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Early detection, diagnosis and treatment of human immune deficiency virus (HIV) infection is the key to reduce acquired immunodeficiency syndrome (AIDS) mortality. In our research, an innovative surface plasmon resonance (SPR) biosensing strategy has been developed for highly sensitive detection of HIV-related DNA based on entropy-driven strand displacement reactions (ESDRs) and double-layer DNA tetrahedrons (DDTs). ESDRs as enzyme-free and label-free signal amplification circuit can be specifically triggered by target DNA, leading to the cyclic utilization of target DNA and the formation of plentiful double-stranded DNA (dsDNA) products. Subsequently, the dsDNA products bind to the immobilized hairpin capture probes and further combine with DDTs nanostructures. Due to the high efficiency of ESDRs and large molecular weight of DDTs, the SPR response signal was enhanced dramatically. The proposed SPR biosensor could detect target DNA sensitively and specifically in a linear range from 1pM to 150nM with a detection limit of 48fM. In addition, the whole detecting process can be accomplished in 60min with high accuracy and duplicability. In particular, the developed SPR biosensor was successfully used to analyze target DNA in complex biological sample, indicating that the developed strategy is promising for rapid and early clinical diagnosis of HIV infection.

A novel colorimetric biosensing strategy, employing coupling spontaneous cascade catalytic hairpin assembly (CHA) circuits and mismatched hairpin, has been developed successfully for ultrasensitive and specific detection of target microRNA (miRNA). This system is composed of two layers of CHA. While target miRNA exists, the toehold-based assembly of the first-layer hairpins comes into being, followed by the generation of the first-layer CHA products and the cyclic release of the target miRNA. Then the first-layer CHA products can act as initiator for the assembly of the second-layer hairpins to produce the second-layer CHA products, with the first-layer CHA products recovered simultaneously. Finally, the second-layer CHA products can combine with hemin to form G-quadruplex/hemin DNAzyme, a well-known horseradish peroxidase (HRP) mimic, for catalyzing a colorimetric reaction. Under the optimal experimental conditions, the established biosensor can detect target miRNA down to 36.2 fM (S/N = 3) with a linear range from 100 fM to 10 nM, and discriminate target miRNA from mismatched miRNA with high selectivity. It was also applied to test the concentration of miRNA spiked into salmon sperm samples. Therefore, this biosensing strategy may become an alternative tool for the detection of miRNA in biomedical research.

Sensitive and specific detection of HIV-related DNA is of great importance for early accurate diagnosis and therapy of HIV-infected patients. Here, we developed a one-step and rapid fluorescence strategy for HIV-related DNA detection based on strand displacement amplification and a Mg2+-dependent DNAzyme reaction. In the presence of target HIV DNA, it can hybridize with template DNA and activate strand displacement amplification to generate numerous DNAzyme sequences. With the introduction of Mg2+, DNAzyme can be activated to circularly cleave the substrate DNA, which leads to the separation of fluorophore reporters from the quenchers, resulting in the recovery of the fluorescence. Under the optimal experimental conditions, the established biosensing method can detect target DNA down to 61 fM with a linear range from 100 fM to 1 nM, and discriminate target DNA from mismatched DNA perfectly. In addition, the developed biosensing strategy was successfully applied to assay target DNA spiked into human serum samples. With the advantages of fast, easy operation and high-performance, this biosensing strategy might be an alternative tool for clinical diagnosis of HIV infection.

In this paper, a co-designed compact filtering monopole antenna based on the recently developed two-stage split ring resonator (SRR)-inspired high-frequency-selective filter is proposed and demonstrated. The used filter is consisting of two groups of twist-modified SRRs and is inserted in the feeding line of a conventional wide band planar monopole antenna to filter out the unwanted out-of-band antenna gain. The impedance matching and radiation gain of the co-designed filtering antenna are numerically and experimentally demonstrated and a good agreement between them is obtained. The measured results show that such filtering antenna has a 3-dB gain bandwidth of 16.7% centered at 2.4 GHz with peak gain of 2.4 dBi and sharp dropped out-of-band radiation gain feature.

The authors describe an electrochemical sensing strategy for highly sensitive and specific detection of target (analyte) DNA based on an amplification scheme mediated by a multicomponent nucleic acid enzyme (MNAzyme). MNAzymes were formed by multicomponent complexes which produce amplified “output” signals in response to specific “input” signal. In the presence of target nucleic acid, multiple partial enzymes (partzymes) oligonucleotides are assembled to form active MNAzymes. These can cleave H0 substrate into two pieces, thereby releasing the activated MNAzyme to undergo an additional cycle of amplification. Here, the two pieces contain a biotin-tagged sequence and a byproduct. The biotin-tagged sequences are specifically captured by the detection probes immobilized on the gold electrode. By employing streptavidinylated alkaline phosphatase as an enzyme label, an electrochemical signal is obtained. The electrode, if operated at a working potential of 0.25 V (vs. Ag/AgCl) in solution of pH 7.5, covers the 100 pM to 0.25 μM DNA concentration range, with a 79 pM detection limit. In our perception, the strategy introduced here has a wider potential in that it may be applied to molecular diagnostics and pathogen detection.

This Letter proposes a circularly polarised (CP) monopole antenna with filtering function, which is achieved by integrating a miniaturised coupled filter based on the bent-loop resonators. The circular-polarisation is obtained by using the falcate-shaped patch as the radiation part, and the existence of the coupled filter in the feeding line would not affect the CP radiation performances. Both numerical simulation and experimental demonstration are performed for the designed CP filtering antenna, and good agreements are obtained. The designed antenna with dimension of 70 × 75 mm2 exhibits good frequency selective performances for the return loss, gain and axial ratio at 2.45 GHz with measured impedance matching bandwidth (|S 11| < 10 dB) of 0.23 GHz. Such CP filtering antenna is a good candidate for the emerging application area, e.g. wearable biotelemetric devices.

In this paper, two co-designed linear and circular polarized compact filtering monopole antennas based on the recently developed miniaturized coupled filter, namely the two-stage split ring resonator (SRR)-inspired high-frequency-selective filter, are proposed and demonstrated. The used filter is consisting of two groups of twist-modified SRRS and is inserted in the feeding line of the conventional wide band planar monopole antennas to filter out the unwanted out-of-band antenna gain. The measured results show that such filtering antennas have sharp dropped out-of-band radiation gain feature. These filtering antennas is suitable for the Internet of Things devices application.

DNA methyltransferase (MTase) activity assay and its inhibitor screening are important for the diagnosis and treatment of methylation-related diseases. Herein, a label-free and highly sensitive biosensing method based on entropy-driven reaction and toehold-initiated rolling circle amplification (TIRCA) was developed for DNA MTase activity detection and inhibitor screening. Briefly, in the presence of MTase, the triple-stranded complex (TSC) could be methylated to avoid cleaving by MboI endonuclease. The complete TSC was able to initiate downstream entropy-driven reaction and TIRCA to produce G-quadruplex that can bind with Thioflavin T (ThT) to output fluorescent signal. Under the optimal experimental conditions, the established biosensing strategy could detect Dam MTase down to 0.06 U/mL with a linear range from 0.1 U/mL to 40 U/mL. Importantly, the signal-to-noise (S/N) of this biosensing strategy was extremely high. This strategy could discriminate target Dam MTase from another two MTases efficiently. Moreover, this developed biosensing method was applied to screen DNA MTase inhibitors. Therefore, we anticipate this unique strategy will serve as an alternative tool to detect DNA MTase activity and screen its inhibitors in clinical diagnosis and therapeutics.

This paper investigates the problem of $H_\infty $ stabilization for nonuniform sampling fuzzy systems. To achieve better performance, a parallel distributed compensation scheme is proposed to design a nonlinear controller. By taking the deviation bounds of asynchronous normalized membership functions into account, the $H_\infty $ stability criterion is first obtained, which is dependent on the deviation bounds of asynchronous normalized membership functions. To reduce the computational complexity, a method for eliminating slack variables and a structured vertex separator for reducing the number of linear matrix inequalities are provided, and then an $H_\infty $ stabilization criterion with less complexity and less conservatism is obtained. Finally, an illustrative example is given to show the effectiveness of the proposed method and the significant improvement on the existing results.