Enhanced surfaces for endothelial cell seeding

The effect of laser preexposure on seeding endothelial cells to a biomaterial surface

OBJECTIVE

In this study, the possible effect of low-level laser (LLL) on improving the adhesion of endothelial cells (ECs) to a biomaterial substrate was evaluated.

BACKGROUND DATA

Despite the numerous studies regarding the effects of LLL on biologic systems, the influence of LLL on the binding between cells and materials was rarely investigated.

MATERIALS AND METHODS

A low-power He-Ne laser apparatus with a continuous wavelength of 632.8 nm (a maximum power output of 50 mW) was used. The average irradiation energy on cells was 1.18 J/cm(2). Cell morphology and the concentrations of nitric oxide and calcium after laser exposure were measured. Biomedical grade poly(carbonate)urethane (PU) was synthesized and used to prepare microporous vascular grafts. ECs exposed to laser were harvested and seeded on the PU grafts. No further exposure was given.

RESULTS

LLL could change the morphology and increase the matrix secretion of ECs, and such effects persisted when preexposed cells were harvested and seeded to another substrate. The number of ECs attached on the biomaterial substrate was not affected. Preexposed ECs on the PU graft, however, were, on average, more resistant to flushing (i.e., greater cell retention).

CONCLUSION

ECs were pretreated with LLL before being seeded onto the PU biomaterial vascular grafts. The retention of LLL-preexposed ECs on the graft surface was enhanced, but not as significantly as that of ECs preexposed to low-intensity ultrasound.

The effect of dynamic culture conditions on endothelial cell seeding and retention on small diameter polyurethane vascular grafts

Due to the limited number of cells available in endothelial cell (EC) seeding of small diameter vascular grafts, high seeding rate and ideal proliferation are normally required and can be achieved by optimizing the EC seeding and culture procedures. In this study, by using rotational seeding at 0.16 rpm for 12 h in an incubator, 90% cells were successfully seeded on the polyurethane vascular grafts. Following a period of 72 h of static culture, the cell retention after 6 h of flushing could reach 90%. The retention was further enhanced after perfuse culture (9 cm/s). The optimal procedures to prepare a polyurethane vascular graft (4-mm i.d., 4 cm long) populated with firmly attached EC were therefore: (1) seeding the graft with 0.5 ml of cell suspension containing approximately 10(5) cells rotated at 0.16 rpm for 12 h; (2) culturing the seeded graft in static for 72 h; and (3) culturing the graft by perfusion (9 cm/s) for another 72 h to 7 days. These procedures consistently resulted in a graft covered with confluent vein EC that fully retained on the surface after 6 h of in vitro flushing.

Ultrasound preexposure improves endothelial cell binding and retention on biomaterial surfaces

In spite of the extensive studies regarding the effects of ultrasound on biological systems, the influence of low-intensity ultrasound on endothelial cells has rarely been investigated. In this work, the effect of ultrasound in improving the binding between endothelial cells and biomaterial substrates was evaluated. Based on the results, low-intensity ultrasound could change the morphology and matrix secretion of endothelial cells, and such effects persisted when preexposed cells were seeded to another substrate. The cells preexposed to ultrasound were spread further on the substrate. The actin stress fibers of ultrasound-preexposed cells on RGD-modified surfaces were especially intense and well oriented. Ultrasound could probably activate cellular integrins and subsequently allow RGD to bind them. A much firmer adhesion of ultrasound-preexposed endothelial cells to the biomaterial surface coated with the RGD-containing protein was demonstrated. Finally, polyurethane small-diameter vascular grafts seeded with ultrasound-preexposed endothelial cells showed enhanced cell retention on graft surfaces upon flushing.

An Unprecedented Surface Oxidation of Polystyrene Substrates by Wet Chemistry under Basic Conditions

The surface of polystyrene substrates has been modified by wet chemistry consisting of a treatment with sodium hydroxide in a water-methanol solution at 50 degrees C for 15 h, under air atmosphere. The resulting samples were analyzed by XPS and AFM. The surface functional groups (hydroxyl and carboxyl functions) were assayed by radiolabeling. All the results are consistent with a surface oxidation process.