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

Surface grafting of rare-earth ions doped hydroxyapatite nanorods (HAp:Ln(Eu/Tb)) with hydrophilic copolymers based on ligand exchange reaction: Biological imaging and cancer treatment

Rare-earth ions doped hydroxyapatite nanoparticles (HAp:Ln NPs) have demonstrated to be very promising candidates for biological imaging applications owing to their small size and chemical compositions similar to bone. However, these HAp:Ln NPs with controllable size and morphology should be prepared under hydrothermal treatment with hydrophobic molecules as the protective layers. The hydrophobic nature of these luminescent HAp:Ln NPs largely impeded their applications in biomedical fields. In this study, a novel and effective strategy has been developed for the surface modification of HAp:Ln nanorods through the combination of surface ligand exchange reaction and reversible-addition fragmentation chain transfer (RAFT) polymerization using 2-methacryloyloxyethyl phosphorylcholine (MPC) and itaconic acid (IA) as the monomers. Herein, a small molecule adenosine 5'-monophosphate disodium salt (AMP) that contains a phosphate group and two hydroxyl groups was used to displace the hydrophobic oleic acid on pristine HAp NPs through surface ligand exchange reaction owing to its stronger interaction with HAp NPs. On the other hand, the MPC and IA were introduced on HAp NPs through RAFT polymerization after the chain transfer agent was immobilized on the HAp NPs through the esterification reaction. The poly(IA-MPC) could not only endow the high water dispersibility but also be used for loading anticancer agent cisplatin (CDDP) through coordination interaction. To evaluate their potential biomedical applications, the cell uptake behavior, drug loading capacity and release behavior as well as cell viability of HAp:Ln-AMP-poly(IA-MPC) polymeric composites were examined. We demonstrated that the method developed in this work is very effective for introduction of functional polymers onto HAp:Ln nanorods. The HAp:Ln-AMP-poly(IA-MPC) composites are promising for cell imaging and controlled delivery of CDDP.

A new strategy for fabrication of water dispersible and biodegradable fluorescent organic nanoparticles with AIE and ESIPT characteristics and their utilization for bioimaging

Fluorescence probes play a crucial role in optical imaging for visualization of complex biological processes. As compared with conventional organic fluorogens, the probes with aggregation-induced emission (AIE) and excited-state intramolecular proton transfer (ESIPT) characteristics show significant advantages in high quantum yield at concentrated and aggregated state, large Stokes shift and low cytotoxicity. However, the synthesis of AIE-active fluorescent probes through the ESIPT mechanism has received only very limited attention. On the other hand, the preparation of biodegradable fluorescent probes through the ESIPT mechanism has not been demonstrated thus far. In this work, we reported for the first time that water dispersible and biodegradable fluorescent polymeric nanoparticles with AIE and ESIPT characteristics could be facilely obtained through conjugation of 2,4-Dihydroxybenzophenone based benzophenone azine (BPA) and polyethylene glycol (PEG) using hexamethylene diisocyanate. The final copolymers contained hydrophilic and biocompatible PEG and biodegradable urethane linkage are readily self-assembled into core-shell nanostructures. Moreover, the self-assembled BPA-PEG₂₀₀₀ fluorescent organic nanoparticles (FONs) displayed obvious AIE feature, high water dispersibility, superb biocompatibility, biodegradability and excellent cell dyeing performance. All of the above properties implied that BPA-PEG₂₀₀₀ FONs are promising candidates for a variety of biomedical applications.

Wettability with Aggregation-Induced Emission Luminogens

Aggregation-induced emission luminogens (AIEgens) have become an emerging field since the concept of AIE was proposed in 2001. Recently, AIEgens have attracted considerable attention due to their abnormal non-emissive fluorescent behavior in solution but strongly emissive behavior in the aggregate state. By utilizing the inherent hydrophobicity, AIEgens can be used to monitor the crystal formation and dewetting behavior in the self-assembly process. More importantly, some stimuli-responsive AIE-active surfaces have been successfully fabricated. In this perspective review, we outline the advances of surface wettability of AIEgens and its applications.

Polymerizable aggregation-induced emission dye for preparation of cross-linkable fluorescent nanoprobes with ultra-low critical micelle concentrations

In recent years, aggregation-induced emission (AIE) dyes based fluorescent organic nanoparticles (FONs) have achieved significant progress in various biomedical applications. In this work, we developed a covalent strategy to prepare biocompatible AIE-active dyes based cross-linked copolymers (MPC-POSS-PhE) via controllable reversible addition fragmentation chain transfer (RAFT) polymerization using zwitterionic 2-methacryloyloxyethyl phosphorylcholine (MPC), polymerizable AIE dye (named as PhE) and 8-vinyl polyoctahedral silsesquioxanes (POSS) as monomers. Due to the existence of hydrophilic MPC and hydrophobic PhE, the resultant copolymers will self-assemble into core-shell nanoparticles in aqueous solution with ultra-low critical micelle concentration (CMC). This could effectively overcome the drawbacks of non-crosslinked micelles and show more attractive properties and better performance for biomedical applications. Furthermore, the characterization results and biological assays demonstrated that the final MPC-POSS-PhE FONs show stable aqueous stability, uniform size and morphology, high water dispersity, desirable optical properties and low cytotoxicity. These remarkable properties make the resultant AIE-active nanoprobes great potential for biomedical applications.

Facile Fabrication of AIE-Active Fluorescent Polymeric Nanoparticles with Ultra-Low Critical Micelle Concentration Based on Ce(IV) Redox Polymerization for Biological Imaging Applications

Fluorescent polymeric nanoparticles (FPNs) with aggregation-induced emission (AIE) property have received increasing attention and possess promising biomedical application potential in the recent years. Many efforts have been devoted to the fabrication methodologies of FPNs and significant advance has been achieved. In this contribution, a novel strategy for the fabrication of AIE-active amphiphilic copolymers is reported for the first time based on the Ce(IV) redox polymerization. As an example, ene group containing AIE-active dye (named as Phe-alc) is directly grafted onto a water soluble polymer polyethylene glycol (PEG) in H₂ O/THF system under low temperature. Thus-obtained amphiphilic fluorescent polymers will self-assemble into FPNs with ultra-low critical micelle concentration, ultra-brightness, and great water dispersibility. Biological evaluation results suggest that the PEG-poly(Phe-alc) possess excellent biocompatibility and can be used for tracing their behavior in cells using confocal laser scanning microscope. These features make PEG-poly(Phe-alc) FPNs promising candidates for many biomedical applications, such as cell imaging, drug delivery vehicles, and targeted tracing. More importantly, many other functional groups can also be incorporated into these AIE-active FPNs through the redox polymerization. Therefore, the redox polymerization should be a facile and effective strategy for fabrication of AIE-active FPNs.

Recent progress and development on polymeric nanomaterials for photothermal therapy: a brief overview

This review article summarizes the recent development and progress of polymeric photothermal agents for photothermal therapy and imaging-guided photothermal therapy applications.