Guangjian Zeng

Recent developments in polydopamine: an emerging soft matter for surface modification and biomedical applications

After more than four billion years of evolution, nature has created a large number of fascinating living organisms, which show numerous peculiar structures and wonderful properties. Nature can provide sources of plentiful inspiration for scientists to create various materials and devices with special functions and uses. Since Messersmith proposed the fabrication of multifunctional coatings through mussel-inspired chemistry, this field has attracted considerable attention for its promising and exiciting applications. Polydopamine (PDA), an emerging soft matter, has been demonstrated to be a crucial component in mussel-inspired chemistry. In this review, the recent developments of PDA for mussel-inspired surface modification are summarized and discussed. The biomedical applications of PDA-based materials are also highlighted. We believe that this review can provide important and timely information regarding mussel-inspired chemistry and will be of great interest for scientists in the chemistry, materials, biology, medicine and interdisciplinary fields.

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.

Towards development of a versatile and efficient strategy for fabrication of GO based polymer nanocomposites

Surface modification of graphene oxide (GO) with polymers is of particular importance for its applications. Although much progress has been made in the surface modification of GO, the surface modification of GO with synthetic polymers in aqueous solution has demonstrated to be problematic. In the present work, we report for the first time a versatile and effective method for the surface modification of GO with synthetic polymers in aqueous solution taking advantage of mussel inspired chemistry. Poly(ethylene glycol) methyl ether methacrylate and itaconic anhydride (IA) monomers were chosen to prepare hydrophilic polymers (poly(IA-co-PEGMA)) via free radical living polymerization. These hydrophilic polymers were further reacted with dopamine through ring-opening reaction between IA and dopamine, which could be highly efficiently attached to the GO surface via mussel inspired chemistry using dopamine as the adhesion component. The successful modification of GO with polymers was confirmed by using a series of characterization techniques. The resulting GO–polymer nanocomposites displayed great dispersibility in aqueous and organic solutions, making them promising for various applications. Compared with previous methods, the biomimic strategy described in this work could facilely and effectively immobilize synthetic polymers on GO in aqueous solution at room temperature and under an air atmosphere. More importantly, this strategy could also be utilized for the fabrication of almost any polymer nanocomposite because of the designability and applicability of living polymerization, and the versatility and strong adhesion of dopamine.

Mussel inspired preparation of highly dispersible and biocompatible carbon nanotubes

The biomedical applications of carbon nanotubes (CNTs) have been intensively investigated. However, poor water dispersibility and obvious toxicity of pristine CNTs are still two major issues for their biomedical applications. Although great efforts have been devoted to solving these problems, a simple and effective strategy for preparation of CNTs with high water dispersibility and desirable biocompatibility is still of great research interest. Herein, surface modification of CNTs with a biocompatible polymer polyethylene glycol (PEG) via a mussel inspired strategy has been developed. The dispersibility as well as biocompatibility of these PEGylated CNTs (named as CNT-poly(PEGMA-co-IA-DA)) was subsequently investigated. These PEGylated CNTs showed remarkable enhancement of dispersibility in aqueous and organic solvents. More importantly, as evidenced by cell viability and reactive oxygen species results, these PEGylated CNTs showed negative toxicity toward cancer cells. Therefore the PEGylated strategy described in this work can provide a general platform for fabrication of multifunctional biomaterials for various biomedical applications because of the advantages of mussel inspired chemistry and the excellent properties of PEGylated materials.

Fabrication and biomedical applications of AIE active nanotheranostics through the combination of a ring-opening reaction and formation of dynamic hydrazones

Aggregation-induced emission (AIE) dyes based on fluorescent organic nanoparticles (FONs) have attracted increasing interest over the past few years. However, the biomedical applications of AIE dyes based on FONs for simultaneous biological imaging and therapeutic applications have rarely been reported thus far. In this study, an amino group terminated phenothiazine (named as ATPHE) with AIE features and red fluorescence was synthesized and utilized for the fabrication of AIE active FONs via a facile one-pot strategy, which relied on the ring-opening reaction between ATPHE and an anhydride containing compound. Then, the keto group of the AIE active polymeric intermediate was subsequently conjugated with hydrazide terminated polyethylene glycol (HTPEG) through the formation of hydrazone bonds. These amphiphilic AIE active copolymers are readily self-assembled into nanoscale particles in an aqueous solution, which resulted in strong luminescence and good water dispersibility of the final HTPEG@ATPHE-co-BTDA FONs. The excellent physicochemical and biological properties of HTPEG@ATPHE-co-BTDA FONs give them high potential for biological imaging and controlled drug delivery applications. Taken together, we developed a simple strategy for the fabrication of AIE active nanoparticles, which are promising for biological imaging and controlled drug delivery.

Facile Fabrication of PEGylated Fluorescent Organic Nanoparticles with Aggregation-Induced Emission Feature via Formation of Dynamic Bonds and Their Biological Imaging Applications.

Driven by the high demand for sensitive and specific tools for optical imaging, fluorescent nanoprobes with various working mechanisms and advanced functionalities are flourishing at an incredible speed. This work reports the design and fabrication of aggregation-induced emission (AIE)-active fluorescent organic nanoparticles (FNPs) via forming dynamic phenyl borate between diol containing hydrophobic AIE dye (APD-PhCHO) and phenylboronic acid pendant hydrophilic polymers (PEGMA-VPBA) within 30 min. The final AIE-active APD-PhCHO-PEGMA-VPBA FNPs display high water dispersibility and strong fluorescence emission because of their amphiphilic properties and AIE feature. Biological evaluation suggests that APD-PhCHO-PEGMA-VPBA FNPs possess negative effect on HeLa cells and desirable optical properties for biological imaging. More importantly, phenyl borate is a dynamic bond with pH and glucose responsiveness. Furthermore, different functions can be designed and introduced into these AIE-active systems through adoption of different monomers for good applicability of free radical polymerization. Therefore, this work provides a novel platform for preparation of multifunctional AIE-active nanosystems with responsiveness for various biomedical applications.

Synthesis and cell imaging applications of amphiphilic AIE-active poly(amino acid)s

The poly(amino acid)s based biomaterials have attracted great research attention over the past few decades because of their biocompatibility, biodegradability and well designability. Although much progress has achieved in the synthesis and biomedical applications of poly(amino acid)s, the synthesis of luminescent poly(amino acid)s has been rarely reported. In this work, novel amphiphilic luminescent poly(amino acid)s with aggregation-induced emission (AIE) feature have been synthesized by a new approach of controlling N-carboxy anhydride (NCA) ring-opening polymerization, in which hydrophobic 2-(4-aminophenyl)-3-(10-hexadecyl-4H-phenothiazin-3-yl)acrylonitrile (Phe-NH2) with AIE feature was used as initiator and hydrophilic oligomeric glycol functionalized glutamate (OEG-glu) NCA was acted as monomer. The successful synthesis of final Phe-OEG-Pglu polymers was confirmed by different characterization techniques. Phe-OEG-Pglu polymers possess amphiphilic properties and can self-assemble into luminescent polymeric nanoparticles (LPNs). Based on cellular imaging experiments, we demonstrated that Phe-OEG-Pglu LPNs have great potential for bio-imaging applications due to their attractive properties including strong fluorescence intensity, great water dispersibility, excellent biocompatibility and high cellular uptake efficiency.

A powerful “one-pot” tool for fabrication of AIE-active luminescent organic nanoparticles through the combination of RAFT polymerization and multicomponent reactions

Multicomponent reactions (MCRs) have recently received increasing attention for the synthesis of structural complexity in a single step from three or more reactants. They have also been considered as a powerful tool for the construction of sequence-controlled multifunctional polymers owing to their good substrate adaptability, simple operation and high efficiency. In this work, we reported methods that are a combination of the three-component mercaptoacetic acid locking imine (MALI) reaction and reversible addition fragmentation chain transfer (RAFT) polymerization in one pot to form luminescent organic nanoparticles (LONs) with aggregation-induced emission (AIE) features, high-brightness, great water dispersibility, ultra-small nanoscale size and excellent biocompatibility. In the reaction system, the MALI reaction and RAFT polymerization happened simultaneously in a “one-pot” route. On the one hand, the AIE-active organic dye with one amino group ((Z)-3-(4-aminophenyl)-2-(10-hexadecyl-10H-phenothiazin-3-yl)acrylonitrile) (named as Phe-NH2) was conjugated with an aldehyde-containing monomer (10-undecenal) by the MALI reaction, while the aldehyde-containing monomer was copolymerized with the hydrophilic monomer polyethylene glycol methyl methacrylate (PEGMA) through RAFT polymerization at the same time. Compared with other fabrication strategies, “one-pot” strategies possess some advantages such as high efficiency, simplicity, and atom economy. On the other hand, due to the good applicability of RAFT polymerization and the MALI reaction, many other multifunctional AIE-active LONs could also be fabricated via adjusting the function of the substrates. Therefore, this strategy should be a general and important route for fabrication of AIE-active materials for different applications.

Facile synthesis and characterization of poly(levodopa)-modified silica nanocomposites via self-polymerization of levodopa and their adsorption behavior toward Cu2+

AbstractIn this study, a facile surface functionalization method was applied to synthesize poly-levodopa (PDOPA)-modified silica nanocomposites (denoted as SiO2-PDOPA). The adsorption capacity of SiO2-PDOPA was found to be higher than that of unmodified SiO2 NPs. The successful preparation of SiO2-PDOPA was confirmed by Fourier transform infrared spectroscopy, transmission electron microscopy, and thermo gravimetric analysis. The adsorption behavior was investigated using SiO2-PDOPA as adsorbents and Cu2+ as a model heavy metal pollutant. Various adsorption parameters, including contact time, solution pH, temperature, and initial Cu2+ concentrations were studied. The results showed that pH could markedly affect the adsorption process of SiO2-PDOPA to Cu2+. The optimum pH for Cu2+ adsorption was found to be 7.0. The adsorption kinetic data were analyzed using pseudofirst-order, pseudosecond-order, and intraparticle diffusion models. The adsorption isotherms could be described by Langmuir and Freundlich isotherm models. The fitting results showed that the adsorption kinetics and isotherms were better described by the pseudosecond-order and Langmuir model, respectively. The values of thermodynamics constants, including entropy change (ΔS0), enthalpy change (ΔH0), and Gibbs free energy (ΔG0) were determined at different temperatures. Results suggested that the adsorption process of SiO2-PDOPA to Cu2+ is a feasible, endothermic, and spontaneous process.