Preparation and characterization of selenium‐decorated graphene quantum dots with high afterglow for application in photodynamic therapy

Graphene quantum dots (GQDs) was synthesized using a simple, rapid and affordable method and decorated with selenium at different molar ratios for the first time to obtain an efficient sample for use in photodynamic therapy. Surface modification of GQDs was carried out using polyethylene glycol (PEG) for conjugation with protoporphyrin IX (PpIX). Synthesized GQDs (Se: 0.3%) at 180°C had an emission spectrum that fairly coincided with the absorption profile of PpIX. A relative decrease of about 62.48% in the emission intensity of anthracene was recorded under illumination with UVC light in the presence of GQDs (Se: 0.3%) and the reduction for clung GQDs (Se: 0.3%) and PpIX during 90 min was about 70.68%. Singlet oxygen (¹O₂) generation was examined using a chemical method that showed significant enhancement in decomposition rate constant in clung GQDs–PEG–PpIX compared with GQDs and PpIX alone. Afterglow over 600 s showed that GQDs (Se: 0.3%) could be effective for near skin and even deep tumours.     

Photobleaching and phototoxicity of KillerRed in tumor spheroids induced by continuous wave and pulsed laser illumination

The purpose of this study was to evaluate photobleaching of the genetically encoded photosensitizer KillerRed in tumor spheroids upon pulsed and continuous wave (CW) laser irradiation and to analyze the mechanisms of cancer cell death after the treatment. We observed the light‐dose dependent mechanism of KillerRed photobleaching over a wide range of fluence rates. Loss of fluorescence was limited to 80% at light doses of 150 J/cm² and more. Based on the bleaching curves, six PDT regimes were applied for irradiation using CW and pulsed regimes at a power density of 160 mW/cm² and light doses of 140 J/cm², 170 J/cm² and 200 J/cm². Irradiation of KillerRed‐expressing spheroids in the pulsed mode (pulse duration 15 ns, pulse repetition rate 10 Hz) induced predominantly apoptotic cell death, while in the case of CW mode the cancer cells underwent necrosis. In general, these results improve our understanding of photobleaching mechanisms in GFP‐like proteins and show the importance of appropriate selection of treatment mode for PDT with KillerRed.

Representative fluorescence image of two KillerRed‐expressing spheroids before and immediately after CW irradiation.     

Using quantum dots to visualize clathrin associations

Our current understanding of clathrin-mediated endocytosis proposes that the process is initiated at a specialized anatomical structure called a coated pit. Electron microscopy has been required for elucidation of the morphology of coated pits and the vesicles produced therein, and the presence of a bristle coat has been taken as suggestive of clathrin surrounding these vesicles. More recently, immunocytochemical methods have confirmed that endocytic vesicles are surrounded by clathrin and its adaptor proteins, but there is a need to identify precisely and to follow the fate of the cellular organelles seen by fluorescence microscopy. We used quantum immune-electron microscopy to localize clathrin in a human adrenal cortical cell line (SW-13). Clathrin was shown to associate with a variety of vesicle types including the classic clathrin-coated vesicles and pits used in receptor internalization, pentilaminar annular gap junction vesicles, and multivesicular bodies. The images obtained with quantum dot technology allow accurate and specific localization of clathrin and the clathrin adaptor protein, AP-2, with cellular organelles and suggest that some of the structures classified as typical coated vesicles by immunocytochemical light microscopic techniques actually may be membrane bound pits.     

荧光量子点探针及其标记技术

量子点作为一种新型荧光标记物,与有机染料和荧光蛋白质相比,它们具有可调谐且宽的吸收光谱,激发可产生多重荧光颜色、强荧光信号、抗光漂白能力强等独特的光学特性,使其广泛应用在生物和医学领域。该文就量子点探针的表面修饰和功能化及其标记技术的研究进展进行了阐述。     

Luminescent gelatin nanospheres by encapsulating CdSe quantum dots

Quantum dots (QDs) have been encapsulated within gelatin nanoparticles (GNPs), which gives GNPs fluorescent properties and improves the biocompatibility of QDs. Hydrophilic CdSe QDs were produced through thermodecomposition following the ligand‐exchange method, and were then encapsulated in GNPs. The results of high‐resolution transmission electron microscopy and transmission electron microscopy show that CdSe QDs and QDs‐encapsulated GNPs (QDs‐GNPs) have average diameters of 5 ± 1 and 150 ± 10 nm, respectively. Results of both high‐resolution transmission electron microscopy and confocal laser scanning microscopy indicate that CdSe QDs are successfully encapsulated within GNPs. The QDs‐GNPs have distinctive fluorescent properties with maximum emission at 654 nm, with a 24 nm red‐shift comapred with hydrophilic mercaptoundecanoic acid (MUA)‐modified QDs. In addition, an in vitro cytotoxicity test shows that QDs‐GNPs do not have any toxic effect on cells. It is expected that QDs‐GNPs might be an excellent candidate as a contrast agent in bio‐imaging. Copyright © 2013 John Wiley & Sons, Ltd.     

Electrochemiluminescence of CdSe quantum dots for immunosensing of human prealbumin

We describe a non-labeled electrochemiluminescence (ECL) immunosensor based on CdSe quantum dots (QDs) for the detection of human prealbumin (PAB, antigen). The immunosensor was fabricated by layer by layer coupled with nanoparticle-amplification techniques. After two gold nanoparticle layers were self-assembled onto the gold electrode surface through cysteamine, anti-PAB (antibody) were conjugated with -COOH groups of both the CdSe QDs and cysteine, which were linked to the gold nanoparticle-modified electrode. The principle of ECL detection was that the immunocomplex inhibited the ECL reaction between CdSe QDs and K(2)S(2)O(8), which resulted in the decrease of ECL intensity. On the one hand, the immunocomplex increased the steric hindrance. On the other hand, the immunocomplex maybe inhibit the transfer of K(2)S(2)O(8) to the surface of the CdSe QD-electrode. The PAB concentration was determined in the range of 5.0 x 10(-10) to 1.0 x 10(-6) g mL(-1), and the detection limit was 1.0 x 10(-11) g mL(-1). The developed CdSe QD-based ECL immunosensor provides a rapid, simple, and sensitive immunoassay protocol for protein detection, which could be applied in more bioanalytical systems.     

荧光量子点的生物合成方法研究进展

作为一种新型纳米材料,荧光量子点的合成方法大致可分为物理法、化学法和生物合成法。生物合成方法因其绿色、环保、产物生物相容性好而备受关注。本文通过对国内外荧光量子点生物合成方法的资料研究,以细菌、真菌、其它生物机体、生物辅助等角度对生物合成荧光量子点的方法进行归纳总结,并着重对基于微生物的合成方法进行了分类。在探讨微生物合成机理的基础上,对生物合成法的未来方向提出展望。     

Tunable excitation properties of ZnCdS:Mn/ZnS quantum dots for cancer imaging

Water‐soluble ZnS:Mn quantum dots (QDs) were synthesized using a hydrothermal method with 3‐mercaptopropionic acid as stabilizer. The optical properties of ZnS:Mn QDs were thoroughly investigated by tuning the doping concentration of Mn²⁺ and the Zn/S precursor ratio, to obtain an optimal parameter for QDs with excellent fluorescence characteristics. ZnS:Mn QDs excited at only one wavelength, however, which seriously limited their further application. Here, a trace Cd ion was doped into a ZnS host, resulting in QD excitation covering a wide adjustable waveband. Furthermore, when a ZnS shell was coated onto the surface of the ZnCdS:Mn QDs, photoluminescence intensity and stability were further enhanced. After coupling with an anti‐CK 19 antibody, the ZnCdS:Mn/ZnS core/shell QDs were able to function by labeling cancer cells, indicating that they could be considered as a suitable bio‐probe for cells and tissue imaging.     

功能化量子点在肿瘤诊治中的应用

量子点是一种半导体纳米晶体,它可发出激发荧光,具有亮度高、稳定时间长和发射光谱可调节等特性,是同时检测多信号的良好材料.这些独特性质使得它们在肿瘤诊治领域中的应用日益受到人们的重视.对量子点进行功能化修饰,如偶联抗体等活性物质后,可以对肿瘤细胞进行特异性识别及示踪,以实现对肿瘤的诊断和治疗.文中分别从分子靶向识别、淋巴结定位和药物传递等方面探讨了功能化量子点在肿瘤诊断和治疗中的最新进展.此外,还讨论了量子点的毒性以及用于肿瘤检测和治疗的多功能量子点的设计方法,并提出了其实际应用的潜在方向.     

量子点荧光标记技术的研究热点及面临的挑战

半导体量子点作为新型荧光标记物,在生物医学领域具有重要应用．与传统的有机染料及荧光蛋白等荧光标记物相比,半导体量子点具有发光颜色可调、激发范围宽、发射光谱窄、化学及光稳定性好、表面化学丰富以及生物偶联技术成熟等诸多优势,为生命体系的靶向示踪,高灵敏、原位、实时、动态荧光成像,DNA及蛋白质检测,靶向药物,临床医学,生物芯片和传感器等研究提供了新的发展契机．基于作者在半导体量子点生物荧光成像和安全性评价研究的基础,综述了半导体量子点荧光标记物在生命科学与医学领域应用的研究热点,并对半导体量子点荧光标记技术走向实用面临的挑战进行了评述．     

Novel fluoroimmunoassays for detecting ochratoxin A using CdTe quantum dots

Novel direct and indirect competitive fluorescence‐linked immunosorbent assays (c FLISA and ic FLISA) for detection of ochratoxin A (OTA) were described using CdTe quantum dots (QDs) as fluorescent label. CdTe QDs were successfully synthesized, which had an emission wavelength of 615 nm. The high purity monoclonal antibody against OTA was prepared through cell thawing and the octylic acid‐ammonium sulfate method. The OTA MAbs were successfully coupled with CdTe QDs, and which also retained the original biological activity. The 50% inhibition values (IC₅₀) of the c FLISA and ic FLISA were 0.630 ng/mL, 0.234 ng/mL, the limits of detection (LOD) were 7.06 × 10^–3 and 4.15 × 10^–3 ng/mL, and detection ranges were 7.06 × 10^–3 ? 18.34 ng/mL and 4.15 × 10^–3 ? 4.88 ng/mL, in‐order. The recoveries were 96.0–104.7% along with coefficients of variation (CVs) below 10%. The FLISA provided novel method for determination of OTA and the potential of MAb–CdTe QDs for the establishment of fluorescent immunochromatographic test strip.

     

Synthesis of CdSe quantum dots with luminescence in the violet region of the solar spectrum

We have designed a simple, one‐step synthesis of CdSe quantum dots with photoluminescence frequencies ranging from the red through to the violet region of the solar spectrum. The photoluminescence peaks have FWHM of 30 nm indicating absorption over a narrow range of wavelengths. The effect of solvent type and solvent boiling point on the physical and photoluminescence properties of the quantum dots has been studied. High boiling point, non‐polar solvents shift the photoluminescence peak to longer wavelengths and low boiling point, polar solvents shift the photoluminescence peak to shorter wavelengths. Copyright © 2009 John Wiley & Sons, Ltd.     

Effects of BAPTA-AM, Forskolin, DSF and Z.VAD.fmk on PDT-induced apoptosis and m-THPC phototoxicity on B16 cells

As many types of cells exposed to photodynamic therapy (PDT) appear to undergo apoptosis, various apoptosis inhibitors have already been used in studies of PDT-induced apoptosis. Although these inhibitors decrease apoptosis, their real effect on the phototoxic efficacy of photosensitisers is unclear. The good phototoxicity of m-THPC was confirmed on murine melanoma B16-A45 cells. Toxicity and phototoxicity studies were then carried out using four apoptosis inhibitors: BAPTA-AM, Forskolin, DSF, and Z.VAD.fmk. Although all inhibitors tested blocked PDT-induced apoptosis, none produced a significant modification of the phototoxic effect of m-THPC on B16 cells. It has been suggested that apoptosis and necrosis share common initiation pathways and that the final outcome is determined by the presence of an active caspase. This implies that apoptosis inhibition reorients cells to necrosis, i.e. those cells sufficiently damaged by PDT appear to be killed, regardless of the mechanism involved.     

碳量子点抗菌活性的研究进展

碳量子点（Carbon quantum dots,CQDs）是一种新型碳纳米材料,具有独特的性质,逐渐得到广泛关注。由于CQDs主要是通过“自下而上”的方法制备,其表面具有更加丰富多样的基团,因此更容易衍生化和功能化,进而更容易得到具有特殊性质和功能的CQDs。同时,CQDs在水溶性、可修饰性、耐光漂白等方面具有明显的优势,并且还兼具低生物毒性和良好的生物相容性,使其在生物成像、生物传感和生物分子/药物传递等方面具有潜在的应用价值。随着CQDs研究的增多,各种不同功能化的CQDs得到发展,并被越来越多地用于抗菌方面。根据CQDs目前在医学领域的发展,本文对CQDs在抗菌方面的最新研究进展作一综述。     

Graphene quantum dot based charge‐reversal nanomaterial for nucleus‐targeted drug delivery and efficiency controllable photodynamic therapy

Graphene quantum dots (GQDs), the new zero‐dimensional carbon nanomaterial, have been demonstrated as a promising material for biomedical applications due to its good biocompatibility and low toxicity. However, the integration of multiple therapeutic approaches into a nanosized platform based on the GQD has not been explored yet to our best knowledge. In this report, we regulate the generation of reactive oxygen species (ROS) when using the GQD as a photosensitizer by varying the doping amount of nitrogen atoms to achieve efficiency controllable photodynamic therapy. On the other hand, charge‐reversal (3‐Aminopropyl) triethoxysilane (APTES) was used to conjugate on the surface of GQD for nucleus targeting drug delivery for the first time. The treatment outcome of produced ROS and nucleus‐targeting drug delivery was investigated by fluorescence imaging. The results demonstrated that the N‐GQD‐DOX‐APTES in dual roles as a drug carrier and photosensitizer could achieve nucleus‐targeting delivery and strong ROS production simultaneously. This approach provides a promising strategy for the development of multifunctional therapy in one nano platform for biomedical applications.      

Preparation of carbon quantum dots based high photostability luminescent membranes

Urethane acrylate (UA) was used to prepare carbon quantum dots (C‐dots) luminescent membranes and the resultants were examined with FT‐IR, mechanical strength, scanning electron microscope (SEM) and quantum yields (QYs). FT‐IR results showed the polyurethane acrylate (PUA) prepolymer –C = C‐vibration at 1101 cm^?1 disappeared but there was strong vibration at1687cm^?1which was contributed from the–C = O groups in cross‐linking PUA. Mechanical strength results showed that the different quantity of C‐dots loadings and UV‐curing time affect the strength. SEM observations on the cross‐sections of the membranes are uniform and have no structural defects, which prove that the C‐dots are compatible with the water‐soluble PUA resin. The C‐dot loading was increased from 0 to 1 g, the maximum tensile stress was nearly 2.67 MPa, but the tensile strain was decreased from 23.4% to 15.1% and 7.2% respectively. QYs results showed that the C‐dots in the membrane were stable after 120 h continuous irradiation. Therefore, the C‐dots photoluminescent film is the promising material for the flexible devices in the future applications.     

Study of photoluminescence characteristics of CdSe quantum dots hybridized with Cu nanowires

The photoluminescence (PL) characteristics of semiconductor CdSe quantum dots (QDs) aggregated on Cu nanowires (NWs) were studied in detail. The PL relaxation dynamic data show that Cu NWs improve the PL intensity of CdSe QDs by accelerating the emission relaxation rate. The temperature‐dependent PL data and excitation intensity‐dependent PL data suggest that the activation energy of CdSe QDs might decrease due to the excellent heat transfer properties and the plasmon effect of Cu NWs. Copyright © 2016 John Wiley & Sons, Ltd.     

Direct and indirect immunolabelling of HeLa cells with quantum dots

With excellent optical properties, quantum dots (QDs) have been made as attractive molecular probes for labelling cells in biological research. In this study high‐quality CdSe QDs prepared in a paraffin–oleic acid system were used as fluorescent labels in direct and indirect detection of carcinoembryonic antigen (CEA), a cancer marker expressed on the surface of HeLa cells. The primary antibody (Ab) (rabbit anti‐CEA8) and secondary Ab (goat anti‐rabbit IgG) were covalently linked to carboxyl‐functioned CdSe QDs, and both the QDs–antibody and QDs–IgG probes were successfully used to label HeLa cells. The present study demonstrates the practicability of CdSe QDs as an attractive type of fluorescent labels for biological applications such as protein probes and cell imaging. Copyright © 2008 John Wiley & Sons, Ltd.     

Size‐dependent temperature sensitivity of photoluminescence peak position of CdTe quantum dots

The size dependence of the temperature coefficient (sensitivity) of the photoluminescence (PL) peak position of CdTe quantum dots stabilized by thioglycolic acid in aqueous solution has been investigated. Temperature sensitivity increases as the average radius of CdTe quantum dots decraeases. This must be taken into account in the design of solar light concentrators and light‐emmiting diode‐monitors as well as other technologies in which a fine tuning of the light emission is important. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis of carbon‐based quantum dots from starch extracts: Optical investigations

Carbon‐based quantum dots (C‐QDs) were synthesized through microwave‐assisted carbonization of an aqueous starch suspension mediated by sulphuric and phosphoric acids. The as‐prepared C‐QDs showed blue, green and yellow luminescence without the addition of any surface‐passivating agent. The C‐QDs were further analyzed by UV?vis spectroscopy to measure the optical response of the organic compound. The energy gaps revealed narrow sizing of C‐QDs in the semiconductor range. The optical refractive index and dielectric constant were investigated. The C‐QDs size distribution was characterized. The results suggested an easy route to the large scale production of C‐QDs materials.