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PubMed2006

The use of biodegradable plates and screws to stabilize facial fractures.

PURPOSE: The purpose of this preliminary retrospective study was to review the demographics and outcome of patients with a variety of facial fractures that were stabilized with PL bone plates and screws. MATERIALS AND METHODS: The records of 295 consecutive patients with facial fractures treated by open reduction and internal fixation, performed by the author from 2001 through 2004, were retrospectively reviewed. Patients were selected to receive biodegradable fixation on the basis of mechanism of injury, the degree of bony displacement demonstrated on clinical and radiographic examination, patient age, and fracture pattern or location. Outcome measures such as infection, non-union, and mal-union were identified and subjectively assessed. Descriptive statistics were recorded and analyzed. RESULTS: Two hundred eighty-one patients met the criteria for inclusion in the study with follow-up of 3 weeks to 3 years. Fifty-nine (21%) patients were identified as having received biodegradable plates and screws. All patients eventually went on to satisfactory healing with favorable restoration of form and function. Complications occurred in 16 patients overall (6%). Of these, 2 patients were treated with resorbable plates and screws; 1 patient with a zygomatico-maxillary complex fracture developed a sterile abscess that presented 1 year postoperatively and responded to local measures. Another patient with a Le Fort I fracture developed an anterior open bite necessitating Le Fort I osteotomy for correction. CONCLUSIONS: Favorable healing can be observed through the use of biodegradable PL plates and screws to stabilize selected midface fractures in patients of all ages, as well as mandible fractures in early childhood.

Abscess↗

PubMed2006

Use of a biodegradable patch for reconstruction of large thoracic cage defects in growing children.

BACKGROUND/PURPOSE: At our institution, procedures were developed to enlarge and stabilize the thoracic cavity of children born with severe-enough abnormalities of the thoracic cage as to result in lack of normal lung growth and function. In addition to the device known as the vertical expandable prosthetic titanium rib (VEPTR), some type of patch material was needed to cover large congenital defects of the chest cage owing to rib absence or to cover defects created because of the expansion process. Initially, synthetic material, polytetrafluorethylene (Gore-Tex, WL Gore and Associates, Flagstaff, Ariz) was used, but this proved itself to be restrictive over time and required removal. Thus, a nonsynthetic biodegradable patch material was adopted for coverage of the defects (Surgisis, Cook, Bloomington, Ind). METHODS: From October 2001 through October 2004, 26 growing children undergoing thoracic cage reconstruction received the biodegradable extracellular matrix patch derived from porcine SIS (Cook). A patch was deemed necessary if any one of the following conditions was obtained: (a) herniation of the lung was likely; (b) chest wall musculature was significantly diminished; (c) injury to the lung was likely at reoperation; (d) the defect was greater than 2 x 2 cm. RESULTS: During the follow-up period, 41 months thus far, each of the 26 children has undergone routine, scheduled expansions or change-out procedures every 6 months. The SIS has not required removal for any reason and has not restricted growth of the thoracic cage. CONCLUSIONS: Compared with synthetic soft tissue patch material, the nonsynthetic, biodegradable soft tissue patch (SIS) has proven to be a superior alternative, thus far, to others for use in our population of patients for reconstruction of the thoracic cage in the growing child.

Absorbable Implants↗

PubMed2004

In vivo study of biodegradable alginate antibiotic beads in rabbits.

The authors investigated the lyophilized poly-L-lysine-coated alginate antibiotic delivery system in vivo for the treatment of musculoskeletal infections. The sodium alginate was mixed with vancomycin, coated with poly-L-lysine and lyophilized to form 3 mm in diameter biodegradable antibiotic beads. The antibiotic beads were implanted in the distal femoral cavities of rabbits for in vivo investigation. The local concentration of vancomycin was well above the minimal inhibitory concentration of Staphylococcus aureus for 21 days. The release was most marked during the first two days. The diameters of sample inhibition zone ranged from 8 to 16 mm, the relative activity of vancomycin ranged from 12.5% to 100%. The blood level of vancomycin reached its peak (46.0 mg/l) two days after implantation and fell to 3.2 mg/l at two weeks. It was undetectable after three weeks. There was no increase in the concentration of blood urea nitrogen and serum creatinine after the implantation. Histological observations showed that bead materials were biodegradable, resorbed slowly and only cause mild host reaction. This study offers a biodegradable delivery system of antibiotics to treat musculoskeletal infections.

Alginates↗

PubMed2001

Retinal pigment epithelium engineering using synthetic biodegradable polymers.

Retinal pigment epithelium (RPE) plays a key role in the maintenance of the normal functions of the retina, especially photoreceptors. Alteration in RPE structure and function is implicated in a variety of ocular disorders. Tissue engineering strategies using synthetic biodegradable polymers as temporary substrates for RPE cell culture and subsequent transplantation may provide a promising new therapy. In this review article, the manufacture of thin biodegradable poly(DL-lactic-co-glycolic acid) (PLGA) films and their degradation behavior in vitro are discussed. RPE cell proliferation and differentiation on these PLGA films are reviewed. The fabrication of model substrates with desired chemical micropatterns in the micrometer scale is discussed and the effects of surface patterning on RPE morphology and function are assessed. Finally. the preparation of biodegradable micropatterns with adhesive PLGA and non-adhesive poly(ethylene glycol)/PLA domains to modulate RPE cell adhesion is presented.

Animals↗

PubMedDate not supplied

Biodegradation of poly(ethylene adipate) microcapsules in physiological media.

Spherical reservoir-type microcapsules fabricated using a water/oil/water (W/O/W) double emulsion technique with solvent evaporation and composed of poly(ethylene adipate) (PEAD) blended with 20% poly-epsilon-caprolactone (PCL II) containing a range of bovine serum albumin (BSA) loadings were incubated in Hank's buffer, pH 7.4, newborn calf serum, 1.5% pancreatin and synthetic gastric juice containing 10% pepsin A over 30 days and their percentage weight loss (PWL) and changes in ultrastructural morphology monitored by gravimetry and stereoscan electron microscopy (SEM) respectively. The greatest PWL from microcapsules was observed after incubation in newborn calf serum (NCS) and pancreatin and decreased in the order NCS > pancreatin > synthetic gastric juice > Hank's buffer. Only microcapsules theoretically loaded with 5-20% BSA and incubated in synthetic gastric juice showed a significant increase in PWL with increasing percentage BSA loading. The structural biodegradation of PEAD microcapsules in both Hank's buffer and synthetic gastric juice was minimal whilst the morphological changes observed during incubation in NCS involved pitting of the membrane, some surface erosion and reduction in diameter, followed by microcapsule membrane disruption and loss of reservoir contents. Biodegradation in pancreatin was associated with surface flaking and loss of large fragments of the microcapsule membrane. Only in NCS and pancreatin, where one would expect to see the effects of enzyme activity in addition to simple ester hydrolysis, did biodegradation proceed to the stage where there was a loss of spherical shape and almost total disruption of the microcapsule structure within 30 days.

Adipates↗

PubMed1998

Manufacture of porous biodegradable polymer conduits by an extrusion process for guided tissue regeneration.

We have fabricated porous, biodegradable tubular conduits for guided tissue regeneration using a combined solvent casting and extrusion technique. The biodegradable polymers used in this study were poly(DL-lactic-co-glycolic acid) (PLGA) and poly(L-lactic acid) (PLLA). A polymer/salt composite was first prepared by a solvent casting process. After drying, the composite was extruded to form a tubular construct. The salt particles in the construct were then leached out leaving a conduit with an open-pore structure. PLGA was studied as a model polymer to analyze the effects of salt weight fraction, salt particle size, and processing temperature on porosity and pore size of the extruded conduits. The porosity and pore size were found to increase with increasing salt weight fraction. Increasing the salt particle size increased the pore diameter but did not affect the porosity. High extrusion temperatures decreased the pore diameter without altering the porosity. Greater decrease in molecular weight was observed for conduits manufactured at higher temperatures. The mechanical properties of both PLGA and PLLA conduits were tested after degradation in vitro for up to 8 weeks. The modulus and failure strength of PLLA conduits were approximately 10 times higher than those of PLGA conduits. Failure strain was similar for both conduits. After degradation for 8 weeks, the molecular weights of the PLGA and PLLA conduits decreased to 38% and 43% of the initial values, respectively. However, both conduits maintained their shape and did not collapse. The PLGA also remained amorphous throughout the time course, while the crystallinity of PLLA increased from 5.2% to 11.5%. The potential of seeding the conduits with cells for transplantation or with biodegradable polymer microparticles for drug delivery was also tested with dyed microspheres. These porous tubular structures hold great promise for the regeneration of tissues which require tubular scaffolds such as peripheral nerve, long bone, intestine, or blood vessel.

Biocompatible Materials↗

PubMed2001

Biodegradable block copolymers for delivery of proteins and water-insoluble drugs.

Release of several drugs from new ABA-type biodegradable thermal gels, ReGel, including proteins and conventional molecules, are presented. These are biodegradable, biocompatible polymers that demonstrate reverse thermal gelation properties. Organic solvents are not used in the synthesis, purification, or formulation of these polymers. The unique characteristics of ReGel hinge on the following two key properties: (1) ReGel is a water soluble, biodegradable polymer at temperatures below the gel transition temperature; (2) ReGel forms a water-insoluble gel once injected. This is consistent with a hydrophobically bonded gel state where all interactions are physical, with no covalent crosslinking. An increase in viscosity of approximately 4 orders of magnitude accompanies the sol--gel transition. The gel forms a controlled release drug depot with delivery times ranging from 1 to 6 weeks. ReGel's inherent ability to solubilize (400 to >2000-fold) and stabilize poorly soluble and sensitive drugs, including proteins is a substantial benefit. The gel provided excellent control of the release of paclitaxel for approximately 50 days. Direct intratumoral injection of ReGel/paclitaxel (OncoGel) results in a slow clearance of paclitaxel from the injection site with minimal distribution into any organ. Efficacies equivalent to maximum tolerated systemic dosing were observed at OncoGel doses that were 10-fold lower. Data on protein release (pGH, G-CSF, insulin, rHbsAg) and polymer biocompatibility are discussed.

Drug Delivery Systems↗

PubMed1996

Biodegradable pins versus Kirschner wires in hand surgery.

We compared biodegradable pins with standard Kirschner wires in the fixation of fractures, arthrodeses and osteotomies in the hand in a prospective, randomized study. Eleven patients were allocated to the biodegradable pin group and 12 to the Kirschner wire group. Age, gender, operative procedure and postoperative treatment did not differ in the two groups. All patients were evaluated after 6 months. No differences in time to union or complication rates were found, but the number of additional operative procedures in the Kirschner wire group significantly exceeded the number needed in the biodegradable pin group.

Adult↗

PubMed2002

The use of biodegradable PGA stents to judge the risk of post-TURP incontinence in patients with combined bladder outlet obstruction and overactive bladder.

OBJECTIVE: For patients with the combination of severe bladder outlet obstruction (BOO) and severe overactive bladder (OB), no straightforward and safe treatment exists due to the risk of urge incontinence after TURP. In this study we have used a biodegradable polyglycolic stent to simulate the status after TURP and register the risk for urge incontinence. METHODS: A total of 37 patients with severe OB, combined with moderate to severe BOO, were asked if they wanted to participate. Under cystoscopic vision a polyglycolic biodegradable stent was inserted in the prostatic urethra. RESULTS: Twenty-five of the patients noticed no or only minor leakage and 19 of these have been subjected to TURP with good results. Three patients are on the waiting-list for TURP. Twelve of 37 patients were found to have major leakage after stent insertion. During the stent period, we noted five cases of complications, due to UTI, stent crash and irritation. All of these patients recovered within three weeks. CONCLUSIONS: A biodegradable PGA stent seems to be a new and unique tool to test the risk for post-TURP incontinence in patients with combined BOO and severe OB.

Absorbable Implants↗

PubMed1998

Intramural delivery of a specific tyrosine kinase inhibitor with biodegradable stent suppresses the restenotic changes of the coronary artery in pigs in vivo.

OBJECTIVES: This study was designed to examine whether or not intramural delivery of ST638 (a specific tyrosine kinase inhibitor) with biodegradable stent can suppress the restenotic changes of the coronary artery in vivo. BACKGROUND: Clinical and animal studies demonstrated that restenosis after coronary intervention results from a combined effect of neointimal formation and geometric remodeling (decrease in total cross-sectional area). Thus, the most effective strategy to prevent the restenosis appears to inhibit both the neointimal formation and geometric remodeling by antiproliferative agent and stent, respectively. We have previously shown that ST638 markedly suppresses the restenotic changes of the porcine coronary artery when applied from the adventitial site. METHODS: A poly-L-lactic acid biodegradable stent was coated with either ST638 (0.8 mg) or equimolar of its inactive metabolite, ST494. A pair of these stents were implanted alternatively in the left anterior descending or circumflex coronary artery in pigs (n=6). Three weeks after the procedure, coronary stenosis was assessed by angiography followed by histological examination. RESULTS: Coronary stenosis was significantly less at the ST638 stent site than at the ST494 stent site (47+/-5% vs. 25+/-4%, p < 0.01). Histological examination also showed that the extent of neointimal formation and that of geometric remodeling were significantly less at the ST638 stent site than at the ST494 stent site (p < 0.05). CONCLUSIONS: These results indicate that intramural delivery of a specific tyrosine kinase inhibitor with biodegradable stent overcomes the proliferative stimuli caused by balloon injury, the stent itself, and the drug coating on the stent, resulting in the suppression of the restenotic changes of the coronary artery in vivo. This strategy might also be useful in the clinical setting in humans.

Animals↗

PubMed2000

Biodegradable implants in sports medicine: the biological base.

Biodegradable implants are increasingly used in the field of operative sports medicine. Today, a tremendous variety of implants such as interference screws, staples, sutures, tacks, suture anchors, and devices for meniscal repair are available. These implants consist of different biodegradable polymers that have substantially different raw material characteristics such as in vivo degradation, host-tissue response, and osseous replacement. Because these devices have become the standard implant for several operative procedures, it is essential to understand their biological base. The purpose of this report is to provide a comprehensive insight into biodegradable implant biology for a better understanding of the advantages and risks associated with using these implants in the field of operative sports medicine. In particular, in vivo degradation, biocompatibility, and the osseous replacement of the implants are discussed. A standardized classification system to document and treat possible adverse tissue reactions is given, with special regard to extra-articular and intra-articular soft-tissue response and to osteolytic lesions.

Absorbable Implants↗

PubMed1997

Fixation strength of a biodegradable interference screw and a press-fit technique in anterior cruciate ligament reconstruction with a BPTB graft.

The objective of this study was to evaluate the fixation strength of a biodegradable interference screw (Arthrex, Naples, FL) compared with press fit fixation and a titanium interference screw in anterior cruciate ligament (ACL) reconstruction using a bone-patellar tendon-bone (BPTB) graft. Porcine lower limbs were used. Ultimate failure loads of the biodegradable screw (805.2 N; range 680 to 995 N) did not differ significantly from ultimate failure loads of titanium interference screws (768.6 N; range 544 to 1094 N). Press fit fixation provided significant (P < .01) lower fixation strength (462.5 N; range 80 to 825 N). These results support the conclusion that biodegradable interference screws are a reasonable alternative in terms of primary fixation strength.

Animals↗

PubMed2002

Recovery of resources for advanced life support space applications: effect of retention time on biodegradation of two crop residues in a fed-batch, continuous stirred tank reactor.

Bioreactor retention time is a key process variable that will influence costs that are relevant to long distance space travel or long duration space habitation. However. little is known about the effects of this parameter on the microbiological treatment options that are being proposed for Advanced Life Support (ALS) systems. Two bioreactor studies were designed to examine this variable. In the first one, six retention times ranging from 1.3 to 21.3 days--were run in duplicate, 81 working-volume continuous stirred tank reactors (CSTR) that were fed ALS wheat residues. Ash-free dry weight loss, carbon mineralization, soluble TOC reduction, changes in fiber content (cellulose, hemicellulose, and lignin), bacterial numbers, and mineral recoveries were monitored. At short retention times--1.33 days--biodegradation was poor (total: 16-20%, cellulose - 12%, hemicellulose - 28%) but soluble TOC was decreased by 75-80% and recovery of major crop inorganic nutrients was adequate, except for phosphorus. A high proportion of the total bacteria (ca. 83%) was actively respiring. At the longest retention time tested, 21.3 days, biodegradation was good (total: 55-60%, cellulose ca. 70%, hemicellulose - ca. 55%) and soluble TOC was decreased by 80%. Recovery of major nutrients, except phosphorus, remained adequate. A very low proportion of total bacteria was actively respiring (ca. 16%). The second bioreactor study used potato residue to determine if even shorter retention times could be used (range 0.25-2.0 days). Although overall biodegradation deteriorated, the degradation of soluble TOC continued to be ca. 75%. We conclude that if the goal of ALS bioprocessing is maximal degradation of crop residues, including cellulose, then retention times of 10 days or longer will be needed. If the goal is to provide inorganic nutrients with the smallest volume/weight bioreactor possible, then a retention time of 1 day (or less) is sufficient.

Aerobiosis↗

PubMed2002

Quantitative TOF-SIMS analysis of oligomeric degradation products at the surface of biodegradable poly(alpha-hydroxy acid)s.

This paper reports the development of a new method for quantification of the hydrolytic surface degradation kinetics of biodegradable poly(alpha-hydroxy acid)s using time-of-flight secondary ion mass spectrometry (TOF-SIMS). We report results from static SIMS spectra of a series of poly(alpha-hydroxy acid)s including poly(glycolic acid), poly(L-lactic acid), and random poly(D,L-lactic acid-co-glycolic acid) hydrolyzed in various buffer systems. The distribution of the most intense peak intensities of ions generated in high mass range of the spectrum reflects the intact degradation products (oligomeric hydrolysis products) of each biodegradable polymer. First, a detailed analysis of the oligomeric ions is given based on rearrangement of the intact hydrolysis products. The pattern of ions can distinguish both degradation-generated intact oligomers and their fragment ion peaks with a variety of combinations of each repeat unit. Then, the integration and summation of the area of all ion peaks with the same number of repeat units is proposed as a measurement that provides a more accurate MW average than the typically used method which counts only the most intense peak. The multiple ion summation method described in this paper would be practical in the improvement of quantitative TOF-SIMS studies as a better data reduction method, especially in the surface degradation kinetics of biodegradable polymers.

Journal Article↗

PubMed2006

Recent developments in biodegradable synthetic polymers.

This chapter reviews recent developments in biodegradable synthetic polymers focusing on tailoring polymer structures to meet material specification for emerging applications such as tissue engineered products and therapies. Major classes and new families of synthetic polymers are discussed with regard to synthesis, properties and biodegradability, and known degradation modes and products are summarized based on studies reported during the past 10-15 years. Polyesters and their copolymers, polyurethanes, polyphosphazenes, polyanhydrides, polycarbonates, polyesteramides and recently developed injectable polymer systems based on polypropylenefumarates, polyurethanes and acrylate/urethane systems are reviewed. Polyesters such as polyglycolides, polylactides and their copolymers still remain as the major class of synthetic biodegradable polymers with products in clinical use. Although various copolymerization methods have addressed needs of different applications, release of acidic degradation products, processing difficulties and limited range of mechanical properties remains as major disadvantages of this family of polymers. Injectable polymers based on urethane and urethane/acrylate have shown great promise in developing delivery systems for tissue engineered products and therapies.

Absorbable Implants↗

PubMed2000

Factors affecting the biodegradation of cyanide by Burkholderia cepacia strain C-3.

The utilization of cyanide as a nitrogen source for growth in a liquid minimal medium by Burkholderia cepacia strain C-3 isolated from soil was demonstrated. The effects of various parameters on the biodegradation of cyanide by the strain were investigated. Growth at the expense of cyanide occurred over a pH range from 8 to 10, and was optimal at pH 10. Growth and cyanide biodegradation were optimal at 30 degrees C. The presence of Cu2+ or Fe2+ in the liquid medium at a concentration of 1 mM inhibited both the growth of the bacterium and its cyanide degradation. The effects of Ni2+ and Co2+, and to a lesser extent Mn2+ and Mo2+, on cyanide degradation rate were concentration dependent. Addition of the cyanide-containing waste contaminants ethanol and methanol reduced the cyanide utilization of the isolate, but phenol was completely inhibitory. Microbial depletion of cyanide occurred even in the presence of other organic and inorganic nitrogen sources. Fructose, glucose, and mannose were the preferred carbon sources for cyanide biodegradation. The highest rate of cyanide degradation by B. cepacia C-3, 1.85 mg CN h(-1), was observed with 0.25% (w/v) fructose; the degradation rate decreased progressively thereafter with increasing fructose concentration.

Journal Article↗

PubMed2003

Optimization for biodegradation of 2,4,6-trinitrotoluene (TNT) by Pseudomonas putida.

In this study, a strain of Pseudomonas putida KP-T202, isolated from the soil in a contaminated site, degraded 2,4,6-trinitrotoluene (TNT). In order to make this biodegradation process commercially feasible and reduce biodegradation time, optimal environmental factors are determined. At an initial concentration of 100 mg/l, TNT was totally degraded within 15 h under aerobic conditions. The optimal conditions for the biodegradation of TNT were found to be 30 degrees C, pH 7, 1% corn steep liquor (CSL), 0.025% NH,CI and 0.1% Tween 80; the reaction rate constant was 0.348 h(-1) These environmental conditions can be used to improve the efficiency of large-scale reactors for the treatment of TNT-contaminated wastewater and soil. In addition, the intermediates were identified as 2-amino-4,6-dinitrotoluene, 4-amino-2,6-dinitrotoluene, 2,4-dinitrotoluene and 2,6-dinitrotoluene.

Journal Article↗

PubMed2001

Local application of growth factors (insulin-like growth factor-1 and transforming growth factor-beta1) from a biodegradable poly(D,L-lactide) coating of osteosynthetic implants accelerates fracture healing in rats.

In vitro and in vivo studies have demonstrated an osteoinductive effect of growth factors such as insulin-like growth factor-1 (IGF-1) and transforming growth factor-beta1 (TGF-beta1). However, for therapeutic use in fracture treatment, questions remain with regard to the local application of these proteins. A controlled, local release of growth factors from a biodegradable polylactide coating of osteosynthetic implants may have a stimulating effect on fracture healing. Such implants could stabilize the fracture and their bioactive surface could function simultaneously as a local drug-delivery system. Previous studies have demonstrated the high mechanical stability of an approximately 10-14-microm-thick poly(D,L-lactide) (PDLLA) coating on metallic implants, which can even withstand the process of intramedullary insertion. Following an initial peak, 80% of incorporated growth factors IGF-1 and TGF-beta1 were continuously released within 42 days. The effect of locally applied IGF-1 and TGF-beta1 from a biodegradable PDLLA coating of intramedullary implants on fracture healing was investigated in a rat model. Midshaft fractures of the right tibia of 5-month-old female Sprague-Dawley rats (n = 127) were stabilized with coated vs. uncoated titanium Kirschner wires. X-ray examinations and blood analyses were performed, and body weight and body temperature measurements were taken throughout the experimental period. After 28 and 42 days, respectively, tibiae were dissected for mechanical torsional testing and histomorphometrical analyses. X-rays demonstrated an almost completely consolidated fracture, biomechanical testing showed a significantly higher maximum load and torsional stiffness, and histological and histomorphometric analyses demonstrated progressed remodeling after 28 and 42 days in the group treated with growth factors as compared with controls. Interestingly, the PDLLA coating itself revealed a positive effect on fracture healing even without incorporated growth factors. No systemic changes of serum parameters, including IGF-1 and IGF binding proteins, and no differences in body weight and body temperature were observed within and between groups. These findings suggest that the local application of growth factors from a biodegradable PDLLA coating of osteosynthetic implants accelerates fracture healing significantly without systemic side effects.

Animals↗