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

<p>Abstract</p> <p>Background</p> <p>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 <it>in vitro </it>artery model.</p> <p>Methods</p> <p>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.</p> <p>Results</p> <p>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.</p> <p>Conclusion</p> <p>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.</p

Collagen films adsorbed on native and oxidized poly(ethylene terephtalate): morphology after drying

The collagen layer formed by adsorption of collagen on native (PETn) and surface oxidized poly(ethylene terephtalate) (PETox) was studied by X-ray photoelectron spectroscopy and atomic force microscopy (AFM). On PETox, for adsorption times up to a few hours. the collagen molecules form a network, the nodes of which seem to be responsible for a dot-like morphology, On PETn, at very short adsorption times and consequently low surface coverages, the adsorbed molecules are displaced by the AFM tip. This effect reveals lower interactions between the collagen and the surface after drying compared to PETox. At higher coverages, the surface morphology is similar to that obtained for PETox. After an adsorption time of 24 h, an aggregation of collagen molecules is observed for both substrates. The results are discussed with regard to the interactions between collagen and the substrate in water, the events occurring during the drying process and the mobility of collagen molecules in the dry state, (C) 2001 Elsevier Science B.V. All rights reserved

A bisphosphonatecoating improves the fixation of metal implants in human bone. A randomized trial of dental implants

Abstract Many surgical procedures use metal implants in bone. The clinical results depend on the strength of the bone holding these implants. Our objective was to show that a drug released from the implant surface can improve parameters reflecting the quality or amount of this bone. Sixteen patients received paired dental titanium implants in the maxilla, in a randomized, double-blinded fashion. One implant in each pair was coated with a thin fibrinogen layer containing 2 bisphosphonates. The other implant was untreated. Fixation was evaluated by measurement of resonance frequency (implant stability quotient; ISQ) serving as a proxy for stiffness of the implant-bone construct. Increase in ISQ at 6 months of follow-up was the primary variable. None of the patients had any complications. The resonance frequency increased 6.9 ISQ units more for the coated implants (p = 0.0001; Cohen&apos;s d = 1.3). The average difference in increase in ISQ, and the effect size, suggested a clinically relevant improvement. X-ray showed less bone resorption at the margin of the implant both at 2 months (p = 0.012) and at 6 months (p = 0.012). In conclusion, a thin, bisphosphonate-eluting fibrinogen coating might improve the fixation of metal implants in human bone. This might lead to new possibilities for orthopedic surgery in osteoporotic bone and for dental implants. Highlights Dental implants coated with bisphosphonates showed higher resonance frequency. Resonance frequency reflects stiffness of the bone-implant construct. Randomized double-blinded trial with internal controls. First clinical study to show improved implant fixation in bone by coating with a drug