two-dimensional-super-resolution-visualization-rat-brain

Two-Dimensional Super-Resolution Visualization of Rat Brain Microvasculature Using Ultrasound Localization Microscopy

The cerebral microvasculature forms a complex network of vessels essential for maintaining brain function. Diseases such as stroke, Alzheimer's disease, ...

Fudan University

Silk and silk fibroin, the biomaterial from nature, nowadays are being widely utilized in many cutting-edge micro/nanodevices/systems via advanced micro/nanofabrication techniques. Herein, for the first time to our knowledge, we report aqueous multiphoton lithography of diversiform-regenerated-silk-fibroin-centric inks using noncontact and maskless femtosecond laser direct writing (FsLDW). Initially, silk fibroin was FsLDW-crosslinked into arbitrary two/three-dimensional micro/nanostructures with good elastic properties merely using proper photosensitizers. More interestingly, silk/metal composite micro/nanodevices with multidimension-controllable metal content can be FsLDW-customized through laser-induced simultaneous fibroin oxidation/crosslinking and metal photoreduction using the simplest silk/Ag(+) or silk/[AuCl4](-) aqueous resists. Noticeably, during FsLDW, fibroin functions as biological reductant and matrix, while metal ions act as the oxidant. A FsLDW-fabricated prototyping silk/Ag microelectrode exhibited 10(4)-Ω(-1 ) m(-1)-scale adjustable electric conductivity. This work not only provides a powerful development to silk micro/nanoprocessing techniques but also creates a novel way to fabricate multifunctional metal/biomacromolecule complex micro/nanodevices for applications such as micro/nanoscale mechanical and electrical bioengineering and biosystems.

Aqueous multiphoton lithography with multifunctional silk-centred bio-resists.

Controllable degradation and excellent biocompatibility during/after a lifetime endow emerging transient electronics with special superiority in implantable biomedical applications. Currently, most of these devices need external power sources, limiting their real-world utilizations. Optimizing existing bioresorbable electronic devices requires natural-material-based construction and, more importantly, diverse or even all-in-one multifunctionalization. Herein, silk-based implantable, biodegradable, and multifunctional systems, self-powered with transient triboelectric nanogenerators (T ENGs), for real-time in vivo monitoring and therapeutic treatments of epileptic seizures, are reported. These T ENGs are of customizable in vitro/in vivo operating life and biomechanical sensitivity via the adjustments of silk molecular size, surface structuralization, and device configuration. Functions, such as drug delivery and structural-integrity optical readout (parallel to electronic signals), are enabled for localized anti-infection and noninvasive degradation indication, respectively. A proof-of-principle wireless system is built with mobile-device readout and "smart" treatment triggered by specific symptoms (i.e., epilepsy), exhibiting the practical potential of these silk T ENGs as self-powered, transient, and multifunctional implantable bioelectronic platforms.

Self-Powered Multifunctional Transient Bioelectronics.

Flexible electronics can serve as powerful tools for biomedical diagnosis and therapies of neurological disorders, particularly for application cases with brain-machine interfaces (BMIs). Existing conformal soft bioelectrodes are applicable for basic electrocorticogram (ECoG) collecting/monitoring. Nevertheless, as an emerging and promising approach, further multidisciplinary efforts are still demanded for in-depth exploitations with these conformal soft electronics toward their practical neurophysiological applications in both scientific research and real-world clinical operation. Here, clinically-friendly silk-supported/delivered soft bioelectronics are developed, and multiple functions and features valuable for customizable intracranial applications (e.g., biocompatible and spontaneously conformal coupling with cortical surface, spatiotemporal ECoG detecting/monitoring, electro-neurophysiological neural stimulating/decoding, controllable loading/delivery of therapeutic molecules, and parallel optical readouts of operating states) are integrated.

Silk-Enabled Conformal Multifunctional Bioelectronics for Investigation of Spatiotemporal Epileptiform Activities and Multimodal Neural Encoding/Decoding.

Modification-free biosensing with high specificity and sensitivity is essential for miniaturized, online, integrated, and rapid, or even real-time molecular analyses. However, most optical biosensors are based on surface pre-modification or fluorescent labeling, and have either low sensitivity or low quality factor (Q). To address these difficulties, in this study, an optical sensor prototype was developed with a microbubble optofluidic channel integrated inside a Fabry-Pérot cavity to three-dimensionally tailor the intra-cavity light field via the intra-cavity lensing (microbubble) configuration. A high Q-factor (∼10), small mode volume, and high light energy density were experimentally achieved with this "stereo-sensor" while maintaining an ultrahigh refractive index (RI) sensitivity (679 nm/RIU) and ultra-small RI resolution (∼10 RIU at 950 nm). Moreover, specific detection of very low concentration of biomolecules (5 fg/mL for human IgG and 0.5 pg/mL for human serum albumin (HSA)) and wide range of protein concentrations (e.g., fg/mL-ng/mL for human IgG and pg/mL-ng/mL for HSA) without probe pre-modification were achieved owing to the RI change specifically associated with the probe-target binding and the corresponding bio-macromolecular conformation change. This modification-free stereosensing scenario is applicable to continuous, real-time, and multiplexed operations, thus showing potential for online, integrated, dynamic, biomolecular analyses in vitro or in vivo, such as the dynamic metabolic analysis of single cells or organoids and point-of-care tests.

Highly sensitive, modification-free, and dynamic real-time stereo-optical immuno-sensor.

Mechano-sensitive hair-like sensilla (MSHS) have an ingenious and compact three-dimensional structure and have evolved widely in living organisms to perceive multidirectional mechanical signals. Nearly all MSHS are iontronic or electronic, including their biomimetic counterparts. Here, an all-optical mechano-sensor mimicking MSHS is prototyped and integrated based on a thin-walled glass microbubble as a flexible whispering-gallery-mode resonator. The minimalist integrated device has a good directionality of 32.31 dB in the radial plane of the micro-hair and can detect multidirectional displacements and forces as small as 70 nm and 0.9 μN, respectively. The device can also detect displacements and forces in the axial direction of the micro-hair as small as 2.29 nm and 3.65 μN, respectively, and perceive different vibrations. This mechano-sensor works well as a real-time, directional mechano-sensory whisker in a quadruped cat-type robot, showing its potential for innovative mechano-transduction, artificial perception, and robotics applications.

An all-optical multidirectional mechano-sensor inspired by biologically mechano-sensitive hair sensilla.

The ultrafast-laser-matter interactions enable "top-down" laser surface structuring, especially for materials difficult to process, with "bottom-up" self-organizing features. The subwavelength scenarios of laser-induced structuring are improved in defects and long-range order by applying positive/negative feedbacks. It is still hardly reported for supra-wavelength laser structuring more associated with complicated thermo/hydro-dynamics. For the first time to the knowledge, the near-field-regulated ultrafast-laser lithography of self-arrayed supra-wavelength micro/nano-pores directly on ultra-hard metallic glass is developed here. The plasmonic hot spots on pre-structures, as the positive feedback, clamped the lateral geometries (i.e., position, size). Simultaneously, it drilled and self-organized into micro/nano-pore arrays by photo-dynamic plasma ablation and Marangoni removal confined under specific femtosecond-laser irradiation, as the negative feedback. The mechanisms and finite element modeling of the multi-physical transduction (based on the two-temperature model), the far-field/near-field coupling, and the polarization dependence during laser-matter interactions are studied. Large-area micro/nano-pore arrays (centimeter scale or larger)  are manufactured with tunable periods (1-5 µm) and geometries (e.g., diameters of 500 nm-6 µm using 343, 515, and 1030 lasers, respectively). Consequently, the mid/far-infrared reflectivity at 2.5-6.5 µm iss decreased from ≈80% to ≈5%. The universality of multi-physical coupling and near-field enhancements makes this approach widely applicable, or even irreplaceable, in various applications.

Near-Field-Regulated Ultrafast Laser Supra-Wavelength Structuring Directly on Ultrahard Metallic Glasses.

Intrinsically flexible micro-/nano-electronics are increasingly in demand for wearable/implantable bio-machine interfacing optical electronics and soft robots. In this work, we developed intrinsically flexible and soft wearable micro-/nano-electronics by femtosecond laser direct writing  sericin-based nanocomposites. Sericin was used as the biomacromolecular reductant to photo-reduce metal ions into nanoparticles and the molecular matrix for  nano-compositing. The two/three-dimensional fabrication realized ∼350 nm minimum line width, customizable Young's modulus (∼0.22-3.35 GPa in air), and nano-scale morphology (∼12.1 nm average roughness). The electrical percolation and adjustable conductivity up to 10 S m were studied. Within the sericin/Ag-nanocomposite percolation-threshold range, a miniaturized electro-mechano-sensor was prototyped with gauge factors (GF ∼ 16.95) and linearity ( ∼ 0.996), short response/recovery time (200 ms/120 ms), low detection limit (∼0.06% deformation) and power consumption (<0.1 mW), and remarkable intrinsic flexible performances (, ∼10 time outward bendings). Cell/skin biocompatibilities and detections of human muscle/joint movements and sounds were demonstrated, promising its practical potential towards  or  bio-integrated electronics.

Yun-Lu Sun

School of Information Science and Technology

Fudan University

Two-Dimensional Super-Resolution Visualization of Rat Brain Microvasculature Using Ultrasound Localization Microscopy