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Fabrication and in vitro deployment of a laser-activated shape memory polymer vascular stent.

Baer GM, Small W, Wilson TS, Benett WJ, Matthews DL, Hartman J, Maitland DJ - Biomed Eng Online (2007)

Bottom Line: A shape memory polymer (SMP) stent may enhance flexibility, compliance, and drug elution compared to its current metallic counterparts.At a physiological flow rate, the stent did not fully expand at the maximum laser power (8.6 W) due to convective cooling.Though further studies are required to optimize the device and assess thermal tissue damage, photothermal actuation of the SMP stent was demonstrated.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biomedical Engineering, University of California, Davis, California 95616 USA. gmbaer@ucdavis.edu

ABSTRACT

Background: Vascular stents are small tubular scaffolds used in the treatment of arterial stenosis (narrowing of the vessel). Most vascular stents are metallic and are deployed either by balloon expansion or by self-expansion. A shape memory polymer (SMP) stent may enhance flexibility, compliance, and drug elution compared to its current metallic counterparts. The purpose of this study was to describe the fabrication of a laser-activated SMP stent and demonstrate photothermal expansion of the stent in an in vitro artery model.

Methods: A novel SMP stent was fabricated from thermoplastic polyurethane. A solid SMP tube formed by dip coating a stainless steel pin was laser-etched to create the mesh pattern of the finished stent. The stent was crimped over a fiber-optic cylindrical light diffuser coupled to an infrared diode laser. Photothermal actuation of the stent was performed in a water-filled mock artery.

Results: At a physiological flow rate, the stent did not fully expand at the maximum laser power (8.6 W) due to convective cooling. However, under zero flow, simulating the technique of endovascular flow occlusion, complete laser actuation was achieved in the mock artery at a laser power of ~8 W.

Conclusion: We have shown the design and fabrication of an SMP stent and a means of light delivery for photothermal actuation. Though further studies are required to optimize the device and assess thermal tissue damage, photothermal actuation of the SMP stent was demonstrated.

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Related in: MedlinePlus

Artery model. Schematic of the artery model. WB: water bath, PP: peristaltic pump, TB: Touhy Borst valve, SS: stainless steel cylinder, OC: outer chamber, TC: thermocouple probe, MA: mock artery.
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Figure 2: Artery model. Schematic of the artery model. WB: water bath, PP: peristaltic pump, TB: Touhy Borst valve, SS: stainless steel cylinder, OC: outer chamber, TC: thermocouple probe, MA: mock artery.

Mentions: An artery model consisting of a straight mock artery in a chamber was built in-house. The mock artery (4 mm inner diameter, 150 μm wall thickness, 4 cm length) was made of a silicone elastomer (Sylgard 184, Dow Corning) prepared by dip coating pins in a similar manner as the stent. As shown in Fig. 2, two stainless steel cylinders hold the mock artery in place inside the chamber; water at a desired temperature can be pumped independently in the outer chamber and into the mock artery. A thermocouple probe allows temperature reading in the outer chamber. A Touhy Borst valve allows flow of water and delivery of the device into the mock artery. Water temperature in the outer chamber and in the mock artery was maintained at 37°C (body temperature). After coupling the optical fiber to an 810 nm diode laser (UM7800/100/20, Unique Mode), the device was delivered into the mock artery and photothermally actuated.


Fabrication and in vitro deployment of a laser-activated shape memory polymer vascular stent.

Baer GM, Small W, Wilson TS, Benett WJ, Matthews DL, Hartman J, Maitland DJ - Biomed Eng Online (2007)

Artery model. Schematic of the artery model. WB: water bath, PP: peristaltic pump, TB: Touhy Borst valve, SS: stainless steel cylinder, OC: outer chamber, TC: thermocouple probe, MA: mock artery.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2211751&req=5

Figure 2: Artery model. Schematic of the artery model. WB: water bath, PP: peristaltic pump, TB: Touhy Borst valve, SS: stainless steel cylinder, OC: outer chamber, TC: thermocouple probe, MA: mock artery.
Mentions: An artery model consisting of a straight mock artery in a chamber was built in-house. The mock artery (4 mm inner diameter, 150 μm wall thickness, 4 cm length) was made of a silicone elastomer (Sylgard 184, Dow Corning) prepared by dip coating pins in a similar manner as the stent. As shown in Fig. 2, two stainless steel cylinders hold the mock artery in place inside the chamber; water at a desired temperature can be pumped independently in the outer chamber and into the mock artery. A thermocouple probe allows temperature reading in the outer chamber. A Touhy Borst valve allows flow of water and delivery of the device into the mock artery. Water temperature in the outer chamber and in the mock artery was maintained at 37°C (body temperature). After coupling the optical fiber to an 810 nm diode laser (UM7800/100/20, Unique Mode), the device was delivered into the mock artery and photothermally actuated.

Bottom Line: A shape memory polymer (SMP) stent may enhance flexibility, compliance, and drug elution compared to its current metallic counterparts.At a physiological flow rate, the stent did not fully expand at the maximum laser power (8.6 W) due to convective cooling.Though further studies are required to optimize the device and assess thermal tissue damage, photothermal actuation of the SMP stent was demonstrated.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biomedical Engineering, University of California, Davis, California 95616 USA. gmbaer@ucdavis.edu

ABSTRACT

Background: Vascular stents are small tubular scaffolds used in the treatment of arterial stenosis (narrowing of the vessel). Most vascular stents are metallic and are deployed either by balloon expansion or by self-expansion. A shape memory polymer (SMP) stent may enhance flexibility, compliance, and drug elution compared to its current metallic counterparts. The purpose of this study was to describe the fabrication of a laser-activated SMP stent and demonstrate photothermal expansion of the stent in an in vitro artery model.

Methods: A novel SMP stent was fabricated from thermoplastic polyurethane. A solid SMP tube formed by dip coating a stainless steel pin was laser-etched to create the mesh pattern of the finished stent. The stent was crimped over a fiber-optic cylindrical light diffuser coupled to an infrared diode laser. Photothermal actuation of the stent was performed in a water-filled mock artery.

Results: At a physiological flow rate, the stent did not fully expand at the maximum laser power (8.6 W) due to convective cooling. However, under zero flow, simulating the technique of endovascular flow occlusion, complete laser actuation was achieved in the mock artery at a laser power of ~8 W.

Conclusion: We have shown the design and fabrication of an SMP stent and a means of light delivery for photothermal actuation. Though further studies are required to optimize the device and assess thermal tissue damage, photothermal actuation of the SMP stent was demonstrated.

Show MeSH
Related in: MedlinePlus