Preparation of Hybrid Hydrogel Containing Ag Nanoparticles by a Green in Situ Reduction Method

In this Article, large and uniform Ag nanoparticle-containing hybrid hydrogels were prepared by in situ reduction of Ag ions in cross-linked tapioca dialdehyde starch (DAS)–chitosan hydrogels. In the hybrid hydrogels, chitosan was chosen as a macromolecular cross-linker because of its abundant source and good biocompatibility. The hybrid hydrogel showed good water-swelling properties, which could be controlled by varying the ratio of chitosan to tapioca DAS in the hydrogel. The reductive aldehyde groups in the cross-linked hydrogels could be used to reduce Ag ions to Ag nanoparticles without any additional chemical reductants. Interestingly, by controlling the reduction conditions such as the tapioca DAS concentration, aqueous AgNO₃ concentration, reaction time, and aqueous ammonium concentration, Ag nanoparticles with different sizes and morphologies were obtained. Because of their biocompatibility, degradable constituents, mild reaction conditions, and controlled preparation of Ag nanoparticles, these tapioca DAS–chitosan/Ag nanoparticle hybrid hydrogels show promise as functional hydrogels

Self-Assembly of Conjugated Polymer on Hybrid Nanospheres for Cellular Imaging Applications

A new kind of hybrid core–shell nanosphere was fabricated by combining the in situ formation of Au nanoparticles and covalent cross-linking of biocompatible carboxymethyl starch dialdehyde (CMSD) and chitosan (CTS). When the fluorescent dye poly­[9,9′-bis­(6″-(<i>N</i>,<i>N</i>,<i>N</i>-trimethylammonium)-hexyl)­fluorene-2,7-ylenevinylene-<i>co</i>-alt-1,4-phenylene dibromide] (PFV) was assembled on the surface of the hybrid nanospheres through electrostatic attraction, these biocompatible hybrid nanospheres exhibited metal-enhanced fluorescence effects. The fluorescence intensity of (CTS–Au)@CMSD/PFV hybrid nanosphere is 1.43 times that of CTS–CMSD/PFV hybrid nanospheres lacking Au nanoparticle. In addition, the (CTS–Au)@CMSD/PFV hybrid nanospheres exhibit excellent biodegradability upon exposure to enzymatic aqueous solution and good biocompatibility when cocultured with HeLa cervical carcinoma cells; these advantages make them attractive for cellular imaging and biological analysis and detection

Self-Assembly of Fluorescent Organic Nanoparticles for Iron(III) Sensing and Cellular Imaging

Fluorescent organic nanoparticles have attracted increasing attentions for chemical or biological sensing and imaging due to their low-toxicity, facile fabrication and surface functionalization. In this work, we report novel fluorescent organic nanoparticles via facile self-assembly method in aqueous solution. First, the designed water-soluble fluorophore shows a weak and negligible intrinsic fluorescence in water. Upon binding with adenosine-5′-triphosphate (ATP), fluorescent nanoparticles were formed immediately with strongly enhanced fluorescence. These fluorescent nanoparticles exhibit high sensitivity and selectivity toward Fe³⁺ sensing with detection limit of 0.1 nM. In addition, after incubation with HeLa cells, the fluorophore shows excellent imaging performance by interaction with entogenous ATP in cells. Finally, this fluorescent system is also demonstrated to be capable of Fe³⁺ sensing via fluorescence quenching in cellular environment

Fabrication of Au@Pt Multibranched Nanoparticles and Their Application to In Situ SERS Monitoring

Here, we present an Au@Pt core–shell multibranched nanoparticle as a new substrate capable of in situ surface-enhanced Raman scattering (SERS), thereby enabling monitoring of the catalytic reaction on the active surface. By careful control of the amount of Pt deposited bimetallic Au@Pt, nanoparticles with moderate performance both for SERS and catalytic activity were obtained. The Pt-catalyzed reduction of 4-nitrothiophenol by borohydride was chosen as the model reaction. The intermediate during the reaction was captured and clearly identified via SERS spectroscopy. We established in situ SERS spectroscopy as a promising and powerful technique to investigate in situ reactions taking place in heterogeneous catalysis

Binding-Directed Energy Transfer of Conjugated Polymer Materials for Dual-Color Imaging of Cell Membrane

Binding of biomolecules or probes to the plasma membrane is of great importance for investigations of cell morphology and various biological processes. Herein, a water-soluble conjugated polymer is designed as a membrane probe. The probe shows a strong affinity toward lipid membranes owing to the high charge density from abundant imidazolium moieties together with the moderate rigidity and hydrophobicity derived from the conjugated backbone. Upon binding with a membrane, the interchain FRET of the probe was substantially enhanced, which resulted in the emission of both blue and red fluorescence. This is favorable for dual-color imaging. Finally, cellular experiments demonstrate the excellent performance of this macromolecular probe on stable binding with cell membranes without the appearance of cell endocytocysis even after a long retention time

Facile Preparation of Fluorescent Nanoparticles with Tunable Exciplex Emission and Their Application to Targeted Cellular Imaging

Fluorescent nanoparticles with a tunable emission show a good potential for usage in biological imaging. Exciplex emission usually appears with a large red shift from the normal emission peak. The integration of exciplex emission into nanoparticles offers a rational strategy to designing fluorescent nanoparticles with a tunable emission. In this work, we doped electron acceptors into the electron donor poly­(<i>N</i>-vinylcarbazole) (PVK) to develop novel fluorescent nanoparticles with a conveniently modulated PVK emission. Through careful design of the molecular structures of the electron acceptors, we demonstrated that controlled donor–acceptor spatial stacking and electron transitions could regulate the exciplex emission of the PVK/acceptor nanoparticles. Thus, the structurally controlled exciplex formation allowed for the preparation of multicolored fluorescent nanoparticles. Moreover, further modifications with the cyclic peptide RGD showed little disruption to the structure of the PVK/acceptor nanoparticles and the corresponding exciplex emission. Hence, the nanoparticles showed the ability to be used for targeted cellular imaging. On the basis of the RGD-integrin α_vβ₃ (ligand<i>–</i>receptor) interaction, the nanoparticles were effectively endocytosed by target cancer cells. We anticipate that this research could provide a new strategy for the fabrication of fluorescent nanoparticles with a tunable emission, leading to useful materials for fluorescent imaging

Ultrabright Fluorescent Silica Nanoparticles Embedded with Conjugated Oligomers and Their Application in Latent Fingerprint Detection

Fluorescent micro- and nanosized particles have a broad range of applications in biology, medicine, and engineering. For these uses, the materials should have high emission efficiency and good photostability. However, many organic fluorophores suffer from aggregation-induced quenching effects and photobleaching. Here, we used a simple method based on covalently blending a fluorescent conjugated oligomer with silica nanoparticles to achieve emission quantum yields as high as 97%. The resulting system also showed excellent stability under continuous light illumination, in a range of pH values and temperatures, and in common solvents. This fluorescent material showed outstanding properties, including highly efficient blue emission, low cost, low toxicity, and easy synthesis. Furthermore, its effectiveness for latent fingerprint detection was demonstrated as a proof of concept on various substrates. The obtained emissive fingerprint powder gave good optical/fluorescent images with high contrast and resolution between the ridges and spaces

Conjugated Polymer with Aggregation-Directed Intramolecular Förster Resonance Energy Transfer Enabling Efficient Discrimination and Killing of Microbial Pathogens

Rapid and effective differentiation and killing of microbial pathogens are major challenges in the diagnosis and treatment of infectious diseases. Here, we report a novel system based on the conjugated polymer poly­[(9,9-bis­{6′-[<i>N</i>-(triethylene glycol methyl ether)-di­(1<i>H</i>-imidazolium)­methane]­hexyl}-2,7-fluorene)-<i>co</i>-4,7-di-2-thienyl-2,1,3-benzothiadiazole] tetrabromide (PFDBT-BIMEG), which enables efficient microbial pathogen discrimination and killing. The functional side chains of PFDBT-BIMEG enabled both electrostatic and salt bridge interactions with microorganisms. Microorganism binding events caused a change in the aggregation structure of PFDBT-BIMEG, which could be recognized by a change of its fluorescence signal by intramolecular Förster resonance energy transfer (FRET). This sensing strategy allowed rapid and sensitive distinction of microbial pathogens within 15 min. We performed linear discrimination analysis that featured this advance to confirm that the polymer PFDBT-BIMEG could accurately classify microbial pathogens. Owing to the different adhesion mechanism of PFDBT-BIMEG to the surface of the microorganisms, we applied different sterilization strategies for each kind of microbial pathogen. The microbial pathogens could be efficiently killed by reactive oxygen species produced from PFDBT-BIMEG under irradiation, avoiding the use of any other antibacterial agents. This methodology, which combines pathogen discrimination and killing, represents a promising alternative to current diagnostic platforms