Interference-free determination of ischemia-modified albumin using quantum dot coupled X-ray fluorescence spectroscopy.
Ischemia-modified protein (IMA) is the most sensitive diagnostic biomarker of ischemic heart disease, but differentiation of IMA from human serum albumin (HSA), a ubiquitous serum protein, is still challenging owing to the shared antigenicity. In this investigation, we developed a rapid and interference-free approach for IMA determination using quantum dots-coupled X-ray Fluorescence Spectroscopy (Q-XRF). In a typical Q-XRF assay, serum total HSA is quantified using quantum dot-coupled sandwich immunoassay, and intact HSA (iHSA) is determined using a XRF spectroscopy, by measuring XRF intensity of Co (II) bonded to iHSA. IMA concentration is automatically determined within 30 min by calculating the difference between total HSA and iHSA. This strategy can effectively eliminate the interference from native HSA level. Results show that no significant influences have been observed from hemolysis or high levels of cholesterol (7 mg/L), triglyceride (5.2 mg/L), IgG (10 g/L), and fibrinogen (4 g/L). A linearity of 1-100mg/mL is obtained in iHSA determination using XRF (r(2)=0.979). The proposed Q-XRF assay demonstrates a lowest detection limit of 0.05 U/mL. Receiver-operating characteristic (ROC) curves reveal that Q-XRF assay provide an improved sensitivity than ACB assay (95.9% vs. 82.9%) in differentiating ischemic patients from health individuals, at an optimal cutoff point of 79.2U/mL. The proposed approach provides a new strategy for interference-free, simple and rapid evaluation of IMA concentration by combining sandwich immunoassay and XRF spectroscopy.
Department of Laboratory Medicine, Southwest Hospital, the Third Military Medical University, Chong Qing 400038, China. Electronic address: luoyang@tmmu.edu.cn.
Yang
Y
Luo
Chaoming
C
Wang
Tianlun
T
Jiang
Bo
B
Zhang
Junfu
J
Huang
Pu
P
Liao
Weiling
W
Fu
D000328:Adult; D015415:Biomarkers / Q000032:analysis; D003035:Cobalt / Q000737:chemistry; D005260:Female; D006801:Humans; D057230:Limit of Detection; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000097:blood / Q000175:diagnosis*; D045663:Quantum Dots; D012709:Serum Albumin / Q000032:analysis*; D000075462:Serum Albumin, Human; D013052:Spectrometry, X-Ray Emission / Q000379:methods*; D055815:Young Adult
D015415:Biomarkers; D012709:Serum Albumin; C561522:ischemia-modified albumin; D003035:Cobalt; D000075462:Serum Albumin, Human
ACB; Albumin cobalt binding; CI; DTT; HSA; Human serum albumin; IHD; IMA; Ischemia-modified protein; Ischemic heart disease; MI; Myocardial ischemia; Q-XRF; QD; Quantum dot-coupled X-ray fluorescence; Quantum dots; X-ray fluorescence; XRF; albumin cobalt binding; confidence interval; dithiothreitol; iHSA; intact HSA