Effects of carbon dots surface functionalities on cellular behaviors - Mechanistic exploration for opportunities in manipulating uptake and translocation.

Carbon dots (CDots) for their excellent optical and other properties have been widely pursued for potential biomedical applications, in which a more comprehensive understanding on the cellular behaviors and mechanisms of CDots is required. For such a purpose, two kinds of CDots with surface passivation by 3-ethoxypropylamine (EPA-CDots) and oligomeric polyethylenimine (PEI-CDots) were selected for evaluations on their uptakes by human cervical carcinoma HeLa cells at three cell cycle phases (G0/G1, S and G2/M), and on their different internalization pathways and translocations in cells. The results show that HeLa cells could internalize both CDots by different pathways, with an overall slightly higher internalization efficiency for PEI-CDots. The presence of serum in culture media could have major effects, significantly enhancing the cellular uptake of EPA-CDots, yet markedly inhibiting that of PEI-CDots. The HeLa cells at different cell cycle phases have different behaviors in taking up the CDots, which are also affected by the different dot surface moieties and serum in culture media. Mechanistic implications of the results and the opportunities associated with an improved understanding on the cellular behaviors of CDots for potentially the manipulation and control of their cellular uptakes and translocations are discussed.

Carbon "Quantum" Dots for Fluorescence Labeling of Cells.

The specifically synthesized and selected carbon dots of relatively high fluorescence quantum yields were evaluated in their fluorescence labeling of cells. For the cancer cell lines, the cellular uptake of the carbon dots was generally efficient, resulting in the labeling of the cells with bright fluorescence emissions for both one- and two-photon excitations from predominantly the cell membrane and cytoplasm. In the exploration on labeling the live stem cells, the cellular uptake of the carbon dots was relatively less efficient, though fluorescence emissions could still be adequately detected in the labeled cells, with the emissions again predominantly from the cell membrane and cytoplasm. This combined with the observed more efficient internalization of the same carbon dots by the fixed stem cells might suggest some significant selectivity of the stem cells toward surface functionalities of the carbon dots. The needs and possible strategies for more systematic and comparative studies on the fluorescence labeling of different cells, including especially live stem cells, by carbon dots as a new class of brightly fluorescent probes are discussed.

Super-resolution fluorescence imaging of biocompatible carbon dots.

Carbon Dots (CDs) are a new promising type of small (5 nm), biocompatible and multicolor luminescent nanoparticle. Here, we demonstrate super-resolution imaging of CDs at the nanoscale through STimulated Emission Depletion (STED) microscopy. In addition, we report the application of STED for detection of CD localization in both fixed and living cells, achieving a spatial resolution down to 30 nm, far below the diffraction limit, showing great promise for high resolution visualization of cellular dynamics.

Carbon-core silver-shell nanodots as sensitizers for phototherapy and radiotherapy.

Spherical carbon nanoparticles (carbon nanodots) with a silver shell were investigated as potential sensitizing agents. The cytotoxicity of the combination of ultraviolet radiation or x-rays with the nanodots was examined in cancer cells in vitro. The cell viability decreased following the exposure to the radiation. The carbon nanodots enhanced the radiation effects by significantly reducing the amount of surviving cells compared to that of the cells exposed only to the radiation. Carbon-core silver-shell nanodots can be proposed as a bimodal sensitization platform for biological and medicinal applications employing non-ionizing or ionizing radiation.

Effect of injection routes on the biodistribution, clearance, and tumor uptake of carbon dots.

The emergence of photoluminescent carbon-based nanomaterials has shown exciting potential in the development of benign nanoprobes. However, the in vivo kinetic behaviors of these particles that are necessary for clinical translation are poorly understood to date. In this study, fluorescent carbon dots (C-dots) were synthesized and the effect of three injection routes on their fate in vivo was explored by using both near-infrared fluorescence and positron emission tomography imaging techniques. We found that C-dots are efficiently and rapidly excreted from the body after all three injection routes. The clearance rate of C-dots is ranked as intravenous > intramuscular > subcutaneous. The particles had relatively low retention in the reticuloendothelial system and showed high tumor-to-background contrast. Furthermore, different injection routes also resulted in different blood clearance patterns and tumor uptakes of C-dots. These results satisfy the need for clinical translation and should promote efforts to further investigate the possibility of using carbon-based nanoprobes in a clinical setting. More broadly, we provide a testing blueprint for in vivo behavior of nanoplatforms under various injection routes, an important step forward toward safety and efficacy analysis of nanoparticles.

Clinical efficacy and safety of selective trans-cystic intra-operative cholangiography in primary suture following three-port laparoscopic common bile duct exploration.

BACKGROUND: Intra-operative cholangiography has been shown to be a sensitive and specific method of demonstrating bile duct stones. This study investigated the feasibility, safety, and clinical value of selective trans-cystic intra-operative cholangiography in primary suture following three-port laparoscopic common bile duct exploration, and identified the factors that positively predict the presence of common bile duct stones. METHODS: From January 2008 to January 2011, 252 of 1013 patients undergoing laparoscopic cholecystectomy received selective trans-cystic intra-operative cholangiography and primary suture following three-port laparoscopic common bile duct exploration. Their clinical data were analyzed retrospectively. RESULTS: All operations were successful and none was converted to open surgery. The intra-operative cholangiography time was (8.3 ± 2.5) minutes, and the operative duration was (105.4 ± 23.1) minutes. According to selective intra-operative cholangiography, the positive predictive values of current jaundice, small gallstones (< 0.5 cm) and dilated cystic duct (> 0.3 cm), dilated common bile duct (> 0.8 cm), history of jaundice or gallstone pancreatitis, abnormal liver function test, and preoperative demonstration of suspected common bile duct stones on imaging were 87%, 25%, 42%, 15%, 32%, and 75% for common bile duct stones, respectively. Patients with several factors suggestive of common bile duct stones yielded higher numbers of positive cholangiograms. Unexpected stones were found in 13 patients (5.2%) by intra-operative cholangiography. The post-operative hospital stay was (4.7 ± 2.2) days. Post-operative bile leakage occurred in two cases, and these patients recovered by simple drainage for 3 - 7 days without re-operation. Of the 761 patients who underwent laparoscopic cholecystectomy alone, 5 (0.7%) presented with a retained common bile duct stone requiring intervention. The median follow-up was 12 months, and only one patient who once suffered from bile leakage presented with obstructive jaundice due to bile duct stenosis 6 months postoperatively. The other patients recovered without any serious complications. CONCLUSIONS: Selective intra-operative cholangiography yields acceptably high positive results. It is a safe, effective, and minimally invasive approach in patients with suspected choledocholithiasis and primary suture following three-port laparoscopic common bile duct exploration.

Poly(ethylene glycol)-conjugated multi-walled carbon nanotubes as an efficient drug carrier for overcoming multidrug resistance.

The acquisition of multidrug resistance poses a serious problem in chemotherapy, and new types of transporters have been actively sought to overcome it. In the present study, poly(ethylene glycol)-conjugated (PEGylated) multi-walled carbon nanotubes (MWCNTs) were prepared and explored as drug carrier to overcome multidrug resistance. The prepared PEGylated MWCNTs penetrated into mammalian cells without damage plasma membrane, and its accumulation did not affect cell proliferation and cell cycle distribution. More importantly, PEGylated MWCNTs accumulated in the multidrug-resistant cancer cells as efficient as in the sensitive cancer cells. Intracellular translocation of PEGylated MWCNTs was visualized in both multidrug-resistant HepG2-DR cells and sensitive HepG2 cells, as judged by both fluorescent and transmission electron microscopy. PEGylated MWCNTs targeted cancer cells efficiently and multidrug-resistant cells failed to remove the intracellular MWCNTs. However, if used in combination with drugs without conjugation, PEGylated MWCNTs prompted drug efflux in MDR cells by stimulating the ATPase activity of P-glycoprotein. This study suggests that PEGylated MWCNTs can be developed as an efficient drug carrier to conjugate drugs for overcoming multidrug resistance in cancer chemotherapy.

Fullerene-conjugated doxorubicin in cells.

The conjugation of fullerene with well-established drug molecules has been a representative strategy to impart fullerene-specific properties for improved formulation. However, conjugates involving fullerenes or other nanomaterials often differ significantly from the free drug molecules in cellular uptake and distributions. For the highly effective anticancer drug doxorubicin (DOX), its strong absorption and fluorescence in the visible spectral region enable the tracking of DOX-containing conjugates by optical techniques. In this work, a stoimetrically and structurally well-defined fullerene-DOX conjugate was studied in terms of fluorescence microscopy, including the fluorescence imaging with two-photon excitation, to examine the uptake and distribution in human breast cancer cells. The results suggested that the conjugate was distributed mostly in the cytoplasm, significantly different from free DOX molecules (predominantly in the cell nucleus, as already reported in the literature). Mechanistic implications of the results are discussed. Also discussed are potentials of conjugated DOX species as self-labeled fluorescent probes in bioimaging and other mechanistic investigations on drug delivery.

Total synthesis and biological evaluation of cortistatins A and J and analogues thereof.

Total syntheses of the highly selective antiproliferative natural products cortistatins A (1) and J (5) in their naturally occurring enantiomeric forms are described. The modular and convergent strategy employed relies on an intramolecular oxa-Michael addition/aldol/dehydration cascade reaction to cast the ABCD ring framework of the molecule and both Sonogashira and Suzuki-Miyaura coupling reactions to assemble the necessary building blocks into the required heptacyclic skeleton. A divergent approach from a late-stage epoxy ketone leads to both target molecules in a stereoselective manner. The developed synthetic technologies were applied to the construction of several analogues of the cortistatins which were biologically evaluated and compared to the natural products with regards to their antiproliferative activities against a variety of cancer cells. Analogues 8 and 81, lacking both the dimethylamino and hydroxyl groups of cortistatin A, were found to exhibit comparable biological activity as the parent compound, leading to the conclusion that such functionalities are not essential for biological activity.

Aqueous Compatible Fullerene-Doxorubicin Conjugates.

Covalent conjugates of fullerene C(60) and the highly effective anticancer drug doxorubicin (DOX) were prepared and studied. The conjugation was through the amide linkage to preserve the intrinsic properties of DOX and fullerene cage. As designed, the conjugates with hydrophilic ethylene glycol spacers exhibited much improved aqueous compatibility, with significant solubility in water-DMSO mixtures. The anti-neoplastic activities of DOX were apparently unaffected in the conjugates according to evaluations in vitro with a human breast cancer cell line.

Formation and properties of stabilized aluminum nanoparticles.

The wet-chemical synthesis of aluminum nanoparticles was investigated systematically by using dimethylethylamine alane and 1-methylpyrrolidine alane as precursors and molecules with one or a pair of carboxylic acid groups as surface passivation agents. Dimethylethylamine alane was more reactive, capable of yielding well-defined and dispersed aluminum nanoparticles. 1-Methylpyrrolidine alane was less reactive and more complex in the catalytic decomposition reaction, for which various experimental parameters and conditions were used and evaluated. The results suggested that the passivation agent played dual roles of trapping aluminum particles to keep them nanoscale during the alane decomposition and protecting the aluminum nanoparticles postproduction from surface oxidation and that an appropriate balance between the rate of alane decomposition (depending more sensitively on the reaction temperature) and the timing in the introduction of the passivation agent into the reaction mixture was critical to the desired product mixes and/or morphologies. Some fundamental and technical issues on the alane decomposition and the protection of the resulting aluminum nanoparticles are discussed.

Quantum dots and nanoparticles for photodynamic and radiation therapies of cancer.

Semiconductor quantum dots and nanoparticles composed of metals, lipids or polymers have emerged with promising applications for early detection and therapy of cancer. Quantum dots with unique optical properties are commonly composed of cadmium contained semiconductors. Cadmium is potentially hazardous, and toxicity of such quantum dots to living cells, and humans, is not yet systematically investigated. Therefore, search for less toxic materials with similar targeting and optical properties is of further interest. Whereas, the investigation of luminescence nanoparticles as light sources for cancer therapy is very interesting. Despite advances in neurosurgery and radiotherapy the prognosis for patients with malignant gliomas has changed little for the last decades. Cancer treatment requires high accuracy in delivering ionizing radiation to reduce toxicity to surrounding tissues. Recently some research has been focused in developing photosensitizing quantum dots for production of radicals upon absorption of visible light. In spite of the fact that visible light is safe, this approach is suitable to treat only superficial tumours. Ionizing radiation (X-rays and gamma rays) penetrate much deeper thus offering a big advantage in treating patients with tumours in internal organs. Such concept of using quantum dots and nanoparticles to yield electrons and radicals in photodynamic and radiation therapies as well their combination is reviewed in this article.

Chemical synthesis and biological evaluation of palmerolide A analogues.

Molecular design and chemical synthesis of several palmerolide A analogues allowed the first structure activity relationships (SARs) of this newly discovered marine antitumor agent. From several analogues synthesized and tested (ent- 1, 5- 14, 21- 26, 50, 51), compounds 25 (with a phenyl substituent on the side chain) and 51 (lacking the C-7 hydroxyl group) were the most interesting, exhibiting approximately a 10-fold increase in potency and equipotency, respectively, to the natural product. These findings point the way to more focused structure activity relationship studies.

Total synthesis of the originally proposed and revised structures of palmerolide A and isomers thereof.

Palmerolide A is a recently disclosed marine natural product possessing striking biological properties, including potent and selective activity against the melanoma cancer cell line UACC-62. The total syntheses of five palmerolide A stereoisomers, including the originally proposed (1) and the revised [ent-(19-epi-20-epi-1)] structures, have been accomplished. The highly convergent and flexible strategy developed for these syntheses involved the construction of key building blocks 2, 19-epi-2, 20-epi-2, ent-2, 3, ent-3, 4, and ent-4, and their assembly and elaboration to the target compounds. For the union of the building blocks, the Stille coupling reaction, Yamaguchi esterification, Horner-Wadsworth-Emmons olefination, and ring-closing metathesis reaction were employed, the latter being crucial for the stereoselective formation of the macrocycle of the palmerolide structure. The Horner-Wadsworth-Emmons olefination and the Yamaguchi lactonization were also investigated and found successful as a means to construct the palmerolide macrocycle. The syntheses were completed by attachment of the enamide moiety through a copper-catalyzed coupling process.

Nanosized paclitaxel particles from supercritical carbon dioxide processing and their biological evaluation.

The rapid expansion of a supercritical solution into a liquid solvent (RESOLV) technique with benign supercritical carbon dioxide was applied to obtain aqueous suspended nanoparticles of the highly potent anticancer drug paclitaxel. The paclitaxel nanoparticles were protected from agglomeration by using a known nontoxic stabilization agent. The aqueous suspended paclitaxel nanoparticles of different average particle sizes were evaluated in vitro against human breast cancer cells. The results suggest that the nanosized paclitaxel particles are effective, with an antineoplastic activity comparable to that of the commercial paclitaxel formulation. The technique should be generally applicable to the processing of nanoparticles from other important drugs with aqueous solubility problems.

[Etiological study on viral diarrhea among children in Lanzhou, Gansu, from July 2004 through June 2005].

OBJECTIVE: To study molecular epidemiology of four major etiological viruses among children with acute diarrhea in Lanzhou, Gansu province. METHODS: Stool specimens were collected from all 400 inpatients less than 5 years old with acute diarrhea admitted in Department of Pediatrics, the First Hospital, Lanzhou University from Jul. 2004 through Jun. 2005. Dako IDEIA kits were used for detection of rotavirus, adenovirus and astrovirus. Calicivirus detection was done by both reverse transcription-polymerase chain reactions (RT-PCR) and ELISA. Further strain characterization of rotavirus and astrovirus was carried out with RT-PCR. RESULTS: A total of 400 stool samples were collected and tested. Rotavirus was present in 47.3% of the cases: calicivirus in 15.5%, astrovirus in 9.5% and adenoviruses in 7.5%. Mixed infections with multiple enteric viruses were present in 13.5% of all samples. Among 189 rotavirus positive samples, serotype G2 (34.4%) was the predominant strain followed by G3 (32.8%), G1 (1.1%) and mixed-G infection (5.8%). 25.9% of strains remained to be non-typeable. P genotyping showed P [4] (45%) was most common followed by P [8] (22.1%), and non-typeable (32.9%). Strain P [4] G2 (43.6%) was the most common combination followed by P [8] G3 (25.6%), P [4] G3 (13.8%), and P [8] G2, P [4] G1 and P [8] G1. Among 38 astrovirus strains, serotypes 1 (57.8%) was the predominant. Serotype 3 and 8 were found only in one case respectively, 14 strains remained to be non-typeable. A peak admission of rotavirus diarrhea was observed from October through December. More than 95.0% of viral diarrhea patients under hospitalization occurred among children younger than 2 years. The incidence rates of rotavirus were highest in infants aged 6 - 23 months. CONCLUSION: Rotavirus was the most important pathogen for viral diarrhea among children hospitalized in Lanzhou followed by calicivirus, astrovirus, and adenovirus. The predominant rotavirus strain circulated was P [4] G2, which was different from the finding in the previous years. The high rate of mixed infection with different viral agents was notable.

Poly(ethylene-co-vinyl alcohol) functionalized single-walled carbon nanotubes and related nanocomposites.

Single-walled carbon nanotubes (SWNTs) were functionalized by poly(ethylene-co-vinyl alcohol) (EVOH) copolymer under carbodiimide-activated esterification reaction conditions. Similar to the parent EVOH copolymer, the EVOH-functionalized carbon nanotubes are soluble in highly polar solvent systems such as DMSO and hot ethanol-water mixtures. The soluble EVOH-SWNT sample was characterized by various techniques, including optical absorption, Raman, NMR, electron microscopy, and thermogravimetric analysis. The common solubility of EVOH and EVOH-SWNT allowed their intimate mixing in solution, and thus the fabrication of nanocomposites in which the SWNTs are homogeneously dispersed in the polymer matrix.