Label-free detection of biomarker alpha fetoprotein in serum by ssDNA aptamer functionalized magnetic nanoparticles

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors in the clinic, with the characteristics of occult onset, rapid progression, and high degree of malignancy. Alpha fetoprotein (AFP) is the most important biomarker of HCC, which is widely used in early screening, diagnosis, and prognosis observation. A series of immunoassays have been developed and frequently used in the detection of AFP based on antibodies. Unfortunately, the shortcomings of antibodies, such as thermal unstable and fluctuant activity by batches, lead to the inaccuracy in the detection of AFP. In this study, aptamers instead of antibodies were adopted as the specific recognition element for AFP, aiming to seek an alternative strategy to immunoassays. An AFP-specific ssDNA aptamer was grafted to magnetic nanoparticles (Fe₃O₄@SiO₂) via avidin-biotin interaction, and the resultant aptamer functionalized magnetic nanoparticles (Ap-MNPs) were adequately characterized and tested. The Ap-MNPs in solution exhibited a fast response to the outer magnetic field, and can be completely separated in several minutes. It was found that Ap-MNPs have good specificity to the target AFP, as the recovery of AFP (87.0%) was much higher than the competitive proteins IgG (38.9%), HSA (18.5%), and FIB (11.4%). A convenient and efficient label-free detection method of AFP in serum was developed based on Ap-MNPs in combination with high-performance liquid chromatography. The linearity of this method was over a range of 1-50 μg ml^-1 with a correlation coefficient of 0.9999, and the limit of detection was 0.27 μg ml^-1. This study indicated that aptamers are an ideal tool for the recognition and detection of biomarkers, and thus will find wide applications in clinical practice.

Pregnancy outcomes regarding maternal serum AFP value in second trimester screening

AIM

The aim of this study was to evaluate the predictive value of α-fetoprotein in maternal serum (MS-AFP) as a marker for diverse pregnancy outcomes.

METHODS

The study was based on pregnancy and delivery data from 5520 women between 1999 and 2014 at University Hospital of Zurich (UHZ).

INCLUSION CRITERIA

both MS-AFP and pregnancy outcome were known for the same pregnancy. Pregnancy outcomes and characteristics such as fetal malformation, intrauterine fetal death (IUFD) and intrauterine growth retardation as well as maternal age, weight before pregnancy, gestational age (GA) at delivery, newborn weight, length and head circumference were analyzed with respect to the MS-AFP value. MS-AFP value was categorized into three groups: elevated MS-AFP>2.5 multiples of the median (MoM), normal 0.5-2.49 MoM and decreased <0.5 MoM.

RESULTS

Newborn weight (g) and length (cm) were significantly lower in the elevated MS-AFP (P<0.001) group, and infants had 1 week lower GA at delivery (P<0.05). In the group of elevated MS-AFP (n=46), 26.1% of pregnancies were significantly related to adverse pregnancy outcomes, such as fetal malformations, fetuses small for gestational age (SGA) and IUFD. Adverse pregnancy outcomes of 5.6% were registered in the group of normal MS-AFP and 7.3% in the group of low MS-AFP (P<0.05).

CONCLUSION

MS-AFP level in the second trimester is still an important indicator of fetal surface malformations; however, ultrasound still outweighs as a screening method. Nevertheless, pregnant women with elevated MS-AFP values and with no sonographically detected fetal malformations should additionally receive the third trimester ultrasound examination to exclude other possible complications of pregnancy.

Elevated maternal serum α-fetoprotein after minor trauma during pregnancy may predict adverse fetal outcomes

BACKGROUND

We evaluated the relationship between minor trauma during pregnancy and elevated maternal serum α-fetoprotein level.

METHODS

This is a retrospective review of pregnant patients admitted to Fukui Prefectural Hospital with trauma during a 10-year period. Charts were reviewed for maternal age, gestational age, injury characteristics, Injury Severity Score, the presence of abdominal pain, systolic pressure and heart rate on arrival, fetal hemoglobin level, and maternal serum α-fetoprotein (MSAFP) concentration on arrival.

RESULTS

Fifty-one pregnant patients with any trauma were treated at Fukui Prefectural Hospital. All patients were hemodynamically stable and had minor trauma. An adverse pregnancy outcome occurred in three patients (5%). One patient's fetus had a left kidney injury. Intrauterine fetal death occurred in two patients. The time from injury to fatal death was 180 minutes in one patient and 18 hours in the other patient. The mean ± SD fetal hemoglobin was 0.57% ± 0.88%. The mean ± SD MSAFP was 511 ng/mL ± 1,263 ng/mL. Three patients with adverse pregnancy outcome had a high MSAFP of greater than 1,000 ng/mL.

CONCLUSION

High level of MSAFP may be a predictor of poor fetal outcome following trauma during pregnancy regardless of the severity of the trauma or the mother's hemodynamic status.

LEVEL OF EVIDENCE

Epidemiologic study, level V.

Development of high-performance magnetic chemiluminescence enzyme immunoassay for alpha-fetoprotein (AFP) in human serum

BACKGROUND

A high-performance chemiluminescence enzyme immunoassay (CLEIA) for alpha-fetoprotein (AFP), a tumor marker for the diagnosis of hepatocellular carcinoma (HCC), was constructed by using magnetic particles (MPs) as both the immobilization matrix and separation tools.

METHODS

A double sandwiched immunocomplex was formed through the reaction among anti-fluorescein isothiocyanate (FITC) antibody coated MPs, FITC-labeled anti-AFP antibody, AFP antigen, and alkaline phosphatase (ALP)-labeled anti-AFP antibody. The subsequent chemiluminescence reaction of ALP with 4-methoxy-4-(3-phosphate-phenyl)-spiro-(1,2-dioxetane-3,2'-adamantane) (AMPPD) gave light intensity that was directly proportional to the amount of analyte present in the samples. The effects of several physicochemical parameters, including the concentration of FITC-labeled anti-AFP antibody, the dilution ratio of ALP-labeled anti-AFP antibody, the volume of MPs and substrate, the immunoreaction time and other relevant variables upon the immunoassay were studied and optimized. RIA and microplate CLEIA were used as comparison methods.

RESULTS

The proposed method had a sensitivity of 3.0 ng/ml, low cross reactivities, and an assay time of 1 h. The linear range was 0-1200 ng/ml through using MPs and is useful for samples with extremely high AFP concentrations without dilution while avoiding the hook effect. The intra- and inter-assay precision was <3% and <5%. The present method has been successfully applied to the detection of AFP human serum with recoveries from 90 to 108%, and showed a good correlation with the commercially available AFP RIA kit.

CONCLUSIONS

This proposed assay provided apparent advantages over microplate CLEIA and RIA, and facilitated the development of high-throughput screening and automated operation systems in the clinical practice.

Simultaneous determination of alpha-fetoprotein and carcinoembryonic antigen in human serum by time-resolved fluoroimmunoassay

A novel simultaneous measurement method for alpha-fetoprotein (AFP) and carcinoembryonic antigen (CEA) in human sera by time-resolved fluoroimmunoassay (TR-FIA) is described. The proposed approach combines the use of europium-labeled anti-AFP antibody for AFP TR-FIA and biotinylated anti-CEA antibody complexed to samarium-labeled streptavidin for CEA TR-FIA. A 96-well microtiter plate coated with a mixture of anti-AFP and anti-CEA monoclonal antibodies was used for the assay. After it was reacted with a solution containing AFP and CEA, a mixture of anti-AFP antibody labeled with BHHCT-Eu(3+) and biotinylated anti-CEA antibody was added. The AFP concentration was determined by measuring the solid-phase fluorescence of the europium-labeled anti-AFP antibody at 615 nm. Then a BHHCT-Sm(3+)-labeled streptavidin-bovine serum albumin conjugate (SA-BSA) was added to react with the biotinylated anti-CEA antibody. After the reaction, the unreacted SA-BSA was washed out, and a 0.1 M NaOH solution containing 1.0 x 10(-5) M TOPO and 0.05% SDS was added to dissociate the samarium-labeled SA-BSA in the immune complex on the surface of the well into the solution. The CEA concentration was determined by measuring the solution fluorescence of 643 nm from the samarium-labeled SA-BSA. The present method gives detection limits of 0.07 ng/ml for AFP and 0.3 ng/ml for CEA. The coefficient variations of the method are less than 7%, and the recoveries are in the range of 90-110% for serum samples. The AFP and CEA concentrations in 27 human serum samples were determined by the present method as well as by single assay for comparison. A good correlation was obtained with the correlation coefficients of 0.990 for AFP and 0.973 for CEA.

Evaluation of the Abbott system in maternal serum screening for Down syndrome: the AxSym analyzer, AFP and hCG reagents and Maciel Prenatal Interpretive Software

Multi-marker maternal serum screening for Down syndrome in the second trimester is now part of routine care in many centers. Most protocols use a combination of hCG (or its free beta-subunit) and alpha-fetoprotein (AFP) or unconjugated estriol (UE3), or both. Risk calculation is based on these maternal serum marker values combined with maternal age and trisomy 21 maternal age-related risk. Computer programs are therefore necessary. Both technical and statistical efficiency are included in the final risk evaluation. We studied the Abbott system, comprising AxSym analyzer, AFP and hCG kits and Prenatal Interpretive Software (Maciel). Median values were established between 14 and 18 weeks of amenorrhea in a population of 1822 patients and in twin pregnancies in 157 cases. Forty maternal sera from trisomy 21 affected pregnancies were analyzed. Software was evaluated in a population of 429 patients and in 124 cases of trisomy 21. We conclude that this system constitutes an accurate and efficient method of maternal serum screening for Down syndrome.

A new tetradentate beta-diketonate--europium chelate that can be covalently bound to proteins for time-resolved fluoroimmunoassay

A new chlorosulfonylated tetradentate beta-diketone, 4,4'-bis(1",1",1",2",2",3",3"-heptafluoro-4",6"-hexanedion-6 "-yl) chlorosulfo-o-terphenyl (BHHCT), was synthesized as a chelating label for Eu3+. BHHCT can be covalently bound to proteins under mild conditions and forms a strongly fluorescent chelate with Eu3+. Bovine serum albumin (BSA) and streptavidin (SA) were labeled with BHHCH-Eu3+, and the latter was used for time-resolved fluoroimmunoassay of alpha-fetoprotein (AFP) in human sera. A remarkably high sensitivity was obtained, with a detection limit of 4.1 x 10(-3) pg/mL, which corresponds to an improvement of about 4-5 orders of magnitude, compared to those of all conventional immunoassays including fluoroimmunoassay, enzyme immunoassay, and radioimmunoassay. The high sensitivity has been attained both by strong fluorescence of the present label and by the extremely suppressed background level brought about by the direct labeling of proteins with the beta-diketone-Eu3+ complex. A general consideration and ideas are given for designing ideal label ligands for strongly fluorescent Eu3+ complexes.

Amniotic fluid cholinesterase of valproate-induced exencephaly in the mouse: an animal model for prenatal diagnosis of neural tube defects

After a single administration of the antiepileptic drug valproic acid (VPA; i.p.:600 mg/kg) on day 8 of gestation in the mouse embryotoxicity and amniotic fluid (AF) cholinesterase (ChE) were evaluated on day 16 of gestation. VPA treatment induced an increase in embryolethality, neural tube defects (exencephaly), cleft palate, deformed vertebrae, open eyes, and a reduction in fetal weight. In VPA-exposed fetuses AF total ChE (TChE) activity of exencephalic fetuses was higher than that of normal fetuses. However, in 3 out of 110 normal fetuses of the control group TChE activity was found in the AF. There was no correlation between blood contamination of AF and its TChE activity, either in non-exencephalic control or treated embryos. Using ethopropazine as a "pseudo"-ChE inhibitor in vitro, the percentage of acetyl-ChE in blood-contaminated AF was similar to that of fetal rather than maternal serum, indicating that AF was contaminated with fetal and not with maternal blood. VPA-induced exencephaly in mice may provide an animal model to further investigate biochemical markers for prenatal diagnosis of neural tube defects.