Biomedical subjects

R H Doremus

Publications and source records attributed to R H Doremus.

10 recordsLinked to original sources

PubMed2001

Enhanced osteoclast-like cell functions on nanophase ceramics.

Synthesis of tartrate-resistant acid phosphatase (TRAP) and formation of resorption pits by osteoclast-like cells, the bone-resorbing cells, on nanophase (that is, material formulations with grain sizes less than 100nm) alumina and hydroxyapatite (HA) were investigated in the present in vitro study. Compared to conventional (that is, grain sizes larger than 100 nm) ceramics, synthesis of TRAP was significantly greater in osteoclast-like cells cultured on nanophase alumina and on nanophase HA after 10 and 13 days, respectively. In addition, compared to conventional ceramics, formation of resorption pits was significantly greater by osteoclast-like cells cultured on nanophase alumina and on nanophase HA after 7, 10, and 13 days, respectively. The present study, therefore, demonstrated, for the first time, enhanced osteoclast-like cell function on ceramic surfaces with nanometer-size surface topography.

Acid Phosphatase↗

PubMed2001

Uncertainties in retrospective radon exposure of glass: possible effects of hydration and of leaching.

Embedded 210Pb in glass results from exposure to 222Rn and its prompt decay products and is used to estimate integrated, retrospective radon exposures for times up to the 32-y mean life of 210Pb. Certain established uncontrollable factors lead to rather large scatter in the results. We review briefly the known sources that contribute to this scatter and then point out that effects of water and, in particular, hydration layers on glass are probably further sources of error, possibly of major importance, but subject to straightforward checking to reject glass compositions that are unreliable.

Diffusion↗

PubMed2000

Specific proteins mediate enhanced osteoblast adhesion on nanophase ceramics.

Osteoblast, fibroblast, and endothelial cell adhesion on nanophase (that is, materials with grain sizes less than 100 nm) alumina, titania, and hydroxyapatite (HA) was investigated using in vitro cellular models. Osteoblast adhesion was significantly (p < 0.01) greater after 4 h on nanophase alumina, titania, and HA than it was on conventional formulations of the same ceramics. In contrast, compared to conventional alumina, titania, and HA, after 4 h fibroblast adhesion was significantly (p < 0.01) less on nanophase ceramics. Examination of the underlying mechanism(s) of cell adhesion on nanophase ceramics revealed that these ceramics adsorbed significantly (p < 0.01) greater quantities of vitronectin, which, subsequently, may have contributed to the observed select enhanced adhesion of osteoblasts. Select enhanced osteoblast adhesion was independent of surface chemistry and material phase but was dependent on the surface topography (specifically on grain and pore size) of nanophase ceramics. The capability of synthesizing and processing nanomaterials with tailored (through, for example, specific grain and pore size) structures and topographies to control select subsequent cell functions provides the possibility of designing the novel proactive biomaterials (that is, materials that elicit specific, timely, and desirable responses from surrounding cells and tissues) necessary for improved implant efficacy.

Adsorption↗

PubMed2000

Enhanced functions of osteoblasts on nanophase ceramics.

Select functions of osteoblasts (bone-forming cells) on nanophase (materials with grain sizes less than 100 nm) alumina, titania, and hydroxyapatite (HA) were investigated using in vitro cellular models. Compared to conventional ceramics, surface occupancy of osteoblast colonies was significantly less on all nanophase ceramics tested in the present study after 4 and 6 days of culture. Osteoblast proliferation was significantly greater on nanophase alumina, titania, and HA than on conventional formulations of the same ceramic after 3 and 5 days. More importantly, compared to conventional ceramics, synthesis of alkaline phosphatase and deposition of calcium-containing mineral was significantly greater by osteoblasts cultured on nanophase than on conventional ceramics after 21 and 28 days. The results of the present study provided the first evidence of enhanced long-term (on the order of days to weeks) functions of osteoblasts cultured on nanophase ceramics; in this manner, nanophase ceramics clearly represent a unique and promising class of orthopaedic/dental implant formulations with improved osseointegrative properties.

Alkaline Phosphatase↗

PubMed1992

Osteoblasts on hydroxyapatite, alumina and bone surfaces in vitro: morphology during the first 2 h of attachment.

The morphological responses of individual osteoblasts as they attached and spread on hydroxyapatite, bovine bone, alumina with rough and polished surfaces, and tissue culture polystyrene in vitro were examined with scanning electron microscopy. Depending on the surface tested two different morphological sequences were observed during 2 h of adhesion. On alumina, both rough and smooth, bone, and tissue culture polystyrene the cells were round after 0.5 h, and spread radially during the next 1.5 h until they were almost flat, with a nuclear bulge. On hydroxyapatite, however, the cells were flat and circular at 0.5 h, and the edge of the cytoplasm was hardly discernable. This morphology did not change much during the subsequent 1.5 h. The observed cellular morphological response may be related to the bioreactivity of hydroxyapatite.

Aluminum Oxide↗

PubMed1991

Osteoblast responses to orthopedic implant materials in vitro.

Responses of neonatal rat calvarial osteoblasts to a variety of orthopedic implant materials were examined in vitro. Attachment, proliferation, and collagen synthesis of a well-characterized line of osteoblasts with 316L stainless steel, Ti-6Al-4V, Co-Cr-Mo, PMMA, hydroxyapatite, borosilicate glass, and tissue culture polystyrene were studied. Cell adhesion and growth were similar on nonapatitic materials. In contrast, attachment and growth of osteoblasts were significantly lower and slower, respectively, on hydroxyapatite. Collagen synthesis per cell and relative collagen synthesis, however, were comparable on all the materials tested.

Animals↗

PubMed1984

Direct electron microscopy studies of the bone-hydroxylapatite interface.

The bone-hydroxylapatite interface has been examined directly in the transmission electron microscope (TEM). The bone-hydroxylapatite interface was characterized by using several electron microscopy techniques, including bright and dark field imaging, electron diffraction, high-resolution imaging, and energy dispersive analysis in the scanning-transmission electron microscope (STEM EDS). Mechanical grinding followed by argon-ion milling produced interface regions of unstained and undecalcified rat bone and hydroxylapatite that were transparent to electrons. Thus the exact location of the interface could be established and the bone at the interface studied. Conventional and high-resolution imaging in the TEM demonstrated direct chemical bonding between bone and hydroxylapatite. The bone at the ceramic surface was the same as normal bone away from the interface.

Animals↗

PubMed1978

Crystallization of calcium oxalate from synthetic urine.

The precipitation of calcium oxalate from synthetic urine was followed from the disappearance of radioactive oxalate from solution. Rates of precipitation were also estimated from the time of appearance of crystals. Synthetic urine inhibited the rate of crystallization of calcium oxalate; this inhibition was a combined effect of ionic strength and specific inhibition by one or mroe components of the synthetic urine. Polyphosphate and polyacrylate ions strongly inhibited crystallization of calcium oxalate from synthetic urine; phosphonates, heparin, and polystyrene sulfonate showed much less inhibition. Inasmuch as citrate and pyrophosphate ions showed some inhibition, it seems that carboxylate and phosphate groups on a polymer chain are the most effective inhibitors.

Acrylic Resins↗

PubMed1978

Crystal growth inhibitors in human urine. Effect on calcium oxalate kinetics.

The nucleation and growth of oxalate trihydrate from supersaturated solutions containing a high molecular weight inhibitor fraction found in urine were sharply reduced to the extend that calcium oxalate dihydrate was formed. The kinetics of the later hydrate were found to be reduced with increasing inhibitor concentration. The effect of the negatively charged urine inhibitor on crystal growth of calcium oxalate was found to correlate with inhibition found in studies involving high molecular weight mucopolysaccharides such as heparin.

Calcium↗

PubMed1977

Tissue, cellular and subcellular events at a bone-ceramic hydroxylapatite interface.

A new polycrystalline form of hydroxylapatite, durapatite, has been examined as a cortical bone implant in dogs. Utilizing histological and electron optical techniques, it has been found that durapatite does not elicit a foreign body response and that all new bone surrounding the material is normally calcified. Bone was found to strongly adhere to durapatite and preliminary evidence suggests this bonding may be due to direct chemical attachment of bone to the material.

Animals↗