Hybrid Peptide-Agarose Hydrogels for 3D Immunoassays

Recent advances in biosensing analytical platforms have brought relevant outcomes for novel diagnostic and therapy-oriented applications. In this context, 3D droplet microarrays, where hydrogels are used as matrices to stably entrap biomolecules onto analytical surfaces, potentially provide relevant advantages over conventional 2D assays, such as increased loading capacity, lower nonspecific binding, and enhanced signal-to-noise ratio. Here, we describe a hybrid hydrogel composed of a self-assembling peptide and commercial agarose (AG) as a suitable matrix for 3D microarray bioassays. The hybrid hydrogel is printable and self-adhesive and allows analyte diffusion. As a showcase example, we describe its application in a diagnostic immunoassay for the detection of SARS-CoV-2 infection.

Rational Design of Self-Assembling Supramolecular Protein Nanostructures Utilizing the Cucurbit[8]Uril Macrocyclic Host

Self-assembly is a phenomenon that governs molecular structural organization in nature, therefore raising research interest for the fabrication of novel nanomaterials with diverse applications in biocatalysis, biomedicine, material templating, and biosensor development. In this chapter we provide protocols for the development of supramolecular protein complexes based on host-guest interactions in the presence of the macrocyclic host, cucurbit[8]uril (CB[8]). CB[8] is reported to exhibit high binding affinity towards the tripeptide Phe-Gly-Gly (FGG), therefore it can be utilized as a selective adhesive of protein molecules, after fusion of FGG to an accessible protein surface.

Self-Assembling Peptide Hydrogels for 3D Microarrays

Recent advances in biosensing analytical platforms have brought relevant outcomes for novel diagnostic and therapy-oriented applications. In this context, hydrogels have emerged as appealing matrices to locally confine biomolecules onto sensing surfaces under solution mimetic conditions, preserving their structural integrity and function. Here, we describe the application of a self-assembling peptide hydrogel as a suitable matrix for 3D microarray bioassays. The hydrogel is printable and self-adhesive and allows for fast analyte diffusion. As a showcase example, we describe its application in a diagnostic immunoassay for the detection of arbovirus infection.

Self-Repair of Structure and Bioactivity in a Supramolecular Nanostructure

Supramolecular nanostructures formed through self-assembly can have energy landscapes, which determine their structures and functions depending on the pathways selected for their synthesis and processing and on the conditions they are exposed to after their initial formation. We report here on the structural damage that occurs in supramolecular peptide amphiphile nanostructures, during freezing in aqueous media, and the self-repair pathways that restore their functions. We found that freezing converts long supramolecular nanofibers into shorter ones, compromising their ability to support cell adhesion, but a single heating and cooling cycle reverses the damage and rescues their bioactivity. Thermal energy in this cycle enables noncovalent interactions to reconfigure the nanostructures into the thermodynamically preferred long nanofibers, a repair process that is impeded by kinetic traps. In addition, we found that nanofibers disrupted during freeze-drying also exhibit the ability to undergo thermal self-repair and recovery of their bioactivity, despite the extra disruption caused by the dehydration step. Following both freezing and freeze-drying, which shorten the 1D nanostructures, their self-repair capacity through thermally driven elongation is inhibited by kinetically trapped states, which contain highly stable noncovalent interactions that are difficult to rearrange. These states decrease the extent of thermal nanostructure repair, an observation we hypothesize applies to supramolecular systems in general and is mechanistically linked to suppressed molecular exchange dynamics.

Bioinspired supramolecular engineering of self-assembling immunofibers for high affinity binding of immunoglobulin G

Many one-dimensional (1D) nanostructures are constructed by self-assembly of peptides or peptide conjugates containing a short β-sheet sequence as the core building motif essential for the intermolecular hydrogen bonding that promotes directional, anisotropic growth of the resultant assemblies. While this molecular engineering strategy has led to the successful production of a plethora of bioactive filamentous β-sheet assemblies for interfacing with biomolecules and cells, concerns associated with effective presentation of α-helical epitopes and their function preservation have yet to be resolved. In this context, we report on the direct conjugation of the protein A mimicking peptide Z33, a motif containing two α-helices, to linear hydrocarbons to create self-assembling immuno-amphiphiles (IAs). Our results suggest that the resulting amphiphilic peptides can, despite lacking the essential β-sheet segment, effectively associate under physiological conditions into supramolecular immunofibers (IFs) while preserving their native α-helical conformation. Isothermal titration calorimetry (ITC) measurements confirmed that these self-assembling immunofibers can bind to the human immunoglobulin G class 1 (IgG1) with high specificity at pH 7.4, but with significantly weakened binding at pH 2.8. We further demonstrated the accessibility of Z33 ligand in the immunofibers using transmission electron microscopy (TEM) and confocal imaging. We believe these results shed important light into the supramolecular engineering of α-helical peptides into filamentous assemblies that may possess an important potential for antibody isolation.

Drug delivery with nanospherical supramolecular cell penetrating peptide-taxol conjugates containing a high drug loading

HYPOTHESIS

Supramolecular nanostructures via small molecule self-assembly hold great promise for controlled delivery of hydrophobic anticancer drugs. Particularly, taxol has recently been discovered to possess excellent self-assembly property, which may provide new opportunities to develop a new class of functional supramolecular nanomaterials for drug delivery application.

EXPERIMENTS

A cell penetrating peptide (CPP)-taxol conjugate (Taxol-CPP) was designed and synthesized. The self-assembling property of Taxol-CPP was investigated and the resultant nanomaterials were well characterized. Subsequently, the cytotoxicity of the Taxol-CPP after self-assembly against HepG2 cancer cells was evaluated.

FINDINGS

It is found that the Taxol-CPP possesses a high drug loading of 26.4% in each molecule, which is able to self-assemble into supramolecular nanospheres. By taking advantages of the self-assembly ability of taxol, Taxol-CPP supramolecular nanospheres with a mean size of around 130 nm can be obtained, composed of only the functional peptide (CPP) and the drug (taxol). Furthermore, we have demonstrated that the Taxol-CPP nanospheres do not compromise the taxol's potency, which can also be utilized as the carriers for co-delivery of another anticancer drug (doxorubicin).