Hongchi Zhao

A novel water-soluble fluorescent polymer based on perylene bisimides dyes: one-pot preparation and its bio-imaging

Abstract Perylene bisimides dye-based water-soluble fluorescent polymer P3, N,N’-bis(3-amyl)-1-bromo-7-{4’-[3’’-(S-poly(N-acryloyl ethylene diamine hydrochloride)-2’’’-methyl propionic acid)propionyloxy hexyloxy]phenyl} perylene-3,4:9,10-tetracarboxylic bisimides, was synthesized with polyelectrolyte modification via one-pot reaction (the reduction reaction of trithioester and click reaction between the thiol group and carbon–carbon double bond were simultaneously conducted in one pot with high conversion). One-pot method can overcome the limitation that usual click reaction between thiol and other groups has low conversion because thiol group is subject to rapid oxidation during purification and storage. Chemical, structural, and optical properties of P3 and intermediate products were fully characterized by nuclear magnetic resonance spectroscopy, Fourier transform infrared, gel permeation chromatograph, UV–vis spectra, and fluorescence spectra, respectively. The results revealed that P3 displayed excellent water solubility and not only exhibited red strong fluorescence emission band in water but also had the similar photoluminescent spectra to those of intermediate products (M4 and P2) in chloroform. Allowing for the potential application in biological detection field, cell viability and live cell imaging with the presence of P3 were further investigated with Hela cells. The results showed that P3 had low cytotoxicity with strong intracellular fluorescence entry. Meanwhile, with the augment of concentration of P3 (0–0.500 mg mL−1), the cell uptake and accumulation of P3 increased and thereby result in enhancement of the intracellular fluorescence. These experiment results suggested that P3 had enormous potential as a fluorescence probe to be an important component in biological detection field.

Synthesis backbone-dual-responsive of hyperbranched poly(bis(N,N-ethyl acrylamide))s by RAFT

Hyperbranched poly(bis(N,N-ethyl acrylamide))s (HPNAMs) with many vinyls as terminal groups were synthesized successfully using reversible addition fragmentation chain transfer polymerization (RAFT). Detailed analyses, based on the molecular weight, α value, degree of branching (DB), and lower critical solution temperature (LCST) obtained from nuclear magnetic resonance (NMR), multi detector-size exclusion chromatography (MDSEC), ultravioletvisible (UV-vis) spectroscopy, and dynamic light scattering (DLS), indicate that we acquired backbone-temperature and pH responsive HPNAM. Factors, such as DB, molecular weight, and pH value, that affect the LCST were investigated. It was found that the molecular weights of the hyperbranched polymers show significant influence on the LCSTs. For the HPNAMs with low molecular weight, the LCSTs decreased as the DB increased, and the LCSTs can also be adjusted by changing the pH value of solutions. Furthermore, the result of cell cytotoxicity indicates that this new dual responsive hyperbranched polymer has low cytotoxicity and exhibits potential for biomedical applications.

A new method for synthesizing hyperbranched polymers with reductive groups using redox/RAFT/SCVP

The novel hyperbranced polymers containing reductive groups were successfully prepared and characterized using redox/reversible addition fragmentation chain transfer (RAFT)/self-condensing vinyl polymerization (SCVP) method. Several redox initiating chemicals such as Cu(III)/-CONH2, Ce(IV)/-CONH2 and Ce(IV)/-OH were chosen to increase the free radical generating rate, and the chain transfer agent (CTA) was used to reduce the molecular chain propagating rate, in order to obtain polymers with high degree of branching. Detailed analyses based on the molecular weight, α value and the degree of branching of polymers (DB) obtained from 1H-NMR spectra and multi detector size exclusion chromatography (MDSEC) suggested the acquiring of hyperbranced polyacrylamides with Cu(III)/-CONH2 and Ce(IV)/-CONH2 as initiator in the presence of the CTA. Meanwhile, the as-prepared poly(N-hydroxymethyl acrylamide) (PNHAM) with higher DB value (0.48) proved that using Ce(IV)/-OH as the initiator could increase the free radical generating rate and diminish the gap between the propagating rate and the initiation rate during the reaction procedure. In addition, the effect of oxidant concentration on the Mark-Houwink index (α) value and the DB was also studied.

A Novel Water-Soluble Fluorescence Probe with Wash-Free Cellular Imaging Capacity Based on AIE Characteristics

A potential real-time imaging water-soluble fluorescent polymer (P3) is facilely prepared via one-pot method. For P3, tetraphenylethene unit serves as the fluorescent unit, poly(acryloyl ethylene diamine) (a kind of polyelectrolyte) with specific degree of polymerization acts as water-soluble part. 1 H-NMR, gel permeation chromatography (GPC), UV-vis spectroscopy, photoluminescence (PL), and confocal laser scanning microscopy are undertaken to characterize the structure and property of P3. The results of wash-free cellular imaging show that the signal-to-noise ratio is high as the concentration of P3 is 50 μg mL-1 . In addition, the pH-responsive and Cd2+ -responsive are also investigated in this paper. The results coming from pH-responsive show that P3 solution displays significant fluorescence under near neutral. And the result from the cellular imaging shows that intracellular fluorescence intensity enhances with the augment of concentration of Cd2+ , which reveals that P3 can give a hint to resolve the dilemma of traditional fluorescent dyes used as living cellular fluorescent probe.

The Synthesis of Backbone Thermo and pH Responsive Hyperbranched Poly(Bis(N,N-Propyl Acryl Amide))s by RAFT

Hyperbranched poly(methylene-bis-acrylamide), poly(bis(N,N-propyl acryl amide)) (HPNPAM) and poly(bis(N,N-butyl acryl amide)) were synthesized by reversible addition-fragmentation chain transfer polymerization. HPNPAMs showed lower critical solution temperature (LCST) due to an appropriate ratio between hydrophilic and hydrophobic groups. The effects of reaction conditions on polymerization were investigated in detail. The structure of HPNPAM was characterized by 1H NMR, FT-IR, Muti detector-size exclusion chromatography (MDSEC) and Ultravioletvisble (UV-Vis). The α value reached 0.20 and DB was 90%, indicating HPNPAMs with compact topology structure were successfully prepared. LCSTs were tuned by Mw and the pH value of the solution. The change of molecular size was assayed by dynamic light scattering and scanning electron microscope. These results indicated that the stable uniform nanomicelles were destroyed and macromolecules aggregated together, forming large particles as temperature exceeded LCST. In addition, after the cells were incubated for 24 h, the cell viability reached 80%, which confirmed this new dual responsive HPNPAM had low cytotoxicity.

Facile preparation of thermosensitive and water-soluble fluorescent polymer containing curcumin and its cell imaging

ABSTRACT A novel thermosensitive and water-soluble fluorescent polymer PNIPAM-curcumin (P2) containing curcumin unit was synthesized through one-pot method. The chemical structure and optical properties of compounds and polymer were characterized and tested. As the results turned out that P2 displayed excellent water solubility, thermosensitivity and exhibited strong fluorescence emission band in water. Moreover, P2 was further investigated by MTT assay and live cell imaging with HeLa cells. P2 did not have cytotoxicity in concentration of 200 µg · mL−1 within 48 h and the intracellular fluorescence intensity enhanced with the concentration of P2 varying from 0 to 500 µg · mL−1. According to the experimental results, as a fluorescence probe, P2 synthesized does not only possess nice water solubility but also has the advantage of no cytotoxicity, and it can easily enter the cells, which indicates that it is a characteristic of high sensitivity and responsiveness. Therefore, P2 will have immense potential to be applied in biomedical fields. GRAPHICAL ABSTRACT