β-CTx(Alpha Crosslaps) Introduction

The Serum CrossLaps (CTx) enzyme-linked immunosorbent assay (ELISA) is specific for a cross-linked, beta-aspartate-isomerized form of the epitope EKAHDGGR derived from the carboxyterminal telopeptide region of type I collagen alpha(1) chain. Collagen type I fragments reactive in the CTx assay are released during osteoclastic bone resorption and can be used as a measure of bone resorption activity. Our objectives were to assess the intraindividual variation of serum CTx concentration as well as the clinical value of the serum CTx assay for monitoring antiresorptive therapy in individual patients. Standards, control, or unknown urine samples are pipetted into the appropriate microtitre wells coated with streptavidin, followed by application of a mixture of biotinylated antibody and peroxidase-conjugated antibody.  Then, a complex between ALPHA CrossLaps antigens, biotinylated antibody and peroxidase-conjugated antibody is generated, and this complex binds to the streptavidin surface via the biotinylated antibody. Following the one step incubation at 2-8°C, the wells are emptied and washed. A chromogenic substrate is added and the colour reaction is stopped with sulfuric acid. Finally, the absorbance is measured.

Human β-CTx(Beta Crosslaps) ELISA Kit Test method

This kit was based on Competitive-ELISA detection method. The microtiter plate provided in this kit has been pre-coated with target. During the reaction, target in the sample or standard competes with a fixed amount of target on the solid phase supporter for sites on the Biotinylated Detection Antibody specific to target. Excess conjugate and unbound sample or standard are washed from the plate, and HRP-Streptavidin (SABC) is added to each microplate well and incubated. Then TMB substrate solution is added to each well. The enzyme-substrate reaction is terminated by the addition of a sulphuric acid solution and the color change is measured spectrophotometrically at a wavelength of 450nm. The concentration of target in the samples is then determined by comparing the OD of the samples to the standard curve.

Reference:

1, Markers of bone resorption--measurement in serum, plasma or urine?

Huber F, Traber L, Roth HJ, Heckel V, Schmidt-Gayk H.

Clin Lab. 2003;49(5-6):203-7.

PMID: 15285175

2, Significance of serum CrossLaps as a predictor of changes in bone mineral density during estrogen replacement therapy; comparison with serum carboxyterminal telopeptide of type I collagen and urinary deoxypyridinoline.

Okabe R, Inaba M, Nakatsuka K, Miki T, Naka H, Moriguchi A, Nishizawa Y.

J Bone Miner Metab. 2004;22(2):127-31. doi: 10.1007/s00774-003-0460-4.

PMID: 14999523