Ultrasensitive Impedimetric Lectin Biosensors with Efficient Antifouling Properties Applied in Glycoprofiling of Human Serum Samples

Ultrasensitive impedimetric lectin biosensors recognizing different glycan entities on serum glycoproteins were constructed. Lectins were immobilized on a novel mixed self-assembled monolayer containing 11-mercaptoundecanoic acid for covalent immobilization of lectins and betaine terminated thiol to resist nonspecific interactions. Construction of biosensors based on Concanavalin A (Con A), <i>Sambucus nigra</i> agglutinin type I (SNA), and <i>Ricinus communis</i> agglutinin (RCA) on polycrystalline gold electrodes was optimized and characterized with a battery of tools including electrochemical impedance spectroscopy, various electrochemical techniques, quartz crystal microbalance (QCM), Fourier transform infrared (FT-IR) spectroscopy, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) and compared with a protein/lectin microarray. The lectin biosensors were able to detect glycoproteins from 1 fM (Con A), 10 fM (<i>Ricinus communis</i> agglutinin (RCA), or 100 fM (SNA) with a linear range spanning 6 (SNA), 7 (RCA), or 8 (Con A) orders of magnitude. Furthermore, a detection limit for the Con A biosensor down to 1 aM was achieved in a sandwich configuration. A nonspecific binding of proteins for the Con A biosensor was only 6.1% (probed with an oxidized invertase) of the signal toward its analyte invertase and a negligible nonspecific interaction of the Con A biosensor was observed in diluted human sera (1000×), as well. The performance of the lectin biosensors was finally tested by glycoprofiling of human serum samples from healthy individuals and those having rheumatoid arthritis, which resulted in a distinct glycan pattern between these two groups

Factors associated with clinical severity in RA.

<p>Redundancy analysis plot showing that risk alleles in AFF3 gene, together with ACPA positivity are associated with higher clinical severity of RA. ACPA—anti-citrullinated peptides antibodies (□); <i>AFF3</i> (TT, AT, AA)–genotypes in <i>AFF3</i> gene (T risk allele) (▽). Diagram reading clue: Symbols are genetic and serologic factors. Large bold symbols represent genotypes and antibody presence significantly influencing the clinical parameters of disease severity (DAS28, CRP, ESR, TJC, SJC, HAQ-DI). Small empty symbols represent other factors and genotypes of selected genes. Direction of arrow indicates which of the clinical factors are associated with the genetic and serologic parameters and the length of the arrow indicates the magnitude of the association.</p

SNPs associated with seropositivity in RA.

<p>Redundancy discrimination analysis plot showing that IRF5, CD28 and CTLA4 are associated with seropositivity in RA patients. RF+–rheumatoid factor positive RA patients; RF-–rheumatoid factor negative RA patients; ACPA+–anti-citrullinated peptides antibodies positive RA patients; ACPA-–anti-citrullinated peptides antibodies negative RA patients; SE (0,1,2)—number of shared epitope coding alleles in HLA-DRB1 gene (✧); IRF5 (CC, CT, TT)—genotypes in IRF5 gene (C risk allele) (▷); CD28 (CC, CT, TT)–genotypes in CD28 gene (C risk allele) (◁); CTLA4 (AG, GG, AA)–genotypes in CTLA4 gene (G risk allele) (◊). Diagram reading clue: Symbols are genetic factors. Large bold symbols represent genotypes significantly influencing the presence of RF and ACPA. Small empty symbols represent other genotypes of selected genes. Direction of arrow indicates which serologic status is associated with the genetic parameters and the length of the arrow indicates the magnitude of the association.</p

The genetic discrimination of RA patients and controls.

<p>Linear discrimination analysis diagram shows that shared epitope and single nucleotide polymorphisms in PTPN22, STAT4, IRF5 and PADI4 genes significantly discriminated between RA patients and healthy controls. RA—RA patients; C—control group; SE (0,1,2)—number of SE coding allele in HLA-DRB1 gene (✧); IRF5 (CC, CT, TT)—genotypes in IRF5 gene (C risk allele) (◁); PADI4 (TT, CT, CC)–genotypes in PADI4 gene (T risk allele) (▽); PTPN22 (CC, CT, TT)–genotypes in PTPN22 gene (A risk allele) (△); STAT4 (GG, GT, TT)–genotypes in STAT4 gene (T risk allele) (☐). Diagram reading clue: Small circles represent individual cases. Large grey circles—centroids—represent subject groups (RA patients and controls). Symbols are genetic factors. Large bold symbols represent genotypes significantly influencing the distribution of subjects. Small empty symbols represent other genotypes of selected genes. The closer to the group centroid the gene symbol lies, the stronger is its impact on the classification of subjects to particular group.</p

Basic demographics of RA cases and healthy controls.

<p>Basic demographics of RA cases and healthy controls.</p