Hao Ran Jia

Shape-Dependent Radiosensitization Effect of Gold Nanostructures in Cancer Radiotherapy: Comparison of Gold Nanoparticles, Nanospikes, and Nanorods

The shape effect of gold (Au) nanomaterials on the efficiency of cancer radiotherapy has not been fully elucidated. To address this issue, Au nanomaterials with different shapes but similar average size (∼50 nm) including spherical gold nanoparticles (GNPs), gold nanospikes (GNSs), and gold nanorods (GNRs) were synthesized and functionalized with poly(ethylene glycol) (PEG) molecules. Although all of these Au nanostructures were coated with the same PEG molecules, their cellular uptake behavior differed significantly. The GNPs showed the highest cellular responses as compared to the GNSs and the GNRs (based on the same gold mass) after incubation with KB cancer cells for 24 h. The cellular uptake in cells increased in the order of GNPs > GNSs > GNRs. Our comparative studies indicated that all of these PEGylated Au nanostructures could induce enhanced cancer cell-killing rates more or less upon X-ray irradiation. The sensitization enhancement ratios (SERs) calculated by a multitarget single-hit model were 1.62, 1.37, and 1.21 corresponding to the treatments of GNPs, GNSs, and GNRs, respectively, demonstrating that the GNPs showed a higher anticancer efficiency than both GNSs and GNRs upon X-ray irradiation. Almost the same values were obtained by dividing the SERs of the three types of Au nanomaterials by their corresponding cellular uptake amounts, indicating that the higher SER of GNPs was due to their much higher cellular uptake efficiency. The above results indicated that the radiation enhancement effects were determined by the amount of the internalized gold atoms. Therefore, to achieve a strong radiosensitization effect in cancer radiotherapy, it is necessary to use Au-based nanomaterials with a high cellular internalization. Further studies on the radiosensitization mechanisms demonstrated that ROS generation and cell cycle redistribution induced by Au nanostructures played essential roles in enhancing radiosensitization. Taken together, our results indicated that the shape of Au-based nanomaterials had a significant influence on cancer radiotherapy. The present work may provide important guidance for the design and use of Au nanostructures in cancer radiotherapy.

Imaging plasma membranes without cellular internalization: multisite membrane anchoring reagents based on glycol chitosan derivatives

Plasma membrane imaging has received substantial attention due to its capability for dynamically tracing significant biological processes including cell trafficking, vesicle transportation, apoptosis, etc. However, cellular internalization of staining molecules poses challenges to the development of fluorescent dyes to specifically label plasma membranes rather than intracellular organelles. In this work, glycol chitosan, a multifunctional biomaterial derived from natural polymers, was used for the first time to image the plasma membranes based on a strategy of multisite membrane anchoring. A glycol chitosan derivative, glycol chitosan-cholesterol-FITC (Chito-Chol-FITC), was synthesized by using glycol chitosan as the backbone, and PEG-cholesterols and FITC molecules as side chains. The cholesterol groups and FITC molecules serve as hydrophobic anchoring units and fluorescent units, respectively. Benefitting from the strategy, this molecular probe could rapidly stain the cell membrane within 5 min as well as effectively restrain the cellular uptake process-it could tolerate an incubation time of 6 h without substantial cellular internalization. Its imaging performance far exceeds that of the current commercial plasma membrane imaging reagents based on small molecules (such as DiD and FM families), which will be easily internalized by the cells within 10-15 min. The present work shows the biomacromolecular assembly of the glycol chitosan derivative on the cell surface, which may shed new light on the interactions of biomaterials with biological systems. Besides, the multisite membrane anchoring strategy developed herein also provides a novel platform for future cell surface engineering studies.

Cholesterol-Assisted Bacterial Cell Surface Engineering for Photodynamic Inactivation of Gram-Positive and Gram-Negative Bacteria

Antibacterial photodynamic therapy (PDT), which enables effective killing of regular and multidrug-resistant (MDR) bacteria, is a promising treatment modality for bacterial infection. However, because most photosensitizer (PS) molecules fail to strongly interact with the surface of Gram-negative bacteria, this technique is suitable for treating only Gram-positive bacterial infection, which largely hampers its practical applications. Herein, we reveal for the first time that cholesterol could significantly facilitate the hydrophobic binding of PSs to the bacterial surface, achieving the hydrophobic interaction-based bacterial cell surface engineering that could effectively photoinactivate both Gram-negative and Gram-positive bacteria. An amphiphilic polymer composed of a polyethylene glycol (PEG) segment terminated with protoporphyrin IX (PpIX, an anionic PS) and cholesterol was constructed (abbreviated Chol-PEG-PpIX), which could self-assemble into micelle-like nanoparticles (NPs) in aqueous solution. When encountering the Gram-negative Escherichia coli cells, the Chol-PEG-PpIX NPs would disassemble and the PpIX moieties could effectively bind to the bacterial surface with the help of the cholesterol moieties, resulting in the significantly enhanced fluorescence emission of the bacterial surface. Under white light irradiation, the light-triggered singlet oxygen (1O2) generation of the membrane-bound PpIX could not only severely damage the outer membrane but also facilitate the entry of external Chol-PEG-PpIX into the bacteria, achieving >99.99% bactericidal efficiency. Besides, as expected, the Chol-PEG-PpIX NPs also exhibited excellent antibacterial performance against the Gram-positive Staphylococcus aureus. We also verified that this nanoagent possesses negligible dark cytotoxicity toward mammalian cells and good hemocompatibility. To the best of our knowledge, this study demonstrates for the first time the feasibility of constructing a fully hydrophobic interaction-based and outer membrane-anchored antibacterial PDT nanoagent.

Plasma membrane activatable polymeric nanotheranostics with self-enhanced light-triggered photosensitizer cellular influx for photodynamic cancer therapy

&NA; To address the issue of low cellular uptake of photosensitizers by cancer cells in photodynamic therapy (PDT), we designed a smart plasma membrane‐activatable polymeric nanodrug by conjugating the photosensitizer protoporphyrin IX (PpIX) and polyethylene glycol (PEG) with glycol chitosan (GC). The as‐prepared GC‐PEG‐PpIX can self‐assemble into core‐shell nanoparticles (NPs) in aqueous solution and the fluorescence of PpIX moieties in the inner core is highly quenched due to strong &pgr;–&pgr; stacking. Interestingly, when encountering plasma membranes, the GC‐PEG‐PpIX NPs can disassemble and stably attach to plasma membranes due to the membrane affinity of PpIX moieties, which effectively suppresses the self‐quenching of PpIX, leading to significantly enhanced fluorescence and singlet oxygen (1O2) production upon laser irradiation. The massively produced 1O2 can compromise the integrity of the plasma membrane, enabling the influx of extracellular nanoagents into cells to promote cell death upon further laser irradiation. Through local injection, the membrane anchored GC‐PEG‐PpIX enables strong physical association with tumor cells and exhibits highly enhanced in vivo fluorescence at the tumor site. Besides, excellent tumor accumulation and prolonged tumor retention of GC‐PEG‐PpIX were realized after intravenous injection, which ensured its effective imaging‐guided PDT. Graphical abstract Figure. No caption available.

Development of a Light-Controlled Nanoplatform for Direct Nuclear Delivery of Molecular and Nanoscale Materials

Research on nanomedicines has rapidly progressed in the past few years. However, due to the limited size of nuclear pores (9-12 nm), the nuclear membrane remains a difficult barrier to many nucleus-targeting agents. Here, we report the development of a general platform to effectively deliver chemical compounds such as drug molecules or nanomaterials into cell nuclei. This platform consists of a polyamine-containing polyhedral oligomeric silsesquioxane (POSS) unit, a hydrophilic polyethylene glycol (PEG) chain, and the photosensitizer rose bengal (RB), which can self-assemble into nanoparticles (denoted as PPR NPs). Confocal fluorescence imaging showed that PPR NPs mainly located in lysosomes after cellular internalization. After mild light irradiation, however, PPR NPs effectively disrupted lysosomal structures by singlet oxygen (1O2) oxidation and substantially accumulated on nuclear membranes, which enabled further disruption of the membrane integrity and promoted their final nuclear entry. Next, we selected two chemotherapeutic agents (10-hydroxycamptothecine and docetaxel) and a fluorescent dye (DiD) as payloads of PPR NPs and successfully demonstrated that this nanocarrier could efficiently deliver them into cell nuclei in a light-controlled manner. In addition to molecular compounds, we have also demonstrated that PPR NPs could facilitate the nuclear entry of nanomaterials, including Prussian blue NPs as well as gold nanorods. Compared to traditional strategies for nuclear delivery, this highly controllable nanoplatform avoids complicated modification of nucleus-targeting ligands and is generally applicable to both molecular compounds and nanomaterials.