Luminescent Graphene Oxide with a Peptide‐Quencher Complex for Optical Detection of Cell‐Secreted Proteases by a Turn‐On Response

Graphene oxide (GO) is an emerging luminescent nanomaterial with photostable and unique photoluminescence (PL) in the visible and near‐infrared region. Herein, a GO PL‐based optical biosensor consisting of a luminescent GO donor covalently linked with a peptide‐quencher complex is reported for the simple, rapid, and sensitive detection of proteases. To this end, the quenching efficiency of various candidate quenchers of GO fluorescence, such as metalloprotoporphyrins and QXL₅₇₀, are examined and their quenching mechanisms investigated. A fluorescence resonance energy transfer‐based quencher, QXL₅₇₀, is found to be much more effective for quenching the intrinsic fluorescence of GO than other charge transfer‐based quenchers. The designed GO–peptide–QXL system is then able to sensitively detect specific proteases—chymotrypsin and matrix metalloproteinase‐2—via a “turn‐on” response of quenched GO fluorescence after proteolytic cleavage of the quencher. Finally, the GO–peptide–QXL hybrid successfully detects MMP‐2 secreted from living cells—human hepatocytes HepG2—with high sensitivity.     

Live Lymphocyte Arrays for Biosensing

Systems designed to sensitively and accurately detect whole pathogen particles, their components, or other proteins diagnostic of infection or disease are of interest as sensors for biodefense and clinical diagnostics. To this end, we examined the potential of a sensing strategy based on live T‐cell/B‐cell interactions in a biosensor chip format. An approach to fabricate patterned hydrogel microwells functionalized at their bases with antibodies to promote specific immobilization of lymphocytes was developed and used to array single T cells in a regular pattern on a substrate. A sensing platform was created by overlaying arrayed T cells with a confluent layer of antigen‐capturing B cells. In this system, a peptide analyte added to the chip was captured by B cells and physically presented to arrayed T cells by B‐cell‐surface major histocompatibility complex molecules, triggering T cells through their T‐cell receptors. T‐cell recognition of the target peptide was detected by fluorescence measurements of T‐cell intracellular calcium levels, a biochemical read‐out of T‐cell receptor triggering. We demonstrate that this approach allows rapid, sensitive detection of a model peptide analyte, and that T‐cell arrays allow for maximal T‐cell/B‐cell contacts while simultaneously optimizing single‐cell fluorescence detection for analysis of the sensor response. This approach could be of interest for the design of sensing platforms that can detect both peptide fragments and whole intact pathogens, irrespective of surface mutations that might be induced naturally or during “weaponization”.     

Biosensor Array of Interpenetrating Polymer Network with Photonic Film Templated from Reactive Cholesteric Liquid Crystal and Enzyme‐Immobilized Hydrogel Polymer

A biosensor array is fabricated using an interpenetrating polymer network consisting of photonic film templated from reactive cholesteric liquid crystal (CLC) and enzyme‐immobilized polyacrylic acid (PAA). The solid‐state photonic film on the glass substrate is successfully templated by ultraviolet (UV) curing of the reactive CLC mixture of a reactive mesogen mixture of RMM 727 (from Merck) and a nonreactive chiral dopant of (S)‐4‐cyano‐4′‐(2‐methylbutyl)biphenyl following the extraction of the chiral dopant. The acrylic acid monomer mixed with a cross‐linker of tri(propylene glycol) diacrylate is infiltrated into the extracted space of the photonic film, and UV‐cured with a photomask to obtain a patterned array‐dot film. The interpenetrated cholesteric liquid crystal/hydrogel polymer network (CLC‐hydrogel‐IPN) array is further functionalized in the individual dots with urease, for a model study of biosensor array applications. The dots of the CLC‐hydrogel‐IPN array respond independently to the urea by a color change with high sensitivity and stability. Thus, the patterned CLC‐hydrogel‐IPN can be used as a new biosensor array for cost‐effective and easy visual detection without any sophisticated instruments.     

A Protein‐Nanocellulose Paper for Sensing Copper Ions at the Nano‐ to Micromolar Level

Tracing heavy metals is a crucial issue in both environmental and medical samples. In this work, a sensing biomolecule, the cyanobacterial C‐phycocyanin (CPC), is integrated into a nanocellulose matrix, and with this, a biosensor for copper ions is developed. The assembly of CPC‐functionalized nanocellulose into a red‐fluorescent, copper‐sensitive hybrid film “CySense”, enhances protein stability and facilitates the reuse and the regeneration of the sensor for several cycles over 7 days. CySense is suitable for the analysis of complex medical samples such as human serum filtrate. The reported biosensor reliably detects copper ion contents with a lower detection limit of 200 × 10^?9m and an IC50 of 4.9 × 10^?6m as changes in fluorescence emission intensity that can be measured with a fluorimeter or a microarray laser scanner.     

Tumor‐Microenvironment‐Adaptive Nanoparticles Codeliver Paclitaxel and siRNA to Inhibit Growth and Lung Metastasis of Breast Cancer

Prolonged circulation, specific and effective uptake by tumor cells, and rapid intracellular drug release are three main factors for the drug delivery systems to win the battle against metastatic breast cancer. In this work, a tumor microenvironment‐adaptive nanoparticle co‐loading paclitaxel (PTX) and the anti‐metastasis siRNA targeting Twist is prepared. The nanoparticle consists of a pH‐sensitive core, a cationic shell, and a matrix metalloproteinase (MMP)‐cleavable polyethylene glycol (PEG) corona conjugated via a peptide linker. PEG will be cut away by MMPs at the tumor site, which endows the nanoparticle with smaller particle size and higher positive charge, leading to more efficient cellular uptake in tumor cells and higher intra‐tumor accumulation of both PTX and siRNA in the 4T1 tumor‐bearing mice models compared to the nanoparticles with irremovable PEG. In addition, acid‐triggered drug release in endo/lysosomes is achieved through the pH‐sensitive core. As a result, the MMP/pH dual‐sensitive nanoparticles significantly inhibit tumor growth and pulmonary metastasis. Therefore, this tumor‐microenvironment‐adaptive nanoparticle can be a promising codelivery vector for effective therapy of metastatic breast cancer due to simultaneously satisfying the requirements of long circulating time, efficient tumor cell targeting, and fast intracellular drug release.     

Biological reaction signal enhancement in porous silicon Bragg mirror based on quantum dots fluorescence

In this paper, we mainly study the preparation of an optical biosensor based on porous silicon (PSi) Bragg mirror and its feasibility for biological detection. The quantum dot (QD) labeled biotin was pipetted onto streptavidin functionalized PSi Bragg mirror samples, the affinity reaction between QD labeled biotin and streptavidin in PSi occurred, so the QDs were indirectly connected to the PSi. The fluorescence of QD enhanced the signal of biological reactions in PSi. The performance of the sensor is verified by detecting the fluorescence of the QD in PSi. Due to the fluorescence intensity of the QDs can be enhanced by PSi Bragg mirror, the sensitivity of the PSi optical biosensor will be improved.     

Selective Zinc(II)‐Ion Fluorescence Sensing by a Functionalized Mesoporous Material Covalently Grafted with a Fluorescent Chromophore and Consequent Biological Applications

A highly ordered 2D‐hexagonal mesoporous silica material is functionalized with 3‐aminopropyltriethoxysilane. This organically modified mesoporous material is grafted with a dialdehyde fluorescent chromophore, 4‐methyl‐2,6‐diformyl phenol. Powder X‐ray diffraction, transmission electron microscopy, N₂ sorption, Fourier transform infrared spectroscopy, and UV‐visible absorption and emission have been employed to characterize the material. This material shows excellent selective Zn²⁺ sensing, which is due to the fluorophore moiety present at its surface. Fluorescence measurements reveal that the emission intensity of the Zn²⁺‐bound mesoporous material increases significantly upon addition of various concentrations of Zn²⁺, while the introduction of other biologically relevant (Ca²⁺, Mg²⁺, Na⁺, and K⁺) and environmentally hazardous transition‐metal ions results in either unchanged or weakened intensity. The enhancement of fluorescence is attributed to the strong covalent binding of Zn²⁺, evident from the large binding constant value (0.87 × 10⁴ M ^?1). Thus, this functionalized mesoporous material grafted with the fluorescent chromophore could monitor or recognize Zn²⁺ from a mixture of ions that contains Zn²⁺ even in trace amounts and can be considered as a selective fluorescent probe. We have examined the application of this mesoporous zinc(II) sensor to cultured living cells (A375 human melanoma and human cervical cancer cell, HeLa) by fluorescence microscopy.     

A Biosensor Based on Metallic Photonic Crystals for the Detection of Specific Bioreactions

An optical biosensor based on waveguided metallic photonic crystals (MPCs) is reported for the sensitive testing of biomolecular interactions, which provides practical approaches for the label‐free detection of specific bioreactions. The enhancement of the sensitivity or the amplification of the sensor signal by the coupling between the waveguide resonance mode and particle‐plasmon resonance (PPR) breaks through the “bottle‐neck” of the intrinsic response sensitivity defined by the spectral shift of the PPR. The success of this sensor is demonstrated by sensing the specific reaction between the HIV‐1 capsid protein (p24) antigen and the monoclonal anti‐p24 antibody, where the dynamics of the bioreactions can be recorded with a potentially high time resolution. This new sensor stands out due to its compact design and its new physics, compared with conventional devices, its simple operation, the simple fabrication of the MPC chip and the low cost of the whole system.     

A Direct,Multiplex Biosensor Platform for Pathogen Detection Based on Cross‐linked Polydiacetylene (PDA) Supramolecules

This study focuses on the development of a multiplex pathogen‐detection platform based on polydiacetylene (PDA) using a novel immobilization procedure. PDA liposome‐based solid sensors have a critical drawback as the PDA liposomes are not stably immobilized onto the solid substrate. Therefore, to overcome this problem, an interlinker, ethylenediamine, is introduced, which acts as a cross‐linker between individual PDA liposomes. The quantity of ethylenediamine added was optimized to 1 mM, as measured by the fluorescence signal emitted by the stably immobilized PDA liposomes, a concentration at which the fluorescence signal is 10 times higher than for the resulting PDA chips made without the interlinker. This procedure is used to manufacture PDA liposome‐based multiplex biosensor arrays for well‐known water and food‐borne pathogens. The fabricated biosensor was able to perform the simultaneous and quantitative detection of 6 species of pathogens. As such, the results demonstrated from this research can be exploited for the development of more advanced PDA‐based biosensors and diagnostics.     

Graphene‐Functionalized Natural Microcapsules: Modular Building Blocks for Ultrahigh Sensitivity Bioelectronic Platforms

Natural cellular materials with honeycomb or foam microstructures are excellent inspirations for the biomimetic design of sensitive and robust bioelectronic interfaces. Herein, the fabrication of a hierarchical, self‐assembled platform that combines a natural cellular material (Lycopodium clavatum pollen spores) with an electrically conductive material (reduced graphene oxide, defined as rGO) for the first time is reported. The spores function as natural building blocks which are functionalized with crumpled rGO and then deposited on a silicon oxide surface, yielding a 3D architecture with electroactive properties. The hybrid material design is incorporated into a field‐effect transistor device and employed in an antibody‐based detection scheme in order to measure the concentration of a target protein with a limit of detection of 1 × 10^?15 m , which is five orders of magnitude better than a conventional rGO‐based biosensor tested in comparison. The findings in this work highlight the merit of integrating natural cellular materials with electrically conductive materials, offering a framework to develop high‐sensitivity bioelectronic platforms.     

Quantum‐Dot‐Functionalized Poly(styrene‐co‐acrylic acid) Microbeads: Step‐Wise Self‐Assembly,Characterization, and Applications for Sub‐femtomolar Electrochemical Detection of DNA Hybridization

A novel nanoparticle label capable of amplifying the electrochemical signal of DNA hybridization is fabricated by functionalizing poly(styrene‐co‐acrylic acid) microbeads with CdTe quantum dots. CdTe‐tagged polybeads are prepared by a layer‐by‐layer self‐assembly of the CdTe quantum dots (diameter = 3.07 nm) and polyelectrolyte on the polybeads (diameter = 323 nm). The self‐assembly procedure is characterized using scanning and transmission electron microscopy, and X‐ray photoelectron, infrared and photoluminescence spectroscopy. The mean quantum‐dot coverage is (9.54 ± 1.2) × 10³ per polybead. The enormous coverage and the unique properties of the quantum dots make the polybeads an effective candidate as a functionalized amplification platform for labelling of DNA or protein. Herein, as an example, the CdTe‐tagged polybeads are attached to DNA probes specific to breast cancer by streptavidin–biotin binding to construct a DNA biosensor. The detection of the DNA hybridization process is achieved by the square‐wave voltammetry of Cd²⁺ after the dissolution of the CdTe tags with HNO₃. The efficient carrier‐bead amplification platform, coupled with the highly sensitive stripping voltammetric measurement, gives rise to a detection limit of 0.52 fmol L^?1 and a dynamic range spanning 5 orders of magnitude. This proposed nanoparticle label is promising, exhibits an efficient amplification performance, and opens new opportunities for ultrasensitive detection of other biorecognition events.     

High Surface Area Flexible Chemiresistive Biosensor by Oxidative Chemical Vapor Deposition

Fabrication of a chemiresistive biosensor for detection of biomolecules is demonstrated on a high surface area, flexible electro‐spun nylon fiber mat. For the first time, the –OH functionalized conducting copolymer of 3,4‐ethylenedioxythiophene (EDOT) and 3‐thiopheneethanol (3‐TE) is synthesized and conformally deposited on the electro‐spun mats by oxidative chemical vapor deposition (oCVD). The free –OH functional groups of the copolymer are available for immobilization of analyte specific biomolecules. Here, avidin and biotin molecules are employed as the analyte‐specific molecule and analyte respectively for their high specificity to each other. The sensitivities of avidin immobilized conducting copolymer on electro‐spun mats are tested against micro‐molar to nano‐molar concentrations of biotin in aqueous solutions. Application of electro‐spun fiber mat in this case enhances the sensor response 6 times when compared to a flat substrate and also significantly lowers the response time. In addition to the experimental studies, current work also includes modeling of the kinetics of the change of response for the biotin‐avidin interactions as a function of time. Most importantly, this fabrication technique promises an extremely sensitive and field deployable method for the detection of other biomolecules, for example, food pathogens.     

In Vivo Imaging of MMP‐13 Activity Using a Specific Polymer‐FRET Peptide Conjugate Detects Early Osteoarthritis and Inhibitor Efficacy

Imaging early molecular changes in osteoarthritic (OA) joints is instrumental for the development of disease‐modifying drugs. To this end, a fluorescent resonance energy transfer‐based peptide probe that is cleavable by matrix metalloproteinase 13 (MMP‐13) has been developed. This protease degrades type II collagen, a major matrix component of cartilage. The probe exhibits high catalytic efficiency (k_cat/K_M = 6.5 × 10⁵m ^?1 s^?1) and high selectivity for MMP‐13 over a set of nine MMPs. To achieve optimal in vivo pharmacokinetics and tissue penetration, the probe has been further conjugated to a linear l ‐polyglutamate chain of 30 kDa. The conjugate detects early biochemical events that occur in a surgically induced murine model of OA before major histological changes. The nanometric probe is suitable for the monitoring of in vivo efficacy of an orally bioavailable MMP‐13 inhibitor, which effectively blocks cartilage degradation during the development of OA. This new polymer‐probe can therefore be a useful tool in detecting early OA, disease progression, and in developing MMP‐13‐based disease‐modifying drugs for OA.     

A Substitution‐Dependent Light‐Up Fluorescence Probe for Selectively Detecting Fe3+ Ions and Its Cell Imaging Application

Deliberate design of specific and sensitive molecular probes with distinctive physical/chemical properties for analyte sensing is of great significance. Herein, by taking advantage of the position‐dependent substituent effects, an aggregation‐induced emission featured iron (III) probe from ortho‐substituted pyridinyl‐functionalized tetraphenylethylene (TPE‐o‐Py) is synthesized. It displays high sensitivity and selectivity toward iron (III) detection. The recognition arises from the position isomer of ortho‐substitution, and the fact that TPE‐o‐Py has a low acid dissociation constant (pK _a) that is close to that of hydrolyzed Fe³⁺. Importantly, TPE‐o‐Py as a light‐up fluorescence probe could be employed for Fe³⁺ sensing in living cells with a pronounced red‐shift in fluorescence emission.     

Laterally Coupled DFB Lasers for One-Step Growth Photonic Integrated Circuits in InP

Design and characterization of a transmitter building block for one-step growth photonic integration, featuring a 1310 - nm laterally coupled distributed-feedback laser with a front-side passive optical waveguide and a back-side optical power monitor, are presented. Formed on a semi-insulating Fe : InP substrate and processed by means of a stepper optical lithography, the device perfectly suits the multiguide vertical integration-a newly developed one-step growth photonic integrated technique in InP.     

Oxidized Porous Silicon Nanostructures Enabling Electrokinetic Transport for Enhanced DNA Detection

Nanostructured porous silicon (PSi) is a promising material for the label‐free detection of biomolecules, but it currently suffers from limited applicability due to poor sensitivity, typically in micromolar range. This work presents the design, operation concept, and characterization of a novel microfluidic device and assay that integrates an oxidized PSi optical biosensor with electrokinetic focusing for a highly sensitive label‐free detection of nucleic acids. Under proper oxidation conditions, the delicate nanostructure of PSi can be preserved, while providing sufficient dielectric insulation for application of high voltages. This enables the use of signal enhancement techniques, which are based on electric fields. Here, the DNA target molecules are focused using an electric field within a finite and confined zone, and this highly concentrated analyte is delivered to an on‐chip PSi Fabry–Pérot optical transducer, prefunctionalized with capture probes. Using reflective interferometric Fourier transform spectroscopy real‐time monitoring, a 1000‐fold improvement in limit of detection is demonstrated compared to a standard assay, using the same biosensor. Thus, a measured limit of detection of 1 × 10^?9 m is achieved without compromising specificity. The concepts presented herein can be readily applied to other ionic targets, paving way for the development of other highly sensitive chemical and biochemical assays.     

Active CMOS Array Sensor for Time-Resolved Fluorescence Detection

Surface-based sensing assays based on fluorescence-based detection have become commonplace for both environmental and biomedical diagnostics. Traditional array scanners are expensive, large, and complex instruments. This paper describes the design of an active CMOS biosensor substrate for fluorescence-based assays that enables time-gated, time-resolved fluorescence spectroscopy without the need for an external reader. The array is sensitive to photon densities as low as 1.15times10⁸/cm², has a dynamic range of over 74 dB, and has subnanosecond timing resolution. Sensitivity is achieved through subsampling and averaging     

Photon‐Memristive System for Logic Calculation and Nonvolatile Photonic Storage

Memristor‐based architectures have shown great potential for developing future computing systems beyond the era of von Neumann and Moore's law. However, the monotonous electrical input for dynamic resistance regulation limits the developments of memristors. Here, a concept of a photon‐memristive system, which realizes memristance depending on number of photons (optical inputs), is proposed. A detailed theoretical derivation is performed and the memristive characteristics, as stimulated by the optical inputs based on a hybrid system, consisting of a low‐dimension photoelectric semiconductor and a ferroelectric substrate are determined. The photon‐memristive system is also suitable for nonvolatile photonic memory since it possesses three or more‐bit data storage, desirable resistance‐change space, and an ON/OFF ratio of nearly 10⁷. The integrated circuit based on several photon‐memristive systems also realizes available photon‐triggered in‐memory computing. The photon‐memristive system expands the definition of memristors and emerges as a new data storage cell for future photonic neuromorphic computational architectures.     

Integration of a Chemical‐Responsive Hydrogel into a Porous Silicon Photonic Sensor for Visual Colorimetric Readout

The incorporation of a chemo‐responsive hydrogel into a 1D photonic porous silicon (PSi) transducer is demonstrated. A versatile hydrogel backbone is designed via the synthesis of an amine‐functionalized polyacrylamide copolymer where further amine‐specific biochemical reactions can enable control of cross‐links between copolymer chains based on complementary target–probe systems. As an initial demonstration, the incorporation of disulfide chemistry to control cross‐linking of this hydrogel system within a PSi Bragg mirror sensor is reported. Direct optical monitoring of a characteristic peak in the white light reflectivity spectrum of the incorporated PSi Bragg mirror facilitates real‐time detection of the hydrogel dissolution in response to the target analyte (reducing agent) over a timescale of minutes. The hybrid sensor response characteristics are shown to systematically depend on hydrogel cross‐linking density and applied target analyte concentration. Additionally, effects due to responsive hydrogel confinement in a porous template are shown to depend on pore size and architecture of the PSi transducer substrate. Sufficient copolymer and water is removed from the PSi transducer upon dissolution and drying of the hydrogel to induce color changes that can be detected by the unaided eye. This highlights the potential for future development for point‐of‐care diagnostic biosensing.     

Plasmon‐Enhanced Fluorescent Sensor based on Aggregation‐Induced Emission for the Study of Protein Conformational Transformation

The alteration in protein conformation not only affects the performance of its biological functions, but also leads to a variety of protein‐mediated diseases. Developing a sensitive strategy for protein detection and monitoring its conformation changes is of great significance for the diagnosis and treatment of protein conformation diseases. Herein, a plasmon‐enhanced fluorescence (PEF) sensor is developed, based on an aggregation‐induced emission (AIE) molecule to monitor conformational changes in protein, using prion protein as a model. Three anthracene derivatives with AIE characteristics are synthesized and a water‐miscible sulfonate salt of 9,10‐bis(2‐(6‐sulfonaphthalen‐2‐yl)vinyl)anthracene (BSNVA) is selected to construct the PEF–AIE sensor. The sensor is nearly non‐emissive when it is mixed with cellular prion protein while emits fluorescence when mixed with disease‐associated prion protein (PrP^Sc). The kinetic process of conformational conversion can be monitored through the fluorescence changes of the PEF–AIE sensor. By right of the amplified fluorescence signal, this PEF–AIE sensor can achieve a detection limit 10 pM lower than the traditional AIE probe and exhibit a good performance in human serum sample. Furthermore, molecular docking simulations suggest that BSNVA tends to dock in the β‐sheet structure of PrP by hydrophobic interaction between BSNVA and the exposed hydrophobic residues.