MnCO₃ as a New Electrochemiluminescence Emitter for Ultrasensitive Bioanalysis of β-Amyloid_1–42 Oligomers Based on Site-Directed Immobilization of Antibody

Abstract

In this work, an electrochemiluminescence (ECL) immunosensor utilizing MnCO3 nanospheres as a novel ECL luminophor and the HWRGWVC (HC-7) heptapeptide as an efficient antibody capturer for site-directed immobilization with high affinity was proposed. MnCO3 nanospheres prepared by a homogeneous precipitation method exhibited high ECL efficiency, low toxicity, favorable biocompatibility, and excellent stability. After the functionalization of polydimethyldiallylammonium chloride (PDDA), the obtained MnCO3/PDDA could combine with gold nanoparticles (Au NPs) via electrostatic interaction (MnCO3/PDDA/Au). Besides, HC-7 as a small peptide ligand has demonstrated an ability to bind the Fc portion of an antibody with high affinity. Because the end of HC-7 is a cysteine, it can connect to MnCO3/PDDA/Au via a Au–S bond. Then, the antibody could be effectively captured by HC-7 through specific interaction with a better maintained activity than traditional coupling reaction. To verify the practicability of the constructed immunosensor, β-amyloid1–42 oligomers (Aβ) were employed as an analyte. On the basis of the above points, the immunosensor performed favorable ECL property to Aβ concentrations in a wide linear range (0.1 pg/mL to 10 ng/mL) with a low detection limit (19.95 fg/mL). With excellent repeatability, selectivity, and stability, this method opened up a new avenue for realizing the ultrasensitive detection of Aβ and other biomarkers in a real sample analysis.

Synthesis and Application of CeO2/SnS2 Heterostructures as a Highly Efficient Coreaction Accelerator in the Luminol–Dissolved O2 System for Ultrasensitive Biomarkers Immunoassay

“…Circular dichroism (CD) spectra have been regarded as a simple and reliable tool to characterize the maintenance of antibody bioactivity from different immobilization methods . Because the specific absorption peaks of the α-helix in secondary protein structure are shown at wavelengths of 210 and 222 nm, , the antibody bioactivity from different immobilization methods can be distinguished. As shown in Figure B, CD spectra of CeO 2 /SnS 2 –HWR (curve a), CeO 2 /SnS 2 –Ab 1 (curve b), CeO 2 /SnS 2 –HWR–Ab 1 (curve c), and pure Ab 1 (curve d) are presented.…”

“…To maintain the bioactivity of incubated Ab 1 , HWR­GW­VC (HWR), a heptapeptide that can specifically capture the Fc fragment of the antibody in a site-oriented manner, was introduced onto the CeO 2 /SnS 2 surface . This site-oriented strategy has been demonstrated that it can improve the incubation efficiency with better maintained bioactivity than traditional methods in our previous works. , Considering the superiorities of thermal stability, pH tolerance, and enzyme mimic property, ferritin (Ft) as a biocompatible nanocarrier was utilized to immobilize luminol (Lum@Ft) via a one-step cross-linking method for the first time. , Due to the abundant amino groups on the Ft outer nanocage, the detection antibody (Ab 2 ) could easily be captured via an amide bond. Using natural protein as a signal label is advanced since conventional harsh chemical synthesis of nanomaterials and complex antibody conjugations can be avoided .…”

Advances in aptamers against Aβ and applications in Aβ detection and regulation for Alzheimer's disease

“…In recent years, biosensors have played an important role in the detection of Aβ monomers and aggregates. Researchers have constructed electrochemical sensors 20 , 21 , surface plasmon resonance (SPR) sensors 22 , surface enhanced Raman (SERS) sensors 23 , 24 , colorimetric sensors 25 , 26 , etc. for the quantification of Aβ.…”

Quantitative assessment of AD markers using naked eyes: point-of-care testing with paper-based lateral flow immunoassay

“…Histopathological examination of brain autopsy specimens is the only way to diagnose definite AD. Although the exact mechanism of AD pathogenesis remains elusive, amyloid β (Aβ) has been proposed to be an essential biomarker and therapeutic target for AD [7][8][9]. To date, magnetic resonance imaging (MRI) for measuring brain volume and neuronal connections, and Aβ-or taubased positron-emission tomography (PET) for detecting pathological protein deposition in the brain have been used in AD diagnosis [10][11][12][13].…”