Negative Charge-Carrying Glycans Attached to Exosomes as Novel Liquid Biopsy Marker.

Prostate cancer (PCa) is the second most common cancer. In this paper, the isolation and properties of exosomes as potential novel liquid biopsy markers for early PCa liquid biopsy diagnosis are investigated using two prostate human cell lines, i.e., benign (control) cell line RWPE1 and carcinoma cell line 22Rv1. Exosomes produced by both cell lines are characterised by various methods including nanoparticle-tracking analysis, dynamic light scattering, scanning electron microscopy and atomic force microscopy. In addition, surface plasmon resonance (SPR) is used to study three different receptors on the exosomal surface (CD63, CD81 and prostate-specific membrane antigen-PMSA), implementing monoclonal antibodies and identifying the type of glycans present on the surface of exosomes using lectins (glycan-recognising proteins). Electrochemical analysis is used to understand the interfacial properties of exosomes. The results indicate that cancerous exosomes are smaller, are produced at higher concentrations, and exhibit more nega tive zeta potential than the control exosomes. The SPR experiments confirm that negatively charged α-2,3- and α-2,6-sialic acid-containing glycans are found in greater abundance on carcinoma exosomes, whereas bisecting and branched glycans are more abundant in the control exosomes. The SPR results also show that a sandwich antibody/exosomes/lectins configuration could be constructed for effective glycoprofiling of exosomes as a novel liquid biopsy marker.

Redox features of hexaammineruthenium(III) on MXene modified interface: Three options for affinity biosensing.

In this article we describe construction of a bioreceptive interface for detection of a breast cancer biomarker carbohydrate antigen CA15-3. The conductive interface was patterned by a 2D nanomaterial MXene, to which a mixed layer containing sulfobetaine and carboxybetaine was electrochemically grafted through a diazonium moiety. Such a modified interface was then applied for covalent immobilisation of anti-CA15-3 antibody as a bioreceptive probe for detection of a breast cancer biomarker. Two different strategies were applied for final construction of an immunosensor i.e. an interface finally blocked by bovine serum albumin or an immunosensor without such modification. Finally, electrochemical reading was accomplished using a soluble redox probe Ru(NH3)63+ ion for detection of CA15-3 in a clinically relevant range up to 50 U mL-1. The results indicate that immunosensor based on non-blocked interface can be applied for biosensing using two modes of action: 1. differential pulse voltammetry (a plot of a peak current vs. analyte concentration) and 2. an electrochemical impedance spectroscopy (a plot of a charge transfer resistance vs. analyte concentration). The electrode blocked by bovine serum albumin (BSA) can be used by additional 3. mode of action: through detection of changes in the potential (a plot Epvs. c). Additionally, we reveal and explain that Ru(NH3)63+ is redox probe, which can be applied as interfacial molecular nanoscale ruler to distinguish negatively charged protein molecules present in the close proximity (≤ 6 nm) of the electrode (in our case adsorbed BSA molecules) from the negatively charged protein molecules at a larger distance (>12 nm) from the electrode (i.e. CA15-3 analyte).