A bioresorbable polylactide implant used in bone cyst filling.

The aims in treating patients diagnosed with critical-sized bone defects resulting from bone cysts are to replace the lost bone mass after its removal and to restore function. The standard treatment is autologous or allogeneic bone transplantation, notwithstanding the known consequences and risks due to possible bone infection, donor site morbidity, bleeding and nerve injury and possible undesirable immune reactions. Additionally, allogeneic grafts are inhomogeneous, with a mosaic of components with difficult-to-predict regenerative potential, because they consist of cancellous bone obtained from different bones from various cadavers. In the present study, a 22-year-old patient with a history of right humerus fracture due to bone cysts was diagnosed with recurrent cystic lesions based on X-ray results. The patient qualified for an experimental program, in which he was treated with the application of a bioresorbable polylactide hybrid sponge filled with autologous platelet-rich plasma. Computed tomography and magnetic resonance imaging performed 3, 6, and 36 months after surgery showed progressive ossification and bone formation inside the defect cavity in the humerus. Three years after treatment with the bone substitute, the patient is pain free, and the cystic lesions have not reoccurred.

[Studies of interaction between surface of pirolytic carbon and blood cells and proteins]. / Badania interakcji powierzchni wegla pirolitycznego z komórkami i bialkami krwi.

BACKGROUND: Preventing blood clots formation on the biomaterials surface and finding the causes of their appearance are the leading research subjects while working out biomaterials for grafts into the circulation system. Interaction between the biological environment and the carbon implant is closely connected with the properties of its surface. Implants whith surfaces covered with pyrolytic carbon is characterised by athrombogenity have particular significance in medical applications. OBJECTIVES: Assessment of the influence of a pyrolytic carbon surface on the activation of coagulation system. MATERIAL AND METHODS: Full human blood was subjected to temporal contact in vitro with the surface of low-temperature isotropic carbon (LTI). The haemostatic action of pyrolytic carbon was determined through marking the chosen parameters of the coagulation system and the recalcification time on the material surface. The evaluation of the topography of the material was performed in the scanning microscopy. RESULTS: Changes in the values APTT, PT, TT, fibrinogen and activity of factors F XII, F IX, F VIII as well as AT III, protein C and plasminogen were not observed in the studies of the plasmatic coagulation system. The blood coagulation time on the material surface was elongated in comparison with the surface of glass and polystyrene surface. CONCLUSIONS: Direct contact of blood with the surface of carbon LTI elongates clot formation, while not changing the parameters of the plasmatic coagulation system in temporal contact.

Assessment of sheep knee joint after ACL replacement with Achilles tendon autograft and PLA-based implant.

In this study, we propose a new approach in the anterior cruciate ligament (ACL) replacement to provide stability and integration with bone tunnel. A polylactide (PLA)-based tubular implant was used to support the graft stabilization in femoral and tibial bones and to stimulate the healing process after (ACL) replacement on a sheep model. The ACL was replaced with an autologous Achilles tendon split graft. The tendon-to-bone healing in the model was analyzed after 6 and 12 weeks. Two groups of animals were compared, i.e. the group with the PLA-based implant used in the ACL replacement and the control group without the implant. The knee joints were mechanically and clinically evaluated, including the histopathology tests, to determine their stability and integrity. The results indicated that the bioresorbable PLA-based tubular implant may facilitate integration of the tendon graft with bone. Remodeling the allograft inside the implant improves the joint mobility from the first week of healing: no pathological changes were observed at the surgery site and in the animals' mobility. After 6 and 12 weeks of healing no significant changes in the mechanical parameters of the knee joint were observed, regarding the joint failure force, knee displacement, angular mobility range and joint stiffness. Relatively small values of the non-destructive tests in the knee displacement, already 6 weeks after surgery, indicated the early stabilization of the knee joint. The studies showed that the failure forces of knee joints after the ACL replacement with the PLA-based implant are lower than those of an intact joint, although their biomechanical features, including strain-at- failure, are similar. The biomechanical parameters of the knee joint were significantly improved due to the selected method of attaching the autograft ends to the femoral and tibial bone surfaces. After 12 weeks the intra-tunnel tendon-bone site with the PLA implant revealed the better tibia-femur joint mechanical stability, linear force-strain function and the decreasing strain-to-failure value, as compared to the control group.

In vivo biocompatibility assessment of (PTFE-PVDF-PP) terpolymer-based membrane with potential application for glaucoma treatment.

The aim of the work was to evaluate the in vivo biological behaviour of polymeric membrane materials for glaucoma implants. The base material was biostable synthetic terpolymer (PTFE-PVDF-PP) with proved biocompability (PN-EN ISO 10993). The samples manufactured in the form a membrane were subjected to chemical and physical treatment to create an open pore system within the polymer matrix. As a porogenic phase biodegradable natrium alginate in a fibrous form was employed. The non-perforating deep sclerectomy technique was performed in a rabbit model. The clinical observations were made after 14 and 30 days. During the study clinical symptoms of a moderate degree were observed, and histopathological changes were typical for foreign body implantation. At the end stage of the study no significant difference in histopathological assessment was found between control and experimental group. Similarities observed in both groups and relatively mild histopathological changes in the tissue surrounding the implant indicate that the observed symptoms come from a deep scleral trauma caused by surgery, and not by the presence of the implant itself.

Development of Bonded/Riveted Steel Anchorages of Prestressed CFRP Strips for Concrete Strengthening.

CFRP (carbon fiber reinforced polymer) strips are currently often used to strengthen reinforced concrete structures in flexure. In order to ensure effective strengthening, proper connection between FRP material and concrete structure is needed. CFRP strips can be applied passively (only by bonding to the concrete surface) or actively (by prestressing before bonding). In the case of passive strengthening, CFRP strips connecting by bonding to the surface along the strengthened element are usually sufficient. However, active (prestressing) CFRP strips should be additionally anchored at their ends. Anchoring of unidirectional CFRP strips to the reinforced concrete is difficult because of their weak properties in transverse directions. The paper presents a development of mechanical steel anchorages used in an active CFRP flexural strengthening system for reinforced concrete structures. The anchorages were made of steel plates connected to CFRP strips with steel rivets and epoxy adhesive. They were developed within series of tests on specimens from small-scale to full-scale tested in an axial tensile scheme. The paper describes successive modifications of the anchorages as well as the results of full-scale tests. The final version of the anchorage developed during the research had a tensile failure force of 185 kN, which is sufficient value for CFRP strengthening purposes.

Structural and microstructural study of novel stacked toroidal carbon nanotubes.

The work presents a new carbon nanostructure in the form of stacked toroidal carbon nanotubes (STCNT) crystallized from the gas phase through a catalyst-free deposition process. Vapor-grown STCNT were obtained on a graphite substrate using methane as a source of carbon. The carbon structure was analyzed using Transmission Electron Microscopy (TEM), Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM/EDX), Raman spectroscopy, X-ray Diffraction and X-ray photoelectron spectroscopy. The TEM images revealed that the nanostructured carbon phase consisted of a single toroidal element (toroid) that was composed of rolled multi-walled carbon nanotubes. The SEM/EDX study of different substrate sites showed the presence of the pure carbon structure. The average external diameter of a single toroid was 1000 nm, and the average distance between neighboring toroids was 100 nm. The space inside the toroids contained carbon spheres made of turbostratic crystallites.

Bioresorbable Stent in Anterior Cruciate Ligament Reconstruction.

The exact causes of failure of anterior cruciate ligament (ACL) reconstruction are still unknown. A key to successful ACL reconstruction is the prevention of bone tunnel enlargement (BTE). In this study, a new strategy to improve the outcome of ACL reconstruction was analyzed using a bioresorbable polylactide (PLA) stent as a catalyst for the healing process. The study included 24 sheep with 12 months of age. The animals were randomized to the PLA group (n = 16) and control group (n = 8), subjected to the ACL reconstruction with and without the implantation of the PLA tube, respectively. The sheep were sacrificed 6 or 12 weeks post-procedure, and their knee joints were evaluated by X-ray microcomputed tomography with a 50 µm resolution. While the analysis of tibial and femoral tunnel diameters and volumes demonstrated the presence of BTE in both groups, the enlargement was less evident in the PLA group. Also, the microstructural parameters of the bone adjacent to the tunnels tended to be better in the PLA group. This suggested that the implantation of a bioresorbable PLA tube might facilitate osteointegration of the tendon graft after the ACL reconstruction. The beneficial effects of the stent were likely associated with osteogenic and osteoconductive properties of polylactide.

Mechanical assessment of a hip joint stem model made of a PEEK/carbon fibre composite under compression loading.

PURPOSE: The aim of the work was to manufacture a composite stem model consisting of carbon fibres (CF) and polyether ether ketone (PEEK) and to perform the surface strain and stress distributions in the stem-femoral bone model under compression loading. METHODS: Composite stems differing in elasticity were prepared. Three types of composite stems having different arrangements of carbon fibre reinforcements (carbon fibre roving, carbon fibre sleeves and their combinations) in the polymer matrix were made. The stems were cementless fixed in the femoral bone model channel or with the use of the polymer bone cement (PMMA). Mechanical behaviour of composite stems under compression loading was compared with a metallic stem by strain gauge measurements at different parts of stem/bone model systems. RESULTS: The values of stresses in the proximal part of the bone model for cemented and cementless fixations of the composite stem in the femoral bone channel were higher than those noted for the metallic stem. The increase in proximal bone stress was almost similar for both types of fixation of composite stems, i.e., cemented and cementless fixed stems. CONCLUSIONS: The optimal range of mechanical stiffness, strengths and work up to fracture was obtained for composite stem made of carbon fibre sleeves and carbon fibres in the form of roving. Depending on the elasticity of the composite stem model, an increase in the stress in the proximal part of femoral bone model of up to 40% was achieved in comparison with the metallic stem.

De-agglomeration and homogenisation of nanoparticles in coal tar pitch-based carbon materials.

The aim of the work was to characterise coal tar pitch (CTP) modified with selected nanoparticles as a binder precursor for the manufacture of synthetic carbon materials. Different factors influencing the preliminary preparative steps in the preparation of homogenous nanoparticle/CTP composition were studied. Graphene flakes, carbon black and nano-sized silicon carbide were used to modify CTP. Prior to introducing them into liquid CTP, nanoparticles were subjected to sonication. Various dispersants were used to prepare the suspensions, i.e. water, ethanol, dimethylformamide (DMF) and N-methylpyrrolidone (NMP).The results showed that proper dispersant selection is one of the most important factors influencing the de-agglomeration process of nanoparticles. DMF and NMP were found to be effective dispersants for the preparation of homogenous nanoparticle-containing suspensions. The presence of SiC and carbon black nanoparticles in the liquid pitch during heat treatment up to 2000 °C leads to the inhibition of crystallite growth in carbon residue.

Non-penetrating very deep sclerectomy with a hydrophobic polymer implant in a rabbit model.

PURPOSE: The aim of the study was to evaluate the influence of an implant made of a terpolymer (PTFE-PVDF-PP) on the condition of rabbit eyes during a one year observation period. METHODS: The implant in the shape of an equilateral triangle (3 mm side length) was manufactured from a thin hydrophobic porous membrane. There were evaluated 40 eyes of 20 rabbits. The animals had non-penetrating very deep sclerectomy (NPVDS) performed, with insertion of an implant in the form of a triangular thin membrane. The control group consisted of 20 eyes where the animals had NPVDS performed without implant insertion. The evaluations included the study of the anterior part of the eye together with photographic documentation. Histopathological examination of the eyes 52 weeks after NPVDS procedure has been made. The process of wound healing was comparable in both groups. RESULTS: The evaluation of the rabbits did not reveal any acute process of intraocular inflammation. After 12 month period of observation, no statistically significant differences in the process of wound healing or status of eyes were found between the groups. An analysis of fibrous connective tissue attachment to the implant showed that its layer was not thick and did not differ significantly from the control. The procedure of very deep sclerectomy and insertion of a polymer implant were well tolerated by the rabbit eyes. CONCLUSIONS: The in vivo results indicate that the hydrophobic implant in the form of a membrane can serve as a sclera implant after further study.

Histopathological Evaluation of a Hydrophobic Terpolymer (PTFE-PVD-PP) as an Implant Material for Nonpenetrating Very Deep Sclerectomy.

PURPOSE: The purpose of the study was to assess the biocompatibility of porous terpolymer (polytetrafluoroethylene-co-polyvinylidene fluoride-co-polypropylene, PTFE-PVDF-PP) membranes as an implant material to be placed during nonpenetrating very deep sclerectomy (NPVDS). Another study objective was to determine whether the polymer membrane under investigation could be used to manufacture a new-generation implant, which would actively delay the process of fistula closure and facilitate aqueous humor drainage. METHODS: Histological response and tissue tolerance of the implant material were assessed. The study was performed on 38 eyeballs of 19 New Zealand white rabbits (19 implanted, 19 control). Histological assessment was carried out between 2 and 52 weeks after surgery. We routinely assessed inflammatory infiltrate, neovascularization, hemorrhage, and stromal edema as well as connective tissue attachment to the implant and adjacent tissues. RESULTS: At 52 weeks of observation, a statistically significant difference was revealed between the study and control groups in terms of resorptive granulation, tissue, and the inflammatory infiltrate. No features of acute inflammatory response to the implant were observed, and there was an absence of histological features of acute inflammatory infiltrates and subsidence of chronic inflammatory infiltrates and resorptive granulation over time. CONCLUSIONS: Slight fibrotic response and insignificant changes in neighboring eye tissues all indicate good tolerance to bioimplant materials. This allows for some optimism regarding the use of hydrophobic terpolymer in the construction of new intrascleral implants. However, the ultimate decision regarding its usefulness and safety in the treatment of glaucoma requires further investigation.

Influence of different types of carbon nanotubes on muscle cell response.

The aim of this study was to evaluate the impact of multi-walled carbon nanotubes (MWCNTs), before and after chemical surface functionalization on muscle cell response in vitro and in vivo conditions. Prior to biological tests the surface physicochemical properties of the carbon nanotubes (CNTs) deposited on a polymer membrane were investigated. To 'evaluate microstructure and structure of CNTs scanning electron microscopy (SEM) and Fourier transformation infrared spectroscopy (FTIR) were used. During in vitro study CNTs deposited on polymer membrane were contacted directly with myoblast cells, and after 7 days of culture cytotoxicity of samples was analyzed. Moreover, cell morphology in contact with CNTs was observed using SEM and fluorescence microscopy. The cytotoxicity of CNTs modified in a different way was comparable and significantly lower in comparison with pure polymer membrane. Microscopy analysis of cultured myoblasts confirms intense cell proliferation of all investigated samples with CNTs while for two kinds of CNTs myoblasts' differentiation into myotubes was observed. Histochemical reactions for the activity of enzymes such as acid phosphatase, cytochrome C oxidase, and non-specific esterase allowed the analysis of the extent of inflammation, degree of regeneration process of the muscle fibers resulting from the presence of the satellite cells and the neuromuscular junction on muscle fibers in contact with CNTs after implantation of CNTs into gluteal muscle of rat.

[Study on polysiloxane resin-based composites for bone surgery application]. / Badania nad przydatnoscia kompozytów wytworzonych z zywic polisiloksanowych dla chirurgii kostnej.

The study aimed at determination of mechanical and biological properties of three types of carbon fibers-based composites differing in matrix as potential materials for bone surgery. Three types of polymethylphenyl siloxane resins (produced by Lucebni zavody, Kolin, Czech Republic) differing with Si/C ratio were used as matrix. Carbon fibers T-300 (Torayca) were used as the reinforcement. The composite samples were manufactured by liquid impregnation of carbon roving followed by thermal curing. The resins were characterized by means of infrared spectroscopy. The strength and Young's modulus of the composite samples were determined in three-point bending test. The MTT tests were led in the presence of line KMA human macrophages and line hFOB 1.19 human osteoblasts. The results presented in this work indicate that mechanical properties of the composites are adequate from viewpoint of bone surgery requirement for load-bearing implants. The viability of macrophages cultures in contact with all examined samples was higher than 85%. The highest viability of human osteoblasts was obtained for composites based on L 901 and L 4102 resins-above 60%. The results suggest that the investigated polysiloxane-based composites are biocompatible, however their possible use as implants needs further study.

[In vitro study of polymer coatings on electronic elements]. / Badania in vitro powlok polimerowych na elementach elektronicznych.

The paper presents the results of investigations of polymer coatings used as capsules for implantable microelectronic devices for medical applications. Such devices work in artificial pacemakers and as feeding systems, in nerve ending stimulator sets. Biocompatible and biostable polysulfone capsules for integrated circuits and batteries have been prepared. Preliminary investigation of overall chemical stability of encapsulated electronic devices in Ringer's solutions, has been carried out as a function of immersion time. Influence of number of coating polysulfone layers on voltage-stability of batteries immersed in 0.9% NaCl solution has been measured with time. A comparative study of silicone (SIL) coating and double coating with silicone and polysulfone (SIL + PSU) in an in vitro test has been carried out.

[New composite implant for tracheal reconstruction--preliminary study]. / Nowy kompozytowy implant do rekonstrukcji tchawicy--badania wstepne.

Stenosis of trachea's diameter occurs the most often as complications after intubation and tracheotomy. Among the other reasons of narrowing of this organ the following are being named: mechanical injuries, chemical damages, primary and metastasis tumors. The therapy of trachea's stenosis includes both alternative and radical treatments. The radical treatment consists of surgical excision of the narrowed segment followed by reconstruction of trachea (anastomosing of free ends or filling of lost segment with use of auto- or allogenic material). There is no appropriate alloplastic material developed to date, the use of which in reconstructive surgery of large segment trachea defects would bring about positive long-term experimental results. The success of alloplastic material implantation in the reconstruction of large tracheal defects is limited by the fact that the biomechanical characteristics of replaced tissue are distinctly different from synthetic material. The work is devoted to evaluation of complex mechanical characteristic of natural sheep trachea before designing the proper synthetic material for large tracheal defects reconstruction. Various mechanical tests were conducted to study the mechanical behavior of total trachea. Samples of tissue cut out from trachea were also examined. The results revealed strong directional--dependent mechanical properties of trachea. Composite constituents, namely carbon fibers and biocompatible and biostable polysulfone were used to manufacture the implant.

Effect of MWCNT surface and chemical modification on in vitro cellular response.

The aim of this study was to evaluate the impact of multi-walled carbon nanotubes (MWCNTs with diameter in the range of 10-30 nm) before and after chemical surface functionalisation on macrophages response. The study has shown that the detailed analysis of the physicochemical properties of this particular form of carbon nanomaterial is a crucial issue to interpret properly its impact on the cellular response. Effects of carbon nanotubes (CNTs) characteristics, including purity, dispersity, chemistry and dimension upon the nature of the cell environment-material interaction were investigated. Various techniques involving electron microscopy (SEM, TEM), infrared spectroscopy (FTIR), inductively coupled plasma optical emission spectrometry, X-ray photoelectron spectroscopy have been employed to evaluate the physicochemical properties of the materials. The results demonstrate that the way of CNT preparation prior to biological tests has a fundamental impact on their behavior, cell viability and the nature of cell-nanotube interaction. Chemical functionalisation of CNTs in an acidic ambient (MWCNT-Fs) facilitates interaction with cells by two possible mechanisms, namely, endocytosis/phagocytosis and by energy-independent passive process. The results indicate that MWCNT-F in macrophages may decrease the cell proliferation process by interfering with the mitotic apparatus without negative consequences on cell viability. On the contrary, the as-prepared MWCNTs, without any surface treatment produce the least reduction in cell proliferation with reference to control, and the viability of cells exposed to this sample was substantially reduced with respect to control. A possible explanation of such a phenomenon is the presence of MWCNT's agglomerates surrounded by numerous cells releasing toxic substances.

Manufacturing and physico-mechanical characterization of carbon nanohorns/polyacrylonitrile nanocomposites.

The use of carbon nanohorns (SWCNHs) as a modifying filler in a polyacrylonitrile (PAN) matrix is studied with the goal of elaborating nanocomposites. The study deals with assessment of the dispersity of SWCNHs in a PAN polymer suspension. The SWCNHs were introduced into the PAN-based suspension using different methods, including mechanical stirring, ultrasonification and the combination of ultrasonification with addition of a surfactant. Agglomeration and dispersion processes of SWCNH in the polymer suspensions were studied using DLS technique and turbidimetry. The resulting properties of nanocomposite foils after solidification in water ambient were verified in various tests. The mechanical tensile properties (tensile strength, modulus and strain to fracture) of the nanocomposites before and after the dispersion process were compared. The nanocomposites obtained under optimally prepared suspension perform the highest strain to fracture in tensile test. Electrical resistivity and thermal conductivity of nanocomposites samples after appropriate dispersion of SWCNHs in the PAN suspension were also determined. The presence of SWCNH in the PAN suspension affects the structure of nanocomposites after solidification through changing structural ordering of the polymer. The study revealed that the polymeric suspensions prepared in optimum processing conditions contain the carbon aggregates the size of which correspond almost to the mean size of a dahlia flower-like structured particle, i.e., 50-250 nm and it was not possible to separate such particles into a single form of carbon nanohorn by the techniques used.

[The influence of polymerization time on physicochemical properties of the acrylic resin Vertex RS]. / Wplyw czasu polimeryzacji na wlasciwosci fizykochemiczne tworzywa akrylowego Vertex R.S.

INTRODUCTION: A good denture can only be produced through proper actions during the clinical and laboratory stages of the production process. The aim of this study was to determine if a change in polymerization time affects the physicochemical properties of polymethacrylate material used for dentures. MATERIAL AND METHODS: We examined the acrylic resin Vertex R.S. polymerized for 15, 25, 40, or 60 minutes. Palapress Vario was taken as reference material. Static bending, microhardness, surface wettability, and susceptibility to abrasion were determined. RESULTS: The microhardness test showed that most of the samples had similar Vickers hardness (VS) values, except for the sample polymerized for 25 min. which demonstrated a significantly higher value. Grindability was affected by a change in polymerization time. Mass loss was greatest for samples polymerized for 15, 25, and 60 min. and smallest for Vertex 40 and Palapress Vario. We also observed differences in the wetting angle. Vertex 40 and 60 had a relatively low wetting angle signifying that longer polymerization time results in lower hydrophobicity of the material. CONCLUSION: The present study has demonstrated that polymerization time has a significant effect on the hardness and some mechanical properties of the acrylic resin.