Hengchang Ma

AIE-Active Tetraphenylethylene Cross-Linked N-Isopropylacrylamide Polymer: A Long-Term Fluorescent Cellular Tracker

There is a great demand to understand cell transplantation, migration, division, fusion, and lysis. Correspondingly, illuminant object-labeled bioprobes have been employed as long-term cellular tracers, which could provide valuable insights into detecting these biological processes. In this work, we designed and synthesized a fluorescent polymer, which was comprised of hydrophilic N-isopropylacrylamide polymers as matrix and a hydrophobic tetraphenylethene (TPE) unit as AIE-active cross-linkers (DDBV). It was found that when the feed molar ratio of N-isopropylacrylamides to cross-linkers was 22:1, the produced polymers demonstrated the desirable LCST at 37.5 °C. And also, the temperature sensitivity of polymers could induce phase transfer within a narrow window (32-38 °C). Meanwhile, phase transfer was able to lead the florescent response. And thus, we concluded that two responses occur when one stimulus is input. Therefore, the new cross-linker of DDBV rendered a new performance from PNIPAm and a new chance to create new materials. Moreover, the resulted polymers demonstrated very good biocompatibility with living A549 human lung adenocarcinoma cells and L929 mouse fibroblast cells, respectively. Both of these cells retained very active viabilities in the concentration range of 7.8-125 μL/mg of polymers. Notably, P[(NIPAm)22-(DDBV)1] (P6) could be readily internalized by living cells with a noninvasive manner. The cellular staining by the fluorescent polymer is so indelible that it enables cell tracing for at least 10 passages.

One bioprobe: a fluorescent and AIE-active macromolecule; two targets: nucleolus and mitochondria with long term tracking

Specific organelle imaging and long-term cellular tracking are of paramount importance in monitoring biological processes, pathological pathways, and therapeutic effects, etc. Herein, we report a novel macromolecule fluorescent probe (TPPA-DBO), which is synthesized from tris(4-(pyridin-4-yl)phenyl)amine (TPPA) and 1,8-dibromononane (DBO) with a gram scale by a simple method. TPPA-DBO demonstrates a highly specific nucleolus-targeting ability, which is very challenging in the bioimaging research field. We have shown that the green nucleolus-specificity probe TPPA-DBO has advantages over the commercially available nucleolus-staining probes such as DAPI, Hoechst dyes and SYTOs in terms of its AIE-performance, large Stokes shift (175 nm), excellent photostability, and promising usefulness in live cell imaging experiments. Surprisingly, after internalizing TPPA-DBO into the nucleus region for a period of time, some TPPA-DBO are reversely diffused from nucleolus into the cytoplasm, thus resulting in the staining of mitochondria with a redder emission color. This research result may provide a new concept of cellular tracker design and provide insight into biological questions, understanding disease mechanismss, and designing new therapeutic strategies.

Fluorophore-functionalized graphene oxide with application in cell imaging

In this work, we fabricated a novel triphenylamine-derivative (DNDT)-modified nanographene oxide by following a simple gram-scale method. The product showed interesting optical properties and good potential for use in bioimaging applications. This fluorescent carbon material could be readily internalized by HepG2 cells and was clearly visualized to accumulate mainly in the nucleus.

Intriguingly tuning the fluorescence of AIEgen using responsive polyelectrolyte microspheres

In this study, we present a practical approach to tune the fluorescence of AIEgen (the luminogens exhibiting AIE attributes) based on counterion-sensitive polyelectrolyte microspheres. The tunable fluorescence is induced by counterion-driven interactions in polyelectrolyte microspheres by a simple exchange of the counterions. The effects of different types of opposite counterions on the fluorescent properties of a new polyelectrolyte tetraphenylethene-graft-poly[2-(methacryloyloxy)-ethyltrimethylammonium chloride] (TPE–PMETAC), which was synthesized by Atom Transfer Radical Polymerization (ATRP) using a TPE derivative containing four arms as an initiator, were systematically investigated. For cationic microspheres with quaternary ammonium groups, the fluorescence intensity progressively increased according to the counterion series Cl− < ClO4− < PF6− < TFSI−, which is in accord with the ability of exchanged hydrophilic Cl− by hydrophobic anions in the order of ClO4− < PF6− < TFSI−. The mechanism of tuning fluorescence was determined by dynamic light scattering (DLS), zeta-potentials and scanning electron microscopy (SEM). We proved that the size of the microspheres and electrostatic repulsive forces between the microspheres were decreased by the addition of counterions due to the hydrophobic-induced collapse of the surfaces of the microspheres. As a result, the obvious increase in the fluorescence of AIEgen was obtained based on the aggregation of microspheres.

PGS@B–N: an efficient flame retardant to improve simultaneously the interfacial interaction and the flame retardancy of EVA

A novel organic–inorganic hybrid flame retardant of PGS@B–N prepared via the decoration of palygorskite (PGS) by boric acid (B) and dodecylamine (N) was incorporated with an ethylene-vinyl acetate copolymer (EVA) to improve its flame retardance. The structure and morphology of PGS@B–N were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The flame retardance and burning behavior of the EVA/PGS@B–N/EG (expandable graphite) composite were studied through thermogravimetric analysis (TGA), limiting oxygen index (LOI), vertical burning test (UL-94), and cone calorimeter test (CCT). The results of the UL-94 and LOI tests indicated that the flame retardance of EVA/PGS@B–N/EG was better than that of EVA/PGS/EG flame-retardant composites. The data obtained from the CCT illustrated that the peak heat release rate (PHRR) of EVA with the addition of 30 wt% PGS@B–N/EG was reduced by about 25% compared to EVA with equivalent PGS/EG. The heat release rate (HRR), total release rate (THR), smoke production rate (SPR), and mass loss rate (MLR) of the composite were improved significantly. The TGA data showed that the thermal stability of EVA/PGS@B–N/EG was also well improved at high temperatures. SEM images of cryogenically fractured surfaces illustrated that EVA/PGS@B–N/EG had better interfacial interaction compared with that of EVA/PGS/EG.

Positively Charged Hyperbranched Polymers with Tunable Fluorescence and Cell Imaging Application.

Fluorescence-tunable materials are becoming increasingly attractive because of their potential applications in optics, electronics, and biomedical technology. Herein, a multicolor molecular pixel system is realized using a simple copolymerization method. Bleeding of two complementary colors from blue and yellow fluorescence segments reproduced serious multicolor fluorescence materials. Interestingly, the emission colors of the polymers can be fine-tuned in the solid state, solution phase, and in hydrogel state. More importantly, the positive fluorescent polymers exhibited cell-membrane permeable ability and were found to accumulate on the cell nucleus, exhibiting remarkable selectivity to give bright fluorescence. The DNA/RNA selectivity experiments in vitro and in vivo verified that [tris(4-(pyridin-4-yl)phenyl)amine]-[1,8-dibromooctane] has prominent selectivity to DNA over RNA inside cells.

BSA-coated fluorescent organic–inorganic hybrid silica nanoparticles: preparation and drug delivery

It is desirable to engineer bio-compatible construction materials and cargo release vehicles with efficient cargo loading capability and controlled drug delivery ability. Herein, an inorganic–organic hybrid composite DNDT&SiO2–NH2@BSA was established using two steps. Technologically, the fluorescent DNDT was grafted on the particles surface via solid phase synthesis, which was able to report the occurrence of interactions between the silica cores and proteins of bovine serum albumin (BSA) by real-time optical change analysis. It should be noted that the construction method derived from this study can be transposed easily to other surface modification procedures. Interestingly, DNDT&SiO2–NH2@BSA could be dispersed into an aqueous phase very well, leading to a homogeneous distribution of the drug over the matrix with a more efficient manner. Furthermore, due to the temperature-dependent α-helix content changes, the encapsulators of BSA can capture the drugs at low temperature and release them with elevating temperature. In particular, a desirable controlled release is realized at 37 °C.

Multiple cation-doped linear polymers toward ATP sensing and a cell imaging application

A set of multiple cation-doped linear polymers (abbreviated as OPY-1,2-BE, OPY-1,4-BB, OPY-1,8-BO, OPY-1,4-OBB) synthesized from a dipyridine derivative (OPY) and dibrominated compounds were employed as fluorescent probes for adenosine triphosphate (ATP) sensing. Among them, OPY-1,8-BO is particularly able to recognize ATP over its related compounds adenosine diphosphate (ADP), adenosine monophosphate (AMP), and other phosphate anions, with very desirable switch off–on performances. The interesting phenomenon of aggregate-induced emission (AIE) is proposed as the main reason for the ATP sensing, which is due to the ATP being more negative than the polymers and therefore there is more opportunity for connections with the multiple cation doped polymers through electrostatic attractions. Cell imaging measurements were carried out and demonstrated that even though these probes bear the same OPY core and only slightly different linkers, they are able to image different cell environments. The controlled cell imaging verified that the OPY-1,8-BO probe has ATP-specific recognition in living cells.

A direct crossed polymerization of triphenylamines and cyclohexanones via CC bond formation: the method and its bioimaging application

The effective polymerization process is very desirable in the field of macromolecule science. In this study, we present a facile synthetic method via aldol addition and condensation (AAC) that leads to the formation of fluorescent linear and branched polymers by cross coupling triphenylamines (TPA) and cyclohexanones (CYC) via CC bond formation. The methodology has the advantage of easy operations, mild reaction conditions, and high yield. Via the analysis of NMR, FT-IR, GPC, PL, UV, SEM, and theoretical calculation, the structure, physical properties, and optical behaviors of both polymers were well-characterized. The understanding of cell transplantation, migration, division, fusion, and lysis is a very challenging task. In this study, the linear polymer (LP) exhibits excellent biocompatibility and low cytotoxicity, which can be readily internalized by living cells in a noninvasive manner. The images of MPC5 cells indicate that LP can be a promising emissive fluorescence probe for bioimaging application.