Intravascular tissue reactions induced by various types of bioabsorbable polymeric materials: Correlation between the degradation profiles and corresponding tissue reactions

Division of Interventional Neuroradiology, Department of Radiological Sciences, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095-1721, USA.
Neuroradiology (Impact Factor: 2.49). 02/2010; 52(11):1017-24. DOI: 10.1007/s00234-010-0657-x
Source: PubMed


Several different bioabsorbable polymeric coil materials are currently used with the goal of improving treatment outcomes of endovascular embolization of intracranial aneurysms. However, little is known about the correlation between polymer degradation profiles and concomitant tissue responses in a blood vessel. The authors describe in vitro degradation characteristics of nine different polymeric materials and their corresponding tissue responses induced in rabbit carotid arteries.
Mass loss and molecular weight loss of nine commercially available bioabsorbable sutures were evaluated in vitro up to16 weeks. The same nine materials, as well as platinum coils, were implanted into blind-end carotid arteries (n = 44) in rabbits, and their tissue reactions were evaluated histologically 14 days after the implantation.
Five of the nine polymers elicited moderate to strong tissue reactions relative to the remaining materials. While polymer mass loss did not correlate with their histologic findings, polymers that showed a faster rate of molecular weight loss had a tendency to present more active tissue reactions such as strong fibrocellular response around the implanted material with a moderate inflammatory cell infiltration. Maxon exhibited the fastest rate of molecular weight loss and poly-l-lactic acid the slowest.
The rate of molecular weight loss may be an important factor that is associated with the degree of bioactivity when bioabsorbable polymers are implanted into blood vessels. For further quantitative analysis, additional experiments utilizing established aneurysm models need to be conducted.

Download full-text


Available from: Fernando Viñuela, Aug 27, 2014
  • [Show abstract] [Hide abstract]
    ABSTRACT: Biodegradable film-based stents emerged as a promising medical platform for drug delivery to resolve stenosis encountered in physiological conduits (e.g. blood vessels, biliary and urethral tracts). Drug release kinetics significantly affects the pharmacological effects of a stent, thus it is desirable for a stent to possess highly adjustable drug release kinetics. In this study, a series of amphiphilic poly(ɛ-caprolactone)-poly(ethylene glycol)-poly(ɛ-caprolactone) (PCL-PEG-PCL) copolymers were used as additives to adjust 5-fluorouracil (5-FU) release from PCL films. The effects of the copolymer addition on drug release behavior, drug permeability, crystalline states, and surface and internal morphologies of the films were investigated. It was found that, the addition of PCL-PEG-PCL could accelerate 5-FU release. The release rate of 5-FU increased with increasing content of PCL-PEG-PCL in the film, but it decreased with the ratio of PCL blocks in the PCL-PEG-PCL copolymer. The diffusion test results showed that 5-FU diffused through the film containing PCL-PEG-PCL faster than it permeated through the pure PCL film, indicating that the addition of PCL-PEG-PCL can improve the permeability of 5-FU in PCL film. The addition of PCL-PEG-PCL copolymer showed high drug-release-regulating ability in the 5-FU-loaded PCL films.
    International Journal of Pharmaceutics 07/2011; 419(1-2):77-84. DOI:10.1016/j.ijpharm.2011.07.020 · 3.65 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Background: This study evaluates whether thermoreversible gelation polymer (TGP) can be used as a delivery device to deploy dermal fibroblasts and cytokines into experimental aneurysms in rats. Methods: The right common iliac artery of rats was surgically ligated and an experimental aneurysm was created by applying exogenous elastase. Seven days later, two aneurysms were harvested and used as controls (Group A), two were embolized with pure TGP (Group B), two were embolized with TGP and basic fibroblast growth factor (bFGF) (Group C) and two were embolized with TGP loaded with rat dermal fibroblasts (Group D). The aneurysms were also embolized with TGP mixed with dermal fibroblasts and bFGF at different concentrations (10 ng/ml: Group E (n=2), 100 ng/ml: Group F (n=2), 1000 ng/ml: Group G (n=2)). Each aneurysm sample was harvested after 7 days and histologic analyses were performed. Results: The most advanced thrombus organization in the aneurysm, such as prominent fibroblast proliferation and collagen deposition, was observed in Groups E, F and G, although there was no noticeable difference between the groups. Moderate thrombus organization was seen in Group D and minimal thrombus organization was seen in Groups B and C. Conclusions: TGP mixed with both dermal fibroblasts and bFGF induced the most advanced thrombus organization in the experimental aneurysms followed by TGP mixed only with dermal fibroblasts. TGP may be useful as a delivery device to deploy fibroblasts and cytokines into aneurysms.
    Journal of Neurointerventional Surgery 09/2012; 5(6). DOI:10.1136/neurintsurg-2012-010454 · 2.77 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Poly(carbonate-co-esters), were enzymatically synthesized (Novozyme-435) via polycondensation of diethylene carbonate, 1,4-butanediol and ω-pentadecalactone. Random poly(ω-pentadecalactone-co-butylene-co-carbonate) copolymers (PPBC) were obtained over a wide composition range (PDL content 10–75 mol%). Notwithstanding the high degree of compositional and microstructural disorder of the macromolecules, that are composed of randomly distributed ω-hydroxy acid (AB), carbonate (A2), and diol (B2) units, all (AB + A2 + B2) copolymers crystallize (crystallinity degree 30–66% by WAXS). When PDL content is ⩾20 mol%, PPBCs crystallize in the PPDL lattice. The copolymer with 10 mol% PDL shows a more complex crystallization pattern, that was investigated by combined DSC and T-controlled WAXS measurements. This copolymer develops three different types of crystals: two of them with lattice parameters matching those of PPDL and PBC homopolymers, the third one not being earlier reported in the literature. In this copolymer such new phase persists above melting of PPDL crystals, but it disappears before melting of PBC crystals. The new phase is attributed to a yet unknown metastable polymorph of PBC.
    European Polymer Journal 11/2012; 48(11):1883–1891. DOI:10.1016/j.eurpolymj.2012.08.010 · 3.01 Impact Factor
Show more