Polycation-functionalized gold nanodots with tunable near-infrared fluorescence for simultaneous gene delivery and cell imaging

Near-infrared （NIR） fluorescent metal nanodots may have significant advantages in biological detection and bioimaging. Herein, we introduce tunable near-infrared fluorescent gold nanodots （AuNDs） protected by branched polyethylenimine （PEI） modified by surface segmental attachment of sulfhydryl groups （PEI-SH）, abbreviated as PEI-SH-AuNDs, for simultaneous gene delivery and cell imaging. The modified PEI endows the resultant PEI-SH-AuNDs with the following excellent advantages. Sulfhydryl groups of PEI-SH anchor to the surface of AuNDs, and such polycations with amine groups give PEI-SH-AuNDs remarkable stability. The cationic polymer PEI-SH with positive charges enables PEI-SH-AuNDs to perform gene delivery, and the gene transfection efficiency can reach 22.8%. Moreover, the fluorescence of PEI-SH-AuNDs is tunable from visible red light （wavelength 609 nm） to NIR light （wavelength 811 run） via an increase in the size of AuNDs. PEI-SH-AuNDs yielded gene transfection efficiency similar to that of commercial PEI, but showed much lower cytotoxicity and much greater red-shift fluorescence. With excellent photoluminescent properties, such multifunctional fluorescent PEI-SH-AuNDs hold promise in applications to bioimaging and as ideal fluorescent probes for tracking gene transfection behavior.

Dimension-Controllable and Photo-Responsive Supramolecular Organic Framworks through Cucurbit[8]uril-based Self-Assembly

Dimension-controllable supramolecular organic frameworks(SOFs)with aggregation-enhanced fluorescence are hierarchically fabricated through the host-guest interactions of cucurbit[8]uril(CB[8])and coumarin-modified tetraphenylethylene derivatives(TPEC).The three-dimensional layered SOFs could be constructed from the further stacking of two-dimensional mono-layered structures via simply regulating the self-assembly conditions including the culturing time and concentration.Upon light irradiation under the wavelength of 365 nm,the photodimerization of coumarin moieties occurred,which resulted in the transformation of the resultant TPECn/CB[8]4n two-dimensional SOFs into robust covalently-connected 2D polymers with molecular thickness.Interestingly,the supramolecular system of TPEC/CB[8]exhibited intriguing multicolor fluorescence emission from yellow to blue in the time range of 0-24 h at 365 nm irradiation,possessing potential applicability for photochromic fluorescence ink.

Recent advances in two-step energy transfer light-harvesting systems driven by non-covalent self-assembly

Sequential energy transfer is ubiquitous in natural light-harvesting systems(LHSs),which greatly promotes the exploitation of light energy.The LHSs in nature are sophisticated supramolecular assemblies of chlorophyll molecules that carry out efficient light harvesting through cascade energy transfer process.Inspired by nature,scientists have paid much attention to fabricate stepwise LHSs based on assorted supramolecular scaffolds in recent years.Light-harvesting antennas and energy acceptors can be accommodated in particular scaffolds,which offer great convenience for energy transfer between them.These systems not only further mimic photosynthesis,but also demonstrate many potential applications,such as photocatalysis,tunable luminescence,and information encryption,etc.In this review article,aiming at offering a practical guide to this emerging research field,the introduction of construction strategies towards sequential LHSs will be presented.Different scaffolds are classified and highlighted,including host-guest assemblies,metal-coordination assemblies,as well as bio-macromolecular and other supramolecular scaffolds.

Ion-induced white-light-emitting polymeric hydrogels with high mechanical strength and reversible stimuli-responsive properties

We have developed a facile strategy to fabricate model multicolor hydrogels via a straightforward mixing process of poly acrylonitrile-grafted methacrylamide(PANMAM),polymethacrylic acid(PMAA)and doped lanthanide(Eu/Tb)and zinc ions to form the interpenetrating dual-polymer gel networks.The hydrogels exhibit excellent tunability of multi-spectrum emission colors(including white light)by simply varying the stoichiometry of metal ions.Furthermore,taking the advantage of different metal ion response mechanisms,we have demonstrated the reversible acidity/alkalinity stimuli-responsive behaviors of white-light-emitting hydrogel(WLE gel).Meanwhile,the unique cross-linked network formed through hydrogen-bonding,metal-ligand coordination and ionic interaction is introduced to achieve favorable mechanical strength of hydrogels.These properties enable the possibility in obtaining fluorescent patterns on hydrogels,which are promising candidate for encrypted information with improved security.