Novel “zwitterionic” gold nanorods (Au NRs) were constructed through a facile ligand exchange process between cetyltrimethylammonium bromide (CTAB)-Au NRs and the zwitterionic block polymer {poly(2-methacryloyloxyethyl phosohorylcholine)-b-poly(lipoic methacrylate) (pMPC-b-pLA)}. In vitro, they exhibited low dark cytotoxicity and a high therapeutic efficacy to cancer cells. Their blood circulation half-life in vivo (t1/2, ∼10 h) was 20-fold longer than that of CTAB-Au NRs (t1/2, <30 min). After intravenous administration, they accumulated in tumour sites via an enhanced permeability and retention (EPR) effect and enabled destruction of human xenograft tumours in mice after exposure of the tumour location to NIR laser irradiation at 808 nm. These studies showed that the “zwitterionic” Au NRs had low toxicity and high photothermal efficacy both in vitro and in vivo due to the suprahydrophilic, biocompatible zwitterionic polymer coating layer. They may have the potential to be a promising NIR PTT agent in the biomedical field.

Gene therapy through delivery of nucleic acids to the affected cells is a promising option for the treatment of various diseases. However, the delivery process is hampered by a series of barriers including gene packaging, in vivo and intracellular barriers. To overcome these obstacles, numerous vectors have been developed to achieve improved safety and enhanced gene transfection efficiency. Among these vectors, cationic hyperbranched polymers (HBPs) have attracted much attention due to their unique properties (e.g. low viscosity, good solubility, and multi-functionality) and three-dimensional globular structures. Thanks to the flexibility of HBPs, these properties can be tailored to overcome the above-mentioned barriers and develop an optimal gene vector. For example, HBPs with adjustable charge density can tightly condense nucleic acids and maintain polyplexes in solution. Besides, biocompatible HBP-based polyplexes can survive in the blood stream and penetrate the blood vessel wall and surrounding tissue. Furthermore, the stimuli-responsive HBPs release their genes at an appropriate point in the delivery process after endolysosomal escape. All of these properties are important in designing novel vectors for efficient gene delivery. Till now, many works focusing on tailoring cationic HBPs' properties for efficient gene delivery have been reported. This review briefly summarizes the main barriers of gene delivery, how to control the corresponding properties and recent progress of HBPs for gene delivery. After understanding the obstacles deeply, we hope to motivate the delicate design of cationic HBPs for clinical gene delivery applications.

Mimicking the green fluorescent protein (GFP), multicolor fluorescent polymers possessing enhanced fluorescence have been developed and applied to single-excitation cell imaging. The GFP core chromophore was covalently linked to the azide-functionalized amphiphilic block polymer poly(ethylene glycol)–azide–poly(methyl methacrylate). Through macromolecular assembly into micelles, the fluorescence enhanced and further increased with the elongation of poly(methyl methacrylate) chain due to the segmentation effect of the polymeric framework, which could reduce strong π–π interaction and suppress the chromophore’s conformational motion. By a combination of chemically tailoring the core chromophore and macromolecular assembly strategy, multicolor fluorescent polymers showing a color palette from blue to orange were achieved under similar excitation conditions with the highest emission quantum yield approaching 8%, which is more than 80-fold larger than that of the core chromophore. Moreover, fluorescent emission color could be regulated by tuning the coassembling constitution of green and orange fluorescent polymers, generating three new types of emission color. Owing to their low cytotoxicity and good photostability, GFP-mimicking fluorescent polymers were suitable for single-excitation multicolor cell imaging, exhibiting maximum Stokes shift of 202 nm, ascribing to the effect of excited-state proton transfer (ESPT). More importantly, green, yellow, and orange fluorescent cell images were obtained from one single visual field, demonstrating identical information on examined cells, which would improve the accuracy and reliability of biological analysis.

Novel “zwitterionic” gold nanorods (Au NRs) were constructed through a facile ligand exchange process between cetyltrimethylammonium bromide (CTAB)-Au NRs and the zwitterionic block polymer {poly(2-methacryloyloxyethyl phosohorylcholine)-b-poly(lipoic methacrylate) (pMPC-b-pLA)}. In vitro, they exhibited low dark cytotoxicity and a high therapeutic efficacy to cancer cells. Their blood circulation half-life in vivo (t1/2, ∼10 h) was 20-fold longer than that of CTAB-Au NRs (t1/2, <30 min). After intravenous administration, they accumulated in tumour sites via an enhanced permeability and retention (EPR) effect and enabled destruction of human xenograft tumours in mice after exposure of the tumour location to NIR laser irradiation at 808 nm. These studies showed that the “zwitterionic” Au NRs had low toxicity and high photothermal efficacy both in vitro and in vivo due to the suprahydrophilic, biocompatible zwitterionic polymer coating layer. They may have the potential to be a promising NIR PTT agent in the biomedical field.