“Smart” Materials for Biosensing Devices: Cell-Mimicking Supramolecular Assemblies and Colorimetric Detection of Pathogenic Agents

Mimicking cell membrane and the biomolecular recognition associated with membranes represents a great technical challenge, yet it has opened doors to innovative diagnostic and therapeutic methods. Our work has focused on design and synthesis of a class of smart materials exploiting biological principals for use in biosensors: these materials are functional polymeric assemblies that mimic the cell membrane and conveniently report the presence of pathogens with a color change. Biologically active cell membrane components are incorporated into conjugated polymers with desirable optical properties and the binding of the target molecules onto the material triggers conformational and electronic shifts that are reflected in a chromatic change (a so-called biochromic shift) that is conveniently observed and recorded. Langmuir–Blodgett thin films and vesicle bilayers provide ideal configurations for precise delivery of the biological binding entity to the sensing interface, and for control of molecular orientation for effective biomolecular interaction. Polydiacetylenic membrane-mimicking materials containing cell surface receptor gangliosides and sialic acid residues, respectively were formulated into these architectures and used for colorimetric detection of bacterial toxins and influenza virus. One advantage of these biochromic conjugated polymer (BCP) sensors is that their molecular recognition and signal transduction functionalities are resident in a single functional unit, making them amenable to convenient microfabrication and use.     

Hierarchical nanostructured conducting polymer hydrogel with high electrochemical activity

Conducting polymer hydrogels represent a unique class of materials that synergizes the advantageous features of hydrogels and organic conductors and have been used in many applications such as bioelectronics and energy storage devices. They are often synthesized by polymerizing conductive polymer monomer within a nonconducting hydrogel matrix, resulting in deterioration of their electrical properties. Here, we report a scalable and versatile synthesis of multifunctional polyaniline (PAni) hydrogel with excellent electronic conductivity and electrochemical properties. With high surface area and three-dimensional porous nanostructures, the PAni hydrogels demonstrated potential as high-performance supercapacitor electrodes with high specific capacitance (~480 F·g(-1)), unprecedented rate capability, and cycling stability (~83% capacitance retention after 10,000 cycles). The PAni hydrogels can also function as the active component of glucose oxidase sensors with fast response time (~0.3 s) and superior sensitivity (~16.7 μA · mM(-1)). The scalable synthesis and excellent electrode performance of the PAni hydrogel make it an attractive candidate for bioelectronics and future-generation energy storage electrodes.     

Fluorescent Protein-Based Autophagy Biosensors

Autophagy is an essential cellular process of self-degradation for dysfunctional or unnecessary cytosolic constituents and organelles. Dysregulation of autophagy is thus involved in various diseases such as neurodegenerative diseases. To investigate the complex process of autophagy, various biochemical, chemical assays, and imaging methods have been developed. Here we introduce various methods to study autophagy, in particular focusing on the review of designs, principles, and limitations of the fluorescent protein (FP)-based autophagy biosensors. Different physicochemical properties of FPs, such as pH-sensitivity, stability, brightness, spectral profile, and fluorescence resonance energy transfer (FRET), are considered to design autophagy biosensors. These FP-based biosensors allow for sensitive detection and real-time monitoring of autophagy progression in live cells with high spatiotemporal resolution. We also discuss future directions utilizing an optobiochemical strategy to investigate the in-depth mechanisms of autophagy. These cutting-edge technologies will further help us to develop the treatment strategies of autophagy-related diseases.     

Cyclodextrins as Supramolecular Recognition Systems: Applications in the Fabrication of Electrochemical Sensors

Supramolecular chemistry, although focused mainly on noncovalent intermolecular and intramolecular interactions, which are considerably weaker than covalent interactions, can be employed to fabricate sensors with a remarkable affinity for a target analyte. In this review the development of cyclodextrin-based electrochemical sensors is described and discussed. Following a short introduction to the general properties of cyclodextrins and their ability to form inclusion complexes, the cyclodextrin-based sensors are introduced. This includes the combination of cyclodextrins with reduced graphene oxide, carbon nanotubes, conducting polymers, enzymes and aptamers, and electropolymerized cyclodextrin films. The applications of these materials as chiral recognition agents and biosensors and in the electrochemical detection of environmental contaminants, biomolecules and amino acids, drugs and flavonoids are reviewed and compared. Based on the papers reviewed, it is clear that cyclodextrins are promising molecular recognition agents in the creation of electrochemical sensors, chiral sensors, and biosensors. Moreover, they have been combined with a host of materials to enhance the detection of the target analytes. Nevertheless, challenges remain, including the development of more robust methods for the integration of cyclodextrins into the sensing unit.     

Gold nanoparticles in ophthalmology

Many research projects are underway to improve the diagnosis and therapy in ophthalmology. Indeed, visual acuity deficits affect 285 million people worldwide and different strategies are being developed to strengthen patient care. One of these strategies is the use of gold nanoparticles (GNP) for their multiple properties and their ability to be used as both diagnosis and therapy tools. This review exhaustively details research developing GNPs for use in ophthalmology. The toxicity of GNPs and their distribution in the eye are described through in vitro and in vivo studies. All publications addressing the pharmacokinetics of GNPs administered in the eye are extensively reviewed. In addition, their use as biosensors or for imaging with optical coherence tomography is illustrated. The future of GNPs for ophthalmic therapy is also discussed. GNPs can be used to deliver genes or drugs through different administration routes. Their antiangiogenic and anti-inflammatory properties are of great interest for different ocular pathologies. Finally, GNPs can be used to improve stereotactic radiosurgery, brachytherapy, and photothermal therapy because of their many properties.     

Dynamic single-molecule sensing by actively tuning binding kinetics for ultrasensitive biomarker detection

The ability to measure many single molecules simultaneously in large and complex samples is critical to the translation of single-molecule sensors for practical applications in biomarker detection. The challenges lie in the limits imposed by mass transportation and thermodynamics, resulting in long assay time and/or insufficient sensitivity. Here, we report an approach called Sensing Single Molecule under MicroManipulation (SSM³) to circumvent the above limits. In SSM³, single-molecule binding processes were dynamically recorded by surface plasmon resonance microscopy in a nanoparticle-mediated sandwich scheme. The binding kinetics between analyte and probes are fine-tuned by nanoparticle micromanipulations to promote the repetitive binding and dissociation. Quantifying the heterogeneous lifetime of each molecular complex allows the discrimination of specific binding from nonspecific background noise. By digitally counting the number of repetitive specific binding events, we demonstrate the direct detection of microRNAs and amyloid-β proteins with the limit of detection at the subfemtomolar level in buffer and spiked human serum. Together with the nanoparticle micromanipulation to promote the transportation rate of analyte molecules, the assay could be performed within as short as 15 min without the need for preincubation. The advantages over other single-molecule sensors include short assay time, compatible with common probes and ultrasensitive detection. With further improvement on the throughput and automation, we anticipate the proposed approach could find wide applications in fundamental biological research and clinical testing of disease-related biomarkers.

The analytical methods have converged from ensemble measurements of numerous entities to quantized measurements at the single-molecule level. Single-molecule measurements could reveal heterogeneities and stochastic processes within biological systems (1, 2) and set the ultimate detection limit of chemical and biological sensors. By reducing the measurement volume to a few femtoliters, the detection of a single molecule has been realized in various forms [i.e., single-molecule fluorescence (3, 4), nanopores (5, 6), localized surface plasmon resonance (7, 8), and surface-enhanced Raman scattering (9, 10)]. These measurements typically require quantifying many single-molecule events to gain new molecular and mechanistic insights or to achieve better analytical performance. However, it has been difficult to perform quantitative analysis with sufficient efficiency and statistical accuracy because of the concentration limit from mass transportation (11, 12) and the thermodynamic limit from probe affinity (13). For quantification of biomarkers in biological media, in which the required concentrations are usually at the femtomolar level or even lower (14), the single-molecule measurements could take inordinately long, and the nonspecific binding of unwanted species degrades the accuracy.In the past two decades, several single-molecule approaches for biomarker detection have been developed to surpass the above limits by biasing the equilibrium and driving binding reactions (15, 16). A typical scheme involves the usage of nanoparticles to collect the analyte followed by a digital measurement of single molecules at a confined space (17), such as the commercialized, single-molecule enzyme-linked immunosorbent analysis (digital ELISA) (18). The digital ELISA uses the antibody-modified magnetic beads to capture the analyte in solution and loads them into femtoliter-sized reaction chambers termed single-molecule arrays. It effectively improves the sensitivity of conventional ELISA by three orders with a limit of detection (LoD) at the subfemtomolar level but requires sophisticated devices and excessive operation to remove free analyte molecules. Besides, the performance is still limited by the probe affinity and false positive arising from detection antibodies that bind nonspecifically to assay surface.A distinct yet effective strategy is to explore the in-depth heterogeneous information of single-molecule interaction (19). Walter et al. first demonstrated a kinetic fingerprinting approach to perform highly specific and sensitive detection of biomarkers via single-molecule fluorescence microscopy (20–22). This single-molecule recognition through equilibrium Poisson sampling technique surpasses the thermodynamic limit by exploiting the repetitive binding of fluorescently labeled, low-affinity probes to the analyte (23) and discriminating specific binding from background noise by a kinetic signature. The detection limits of microRNAs (miRNAs) and proteins also reach the subfemtomolar level, but screening probes with unique kinetic property is not compatible with current pipelines, and the concentration limit implies long incubation time before detection.Herein, we present the integration of single-molecule manipulation and dynamic sensing to allow rapid and ultrasensitive detection of biomarkers beyond the concentration and thermodynamic limits. In this Sensing Single Molecule under MicroManipulation (SSM³) approach, an external force is applied on the molecular bound between analyte and probes through tethered nanoparticles to actively tune the binding kinetics. This strategy, together with a dynamic sensing approach to exploit the heterogeneity at the single-molecule level, is able to beat the limits in both assay time and sensitivity. We show the principle and realization of the SSM³ technique and demonstrate 15-min assays to directly measure miRNAs and proteins at the subfemtomolar concentration.     

Lanthanide-Doped Upconversion Luminescent Nanoparticles—Evolving Role in Bioimaging,Biosensing, and Drug Delivery

Upconverting luminescent nanoparticles (UCNPs) are “new generation fluorophores” with an evolving landscape of applications in diverse industries, especially life sciences and healthcare. The anti-Stokes emission accompanied by long luminescence lifetimes, multiple absorptions, emission bands, and good photostability, enables background-free and multiplexed detection in deep tissues for enhanced imaging contrast. Their properties such as high color purity, high resistance to photobleaching, less photodamage to biological samples, attractive physical and chemical stability, and low toxicity are affected by the chemical composition; nanoparticle crystal structure, size, shape and the route; reagents; and procedure used in their synthesis. A wide range of hosts and lanthanide ion (Ln³⁺) types have been used to control the luminescent properties of nanosystems. By modification of these properties, the performance of UCNPs can be designed for anticipated end-use applications such as photodynamic therapy (PDT), high-resolution displays, bioimaging, biosensors, and drug delivery. The application landscape of inorganic nanomaterials in biological environments can be expanded by bridging the gap between nanoparticles and biomolecules via surface modifications and appropriate functionalization. This review highlights the synthesis, surface modification, and biomedical applications of UCNPs, such as bioimaging and drug delivery, and presents the scope and future perspective on Ln-doped UCNPs in biomedical applications.     

Recent Advances in Materials and Flexible Sensors for Arrhythmia Detection

Arrhythmias are one of the leading causes of death in the United States, and their early detection is essential for patient wellness. However, traditional arrhythmia diagnosis by expert evaluation from intermittent clinical examinations is time-consuming and often lacks quantitative data. Modern wearable sensors and machine learning algorithms have attempted to alleviate this problem by providing continuous monitoring and real-time arrhythmia detection. However, current devices are still largely limited by the fundamental mismatch between skin and sensor, giving way to motion artifacts. Additionally, the desirable qualities of flexibility, robustness, breathability, adhesiveness, stretchability, and durability cannot all be met at once. Flexible sensors have improved upon the current clinical arrhythmia detection methods by following the topography of skin and reducing the natural interface mismatch between cardiac monitoring sensors and human skin. Flexible bioelectric, optoelectronic, ultrasonic, and mechanoelectrical sensors have been demonstrated to provide essential information about heart-rate variability, which is crucial in detecting and classifying arrhythmias. In this review, we analyze the current trends in flexible wearable sensors for cardiac monitoring and the efficacy of these devices for arrhythmia detection.     

A novel improved design for the first-generation glucose biosensor

A novel improved design for the first-generation glucose biosensor@Wang J     

用于制作于EPR氧生物传感器的功能性有机材料的调查研究

纳米生物技术将纳米技术和生物技术相集成,是现代生物工程的重要组成部分.近年来,基于自然界原型的纳米生物材料、分子马达、芯片技术、纳米生物探针等纳米生物技术取得了迅速发展.本课题组参加Received date:Apr.3,2005了欧盟第六框架计划中的(NACBO)项目,它是建立在以前的研究基础之上,集中了各成员国在该研究领域的领先技术及顶尖专业技术人员,如纳米材料的自组装技术、纳米生物技术、多功能纳米生物材料研究的基础知识,纳米材料的包覆手段与材料、生物体与非生物体之间的界面研究等等.欧盟第六框架计划旨在集中各合作方在各领域的专家和先进技术,加入此框架的成员国的研究项目所取得的成果在各成员国之间具有通用性,可以相互使用,互通有无,使资源得到几乎完全应用.本课题组作为中国在纳米生物学领域唯一的参与者,具备得天独厚的研究条件,在对整个合作研究做出自己应尽的义务同时,还将利用其他成员国的研究成果,进一步开展研究,利国利民.本课题组主要在有机功能性材料的研究方面承担责任.EPR(Electronic Paramagnetic Resonance)氧生物医学传感器是一类具有在线检测能力的传感器,它是利用生物体组织的不同氧分压(或氧含量)来实施对异常组织、肿瘤组织的检测.近年来,EPR在生物体系中氧含量的测定中表现出独特性,提供了全时在线氧含量的测定,而且顺磁氧生物医学传感器因其使用成本较低,受到世界各国的关注.生命科学是EPR应用的一个较大的领域,几乎所涉及的生物体系都曾直接或间接的作过EPR测量,其中也包括生物医学和药物学方面的工作.目前使用的测氧材料多是无机材料,可供选择的种类有限.有机化合物的分子设计为这一领域提供了一个可供发展的极大空间--可以有目的的在所选母体化合物上引入所需的官能团,使之具有EPR信号,且具有氧敏性.将这些可选择的已在实际中应用的有机化合物作为母体,可以使材料的毒性降至最底限度;而且相对于无机材料的选择,有机化合物的合成具有很大的人为性与灵活性,也就是说,一旦得到合适的官能团,就可以有目的的合成众多的材料以供筛选.考虑到材料的应用方向,选择了一些在生物医学方面已经应用的有机功能性材料,如菁染料、卟啉及它们的相关化合物作为研究对象,开发其在生物医学领域的新应用.笔者在现有实验的基础上,利用自由基理论和单线态氧理论,设计并合成对氧敏感的顺磁新材料.进而完成对顺磁性新材料的表面处理及成膜研究,得到可应用的纳米EPR氧生物医学传感器.