Ted from three heart failure patients were serially diluted with buffer. doi:10.1371/journal.pone.0053233.gproBNP in Human PlasmaTable 1. Recovery of standard glycosylated proBNP and BNP added to human plasma.Added peptide concentration, pmol/LRecovery, proBNP assay systemRecovery, total BNP assay system 85 972.0 25.0 100.0 doi:10.1371/journal.pone.0053233.t90 101AntibodiesThe monoclonal antibodies BC203 (IgG1, k) and KY-BNP-II (IgG1, k) were developed by Shionogi Co., Ltd [10]. BC203 and KY-BNP-II recognize the C-terminal region and the ring region of BNP, respectively. The monoclonal antibody 18H5 was purchased from Hytest Ltd. 18H5 recognizes a region (a.a. 13?0) of proBNP. In the proBNP assay, the combination of BC203 (capture) and 18H5 (detection) was used because 18H5 is not affected by glycosylation [11]. In the total BNP assay, the combination of BC203 (capture) and KY-BNP-II (detection) was used because KY-BNP-II recognizes nearly all bioactive BNPs (Figure 1).after which the HMCS-activated ALP was purified on a PD-10 column (GE Healthcare, Chalfont St. Giles, UK). Aliquots of HMCS-activated ALP solution (0.96 mg in 0.192 mL) were each added to 0.441 mg of the Fab’ in 0.15 mL of 0.1 M phosphate buffer (pH 6.0) containing 5 mM EDTA and mixed for 16 h at 4uC. Unlabeled Fab’ antibody was removed using a TSKgel 3000SWxl column. The purified 18H5 (Fab’)-ALP and KY-BNPII (Fab’)-ALP were then diluted with a StabilZyme AP (BioFX Lab.) and stored at 4uC until use.Sandwich 2-step Chemiluminescent Enzyme ImmunoassayAfter the BC203 coated immunoassay plates were washed with a wash buffer, 50 mL of test sample or calibrator and 50 mL of Assay Buffer (0.05 M Tris-HCl buffer (pH 7.4), 1 g/dL BSA, 0.01 g/dL Tween80, 1 mM MgCl2, 0.1 mM ZnCl2, 1000K IU/ mL Aprotinin, 0.1 mg/mL mouse gamma globulin, 0.9 g/dL NaCl) were added to the wells. The plates were then incubated for 3 h at 25uC. After washing with wash buffer, 100 mL of detection antibodies (18H5 (Fab’)-ALP, 100 ng/ml; KY-BNP-II (Fab’)-ALP, 416 ng/ml) were added to the wells. The plates were then incubated for 1 h at 25uC, followed by washing with wash buffer and addition of substrate (CDP/E) solution. The chemiluminescence from each well was then measured using a plate reader (Wallac 1420 Arvo sx, Perkin Elmer, Inc., MA).Preparation of BC203 coated immunoassay platesBC203, which was the purchase CASIN capture antibody in both assays, was biotinylated using an EZ-Link-sulfo-NHS-biotinylation kit MedChemExpress Tetracosactrin according to the manufacturer’s instructions. The biotinylated BC203 (0.2 mg/well in 100 mL PBS) was added to streptavidin-coated plates and incubated for 18 h at 4uC. After washing with a saline containing 0.01 g/dL Tween 20 and 0.05 g/dL sodium azide (Wash Buffer), the BC203 coated immunoassay plates were dried in a desiccator.Preparation of 18H5 (Fab’)-ALP and KY-BNP-II (Fab’)-ALPThe 18H5 and KY-BNP-II mAbs (IgG) were digested with pepsin (IgG/pepsin = 1/0.05) for 4 h at 37uC in 100 mM citrate buffer (pH 4.0) containing 100 mM NaCl. Thereafter, Fab’ solution was prepared by reduction with 10 mM 2-mercaptoethylamine in 0.1 M phosphate buffer (pH 6.0) containing 5 mM EDTA using the standard method [12]. Alkaline phosphatase from calf intestine (ALP; 2.0 mg or 14.2 nmol; Kikkoman, Chiba, Japan) in 0.475 mL 0.1 M Tris-HCl buffer (pH 7.0) containing 1 mM MgCl2 and 0.1 mM ZnCl2 was mixed with 31 mg (71 nmol) of Sulfo-HMCS in 0.05 mL of water for 1.5 h on ice,Study PatientsWe collected blood samples from heart.Ted from three heart failure patients were serially diluted with buffer. doi:10.1371/journal.pone.0053233.gproBNP in Human PlasmaTable 1. Recovery of standard glycosylated proBNP and BNP added to human plasma.Added peptide concentration, pmol/LRecovery, proBNP assay systemRecovery, total BNP assay system 85 972.0 25.0 100.0 doi:10.1371/journal.pone.0053233.t90 101AntibodiesThe monoclonal antibodies BC203 (IgG1, k) and KY-BNP-II (IgG1, k) were developed by Shionogi Co., Ltd [10]. BC203 and KY-BNP-II recognize the C-terminal region and the ring region of BNP, respectively. The monoclonal antibody 18H5 was purchased from Hytest Ltd. 18H5 recognizes a region (a.a. 13?0) of proBNP. In the proBNP assay, the combination of BC203 (capture) and 18H5 (detection) was used because 18H5 is not affected by glycosylation [11]. In the total BNP assay, the combination of BC203 (capture) and KY-BNP-II (detection) was used because KY-BNP-II recognizes nearly all bioactive BNPs (Figure 1).after which the HMCS-activated ALP was purified on a PD-10 column (GE Healthcare, Chalfont St. Giles, UK). Aliquots of HMCS-activated ALP solution (0.96 mg in 0.192 mL) were each added to 0.441 mg of the Fab’ in 0.15 mL of 0.1 M phosphate buffer (pH 6.0) containing 5 mM EDTA and mixed for 16 h at 4uC. Unlabeled Fab’ antibody was removed using a TSKgel 3000SWxl column. The purified 18H5 (Fab’)-ALP and KY-BNPII (Fab’)-ALP were then diluted with a StabilZyme AP (BioFX Lab.) and stored at 4uC until use.Sandwich 2-step Chemiluminescent Enzyme ImmunoassayAfter the BC203 coated immunoassay plates were washed with a wash buffer, 50 mL of test sample or calibrator and 50 mL of Assay Buffer (0.05 M Tris-HCl buffer (pH 7.4), 1 g/dL BSA, 0.01 g/dL Tween80, 1 mM MgCl2, 0.1 mM ZnCl2, 1000K IU/ mL Aprotinin, 0.1 mg/mL mouse gamma globulin, 0.9 g/dL NaCl) were added to the wells. The plates were then incubated for 3 h at 25uC. After washing with wash buffer, 100 mL of detection antibodies (18H5 (Fab’)-ALP, 100 ng/ml; KY-BNP-II (Fab’)-ALP, 416 ng/ml) were added to the wells. The plates were then incubated for 1 h at 25uC, followed by washing with wash buffer and addition of substrate (CDP/E) solution. The chemiluminescence from each well was then measured using a plate reader (Wallac 1420 Arvo sx, Perkin Elmer, Inc., MA).Preparation of BC203 coated immunoassay platesBC203, which was the capture antibody in both assays, was biotinylated using an EZ-Link-sulfo-NHS-biotinylation kit according to the manufacturer’s instructions. The biotinylated BC203 (0.2 mg/well in 100 mL PBS) was added to streptavidin-coated plates and incubated for 18 h at 4uC. After washing with a saline containing 0.01 g/dL Tween 20 and 0.05 g/dL sodium azide (Wash Buffer), the BC203 coated immunoassay plates were dried in a desiccator.Preparation of 18H5 (Fab’)-ALP and KY-BNP-II (Fab’)-ALPThe 18H5 and KY-BNP-II mAbs (IgG) were digested with pepsin (IgG/pepsin = 1/0.05) for 4 h at 37uC in 100 mM citrate buffer (pH 4.0) containing 100 mM NaCl. Thereafter, Fab’ solution was prepared by reduction with 10 mM 2-mercaptoethylamine in 0.1 M phosphate buffer (pH 6.0) containing 5 mM EDTA using the standard method [12]. Alkaline phosphatase from calf intestine (ALP; 2.0 mg or 14.2 nmol; Kikkoman, Chiba, Japan) in 0.475 mL 0.1 M Tris-HCl buffer (pH 7.0) containing 1 mM MgCl2 and 0.1 mM ZnCl2 was mixed with 31 mg (71 nmol) of Sulfo-HMCS in 0.05 mL of water for 1.5 h on ice,Study PatientsWe collected blood samples from heart.
