The effect of different thermal treatment on the physical properties of PGA/PCL copolymer suture material.

Samples of polyglycolic acid PGA/polycaprolactone PCL copolymer absorbable suture materials, which is called Poliglecaprone PGC copolymer suture, were thermally treated by two different processes. The first method is the direct heat exposure, from 20 to 38 °C, in the surrounding medium. Which is an environmental study. The other method is the annealing process at temperatures ranged from 65, 80, 100, 120, and 140 °C, for two different duration periods 60 and 120 min. This is an extensive technical study. The refractive indices of thermally treated PGA/PCL copolymer sutures were measured using multiple-beam Fizeau fringes. The birefringence profiles across the suture cross-sections were studied for different annealing conditions. The effect of heat on the polarizabilty per unit volume, dielectric properties, and suture diameter were investigated. The activation energy for the heating processes was calculated using Arrhenius equation. Microinterferograms are given for illustration.

Preparation of Aqueous Core-Poly(d,l-Lactide-co-Glycolide) Shell Microcapsules With Mononuclear Cores by Internal Phase Separation: Optimization of Formulation Parameters.

Previously, our group employed the internal phase separation method to produce aqueous core-PLGA [poly(d,l-lactide-co-glycolide)] shell microcapsules with polynuclear core morphologies. This report describes the preparation of the more desired and challenging architecture with mononuclear cores. Optimization of formulation parameters including (1) varying the composition of the internal phase and (2) incorporating selected organic solvents (dichloromethane, chloroform, methanol, and acetonitrile) into the internal phase was systematically evaluated. Varying the composition of the internal phase (i.e., PLGA and water levels) failed to produce mononuclear microcapsules. However, incorporating methanol or acetonitrile into the internal phase produced microcapsules with mononuclear cores as confirmed by phase-contrast microscopy, transmission electron microscopy, and scanning electron microscopy. Stability of the prepared emulsions (internal phase of PLGA, acetone, acetonitrile, and water) was optimized by evaluating different types of surfactants with varying concentrations. Among them, lecithin in the range of 0.5%-5% wt/wt provided the best emulsion stability. Interestingly, increasing lecithin concentrations led to the production of microcapsules with smaller sizes (from 2.4 ± 1.6 to 1.1 ± 0.8 µm) and higher percentage of mononuclear cores. The resulting aqueous core-PLGA shell microcapsules are expected to have interesting applications in drug delivery systems with controlled release for hydrophilic drugs and proteins.

Abdominal wound closure--a comparison of monofilament nylon and polyglycolic acid.

The incidence of burst abdomen, incisional herniation, and sinus formation after a vertical abdominal incision was studied in a prospective randomized trial that compared two suture materials--monofilament nylon and polyglycolic acid. Laparotomy wounds were closed with a continuous mass suture technique. Of the 210 patients studied, 15 died between 10 days and 6 months postoperatively with their wounds intact. The remaining patients were followed up for 6 months or longer. The two groups were well matched for known risk factors. The 104 patients in the polyglycolic acid group had a 12.5% wound failure rate (1 burst abdomen and 12 hernias), but the 106 patients in the nylon group had only a 4.7% wound failure rate (1 burst abdomen and 4 hernias) (P = 0.04). There was a significant association between the rate of infection and sinus formation, but there was no difference between the incidence of these complications between the two groups. Closure of abdominal wounds with absorbable sutures does not appear to be justified, and we suggest that nylon and the mass closure technique be used for all abdominal wound closures. Other etiologic factors significantly associated with wound failure include male sex and postoperative chest complications. However, infection remains the most significant postoperative complication because the incidence of incisional hernias and sinus formation would be reduced by the elimination of wound sepsis.

Precise control of PLG microsphere size provides enhanced control of drug release rate.

An important limitation in the development of biodegradable polymer microspheres for controlled-release drug delivery applications has been the difficulty of specifically designing systems exhibiting precisely controlled release rates. Because microparticle size is a primary determinant of drug release, we developed a methodology for controlling release kinetics employing monodisperse poly(D,L-lactide-co-glycolide) (PLG) microspheres. We fabricated 20-, 40- and 65-microm diameter rhodamine-containing microspheres and 10-, 50- and 100-microm diameter piroxicam-containing microspheres at various loadings from 1 to 20%. In vitro release kinetics were determined for each preparation. Drug release depended strongly on microsphere diameter with 10- and 20-microm particles exhibiting concave-downward release profiles while larger particles resulted in sigmoidal release profiles. Overall, the rate of release decreased and the duration increased with increasing microsphere size. Release kinetics from mixtures of uniform microspheres corresponded to mass-weighted averages of the individual microsphere release kinetics. Appropriate mixtures of uniform microspheres were identified that provided constant (zero-order) release of rhodamine and piroxicam for 8 and 14 days, respectively. Mixing of uniform microspheres, as well as control of microsphere size distribution, may provide an improved methodology to tailor small-molecule drug-release kinetics from simple, biodegradable-polymer microparticles.

Breaking strength and diameter of absorbable sutures after in vivo exposure in the rat.

Although absorbable sutures are commonly used in clinical practice, the rate of decay of strength in various tissues has not been studied. The purpose of this study was to assess breaking strength (BS) and diameter of monofilament (chromic gut, polydiaxanone, Maxon, Monocryl) and multifilament (Vicryl, Dexon, Polysorb) absorbable sutures implanted in various sites and measured at specific time intervals. A 15 cm length of 4-0 suture from a single lot of each material was implanted in the pleural space, rectus abdominus muscle, subcutaneous tissue, intravascular space, peritoneal cavity, and stomach lumen in the rat. A precipitous decrease in BS was noted in all multifilament sutures after 7 days, and in chromic gut and Monocryl sutures after 1 day. Polydiaxanone and Maxon sutures maintained the highest BS over the 28-day period, 71 per cent and 59 per cent of their initial BS, respectively. Suture diameter remained essentially unchanged except for chromic gut and the multifilament sutures which exhibited increased diameter. This increase was attributed to inflammatory tissue infiltration.

Knot integrity of coated synthetic absorbable sutures used for extraocular muscle surgery in a rabbit model.

Knot integrity of a new coated polyglycolic acid suture (Dexon Plus) was compared to that using uncoated polyglycolic acid (Dexon-S) and coated polyglactin-910 (Vicryl) for extraocular muscle recessions in rabbits. Knot integrity was found to be virtually identical using 6-0 sutures of any of these materials. Top throws of 5-0 coated Dexon or 5-0 coated Vicryl had a tendency to loosen in a few cases, though this was eliminated in later operations by more careful tightening of knots and avoidance of cutting suture ends to a length less than 2 mm. Subjectively observed differences in "tissue drag" were insignificant in this model.

Vascularized three-dimensional skeletal muscle tissue-engineering.

Medical science continues to battle against the loss or failure of organs or tissues. Since, skeletal muscle loss lead not only to the functional compromise of the affected site, but also a structural deformation; tissue engineering of skeletal muscle attempts to provide solutions to replace loss of tissue contour and function. In our study, myoblasts seeded onto polyglycolic acid (PGA) meshes were used to engineer skeletal muscle tissue in vivo. The cell-polymer constructs harvested after a period of 6-weeks were well vascularized three-dimensional structures with the ability to generate neo-muscle-like tissue. This is the first time that the ability of myoblasts to survive in vivo in the absence of mature skeletal muscle tissue was demonstrated. The successful ability to transplant myoblasts using biodegradable polymer strands without using the traditional transplantation buffer mediums as carriers was also employed for the first time.

[Behavior of modern suture materials in infected urine]. / Das Verhalten moderner Nahtmaterialien im infizierten Urin.

The recently developed absorbable materials demonstrate a constant and reproducible high quality when compared with the resorbable suture materials. However, based on in vitro studies by different authors the use of these materials in infected urine is not recommended. We investigated in vivo in infected urines the stability of the suture materials composed of polyglycolic acid, and compared the results obtained in vitro and in vivo. In a controlled study the stability of the absorbable suture materials polyglycolic acid, polyglactin 910 and polydioxanon 4/0 USP were tested in infected urine in vivo and in vitro. In 21 patients with infected urine the suture materials were placed into the bladder for 7 days. In another experiment these materials were incubated up to 7 days in culture flasks with infected urine. After that the suture materials were examined by densitometry and electrone microscopy. When using the results obtained in vitro in clinical work caution is recommended. However, the in vivo tests show that the stability of the newly developed absorbable materials is not influenced dramatically by the infected urine.

[Comparative evaluation of tensile strength of absorbable threads Dexon and Maxon. Experimental studies]. / Ocena porównawcza wytrzymalosci na zrywanie syntetycznych nici wchlanialnych Dexon i Maxon. Badania doswiadczalne.

This paper submits strength tests on Dexon and Maxon resorbable sutures at the knot and without a knot, the breaking resulting from hydrolysis. The tests were performed on rats, by comparing Maxon monofilament suture with Dexon woven suture. The dissections were done 3, 7, 21 and 42 days after the implantation. What we found out was a remarkably slower process of strength loss displayed by Maxon sutures in time after the implantation. After 21 days, Dexon sutures displayed a minimal strength value, whereas Maxon sutures still retained ca 60% of the initial properties.

Polyglycolic acid (Dexon) sutures in Escherichia coli infected urine.

The tensile strength, knot strength and stretch of polyglycolic acid (Dexon) was studied after emersion in physiological saline, sterile urine and infected urine. Tests were made each day under controlled conditions over a 10 day period. The results are compared with those of other earlier studies. Tensile strength, knot strength and stretch were found to be fully acceptable in all studies, and there are no grounds to advise against the use of Dexon when urine is infected.

[Studies concerning the usefulness of catgut, PGA and polyester for abdominal fascia closure (author's transl)]. / Die Brauchbarkeit von Catgut, PGS und Polyester zum Veruschluss der Abdominalfaszie

The abdominal fascia incisions of 133 rabbits were closed either with plain gut, chromic gut, PGA or polyester threads. The breaking strength of the wounds were determined tensiometrically at different time intervals and the tissue was examined histologically. For a three-week period the strength of the abdominal wall depends significantly on the intactness of the threads. PGA produces minimal inflammatory reactions, but loses its strength after a fortnight. Since longitudinal incisions are endangered by severe muscle pull, this material cannot be recommended because of the possibility of wound disruption and the formation of hernias. The loss of strength of catgut plain and catgut chromic starts later. Catgut causes inflammatory reactions within the wound area leading to loss of strength of the sutured tissue. Thus incisions of the abdominal fascia should not be closed with catgut. The non-resorbable suture material polyester shows satisfactory strength and minimal tissue reaction. As long as there is no synthetic suture material with mild tissue reaction and late resorption the fascial closure should be sutured with polyester.

Mechanical performance of polyglycolic acid and polyglactin 910 synthetic absorbable sutures.

The mechanical performance of polyglycolic acid and polyglactin 910 sutures has been assessed using standardized reproducible tests. The results of these studies demonstrated distinct differences in their performance that can be related, in part, to their structural configuration. The size of the 4-0 polyglactin suture was significantly larger than that of the 4-0 polyglycolic acid suture. Since the strength of any suture is proportional to its cross sectional area, the strength of unknotted and knotted polyglactin 910 sutures was signficantly greater than that of the polyglycolic acid sutures. The strength of both sutures was similarly diminished by the formation of the knot. When these sutures were added to tissue, the breaking strength was even further reduced. The rate of decline in breaking strength of the two absorbable sutures in healing skin wounds was comparable. These absorbable sutures displayed knot security with a two throw square knot, 1 = 1. The ability of these sutures to reach knot break with this knot configuration is characteristic of sutures in which the surface exhibits a high coefficient of friction. Their rough surface also caused them to drag through tissue, making difficult to adjust tension on a continuous running suture.

Resorbable synthetic polymers as replacements for bone graft.

The potential of resorbable synthetic polymers derived from the poly(alpha-hydroxy acids), poly(lactide) and poly(glycolide), to fulfill a role as bone graft substitutes is reviewed. The various elements of the relationship between the degradation behaviour of resorbable implants and polymer synthesis and chain structure, implant morphology, processing and dimensions have been defined. The production of resorbable polymeric implants has been extensively documented so as to provide a wide basis for selection of an appropriate manufacturing technique. The key requirement of implant dimensional stability over the early stages of bone healing is emphasised so as to provide a stable surface on which osteoblasts and/or their precursor cells may migrate and secrete bone matrix. Minimisation of the content of slow resorbing polymers such as poly(L-lactide) is recommended, consistent with retention of an adequate implant degradation characteristic. The review concludes with a summary of alternative resorbable polymers such as the polyphosphazines which are interesting candidate materials for bone repair and reconstruction.

[In vivo investigations on suture reactions under sterile and not sterile conditions. Comparison of absorbable and nonabsorbable suture materials (author's transl)]. / In-vivo-Untersuchungen bei Nahtreaktionen an sterilen und infizierten absorbierbaren und nicht absorbierbaren chirurgischen Nahtmaterialien.

Suture materials from plant and animal substances are increasingly being replaced by synthetics. Among the nonabsorbable materials, synthetics are much superior regarding infection, threading and knot strength. A coating can improve management, which is currently more favourable with silk and cotton. Absorbable polyglycolic-acid sutures enable controlled reduction of thread breaking, but catgut sutures do not. Absorption is significantly accelerated by infections, while pH-fluctuation is less important. For infected tissue, monofile or pseudomonofile sutures are most suitable.

A biologic comparison of polyglactin 910 and polyglycolic acid synthetic absorbable sutures.

Two synthetic absorbable sutures were implanted in rats for a comparative evaluation of breaking strength, tissue reaction and absorption. Polyglactin 910 suture was stronger than polyglycolic acid suture in both sizes tested and at all time periods from zero to 35 days. Both suture types elicited minimal tissure response. Based upon histologic examination, virtually all remnants of the polyglactin 910 were absorbed by 90 days, while considerable quantities of polyglycolic acid persisted at 120 days. The difference in absorption rates was a highly significant feature of the comparative biologic profiles of the two suture materials.

Wound infection following high saphenous ligation. A trial comparing two skin closure techniques: subcuticular polyglycolic acid and interrupted monofilament nylon mattress sutures.

A prospective, randomized trial was performed to compare the incidence of wound infection following skin closure with subcuticular polyglycolic acid and interrupted monofilament nylon mattress sutures in patients undergoing high saphenous ligation (126 patients; 75 polyglycolic acid wounds, 86 interrupted monofilament nylon mattress wounds). By 6 weeks after operation, pus had discharged from 15 (20%) polyglycolic acid wounds compared with seven (8%) interrupted monofilament nylon mattress wounds (P = 0.05), giving an overall infection rate of 13.7%. Infection occurred in 23% of the 56 procedures performed by the two surgeons with the highest infection rates compared with 8% of the 105 procedures performed by the remaining nine surgeons (P = 0.02). The excess of infections in wounds closed with subcuticular polyglycolic acid was caused by an excess of infections in operations performed by the two surgeons with the highest infection rates. The higher infection rate found with subcuticular polyglycolic acid appeared to be operator dependent.

Mechanical characteristics of an absorbable copolymer internal fixation pin.

Absorbable internal fixation is gaining acceptance among foot and ankle surgeons. While absorbable pins made of poly-L-lactic acid, polyglycolic acid, or poly-p-dioxanone are generally effective as applied in the foot, their strength loss profiles and degradation characteristics may not be optimally matched to the healing process. This study investigated a novel absorbable oriented copolymer pin, with unique absorption characteristics, made of 82% poly-L-lactic acid and 18% polyglycolic acid, to determine its suitability for use in fixation in the foot. The pins were incubated in a 37 degrees C buffer bath that simulated in vivo conditions and were mechanically tested in four-point bend and shear at time intervals up to 12 weeks. In vitro strength loss profiles demonstrated peak strength retention (flexural and shear) for about 8 weeks, with 50% of properties remaining by 12 weeks. The initial Young's modulus of the pins was approximately 7 GPa. The mathematical relationship between pin strength and pin diameter was discussed, providing the surgeon with helpful criteria for making an implant selection. The degradation time course of these pins appears to compliment the known healing dynamics of bone, making them a suitable choice for use in foot surgery.