Surface chemistry control of monocyte and macrophage adhesion, morphology, and fusion.
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Cell Adhesion↗
Biomedical subjects
C H Thomas
Publications and source records attributed to C H Thomas.
Protein adsorption and cell attachment to patterned surfaces.
To better understand the events involved in the generation of defined tissue architectures on biomaterials, we have examined the mechanism of attachment of human bone-derived cells (HBDC) to surfaces with patterned surface chemistry in vitro. Photolithography was used to generate alternating domains of N-(2-aminoethyl)-3-aminopropyl-trimethoxysilane (EDS) and dimethyldichlorosilane (DMS). At 90 min after seeding, HBDC were localized preferentially to the EDS regions of the pattern. Using sera specifically depleted of adhesive glycoproteins, this spatial organization was found to be mediated by adsorption of vitronectin (Vn) from serum onto the EDS domains. In contrast, fibronectin (Fn) was unable to adsorb in the face of competition from other serum components. These results were confirmed by immunostaining, which also revealed that both Vn and Fn were able to adsorb to EDS and DMS regions when coated from pure solution, i.e., in the absence of competition. In this situation, each protein was able to mediate cell adhesion across a range of surface densities. Cell spreading was constrained on the EDS domains, as indicated by cell morphology and the lack of integrin receptor clustering and focal adhesion formation. This spatial constraint may have implications for the subsequent expression of differentiated function.
Animals↗
Engineering bone regeneration with bioabsorbable scaffolds with novel microarchitecture.
Critical-sized defects (CSDs) were introduced into rat calvaria to test the hypothesis that absorption of surrounding blood, marrow, and fluid from the osseous wound into a bioabsorbable polymer matrix with unique microarchitecture can induce bone formation via hematoma stabilization. Scaffolds with 90% porosity, specific surface areas of approximately 10 m2/g, and median pore sizes of 16 and 32 microm, respectively, were fabricated using an emulsion freeze-drying process. Contact radiography and radiomorphometry revealed the size of the initial defects (50 mm2) were reduced to 27 +/- 11 mm2 and 34 +/- 17 mm2 for CSDs treated with poly(D,L-lactide-co-glycolide). Histology and histomorphometry revealed scaffolds filled with significantly more de novo bone than negative controls (p < 0. 007), more osteoid than both the negative and autograft controls (p < 0.002), and small masses of mineralized tissue (< 15 mm in diameter) observed within the scaffolds. Based on these findings, we propose a change in the current paradigm regarding the microarchitecture of scaffolds for in vivo bone regeneration to include mechanisms based on hematoma stabilization.
Absorbable Implants↗
Surfaces designed to control the projected area and shape of individual cells.
Materials with spatially resolved surface chemistry were designed to isolate individual mammalian cells to determine the influence of projected area on specific cell functions (e.g., proliferation, cytoskeletal organization). Surfaces were fabricated using a photolithographic process resulting in islands of cell binding N-(2-aminoethyl)-3-aminopropyl-trimethoxysilane (EDS) separated by a nonadhesive interpenetrating polymer network [poly (acrylamide-co-ethylene glycol); P (AAm-co-EG)]. The surfaces contained over 3800 adhesive islands/cm2, allowing for isolation of single cells with projected areas ranging from 100 microns 2 to 10,000 microns 2. These surfaces provide a useful tool for researching how cell morphology and mechanical forces affect cell function.
Actins↗
The reduction half cell in biomaterials corrosion: oxygen diffusion profiles near and cell response to polarized titanium surfaces.
Mechanically assisted corrosion processes can greatly increase the oxidation currents generated in passivating alloy systems like Co-Cr and titanium due to oxide film disruption. When oxide films are abraded, repassivation and ionic dissolution both occur at rates that are orders of magnitude higher than undisrupted surfaces. The excess electrons generated by these anodic processes must be consumed in corresponding reduction reactions that include the reduction of oxygen. If large enough, these reduction reactions may locally deplete the concentration of solution-dissolved oxygen and, in turn, affect cell behavior in the vicinity of the implant surface. To date, this hypothesis has not been tested. In the present study, a scanning electrochemical microscope was used to measure oxygen concentration profiles in vitro near a planar titanium electrode polarized to different voltages representative of those attainable by titanium undergoing mechanically assisted corrosion. The potentials investigated ranged from 0 mV to -1000 mV (AgCl). The oxygen concentration as a function of distance from the titanium surface was measured using a platinum-iridium microelectrode and an amperometric technique. Also, preliminary experiments were performed to assess the response of rat calvarial osteoblast-rich cells cultured for 2 h on titanium samples polarized to two different potentials (0 mV and -1000 mV versus AgCl). The results of this study indicate that oxygen concentrations near titanium surfaces are affected by sample potentials out to probe-sample distances as great as 500 microm. Within 2 microm of the surface, oxygen concentrations decreased by 15 to 25% for sample potentials between -100 and -500 mV. At potentials more negative than -600 mV, the oxygen concentration dropped rapidly to near zero by -900 mV. The cell experiments showed a statistically significant difference in the amount of cell spreading, as measured by projected cell area, between the two groups (p < 0.03), with the cells cultured at -1000 mV undergoing much less spreading. This implies that -1000 mV inhibits normal cell behavior at the titanium surface and that this is most likely due, at least in part, to a diminished oxygen supply.
Animals↗
The role of vitronectin in the attachment and spatial distribution of bone-derived cells on materials with patterned surface chemistry.
In recent years a central objective of tissue engineering has been understanding the interaction of cells with biomaterial surfaces. In this study we examined the protein adsorption events necessary to control the attachment and the subsequent spatial distribution of bone-derived cells exposed to chemically modified surfaces. Silane chemistry and photolithography techniques were used to create substrates with alternating regions of an aminosilane, N-(2-aminoethyl)-3-aminopropyl-trimethoxysilane (EDS), along side an alkylsilane, dimethyldichlorosilane (DMS), on quartz surfaces. Sera depleted of fibronectin (Fn), vitronectin (Vn), or both were used to determine if these proteins were necessary for the initial attachment and spatial distribution of bone-derived cells exposed to modified surfaces in vitro. The kinetics and mechanisms of the spatial distribution of cells were examined using light microscopy and digital image acquisition and subsequently were analyzed. Compared to complete serum, the use of serum depleted of fibronectin with vitronectin included had minimal effect on the cell attachment, spreading, and spatial distribution on the EDS regions of the surface. However, the use of serum depleted of vitronectin with or without fibronectin included resulted in greatly reduced cell attachment and spreading. Thus the presence of vitronectin was required for the attachment, spreading, and spatial distribution of bone-derived cells exposed to EDS/DMS-patterned surfaces.
Adsorption↗
The detachment strength and morphology of bone cells contacting materials modified with a peptide sequence found within bone sialoprotein.
Adhesion, spreading, and focal contact formation of primary bone-derived cells on quartz surfaces grafted with a 15 amino acid peptide that contained a -RGD-(-Arg-Gly-Asp-) sequence unique to bone sialoprotein was investigated. The peptide surfaces were fabricated by using a heterbifunctional crosslinker, sulfosuccinimidyal 4-(N-maleimidomethyl)cyclohexane-1-carboxylate, to link the peptide to amine functionalized quartz surfaces. Contact angle measurements, spectroscopic ellipsometry, and X-ray photoelectron spectroscopy were used to confirm the chemistry and thickness of the overlayers. A radial flow apparatus was used to characterize cell detachment from peptide-grafted surfaces. After 20 min of cell incubation, the strength of cell adhesion was significantly (p < 0.05) higher on the -RGD- compared to -RGE- (control) surfaces. Furthermore, the mean area of cells contacting the -RGD- was significantly (p < 0.05) higher than -RGE- surfaces. Vinculin staining showed formation of small focal contact patches on the periphery of bone cells incubated for 2 h on the -RGD- surfaces; however, few or no focal contacts were formed by cells seeded on the -RGE-grafted surfaces. The methods of peptide immobilization utilized in this study can be applied to implants, biosensors, and diagnostic devices that require specificity in cell adhesion.
Amino Acid Sequence↗
Managing chronic back pain: impact of an interdisciplinary team approach.
OBJECTIVE: To evaluate the effectiveness of a six-week outpatient program in pain management for patients with chronic back pain. DESIGN: Retrospective review. SETTING: Rehabilitation Clinical Business Unit, Essendon campus of the Royal Melbourne Hospital. SUBJECTS: 138 consecutive patients who participated in the unit's Chronic Back Pain Programme between 1991 and 1993. INTERVENTION: Multidisciplinary program that promoted pain management rather than "cure", with two six-hour group sessions per week for six weeks. OUTCOME MEASURES: Patient assessments before the program and at program completion and at three months' follow-up, with the West Haven-Yale Multidimensional Pain Inventory (WHYMPI) and a four-minute walk test. RESULTS: At program completion, the WHYMPI showed significant decreases in the amount pain interfered with life and significant increases in patient sense of control and activity level. However, severity of pain remained the same. All these effects were maintained three months later. CONCLUSIONS: A brief outpatient program was effective in improving pain management in a group of chronic back pain sufferers. This seems a useful and relatively inexpensive option in managing this problematic group of patients.
Activities of Daily Living↗
Kinetics of bone cell organization and mineralization on materials with patterned surface chemistry.
Materials with spatially resolved chemistries (i.e. patterned surfaces) have been used to guide and organize the position of mammalian cells in vitro. A common theme in guiding the spatial distribution of cells has been the use of patterned alkylsiloxanes, where one region contains an aminosilane and the other an alkylsilane. The regions of the aminosilane served as preferential sites for cell attachment and spreading, presumably dependent on the association between cell surface proteoglycans the positively charged amine. In this study, experiments were conducted with patterns of N-(2-aminoethyl)-3-aminopropyl-trimethoxysilane (EDS) and dimethyldichlorosilane (DMS) to determine the kinetics of spatial organization of bone-derived cells, and whether initial attachment and spreading affected the rate of matrix mineralization (i.e. bone formation) in extended cultures. The bone cells required the presence of serum or preadsorption of serum proteins to the patterned EDS/DMS surface to organize according to the lithographically defined surface chemistry. Time-lapse video microscopy indicated that cells were randomly distributed over the EDS/DMS surface at the time of plating, but organized on the EDS regions within 30 min. When cultures were extended for 15 and 25 days, the matrix synthesized by the cells was preferentially mineralized on the EDS chemistry. These results demonstrate the ability of surface chemistry modifications to organize cells and form mineralized tissue in vitro. The methods employed should have general value to the engineering of tissues in vitro.
Animals↗
Welsh water should reinstate fluoridation on Anglesey.
In 1992, Welsh Water withdrew the successful water fluoridation scheme on Anglesey. Despite evidence of the benefits of water fluoridation and the rise in number of children with tooth decay since the scheme's withdrawal, Welsh Water is still not prepared to re-establish the scheme.
Child, Preschool↗
Malignant hyperthermia in a patient with an ankylosed jaw.
Difficult intubation was followed by malignant hyperthermia in a girl with an ankylosed jaw. The treatment, including the use of intravenous dantrolene, is described. The patient's subsequent management, and the anaesthetic implications of these two conditions are discussed.
Adolescent↗
Non-medical administrators in the medical alliance.
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Delivery of Health Care↗
Plasma free amino acids of swine as influenced by diet protein level, animal age and time of sampling.
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Age Factors↗
Free amino acid composition of porcine seminal, epididymal and seminal vesicle fluids.
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Amino Acids↗
A probabilistic approach to measure the strength of bone cell adhesion to chemically modified surfaces.
Patterned surfaces with alternating regions of amino silanes [N-(2-aminoethyl)-3-aminopropyl-trimethoxysilane (EDS)] and alkyl silanes [dimethyldichlorosilane (DMS)] have been used to alter the kinetics of spatial distribution of cells in vitro. In particular, we have previously observed the preferential spatial distribution of bone cells on the EDS regions of EDS/ DMS patterned surfaces (10). In this study, we examined whether the mechanism of spatial distribution of cells on the EDS regions was adhesion mediated. Homogeneous layers of EDS and DMS were immobilized on quartz substrates and characterized by contact angle. X-ray photoelectron spectroscopy, and spectroscopic ellipsometry. The strength of bone cell attachment to the modified substrates was examined using a radial flow apparatus, within either 20 min or 2 hr of cell incubation in the presence of serum. A Weibull distribution was chosen to characterize the strength of cell-substratum adhesion. Within 20 min of cell exposure, the strength of adhesion was significantly larger on EDS and clean surfaces, compared with DMS surfaces (p < 0.001). Within 2 hr of cell incubation, there was no statistical difference between the strength of cell adhesion to EDS, DMS, and clean surfaces. The results of this study suggest that the surface chemistry mediates adhesion-based spatial cell arrangement through a layer of adsorbed serum proteins.
Animals↗
Spinal instrumentation for Duchenne's muscular dystrophy: experience of hypotensive anaesthesia to minimise blood loss.
Nineteen patients with Duchenne's muscular dystrophy underwent segmental spinal instrumentation and posterior fusion between 1989 and 1994. The indication for surgery was loss of the ability to walk and development of scoliosis with sitting discomfort. Preoperative assessment included evaluation of pulmonary function. Average age at operation was 12.5 years. Instrumentation and fusion extended from upper thoracic levels to L-5 or the sacrum. A Hartshill rectangle was used in all cases, with banked allograft bone. Severe intraoperative blood loss was avoided by use of hypotensive anaesthesia. Peroperatively, systolic blood pressure was maintained between 75 and 85 mm Hg. Average blood loss was 1,246 ml (range, 400-3,100) or 30% of estimated total blood volume. Average transfusion requirements were 3 units of packed cells. Postoperative analgesia was provided by infusion via an epidural catheter. There were no postoperative wound or chest infections. Three patients required catheterisation for urinary retention. Postoperatively patients were fitted with a Neofract jacket to allow early mobilisation and discharge. Mean postoperative length of stay was 16 days. Posterior spinal fusion by using the Hartshill rectangle provided good correction and fixation. Hypotensive anaesthesia permitted surgery to be performed rapidly in a relatively dry field and avoided the complications of severe intraoperative blood loss and massive transfusion.
Anesthesia↗