This study investigated four different connective tissue cell types to determine which cell type should be the source for seeding a tissue-engineered anterior cruciate ligament (ACL) replacement. Cells derived from the ACL, medial collateral ligament (MCL), achilles tendon (AT), and patellar tendon (PT) of New Zealand White rabbits were isolated and cultured. Each cell type was cultured in vitro after seeding on three-dimensional (3-D) braided polymer scaffolds and on tissue culture polystyrene that served as a control. Samples were evaluated and compared for their morphology, proliferation, and gene expression of fibronectin, type I and type III collagen. Scanning electron microscopy (SEM) photomicrographs verified cell attachment of all four types of connective tissue fibroblasts to the scaffolds. Preliminary results comparing proliferation indicate that cells obtained from the PT and AT have the fastest proliferation. Whereas gene expression of the phenotypic markers measured using real-time reverse transcription polymerase chain reaction (RT-PCR) indicates ACL cells have the highest gene expression for the matrix markers. This leads to the question of which cell type should be the cell source for tissue-engineering of ligament, the highly proliferating cells or the differentiated matrix producing cells. This study would suggest that ACL differentiated matrix producing cells are the most suitable cells for further study and development of a tissue-engineered ligament.
The effects of co-monomer composition and irradiation time in a model two-component dimethacrylate dental resin blend were evaluated using combinatorial methods to determine the degree of methacrylate conversion and resulting mechanical properties. 2-Dimensional gradient samples varying in monomer composition and light exposure time were fabricated. The conversion was measured using near infrared spectroscopy (NIR) and the mechanical properties (i.e., hardness and elastic modulus) were determined using nanoindentation via the continuous stiffness method. An excellent correlation was observed between the reaction conversion and mechanical properties for the cross-linked networks. The methacrylate conversion ranged from 40% to 85% and the mechanical properties increased over two orders of magnitude over this conversion range. The ultimate reaction conversion and mechanical properties depended on both the co-monomer composition and cure time.
In this study, 80% SiO2–20% CaO (mole fraction) three-dimensionally ordered macroporous sol–gel bioactive glass (3DOM-BG, average pore size: 345nm) particles were prepared and characterized. Since the 3DOM-BGs have a novel microstructure and ion-releasing profile, the cytotoxicity of 3DOM-BG particles was tested. The cytotoxicity tests were performed using MC3T3-E1 osteoblast-like cells: (1) Wst-1 assay for cell viability after culture in extracts from 3DOM-BG particles; (2) phase contrast microscopy for cell morphology after culture with 3DOM-BG particles; and (3) fluorescence microscopy for imaging cells cultured directly on 3DOM-BG particles. The results showed that 3DOM-BG particles were not cytotoxic, and that cells attached, spread and proliferated on and around 3DOM-BG particles.
A series of sorbitol-containing polyesters were synthesized via a one-pot lipase-catalyzed condensation polymerization. Thin films were prepared by spin coating on silicon wafers and surfaces were analyzed by tapping mode atomic force microscopy and contact angle measurements. Surface morphologies and surface energies across the series of polyester films, including a poly(ε-caprolactone) (PCL) control were nearly indistinguishable. Biocompatibility of the sorbitol-containing polyester series was evaluated against a PCL control by measuring cell spreading and proliferation of a mouse fibroblast 3T3 cell line in vitro. Results confirmed that the sorbitol-containing polyester surfaces elicited cell behavior similar to the PCL control. These results establish the sorbitol-containing polyester series as a promising material for tissue engineering research and development.
A high-throughput method for analyzing cellular response to crystallinity in a polymer material is presented. Variations in crystallinity lead to changes in surface roughness on nanometer length scales, and it is shown that cells are exquisitely sensitive to these changes. Gradients of polymer crystallinity were fabricated on films of poly(l-lactic acid) using a gradient in annealing temperature. The resultant morphologies were characterized using an atomic force microscope. Root-mean-square (rms) roughness values ranging from 0.5 to 13 nm were created on a single sample. MC3T3-E1 osteoblastic cells were cultured for 1, 3 and 5 d, and the number of cells was measured using automated fluorescence microscopy. It is shown that the rate of proliferation on the smooth regions of the films is much greater than that on the rough regions, and a monotonic variation in rate is observed as a function of roughness. The critical rms roughness, above which a statistically significant reduction in rate of proliferation occurs, was approximately 1.1 nm. Fluorescence microscopy measurements on immunostained cells indicate there is no significant change in cell area, the number or type of adhesions formed, or the degree of actin polymerization. Results from enzyme-linked immunofluorescence assays indicated that there was no detectable change in adhesion protein accessibility, suggesting the cells directly respond to substrate topography. The use of the gradient library approach yielded the functional dependence of cell proliferation on nanometer-scale roughness and gave a sensitive estimate of the critical roughness for which a decrease in proliferation is observed.
A series of blends of the biodegradable polymers poly(D,L-lactic acid) and poly( epsilon -caprolactone) were prepared by varying mass fraction across the range of compositions. Tensile testing was performed at room temperature using an extensometer and the elastic modulus was calculated for each blend. The blends were also tested to failure, and the strain-at-failure and yield stress recorded. While the blend has been shown to have a lower critical solution temperature, the mechanical properties were insensitive to the annealing conditions. Scanning electron microscopy was used to characterize the blend microstructure and poor adhesion was observed at the interface between blend components. Differential scanning calorimetry was performed but the results were somewhat variable, indicating this blend may have complex phase behavior that depends sensitively on the method of preparation. However, nuclear magnetic resonance data indicate the two components are phase separated. A percolation model is used to explain the observed mechanical data and the results are consistent with the predictions of the Kerner-Uemura-Takayangi model. The results of these experiments demonstrate the utility of polymer blending in tuning material properties.
Because of its relatively high solubility in aqueous media and its rapid transformation to hydroxyapatite, amorphous calcium phosphate (ACP) has been utilized as the filler phase of resin-based bioactive composites that have remineralization potential. The objectives of this study were to determine how various methacrylate resins and various types of ACP fillers affect acrylic vinyl conversion and polymerization shrinkage (PS). Several types of photo-crosslinkable resin systems were prepared and admixed with a mass fraction of 40% of either unhybridized, silica- or zirconia-hybridized ACP. After visible light-activated photo-polymerization ACP composites were assessed by near infrared spectroscopy for degree of vinyl conversion and by mercury dilatometry for PS. It was found for these composites that vinyl conversion was independent of filler type but strongly dependent on the type and composition of the resin phase. PS, on the other hand, showed more complex dependence both on the resin type and composition and, in some cases, on the type of ACP. In order to obtain ACP/methacrylate-based composites with maximal vinyl conversion, resin type and composition are of primary importance. However, in order to minimize volume contraction on polymerization it appears necessary to consider both the resin and filler type of these bioactive composites.
Surgical implants need to be free from contaminants before implantation. The effectiveness of a presently used Clemson bioengineering cleaning (CBC) protocol was evaluated for cleaning three different biomaterials (titanium, aluminum oxide, and polyethylene terephthalate, PET) contaminated with three different contaminants (calcium chloride, zinc chloride, and hexadecane). Radiolabeled tracer analysis (RTA), with the use of liquid scintillation, was used as the surface analytical technique to quantitatively determine the removed from the biomaterial surface. On average, the ultrasonic cleaning step removed 99.96% of all three contaminants from both titanium and aluminum oxide. The CBC protocol did not sufficiently clean PET fabric contaminated with hexadecane leaving 11.76% of the contaminant after the ultrasonic step. With the use of isopropyl alcohol in series with 1% Liquinox, the ultrasonic step cleaned the fabric soiled with hexadecane within 30 min, removing 99.85% of the hexadecane initially on the surface. RTA proved to be an excellent method of quantifying surface contamination on implant materials, and for assessing the effectiveness of cleaning protocols in question. © 1995 John Wiley & Sons, Inc.
Grit blasting is a common procedure of roughening surfaces to promote physical attachment of porous coatings, but it has been shown to reduce fatigue strength. Shot peening is known to increase fatigue strength by inducing compressive surface stresses; however, it is not known how subsequent grit blasting affects these benefits. This study examines the endurance limits, S e , of ELI grade Ti-6A1-4V specimens under rotating cyclic bending, including polished (control); belted and beaded; belted, beaded, and grit blasted; and belted, beaded, shot peened, and grit blasted. Belting and beading resulted in a slight increase in S e ; grit blasting caused a 15% reduction in S e from polished. Fifty percent of this reduction was recovered when shot peening preceded grit blasting, suggesting that residual compressive surface stresses, induced by peening, were not eliminated by the blast process. Roughness averages and RMS values did not correlate with S e trends. SEM results showed classical fatigue fractures, consistent with surface crack initiation. © 1995 John Wiley & Sons, Inc.
Journal of Applied BiomaterialsVolume 6, Issue 4 p. 305-305 ErratumFree Access Erratum. Self-reported signs and symptoms in breast implant patients with novel antibodies to silicone surface associated antigens [anti-SSAA(x)] Nir Kossovsky, Nir Kossovsky Biomaterials Bioreactivity Characterization Laboratory, University of California, Los Angeles, School of Medicine, Los Angeles, California Originally published ni J. Appl. biomat. 6:153–160; 1995Search for more papers by this authorJeffrey A. Gornbein, Jeffrey A. Gornbein Department of Pathology and Laboratory Medicine, UCLA Medical CenterUniversity of California, Los Angeles, School of Medicine, Los Angeles, California Originally published ni J. Appl. biomat. 6:153–160; 1995 Department of Biomathematics, University of California, Los Angeles, School of Medicine, Los Angeles, California Originally published ni J. Appl. biomat. 6:153–160; 1995Search for more papers by this authorMichelle Zeidler, Michelle Zeidler Biomaterials Bioreactivity Characterization Laboratory, University of California, Los Angeles, School of Medicine, Los Angeles, California Originally published ni J. Appl. biomat. 6:153–160; 1995Search for more papers by this authorJohn Stassi, John Stassi Biomaterials Bioreactivity Characterization Laboratory, University of California, Los Angeles, School of Medicine, Los Angeles, California Originally published ni J. Appl. biomat. 6:153–160; 1995Search for more papers by this authorGrace Chun, Grace Chun Biomaterials Bioreactivity Characterization Laboratory, University of California, Los Angeles, School of Medicine, Los Angeles, California Originally published ni J. Appl. biomat. 6:153–160; 1995Search for more papers by this authorNora Papasian, Nora Papasian Biomaterials Bioreactivity Characterization Laboratory, University of California, Los Angeles, School of Medicine, Los Angeles, California Originally published ni J. Appl. biomat. 6:153–160; 1995Search for more papers by this authorRachel Nguyen, Rachel Nguyen Biomaterials Bioreactivity Characterization Laboratory, University of California, Los Angeles, School of Medicine, Los Angeles, California Originally published ni J. Appl. biomat. 6:153–160; 1995Search for more papers by this authorKahn Ly, Kahn Ly Biomaterials Bioreactivity Characterization Laboratory, University of California, Los Angeles, School of Medicine, Los Angeles, California Originally published ni J. Appl. biomat. 6:153–160; 1995Search for more papers by this authorSamir Rajguru, Samir Rajguru Biomaterials Bioreactivity Characterization Laboratory, University of California, Los Angeles, School of Medicine, Los Angeles, California Originally published ni J. Appl. biomat. 6:153–160; 1995Search for more papers by this author Nir Kossovsky, Nir Kossovsky Biomaterials Bioreactivity Characterization Laboratory, University of California, Los Angeles, School of Medicine, Los Angeles, California Originally published ni J. Appl. biomat. 6:153–160; 1995Search for more papers by this authorJeffrey A. Gornbein, Jeffrey A. Gornbein Department of Pathology and Laboratory Medicine, UCLA Medical CenterUniversity of California, Los Angeles, School of Medicine, Los Angeles, California Originally published ni J. Appl. biomat. 6:153–160; 1995 Department of Biomathematics, University of California, Los Angeles, School of Medicine, Los Angeles, California Originally published ni J. Appl. biomat. 6:153–160; 1995Search for more papers by this authorMichelle Zeidler, Michelle Zeidler Biomaterials Bioreactivity Characterization Laboratory, University of California, Los Angeles, School of Medicine, Los Angeles, California Originally published ni J. Appl. biomat. 6:153–160; 1995Search for more papers by this authorJohn Stassi, John Stassi Biomaterials Bioreactivity Characterization Laboratory, University of California, Los Angeles, School of Medicine, Los Angeles, California Originally published ni J. Appl. biomat. 6:153–160; 1995Search for more papers by this authorGrace Chun, Grace Chun Biomaterials Bioreactivity Characterization Laboratory, University of California, Los Angeles, School of Medicine, Los Angeles, California Originally published ni J. Appl. biomat. 6:153–160; 1995Search for more papers by this authorNora Papasian, Nora Papasian Biomaterials Bioreactivity Characterization Laboratory, University of California, Los Angeles, School of Medicine, Los Angeles, California Originally published ni J. Appl. biomat. 6:153–160; 1995Search for more papers by this authorRachel Nguyen, Rachel Nguyen Biomaterials Bioreactivity Characterization Laboratory, University of California, Los Angeles, School of Medicine, Los Angeles, California Originally published ni J. Appl. biomat. 6:153–160; 1995Search for more papers by this authorKahn Ly, Kahn Ly Biomaterials Bioreactivity Characterization Laboratory, University of California, Los Angeles, School of Medicine, Los Angeles, California Originally published ni J. Appl. biomat. 6:153–160; 1995Search for more papers by this authorSamir Rajguru, Samir Rajguru Biomaterials Bioreactivity Characterization Laboratory, University of California, Los Angeles, School of Medicine, Los Angeles, California Originally published ni J. Appl. biomat. 6:153–160; 1995Search for more papers by this author First published: Winter 1995 https://doi.org/10.1002/jab.770060413AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume6, Issue4Winter 1995Pages 305-305 RelatedInformation
Two experimental methods for restoring flexor tendon sheath integrity and preventing adhesions around traumatized flexor tendons utilizing artificial tendon sheaths made of either hydroxyapatite (HAp) or alumina were studied in a flexor tendon-trauma model and compared to a standard tendon sheath repair and a control. Eighty toes were divided equally into a control group, a sheath repair group, an HAp group, and an alumina group. Profundus tendons in zone II were divided and repaired after sublimis excision in all groups. In the sheath repair group, the flexor sheath was also repaired after suturing the tendon. In artificial sheath groups, sheaths made of HAp and alumina were placed over the repair sites to protect them from the surrounding tissues. In the control group, after repairing the tendon, the flexor sheath was excised and no artificial sheaths were used. Each toe was immobilized in a plaster cast for 3 weeks. After three weeks, the plaster cast was removed followed by the removal of the sheaths in the artificial sheath groups through a small incision in the skin in zone II. Active mobilization was encouraged in each group. Postoperative adhesions were examined at 3, 6, 9, and 12 week intervals by using light microscopic techniques. To further explore the effects of artificial sheaths on tendon healing, transmission electron microscopy was done for the HAp and alumina groups at 3, 6, and 12 week intervals. Results demonstrated decreased severity of postoperative adhesions in the HAp as well as in the alumina groups in comparison with the sheath repair and controls. A space resembling the fibro-osseous canal was formed around the tendon after removing the sheaths. This space remained patent until 12 weeks, 9 weeks after removing the sheaths, and a newly formed tendon sheath-like structure lined by synovial cells and with a peritenon-like structure over the tendon surface was observed. In the sheath repair and control groups, the severity of adhesions was decreased with the passage of time, to some extent due to unrestricted mobility. However, a newly formed tendon sheath or peritenon-like structure was not observed. Electron microscopic studies confirmed good healing at the suture in the HAp and alumina groups with no evidence of necrosis. These results are qualitative in nature as no statistical tests were performed. From these results we conclude that if the tendon is separated from the surrounding granulation tissue by a barrier with good biocompatibility, the tendon can heal with fewer adhesions. Artificial sheaths may be used to reduce adhesions in severe injuries of the hand where postoperative immobilization is necessary due to fractures, vascular, or nerve injuries. © 1995 John Wiley & Sons, Inc.
Crestal bone loss is observed around various designs of dental implants. A possible cause of this bone loss is related to the stresses acting on periimplant bone. To investigate the relationship between stress state and bone loss, two-dimensional finite element models corresponding to bucco-lingual and mesio-distal sections of canine mandibles with one of two designs of porous-coated dental implants were analyzed. A fully porous-coated design consisting of a solid Ti6A14V core had a porous coating over the entire outer surface of the implant component, while a partially porous-coated design had the porous coating over the apical two-thirds of the implant surface only. Occlusal forces with axial and transverse components were assumed to act on the implant with interface bonding and effective force transfer at all porous coat-bone interfaces and no bonding for the non-porous-coated regions. The results of the analysis indicated that at most implant aspects (buccal, lingual, mesial, and distal), the equivalent stresses in crestal bone adjacent to the coronal-most, non-porous-coated zone of the partially porous-coated implants were lower than around the most coronal region of the fully porous-coated implants. The region of lower stresses around the partially porous-coated implants corresponded to observed areas of crestal bone loss in animal studies, suggesting that crestal bone loss in this case was due to bone disuse atrophy. A number of parameters of the finite element models were varied to determine the effect on the resulting stress fields and, therefore, possible long-term bone remodeling. Based on differences in observed bone structures by histological examination and results of finite element analyses with fully and partially porous-coated implants, an equivalent stress equal to 1.6 MPa was determined to be sufficient to avoid bone loss due to disuse atrophy in the canine mandibular premolar region. © 1995 John Wiley & Sons, Inc.
A quantitative method of reporting surface degradation of the ultra-high molecular weight polyethylene (UHMWPE) tibial component from retrieved total knee replacements (TKR) was developed. Specific features include a qualitative assessment expressing the patterns in which the damage was detected as well as a quantitative summary of the observed degradation mechanisms. In addition, a method of measuring lower limb alignment changes with time is described and related to the observed damage patterns. Two case studies are presented. One case illustrated that changes in alignment resulted from factors other than wear. The damage observed on the tibial plateau appeared to occur subsequent to the changes in alignment. The second case illustrated that the wear of the UHMWPE tibial insert lead to the changes in the overall lower limb alignment. The methods described provide additional information regarding TKR failure mechanisms compared to reporting methods currently available. In particular, the collection of temporal alignment data at clinical follow-up visits enhanced the assessment of the retrieved TKR.
Biological materials have been used as prosthetic devices such as heart valves, vascular grafts, and pericardial patches. These biological materials have to be fixed with crosslinking reagents and sterilized subsequently before they can be implanted in humans. Recently, a new crosslinking reagent, epoxy compound, has been used to fix bioprostheses. In this fixation technique, heparin may be ionically bound on the tissue surface. It has been shown that the amount of heparin bound to the tissue surface is proportional to the quantity of protamine impregnated in the biological tissues. However, it is not known if the impregnation of protamine will affect the crosslinking density of the biological tissues. This study was designed to compare the crosslinking densities of the epoxy compound fixed biological tissues with or without heparinization. Fresh porcine aortic valves procured from a slaughter house were first impregnated in various concentrations of protamine sulfate (0, 0.5, 1.0, or 1.5%) for about 30 min. The porcine aortic valves were then crosslinked in a 4% epoxy compound solution (Denacol® EX-313). The porcine samples were taken out at various elapsed fixation periods: 18, 25, 48, 72, 96, and 120 h. Finally, the crosslinked porcine aortic valves were heparinized in a 0.5% sodium heparin solution for about 1 h. The crosslinking densities of the porcine leaflet and the aortic wall of each sample were determined by measuring their shrinkage temperatures. It was revealed that the impregnation of various concentrations of protamine did not seem to significantly alter the shrinkage temperatures of the porcine leaflet and the aortic wall throughout the entire fixation process ( p > 0.05). This indicated that the impregnation of protamine did not significantly change the crosslinking density of the biological tissues. However, it was found that protamine tended to discolor the tissue and to stiffen the porcine leaflet and the aortic wall. Although the impregnation of protamine did not seem to significantly alter the crosslinking density of the epoxy compound fixed biological tissues, the increase of the stiffness of the heparinized tissues may cause concerns in some clinical applications. © 1995 John Wiley & Sons, Inc.
A novel drug delivery system for osteomyelitis was developed using porous hydroxyapatite blocks (HA-b) loaded with antibiotics by centrifugation. In the study, 10 mm3 HA-b was placed in a container and mixed with antibiotic solution; the antibiotic was then loaded into the pores of the HA-b by centrifuging at 1500 rpm for 15 min. Slow release of HA-b in both moist form and dried form (by heating at 160 degrees C) was tested after loading with the antibiotic arbekacin sulfate (ABK), 1-N-(S)-4 amino-2-hydroxybutyryl dibekacin. To estimate the concentration of antibiotic, both forms of HA-b were placed in 3 mL of phosphate buffered saline (PBS), which was replaced every 48 h. In both groups, which were loaded with 70 mg ABK per one block of HA (concn 0.5 microgram/mL) which is sufficiently high to control most pathogens, was maintained for 21 exchanges of PBS (after 42 days). Minimum inhibitory concentration for methicillin-resistant Staphylococcus aureus (MRSA), 3.13 micrograms/mL, was maintained until nine exchanges took place (after 18 days). The centrifugation method is simple, and dried ABK produced by heating loaded HA-b is particularly useful in clinical applications for osteomyelitis.
Heparin oligosaccharides with different anticoagulant activities were prepared and immobilized onto pyrolytic carbon coated graphite (PC) heart valve materials commonly used in mechanical heart valve prostheses. Prior to immobilization, PC surfaces were modified by radiofrequency plasma polymerized N-vinyl-2-pyrrolidone (PPNVP) thin films (approximately 100 nm) and derivatized to provide surface hydroxyl groups. Cleaved, low affinity heparin (C-heparin) with factor Xa inhibition activity of 107 to 130 IU/mg, was prepared by partial deaminative cleavage of commercial crude heparin, and high-affinity heparin (HA-heparin) with factor Xa inhibition activity of 550 to 1000 IU/mg was prepared by fractionation of C-heparin using agarose-ATIII affinity chromatography. C-heparin and HA-heparin were immobilized to surface modified PC by reductive amination. Anticoagulant activity of the heparin immobilized surfaces was determined by chromogenic assay for the inhibition of factor Xa. Highest surface anticoagulant activity was measured on C-heparin immobilized surfaces (64.0 +/- 7.3 mIU/cm2) compared with HA-heparin immobilized surfaces (27.2 +/- 12.2 mIU/cm2), suggesting higher binding of C-heparin than HA-heparin on the modified PC surfaces. Immobilized surfaces were evaluated under dynamic flow conditions, by subjecting samples to shear stress of up to 206 dyn/cm2 in the presence of 5% albumin solution or human plasma. Anticoagulant activity of the immobilized heparin was retained, although reduced, and the modified surfaces showed evidence for protein resistance.
