|Articles about Biomaterials|
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| The effect of irradiation modification and RGD sequence adsorption on the response of human osteoblasts to polycaprolactone
Marletta, G., G. Ciapetti, et al. (2005), Biomaterials 26(23): 4793-804.
Abstract: Using techniques of tissue engineering, synthetic substitutes can be applied for the repair and regeneration of damaged bone. It has been found that material surface properties are crucial for cell adhesion and spreading, i.e. cell activities that are related directly to the ability of osteoblasts to proliferate. This fact has promoted the strategy of creating an ECM-like layer onto materials, so as to influence the cell response. In this study human bone-derived osteoblasts have been used to test the effects of surface modification by low energy ion beams of a poly epsilon-caprolactone (PCL) substrate and subsequent RGD adsorption. Osteoblasts were seeded and grown onto untreated and irradiated poly epsilon-caprolactone films, with or without RGD-adsorption step, and viability, morphology, and spreading of the osteoblasts were studied at different time endpoints. Differences were observed in the organization of cytoskeleton within cells: stress fibers were more evident in irradiated samples vs. untreated and total cell adhesion was higher. Surface characterization by X-ray Photoelectron Spectroscopy, Atomic Force Microscopy, and surface free energy measurements showed that the polar character of PCL, i.e., the acid-base term, was increased following irradiation treatment. Moreover the irradiated PCL had a nano-sized topography, which also could improve osteoblasts adhesion. We found that the treatment of the surface with ion beam is per se improving osteoblasts adhesion and spreading onto PCL. Furthermore, also if a significant RGD adsorption was obtained for irradiated PCL surfaces, it was found that in the investigated conditions it seems to have only a minor effect on the cell response. This study suggests that new strategies involving irradiation-based treatments can be adopted to promote the initial steps of bone deposition onto synthetic surfaces, exploiting the surface-induced reorganization of the ECM matrix.
| The effect of limited lateral resolution in the measurement of implant surface roughness: a computer simulation
Hansson, S. and K. N. Hansson (2005), J Biomed Mater Res A 75(2): 472-7.
Abstract: The surface roughness of dental implants affects the bone response elicited. Surface roughness is generally described by a range of surface texture parameters. The aim of the present study was to use computerized simulation to investigate the extent to which the lateral resolution of an instrument/method limits the accuracy of certain surface roughness parameters. The lateral resolution was defined as the pixel size of a profiling system. A surface roughness was simulated by a trigonometric function with random periodicity and amplitude. The function was divided into an array of pixels simulating the pixels of the profiling system. The mean height value for each pixel was used to calculate the surface roughness parameters. It was found that the accuracy of all the surface roughness parameters investigated decreased with increasing pixel size. This tendency was most pronounced for mean slope and developed length ratio; amounting to about 80% of their true values for a pixel size of 20% of the true mean high-spot spacing. It was concluded that the lateral resolution of an instrument/method severely compromises the precision of surface roughness parameters measured for roughness features with a mean high-spot spacing less than five times the lateral resolution.
| The effect of matrix composition of 3D constructs on embryonic stem cell differentiation
Battista, S., D. Guarnieri, et al. (2005), Biomaterials 26(31): 6194-207.
Abstract: The use of embryonic stem (ES) cells as unlimited cell source in tissue engineering has ignited the hope of regenerating any kind of tissue in vitro. However, the role of the material in control and guidance of their development and commitment into complex and viable three-dimensional (3D) tissues is still poorly understood. In this work, we investigate the role of material composition and structure on promoting ES cells growth and differentiation, by culturing mouse ES cell-derived embryoid bodies (EBs) in various semi-interpenetrating polymer networks (SIPNs), made of collagen, fibronectin (FN) and laminin (LM). We show that both composition and strength of the supportive matrix play an important role in EBs development. High collagen concentrations inhibit EBs cavitation and hence the following EBs differentiation, by inhibiting apoptosis. The presence of FN in 3D collagen constructs strongly stimulates endothelial cell differentiation and vascularization. Conversely, LM increases the ability of ES cells to differentiate into beating cardiomyocytes. Our data suggest that matrix composition has an important role in EBs development and that it is possible to influence stem cell differentiation toward preferential pattern, by modulating the physical and biochemical properties of the scaffold.
| The effect of methanol washing of plasticized polyvinyl chloride on biomaterial-contact-mediated CD11b (mac-1) expression in a rat recirculation model
Gourlay, T., D. Stefanou, et al. (2002), Artif Organs 26(1): 5-9.
Abstract: Our objective was to assess whether using a methanol wash to reduce the level of plasticizer present on the surface of medical-grade polyvinyl chloride (PVC) has a moderating effect on the expression of CD11b (mac-1) on neutrophils in rats undergoing recirculation. The study was carried out on 3 groups of 10 adult male Sprague-Dawley rats weighing between 350 and 450 g. In the 2 test groups, the animals were exposed to 48 cm(2) of di-(2-ethyl-hexyl)-phthalate (DEHP)-plasticized PVC in a parallel plate recirculating test cell through which blood was recirculated at 1.5 ml/min. In the first test group, the PVC was untreated; in the second test group, the PVC was washed in methanol to reduce the level of plasticizer on the surface. The test cell was connected to the right femoral circulation, and recirculation was established for a period of 60 min. Blood samples were taken at 0, 30, and 60 min for assessment of CD11b expression on neutrophils using flow cytometric analysis. In a third group of 10 control experiments, rats underwent the entire surgical procedure, but without recirculation through the test cell. There was statistically significant (p < 0.001) lower Cd11b expression on neutrophils in the blood of rats perfused through the cell containing methanol-washed PVC after 30 min and at 60 min. CD11b expression was significantly (p < 0.001) lower in the control group than in both test groups at both the 30 and 60 min time points and at the 60 min time point on comparison with the group where blood was perfused through methanol-washed PVC. These results demonstrate that the biomaterial-contact-mediated upregulation of CD11b may be significantly reduced by employing a methanol-washing technique on the plasticized PVC. Although this technique does not entirely eliminate the expression of CD11b on neutrophils, the difference is significant and suggests the role of the plasticizer in the development of this inappropriate inflammatory response.
| The effect of omeprazole pre-treatment on rafts formed by reflux suppressant tablets containing alginate
Dettmar, P. W., S. L. Little, et al. (2005), J Int Med Res 33(3): 301-8.
Abstract: Alginate-based reflux suppressant preparations provide symptom relief by forming a physical barrier on top of the stomach contents in the form of a neutral floating gel or raft. This study investigated whether reduced acidity in the stomach brought about by omeprazole pre-treatment affected the formation and gastric residence time of alginate rafts. It was a balanced, cross-over study in 12 healthy non-patient volunteers following a single dose of two indium-111-labelled alginate tablets in the presence or absence of 3 days' pre-treatment with omeprazole. Raft formation and gastric residence, in the presence of a technetium-99m-labelled meal, were assessed by gamma scintigraphy for 3 h after alginate tablet administration. The relative raft-forming ability of alginate tablets after omeprazole compared with alginate tablets alone was 0.950 with 95% confidence intervals of 0.882 and 1.018. Pre-treatment and co-administration with omeprazole has no significant effect on the raft-forming ability of alginate tablets.
| The effect of osteopenia on the osteointegration of different biomaterials: histomorphometric study in rats
Fini, M., G. Giavaresi, et al. (2000), J Mater Sci Mater Med 11(9): 579-85.
Abstract: The osteointegration of Hydroxyapatite (HA), Titanium (Ti-6Al-4V: Ti), Zirconia (ZrO2), Alumina (Al2O3) and 2 biological glasses (AP40 and RKKP) was comparatively investigated in normal and osteopenic rats by means of histomorphometry. Thirty-six Sprague Dawley female rats were left intact (Group C) while 36 were ovariectomized (Group OVX). Group C and OVX were further divided into 6 subgroups. After 16 weeks all animals were submitted to the femoral implant of nails made of the above-mentioned materials. Eight weeks after implantation the animals were euthanized, the femurs were harvested for histomorphometric analysis. The data showed that: (1) all the tested materials were biocompatible in vitro; (2) no significant differences existed in Affinity Index (AI) of Group C; and (3) results from paired comparison applied to the AI showed significant differences among the Groups C and OVX. The AI did not significantly change among intact groups, while it significantly decreased when some materials were implanted in OVX subgroups (AP40, ZrO2 and Ti-6Al-4V: p < 0.0005, p < 0.05 and p < 0.01). It is confirmed that bone mineral density is a strong predictor of the osteointegration of an orthopedic implant and that the use of pathological animal models is necessary to completely characterize biomaterials.
| The effect of PAMAM dendrimers on human and bovine serum albumin at different pH and NaCl concentrations
Shcharbin, D., B. Klajnert, et al. (2005), J Biomater Sci Polym Ed 16(9): 1081-93.
Abstract: The effect of PAMAM G3.5, PAMAM G4 and PAMAM-OH G4 dendrimers on human and bovine serum albumins has been studied by fluorescence spectroscopy at different pH and ionic strength. It has been shown that the interactions between dendrimers and proteins depend on pH and the efficiency of interactions can be regulated by changing pH. The maximal pH dependence was observed for interactions between albumins and PAMAM G4 dendrimer. At physiological pH all dendrimers affect proteins in the maximum degree. Dendrimers had no effect on N-F and N-B transitions of albumins. The effect of dendrimers on HSA was smaller than for BSA. The increase of NaCl concentration led to a decrease of interactions between dendrimers and proteins.
| The effect of patient gait on the material properties of UHMWPE in hip replacements
Davey, S. M., J. F. Orr, et al. (2005), Biomaterials 26(24): 4993-5001.
Abstract: The wear of ultra-high molecular weight polyethylene (UHMWPE) acetabular components in total hip replacements (THRs) has been shown to be highly dependent on the direction of shear. Greatly reduced wear rates have been reported for unidirectional, compared to multidirectional, articulation in vitro. This work for the first time enables investigation of a relationship between clinical wear conditions, as determined by patient gait path, and the mechanical and structural changes that occur within the UHMWPE acetabular component. Individual patients' wear paths were determined prior to revision operation from hip joint kinematics measured by clinical gait analysis. The material properties of the acetabular components removed during the revision operation were subsequently analysed. A technique using Fourier transform infra- red analysis (FTIR) was developed to quantify the orientation of the individual UHMWPE lamellae. This study shows that there is a direct relationship between a patient's clinical gait path and the molecular properties of their UHMWPE acetabular socket. Patient kinematics are an important factor affecting the wear and long-term biocompatibility of UHMWPE used as a bearing surface in THR.
| The effect of polymer coating biomaterials individually and incombination on the behavior of transformed RAW macrophage cells
Newman, D., M. Tucci, et al. (1999), Biomed Sci Instrum 35: 229-34.
Abstract: The use of homopolymers as coatings for biomaterials has received much attention in the last decade. However, the modifications and alterations induced by using such materials towards inflammatory cells have not been fully investigated. The specific objectives of this study were to investigate the role of hetero and homopolymers of amino acids on cell proliferation, and to determine the biochemical behavior associated with the incubation of RAW cells with various polymers. The RAW macrophage cell line was obtained from the American Type Culture Collection (Rockville, MD) and maintained in sterile media (RPMI) supplemented with 10% fetal bovine serum and 1% antibiotics and antimycotics. The cells were plated at a density of 1 x 10(6) cells/ml onto 24 well plates. The plates were divided into four groups of six wells per group per phase (24, 48, and 72 hours). Cells in the first group were treated with RGD, cells in group II were treated with poly-L-lysine, group III cells were treated with RGD + poly-L-lysine, and cells in group IV were treated with media alone, and served as controls. Cell number, as well as, protein, MDA, lactate dehydrogenase (LDH), and cytochrome C (cyto C) were determined at the end of 24, 48 and 72 hours. Data obtained from this investigation revealed that: (I) there were no significant difference in total cell counts between all experimental groups and control at the end of the 48 hour phase. However, at 24 hours there were fewer cells in the poly-L-lysine treated wells in comparison to control group (p < 0.05), (II) RGD and poly-L-lysine treatments did not cause changes in MDA or protein concentrations for the entire duration of the experiment, and (III) RGD treatment for 48 and 72 hours did not cause a reduction in the LDH activity compared to control and poly-L-lysine treated groups. Data obtained from this investigation could provide more insight regarding the design and development for safe and biocompatible orthopedic, dental and drug delivery devices.
| The effect of porosity and biomaterial on the healing and long-term mechanical properties of vascular prostheses
White, R. A. (1988), ASAIO Trans 34(2): 95-100.
Abstract: Continuing efforts in vascular prosthetic design are focused on understanding the characteristics required for function of small internal diameter and low-flow prostheses. The pioneers of vascular surgery developed large diameter textile prostheses for successful reconstruction of the aortoiliac vessels, but fabric grafts function poorly in diameters less than six millimeters. Major advances in small vessel reconstruction include the use of autogenous vessels for coronary artery lesions and microvascular surgery of digital and cerebral vessels. The author believes that future advances in graft design will enable prosthetic repair of two to four millimeter arteries and reconstruction of veins. This manuscript discusses the development of improved synthetic blood compatible surfaces with detailed consideration of prosthetic design factors such as pore size, biomaterial mechanical properties and thrombogenicity of the blood flow surface.
| The effect of protein-free versus protein-containing medium on the mechanical properties and uptake of ions of PVA/PVP hydrogels
Fussell, G., J. Thomas, et al. (2005), J Biomater Sci Polym Ed 16(4): 489-503.
Abstract: The effect of two simulated biological environments (protein-free and protein-containing) on ion uptake and physical properties of PVA/PVP hydrogels were explored in this work. It was found that over the immersion period in both media, wet mass of the hydrogels decreased and compressive moduli increased, likely due to increased polymer content with water loss as the hydrogels equilibrated with water. These changes were independent of polymer content and immersion medium. However, dry mass of the hydrogels increased dramatically when immersed in protein-free medium, changing only moderately in protein-containing medium. The increase in dry mass was attributed to ion uptake from immersion medium, as confirmed by EDXA. We postulate that differences between ion uptake in protein-free versus protein-containing medium is likely the result of serum proteins in the protein-containing medium adsorbing to the surface, inhibiting transport of ions into the hydrogel.
| The effect of RGD peptide-conjugated magnetite cationic liposomes on cell growth and cell sheet harvesting
Ito, A., K. Ino, et al. (2005), Biomaterials 26(31): 6185-93.
Abstract: Tissue engineering requires novel technologies for establishing 3D constructs, and the layered method of culturing cell sheets (cell sheet engineering) is one potentially useful approach. In the present study, we investigated whether coating the culture surface with RGD (Arg-Gly-Asp) peptide-conjugated magnetite cationic liposomes (RGD-MCLs) was able to facilitate cell growth, cell sheet construction and cell sheet harvest using magnetic force without enzymatic treatment. To promote cell attachment, an RGD-motif-containing peptide was coupled to the phospholipid of our original magnetite cationic liposomes (MCLs). The RGD-MCLs were added to a commercially available 24-well ultra-low-attachment plate the surface of which comprised a covalently bound hydrogel layer that was hydrophilic and neutrally charged. A magnet was placed on the underside of the well in order to attract the RGD-MCLs to the surface of the well, and then NIH/3T3 cells were seeded into the well. Cells adhered to the bottom of the culture surface, which was coated with RGD-MCLs, and the cells spread and proliferated to confluency. After incubation, the magnet was removed and the cells were detached from the bottom of the plates, forming a contiguous cell sheet. Because the sheets contained magnetite nanoparticles, they could be harvested using a magnet inserted into the well. These results suggest that this novel methodology using RGD-MCLs and magnetic force, which we have termed 'magnetic force-based tissue engineering (Mag-TE)', is a promising approach for tissue engineering.
| The effect of structural alterations of PEG-fibrinogen hydrogel scaffolds on 3-D cellular morphology and cellular migration
Dikovsky, D., H. Bianco-Peled, et al. (2006), Biomaterials 27(8): 1496-506.
Abstract: The need for alternative scaffolds in tissue engineering has motivated the establishment of advanced biomaterial technologies based on biosynthetic polymers. Networks of synthetic and biologic building blocks are created into a biomimetic environment for enhanced tissue compatibility with precise structural properties. The current investigation describes a unique biosynthetic hybrid scaffold comprised of synthetic polyethylene glycol (PEG) and endogenous fibrinogen precursor molecules. The PEGylated fibrinogen is cross-linked using photoinitation in the presence of cells to form a dense cellularized hydrogel network. The fibrin-like scaffold material maintains its biofunctionality through the fibrinogen backbone, while changes in the molecular architecture of the synthetic precursor are used to alter the nanostructrual properties of the scaffold, including mesh size and permeability. The structural properties of 6- and 10-kDa PEG-fibrinogen hydrogels are characterized by measuring the swelling properties and relating them to the degradation kinetics of the scaffold. Increased concentrations of the synthetic PEG are used to further alter the network structure of the PEG-fibrinogen hydrogel. Experiments using smooth muscle cells cultured inside the PEG-fibrinogen scaffold demonstrates a qualitative relationship between the molecular architecture of the matrix and the cellular morphology. A quantitative assessment of cell migration into the hydrogel network demonstrates a strong correlation between rate of cellular invasion and the network structure of the matrix. The ability to regulate cellular characteristics using structural modifications to the PEG-fibrinogen scaffold can be a valuable tool in tissue engineering and tissue regeneration.
| The effect of surface chemistry modification of titanium alloy on signalling pathways in human osteoblasts
Zreiqat, H., S. M. Valenzuela, et al. (2005), Biomaterials 26(36): 7579-86.
Abstract: Establishing and maintaining mature bone at the bone-device interface is critical to the long-term success of prosthesis. Poor cell adhesion to orthopaedic and dental implants results in implant failure. Considerable effort has been devoted to alter the surface characteristics of these biomaterials in order to improve the initial interlocking of the device and skeleton. We investigated the effect of surface chemistry modification of titanium alloy (Ti-6Al-4V) with zinc, magnesium or alkoxide-derived hydroxy carbonate apatite (CHAP) on the regulation of key intracellular signalling proteins in human bone-derived cells (HBDC) cultured on these modified Ti-6Al-4V surfaces. Western blotting demonstrated that modifying Ti-6Al-4V with CHAP or Mg results in modulation of key intracellular signalling proteins. We showed an enhanced activation of Shc, a common point of integration between integrins and the Ras/Mapkinase pathway. Mapkinase pathway was also upregulated, suggesting its role in mediating osteoblastic cell interactions with biomaterials. The signalling pathway involving c-fos (member of the activated protein-1) was also shown to be upregulated in osteoblasts cultured on the Mg and CHAP modified Ti-6Al-4V. Thus surface modification with CHAP or Mg may contribute to successful osteoblast function and differentiation at the skeletal tissue-device interface.
| The effect of surface hydrophilicity on biomaterial-leukocyte interactions
Lim, F. and S. L. Cooper (1991), ASAIO Trans 37(3): M146-7.
Abstract: Leukocyte adhesion onto a series of polyetherurethanes containing various ratios of polyethylene oxide (PEO) to polytetramethylene oxide (PTMO) in the soft segment was evaluated using an in vitro series shunt. The deposition of polymorphonuclear (PMN) and mononuclear (MN) leukocytes was measured quantitatively using labelling techniques. Results showed that H/H-1, the most hydrophobic surface, adsorbed higher amounts of PMN leukocytes. It was also observed that for most materials the number of PMN and MN leukocytes deposited reached a plateau within 15 minutes. Unlike MN adherence, the presence of plasma proteins increased the number of PMN leukocytes deposited on the materials.
| The effect of surface modification of a porous TiO(2)/perlite composite on the ingrowth of bone tissue in vivo
Erli, H. J., M. Ruger, et al. (2006), Biomaterials 27(8): 1270-1276.
Abstract: The porous TiO(2)/perlite composite Ecopore is a synthetic biomaterial with possible clinical application in bone substitution. In our previous work, we demonstrated that surface modification of Ecopore with fibronectin (FN) enhanced spreading and growth of human osteoblasts in vitro. In the present study, we implanted untreated, alkaline-etched and FN-coated Ecopore cylinders into critical size defects of rabbit femora and applied pulsed polychrome sequence staining. After 6 weeks, sections of the implants were investigated via conventional and fluorescence microscopy. A partial ingrowth of bone matrix into the pore system of the Ecopore implants was observed. At the contact zones, the bone appeared to be directly connected to the implant without detectable gaps. Defect healing was complete within 6 weeks, while fibrous tissue generation or inflammation were absent in the implant modification groups, demonstrating basic Ecopore biocompatibility. The mean bone apposition rates within the implant cross-section were 4.1+/-0.6mum/day (p<0.001) in the FN-coated group and 3.3+/-0.5mum/day (p<0.05) in the NaOH-etched group. In both treated Ecopore modification groups, the apposition rates were significantly higher than in the non-modified control (2.9+/-0.6mum/day), indicating bone growth stimulation by pre-treatment. Energy-dispersive X-ray analysis confirmed that significantly more bone tissue was formed inside the pores of the FN-coated implants compared to the unmodified control. The cross-sectional areas identified as ingrown bone amounted to 18.5+/-6.1% (p<0.05) in the FN group, 13.4+/-5.1% (p>0.05) in the NaOH-etched group and 10.2+/-5.5% in the unmodified group. In summary, we conclude that bone tissue tolerates Ecopore well and that tissue ingrowth can be enhanced by etching and coating with FN.
| The effect of temperature-dependent thermal conductivity in heat transfer simulations of frozen biomaterials
Rabin, Y. (2000), Cryo Letters 21(3): 163-170.
Abstract: The thermal conductivity value of pure water ice is inversely proportional to the temperature and decreases about 5-fold as the temperature increases from the liquid nitrogen boiling temperature (77 K to the freezing point of pure water. The temperature dependency of the thermal conductivity is typically overlooked in bioheat transfer simulations. A closed-form solution of the one-dimensional temperature distribution in frozen water and blood is presented in this study, based on a new thermal conductivity model. Results indicate that temperatures are overestimated up to 38K, and heat fluxes through the frozen region boundaries are underestimated by a factor of 2, when the temperature dependency of the thermal conductivity is neglected.
| The effect of the addition of a polyglutamate motif to RGD on peptide tethering to hydroxyapatite and the promotion of mesenchymal stem cell adhesion
Sawyer, A. A., D. M. Weeks, et al. (2005), Biomaterials 26(34): 7046-56.
Abstract: Mimicking endogenous bone-binding proteins, RGD peptides have been synthesized with polyacidic amino acid domains in order to ionically tether the peptides to bone-like synthetic biomaterials, including hydroxyapatite (HA). However, a direct comparison of unmodified RGD with polyacidic-conjugated RGD has not been performed, and thus a benefit for the acidic domain has not been established. We evaluated the peptide/HA bond of RGD peptides with and without an attached polyglutamate sequence (E(7)), as well as examined mesenchymal stem cell (MSC) adhesion and morphology as they were affected by the conjugated peptide. We found that significantly more E(7)RGD was bound to HA than RGD at all coating concentrations tested, and moreover, more E(7)RGD was retained on the HA surface even after extended washing in serum-free media. Consistent with in vitro results, higher levels of E(7)RGD than RGD remained on HA that had been implanted in vivo for 24 h, indicating that the polyacidic domain improved peptide-binding efficiency. At several peptide concentrations, E(7)RGD increased cell adhesion compared to RGD surfaces, establishing a biological benefit for the E(7) modification. In addition, HA pre-coated sequentially with low-density E(7)RGD (1-10 microg/ml) and serum (FBS) stimulated cell adhesion and spreading, compared to either coating alone, suggesting that an ionic linkage allows for the potential adsorption of serum proteins to unoccupied sites, which may be important for bone formation in vivo. Collectively, these results suggest that tethering peptides to HA via a polyglutamate domain is an effective method for improving the peptide/HA bond, as well as for enhancing MSC adhesion.
| The effect of the antimicrobial peptide, Dhvar-5, on gentamicin release from a polymethyl methacrylate bone cement
Faber, C., R. J. Hoogendoorn, et al. (2005), Biomaterials 26(28): 5717-26.
Abstract: The objective of this study was to investigate the release mechanism and kinetics of the antimicrobial peptide, Dhvar-5, both alone and in combination with gentamicin, from a standard commercial polymethyl methacrylate (PMMA) bone cement. Different amounts of Dhvar-5 were mixed with the bone cement powders of Osteopal and the gentamicin-containing Osteopal G bone cement and their release kinetics from the polymerized cement were investigated. Additionally, the internal structure of the bone cements were analysed by scanning electron microscopy (SEM) of the fracture surfaces. Secondly, porosity was investigated with the mercury intrusion method and related to the observed release profiles. In order to obtain an insight into the mechanical characteristics of the bone cement mixtures, the compressive strength of Osteopal and Osteopal G with Dhvar-5 was also investigated. The total Dhvar-5 release reached 96% in the 100 mg Dhvar-5/g Osteopal cement, whereas total gentamicin release from Osteopal G reached only 18%. Total gentamicin release increased significantly to 67% with the addition of 50mg Dhvar-5/g, but the Dhvar-5 release was not influenced. SEM showed an increase of dissolved gentamicin crystals with the addition of Dhvar-5. The mercury intrusion results suggested an increase of small pores (< 0.1 microm) with the addition of Dhvar-5. Compressive strength of Osteopal was reduced by the addition of Dhvar-5 and gentamicin, but still remained above the limit prescribed by the ISO standard for clinical bone cements. We therefore conclude that the antimicrobial peptide, Dhvar-5, was released in high amounts from PMMA bone cement. When used together with gentamicin sulphate, Dhvar-5 made the gentamicin crystals accessible for the release medium presumably through increased micro-porosity (< 0.1 microm) resulting in a fourfold increase of gentamicin release.
| The effect of the physiological environment on the mechanical properties of biomaterials in cardiovascular applications
Bruck, S. D. (1978), Biomater Med Devices Artif Organs 6(4): 341-59.
Abstract: The long-term biocompatibility and physical performance of polymeric materials in the physiological environment depend both on adsorption and absorption processes. While the former has received significant attention in the literature, the latter has not been sufficiently appreciated. Accelerated testing of prosthetic devices in the wrong media and temperatures yield misleading information as exemplified by pumping bladders of heart assist devices and heart valves. Although glutaraldehyde-treated porcine heterograft heart valves performed better than expected in humans over a period of several years, physical degradations that have been observed may be associated with the breakdown of the cross-links. Appropriately selected smooth-surfaced biomaterials and hydrogels are far better suited for temporary blood contacting prosthetic applications such as left ventricular heart assist devices (LVADs) than polyester flocked fibril surfaces that result in the deposition of a thick layer of fibrin/cellular mesh with clot-like morphology with inherent dangers of loss of polyester fibrils, and the shedding of clots as the result of cyclic flexing of the pump bladders. With the proliferation of various medical devices, the possibility of increased litigations with secondary and tertiary liabilities involving not only physicians, surgeons, and device manufacturers, but also suppliers of materials and components, it is essential to select pertinent rather than complex test procedures.
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