Publications by authors named "Wenyong Liu"

47 Publications

Stereotactic technology for 3D bioprinting: from the perspective of robot mechanism.

Biofabrication 2021 08 13;13(4). Epub 2021 Aug 13.

Key Laboratory for Biomechanics and Mechanobiology of Chinese Education Ministry, Beijing Advanced Innovation Centre for Biomedical Engineering, School of Biological Science and Medical Engineering, Beihang University, Beijing 100083, People's Republic of China.

Three-dimensional (3D) bioprinting has been widely applied in the field of biomedical engineering because of its rapidly individualized fabrication and precisely geometric designability. The emerging demand for bioprinted tissues/organs with bio-inspired anisotropic property is stimulating new bioprinting strategies. Stereotactic bioprinting is regarded as a preferable strategy for this purpose, which can perform bioprinting at the target position from any desired orientation in 3D space. In this work, based on the motion characteristics analysis of the stacked bioprinting technologies, mechanism configurations and path planning methods for robotic stereotactic bioprinting were investigated and a prototype system based on the double parallelogram mechanism was introduced in detail. Moreover, the influence of the time dimension on stereotactic bioprinting was discussed. Finally, technical challenges and future trends of stereotactic bioprinting within the field of biomedical engineering were summarized.
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http://dx.doi.org/10.1088/1758-5090/ac1846DOI Listing
August 2021

Applications of 3D bioprinting in tissue engineering: advantages, deficiencies, improvements, and future perspectives.

J Mater Chem B 2021 Jul;9(27):5385-5413

Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, Beihang University, Beijing 100083, China.

Over the past decade, 3D bioprinting technology has progressed tremendously in the field of tissue engineering in its ability to fabricate individualized biological constructs with precise geometric designability, which offers us the capability to bridge the divergence between engineered tissue constructs and natural tissues. In this work, we first review the current widely used 3D bioprinting approaches, cells, and materials. Next, the updated applications of this technique in tissue engineering, including bone tissue, cartilage tissue, vascular grafts, skin, neural tissue, heart tissue, liver tissue and lung tissue, are briefly introduced. Then, the prominent advantages of 3D bioprinting in tissue engineering are summarized in detail: rapidly prototyping the customized structure, delivering cell-laden materials with high precision in space, and engineering with a highly controllable microenvironment. The current technical deficiencies of 3D bioprinted constructs in terms of mechanical properties and cell behaviors are afterward illustrated, as well as corresponding improvements. Finally, we conclude with future perspectives about 3D bioprinting in tissue engineering.
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http://dx.doi.org/10.1039/d1tb00172hDOI Listing
July 2021

Warpage Prediction of RHCM Crystalline Parts Based on Multi-Layers.

Polymers (Basel) 2021 May 31;13(11). Epub 2021 May 31.

College of Mechanical Engineering, Zhejiang University of Technology, Hangzhou 310014, China.

Warpage is a typical defect for injection-molded parts, especially for crystalline parts molded by rapid heat cycle molding (RHCM). In this paper, a prediction method is proposed for predicting the warpage of crystalline parts molded by the RHCM process. Multi-layer models were established to predict warpage with the same thicknesses as the skin-core structures in the molded parts. Warpages were defined as the deformations calculated by the multi-layer models. The deformations were solved using the classical laminated plate theory by Abaqus. A model was introduced to describe the elastic modulus with the influence of temperature and crystallinity. The simulation process was divided into two procedures, before ejection and after ejection. Thermal stresses and thermal strains were simulated, respectively, in the procedure before ejection and after ejection. The prediction results were compared with the experimental results, which showed that the average errors between predicted warpage and average experimental warpage are, respectively, 7.0%, 3.5%, and 4.4% in conventional injection molding (CIM), in RHCM under a 60 °C heating mold (RHCM60), and in RHCM under a 90 °C heating mold (RHCM90).
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http://dx.doi.org/10.3390/polym13111814DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8198935PMC
May 2021

Biopsy Needle System With a Steerable Concentric Tube and Online Monitoring of Electrical Resistivity and Insertion Forces.

IEEE Trans Biomed Eng 2021 05 21;68(5):1702-1713. Epub 2021 Apr 21.

Objective: Biopsies are the gold standard for clinical diagnosis. However, a discrepancy between the biopsy sample and target tissue because of misplacement of the biopsy spoon can lead to errors in the diagnosis and subsequent treatment. Thus, correctly determining whether the needle tip is in the tumor is crucial for accurate biopsy results.

Methods: A biopsy needle system was designed with a steerable, flexible, and superelastic concentric tube; electrodes to monitor the electrical resistivity; and load cells to monitor the insertion force. The degrees of freedom were analyzed for two working modes: straight-line and deflection.

Results: Experimental results showed that the system could perceive the tissue type in online based on the electrical resistivity. In addition, changes in the insertion force indicated transitions between the interfaces of adjacent tissue layers.

Conclusion: The two monitoring methods guarantee that the biopsy spoon is at the desired position inside the tumor during an operation.

Significance: The proposed biopsy needle system can be integrated into an autonomous robotic biopsy system.
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http://dx.doi.org/10.1109/TBME.2021.3060541DOI Listing
May 2021

A novel fluoroscopy-based robot system for pedicle screw fixation surgery.

Int J Med Robot 2020 Dec 25;16(6):1-8. Epub 2020 Sep 25.

Department of Orthopaedics, Peking University Third Hospital, Beijing, China.

Background: Robot-assisted pedicle screw insertion has gained popularity in the spinal surgery field. Due to high cost, these spinal robots are not extensively applied in clinical surgeries. Developing an effective robot system with low cost and high clinical acceptability is one of the future trends.

Methods: We developed a novel fluoroscopy-based robot system for pedicle screw insertion. Four live pigs were conducted with percutaneous pedicle screw insertion. Robot-assisted surgery was performed on the left side of pedicle, while the right opposite side is placed by freehand. The respect accuracy, surgical time and fluoroscopy time were recorded.

Results: Robot-assisted group achieved 100% (23/23) accuracy. The average times (6.4 ± 1.7) for intraoperative fluoroscopy usage per procedure were lesser than freehand group (12.5 ± 3.6), and the surgical time (6.8 ± 2.1 min) per screw was reduced compared with freehand group (12.1 ± 4.8 min).

Conclusions: Our robot system is cost-effective and feasible for pedicle screw placement. Low economic cost makes it easier for extensive application in primary hospitals.
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http://dx.doi.org/10.1002/rcs.2171DOI Listing
December 2020

High efficiency and stability of ink-jet printed quantum dot light emitting diodes.

Nat Commun 2020 Apr 2;11(1):1646. Epub 2020 Apr 2.

TCL Research, No. 1001 Zhongshan Park Road, Nanshan District, Shenzhen, 518067, People's Republic of China.

The low efficiency and fast degradation of devices from ink-jet printing process hinders the application of quantum dot light emitting diodes on next generation displays. Passivating the trap states caused by both anion and cation under-coordinated sites on the quantum dot surface with proper ligands for ink-jet printing processing reminds a problem. Here we show, by adapting the idea of dual ionic passivation of quantum dots, ink-jet printed quantum dot light emitting diodes with an external quantum efficiency over 16% and half lifetime of more than 1,721,000 hours were reported for the first time. The liquid phase exchange of ligands fulfills the requirements of ink-jet printing processing for possible mass production. And the performance from ink-jet printed quantum dot light emitting diodes truly opens the gate of quantum dot light emitting diode application for industry.
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http://dx.doi.org/10.1038/s41467-020-15481-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7118149PMC
April 2020

Tailoring ordered microporous structure of cellulose-based membranes through molecular hydrophobicity design.

Carbohydr Polym 2020 Feb 4;229:115425. Epub 2019 Oct 4.

National and Local Joint Engineering Research Center of Advanced Packaging Materials Research and Development Technology, Hunan Key Laboratory of Advanced Packaging Materials and Technology, College of Packaging and Material Engineering, Hunan University of Technology, Zhuzhou, 412007, China.

Ordered porous polymer membranes can be facilely prepared by breath figures. Previous studies have confirmed that the solidifying of polymer is crucial for the formation of ordered porous structures, which directly depends on the hydrophobicity of polymer. However, it is still unknown how strong hydrophobicity is required. Here, cellulose acetate derivatives (CADs) were used to investigate the effect of hydrophobicity on ordered porous structures. The CADs with different hydrophobicity were firstly synthesized via simple reactions, and then the porous membranes were fabricated by the breath figure method. It was found that the pore size showed a decreasing trend with hydrophobicity, and the degree of order of porous structures firstly increased and then dropped, showing a critical hydrophobicity value for the transition of the degree of order. Therefore, it was confirmed that suitable hydrophobicity is critical for ordered porous structures of CADs while excessive hydrophobicity may impair the ordered structures.
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http://dx.doi.org/10.1016/j.carbpol.2019.115425DOI Listing
February 2020

Hot-electron dynamics in quantum dots manipulated by spin-exchange Auger interactions.

Nat Nanotechnol 2019 11 7;14(11):1035-1041. Epub 2019 Oct 7.

Chemistry Division, Los Alamos National Laboratory, Los Alamos, NM, USA.

The ability to effectively manipulate non-equilibrium 'hot' carriers could enable novel schemes for highly efficient energy harvesting and interconversion. In the case of semiconductor materials, realization of such hot-carrier schemes is complicated by extremely fast intraband cooling (picosecond to subpicosecond time scales) due to processes such as phonon emission. Here we show that using magnetically doped colloidal semiconductor quantum dots we can achieve extremely fast rates of spin-exchange processes that allow for 'uphill' energy transfer with an energy-gain rate that greatly exceeds the intraband cooling rate. This represents a dramatic departure from the usual situation where energy-dissipation via phonon emission outpaces energy gains due to standard Auger-type energy transfer at least by a factor of three. A highly favourable energy gain/loss rate ratio realized in magnetically doped quantum dots can enable effective schemes for capturing kinetic energy of hot, unrelaxed carriers via processes such as spin-exchange-mediated carrier multiplication and upconversion, hot-carrier extraction and electron photoemission.
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http://dx.doi.org/10.1038/s41565-019-0548-1DOI Listing
November 2019

Preparation and characterization of reinforced starch-based composites with compatibilizer by simple extrusion.

Carbohydr Polym 2019 Nov 23;223:115122. Epub 2019 Jul 23.

State Key Laboratory of Polymer Physics and Chemistry, Joint Laboratory of Polymer Science and Materials, Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.

Because of the poor performance of starch-based composites, we prepared the starch-based composites with good mechanical properties by a simple two-step melt-blending extrusion. Glycerol and nano-SiO were firstly introduced into starch to prepare the TPS/nano-SiO composite by the first extrusion, and poly(butylene adipate-co-terephthalate) (PBAT) and the compatibilizers were then incorporated to obtain the improved composites by the second extrusion. The mechanical properties, thermal properties, morphology, and structure of the composites were characterized. The results showed that the strength dramatically increased after the addition of nano-SiO into starch, and the elongation at break was significantly improved by the incorporation of PBAT. The tensile strength was increased distinctly after the addition of the compatibilizers. All the composites exhibited good mechanical properties. The melting transition, the thermal stability, and the crystalline structure did not change with the additives, whereas the glass transition of the starch-rich phase shifted to a lower temperature. The results indicated that the combined compatibilizers had better compatibilization than each one alone.
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http://dx.doi.org/10.1016/j.carbpol.2019.115122DOI Listing
November 2019

POSS Hybrid Robust Biomass IPN Hydrogels with Temperature Responsiveness.

Polymers (Basel) 2019 Mar 20;11(3). Epub 2019 Mar 20.

Hunan Provincial Engineering Laboratory of Key Technique of Non-metallic Packaging Waste Resources Utilization, Hunan University of Technology, Zhuzhou 412007, China.

In order to improve the performance of traditional sodium alginate (SA) hydrogels cross-linked by Ca ions to meet greater application demand, a strategy was designed to structure novel SA-based gels (named OP-PN gels) to achieve both stimulus responsiveness and improved mechanical strength. In this strategy, the SA chains are co-cross-linked by CaCl₂ and cationic octa-ammonium polyhedral oligomeric silsesquioxane (Oa-POSS) particles as the first network, and an organically cross-linked poly(N-isopropyl acrylamide) (PNIPA) network is introduced into the gels as the second network. Several main results are obtained from the synthesis and characterization of the gels. For OP-PN gels, their properties depend on the content of both uniformly dispersed Oa-POSS and PNIPA network directly. The increased Oa-POSS and PNIPA network content significantly improves both the strength and resilience of gels. Relatively, the increased Oa-POSS is greatly beneficial to the modulus of gels, and the increased PNIPA network is more favorable to advancing the tensile deformation of gels. The gels with hydrophilic PNIPA network exhibit better swelling ability and remarkable temperature responsiveness, and their volume phase transition temperature can be adjusted by altering the content of Oa-POSS. The deswelling rate of gels increases gradually with the increase of POSS content due to the hydrophobic Si⁻O skeleton of POSS. Moreover, the enhanced drug loading and sustained release ability of the target drug bovine serum albumin displays great potential for this hybrid gel in the biomedical field.
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http://dx.doi.org/10.3390/polym11030524DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6473450PMC
March 2019

Multi-object Model-Based Multi-atlas Segmentation Constrained Grid Cut for Automatic Segmentation of Lumbar Vertebrae from CT Images.

Adv Exp Med Biol 2018;1093:65-71

Institute for Surgical Technology and Biomechanics, University of Bern, Bern, Switzerland.

In this chapter, we present a multi-object model-based multi-atlas segmentation constrained grid cut method for automatic segmentation of lumbar vertebrae from a given lumbar spinal CT image. More specifically, our automatic lumbar vertebrae segmentation method consists of two steps: affine atlas-target registration-based label fusion and bone-sheetness assisted multi-label grid cut which has the inherent advantage of automatic separation of the five lumbar vertebrae from each other. We evaluate our method on 21 clinical lumbar spinal CT images with the associated manual segmentation and conduct a leave-one-out study. Our method achieved an average Dice coefficient of 93.9 ± 1.0% and an average symmetric surface distance of 0.41 ± 0.08 mm.
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http://dx.doi.org/10.1007/978-981-13-1396-7_5DOI Listing
July 2019

Epithelioid angiosarcoma of the liver: report of two cases and review of the literature.

Int J Clin Exp Pathol 2018 1;11(6):3191-3198. Epub 2018 Jun 1.

Department of Pathology, Shanghai Ninth People's Hospital, School of Medicine, Shanghai Jiao Tong University, Center for Specialty Strategy Research of Shanghai Jiao Tong University China Hospital Development Institute Shanghai, China.

Angiosarcoma is a malignant tumor of endothelial origin. Epithelioid angiosarcoma is a subtype of angiosarcoma, in which the malignant endothelial cells have a predominantly epithelioid appearance. So far, few cases of primary hepatic epithelioid andiosarcoma (PHEA) have been described. In this case report, we describe two rare cases of PHEA. Microscopically, the tumors were consistently composed of atypical epithelioid cells with vesicular nuclei, prominent nucleoli, and eosinophilic cytoplasm. One patient had metastatic disease and underwent palliative hepatic surgery following radiotherapy and chemotherapy, and had a postoperative survival time of 12 months, while the other patient is still alive after tumor resection. PHEA is an aggressive malignant tumor with a high rate of metastasis.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6958078PMC
June 2018

A new hand-eye calibration approach for fracture reduction robot.

Comput Assist Surg (Abingdon) 2017 12 22;22(sup1):113-119. Epub 2017 Sep 22.

d Department of Biomedical Engineering , National University of Singapore , Singapore, Singapore.

Objective: The hand-eye calibration is used to determine the transformation between the end-effector and the camera marker of the robot. But the robot movement in traditional method would be time-consuming, inaccurate and even unavailable in some conditions. The method presented in this article can complete the calibration without any movement and is more suitable in clinical applications.

Methods: Instead of solving the classic non-linear equation AX = XB, we collected the points on X and Y axes of the tool coordinate system (TCS) with the visual probe and fitted them using the singular value decomposition algorithm (SVD). Then, the transformation was obtained with the data of the tool center point (TCP). A comparison test was conducted to verify the performance of the method.

Results: The average translation error and orientation error of the new method are 0.12 ± 0.122 mm and 0.18 ± 0.112° respectively, while they are 0.357 ± 0.347 mm and 0.416 ± 0.234° correspondingly in the traditional method.

Conclusions: The high accuracy of the method indicates that it is a good candidate for medical robots, which usually need to work in a sterile environment.
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http://dx.doi.org/10.1080/24699322.2017.1379254DOI Listing
December 2017

Phase-Transfer Ligand Exchange of Lead Chalcogenide Quantum Dots for Direct Deposition of Thick, Highly Conductive Films.

J Am Chem Soc 2017 05 5;139(19):6644-6653. Epub 2017 May 5.

Chemistry Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States.

The use of semiconductor nanocrystal quantum dots (QDs) in optoelectronic devices typically requires postsynthetic chemical surface treatments to enhance electronic coupling between QDs and allow for efficient charge transport in QD films. Despite their importance in solar cells and infrared (IR) light-emitting diodes and photodetectors, advances in these chemical treatments for lead chalcogenide (PbE; E = S, Se, Te) QDs have lagged behind those of, for instance, II-VI semiconductor QDs. Here, we introduce a method for fast and effective ligand exchange for PbE QDs in solution, resulting in QDs completely passivated by a wide range of small anionic ligands. Due to electrostatic stabilization, these QDs are readily dispersible in polar solvents, in which they form highly concentrated solutions that remain stable for months. QDs of all three Pb chalcogenides retain their photoluminescence, allowing for a detailed study of the effect of the surface ionic double layer on electronic passivation of QD surfaces, which we find can be explained using the hard/soft acid-base theory. Importantly, we prepare highly conductive films of PbS, PbSe, and PbTe QDs by directly casting from solution without further chemical treatment, as determined by field-effect transistor measurements. This method allows for precise control over the surface chemistry, and therefore the transport properties of deposited films. It also permits single-step deposition of films of unprecedented thickness via continuous processing techniques, as we demonstrate by preparing a dense, smooth, 5.3-μm-thick PbSe QD film via doctor-blading. As such, it offers important advantages over laborious layer-by-layer methods for solar cells and photodetectors, while opening the door to new possibilities in ionizing-radiation detectors.
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http://dx.doi.org/10.1021/jacs.7b01327DOI Listing
May 2017

Understanding and Curing Structural Defects in Colloidal GaAs Nanocrystals.

Nano Lett 2017 03 22;17(3):2094-2101. Epub 2017 Feb 22.

Department of Chemistry and James Franck Institute, University of Chicago , Chicago, Illinois 60637, United States.

GaAs is one of the most important semiconductors. However, colloidal GaAs nanocrystals remain largely unexplored because of the difficulties with their synthesis. Traditional synthetic routes either fail to produce pure GaAs phase or result in materials whose optical properties are very different from the behavior expected for quantum dots of direct-gap semiconductors. In this work, we demonstrate a variety of synthetic routes toward crystalline GaAs NCs. By using a combination of Raman, EXAFS, transient absorption, and EPR spectroscopies, we conclude that unusual optical properties of colloidal GaAs NCs can be related to the presence of Ga vacancies and lattice disorder. These defects do not manifest themselves in TEM images and powder X-ray diffraction patterns but are responsible for the lack of absorption features even in apparently crystalline GaAs nanoparticles. We introduce a novel molten salt based annealing approach to alleviate these structural defects and show the emergence of size-dependent excitonic transitions in colloidal GaAs quantum dots.
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http://dx.doi.org/10.1021/acs.nanolett.7b00481DOI Listing
March 2017

Mn-Doped Lead Halide Perovskite Nanocrystals with Dual-Color Emission Controlled by Halide Content.

J Am Chem Soc 2016 11 7;138(45):14954-14961. Epub 2016 Nov 7.

Chemistry Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States.

Impurity doping has been widely used to endow semiconductor nanocrystals with novel optical, electronic, and magnetic functionalities. Here, we introduce a new family of doped NCs offering unique insights into the chemical mechanism of doping, as well as into the fundamental interactions between the dopant and the semiconductor host. Specifically, by elucidating the role of relative bond strengths within the precursor and the host lattice, we develop an effective approach for incorporating manganese (Mn) ions into nanocrystals of lead-halide perovskites (CsPbX, where X = Cl, Br, or I). In a key enabling step not possible in, for example, II-VI nanocrystals, we use gentle chemical means to finely and reversibly tune the nanocrystal band gap over a wide range of energies (1.8-3.1 eV) via postsynthetic anion exchange. We observe a dramatic effect of halide identity on relative intensities of intrinsic band-edge and Mn emission bands, which we ascribe to the influence of the energy difference between the corresponding transitions on the characteristics of energy transfer between the Mn ion and the semiconductor host.
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http://dx.doi.org/10.1021/jacs.6b08085DOI Listing
November 2016

The development and error analysis of a kinematic parameters based spatial positioning method for an orthopedic navigation robot system.

Int J Med Robot 2017 Sep 9;13(3). Epub 2016 Oct 9.

School of Biological Science and Medical Engineering, Beihang University, China.

Background: Spatial positioning is the key function of a surgical navigation robot system, and accuracy is the most important performance index of such a system.

Methods: The kinematic parameters of a six degrees of freedom (DOF) robot arm were used to form the transformation from intraoperative fluoroscopy images to a robot's coordinate system without C-arm calibration and to solve the redundant DOF problem. The influences of three typical error sources and their combination on the final navigation error were investigated through Monte Carlo simulation.

Results: The navigation error of the proposed method is less than 0.6 mm, and the feasibility was verified through cadaver experiments. Error analysis suggests that the robot kinematic error has a linear relationship with final navigation error, while the image error and gauge error have nonlinear influences.

Conclusions: This kinematic parameters based method can provide accurate and convenient navigation for orthopedic surgeries. The result of error analysis will help error design and assignment for surgical robots.
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http://dx.doi.org/10.1002/rcs.1782DOI Listing
September 2017

Erastin Disrupts Mitochondrial Permeability Transition Pore (mPTP) and Induces Apoptotic Death of Colorectal Cancer Cells.

PLoS One 2016 12;11(5):e0154605. Epub 2016 May 12.

Department of General Surgery, The Ninth People's Hospital Affiliated to Shanghai Jiao-Tong University School of Medicine, Shanghai, China.

We here evaluated the potential anti-colorectal cancer activity by erastin, a voltage-dependent anion channel (VDAC)-binding compound. Our in vitro studies showed that erastin exerted potent cytotoxic effects against multiple human colorectal cancer cell lines, possibly via inducing oxidative stress and caspase-9 dependent cell apoptosis. Further, mitochondrial permeability transition pore (mPTP) opening was observed in erastin-treated cancer cells, which was evidenced by VDAC-1 and cyclophilin-D (Cyp-D) association, mitochondrial depolarization, and cytochrome C release. Caspase inhibitors, the ROS scavenger MnTBAP, and mPTP blockers (sanglifehrin A, cyclosporin A and bongkrekic acid), as well as shRNA-mediated knockdown of VDAC-1, all significantly attenuated erastin-induced cytotoxicity and apoptosis in colorectal cancer cells. On the other hand, over-expression of VDAC-1 augmented erastin-induced ROS production, mPTP opening, and colorectal cancer cell apoptosis. In vivo studies showed that intraperitoneal injection of erastin at well-tolerated doses dramatically inhibited HT-29 xenograft growth in severe combined immunodeficient (SCID) mice. Together, these results demonstrate that erastin is cytotoxic and pro-apoptotic to colorectal cancer cells. Erastin may be further investigated as a novel anti-colorectal cancer agent.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0154605PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4865238PMC
July 2017

Robust and stimuli-responsive POSS hybrid PDMAEMA hydrogels for controlled drug release.

J Biomed Mater Res A 2016 09 18;104(9):2345-55. Epub 2016 May 18.

Department of Polymer Materials and Engineering, Institute of Packaging and Materials Engineering, Hunan University of Technology, Zhuzhou, People's Republic of China.

A new polyhedral oligomeric silsesquioxane (POSS) hybrid hydrogels were desinged and fabricated by introducing cationic octa-ammonium (Oa)-POSS) into chemically cross-linked cationic PDMAEMA hydrogels via in situ radical freezing polymerization. The prepared gels (shorten as OP-PD gels) show considerably improved properties through the effective incorporation and dispersion of Oa-POSS particles in gels. Comparing to the Oa-POSS-free gels, the hybrid gels own better mechanical properties with higher tensile and compressive strength. Meantime, except the decreased swelling ratio in acid condition, the OP-PD gels still keep excellent swelling ability with obvious pH and temperature double responsiveness, which is affected by the content of Oa-POSS slightly. All OP-PD gels exhibit an ultrarapid deswelling rate due to the interconnected micropores structure caused by freezing and the formation of microhydrophobic region around POSS particles. Moreover, the application potential of OP-PD gels in drug release was exploited by using flutamide as target drug, the result showed that the increased Oa-POSS could improve the drug loading ability, and OP-PD gels showed well controlled-release effect in simulated human stomachic condition. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2345-2355, 2016.
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http://dx.doi.org/10.1002/jbm.a.35771DOI Listing
September 2016

Spectral and Dynamical Properties of Single Excitons, Biexcitons, and Trions in Cesium-Lead-Halide Perovskite Quantum Dots.

Nano Lett 2016 Apr 1;16(4):2349-62. Epub 2016 Mar 1.

Chemistry Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States.

Organic-inorganic lead-halide perovskites have been the subject of recent intense interest due to their unusually strong photovoltaic performance. A new addition to the perovskite family is all-inorganic Cs-Pb-halide perovskite nanocrystals, or quantum dots, fabricated via a moderate-temperature colloidal synthesis. While being only recently introduced to the research community, these nanomaterials have already shown promise for a range of applications from color-converting phosphors and light-emitting diodes to lasers, and even room-temperature single-photon sources. Knowledge of the optical properties of perovskite quantum dots still remains vastly incomplete. Here we apply various time-resolved spectroscopic techniques to conduct a comprehensive study of spectral and dynamical characteristics of single- and multiexciton states in CsPbX3 nanocrystals with X being either Br, I, or their mixture. Specifically, we measure exciton radiative lifetimes, absorption cross-sections, and derive the degeneracies of the band-edge electron and hole states. We also characterize the rates of intraband cooling and nonradiative Auger recombination and evaluate the strength of exciton-exciton coupling. The overall conclusion of this work is that spectroscopic properties of Cs-Pb-halide quantum dots are largely similar to those of quantum dots of more traditional semiconductors such as CdSe and PbSe. At the same time, we observe some distinctions including, for example, an appreciable effect of the halide identity on radiative lifetimes, considerably shorter biexciton Auger lifetimes, and apparent deviation of their size dependence from the "universal volume scaling" previously observed for many traditional nanocrystal systems. The high efficiency of Auger decay in perovskite quantum dots is detrimental to their prospective applications in light-emitting devices and lasers. This points toward the need for the development of approaches for effective suppression of Auger recombination in these nanomaterials, using perhaps insights gained from previous studies of II-VI nanocrystals.
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http://dx.doi.org/10.1021/acs.nanolett.5b05077DOI Listing
April 2016

TMP21 modulates cell growth in papillary thyroid cancer cells by inducing autophagy through activation of the AMPK/mTOR pathway.

Int J Clin Exp Pathol 2015 1;8(9):10824-31. Epub 2015 Sep 1.

Department of General Surgery, Shanghai Ninth People's Hospital, Shanghai JiaoTong University School of Medicine Shanghai 200011, China.

Objective: To investigate the role of transmembrane protein (TMP) 21 in human thyroid cancer.

Methods: The recombinant expression vector pcDNA3.1 (+)-TMP21 and specific small interfering RNAs (siRNA) against TMP21 were transfected into a papillary thyroid cancer cell line (TPC1). After transfection, the expression of TMP21 was confirmed by quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting. Moreover, cell viability and apoptosis rate were respectively determined by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) colorimetric assay and flow cytometry (FCM). Additionally, Western blotting was performed to analyze the adenosine monophosphate (AMP)-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) pathways associated protein (P-AMPKα(Thr172), P-mTOR(Ser2448), light chain (LC)-II/LC3-I, and P-S6K(Thr389)) after pre-treatment with AMPK inhibitor, compound C (Com C) and siTMP21.

Results: The TMP21 protein level and cell viability were significantly higher, but apoptotic rate was significantly lower by transfection with pcDNA3.1-TMP21 than those in control group (P < 0.05), and reverse results were obtained by transfection with siTMP21. However, qRT-PCR showed different results due to the feedback inhibition of mRNA. Besides, silencing of TMP21 significantly reduced the levels of P-mTOR(Ser2448) and P-S6K(Thr389) (P < 0.05), but significantly increased the levels of P-AMPKα(Thr172) and LC3-II/LC3-I compared with the control group (P < 0.01). Whereas, the levels of P-AMPKα(Thr172) and LC3-II/LC3-I were significantly decreased by Com C compared with the control group (P < 0.05).

Conclusion: TMP21 modulates cell growth in TPC1 cells by inducing autophagy, which may be associated with activation of AMPK/mTOR pathway.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4637610PMC
September 2016

Revealing giant internal magnetic fields due to spin fluctuations in magnetically doped colloidal nanocrystals.

Nat Nanotechnol 2016 Feb 23;11(2):137-42. Epub 2015 Nov 23.

National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.

Strong quantum confinement in semiconductors can compress the wavefunctions of band electrons and holes to nanometre-scale volumes, significantly enhancing interactions between themselves and individual dopants. In magnetically doped semiconductors, where paramagnetic dopants (such as Mn(2+), Co(2+) and so on) couple to band carriers via strong sp-d spin exchange, giant magneto-optical effects can therefore be realized in confined geometries using few or even single impurity spins. Importantly, however, thermodynamic spin fluctuations become increasingly relevant in this few-spin limit. In nanoscale volumes, the statistical fluctuations of N spins are expected to generate giant effective magnetic fields Beff, which should dramatically impact carrier spin dynamics, even in the absence of any applied field. Here we directly and unambiguously reveal the large Beff that exist in Mn(2+)-doped CdSe colloidal nanocrystals using ultrafast optical spectroscopy. At zero applied magnetic field, extremely rapid (300-600 GHz) spin precession of photoinjected electrons is observed, indicating Beff ∼ 15 -30 T for electrons. Precession frequencies exceed 2 THz in applied magnetic fields. These signals arise from electron precession about the random fields due to statistically incomplete cancellation of the embedded Mn(2+) moments, thereby revealing the initial coherent dynamics of magnetic polaron formation, and highlighting the importance of magnetization fluctuations on carrier spin dynamics in nanomaterials.
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http://dx.doi.org/10.1038/nnano.2015.258DOI Listing
February 2016

Responsiveness and Release Characteristic of Semi-IPN Hydrogels Consisting of Nano-Sized Clay Crosslinked Poly(Dimethylaminoethyl Methacrylate) and Linear Carboxymethyl Chitosan.

J Nanosci Nanotechnol 2015 Jan;15(1):164-71

PH and temperature double responsive semi-IPN hydrogels consisting of poly(dimethylaminoethyl methacrylate) (PDMAEMA) network crosslinked by nano-sized inorganic clay and linear carboxymethyl chitosan (CMCS) were synthesized by in situ, free radical polymerization in aqueous solution. The effect of the mass and carboxymethyl substitution of CMCS on the responsiveness, swelling/deswelling and drug release characteristic of gels were investigated. Comparing to the gels without CMCS, the resulting gels (named as C-NC gels) showed similar LCST and temperature response behavior. However, with the increase of added CMCS, the swelling ratio of gels decreased considerably around the isoelectric point (IEP) of CMCS, while increased in both strong acidic and alkaline condition. The deswelling rate was improved significantly when the content of CMCS is high. In drug load and release test by using theophylline as target, the C-NC gels exhibited an excellent load ability and controlled-release in simulated human intestinal and stomachic condition. Additionally, all properties of gels were affected by the DS of added CMCS due to the different ratio and interaction of negative and positive ions in gels.
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http://dx.doi.org/10.1166/jnn.2015.8768DOI Listing
January 2015

Solution-Processed Transistors Using Colloidal Nanocrystals with Composition-Matched Molecular "Solders": Approaching Single Crystal Mobility.

Nano Lett 2015 Oct 2;15(10):6309-17. Epub 2015 Sep 2.

Department of Chemistry and James Franck Institute, University of Chicago , Chicago, Illinois 60637, United States.

Crystalline silicon-based complementary metal-oxide-semiconductor transistors have become a dominant platform for today's electronics. For such devices, expensive and complicated vacuum processes are used in the preparation of active layers. This increases cost and restricts the scope of applications. Here, we demonstrate high-performance solution-processed CdSe nanocrystal (NC) field-effect transistors (FETs) that exhibit very high carrier mobilities (over 400 cm(2)/(V s)). This is comparable to the carrier mobilities of crystalline silicon-based transistors. Furthermore, our NC FETs exhibit high operational stability and MHz switching speeds. These NC FETs are prepared by spin coating colloidal solutions of CdSe NCs capped with molecular solders [Cd2Se3](2-) onto various oxide gate dielectrics followed by thermal annealing. We show that the nature of gate dielectrics plays an important role in soldered CdSe NC FETs. The capacitance of dielectrics and the NC electronic structure near gate dielectric affect the distribution of localized traps and trap filling, determining carrier mobility and operational stability of the NC FETs. We expand the application of the NC soldering process to core-shell NCs consisting of a III-V InAs core and a CdSe shell with composition-matched [Cd2Se3](2-) molecular solders. Soldering CdSe shells forms nanoheterostructured material that combines high electron mobility and near-IR photoresponse.
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http://dx.doi.org/10.1021/acs.nanolett.5b01258DOI Listing
October 2015

Clinical factors affecting the accuracy of a CT-based active infrared navigation system.

Int J Med Robot 2016 Sep 31;12(3):568-71. Epub 2015 Jul 31.

Department of Spine Surgery, Beijing Jishuitan Hospital, Beijing, People's Republic of China.

Background: Computer-assisted navigation technology has been widely used during spine surgery; however, the desired accuracy cannot be easily obtained and sustained. Our goal was to determine whether and how clinical factors affect the accuracy of a CT-based active infrared navigation system.

Methods: Using the Sawbone model, we recorded the clinical accuracy of the navigation system, based on several clinical statuses.

Results: Clinical accuracy may change when the height or angle of the bed is changed. Within the visible area of the camera, the nearer the distance between the camera and the model, the better the clinical accuracy. The clinical accuracy of the CT-based active infrared navigation system may decrease due to exposure to shadowless lamps.

Conclusions: The clinical accuracy of the CT-based active infrared navigation system may be influenced by the clinical status of shadowless lamps, different distances between the camera and model and different postures of the surgical bed. Copyright © 2015 John Wiley & Sons, Ltd.
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http://dx.doi.org/10.1002/rcs.1693DOI Listing
September 2016

A preliminary study of side population cells in human gastric cancer cell line HGC-27.

Ann Transplant 2015 Mar 16;20:147-53. Epub 2015 Mar 16.

Department of General Surgery, Shanghai Fengxian Central Hospital, Shanghai, Zhabei, China (mainland).

Background: Cancer stem cell-like side population (SP) cells, which may be responsible for recurrence, tumor metastasis, and resistance to cancer therapy, have been identified and characterized in several types of cell lines from gastric cancer. However, there is no report on isolation of SP cells from human gastric cancer cell line HGC-27. This study aims to analyze the proportion of SP cells in HGC-27 cell line, differentiate SP from non-side population (NSP) cells, and determine whether the SP cells have certain biological properties of stem cells.

Material And Methods: (1) HGC-27 suspension was prepared and stained with Hoechst33342 and PI for flow cytometric isolation of SP (2). Differences in proliferation and stemness-related gene expression profiles (CD133, CD44, OCT-4, MDR1, EpCAM, and ABCG2) between SP and NSP cells were detected by gastric formation assay and quantitative real-time PCR (3). Oncogenicity of SP and NSP cells was determined in nude mice in vivo.

Results: (1) SP cells accounted for 0.1-1.0% of HGC-27 cells, and decreased to 0% after verapamil inhibition. Using flow cytometry, we sorted 7.5×10⁵ SP cells and most HGC-27 cells were NSP cells (2). Gastric formation assay and MTT demonstrated that there was a significant difference in proliferation between SP and NSP cells. Gene expression analysis showed that the expression of genes was significantly higher in SP cells (3). The oncogenicity experiment in nude mice revealed that 105 SP cells were able to form tumors, which demonstrated higher tumorigenicity than non-SP cells.

Conclusions: These results collectively suggested that SP cells from HGC-27 cell line have some cancer stem cell properties and could be used for studying the pathogenesis of gastric cancer, which may contribute to discovery of novel therapeutic targets.
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http://dx.doi.org/10.12659/AOT.892197DOI Listing
March 2015

Size-dependent energy levels of InSb quantum dots measured by scanning tunneling spectroscopy.

ACS Nano 2015 Jan 22;9(1):725-32. Epub 2014 Dec 22.

The James Franck Institute and Department of Chemistry, The University of Chicago , Chicago, Illinois 60637, United States.

The electronic structure of single InSb quantum dots (QDs) with diameters between 3 and 7 nm was investigated using atomic force microscopy (AFM) and scanning tunneling spectroscopy (STS). In this size regime, InSb QDs show strong quantum confinement effects which lead to discrete energy levels on both valence and conduction band states. Decrease of the QD size increases the measured band gap and the spacing between energy levels. Multiplets of equally spaced resonance peaks are observed in the tunneling spectra. There, multiplets originate from degeneracy lifting induced by QD charging. The tunneling spectra of InSb QDs are qualitatively different from those observed in the STS of other III-V materials, for example, InAs QDs, with similar band gap energy. Theoretical calculations suggest the electron tunneling occurs through the states connected with L-valley of InSb QDs rather than through states of the Γ-valley. This observation calls for better understanding of the role of indirect valleys in strongly quantum-confined III-V nanomaterials.
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http://dx.doi.org/10.1021/nn5061805DOI Listing
January 2015

Surface functionalization of semiconductor and oxide nanocrystals with small inorganic oxoanions (PO4(3-), MoO4(2-)) and polyoxometalate ligands.

ACS Nano 2014 Sep 2;8(9):9388-402. Epub 2014 Sep 2.

Department of Chemistry and James Franck Institute, University of Chicago , Chicago, Illinois 60637, United States.

In this work, we study the functionalization of the nanocrystal (NC) surface with inorganic oxo ligands, which bring a new set of functionalities to all-inorganic colloidal nanomaterials. We show that simple inorganic oxoanions, such as PO4(3-) and MoO4(2-), exhibit strong binding affinity to the surface of various II-VI and III-V semiconductor and metal oxide NCs. ζ-Potential titration offered a useful tool to differentiate the binding affinities of inorganic ligands toward different NCs. Direct comparison of the binding affinity of oxo and chalcogenidometallate ligands revealed that the former ligands form a stronger bond with oxide NCs (e.g., Fe2O3, ZnO, and TiO2), while the latter prefer binding to metal chalcogenide NCs (e.g., CdSe). The binding between NCs and oxo ligands strengthens when moving from small oxoanions to polyoxometallates (POMs). We also show that small oxo ligands and POMs make it possible to tailor NC properties. For example, we observed improved stability upon Li(+)-ion intercalation into the films of Fe2O3 hollow NCs when capped with MoO4(2-) ligands. We also observed lower overpotential and enhanced exchange current density for water oxidation using Fe2O3 NCs capped with [P2Mo18O62](6-) ligands and even more so for [{Ru4O4(OH)2(H2O)4}(γ-SiW10O36)2] with POM as the capping ligand.
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http://dx.doi.org/10.1021/nn503458yDOI Listing
September 2014

Carrier dynamics in highly quantum-confined, colloidal indium antimonide nanocrystals.

ACS Nano 2014 Aug 14;8(8):8513-9. Epub 2014 Aug 14.

Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States.

Nanometer-sized particles of indium antimonide (InSb) offer opportunities in areas such as solar energy conversion and single photon sources. Here, we measure electron-hole pair dynamics, spectra, and absorption cross sections of strongly quantum-confined colloidal InSb nanocrystal quantum dots using femtosecond transient absorption. For all samples, we observe a bleach feature that develops on ultrafast time scales, which notably moves to lower energy during the first several picoseconds following excitation. We associate this unusual red shift, which becomes larger for larger particles and more distinct at lower sample temperatures, with hot exciton cooling through states that we suggest arise from energetically proximal conduction band levels. From controlled optical excitation intensities, we determine biexciton lifetimes, which range from 2 to 20 ps for the studied 3-6 nm diameter particle sizes.
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http://dx.doi.org/10.1021/nn5031274DOI Listing
August 2014

Colloidal nanocrystals with inorganic halide, pseudohalide, and halometallate ligands.

ACS Nano 2014 Jul 8;8(7):7359-69. Epub 2014 Jul 8.

Department of Chemistry and James Franck Institute, University of Chicago , Chicago, Illinois 60637, United States.

We investigate simple halides and pseudohalides as an important class of inorganic ligands for nanocrystals (NCs) in solution phase ligand exchange. These short, robust, and easy to model ligands bind to the NC surface and provide electrostatic stabilization of NC dispersions in N-methylformamide. The replacement of organic ligands on NCs with compact halide and pseudohalide ligands greatly facilitates electronic communication between NCs. For example, a high electron mobility of μ ≈ 12 cm(2) V(-1) s(-1) has been observed in thin films made of I(-)-capped CdSe NCs. We also studied charge transport properties of thin films based on the pseudohalide N3(-)-capped InAs NCs, suggesting the possibility of obtaining "all III-V" NC solids. In addition, we extend the surface chemistry of halometallates (e.g., CH3NH3PbI3), which can stabilize colloidal solutions of lead chalcogenide NCs. These halide, pseudohalide, and halometallate ligands enrich the current family of inorganic ligands and can open up more opportunities for applications of NCs in the fields of electronics, optoelectronics, and thermoelectrics.
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http://dx.doi.org/10.1021/nn502470vDOI Listing
July 2014
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