Electrospinning/electrospraying coatings for metal microneedles: A design of experiments (DOE) and quality by design (QbD) approach.

The research presented here shows QbD implementation for the optimisation of the key process parameters in electrohydrodynamic atomisation (EHDA). Here, the electrosprayed nanoparticles and electrospun fibers consisting of a polymeric matrix and dye. Eight formulations were assessed consisting of 5% w/v of polycaprolactone (PCL) in dichloromethane (DCM) and 5% w/v polyvinylpyrrolidone (PVP) in ethanol. A full factorial DOE was used to assess the various parameters (applied voltage, deposition distance, flow rate). Further particle and fiber analysis using Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), Fourier Transform Infrared Spectroscopy (FTIR), particle/fiber size distribution. In addition to this in vitro release studied were carried out using fluorescein and Rhodamine B as model dyes and in vitro permeation studies were applied. The results show a significant difference in the morphology of resultant structures as well as a more rapid release profile for the PVP particles and fibers in comparison to the sustained release profiles found with PCL. In vitro drug release studies showed 100% drug release after 7 days for PCL particles and showed 100% drug release within 120 min for PVP particles. The release kinetics and the permeation study showed that the MN successfully pierced the membrane and the electrospun MN coating released a large amount of the loaded drug within 6 h. This study has demonstrated the capability of these robust MNs to encapsulate a diverse range drugs within a polymeric matrix giving rise to the potential of developed personalised medical devices.

Absorbable sutures in general surgery - review, available materials, and optimum choices.

Sutures are the most versatile materials used in surgery. Despite recent technological advances and availability of novel materials such as tissue cements, it appears that surgical sutures will continue to be used for many years to come. The objective of this study was to provide an overview of the most common absorbable sutures used in general surgery. The appropriate suture choice for a particular procedure is of key importance for the success of that procedure.

Usability and effectiveness of Suprathel® in partial thickness burns in children.

PURPOSE: Evaluation of usability and effectiveness of Suprathel® in the treatment of partial thickness burns in children. METHODS: A prospective, observational study to evaluate adherence of Suprathel® to the wound bed, reepithelialization time, grafting, wound colonization and infection, pain, dressing changes, length of hospital stay (LOS) and scar formation. RESULTS: Twenty-one children (median age 2.4 years, range 5 months-14 years) with a median total body surface area (TBSA) of 4 % (range 1-18) were included. Median LOS was 10 days (range 3-20). Median outer layer dressing changes was 3 (range 1-14). Suprathel® was only adherent in wounds debrided with Versajet®. Median reepithelialization time was 13 days (range 7-29). Three patients needed a split skin graft. There were 7 (33 %) patients with wound colonization before application of Suprathel®. This increased to 12 (57 %) patients during treatment. One patient developed a wound infection. Median visual analog scale (VAS) scores for background and procedural pain in patients >7 years were 3.2 (range 2-5) and 3.5 (range 2-5), respectively. In younger patients, median background and procedural COMFORT-B scores were 13.8 (range 10-23) and 14.8 (range 13-23, p = 0.03), respectively. Patient and Observer Scar Assessment Scale (POSAS) scores were favorable after 3 and 6 months post burn. CONCLUSIONS: Suprathel® provides potential advantages regarding pain and scar formation, but extensive wound debridement is needed to achieve adequate adherence.

A randomized, prospective trial evaluating surgeon preference in selection of absorbable suture material.

This study is the first double-blinded, randomized comparison of two absorbable sutures. To better understand product characteristics and surgeon preference, we conducted a study of two similar-appearing FDA-approved sutures, glyconate and poliglecaprone 25. Four dermatologic surgeons were enlisted. A total of 48 patients with 53 surgical sites were examined. One half of each surgical wound was closed with one type of suture and the other half with the other type. Each half was evaluated for product characteristics. There was no statistically significant difference in surgeon preference for glyconate versus poliglecaprone 25 (P=0.64). Of the cohort preferring poliglecaprone 25, there was a correlation with speed of closure (P=0.06). Of the surgeons that preferred glyconate, we found significantly better visibility (P=0.03), reduced suture breakage during knot tying (P=0.05), and correlation with better handling properties (P=0.06) associated with that preference. The data from this study will enable products to be designed towards these needs and allow surgeons to select sutures that more precisely fit their particular requirements.

Osteolysis following resorbable poly-L-lactide-co-D, L-lactide PLIF cage use: a review of cases.

STUDY DESIGN: Report of case series. OBJECTIVE: To report a problem with bioabsorbable poly-L-lactide-co-D, L-lactide, PLDLLA, posterior lumbar instrumented fusion (PLIF) cage implants. SUMMARY OF BACKGROUND DATA: Synthetic bioabsorbable implants have recently been introduced to spinal surgery and their indications and applications are still being explored. There is evidence that the use of bioabsorbable cages may be of benefit in interbody spinal fusion. METHODS: We present a case series of nine patients who have undergone PLIF with bioabsorbable cages in the lumbar spine. RESULTS: At follow-up over at least 1 year, four of these patients were found to have osteolysis around the implant on CT scanning. One of these patients underwent an operation to remove the cage and histology sent during surgery suggested that the implant had caused the bone loss and there was no evidence of infection. Another patient had ongoing pain in relation to the lysis, while the other two patients with lysis remained asymptomatic. CONCLUSIONS: PLDLLA cage, which has high osteolytic nature, is considered not suitable as a fusion cage.

On the determination of Darcy permeability coefficients for a microporous tissue scaffold.

Structural characterization of porous tissue scaffolds is challenging due to their complexity. Most investigators report the porosity of the material together with an estimate of the mean pore size and the pore size distribution. The usefulness of these measures is limited, especially in predicting the time-dependent permeation characteristics of a biodegradable, cell-seeded scaffold. A potential solution to this problem is to measure the permeability of the matrix and determine the Darcy permeability coefficient. Darcy permeability coefficients of 3.1 x 10(-14) and 6.3 x 10(-14) m(2) were measured for air and water, respectively, in microporous polycaprolactone scaffolds by monitoring fluid flow in response to a range of pressure differentials. Permeability coefficients for phosphate-buffered saline (5.3 x 10(-14) m(2)), glucose (5.7 x 10(-14) m(2)), and bovine serum albumin (1.8 x 10(-14) m(2)) were obtained by monitoring the change in concentration of molecular probes. This approach revealed the efficiency of transport of glucose molecules through the porous material and the existence of protein-scaffold interactions that resulted in protein retention and a reduction in fluid permeation rate. Darcy permeability measurements can provide valuable insights concerning the transport properties of nutrients, metabolites, and polypeptide growth factors in porous tissue engineering scaffolds and a method of quality assurance in scaffold processing.

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.

OBJETIVO: Estudar a resistência tênsil da parede abdominal após síntese de laparotomia utilizando três tipos de fios cirúrgicos. MÉTODOS: Trinta ratos da linhagem Wistar randomizados em três grupos de dez exemplares cada um. Em cada grupo fez-se uma laparotomia de dois centímetros que foi fechada com fios 3-0 de poliglactina 910, poliglecaprone e categute. Após 63 dias, foi feita a eutanásia e retirou-se uma área da parede abdominal com a qual fez-se uma tira medindo 2,0 cm de comprimento por 6,0 cm de largura englobando os músculos abdominais com a tela implantada. A amostra foi fixada em máquina de ensaios mecânicos na qual se aplicou força constante contrária às tiras de tecido. Foi considerada a força máxima expressa em Newton até ocorrer a ruptura total da amostra. Para a análise estatística, utilizou-se teste não paramétrico de Kruskal - Wallis admitindo-se p<0,05. RESULTADOS: A média de resistência do grupo categute foi ligeiramente menor (33.50 N) ao da poliglactina (34.23 N), sendo essa diferença não estatisticamente significativa (p=0,733). O grupo poliglecaprone foi o que apresentou menor resistência entre os três fios analisados (29.86 N). Comparando as resistências do grupo poliglecaprone ao grupo categute não se obteve significância estatística (p=0,06). Entretanto quando o grupo poliglecaprone foi comparado à poliglactina 910 houve significância estatística (p=0,029). CONCLUSÃO: O fio de poliglactina apresentou a maior resistência tênsil dentre os três fios analisados, sendo esta estatisticamente significativa quando comparado ao fio de poliglecaprone.

Clinical evaluation of the polypropylene-polyester knit used as a cranioplasty material.

UNLABELLED: The paper presents clinical evaluation of the polypropylene-polyester knit used as a cranioplasty material. MATERIAL: Between year 1980 and 2002 275 cranioplastic procedures using the polypropylene-polyester plates Codubix were carried out in the Department of Neurosurgery of the Medical University of Lódz. There were 146 patients who primarily sustained head injuries and 129 non-traumatic patients with craniectomies carried out for various other reasons. In the majority of cases, i.e. in 158 patients, cranioplasty was performed later than 6 months after the primary surgery. The largest implant measured 430 cm2. RESULTS: Excellent and good outcome was achieved in 92% of the patients whereas the rate of local infection was 8%. CONCLUSIONS: Codubix knitted polypropylene-polyester implant proved to be useful and a safe cranioplastic material.

In vitro study of Human Dermal Fibroblasts seeded on two kinds of surgical meshes: monofilamented Polypropylene and multifilamented Polyestere.

Many different synthetic biomaterials have been recently proposed in the majority of the techniques for hernioplasty and pelvic floor surgery. Required qualities of an implantable prosthetic material have been well established in the past and today the biomaterials better performing to this purpose are the monofilamented Polypropylene (Marlex) and the multifilamented Polyestere (Mersilene). But, in spite of a wide surgical use of these two kinds of meshes, many failures of these implantations are reported leading to removal of the prosthetic implanted material. If some of these failures are due to errors in surgical technique, others seem to be due to inadequacy of the selected material, too much soft or too much stiff, or too much or too little incorporated into the host tissue. This experiment investigated the different behaviour of in vitro cultured Human Dermal Fibroblasts, seeded on specimens of both meshes and then observed by Light (LM) and Scanning Electron Microscopy (SEM). Around the multifilamented threads of Polyestere mesh, fibroblasts could grow very well, filling the holes and making a continous cell layer completely envelopping the mesh. At the same culture time, around the Polypropylene mesh only big groups of fibroblasts were evident at the thread interlacing points. Therefore, it could be concluded that both meshes stimulate good fibroblast attachment and proliferation but in a very different way and amount; it will be up to the surgeon to select the appropriate mesh according to the specific surgical purpose.

Lactic acid based PEU/HA and PEU/BCP composites: Dynamic mechanical characterization of hydrolysis.

Lactic acid based poly(ester-urethane) (PEU-BDI) and its composites with 20 and 40 vol.% bioceramic filler were characterized prior to their use as biocompatible and bioabsorbable artificial bone materials. Morphological, dynamic mechanical properties, and degradation of these either hydroxyapatite or biphasic calcium phosphate containing composites were determined. Addition of particulate bioactive filler increased the composite stiffness and the glass transition temperature, indicating strong interactions between the filler and matrix. Materials were sterilized by gamma-irradiation, which reduced the average molecular weights by 30-40%. However, dynamic mechanical properties were not significantly affected by irradiation. Specimens were immersed in 0.85 w/v saline at 37 degrees C for 5 weeks, and changes in molecular weights, mass, water absorption, and dynamic mechanical properties were recorded. All the composite materials showed promising dynamic mechanical performance over the 5 weeks of hydrolysis. Average molecular weights of PEU-BDI and its composites did not change substantially during the test period. PEU-BDI retained its modulus values relatively well, and although the moduli of the composite materials were much higher, especially at high filler content, they exhibited faster loss of mechanical integrity.

Biomechanical analysis of suture anchors and suture materials used for toggle pin stabilization of hip joint luxation in dogs.

OBJECTIVE: To compare in vitro mechanical properties of toggle pins and toggle rods used as suture anchors and of 3 suture materials (50-lb monofilament polybutester, No. 5 braided polyester, and 5-mm woven polyester) commonly used as prosthetic ligaments in the repair of hip joint luxation in dogs. SAMPLE POPULATION: Femoropelvic specimens from the cadavers of 18 dogs. PROCEDURE: Suture anchors were compared by use of pullout tests. Suture materials were compared by use of monotonic and cyclic tensile tests; cyclic tensile tests were performed with the suture placed over the edge of an aluminum bar to simulate the edge of the femoral bone tunnel. In vitro mechanical properties of the ligament of the femoral head were determined by use of monotonic tensile tests, using bone-ligament-bone cadaveric specimens. The in vitro mechanical properties of the acetabulum-ligament-femur complex and of this complex following rupture of the ligament and stabilization with a toggle rod and 5-mm woven polyester were determined by use of compression tests that simulated weight-bearing. RESULTS: Mechanical properties of the toggle rod were not significantly different from those of the toggle pin. Woven polyester had the longest fatigue life in cyclic testing. Hip joints stabilized with a toggle rod and woven polyester had less than half the strength in vitro of intact joints. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that a toggle rod or toggle pin can be used for stabilization of hip joint luxations in dogs. Of the materials tested, braided polyester had the best in vitro mechanical properties.

Can knitting structure affect dilation of polyester bifurcated prostheses? A randomized study with the use of helical computed tomography scanning.

PURPOSE: The aim of this study was to prospectively evaluate the postoperative dilation of two types of knitted polyester arterial prostheses with the use of helical computed tomographic scanning. METHODS: Thirty-four patients who underwent aortoiliac or aortofemoral bifurcation grafting were randomized to receive a collagen-sealed warp-knitted polyester graft (n = 16 patients) or a gelatin-sealed Köper-knitted polyester graft (n = 18 patients). Alterations in size of all parts of the grafts were evaluated by helical computed tomographic scanning at postoperative day 8, at 3 months, and at 6 months. RESULTS: On postoperative day 8, the mean dilation of the Köper-knitted grafts was 18% +/- 8% for the stem and 15% +/- 12% for the limbs. At the same time period, the mean dilation of warp-knitted grafts was 27% +/- 13% for the stem and 33% +/- 18% for the limbs. No increase in graft dilation was observed at 3 and 6 months. Despite the wide range of values among patients with the same graft type, at each time interval, the Köper-knitted grafts dilated significantly less than the warp-knitted grafts (P <. 05). CONCLUSION: In this randomized study, helical computed tomographic scanning was an accurate technique with which to assess graft dilation. For a 6-month follow-up interval, the Köper-knitted polyester structure dilated less than the warp-knitted structure. Longer-term serial scans should allow a better understanding of the clinical significance of graft dilation.

Analysis of 274 Omniflow Vascular Prostheses implanted over an eight-year period.

BACKGROUND: Polytetrafluoroethylene (PTFE), dacron, and, more recently, collagen prostheses are finding increasing use for femoropopliteal reconstruction when a suitable vein is not available. The main factors to be considered when choosing a prosthesis are patency, susceptibility to infection and formation of aneurysms. METHODS: Sheep collagen prostheses were implanted on 274 occasions in the femoropopliteal or crural regions. RESULTS: The patency rate for supragenual bypass after 3 years was 61.9% with good vascular periphery and 44% with poor vascular periphery. If the prosthesis extended below the knee, the patency rate was 55.4% with good and 35.3% with unfavourable vascular periphery. Patency for the femorocrural bypass was 28.7% after 2 years. The rate of infection was 0% and an aneurysm occurred in three patients (1.1%). CONCLUSIONS: With this low infection rate and very slight danger of aneurysm, the long-term results suggest that the ovine collagen prosthesis can be recommended for use when no suitable vein is available.

Mechanical comparison of materials used for extra-capsular stabilisation of the stifle joint in dogs.

OBJECTIVE: The mechanical properties of three materials (No. 2 polypropylene, No. 5 polybutilate-coated multifilament polyester and 18, 27 and 36 kg test monofilament nylon leader material) commonly used for extra-capsular stabilisation of the stifle in dogs with cranial cruciate ligament insufficiency were determined. The ability of No. 5 polybutilate-coated multifilament polyester and 36 kg test monofilament nylon leader material, when placed as extra-capsular sutures, to mitigate cranial drawer was evaluated in hindlimbs of cadavers. DESIGN: An in vitro mechanical study. ANIMALS: Seven pairs of hindlimbs harvested from adult greyhound dogs recently euthanased for other reasons. PROCEDURE: Samples of each material, including samples of 27 kg test leader material that had been sterilised by one of three methods (ethylene oxide, one or five cycles in an auto-clave), were loaded to determine tensile and stress relaxation properties. The effect of cyclic loading on a No. 5 polybutilate-coated multifilament polyester and 36 kg test leader material was also determined. Using the harvested hindlimbs, cranial drawer was measured before and after transection of the cranial cruciate ligament and on the first and twelfth cycle following extra-capsular stabilisation with either No. 5 polybutilate-coated multifilament suture or 36 kg test leader material. RESULTS: Leader material was found to have the most suitable mechanical characteristics for use as extracapsular stabilisation of the cranial cruciate ligament deficient stifle. Of the sterilisation methods, ethylene oxide was found to have the least detrimental effects on the handling and material characteristics of the leader material. Stifles stabilised with 36 kg test leader material had significantly less drawer than those stabilised with No. 5 polybutilate-coated multifilament polyester suture. CLINICAL IMPLICATIONS: Monofilament nylon leader material would appear to have suitable mechanical properties for extra-capsular stabilisation of the cranial cruciate ligament deficient stifle. If possible the material should be sterilised using ethylene oxide.

Biodegradable and titanium plating in experimental craniotomies: a radiographic follow-up study.

Plain film radiography and computed tomography (CT) were evaluated in assessing the consolidation of experimental craniotomy lines covered with titanium miniplates or biodegradable self-reinforced poly-L-lactide (SR-PLLA) plates. Two sagittal (2.3-2.5 mm wide and 22 mm long) symmetrical craniotomy lines were made in the skulls of eight young sheep. One craniotomy line was covered with a biodegradable SR-PLLA plate and the other with a titanium miniplate. Both plates were fixed with four titanium miniscrews. Consolidation of the osteotomies was studied using plain film radiography and CT 6, 12, 20, and 52 weeks postoperatively. Microradiography and histology were used for reference. Plain film was not reliable in assessing osseous consolidation because false-positive results were obtained in three osteotomies. Osseous consolidation was more reliably assessed by CT, which showed consolidation on the SR-PLLA side within 20 weeks, whereas none of the titanium-plated lines was consolidated by 52 weeks. Superior consolidation under the resorbable plate was confirmed in histology and microradiography. The radiolucent SR-PLLA plates did not interfere with CT, whereas the titanium plates caused minor CT artifacts.

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.

Unique performance characteristics of Novafil.

Polybutester is a unique copolymer that can be extruded as a flexible monofilament nonabsorbable suture. The mechanical performance of this new suture material was compared with that of polypropylene and nylon. The results indicate that polybutester sutures are as strong, have the same degree of total elongation at break and knot as the other monofilament sutures. In contrast with polypropylene and nylon sutures, the polybutester sutures have a perceptible stretch, are more elastic and flexible, and exhibit less creep. Polybutester sutures appear to be an acceptable alternative to polypropylene and nylon sutures and their unique mechanical properties may even prove to be superior in vivo.

PDS (polydioxanone suture): a new synthetic absorbable suture in cataract surgery. A preliminary study.

PDS (polydioxanone suture), a new synthetic absorbable suture, was used in 21 patients undergoing cataract surgery. It still retains 25% of its tensile strength at 42 days but absorption takes 130-180 days. 1 braided coated and 1 monofilament PDS were adequate as conjunctival sutures but offered no advantage over available materials. 0.5 monofilament PDS was superior in handling qualities to 0.4 virgin silk. It does not need to be removed but retains tensile strength for longer than other absorbable sutures.

[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.