High-sensitivity in vivo imaging for tumors using a spectral up-conversion nanoparticle NaYF4: Yb3+, Er3+ in cooperation with a microtubulin inhibitor

Fluorescein has been used for in vivo imaging to identify tumors. However, this technique presents several limitations, mainly due to its limited targeting efficiency, tissue autofluorescence and poor light penetration in tissue. In the present study, an alternative fluorescence imaging technique to localize tumors has been developed by using up-conversion nanoparticles (UCNs) and enhanced targeting approaches. A folic acid molecule is conjoined with UCNs (NaYF(4): Yb(3+), Er(3+)) to improve the tumor-specificity; the UCN is also loaded with the microtubule inhibitor CA4P, to further improve the local delivery of particles in the tumor. The proposed imaging technique combines several well-established individual concepts into one novel integrated procedure and significantly improves its tumor-imaging capability: the near-infrared excitation for UCNs minimizes tissue autofluorescence and allows imaging into deeper tissue; the improvement in the signal to noise ratio (SNR) is at least a magnitude better than that of a conventional fluorescence imaging technique, and the modification of UCNs with folic acid significantly improves the tumor targeting efficiency by utilizing its affinity for the folic acid receptor that is often over expressed in tumors. The loading of CA4P further helps UCNs to cross blood vessel walls to reach tumor cells by depolymerizing the microtubules of endothelial cells. The integrated nanoparticle possesses the near-infrared-identical optical properties of UCNs alone, thus achieving a highly effective fluorescence imaging probe. The results demonstrated that the proposed method provides an excellent alternative for tumor localization and a potential traceable vehicle for highly efficient drug delivery.

Over-expression of Arabidopsis Bax inhibitor-1 delays methyl jasmonate-induced leaf senescence by suppressing the activation of MAP kinase 6

Methyl jasmonate (MeJA) is an important signalling molecule that has been reported to be able to promote plant senescence. The cell death suppressor Bax inhibitor-1 (BI1) has been found to suppress stress factor-mediated cell death in yeast and Arabidopsis. However, the effect and the genetic mechanism of Arabidopsis thaliana BI1 (AtBI1) on leaf senescence remain unclear. It was found here that the AtBI1 mutant, atbi1-2 (a gene knock-out), showed accelerated progression of MeJA-induced leaf senescence, while the AtBI1 complementation lines displayed similar symptoms as the WT during the senescence process. In addition, over-expression of the AtBI1 gene delayed the onset of MeJA-induced leaf senescence. Further analyses showed that during the process of MeJA-induced senescence, the activity of MPK6, a mitogen-activated protein kinase (MAPK), increased in WT plants, whereas it was significantly suppressed in AtBI1-overexpressing plants. Under the MeJA treatment, cytosolic calcium ([Ca(2+)](cyt)) functioned upstream of MPK6 activation and the elevation of [Ca(2+)](cyt) was reduced in AtBI1-overexpressing leaves. These results suggested a role of AtBI1 over-expression in delaying MeJA-induced leaf senescence by suppressing the [Ca(2+)](cyt)-dependent activation of MPK6, thus providing a new insight into the function and mechanism of AtBI1 in plant senescence.

MAP Kinase 6-mediated activation of vacuolar processing enzyme modulates heat shock-induced programmed cell death in Arabidopsis

• Vacuolar processing enzyme (VPE), a cysteine protease, has been intensively studied in plant hypersensitive cell death, but the role and molecular mechanism of VPEs in response to abiotic stresses remain unclear. This work investigated the involvement of VPEs in Arabidopsis response to heat stress. • Under heat shock (HS), Arabidopsis VPE activity and the transcript level of γVPE were both upregulated, and γVPE deficiency suppressed vacuolar disruption and delayed caspase-3-like activation in HS-induced programmed cell death (PCD). Moreover, the change of VPE activity generally paralleled the alteration of caspase-1-like activity under HS treatment, indicating that HS-induced VPE activity might exhibit the caspase-1-like activity. • Further studies showed that MAP Kinase 6 (MPK6) activity was increased after HS treatment, and experiments with inhibitors and mutants suggested that MPK6 was responsible for the γVPE activation after HS treatment. In response to HS stress, reactive oxygen species (ROS) production, increase of cytoplasmic calcium concentration ([Ca(2+) ](cyt)) and the upregulation of calmodulin 3 (CaM3) transcript level occurred upstream of MPK6 activation. • Our results suggested that activation of Arabidopsis γVPE was mediated by MPK6 and played an important role in HS-induced Arabidopsis PCD, providing new insight into the mechanistic study of plant VPEs.

Characterization of target site of aluminum phytotoxicity in photosynthetic electron transport by fluorescence techniques in tobacco leaves

Aluminum (Al) toxicity limits crop yield in acidic soil through affecting diverse metabolic processes, especially photosynthesis. The aim of this work was to examine the effect of Al on photosynthetic electron transport in vivo as determined by chlorophyll fluorescence and delayed fluorescence of tobacco leaves. Results showed that Al treatment inhibited the photosynthetic rate and electron transfer, and decreased photosystem (PS) II photochemical activity in a time- and concentration-dependent manner, which could not be obviously alleviated by the addition of the reactive oxygen species (ROS) scavenger ascorbic acid (AsA). These results suggested that photosynthetic electron transfer chain components, especially PSII, might be directly damaged by Al instead of in an ROS-dependent manner. Furthermore, the fluorescence imaging and biochemical analysis exhibited that Al, after entering the cells, could accumulate in the chloroplasts, which paralleled the decreased content of Fe in the chloroplast. The changes in the chlorophyll fluorescence decay curve, the delayed fluorescence decay curve and the chlorophyll fluorescence parameters indicated that Al, through interacting with or replacing the non-heme iron between Q(A) and Q(B), caused the inhibition of electron transfer between Q(A) and Q(B), resulting in PSII photochemical damage and inhibition of the photosynthetic rate. In summary, our results characterized the target site of Al phytotoxicity in photosynthetic electron transport, providing new insight into the mechanism of Al phytotoxicity-induced chloroplast dysfunction and photosynthetic damage.

Detection and widespread distribution of sodium channel alleles characteristic of insecticide resistance in Culex pipiens complex mosquitoes in China

Culex pipiens complex mosquitoes are widely distributed throughout China and are known to be important disease vectors. Two pyrethroid resistance associated mutations have been identified in Cx. pipiens complex (Diptera: Culicidae), but there is little information on the diversity and distribution of kdr alleles in pyrethroid resistance in Cx. pipiens complex mosquitoes in China. In the present study, we report on a modified three tube allele-specific (AS)-PCR method for detecting the 1014F and 1014S alleles. The new technique was applied to identify the distribution of the two alleles in natural Cx. pipiens complex populations in China. The results confirmed that the new method is both sensitive and specific. The 1014F allele was found in all 14 of the field populations tested (frequency ranged from 6.8 to 76.2%) and the 1014S allele was found in almost two-thirds (frequency from 2.4 to 28.6%), indicating that the genotypes known to be associated with pyrethroid resistance are widespread in China. The resistance-associated alleles were more common in southern Chinese sampling sites than in northern sites. The coexistence of the two resistant mutations in individual mosquitoes was also observed in five of the field populations. Two alternative mutations within the L1014 codon were identified in Culex pipiens molestus Forskal, 1775, including a non-synonymous mutation resulting in a 1014C substitution.

Mitochondria-targeting photoacoustic therapy using single-walled carbon nanotubes

In vitro photoacoustic therapy using modified single-walled carbon nanotubes (SWNTs) as "bomb" agents is a newly reported approach for cancer. Herein, a mitochondria-targeting photoacoustic modality using unmodified SWNTs and its in vitro and in vivo antitumor effect are reported. Unmodified SWNTs can be taken up into cancer cells due to a higher mitochondrial transmembrane potential in cancerous cells than normal cells. Under the irradiation of a 1064 nm pulse laser, 79.4% of cancer cells with intracellular SWNTs die within 20 s, while 82.3% of normal cells without SWNTs remain alive. This modality kills cancer cells mainly by triggering cell apoptosis that initiates from mitochondrial damage, through the depolarization of mitochondria and the subsequent release of cytochrome c after photoacoustic therapy. It is very effective in suppressing tumor growth by selectively destroying tumor tissue without causing epidermis injury. Taken together, these discoveries provide a new method using mitochondria-localized SWNTs as photoacoustic transducers for cancer treatment.

Pyropheophorbide A and c(RGDyK) comodified chitosan-wrapped upconversion nanoparticle for targeted near-infrared photodynamic therapy

Near-infrared (NIR)-to-visible upconversion nanoparticle (UCNP) has shown promising prospects in photodynamic therapy (PDT) as a drug carrier or energy donor. In this work, a photosensitizer pyropheophorbide a (Ppa) and RGD peptide c(RGDyK) comodified chitosan-wrapped NaYF(4):Yb/Er upconversion nanoparticle UCNP-Ppa-RGD was developed for targeted near-infrared photodynamic therapy. The properties of UCNP-Ppa-RGD, such as morphology, stability, optical spectroscopy and singlet oxygen generation efficiency, were investigated. The results show that covalently linked pyropheophorbide a molecule not only is stable but also retains its spectroscopic and functional properties. In vitro studies confirm a stronger targeting specificity of UCNP-Ppa-RGD to integrin α(v)β(3)-positive U87-MG cells compared with that in the corresponding negative group. The photosensitizer-attached nanostructure exhibited low dark toxicity and high phototoxicity against cancer cells upon 980 nm laser irradiation at an appropriate dosage. These results represent the first demonstration of a highly stable and efficient photosensitizer modified upconversion nanostructure for targeted near-infrared photodynamic therapy of cancer cells. The novel UCNP-Ppa-RGD nanoparticle may provide a powerful alternative for near-infrared photodynamic therapy with an improved tumor targeting specificity.

Assays for human telomerase activity: progress and prospects

Human telomerase is a ribonucleoprotein complex that functions as a telomere terminal transferase by adding multiple TTAGGG hexamer repeats using its integral RNA as the template. There is a very strong association between telomerase activity and malignancy in nearly all types of cancer, suggesting that telomerase could be used not only as a diagnostic and prognostic marker but also as a therapeutic target for managing cancer. The significant progress in biomedical telomerase research has necessitated the development of new bioanalytical methods for the rapid, sensitive, and reliable detection of telomerase activity in a particular cell or clinical tissue and body fluids. In this review, we highlight some of the latest methods for identifying telomerase activity and inhibition and discuss some of the challenges for designing innovative telomerase assays. We also summarise the current technologies and speculate on future directions for telomerase testing.

A pathway from JNK through decreased ERK and Akt activities for FOXO3a nuclear translocation in response to UV irradiation

Forkhead box O (FOXO) transcription factors play an important role in physiological and pathological processes. Extracellular signal-regulated kinase (ERK) and protein kinase B (Akt) can phosphorylate FOXO and cause its degradation or cytoplasmic retention, respectively, leading to tumorigenesis. In addition, C-Jun N-terminal protein kinase (JNK) can promote FOXO nuclear localization, leading to apoptosis. Using confocal imaging of cells transfected with GFP-FOXO3a, we visualized the dynamic translocation of GFP-FOXO3a from the cytoplasm to the nucleus after UV irradiation in a time- and dose-dependent manner. We also found that UV irradiation caused activation of JNK, which in turn inactivated ERK and Akt, leading to FOXO3a translocation and Bim expression. Our results indicate that nuclear translocation of FOXO3a can be regulated by UV irradiation through the JNK-ERK/Akt pathway.

Intracellular label-free gold nanorods imaging with photoacoustic microscopy

Noninvasive photoacoustic microscopy was developed to image intracellular gold nanorods with high optical-absorption contrast. The endocytosed gold nanorods in MCF7 cells can be detected and imaged with the home-made photoacoustic microscope. Cell nucleus and gold nanorods in cytoplasm were clearly identified after hematoxylin and eosin (H&E) staining with dual-wavelength excitation. The intracellular gold nanorods were successfully monitored, and that the time-dependent uptake and distribution of the gold nanorods in the cells were clearly shown. The result demonstrated an application of photoacoustic microscopy for complements to imaging of nonfluorescent nanoparticles, which will arm the in vivo microscopic imaging method to the nano-bio research.

Sensitive and homogeneous protein detection based on target-triggered aptamer hairpin switch and nicking enzyme assisted fluorescence signal amplification

Specific and sensitive detection of proteins in biotechnological applications and medical diagnostics is one of the most important goals for the scientific community. In this study, a new protein assay is developed on the basis of hairpin probe and nicking enzyme assisted signal amplification strategy. The metastable state hairpin probe with short loop and long stem is designed to contain a protein aptamer for target recognition. A short Black Hole Quencher (BHQ)-quenching fluorescence DNA probe (BQF probe) carrying the recognition sequence and cleavage site for the nicking enzyme is employed for fluorescence detection. Introduction of target protein into the assay leads to the formation change of hairpin probe from hairpin shape to open form, thus faciliating the hybridization between the hairpin probe and BQF probe. The fluorescence signal is amplified through continuous enzyme cleavage. Thrombin is used as model analyte in the current proof-of-concept experiments. This method can detect thrombin specifically with a detection limit as low as 100 pM. Additionally, the proposed protein detection strategy can achieve separation-free measurement, thus eliminating the washing steps. Moreover, it is potentially universal because hairpin probe can be easily designed for other proteins by changing the corresponding aptamer sequence.

Phosphatidylinositol 3-kinase plays a vital role in regulation of rice seed vigor via altering NADPH oxidase activity

Phosphatidylinositol 3-kinase (PI3K) has been reported to be important in normal plant growth and stress responses. In this study, it was verified that PI3K played a vital role in rice seed germination through regulating NADPH oxidase activity. Suppression of PI3K activity by inhibitors wortmannin or LY294002 could abate the reactive oxygen species (ROS) formation, which resulted in disturbance to the seed germination. And then, the signal cascades that PI3K promoted the ROS liberation was also evaluated. Diphenylene iodonium (DPI), an NADPH oxidase inhibitor, suppressed most of ROS generation in rice seed germination, which suggested that NADPH oxidase was the main source of ROS in this process. Pharmacological experiment and RT-PCR demonstrated that PI3K promoted the expression of Os rboh9. Moreover, functional analysis by native PAGE and the measurement of the 2, 3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazo-lium-5- carboxanilide (XTT) formazan concentration both showed that PI3K promoted the activity of NADPH oxidase. Furthermore, the western blot analysis of OsRac-1 demonstrated that the translocation of Rac-1 from cytoplasm to plasma membrane, which was known as a key factor in the assembly of NADPH oxidase, was suppressed by treatment with PI3K inhibitors, resulting in the decreased activity of NADPH oxidase. Taken together, these data favored the novel conclusion that PI3K regulated NADPH oxidase activity through modulating the recruitment of Rac-1 to plasma membrane and accelerated the process of rice seed germination.

Ultrasensitive aptamer-based bio bar code immunomagnetic separation and electrochemiluminescence method for the detection of protein

An ultrasensitive aptamer-based bio bar code immunomagnetic separation and electrochemiluminescence (IM-ECL) method for the detection of protein is developed. The target protein is captured by biotin-labeled aptamer (biotin probe) and [Ru(bpy)(3)](2+) (TBR)-Au bio bar code-labeled aptamer (ECL nanoprobe), to form a double aptamer-protein sandwich complex. The complex is then immobilized on the streptavidin microbeads through biotin-streptavidin linkage and detected by ECL assay. The ECL signal of the target protein is amplified by the TBR-bio bar code DNAs. As an example, platelet-derived growth factor B-chain homodimer (PDGF-BB) was detected by the method. Experimental results show that the detection limit of the assay is 1 pM of PDGF-BB. A calibration curve with a linearity range from 1 pM to 10 nM is established, thus, make quantitative analysis possible. The method has been used to detect PDGF-BB in fetal calf serum with minimum background interference. Due to the wide availability of aptamer for numerous proteins, this aptamer-based bio bar code IM-ECL method holds great promise in protein detection.

Highly sensitive detection of protein and small molecules based on aptamer-modified electrochemiluminescence nanoprobe

Amplified optical detection of biomolecules using nanoparticle as the carrier has attracted considerable interest in the scientific community. In this study, a promising aptasensor was developed for highly sensitive detection of protein and small molecules based on the construction of aptamer-modified electrochemiluminescence (ECL) nanoprobe. Specifically, thrombin and ATP serve as the examples for detection. By taking advantage of sandwich binding of two affinity aptamers for high specificity, tris-(2,2'-bipyridyl)ruthenium (TBR)-cysteamine loaded in gold nanoparticle (GNP) as barcodes for signal amplification, and micromagnetic particles (MMPs) based ECL technology for rapid detection, a novel assay for biomolecules quantification was developed. The sandwich complex containing targets could be selectively captured by MMPs and then quantified by ECL intensity. We have demonstrated that the detection limits of human thrombin and ATP are 1 pM and 10 pM, respectively, with high specificity. The proposed technology is expected to become a powerful tool for biomolecule analysis.

Enhanced tumor treatment using biofunctional indocyanine green-containing nanostructure by intratumoral or intravenous injection

Indocyanine green (ICG) is a conventional dye that can be used in clinical near-infrared (NIR) imaging, and it is also an effective light absorber for laser-mediated photothermal therapy. However, applications of ICG were limited due to its fast degradation in aqueous media and quick clearance from the body. Herein, an ICG-containing nanostructure, ICG-PL-PEG, was developed for photothermal therapy, which was self-assembled by ICG and phospholipid-polyethylene glycol (PL-PEG). Our in vitro and in vivo experiments demonstrated that ICG-PL-PEG suspension was more efficient in producing a NIR-dependent temperature increase than ICG alone, due to the increase of ICG monomers from the addition of PL-PEG to match the central wavelength of the 808 nm laser. When conjugated with integrin α(v)β(3) monoclonal antibody (mAb), ICG-PL-PEG could be selectively internalized and retained in target tumor cells. Irradiation of an 808 nm laser after intravenous administration of ICG-PL-PEG-mAb resulted in tumor suppression in mice, while ICG alone had only limited effect. This is the first time an ICG-containing nanostructure has been used through systemic administration to achieve an efficient in vivo photothermal effect for cancer treatment. Therefore, ICG-PL-PEG could be used as a fluorescent marker as well as a light-absorber for imaging-guided photothermal therapy. All the components of ICG-PL-PEG have been approved for human use. Therefore, this unique ICG-containing nanostructure has great potential in clinical applications.

Multichannel oscillatory-flow multiplex PCR microfluidics for high-throughput and fast detection of foodborne bacterial pathogens

In the field of continuous-flow PCR, the amplification throughput in a single reaction solution is low and the single-plex PCR is often used. In this work, we reported a flow-based multiplex PCR microfluidic system capable of performing high-throughput and fast DNA amplification for detection of foodborne bacterial pathogens. As a demonstration, the mixture of DNA targets associated with three different foodborne pathogens was included in a single PCR solution. Then, the solution flowed through microchannels incorporated onto three temperature zones in an oscillatory manner. The effect factors of this oscillatory-flow multiplex PCR thermocycling have been demonstrated, including effects of polymerase concentration, cycling times, number of cycles, and DNA template concentration. The experimental results have shown that the oscillatory-flow multiplex PCR, with a volume of only 5 μl, could be completed in about 13 min after 35 cycles (25 cycles) at 100 μl/min (70 μl/min), which is about one-sixth of the time required on the conventional machine (70 min). By using the presently designed DNA sample model, the minimum target concentration that could be detected at 30 μl/min was 9.8 × 10(-2) ng/μl (278-bp, S. enterica), 11.2 × 10(-2) ng/μl (168-bp, E. coli O157: H7), and 2.88 × 10(-2) ng/μl (106-bp, L. monocytogenes), which corresponds to approximately 3.72 × 10(4) copies/μl, 3.58 × 10(4) copies/μl, and 1.79 × 10(4) copies/μl, respectively. This level of speed and sensitivity is comparable to that achievable in most other continuous-flow PCR systems. In addition, the four individual channels were used to achieve multi-target PCR analysis of three different DNA samples from different food sources in parallel, thereby achieving another level of multiplexing.

Low-power laser irradiation (LPLI) promotes VEGF expression and vascular endothelial cell proliferation through the activation of ERK/Sp1 pathway

Angiogenesis, the growth of new blood vessels from pre-existing vessels, represents an excellent therapeutic target for the treatment of wound healing and cardiovascular disease. Herein, we report that LPLI (low-power laser irradiation) activates ERK/Sp1 (extracellular signal-regulated kinase/specificity protein 1) pathway to promote VEGF expression and vascular endothelial cell proliferation. We demonstrate for the first time that LPLI enhances DNA-binding and transactivation activity of Sp1 on VEGF promoter in vascular endothelial cells. Moreover, Sp1-regulated transcription is in an ERK-dependent manner. Activated ERK by LPLI translocates from cytoplasm to nuclear and leads to increasing interaction with Sp1, triggering a progressive phosphorylation of Sp1 on Thr453 and Thr739, resulting in the upregulation of VEGF expression. Furthermore, selective inhibition of Sp1 by mithramycin-A or shRNA suppresses the promotion effect of LPLI on cell cycle progression and proliferation, which is also significantly abolished by inhibition of ERK activity. These findings highlight the important roles of ERK/Sp1 pathway in angiogenesis, supplying potential strategy for angiogenesis-related diseases with LPLI treatment.

Antitumor immunologically modified carbon nanotubes for photothermal therapy

An immunologically modified nanotube system was developed using an immunoadjuvant, glycated chitosan (GC), as surfactant of single-walled carbon nanotube (SWNTs). This SWNT-GC system not only retained both optical properties of SWNTs and immunological functions of GC, but also could enter cells due to the carrier properties of SWNTs. Cellular SWNTs induced thermal destruction of tumor cells when irradiated by a near-infrared laser and, at the same time, cellular GC could serve both as damage associated molecular pattern molecules (DAMPs) and pathogen associated molecular pattern molecules (PAMPs) to enhance the tumor immunogenicity and enhance the uptake and presentation of tumor antigens, leading to special antitumor response. Using this system and a 980 nm laser, we treated tumors, both in vitro and in vivo, and investigated the induced thermal and immunological effects. Laser + SWNT-GC afford a remarkable efficacy in suppressing tumor growth in animal cancer models, in many cases resulting in complete tumor regression and long-term survival. Mice successfully treated by Laser + SWNT-GC could establish resistance to tumor rechallenge. This system forms a multifunctional temporal-spatial continuum, which can synergize photothermal and immunological effects. The Laser + SWNT-GC could represent a promising treatment modality to induce systemic antitumor response through a local intervention, while minimizing the adverse side effects.

Mechanism of mitochondrial membrane permeabilization during apoptosis under photofrin-mediated photodynamic therapy

Photofrin-mediated photodynamic therapy (PF-PDT) can induce cell apoptosis via the mitochondria/caspase-3 pathway. Here, we further investigate the mechanism involved in the mitochondrial apoptotic process induced by PF-PDT. A high-level intracellular reactive oxygen species (ROS) generation in mitochondria, mitochondrial swelling, and dissipation of mitochondrial transmembrane potential were observed immediately after irradiation, indicating that mitochondria were the major ROS generation sites and also the first oxidative damage sites after PF-PDT treatment. For mitochondrial permeability detection, the decrease of calcein fluorescence emission intensity and release of cytochrome c were observed immediately after PF-PDT treatment, indicating the occurrence of mitochondrial inner membrane permeabilization (MIMP) and the mitochondrial outer membrane permeabilization (MOMP). However, cytochrome c release was not prevented by cyclosporine (CsA), a specific inhibitor of mitochondrial permeability transition (MPT). Taken together, these results demonstrated that PF-PDT caused simultaneous onset of MIMP and MOMP immediately after the treatment, and MOMP was independent of the MPT. Besides, inducible mitochondrial ROS generation played key roles in PF-PDT-induced cell apoptosis. This study will be benefit for understanding the mechanism involved in the initial mitochondrial oxidative damage by PF-PDT.