Qinmei Li

Dual-stimuli sensitive nanogels fabricated by self-association of thiolated hydroxypropyl cellulose

A new type of cellulose derivative was synthesized by means of conjugating cysteamine to hydroxypropyl cellulose (HPC) and the degree of thiol groups could be controlled by the feed ratio of the reactants. The thiolated HPC (HPC–SH) maintains the thermosensitivity of HPC and the thiol groups on the HPC chain can be oxidized to disulfide bonds. Cytotoxity tests performed on MG-63 cells proved that HPC–SH is not harmful to the cells. Nanogels can be fabricated by the self-association of HPC–HS in the solution at 45 °C and then oxidation of thiol groups to disulfide bonds occurs to stabilize the associated structure. The crosslinking degree of the nanogels could be controlled by the substitution degree of thiol groups (–SH) in the thiolated HPC. The hydrodynamic radius of the nanogels can be tuned by adjusting the degree of crosslinking and the concentration of the initial thiolated HPC solution in the self-association process. The hydrodynamic radius of the nanogels can be changed with the temperature and the dissociation process can happen by adding the reducing agent dithiothreitol (DTT). The dual-stimuli sensitive nanogels may have potential applications in controlled drug release, transfer switch device and sensors.

Osmium Bipyridine-Containing Redox Polymers Based on Cellulose and Their Reversible Redox Activity

Thermo-, pH-, and electrochemical-sensitive cellulose graft copolymers, hydroxypropyl cellulose-g-poly(4-vinylpyridine)-Os(bipyridine) (HPC-g-P4VP-Os(bpy)), were synthesized and characterized. The electrochemical properties of the resulting material were investigated via cyclic voltammetry by coating the graft copolymers on the platinized carbon electrode. The results indicated that the electrochemical properties of the graft copolymer modified electrode were responsive to the pH values of the electrolyte solution. The reversible transformation between the active and inactive state originated from the changes in the architecture of the HPC-g-P4VP-Os(bpy) graft copolymer at different pH values. At high pH (e.g., above the pK(a) of P4VP), the chains of P4VP collapsed, and the electrochemical activity of the electrode was reduced. With immobilization of glucose oxidase (GOx) on the graft copolymer decorated electrode, a biosensor for glucose detection was prepared. The current of the biosensor depended on the glucose concentration in the detected solution and increased with the successive addition of glucose.

An interface nanostructured array guided high performance electrochemical actuator

Here we report a novel electrochemical actuator using a hierarchically architectured nanostructure electrode. Vertically aligned NiO nanowall arrays, which act as an interface layer, are in situ grown on a free-standing graphene–carbon nanotube hybrid film. The large specific surface area and fast ion transmission channels of this nanostructured array interface enable us to achieve large deformation in quick switching response (18.4 mm per 0.05 s), high strain and stress rates (8.31% s−1, 12.16 MPa s−1) and excellent durability upon 500 000 times continuous operations in air.

Dual-stimuli sensitive keratin graft PHPMA as physiological trigger responsive drug carriers

Keratin graft poly(N-(2-hydroxypropyl)methacrylamide) (K-g-PHPMA) copolymers were synthesized and characterized. On account of the thiol groups of keratin and the amphiphilicity of the graft copolymers, micelles with cleavable cross-links on a keratin core were fabricated in water. The K-g-PHPMA micelles can efficiently encapsulate doxorubicin (DOX) and can be used as a drug carrier. The DOX content in the micelles increases with the keratin content of the graft copolymers. The release of the encapsulated DOX in the micelles is sensitive to the physiological environment. Redox trigger glutathione (GSH), especially at the intracellular level, and trypsin can effectively trigger the release of the encapsulated DOX. In vitro cellular uptake experiments indicate that the DOX released from the DOX-loaded K-g-PHPMA micelles can be efficiently internalized into cells. Under higher GSH condition, the DOX shows a much faster release into the nucleus of the cells. The K-g-PHPMA copolymers have promising applications as drug carriers for enhanced intracellular drug delivery in cancer therapy.

Improving the blood clearance time of 125I labeled Dex-g-PMAGGCONHTyr by copolymerization

Dextran graft copolymers, including dextran graft poly(N-methacryloylglycylglycine) copolymers conjugated with polyethylene glycol and tyrosine (Dex-g-PMAGGCONHPEG3k-NHTyr), dextran graft poly(N-(2-hydroxypropyl) methacrylamide-co-N-methacryloylglycylglycine)-tyrosine conjugates (Dex-g-P(HPMA-co-MAGGCONHTyr)), and dextran graft poly(methacrylpolyethylene glycol-co-N-methacryloylglycylglycine)-tyrosine conjugates (Dex-g-P(MPEG-co-MAGGCONHTyr)) were synthesized for the purpose to improve the biodistribution and blood clearance time of ploy(N-methacryloylglycylglycine)-tyrosine conjugates (Dex-g-PMAGGCONHTyr). Dynamic light scattering (DLS) results indicated that no aggregation formed in 0.9% saline solution. The graft copolymers were labeled with 125I and the labeled copolymers are stable in 0.9% saline and 1% BSA of PBS solutions. Pharmacokinetics studies showed that 125I labeled graft copolymer Dex-g-P(HPMA-co-MAGGCONHTyr) had a longer blood clearance time than the others. Biodistribution images confirmed the preferable liver and spleen accumulation at 1 h after injection, and especially for blood tissue, the mean %ID/g value of the PHPMA-modified graft copolymer Dex-g-P(HPMA-co-MAGGCONHTyr) is 7 folds higher than that of Dex-g-PMAGGCONHTyr.

Synthesis, characterization, and in vivo biodistribution of 125I-labeled Dex-g-PMAGGCONHTyr.

Dextran graft poly (N-methacryloylglycylglycine) copolymer-tyrosine conjugates (dextran-g-PMAGGCONHTyr) were synthesized and characterized. Dynamic light scattering (DLS) results indicated that the graft copolymers are soluble in pH 7.4 PBS and 0.9% saline solutions. The graft copolymers were labeled with (125)I, and the labeling stability in 0.9% saline solution was investigated. Pharmacokinetics studies showed a rapid clearance of (125)I-labeled graft copolymers from the blood pool. Biodistribution images confirmed the preferable liver and spleen accumulation within 1 h after injection and rapid clearance from all the organs over time. The graft copolymer with molecular weight of 9.8 kDa was eliminated from the kidney significantly faster than those with higher molecular weight. The effect of the numbers of -COOH groups on the graft copolymers on the biodistribution was also investigated. It was found that the graft copolymers with the average number of -COOH groups per glucopyranose unit (DS(-COOH)) of 0.57 and 0.18 are mainly distributed in liver and spleen at 1 h after injection, whereas the graft copolymer with DS(-COOH) of 0.07 is mainly accumulated in kidney.

Ultrathin core-sheath fibers for liposome stabilization.

Ultrathin core-sheath fibers with small unilamellar vesicles (SUVs) in the core were prepared by coaxial electrospinning. SUVs/sodium hyaluranate (HA-Na)/water and polyvinylpyrrolidone (PVP)/ethanol solutions were used as core and sheath fluid in electrospinning, respectively. The ultrathin fibers were characterized by scanning and transmission electron microscopy (SEM and TEM) and laser scanning confocal microscopy (LSCM). The SUVs were successfully encapsulated in the core HA-Na matrix of the ultrathin fibers and are in the elliptic shape. The SUVs encapsulated in the core matrix of the ultrathin fibers have an excellent stability. The SUVs embedded in the ultrathin fibers are stable. When the ultrathin fibers were re-dissolved in water after one-month storage at room temperature, the rehydrated SUVs have the similar size and size distribution as the as-prepared SUVs. The liposome-loaded ultrathin fiber mats have the promising applications in wound healing materials.

Inhibiting Survivin Expression Increases the Radiosensitivity of Human Hepatoma HepG2 Cells to High-LET Carbon Ions

In this study, we investigated whether survivin plays a direct role in mediating high-LET radiosensitivity. We designed small interfering RNA (siRNA) targeting survivin mRNA, in vitro chemo-synthesized and transfected into HepG2 human hepatoma cells. Real-time PCR assay and western bolting were used to determine survivin expressions at transcriptional and post-transcriptional levels, respectively. The survivin expressions decreased at both the transcriptional and post-transcriptional levels after treatment with survivinspecific siRNA. This observation indicates that survivinspecific siRNA could make survivin gene silent effectively. After exposure to high-LET carbon ion radiation, a reduced clonogenic survival effect was observed in cells treated with siRNA compared with those untreated with siRNA. Furthermore, Annexin V assay was used to determine apoptotic rate. Compared with siRNA mismatch and irradiation alone, siRNA treated cells showed increased apoptotic rates. We also found that transfection with survivin siRNA increased levels of G2/M arrest. These results suggest that the radiosensitivity of HepG2 cells to high-LET carbon ions is increased after inhibiting survivin expression and gene therapy for constitutive survivin may be effective for therapeutic improvement in radioresistant solid tumors by high-LET radiation.

Neural Mechanisms of Reward Seeking Behavior and Cognitive Control in Individuals With Internet Addiction

Internet addiction(IA) as a behavioral addiction is currently becoming a serious mental health issue around the globe. According to the neurobiological model of brain development, exploring the neural mechanisms of reward seeking behavior and cognitive control in internet addicts may help in developing treatments for individuals with IA. Behavioral research has indicated that IA is commonly associated with enhanced reward sensitivity and decreased inhibitory control. Additionally, research focused on the neural mechanisms of IA indicates that deficits in the reward or cognitive control systems might be a high risk factor for addictive behaviors.Compared with substance addictions, IA, as a kind of psychological addiction, has a specific reward mechanism.While previous research has deepened the understanding of the psychological and neural mechanisms in IA, there still exist many issues surrounding diagnosis and treatment of IA: the screening criteria are not scientific; the classification is ambiguous; the effect of intervention and treatment is controversial; causal research is scarce; and research paradigms are flawed. Substantial future research is needed to explore, fully understand, and treat IA.

Heavy Ion Radiotherapy for Shallow-Seated Tumors at IMP

By the end of 2008, clinical trials of heavy-ion radiotherapy for shallow-seated tumors have been carried out for seven times and 82 selected patients have been treated with 80-100 MeVu− 1 carbon ions supplied by the Heavy Ion Research Facility in Lanzhou (HIRFL) at the Institute of Modern Physics, Chinese Academy of Sciences (IMP-CAS) since November, 2006. A passive irradiation system for 2D layer-stacking method and a dose optimization method for radiotherapy with carbon ions have been developed. The present paper will describe the approach of how we carry out the treatment of shallow-seated tumors. Experimental verification of longitudinally therapeutic dose distribution was conducted under the condition of simulating patient treatment in the therapy terminal at HIRFL. The experimental and clinical results indicate that the therapy system is effective and the heavy ion radiotherapy for superficially-placed tumors at IMP is successful.