Finer Structures of Polyelectrolyte Multilayers Reflected by Solution ¹H NMR

Water-dispersible polyelectrolyte multilayers (PEM) were obtained by layer-by-layer assembly of poly(allylamine hydrochloride) (PAH) and poly(sodium 4-styrene sulfonate) (PSS) on water-soluble poly(ethylene glycol)-graft-multiwalled carbon nanotubes (PEG-g-MWNTs), and their structures were investigated using solution 1H NMR. It was clearly shown that some segments of the adsorbed topmost layers formed in layer-by-layer assembly processes are still highly mobile in aqueous solution, and these segments are totally compensated by subsequent coatings of the oppositely charged layers to form ionically cross-linked polyelectrolyte complexes (PEC) layers; it was demonstrated that the ionization behaviors of the highly mobile segments of the topmost PAH layers are similar to those in solution rather than those in the bulk multilayers at different pH. Furthermore, the similarity among the PEM on substrates and the PEC colloids prepared under similar conditions in solution was supported by solution 1H NMR results, and the unequal stiochiometry of the cationic group from PAH and the anionic group from PSS in the cores of the PEC colloids in solution was identified from solution 1H NMR results using PEG as external references. On the basis of these, it is suggested that the PEC layers in PEM formed from coating of the adsorbed topmost PAH layers with PSS solution contain excess PSS, and reversely those formed from coating of the adsorbed topmost PSS layers with PAH solution contain excess PAH. Hence a new description of PEM is put forward that the polyelectrolyte multilayers are composed of alternate layers excess either in PSS or in PAH

‘Living’ Controlled <i>in Situ</i> Gelling Systems: Thiol−Disulfide Exchange Method toward Tailor-Made Biodegradable Hydrogels

A ‘living’ controlled hydrogel formation method was first reported to create loose and compact in situ biodegradable hydrogels. The method executed under mild reaction conditions can conveniently tailor the hydrogel properties, and it has the potential to develop into a powerful tool for the design, synthesis, and self-assembly of novel tailor-made biomaterials and drug delivery systems

Transformative Two-Dimensional Array Configurations by Geometrical Shape-Shifting Protein Microstructures

Two-dimensional (2D) geometrical shape-shifting is prevalent in nature, but remains challenging in man-made “smart” materials, which are typically limited to single-direction responses. Here, we fabricate geometrical shape-shifting bovine serum albumin (BSA) microstructures to achieve circle-to-polygon and polygon-to-circle geometrical transformations. In addition, transformative two-dimensional microstructure arrays are demonstrated by the ensemble of these responsive microstructures to confer structure-to-function properties. The design strategy of our geometrical shape-shifting microstructures focuses on embedding precisely positioned rigid skeletal frames within responsive BSA matrices to direct their anisotropic swelling under pH stimulus. This is achieved using layer-by-layer two photon lithography, which is a direct laser writing technique capable of rendering spatial resolution in the sub-micrometer length scale. By controlling the shape, orientation and number of the embedded skeletal frames, we have demonstrated well-defined arc-to-corner and corner-to-arc transformations, which are essential for dynamic circle-to-polygon and polygon-to-circle shape-shifting, respectively. We further fabricate our shape-shifting microstructures in periodic arrays to experimentally demonstrate the first transformative 2D patterned arrays. Such versatile array configuration transformations give rise to structure-to-physical properties, including array porosity and pore shape, which are crucial for the development of on-demand multifunctional “smart” materials, especially in the field of photonics and microfluidics

Transformative Two-Dimensional Array Configurations by Geometrical Shape-Shifting Protein Microstructures

Two-dimensional (2D) geometrical shape-shifting is prevalent in nature, but remains challenging in man-made “smart” materials, which are typically limited to single-direction responses. Here, we fabricate geometrical shape-shifting bovine serum albumin (BSA) microstructures to achieve circle-to-polygon and polygon-to-circle geometrical transformations. In addition, transformative two-dimensional microstructure arrays are demonstrated by the ensemble of these responsive microstructures to confer structure-to-function properties. The design strategy of our geometrical shape-shifting microstructures focuses on embedding precisely positioned rigid skeletal frames within responsive BSA matrices to direct their anisotropic swelling under pH stimulus. This is achieved using layer-by-layer two photon lithography, which is a direct laser writing technique capable of rendering spatial resolution in the sub-micrometer length scale. By controlling the shape, orientation and number of the embedded skeletal frames, we have demonstrated well-defined arc-to-corner and corner-to-arc transformations, which are essential for dynamic circle-to-polygon and polygon-to-circle shape-shifting, respectively. We further fabricate our shape-shifting microstructures in periodic arrays to experimentally demonstrate the first transformative 2D patterned arrays. Such versatile array configuration transformations give rise to structure-to-physical properties, including array porosity and pore shape, which are crucial for the development of on-demand multifunctional “smart” materials, especially in the field of photonics and microfluidics

3D Security Labels: Photostable Multimaterial Multilayered QR Codes via Two-Photon Lithography

Current 3D micrometer-sized covert security labels are limited to simple designs involving graphics, texts, and numerical elements that constrain coding/decoding complexity and data density. Herein, we introduce photostable perylene dye-doped 3D security labels that feature intricate multimaterial and multilayered machine-readable quick-response (QR) codes fabricated using two-photon lithography (TPL). Leveraging precise label sizing and positioning, our innovative “QR codes-in-QR code” approach significantly enhances data storage capacity by over 250%. To bolster security, we employ a 2.0 μm thick 3D cover engraved with QR codes to conceal the 2D QR codes. We extend our advancements by introducing QR code-engraved 3D covers with stair-step patterns and 3D security labels featuring multimaterial, multilayered machine-decipherable QR codes. These 3D QR code-based security labels demonstrate minimal color and information interference and offer exceptional security levels. Even after 6 months of storage, they consistently provide repetitive readouts without degradation and photobleaching. These labels augment data concealment, decoding complexity, and photostability in enhancing their efficacy and longevity in data storage, communication, and anticounterfeiting applications

Formulating an Ideal Protein Photoresist for Fabricating Dynamic Microstructures with High Aspect Ratios and Uniform Responsiveness

The physical properties of aqueous-based stimuli-responsive photoresists are crucial in fabricating microstructures with high structural integrity and uniform responsiveness during two-photon lithography. Here, we quantitatively investigate how various components within bovine serum albumin (BSA) photoresists affect our ability to achieve BSA microstructures with consistent stimuli-responsive properties over areas exceeding 10⁴ μm². We unveil a relationship between BSA concentration and dynamic viscosity, establishing a threshold viscosity to achieve robust BSA microstructures. We also demonstrate the addition of an inert polymer to the photoresist as viscosity enhancer. A set of systematically optimized processing parameters is derived for the construction of dynamic BSA microstructures. The optimized BSA photoresists and processing parameters enable us to extend the two-dimensional (2D) microstructures to three-dimensional (3D) ones, culminating in arrays of micropillars with aspect ratio > 10. Our findings foster the development of liquid stimuli-responsive photoresists to build multifunctional complex 3D geometries for applications such as bioimplantable devices or adaptive photonic systems

3D Security Labels: Photostable Multimaterial Multilayered QR Codes via Two-Photon Lithography

Current 3D micrometer-sized covert security labels are limited to simple designs involving graphics, texts, and numerical elements that constrain coding/decoding complexity and data density. Herein, we introduce photostable perylene dye-doped 3D security labels that feature intricate multimaterial and multilayered machine-readable quick-response (QR) codes fabricated using two-photon lithography (TPL). Leveraging precise label sizing and positioning, our innovative “QR codes-in-QR code” approach significantly enhances data storage capacity by over 250%. To bolster security, we employ a 2.0 μm thick 3D cover engraved with QR codes to conceal the 2D QR codes. We extend our advancements by introducing QR code-engraved 3D covers with stair-step patterns and 3D security labels featuring multimaterial, multilayered machine-decipherable QR codes. These 3D QR code-based security labels demonstrate minimal color and information interference and offer exceptional security levels. Even after 6 months of storage, they consistently provide repetitive readouts without degradation and photobleaching. These labels augment data concealment, decoding complexity, and photostability in enhancing their efficacy and longevity in data storage, communication, and anticounterfeiting applications

3D Security Labels: Photostable Multimaterial Multilayered QR Codes via Two-Photon Lithography

Current 3D micrometer-sized covert security labels are limited to simple designs involving graphics, texts, and numerical elements that constrain coding/decoding complexity and data density. Herein, we introduce photostable perylene dye-doped 3D security labels that feature intricate multimaterial and multilayered machine-readable quick-response (QR) codes fabricated using two-photon lithography (TPL). Leveraging precise label sizing and positioning, our innovative “QR codes-in-QR code” approach significantly enhances data storage capacity by over 250%. To bolster security, we employ a 2.0 μm thick 3D cover engraved with QR codes to conceal the 2D QR codes. We extend our advancements by introducing QR code-engraved 3D covers with stair-step patterns and 3D security labels featuring multimaterial, multilayered machine-decipherable QR codes. These 3D QR code-based security labels demonstrate minimal color and information interference and offer exceptional security levels. Even after 6 months of storage, they consistently provide repetitive readouts without degradation and photobleaching. These labels augment data concealment, decoding complexity, and photostability in enhancing their efficacy and longevity in data storage, communication, and anticounterfeiting applications

3D Security Labels: Photostable Multimaterial Multilayered QR Codes via Two-Photon Lithography

Current 3D micrometer-sized covert security labels are limited to simple designs involving graphics, texts, and numerical elements that constrain coding/decoding complexity and data density. Herein, we introduce photostable perylene dye-doped 3D security labels that feature intricate multimaterial and multilayered machine-readable quick-response (QR) codes fabricated using two-photon lithography (TPL). Leveraging precise label sizing and positioning, our innovative “QR codes-in-QR code” approach significantly enhances data storage capacity by over 250%. To bolster security, we employ a 2.0 μm thick 3D cover engraved with QR codes to conceal the 2D QR codes. We extend our advancements by introducing QR code-engraved 3D covers with stair-step patterns and 3D security labels featuring multimaterial, multilayered machine-decipherable QR codes. These 3D QR code-based security labels demonstrate minimal color and information interference and offer exceptional security levels. Even after 6 months of storage, they consistently provide repetitive readouts without degradation and photobleaching. These labels augment data concealment, decoding complexity, and photostability in enhancing their efficacy and longevity in data storage, communication, and anticounterfeiting applications

Redox-Responsive Hyperbranched Poly(amido amine)s with Tertiary Amino Cores for Gene Delivery

Redox-responsive hyperbranched poly­(amido amine)­s (PAAs) with tertiary amino cores and amine, poly­(ethylene glycol) (PEG) and hydroxyl terminal groups were prepared for DNA delivery respectively. The DNA condensation capability of PAAs was investigated using gel electrophoresis, and the results showed that PAA terminated with 1-(2-aminoethyl)­piperazine (AEPZ) (BAA) is the most efficient in binding plasmid DNA (pDNA). The diameter and zeta-potential of polyplexes from PAAs were characterized using dynamic light scattering (DLS), and the morphology of the polyplexes was obtained using atomic force microscopy (AFM). All the PAAs were able to condense pDNA into nanoparticles with diameters between 50 and 200 nm with a positive surface charge when the weight ratio of polymer/DNA was higher than 20. Glutathione (GSH)-induced DNA release from polyplexes and the buffering capability of PAAs were investigated as well. Cytotoxicity of PAAs and <i>in vitro</i> gene transfection of polyplexes were evaluated in HEK293, COS-7, MCF-7 and Hep G2 cell lines, respectively. The results reflect that PAAs show remarkably low or even no cytotoxicity, and that PAA with amino terminal groups mediates the most efficient gene transfection with the transfection efficiency comparable to that of 25 kDa polyethylenimine. Further the effects of the presence of buthionine sulfoximine (BSO) on the transfection efficiency and cytotoxicity of BAA polyplexes were investigated