Visual detection of gene vectors has attracted a great deal of attention due to the application of these vectors in monitoring and evaluating the effect of gene carriers in living cells. A non-viral vector, the fluorescent PAMAM dendrimer (F-PAMAM), was synthesized through conjugation of PAMAM dendrimers and fluorescein. In vitro and ex vivo experiments show that F-PAMAM exhibits superphotostability, low cytotoxicity and facilitates endocytosis by A549 cells. The vector has a high siRNA binding affinity and it increases the efficiency of cy5-siRNA delivery in A549 cells, in comparison with a cy5-siRNA monomer. Our results provide a new method for simultaneously monitoring the delivery of siRNA and its non-viral carriers in living cells.

•NPA–TPP can accumulate in mitochondria of live cells with high specificity.•NPA–TPP exhibits superior photostability which makes it well suitable for real-time tracking movement changes of mitochondria within a long term.•High water solubility and low cytotoxicity manifest superiority for the imaging and analysis in vitro.•Mitochondrial dynamics morphology, movement and number of changes induced by stimulus can be real-time tracking depending on NPA–TPP.Monitoring mitochondria morphological changes temporally and spatially exhibits significant importance for diagnosing, preventing and treating various diseases related to mitochondrial dysfunction. However, the application of commercially available mitochondria trackers is limited due to their poor photostability. To overcome these disadvantages, we designed and synthesized a mitochondria-localized fluorescent probe by conjugating 1,8-naphthalimide with triphenylphosphonium (i.e. NPA–TPP). The structure and characteristic of NPA–TPP was characterized by UV–vis, fluorescence spectroscopy, 1HNMR, 13CNMR, FTIR, MS, etc. The photostability and cell imaging were performed on the laser scanning confocal microscopy. Moreover, the cytotoxicity of NPA–TPP on cells was evaluated using (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) assay. The results showed that NPA–TPP not only has high sensitivity and specificity to mitochondria, but also exhibits super-high photostability, negligible cytotoxicity and good water solubility. In short, NPA–TPP indicates great potential for targeting mitochondria and enables a real-time and long-term tracking mitochondrial dynamics changes.

Polyethylene glycol-functionalized gold nanoparticles (PEGylated AuNPs) have been widely used as nanocarriers for the delivery of various drugs. However, little attention has been paid to whether the PEGylated AuNPs could affect the primary function of human erythrocytes, which is the main cellular component in the blood. In the current study, we show that both the deformability and oxygen-delivering ability of erythrocytes are decreased when treated with PEGyalted AuNPs of various sizes, which can be attributed to the interaction between PEGylated AuNPs and erythrocyte membranes. It is observed that the PEGylated AuNPs could also induce the aggregation of band-3 and the ATP decrease of erythrocytes. In addition, the PEGylated AuNPs can accelerate the loss of CD47 on erythrocyte membranes, possibly enhancing the senescent process of erythrocytes and the following clearance by SIRPα-expressing leukocytes in bloodstream. The results suggested that PEGylated AuNPs have the potential to affect the primary function of human erythrocytes, which should be considered when using them as drug carriers.

Antioxidants have potentials to treat hypoxia-mediated oxidative stress related diseases. However, their therapeutic efficacy is restricted due to its poor cellular uptake efficiency and poor cell membrane permeability. To resolve these issues, we prepare the hydroxyethylated chitosan nanoparticles as drug carriers for the delivery of 6-hydroxy-2, 5, 7, 8-tetramethylchroman-2-carboxylic acid (Trolox), which was considered as a model compound. The experiment on cellular uptake and subcellular localization of Trolox-loaded chitosan nanoparticles (Trolox-CSNPs) indicate that Trolox-CSNPs enter the cells via the caveolae-mediated endocytosis pathway and traffic with endosomes. Furthermore, compared with Trolox, Trolox-CSNPs exert a higher protective effect against the hypoxia-mediated oxidative stress. Molecular basis of apoptosis study reveals that Trolox-CSNPs can directly block the mitochondria dependent apoptotic pathway through up-regulation of Bcl-2 expression and inhibiting the activation of Bax, Caspase-3 expression. In conclusion, the hydroxyethylated chitosan is a promising drug nanocarrier to deliver antioxidants for the treatment of hypoxia-mediated disease.From the Clinical EditorAntioxidants are potentially beneficial in oxidative stress-related diseases, although cellular uptake of most antioxidants is suboptimal. In this study, hydroxyethylated chitosan nanoparticles are demonstrated as promising drug carriers in a Trolox-model system.The Trolox loaded chitosan nanoparticles could be used for the protection of the PC12 cells against the hypoxia-mediated oxidative stress through inhibiting the production of reactive oxygen species.

A non-viral gene vector based on hydroxyethyl ultra-low molecular weight chitosan nanoparticles (HE-ULMWCh NPs) has been synthesized. The HE-ULMWCh is used to form nanoparticles with an enhanced green fluorescence protein (pEGFP) encoding plasmid that possesses diameters of 30–50 nm and a molecular weight of less than 2 kDa. The cytotoxicity assay shows that this new gene vector is significantly less cytotoxic than polyethylenimine whilst still retaining the characteristics of a cationic polyelectrolyte. Cellular uptake of HE-ULMWCh NP–pDNA nanocomplexes shows that HE-ULMWCh NPs can readily enter into cells via endocytosis and then be delivered to lysosomes. pDNA can be easily released from HE-ULMWCh NPs in the acidic vesicles of lysosomes, therefore resulting in a significant increase in the transfection efficiency in three different cell lines compared to naked pDNA. The in vitro results using the new gene vector are further confirmed by in vivo transfection in which HE-ULMWCh NPs provided 3.2 fold greater transfection efficiency than naked pDNA. The HE-ULMWCh NPs can therefore be concluded to be a promising delivery system for in vitro and in vivo gene transfection.