluorescence lifetime imaging. As the biological applications of ZnO NPs develop rapidly, the toxicity of ZnO NPs has attracted more and more attention because ZnO can produce the reactive oxygen species (ROS) and release Zn2+ ions. Just as a coin has two sides, both the drug delivery and the antibacterial effects of ZnO NPs become attractive at the same time. Hence, in this review, we will focus on the progress in the synthetic methods, luminescent properties, and biological applications of ZnO NPs.

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In the past decades, drug delivery systems (DDSs) based on nanotechnology have been studied extensively to overcome the nonselectivity of chemotherapy, to avoid damaging healthy tissues, and to improve cancer cure rates. [1][2][3] A practical DDS should possess the two general characteristics of specific targeting and controllable release. With regard to specific targeting, it is widely accepted that nanocarriers are able to enter cells rapidly through intracellular endocytic pathways [4] and effectively release drugs at target sites. With regard to controllable release, different responding agents or conditions have been employed, such as pH, [5] temperature, [6] enzyme, [7,8] biomolecules [9,10] and light. [11][12][13] Among these, pH-responsive DDSs have shown great advantages as a result of their simple design and universal applicability, because pH values in tumors and inflammatory tissues are significantly lower than those in blood and normal tissues. [14][15][16] The pH-responsive systems usually employ pH-sensitive linkers, [17] pH-responsive polymeric micelles, [18] pH-tunable calcium phosphate, [19] etc. For instance, pH-responsive molecules [20] or ZnO nanoparticles [21] can be used as cappers to cover the pores of mesoporous silica nanoparticles (MSNs). However, the strong adsorption ability of MSNs hinders the complete release of the drug and the biodegradability of MSNs also remains a controversial problem. [22] As we reported previously, these problems cannot be resolved by using nanocarriers based on carbon nanotubes and mesoporous carbon materials. [23,24] As a cheap nanomaterial with low toxicity, ZnO quantum dots (QDs) have shown great potential for application in bioimaging. [25][26][27][28] Because the unprotected ZnO QDs are decomposed completely at pH 5 in aqueous solution, these materials can be employed as nanocarriers for drug delivery. Herein, we synthesized biodegradable ZnO@polymer coreshell QDs with excellent water solubility, biocompatibility, and pH sensitivity as drug carriers in order to study the release process and activity in vitro. Polyacrylamide, which is nontoxic to animals, [29] was used as a protecting shell for the ZnO QDs. The well-known doxorubicin hydrochloride (DOX) was selected as anticancer drug because its clinical application has so far been hampered by nonselective biodistribution and severe damage to healthy tissues. [30] Furthermore, human glioblastoma cells (U251), the most common cells in malignancies of the human brain, [31] were chosen as model cells. DOX is a hydrophilic molecule and its ability to pass through biological barriers such as the bloodbrain barrier is rather weak, hence treatment of brain tumors with DOX remains a challenge. [32] After they were loaded with DOX, our ZnO@polymer QDs crossed the cell membrane through a cellular uptake pathway, decomposed at the endosomes or lysosomes to release DOX molecules, which finally penetrated into the nuclei to kill the cells. This process and the drug release mechanism were proven by direct observation...

Development and comparison of the latent fingerprints (LFPs) are two major studies in detection and identification of LFPs, respectively. However, integrated research studies on both fluorescent materials for LFP development and digital-processing programs for LFP comparison are scarcely seen in the literature. In this work, highly efficient red-emissive carbon dots (R-CDs) are synthesized in one pot and mixed with starch to form R-CDs/starch phosphors. Such phosphors are comparable with various substrates and suitable for the typical powder dusting method to develop LFPs. The fluorescence images of the developed LFPs are handled with an artificial intelligence program. For the optimal sample, this program presents an excellent matching score of 93%, indicating that the developed sample has very high similarity with the standard control. Our results are significantly better than the benchmark obtained by the traditional method, and thus, both the R-CDs/starch phosphors and the digital processing program fit well for the practical applications.

It is possible to accurately image and measure the cross-sectional structures of the bulbar conjunctival tissue with high resolution OCT.

Targeting peptide-modified magnetic graphene-based mesoporous silica (MGMSPI) are synthesized, characterized, and developed as a multifunctional theranostic platform. This system exhibits many merits, such as biocompatibility, high near-infrared photothermal heating, facile magnetic separation, large T2 relaxation rates (r2), and a high doxorubicin (DOX) loading capacity. In vitro and in vivo results demonstrate that DOX-loaded MGMSPI (MGMSPID) can integrate magnetic resonance imaging, dual-targeting recognition (magnetic targeting and receptor-mediated active targeting), and chemo-photothermal therapy into a single system for a visualized-synergistic therapy of glioma. In addition, it is observed that the MGMSPID system has heat-stimulated, pH-responsive, sustained release properties. All of these characteristics would provide a robust multifunctional theranostic platform for visualized glioma therapy.

Rapid and efficient measurement of cancer cells is a major challenge in early cancer diagnosis. In the present study, a miniature multiplex chip was created for in situ detection of cancer cells by implementing a novel graphene oxide (GO)-based Förster resonance energy transfer (FRET) biosensor strategy, i.e. assaying the cell-induced fluorescence recovery from the dye-labeled aptamer/graphene oxide complex. Fluorescence intensity measurement and image analyses demonstrated that this microfluidic biosensing method exhibited rapid, selective and sensitive fluorescence responses to the quantities of the target cancer cells, CCRF-CEM cells. Seven different cancer cell samples can be measured at the same time in such a microfluidic chip. The linear response for target CCRF-CEM cells in a concentration range from 2.5 × 10(1) to 2.5 × 10(4) cells mL(-1) was obtained, with a detection limit about 25 cells mL(-1), which is about ten times lower than those of normal biosensors. The novel fluorescence biosensing microfluidic chip supplies a rapid, visible and high-throughput approach for early cancer diagnosis with high sensitivity and specificity.

The second near-infrared window (NIR-II, wavelength of 1.0-1.4 μm) is optimal for the bioimaging of live animals due to their low albedo and endogenous autofluorescence. Herein, we report a facile and one-pot biomimetic synthesis approach to prepare water-dispersible NIR-II-emitting ultrasmall Ag(2)S quantum dots (QDs). Photoluminescence spectra showed that the emission peaks could be tuned from 1294 to 1050 nm as the size of the Ag(2)S QDs varied from 6.8 to 1.6 nm. The x-ray diffraction patterns and x-ray photoelectron spectra confirmed that the products were monoclinic α-Ag(2)S. Fourier transform infrared spectrograph analysis indicated that the products were protein-conjugated Ag(2)S QDs. Examination of cytotoxicity and the hemolysis test showed that the obtained Ag(2)S QDs had good biocompatibility, indicating that such a nanomaterial could be a new kind of fluorescent label for in vivo imaging.