Peptoids are peptidomimetic oligomers that predominantly harness similarities to peptides for biomimetic functionality. They have potential for use in biomedical applications and biosensors due to ...resistance to proteolytic degradation and low immunogenicity. The incorporation of chiral, aromatic side chains in the peptoid sequence allows for the formation of distinct secondary structures and self‐assembly into supramolecular assemblies, including microspheres. Peptoid microspheres can be coated onto substrates for potential use in biosensor technologies, tissue engineering platforms, and drug‐delivery systems. In order to be useful for these applications, the peptoid coatings must be robust under physiological conditions. In this study, we report the effects of various conditions on the peptoid microsphere coatings, including (i) helicity, (ii) temperature, (iii) pH, and (iv) ionic strength. These studies show that microsphere size decreases with increasing peptoid helicity and the positively charged side chains are positioned on the outside of the microspheres. The peptoid microsphere coatings are robust under physiological conditions but degrade in acidic conditions (pH < 7) and at low ionic strengths (<150 μM).
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Strategies to improve the early diagnosis of prostate cancer will provide opportunities for earlier intervention. The blood-based prostate-specific antigen (PSA) assay is widely used for prostate ...cancer diagnosis but specificity of the assay is not satisfactory. An algorithm based on serum levels of PSA combined with other serum biomarkers may significantly improve prostate cancer diagnosis. Plasma glycan-binding IgG/IgM studies suggested that glycan patterns differ between normal and tumor cells. We hypothesize that in prostate cancer glycoproteins or glycolipids are secreted from tumor tissues into the blood and induce auto-immunoglobulin (Ig) production. A 24-glycan microarray and a 5-glycan subarray were developed using plasma samples obtained from 35 prostate cancer patients and 54 healthy subjects to identify glycan-binding auto-IgGs. Neu5Acα2-8Neu5Acα2-8Neu5Acα (G81)-binding auto-IgG was higher in prostate cancer samples and, when levels of G81-binding auto-IgG and growth differentiation factor-15 (GDF-15 or NAG-1) were combined with levels of PSA, the prediction rate of prostate cancer increased from 78.2% to 86.2% than with PSA levels alone. The G81 glycan-binding auto-IgG fraction was isolated from plasma samples using G81 glycan-affinity chromatography and identified by N-terminal sequencing of the 50 kDa heavy chain variable region of the IgG. G81 glycan-binding 25 kDa fibroblast growth factor-1 (FGF1) fragment was also identified by N-terminal sequencing. Our results demonstrated that a multiplex diagnostic combining G81 glycan-binding auto-IgG, GDF-15/NAG-1 and PSA (≥ 2.1 ng PSA/ml for cancer) increased the specificity of prostate cancer diagnosis by 8%. The multiplex assessment could improve the early diagnosis of prostate cancer thereby allowing the prompt delivery of prostate cancer treatment.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Peptoids are a versatile family of oligomeric synthetic molecules that can be customized for many applications. The submonomer solid-phase synthesis of peptoids allows for quick and inexpensive ...manufacturing and the selection of side chains is nearly limitless. In addition, peptoids that include chiral, aromatic side chains form stable helical secondary structure that leads to the potential for the formation of supramolecular assemblies. The effects of water solubility, helical content, charge placement, and side chain bulk on microsphere formation were studied for seven peptoid sequences. We found that secondary structure and partial water solubility were essential for microsphere formation. In addition, charge placement and side chain bulk affect both the ability to form microspheres and the diameter of the microspheres.
Enzyme-linked immunosorbent assay (ELISA) microarray performance is limited by low assay sensitivity and dynamic range. Increasing the surface area for reagent binding can help to improve ...performance, but standard techniques such as roughening the surface or adding a polymer coating lead to increased non-specific fluorescence and do not have reproducibly improved performance. Another approach to increase surface area is adding a microsphere coating on the surface. Poly-N-substituted glycine (peptoid) microspheres are ideal for this application due to low immunogenicity, protease-resistance, and biocompatibility. Peptoids are polymers with a backbone similar to peptides, but with the side chains appended to nitrogen rather than the alpha carbon. A variety of side chain chemistries can be incorporated into peptoids through a solid-phase, sequence-specific synthesis protocol. Here we report the development of sandwich ELISA microarray on peptoid microsphere coated glass slides. Coating morphology was evaluated via SEM and efficacy was assessed by ELISA microarray performance. Peptoid microsphere coated glass slides exhibit an increase in signal intensity and dynamic range as compared to commercially available microarray slides. These studies show the potential for peptoid microspheres as coatings for ELISA microarray slides, as well as for use in other biosensor applications.
•Peptoid microsphere coatings outperform poly-l-lysine glass slides for biosensor applications.•Strong covalent antibody attachment on peptoid microsphere coatings.•Enhanced signal to noise ratio, limit of detection, and standard curve dynamic range.•Increased surface area enables higher binding capacities.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Sandwich enzyme-linked immunosorbent assay (ELISA) microarrays are emerging as a strong candidate platform for multiplex biomarker analysis because of the ELISA’s ability to quantitatively measure ...rare proteins in complex biological fluids. Advantages of this platform are high-throughput potential, assay sensitivity and stringency, and the similarity to the standard ELISA test, which facilitates assay transfer from a research setting to a clinical laboratory. However, a major concern with the multiplexing of ELISAs is maintaining high assay specificity. In this study, we systematically determine the amount of assay interference and noise contributed by individual components of a multiplexed 24-assay system. We find that nonspecific reagent cross-reactivity problems are relatively rare. We did identify the presence of contaminant antigens in a “purified antigen”. We tested the validated ELISA microarray chip using paired serum samples that had been collected from four women at a 6-month interval. This analysis demonstrated that protein levels typically vary much more between individuals than within an individual over time, a result which suggests that longitudinal studies may be useful in controlling for biomarker variability across a population. Overall, this research demonstrates the importance of a stringent screening protocol and the value of optimizing the antibody and antigen concentrations when designing chips for ELISA microarrays.
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IJS, KILJ, NUK, PNG, UL, UM
Alzheimer’s disease (AD) is the most common form of dementia and the sixth leading cause of death in the United States. Plaques composed of aggregated amyloid-beta protein (Aβ) accumulate between the ...neural cells in the brain and are associated with dementia and cellular death. Many strategies have been investigated to prevent Aβ self-assembly into disease-associated β-sheet amyloid aggregates; however, a promising therapeutic has not yet been identified. In this study, a peptoid-based mimic of the peptide KLVFF (residues 16–20 of Aβ) was tested for its ability to modulate Aβ aggregation. Peptoid JPT1 includes chiral, aromatic side chains to induce formation of a stable helical secondary structure that allows for greater interaction between the aromatic side chains and the cross β-sheet of Aβ. JPT1 was found to modulate Aβ40 aggregation, specifically decreasing lag time to β-sheet aggregate formation as well as the total number of fibrillar, β-sheet structured aggregates formed. These results suggest that peptoids may be able to limit the formation of Aβ aggregates that are associated with AD.
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The hydrophobic proteins of lung surfactant (LS), SP-B and SP-C, are critical constituents of an effective surfactant replacement therapy for the treatment of respiratory distress syndrome. Because ...of concerns and difficulties associated with animal-derived surfactants, recent investigations have focused on the creation of synthetic analogues of the LS proteins. However, creating an accurate mimic of SP-C that retains its biophysical surface activity is extraordinarily challenging given the lipopeptide's extreme hydrophobicity and propensity to misfold and aggregate. One successful approach that overcomes these difficulties is the use of poly-N-substituted glycines, or peptoids, to mimic SP-C. To develop a non-natural, bioactive mimic of SP-C and to investigate the effects of side chain chemistry and length of the helical hydrophobic region, we synthesized, purified, and performed in vitro testing of two classes of peptoid SP-C mimics: those having a rigid α-chiral aromatic helix and those having a biomimetic α-chiral aliphatic helix. The length of the two classes of mimics was also systematically altered. Circular dichroism spectroscopy gave evidence that all of the peptoid-based mimics studied here emulated SP-C's secondary structure, forming stable helical structures in solution. Langmuir−Wilhelmy surface balance, fluorescence microscopy, and pulsating bubble surfactometry experiments provide evidence that the aromatic-based SP-C peptoid mimics, in conjunction with a synthetic lipid mixture, have superior surface activity and biomimetic film morphology in comparison to the aliphatic-based mimics and that there is an increase in surface activity corresponding to increasing helical length.
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IJS, KILJ, NUK, PNG, UL, UM
Enzyme-linked immunosorbent assay (ELISA) microarrays promise to be a powerful tool for the detection of disease biomarkers. The original technology for printing ELISA microarray chips and capturing ...antibodies on slides was derived from the DNA microarray field. However, due to the need to maintain antibody structure and function when immobilized, surface chemistries used for DNA microarrays are not always appropriate for ELISA microarrays. In order to identify better surface chemistries for antibody capture, a number of commercial companies and academic research groups have developed new slide types that could improve antibody function in microarray applications. In this review we compare and contrast the commercially available slide chemistries, as well as highlight some promising recent advances in the field.
Surfactant protein B (SP-B) is one of two helical, amphipathic proteins critical for the biophysical functioning of lung surfactant (LS) and hence is an important therapeutic protein. This small, ...complex 79mer has three internal disulfide bonds and homodimerizes via another disulfide bridge. A helical, amphipathic 25mer from the amino terminus (SP-B1 - 25) exhibits surface-active properties similar to those of full-length, synthetic SP-B. In previous work, we created helical, non-natural mimics of SP-B1 - 25 based on sequence-specific peptoid 17mers and demonstrated their biomimetic surface activity. Like SP-B1 - 25, the peptoids were designed to adopt helical structures with cationic and nonpolar faces. Here, we compare the surface activities of six different helical peptoid analogues of SP-B1 - 25 to investigate the importance of mimicking its N-terminal insertion domain as well as its two arginine residues, both thought to be important for the peptide's proper function. Although the peptoid analogues of SP-B1 - 25 studied here share many similar features and all functionally mimic SP-B1 - 25 to some degree, it is notable that small differences in their sequences and side chain chemistries lead to substantial differences in their observed interactions with a lipid film. A peptoid comprising a hydrophobic, helical insertion region with aromatic side chains shows more biomimetic surface activity than simpler peptoids, and even better activity, by comparison to natural LS, than SP-B1 - 25. However, the substitution of lysine-like side chains for arginine-like side chains in the peptoid has little effect on biomimetic surface activity, indicating that interactions of the guanidino groups with lipids may not be critical for the function of these SP-B mimics.
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