|Articles about Biomaterials|
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| Effect of titanium dioxide on photostability of solid-state mequitazine
Kakinoki, K., K. Yamane, et al. (2005), Chem Pharm Bull (Tokyo) 53(9): 1092-6.
Abstract: TiO(2) has been widely used in pharmaceutical products, and it also has been used as a photocatalyst. In this study, the influence of photocatalytic activity on the stability of solid-state mequitazine, an H(1)-blocker, was investigated. The photo-degradation of mequitazine with TiO(2) occurred under irradiation with both light sources. The degree of degradation of mequitazine with anatase was higher than that of rutile. The degradation was significantly enhanced with increasing relative humidity. The relationship between the apparent degradation rate constant and water vapor pressure could be clearly described by a simple power law. The major photo-degradation products of mequitazine, resulting from photocatalytic activity of TiO(2), were mequitazine-S-oxide and mequitazine-sulphone. A remarkable degradation of mequitadine occurred with addition of TiO(2), and its photocatalytic activity was controlled by water vapor pressure. The photo-degradation of mequitazine with TiO(2) is a different process from mequitazine without TiO(2), because mequitazine-S-oxide and mequitazine-sulphone are not formed with normal photo-degradation of mequitazine.
| Effect of titanium surface texture on the cell-biomaterial interface
Jain, R. and A. F. von Recum (2003), J Invest Surg 16(5): 263-73.
Abstract: To improve the in vivo performance of engineered implants, this study examines the independent effects of surface chemistry and topography on fibroblast morphology and density in vitro. Titanium (Ti) was sputter-coated onto smooth and microtextured polyethylene terephthalate (PET). Test specimens were evaluated in 24-h, fibroblast cultures and assessed with scanning electron microscopy (SEM) for cellular morphology and density. Fibroblast density increased, as the Ti film thickness increased. The fibroblasts exhibited contact guidance on the textured test specimens. The greatest cellular density was found on the Ti-coated, textured test specimens. In conclusion, Ti and surface texture appeared to strongly influence fibroblast density and morphology as compared to PET and smooth surfaces.
| Effect of vitamin E addition to poly(D,L)-lactic acid on surface properties and osteoblast behaviour
Reno, F., V. Aina, et al. (2005), Biomaterials 26(28): 5594-9.
Abstract: Vitamin E (Vit.E, alpha-tocoferol) is a natural agent with anti-oxidative and anti-inflammatory properties and it has been suggested that it could act as a stimulating factor for osteoblast proliferation and maturation. We produced poly(D,L)-lactic acid films enriched with Vit.E (1, 5 and 10% w/w) and investigated their surface properties using the FTIR analysis, sessile measure of wettability and serum protein adsorption, and evaluated attachment and spreading of MC-3T3 E1 murine osteoblast cells. FTIR analysis showed the presence of Vit.E on the polymer surface and Vit.E increased the polymer wettability in a concentration-dependent manner. The serum total protein adsorption increased significantly onto the 10% Vit.E P(D,L)-LA and the main protein adsorbed was albumin. The presence of albumin, considered as an anti-adhesive protein, on the surface of Vit.E enriched P(D,L)-LA films (especially 5 and 10% Vit.E) could explain, at least in part, the behaviour of MC-3T3 osteoblast cells seeded onto the polymers. Cell adhesion and spreading were strongly decreased by Vit.E (5 and 10%) in spite of the increased wettability. This reaction could be cell type-specific, independent by the surface wettability and linked to cell-specific characteristics (membrane phospholipid composition, integrins expression). Moreover a direct effect of Vit.E on cell adhesion and spreading cannot be completely excluded.
| Effect of wear of bearing surfaces on elastohydrodynamic lubrication of metal-on-metal hip implants
Liu, F., Z. M. Jin, et al. (2005), Proc Inst Mech Eng [H] 219(5): 319-28.
Abstract: The effect of geometry change of the bearing surfaces owing to wear on the elastohydrodynamic lubrication (EHL) of metal-on-metal (MOM) hip bearings has been investigated theoretically in the present study. A particular MOM Metasul bearing (Zimmer GmbH) was considered, and was tested in a hip simulator using diluted bovine serum. The geometry of the worn bearing surface was measured using a coordinate measuring machine (CMM) and was modelled theoretically on the assumption of spherical geometries determined from the maximum linear wear depth and the angle of the worn region. Both the CMM measurement and the theoretical calculation were directly incorporated into the elastohydrodynamic lubrication analysis. It was found that the geometry of the original machined bearing surfaces, particularly of the femoral head with its out-of-roundness, could lead to a large reduction in the predicted lubricant film thickness and an increase in pressure. However, these non-spherical deviations can be expected to be smoothed out quickly during the initial running-in period. For a given worn bearing surface, the predicted lubricant film thickness and pressure distribution, based on CMM measurement, were found to be in good overall agreement with those obtained with the theoretical model based on the maximum linear wear depth and the angle of the worn region. The gradual increase in linear wear during the running-in period resulted in an improvement in the conformity and consequently an increase in the predicted lubricant film thickness and a decrease in the pressure. For the Metasul bearing tested in an AMTI hip simulator, a maximum total linear wear depth of approximately 13 microm was measured after 1 million cycles and remained unchanged up to 5 million cycles. This resulted in a threefold increase in the predicted average lubricant film thickness. Consequently, it was possible for the Metasul bearing to achieve a fluid film lubrication regime during this period, and this was consistent with the minimal wear observed between 1 and 5 million cycles. However, under adverse in vivo conditions associated with start-up and stopping and depleted lubrication, wear of the bearing surfaces can still occur. An increase in the wear depth beyond a certain limit was shown to lead to the constriction of the lubricant film around the edge of the contact conjunction and consequently to a decrease in the lubricant film thickness. Continuous cycles of a running-in wear period followed by a steady state wear period may be inevitable in MOM hip implants. This highlights the importance of minimizing the wear in these devices during the initial running-in period, particularly from design and manufacturing points of view.
| Effective angiostatic treatment in a murine metastatic and orthotopic hepatoma model
Raskopf, E., C. Dzienisowicz, et al. (2005), Hepatology 41(6): 1233-40.
Abstract: Vascular endothelial growth factor (VEGF) activity is correlated with a progressive tumor disease in patients with hepatocellular carcinoma (HCC). In spite of the well-recognized role of VEGF in HCC, there are few data available regarding therapeutic strategies to block VEGF activity. Therefore, we employed a recombinant adenoviral vector encoding a soluble dominant negative fragment of VEGF receptor 2 (Flk-1), AdsFlk-1, to control pre-established murine orthotopic and metastatic hepatomas. Vector function was confirmed via reverse-transcriptase polymerase chain reaction and ELISA, and angiostatic effects were analyzed in vitro and in vivo. Antitumoral effects of systemic AdsFlk-1 application were studied in a subcutaneous and orthotopic Hepa129 HCC model. Cell supernatant containing the truncated form of Flk-1 had no direct effect on cell proliferation of Hepa129 cells in vitro but reduced endothelial tube formation on matrigel matrix by approximately 80% in vitro. Endothelial-like cell infiltration into matrigel plugs in vivo was also decreased by 80%. Systemic treatment of tumor-bearing mice inhibited tumor growth by 84% compared with the corresponding control group within 16 days after vector application. Likewise, the survival rate was significantly improved in the AdsFlk-1 group compared with control. Orthotopic tumor growth was reduced by 82%, and development of malignant ascites was also retarded. In conclusion, systemic adenoviral-mediated gene transfer of an Flk-1 fragment significantly inhibited tumor growth in orthotopic and metastatic murine HCC. The data support the value of VEGF blockade as an effective target for HCC treatment.
| Effective nasal influenza vaccine delivery using chitosan
Read, R. C., S. C. Naylor, et al. (2005), Vaccine 23(35): 4367-74.
Abstract: Nasal influenza vaccination may prove to be a good alternative to parenteral injection because of the enhancement of the mucosal immune response and the ease of vaccine administration. This study investigated the use of chitosan, a bioadhesive polymer, as a nasal delivery system with inactivated, subunit influenza vaccine. Subjects received nasally 15 or 7.5 microg of the standard inactivated trivalent influenza vaccine with chitosan or 15 microg of the same vaccine intramuscularly. Serum haemagglutination inhibition (HI) titres for all three vaccine components were measured prior to, and at time points up to 14 weeks after dosing. Serum HI titres following intranasal vaccination with the nasal chitosan-influenza vaccine met the criteria set by the Committee for Proprietary Medicinal Products in terms of seroprotection rate, seroconversion rate and mean fold increase of HI titre for at least one of the three antigens in the vaccination schedules used. These data show that nasal immunisation with chitosan plus trivalent inactivated influenza is a potentially effective, easily-administered form of vaccination.
| Effectiveness of an extracellular matrix graft (OASIS Wound Matrix) in the treatment of chronic leg ulcers: a randomized clinical trial
Mostow, E. N., G. D. Haraway, et al. (2005), J Vasc Surg 41(5): 837-43.
Abstract: BACKGROUND: Venous leg ulcers are a major cause of morbidity, economic loss, and decreased quality of life in affected patients. Recently, biomaterials derived from natural tissue sources have been used to stimulate wound closure. One such biomaterial obtained from porcine small-intestine submucosa (SIS) has shown promise as an effective treatment to manage full-thickness wounds. Our objective was to compare the effectiveness of SIS wound matrix with compression vs compression alone in healing chronic leg ulcers within 12 weeks. METHODS: This was a prospective, randomized, controlled multicenter trial. Patients were 120 patients with at least 1 chronic leg ulcer. Patients were randomly assigned to receive either weekly topical treatment of SIS plus compression therapy (n = 62) or compression therapy alone (n = 58). Ulcer size was determined at enrollment and weekly throughout the treatment. Healing was assessed weekly for up to 12 weeks. Recurrence after 6 months was recorded. The primary outcome measure was the proportion of ulcers healed in each group at 12 weeks. RESULTS: After 12 weeks of treatment, 55% of the wounds in the SIS group were healed, as compared with 34% in the standard-care group (P =.0196). None of the healed patients treated with SIS wound matrix and seen for the 6-month follow-up experienced ulcer recurrence. CONCLUSIONS: The SIS wound matrix, as an adjunct therapy, significantly improves healing of chronic leg ulcers over compression therapy alone.
| Effectiveness of hydroxyapatite-vancomycin bone cement in the treatment of Staphylococcus aureus induced chronic osteomyelitis
Joosten, U., A. Joist, et al. (2005), Biomaterials 26(25): 5251-8.
Abstract: In the field of local application of antimicrobials, a number of novel drugs and/or new drug delivery systems have been developed in recent years. The present study aimed to investigate hydroxyapatite cement (HAC) as a carrier for vancomycin in the treatment of chronic osteomyelitis due to Staphylococcus aureus strains with various mechanisms of resistance. The release of vancomycin from standard test cylinders was determined in vitro and the efficacy of the delivery system was measured in vivo using a rabbit model of chronic osteomyelitis. First, powdered HAC was mixed with vancomycin at 80, 160 and 240 mg/g. After hardening, formed cylinders were eluted in phosphate buffer and antibiotic release was measured by agar diffusion. High levels of release (1512+/-318 to 1937+/-336 microg/ml) were obtained for 12 to 20 days depending on the dosage of vancomycin. Additionally, bone infection was induced in the tibia of 30 New Zealand white rabbits by injecting either a methicillin-resistant S. aureus strain (MRSA) or a S. aureus strain with a small colony variant (SCV) phenotype. After 3 weeks (chronic infection), all animals were treated by debridement. Moreover, group 1 (challenged with SCVs) and group 2 (challenged with MRSA) were treated by filling the marrow with HAC alone, whereas in groups 3 (SCVs) and 4 (MRSA) the marrow was filled with HAC/vancomycin (160 mg/g). After 6 weeks all animals were sacrificed. At 3 weeks, pathogens were detected in 24 of 30 animals. All swabs of the control groups, positive for S. aureus on day 21, were also positive on day 42 and S. aureus strains recovered were shown to be clonal to the strains used for induction of osteomyelitis. By contrast, no growth was found in the treatment group following 7 days of incubation in BHI bouillon. HAC/vancomycin-treated animals showed no histological evidence of infection on day 42. In the other groups, different stages of chronic osteomyelitis were found histologically. No local or systemic side effects due to HAC or vancomycin were seen. HAC is an effective carrier material for antibiotic compounds even in refractory infections due to MRSA or S. aureus SCVs.
| Effectiveness of some means using against root rot on parsley seedling root
Nawrocki, J. and S. Mazur (2004), Commun Agric Appl Biol Sci 69(4): 693-6.
Abstract: The results of a two-year study concern the effectiveness of 4 substances--biopreparate Chitosol (beta-1,4 D-glucosamine polymer) and fungicides: Rovral Flo 255 SC (BAS iprodione 255 g/dm3), Sportak Alpha 380 EC (BAS prochloraz 0,300 dm3/dm3 and carbendazim 80 g/dm3) and Zaprawa Funaben T (carbendazim 20% + tiuram 45%)--used against root rot and plant rot was described. These experiments were conducted in glasshouse and field conditions. Root of parsley cultivar Berlinska were treated one of tested substances autumn before storage period in clamp or spring immediately before planting seedling roots. The results showed that autumn dressing was ineffective, indices of root infestation were similar in each combination including control in both years of observation. Spring dressing was better, but not only in controls were many parsley plants decaying in the fields. Among substances used for spring dressing of seedling roots, the best efficacy exhibited Zaprawa Funaben T and Sportak Alpha 380 EC.
| Effectiveness of the concomitant use of bivalirudin and drug-eluting stents (from the prospective, multicenter BivAlirudin and Drug-Eluting STents [ADEST] study)
Dangas, G., Z. Lasic, et al. (2005), Am J Cardiol 96(5): 659-63.
Abstract: Sirolimus-eluting stents (SESs) reduce restenosis compared with bare metal stents. Safety issues with drug-eluting stents are particularly important given concerns of possible increased thrombogenicity. Compared with heparin plus glycoprotein IIb/IIIa inhibitors, the direct thrombin inhibitor bivalirudin has been shown to reduce the risk of hemorrhagic complications in patients receiving bare metal stents, with similar efficacy in preventing ischemic complications. The safety and efficacy of percutaneous coronary intervention (PCI) with SESs and bivalirudin anticoagulation have not been prospectively studied. This prospective study performed at 9 United States hospitals evaluated 1,182 patients referred for PCI with SESs in whom the procedural anticoagulant was bivalirudin. Clopidogrel was administered before PCI in 79% of patients, and only 5.3% received procedural glycoprotein IIb/IIIa inhibitors. At 30 days, major adverse cardiac events occurred in 7.1% of patients, including 0.3% mortality, 4.4% myocardial infarction (defined as creatine kinase-MB >3x normal), 1.7% target vessel revascularization, and 0.6% stent thrombosis. Major bleeding occurred in only 0.8% of patients. Thus, use of bivalirudin as the procedural anticoagulant to support SES implantation in a "real world" population of patients undergoing PCI results in low rates of major adverse cardiac events, stent thrombosis, and major bleeding.
| Effectiveness of three extraction techniques in the development of a decellularized bone-anterior cruciate ligament-bone graft
Woods, T. and P. F. Gratzer (2005), Biomaterials 26(35): 7339-49.
Abstract: In this study, porcine bone-anterior cruciate ligament-bone (B-ACL-B) grafts were decellularized using one of three protocols incorporating surfactants lauryl sulfate (SDS), Triton X-100, and/or an organic solvent (tributyl phosphate (TnBP)). The effectiveness of Triton-SDS, Triton-Triton or Triton-TnBP treatments in removing cellular materials was determined and possible changes in biochemical composition and mechanical properties due to each treatment were investigated. Treatment with Triton-SDS was most effective at removing cell nuclei and intracellular protein (vimentin) from the ACL but affected both the collagen and glycosaminoglycan (GAG) components of the extracellular matrix while increasing the tensile stiffness of the ligament. Triton-Triton was the least effective of the three treatments in terms of cellular extraction, but did not significantly change the mechanical and biochemical properties of the ACL. Triton-TnBP matched the level of decellularization achieved by Triton-SDS in terms of visible cell nuclei; however, the extraction of intracellular vimentin was less consistent. TnBP treatment also slightly decreased the collagen content of the ACL but did not alter its mechanical properties. Overall, all three decellularization treatments maintained adequate mechanical and biochemical properties of B-ACL-B grafts to justify the further investigation of all three decellularization protocols. The selection of a superior treatment will depend on future studies of the propensity of treated tissues for repopulation by host ACL fibroblasts and, ultimately, on any immunogenic and/or remodeling host response induced in vivo.
| Effects of "wettability" of biomaterials on culture cells
Yanagisawa, I., H. Sakuma, et al. (1989), J Oral Implantol 15(3): 168-77.
Abstract: New objectives of the development of biomaterials in recent years include how to control surface characteristics of materials and the attachment of cells to implant sites. This study clarified the effect of "wettability" of materials on culture cells, with wettability being expressed by the contact angle of the material to the water. First, low-temperature plasma treatment was administered so that samples of the same materials and shapes could be obtained, differing only in wettability. The contact angles at the surfaces of the samples and their surface roughness were then measured, and surfaces were analyzed by ESCA. For clarification of the biological response of the cell to wettability, attachment of connective tissues and epithelial-tissue-originated established cell lines to the material and its cell spreading were investigated in each test sample. As a result, it was found that the contact angle of each material used in the experiment affected both the cell attachment and spreading rates; thus, wettability of biomaterials is considered to be an important parameter of biological effect at the cell level.
| Effects of a laminin peptide (YIGSR) immobilized on crab-tendon chitosan tubes on nerve regeneration
Itoh, S., A. Matsuda, et al. (2005), J Biomed Mater Res B Appl Biomater 73(2): 375-82.
Abstract: Thiolated and nonthiolated hydroxyapatite-coated crab-tendon chitosan (t-chitosan/HAp-SH and t-chitosan/HAp, respectively) tubes, both alone and conjugated with CDPGYIGSR (YIGSR) peptide, were compared, in order to determine their biocompatibility and efficacy as nerve conduits. YIGSR peptide was adsorbed on the t-chitosan/HAp (HAp) tubes, and covalently bound on the t-chitosan/HAp-SH (HAp-SH) tubes (Y/HAp and Y/HAp-SH tubes, respectively). HAp, HAp-SH, Y/HAp, or Y/HAp-SH tubes measuring 15 mm were bridge grafted into the sciatic nerve of SD rats. Grafting of 15-mm-long Type I atelocollagen tubes and isografting of sciatic nerves were also carried out (N = 6 in each group). After 12 weeks, evoked muscle action potentials were recorded to calculate the terminal latency quotient. Histological observation and analysis of myelinated axons were also carried out. Nerve-tissue regeneration did not occur directly on the tubes' surfaces in the YIGSR peptide-unconjugated groups. Transplantation of YIGSR-conjugated tubes, however, gave rise to regenerated nerve tissue attached to thin layers of epineurium-like structure formed on the inner-tube surface. Histological and electrophysiological analyses suggested that although thiolation retards nerve-tissue regeneration, adsorbed YIGSR, and, to a lesser extent, peptide that had been covalently bound onto the tube surfaces, enhance nerve regeneration, promoting sprouting from the proximal nerve stump and bridging of regenerated axons throughout the tube.
| Effects of a new bone-inducing biomaterial on mesenchymal cells in vitro
Joos, U. E., E. Fehrenbach, et al. (1992), Artif Organs 16(4): 354-60.
Abstract: A purified bone-inducing protein complex (BIC), isolated from bovine bone and causing de novo bone formation in vivo, induces defined effects on rat mesenchymal cells in vitro. Spindle-like mesenchymal cells growing in monolayers change to polygonal cells, forming a multilayered growth pattern. The mesenchymal cells acquire alkaline phosphatase activity. Upon culture with BIC, the typical collagen Type III deposition of these mesenchymal cells is remarkably reduced whereas the collagen Type I expression remains unaffected. All these in vitro effects are consistent with the strong bone-forming capacity of BIC in vivo. A combination of two cytokines, transforming growth factor beta 1 (TGF beta 1) and epidermal growth factor (EGF), shows a similar activity to BIC. Neutralizing anti-TGF beta antibodies interfere with all in vitro effects of BIC. The neutralization of BIC and the inductive capacity of the combination of TGF beta 1 plus EGF point to the substantial role of TGF beta or TGF beta-like molecules in BIC; whether the active polypeptides are identical to TGF beta or somewhat structurally homologous to TGF beta remains to be elucidated.
| Effects of a positively charged biomaterial for dermal and subcutaneous augmentation
Eppley, B. L., D. J. Summerlin, et al. (1994), Aesthetic Plast Surg 18(4): 413-6.
Abstract: Based on previous experimental connective tissue work, the use of a positively charged dextran-based biomaterial in subcutaneous tissue sites was evaluated. After hydration with saline, the biomaterial was injected beneath the abdominal skin in rats. A robust macrophage response was initially seen at 30 days without acute inflammation. By one year postoperatively, extensive intermaterial fibroblast and collagen ingrowth had occurred. No evidence of a foreign-body or chronic inflammatory response was seen. These preliminary findings suggest good tissue compatibility of this biomaterial and suggests that when combined with a biocompatible liquid medium, the potential for development of a bioactive dermal and subcutaneous injectable substance exists.
| Effects of adhesion molecules on the behavior of osteoblast-like cells and normal human fibroblasts on different titanium surfaces
Park, B. S., S. J. Heo, et al. (2005), J Biomed Mater Res A 74(4): 640-51.
Abstract: This study examined the influences of titanium (Ti) discs with similar surface roughnesses (R(a) values), but with different topographies and chemical compositions, on the adhesion, spreading, and the alkaline phosphatase (ALP) activity of osteoblast-like cells and normal human fibroblasts. The presence of adhesion molecules on the Ti surfaces and their effects on cell activity were also investigated. Two types of Ti discs were prepared. One kind was a mechanically polished Ti disc, and the other type was a disc obtained by the heating of hydroxyapatite (HA) dip-coated Ti. Scanning electron microscopy, optical interferometry, and scanning Auger electron spectroscopy were used to examine the surface morphology, roughness, and chemical composition, respectively, of the superficial Ti layer. The two types of Ti discs had different topographies and chemical compositions, but had similar R(a) values. The cells on both surface types had similar behaviors and ALP activities. A biological evaluation of the surface-modified Ti discs showed that the type I collagen coating was functionally active in terms of cell spreading in both types of Ti discs. In the mechanically polished Ti discs, fibronectin was functionally active in the normal human fibroblasts, but not in the osteoblast-like cells. Cell adhesion was slightly better on the heat-treated HA dip-coated Ti discs, but not on the mechanically polished Ti discs. Type I collagen and fibronectin mediated the adhesion and spreading of osteoblast-like cells through alpha2beta1 integrin and alpha5beta1 integrin, respectively. These results suggest that type I collagen might be a good candidate for the biochemical modification of Ti surfaces, particularly those surfaces obtained by heating of HA dip-coated Ti.
| Effects of adsorbed heat labile serum proteins and fibrinogen on adhesion and apoptosis of monocytes/macrophages on biomaterials
Brodbeck, W. G., E. Colton, et al. (2003), J Mater Sci Mater Med 14(8): 671-5.
Abstract: A previously established human monocyte culture protocol was used to determine the effects of varying adsorbed proteins on monocyte/macrophage adhesion and survival on dimethyl-silane (DM) or RGD modified glass coverslips. Cells were allowed to adhere for 2 h in the absence of protein or in the presence of serum, fibrinogen (Fg), heat inactivated serum (HIS), serum supplemented with Fg or HIS with Fg. Cell adhesion and apoptosis rates were determined on days 0 (2 h), 3, 7 and 10 of culture. The presence of serum alone in the initial culture was sufficient to optimize monocyte/macrophage adhesion and survival rates. Adding Fg to serum did not increase adhesion nor decrease apoptotic rates. No protein or the addition of HIS during the initial incubation period significantly decreased monocyte/macrophage adhesion and survival on both surfaces, however, the addition of Fg to HIS restored adhesion and survival rates to those seen with in the presence of serum alone on RGD surfaces. These studies demonstrate that monocyte/macrophage adhesion and survival on biomaterial surfaces are optimized by adsorbed heat labile serum proteins while adsorbed Fg plays a surface property-dependent role.
| Effects of alginate coated on PLGA microspheres for delivery tetracycline hydrochloride to periodontal pockets
Liu, D. Z., W. P. Chen, et al. (2004), J Microencapsul 21(6): 643-52.
Abstract: The effects of alginate coated on tetracycline (Tc) loaded poly (D, L-lactic-co-glycolic acid) (PLGA) microspheres fabricated by double emulsion solvent evaporation technique for local delivery to periodontal pocket were investigated. Alginate coated PLGA microspheres showed smoother surface but enlarged their particle sizes compared with those of uncoated ones. In addition, alginate coated microspheres enhanced Tc encapsulation efficiency (E.E.) from 11.5 +/- 0.5% of uncoated ones to 17.9 +/- 0.5%. Moreover, all of the coated PLGA microspheres even fabricated at different conditions could prolong Tc release from 9-12 days with 50% or higher in cumulative release of Tc compared with those of uncoated ones. The swelling ratios of PLGA microspheres for alginate coated or uncoated ones, one of the possible mechanisms for enhancing Tc release for the coated ones, were measured. The results showed that 20% or higher in swelling ratio for the coated microspheres at the earlier stage of hydration (e.g. < or = 24 h) could be an important factor to result in high Tc release compared to the uncoated ones. In conclusion, alginate coated Tc loaded PLGA microspheres could enhance Tc delivery to periodontal pocket by enhancing drug encapsulated efficiency, released quantities and sustained release period compared with uncoated ones.
| Effects of alginate encapsulation on mitochondrial activity
Oca-Cossio, J., N. E. Simpson, et al. (2005), J Mater Sci Mater Med 16(6): 521-4.
Abstract: The long-term objective of our research is to study the biochemical consequences of primary genetic defects of the Pyruvate Dehydrogenase Complex, a key mitochondrial enzyme complex, by NMR spectroscopy. An established method to obtain energetic and metabolic information from intact cells involves the use of 31P and 13C NMR spectroscopic techniques. NMR spectra from live and fully functional cells can be obtained from cells encapsulated within alginate beads and maintained in a perfusion bioreactor throughout the NMR experiment. However, before spectroscopic studies can commence, the effects of alginate encapsulation on the general metabolism and mitochondrial activity of fibroblasts need to be determined. in this study we report glucose consumption and flow cytometry measurements (with the fluorescent markers MitoTracker GreenFM and Nonyl-acridine Orange to determine the mitochondrial status and mass) of healthy human fibroblasts encapsulated in a mannuronic acid-rich alginate matrix. The results show that alginate encapsulation of fibroblasts does not affect the glucose consumption, the mitochondrial integrity, or the mitochondrial mass during 21 days of in vitro culture.
| Effects of an avidin-biotin binding system on chondrocyte adhesion and growth on biodegradable polymers
Tsai, W. B. and M. C. Wang (2005), Macromol Biosci 5(3): 214-21.
Abstract: Cell adhesion to a scaffold is a prerequisite for tissue engineering. Many studies have been focused on enhancing cell adhesion to synthetic materials that are used for scaffold fabrication. In this study, we applied an avidin-biotin binding system to enhance chondrocyte adhesion to biodegradable polymers. Biotin molecules were conjugated to the cell membrane of chondrocytes, and mediated cell adhesion to avidin-coated surfaces. We demonstrated that immobilization of biotin molecules to chondrocyte surfaces enhanced cell adhesion to avidin-coated biodegradable polymers such as poly(L-lactic acid), poly(D,L-lactic acid), and polycaprolactone, compared to the adhesion of normal chondrocytes to the same type of biodegradable polymer. The biotinylated chondrocytes still maintained their proliferation ability. This study showed the promise of applying the avidin-biotin system in cartilage tissue engineering. [diagram in text].
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