Most polymeric vascular prosthetic materials have low patency rate for replacement of small diameter vessels (<5 mm), mainly due to failure to generate healthy endothelium. In this study, we present polydopamine-mediated immobilization of growth factors on the surface of polymeric materials as a versatile tool to modify surface characteristics of vascular grafts potentially for accelerated endothelialization. Polydopamine was deposited on the surface of biocompatible poly(L-lactide-co-ε-caprolactone) (PLCL) elastomer, on which vascular endothelial growth factor (VEGF) was subsequently immobilized by simple dipping. Surface characteristics and composition were investigated by using scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. Immobilization of VEGF on the polydopamine-deposited PLCL films was effective (19.8 ± 0.4 and 197.4 ± 19.7 ng/cm(2) for DPv20 and DPv200 films, respectively), and biotin-mediated labeling of immobilized VEGF revealed that the fluorescence intensity increased as a function of the concentration of VEGF solution. The effect of VEGF on adhesion of HUVECs was marginal, which may have been masked by polydopamine layer that also enhanced cell adhesion. However, VEGF-immobilized substrate significantly enhanced proliferation of HUVECs for over 7 days of in vitro culture and also improved their migration. In addition, immobilized VEGF supported robust cell to cell interactions with strong expression of CD 31 marker. The same process was effective for immobilization of basic fibroblast growth factor, demonstrating the robustness of polydopamine layer for secondary ligation of growth factors as a simple and novel surface modification strategy for vascular graft materials.
Magnetic and AC magnetically induced heating characteristics of Fe 3 O 4 nanoparticles (IONs) with different mean diameters, d, systematically controlled from 4.2 to 22.5 nm were investigated to explore the physical relationship between magnetic phase and specific loss power (SLP) for hyperthermia agent applications. It was experimentally confirmed that the IONs had three magnetic phases and correspondingly different SLP characteristics depending on the particle sizes. Furthermore, it was demonstrated that pure superparamagnetic phase IONs (d < 9.8 nm) showed insufficient SLPs critically limiting for hyperthermia applications due to smaller AC hysteresis loss power (Néel relaxation loss power) originated from lower out-of-phase magnetic susceptibility. V C 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3689751]In recent, superparamagnetic Fe 3 O 4 nanoparticles (SPIONs) have been paid considerable attentions for a local hyperthermia agent in nanomedicine due to its officially approved high biocompatibility. 1 Accordingly, various technical and engineering approaches, i.e., developing various synthesis methods, controlling particle dipole-dipole interaction and particle dispersion status in ferrofluidics, and studying the effects of Fe 2þ /Fe 3þ ion distributions on heating ability etc., have been and are being made to improve the AC magnetically induced heating characteristics and the relevant magnetic properties of SPIONs for theragonosis agent applications. [2][3][4] For the applications to an in-vivo magnetic fluidic hyperthermia agent, magnetic nanoparticles should have pure superparamagnetic phase for easy transportation, good circulation, and no agglomeration in the blood vessel as well as have a smaller particle size, d < 7 9 nm, with a narrow size distribution (<10%) for both effective injection, i.e., intravenous injection, intraarterial injection, or intratumoral injection, into and excretion from human body. 5 In particular, they should produce a heat generation as high as possible at a small concentration (a higher specific loss power (SLP)) in the biological safe and physiologically tolerable range of the applied magnetic field (H appl < 190 Oe) and frequency (f appl < 120 kHz) to completely necrotize tumors with minimized systemic "side effects." 6-9 Considering these biotechnical requirements, the SPIONs reported so far have critical challenges for a hyperthermia agent, because the magnetic phase (intrinsic magnetic property) of the developed SPIONs is not well defined and has strong dependence on the particle sizes as well as correspondingly wide distribution of SLP values (5 500 W/g). 2-4,10 Therefore, systematic studies on the magnetic nature and the AC heating characteristics of IONs accurately controlled the particle sizes are essentially required to evaluate the biotechnical feasibility of IONs, particularly SPIONs, for a clinical hyperthermia agent in nanomedicine.In this letter, we investigated the magnetic properties and the AC heating characteristics of IONs with differ...
BackgroundThe initial procedure of the development of engineered tissues is cell seeding into three-dimensional polymer scaffolds. However, it is hard to make the cells invade into scaffold due to the characteristic of pore and material. Electrospun poly (L-lactic acid) scaffold and flow perfusion system were used to overcome these seeding problems.ResultsBefore starting the experiment, we set up the parallel plate chamber system to observe endothelial cell migration under flow condition. In individual cell migration model, human umbilical endothelial cells started to migrate in the direction of flow at 8 dyne/cm2 and we observed the cytoskeleton alignment at 8 dyne/cm2.This study has demonstrated the possibility to evaluate and analyze cell migration using the parallel plate chamber system and we may predict in vivo cell migration under flow condition based on these results. Also the flow perfusion system was established for the effective cell seeding into at three dimensional scaffolds. Moreover, shear stress induced by flow can enhance cell migration into PLLA scaffold that is in the form of cotton.ConclusionsResult indicated that cell penetration was achieved under flow condition better and more than under static condition throughout the matrix.
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