Fabricage van een biologisch actief, PCL-based "Self-fitting" Shape Memory Polymer Steiger

The overall goal of the following experiment is to fabricate a shape memory polymer or SMP scaffold that is capable of self fitting into an irregular cranio maxillofacial defect in order to promote OS osteointegration and healing. This is achieved by first forming a fused salt template use of solvent casting and the photochemical cure of polycaprolactone di acrl. Over the salt template forms a scaffold with the highly interconnected porosity required for osteo conductivity.

As a second step, the scaffold is coated with poly dopamine, which provides bioactivity. Next, the scaffold is treated with warm saline, which allows it to be press fitted into an irregular model. Defect results are obtained that show self fitting, poor interconnectivity and bioactivity based on press fit results, scanning electron microscopy imaging, and the in vitro formation of hydroxy appetite.

The main advantage of this technique over existing methods, such as auto grafting, is that the conformable fitting achieved critically supports osteointegration and bone healing. Demonstrating this procedure is Lindsey Nail, a PhD student researcher in my laboratory. To begin preparation of the scaffold, first sieve sodium chloride through a 425 micron sieve and transfer 1.8 grams of it into a three liter glass vial in four portions slowly add 146 milligrams of deionized water to the vial, mixing with a metal spatula.

After each addition, cap the vial, wrap it in tissue, and place it vertically into a centrifuge tube. Centrifuge the tube for 15 minutes before decapping and letting the solution air dry overnight. After synthesizing P-C-L-D-A as indicated in the text protocol, prepare a macer solution containing 150 milligrams of P-C-L-D-A per milliliter of chloro methane in a glass vial, cap the vial, wrap it in foil and vortex it for one minute.

Next, prepare a photo initiator solution containing 115 milligrams of DMP in one milliliter of one vinyl, two Perone in a glass vial. Again, cap the vial, wrap it in foil, and vortex it for one minute. Pipette the photo initiator solution into the macer solution to make a 15%by volume mixture and vortex the vial for one minute.

Next, wrap the vial containing the salt scaffold in foil, and add the photo initiator macer mixture until the salt is covered. Cap the vial, wrap it in tissue and place it vertically into a centrifuge tube. Centrifuge the tube for 10 minutes.

Next, remove the foil, uncap the vial, and expose the solution to ultraviolet light for three minutes. Then allow the solution to air dry overnight score and fracture the glass to remove the top of the vial using tweezers. Transfer the scaffold in a one-to-one water ethanol solution for four days changing the solution daily.

Finally, remove the SMP scaffold and air dry it overnight. To apply the poly dopamine coat first, insert a 20 gauge needle halfway through the SMP scaffold and then wrap a wire around the needle hub. Submerge the scaffold in 200 milliliters of a stirring dopamine solution and keep the needle hub above the solution by anchoring the wire to the rim of the beaker.

Next, place a syringe into the needle hub and pull the plunger to remove air from the scaffold. Once completely Degas, leave the scaffold submerged for 16 hours. Remove the scaffold from the solution and take out the needle.

Then rinse the scaffold with deionized water and dry it in a vacuum oven at room temperature for 24 hours. Place the scaffold in a drying oven at 85 degrees Celsius for one hour. Finally, remove the scaffold and allow it to cool to room temperature.

First, prepare a defect model by drilling an irregular void with an average diameter of approximately six millimeters in a five millimeter thick sheet of rigid plastic. Then submerge the SMP scaffold in a beaker of deionized water at approximately 60 degrees Celsius for two minutes. Test that the scaffold is noticeably softened by using tweezers to manipulate its shape.

Remove the softened scaffold from the water with tweezers and press it by hand into the defect model. Allow the scaffold to cool to room temperature and then remove it from the defect model. Observe the new fixed temporary shape to visualize pour, interconnectivity and size.

First, submerge the SMP scaffold in liquid nitrogen for one minute using tweezers. Then fracture the scaffold along the middle with a clean razor blade. Next, fix one of the scaffold halves with the fractured surface facing up onto the sample stage.

Using carbon tape sputter coat the scaffold with gold and platinum alloy to approximately four nanometers in depth. Load the sample into the SEM and then capture the image at an accelerating voltage of 10 to 15 kilovolts. To characterize in vitro bioactivity.

First cut a cylindrical SMP scaffold in half across the circular edge using a clean blade. Place one half of the scaffold into a tube containing 30 milliliters of simulated body fluid, and then place the tube in a stationary water bath at 37 degrees Celsius after 14 days. Remove the scaffold from the tube and allow it to air dry for 24 hours.

Next, fix the scaffold with the cut surface facing up onto the sample stage of an electron microscope using carbon tape. Then sputter coat the scaffold surface with gold and platinum alloy to approximately four nanometers in depth. As before, load the sample into the SEM and capture the image at an accelerating voltage of 10 to 15 kilovolts.

An SMP scaffold becomes malleable upon heating at 60 degrees Celsius and can be fitted within a defect model. After cooling to room temperature, the SMP scaffold is removed and retains its new fixed temporary shape. Shown in the scanning electron micrograph of the uncoated SMP scaffold are the pore structure and the highly interconnected morphology.

G bioactivity of the poly dopamine coated SMP scaffold is demonstrated by the formation hydroxyapatite in the pores as shown in the scanning electron micrograph. After watching this video, you should have a good understanding of how to prepare a bioactive self fitting shape memory polymer scaffold using a process involving solvent casting over a few salt template particulate leaching, and the application of a poly dopamine coating.