Flexible Polydopamine Bioelectronics

Flexible bioelectronics have attracted increasing research interests due to their wide range of potential applications in human motion detection, personal healthcare monitoring, and medical diagnosis. Recently, design and fabrication strategies integrated with mussel-inspired polydopamine (PDA) have demonstrated many appealing properties, which meet the structural and functional requirements of high-performance flexible bioelectronics. The inherent multiple reactive sites and hierarchical interactions within PDA can promote the total electrochemical activities, self-healing, surface activation, and biocompatibility of the composite system. This review paper strives to provide a comprehensive overview on this emerging area, including the fabrication methodology, the structural and functional contributions of PDA on the whole composites, and various applications of PDA-based flexible bioelectronics. The current challenges and future outlook in this field are also extensively discussed at the end. This paper aims to serve as a guideline in this emerging area and provide new inspirations toward next-generation integrated multifunctional flexible PDA bioelectronics with a broad range of healthcare applications.     

光纤荧光传感器衰减寿命的加权对数拟合法

荧光寿命的检测是荧光光学传感器的核心内容，国际上尝试了多种方法来拟合这种理论上为单指数衰减信号的荧光衰减曲线。这些方法包括非线性函数标准拟合方法。即Levenburg-Marquardt方法，以及Prony方法、FFT方法，对数拟合法等等。为了克服在实际应用中发生的信号退化，需要在测量信号衰减寿命的同时测量信号的初始强度。文章介绍了一种加权的对数拟合法，经计算机仿真及实际数据测试均可以得到和Levenburg-Marquardt方法非常接近的结果，且拟合时间大大缩短，测量稳定性大大提高。仿真测试及具体实验测试结果显示了这种方法的有效性。该方法不仅与Levenburg-Marquardt方法的偏差曲线非常相似，而且实验测得的荧光寿命与Levenburg-Marquardt方法偏差在0．2％以内。     

Skin Pigmentation‐Inspired Polydopamine Sunscreens

Commercial sunscreens usually rely on multiple component formulas against solar irradiation, including UV filters, antioxidants, and nanomaterial matrices. While many efforts are devoted, concern has arisen that the effectiveness and safety issues of most sunscreens are largely limited by their complex formulations, photostability, and toxicity. Inspired by skin pigmentation as primary photoprotective mechanism in human body, novel sunscreen products based on polydopamine (PDA) gels, with a bioinspired protection concept and improved photoprotective capacities, were rationally designed and facilely prepared. The diverse formula of those sunscreen gels can be achieved by the use of PDA nanoparticle, a kind of naturally melanin mimics, to complex/conjugate with different polymers. The resulting PDA sunscreens are bioadhesive, water resistant, and nonskin penetration, yet can be directly removed by towel wiping. They also perform many promising features including superior UV shielding properties, high in vitro and in vivo UV protection efficiencies, nonphototoxicity, and nonirritating nature. These PDA materials in an initial proof‐of‐concept study were described and it is proposed that this class of bioinspired gels will be useful for incident UV protection where simple, safe, and efficient sunscreens are still highly desirable.     

Self‐Assembly of Mechanoplasmonic Bacterial Cellulose–Metal Nanoparticle Composites

Nanocomposites of metal nanoparticles (NPs) and bacterial nanocellulose (BC) enable fabrication of soft and biocompatible materials for optical, catalytic, electronic, and biomedical applications. Current BC–NP nanocomposites are typically prepared by in situ synthesis of the NPs or electrostatic adsorption of surface functionalized NPs, which limits possibilities to control and tune NP size, shape, concentration, and surface chemistry and influences the properties and performance of the materials. Here a self‐assembly strategy is described for fabrication of complex and well‐defined BC–NP composites using colloidal gold and silver NPs of different sizes, shapes, and concentrations. The self‐assembly process results in nanocomposites with distinct biophysical and optical properties. In addition to antibacterial materials and materials with excellent senor performance, materials with unique mechanoplasmonic properties are developed. The homogenous incorporation of plasmonic gold NPs in the BC enables extensive modulation of the optical properties by mechanical stimuli. Compression gives rise to near‐field coupling between adsorbed NPs, resulting in tunable spectral variations and enhanced broadband absorption that amplify both nonlinear optical and thermoplasmonic effects and enables novel biosensing strategies.     

Organic Nanoprobe Cocktails for Multilocal and Multicolor Fluorescence Imaging of Reactive Oxygen Species

Hypochlorite (ClO^?) as a highly reactive oxygen species not only acts as a powerful “guarder” in innate host defense but also regulates inflammation‐related pathological conditions. Despite the availability of fluorescence probes for detection of ClO^? in cells, most of them can only detect ClO^? in single cellular organelle, limiting the capability to fully elucidate the synergistic effect of different organelles on the generation of ClO^?. This study proposes a nanoprobe cocktail approach for multicolor and multiorganelle imaging of ClO^? in cells. Two semiconducting oligomers with different π‐conjugation length are synthesized, both of which contain phenothiazine to specifically react with ClO^? but show different fluorescent color responses. These sensing components are self‐assembled into the nanoprobes with the ability to target cellular lysosome and mitochondria, respectively. The mixture of these nanoprobes forms a nano‐cocktail that allows for simultaneous imaging of elevated level of ClO^? in lysosome and mitochondria according to fluorescence color variations under selective excitation of each nanoprobe. Thus, this study provides a general concept to design probe cocktails for multilocal and multicolor imaging.     

Multifunctional and Stimuli‐Responsive Polydopamine Nanoparticle‐Based Platform for Targeted Antimicrobial Applications

The rising threat of antimicrobial resistance is a crisis of a global scale. If not addressed, it can lead to health care system problems worldwide. This warrants alternative therapeutic approaches whose mechanism of action starkly differs from conventional antibiotic‐based therapies. Here, a multifunctional and stimuli‐responsive (NIR laser‐activated) antimicrobial platform is engineered by combining the intrinsic photothermal capability and excellent biocompatibility of polydopamine nanoparticles (PdNPs), with the membrane targeting and lytic activities of an antimicrobial peptide (AMP). The resulting PdNP‐AMP nanosystem can specifically target and destabilize the mechanical integrity of the outer membrane of Escherichia coli, as measured using the atomic force microscope. Furthermore, the laser‐induced nano‐localized heating of PdNP—in close proximity to the already compromised bacterial envelope—induces further membrane damage. This results in a more efficient, laser‐activated, bacterial killing action of PdNP‐AMP. The antimicrobial platform developed in this work is shown to be effective against a drug‐resistant E. coli. Overall, this work highlights the advantage and strength of combining multiple and coordinated biocidal mechanisms, into one nanomaterial‐based system and its promise in treating drug‐resistant pathogens.     

High Performance Bacterial Cellulose Organogel-Based Thermoelectrochemical Cells by Organic Solvent-Driven Crystallization for Body Heat Harvest and Self-Powered Wearable Strain Sensors

As a low-grade sustainable heat source, the human body provides a great driving force for converting heat into electric energy using thermoelectric materials, which can effectively power wearable electronics. However, the low thermoelectric conversion efficiency is not sufficient to achieve energy autonomy in the operation of wearable devices. Herein, wearable bacterial cellulose (BC) organogel-based thermoelectrochemical cells (TECs) are designed and prepared with K₄Fe(CN)₆/K₃Fe(CN)₆ as a redox couple. The addition of propylene glycol significantly improves the mechanical properties of the TECs and drives K₄Fe(CN)₆ to gradually crystallize, resulting in the concentration gradient of redox ions, which significantly enhanced the heat-to-electricity conversion efficiency (from 1.27 to 2.30 mV K⁻¹), proving that they are promising candidates for powering flexible and wearable devices in various application scenarios. The TECs are further assembled into self-powered strain sensors, which can detect the movement of the human body under various tensions and pressures in real time with high sensitivity. This indicates that the BC organogel-based TECs for self-powered strain sensors have great application potential in the wearable field.     

Polydopamine Encapsulation of Fluorescent Nanodiamonds for Biomedical Applications

Fluorescent nanodiamonds (FNDs) are promising bioimaging probes compared with other fluorescent nanomaterials such as quantum dots, dye‐doped nanoparticles, and metallic nanoclusters, due to their remarkable optical properties and excellent biocompatibility. Nevertheless, they are prone to aggregation in physiological salt solutions, and modifying their surface to conjugate biologically active agents remains challenging. Here, inspired by the adhesive protein of marine mussels, encapsulation of FNDs within a polydopamine (PDA) shell is demonstrated. These PDA surfaces are readily modified via Michael addition or Schiff base reactions with molecules presenting thiol or nitrogen derivatives. Modification of PDA shells by thiol terminated poly(ethylene glycol) (PEG‐SH) molecules to enhance colloidal stability and biocompatibility of FNDs is described. Their use as fluorescent probes for cell imaging is demonstrated; it is found that PEGylated FNDs are taken up by HeLa cells and mouse bone marrow‐derived dendritic cells and exhibit reduced nonspecific membrane adhesion. Furthermore, functionalization with biotin‐PEG‐SH is demonstrated and long‐term high‐resolution single‐molecule fluorescence based tracking measurements of FNDs tethered via streptavidin to individual biotinylated DNA molecules are performed. This robust polydopamine encapsulation and functionalization strategy presents a facile route to develop FNDs as multifunctional labels, drug delivery vehicles, and targeting agents for biomedical applications.     

Cadmium(II) (8‐Hydroxyquinoline) Chloride Nanowires: Synthesis,Characterization and Glucose‐Sensing Application

Luminescent cadmium(II) (8‐hydroxyquinoline) chloride (CdqCl) complex nanowires are synthesized via a sonochemical solution route. The results of X‐ray photoelectron spectroscopy, energy dispersive X‐ray analysis, infrared spectroscopy, elemental analysis (EA), and atomic absorption spectroscopy demonstrate that the chemical composition of the product is Cd(C₉H₆NO)Cl. Transmission electron microscopy and scanning electron microscopy images show that the CdqCl product is wire‐like in structure, with a diameter of approximately 50 nm and an approximate length of 2–4 µm. The morphology and composition of the product can be transformed from Cdq₂ micrometer‐scaled flakes to CdqCl nanowires by increasing the ratio of CdCl₂/q. A new fluorescent sensing strategy for detecting H₂O₂ and glucose is developed and is based on the combination of the luminescent nanowires and the biocatalytic growth of Au nanoparticles. The quenching effects of Au nanoparticles and on the fluorescence of CdqCl nanowires are investigated. The dominant factor for the fluorescence quenching of CdqCl nanowires is that the Stern–Volmer quenching constant of Au nanoparticles is larger than that of .     

共形阵列天线互耦校正的辅助阵元法

 针对共形天线载体曲率和单元方向图指向的变化,建立了三维共形天线导向矢量的数学模型;推导了阵列互耦与方位依赖幅相误差的等价关系;通过引入少量远离共形载体的辅助阵元和方向未知的校正信源,提出了共形阵列天线互耦校正的辅助阵元法.辅助阵元法只需要参数的一维搜索和线性方程组求解,可以实现校正信源方位和共形天线互耦系数的联合估计.计算机Monte-Carlo仿真实验验证了辅助阵元法互耦校正的有效性.     

Photoporation with Biodegradable Polydopamine Nanosensitizers Enables Safe and Efficient Delivery of mRNA in Human T Cells

Safe and efficient production of chimeric antigen receptor (CAR)-T cells is of crucial importance for cell-based cancer immunotherapy. Physical transfection methods have quickly gained in importance in the context of transfecting T-cells, since they are readily compatible with different cell types and a broad variety of cargo molecules. In particular, nanoparticle-sensitized photoporation has been introduced in recent years as a gentle yet efficient method to transiently permeabilize cells, allowing subsequent entry of external cargo molecules into the cells. Gold nanoparticles (AuNPs) have been used the most as photothermal sensitizers because they can easily form laser-induced vapor nanobubbles, a photothermal phenomenon that is shown to be particularly efficient for permeabilizing cells. However, as AuNPs are not biodegradable, clinical translation is hampered. Here, for the first time, the possibility to form laser-induced vapor nanobubbles from biocompatible polymeric nanoparticles is reported. Compared to electroporation, the most used physical transfection method for T cells, 2.5 times more living mRNA transfected human T cells are obtained via photoporation sensitized by polydopamine nanoparticles. This shows that photoporation is a viable approach for efficiently producing therapeutic engineered T-cells at a throughput easily exceeding 10⁵ cells per second.     

Response Regulation for Epidermal Fabric Strain Sensors via Mechanical Strategy

Advances in fabric strain sensors have established a route to comfortable-to-wear flexible electronics with particularly remarkable permeability and low modulus due to their porous fabric microstructure. A key challenge that remains unsolved is to regulate the sensor response via on-demand design for a variety of application scenarios to sufficiently exploit the highest possible sensitivity. While recent reports have described a variety of options in varying the material and orientation of the overall fiber mat, the development of approaches where multiple sensors with different responses can be integrated on a single substrate without affecting macroscopic mechanical properties remains an area of continued interest. Herein, a simple mechanical strategy is reported, which plates the patterned functional material on the fabric mat at a pre-stretched state in the prescribed direction, and control of direction and prestrain forms either sensors with different responses or strain-insensitive interconnects. A systematic study has revealed the underlying mechanism of this strategy, which can serve as a guideline for the on-demand design and fabrication of fabric strain sensors. Demonstration applications in motion monitoring bandages and gesture recognition gloves illustrate capabilities in functional epidermal sensing devices.     

Printing Ultrasensitive Artificially Intelligent Sensors Array with a Single Self‐Propelled Droplet Containing Nanoparticles

The fabrication and implementation of artificially intelligent sensor arrays has faced serious technical and/or cost‐effectiveness challenges. Here, a new printing method is presented to produce a fully functional array of sensors based on monolayer‐capped gold nanoparticles. The proposed printing technique is based on the so‐called self‐propelled antipinning ink droplet, from which evaporative deposition takes place along the path of motion. By applying actuating forces, different deposition line patterns with different thicknesses and morphology from a single droplet are generated. The functionality of the produced sensors is demonstrated by their ability to detect different representative volatile organic compounds (VOCs) belonging to different chemical families, including alcohols, alkanes, ethers, and aromatics, and under extremely different humidity levels resembling those encountered in real‐world conditions. The results show that the sensors exhibit ultrasensitive sensing features, with an ability to detect and differentiate between different VOCs at low ppb levels. Additionally, the results show that the sensors are able to accurately predict VOC concentrations, viz. enable quantification capabilities, while nevertheless being inexpensive, do not need complicated and expensive printing equipment and prepatterning processes, allow low voltage operation, and provide a platform for multifunctional applications.     

Cross‐Linked Gold Nanoparticle Composite Membranes as Highly Sensitive Pressure Sensors

In this article, highly sensitive differential pressure sensors based on free‐standing membranes of cross‐linked gold nanoparticles are demonstrated. The nanoparticle membranes are employed as both diaphragms and resistive transducers. The elasticity and the pronounced resistive strain sensitivity of these nanometer‐thin composites enable the fabrication of sensors achieving high sensitivities exceeding 10^?3 mbar^?1 while maintaining an overall small membrane area. Furthermore, by combining micro‐bulge tests with atomic force microscopy and in situ resistance measurements the membranes’ electromechanical responses are studied through precise observation of the concomitant changes of the membranes’ topography. The study demonstrates the high potential of free‐standing nanoparticle composites for the fabrication of highly sensitive force and pressure sensors and introduces a unique and powerful method for the electromechanical investigation of these materials.     

Gold‐Nanocluster‐Based Fluorescent Sensors for Highly Sensitive and Selective Detection of Cyanide in Water

A novel, gold‐nanocluster‐based fluorescent sensor for cyanide in aqueous solution, which is based on the cyanide etching‐induced fluorescence quenching of gold nanoclusters, is reported. In addition to offering high selectivity due to the unique Elsner reaction between cyanide and the gold atoms of gold nanoclusters, this facile, environmentally friendly and cost‐effective method provides high sensitivity. With this sensor, the lowest concentration to quantify cyanide ions could be down to 200 × 10^?9 M , which is approximately 14 times lower than the maximum level (2.7 × 10^?6 M ) of cyanide in drinking water permitted by the World Health Organization (WHO). Furthermore, several real water samples spiked with cyanide, including local groundwater, tap water, pond water, and lake water, are analyzed using the sensing system, and experimental results show that this fluorescent sensor exhibits excellent recoveries (over 93%). This gold‐nanocluster‐based fluorescent sensor could find applications in highly sensitive and selective detection of cyanide in food, soil, water, and biological samples.     

Polydopamine as a Biocompatible Multifunctional Nanocarrier for Combined Radioisotope Therapy and Chemotherapy of Cancer

Development of biodegradable nanomaterials for drug delivery and cancer theranostics has attracted great attention in recent years. In this work, polydopamine (PDA), a biocompatible polymer, is developed as a promising carrier for loading of both radionuclides and an anticancer drug to realize nuclear‐imaging‐guided combined radioisotope therapy (RIT) and chemotherapy of cancer in one system. It is found that PDA nanoparticles after modification with poly(ethylene glycol) (PEG) can successfully load several different radionuclides such as ^99mTc and ¹³¹I, as well as an anticancer drug doxorubicin (DOX). While labeling PDA‐PEG with ^99mTc (^99mTc‐PDA‐PEG) enables in vivo single photon emission computed tomography imaging, nanoparticles co‐loaded with ¹³¹I and DOX (¹³¹I‐PDA‐PEG/DOX) can be utilized for combined RIT and chemotherapy, which offers effective cancer treatment efficacy in a remarkably synergistic manner, without rendering significant toxicity to the treated animals. Therefore, this study presents an interesting class of biocompatible nanocarriers, which allow the combination of RIT and chemotherapy, the two extensively applied cancer therapeutic strategies, promising for future clinic translations in cancer treatment.