Fengjie Deng

Interaction of tannic acid with carbon nanotubes: enhancement of dispersibility and biocompatibility

The interaction of manufactured nanomaterials with environmental and biological systems has been a subject of great research interest for a long time. In the present study, adsorption of a universal environmental organic material (named tannic acid (TA)) on carbon nanotubes (CNTs) was investigated. The influence of CNT properties and pH values on the sorption capacity of CNTs for TA was also evaluated. Our results demonstrated that the sorption capacity of CNTs was positively correlated with their specific surface areas. Furthermore, TA could effectively enhance the water dispersibility of CNTs and reduce their cytotoxicity. Our results implied that TA could influence the environmental behavior and biological responses of the manufactured nanomaterials, reminding us that much more attention should be paid to the synergistic toxicity of nanomaterials when we evaluate their environmental impacts.

Self-polymerization of dopamine and polyethyleneimine: novel fluorescent organic nanoprobes for biological imaging applications

The development of novel fluorescent nanoprobes has attracted great current research interest over the past few decades due to their superior optical properties and multifunctional capability as compared with small organic dyes. Although great advance has been made in the utilization of fluorescent nanoprobes for biomedical applications, development of novel fluorescent nanoprobes that possess good fluorescent properties, biocompatibility, biodegradability and water dispersibility through a convenient and effective route is still highly desirable. In this work, we reported for the first time that novel fluorescent organic nanoparticles (FONs) can be conveniently fabricated via self-polymerization of dopamine and polyethyleneimine at room temperature and in an air atmosphere within 2 h. These FONs exhibited strong green fluorescence, high water stability and excellent biocompatibility, making them highly potential for biological imaging applications. More importantly, due to the high reactivity of polydopamine, these FONs might also be further functionalized with other functional components through Michael addition or Schiff base reaction. Therefore the method described in this work would open new avenues for the fabrication of fluorescent nanoprobes for various biomedical applications.

Surface modification of carbon nanotubes by combination of mussel inspired chemistry and SET-LRP

An efficient and facile strategy was developed for the surface modification of functional carbon nanotubes (CNTs) by the combination of mussel inspired chemistry and single electron transfer living radical polymerization (SET-LRP). This method involves the dopamine (DA) formation of polydopamine (PDA), which was coated on the surface of pristine CNTs via self-polymerization in alkaline solution. Then, the Br-containing initiator was covalently attached on the surface of CNTs modified with PDA. Subsequently, the poly[poly(ethylene glycol) methyl ether methacrylate] (PPEGMA) was in situ grown on the surface of Br-containing CNTs via the SET-LRP method. The resulting functional materials were characterized by a series of characterization techniques. It was demonstrated that PPEGMA chains were successfully conjugated to the surface of CNTs via a combination of mussel inspired chemistry and SET-LRP. After modifying with PPEGMA, the functional CNTs retain their pristine structure, but their dispersibility was significantly improved in polar and nonpolar solutions. Compared with previous methods, the strategy developed in this work is rather simple and effective. More importantly, due to the universality of mussel inspired chemistry, this novel strategy could also be used for the surface modification of many other materials.

Stimulus responsive cross-linked AIE-active polymeric nanoprobes: fabrication and biological imaging application

The combination of functional polymers and hydrophobic AIE dyes to prepare luminescent organic nanoparticles (LONs) with strong fluorescence, great water dispersibility and desirable biocompatibility has received a lot of attention for potential applications in cell imaging and theranostics. Although great effort has been devoted to preparing AIE dye based LONs through both covalent and noncovalent strategies, the fabrication of cross-linked AIE dye based LONs with stimulus responsive behavior has not been reported previously. In this work, the AIE dye based LONs were constructed via cross-linking aldehyde-containing polymers and AIE dye (2,2′-diaminotetraphenyl ethylene) with two amino groups through formation of a Schiff base, which is a well-known dynamic bond with pH responsiveness. After successful incorporation of the hydrophobic AIE dye into the copolymers, cross-linked core–shell luminescent nanoparticles can be formed. The obtained AIE dye based LONs exhibited strong fluorescence and high water dispersibility because the AIE dye aggregated in the core and the hydrophilic polymers were covered on the shell. Biological evaluation results demonstrated that the AIE dye based LONs exhibited excellent biocompatibility and biological imaging properties. More importantly, these AIE dye based LONs exhibited desirable pH responsiveness, implying that these polymeric LONs can be potentially utilized for pH sensors and controlled drug delivery. With the combination of dynamic crosslinking and pH responsiveness, the obtained AIE dye based LONs should be of great significance for biomedical applications.

Facile synthesis of AIE-active amphiphilic polymers: Self-assembly and biological imaging applications.

In this work, we reported a rather facile method for fabrication of ultrabright, well dispersible and biocompatible fluorescent organic nanoparticles (FONs) with aggregation-induced emission (AIE) properties through combination of esterification and ring-opening reaction. The hydroxyl groups of Pluronic F127 was first reacted with the chloride of trimellitic anhydride chloride (TMAC), and its anhydride groups were further reacted with the amino groups of amino-terminated AIE dye (PhNH2) through ring-opening reaction. The optical properties, biocompatibility as well as cell uptake behavior of these obtained AIE-active nanoparticles (F127-TMAC-PhNH2 FONs) were examined by a series of characterization techniques and assays. We demonstrated that uniform organic nanoparticles with high water dispersibility, strong luminescence and desirable biocompatibility can be facilely obtained, which are promising for biological imaging applications. More importantly, a number of carboxyl groups were introduced into these AIE-active nanoparticles, which can be further utilized for further conjugation reaction and carrying anticancer drugs such as cisplatin. Therefore, the strategy of described in this work should be a simple and useful route for fabrication of multifunctional AIE-active luminescent nanotheranostic systems.

A rather facile strategy for the fabrication of PEGylated AIE nanoprobes

Fluorescent organic nanoparticles (FNPs) have attracted great research interest for biological sensors, biological imaging and disease treatment. However, the preparation of ultrabright FNPs using conventional organic dyes is still a challenge for their aggregation caused quenching effect. In this work, we reported for the first time that polyethylene glycol (PEG) and an aggregation induced emission (AIE) dye, 2,2′-diaminotetraphenyl ethylene (DATPE), can be facilely conjugated by trimellitic anhydride chloride. Taking advantage of the different reaction activities of anhydride and chloride, anhydride-terminated PEG (ADPEG) was first synthesized through the reaction between hydroxyl groups and benzoyl chloride. Then ADPEG could further react with the amino groups of DATPE. Because of the AIE properties of DATPE, these amphiphilic triblock copolymers can self-assemble into FNPs (PEG-TPE FNPs) and emit strong blue-green fluorescence in aqueous solution. Cell uptake behavior and cytotoxicity evaluation suggested that PEG-TPE FNPs possessed excellent cytocompatibility and could be facilely taken up by cells, implying that PEG-TPE FNPs are promising for biomedical applications. More importantly, the method described in this work is rather simple and effective and, more importantly, can be extended to fabricate many other multifunctional FNPs on a large scale for various biomedical applications.

Bioinspired preparation of thermo-responsive graphene oxide nanocomposites in an aqueous solution

Graphene oxide (GO), as the precursor of graphene, has inspired great research interest over the past few years due to its excellent physicochemical properties and promising applications. Surface modification of GO with polymers is a general route for enhancing its processibility and improving its performance. Although great effort has been put into this field, the surface modification of GO with polymers in an aqueous solution has proven to be problematic due to the restacking of GO. In this work, we have developed a novel strategy for the preparation of GO thermo-responsive polymer nanocomposites in an aqueous solution via a combination of mussel inspired chemistry and a reversible addition–fragmentation chain transfer (RAFT) polymerization. Two simple steps are involved in this strategy. First, GO was coated with polydopamine (PDA) through a self polymerization of dopamine in a weakly alkaline aqueous solution. Then, the thermo-sensitive polymer poly(N-isopropylacrylamide) (PNIPAM), derived from a polymerization, was facilely grafted onto the PDA coated GO (GO-PDA) through a Michael addition reaction. The finally product (GO-PDA-PNIPAM) was characterized in detail by a series of methods, including Fourier transform infrared spectroscopy, thermal gravimetric analysis, transmission electron microscopy and X-ray photoelectron spectroscopy. These results suggested that PNIPAM can successfully and effectively functionalize GO through a rather facile strategy in an aqueous solution, at room temperature and in an air atmosphere. More importantly, GO-PDA-PNIPAM exhibited excellent dispersibility in aqueous solutions and some organic media, and displayed a good thermo-responsiveness. Taking advantage of PDA and polymerizations, this strategy is expected to be extended for the preparation of many other polymer nanocomposites by employing different nanomaterials and monomers. Therefore, the strategy described in this work should be of great research interest for the preparation and applications of nanocomposites.

Fabrication and biological imaging application of AIE-active luminescent starch based nanoprobes.

Fabrication of water dispersible, biocompatible and ultrabright luminescent polymeric nanoprobes (LPNs) has been the subject of great research interest. Although a number of LPNs have been fabricated previously through different strategies, the preparation of luminescent carbohydrate polymers with aggregation-induced emission (AIE) characterstic has received only limited attention. In this work, we reported for the first time that AIE-active luminescent starch can be facilely fabricated via mixing the aldehyde-contained AIE dye 4-(1,2,2-triphenylvinyl) benzaldehyde (TPE-CHO) with carboxyl methyl starch sodium (CMS) and amino phenylboronic acid in a one-pot procedure, in which aminophenylboronic acid can serve as the linkage for conjugation of TPE-CHO and CMS. The final products (TPE-CMS LPNs) were characterized by a number of characterization techniques such as (1)H nuclear magnetic resonance spectroscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and fluorescence Spectroscopy in detail. To examine their biomedical application potential, the biocompatibility as well as cell uptake behavior of TPE-CMS LPNs were further determined. We demonstrated that TPE-CMS LPNs showed high water dispersibility and strong fluorescence, well biocompatibility and efficient cell internalization behavior, making them promising candidates for various biomedical applications.

Polylysine crosslinked AIE dye based fluorescent organic nanoparticles for biological imaging applications.

Fluorescent organic nanoparticles based on aggregation induced emission dyes are fabricated through a ring-opening reaction using polylysine as the linker. The fluorescent organic nanoparticles obtained are characterized by a series of techniques including UV-vis absorption spectroscopy, fluorescence spectroscopy, Fourier Transform infrared spectroscopy, and transmission electron microscopy. A biocompatibility evaluation and the cell uptake behavior of the fluorescent organic nanoparticles are further investigated to evaluate their potential biomedical applications. It is demonstrated that these fluorescent organic nanoparticles can be obtained at room temperature in an air atmosphere without the need for catalyst or initiator. Furthermore, these crosslinked aggregation induced emission dye based fluorescent organic nanoparticles show uniform morphology, strong red fluorescence, high water dispersability, and excellent biocompatibility, making them promising candidates for various biomedical applications.

Ultrabright and biocompatible AIE dye based zwitterionic polymeric nanoparticles for biological imaging

The development of novel fluorescent nanoprobes with remarkable optical properties, suitable particle size, high water dispersibility and good biocompatibility has recently attracted increasing interest for various biomedical applications. In this work, a novel type of luminescent polymeric nanoparticle based on polymerizable dyes with aggregation induced emission (AIE) properties and a zwitterionic monomer were prepared via reversible addition fragmentation chain transfer polymerization. Due to their amphiphilic properties, these copolymers could facilely self-assemble into AIE dye containing luminescent zwitterionic polymeric nanoparticles, which were characterized by a series of characterization techniques including transmission electronic microscopy, Fourier transform infrared spectroscopy, fluorescence spectroscopy and X-ray photoelectron spectroscopy. The results showed that these luminescent polymeric nanoparticles with diameters of tens of nanometers showed high water dispersibility and strong fluorescence in aqueous solution. To explore their potential for biomedical applications, biocompatibility and cell uptake behavior of these luminescent polymeric nanopartilces were further evaluated. We demonstrated that these polymeric nanoparticles are biocompatible with A549 cells and promising for bioimaging applications. Taken advantage of these merits of the AIE dye based zwitterionic polymeric nanoparticles, which could elegantly avoid the aggregation induced quenching of conventional organic dyes and nonbiodegradability of fluorescent inorganic nanoparticles, the ultrabright and biocompatible luminescent polymeric nanoparticles described in this work should be of highly potential for various biomedical applications.