Monocryl suture, a new ultra-pliable absorbable monofilament suture

Poly-epsilon-caprolactone/hydroxyapatite composites for bone regeneration: in vitro characterization and human osteoblast response

Polycaprolactone (PCL), a semicrystalline linear resorbable aliphatic polyester, is a good candidate as a scaffold for bone tissue engineering, due to its biocompatibility and biodegradability. However, the poor mechanical properties of PCL impair its use as scaffold for hard tissue regeneration, unless mechanical reinforcement is provided. To enhance mechanical properties and promote osteoconductivity, hydroxyapatite (HA) particles were added to the PCL matrix: three PCL-based composites with different volume ratio of HA (13%, 20%, and 32%) were studied. Mechanical properties and structure were analysed, along with biocompatibility and osteoconductivity. The addition of HA particles (in particular in the range of 20% and 32%) led to a significant improvement in mechanical performance (e.g., elastic modulus) of scaffold. Saos-2 cells and osteoblasts from human trabecular bone (hOB) retrieved during total hip replacement surgery were seeded onto 3D PCL samples for 1-4 weeks. Following the assessment of cell viability, proliferation, morphology, and ALP release, HA-loaded PCL was found to improve osteoconduction compared to the PCL alone. The results indicated that PCL represents a potential candidate as an efficient substrate for bone substitution through an accurate balance between structural/ mechanical properties of polymer and biological activities.

Alkaline-treated poly(ε-caprolactone) films: Degradation in the presence or absence of fibroblasts

In the first stage, we observed the study of the degradation behavior of alkaline-treated poly(epsilon-caprolactone) (PCL) in two biologically-related media: phosphate buffered saline (PBS) and Dulbecco's modified Eagle's medium (DMEM) for 18 months, finding a much accelerated degradation in the last one. As expected, the degradation in the presence of cells is much pronounced even considering that the study is limited to 6 months. The characterization of the degraded substrates by chemiluminescence (CL) allows to explain the modifications of the substrate and their relations with transitory oxidative stress phenomena described in the fibroblasts seeded onto the PCL membranes.

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.

Influence of polyglecaprone 25 (Monocryl) supplementation on the biocompatibility of a polypropylene mesh for hernia repair

BACKGROUND

Supplementary polyglecaprone 25 (Monocryl) monofilaments were added to a lightweight pure monofilament polypropylene mesh (PP mesh) to improve intraoperative handling (PP+M mesh). This study was designed to evaluate the influence of this additional supplementation on the biocompatibility in a rodent animal model.

METHODS

Two mesh materials, a composite mesh (PP+M) and the pure polypropylene variant (PP), were compared after subcutaneous implantation in a standardized rat model. Histological analysis of the inflammatory response was performed after 28, 56 and 84 days of implantation. Material absorption, inflammatory tissue reaction, fibrosis and granuloma formation were investigated, as well as the percentage of proliferating and apoptotic cells at the interface.

RESULTS

Both mesh materials showed a slight foreign body reaction involving mainly macrophages and foreign body giant cells. Total absorption of the Monocryl filaments of the PP+M mesh occurred between 56 and 84 days of implantation. Both the inflammatory and the fibrotic reaction were decreased (n.s.) in the PP+M mesh group compared to the pure PP mesh. Whereas the percentage of proliferating cells showed no significant difference, the rate of apoptotic cells was significantly decreased in the PP+M mesh group over the whole implantation period.

CONCLUSION

Compared to the pure polypropylene mesh, our data confirm that the use of a polypropylene mesh supplemented with absorbable Monocryl filaments is feasible without additional short-term mesh-related complications in the experimental model or negative side effects on biocompatibility.

Susceptibility of a polycaprolactone-based root canal filling material to degradation. I. Alkaline hydrolysis

Polycaprolactone, a thermoplastic aliphatic polyester, is reportedly susceptible to both alkaline and enzymatic hydrolyzes. This screening study examined the susceptibility of Resilon, a polycaprolactone-based root filling composite, to alkaline hydrolysis. There were 15-mm diameter disks of Resilon and Obtura gutta-percha prepared by compressive molding and immersed in 20% sodium ethoxide for 20 or 60 min. Control disks were immersed in ethanol for 60 min. These disks were examined using field-emission scanning electron microscopy and energy dispersive X-ray analysis. For Resilon, the surface resinous component was hydrolyzed after 20 min of sodium ethoxide immersion, exposing the spherulitic polymer structure and subsurface glass and bismuth oxychloride fillers. More severe erosion occurred after 60 min of sodium ethoxide treatment. Gutta-percha was unaffected after immersion in sodium ethoxide. As Resilon is susceptible to alkaline hydrolysis, it is possible that enzymatic hydrolysis may occur. Biodegradation of Resilon by bacterial/salivary enzymes and endodontically relevant bacteria warrants further investigation.

Synthesis, characterization and melt spinning of a block copolymer of L-lactide and epsilon-caprolactone for potential use as an absorbable monofilament surgical suture

This paper describes the synthesis and characterization of a block copolymer of L-lactide (LL) and epsilon -caprolactone (CL) and its subsequent melt spinning into a monofilament fiber. The synthesis reaction was a two-step process. In the first step, an approximately 50:50 mol% random copolymer, P(LL-co-CL), was synthesized via bulk copolymerization of LL and CL. This first-step prepolymer then became the macroinitiator in the second-step reaction in which more LL monomer was added to form a block copolymer, PLL-b-P(LL-co-CL)-b-PLL. Both the prepolymer and block copolymer were characterized by a combination of analytical techniques comprising dilute-solution viscometry, GPC, 1H and 13C NMR, DSC and TG. The block copolymer was then processed into a monofilament fiber using a small-scale melt spinning apparatus. The fiber was spun with a minimum amount of chain orientation and crystallinity so that its semi-crystalline morphology could be constructed under more controlled conditions in subsequent off-line hot-drawing and annealing steps. In this way, the fiber's tensile properties and dimensional stability were developed, as indicated by the changes in its stress-strain curve. The final drawn and annealed fiber had a tensile strength (>400 MPa) approaching that of a commercial PDS II suture of similar size. It is considered that this type of block copolymer has the potential to be developed further as a lower-cost alternative to the current commercial monofilament surgical sutures.

Estudo clínico e histopatológico da reação tecidual às suturas interna e externa dos fios monofilamentares de nylon e poliglecaprone 25 em ratos

OBJETIVOS: Neste estudo realizamos a análise clínica e histopatológica da reação tecidual dos fios de nylon e poliglecaprone 25 monofilamentares nas suturas interna e externa em ratos. MÉTODOS: Foram utilizados 40 Rattus norvegicus (Wistar) machos. O ato operatório consistiu de incisão e divulsão dos planos muscular e cutâneo realizadas na região posterior das coxas dos animais. As suturas internas e externas da coxa direita foram realizadas com o fio de nylon n°5-0, e na coxa esquerda aplicamos o poliglecaprone 25 n°5-0. Os animais foram divididos em 4 grupos (n=10) de acordo com o tempo pós-operatório G1 (7 dias), G2 (14 dias), G3 (21 dias) e G4 (28 dias). Para a avaliação cínica foi considerada a ocorrência de deiscência, de exsudato e edema. Na análise histopatológica objetivou-se avaliar reação inflamatória, células gigantes de corpo estranho, proliferação fibroblástica e fibrose. RESULTADOS: Clinicamente, não foram observadas alterações nos grupos estudados. Histopatologicamente a reação inflamatória, presença de células gigantes de corpo estranho, proliferação fibroblástica e fibrose foram maiores nas suturas internas realizadas com Nylon. Nas suturas realizadas com poliglecaprone 25 essa reação declinou com o passar do tempo pós-operatório. CONCLUSÃO: De acordo com a metodologia empregada podemos concluir que as suturas externas realizadas com nylon induziram menor reação tecidual, enquanto que nas suturas internas este fio contribuiu para perpetuar a reação tecidual. As suturas externas realizadas com poliglecaprone 25 apresentaram maior reação tecidual, e suturas internas realizadas com o mesmo fio a reação tecidual declinou na medida em que o fio estava sendo absorvido.

Effect of load and temperature on in vitro degradation of poly(glycolide-co-l-lactide) multifilament braids

The effects of load and temperature on in vitro degradation behaviors of poly(glycolide-co-L-lactide) 90/10 multifilament braids were investigated in phosphate buffer solution at pH 7.4. The property changes of the braids with time were monitored by tensile test, gel permeation chromatography analysis, and scanning electron microscopy. The interrelationships between material properties, time and experimental conditions were explored. The results showed that the polymer braids gradually lost their strength and molecular weight with the increasing in vitro time. While the load levels applied had no effect on the materials, raising temperatures significantly accelerated the degradation. It was found that for a given tensile breaking strength retention (BSR), the dependence of degradation time on temperature could be illustrated by an Arrhenius-type equation, from which the activation energy could be derived. Further analysis indicated that there are well-defined relationships between molecular weight, BSR and breaking strain retention, and these relationships can be illustrated mathematically. Finally, the surface morphology of the fiber showed visible change during the degradation process.

Foreign body attachment to polypropylene suture material extruded into the small intestinal lumen after enteric closure in three dogs

Three dogs in which polypropylene suture material was used to close an enteric surgery site in a continuous pattern were evaluated at a later date because of recurrence of signs of intestinal disease. Surgery in each dog revealed that the suture material had been extruded into the lumen of the intestine and acted as a site for attachment of a foreign body. The nonabsorbable nature of polypropylene and its use in a continuous pattern are possible explanations for this complication. Polydioxanone or poliglecaprone 25 may be suitable alternatives to polypropylene for use in a continuous pattern for closure of small intestinal surgery sites.

Bacterial colonization on different suture materials—A potential risk for intraoral dentoalveolar surgery

In this in vivo and in vitro study on resorbable (Monocryl and nonresorbable (Deknalon) monofilament sutures used in intraoral dentoalveolar surgery the bacterial colonization was compared. For the in vivo study the sutures were applied in 11 patients during dental surgery. Eight days postoperative the sutures were removed and the adhered bacteria were isolated and identified by biochemistry, morphology, antibiotic susceptibility, and gas chromatography. The colonization was studied by scanning electron microscopy. Aerobic and anaerobic bacteria were isolated in nearly equal colony-forming units (cfu) on each suture. In comparison with Monocryl about 15% more aerobic and anaerobic strains were isolated on Deknalon. Regarding the pathogens only, about three times more anaerobic strains were isolated on both sutures in total. Additionally, more pathogens were found on Deknalon than on Monocryl (aerobic >40%, anaerobic >25%). The variety of bacteria correspond with purulent infections, not with normal oral flora. Intraindividual comparisons of cfu showed differences in dependence of the patient as described for subgingivale plaques. For the in vitro study the sutures were incubated with Streptococcus intermedius and Prevotella intermedia for 0.5 h. Scanning electron microscopy was performed to examine qualitatively the level of bacterial adherence. After 0.5 h the bacteria adhered very well. The colonization rate of Streptococcus intermedius on both sutures was similar. Coccoid bacteria within biofilms were seen. The growth of Prevotella intermedia was much better on Deknalon than on Monocryl. The risk of bacteremia at the time of suture removal is discussed.

Biodegradable polyester elastomers in tissue engineering

Tissue engineering often makes use of biodegradable scaffolds to guide and promote controlled cellular growth and differentiation in order to generate new tissue. There has been significant research regarding the effects of scaffold surface chemistry and degradation rate on tissue formation and the importance of these parameters is widely recognised. Nevertheless, studies describing the role of mechanical stimuli during tissue development and function suggest that the mechanical properties of the scaffold will also be important. In particular, scaffold mechanics should be taken into account if mechanical stimulation, such as cyclic strain, will be incorporated into strategies to grow improved tissues or the target tissue to be replaced has elastomeric properties. Biodegradable polyesters, such as polyglycolide, polylactide and poly(lactide-co-glycolide), although commonly used in tissue engineering, undergo plastic deformation and failure when exposed to long-term cyclic strain, limiting their use in engineering elastomeric tissues. This review will cover the latest advances in the development of biodegradable polyester elastomers for use as scaffolds to engineer tissues, such as heart valves and blood vessels.

Anastomose trachéale : fil monofilament résorbable versus non résorbable

OBJECTIVES

When tracheal stenosis is symptomatic, the treatment may consist of surgical resection and anastomosis. A multifilament absorbable suture is usually used. The aim of this experimental work on rats was to study the benefits of using a monofilament absorbable suture with high initial resistance.

MATERIAL AND METHODS

We compared Ethilon, a nylon monofilament non-absorbable suture (MNA), with Monocryl, a polyglecaprone 25 (P25) monofilament absorbable suture (MA). The sutures were used for tracheal anastomosis on 16 rats. P25 has a high initial strength but its intra-tissular disappearance is fast. Animals were killed at 1, 2 and 3 months. Anastomoses were studied by optical microscopy and histological analysis.

RESULTS

At 3 months no disunity or stenosis was seen with the MA. With the MNA, a modification of the tracheal transverse section and a stenosis were observed. The histological examination showed an initial important inflammatory cell reaction with the MA and at 3 months, a surgery-free like tracheal aspect. At 3 months the rats with MNA had a persistent foreign body cell reaction.

CONCLUSION

Good results obtained by using P25 could be due to high initial resistance of the suture protecting the anastomosis. The semi-fast absorption of the suture avoided persistent inflammatory cell reaction. Confirmation of these results by working on larger animals and tracheal anastomosis under tension could allow the use of this suture on human beings, in this instance.

Evaluation of the tensile strengths of four monofilament absorbable suture materials after immersion in canine urine with or without bacteria

OBJECTIVE

To evaluate the tensile strength, elongation, and degradation of 4 monofilament absorbable suture materials that undergo degradation by hydrolysis in specimens of canine urine with various physical characteristics.

SAMPLE POPULATION

4 monofilament absorbable sutures (polydioxanone, poliglecaprone 25, polyglyconate, and glycomer 631).

PROCEDURE

Voided urine was collected from 6 healthy dogs, pooled, filter-sterilized, and prepared to provide 5 media: sterile neutral (pH, 7.0), sterile acidic (pH, 6.2), sterile basic (pH, 8.8), Escherichia coli-inoculated, and Proteus mirabilis-inoculated urine. Ten strands of each suture material were immersed in each of the media for 0 to 28 days. Tensile strength and elongation of each suture material were evaluated by use of a texture analyzer on days 0, 1, 3, 7, 10, 14, 21, and 28.

RESULTS

Reduction in tensile strength was detected for all materials in all urine specimens over time. Polyglyconate and polydioxanone had superior tensile strengths in sterile neutral and E. coli-inoculated urine, and polydioxanone retained the greatest tensile strength throughout the study period. All suture materials disintegrated before day 7 in P. mirabilis-inoculated urine.

CONCLUSIONS AND CLINICAL RELEVANCE

Polydioxanone, polyglyconate, and glycomer 631 may be acceptable for urinary bladder closure in the presence of sterile neutral and E. coli-contaminated urine. Tensile strength of poliglecaprone 25 in urine may be unacceptable by the critical healing time for bladder tissue (14 to 21 days). During bladder surgery, exposure of suture material that degrades via hydrolysis to urine containing Proteus spp should be minimized.

Recent Developments in Ring Opening Polymerization of Lactones for Biomedical Applications

Aliphatic polyesters prepared by ring-opening polymerization of lactones are now used worldwide as bioresorbable devices in surgery (orthopaedic devices, sutures, stents, tissue engineering, and adhesion barriers) and in pharmacology (control drug delivery). This review presents the various methods of the synthesis of polyesters and tailoring the properties by proper control of molecular weight, composition, and architecture so as to meet the stringent requirements of devices in the medical field. The effect of structure on properties and degradation has been discussed. The applications of these polymers in the biomedical field are described in detail.

Repair of Calvarial Defects with Customised Tissue-Engineered Bone Grafts II. Evaluation of Cellular Efficiency and Efficacyin Vivo

We have demonstrated in Part I of this study [see Schantz, J.-T., et al., Tissue Eng. 2003;9(Suppl. 1): S-113-S-126; this issue] that bone marrow-derived progenitor cells and calvarial osteoblasts could be successfully directed into the osteogenic lineage and cultured in three-dimensional (3-D) polycaprolactone (PCL) scaffolds. The objective of the second part of the study was to evaluate and to compare tissue engineered cell-polymer constructs using calvarial osteoblasts (group I) and mesenchymal progenitor cells (MPCs; group II) for the reconstruction of critical-size and three-dimensionally complex cranial defects. In 30 New Zealand White rabbits, bilateral parietal critical-size defects were created. On the basis of computed tomography scans, customized PCL scaffolds with precisely controlled microarchitecture were fabricated, using a rapid prototyping technology. Bone marrow-derived progenitor cells and osteoblasts were isolated and expanded in culture. Osteoblasts (group I) and mesenchymal progenitor cells (group II) were seeded in combination with a fibrin glue suspension into 40 PCL scaffolds. After incubating for 3 days in static culture, the PCL scaffold-cell constructs as well as nonseeded PCL scaffolds (control group) were implanted into 15-mm-diameter calvarial defects. Reconstruction of the cranium and bone formation were evaluated after 3 months. In vivo results indicated osseous tissue integration within the implant and functionally stable restoration of the calvarium. Islands of early bone formation could be observed in X-ray radiographs and in histological sections. Implants showed a high cell:ECM ratio and a dense vascular network. Mechanical testing of the reconstructed area revealed partial integration with the surrounding corticocancellous calvarial bone. The amount (area) of calcification, measured by clinical computed tomography, indicated that cell-seeded constructs measured about 60% more than unrepaired or unseeded scaffolds. Mechanical investigations revealed that stiffness reached 52 +/- 29 and 44 +/- 16 MPa for MPC- and osteoblast-seeded scaffolds, respectively. The yield strength for the push-out tests was 180 +/- 36 N for normal calvarial bone, 90 +/- 1 N for unrepaired site, and 106 +/- 10 N for unseeded constructs, which is about 60% of normal bone strength. MPC- and osteoblast-seeded scaffolds indicated a yield strength of 149 +/- 15 and 164 +/- 42 N, respectively, which is about 85-90% of normal bone. This study demonstrated that customized biodegradable polymeric implants may be used to deliver osteogenic cells and enhance bone formation within critically-sized defects in vivo. The use of rapid prototyping technology to produce scaffolds with controlled external geometry and microarchitecture offers new possibilities in the functional and aesthetic reconstruction of complex craniofacial defects.

Elastic biodegradable poly(glycolide-co-caprolactone) scaffold for tissue engineering

Cyclic mechanical strain has been demonstrated to enhance the development and function of engineered smooth muscle (SM) tissues, and it would be necessary for the development of the elastic scaffolds if one wishes to engineer SM tissues under cyclic mechanical loading. This study reports on the development of an elastic scaffold fabricated from a biodegradable polymer. Biodegradable poly(glycolide-co-caprolactone) (PGCL) copolymer was synthesized from glycolide and epsilon-caprolactone in the presence of stannous octoate as catalyst. The copolymer was characterized by (1)H-NMR, gel permeation chromatography and differential scanning calorimetry. Scaffolds for tissue engineering applications were fabricated from PGCL copolymer using the solvent-casting and particle-leaching technique. The PGCL scaffolds produced in this fashion had open pore structures (average pore size = 250 microm) without the usual nonporous skin layer on external surfaces. Mechanical testing revealed that PGCL scaffolds were far more elastic than poly(lactic-co-glycolic acid) (PLGA) scaffolds fabricated using the same method. Tensile mechanical tests indicated that PGCL scaffolds could withstand an extension of 250% without cracking, which was much higher than withstood by PLGA scaffolds (10-15%). In addition, PGCL scaffolds achieved recoveries exceeding 96% at applied extensions of up to 230%, whereas PLGA scaffolds failed (cracked) at an applied strain of 20%. Dynamic mechanical tests showed that the permanent deformation of the PGCL scaffolds in a dry condition produced was less than 4% of the applied strain, when an elongation of 20% at a frequency of 1 Hz (1 cycle per second) was applied for 6 days. Moreover, PGCL scaffolds in a buffer solution also had permanent deformations less than 5% of the applied strain when an elongation of 10% at a frequency of 1 Hz was applied for 2 days. The usefulness of the PGCL scaffolds was demonstrated by engineering SM tissues in vivo. This study shows that the elastic PGCL scaffolds produced in this study could be used to engineer SM-containing tissues (e.g. blood vessels and bladders) in mechanically dynamic environments.

Polyhydroxyalkanonate derivatives in current clinical applications and trials

Polyhydroxyalkanonate is a typical biodegradable material, which is permitted for use in the medical and pharmaceutical fields. For its biodegradability, biocompatibility, and toxicological safety, the majority of products practically used are composed of homo-polymers of poly(lactic acid), poly(glycolic acid), and poly(epsilon-caprolactone) and their co-polymers. On the market, suture strings are still the main usage. The needs of biodegradable materials have been being gradually increased by the development of drug delivery systems, tissue engineering, and regenerative medicine. Some types of formulation, that is, mono-fibers, twisted fibers, films, fabrics, sponges, and injectable particles are developed to match each purpose. This article reviews the current clinical applications and trials of polyhydroxyalcanonate products.

Vancomycin encapsulation in biodegradable poly(epsilon-caprolactone) microparticles for bone implantation. Influence of the formulation process on size, drug loading, in vitro release and cytocompatibility

Vancomycin encapsulation in biodegradable poly(epsilon-caprolactone) microparticles (200 microm mean diameter) was most efficient with a simple emulsion technique that dispersed 122.5 mg/g of polymer. Scanning electron micrographs showed smooth or pitted particles. Dissolution studies were correlated with microparticle morphology, indicating higher release with pitted particles when vancomycin was encapsulated in a dissolved state. The cytocompatibility of these poly(epsilon-caprolactone) microparticles was demonstrated by a direct contact cytotoxic assay. This material can be considered as an efficient drug delivery system for bone implantation.

Comparative study of tissue response to polyglecaprone 25, polyglactin 910 and polytetrafluorethylene suture materials in rats

The authors evaluated the biocompatibility of three suture materials, polyglecaprone 25, polyglactin 910 and polytetrafluorethylene, implanted into subcutaneous tissue in the dorsal region of 20 Wistar albinus rats. After periods of 2, 7, 14 and 21 days, the rats were sacrificed and the specimens were processed for routine histotechnical analysis and stained with hematoxylin and eosin. The rate of fibrosis, angioblastic and fibroblastic proliferation, and also the intensity of inflammation were observed with the optic microscope. The results showed that polyglecaprone 25 suture material induced a mild inflammatory reaction, followed by polyglactin 910 and polytetrafluorethylene, respectively. Such biological behavior must be considered during the selection of the suture material to be used in oral surgery.

Liquid acrylate-endcapped biodegradable poly(epsilon-caprolactone-co-trimethylene carbonate). I. Preparation and visible light-induced photocuring characteristics

Photocurable liquid biodegradable copolymers were prepared by ring-opening copolymerization of epsilon-caprolactone (CL) and trimethylene carbonate (TMC) in the presence of a multifunctional hydroxyl group-bearing substance (di-, tri-, and tetra-functional alcohol and poly(ethylene glycol) (PEG) and its four-branched derivative) as an initiator and subsequent endcapping with acryloyl chloride at their hydroxyl terminals. These multifunctional, viscous liquid copolymers (molecular weights; approximately 2 x 10(3) to 7 x 10(3) g/mol) were converted to crosslinked solids by visible-light irradiation in the presence of camphorquinone as an initiator. The photocuring rate of these copolymers was enhanced by both higher functionality and lower molecule weight of the copolymers used. The photocuring rate depended on the amount of reducing agent (methacrylic acid 2-dimethylaminoethyl ester). Upon immersion in a phosphate buffer solution (pH 7.4), hydrolysis occurred preferentially on the surface except for photocured PEG-based copolymers that were degraded faster via both surface erosion and bulk degradation than low molecular weight alcohols-based copolymers. Cylindrical photocured constructs prepared by photoirradiation to the whole body in a mold filled with the liquid copolymer was demonstrated as an example of shape fabrication of biodegradable biomedical devices.

Fused deposition modeling of novel scaffold architectures for tissue engineering applications

Fused deposition modeling, a rapid prototyping technology, was used to produce novel scaffolds with honeycomb-like pattern, fully interconnected channel network, and controllable porosity and channel size. A bioresorbable polymer poly(epsilon-caprolactone) (PCL) was developed as a filament modeling material to produce porous scaffolds, made of layers of directionally aligned microfilaments, using this computer-controlled extrusion and deposition process. The PCL scaffolds were produced with a range of channel size 160-700 microm, filament diameter 260-370 microm and porosity 48-77%, and regular geometrical honeycomb pores, depending on the processing parameters. The scaffolds of different porosity also exhibited a pattern of compressive stress-strain behavior characteristic of porous solids under such loading. The compressive stiffness ranged from 4 to 77 MPa, yield strength from 0.4 to 3.6 MPa and yield strain from 4% to 28%. Analysis of the measured data shows a high correlation between the scaffold porosity and the compressive properties based on a power-law relationship.

The pH dependence of monofilament sutures on hydrolytic degradation

Hydrolytic degradation of two nonabsorbable sutures, four absorbable sutures, and a new type of absorbable suture was studied in buffered media of various pHs at 37 degrees C. The pH levels fixed in this study were 1.0, 7.4, 8.5, and 10.5. Physical measurements were made on the retention of tensile strength and melting temperature of the sutures after hydrolysis for 12 weeks. Sutures containing glycolic acid as a comonomer exhibited enhanced degradation in alkaline media, similar to polyglycolide multifilament sutures. Poly-p-dioxanone (PDS II) suture lost strength to a significant extent at pH 1.0, suggesting that care should be taken when this suture is used for closing tissues in contact with acidic media, such as the stomach. In marked contrast, the degradation of lactide-epsilon-caprolactone copolymer [P(LA/CL)] suture was not sensitive to the pH of media. The surface morphology of hydrolyzed sutures varied, depending on the pH of media. Particularly, moon-crater-shaped impressions were observed on glycolide-epsilon-caprolactone copolymer (MONOCRYL) and glycolide-trimethylene carbonate-dioxanone copolymer (BIOSYN) sutures. Among the nonabsorbable sutures, nylon (ETHILON) exhibited the fastest loss of strength in acidic buffer solution, and polypropylene (PROLENE) suture retained most of its initial strength at all pHs studied.

A new injectable bone substitute combining poly(epsilon-caprolactone) microparticles with biphasic calcium phosphate granules

Previous studies have shown the effectiveness of an injectable bone substitute (IBS) composed of biphasic calcium phosphate in 2% hydroxypropyl methylcellulose gel (50/50 w/w). A therapeutic agent in the form of a drug can be added to the biomaterial by encapsulation into microparticles to protect the active agent, control its release and preserve the material rheological properties. Poly(epsilon-caprolactone) was used in this study because of its biocompatibility and resorbability, as tested in orthopaedic implants and surgical sutures. Particles (80-200 microm) were manufactured by a solvent evaporation-extraction process (1 g of polymer, 11-15 ml methylene chloride, with a stirring speed of 400-600 rpm) and introduced into the IBS in a 5-50% (V/V) range. Injectability was evaluated by texture analysis. With less than 45% of particles, the material had rheological properties similar to those of the reference IBS, whereas injectability decreased markedly with more than 45% of particles. A preliminary in vitro release study showed that this type of triphasic IBS could be efficient for drug delivery systems with osteoconduction properties.

Mechanical properties and cell cultural response of polycaprolactone scaffolds designed and fabricated via fused deposition modeling

A number of different processing techniques have been developed to design and fabricate three-dimensional (3D) scaffolds for tissue-engineering applications. The imperfection of the current techniques has encouraged the use of a rapid prototyping technology known as fused deposition modeling (FDM). Our results show that FDM allows the design and fabrication of highly reproducible bioresorbable 3D scaffolds with a fully interconnected pore network. The mechanical properties and in vitro biocompatibility of polycaprolactone scaffolds with a porosity of 61 +/- 1% and two matrix architectures were studied. The honeycomb-like pores had a size falling within the range of 360 x 430 x 620 microm. The scaffolds with a 0/60/120 degrees lay-down pattern had a compressive stiffness and a 1% offset yield strength in air of 41.9 +/- 3.5 and 3.1 +/- 0.1 MPa, respectively, and a compressive stiffness and a 1% offset yield strength in simulated physiological conditions (a saline solution at 37 degrees C) of 29.4 +/- 4.0 and 2.3 +/- 0.2 MPa, respectively. In comparison, the scaffolds with a 0/72/144/36/108 degrees lay-down pattern had a compressive stiffness and a 1% offset yield strength in air of 20.2 +/- 1.7 and 2.4 +/- 0.1 MPa, respectively, and a compressive stiffness and a 1% offset yield strength in simulated physiological conditions (a saline solution at 37 degrees C) of 21.5 +/- 2.9 and 2.0 +/- 0.2 MPa, respectively. Statistical analysis confirmed that the five-angle scaffolds had significantly lower stiffness and 1% offset yield strengths under compression loading than those with a three-angle pattern under both testing conditions (p < or = 0.05). The obtained stress-strain curves for both scaffold architectures demonstrate the typical behavior of a honeycomb structure undergoing deformation. In vitro studies were conducted with primary human fibroblasts and periosteal cells. Light, environmental scanning electron, and confocal laser microscopy as well as immunohistochemistry showed cell proliferation and extracellular matrix production on the polycaprolactone surface in the 1st culturing week. Over a period of 3-4 weeks in a culture, the fully interconnected scaffold architecture was completely 3D-filled by cellular tissue. Our cell culture study shows that fibroblasts and osteoblast-like cells can proliferate, differentiate, and produce a cellular tissue in an entirely interconnected 3D polycaprolactone matrix.

Surgery: Comparison of three closure methods and two absorbable suture materials for closure of jejunal enterotomy incisions in healthy dogs

The macroscopic and histological appearance of jejunal antimesenteric incisions approximated with two different absorbable suture materials (monofilament versus multifilament) and three closure techniques (appositional single layer, crushing single layer, and double layer) were compared in healthy dogs at 14 or 28 days, postoperatively. No significant differences between the two suture materials were observed for most of the macroscopic or histological variables. However, the monofilament suture material caused significantly more fibrous tissue reaction in the muscular layer of the jejunum than did the multifilament suture material. Of the three enterotomy closure techniques used in this study, the appositional single-layer method proved to be the best. The double-layer closure method caused a significant decrease in the incisional circumference, the relative circumference, and volume of the jejunum, and a significant increase in jejunal wall thickness. Our findings suggest that canine jejunal enterotomy incisions can be closed using an appositional suture pattern with relatively rapidly absorbable monofilament suture material. The use of double-layer suture patterns for closure of jejunal enterotomy incisions should be avoided because the size of the intestinal lumen may be reduced.

Bioresorbable polymers in trauma and bone surgery

During the last few decades interest in resorbable polymeric materials has been steadily increasing. As with other materials for implantable devices, they have to satisfy several biological and technical requirements. Implants should maintain adequate mechanical properties in vivo for the time required and degrade at an effective rate. The conditions of polymer synthesis, further processing into implants and the sterilization process determine the mechanical properties of resorbable implants. Degradation of implants is manifested by implant fragmentation, strength loss and the decrease of polymer molecular weight. The rate of degradation and the tissue reaction are strongly affected by the material chemical composition and to some extent also by the mechanical properties. Potentially, devices made from bioresorbable polymers can overcome problems associated with metal implants like stress protection, potential for corrosion, wear and debris formation, as well as the necessity of implant removal. Resorbable polymers have proven to be good materials for a range of devices in trauma surgery. However, modifications and optimizations are still required. Three-dimensional porous scaffolds in various geometrical forms offer a good potential for the manufacture of tissue-engineered implants in the future.

Double butterfly suture for high tension: a broadly anchored, horizontal, buried interrupted suture

BACKGROUND

The excision of skin lesions such as tumors, nevi, and scars frequently results in tension on surgical wound margins. This tension is commonly counteracted surgically with buried, intracutaneous, interrupted sutures of absorbable material which are anchored vertically in the corium.

METHOD

The horizontal, buried, intracutaneous butterfly suture has been described elsewhere. It is firmly anchored in the corium, everts wound margins, and adapts them nearly as broadly as two vertical sutures. It can also be laid as a double butterfly suture, as described here, and then has the shape of an "8." This double butterfly suture is equivalent to three vertical sutures because of its broad base in the corium. Moreover, it can cope with much greater tension because of its "pulley" effect. A single double butterfly suture usually suffices for small defects, particularly when the wound edges are cut obliquely with a longer rim of epidermis.

MATERIALS

We have laid the traditional butterfly suture in more than 35,000 skin lesion excisions since 1985 and the double butterfly suture alone or as a supplement in more than 10,000 sutures since 1992. We use 2-0 to 6-0 polydioxanone for these procedures, since it has proven in trials to be the best-absorbed suture material.

RESULTS

In most cases, the resulting scars were narrow and smooth in spite of high tension. Results were unsatisfactory in only 6.2% of procedures.

CONCLUSION

The double butterfly suture described here has the advantages of withstanding tension better while everting wound margins and requiring fewer stitches for wound closure. However, it is important that the suture knot be deeply anchored beneath the corium.

Comparative study on biocompatibility and absorption times of three absorbable monofilament suture materials (Polydioxanone, Poliglecaprone 25, Glycomer 631)

Monofilament synthetic absorbable suture materials offer excellent glide characteristics and cause minimal tissue trauma as a result of their smooth monofilament structure and gradual bio-absorption. An investigation was conducted on 72 rats to compare three types of monofilament absorbable suture material (Polydioxanone, Poliglecaprone 25, Glycomer 631), with respect to their clinical characteristics, tissue inflammatory reaction and suture absorption times. The results identified different qualities for each suture: Poliglecaprone 25 and Glycomer 631 suture materials were found to be less reactive than Polydioxanone in rat skin. However, because of their extremely low tissue reaction values, all three materials were deemed particularly suitable for use as intracuticular sutures. Absorption times in rat skin were less than 3 months for Poliglecaprone 25, between 3 and 6 months for Glycomer 631 and 6 months for Polydioxanone. The differences in suture characteristics which were detected in our study can help in the surgical selection of the most appropriate suture material.

Biocompatibility of a biodegradable in situ forming implant system in rhesus monkeys

Formulations of a polymeric delivery system containing a 75/25 poly(DL-lactide-co-caprolactone dissolved in either N-methyl-2-pyrrolidone or dimethyl sulfoxide were injected both subcutaneously (SC) and intramuscularly (IM) into rhesus monkeys. Each monkey received an SC and IM injection of each of the two formulations, for a total injection volume of 4 mL. The monkeys were observed daily for overt signs of toxicity, and after 4 weeks biopsies of each implant site were fixed, stained, and evaluated histologically for tissue reaction to the polymer system. Tissue response was graded upon the presence and level of fibrous connective tissue and inflammatory cell infiltrate. The polymer formulations appeared to be safe, as the animals remained healthy and active throughout the study with no changes in food or water consumption, weight loss, or abnormal behavior observed. Tissue response to both formulations was considered mild and similar to that for other biodegradable polymers, in that the reaction was limited to tissue immediately adjacent to the residual polymer fragments and consisted of a mild fibroplasia with the presence of a few lymphocytes and macrophages. There were no differences between the two formulations in tissue response, and both formulations were considered acceptable for use as injectable implant systems.

Surgical materials and wound closure techniques

Recent innovations in surgical materials have helped to enhance wound healing and protect surgical wounds from infection. Materials such as polyglyconate have been evaluated in equine tissues and found efficacious. Other materials, such as poliglecaprone 25, appear to have qualities useful to equine surgery but are untested in equine tissues. Care must be taken to fully evaluate a new surgical material because its usefulness in equine tissues may not match that in human or laboratory animal tissues. Furthermore, use of disposable materials in surgery, although considered ideal for maintenance of sterility, may come under more scrutiny in the future as environmental issues gain prominence. We tend to reserve disposable materials for prolonged procedures and for procedures that carry high risk of failure if infection develops.