Adsorption and Fibrillization of Islet Amyloid Polypeptide at Self-Assembled Monolayers Studied by QCM-D, AFM, and PM-IRRAS

Abstract

Aggregation and fibrillization of human islet amyloid polypeptide (hIAPP) plays an important role in the development of type 2 diabetes mellitus. Understanding the interaction of hIAPP with interfaces such as cell membranes at a molecular level therefore represents an important step toward new therapies. Here, we investigate the fibrillization of hIAPP at different self-assembled alkanethiol monolayers (SAMs) by quartz crystal microbalance with dissipation monitoring (QCM-D), atomic force microscopy (AFM), and polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS). We find that hydrophobic interactions with the CH-terminated SAM tend to retard hIAPP fibrillization compared to the carboxylic acid-terminated SAM where attractive electrostatic interactions lead to the formation of a three-dimensional network of interwoven fibrils. At the hydroxyl- and amino-terminated SAMs, fibrillization appears to be governed by hydrogen bonding between the peptide and the terminating groups which may even overcome electrostatic repulsion. These results thus provide fundamental insights into the molecular mechanisms governing amyloid assembly at interfaces.

Application of QCM in Peptide and Protein-Based Drug Product Development

“…Due to the application of selected transduction techniques in chemo- and bio-sensors [ 18 , 19 , 20 , 21 , 22 , 23 ], it is possible to evaluate the deposition degree of particular materials [ 24 ], for instance in the form of self-assembled monolayers (SAM) [ 12 , 25 ], and to analyze gas phase composition [ 14 , 26 , 27 ]. Nowadays, the priority in design and development of QCM analytical platforms is given to naturally occurring compounds, since they are excellent receptors with superior selectivity for the target analytes [ 28 ].…”

“…This technique is widely utilized for investigation of the aggregation process as well as identification and characterization of inhibitors and modulators of that process. Evaluation of the rate of fibril growth on different surfaces is currently widely examined [ 96 , 97 ], as well as the possibility of QCM-D application to study amyloid aggregation upon contact with various model surfaces, for example double lipid layers, self-assembled monolayers (SAMs), and metal oxides [ 25 , 83 , 98 , 99 , 100 ]. The benefits stemming from monitoring of dispersion changes include the option of discrimination between the types of amyloid adsorption [ 85 ] and characteristic fibril growth and conformations [ 25 ].…”

“…Evaluation of the rate of fibril growth on different surfaces is currently widely examined [ 96 , 97 ], as well as the possibility of QCM-D application to study amyloid aggregation upon contact with various model surfaces, for example double lipid layers, self-assembled monolayers (SAMs), and metal oxides [ 25 , 83 , 98 , 99 , 100 ]. The benefits stemming from monitoring of dispersion changes include the option of discrimination between the types of amyloid adsorption [ 85 ] and characteristic fibril growth and conformations [ 25 ]. Formation of the fibrils often generates complex sensors response requiring application of appropriate sensor models and supplementary microscopic measurements, e.g., ex-situ AFM, fluorescence microscopy [ 25 ], or total internal reflection fluorescence (TIRF) [ 101 ].…”

“…The benefits stemming from monitoring of dispersion changes include the option of discrimination between the types of amyloid adsorption [ 85 ] and characteristic fibril growth and conformations [ 25 ]. Formation of the fibrils often generates complex sensors response requiring application of appropriate sensor models and supplementary microscopic measurements, e.g., ex-situ AFM, fluorescence microscopy [ 25 ], or total internal reflection fluorescence (TIRF) [ 101 ]. One of the latest achievements is the elaboration of a combined QCM-TIRF technique allowing simultaneous measurement of the mass of a peptide adsorbed on the sensor’s surface and visualization of fibril growth using the TIRF microscope [ 24 ].…”

Interaction of synthetic and lignin-based sulfonated polymers with hydrophilic, hydrophobic, and charged self-assembled monolayers

“…The S 2p level of -OH, -COOH, -CH 3 , and -NH 2 SAMterminated surfaces were studied, and it has been found that the partial oxidation of -SH to sulfonate happened only in NH 2 terminated SAM, which could be attributed to the HCl used to stabilize amino compound. 52 Table 2 demonstrates the properties of the four types of SAMs. The sessile drop method was used to measure the deionized water contact angle on SAM coated sensors.…”