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Plasma-based sterilization is a promising alternative to the use of pure ethylene oxide (EO), for low-temperature clinical sterilization of medical instruments and devices. However, few studies have been published that evaluate its safety in terms of possible damage to materials, particularly polymers. The objective of this work was to evaluate polymer surface modifications induced by commercial plasma-based sterilizers, in comparison with pure EO: Samples from 5 polymer-based devices were subjected to 1, 5, and 10 sterilization cycles by Sterrad-100, Plazlyte, and pure EO. Surface analysis was carried out by X-ray photoelectron spectroscopy (XPS), dynamic contact angle measurements (DCA), and scanning electron microscopy (SEM). Surface oxidation and wettability changes were observed on all samples sterilized by plasma-based techniques, the degree of modifications depending on the sterilizer (Sterrad, Plazlyte) and the type of polymer. Drastic changes of surface appearance were also observed by SEM on PVC samples sterilized by Plazlyte and by pure EO. Possible repercussions on safety are discussed.

Natural coral graft substitutes are derived from the exoskeleton of marine madreporic corals. Researchers first started evaluating corals as potential bone graft substitutes in the early 1970s in animals and in 1979 in humans. The structure of the commonly used coral, Porites, is similar to that of cancellous bone and its initial mechanical properties resemble those of bone. The exoskeleton of these high content calcium carbonate scaffolds has since been shown to be biocompatible, osteoconductive, and biodegradable at variable rates depending on the exoskeleton porosity, the implantation site and the species. Although not osteoinductive or osteogenic, coral grafts act as an adequate carrier for growth factors and allow cell attachment, growth, spreading and differentiation. When applied appropriately and when selected to match the resorption rate with the bone formation rate of the implantation site, natural coral exoskeletons have been found to be impressive bone graft substitutes. The purpose of this article is to review and summarize all the pertinent work that has been published on natural coral as a bone graft including in vitro, animal and clinical human studies. Preliminary report of our own experiments as well as our recommendations on the use of coral are also included.

Utilizing an ionized gas (plasma) to achieve sterilization is an alternative to conventional sterilization means as far as sterilization of heat-sensitive materials and innocuity of sterilizing agents are concerned. The literature on plasma sterilization is reviewed. A major issue of plasma sterilization is the respective roles of UV photons and reactive species such as atomic and radicals. Insight into this matter is obtained by analyzing the survival curves of microorganisms. In contrast to classical sterilization where such plots show a unique straight line, plasma sterilization yields survival diagrams with two or three different linear segments. Three basic mechanisms are involved in the plasma inactivation of microorganisms: (A) direct destruction by UV irradiation of the genetic material of microorganisms; (B) erosion of the microorganisms atom by atom, through intrinsic photodesorption by UV irradiation to form volatile compounds combining atoms intrinsic to the microorganisms; (C) erosion of the microorganisms, atom by atom, through etching to form volatile compounds as a result of slow combustion using oxygen atoms or radicals emanating from the plasma. In some cases, etching is further activated by UV photons, increasing the elimination rate of microorganisms. These mechanisms make plasma sterilization totally different from classical sterilization techniques and suggest its use to inactivate nonconventional infectious agents such as the abnormal prions.

Plasma-based sterilization is a promising alternative to ethylene oxide (EO) for reprocessing of electrophysiology catheters. To assess its safety in terms of material damage, modifications of surface and bulk properties as well as hydrolytic stability of sterilized catheters were evaluated. Polyurethane (PU) single-use electrophysiology catheters were subjected to one, five, and ten sterilization cycles by Sterrad-100S and Plazlyte, as well as by pure EO for comparison. Surface analysis techniques (ATR-FTIR, XPS, DCA) showed oxidation limited to the near-surface layer induced by both plasma-based sterilizers, whereas EO induced slight but deeper alkylation. Using bulk analysis techniques (RP-HPLC, SEC), oligomer alteration was observed after all three sterilization techniques, without modification of molecular weights. Hydrolytic stability of catheters was slightly changed by plasma-based sterilization, with a small increase in released oligomers. Finally, although Plazlyte and Sterrad are both plasma-based techniques, they induced different impacts on catheters, such as the degradation of an additive with Sterrad, and a clear difference in coloration with Plazlyte.

Nickel-titanium (NiTi) alloy derives its biocompatibility and good corrosion resistance from a homogeneous oxide layer mainly composed of TiO(2), with a very low concentration of nickel. In this article, we described the corrosion behavior of NiTi alloys after mechanical polishing, electropolishing, and sterilization processes using cyclic polarization and atomic absorption. As a preparative surface treatment, electropolishing decreased the amount of nickel on the surface and remarkably improved the corrosion behavior of the alloy by increasing the mean breakdown potential value and the reproducibility of the results (0.99 +/- 0.05 V/SCE vs. 0.53 +/- 0. 42). Ethylene oxide and Sterrad(R) sterilization techniques did not modify the corrosion resistance of electropolished NiTi, whereas a steam autoclave and, to a lesser extent, peracetic acid sterilization produced scattered breakdown potential. In comparing the corrosion resistance of common biomaterials, NiTi ranked between 316L stainless steel and Ti6A14V even after sterilization. Electropolished NiTi and 316L stainless-steel alloys released similar amounts of nickel after a few days of immersion in Hank's solution. Measurements by atomic absorption have shown that the amount of released nickel from passive dissolution was below the expected toxic level in the human body. Auger electron spectroscopy analyses indicated surface contamination by Ca and P on NiTi during immersion, but no significant modification in oxide thickness was observed.

Microspheres of a polyelectrolyte complex hydrogel were prepared from chitosan and xanthan after interaction between the two polyionic polymers. Their biodegradation was studied vs. chitosan. Simulated gastric fluid (SGF, pH 1.2) and intestinal fluid (SIF, pH 7.5) both as biodegradation media and phosphate buffered saline (PBS, pH 7.4) as a negative control were used. The degradation studies were performed at 37 degrees C at 240 rpm permanent stirring to mimic the physiologic conditions. High performance liquid chromatography (HPLC) was carried out to quantify the chitosan degradation products using glucosamine (GA) and N-acetyl-D-glucosamine (N-Ac-GA) as references. The peaks area integration method was used to determine the amount of each degradation product as a function of incubation time in the media. The effect of the media on the morphological structure of microspheres was assessed by scanning electron microscopy. From HPLC studies, it appeared that in SGF and SIF the major degradation products were glucosamine (GA) and N-acetyl-D-glucosamine (NAc-GA). In the first 15 days, oligochitosan fractions were released from the complex, whereas N-acetyl-D-glucosamine was detected in the media after this period. The degradation kinetics were assessed by the measurement of the cumulative degradation products, which showed faster degradation of chitosan than the complex in SGF and SIF. SEM micrographs showed an enhancement of microsphere porosity as a function of incubation time in the simulated physiological media. Our results suggest a better control of the degradation kinetics when chitosan is complexed to xanthan., (Copyright 2000 John Wiley & Sons, Inc.)

A novel hydrogel, CHITOXAN(TM) (CH-X), has potential as a vehicle for controlled drug delivery. The hydrogel is obtained by complexation of two polysaccharides, chitosan and xanthan. In the present work we investigated the biocompatibility of the complex using in vitro and in vivo models. The cytotoxic effects of CH-X microspheres as well as their degradation products at different concentrations were assessed on fibroblasts (fibroblast cell line L-929) using 3-(4,5-dimethylthiazole-2yl)-2,5-triphenyl tetrazolium) (MTT). The test is based on mitochondrial dehydrogenase cell activity as an indicator of cell viability. Interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha) cytokines as well as nitric oxide (NO) production by macrophages (macrophage cell line J-774) were examined as indicators of cell activation. In vivo biocompatibility assessment was performed for 1 to 12 weeks. This study was performed using tablets obtained after compression of CH-X particles implanted at the subcutaneous level in male Wistar rats. CH-X biocompatibility and degradation were investigated using histological studies. Light and transmission electron microscopy (TEM) analyses were used to determine the foreign-body reaction and phagocytosis of the implants by macrophages. Fibroblast exposition to CH-X particles and degradation products did not show cytotoxic effects as measured by MTT test. TNF-alpha production was dependent on CH-X particles concentration, whereas IL-1beta production was found to be dose independent. CH-X extract products stimulated TNF-alpha secretion when used at the highest concentration (10 mg/mL), notably after 28 days' degradation time. No effect was observed on IL-1beta production when CH-X extracts were used in comparison to the control. The effects of CH-X particles on NO secretion were similar as on TNF-alpha. Histological studies showed that CH-X tablets broke down into particles which progressively degraded into smaller fragments. A significant fraction of the fragments was ingested by the macrophages after 12 weeks of implantation. Light microscopy studies showed a weak foreign-body reaction as a function of time and the fibrous layer thickness decreased with time of implantation., (Copyright 2000 John Wiley & Sons, Inc.)

The aim of this work was to investigate possible mechanisms of sterilization by low-temperature gas plasma: spore destruction by plasma is compared with etching of synthetic polymers. Bacillus subtilis spores were inoculated at the bottom of glass vials and subjected to different plasma gas compositions (O(2), O(2)/Ar, O(2)/H(2), CO(2), and O(2)/CF(4)), all known to etch polymers. O(2)/CF(4) plasma exhibited much higher efficacy than all other gases or gas mixtures tested, with a more than 5 log decrease in 7.5 min, compared with a 2 log decrease with pure oxygen. Examination by scanning electron microscopy showed that spores were significantly etched after 30 min of plasma exposure, but not completely. We speculate about their etch resistance compared with that of synthetic polymers on the basis of their morphology and complex coating structure. In contrast to so-called in-house plasma, sterilization by Sterrad(R) tended to increase the observed spores' size; chemical modification (oxidation), rather than etching, is believed to be the sterilization mechanism of Sterrad(R)., (Copyright 2000 John Wiley & Sons, Inc.)

Sterilization is required for using any device in contact with the human body. Numerous authors have studied device properties after sterilization and reported on bulk and surface modifications of many materials after processing. These surface modifications may in turn influence device biocompatibility. Still, data are missing on the effect of sterilization procedures on new biomaterials such as nickel-titanium (NiTi). Herein we report on the effect of dry heat, steam autoclaving, ethylene oxide, peracetic acid, and plasma-based sterilization techniques on the surface properties of NiTi. After processing electropolished NiTi disks with these techniques, surface analyses were performed by Auger electron spectroscopy (AES), atomic force microscopy (AFM), and contact angle measurements. AES analyses revealed a higher Ni concentration (6-7 vs. 1%) and a slightly thicker oxide layer on the surface for heat and ethylene oxide processed materials. Studies of surface topography by AFM showed up to a threefold increase of the surface roughness when disks were dry heat sterilized. An increase of the surface energy of up to 100% was calculated for plasma treated surfaces. Our results point out that some surface modifications are induced by sterilization procedures. Further work is required to assess the effect of these modifications on biocompatibility, and to determine the most appropriate methods to sterilize NiTi., (Copyright 2000 John Wiley & Sons, Inc.)

Nickel-titanium (NiTi) offers many advantages for the fabrication of coronary stents: shape memory, superelasticity, and radiopacity. However, many authors highlighted the selective dissolution of Ni from the alloy during the corrosion process that could lead to potential toxicity. The improvement of the NiTi stent's corrosion resistance by different surface treatments (electropolishing, heat treatment, and nitric acid passivation) was reported in a previous article. In the present study a comparative biocompatibility evaluation of such stents was performed through in vitro and in vivo assays. A cell proliferation test was completed to evaluate the cytotoxicity of surface treated NiTi using human fibroblasts. Then a stent implantation was performed in rabbit paramuscular muscle to study the inflammatory response generated by the same implants. Cell proliferation tests generally indicated an in vitro biocompatibility of our samples similar to the control group. An in vivo implantation study demonstrated the gradual overall reduction with time of the fibrocellular capsule thickness surrounding the implants. After a 12-week implantation period, the fibrous capsules surrounding the different implants tended toward the same value of 0.07 mm, which suggested that all surface treatments produced a similar biological response. This low value of the fibrocellular capsule indicated that our NiTi surface treated implants were relatively inert.

Porous nickel-titanium (NiTi) alloys have demonstrated bone attachment as well as tissue ingrowth in the past. However, very few studies have compared porous NiTi soft and hard tissue reactions, and in vitro cell response. We therefore have evaluated the general muscle and bone reaction to porous nickel-titanium. The latter material was implanted in rabbit tibias and back muscle, and assessed after three, six and twelve weeks of implantation. Porous NiTi specimens did not cause any adverse effect regardless of both implantation site and post-surgery recovery time. Muscle tissue exhibited thin tightly adherent fibrous capsules with fibers penetrating into implant pores. We observed that attachment strength of the soft tissue to the porous implant seemed to increase with post-implantation time. Bone tissue demonstrated good healing of the osteotomy. There was bone remodeling characterized by osteoclastic and osteoblastic activity in the cortex. This general good in vivo biocompatibility with muscle and bone tissue corresponded very well with the in vitro cell culture results we obtained. Fibroblasts seeded on porous nickel-titanium sheets managed to grow into the pores and all around specimen edges showing an another interesting cytocompatibility behavior. These results indicate good biocompatibility acceptance of porous nickel-titanium and are very promising towards eventual NiTi medical device approbation.

Because of its good radiopacity, superelasticity, and shape memory properties, nickel-titanium (NiTi) is a potential material for fabrication of stents because these properties can facilitate their implantation and precise positioning. However, in vitro studies of NiTi alloys report the dependence of alloy biocompatibility and corrosion behavior on surface conditions. Surface oxidation seems to be very promising for improving the corrosion resistance and biocompatibility of NiTi. In this work, we studied the effect on corrosion resistance and surface characteristics of electropolishing, heat treatment, and nitric acid passivation of NiTi stents. Characterization techniques such as potentiodynamic polarization tests, scanning electron microscopy, Auger electron spectroscopy, and X-ray photoelectron spectroscopy were used to relate corrosion behavior to surface characteristics and surface treatments. Results show that all of these surface treatments improve the corrosion resistance of the alloy. This improvement is attributed to the plastically deformed native oxide layer removal and replacement by a newly grown, more uniform one. The uniformity of the oxide layer, rather than its thickness and composition, seems to be the predominant factor to explain the corrosion resistance improvement.

NiTi shape Memory Alloys (SMA) are potential biomaterial candidates for medical devices such as osteosynthesis staples. However, Ni dissolution induced by uniform or localized corrosion could lead to toxicity. In this work, plasma polymerized tetrafluoroethylene (PPFTE) coating is used to improve the corrosion resistance of NiTi plates and corresponding NiTi stables. The scratch test indicates a good surface adhesion of the film but that it lacks cohesiveness. Potentiodynamic tests in physiological Hank's solution show that PPTFE coating improved the pitting corrosion resistance. The passivation range is increased from 35% to 96% compared to the untreated sample and the pit diameter is decreased from 100 microns to 10 microns. The uniformity of the deposited film is a very important parameter. When the film is damaged, the corrosion seems to increase in comparison to the untreated samples. Otherwise, if the staple is carefully manipulated, the coating follows the large deformations induced by the memory effect of the alloy without cracking, and then, protects efficiently the staple from pitting.

Focal ischemia of the small intestine does not always lead to necrosis and perforation, but may induce fibrous stenosis which is evidenced clinically by acute or chronic intestinal occlusion. Among 8 intestinal stenoses 5 were revealed by the presence of an intestinal occlusion whereas the others were manifested by intestinal occlusions complicated by subsequent perforation of the intestinal wall. Annulo-tubular stenoses of ischemic origin are frequently accompanied by inflammatory mesenteric adenopathies due to mucosal ulcerations in the septic environment of the intestinal lumen. Their aspect is reminiscent of Crohn's disease or annular carcinoma. Histological examination of the resected loop frequently reveals the primary oschemic origin of the stenotic lesion, characterized by the presence of macrophages loaded with hemosiderin in the thickened inflamed mucosa. The tissue alterations observed resemble those found in myocardial infarction, but the inflammatory response is more pronounced due to the septic medium. Although such stenoses are relatively rare, they should be distinguished from other lesions provoking a narrowing of the intestinal lumen, since their treatment calls for certain therapeutic precautions. In some cases, angioplastic intervention is required in order to improve perfusion of the vascular bed irrigated by the superior mesenteric artery following resection of the stenotic loop and termino-terminal anastomosis. Furthermore, during any operation requiring revascularization of the mesenteric vessels for intestinal angina, it is important to carry out a very careful examination of the state of the small intestine.

To repair defects in the common bile duct, part of the gallbladder and the cystic duct may be used as a pedicled graft. This has the advantage of an independent blood supply and a related mucosal lining. The method is illustrated by four patients who had excellent primary and short term results. In two patients, the defect was due to large cholecystocholedochal fistulas caused by migrating large gallstones. In one patient with marked stenosis of the duct, the defect occurred when the stenosis was opened through a longitudinal incision. The fourth patient had a large duodenal ulcer that penetrated into the common duct, causing a defect that could not be closed by suture. A definite evaluation of the procedure must await a longer period of follow-up study.