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Liu Y.,Nanjing University | Zhong Q.,Nanjing University | Zhang T.,Nanjing University | Zhang T.,Nanjing Excellence Technology Center for Interventional Medical Devices
Fullerenes Nanotubes and Carbon Nanostructures | Year: 2014

Graphene Oxide (GO) was prepared from natural graphite and treated with different types and various amounts of cationic surfactants to form the intercalation nanocomposites. The resulting specimens were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectrum (FT-IR), X-ray diffraction (XRD), and Thermogravimetric analysis (TGA). X-ray diffraction patterns revealed that the interlamellar spacing strongly depended on the mole mass ratios between GO to cationic surfactants and the alkyl chain length of surfactants. In addition, a model was proposed to illustrate the procedure of cetyltrimethylammonium chloride (CTAC)-GO intercalation, and the angles of inclination between the alkyl chains and GO planes were calculated based on the model. © 2014 Taylor & Francis Group, LLC. Source


Zhong Q.,Nanjing University | Mao Q.,Nanjing University | Yan J.,Nanjing University | Liu W.,Nanjing University | And 3 more authors.
Journal of Biomedical Materials Research - Part B Applied Biomaterials | Year: 2015

Monitoring erosion progress of biodegradable drug carrying polymer coated on coronary drug eluting stents (DES) is largely hindered because of the small amount of coating material as well as the irregular profile of coating, both of which make the monitoring using traditional methods highly challenging. In our study, electrochemical impedance spectroscopy (EIS), a widely used method in the study of metal corrosion, was used to address the challenges traditional methods face. In vitro, remained mass and molecular weight drop data of film-like poly(lactide-co-glycolide) (PLGA) samples due to degradation were monitored using traditional mass loss measurement and size exclusion chromatography (SEC) methods. The obtained data were compared to the changes of capacitance and impedance measured by EIS from PLGA-coated stainless slices with an equivalent electrical circuit model. The results showed that the changes of the resistance and capacitance obtained by EIS, which indicates transformations of PLGA coating, can be correlated to the degradation measured by traditional methods, such as SEC. Furthermore, EIS method was applied to monitor and evaluate the erosion progress of a real stent with PLGA coating. Our results suggested that EIS method can accurately monitor real-time erosion process of thin polymer coatings on DES in situ. © 2014 Wiley Periodicals, Inc. All rights reserved. Source


Zhong Q.,Nanjing University | Yan J.,Nanjing University | Qian X.,Nanjing University | Zhang T.,Nanjing University | And 3 more authors.
Colloids and Surfaces B: Biointerfaces | Year: 2014

In-stent restenosis (ISR) and re-endothelialization delay are two major issues of intravascular stent in terms of clinical safety and effects. Construction of mimetic cell membrane surface on stents using phosphorylcholine have been regarded as one of the most powerful strategies to resolve these two issues and improve the performance of stents. In this study, atomic layer deposition (ALD) technology, which is widely used in semiconductor industry, was utilized to fabricate ultra-thin layer (10nm) of alumina (Al2O3) on 316L stainless steel (SS), then the alumina covered surface was modified with 3-aminopropyltriethoxysilane (APS) and 2-methacryloyloxyethyl phosphorylcholine (MPC) sequentially in order to produce phosphorylcholine mimetic cell membrane surface. The pristine and modified surfaces were characterized using X-ray photoelectron spectroscopy, atomic force microscope and water contact angle measurement. Furthermore, the abilities of protein adsorption, platelet adhesion and cell proliferation on the surfaces were investigated. It was found that alumina layer can significantly enhance the surface grafting of APS and MPC on SS; and in turn efficiently inhibit protein adsorption and platelet adhesion, and promote the attachment and proliferation of human umbilical vein endothelial cells (HUVEC) on the surfaces. In association with the fact that the deposition of alumina layer is also beneficial to the improvement of adhesion and integrity of drug-carrying polymer coating on drug eluting stents, we expect that ALD technology can largely assist in the modifications on inert metallic surfaces and benefit implantable medical devices, especially intravascular stents. © 2014 Elsevier B.V. Source


Mao Q.,Nanjing University | Zhang Y.,Nanjing University | Zhang Y.,Nanjing Excellence Technology Center for Interventional Medical Devices | Zhang T.,Nanjing University | Zhang T.,Nanjing Excellence Technology Center for Interventional Medical Devices
Gaofenzi Cailiao Kexue Yu Gongcheng/Polymeric Materials Science and Engineering | Year: 2013

Fourier transform infrared spectroscopy (FT-IR) was applied to real-time monitor the reactions of functional groups in polyethyleneimine/glycidyl methacrylate (PEI/GMA) system, to analyze the mechanism and the reactions kinetics. The variation of FT-IR spectra indicates that the primary amine group could react with both epoxy group and alkene group with different reaction rates. Using the transmittance FT-IR spectra of carbonyl group in GMA as a reference, the change of relative amounts and the amounts fluctuations of epoxy and alkene groups were semi-quantitatively determined with the reaction time. The results show that the epoxy group is more active than alkene group in the reaction system. Moreover, between 5°C and 40°C temperature range, heating could accelerate both reactions in favor of the reaction between epoxy and amine group. The results prove that FT-IR is a simple and effective method applied in the studies of reaction mechanisms and is helpful to confirm a suitable reaction condition. Source


Wang F.,Nanjing University | Zhang Y.,Nanjing University | Zhang Y.,Nanjing Excellence Technology Center for Interventional Medical Devices | Chen X.,Nanjing University | And 5 more authors.
Colloids and Surfaces B: Biointerfaces | Year: 2016

Carotid-artery atherosclerosis is a common cause of ischemic stroke. Carotid-artery stenting (CAS) is one of the most effective treatments. However, In-stent restenosis (ISR) and re-endothelialization delay are two major issues of intravascular stent which affect clinical safety and reduce effects. In this study, atomic layer deposition (ALD) technology was applied to deposit a layer (10 nm) of Al2O3 on Nitinol surface as an intermediate functional layer. The alumina covered surface was then modified with a coupling agent 3-aminopropyltriethoxysilane (APS) and heparin sequentially in order to improve the hemocompatibility of Nitinol stents. The successful graft of APS and heparin onto Nitinol was proven by X-ray photoelectron spectroscopy. Furthermore, the predicted improvement in the biocompatibilities of modified Nitinol was confirmed by water contact angle measurement, protein adsorption, platelet adhesion, and plasma recalcification time determination. The results of hemolysis assay, cell proliferation and cytotoxicity tests revealed that the grafting of heparin on NiTi kept the original positive performance of nitinol material. The results indicate that ALD technology is of great potential for the manufacture of medical devices, especially for surface modifications and functionalization. ALD technology can help with modifications of inert metallic surfaces and therefore benefit implantable medical devices, especially intravascular stents. © 2016 Elsevier B.V. Source

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