Monocryl suture, a new ultra-pliable absorbable monofilament suture

Review Paper: Absorbable Polymeric Surgical Sutures: Chemistry, Production, Properties, Biodegradability, and Performance

Among biomaterials used as implants in human body, sutures constitute the largest groups of materials having a huge market exceeding $1.3 billion annually. Sutures are the most widely used materials in wound closure and have been in use for many centuries. With the development of the synthetic absorbable polymer, poly(glycolic acid) (PGA) in the early 1970s, a new chapter has opened on absorbable polymeric sutures that got unprecedented commercial successes. Although several comparative evaluations of suture materials have been published, there were no serious attempts of late on a comprehensive review of production, properties, biodegradability, and performance of suture materials. This review proposes to bring to focus scattered data on chemistry, properties, biodegradability, and performance of absorbable polymeric sutures.

Osteogenic differentiation of bone marrow stromal cells on poly(epsilon-caprolactone) nanofiber scaffolds

Nanofiber poly(epsilon-caprolactone) (PCL) scaffolds were fabricated by electrospinning, and their ability to enhance the osteoblastic behavior of marrow stromal cells (MSCs) in osteogenic media was investigated. MSCs were isolated from Wistar rats and cultured on nanofiber scaffolds to assess short-term cytocompatibility and long-term phenotypic behavior. Smooth PCL substrates were used as control surfaces. The short-term cytocompatibility results indicated that nanofiber scaffolds supported greater cell adhesion and viability compared with control surfaces. In osteogenic conditions, MSCs cultured on nanofiber scaffolds also displayed increased levels of alkaline phosphatase activity for 3 weeks of culture. Calcium phosphate mineralization was substantially accelerated on nanofiber scaffolds compared to control surfaces as indicated through von Kossa and calcium staining, scanning electron microscopy and energy-dispersive X-ray spectroscopy. Increased levels of intra- and extracellular levels of osteocalcin and osteopontin were observed on nanofiber scaffolds using immunofluorescence techniques after 3 weeks of culture. These results demonstrate the enhanced tissue regeneration property of nanofiber scaffolds, which may be of potential use for engineering osteogenic scaffolds for orthopedic applications.

A Proposed Fabrication Method of Novel PCL-GEL-HAp Nanocomposite Scaffolds for Bone Tissue Engineering Applications

In this study, poly(∊-caprolactone) (PCL), gelatin (GEL) and nanocrystalline hydroxyapatite (HAp) was applied to fabricate novel PCL-GEL-HAp nanaocomposite scaffolds through a new fabrication method. With the aim of finding the best fabrication method, after testing different methods and solvents, the best method and solvents were found, and the nanocomposites were prepared through layer solvent casting combined with freeze-drying. Acetone and distillated water were used as the PCL and GEL solvents, respectively. The mechanical test showed that the increasing of the PCL weight through the scaffolds caused the improvement of the final nanocomposite mechanical behavior due to the increasing of the ultimate stress, stiffness and elastic modulus (8 MPa for 0% wt PCL to 23.5 MPa for 50% wt PCL). The biomineralization investigation of the scaffolds revealed the formation of bone-like apatite layers after immersion in simulated body fluid (SBF). In addition, the in vitro cytotoxity of the scaffolds using L929 mouse fibroblast cell line (ATCC) indicated no sign of toxicity. These results indicated that the fabricated scaffold possesses the prerequisites for bone tissue engineering applications.

Surface Engineering of Polycaprolactone by Biomacromolecules and their Blood Compatibility

Improving blood compatibility of biodegradable polymers is an area of intensive research in blood contacting devices. In this study, curdlan sulphate and heparin-modified poly (caprolactone) (PCL) hybrids were developed by physically entrapping these molecules on the PCL surface. This modification technique was performed by reversible gelation of the PCL surface region following exposure to a solvent and nonsolvent mixture. The presence of these biomacromolecules on the PCL surface was verified by atomic force microscopy (AFM) and scanning electron microscopy and energy dispersive X-ray analysis (SEM-EDAX) analysis, while wettability of the films was investigated by dynamic contact angle measurements. The blood compatibilities of the surface-modified films were examined using in vitro platelet and leukocyte adhesion and thrombus formation. Mouse RAW 264.7 macrophage cells were used to assess the cell adhesion and inflammatory response to the modified surface by quantifying mRNA expression levels of proinflammatory cytokines namely TNF-α and IL-1β using real-time polymerase chain reaction (RT-PCR). A lower platelet and leukocyte adhesion and activation was observed on the modified films incubated with whole human blood for 2 h. The thrombus formation on the PCL was significantly decreased upon immobilization of both curdlan sulphate (39%, *p<0.05) and heparin (28%, *p<0.01) when compared to bare PCL (80%). All of these results revealed that improved blood compatibility was obtained by surface entrapment of both curdlan sulphate (CURS) and heparin (HEP) onto PCL films. Both PCL-CURS and PCL-HEP films reduced RAW 264.7 macrophage cell adhesion (*p<0.05) with respect to the base unmodified PCL. The cellular inflammatory response was suppressed on the modified substrates. The mRNA expression levels of proinflammmatory cytokines (TNF-α and IL-1β) were upregulated on bare PCL, while it was significantly lower on PCL-CURS and PCL-HEP substrates (**p<0.001). Thus, this biomacromolecule entrapment process can be applied on PCL in order to achieve improved blood compatibility and reduced inflammatory host response for its future blood contacting applications.

A cascade biodegradable polymer based on alternating cyclization and elimination reactions

Polymers that depolymerize by a cascade of intramolecular reactions in response to the removal of a stabilizing end-cap can allow for an unprecedented degree of control over the polymer degradation process. Described here is the development of polymers comprising N,N'-dimethylethylenediamine and 4-hydroxybenzyl alcohol linked by carbamate linkages. The polycarbamate backbone is stable in aqueous solution, but removal of a protective end-cap from the amine terminus allows the diamine to cyclize, forming N,N'-dimethylimidazolidinone and releasing the phenol, which undergoes a 1,6-elimination followed by the release of CO(2) to reveal the next amine to continue the cascade. These polymers therefore degrade by alternating cyclization and elimination reactions. First, a tert-butylcarbamate (Boc) group was introduced as a cleavable end-cap, and the degradation kinetics and mechanism were studied by (1)H nuclear magnetic resonance (NMR) spectroscopy and size exclusion chromatography. Next, to demonstrate the degradability of these polymers under biologically relevant conditions, poly(ethylene oxide) was introduced as an end-cap via an ester linkage, to provide an amphiphilic block copolymer. This copolymer was found to assemble into cascade degradable nanoparticles that were capable of encapsulating and subsequently releasing a fluorescent dye in aqueous solution. This new class of polymers therefore provides highly promising materials that can be used for the development of medical devices, drug delivery vehicles, and tissue engineering scaffolds with unique biodegradation properties.

Advances in progenitor cell therapy using scaffolding constructs for central nervous system injury

Traumatic brain injury (TBI) is a major cause of morbidity and mortality in the United States. Current clinical therapy is focused on optimization of the acute/subacute intracerebral milieu, minimizing continued cell death, and subsequent intense rehabilitation to ameliorate the prolonged physical, cognitive, and psychosocial deficits that result from TBI. Adult progenitor (stem) cell therapies have shown promise in pre-clinical studies and remain a focus of intense scientific investigation. One of the fundamental challenges to successful translation of the large body of pre-clinical work is the delivery of progenitor cells to the target location/organ. Classically used vehicles such as intravenous and intra arterial infusion have shown low engraftment rates and risk of distal emboli. Novel delivery methods such as nanofiber scaffold implantation could provide the structural and nutritive support required for progenitor cell proliferation, engraftment, and differentiation. The focus of this review is to explore the current state of the art as it relates to current and novel progenitor cell delivery methods.

Layer-by-layer deposition of polymeric microgel films on surgical sutures for loading and release of ibuprofen

Surgical sutures capable of drug loading and sustained release are important in wound healing applications. In this work, a facile way to incorporate anti-inflammatory drug of ibuprofen in surgical sutures has been established. First, surgical sutures were deposited with multilayer films containing microgels of chemically cross-linked poly(allylamine hydrochloride) (PAH) and dextran (named PAH-D) by layer-by-layer deposition of PAH-D and hyaloplasm acid (HA). Ibuprofen was then incorporated in the PAH-D/HA films to obtain ibuprofen-loaded sutures. Ibuprofen incorporated in the surgical sutures can be released in 0.9% normal saline in a sustainable way. The successful incorporation of ibuprofen in surgical sutures depends largely on PAH-D microgels, which can deposit directly on the hydrophobic surgical sutures without any surface modification and load ibuprofen based on electrostatic interaction between them. The present study provides a facile and generally applicable way to incorporate drugs in surgical sutures that is highly useful to accelerate the healing of cuts and wounds.

Physicochemical characterisation of novel ultra-thin biodegradable scaffolds for peripheral nerve repair

In this study, the physicochemical properties of microporous poly (epsilon-caprolactone) (PCL) films and a composite material made of PCL and polylactic acid (PLA) blend were tested. Fabricated by solvent casting using dichloromethane, these ultra-thin films (60 +/- 5 microm in thickness) have a novel double-sided surface topography, i.e. a porous surface with pores 1-10 microm in diameter and a relatively smooth surface with nano-scaled texture. Porous surfaces were found to be associated with increased protein adsorption and the treatment of these polyester scaffolds with NaOH rendered them more hydrophilic. Differential Scanning Calorimetry (DSC) showed that the incorporation of PLA reduced the crystallinity of the original homopolymer. Chemical changes were investigated by means of Fourier Transform Infrared Spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Average surface roughness (Ra), hydrophilicity/hydrophobicity and mechanical properties of these materials were also assessed for the suitability of these materials as nerve conduits.

Microfluidic assisted synthesis of multi-functional polycaprolactone microcapsules: incorporation of CdTe quantum dots, Fe3O4 superparamagnetic nanoparticles and tamoxifen anticancer drugs

This paper demonstrates a proof-of-concept approach for encapsulating the anticancer drug tamoxifen, Fe3O4 nanoparticles (NPs) and CdTe quantum dots (QDs) into size-controlled polycaprolactone (PCL) microcapsules utilizing microfluidic emulsification, which combined magnetic targeting, fluorescence imaging and drug controlled release properties into one drug delivery system. Cross-linking the composite PCL microcapsules with poly(vinyl alcohol) (PVA) tailored their size, morphology, optical and magnetic properties and drug release behaviors. The flow conditions of the two immiscible solutions were adjusted in order to successfully generate various sizes of polymer droplets. The result showed superparamagnetic and fluorescent properties, and was used as a controlled drug release vehicle. The composite magnetic and fluorescent PCL microcapsules are potential candidates for a smart drug delivery system.

Synthesis and water-swelling of thermo-responsive poly(ester urethane)s containing poly(epsilon-caprolactone), poly(ethylene glycol) and poly(propylene glycol)

Thermo-responsive multiblock poly(ester urethane)s comprising poly(epsilon-caprolactone) (PCL), poly(ethylene glycol) (PEG), and poly(propylene glycol) (PPG) segments were synthesized. The copolymers were characterized by GPC, NMR, FTIR, XRD, DSC and TGA. Water-swelling analysis carried out at different temperatures revealed that the bulk hydrophilicity of the copolymers could be controlled either by adjusting the composition of the copolymer or by changing the temperature of the environment. These thermo-responsive copolymer films formed highly swollen hydrogel-like materials when soaked in cold water and shrank when soaked in warm water. The changes are reversible. The mechanical properties of the copolymer films were assessed by tensile strength measurement. These copolymers were ductile when compared to PCL homopolymers. Young's modulus and the stress at break increased with increasing PCL content, whereas the strain at break increased with increasing PEG content. The results of the cytotoxicity tests based on the ISO 10993-5 protocol demonstrated that the copolymers were non-cytotoxic and could be potentially used in biomedical applications.

Tensile strength study of the abdominal wall following laparotomy synthesis using three types of surgical wires in Wistar rats

PURPOSE: To study the tensile strength of the abdominal wall following laparotomy synthesis utilizing three types of surgical wires. METHODS: Thirty Wistar rats were randomized into three groups of ten rats each. Each group underwent a 3cm-laparotomy which was closed with 3-0 polyglactin 910, polyglecrapone and catgut wires. After 63 days, euthanasia was performed and part of the abdominal wall was removed with which a strip was produced measuring 2.0 cm in length by 6.0 cm in width comprising the abdominal muscles with the implanted mesh. The sample was fixed in a mechanical test machine in which constant force was applied contrary to the tissue strips. Maximum force was considered, expressed in Newton, until full rupture of the tissue occurred. The non-parametrical Kruskal - Wallis test was used for the statistical analysis, admitting p<0.05. RESULTS: The average strength of the catgut group was slightly lower (33.50 N) than that of the polyglactin group (34.23 N), the difference not being statistically significant (p=0.733). The polyglecaprone group was the one which presented the lowest strength value of all three wires analyzed (29.86 N). No statistical difference was obtained when comparing the strength values of the polyglecaprone group and the catgut group (p=0.06 ). However, when the polyglecaprone group was compared to the polyglactin 910 group no statistical difference was obtained (p=0.029). CONCLUSION: The polyglactin wire presented the highest tensile strength among the three wires analyzed, such value being statistically significant when polyglactin was compared to the polyglecaprone wire.

Development of a biodegradable bioadhesive containing urethane groups

Surgical adhesives consist on an attractive alternative to suturing or stapling since they can accomplish other tasks, such as haemostasis and the ability to seal air leakages. The application of adhesives would also reduce the surgeries procedure time since they represent an easier and faster method to establish tissue adhesion. The aim of this work was the development of a biodegradable urethane pre-polymer that presents the capacity of reacting with the amino groups present in the biological molecules. Urethanes based on polycaprolactone diol (PCL) were synthesized by reaction of the molecule either with isophorone diisocyanate (IPD-isocyanate) or hexamethylene diisocyanate (HDI-isocyanate). The characterization of the materials was accomplished by: ATR-FTIR (Attenuated Total Reflectance-Fourier Transform Infrared), determination of swelling capacity, stability of NCO groups in the presence of humidity conditions, reaction with aminated substrates (as a simulation of the living tissues) and determination of surface energy by contact angle measurement. The haemocompatibility of the PU was also evaluated by thrombosis and haemolysis tests.

Comparative study of the cytotoxic effect of resilon against two cell lines

Resilon is a new material that is a candidate to replace gutta-percha as a root filling material. This study evaluated the antiproliferative effect of Resilon and two commercially available gutta-percha points (Roeko, Dentsply). Two established cell lines (L929 and RPC-C2A) were used for the experiment. Cell survival fraction was estimated by the sulforhodamine-B assay, in reference to controls after 48-h exposure. Non-parametric tests (Kruskal-Wallis followed by Dunn's multiple comparisons) were used to evaluate the statistical significance of the results (α=0.05). Cytotoxicity in a descending order was: Resilon > Roeko gutta-percha > Dentsply gutta-percha. At 24-h exposure, no statistically significant differences (p>0.05) were observed between tested materials in both cell lines. At 48-h exposure, statistically significant differences (p<0.05) were found between Resilon and the other materials in the L929 cell line. In the RPC-C2A cell line Resilon was significantly more cytotoxic than Dentsply gutta-percha (p<0.05), but no statistically significant differences (p>0.05) were found between Resilon and Roeko gutta-percha. The cytotoxicity of Resilon increased significantly from 24 h to 48 h in both cell lines. Resilon points were more cytotoxic than gutta-percha points. The cytotoxicity was time dependent and increased after 48 h.

Development of a new photocrosslinkable biodegradable bioadhesive

Adhesives provide a needle-free method of wound closure and do not require local anaesthetics. Polymeric adhesives have been used for about 3 decades for joining several tissues of the organism. Also, they can accomplish other tasks, such as haemostasis and the ability to seal air leakages and have the potential to serve as delivery systems. PCL was modified with 2-isocyanatoethylmethacrylate to form a macromer that was crosslinked via UV irradiation using Irgacure 2959 by CIBA as the photoinitiating agent. The characterization of the materials was accomplished by: attenuated total reflectance-Fourier transform infrared (ATR-FTIR), swelling capacity determination, evaluation of adhesive capacity (by reaction with aminated substrates) and determination of surface energy by contact angle measurement. Thermal characterization of the adhesive was performed by dynamical mechanical thermal analysis (DMTA) and thermogravimetric analysis (TGA). The morphology of PCL networks was observed using scanning electron microscopy (SEM) both after crosslinking process and following biodegradation in human plasma. The haemocompatibility of the membranes was also evaluated by thrombosis and haemolysis tests.

A Novel Polycaprolactone/Hydroxyapatite Scaffold for Bone Tissue Engineering

In this study, novel polycaprolactone/hydroxyapatite (PCL/HA) scaffolds were prepared to increase mechanical properties and degradation of PCL/HA ones for bone tissue engineering. PCL macromers were synthesized through the reaction of PCL diol (Mn: 530, 1250, and 2000) and PCL triol (Mn: 900) with acryloyl chloride and confirmed using nuclear magnetic resonance spectrometer (NMR) and fourier transform infrared (FTIR). The PCL/HA scaffolds were prepared by cross-linking of PCL macromer in the presence of HA by UV treatment and freeze drying methods. Mechanical property and porosity as well as degradability of the PCL/HA scaffolds were also investigated. PCL/HA scaffolds showed faster degradation and higher compressive modulus than those of PCL itself due to their low crystallinity and modification of terminal groups. The pore morphology and pore sizes of the PCL/HA scaffold were checked by scanning electron microscope (SEM). Cell cytotoxicity and proliferation of MG-63 osteoblast cultured onto the PCL/HA scaffold was assessed by lactate dehydrogenase (LDH) assay and Alamar blue assay, respectively. The novel PCL/HA scaffold appears to be suitable for bone substitutes.

Recent Advances in Star Polymer Design: Degradability and the Potential for Drug Delivery

The use of polymers as drug delivery devices represents an exciting area of development in the biomedical industry. This paper briefly highlights some of the different types of macromolecules that have attracted attention as potential drug delivery devices, with a particular focus on the class of star polymers known as core cross-linked star (CCS) polymers. The ability to control the rate at which encapsulated molecules can be released is an important factor in the design of efficient drug delivery devices. In this regard, several different techniques to incorporate degradable functionality into CCS polymers are examined as a potential means of controlling release kinetics.

Characteristics of novel monofilament sutures prepared by conjugate spinning

Compared with braided multifilament sutures, absorbable monofilaments are attractive suture materials as they exhibit less tissue drag and cause less tearing because of their smooth surfaces. However, monofilament sutures are less flexible and more difficult to tie a knot than multifilament ones, and their knots are more likely to loosen due to inferior knot security. Although various approaches have been reported to improve the flexibility of monofilament sutures, they still have limitations regarding poor knot security. To address this problem, we developed a novel technique to fabricate monofilament sutures by a conjugate spinning method, resulting in the formation of a sea/islands type of bicomponent monofilament suture. These sea/islands type bicomponent monofilament sutures, which can place many fine strands of a polymeric fiber within a matrix of another polymer, exhibited excellent knot security, flexibility, and low strain energy, compared with commercially available monofilament sutures.

Tissue reaction and surface morphology of absorbable sutures after in vivo exposure

Tissue reaction to suture materials depends mainly on how the polymer they are composed of interacts with the tissues. There are few in vivo studies evaluating the suture material modifications resulting from its interaction with tissues. This paper aimed to study rat subcutaneous tissue reaction to irradiated polyglactin 910, polydioxanone, poliglecaprone 25 and chromic gut and its correlation with the ultra-structural alterations the materials undergo. The histological alterations were studied on the 1st, 2nd, 3rd, 7th and 14th day after suture implantations. In these periods, the materials were removed from the tissues and their surfaces were analyzed by scanning electron microscopy. Irradiated polyglactin 910 stimulated the formation of multinucleated giant cells and its filaments underwent cleavage and dissolution. In potydioxanone, a few inflammatory cells and scar fibrosis was observed, and triangular cracks appeared on its surface. Around the poliglecaprone 25, a diffused infiltration of a few mononuclear cells and fibrosis was recorded and formation of craters was observed on its surface. Chromic gut induced necrosis and granulation tissue and underwent dissolution in the tissues during the studied periods. In this study, it was observed that suture materials induced differentiated tissue reactions and morphologic surface changes, suggesting that indications should be individualized.

Biomechanical and histologic comparison of single-layer continuous Cushing and simple continuous appositional cystotomy closure by use of poliglecaprone 25 in rats with experimentally induced inflammation of the urinary bladder

OBJECTIVE

To biomechanically and histologically compare single-layer continuous Cushing and simple continuous appositional cystotomy closure in rats with xylene-induced cystitis.

ANIMALS

40 female Sprague-Dawley rats.

PROCEDURE

Rats were anesthetized, their urinary bladders catheterized and evacuated, and xylene instilled in each bladder for 5 minutes and then aspirated. Forty-eight hours later, ventral midline celiotomy and cystotomy (8 mm) were performed. Cystotomies were closed with 6-0 poliglecaprone 25 by use of a single-layer continuous Cushing or simple continuous appositional pattern (20 rats/group), and cystotomy times were recorded. Rats were allocated to healing durations (5 rats/group) of 0, 3, 7, and 14 days. Celiotomies were closed in a routine manner. After the allotted healing interval, another celiotomy was performed, the urethra cannulated, and ureters ligated. The cannula was secured to the urethra, and the bladder infused at 0.1 mL/min. Leak pressure volume, leak pressure, peak pressure volume, and peak pressure were recorded via a pressure transducer. Bladders were harvested and histologically assessed.

RESULTS

Cystotomy time, biomechanical testing values, and overall inflammation scores did not differ between closure methods for any healing duration. Both methods had significantly greater leak pressures, with the appositional method also having significantly greater peak pressures on day 7, compared to day 0. Biomechanical testing values decreased from day 7 to 14 as a result of juxtaincisional weakening of the bladder and xylene-induced changes in collagen.

CONCLUSIONS AND CLINICAL RELEVANCE

Simple continuous appositional was equal biomechanically and histologically to continuous Cushing for all comparison variables. Poliglecaprone 25 was acceptable for cystotomy closure.