Low-noise fluorescent detection of cardiac troponin I in human serum based on surface acoustic wave separation.

Acute myocardial infarction (AMI) is a life-threatening disease when sudden blockage of coronary artery occurs. As the most specific biomarker, cardiac troponin I (cTnI) is usually checked separately to diagnose or eliminate AMI, and achieving the accurate detection of cTnI is of great significance to patients' life and health. Compared with other methods, fluorescent detection has the advantages of simple operation, high sensitivity and wide applicability. However, due to the strong fluorescence interference of biological molecules in body fluids, it is often difficult to obtain high sensitivity. In order to solve this problem, in this study, surface acoustic wave separation is designed to purify the target to achieve more sensitive detection performance of fluorescent detection. Specifically, the interference of background noise is almost completely removed on a microfluidic chip by isolating microbeads through acoustic radiation force, on which the biomarkers are captured by the immobilized detection probe. And then, the concentration of cTnI in human serum is detected by the fluorescence intensity change of the isolated functionalized beads. By this way, the detection limit of our biosensor calculated by 3σ/K method is 44 pg/mL and 0.34 ng/mL in PBS buffer and human serum respectively. Finally, the reliability of this method has been validated by comparison with clinical tests from the nephelometric analyzer in hospital.

Multiple virus sorting based on aptamer-modified microspheres in a TSAW device.

Due to the overlapping epidemiology and clinical manifestations of flaviviruses, differential diagnosis of these viral diseases is complicated, and the results are unreliable. There is perpetual demand for a simplified, sensitive, rapid and inexpensive assay with less cross-reactivity. The ability to sort distinct virus particles from a mixture of biological samples is crucial for improving the sensitivity of diagnoses. Therefore, we developed a sorting system for the subsequent differential diagnosis of dengue and tick-borne encephalitis in the early stage. We employed aptamer-modified polystyrene (PS) microspheres with different diameters to specifically capture dengue virus (DENV) and tick-borne encephalitis virus (TBEV), and utilized a traveling surface acoustic wave (TSAW) device to accomplish microsphere sorting according to particle size. The captured viruses were then characterized by laser scanning confocal microscopy (LSCM), field emission scanning electron microscopy (FE-SEM) and reverse transcription-polymerase chain reaction (RT‒PCR). The characterization results indicated that the acoustic sorting process was effective and damage-free for subsequent analysis. Furthermore, the strategy can be utilized for sample pretreatment in the differential diagnosis of viral diseases.

A rapid fluorescent aptasensor for point-of-care detection of C-reactive protein.

In this paper, we report on a novel fluorescent aptasensor based on aptamers modified by both nitrogen-doped graphene quantum dots (N-GQDs) and gold nanoparticles (AuNPs) for the detection of C-reactive protein (CRP). FRET effect is utilized in our aptasensor by the change of aptamers conformation when binding with the target. An obvious fluorescence quench of the N-GQDs can be observed when CRP appears in the assay due to electron transfer between the donor and accepter. A detection limit of 0.2 ng/mL can be achieved by our sensor in PBS buffer which is much lower than the physiological CRP level in human serum. Also, CRP levels in different patients' serum are tested with our assay. Since our aptasensor is rapid (detection time less than 40 min), one-step and very simple to operate, we believe it has great potential to apply for point-of-care testing (POCT).

Topological cavity laser with valley edge states.

Topological edge states (ES) arise at the boundary between spatial domains with diverse topological properties in photonic crystals, which can transmit unidirectionally to suppress the backscattering and robustly to be immune to defects and disorders. In addition, optical devices with arbitrary geometries of cavities, such as lasers, are expected to be designed on the basis of ES. Herein, we first propose a topological cavity laser based on a honeycomb lattice of ring holes with the bearded interface in two-dimensional (2D) all-dielectric valley photonic crystals (VPhCs) at telecommunication wavelengths. Specifically, we construct a topological cavity using topological valley edge states (VES) and further study the lasing action of the optically pumped cavity with high-quality factors. Our findings could provide opportunities for practical applications of VES-based lasers as ultra-small light sources with the topological protection.

Improved Thermoelectric Performance of P-type SnTe through Synergistic Engineering of Electronic and Phonon Transports.

SnTe has been regarded as a potential alternative to PbTe in thermoelectrics because of its environmentally friendly features. However, it is a challenge to optimize its thermoelectric (TE) performance as it has an inherent high hole concentration (nH∼2 × 1020 cm-3) and low mobility (µH∼18 cm2 V-1 s-1) at room temperature (RT), arising from a high intrinsic Sn vacancy concentration and large energy separation between its light and heavy valence bands. Therefore, its TE figure of merit is only 0.38 at ∼900 K. Herein, both the electronic and phonon transports of SnTe were engineered by alloying species Ag0.5Bi0.5Se and ZnO in succession, thus increasing the Seebeck coefficient and, at the same time, reducing the thermal conductivity. As a result, the TE performance improves significantly with the peak ZT value of ∼1.2 at ∼870 K for the sample (SnGe0.03Te)0.9(Ag0.5Bi0.5Se)0.1 + 1.0 wt % ZnO. This result proves that synergistic engineering of the electronic and phonon transports in SnTe is a good approach to improve its TE performance.

Co-regulation of the copper vacancy concentration and point defects leading to the enhanced thermoelectric performance of Cu3In5Te9-based chalcogenides.

Copper vacancy concentration (V c) in ternary Cu-In-Te chalcogenides is an important factor to engineer carrier concentration (n H) and thermoelectric performance. However, it is not sufficient to regulate the phonon scattering in the Cu3In5Te9-based chalcogenides. In this work we manipulate the V c value and point defects simultaneously through addition of Cu along with Ga substitution for In in Cu3In5Te9, and thereby increase the carrier concentration and reduce the lattice thermal conductivity. This strategy finally enables us to achieve ∼60% enhancement of the TE figure of merit (ZT) at V c = 0.078 compared with the pristine Cu3In5Te9. It is also used as guidance to achieve the high TE performance of the ternary chalcogenides.

Improved thermoelectric performance of solid solution Cu4Sn7.5S16 through isoelectronic substitution of Se for S.

Cu-Sn-S family of compounds have been considered as very competitive thermoelectric candidates in recent years due to their abundance and eco-friendliness. The first-principles calculation reveals that the density of states (DOS) increases in the vicinity of the Fermi level (Ef) upon an incorporation of Se in the Cu4Sn7.5S16-xSe x (x = 0-2.0) system, which indicates the occurrence of resonant states. Besides, the formation of Cu(Sn)-Se network upon the occupation of Se in S site reduces the Debye temperature from 395 K for Cu4Sn7S16 (x = 0) to 180.8 K for Cu4Sn7.5S16-xSe x (x = 1.0). Although the point defects mainly impact the phonon scattering, an electron-phonon interaction also bears significance in the increase in phonon scattering and the further reducion of lattice thermal conductivity at high temperatures. As a consequence, the resultant TE figure of merit (ZT) reaches 0.5 at 873 K, which is 25% higher compared to 0.4 for Cu4Sn7.5S16.

Unequal bonding in Ag-CuIn3Se5-based solid solutions responsible for reduction in lattice thermal conductivity and improvement in thermoelectric performance.

Owing to their unique crystal and band structures, in thermoelectrics increasing attention has recently been paid to compounds of the ternary I-III-VI chalcopyrite family. In this work, unequal bonding between cation and anion pairs in Cu1-y Ag y In3Se4.9Te0.1 solid solutions, which can be effectively used to disturb phonon transport, has been proposed. The unequal bonding, which is represented by the difference of bond lengths Δd, Δd = d (Cu-Se) - d (In-Se) and anion position displacement from its equilibrium position Δu = u - 0.25, is created by the isoelectronic substitution of Ag for Cu. At y = 0.2 both the Δd and Δu values reach their maxima, resulting in a remarkable reduction in lattice thermal conductivity (κ L) and an improvement in TE performance. However, as the y value increase to 0.3 both Δd and Δu values decrease, causing the κ L value to increase and the ZT value to decrease from 0.5 to 0.24 at 930 K. Accordingly, unequal bonding might be an alternative way to improve the TE performance of ternary chalcopyrites.

PKA/CREB and NF-κB pathway regulates AKNA transcription: A novel insight into T-2 toxin-induced inflammation and GH deficiency in GH3 cells.

Chronic exposure to low dose of T-2 toxin causes growth retardation and reduced body weight, resulting in economic losses. Excessive inflammatory cytokines and GH deficiency are important mechanisms that contribute to growth inhibition induced by T-2 toxin. However, the regulation of the inflammatory cytokines expecially IL-6, IL-1ß, and TNF-α induced by T-2 toxin still remained unclear. The new transcription factor AKNA, belonging to AT-hook protein family, is closely associated with inflammation. However, it was unclear how AKNA regulate the expression of inflammatory cytokines, and there was no report on the role of AKNA in T-2 toxin mediated toxicity. Here, we investigated the role of AKNA in T-2 toxin-mediated inflammatory response and GH deficiency and the signal transduction pathway of AKNA. We showed that AKNA regulated by PKA/CREB and NF-κB pathway is a novel downstream molecular target in T-2 toxin-mediated inflammation and GH deficiency. T-2 toxin activates the PKA/CREB and NF-κB/p65 pathways, thereby promoting the direct binding of phospho-CREB and phospho-p65 to the AKNA promoter, thus inhibiting AKNA expression. GH and inflammatory cytokines (TNF-α, IL-1ß, and IL-6) expression were significantly downregulated after AKNA silencing. Furthermore, the expression of differential genes induced by T-2 toxin in the rat pituitary was further confirmed by acute toxicity tests in rats, which was consistent with the results in GH3 cells. By histopathological analysis, we confirmed the pituitary might be a novel direct target organ of T-2 toxin. These findings provided new insights into the significant role of AKNA in T-2 toxin-induced inflammatory response and growth inhibition.

Real-time online photonic random number generation.

We present a real-time scheme for ultrafast random number (RN) extraction from a broadband photonic entropy source. Ultralow jitter mode-locked pulses are used to sample the stochastic intensity fluctuations of the entropy source in the optical domain. A discrete self-delay comparison technology is exploited to quantize the sampled pulses into continuous RN streams directly. This scheme is bias free, eliminates the electronic jitter bottleneck confronted by currently available physical RN generators, and has no need for threshold tuning and post-processing. To demonstrate its feasibility, we perform a proof-of-principle experiment using an optically injected chaotic laser diode. RN streams at up to 7 Gb/s with verified randomness were thereby successfully extracted in real time. With the provision of a photonic entropy source with sufficient bandwidth, the present approach is expected to provide RN generation rates of several tens of gigabits per second.

Nitric oxide (NO)-mediated mitochondrial damage plays a critical role in T-2 toxin-induced apoptosis and growth hormone deficiency in rat anterior pituitary GH3 cells.

T-2 toxin, a major compound of trichothecenes, induces cell apoptosis and growth hormone (GH) deficiency and causes considerable growth retardation in animals and human cells. However, the mechanism underlying its growth suppression still remains unclear. Recent studies have suggested that ROS induced cell apoptosis and animal feed intake reduction, but there are limited reports on the role of RNS in T-2 toxin-mediated mitochondrial damage, cell apoptosis and growth retardation. Herein, T-2 toxin-induced GH3 cell damage and apoptosis were tested by MTT assay, LDH leakage and flow cytometry, respectively. Intracellular NO and antioxidant enzyme activity, ΔΨm, morphometric changes of mitochondria, the caspase pathway, and inflammatory factors were investigated. Free radical scavengers NAC, SOD and NO scavenger haemoglobin were used to explore the role of oxidative stress and the relationship between NO production and caspase pathway. The results clearly revealed that T-2 toxin caused significant increases in NO generation, cell apoptosis, GH deficiency, increased iNOS activity, upregulation of inflammatory factors and caspase pathway, decreases in ΔΨm and morphosis damage. These data suggest that mitochondria are a primary target of T-2 toxin-induced NO, and NO is a key mediator of T-2 toxin-induced cell apoptosis and GH deficiency via the mitochondria-dependent pathway in cells.

All-optical analog comparator.

An analog comparator is one of the core units in all-optical analog-to-digital conversion (AO-ADC) systems, which digitizes different amplitude levels into two levels of logical '1' or '0' by comparing with a defined decision threshold. Although various outstanding photonic ADC approaches have been reported, almost all of them necessitate an electrical comparator to carry out this binarization. The use of an electrical comparator is in contradiction to the aim of developing all-optical devices. In this work, we propose a new concept of an all-optical analog comparator and numerically demonstrate an implementation based on a quarter-wavelength-shifted distributed feedback laser diode (QWS DFB-LD) with multiple quantum well (MQW) structures. Our results show that the all-optical comparator is very well suited for true AO-ADCs, enabling the whole digital conversion from an analog optical signal (continuous-time signal or discrete pulse signal) to a binary representation totally in the optical domain. In particular, this all-optical analog comparator possesses a low threshold power (several mW), high extinction ratio (up to 40 dB), fast operation rate (of the order of tens of Gb/s) and a step-like transfer function.

Brownian motion properties of optoelectronic random bit generators based on laser chaos.

The nondeterministic property of the optoelectronic random bit generator (RBG) based on laser chaos are experimentally analyzed from two aspects of the central limit theorem and law of iterated logarithm. The random bits are extracted from an optical feedback chaotic laser diode using a multi-bit extraction technique in the electrical domain. Our experimental results demonstrate that the generated random bits have no statistical distance from the Brownian motion, besides that they can pass the state-of-the-art industry-benchmark statistical test suite (NIST SP800-22). All of them give a mathematically provable evidence that the ultrafast random bit generator based on laser chaos can be used as a nondeterministic random bit source.

Fully photonics-based physical random bit generator.

We propose a fully photonics-based approach for ultrafast physical random bit generation. This approach exploits a compact nonlinear loop mirror (called a terahertz optical asymmetric demultiplexer, TOAD) to sample the chaotic optical waveform in an all-optical domain and then generate random bit streams through further comparison with a threshold level. This method can efficiently overcome the electronic jitter bottleneck confronted by existing RBGs in practice. A proof-of-concept experiment demonstrates that this method can continuously extract 5 Gb/s random bit streams from the chaotic output of a distributed feedback laser diode (DFB-LD) with optical feedback. This limited generation rate is caused by the bandwidth of the used optical chaos.

Further investigations into the genotoxicity of quinoxaline-di-N-oxides and their primary metabolites.

Quinoxaline-di-N-oxides (QdNOs) are potential antibacterial agents with a wide range of biological properties. Quinocetone (QCT), carbadox (CBX), olaquindox (OLA), mequindox (MEQ) and cyadox (CYA) are classical QdNOs. Though the genotoxicity of parent drugs has been evaluated, the genotoxicity of their primary N â†’ O reduced metabolites remains unclear. In the present study, a battery of four different short-term tests, mouse lymphoma assay (MLA), Ames test, chromosomal aberration assay in vitro and bone marrow erythrocyte micronucleus assay in vivo was carried out to investigate the genotoxicity of the six primary N â†’ O reduced metabolites. Additionally, the genotoxicity of five parent drugs was evaluated by the MLA. Strong genotoxicity of N1-MEQ, B-MEQ and B-CBX was found in three of the assays but not in the Ames assay, and the rank order was N1-MEQ>B-MEQ>B-CBX that is consistent with prototype QdNOs. Negative results for the five QdNOs were noted in the MLA. We present for the first time a comparison of the genotoxicity of primary N â†’ O reduced metabolites, and evaluate the ability of five QdNOs to cause mutations in the MLA. The present study demonstrates that metabolites are involved in genetic toxicity mediated by QdNOs, and improve the prudent use of QdNOs for public health.

Lattice defects and thermoelectric properties: the case of p-type CuInTe2 chalcopyrite on introduction of zinc.

I-III-VI2 chalcopyrites have unique inherent crystal structure defects, and hence are potential candidates for thermoelectric materials. Here, we identified mixed polyanionic/polycationic site defects (ZnIn(-), VCu(-), InCu(2+) and/or ZnCu(+)) upon Zn substitution for either Cu or In or both in CuInTe2, with the ZnIn(-) species originating from the preference of Zn for the cation 4b site. Because of the mutual reactions among these charged defects, Zn substitution in CuInTe2 alters the basic conducting mechanism, and simultaneously changes the lattice structure. The alteration of the lattice structure can be embodied in an increased anion position displacement (u) or a reduced bond length difference (Δd) between d(Cu-Te)4a and d(In-Te)4b with increasing Zn content. Because of this, the lattice distortion is diminished and the lattice thermal conductivity (κL) is enhanced. The material with simultaneous Zn substitution for both Cu and In had a low κL, thereby we attained the highest ZT value of 0.69 at 737 K, which is 1.65 times that of Zn-free CuInTe2.

All-fiber normal-dispersion single-polarization passively mode-locked laser based on a 45°-tilted fiber grating.

An all-fiber normal-dispersion Yb-doped fiber laser with 45°-tilted fiber grating (TFG) is, to the best of our knowledge, experimentally demonstrated for the first time. Stable linearly-chirped pulses with the duration of 4 ps and the bandwidth of 9 nm can be directly generated from the laser cavity. By employing the 45° TFG with the polarization-dependent loss of 33 dB, output pulses with high polarization extinction ratio of 26 dB are implemented in the experiment. Our result shows that the 45° TFG can work effectively as a polarizer, which could be exploited to single-polarization all-fiber lasers.