Bioactive Plasma-Polymerized Bipolar Films for Enhanced Endothelial Cell Mobility

Vascular Remodeling Process of Heparin-Conjugated Poly(ε-Caprolactone) Scaffold in a Rat Abdominal Aorta Replacement Model

In the field of vascular graft research, poly-ε-caprolactone (PCL) is used owing to its good mechanical strength and biocompatibility. In this study, PCL scaffold was prepared by electrospinning and surface modification with heparin via hexamethylenediamine. Then the scaffolds were implanted into the infrarenal abdominal aorta of Wistar rats and contrast-enhanced micro-ultrasound was used to monitor the patency of grafts after implantation. These grafts were extracted from the rats at 1, 3, and 6 months for histological analysis, immunofluorescence staining, and scanning electron microscopy observation. Although some grafts experienced aneurysmal change, results showed that all implanted grafts were patent during the course of 6 months and these grafts demonstrated well-organized neotissue with endothelium formation, smooth muscle regeneration, and extracellular matrix formation. Such findings confirm feasibility to create heparin-conjugated scaffolds of next-generation vascular grafts.

Poly-L-arginine based materials as instructive substrates for fibroblast synthesis of collagen

The interactions of cells and surrounding tissues with biomaterials used in tissue engineering, wound healing, and artificial organs ultimately determine their fate in vivo. We have demonstrated the ability to tune fibroblast responses with the use of varied material chemistries. In particular, we examined cell morphology, cytokine production, and collagen fiber deposition angles in response to a library of arginine-based polymeric materials. The data presented here shows a large range of vascular endothelial growth factor (VEGF) secretion (0.637 ng/10(6) cells/day to 3.25 ng/10(6) cells/day), cell migration (∼15 min < persistence time < 120 min, 0.11 μm/min < speed < 0.23 μm/min), and cell morphology (0.039 < form factor (FF) < 0.107). Collagen orientation, quantified by shape descriptor (D) values that ranges from 0 to 1, representing completely random (D = 0) to aligned (D = 1) fibers, exhibited large variation both in vitro and in vivo (0.167 < D < 0.36 and 0.17 < D < 0.52, respectively). These findings demonstrate the ability to exert a certain level of control over cellular responses with biomaterials and the potential to attain a desired cellular response such as, increased VEGF production or isotropic collagen deposition upon exposure to these materials in wound healing and tissue engineering applications.

Use of two-step grafting to fabricate dual-functional films and site-specific functionalized scaffolds

Polycaprolactone (PCL) is a widely utilized bioresorbable polymer in tissue engineering applications. However, the absence of intrinsic functional groups in the polymer backbone necessitates the incorporation of functional chemistries to enable the further addition of bioactive molecules to PCL-based surfaces and scaffolds. The current study aimed to incorporate two different functional groups, amine and carboxylate, first on two-dimensional (2D) spin-coated PCL films and, thereafter, throughout all surfaces within three-dimensional (3D) porous PCL-based scaffolds, produced using the thermally induced phase separation (TIPS) method, but in a spatially separated manner. Specifically, gamma irradiation induced grafting of acrylic acid (AA) and 2-aminoethyl methacrylate hydrochloride (AEMA) onto PCL was performed in selected solvents and the resulting substrates were characterized using X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and contact angle measurements to determine the surface free energy. Results demonstrated that stepwise graft copolymerization of AEMA and AA allows the fabrication of dual-functional surfaces, with chemistry depending on the order of grafting of the two monomers. In addition, 3D scaffolds could be decorated exclusively with carboxylate groups in the interior, while the outer surface displayed dual-functionality. This simple surface modification methodology, with the ability to create spatially separated surface functional groups throughout 3D porous scaffolds post their fabrication, has the potential to be applied to many current and future scaffold systems being investigated in the field of tissue engineering.

Robust and flexible fabrication of chemical micropatterns for tumor spheroid preparation

A robust and flexible approach is described for the straightforward preparation of multicellular tumor spheroids of controllable dimensions. The approach is based on a one-step plasma polymerization of the monomer allylamine carried out through conformal micropatterning physical masks that is used to deposit amine-rich (PolyAA) micrometer-scale features that promote cellular attachment and initiate the formation of multicellular spheroids. A simple backfilling step of the nonpolymerized poly(dimethylsiloxane) background with Pluronic F127 significantly reduced background cellular adhesion on the untreated substrate and, in turn, improved the quality of the spheroid formed. Tumor cells grown on the PolyAA/F127 patterned surfaces reliably formed multicellular spheroids within 24-48 h depending on the cell type. The dimension of the spheroids could be readily controlled by the dimension of the amine-rich micropatterns. This simple approach is compatible with the long-term culture of multicellular spheroids and their characterization with high-resolution optical microscopy. These features facilitate the development of on-chip assays, as demonstrated here for the study of the binding of transferrin-functionalized gold nanoparticles to multicellular tumor spheroids.

Gallic acid tailoring surface functionalities of plasma-polymerized allylamine-coated 316L SS to selectively direct vascular endothelial and smooth muscle cell fate for enhanced endothelialization

The creation of a platform for enhanced vascular endothelia cell (VEC) growth while suppressing vascular smooth muscle cell (VSMC) proliferation offers possibility for advanced coatings of vascular stents. Gallic acid (GA), a chemically unique phenolic acid with important biological functions, presents benefits to the cardiovascular disease therapy because of its superior antioxidant effect and a selectivity to support the growth of ECs more than SMCs. In this study, GA was explored to tailor such a multifunctional stent surface combined with plasma polymerization technique. On the basis of the chemical coupling reaction, GA was bound to an amine-group-rich plasma-polymerized allylamine (PPAam) coating. The GA-functionalized PPAam (GA-PPAam) surface created a favorable microenvironment to obtain high ECs and SMCs selectivity. The GA-PPAam coating showed remarkable enhancement in the adhesion, viability, proliferation, migration, and release of nitric oxide (NO) of human umbilical vein endothelial cells (HUVECs). The GA-PPAam coating also resulted in remarkable inhibition effect on human umbilical artery smooth muscle cell (HUASMC) adhesion and proliferation. These striking findings may provide a guide for designing the new generation of multifunctional vascular devices.

Construction of polyfunctional coatings assisted by gallic acid to facilitate co-immobilization of diverse biomolecules

Designing a multifunctional surface based on the coimmobilization of two or more diverse biomolecules with synergic action is very important in certain cases. In this work, a facile method by two-step aimed to construct a polyfunctional coating containing -COOH, -NH2, and phenol/quinine groups was reported. The first-step was to introduce amine groups onto target modified-surface by coating with plasma polymerized allylamine (PPAam), followed by the second-step conjugation of gallic acid (3,4,5-trihydroxybenzoic acid) onto the PPAam surface. The density of -COOH, -NH2, and phenol/quinone groups could be regulated easily by adjusting the reaction time of GA conjugation, making it possible to coimmobilize two or three diverse molecules. This has been shown by the successful coimmobilization of anti-CD34 antibody and vascular endothelial growth factor (VEGF). The surface coimmobilized with the anti-CD34 antibody and VEGF presented significant enhancement in the capture of endothelial progenitor cells (EPCs) and the growth of human umbilical vein endothelial cells (HUVECs). These data suggest the huge potential of such polyfunctional coating for tailoring the desired interfacial properties of materials through selectively conjugating two or more diverse bioactive molecules with synergic action.

Mussel-inspired coating of polydopamine directs endothelial and smooth muscle cell fate for re-endothelialization of vascular devices

Polydopamine (PDAM), a mussel adhesive protein inspired coating that can be easily deposited onto a wide range of metallic, inorganic, and organic materials, gains interest also in the field of biomaterials. In this work, PDAM is applied as coating on 316L stainless steel (SS) stents and the response of cells of the blood vessel wall, human umbilical vein endothelial cell (HUVEC), and human umbilical artery smooth muscle cell (HUASMC) as predictors for re-endothelialization is tested. It is found that the PDAM-modified surface significantly enhances HUVEC adhesion, proliferation, and migration, release of nitric oxide (NO), and secretion of prostaglandin I(2) (PGI(2) ). Additionally, the PDAM-modified surface shows a remarkable ability to decrease the adhesion and proliferation of HUASMCs. As a blood-contacting material, the PDAM tends to improve the hemocompatibility compared with the substrate 316L SS. It is noteworthy that the PDAM coating shows good resistance to the deformation behavior of compression and expansion of a stent. These data suggest the potential of PDAM as a blood-contacting material for the application in vascular stents or grafts.