Biomaterials.info - Resources for Engineers

Record 3821 to 3840

Sub-micron texturing for reducing platelet adhesion to polyurethane biomaterials
Milner, K. R., A. J. Snyder, et al. (2005), J Biomed Mater Res A
Abstract: Platelet adhesion is a key event in thrombus development on blood-contacting medical devices. It has been demonstrated that changes to the chemistry of a material surface can reduce platelet adhesion. In this work, it is hypothesized that sub-micron surface textures may also reduce adhesion via a decrease in the surface area of material with which platelets can make contact, and hence a decreased probability of interaction with adhesive ligands. A polyether(urethane urea) was textured with two different sizes of sub-micron pillars using a replication molding technique that did not alter the material surface chemistry. Adhesion of platelets was assessed in a physiologically relevant shear stress range of 0-67 dyn/cm(2) using a rotating disk system. Platelets were immunofluorescently labeled and adhesion was compared on smooth and textured samples. Platelet adhesion was greatest at low shear stress ranging from 0 to 5 dyn/cm(2), and sub-micron textures were observed to reduce platelet adhesion in this range. Additionally, non-adherent platelets did not demonstrate large-scale activation after exposure to textured samples. We conclude that surface textures with sub-platelet dimensions may reduce platelet adhesion from plasma to polyether(urethane urea) at low shear stress. (c) 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2005.

Submucosal injection of poly(lactic-co-glycolic acid) microspheres in rabbit bladder as a potential treatment for urinary incontinence and vesicoureteral reflux: preliminary results
Cho, E. R., S. W. Kang, et al. (2005), J Biomater Sci Polym Ed 16(9): 1109-20.
Abstract: Endoscopic injection of bulking agents has been gaining attention as a therapy for urinary incontinence and vesicoureteral reflux because this therapy is simpler, less operation time-consuming and less painful than traditional surgical operations. The ideal bulking agent for the injection therapies must be easily injectable, biocompatible, volume-stable, non-antigenic and non-migratory. We evaluated poly(lactic-co-glycolic acid) (PLGA) microspheres as an injectable bulking agent for urologic injection therapies. To determine whether PLGA microspheres meet the requirements of an ideal bulking agent, PLGA microspheres were injected into the submucosal sites of a rabbit bladder wall. The microspheres were easily injectable. Two and five weeks post-implantation, histological examinations indicated that host cells from the surrounding bladder tissues migrated to the space between the injected microspheres and formed new hybrid tissue structures. Lymphocyte migration was noted around the implanted microspheres, but the inflammatory reaction diminished at 5 weeks. The hybrid tissue volume did not significantly decrease over time. There was no evidence of microsphere migration to the distant organs. Although long-term studies are needed to evaluate the therapeutic potential of this method, these preliminary results suggest the possibility of PLGA microspheres as a potentially useful injection material for urinary injection therapies.

Substrate chemistry influences the morphology and biological function of adsorbed extracellular matrix assemblies
Sherratt, M. J., D. V. Bax, et al. (2005), Biomaterials 26(34): 7192-206.
Abstract: In addition to mediating cell signalling events, native extracellular matrix (ECM) assemblies interact with other ECM components, act as reservoirs for soluble signalling molecules and perform structural roles. The potential of native ECM assemblies in the manufacture of biomimetic materials has not been fully exploited due, in part, to the effects of substrate interactions on their morphology. We have previously demonstrated that the ECM components, fibrillin and type VI collagen microfibrils, exhibit substrate dependent morphologies on chemically and topographically variable heterogeneous surfaces. Using both cleaning and coating approaches on silicon wafers and glass coverslips we have produced chemically homogeneous, topographically similar substrates which cover a large amphiphilic range. Extremes of substrate amphiphilicity induced morphological changes in periodicity, curvature and lateral spreading which may mask binding sites or disrupt domain structure. Biological functionality, as assayed by the ability to support cell spreading, was significantly reduced for fibrillin microfibrils adsorbed on highly hydrophilic substrates (contact angle 20.7 degrees) compared with less hydrophilic (contact angle 38.3 degrees) and hydrophobic (contact angle 92.8 degrees) substrates. With an appropriate choice of surface chemistry, multifunctional ECM assemblies retain their native morphology and biological functionality.

Substrate-supported phospholipid membranes studied by surface plasmon resonance and surface plasmon fluorescence spectroscopy
Tawa, K. and K. Morigaki (2005), Biophys J 89(4): 2750-8.
Abstract: Substrate-supported planar lipid bilayer membranes are attractive model cellular membranes for biotechnological applications such as biochips and sensors. However, reliable fabrication of the lipid membranes on solid surfaces still poses significant technological challenges. In this study, simultaneous surface plasmon resonance (SPR) and surface plasmon fluorescence spectroscopy (SPFS) measurements were applied to the monitoring of adsorption and subsequent reorganization of phospholipid vesicles on solid substrates. The fluorescence intensity of SPFS depends very sensitively on the distance between the gold substrate and the fluorophore because of the excitation energy transfer to gold. By utilizing this distance dependency, we could obtain information about the topography of the adsorbed membranes: Adsorbed vesicles could be clearly distinguished from planar bilayers due to the high fluorescence intensity. SPSF can also incorporate various analytical techniques to evaluate the physicochemical properties of the adsorbed membranes. As an example, we demonstrated that the lateral mobility of lipid molecules could be estimated by observing the recovery of fluorescence after photobleaching. Combined with the film thickness information obtained by SPR, SPR-SPFS proved to be a highly informative technique to monitor the lipid membrane assembly processes on solid substrates.

Success of mineral trioxide aggregate in pulpotomized primary molars
Farsi, N., N. Alamoudi, et al. (2005), J Clin Pediatr Dent 29(4): 307-11.
Abstract: The aim of the present study was to compare, clinically and radiographically, the mineral trioxide aggregate (MTA) to formocresol (FC) when used as medicaments in pulpotomized vital human primary molars. METHODS: The sample consisted of 120 primary molars, all teeth were treated with the same conventional pulpotomy technique. Sixty molars received FC and 60 received MTA throughout a random selection technique. RESULTS: At the end of 24-month evaluation period, 74 molars (36 FC, 38 MTA) were available for clinical and radiographic evaluation. None of the MTA treated teeth showed any clinical or radiographic pathology, while the FC group showed a success rate of 86.8% radiographically and 98.6% clinically. The difference between the two groups in the radiographic outcomes was statistically significant. It was concluded that MTA treated molars demonstrated significantly greater success. MTA seems to be a suitable replacement for formocresol in pulpotomized primary teeth.

Successful repair of esophageal injury using an elastin based biomaterial patch
Kajitani, M., Y. Wadia, et al. (2001), Asaio J 47(4): 342-5.
Abstract: An esophageal injury with significant tissue loss is very difficult to repair. We conducted an in vivo study to test our elastin based acellular biomaterial patch to repair such defect. The patch was made from porcine aorta, by decellularization and sterilization. Collagen fibers were preserved to retain mechanical strength and enhance cellular in-growth. Ten domestic pigs underwent right thoracotomy. A 2 cm circular defect was made on the distal esophagus, excising half its circumference, and was repaired using the biomaterial patch and sutures. Soon after the procedure, the animals resumed oral feeding. They were followed for clinical status, weight gain, barium studies, and endoscopic studies, and were killed after 6 weeks to 4 months. All ten animals survived long term, with a procedure success rate of 100% (10 of 10). With the exception of one pneumothorax, no complications occurred, and all animals resumed oral feeding and gained weight. Endoscopic studies showed mucosal coverage by 6 weeks, with minimal stricture at the repair site. Excised specimens showed complete mucosal coverage with regeneration of all three layers. Our biomaterial patch can be used safely and reliably for repair of esophageal injury with significant tissue loss when repaired immediately as in our experiment.

Sudan black B as a histological stain for polymeric biomaterials embedded in glycol methacrylate
Hoeksma, E. A., B. van der Lei, et al. (1988), Biomaterials 9(5): 463-5.
Abstract: Sudan black B, usually a stain for all kinds of lipid, turned out to be an excellent histological stain for polymeric biomaterials embedded in glycol methacrylate. Staining the surrounding connective tissue with toluidine blue-basic fuchsin makes details of the polymer-tissue interface clearly visible. Sudan black B might be used to visualize the biodegradation process of polymeric biomaterials.

Sugar micro needles as transdermic drug delivery system
Miyano, T., Y. Tobinaga, et al. (2005), Biomed Microdevices 7(3): 185-8.
Abstract: We designed and fabricated an array of sugar micro needles of the length ranging from 150 micro m to 2 mm for transdermic delivery of drugs. Micro needles were molded out of maltose mixed with pharmaceutical material, being expected bio-degradable in the human skin. To test basic tolerance to the healthy human skin, a clinical experiment was carried out for 10 healthy adult volunteers. 500 microm-needles containing 5 wt% of ascorbate-2-glycoside were inserted into the skin of the forearm and snapped off to be left in the skin. They spontaneously dissolved by hydrolysis to release ascorbate in the epidermis and the dermis. No dermatological problems were observed in terms of the International Contact Dermatitis Research Group criteria. These observations indicate that the present system is a novel approach to achieve transdermic drug delivery.

Sulfonated poly(vinylidene fluoride) as a biomaterial: immobilization of urokinase and biocompatibility
Aoshima, R., Y. Kanda, et al. (1982), J Biomed Mater Res 16(3): 289-99.
Abstract: The adsorption of urokinase (UK) on sulfonated poly(vinylidene fluoride) (PVDF) films was examined. The amount of adsorbed UK on sulfonated PVDF films increased linearly with the degree of the ion exchange capacity (IEC) of sulfonated film. Moderately sulfonated PVDF film (IEC = 0.25 meq/g) adsorbed 3 IU/cm2 UK, and highly sulfonated film (IEC = 0.54 meq/g) adsorbed 5 IU/cm2 UK. All UK-immobilized PVDF films were active for ten weeks. The presence of the sulfonated films in the culture of rat lymphocytes did not result in any change of their viability. The implant of the film (IEC greater than 0.48 meq/g) into the subcutaneous layer of rats resulted in the cell infiltration composed of lymphocytes and plasma cells or the blastogenesis within the surrounding tissues of the implant and the regional lymph nodes. On the contrary, the implant of the films (IEC less than 0.27 meq/g) did not exert any visible changes, indicating that the lightly sulfonated films may be applicable in the sense of biocompatibility in vivo.

Summary statement: biomaterials
Coe, J. D. and K. Cheung (2005), Spine 30(17 Suppl): S75.

Summary-Joint regeneration using functional tissue engineering
Sumner, D. R. (2004), J Musculoskelet Neuronal Interact 4(4): 401.

Super pH-sensitive multifunctional polymeric micelle
Lee, E. S., K. Na, et al. (2005), Nano Lett 5(2): 325-9.
Abstract: To endow enhanced tumor specificity and endosome disruption property on the carrier, a multifunctional polymeric micelle was investigated. The micelle exposes the cell interacting ligand (biotin) on the surface under slightly acidic environmental conditions of various solid tumors and is internalized by biotin receptor-mediated endocytosis in a short time period. The micelle also showed pH-dependent dissociation, causing the enhanced release of doxorubicin from the carrier in early endosomal pH. The dissociated micellar components subsequently disrupt endosomal membrane.

Superior cell delivery features of poly(ethylene glycol) incorporated alginate, chitosan, and poly-L-lysine microcapsules
Haque, T., H. Chen, et al. (2005), Mol Pharm 2(1): 29-36.
Abstract: Microencapsulation is an emerging technology in the development of bioartificial organs for drug, protein, and delivery systems. One of the advancements in establishing an appropriate membrane material for live cell and tissue encapsulation is the incorporation of poly(ethylene glycol) (PEG) to the widely studied alginate microcapsules. The current study investigates the properties of integrating PEG to microcapsules coated with poly-L-lysine (PLL) and chitosan as well as a novel microcapsule membrane which combines both PLL and chitosan. Results show that microcapsules containing PEG can support cell viability and protein secretion. The addition of PEG to PLL and chitosan-coated microcapsules improves the stability of microcapsules when exposed to a hypotonic solution. We also compared the novel microcapsule with two other previously used microcapsules including alginate-chitosan-PEG and alginate-PLL-PEG-alginate. Results show that all three membranes are capable of providing immunoprotection to the cells and have the potential for long-term storage at -80 degrees C. The novel membrane containing PEG, chitosan, and PLL, however, revealed the highest cell viability and mechanical strength when exposed to external rotational force, but it was unable to sustain osmotic pressure. The study revealed the potential of using PEG-incorporated alginate, chitosan, and PLL microcapsules for encapsulating live cells producing proteins and hormones for therapy.

Superior sealing effect of hydroxyapatite in porous-coated implants: experimental studies on the migration of polyethylene particles around stable and unstable implants in dogs
Rahbek, O., S. Kold, et al. (2005), Acta Orthop 76(3): 375-85.
Abstract: BACKGROUND: Migration of wear debris to the periprosthetic bone is a major cause of osteolysis and implant failure. Both closed-pore porous coatings and hydroxyapatite (HA) coatings have been claimed to prevent the migration of wear debris. We investigated whether HA could augment the sealing effect of a porous coating under both stable and unstable conditions. METHODS: We inserted porous-surfaced knee implants, with and without HA coating, in 16 dogs, according to a paired, randomized study design. 8 dogs had 2 implants inserted into each knee using a stable implant device and 8 dogs received 1 implant in each knee using a micromotion (500 microm) implant device. Implants had a peri-implant gap of 0.75 mm. We then injected polyethylene (PE) particles or a control solution into the knee joints on a weekly basis. RESULTS: After 16 weeks, the rating of particles around stable implants was reduced by the HA coating froma median value of 2 (1-4) to 1 (0-1) (p = 0.01) and during micromotion from 3 (2-4) to 1 (0-3) (p = 0.002). HA-coated implants had superior bone ongrowth during stable and unstable conditions. We found no difference in bone ongrowth between PE-exposed and vehicle-exposed implants. INTERPRETATION: Compared to a pure plasma-sprayed porous coating, a layer of HA coating provides bettter bone ongrowth and protects the bone-implant interface against the migration of wear debris under both stable and unstable conditions.

Supernova antineutrino interactions cause chiral symmetry breaking and possibly homochiral biomaterials for life
Cline, D. B. (2005), Chirality 17 Suppl: S234-9.
Abstract: There is some evidence that nonracemic hydrocarbons occur in meteorites. This would indicate an extraterrestrial origin of the homochirality in living systems (proteins, DNA, RNA). The weak interaction breaks chiral symmetry, but a robust process is needed. We propose that, in an SNII explosion, antineutrinos could provide this mechanism in the solar cloud. Pre-simple estimates of this possibility are given here.

Superoxide release by neutrophils exposed to different biomaterials
Mora, E. M., S. S. Kaplan, et al. (1990), Curr Surg 47(6): 430-1.

Supplement Report Of The Task Force On Biomaterials To The Cardiology Advisory Committee Of The Nhlbi
Galletti, P. M., J. L. Brash, et al. (1978), Cardiovasc Dis 5(3): 293-314.

Suppression of arsenopyrite surface oxidation by sol-gel coatings
Khummalai, N. and V. Boonamnuayvitaya (2005), J Biosci Bioeng 99(3): 277-84.
Abstract: Oxidation of arsenopyrite (FeAsS) in mine tailings is considered as the major cause of arsenic release in groundwater around mineral mine sites. Oxidation rate is increased by the biooxidation of chemolithoautotrophic bacteria, such as Acidithiobacillus ferrooxidans via the adsorption mechanism. Hence, coating with thin films as a physical barrier for oxidants surrounding the mineral surface is one of the effective abatement strategies. In this work, we studied and characterized the formation of thin films using sol-gel on arsenopyrite and investigated the resistance of thin films to biological and chemical oxidations. We selected methyltrimethoxysilane (MTMOS), tetramethoxysilane (TMOS), tetraethoxysilane (TEOS) and N-(2-aminoethyl)-3-aminopropyl trimethoxysilane (AAPS) as sol-gel precursors. MTMOS coating arsenopyrite particles at a H2O/Si molar ratio of 2 suppressed both biological oxidation and chemical oxidation and was superior to other alkoxysilane monomers. Factors involved in oxidation suppression are the crack-free morphology and the hydrophobicity of MTMOS coating. The Si-O-Si spectrum by Fourier transform infrared (FTIR) distinctly found for the MTMOS film is considered to indicate the formation of the networks of the film, and the Fe-O-Si spectrum confirmed the bonding of the film to the arsenopyrite surface.

Suppression of polyethylene particle-induced osteolysis by exogenous osteoprotegerin
von Knoch, F., A. Heckelei, et al. (2005), J Biomed Mater Res A 75(2): 288-94.
Abstract: Alterations of the key regulators of osteoclastogenesis, receptor activator of NF-kappaB (RANK), RANK ligand (RANKL), and osteoprotegerin (OPG) have been implicated in wear particle-induced osteolysis, the most common cause for implant failure in total joint replacements. This study investigated the effect of exogenous OPG on ultra-high-molecular-weight polyethylene (UHMWPE) particle-induced osteolysis. The murine calvarial osteolysis model was utilized in 28 C57BL/6J mice randomized to four groups. Group I underwent sham surgery only, group II received UHMWPE particles, and group III and IV particles and subcutaneous OPG starting from day 0 (group III) or day 5 (group IV) until sacrifice. After 2 weeks, calvaria were prepared for histology and histomorphometry. Bone resorption was measured within the midline suture using Giemsa staining and osteoclast numbers were determined using TRAP staining. UHMWPE particle implantation resulted in grossly pronounced osteoclastogenesis and bone resorption. Both immediate and delayed treatment with OPG counteracted these particle-induced effects significantly, suppressing osteoclast formation and bone resorption (p < 0.001 and p < 0.001, respectively). In conclusion, exogenous OPG markedly suppressed UHMWPE particle-induced osteolysis in a murine calvarial model. This important finding underscores the crucial significance of the OPG-RANKL-RANK signaling in wear particle-induced osteolysis. Exogenous OPG may prove an effective treatment modality for wear debris-mediated periprosthetic osteolysis after total joint arthroplasty.

Suppression of tumor cell invasiveness by hydrolyzable tannins (plant polyphenols) via the inhibition of matrix metalloproteinase-2/-9 activity
Tanimura, S., R. Kadomoto, et al. (2005), Biochem Biophys Res Commun 330(4): 1306-13.
Abstract: Elevated expression of matrix metalloproteinases (MMPs), especially that of MMP-2 and MMP-9, is associated with increased metastatic potential in many tumor cells. Recently, green tea polyphenol epigallocatechin-3-O-gallate (EGCG) has been shown to inhibit the MMP-2/-9 activity as well as the invasiveness of tumor cells. In this study, we have examined the inhibitory effect of hydrolyzable tannins (plant polyphenols) on the tumor cell invasion. Our results demonstrate that beta-d-glucose whose hydroxy groups are substituted entirely with galloyl group and further some of them are cross-linked to form hexahydroxydiphenoyl group, for example, suppresses the invasiveness of tumor cells much more potently than EGCG via direct inhibition of the MMP-2/-9 activity. Among those examined, 1,2,4-tri-O-galloyl-3,6-hexahydroxydiphenoyl-beta-d-glucose (punicafolin) inhibits the invasion of HT1080 fibrosarcoma cells most potently. These hydrolyzable tannins would provide new leads for the development of potent inhibitors against tumor metastasis.

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