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Results for “Biodegradation”

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At least 901 records · Page 50Linked to original sources

PubMed2005

Development of a perforated biodegradable interference screw.

PURPOSE: The objective was to develop a perforated biodegradable interference screw to allow for enhanced osseous implant integration without impairing screw stability during insertion. TYPE OF STUDY: Mechanical testing, followed by animal study. METHODS: At first, manual perforation of 8 x 23-mm biodegradable poly-(L-co-D,L-lactide) interference screws was performed, using 3 different perforation patterns (clockwise spiral, counter-clockwise spiral, and parallel perforation), followed by torsional tests. Next, parallel perforated screws (n = 6) and unperforated control screws (n = 6) were applied to the proximal tibia of 12 sheep. The sheep were put down after 24 weeks and the screw site was examined histologically. Subsequently, molding of a parallel perforated screw followed by torsional tests was undertaken. RESULTS: The parallel perforated screw presented a torsional strength insignificantly different from the unperforated control screw and well beyond the reported maximum manual insertion torques of biodegradable interference screws in young human bone. When compared with the regular unperforated interference screw, the molded perforated screw exhibited a torsional strength of 91%, indicating a secure surgical application. In contrast to the unperforated screw, histologic evaluations revealed clear bone ingrowth into the perforations including the core of the perforated interference screw. CONCLUSIONS: Perforated, "cage-like" interference screws may be promising for the acceleration of osseous implant integration into the bone with a very low risk of screw breakage during insertion. CLINICAL RELEVANCE: To ameliorate osseous implant integration and possibly enhance ossification of former implant site in anterior cruciate ligament surgery.

Absorbable Implants↗

PubMed2006

False magnetic resonance imaging persistence of a biodegradable anterior cruciate ligament interference screw with chronic inflammation after 4 years in vivo.

Surgeons should be aware that the degradation kinetics of biodegradable implants likely influence the rate of osseous integration, and depend on numerous factors such as polymer weight, crystallinity, and stereocopolymer ratio. We present a case of inflammatory reaction at a polylactide tibial interference screw site more than 4 years after primary anterior cruciate ligament (ACL) reconstruction. This inflammation was presumptively treated as an infection with surgical irrigation and debridement. Preoperatively, the screw was clearly delineated by magnetic resonance imaging (MRI), yet was grossly absent at surgery. Postoperative MRI confirmed thorough debridement and complete absence of the screw. This report shows that not only can a late inflammatory reaction occur, after up to 4 years in vivo, but that the MRI may show a persistent screw despite significant biodegradation. False MRI-persistent screws should be considered when critically reviewing studies that use MRI in the methods for evaluating biodegradable implants. More importantly, false MRI-persistent screws may have significant ramifications when planning revision surgery after primary ACL reconstruction having used interference screws that can degrade over several years.

Absorbable Implants↗

PubMed2006

Arthroscopic stabilization of superior labral (SLAP) tears with biodegradable tack: outcomes to 2 years.

PURPOSE: This prospective study aimed to document the pain and functional outcomes, over time, of patients whose SLAP lesions had been repaired with biodegradable tacks. METHODS: Superior labral tears were identified in 24 patients from a cohort of 500 patients who had shoulder problems sufficiently disabling to warrant arthroscopic evaluation and management. These labral tears were arthroscopically repaired with 1 to 3 biodegradable tacks (mean, 1.6). Before surgery, all patients completed a questionnaire regarding their shoulder pain and function and were given a systematic clinical examination. To observe their postoperative outcomes over time, the same assessments were made at 2 weeks, 6 weeks, 3 months, 6 months, 1 year, and 2 years after surgery. RESULTS: After labral reattachment, decreases were noted in the patients' mean shoulder pain scores at rest (64% at 3 months), at night (76% at 3 months), and with activity (73% at 6 months). The most significant reductions in mean scores occurred between 6 and 12 weeks (P < .001). Patient-perceived weakness, instability, and stiffness scores also improved from week 6. The ranking of the patients' "overall problem" reduced from an average ranking of "severe" to "mild" by the third preoperative month (P < .001) and was still at this level by the time of their 2-year follow-up appointment. Activity levels for 22 of 24 patients returned to their preinjury levels by 6 months after surgery. CONCLUSIONS: Arthroscopically delivered biodegradable tacks effectively managed superior labral tears and, on average, resulted in a near-complete improvement of pain and recovery of function by 3 months. These good outcomes did not improve further or deteriorate at the 2-year follow-up appointment. LEVEL OF EVIDENCE: Level IV, therapeutic case series.

Absorbable Implants↗

PubMed2005

Novel tissue-engineered biodegradable material for reconstruction of vascular wall.

BACKGROUND: To solve several problems with artificial grafts, we sought to develop a novel bioengineered material that can promote tissue regeneration without ex vivo cell seeding and that has sufficient durability to be used for artery reconstruction. Here, we tested whether this biodegradable material could accelerate the in situ regeneration of autologous cardiovascular tissue, especially of the arterial wall, in various models of cardiovascular surgeries. METHODS: The tissue-engineered patch was fabricated by compounding a collagen-microsponge with a biodegradable polymeric scaffold composed of polyglycolic acid knitted mesh, reinforced on the outside with woven polylactic acid. Tissue-engineered patches without precellularization were grafted into the porcine descending aorta (n = 5), the porcine pulmonary arterial trunk (n = 8), or the canine right ventricular outflow tract (as the large graft model; n = 4). Histologic and biochemical assessments were performed 1, 2, and 6 months after the implantation. RESULTS: There was no thrombus formation in any animal. Two months after grafting, all the grafts showed good in situ cellularization by hematoxylin/eosin and immunostaining. The quantification of the cell population by polymerase chain reaction showed a large number of endothelial and smooth muscle cells 2 months after implantation. In the large graft model, the architecture of the patch was similar to that of native tissue 6 months after implantation. CONCLUSIONS: A tissue-engineered patch made of our biodegradable polymer and collagen-microsponge provided good in situ regeneration at both the venous and arterial wall, suggesting that this patch can be used as a novel surgical material for the repair of the cardiovascular system.

Absorbable Implants↗

PubMed2005

Phospholipase A2 pathway association with macrophage-mediated polycarbonate-urethane biodegradation.

Activation of the phospholipase A2 (PLA2) pathway is a key cell signaling event in the inflammatory response. The PLA2 family consists of a group of enzymes that hydrolyze membrane phospholipids, resulting in the liberation of arachidonic acid (AA), a precursor to pro-inflammatory molecules. Given the well-documented activating role of biomaterials in the inflammatory response to medical implants, the present study investigated the link between PLA2 and polycarbonate-based polyurethane (PCNU) biodegradation, and the effect that material surface had on PLA2 activation in the U937 cell line. PCNUs were synthesized with poly(1,6-hexyl 1,2-ethyl carbonate)diol, 1,4-butanediol and one of two diisocyanates (hexane 1,6-diisocyanate or 4,4'-methylene bisphenyl diisocyanate) in varying stoichiometries and incubated with adherent U937 cells. PLA2 inhibiting agents resulted in significantly decreased PCNU biodegradation (p < 0.05). Moreover, when activation of PLA2 was assessed (3H-AA release), significantly more 3H-AA was released from PCNU-adherent U937 cells than polystyrene-adherent U937 cells (p < 0.05) which was significantly decreased in the presence of PLA2 inhibitors. The pattern of inhibition of U937 cell-mediated biodegradation and 3H-AA release that was modulated by PCNU surface differences, suggests a role for secretory PLA2 along with cytosolic PLA2. Understanding PCNU activation of intracellular pathways, such as PLA2, will allow the design of materials optimized for their intended use.

Absorbable Implants↗

PubMed2005

Preparation and characterization of highly porous, biodegradable polyurethane scaffolds for soft tissue applications.

In the engineering of soft tissues, scaffolds with high elastance and strength coupled with controllable biodegradable properties are necessary. To fulfill such design criteria we have previously synthesized two kinds of biodegradable polyurethaneureas, namely poly(ester urethane)urea (PEUU) and poly(ether ester urethane)urea (PEEUU) from polycaprolactone, polycaprolactone-b-polyethylene glycol-b-polycaprolactone, 1,4-diisocyanatobutane and putrescine. PEUU and PEEUU were further fabricated into scaffolds by thermally induced phase separation using dimethyl sulfoxide (DMSO) as a solvent. The effect of polymer solution concentration, quenching temperature and polymer type on pore morphology and porosity was investigated. Scaffolds were obtained with open and interconnected pores having sizes ranging from several mum to more than 150 microm and porosities of 80-97%. By changing the polymer solution concentration or quenching temperature, scaffolds with random or oriented tubular pores could be obtained. The PEUU scaffolds were flexible with breaking strains of 214% and higher, and tensile strengths of approximately 1.0 MPa, whereas the PEEUU scaffolds generally had lower strengths and breaking strains. Scaffold degradation in aqueous buffer was related to the porosity and polymer hydrophilicity. Smooth muscle cells were filtration seeded in the scaffolds and it was shown that both scaffolds supported cell adhesion and growth, with smooth muscle cells growing more extensively in the PEEUU scaffold. These biodegradable and flexible scaffolds demonstrate potential for future application as cell scaffolds in cardiovascular tissue engineering or other soft tissue applications.

Absorbable Implants↗

PubMed2005

Evaluation of biodegradable synthetic scaffold coated on arterial prostheses implanted in rat subcutaneous tissue.

Polyester arterial prostheses impregnated with various synthetic biodegradable materials and with gelatin were implanted subcutaneously in rats for 3-180 days. The inflammation was assessed by quantifying the activity of alkaline phosphatase and by histology. The degradation of the scaffold materials was determined by scanning electron microscopy (SEM), size exclusion chromatography (SEC), and differential scanning calorimetry (DSC). The alkaline phosphatase activity induced by the polymer-impregnated grafts was similar to that induced by the non-impregnated controls during most of the post-implantation periods. Histological studies revealed that the acute inflammatory response was moderate to mild and was similar for all types of specimens, except for the gelatin-impregnated grafts that induced a severe acute inflammation during the first 2 weeks post-implantation. At 4 and 6 months, significant disintegration of the scaffold was observed, accompanied by enhanced tissue infiltration and a reactivation of the acute inflammatory phase. Linear and exponential degradation rates of the synthetic polymers were described. The relative degradation rates of the biodegradable polymers were ranked as following: PLLACL > PDLLA > PLLA > PCEL. In conclusion, biodegradable polymers may provide an option as sealant/scaffolding materials for vascular prosthesis. It is suggested that the degradation rate of the polymer scaffolding materials should be higher to achieve early healing while without inducing strong inflammation.

Absorbable Implants↗

PubMed2005

Microintegrating smooth muscle cells into a biodegradable, elastomeric fiber matrix.

Electrospinning permits fabrication of biodegradable elastomers into matrices that can resemble the scale and mechanical behavior of the native extracellular matrix. However, achieving high-cellular density and infiltration with this technique remains challenging and time consuming. We have overcome this limitation by electrospraying vascular smooth muscle cells (SMCs) concurrently with electrospinning a biodegradable, elastomeric poly(ester urethane)urea (PEUU). Trypan blue staining revealed no significant decrease in cell viability from the fabrication process and electrosprayed SMCs spread and proliferated similar to control unprocessed SMCs. The resulting SMC microintegrated PEUU constructs were cultured under static conditions or transmural perfusion. Higher cell numbers resulted with perfusion culture with 131% and 98% more viable cells versus static culture at days 4 and 7 (p<0.05). Fluorescent imaging and hematoxylin and eosin staining further illustrated high cell densities integrated between the elastomeric fibers after perfusion culture. SMC microintegrated PEUU was strong, flexible and anisotropic with tensile strengths ranging from 2.0 to 6.5 MPa and breaking strains from 850 to 1,700% dependent on the material axis. The ability to microintegrate smooth muscle or other cell types into a biodegradable elastomer fiber matrix embodies a novel tissue engineering approach that could be applied to fabricate high cell density elastic tissue mimetics, blood vessels or other cardiovascular tissues.

Absorbable Implants↗

PubMed2005

Highly effective and slow-biodegradable network-type cationic gene delivery polymer: small library-like approach synthesis and characterization.

Over the past years, macromolecular biodegradable polymers have been attracting considerable attention as gene delivery vehicles due to their safety and many potential applications. In the process of developing such biopolymers, we synthesized a biodegradable, network-type poly(amino ester) polymer (nt-PAE), which showed desirable chemical properties and a mechanical durability with high transfection efficiency. A small library-like approach to polymer synthesis using melt polycondensation followed by surface modification with aminohexanoic acid resulted in the final polymer, nt-PAE. The network-type structure of nt-PAE consists of biodegradable ester linkages and tertiary amines embedded in the backbone, and primary amines positioned at the surface. Unlike other rapidly degrading ester polymers, the nt-PAE exhibited fairly slow degradation, as the polymer sustained its DNA complexing ability for 10 days under physiological buffer conditions. In addition, the transfection efficiency of the nt-PAE could be increased to the same level comparable with that of PEI even in the presence of serum. Low toxicity and high transfection efficiency with a slow degradation profile implies that the nt-PAE can be used as a valuable nonviral gene delivery system.

Biocompatible Materials↗

PubMed2006

Biodegradable nanoparticles of amphiphilic triblock copolymers based on poly(3-hydroxybutyrate) and poly(ethylene glycol) as drug carriers.

New amorphous amphiphilic triblock copolymers of poly(3-hydroxybutyrate)-poly(ethylene glycol)-poly(3-hydroxybutyrate) (PHB-PEG-PHB) were synthesized using the ring-opening copolymerization of beta-butyrolactone monomer. They were characterized by fluorescence, SEM and (1)H NMR. These triblock copolymers can form biodegradable nanoparticles with core-shell structure in aqueous solution. Comparing to the poly(ethylene oxide)-PHB-poly(ethylene oxide) (PEO-PHB-PEO) copolymers, these nanoparticles exhibited much smaller critical micelle concentrations and better drug loading properties, which indicated that the nanoparticles were very suitable for delivery carriers of hydrophobic drugs. The drug release profile monitored by fluorescence showed that the release of pyrene from the PHB-PEG-PHB nanoparticles exhibited the second-order exponential decay behavior. The initial biodegradation rate of the PHB-PEG-PHB nanoparticles was related to the enzyme amount, the initial concentrations of nanoparticle dispersions and the PHB block length. The biodegraded products detected by (1)H NMR contained 3HB monomer, dimer and minor trimer, which were safe to the body.

Absorbable Implants↗

PubMed2006

2,4-Dichlorophenoxyacetic acid (2,4-D) biodegradation in river sediments of Northeast-Scotland and its effect on the microbial communities (PLFA and DGGE).

A bench-scale study was conducted to investigate 2,4-D biodegradation rates at different concentrations (10, 100 and 1000 microg per gram of dry weight) in distinct sediments samples collected on the River Ythan, Northeast-Scotland. Mineralisation of 14C 2,4-D occurred mostly within 30 days for all tested concentrations with a degradation rate ranging from 5 to 750 microg d(-1). Biodegradation rates were affected by the biological and biochemical characteristics of the indigenous microbial community in the studied sediments rather than factors such as compound bioavailability and/or toxicity. PLFA-profiling provided evidences of the effect of 2,4-D amendments on the microbial communities and DGGE-profiling showed changes in the genetic potential of the microbial populations which might affect metabolic characteristics of the sediment. PLFAs biomarkers suggested that the pathway of alpha-ketoglutarate-dependent dioxygenase was the main route of 2,4-D biodegradation. This pathway is commonly found in microorganisms of the beta-subdivision of proteobacteria.

2,4-Dichlorophenoxyacetic Acid↗

PubMed2004

A retrospective evaluation of rigid fixation in orthognathic surgery using a biodegradable self-reinforced (70L:30DL) polylactide.

OBJECTIVE: This study was designed to evaluate clinical and radiological evidence of osteotomy site healing in orthognathic surgery after rigid fixation using a biodegradable plating system. STUDY DESIGN: A follow up of 30 patients who underwent orthognathic surgery using a biodegradable self-reinforced (70L:30DL) polylactide plating system was presented. The follow-up schedule for all patients consisted of regular appointments at 1-180 days after surgery. Clinical evaluation involved notation of any abnormal swelling, infection, discoloration, or discharge at the osteotomy sites. Stability was evaluated by manual palpation. For radiographic evaluation, panoramic radiographs were taken immediately after surgery, and again at 7-180 days. The radiographs were analyzed for any visual changes in osteotomy fragments, resorptive changes in osteotomy fragments, callus formation, and union of the osteotomy segments. RESULTS: No clinical complications and no radiological changes in the osteotomy sites were observed. Regarding the clinical usefulness of the biodegradable fixation system, fixation at the time of operation was considered as excellent in all 30 cases. CONCLUSIONS: The conclusions of this study were that self-reinforced (70L:30DL) polylactide was considered to be comparable to other forms of rigid internal fixation for orthognathic surgery.

Absorbable Implants↗

PubMed2005

Fixation of zygomatic fractures with a biodegradable copolymer osteosynthesis system: short- and long-term results.

Biodegradable osteosynthesis devices can be viewed as addition to, not yet replacement for conventional metal osteosynthesis materials. In a series of 65 patients with zygomatic fractures, a short-term complication/sequelae rate of 22.8% and a long-term complication rate of 9.4% were recorded. Lactosorb plates, panels and screws were the only devices used for osteosynthesis. All complications associated with the biodegradable material could be considered minor and were resolved by the use of minor surgical procedures or conservative measures. The results of this study indicate that treatment of zygomatic fractures with biodegradable osteosynthesis material has no major long-term adverse effects beyond the total material resorption time.

Absorbable Implants↗

PubMed2006

Preparation of prefabricated vascularized bone graft with neoangiogenesis by combination of autologous tissue and biodegradable materials.

Prefabricated vascularized bone grafts have previously been prepared by combining an autologous vessel bundle with auto-particulate cancellous bone and marrow (PCBM) and a biodegradable membrane. Only small quantities of low-density vascularized bone tissue have been formed using this method. The authors of the present study combined beta-tricalcium phosphate (beta-TCP), a biodegradable ceramic, with a prefabricated vascularized bone graft to augment osteogenesis. A saphenous vessel bundle from a rat was wrapped in a biodegradable membrane. Then, autologous PCBM was mixed with beta-TCP granules and packed into the rolled membrane. In the control group, beta-TCP was omitted. Bone formation was histologically assessed 6 and 9 weeks after implantation. The volume of newly formed bone tissue in the rolled membrane was greater in the presence of beta-TCP granules than in the control. Microvessels had formed throughout the new bone tissue. When a prefabricated vascularized bone graft was onlay-grafted to the femur of the same rat, the prefabricated vascularized bone graft directly fused to the cortical surface of the femur, with no intervening fibrous tissue. These findings suggest that beta-TCP in combination with PCBM enhances the volume and density of bone tissue in prefabricated vascularized bone grafts.

Absorbable Implants↗

PubMed2005

In vivo tumor transfection mediated by polyplexes based on biodegradable poly(DMAEA)-phosphazene.

In recent years, increasing interest is being paid to the design of transfectants based on non-toxic and biodegradable polymers for gene therapy purposes. We recently reported on a novel, biodegradable polymer, poly(2-dimethylamino ethylamino)phosphazene (p(DMAEA)-ppz) for use in non-viral gene delivery. In this study, the biodistribution and in vivo transfection efficiency of polyplexes composed of plasmid DNA and p(DMAEA)-ppz were investigated after intravenous administration in tumor bearing mice. Data were compared with those of polyplexes based on the non-biodegradable polyethylenimine (PEI 22kDa). Both polyplex systems were rapidly cleared from the circulation (<7% ID, at 60 min after administration) and showed considerable disposition in the liver and the lung, all in line with earlier work on cationic polyplex systems. The lung disposition is attributed to aggregates formed by interaction of the polyplexes with blood constituents. Redistribution of the polyplexes from the lung was observed for both polyplex formulations. Importantly, both polyplex systems showed a substantial tumor accumulation of 5% and 8% ID/g for p(DMAEA)-ppz and PEI22 polyplexes, respectively, at 240 min after administration. The tumor disposition of the p(DMAEA)-ppz and PEI22 polyplexes was associated with considerable expression levels of the reporter gene. In contrast to PEI22 polyplexes, p(DMAEA)-ppz polyplexes did not display substantial gene expression in the lung or other organs (organ gene expression<1/100 of tumor gene expression). The observed preferential tumor gene expression mediated by the p(DMAEA)-ppz polyplexes enables the application of this polymer to deliver therapeutic genes to tumors.

Animals↗

PubMed2006

Molecular design of biodegradable polymeric micelles for temperature-responsive drug release.

We designed thermo-responsive and biodegradable polymeric micelles for an ideal drug delivery system whose target sites are where external stimuli selectively release drugs from the polymeric micelles. The thermo-responsive micelles formed from block copolymers that were composed both of a hydrophobic block and a thermo-responsive block. Poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) showing a lower critical solution temperature (LCST) around 40 degrees C was synthesized for the thermo-responsive block, while biodegradable poly(D,L-lactide), poly(epsilon-caprolactone), or poly(D,L-lactide-co-epsilon-caprolactone) was used for the hydrophobic block. By changing both the block lengths of the poly(D,L-lactide)-containing block copolymers, physical parameters such as micelle diameter and critical micelle concentration were varied. On the other hand, the choice of the hydrophobic block was revealed to be critical in relation to both on the thermo-responsive release of the incorporated anti-cancer drug, doxorubicin, and the temperature-dependent change of the hydrophobicity of the micelles' inner core. One polymeric micelle composition successfully exhibited rapid and thermo-responsive drug release while possessing a biodegradable character.

Antibiotics, Antineoplastic↗

PubMed2006

Simultaneous removal of phenol, ammonium and thiocyanate from coke wastewater by aerobic biodegradation.

A laboratory-scale activated sludge plant composed of a 20 L volume aerobic reactor followed by a 12 L volume settling tank and operating at 35 degrees C was used to study the biodegradation of coke wastewater. The concentrations of ammonium nitrogen (NH(4)(+) -N), phenols, chemical oxygen demand (COD) and thiocyanate (SCN(-)) in the wastewater ranged between 504 and 2,340, 110 and 350, 807 and 3,275 and 185 and 370 mg/L, respectively. The study was undertaken with and without the addition of bicarbonate. The addition of this inorganic carbon source was necessary to favour nitrification, as the alkalinity of the wastewater was very low. Maximum removal efficiencies of 75%, 98% and 90% were obtained for COD, phenols and thyocianates, respectively, without the addition of bicarbonate. The concentration of ammonia increased in the effluent due to both the formation of NH(4)(+) as a result of SCN(-) biodegradation and to organic nitrogen oxidation. A maximum nitrification efficiency of 71% was achieved when bicarbonate was added, the removals of COD and phenols being almost similar to those obtained in the absence of nitrification. Batch experiments were performed to study the influence of pH and alkalinity on the biodegradation of phenols and thiocyanate.

Aerobiosis↗

PubMed2006

Use of biosurfactant to remediate phenanthrene-contaminated soil by the combined solubilization-biodegradation process.

The applicability of the combined solubilization-biodegradation process was examined using soil-packed column. In the solubilization step, 50 pore volumes of 150 mg/l biosurfactants solution was injected and the percentage removal of phenanthrene (mg) was 17.3% and 9.5% from soil with pH 5 and 7, respectively. The highest solubility was detected at pH 5 and this result confirmed that adjusting the pH of the biosurfactants solution injected could enhance the solubility of phenanthrene. Following this, soil samples were completely transferred to batches and incubated for 10 weeks to monitor phenanthrene degradation. The phenanthrene concentration in the soil samples decreased significantly during the biodegradation step in all soil samples, except for the soil sample that was flushed with biosurfactants solution with pH 4. This indicated that the degradation of contaminants by specific species might not be affected by the residual biosurfactants following application of the solubilization process. Moreover, these results suggested that the biosurfactant-enhanced flushing process could be developed as a useful technology with no negative effects on subsurface environments and could be combined with the biodegradation process to increase the removal efficiency.

Hydrogen-Ion Concentration↗