Zhitao Zhou

The Use of Functionalized Silk Fibroin Films as a Platform for Optical Diffraction‐Based Sensing Applications

A set of biocompatible, biodegradable, and biofunctionalizable diffractive optical elements (DOEs) using silk proteins as the building materials is reported. The diffraction pattern of a DOE is highly sensitive to the surrounding environment and the structural integrity, offering numerous opportunities for biosensing applications.

Nanoscale probing of electron-regulated structural transitions in silk proteins by near-field IR imaging and nano-spectroscopy

Silk protein fibres produced by silkworms and spiders are renowned for their unparalleled mechanical strength and extensibility arising from their high-β-sheet crystal contents as natural materials. Investigation of β-sheet-oriented conformational transitions in silk proteins at the nanoscale remains a challenge using conventional imaging techniques given their limitations in chemical sensitivity or limited spatial resolution. Here, we report on electron-regulated nanoscale polymorphic transitions in silk proteins revealed by near-field infrared imaging and nano-spectroscopy at resolutions approaching the molecular level. The ability to locally probe nanoscale protein structural transitions combined with nanometre-precision electron-beam lithography offers us the capability to finely control the structure of silk proteins in two and three dimensions. Our work paves the way for unlocking essential nanoscopic protein structures and critical conditions for electron-induced conformational transitions, offering new rules to design protein-based nanoarchitectures.

Precise Protein Photolithography (P3): High Performance Biopatterning Using Silk Fibroin Light Chain as the Resist

Precise patterning of biomaterials has widespread applications, including drug release, degradable implants, tissue engineering, and regenerative medicine. Patterning of protein‐based microstructures using UV‐photolithography has been demonstrated using protein as the resist material. The Achilles heel of existing protein‐based biophotoresists is the inevitable wide molecular weight distribution during the protein extraction/regeneration process, hindering their practical uses in the semiconductor industry where reliability and repeatability are paramount. A wafer‐scale high resolution patterning of bio‐microstructures using well‐defined silk fibroin light chain as the resist material is presented showing unprecedent performances. The lithographic and etching performance of silk fibroin light chain resists are evaluated systematically and the underlying mechanisms are thoroughly discussed. The micropatterned silk structures are tested as cellular substrates for the successful spatial guidance of fetal neural stems cells seeded on the patterned substrates. The enhanced patterning resolution, the improved etch resistance, and the inherent biocompatibility of such protein‐based photoresist provide new opportunities in fabricating large scale biocompatible functional microstructures.

Protein Bricks: 2D and 3D Bio‐Nanostructures with Shape and Function on Demand

Precise patterning of polymer-based biomaterials for functional bio-nanostructures has extensive applications including biosensing, tissue engineering, and regenerative medicine. Remarkable progress is made in both top-down (based on lithographic methods) and bottom-up (via self-assembly) approaches with natural and synthetic biopolymers. However, most methods only yield 2D and pseudo-3D structures with restricted geometries and functionalities. Here, it is reported that precise nanostructuring on genetically engineered spider silk by accurately directing ion and electron beam interactions with the proteins matrix at the nanoscale to create well-defined 2D bionanopatterns and further assemble 3D bionanoarchitectures with shape and function on demand, termed Protein Bricks. The added control over protein sequence and molecular weight of recombinant spider silk via genetic engineering provides unprecedented lithographic resolution (approaching the molecular limit), sharpness, and biological functions compared to natural proteins. This approach provides a facile method for patterning and immobilizing functional molecules within nanoscopic, hierarchical protein structures, which sheds light on a wide range of biomedical applications such as structure-enhanced fluorescence and biomimetic microenvironments for controlling cell fate.

Self-Powered Multifunctional Transient Bioelectronics

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 (T2 ENGs), for real-time in vivo monitoring and therapeutic treatments of epileptic seizures, are reported. These T2 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 T2 ENGs as self-powered, transient, and multifunctional implantable bioelectronic platforms.

Multicolor T-Ray Imaging Using Multispectral Metamaterials

Abstract Recent progress in ultrafast spectroscopy and semiconductor technology is enabling unique applications in screening, detection, and diagnostics in the Terahertz (T‐ray) regime. The promise of efficaciously operation in this spectral region is tempered by the lack of devices that can spectrally analyze samples at sufficient temporal and spatial resolution. Real‐time, multispectral T‐ray (Mul‐T) imaging is reported by designing and demonstrating hyperspectral metamaterial focal plane array (MM‐FPA) interfaces allowing multiband (and individually tunable) responses without compromising on the pixel size. These MM‐FPAs are fully compatible with existing microfabrication technologies and have low noise when operating in the ambient environment. When tested with a set of frequency switchable quantum cascade lasers (QCLs) for multicolor illumination, both MM‐FPAs and QCLs can be tuned to operate at multiple discrete THz frequencies to match analyte “fingerprints.” Versatile imaging capabilities are presented, including unambiguous identification of concealed substances with intrinsic and/or human‐engineered THz characteristics as well as effective diagnosis of cancerous tissues without notable spectral signatures in the THz range, underscoring the utility of applying multispectral approaches in this compelling wavelength range for sensing/identification and medical imaging.

Engineering the Future of Silk Materials through Advanced Manufacturing

Silk is a natural fiber renowned for its outstanding mechanical properties that have enabled the manufacturing of ultralight and ultrastrong textiles. Recent advances in silk processing and manufacturing have underpinned a re-interpretation of silk from textiles to technological materials. Here, it is argued that silk materials-optimized by selective pressure to work in the environment at the biotic-abiotic interface-can be harnessed by human micro- and nanomanufacturing technology to impart new functionalities and opportunities. A critical overview of recent progress in silk technology is presented with emphasis on high-tech applications enabled by recent innovations in multilevel modifications, multiscale manufacturing, and multimodal characterization of silk materials. These advances have enabled successful demonstrations of silk materials across several disciplines, including tissue engineering, drug delivery, implantable medical devices, and biodissolvable/degradable devices.

“Print-to-pattern”: Silk-Based Water Lithography

The requirement of nontoxic and versatile manufacturing frameworks for biologically relevant applications has imposed significant constraints on the choice of functional materials and the complementary fabrication tools. In this context, silk is actively studied, thanks to its mechanical robustness, biocompatibility, wide availability, aqueous processing conditions, and ease of functionalization. The inherent matching between the water solubility of silk and the aqueous inks of the inkjet printing (IJP) process has derived a biofriendly and versatile print-to-pattern scheme-termed silk-based water lithography-toward scalable functional biomanufacturing. The deposition mode of IJP and the etching effect of silk film by water features a dual tone fabrication where functional molecules are dispensed additively, while the silk film is patterned in a subtractive fashion. Such versatility and scalability pave the way to a wide range of opportunities in the biomedical field.

“Genetically Engineered” Biofunctional Triboelectric Nanogenerators Using Recombinant Spider Silk

Self-powered electronics using triboelectric nanogenerators (TENGs) is drawing increasing efforts and rapid advancements in eco/biocompatible energy harvesting, intelligent sensing, and biomedical applications. Currently, the triboelectric performances are mainly determined by the pair materials inherent electron affinity difference, and merely tuned by chemical or physical methods, which significantly limit the optional variety and output capability, especially for natural-biomaterial-based TENGs. Herein, a biocompatible triboelectric material with a programmable triboelectric property, multiple functionalization, large-scale-fabrication capability, and transcendent output performance is designed, by genetically engineering recombinant spider silk proteins (RSSP). Featuring totally green large-scale manufacturing, the water lithography technique is introduced to the RSSP-TENG with facilely adjustable surface morphology, chemically modifiable surface properties, and controllable protein conformation. By virtue of the high electrical power, a proof-of-principle drug-free RSSP-patch is built, showing outstanding antibacterial performances both in vitro and in vivo. This work provides a novel high-performance biomaterial-based TENG and extends its potential for multifunctional applications.

A Silk Cranial Fixation System for Neurosurgery

Cranial fixation should be safe, reliable, ideally degradable, and produce no hazardous residues and no artifacts on neuroimaging. Protein-based fixation devices offer an exciting opportunity for this application. Here, the preclinical development and in vivo efficacy verification of a silk cranial fixation system in functional models are reported by addressing key challenges toward clinical use. A comprehensive study on this fixation system in rodent and canine animal models for up to 12 months is carried out. The silk fixation system shows a superb performance on the long-term stability of the internal structural support for cranial flap fixation and bone reconnection and has good magnetic resonance imaging compatibility, and tolerability to high dose radiotherapy, underscoring the favorable clinical application of this system for neurosurgery compared to the current gold standard.