A physical vapor deposition method for controlled evaluation of biological response to biomaterial chemistry and topography.

The purpose of this study was to characterize a technique to effectively mask surface chemistry without modifying surface topography. A thin layer of titanium was deposited by physical vapor deposition (PVD) onto different biomaterial surfaces. Commercially pure titanium disks were equally divided into three groups. Disks were either polished to a mirror finish, grit blasted with alumina particles, or grit blasted and subsequently plasma sprayed with a commercial grade of hydroxyapatite (HA). A subgroup of each of these treatment types was further treated by masking the entire disk surface with a thin layer of commercially pure titanium deposited by PVD. A comparison of surface topography and chemical composition was carried out between disks within each treatment group. Canine marrow cells were seeded on all disk surfaces to determine the stability of the PVD Ti mask under culture conditions. The PVD process did not significantly alter the surface topography of any samples. The thin titanium layer completely masked the underlying chemistry of the plasma sprayed HA surface and the chemistry of the plasma vapor deposited titanium layer did not differ from that of the commercially pure titanium disks. Aliquots obtained from the media during culture did not indicate any significant differences in Ti concentration amongst the Ti and Ti-masked surfaces. The PVD application of a Ti layer on HA coatings formed a stable, durable, and homogenous layer that effectively masked the underlying surface chemistry without altering the surface topography.

The lack of correlation of gallium (67Ga) scans with known prognostic indicators in childhood acute lymphocytic leukemia.

67Gallium-citrate scans were performed on 45 patients with acute lymphoblastic leukemia (ALL) at the time of diagnosis. The extent of uptake and distribution of gallium were compared to known prognostic indicators of age, initial white count, and bone marrow lymphoblast immune markers (T, B, and null cell). Selective increased uptake was noted in bone, kidney, liver/spleen, lymph nodes, or other sites in 29 patients, and 16 patients had "normal" scans. A scoring system giving one point for selective uptake in each organ system was used. Patients were grouped according to scores of zero, 1--2, and 3 or greater. There was no significant correlation found between total gallium scores and any of the three prognostic indicators. There was also no significant correlation when prognostic factors were compared to uptake in the individual organ systems except that T cell disease was associated with a significantly greater propensity for lymph node uptake. There was a suggestion that children with "normal" gallium scans may have a better long-term prognosis, since 6 of 7 nonrelapsers observed for longer than 18 months had scores of zero at diagnosis compared to 4 of 6 early deaths with scores greater than zero. This study indicates that the 67Ga scan does not significantly correlate with known prognostic indicators, with the possible exception of lymph node uptake in T cell disease, and its value as an independent indicator of long-term survival will require longer follow-up.