A Pyranoxanthone as a Potent Antimitotic and Sensitizer of Cancer Cells to Low Doses of Paclitaxel

Microtubule-targeting agents (MTAs) remain a gold standard for the treatment of several cancer types. By interfering with microtubules dynamic, MTAs induce a mitotic arrest followed by cell death. This antimitotic activity of MTAs is dependent on the spindle assembly checkpoint (SAC), which monitors the integrity of the mitotic spindle and proper chromosome attachments to microtubules in order to ensure accurate chromosome segregation and timely anaphase onset. However, the cytotoxic activity of MTAs is restrained by drug resistance and/or toxicities, and had motivated the search for new compounds and/or alternative therapeutic strategies. Here, we describe the synthesis and mechanism of action of the xanthone derivative pyranoxanthone 2 that exhibits a potent anti-growth activity against cancer cells. We found that cancer cells treated with the pyranoxanthone 2 exhibited persistent defects in chromosome congression during mitosis that were not corrected over time, which induced a prolonged SAC-dependent mitotic arrest followed by massive apoptosis. Importantly, pyranoxanthone 2 was able to potentiate apoptosis of cancer cells treated with nanomolar concentrations of paclitaxel. Our data identified the potential of the pyranoxanthone 2 as a new potent antimitotic with promising antitumor potential, either alone or in combination regimens.     

Zn-Al类水滑石的荧光性质

报道了一种新的Zn-Al类水滑石的荧光现象, 即在没有任何荧光物质插层的情况下, Zn-Al类水滑石本身就具有荧光性质, 其最大激发波长位于375 nm, 最大发射波长处于443 nm, 显示的荧光为蓝色可见光. 这一光学功能的发现将有助于类水滑石在光学材料领域中的进一步应用.     

Effect of cyclodextrins on the stability of adriamycin, adriamycinol, adriamycinone and daunomycin

The stability of adriamycin (ADR), adriamycinol, adriamycinone (ADR-ONE) and daunomycin in the presence of alpha-, beta- and gamma-cyclodextrins (CDs) was studied using high-performance liquid chromatography. It was found that alpha-CD did not affect the degradation of tested compounds, beta-CD caused a little effect and gamma-CD resulted in pronounced stabilizing effect. The formation of complexes between ADR and ADR-ONE with CDs was monitored by fluorescence spectroscopy. The fluorescence spectrum of ADR-gamma-CD complex had an activation maximum at 460 nm, emission maximum at 555 nm and a shoulder at 585 nm. A similar finding was observed in case of alpha-CD. In case of beta-CD, the fluorescence intensity at 580 nm peak enhanced less than in case of gamma-CD. With ADR-ONE, alpha-CD did not cause any significant change compared with the spectrum of free molecule. On the other hand, it was noticed that, the fluorescence spectra of ADR-ONE with both beta- and gamma-CD were the same but showed a significant difference to the spectrum of free molecule, especially the molar fluorescence of the 585 nm emission peak.     

Spectroscopic studies into the influence of UV radiation on elastin hydrolysates in water solution

An investigation into the influence of UV irradiation on elastin hydrolysates dissolved in water was carried out using UV-Vis spectroscopy and spectrofluorometry. It was found that the absorption of elastin hydrolysates in solution increased during irradiation of the sample. For fluorescence of elastin hydrolysates we observed both, a decrease and increase of this value during irradiation of the sample. After UV irradiation of the elastin solution we observed a minor increase of overall absorption, most notably between 250 nm and 280 nm. Moreover, after UV irradiation a wide peak emerged between 290 nm and 310 nm with maximum at about 305 nm. The new peak suggests that new photoproducts are formed during UV irradiation of elastin hydrolysates. The fluorescence of elastin hydrolysates was observed at 305 nm and at 380 nm after excitation at 270 nm. UV irradiation caused fluorescence fading at 305 nm and 380 nm. After 30 min of irradiation a new broad weak band of fluorescence, attributable to new photoproducts, emerged in the UV wavelength region with emission maximum between 400 nm and 500 nm.     

The influence of UV radiation on silk fibroin

An investigation into the influence of UV-irradiation on regenerated silk fibroin dissolved in water was carried out using UV-Vis and fluorescence spectroscopy. It was found that the absorption of regenerated silk fibroin in solution increased during UV-irradiation of the sample, most notably between 250 and 400 nm. Moreover, after UV-irradiation a wide peak emerged between 290 and 340 nm with maximum at about 305 nm. The new peak suggests that new photoproducts are formed during UV-irradiation of regenerated silk fibroin.The fluorescence of regenerated silk fibroin was observed at 305 nm, at 480 nm and at 601 nm after excitation at 275 nm. UV-irradiation caused fluorescence fading at 305 nm and at 601 nm. The increase of fluorescence was observed at 480 nm, probably due to formation of new photoproducts. After excitation at 305 nm the fluorescence of regenerated silk fibroin was observed at 340 nm and at 400 nm. UV-irradiation caused fluorescence fading at 340 nm. FTIR spectroscopy showed that primary structure of regenerated silk fibroin was not significantly affected by UV radiation. SDS-PAGE chromatography showed alterations of molecular weight of silk after UV exposure.     

Fluorometric determination of DNA using a new ruthenium complex Ru(bpy)2PIP(V) as a nucleic acid probe.

A new ligand, 2-phenyl(5-fluoro)imidazo[f]-1,10-phenanthroline (PIP(V)), and its coordination compounds, Ru(bpy)2PIP(V), were synthesized. The fluorescence spectrum of the interaction between Ru(bpy)2PIP(V) and DNA was studied, and a very strong fluorescence peak at a wavelength of 589 nm appeared. The optimum condition of analyzing DNA was decided. The method is simple, convenient and fast, and also has high sensitivity and good selectivity. It has been satisfactorily employed for determinations in synthesized samples.     

Normal phase high performance liquid chromatography for determination of paclitaxel incorporated in a lipophilic polymer matrix

A normal phase (NP) high performance liquid chromatography (HPLC) method was developed for analysis of paclitaxel incorporated in poly(sebacic-co-ricinoleic acid), a lipophilic polymer matrix utilized for preparation of an injectable formulation for the localized delivery of paclitaxel. Thin layer chromatography experiments revealed that separation of paclitaxel from the polymer is dependent on the eluting strength (solvent strength) of the mobile phase. The HPLC system consists of a Purospher STRAR Si analytical HPLC column (5 microm, 250mm x 4mm, Merck), and 1-2.5% (v/v) methanol in dichloromethane as the mobile phase. Detection was by UV absorbance at 240 and 254 nm. The effect of the mobile phase composition on paclitaxel retention, peak shape and column efficiency, and the influence of the sample loading on the shape of the paclitaxel peak were studied. The mobile phases used for the chromatography consisted of 1.5% (v/v) methanol in dichloromethane. Paclitaxel was determined in the formulation and in the samples from degradation studies using UV detection at a wavelength of 254 nm. UV detection at 240 nm has advantages for following polymer matrix degradation products due to higher detector response at this wavelength. The utility of the proposed NP HPLC approach was demonstrated by assessment of intra- and inter-batch content uniformity, and by the determination of paclitaxel content after 7 and 60 days exposure of the paclitaxel-loaded polymer matrix to in vitro and in vivo degradation.     

Phosphonated Near‐Infrared Fluorophores for Biomedical Imaging of Bone

The conventional method for creating targeted contrast agents is to conjugate separate targeting and fluorophore domains. A new strategy is based on the incorporation of targeting moieties into the non‐delocalized structure of pentamethine and heptamethine indocyanines. Using the known affinity of phosphonates for bone minerals in a model system, two families of bifunctional molecules that target bone without requiring a traditional bisphosphonate are synthesized. With peak fluorescence emissions at approximately 700 or 800 nm, these molecules can be used for fluorescence‐assisted resection and exploration (FLARE) dual‐channel imaging. Longitudinal FLARE studies in mice demonstrate that phosphonated near‐infrared fluorophores remain stable in bone for over five weeks, and histological analysis confirms their incorporation into the bone matrix. Taken together, a new strategy for creating ultra‐compact, targeted near‐infrared fluorophores for various bioimaging applications is described.     

High throughput screening of beta-amyloid secretion inhibitors using homogenous time-resolved fluorescence

A cell-based assay using homogeneous time-resolved fluorescence has been developed for high throughput screening of putative beta-amyloid (Abeta)production inhibitors. In this assay, total Abeta is detected by simply adding two commercially available antibody complexes. The first was a biotinylated monoclonal antibody (4G8), specifically recognizing an epitope comprising the residues 17-24 of the Abetapeptide, complexed with europium cryptate-streptavidin conjugate. The second was a polyclonal antibody (BioS-N), raised against the N-terminus of the Abeta peptide, complexed with an allophycocyanin-anti rabbit antibody conjugate. Binding of the two complexes to the Abeta peptide brought europium cryptate (fluorescence donor) and allophycocyanin (fluorescence acceptor) into close proximity, consequently a fluorescent resonance energy transfer signal was produced upon excitation at 337 nm. The resulting fluorescence signal (665 nm) was then detected using a Discovery or a ViewLux reader. Detection of Abeta by the proposed method is possible at concentrations of approximately 1 nM. The method was employed for the detection of Abeta secreted from a stable transfected human neuroglioma cell line (H4) overexpressing a mutated form of the human amyloid precursor protein (APP695NL) and developed for robotic automation. At optimized conditions, signal-to-background ratios exceeding 5 and Z' factors around 0.7 were achieved in a 384-well format. High throughput screening of 56,913 potential Abeta production inhibitors led to identification of new non-cytotoxic and cell permeable compounds with potencies in the submicromolar range.     

Screening and investigation of triplex DNA binders from Stephania tetrandra S. Moore by a combination of peak area‐fading ultra high‐performance liquid chromatography with orbitrap mass spectrometry and optical spectroscopies

The identification and screening of triplex DNA binders are important because these compounds, in many cases, are potential anticancer agents as well as promising drug candidates. Therefore, the ability to screen for these compounds in a high‐throughput mode could dramatically improve the drug screening process. A method involving a combination of 96‐well plate format and peak area‐fading ultra high‐performance liquid chromatography coupled with Orbitrap mass spectrometry was employed for screening bioactive compounds binding to the triplex DNA from the extracts of Stephania tetrandra S. Moore. Two compounds were screened out and identified as fangchinoline and tetrandrine based on the comparison of retention time and tandem mass spectrometry data with those of standards. The binding mechanisms of fangchinoline and tetrandrine at the molecular level were explored using tandem mass spectrometry, fluorescence spectroscopy, ultraviolet‐visible spectroscopy, and circular dichroism. Collision‐induced dissociation experiments showed that the complexes with fangchinoline and tetrandrine were dissociated by ligand elimination. According to these measurements, an intercalating binding is the most appropriate binding mode of these two alkaloids to the triplex DNA. The current work provides not only deep insight into alkaloid‐triplex DNA complexes but also useful guidelines for the design of efficient anticancer agents.     

新型紫杉烷类衍生物的制备及生物活性评价

多药耐药性问题是导致第一代紫杉烷药物在临床化疗失败的主要原因。本文对紫杉醇C7、C10、C14、C3′多个位点的取代基进行改造,针对合成的6个新型的紫杉烷化合物,在体外考察其对多药耐药肿瘤细胞株以及人结肠癌HCT-116干细胞的增殖抑制活性,实验结果表明6个化合物的抗多药耐药活性均优于紫杉醇。采用P-gp高表达的犬肾细胞MDCK-MDR1进一步研究高活性候选化合物JT-3与P-gp的相互作用。以此研发抗多药耐药型的新一代紫杉烷类药物,对开发扩大抗癌新适应症的新一代紫杉烷类抗癌药意义重大。     

EFFECT OF PHOSPHATE ION ON FLUORESCENT CHARACTERISTICS OF TYROSINE AND ITS CONJUGATE BASE

Abstract—The UV fluorescence spectrum of tyrosine (Tyr) is markedly affected by the interaction with phosphate ion. In order to elucidate the mechanism of the specific fluorescence quenching by phosphate and the simultaneous appearance of a new emission, the effect of phosphate on the spectro-scopic characteristics of Tyr was investigated. Employing a fluorimetric method, we have obtained the following results. Namely, potassium phosphate was found to enhance the fluorescence intensity of tyrosinate ion. When Tyr is excited in the phosphate-containing solution, the emission with a peak around 345 nm is observed besides the normal fluorescence of Tyr around 303 nm with a reduced quantum yield. The abnormal emission may be ascribed to the tyrosinate ion in the excited state resulting from the deprotonation of the phenolic OH group of the excited Tyr. although the tyrosinate ion in the ground state is not predominant in the aqueous solution examined.     

Multimodal coupling of optical transitions and plasmonic oscillations in rhodamine B modified gold nanoparticles

The optical properties of a photoluminescent dye rhodamine B (RhB) interacting with gold nanoparticles (AuNP) have been investigated using plasmonic absorbance, fluorescence, and resonance elastic light scattering (RELS) spectroscopy. We have found that these interactions result in a multimodal coupling that influence optical transitions in RhB. In absorbance measurements, we have observed for the first time the coupling resulting in strong screening of RhB π-π* transitions, likely caused by a contact adsorption of RhB on a conductive surface of AuNP. The nanoparticles quench also very efficiently the RhB fluorescence. We have determined that the static quenching mechanism with a non-F?rster fluorescence resonance energy transfer (FRET) from RhB molecules to AuNP is involved. The Stern-Volmer dependence F(0)/F = f(Q) shows an upward deviation from linearity, attributed to the ultra-high quenching efficiency of AuNP leading to the new extended Stern-Volmer model. A sharp RELS peak of RhB alone (λ(max) = 566 nm) has been observed for the first time and attributed to the resonance fluorescence and enhanced scattering. This peak is completely quenched in the presence of AuNP(22nm). Our quantum mechanical calculations confirm that the distance between AuNP surface and conjugated π-electron system in RhB is well within the range of plasmonic fields extending from AuNP. The optical transition coupling to plasmonic oscillations and the efficient energy transfer due to the interactions of fluorescent dyes with nanoparticles are important for biophysical studies of life processes and applications in nanomedicine.     

Fluorescence spectroscopy of normal mouse skin exposed to 5-aminolaevulinic acid and red light

Photobleaching and phototransformation of protoporphyrin IX (PpIX) was investigated in normal mouse skin. The PpIX was induced by topical application of 5-aminolaevulinic acid (ALA). Exposure to laser light (635 nm) caused photobleaching of PpIX fluorescence and formation of fluorescent products. Analysis of the fluorescence spectra revealed appearance of new fluorescent photoproducts during light exposure. The main photoproduct, supposedly chlorin-type photoprotoporphyrin (PPp), exhibited fluorescence with an emission maximum at 675 nm. The other products exhibited main fluorescence peaks at around 588 and 623 nm that can presumably be attributed to an endogenous metallo-porphyrin and water-soluble porphyrin(s), respectively. Our results indicate that light exposure causes alterations in the enzymatic pathway of PpIX synthesis from ALA and leads to accumulation of intermediate water-soluble porphyrins. ALA-induced porphyrins are transported away from the treated area and partly deposited in remote skin sites.     

A study on silver nanoparticles-sensitized fluorescence and second-order scattering of the complexes of Tb(III) with ciprofloxacin and its applications

Fluorescence of terbium(III) is sensitized when excited in the presence of ciprofloxacin (CPLX) in the aqueous solution because a Tb(III)-CPLX complex is formed and the maximum fluorescence peak locates at 545 nm. The second-order scattering (SOS) peak at 545 nm also appears for the Tb(III)-CPLX complexes with the excitation wavelength of 272 nm. The intensity at 545 nm obviously increases when the silver nanoparticles are added to the Tb(III)-CPLX system, and the relative intensity is proportional to the concentration of CPLX. Based on this phenomenon, a new method for the determination of CPLX has been developed by using a common spectrofluorometer to measure the intensity of fluorescence and SOS. The intensity is enhanced most by silver nanoparticles at pH 6.0. The calibration graph for CPLX is linear in the range of 3.0 x 10(-9) to 1.0 x 10(-5) mol l(-1). The detection limit is 8.5 x 10(-10) mol l(-1). The method was applied satisfactorily to the determination of CPLX in tablets and capsules. The results show that silver nanoparticles with certain size and concentration can enhance the fluorescence and SOS intensity of the system.     

Properties of the bimodal fluorescent protein produced by Photobacterium phosphoreum

A fluorescent protein isolated from the deep-sea luminous bacterium Photobacterium phosphoreum strain bmFP has been purified, cloned and sequenced. The protein is 96.5% identical in amino acid sequence to FP390, the weakly fluorescent flavoprotein encoded by the luxF gene characteristic of Photobacterium species. Similar to FP390, bmFP is a dimer of two homologous subunits binding four FMN-myristate chromophores but has the distinctive feature of emitting a bimodal fluorescence with maxima at about 488 and 517 nm, hence the name bmFP. For both bands of this fluorescence, the excitation spectrum exhibits a peak at 336 nm, not corresponding to its flavin-like absorption spectrum. Heating of bmFP in urea resulted in a decrease in the intensity of the 488 nm band along with the appearance of a new fluorescence peaking at 423 nm, partially reversible upon the removal of the urea. Upon complete denaturation, either by heat or guanidium chloride at 65 degrees C, fluorescence characteristic of both free flavin and this 423 nm species appears. It is speculated that chromophores in different states of protonation, associated with a single protein, are responsible for the unusual spectral properties of bmFP.     

Luminescence effect of silver nanoparticle in water phase

Yellow silver nanoparticles in water phase were prepared by microwave synthesis method. Study found that there is a fluorescence peak at 465 nm and a strongest resonance scattering peak at 460 nm for the nanoparticles. The resonance scattering intensity at 465 nm I(460 nm). fluorescence intensity at 465 nm F(465)(nm) and absorbance at 455 nm A(455 nm) were found linear to the concentration c(Ag) in the range from 0 to 3.5x10(-4)mol/L Ag, with linear regression equation for I(460 nm)=48.1x10(4) c(Ag)+3.69 and F(465 nm)=28.7x10(4)c(Ag)+3.50 and A(455 nm)1.23x10(4)c(Ag)+0.01, their regression coefficient for 0.9976, 0.9954 and 0.9957, respectively. When the c(Ag) was over 3.5x10(-4)mol/L, the resonance scattering peak and fluorescence peak of 465 nm take place red-shift and display luminescence quenching, but the absorption peak place does not change and the absorption intensity enhances. The paper reports the spectral properties of silver nanoparticles in water phase, and offers the principle of interface luminescence electron to state the luminescence effect of silver nanoparticles.     

Fluorescent MOF-based nanozymes for discrimination of phenylenediamine isomers and ratiometric sensing of o-phenylenediamine

Although peroxidase-like nanozymes have made great progress in bioanalysis,few current nanozymebased biosensors are constructed for discriminating isomers of organic compounds.Herein,fluorescent metal-organic framework（MOF）-based nanozyme is utilized for phenylenediamine isomers discrimination and detection.NH₂-MIL-101（Fe）,as a member of Fe-based MOFs,functions as not only fluorescent indicator but also peroxidase mimics.In the presence of H₂ O₂,NH2-MIL-101（Fe） c...     

四苯基卟啉镁的合成、表征及光化学性质

提出一种以乙酸镁和乙酸钠为原料合成四苯基卟啉镁(MgTPP)的新方法, 合成样品以柱层析法进行分离纯化. 分离产物经UV-Vis、1H-NMR、MALDI-TOF-MS(基质辅助激光解吸电离飞行时间质谱)等技术表征, 确定为MgTPP. UV-Vis光谱分析结果表明, 四苯基卟啉镁的Soret 吸收带为424 nm, Q 吸收带为563 nm 和602 nm. 此外, 光照对MgTPP的二氯甲烷溶液光谱性质的影响结果表明, 经光照射后MgTPP的UV-Vis光谱的Soret吸收带吸收强度明显降低, 同时, 经550 nm的光激发产生的荧光有明显的猝灭. 对光照后的MgTPP样品进行MALDI-TOF-MS分析, 发现有新的质核比(m/z)出现, 其为668, 这一结果表明, 在光照条件下, MgTPP分子可能与氧分子发生光化学作用, 形成MgTPP与氧的复合物MgTPP-O2.     

氯金酸-罗丹明S缔合纳米微粒体系的共振散射增强与荧光猝灭研究

在0．2mol/L HCl介质中，罗丹明S(RDS)分别在520nm和550nm处有一个吸收峰和荧光峰。当有Au(Ⅲ）存在时，Au（Ⅲ）与Cl^-形成AuCl4^-，AuCl^-与RDS^ 借助于静电引力形成疏水性的AuCl4-RDS缔合物分子。AuCl4-RDS分子间存在较强的分子间作用力和疏水作用力而生成(AuCl4-RDS)。缔合纳米微粒，粒径为45nm。在360nm产生瑞利散射峰，在600nm产生共振散射峰。由于纳米微粒形成后，只有裹露在(AuCl4-RDS)n纳米微粒界面的RDS荧光分子才能吸收激发光子跃迁到激发态，进而返回基态产生荧光。而体相的RDS荧光分子无法与激发光作用产生荧光，即受激RDS分子数大为降低，故550nm荧光峰和520nm吸收峰的降低。当缔合纳米微粒体系加入乙醇后，体系的红紫色和共振散射峰消失，吸收峰和荧光峰恢复，由于乙醇致使(AuCl4-RDS)。纳米微粒分解为AuCl4-RDS分子。结果表明：红紫色(AuCl4-RDS)n纳米粒子的形成是其共振散射增强、荧光猝灭和产生共振散射峰的根本原因。