Biomaterials.info - Resources for Engineers

Record 1381 to 1400

Comparative study of hyaluronic derivatives: rheological behaviour, mechanical and chemical degradation
Prieto, J. G., M. M. Pulido, et al. (2005), Int J Biol Macromol 35(1-2): 63-9.
Abstract: Depolymerisation by oxytetracycline (OTC) as well as the progressive cleavage of hyaluronic acid induced by ultrasound was investigated in nine commercially available hyaluronic polymers. Sample solutions differed in molecular weight, from 500 to 7000 kDa, and in their source. The hyaluronic acid concentration in each sample was analysed by HPLC. The concentration range was over 8.39-10.18 mg ml(-1) in samples with a nominal concentration of 1%, and 14.05 mg ml(-1) in one sample with a nominal concentration of 1.5%. It was found that stability was dependent on both molecular weight and the concentration of the samples. The rheological parameters n (power law index) and K (consistency coefficient) were good predictors regarding the degradation behaviour. Although many factors are involved in obtaining a therapeutic response, the results obtained in this work support the notion that both mechanical and chemical degradation are reduced in hyaluronate solutions with low molecular weight, the final concentration of the product being a critical factor.

Comparative study of metallic biomaterials toxicity: a histochemical and immunohistochemical demonstration in mouse spleen
Ferreira, M. E., M. de Lourdes Pereira, et al. (2003), J Trace Elem Med Biol 17(1): 45-9.
Abstract: Metallic biomaterials available for orthopaedic purposes become essential to perform important physical activities, due to their low cost and excellent mechanical properties. In addition, they are frequently used in dentistry. However, corrosion phenomena of such devices are the main problems resulting in subsequent spreading of the elements through the whole body via lymph and blood. The spleen is the most important lymphoid organ and the only one included in the blood circulation. Thus, the aim of this study was to evaluate the short-term effects on spleen tissues of heavy metals released from stainless steel and Cr-Co-Mo alloys, as well as from titanium, at histochemical and immunohistochemical levels. For this purpose, metallic suspensions were obtained by electrochemical dissolution of the mentioned biomaterials: stainless steel (Fe 490 mg/L, Cr 224 mg/L, Ni 150 mg/L), Cr-Co-Mo (Cr 200 mg/L, Co 375 mg/L), and titanium (400 mg/L). Then 0.5 ml of each solution was subcutaneously administered to male Charles River mice each 72 hours during 30 days. Cryostat sections of the spleen from all groups were submitted to routine staining with haematoxylin/eosin, peroxidase detection by 3-3' diaminobenzidine (DAB), and alkaline phosphatase anti-alkaline phosphatase (APAAP) for lymphocyte detection. Several pronounced alterations were found in the spleen architecture, as manifested by irregular features within the capsule and medulla, namely depletion of T4 and B cells. Altogether these results suggest toxic alterations within the spleen induced by some of the metallic elements, indicating that the immune system may be hampered and so interfering in the body mechanisms of defence.

Comparative study of microcapsules elaborated with three polycations (PLL, PDL, PLO) for cell immobilization
De Castro, M., G. Orive, et al. (2005), J Microencapsul 22(3): 303-15.
Abstract: Alginate-poly-L-lysine (PLL)-alginate microcapsules have been widely used in cell microencapsulation technology. However, the mechanical fragility and low tensile resistance against swelling of this membrane chemistry and the difficult handling, immunogenicity and cytotoxicity of PLL have stimulated the study of novel polycations. In this paper, alginate microcapsules coated with three different polycations: poly-L-lysine (PLL), poly-D-lysine (PDL) and poly-L-ornithine (PLO) were fabricated to evaluate if the use of novel membrane chemistries (PDL, PLO) had a positive effect on the morphology, osmotic resistance and mechanical stability of the capsules as well as the viability of the immobilized C2C12 myoblast cells when compared to the classical PLL microcapsules. Results indicate that liquefied capsules presented worse mechanical properties than the polymerized solid capsules in the three type of membrane chemistries. In addition, PLL membrane chemistry exerted the highest resistance against compressions after culture in several mediums, while PDL microcapsules showed the highest resistance to the tensile stress of the osmotic pressure. No important differences were detected when the physiological activity of the enclosed cells was evaluated. In summary, although further in vivo assays are needed, in general none of the new membrane formulations represented a significant improvement over classical PLL microcapsules.

Comparative study of tacrolimus and paclitaxel stent coating in the porcine coronary model
Scheller, B., A. Grandt, et al. (2005), Z Kardiol 94(7): 445-52.
Abstract: BACKGROUND: Tacrolimus is a potent antiproliferative and immunosuppressive agent allowing for improved endothelial regeneration. The aim of our study was the preclinical evaluation of tacrolimus in a drug eluting nonerodable polymer stent system and its comparison with paclitaxel. METHODS AND RESULTS: A total of 40 domestic pigs and 10 mini-pigs underwent coronary stenting with a follow-up time between 6 hours and 3 months. Stents were implanted in coronary arteries with an overstretch ratio of 1.2. After 3 days, a 1.73 microg/mm(2) coating produced tacrolimus tissue levels of 20 mumol/l in the coronary artery wall. Effective tissue concentrations were sustained for 28 days. Based on histomorphometric analysis, tacrolimus stent treated vessels had a reduced extent of neointima formation compared with controls at 28 days (-51% compared to control) but not at 3 months. High dose paclitaxel stent coating (1.44 microg/mm(2)) was complicated by unexpected deaths of pigs and thrombotic stent occlusion at control angiography. Long-term porcine data showed no persistent inhibition of neointimal growth by paclitaxel and tacrolimus stent coating. CONCLUSIONS: Similar to paclitaxel, tacrolimus stent coating reduces neointimal proliferation in the porcine coronary model. However, dosing and long-term efficacy remains a critical issue in stent-based local drug delivery.

Comparative study of the corrosion behavior of MA-956 and conventional metallic biomaterials
Escudero, M. L., M. F. Lopez, et al. (1996), J Biomed Mater Res 31(3): 313-7.
Abstract: In this work the corrosion behavior of a new biomaterial, the MA-956 superalloy, immersed in Hank's solution is evaluated. A comparison with conventional metallic alloys used as articular implants is established. To determine the corrosion behavior we employed electrochemical methods: evaluation of corrosion potential Ecorr, electrochemical impedance spectroscopy (EIS), and anodic polarization curves. The corrosion resistance of the MA-956 superalloy preoxidized at 1100 degrees C during 100 h is at least two orders of magnitude higher than for the other alloys. This satisfactory behavior is stationary with time. Also the probability of the appearance of the pitting corrosion process is very low. When cracking is generated in the alpha-alumina layer the repassivation process is assured because of the high Cr content in the superalloy. This study is the first step in proposing this new alloy as a biomaterial. The low toxicity of these metallic alloys in the physiological environment suggests that in vivo their biocompatibility could be satisfactory.

Comparison between RGD-peptide-modified titanium and borosilicate surfaces
Senyah, N., G. Hildebrand, et al. (2005), Anal Bioanal Chem 383(5): 758-62.
Abstract: The use of synthetic peptides containing adhesive sequences, such as the Arg-Gly-Asp (RGD) motif, represents a promising strategy to control biological interactions at the cell-material interface. These peptides are known to improve the tissue-material contact owing to highly specific binding to cellular membrane receptors known as integrins, thereby promoting the adhesion, migration and proliferation of cells. The peptides were coupled to borosilicate glass and titanium surfaces using silanisation chemistry. A tryptophan residue was incorporated into the amino acid sequences of selected peptides to facilitate the detection of the covalently bound peptides. Successful peptide immobilisation was proven by fluorimetric measurements. The confocal imaging analysis suggests a homogeneous distribution of the immobilised peptide across the biomaterial surface. In vitro cell proliferation assays were employed to compare the adhesion potentials of the well-known RGD-containing peptides GRGDSP, GRADSP and RGDS to the three peptides designed by our group. The results demonstrate that the RGD sequence is not necessarily required to enhance the adhesion of cells to non-biological surfaces. Moreover, it is shown that the number of adhering cells can be increased by changes in the peptide hydrophobicity. Changes in the cytoskeleton are observed depending on the type of RGD-peptide modification.

Comparison of 2 preferred methods used for frontal sinus obliteration
Fattahi, T., C. Johnson, et al. (2005), J Oral Maxillofac Surg 63(4): 487-91.
Abstract: PURPOSE: This study was undertaken to compare total operating room cost, total operating time, and potential complications in frontal sinus obliteration using 2 different techniques. PATIENTS AND METHODS: Hospital records of all patients with frontal sinus fractures treated by the Division of Maxillofacial Surgery at the University of Florida, Jacksonville between October 1998 and December 2003 were reviewed. Twelve patients required frontal sinus obliteration based on the severity and location of injury. All cases were caused by traumatic etiology. Patients were divided into group A or B. Six patients (group A) were treated using autogenous abdominal fat for obliteration purposes, while the other 6 patients (group B) underwent frontal sinus obliteration using a hydroxyapatite cement. Total operating cost, total operating time, and any complications were recorded and analyzed for each group and then statistically evaluated using a t test. RESULTS: Follow-up ranged from 2 weeks to 6 months. Patients in group A had a lower total operating cost compared with group B. This cost difference was statistically significant. Total operating time was slightly greater in group A versus group B, although this was not statistically significant. CONCLUSION: Frontal sinus obliteration using autogenous abdominal fat appears to be more cost effective compared with hydroxyapatite cement. The slight difference in total operating time was not statistically significant and this factor alone should not be a deterrent from performing this surgical procedure.

Comparison of adhesive properties of five different prosthetic materials used in hernioplasty
Kayaoglu, H. A., N. Ozkan, et al. (2005), J Invest Surg 18(2): 89-95.
Abstract: This experimental study was designed to assess and to compare intra-abdominal adhesions following the use of five commercially available prosthetic mesh grafts in the repair if abdominal wall defects. Sixty Wistar albino rats were randomly divided into six groups (n = 10). A 2 x 1 cm defect at abdominal wall was created and defects were closed either primarily or with one of the following prosthetic mesh grafts: monofilament polypropylene, polytetrafluoroethylene, sodium hyaluronate/carboxymethylcellulose-coated polypropylene, polypropylene/polyglactin 910 composite, or resorbable hydrophilic collagen-coated multifiber polyester. The severity of adhesions was graded, tensile strengths of adhesions were measured, and histopathological grades of inflammation and fibrosis were evaluated. Polypropylene mesh resulted in more adhesion formation in comparison to primary repair and other grafts used in this study, except polypropylene/polyglactin 910 composite mesh. In addition, the highest tensile strength of omental adhesions was detected in the polypropylene group (chi2 = 26.249; p =.0001). Polyester composite mesh caused the least adhesion formation among the groups. Sodium hyaluronate/carboxymethylcellulose-coated polypropylene and polyester composite meshes revealed the highest fibrosis scores (chi2 = 50.776; p =.0001). The highest inflammatory activity was detected in the polytetrafluoroethylene mesh group (chi2 = 16.564; p =.005). Thus, sodium hyaluronate/carboxymethylcellulose-coated polypropylene and polytetrafluoroethylene meshes following polyester composite mesh were the minimal adhesion-forming grafts in this study. Disadvantages of the polytetrafluoroethylene mesh were lower fibrotic activity and higher inflammatory reaction to the graft.

Comparison of bacterial and tissue cell initial adhesion on hydrophilic/hydrophobic biomaterials
Karakecili, A. G. and M. Gumusderelioglu (2002), J Biomater Sci Polym Ed 13(2): 185-96.
Abstract: In this study, interactions of widely-used polymeric biomaterials, i.e. poly(hydroxyethyl methacrylate) (PHEMA) and its copolymer with dimethylaminoethyl methacrylate (PHEMA-20% DMAEMA), polyurethane (PU), polypropylene (PP), poly(vinyl chloride) (PVC), and poly(lactide-glycolide) (PLGA), with three pathogenic bacteria and one nonpathogen were investigated comparatively with the adhesion of two tissue cells in different morphologies, i.e. fibroblast-like baby hamster kidney (BHK 21) cells and epithelial Madine Darby kidney (MDBK) cells. Biomaterials were prepared in the membrane form by bulk polymerization or solvent casting. Surface characterization studies showed that these polymers have different surface free energies in the range of 26.9-63.1 erg cm(-2) and they have smooth surfaces. The bacteria used were; Escherichia coli ATCC 25922, Staphylococcus epidermidis ATCC 12228, Staphylococcus aureus, and Lactobacillus acidophilus B-13. Initial adhesion of bacteria to the polymeric surfaces was examined under static conditions and in a laminar flow cell. The adhesion behaviour of S. aureus and S. epidermidis was found independent of the polymeric surface hydrophobicity. However, the percentage of attached E. coli decreased when increasing the surface free energy of the polymer, while L. acidophilus showed just the opposite behaviour. The comparative results indicated that the adhesion of BHK and MDBK cell was lowest on the most hydrophilic PHEMA surface and highest on the most hydrophobic PP surface. In contrast to the case of bacterial adhesion, no relationship was found between polymer hydrophobicity and mammalian cell adherence.

Comparison of bioengineered human bone construct from four sources of osteogenic cells
Ng, A. M., A. B. Saim, et al. (2005), J Orthop Sci 10(2): 192-9.
Abstract: Osteoprogenitor cells have been reported to be present in periosteum, cancellous and cortical bone, and bone marrow; but no attempt to identify the best cell source for bone tissue engineering has yet been reported. In this study, we aimed to investigate the growth and differentiation pattern of cells derived from these four sources in terms of cell doubling time and expression of osteoblast-specific markers in both monolayer cells and three-dimensional cell constructs in vitro. In parallel, human plasma derived-fibrin was evaluated for use as biomaterial when forming three-dimensional bone constructs. Our findings showed osteoprogenitor cells derived from periosteum to be most proliferative followed by cortical bone, cancellous bone, and then bone marrow aspirate. Bone-forming activity was observed in constructs formed with cells derived from periosteum, whereas calcium deposition was seen throughout the constructs formed with cells derived from cancellous and cortical bones. Although no mineralization activity was seen in constructs formed with osteoprogenitor cells derived from bone marrow, well-organized lacunae as would appear in the early phase of bone reconstruction were noted. Scanning electron microscopy evaluation showed cell proliferation throughout the fibrin matrix, suggesting the possible application of human fibrin as the bioengineered tissue scaffold at non-load-bearing sites.

Comparison of biomaterials for facial bone augmentation
Maas, C. S., G. E. Merwin, et al. (1990), Arch Otolaryngol Head Neck Surg 116(5): 551-6.
Abstract: We compared the gross behavior of and microscopic response to implant materials currently in clinical use for facial bone augmentation at different sites in dogs. Materials evaluated include porous polytetrafluoroethylene carbon (Proplast), large-pore high-density polyethylene (Medpor), solid medical-grade silicone rubber (Silastic), polyamide mesh (Supramid), and autogenous rib bone. The subjects were 12 mixed-breed dogs and the materials were implanted directly on bone with periosteum removed at one of three sites in the dog's face (malar eminence, nasal dorsum, and chin). Animals were killed 3 months after surgery and stability of the implants was graded by manual manipulation. Blocks of tissue, including the study materials and underlying bone, were examined microscopically after sectioning. Stability results are tabulated and histologic appearance is described by site for each material evaluated. These data demonstrate marked variability of stability and cellular response depending on the site of implantation. From these data one may conclude that the site of implantation and implant movement are essential factors in determining the nature of the tissue response and fate of an implant. Solid and porous alloplastic materials show an acceptable tissue response, but neither demonstrates the ability to consistently provide an implant that is stable on underlying bone.

Comparison of biomaterials in the early postoperative period
Langenbach, M. R., J. Schmidt, et al. (2003), Surg Endosc 17(7): 1105-9.
Abstract: BACKGROUND: Laparoscopic hernia repair necessitates the use of biocompatible materials. A prospective, double-blind study was conducted to compare two different polypropylene meshes. METHODS: The study included 40 men with primary inguinal hernia undergoing transabdominal preperitoneal polypropylene mesh repair. In 20 of these men, a monofile, heavy-weight, rigid mesh was implanted (group A), and in the remaining 20 men, a smooth, heavy-weight variant of polypropylene mesh was implanted (group B). Complications, pain development, inability to work, physical conditions, testicular volume, and blood circulation were documented. RESULTS: Reconvalescence in group A was slower than in group B. In group A, the postoperative values of the visual scales for pain development were higher; inability to work was 7.3 days longer; urologic disorders were worse; activities of everyday life were more reduced; and SF-36 data showed a significant reduction of physical problems (p < 0.05). CONCLUSIONS: The polypropylene mesh variant seems to be more compatible with the human organism than conventional mesh. Not only the material, but also the structure seems to influence the comfort of the mesh.

Comparison of bone marrow cell growth on 2D and 3D alginate hydrogels
Barralet, J. E., L. Wang, et al. (2005), J Mater Sci Mater Med 16(6): 515-9.
Abstract: Calcium cross-linked sodium alginate hydrogels have several advantageous features making them potentially suitable as tissue engineering scaffolds and this material has been previously used in many biomedical applications. 3D cell culture systems are often very different from 2D petri dish type cultures. in this study the effect of alginate hydrogel architecture was investigated by comparing rat bone marrow cell proliferation and differentiation on calcium cross linked sodium alginate discs and 1mm internal diameter tubes. It was found that bone marrow cell proliferation was diminished as the concentration of alginate in the 2D hydrogel substrates increased, yet proliferation was extensive on tubular alginate constructs with high alginate contents. Alginate gel thickness was found to be an important parameter in determining cell behaviour and the different geometries did not generate significant alterations in BMC differentiation profiles.

Comparison of coagulation activity tests in vitro for selected biomaterials
van Oeveren, W., J. Haan, et al. (2002), Artif Organs 26(6): 506-11.
Abstract: Testing of coagulation induced by external communicating medical devices is an International Standardisation Organization (ISO) requirement for products exposed to human blood. Four categories of tests are indicated by ISO 10993/4: a clotting test (partial thromboplastin time; PTT), thrombin generation, fibrinogen deposition, or measurement of coagulation split products. We evaluated the specificity of these tests on various polymers and found only thrombin generation and fibrinogen binding sensitive and reproducible tests while thrombin generation correlated best with the classical PTT. The thrombin generation assay is therefore the method of choice for testing coagulation induced by biomaterials and medical devices.

Comparison of coatings from reactive star shaped PEG-stat-PPG prepolymers and grafted linear PEG for biological and medical applications
Groll, J., Z. Ademovic, et al. (2005), Biomacromolecules 6(2): 956-62.
Abstract: Grafting of poly(ethylene glycol) (PEG) is a common strategy for reducing nonspecific interactions of surfaces with proteins. We have used grafting at "cloud point" solution conditions that ensures maximum grafting density of linear methoxy terminated PEG-aldehyde (mPEG-ald, M(w) = 5000 and 30000). In an alternative approach, surfaces were modified with layers prepared from isocyanate terminated, star shaped poly(ethylene glycol-stat-propylene glycol) prepolymers (80% ethylene glycol, six arms, M(w) = 3000, 12,000, and 18,000; this compound will be referred to as "Star PEG" in the text). Due to the highly reactive endgroups, these molecules form a dense network on the substrate with a high polymer surface coverage. The two systems were compared regarding their ability to prevent unspecific adsorption of insulin and lysozyme. The layers were analyzed by ellipsometry, contact angle measurements, and XPS. Protein adsorption was monitored by surface MALDI-TOF MS and fluorescence microscopy. No protein adsorption could be detected on Star PEG coatings and on mPEG-ald 5000, whereas mPEG-ald 30,000 could only prevent adsorption of lysozyme but not of the smaller insulin.

Comparison of contrast sensitivity and color discrimination after clear and yellow intraocular lens implantation
Rodriguez-Galietero, A., R. Montes-Mico, et al. (2005), J Cataract Refract Surg 31(9): 1736-40.
Abstract: PURPOSE: To compare contrast sensitivity and color vision in patients in whom blue-light filtering and non-yellow-tinted intraocular lenses (IOLs) were implanted. SETTING: Refractive Surgery Unit, Hospital NISA Valencia al Mar, Valencia, Spain. METHODS: Forty eyes of 20 patients were enrolled in a blue-light filtering fellow-eye control study; patients were implanted with a yellow-tinted IOL (AcrySof Natural, Alcon) in 1 eye and a non-yellow-tinted IOL (AcrySof SA60AT, Alcon) in the fellow eye after cataract surgery. Three months postoperatively, monocular contrast sensitivity function was measured with the CSV 1000-E contrast sensitivity chart at distance and the color discrimination with the Farnsworth-Munsell 100 Hue test. RESULTS: Eyes implanted with blue-light filtering IOLs showed similar contrast sensitivity to that in fellow eyes implanted with non-yellow-tinted IOLs (P>.1). Both types of IOLs showed normal contrast sensitivity values (normalized log-contrast sensitivity about 1.0). There were no statistically significant differences in chromatic discrimination between the 2 types of IOLs (P =.56). CONCLUSION: The use of blue-light filtering IOLs is more advisable because they are capable of protecting the retina against ultraviolet light without disturbance of contrast sensitivity and chromatic vision, which produces subjective impairment in visual function.

Comparison of cytocompatibility of zein film with other biomaterials and its degradability in vitro
Sun, Q. S., J. Dong, et al. (2005), Biopolymers 78(5): 268-74.
Abstract: Cytocompatibility of particle zein (Pzein) and film zein (Fzein) was evaluated and compared with polyhydroxybutyrate (PHB), its copolymer poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV), polylactic acid (PLA), and collagen, using HL-7702 cells, in terms of cell attachment rate within 3 h, and cell viabilities at 3 and 6 days determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) method. The zein degradation test was carried out using collagenase and trypsin, and the degradation product was added to the culture medium at different concentrations in order to examine the concentration-dependent cytotoxic effect. RESULT: The adhesion rate of the HL-7702 cells on both Pzein and Fzein was higher than that on collagen film. Cell viabilities were higher on both Pzein and Fzein than on films of PLA, PHB, PHBV, and collagen from fish skin. Zein can be degraded by both trypsin and collagenase, and the degradation product can enhance cell viability within a certain range of concentrations.

Comparison of diced cartilage graft wrapped in surgicell and diced cartilage graft wrapped in fascia: an experimental study
Coskun, B. U., H. Seven, et al. (2005), Laryngoscope 115(4): 668-71.
Abstract: HYPOTHESIS: This study was conducted to compare diced cartilage grafts wrapped in fascia and diced cartilage grafts wrapped in surgicell with respect to their resorption. STUDY DESIGN: Experimental study. METHODS: Eight male Wistar Albino rats were used. After general anesthesia, two different subcutaneous pockets (upper and lower pocket) were prepared in the rat's abdomen. Surgicell-wrapped homograft that was taken from the ear was placed into the upper subcutaneous pocket. Fascia-wrapped homograft which was taken from the ear was placed into the lower subcutaneous pocket. All the rats were killed at the end of 2 months, and the samples were collected to be examined histopathologically. Cartilage mass, foreign body reaction, fibrosis, chronic inflammation, and vascularization were researched. RESULTS: Diced cartilage wrapped surgicell stained negative for glial fibrillary acidic protein (GFAP). Diced cartilage wrapped in fascia stained positive for GFAP. There was a significant difference between two groups with respect to fibrosis, chronic inflammation, and cartilage mass. There was no significant difference between the two groups regarding vascularization. CONCLUSIONS: This study suggests that diced cartilage graft wrapped in surgicell was absorbed, whereas diced cartilage graft wrapped in fascia was not.

Comparison of different biomaterials for glaucoma drainage devices
Ayyala, R. S., L. E. Harman, et al. (1999), Arch Ophthalmol 117(2): 233-6.
Abstract: OBJECTIVES: To compare the inflammatory reaction associated with the insertion of silicone and polypropylene endplates and endplates made of a new biocompatible polymer, Vivathane, in the rabbit subconjunctival space. METHODS: Similar-sized endplates made of 3 different biomaterials were sutured to the sclera in the superotemporal quadrant of the rabbit eye. Thirty eyes of 15 albino New Zealand rabbits were randomly assigned to the 3 groups. Conjunctival vascular hyperemia was graded in a masked fashion among groups. At the end of 3 weeks, the enucleated eyes were examined histologically and using scanning electron microscopy. RESULTS: Polypropylene and Vivathane were associated with significantly more inflammation in clinical observations and based on histological grading. Silicone was associated with the least amount of inflammation. Three polypropylene and 1 Vivathane plate were extruded between the second and third week. CONCLUSIONS: Silicone is the most inert of the 3 materials tested. Inflammation associated with biomaterials may contribute to the failure of the glaucoma drainage devices. CLINICAL RELEVANCE: Bleb inflammation may be related to the biomaterial being used as the endplate. Endplates should be handled carefully during surgery to avoid creating rough spots.

Comparison of different biomaterials for glaucoma drainage devices: part 2
Ayyala, R. S., B. Michelini-Norris, et al. (2000), Arch Ophthalmol 118(8): 1081-4.
Abstract: BACKGROUND: Inflammation associated with biomaterials may contribute to the failure of glaucoma drainage devices. OBJECTIVE: To compare the inflammatory reaction associated with the insertion of Krupin silicone, Molteno polypropylene, and Acrosof end plates in the subconjunctival space of rabbits. METHODS: Similar-sized glaucoma end plates made of 3 different biomaterials were sutured to the sclera in the superotemporal quadrant of the rabbit eye. Thirty eyes of 15 albino New Zealand rabbits were randomly assigned to the 3 groups. Conjunctival vascular hyperemia was graded in a masked fashion among the 3 groups. At the end of 3 weeks, the enucleated eyes were examined histologically and by scanning electron microscopy. RESULTS: Molteno polypropylene was associated with more inflammation both in clinical observations and based on histological grading. Silicone and Acrosof were associated with less intense inflammation. One polypropylene end plate was extruded on day 21. CONCLUSIONS: Polypropylene appears to be more inflammatory than silicone. Flexible biomaterials appear to be less inflammatory than rigid ones. CLINICAL RELEVANCE: Bleb failure following glaucoma drainage device implantation could be related to the biomaterial-associated inflammation. Choosing a biomaterial with the least inflammatory potential might enhance the success rate of the glaucoma drainage device. Arch Ophthalmol. 2000;118:1081-1084

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