|Articles about Biomaterials|
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| A new biotechnology for articular cartilage repair: subchondral implantation of a composite of interconnected porous hydroxyapatite, synthetic polymer (PLA-PEG), and bone morphogenetic protein-2 (rhBMP-2)
Tamai, N., A. Myoui, et al. (2005), Osteoarthritis Cartilage 13(5): 405-17.
Abstract: OBJECTIVE: Articular cartilage repair remains a major obstacle in tissue engineering. We recently developed a novel tool for articular cartilage repair, consisting of a triple composite of an interconnected porous hydroxyapatite (IP-CHA), recombinant human bone morphogenetic protein-2 (rhBMP-2), and a synthetic biodegradable polymer [poly-d,l-lactic acid/polyethylene glycol (PLA-PEG)] as a carrier for rhBMP-2. In the present study, we evaluated the capacity of the triple composite to induce the regeneration of articular cartilage. METHODS: Full-thickness cartilage defects were created in the trochlear groove of 52 New Zealand White rabbits. Sixteen defects were filled with the bone morphogenetic protein (BMP)/PLA-PEG/IP-CHA composite (group I), 12 with PLA-PEG/IP-CHA (group II), 12 with IP-CHA alone (group III), and 12 were left empty (group IV). The animals were killed 1, 3, and 6 weeks after surgery, and the gross appearance of the defect sites was assessed. The harvested tissues were examined radiographically and histologically. RESULTS: One week after implantation with the BMP/PLA-PEG/IP-CHA composite (group I), vigorous repair had occurred in the subchondral defect. It contained an agglomeration of mesenchymal cells which had migrated from the surrounding bone marrow either directly, or indirectly via the interconnecting pores of the IP-CHA scaffold. At 6 weeks, these defects were completely repaired. The regenerated cartilage manifested a hyaline-like appearance, with a mature matrix and a columnar organization of chondrocytes. CONCLUSIONS: The triple composite of rhBMP-2, PLA-PEG, and IP-CHA promotes the repair of full-thickness articular cartilage defects within as short a period as 3 weeks in the rabbit model. Hence, this novel cell-free implant biotechnology could mark a new development in the field of articular cartilage repair.
| A new class of inhibitors of 2-arachidonoylglycerol hydrolysis and invasion of prostate cancer cells
Nithipatikom, K., M. P. Endsley, et al. (2005), Biochem Biophys Res Commun 332(4): 1028-33.
Abstract: Endogenous 2-arachidonoylglycerol (2-AG) inhibits invasion of androgen-independent prostate cancer cells. Blocking cellular hydrolysis of 2-AG to increase its endogenous concentration results in a decrease in cell invasion. A series of compounds containing a trifluoromethyl ketone (TFK) moiety or the methyl analog (known to inhibit carboxylesterases) were investigated for their ability to inhibit 2-AG hydrolysis and prostate cancer cell invasion. Compounds containing a thioether beta to a TFK moiety inhibited 2-AG hydrolysis as well as cell invasion in a concentration-dependent manner. Inhibition of 2-AG hydrolysis increased concomitantly with inhibitor alkyl chain length from 4- to 12-carbons while inhibition of cell invasion exhibited a maximum at 8- to 10-carbons of the compounds. These results demonstrate a new series of 2-AG hydrolysis inhibitors as a potential therapeutic approach for prostate cancer.
| A new device for in vitro evaluation of thrombogenicity
Lermusiaux, P., T. V. How, et al. (2005), Med Eng Phys
Abstract: A device to measure the time of coagulation of whole blood has been designed in order to facilitate testing of thrombogenicity of biomaterials. The principle of operation of the apparatus is to record the time taken for a sphere to fall through a sample of blood. The coagulation time is defined here as the time from collection of the blood sample to coagulation, coagulation having deemed to have occurred when the sphere is prevented from falling by the presence of the fibrin-cell network. The device was tested with homogeneous fluids of different viscosity, milk containing different amounts of rennin and calcium chloride and non anti-coagulated whole blood obtained from five volunteers. Repeat measurements made with each homogeneous fluid show that the variance in the transit time of the sphere is small and consistent with small dispersion. In contrast, the onset of coagulation in milk and blood samples was readily detected. The clotting of milk was highly dependant on the concentration of rennin and calcium chloride. The coagulation time of blood samples from five individuals ranged from 23 to 33min but simultaneous measurements of samples from the same individual in two identical devices agreed to within +/-1min in all cases. This device may be easily adapted for use in studies to determine the thromboresistance of biomaterials where the onset of coagulation of whole blood in contact with different materials may be readily compared.
| A new ESR dosimeter based on bioglass material
Hassan, G. M., M. A. Sharaf, et al. (2004), Radiat Meas 38(3): 311-5.
Abstract: Bioglass (Bio-G) samples were irradiated with 60Co gamma-rays to study radicals for dosimetric materials with electron spin resonance (ESR). The ESR spectrum of Bio-G is characterized by two main signals. The first signal at g approximately = 4.3 corresponds to Fe3+ impurities and the second signal at g approximately = 2.0130 with line-width 10.85 G is ascribed as a hole center. The gamma-ray dose response and thermal stability were studied to establish the suitability of bioglass as an ESR dosimeter. A radical formation efficiency, G-value, of 0.53 +/- 0.11 was obtained. The lifetime of radicals and the activation energy were estimated from Arrhenius plots to be approximately 255 +/- 46 days and 0.71 eV, respectively.
| A new flow chamber for the study of shear stress and transmural pressure upon cells adhering to a porous biomaterial
Chotard-Ghodsnia, R., A. Drochon, et al. (2002), J Biomech Eng 124(2): 258-61.
Abstract: Biomaterials used in some biomedical devices are porous and exposed to normal and tangential flow of biofluids. To examine the influence of flow induced forces on the morphology and the biochemical responses of cells adhering to such biomaterials, a Hele-Shaw cell with a porous bottom wall was designed and characterized experimentally. Theoretical predictions for the flow in the chamber are provided and allow to quantify the shear stress and/or transmural pressure exerted on cells. It is thus possible to follow up continuously the shape changes of cells that are adherent on a permeable membrane used in bioreactors.
| A new hydrophilic polymer for biomaterial coatings with low protein adsorption
Braatz, J. A., A. H. Heifetz, et al. (1992), J Biomater Sci Polym Ed 3(6): 451-62.
Abstract: BIOPOL polyurethane polymers, an extension of the HYPOL Polymer series of foamable hydrophilic polymers, have been developed which exhibit improved performance for selected biomedical applications. Members of the BIOPOL polyurethane polymer series, with molecular weights in the range of 7000 to 30,000, are larger molecules than HYPOL polymers (MW less than 3000) and produce hydrogels, rather than foams, when mixed with water. The prototype material in this series, BIOPOL XP-5, is a liquid prepolymer which chain extends in water and forms a hydrogel which can contain greater than 85% water. The time required for polymerization with water was dependent on the prepolymer: water ratio. This prepolymer was coated onto silica and medical grade tubing and then cured in place with water to form a stable coating which was resistant to non-specific protein binding. In addition, soluble, isocyanate-free forms of the prepolymer were tested for toxicity and shown to produce no adverse effects when injected intravenously into mice or when applied to a chicken chorioallantoic membrane. BIOPOL polymers can be useful in applications where protein adsorption is an undesirable event.
| A new hypothesis of tumorigenesis induced by biomaterials: inhibitory potentials of intercellular communication play an important role on the tumor-promotion stage
Tsuchiya, T. and A. Nakamura (1995), J Long Term Eff Med Implants 5(4): 233-42.
Abstract: A possible mechanism of tumorigenesis induced by the polyetherurethanes (PEUs) is clarified as follows: the tumor-promoting activities of the PEUs were stronger than the initiating activities; the promotion was facilitated by the polyether soft segment moiety such as poly (tetramethylene oxide) (PTMO), resulting in the inhibition of the gap-junctional intercellular communication; this inhibition was caused by leachable oligomers, degradation, and direct cell/material interaction. On the basis of our recent studies, we also propose a new hypothesis that inhibitory potentials of the intercellular communication play an important role on the tumor-promoting stage in various biomaterials.
| A new in vitro model to study interaction between whole blood and biomaterials. Studies of platelet and coagulation activation and the effect of aspirin
Hong, J., K. Nilsson Ekdahl, et al. (1999), Biomaterials 20(7): 603-11.
Abstract: We have developed a versatile in vitro chamber model with a double purpose: first, to be able to study mechanisms of bio-incompatibility, and, second, to test biomaterials at all levels of interactions, in whole blood. The use of biomaterials in the form of microscope slides as walls in the chamber makes it possible to analyse both the biomaterial surface with regard to protein and cell binding, as well as the molecular events taking place in the fluid. Incubation of blood in the chamber, for 60 min at 37 degrees C resulted in the rapid binding of complement and coagulation proteins and of leukocytes and platelets to polyvinylchloride (PVC) slides. The cells formed a layer which more or less covered the underlying surface. Unlike complement activation, as reflected by soluble C3a and C5b-9, the thrombin-antithrombin formation was completely nullified in cell-depleted plasma. Despite the fact that thrombin-antithrombin generation was also negligible in platelet-rich plasma, inhibition of platelet aggregation on the material surface with aspirin resulted in suppressed generation of thrombin antithrombin complexes. Taken together, the coagulation activation in the chamber was dependent on the presence of blood cells which suggests that bound/aggregated platelets initiate a sequence of events involving leukocytes that results in coagulation activation.
| A new in vivo model for testing cartilage grafts and biomaterials: the 'rabbit pinna punch-hole' model
ten Koppel, P. G., G. J. van Osch, et al. (2001), Biomaterials 22(11): 1407-14.
Abstract: In this study an animal model was developed for evaluation of the feasibility of cartilage grafts. In the cartilage of the external ear of the rabbit multiple holes, 6 mm in diameter, were punched, leaving the adherent skin intact. Different experimental groups were evaluated. First, the punch-hole model was validated under various conditions to study spontaneous or perichondrial initiated regeneration of the cartilage defect. When both cartilage and perichondrium was excised no spontaneous repair of the cartilage defect was observed. When perichondrium is present, variable patch-like closure of the punch hole was found. As 'golden standard' a punched out piece of cartilage was reimplanted directly. This condition showed adequate closure of the punch hole, however, no perfect integration of graft and surrounding cartilage was observed. Secondly, to evaluate the 'punch-hole model' a biomaterial, trabecular demineralized bovine bone matrix (DBM), was implanted and tested as a scaffold for tissue engineering techniques in vivo and in vitro. Direct implantation of DBM did not lead to any cartilage formation to close the defect. In vivo engineered cartilage, generated by enveloping DBM in perichondrium for 3 weeks, could adequately close the punch hole. When DBM was seeded with isolated chondrocytes in vitro before implantation in the defect, a highly fragmented graft, with some islets of viable cells was seen. To promote an efficient and reliable evaluation of cartilage grafts a semi-quantitative grading system was developed. Items such as quality, quantity and integrity of the cartilage graft were included in a histomorphological grading system to provide information about the properties of a specific cartilage graft. To validate the grading system, all conditions were scored by two independent observers. An excellent reliability (R = 0.96) was seen between the observers. In summary, the rabbit pinna punch-hole model is a reliable and efficient method for first evaluation of cartilage grafts. The results can be easily analyzed using a semi-quantitative grading system.
| A new injectable calcium phosphate biomaterial for immediate bone filling of extraction sockets: a preliminary study in dogs
Gauthier, O., D. Boix, et al. (1999), J Periodontol 70(4): 375-83.
Abstract: BACKGROUND: Many different bone substitutes, such as autografts, allografts or synthetic biomaterials have been proposed to restore alveolar bone loss and support efficient placement of dental implants. This experimental study evaluated the osteoconductive properties of an injectable bone substitute (IBS) composed of a polymeric carrier and a calcium phosphate mineral phase, used to fill mandibular and maxillary canine extraction sockets. METHODS: The polymer was a cellulose derivative (methyl-hydroxy-propyl-cellulose, MHPC), and the mineral phase consisted of granules of biphasic calcium phosphate (BCP) ceramics 200 to 500 microm in diameter. Mandibular and maxillary premolars extracted from 3 dogs (a total of 60 extraction sites) were immediately treated with the IBS or left unfilled as control sites. Animals were sacrificed 3 months after implantation and all extraction sockets were prepared for histological evaluation. RESULTS: Qualitative histological studies showed that the IBS was able to support the extensive apposition of well-mineralized newly formed lamellar bone over the entire socket surface and appeared to prevent alveolar ridge bone loss in treated extraction sites. Quantitative evaluation showed that the amount of newly formed bone was significantly higher in mandibular than maxillary extraction sockets for both treated and control sites. CONCLUSIONS: An injectable bone substitute composed of a polymeric carrier and calcium phosphate was effective in enhancing the bone fill of extraction sockets. This approach may prove promising for periodontal lesions. The material expressed osteoconductive capacities, and the biological properties of the mineral phase were conserved.
| A new method for analysis of the adsorbed plasma protein layer on biomaterial surfaces
Weathersby, P. K., T. A. Horbett, et al. (1976), Trans Am Soc Artif Intern Organs 22: 242-52.
Abstract: The composition and dynamics of the protein film adsorbed onto surfaces from blood plasma remains unknown to biomaterials development. In situ radioiodination followed by elution and electrophoretic analysis has been demonstrated as a sensitive and versatile technique for analysis of these films. Iodine-125I was incorporated into protein using iodine monochloride. After film washing, and elution with sodium dodecylsulfate (SDS), proteins were subject to SDS gel electrophoresis for MW determination. Disulfide bond reduction with dithiothreitol was also employed to detect the presence of protein subunits. Fibrinogen, albumin and IgG were readily identified when adsorbed from a single protein solution onto teflon or silicone rubber. Electrophoretic analysis of the protein layer adsorbed from plasma revealed a complex pattern of up to 8 iodinated protein species. Iodinated protein with electrophoretic behavior consistent with fibrinogen and albumin was always found after plasma exposure, but proteins of apparent MW 7-10,000; 12,000; 25,000 and others remain unidentified. Adsorbed protein patterns varied with plasma source, type of material, and time of plasma exposure.
| A new method for quantifying the intensity of the C=C band of dimethacrylate dental monomers in their FTIR and Raman spectra
Gauthier, M. A., I. Stangel, et al. (2005), Biomaterials 26(33): 6440-8.
Abstract: The degree of conversion (DC) of methacrylate dental resins is typically determined by spectroscopically measuring the decrease of the vinyl (C=C) stretching band at 1640 cm(-1), ratioed before and after polymerization to an internal standard (aromatic ring quadrant stretching vibration (Ph)) at around 1609 cm(-1). While standard methods exist for measuring the intensity of the C=C and Ph peaks from the FTIR or Raman spectrum, these methods either fail under certain circumstances, or lack a physical basis, being purely based on spectral features. In this study, we present a rigorous method (named rotational isomerism method) for determining the intensity of the vinyl and aromatic bands from the FTIR and Raman spectra of dental monomer mixtures, and compare it to a standard baseline method (SBM) and a standard curve fitting method. Model triethyleneglycol dimethacrylate (TEGDMA)/2,2-bis(4-hydroxyphenyl)propane (Bisphenol-A) and TEGDMA/2,2-bis(4-(2-hydroxy-3-methacryloxypropoxy)phenyl)propane (Bis-GMA) mixtures with a series of known C=C/Ph molar ratios were prepared in order to simulate the effect of curing. The accuracy of the new method for measuring the DC was found to be as good as the commonly used SBM. The standard curve fitting method was shown to be inappropriate for measuring C=C/Ph ratios by FTIR spectroscopy due to its inability to realistically simulate the features of the spectra. The insight gained through the use of this new method may be useful for the characterization of other methacrylate biomaterials.
| A new method for screening anti-infective biomaterials
Bechert, T., P. Steinrucke, et al. (2000), Nat Med 6(9): 1053-6.
| A new method for targeted drug delivery using polymeric microcapsules: implications for treatment of Crohn's disease
Metz, T., M. L. Jones, et al. (2005), Cell Biochem Biophys 43(1): 77-85.
Abstract: Recent research and clinical evidence suggest that thalidomide could potentially be used to treat inflammation associated with Crohn's disease. However, systemic side effects associated with large doses of this drug have limited its widespread use. Treatment with thalidomide would prove more efficacious if the drug could be delivered directly to target areas in the gut, thereby reducing systemic circulation. Microcapsule encapsulation could enable direct delivery of the drug. To assess the latter, we designed and tested drug-targeting release characteristics of alginate-poly-L-lysine-alginate (APA) microcapsules in simulated gastrointestinal environments. The results show that APA capsules enabled delivery of thalidomide in the middle and distal portions of the small intestine. We also compared the APA membrane formulation with an earlier designed alginate chitosan (AC) membrane thalidomide formulation. The results show that both APA and AC capsules allow for successful delivery of thalidomide in the gut and could prove beneficial in the treatment of Crohn's disease. However, further research is required.
| A New Method for the Removal of Toxic Metal Ions from Acid-Sensitive Biomaterial
Seki, H. and A. Suzuki (1997), J Colloid Interface Sci 190(1): 206-11.
Abstract: A new method (competitive adsorption method) for the removal of toxic heavy metals from acid-sensitive biomaterials was proposed and it was applied to the removal of cadmium from the mid-gut gland (MG) of scallop, Patinopecten yessoensis. Insolubilized humic acid, which has been developed in our laboratory, was used as a competitive adsorbent. A metal-complexation model was used to determine the adsorption characteristics of cadmium onto MG. Furthermore, the model was applied to the competitive adsorption system. The results showed that the competitive adsorption method enabled the simultaneous removal of toxic cadmium from both liquid and MG phase under mild acidic condition (pH 5).
| A new method of in vivo screening of thromboresistant biomaterials utilizing flow measurement
Whalen, R. L., D. L. Jeffery, et al. (1973), Trans Am Soc Artif Intern Organs 19: 19-23.
| A new numerical concept for modeling hydroxyapatite in human cortical bone
Crolet, J. M., M. Racila, et al. (2005), Comput Methods Biomech Biomed Engin 8(2): 139-43.
Abstract: This research presents a new modelling procedure which allows the computation of the physical properties of the human cortical bone, considered as a strongly heterogeneous medium consisting of bony architecture and the physical properties of the two basic components: the collagen and the hydroxyapatite (Hap). The numerical simulations are based on the homogenisation theory, however, since the size of the Hap crystals are small compared to the size of a collagen stick, a new entity (the elementary volume of mineral content (EVMC)) is defined at the nanoscopic scale. This model permits the testing of all the possible structural configurations that may be present and suggests that the anisotropy of the bone is not only induced by the haversian structure but by the properties of the Hap crystals and their special organisation.
| A new process for cell microencapsulation and other biomaterial applications: Thermal gelation and chemical cross-linking in "tandem"
Cellesi, F. and N. Tirelli (2005), J Mater Sci Mater Med 16(6): 559-65.
Abstract: The very rapid gelation of a cell- or biomolecule-containing solution is at the basis of most processes employed in microencapsulation. Adequately quick ('instantaneous') gelation kinetics are provided by a number of phenomena based on physical association. On the other hand, physical gels are inherently reversible structures, which can be solubilized or disrupted in response to often poorly controllable phenomena in the environment of application, such as dilution, changes in temperature, ion strength and composition, pH, or other physical or chemical parameters. Chemically cross-linked hydrogels would have therefore significant advantages in terms of stability and end-properties; however, the time required for chemical reactions to produce a chemically cross-linked material is in a more general case hardly compatible with microencapsulation processes. In a recent study of our laboratory we have proposed a new approach for providing both quick gelation kinetics and good stability, by simply combining the rapid kinetics of a physical hardening phenomenon with a slower chemical curing; the former process is thus responsible of the morphogenesis of the material, while the latter develops its end-properties.
| A new technique combining both polypropylene and vaginal wall sling procedures: can it minimize the risk of urethral and vaginal erosion occurring with synthetic materials?
Emir, L., D. Erol, et al. (2005), World J Urol 23(3): 221-4.
Abstract: We describe a new technique combining in situ vaginal wall and polypropylene mesh slings that may decrease potential erosive complications caused by synthetic materials. A folded mucosal patch harboring the polypropylene mesh was placed between mid-urethra and bladder neck. Using this technique, 12 consecutive women (age range 44-66 years) were operated. Preoperative evaluation included a detailed history, pelvic examination, stress test, cystourethroscopy, basic urodynamic evaluation (cystometry, Valsalva leak point pressure measurement), and urine culture. Based on these evaluations, three, seven, and two patients had type I, II, and III stress urinary incontinence, respectively. A paraurethral cyst excision was carried out in one patient and anterior colporrhaphy in four patients during the same operation. No ischemia or sloughing at the operation site occurred in any case. Pelvic examination was repeated in all patients after 3 and 6 months of follow-up and symptoms were determined after 12 months of follow-up in eight patients by telephone interview. Average follow-up was 10 months (range: 6-14 months). None of the patients were incontinent, or complained of sexual dysfunction or erosive complications after 1 year. Since there are two distinct barriers between the sling and both urethra and vagina, our technique covers all advantages of a sling procedure with synthetic materials and avoids the risk of urethral and vaginal erosion. The other advantage of this technique is the concomitant utilization of the vaginal wall as sling material.
| A new technique utilizing thermistor probes for the measurement of thermal properties of biomaterials
Bowman, H. F. and T. A. Balasubramaniam (1976), Cryobiology 13(5): 572-80.
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