Bioinspired sensor chip for detection of miRNA-21 based on photonic crystals assisted cyclic enzymatic amplification method

Photonic crystal-enhanced fluorescence biosensor with logic gate operation based on one-pot cascade amplification DNA circuit for enzyme-free and ultrasensitive analysis of two microRNAs

The development of sensitive and efficient analytical methods for multiple biomarkers is crucial for cancer screening at early stage. MicroRNAs (miRNAs) are a kind of biomarkers with diagnostic potential for cancer. However, the ultrasensitive and logical analysis of multiple miRNAs with simple operation still faces some challenges. Herein, a photonic crystal (PC)-enhanced fluorescence biosensor with logic gate operation based on one-pot cascade amplification DNA circuit was developed for enzyme-free and ultrasensitive analysis of two cancer-related miRNAs. The fluorescence biosensor was performed by biochemical recognition amplification module (BCRAM) and physical enhancement module (PEM) to achieve logical and sensitive detection. In the BCRAM, one-pot cascade amplification circuit consisted of the upstream parallel entropy-driven circuit (EDC) and the downstream shared catalytic hairpin assembly (CHA). The input of target miRNA would trigger each corresponding EDC, and the parallel EDCs released the same R strand for triggering subsequent CHA; thus, the OR logic gate was obtained with minimization of design and operation. In the PEM, photonic crystal (PC) array was prepared easily for specifically enhancing the fluorescence output from BCRAM by the optical modulation capabilities; meanwhile, the high-throughput signal readout was achieved by microplate analyzer. Benefiting from the integrated advantages of two modules, the proposed biosensor achieved ultrasensitive detection of two miRNAs with easy logic gate operation, obtaining the LODs of 8.6 fM and 6.7 fM under isothermal and enzyme-free conditions. Hence, the biosensor has the advantages of high sensitivity, easy operation, multiplex and high-throughput analysis, showing great potential for cancer screening at early stage.

DSN signal amplification strategy based nanochannels biosensor for the detection of miRNAs

MiRNA-21 is recognized as an important biological marker for the diagnosis, treatment, and prognosis of breast cancer. Here, we have created a nanochannel biosensor utilizing the duplex-specific nuclease (DSN) signal amplification strategy to achieve the detection of miRNAs. In this system, DNA as the capture probe was covalently immobilized on the surface of nanochannels, which hybridized with the target miRNA and forms RNA/DNA duplexes. DSN could cleave the probe DNA in RNA/DNA duplexes, recycling target miRNA, which may again hybridized with other DNA probes. After N cycles, most of the DNA probes had been cleaved, and the content of miRNA could be quantified by detecting changes in surface charge density. This biosensor can distinguish miR-21 from non-complementary miRNAs and one-base mismatched miRNAs, with reliable detection limits as low as 1 fM in PBS. In addition, we had successfully applied this method to analysis of total RNA samples in MCF-7 cells and HeLa cells, and the nanochannels had also shown excellent responsiveness and strong anti-interference ability. This new method is expected to contribute to miRNA detection in clinical diagnostics, providing a unique approach to detecting and distinguishing disease-associated molecules.

Superparamagnetic photonic crystals with DNA probes for rapid visual detection of mercury

A novel superparamagnetic photonic crystal DNA probe (Fe3O4@SiO2@amino@DNA SPC) was developed to enable rapid visual detection of Hg2+. This unique photonic crystal (PC) was synthesized by combining superparamagnetic nanospheres with DNA probes. The DNA probe, rich in thymine (T), detects mercury ions through base mismatch, resulting in the formation of T-Hg2+-T loop hairpin structures. With the binding of Hg2+ to the probe attached to superparamagnetic nanospheres, the PC structure assembled by these nanospheres, formed by the magnetic field, was changed. This change enhanced the reflection intensity; it could be quantified using a fiber optic spectrometer and was visible to the naked eye. The Fe3O4@SiO2@amino@DNA SPC, specific to Hg2+, exhibited a reflection peak at 679 nm, which intensified with increasing Hg2+ concentration. The reflection intensity increased by 132.58 a.u., and the PC color shifted from red to yellow as the Hg2+ concentration increased from 0.1 μg/L to 1 mg/L.

Photon Management Enabled by Opal and Inverse Opal Photonic Crystals: from Photocatalysis to Photoluminescence Regulation

Light is a promising renewable energy source and can be converted into heat, electricity, and chemical energy. However, the efficiency of light-energy conversion is largely hindered by limited light-absorption coefficients and the low quantum yield of current-generation materials. Photonic crystals (PCs) can adjust the propagation and distribution of photons because of their unique periodic structures, which offers a compelling platform for photon management. The periodicity of materials with an alternating refractive index can be used to manipulate the dispersion of photons to generate the photonic bandgap (PBG), in which light is reflected. The slow photon effect, i. e., photon propagation at a reduced group velocity near the edges of the PBG, is widely regarded as another valuable optical property for manipulating light. Furthermore, multiple light scattering can increase the optical path, which is a vital optical property for PCs. Recently, the light reflected by PBG, the slow photon effect, and multiple light scattering have been exploited to improve light utilization efficiency in photoelectrochemistry, materials chemistry, and biomedicine to enhance light-energy conversion efficiency. In this review, the fabrication of opal or inverse opal PCs and the theory for improving the light utilization efficiency of photocatalysis, solar cells, and photoluminescence regulation are discussed. We envision photon management of opal or inverse opal PCs may provide a promising avenue for light-assisted applications to improve light-energy-conversion efficiency.

Cytosine-rich mismatched DNA aptamer combined with superparamagnetic photonic crystal sensing material for the specific visual detection of silver ions

DNA aptamer superparamagnetic photonic crystals (DSPCs), enriched with a highly selective cytosine-rich mismatched single-stranded DNA aptamer (CRDA), were successfully employed in a novel visual detection strategy for the detection of silver ions (Ag+). The technologies of superparamagnetic colloidal nanospheres (SCNs), DNA aptamer, and photonic crystals were combined to fabricate DPSCs. The aptamer was immobilized via electrostatic adsorption with amino groups that were chemically introduced on the surface of the SCNs, forming D-NH-SCNs. The detection is achieved by forming an Ag+ complex (C-Ag+-C) between Ag+ and D-NH-SCN. The DSPCs assembled under a magnetic field by D-NH-SCNs effectively detected Ag+ in the range of 1 μg/L to 5 mg/L, corresponding to the critical concentration range for heavy metals in drinking water. During the detection, the DSPC exhibited a wavelength blueshift from 652.8 nm to 626.4 nm (26.4 nm), as well as changes in reflection intensity. Notably, when detecting Ag+, a change in DSPC color from orange to yellow was observed. In summary, the developed visual detection material facilitates direct Ag + sensing. In the future, different DNA aptamers will be modified further to detect various targets in the fields of medicine, environmental monitoring, and food safety.

Target-initiated triplex signal amplification cascades for non-label and sensitive fluorescence sensing of microRNA

The aberrant expression of microRNAs (miRs) in cells is closely linked to the initiation and progression of various diseases. Sensitive monitoring of their level is hence vital for biomedical research and disease diagnosis. Herein, a highly sensitive and non-label fluorescence sensor based on multiple recycling signal amplification cascades is constructed for the detection of miR-21 in human sera. The presence of miR-21 initiates the primer-fueled target recycling process for the generation of many primer/hairpin templates for the subsequent auto-cycling primer extension (APE) amplification cycles, which result in the formation of lots of long-stem hairpins. The enzyme-based cleavage of such hairpins via polymerization/excision cycles further leads to the generation of abundant G-quadruplex strands, which associate with the thioflavin T (ThT) dye to emit remarkably magnified fluorescence for detecting miR-21 in the range of 1 pM-100 nM with a 0.32 pM detection limit without labeling the probes. Besides, the proposed assay can selectively discriminate miR-21 against other control molecules and realize the sensing of low levels of miR-21 in diluted sera. With features of high sensitivity via the triplex signal amplification cycles and simplicity in a non-label homogeneous manner, our miR sensing protocol can be a robust means for detecting various nucleic acids for the early diagnosis of diseases.

Label-Free, High-Throughput, Sensitive, and Logical Analysis Using Biomimetic Array Based on Stable Luminescent Copper Nanoclusters and Entropy-Driven Nanomachine

The development of an array for high-throughput and logical analysis of biomarkers is significant for disease diagnosis. DNA-templated copper nanoclusters (CuNCs) have a strong potential to serve as a label-free photoluminescence source in array platforms, but their luminescent stability and sensitivity need to be improved. Herein, we report a facile, sensitive, and robust biomimetic array assay by integrating with stable luminescent CuNCs and entropy-driven nanomachine (EDN). In this strategy, the luminescent stability of CuNCs was improved by adding fructose in CuNCs synthesis to offer a reliable label-free signal. Meanwhile, the DNA template for CuNCs synthesis was introduced into EDN with excellent signal amplification ability, in which the reaction triggered by target miRNA would cause the blunt/protruding conformation change of 3'-terminus accompanied by the production or loss of luminescence. In addition, a biomimetic array fabricated by photonic crystals (PCs) physically enhanced the emitted luminescent signal of CuNCs and achieved high-throughput signal readout by a microplate reader. The proposed assay can isothermally detect as low as 4.5 pM of miR-21. Moreover, the logical EDN was constructed to achieve logical analysis of multiple miRNAs by "AND" or "OR" logic gate operation. Therefore, the proposed assay has the advantages of label-free property, high sensitivity, flexible design, and high-throughput analysis, which provides ideas for developing a new generation of facile and smart platforms in the fields of biological analysis and clinical application.

Smartphone conducted DNA portable quantitative detection platform based on photonic crystals chip and magnetic nanoparticles

It is of great significance to develop a highly sensitive and intuitive virus detection tool. A portable platform is constructed for quantitative detection of viral DNA based on the principle of fluorescence resonance energy transfer (FRET) between upconversion nanoparticles (UCNPs) and graphene oxide nanosheets (GOs) in this work. To implement a high sensitivity and low detection limit, GOs are modified by magnetic nanoparticles to prepare magnetic graphene oxide nanosheets (MGOs). Among them, the application of MGOs can not only eliminate the background interference, but also amplify the fluorescence intensity to a certain extent. Whereafter, a simple carrier chip based on photonic crystals (PCs) is introduced to realize a visual solid-phase detection, which also amplifies the luminescence intensity of the detection system. Finally, under the application of the 3D printed accessory and smartphone program of red-green-blue (RGB) evaluation, the portable detection can be completed simply and accurately. In a word, this work proposes a portable DNA biosensor with the triple functions of quantification, visualization and real-time detection can be used as a high-quality viral detection strategy and clinical diagnosis method.

A combination of angle insensitive stopband/passband filters based on one-dimensional hyperbolic metamaterial quasiperiodic photonic crystals

In the present work, we demonstrate the transmittance properties of one dimensional (1D) quasi-periodic photonic crystals that contain a superconductor material and a hyperbolic metamaterial (HMM). A HMM layer is engineered by the subwavelength undoped and doped Indium Arsenide (InAs) multilayers. Many resonance peaks with angle stability are obtained from the proposed Fibonacci sequence structure using the transfer matrix method (TMM). In this case, the Fibonacci sequence serves as the mainstay in the design of our structure. The permittivity of the utilized superconductor and the HMM are also analyzed, respectively. The numerical findings showed that the incident angle has no effect on the wavelength positions of the resonance peaks. The effects of many parameters such as the superconductor material thickness, Fibonacci sequence number, and sequence type are discussed for the proposed structure. At various operating temperatures and superconductor material types, the transmittance characteristics of the proposed structure were also examined. The designed structure can serve as a combination of pass/stop band filters for near-infrared (NIR) applications.

Bioinspired Materials for Wearable Devices and Point-of-Care Testing of Cancer

Wearable, point-of-care diagnostics, and biosensors are on the verge of bringing transformative changes in detection, management, and treatment of cancer. Bioinspired materials with new forms and functions have frequently been used, in both translational and commercial spaces, to fabricate such diagnostic platforms. Engineered from organic or inorganic molecules, bioinspired systems are naturally equipped with biorecognition and stimuli-sensitive properties. Mechanisms of action of bioinspired materials are deeply connected with thermodynamically or kinetically controlled self-assembly at the molecular and supramolecular levels. Thus, integration of bioinspired materials into wearable devices, either as triggers or sensors, brings about unique device properties usable for detection, capture, or rapid readout for an analyte of interest. In this review, we present the basic principles and mechanisms of action of diagnostic devices engineered from bioinspired materials, describe current advances, and discuss future trends of the field, particularly in the context of cancer.

Engineered Biosensors for Diagnosing Multidrug Resistance in Microbial and Malignant Cells

To curtail pathogens or tumors, antimicrobial or antineoplastic drugs have been developed. These drugs target microbial/cancer growth and survival, thereby improving the host's health. In attempts to evade the detrimental effects of such drugs, these cells have evolved several mechanisms over time. Some variants of the cells have developed resistances against multiple drugs or antimicrobial agents. Such microorganisms or cancer cells are said to exhibit multidrug resistance (MDR). The drug resistance status of a cell can be determined by analyzing several genotypic and phenotypic changes, which are brought about by significant physiological and biochemical alterations. Owing to their resilient nature, treatment and management of MDR cases in clinics is arduous and requires a meticulous approach. Currently, techniques such as plating and culturing, biopsy, gene sequencing, and magnetic resonance imaging are prevalent in clinical practices for determining drug resistance status. However, the major drawbacks of using these methods lie in their time-consuming nature and the problem of translating them into point-of-care or mass-detection tools. To overcome the shortcomings of conventional techniques, biosensors with a low detection limit have been engineered to provide quick and reliable results conveniently. These devices are highly versatile in terms of analyte range and quantities that can be detected to report drug resistance in a given sample. A brief introduction to MDR, along with a detailed insight into recent biosensor design trends and use for identifying multidrug-resistant microorganisms and tumors, is presented in this review.

A "turn-on" inverse opal photonic crystal fluorescent sensing film for detection of cysteine and its bioimaging of living cells

A "turn-on" inverse opal photonic crystal fluorescent sensing film infiltrated with a coumarin derivative is reported for the reliable and accurate detection of cysteine in human serum and fluorescence imaging of living cells. The coumarin derivative containing allyl ester specifically reacts with cysteine by ammonolysis to generate a fluorescent product whose emission wavelength is at ~ 535 nm, providing a selective fluorescence detection for cysteine. The emitted fluorescence is significantly enhanced due to the slow photon effect derived from the photonic crystal film. This is because the emission wavelength is overlapped with the blue-band edge of the photonic stopband of the selected inverse opal film. The fluorescence enhancement effect endows the prepared inverse opal film with highly sensitive detection with a limit of detection of 3.23 × 10^-9 mol/L and a wide linear detection range of 1 × 10^-7 - 1 × 10^-3 mol/L. A fast response within 30 s toward cysteine is also achieved due to the three-dimensional interconnected macroporous structure with a high-specific surface area of the inverse opal film. The prepared inverse opal fluorescent sensing film has been successfully applied to the detection of cysteine in human serum and bioimaging of living cells. In the diluted human serum, the recoveries for the detection of cysteine were 97.92 - 107.20%, and the relative standard deviations were 2.61-9.04%, demonstrating the potential applicability of the inverse opal fluorescent sensing film to real sample analysis. The method may provide a universal strategy for constructing various photonic crystal fluorescent sensing films by using different fluorescent probes.

A sensitive and facile microRNA detection based on CRISPR-Cas12a coupled with strand displacement amplification

MicroRNAs (miRNAs) are important biomarkers that are closely associated with certain diseases. The detection of miRNA is critical because it provides the necessary information for Disease Diagnosis. In this study, we achieved miRNA determination by coupling the CRISPR-Cas (Clustered regularly interspaced short palindromic repeats-CRISPR-associated) system with strand displacement amplification (SDA). In the experiment, miRNA was used as the initiator of SDA, and the activator of Cas12a nuclease activity was amplified by SDA. Subsequently, the unique nuclease activity of Cas12a was exploited to carry out trans cleaving on the ssDNA reporting probe modified with carboxyfluorescein(FAM) and BHQ1(dark Quencher: 480-580 nm) to achieve a signal output. In addition to chain design and reaction simplification, this method is lofty sensitive and selective for the determination of miRNA with a good linear range of 250 fmol·L^-1 ∼ 40 pmol·L^-1, the detection limit of 150 fmol·L^-1 (S/N = 3), and the method showed good recovery in spiked human serum. Overall, this method is expected to be applied to diagnosis with miRNA biomarkers because of its rapidity, high sensitivity, and high selectivity.

Amplification of the Fluorescence Signal with Clustered Regularly Interspaced Short Palindromic Repeats-Cas12a Based on Au Nanoparticle-DNAzyme Probe and On-Site Detection of Pb2+ Via the Photonic Crystal Chip

Although great headway has been made in DNAzyme-based detection of Pb²⁺, its adaptability, sensitivity, and accessibility in complex media still need to be improved. For this, we introduce new ways to surmount these hurdles. First, a spherical nucleic acid (SNA) fluorescence probe (Au nanoparticles-DNAzyme probe) is utilized to specifically identify Pb²⁺ and its suitability for precise detection of Pb²⁺ in complex samples due to its excellent nuclease resistance. Second, the sensitivity of Pb²⁺ detection is greatly enhanced via the use of a clustered regularly interspaced short palindromic repeats-Cas12a with target recognition accuracy to amplify the fluorescent signal upon the trans cleavage of the SNA (signal probe), and the limit of detection reaches as low as 86 fM. Third, we boost the fluorescence on photonic crystal chips with a bionic periodic arrangement by employing a straightforward detection device (smartphone and portable UV lamp) to achieve on-site detection of Pb²⁺ with the limit of detection as low as 24 pM. Based on the abovementioned efforts, the modified Pb²⁺ fluorescence sensor has the advantages of higher sensitivity, better specificity, accessibility, less sample consumption, and so forth. Moreover, it can be applied to accurately detect Pb²⁺ in complex biological or environmental samples, which is of great promise for widespread applications.

Functional nucleic acids in glycobiology: A versatile tool in the analysis of disease-related carbohydrates and glycoconjugates

As significant components of the organism, carbohydrates and glycoconjugates play indispensable roles in energy supply, cell signaling, immune modulation, and tumor cell invasion, and function as biomarkers since aberrance of them has been proved to be associated with the emergence and development of certain diseases. Functional nucleic acids (FNAs) have properties including easy-to-synthesize, good stability, good biocompatibility, low cost, and high programmability, they have attracted significant research attention and been incorporated into biosensors for detecting disease-related carbohydrates and glycoconjugates. This review summarizes the construction strategies and biosensing applications of FNAs-based biosensors in glycobiology in terms of target recognition and signal transduction. By illustrating the mechanisms and comparing the performances, the challenges and development opportunities in this area have been critically elaborated. We believe that this review will provide a better understanding of the role of FNAs in the analysis of disease-related carbohydrates and glycoconjugates, and inspire further discovery in fields that include glycobiology, chemical biology, clinical diagnosis, and drug development.

A Photoresponsive and Metal-Organic Framework Encapsulated DNA Tetrahedral Entropy-Driven Amplifier for High-Performance Imaging Intracellular MicroRNA

The further development of high-performance fluorescent biosensors to image intracellular microRNAs is beneficial to cancer medicine. By virtue of the need for enzymes and hairpin DNA probes, the entropy-driven reaction-assisted signal amplification strategy has shown an enormous potential to accomplish this task. Nevertheless, this good option still meets with poor biostability, low cell uptake efficiency, and unsatisfactory accuracy. On the basis of these challenges, we put forward here a battery of solving pathways. First, the straight DNA probes are anchored onto the vertexes of dual DNA tetrahedrons, and thus the enzyme resistance of the whole sensing system is observably enhanced. A metal-organic framework (ZIF-8 nanoparticle), which can be effectively dissociated into a weakly acidic environment, then is employed as an additional delivery vehicle to encapsulate such a DNA tetrahedron sustained biosensor and finally bring about a more efficient endocytosis. Last, a kind of photocleavage-linker triggered photoresponsive manner is incorporated to achieve an exceptional precise target identification, by which the biosensor can only be initiated under the irradiation of an externally mild 365 nm ultraviolet light source. In accordance with the above efforts, worthy assay performance toward microRNA-196a has given rise to this newly constructed biosensor, whose sensitivity is down to 2.7 pM and also able to distinguish single-base variation. Beyond that, the amplifier can work as a powerful imaging toolbox to accurately determine the targets in living cells, providing a promising intracellular sensing platform.

Optical Biosensors for Diagnostics of Infectious Viral Disease: A Recent Update

The design and development of biosensors, analytical devices used to detect various analytes in different matrices, has emerged. Biosensors indicate a biorecognition element with a physicochemical analyzer or detector, i.e., a transducer. In the present scenario, various types of biosensors have been deployed in healthcare and clinical research, for instance, biosensors for blood glucose monitoring. Pathogenic microbes are contributing mediators of numerous infectious diseases that are becoming extremely serious worldwide. The recent outbreak of COVID-19 is one of the most recent examples of such communal and deadly diseases. In efforts to work towards the efficacious treatment of pathogenic viral contagions, a fast and precise detection method is of the utmost importance in biomedical and healthcare sectors for early diagnostics and timely countermeasures. Among various available sensor systems, optical biosensors offer easy-to-use, fast, portable, handy, multiplexed, direct, real-time, and inexpensive diagnosis with the added advantages of specificity and sensitivity. Many progressive concepts and extremely multidisciplinary approaches, including microelectronics, microelectromechanical systems (MEMSs), nanotechnologies, molecular biology, and biotechnology with chemistry, are used to operate optical biosensors. A portable and handheld optical biosensing device would provide fast and reliable results for the identification and quantitation of pathogenic virus particles in each sample. In the modern day, the integration of intelligent nanomaterials in the developed devices provides much more sensitive and highly advanced sensors that may produce the results in no time and eventually help clinicians and doctors enormously. This review accentuates the existing challenges engaged in converting laboratory research to real-world device applications and optical diagnostics methods for virus infections. The review's background and progress are expected to be insightful to the researchers in the sensor field and facilitate the design and fabrication of optical sensors for life-threatening viruses with broader applicability to any desired pathogens.

A novel electrochemical biosensor for lung cancer-related gene detection based on copper ferrite-enhanced photoinitiated chain-growth amplification

We reported an electrochemical biosensor via CuFe₂O₄-enhanced photoinitiated chain-growth polymerization for ultrasensitive detection of lung cancer-related gene. In this work, photoinitiated atom transfer radical polymerization (ATRP) was applied to amplify the electrochemical signal corresponding to lung cancer-related gene, and polymerization was triggered off under the illumination of blue light which was involved in copper-mediated reductive quenching cycle. At the same time, CuFe₂O₄-H₂O₂ system was also activated to enhance polymerization based on the photocatalysis of CuFe₂O₄, which was based on the reaction between •OH and methacrylic monomers to generate carbon-based radicals. Numerous ferrocene-based polymer was graft onto electrode surface through this amplification stages. The limit of detection was low to 1.98 aM (in 10 μL, ∼11.9 molecules) (R² = 0.998) with a wide linear range from 0.1 fM to 10 pM. This strategy made a good trade-off between cost-effectiveness and sensitivity, and it also presented a high selectivity and anti-interference. In addition, the operation was greatly simplified and detection time was also shortened, which endowed this electrochemical DNA biosensor great application potential.

Biomimetic Chip Enhanced Time-Gated Luminescent CRISPR-Cas12a Biosensors under Functional DNA Regulation

Despite that the currently discovered CRISPR-Cas12a system is beneficial for improving the detection accuracy and design flexibility of luminescent biosensors, there are still challenges to extend target species and strengthen adaptability in complicated biological media. To conquer these obstacles, we present here some useful strategies. For the former, the limitation to nucleic acids assay is broken through by introducing a simple functional DNA regulation pathway to activate the unique trans-cleavage effect of this CRISPR system, under which the expected biosensors are capable of effectively transducing a protein (employing dual aptamers) and a metal ion (employing DNAzyme). For the latter, a time-gated luminescence resonance energy transfer imaging manner using a long-persistent nanophosphor as the energy donor is performed to completely eliminate the background interference and a nature-inspired biomimetic periodic chip constructed by photonic crystals is further combined to enhance the persistent luminescence. In line with the above efforts, the improved CRISPR-Cas12a luminescent biosensor not only exhibits a sound analysis performance toward the model targets (carcinoembryonic antigen and Na⁺) but also owns a strong anti-interference feature to actualize accurate sensing in human plasma samples, offering a new and applicative analytical tool for laboratory medicine.

PlasmiR: A Manual Collection of Circulating microRNAs of Prognostic and Diagnostic Value

Only recently, microRNAs (miRNAs) were found to exist in traceable and distinctive amounts in the human circulatory system, bringing forth the intriguing possibility of using them as minimally invasive biomarkers. miRNAs are short non-coding RNAs that act as potent post-transcriptional regulators of gene expression. Extensive studies in cancer and other disease landscapes investigate the protective/pathogenic functions of dysregulated miRNAs, as well as their biomarker potential. A specialized resource amassing experimentally verified, circulating miRNA biomarkers does not exist. We queried the existing literature to identify articles assessing diagnostic/prognostic roles of miRNAs in blood, serum, or plasma samples. Articles were scrutinized in order to exclude instances lacking sufficient experimental documentation or employing no biomarker assessment methods. We incorporated information from more than 200 biomedical articles, annotating crucial meta-information including cohort sizes, inclusion-exclusion criteria, disease/healthy confirmation methods and quantification details. miRNAs and diseases were systematically characterized using reference resources. Our circulating miRNA biomarker collection is provided as an online database, plasmiR. It consists of 1021 entries regarding 251 miRNAs and 112 diseases. More than half of plasmiR's entries refer to cancerous and neoplastic conditions, 183 of them (32%) describing prognostic associations. plasmiR facilitates smart queries, emphasizing visualization and exploratory modes for all researchers.

Optical Devices Constructed From Responsive Microgels for Polyphenols Detection

Polyphenols are used as antioxidants in various foods and beverages, which are considered to be a health benefit. The measurement of polyphenols contents is of great interest in food chemistry and health science. This work reported a microgels based photonic device (etalon) to detect polyphenols. Dopamine was used as a model compound of polyphenols. Herein, we proposed a “block” concept for dopamine detection. The dopamine was oxidized and formed dopamine films catalyzed by tyrosinase on the surface of etalon. As the etalon was immersed in ZnCl₂, the dopamine films blocked the ZnCl₂ diffusion into etalon that caused optical property changes. The film thickness is associated with the concentration of dopamine which can be readout via optical signals.

Sensitive detection of RNA based on concatenated self-fuelled strand displacement amplification and hairpin-AgNCs

Herein, a self-fuelled amplification strategy (SFAS) is proposed, in which two strand displacement amplification (SDA) processes were concatenated for the proliferation of ssDNA. The ssDNA then initiated a polymerase action and caused the destruction of hairpin-templated silver nanoclusters (AgNCs), resulting in decreased fluorescence for sensing miRNA-21. This SFAS-based sensor is less complicated in design and facile in operation, because of the easy concatenation of SDA and mutual enzymes used in the signal output process. The sensitivity of this SFAS-based miRNA sensor was 1.78 × 10^-11 M with a linear relationship in the range 0.02-1.0 × 10^-9 M, and the recoveries of this method ranged from 82.07% to 106.58% with an average RSD of 10.96%.

A two-dimensional photonic crystal hydrogel biosensor for colorimetric detection of penicillin G and penicillinase inhibitors

A simple penicillinase functionalized two-dimensional photonic crystal hydrogel (2DPPCH) biosensor was developed for colorimetric detection of penicillin G and penicillinase inhibitors. The penicillinase can specifically recognize penicillin G and catalyze it to produce penicilloic acid, which decreases the pH of the hydrogel microenvironment and shrinks the pH-sensitive hydrogel. The particle spacing decrease of the 2D photonic crystal array induced by the hydrogel shrinkage further causes a blue-shift in the diffraction wavelength. While the hydrolysis reaction is repressed upon treatment with clavulanate potassium (a kind of penicillinase inhibitor), no significant change in the diffraction wavelength is found. The detection of targets can be achieved by measuring the Debye diffraction ring diameter or observing the structural color change in the visible region. The lowest detectable concentrations for penicillin G and clavulanate potassium are 1 μM and 0.1 μM, respectively. Moreover, the 2DPPCH is proved to exhibit high selectivity and an excellent regeneration property, and it shows satisfactory performance for penicillin G analysis in real water samples.

Photonic crystal based biosensors: Emerging inverse opals for biomarker detection

Photonic crystal (PC)-based inverse opal (IO) arrays are one of the substrates for label-free sensing mechanism. IO-based materials with their advanced and ordered three-dimensional microporous structures have recently found attractive optical sensor and biological applications in the detection of biomolecules like proteins, DNA, viruses, etc. The unique optical and structural properties of IO materials can simplify the improvements in non-destructive optical study capabilities for point of care testing (POCT) used within a wide variety of biosensor research. In this review, which is an interdisciplinary investigation among nanotechnology, biology, chemistry and medical sciences, the recent fabrication methodologies and the main challenges regarding the application of (inverse opals) IOs in terms of their bio-sensing capability are summarized.

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The recent main challenges regarding the application of inverse opals (IOs) in the detection of biomolecules are reviewed.

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Sensing mechanisms of biomolecules including glucose, proteins, DNA, viruses were summarized.

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IO materials with their ordered 3D microporous structures have found attractive optical biosensor applications.