Human monocyte response to retrieved polymethylmethacrylate particles

The osteolytic response of macrophages to challenge with particles of Simplex P, Endurance, Palacos R, and Vertebroplastic bone cement particles in vitro

The capacity of clinically relevant wear particles from Simplex P, Endurance, Vertebroplastic and Palacos R bone cements to activate macrophages to produce cytokines and bone resorbing activity in vitro was compared. Cement particles were generated aseptically by using a pin on plate rig. The particles were irregular in shape, and there were no significant differences in the particle characteristics of the different bone cement types (mean equivalent circle diameter range 0.225--0.36 mum, mean area range 0.048--0.063 microm(2), mean aspect ratio range 1.481--1.593, and mean length 0.412--0.523 microm). The volumetric concentration of particles in the 0.1- to 1.0-microm size range was 85% Palacos R, 82% Endurance, 80% Simplex P, and 77% Vertebroplastic. Particles were cultured with C3H macrophages at 100 microm(3) per cell for 24 h. Cytokines were determined by enzyme-linked immunosorbent assay and bone resorption (BR) measured by Ca(45) release from murine calvarias. Particles of Palacos R and Endurance stimulated enhanced production of TNF-alpha, IL-1-beta, and IL-6 (p<0.05; ANOVA). Simplex P particles only stimulated IL-1-beta (p<0.05; ANOVA). Vertebroplastic particles did not stimulate production of any of the cytokines. Particles of Palacos R generated the highest BR (1.38), but this did not reach statistical significance. The BRs for the other bone cements were no greater than the control. Hence, compared with the same volumetric concentrations, particles of Palacos R and Endurance were the most, and particles of Vertebroplastic were the least biologically reactive.

Independent risk factors for postoperative shivering

Postoperative shivering (PAS) is uncomfortable for patients and potentially risky. In this observational trial we sought to identify independent risk factors for PAS after general anesthesia. Potential risk factors for PAS were recorded in 1340 consecutive patients. Signs of shivering, peripheral and core temperature, and thermal comfort were recorded in the postanesthetic care unit. The data were split into an evaluation data set (n = 1000) and a validation data set (n = 340). The first was used to identify independent risk factors for PAS and to formulate a risk score using backward-elimination logistic regression analysis. The proposed model was subsequently tested for its discrimination and calibration properties using receiver operating characteristic (ROC)-curve analysis and linear correlation between the predicted and the actual incidences of PAS in the validation group. The incidence of PAS was 11.6%. There were three major risk factors: young age, endoprosthetic surgery, and core hypothermia, with age being the most important. The risk score derived from this analysis had a reasonable discriminating power, with an area under the ROC-curve of 0.69 (95% confidence interval, 0.60-0.78; P < 0.0001). Furthermore the equation of the calibration curve (y = 0.69x + 6; R2= 0.82; P < 0.05) indicated a good and statistically significant agreement between predicted and actual PAS incidence. Postoperative shivering can be predicted with acceptable accuracy using the four risk factors identified in the present study. The presented model may serve as a clinical tool to help clinicians to rationally administer prophylactic antishivering drugs.

Biodegradability of poly (2-hydroxyethyl methacrylate) in the presence of the J774.2 macrophage cell line

The degradation of cross-linked and linear poly(2-hydroxyethyl methacrylate) (pHEMA), was examined in vitro with J774.2 cells. pHEMA microbeads were prepared with both types of polymers. Only cells in contact with the microbeads increased their production of lysosomal enzymes (TRAcP and ANAE) and released large amounts of reactive oxygen species with both types of pHEMA microbeads. Electron microscopy showed that macrophages were able to erode the surface of linear pHEMA but unable to erode the surface of the cross-linked polymer. Cells appeared wrapped by the linear pHEMA surface, but those cultured on the cross-linked polymer were only laying at the surface. After cell culture, the surface roughness of pHEMA slices was observed by atomic force microscopy (AFM). There was a significant increase in roughness (R(a)) of the surface of linear pHEMA slices cultured with J774.2 cells whereas no difference in R(a) between the surface of cross-linked pHEMA slices could be measured. AFM image of the hydrated materials were done: the surface of linear pHEMA swelled considerably in saline whereas the hydrated cross-linked polymer did not differ from the air-dried appearance. In conclusion, linear pHEMA swells in biological fluids, activates macrophages in close contact with the polymer and can be progressively eroded.

In vivo evaluation of a biomimetic apatite coating grown on titanium surfaces

Osteoconductive mineral coatings represent an established technology for enhancing the integration of orthopedic implants with living bone. However, current coatings have limitations related to fabrication methods, attachment strength to metal substrates, and in vivo performance. Low temperature biomimetic growth is a coating technique wherein the device to be coated is immersed in a meta-stable saturated solution of the coating constituents and growth of the coating is then allowed to proceed on the surface of the device. This study focused on the in vivo evaluation of a biomimetic apatite coating fabricated under these conditions. The experiment was designed to specifically test the amount of bone ingrowth into the coated channels versus the uncoated channels of an established bone chamber system, with emphasis placed on the amount of bone present on the coupon surface. Three types of measurements were taken on each channel: linear ingrowth %, area ingrowth %, and continuous bone apposition %. The experiments demonstrated that under controlled conditions, the apatite coating appears to resorb in 8 weeks and did stimulate early osseointegration with the metal surface with a reduction in fibrous tissue encapsulation. This coating may, therefore, be useful in facilitating early bone ingrowth into porous surfaces without the potential for coating debris, macrophage infiltration, fibrous tissue encapsulation, and eventual coating failure as may occur with current plasma-sprayed hydroxapatite coating techniques.

The potential environmental impact of engineered nanomaterials

With the increased presence of nanomaterials in commercial products, a growing public debate is emerging on whether the environmental and social costs of nanotechnology outweigh its many benefits. To date, few studies have investigated the toxicological and environmental effects of direct and indirect exposure to nanomaterials and no clear guidelines exist to quantify these effects.