Platinum measurements in Dulbecco's phosphate-buffered saline are lower than in plasma and can be sampled with ultrafiltration probes in vitro.

Abstract

To compare the influence of fluid on carboplatin elution, and assess the feasibility of ultrafiltration (UF) probe sampling. 20 samples of 5 mg carboplatin in 1.0 mL 30% poloxamer 407 eluting in Dulbecco's phosphate-buffered saline (DPBS) or canine plasma and 6 samples of UF probe sampling in 0.01 mg/mL carboplatin in DPBS or plasma. Carboplatin-gel specimens in dialysis tubing (12- to 14-kDa pores) were placed in 100 mL of DPBS or canine plasma (37 °C and 600 rpm stirring) in a nonlidded and lidded experiment. Samples were collected in decreasing frequency for 96 hours. The 0.01-mg/mL carboplatin solutions in DPBS and plasma were sampled 6 times by UF probe (30-kDa pores) or direct aspiration. Platinum was measured using inductively coupled plasma mass spectrometry. High fluid evaporation was noted in the nonlidded but not the lidded experiment. A burst release was seen in plasma (first 2 hours) and DPBS (first 5 hours) with the highest hourly increase in the first hour in both DPBS (6,040 ppb/h) and plasma (2,612 ppb/h), with no further increase after the first 22 hours. Platinum content in the specimens was higher at 96 hours than the surrounding fluid. Higher platinum concentrations were measured by both direct and UF probe sampling in DPBS than in plasma. Platinum concentrations measured in DPBS were higher than in plasma, but elution patterns were similar. Ultrafiltration probes can be used to sample platinum in vitro and could be used in vivo to measure local unbound Pt tissue concentrations in local chemotherapy delivery.