Qi An

A Supramolecular System for the Electrochemically Controlled Release of Cells

Please release me: Electrochemically activated cell release is achieved using a redox-active supramolecular complex. Host molecule CB[8] (green) links surface-bound viologen (purple) with solution-exposed RGD peptides (red). Electrochemical reduction dissociates the complex, releases the peptides, and thus releases the cells from the substrates. This supramolecular strategy is also applicable to microelectrodes.

Facile Method for the Fabrication of Robust Polyelectrolyte Multilayers by Post-Photo-Cross-Linking of Azido Groups

In this letter, we have developed a facile method to enhance the stability of polyelectrolyte multilayers. We fabricate conventional polyelectrolyte multilayers of PAH/PAA through electrostatic layer-by-layer (LbL) assembly and then postinfiltrate photosensitive cross-linking agent 4,4-diazostilbene-2,2-disulfonic acid disodium salt into the LbL films. After cross-linking by UV irradiation, the stability of the photo-cross-linked multilayer is highly improved as evidenced by the lack of dissolution under ultrasonication in saturated SDS aqueous solutions for 10 min. Moreover, by taking advantage of the different stability of the LbL film before and after UV irradiation, a patterned surface can be achieved.

A facile method to prepare molecularly imprinted layer-by-layer nanostructured multilayers using postinfiltration and a subsequent photo-cross-linking strategy.

In this paper, we have demonstrated a facile strategy to prepare molecularly imprinted layer-by-layer nanostructured films. This strategy has circumvented the requirement of using photocross-linkable polymers, which suffered from tedious synthetic processes in the construction of surface molecular imprinting in layer-by-layer (SMI-LbL) devices. The described SMI-LbL device was constructed by employing the traditional construction procedures of LbL systems, followed by the postinfiltration of bifunctional photosensitive cross-linking agent 4,4-diazostilbene-2,2-disulfonic acid disodium salt into the prepared multilayers, and subsequent photocross-linking. A robust SMI-LbL device with high fatigue-resistance was achieved. The preparation conditions have been optimized to achieve repeated unloading and rebinding of the targeting molecule with high fidelity. The combination of templating and cross-linking is the core factor to achieve high fidelity and high efficiency of the SMI-LbL device.

Layer-by-layer self-assembly under high gravity field.

In the present article, we have developed a facile and rapid method to fabricate a polyelectrolyte multilayer under high gravity field and investigated the difference of mass transfer in the diffusing process between LbL self-assembled technique under high gravity field (HG-LbL) and dipping assembly. Herein, we have employed polyethyleneimine and zinc oxide nanoparticles, which is a well-known UV blocking material with typical absorption properties in the range of 300-400 nm, as building blocks and applied hydrogen bonding as the driving force to construct the multilayer under HG-LbL and dipping assembly. The results show that, compared with dipping assembly, HG-LbL can highly improve the utilization and adsorption efficiency of building blocks by hastening the diffusing process, and meanwhile the resulting multilayer films still achieve comparable quality as those prepared from dipping assembly.

A facile method for the construction of stable polymer–inorganic nanoparticle composite multilayers

In this paper, we have developed a facile and general strategy to enhance the stability of multilayers incorporating nanoparticles and the weak polyelectrolyte poly(allylamine hydrochloride) (PAH). Using Fe3O4 nanoparticles (Fe3O4 NPs) and Au nanoparticles (Au NPs) as separate model systems, after multilayers of nanoparticles and PAH were constructed employing the layer-by-layer (LbL) technique, 4,4′-diazostilbene-2,2′-disulphonic acid disodium salt (DAS) was post-infiltrated into the multilayers and subsequent photochemical cross-linking was completed under UV irradiation. The stability of multilayers with Fe3O4 NPs and Au NPs were both improved significantly, and less than 15% of the nanoparticles were lost from the multilayers after an intensive agitation. The UV-visible spectroscopy and atomic force microscopy measurements supported the improvement of the stability of the multilayers.

Post-infiltration and subsequent photo-crosslinking strategy for layer-by-layer fabrication of stable dendrimers enabling repeated loading and release of hydrophobic molecules

The layer-by-layer (LbL) technique has been intensively investigated as a straightforward method for the incorporation of drug molecules or other bioactive species, enabling retarded release in drug delivery devices, in bioactive interfaces, in tissue engineering, and in regenerative medicine. The preparation of crosslinked LbL multilayers with embedded drug reservoirs for delayed release remains a challenging task, however. In the present study we have developed a method for the simultaneous utilisation of covalent interlayer linkages and drug reservoirs that can hold model drug molecules. A strategy of post-infiltration of photoactive bifunctional small molecules followed by UV irradiation has been employed for crosslinking the LbL multilayers, incorporating poly(amido amine) (PAMAM) molecules, which serve as a drug reservoir. The covalent linkage significantly alters the release profile of the model drug from the multilayers, with retarded release of hydrophobic molecules from a solvent, and enabling the loaded multilayers to withstand rinsing with 75% ethanol, the most commonly used sterilization procedure.

Immobilization of Ferrocene-Modified SNAP-Fusion Proteins

The supramolecular assembly of proteins on surfaces has been investigated via the site-selective incorporation of a supramolecular moiety on proteins. To this end, fluorescent proteins have been site-selectively labeled with ferrocenes, as supramolecular guest moieties, via SNAP-tag technology. The assembly of guest-functionalized SNAP-fusion proteins on cyclodextrin- and cucurbit [7]uril-coated surfaces yielded stable monolayers. The binding of all ferrocene fusion proteins is specific as determined by surface plasmon resonance. Micropatterns of the fusion proteins, on patterned cyclodextrin and cucurbituril surfaces, have been visualized using fluorescence microscopy. The SNAP-fusion proteins were also immobilized on cyclodextrin vesicles. The supramolecular SNAP-tag labeling of proteins, thus, allows for the assembly of modified proteins via supramolecular host-guest interaction on different surfaces in a controlled manner. These findings extend the toolbox of fabricating supramolecular protein patterns on surfaces taking advantage of the high labeling efficiency of the SNAP-tag with versatile supramolecular moieties.

A facile method to immobilize cucurbituril on surfaces through photocrosslinking with azido groups

We develop a facile method to immobilize cucurbituril on silicon substrates through photochemical reaction with azido groups. Combining photolithography and the competitive molecular recognition between CB[7] and acridine orange base or 1-adamantanecarboxylic acid, a patterned surface with reversible fluorescence emission can be obtained.

Combined Photothermal and Surface-Enhanced Raman Spectroscopy Effect from Spiky Noble Metal Nanoparticles Wrapped within Graphene-Polymer Layers: Using Layer-by-layer Modified Reduced Graphene Oxide as Reactive Precursors

To fabricate functionally integrated hybrid nanoparticles holds high importance in biomedical applications and is still a challenging task. In this study, we report the first reduced graphene oxide (rGO)-nobel metal hybrid particles that present simultaneously the photothermal and surface-enhanced Raman spectroscopy (SERS) effect from the inorganic part and drug loading, dispersibility, and controllability features from LbL polyelectrolyte multilayers. The hybrid particles where spiky noble metal particles were wrapped within rGO-polyelectrolyte layers were prepared by a facile and controllable method. rGO template modified using polyethylenimine (PEI) and poly(acrylic acid) (PAA) via layer-by-layer technology served as the reactive precursors, and the morphologies of the particles could be facilely controlled via controlling the number of bilayers around the rGO template. The hybrid particle presented low cytotoxicity. After loading doxorubicin hydrochloride, the particles effectively induced cell death, and photothermal treatment further decreased cell viability. rGO-Ag hybrid particles could be prepared similarly. We expect the reported method provides an effective strategy to prepare rGO-noble metal hybrid nanoparticles that find potential biomedical applications.

A facile method for the fabrication of covalently linked PAH/PSS layer-by-layer films

We report a facile method for the fabrication of robust polyelectrolyte multilayers including strong polyanions. Covalently cross-linked PAH/PSS [PAH: poly(allylamine hydrochloride); PSS: poly(sodium-p-styrene sulfonate)] multilayered films are fabricated using a traditional layer-by-layer technique, followed by post-infiltration of a bifunctional photoactive molecule 4,4′-diazido-2,2′-stilbenedisulfonic acid disodium (DAS) and subsequent photochemical cross-linking. The stability of the cross-linked multilayers was enhanced significantly. Over 90% of the cross-linked multilayers were preserved in a basic solution or good solvent of the polyelectrolyte, forming a clear comparison with the un-crosslinked multilayers, which almost completely decomposed under the circumstances mentioned above.