•Two novel aggregation-induced emission polymers were synthesized.•The polymers could self-assemble into fluorescent polymeric nanoparticles (FPNs) in water.•The FPNs showed excellent biocompatibility for cell imaging.•The FPNs exhibited good particle stability and high photostability.Novel aggregation-induced emission (AIE) polymers (NS1 and NS2) were prepared through reversible addition fragmentation chain transfer polymerization of poly(ethylene glycol) monomethyl ether methacylate and a new AIE monomer with a vinyl group. The NS1 and NS2 copolymers were characterized by gel permeation chromatography, 1H NMR spectroscopy, FT-IR spectroscopy, X-ray photoelectron spectroscopy, which proved their successful syntheses. Such amphiphilic copolymers could self-assemble into fluorescent polymeric nanoparticles (FPNs) in water with good dispersibility, which were spherical in shape. The prepared FPNs of NS1 had a size range of 50–150 nm, strong green fluorescence in aqueous solution with fluorescence quantum yield of 31%, and low critical micelle concentration (CMC) of 0.030 mg mL−1. The NS2 FPNs exhibited size range of 200–300 nm, intense green fluorescence with quantum yield of 38%, and CMC of 0.037 mg mL−1. These FPNs were demonstrated highly biocompatible for cell imaging. By virtue of excellent biocompatibility via PEG modification, good particle stability with low CMC, and AIE fluorescent polymers with high photostability, the FPNs constructed in this work showed obvious advantages. This strategy should inspire new approaches to prepare novel biocompatible AIE fluorescent polymers for biomedical application.

•Poly(MPC) grafted red fluorescent NPs were facilely fabricated.•The zwitterionic polymers on NPs would facilitate their cellular uptake.•The NPs demonstrated excellent photostability and live cell imaging performance.Poly(2-methacryloyloxyethyl phosphorylcholine) conjugated red fluorescent chitosan nanoparticles (GCC-pMPC) were facilely fabricated by “grafting from” method via surface initiated atom transfer radical polymerization (ATRP). Firstly, glutaraldehyde crosslinked red fluorescent chitosan nanoparticles (GCC NPs) with many amino groups and hydroxyl groups on their surface were prepared, which were then reacted with 2-bromoisobutyryl bromide to form GCC-Br; subsequently, poly(MPC) (pMPC) brushes were grafted onto GCC NPs surface using GCC-Br as initiator via ATRP. Compared with PEGylated nanoparticles, zwitterionic polymers modified nanoparticles demonstrated better performance in their cellular uptake. Moreover, the obtained GCC-pMPC demonstrated excellent water-dispersibility, biocompatibility, and photostability, which made them highly potential for long-term tracing applications. Importantly, the successful live cell imaging of GCC-pMPC would remarkably advance the research of their further bioapplications.

Novel aggregation induced emission (AIE) dye based cross-linked amphiphilic fluorescent polymers have been prepared facilely by a one pot method. This was carried out first by free radical polymerization between the AIE monomer (PhE) and glycidyl methacrylate (GM), then by the ring-opening reaction between GM and polyethyleneimine (PEI) to obtain the cross-linked polymer. The resultant cross-linked amphiphilic polymer was prone to self-assemble into stable nanoparticles with high water dispersibility due to the surplus amino groups and hydroxyl groups covered on the surface, which can also be further functionalized. The thus obtained nanoparticles demonstrated strong orange fluorescent emission with a quantum yield of about 41% owing to the AIE dyes in the cores of the nanoparticles. Biocompatibility evaluation and cell uptake behaviour of the nanoparticles were further investigated to explore their potential biomedical applications and the demonstrated excellent biocompatibility made them promising for cell imaging.

PEGylated red fluorescent nanoparticles with excellent biocompatibility and photostablity were facilely prepared from nonluminous materials: first red fluorescent nanoparticles (GCC NPs) were robustly prepared from chitosan and glutaraldehyde; then the amino groups and hydroxyl groups on the GCC NP surfaces were modified with 2-bromoisobutyryl bromide to obtain GCC-Br, which was employed as the nanoparticles’ initiator in the ATRP system to finally obtain the GCC–poly(PEGMA) conjugates. The resulting GCC–poly(PEGMA) can emit a biofavorable deep red luminescence, which is quite stable and anti-photobleaching. Furthermore, GCC–poly(PEGMA) demonstrated excellent biocompatibility and water dispersibility due to the PEGMA chains conjugated on the surface; and the abundant hydroxyl groups on the surface can be further functionalized with diverse other groups or large biomolecules. This construction method demonstrated great advantages due to its simple strategy and economic value, and the NPs’ successful cellular imaging endows them with a lot of potential for various biomedical applications.

Aggregation induced emission (AIE) dye based cross-linked fluorescent glycopolymer nanoparticles (FGNs) with red emission are synthesized for the first time. This is carried out firstly by free radical polymerization between the AIE monomer (R-E) and a renewable biobased monomer itaconic anhydride, and then by the ring-opening reaction between itaconic anhydride and glucosamine hydrochloride to obtain a glycopolymer with plenty of glycosyl groups. The resulting cross-linked amphiphilic glycopolymer was prone to self-assemble into stable nanoparticles with high water dispersibility due to the surplus carboxyl groups and glycosyl groups covering the surface which can also be further functionalized. The thus-obtained nanoparticles demonstrated strong red fluorescence emission owing to the AIE dyes in the core of the nanoparticles. Biocompatibility evaluation and cell uptake behaviour of the nanoparticles were further investigated to explore their potential biomedical applications; the demonstrated excellent biocompatibility made them promising for cell imaging.

A novel amphiphilic glucose-containing fluorescent polymer based on aggregation induced emission (AIE) dyes, which could self-assemble into nanoparticles in aqueous media, has been facilely prepared. This glucose-containing polymer was synthesized in one pot; firstly, by free radical polymerization between the AIE monomer (PhE) and glycidyl methacrylate (GM), and subsequently, by the ring-opening reaction between GM and glucosamine hydrochloride (Glu). The resulting amphiphilic glycopolymer would readily self-assemble into nanoparticles with AIE dyes in the core and glycosyl groups on the surface. The AIE dyes in the core gave the nanoparticles a demonstrated strong orange fluorescence emission with high quantum yield of about 41% due to their aggregation induced emission characteristics, and the glycosyl groups on the surface endowed the nanoparticles with great water dispersibility. These nanoparticles showed excellent cell uptake behaviour and biocompatibility, and their cell imaging abilities were also confirmed, which makes them promising for further biomedical applications.

Biocompatible and stable fluorescent polymer nanoparticles play significant roles in bioimaging and biomedical applications due to their convenient preparation strategies and unique properties. However, the construction methods are still limited now. Herein novel water dispersible and bright fluorescent polymer nanoparticles (PhE-TT-PEG FPNs) with great biocompatibility and stability have been facilely fabricated, and their cellular imaging applications were successfully demonstrated. The PhE-TT-PEG FPNs were readily prepared by self-assembly of amphiphilic copolymer PhE-TT-PEG, which was synthesized through free radical polymerization in one pot from AIE monomer PhE, trifunctional cross-linker TT, and biofavorable monomer PEGMA. A series of characterizations have been conducted to confirm the successful synthesis of PhE-TT-PEG, including gel permeation chromatography, X-ray photoelectron spectroscopy, FTIR spectroscopy, and 1H NMR spectroscopy. The morphology and optical properties of PhE-TT-PEG FPNs have been tested by transmission electron microscopy, dynamic light scattering, UV-Visible absorption spectroscopy and fluorescence spectroscopy. The PhE-TT-PEG FPNs can emit strong fluorescence with a high quantum yield of 40%, and they also demonstrate superb water dispersibility, morphology stability, photostability and biocompatibility. Finally, the fluorescence imaging of HeLa cells with PhE-TT-PEG FPNs is investigated in detail.

Glycosylated cross-linked red fluorescent amphiphilic polymer has been facilely synthesized in one pot, which would readily self-assemble into nanoparticles with high water dispersibility in aqueous media. The resulted nanoparticles have surplus carboxyl groups and glycosyl groups on the surface, which can be further functionalized, and they can demonstrate strong bio-favorable red fluorescence with a fluorescence quantum yield of 18% due to the aggregation induced emission (AIE) dyes aggregated in the core. Moreover, the nanoparticles also revealed great photostability and structure stability with an ultralow critical micelle concentration of 0.0018 mg mL−1. Their excellent biocompatibility and cell uptake behavior make them promising for cellular imaging.

•Novel aggregation induced emission (AIE) dyes based cross-linked amphiphilic fluorescent polymer has been facilely prepared in one pot.•The polymer can self-assemble into stable nanoparticles with strong fluorescence and water dispersibility.•The fluorescent polymer nanoparticles were promising for cell imaging due to their excellent biocompatibilities.Facile one-pot preparation of cross-linked amphiphilic fluorescent polymer based on aggregation induced emission (AIE) dyes and 2-isocyanatoethyl methacrylate (IM) has been developed. This was carried out first by free radical polymerization between AIE monomer (PhE) and IM, and then polyethyleneimine (PEI) was introduced to obtain the cross-linked fluorescent polymer. The resulted cross-linked amphiphilic polymer was prone to self-assemble into stable nanoparticles in aqueous solution with surplus amino groups on the surface which made them highly water dispersible and can be further functionalized. The as-prepared fluorescent polymer nanoparticles (PhE-IM-PEI FPNs) were fully characterized by a series of techniques including 1H NMR spectrum, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, dynamic light scattering, UV–vis absorption spectrum, and fluorescence spectra. Such FPNs demonstrated intense orange fluorescence with a high quantum yield of about 40%. Biocompatibility evaluation and cell uptake behavior of the nanoparticles were further investigated to explore their potential biomedical applications; the demonstrated excellent biocompatibility made them promising for cell imaging.

•Glutaraldehyde-cross-linked chitosan of different states (solution, gel, nanoparticle, etc.) with luminesce at ca. 670 nm were prepared for the first time.•They are quite inert and anti-photobleaching.•Their nanoparticles (5.6 nm) could image the nucleoli of living HeLa cells with low cytotoxicity.Biocompatible glutaraldehyde-cross-linked chitosan with new red fluorescence were prepared for the first time and were shaped into nanoparticles via inverse-microemulsion method. They could luminesce at ca. 670 nm either as powders and nanoparticles or in real and gelling solutions or suspensions, having a lifetime of 1.353 ns and a quantum yield of 0.08 in solution or 0.01 in solid state. The new-formed pyridinium structures and the intramolecular charge transfer effect are considered to be responsible for the new red emission, which have been proved by FTIR, 13C NMR, and some calculation using Gaussian 09, respectively. Strikingly, they are quite inert and anti-photobleaching, with only <3% loss of fluorescent intensity per minute in average under a continuous laser illumination at 633 nm and 50 μW. Especially, their nanoparticles (5.6 nm) could enter into the negative nucleoli of living HeLa cells with low cytotoxicity for high contrast imaging inspections.

Novel aggregation induced emission (AIE) dye based cross-linked amphiphilic fluorescent polymers have been prepared facilely by a one pot method. This was carried out first by free radical polymerization between the AIE monomer (PhE) and glycidyl methacrylate (GM), then by the ring-opening reaction between GM and polyethyleneimine (PEI) to obtain the cross-linked polymer. The resultant cross-linked amphiphilic polymer was prone to self-assemble into stable nanoparticles with high water dispersibility due to the surplus amino groups and hydroxyl groups covered on the surface, which can also be further functionalized. The thus obtained nanoparticles demonstrated strong orange fluorescent emission with a quantum yield of about 41% owing to the AIE dyes in the cores of the nanoparticles. Biocompatibility evaluation and cell uptake behaviour of the nanoparticles were further investigated to explore their potential biomedical applications and the demonstrated excellent biocompatibility made them promising for cell imaging.

Here we report the ring-opening crosslinking PEGylation of an AIE epoxy monomer and a 4-arm PEG-amine to prepare a new cross-linked fluorescent polymer (PEG-EP3). When PEG-EP3 was dispersed in aqueous solution, the AIE components formed the hydrophobic cores and the PEG parts covered the surfaces, resulting in fluorescent polymeric nanoparticles (FPNs) with good dispersibility. PEG-EP3 and the resulting FPNs were characterized by gel permeation chromatography, 1H NMR spectroscopy, FT-IR spectroscopy, X-ray photoelectron spectroscopy, dynamic light scattering, transmission electron microscopy, UV-Visible absorption and fluorescence spectra. The results confirmed the successful synthesis of PEG-EP3, which showed high water dispersibility with a size distribution of 249 ± 1 nm, intense yellow-green fluorescence in aqueous solution with a fluorescence quantum yield of 35%, and a low critical micelle concentration (CMC) of 0.039 mg mL−1. The cell uptake behaviour and cell imaging of the PEG-EP3 FPNs proved their high biocompatibility for biomedical applications. Owing to their excellent biocompatibility by the introduction of PEG as the main component, good colloidal stability with low CMC, and high fluorescence stability, the strategy in this work would provide a new approach to prepare novel biocompatible and robust cross-linked FPNs for biomedical applications.