Nan Qin

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.

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.

Electron regulated 3D nanostructuring of natural silk fibroin protein revealed by near-field nano-spectroscopy

In this work, we report on the discovery of the full ß-sheet structural evolution in natural silk fibroin protein due to electron-protein interaction and its application in complex 3D protein nanofabrication. Using near-field infrared nano-imaging and nano-spectroscopy, the electron regulated silk fibroin protein polymorphic transitions are revealed at the resolution approaching the molecular limit. Taking advantage of the nature of the protein-electron interaction, which enables the protein to be used as an Electron Beam Lithography (EBL) resist with different structure formation mechanism, silk fibroin based complex 3D nanostructures can be fabricated.

Micropatterning of silk proteins for soft bioactive diffractive optical elements

We present a method of making green, bioactive, low cost diffractive optical elements (DOEs) using silk fibroin proteins. DOEs usually permit a reduction in the number of optical elements in a design, reducing costs and lens weight. Compared with conventional DOEs made of glass or other transparent materials, silk protein based DOE structures are usually more flexible, thinner, lighter, and more importantly biocompatible and bioactive. The green silk protein films can be used to lock and unlock the information stored in DOE made on silica with only water being used. The whole process is simple, inexpensive, and environment-friendly.

Silk: New opportunities for an ancient material in MEMS/NEMS

This paper demonstrates potential uses of naturally regenerated/extracted silk proteins as a promising biopolymer platform for applications in micro- and nanofabrication with initial attempts and successes on commonly used pattern transfer techniques such as e-beam lithography, soft lithography and nano-imprinting.