Gd(III)-induced Supramolecular Hydrogelation with Enhanced Magnetic Resonance Performance for Enzyme Detection

Recent progress in quantitative analysis of self-assembled peptides

Self-assembled peptides have been among the important biomaterials due to its excellent biocompatibility and diverse functions. Over the past decades, substantial progress and breakthroughs have been made in designing self-assembled peptides with multifaceted biomedical applications. The techniques for quantitative analysis, including imaging-based quantitative techniques, chromatographic technique and computational approach (molecular dynamics simulation), are becoming powerful tools for exploring the structure, properties, biomedical applications, and even supramolecular assembly processes of self-assembled peptides. However, a comprehensive review concerning these quantitative techniques remains scarce. In this review, recent progress in techniques for quantitative investigation of biostability, cellular uptake, biodistribution, self-assembly behaviors of self-assembled peptide etc., are summarized. Specific applications and roles of these techniques are highlighted in detail. Finally, challenges and outlook in this field are concluded. It is believed that this review will provide technical guidance for researchers in the field of peptide-based materials and pharmaceuticals, and facilitate related research for newcomers in this field.

Rational design of peptide-based implants for corneal bioengineering

Regeneration of damaged cornea can save vision for millions of patients. Most of these patients are waiting for transplantation of a donor cornea or suitable substitute to restore vision. Although donor cornea transplantation is the most clinically accepted treatment, shortage of donor cornea results in almost 69 out of every 70 patients untreated with the waiting list for transplantation drastically increasing every year according to a prepandemic estimation. Therefore, corneal replacements are coming up as a cutting-edge alternative strategy. In view of the peptides, especially collagen-like peptides and peptide amphiphiles with bioactive functional motifs demonstrate promising avenue for the corneal tissue engineering and promoting regeneration, by their hierarchical self-assembling propensity to acquire desired nano- to macroscale 3D architecture. Here, we analyze rational peptide designing, self-assembly, and strategies of peptide/peptide-based nanoscale building blocks to create the extracellular matrix mimetic implants for functional regeneration of the cornea.

Metal-Coordinated Supramolecular Self-Assemblies for Cancer Theranostics

Metal-coordinated supramolecular nanoassemblies have recently attracted extensive attention as materials for cancer theranostics. Owing to their unique physicochemical properties, metal-coordinated supramolecular self-assemblies can bridge the boundary between traditional inorganic and organic materials. By tailoring the structural components of the metal ions and binding ligands, numerous multifunctional theranostic nanomedicines can be constructed. Metal-coordinated supramolecular nanoassemblies can modulate the tumor microenvironment (TME), thus facilitating the development of TME-responsive nanomedicines. More importantly, TME-responsive organic-inorganic hybrid nanomaterials can be constructed in vivo by exploiting the metal-coordinated self-assembly of a variety of functional ligands, which is a promising strategy for enhancing the tumor accumulation of theranostic molecules. In this review, recent advancements in the design and fabrication of metal-coordinated supramolecular nanomedicines for cancer theranostics are highlighted. These supramolecular compounds are classified according to the order in which the coordinated metal ions appear in the periodic table. Furthermore, the prospects and challenges of metal-coordinated supramolecular self-assemblies for both technical advances and clinical translation are discussed. In particular, the superiority of TME-responsive nanomedicines for in vivo coordinated self-assembly is elaborated, with an emphasis on strategies that enhance the accumulation of functional components in tumors for an ideal theranostic outcome.

Peptide-based supramolecular hydrogels for bioimaging applications

Peptide-based supramolecular hydrogels have unique merits in bioimaging applications.

Dual-Mode Fluorescence and Magnetic Resonance Imaging by Perylene Diimide-Based Gd-Containing Magnetic Ionic Liquids

Bioimaging plays a key role in the diagnosis/treatment of diseases and in scientific research studies. Compared with single imaging techniques, dual-mode and multimode imaging techniques facilitate high accuracy. In this work, a perylene diimide (PDI)-based Gd-containing magnetic ionic liquid, Per-6-Diimi[Gd(NO₃)₄], is reported for dual-modal imaging, in which a Gd(III) complex was used for magnetic resonance imaging (MRI), while PDI was used for fluorescence imaging. Because of the difference in the biological microenvironment, there is a switch between dispersed and aggregated states of Per-6-Diimi[Gd(NO₃)₄] molecules in hydrophobic and hydrophilic media. When it was in the aqueous solution, the intensive π-π interaction of PDI cores made Per-6-Diimi[Gd(NO₃)₄] aggregates to form particles. The paramagnetic nanoparticles ensure prolonging the rotational correlation time, which results in a strong enhancement of MRI with a longitude relaxation coefficient of 14.94 mM^-1 s^-1. In an in vivo MRI experiment, the tumor site is imaged by MRI through the enhanced permeability and retention effect. However, when the molecule is present on the hydrophobic membrane of the cells, the dispersed Per-6-Diimi[Gd(NO₃)₄] showed good fluorescence imaging capabilities due to the high fluorescence quantum yield of PDI. Thus, the fluorescence imaging of cells can be carried out. Moreover, ex vivo fluorescence imaging of organs is performed after MRI. Per-6-Diimi[Gd(NO₃)₄] is enriched in the liver, kidneys, and tumors.

Systematic overview of soft materials as a novel frontier for MRI contrast agents

Magnetic resonance imaging (MRI) is a well-known diagnostic technique used to obtain high quality images in a non-invasive manner. In order to increase the contrast between normal and pathological regions in the human body, positive (T1) or negative (T2) contrast agents (CAs) are commonly intravenously administered. The most efficient class of T1-CAs are based on kinetically stable and thermodynamically inert gadolinium complexes. In the last two decades many novel macro- and supramolecular CAs have been proposed. These approaches have been optimized to increase the performance of the CAs in terms of the relaxivity values and to reduce the administered dose, decreasing the toxicity and giving better safety and pharmacokinetic profiles. The improved performances may also allow further information to be gained on the pathological and physiological state of the human body. The goal of this review is to report a systematic overview of the nanostructurated CAs obtained and developed by manipulating soft materials at the nanometer scale. Specifically, our attention is centered on recent examples of fibers, hydrogels and nanogel formulations, that seem particularly promising for overcoming the problematic issues that have recently pushed the European Medicines Agency (EMA) to withdraw linear CAs from the market.

Gd(iii)-nanostructurated Constrast Agents (CAs) for Magnetic Resonance Imaging (MRI) can be designed and developed by manipulating soft material, including fibers, hydrogels and nanogels, in the nanometer scale.

Delivery of MSCs with a Hybrid β-Sheet Peptide Hydrogel Consisting IGF-1C Domain and D-Form Peptide for Acute Kidney Injury Therapy

Purpose

By providing a stem cell microenvironment with particular bioactive constituents in vivo, synthetic biomaterials have been progressively successful in stem cell-based tissue regeneration by enhancing the engraftment and survival of transplanted cells. Designs with bioactive motifs to influence cell behavior and with D-form amino acids to modulate scaffold stability may be critical for the development and optimization of self-assembling biomimetic hydrogel scaffolds for stem cell therapy.

Materials and Methods

In this study, we linked naphthalene (Nap) covalently to a short D-form peptide (Nap-^DF^DFG) and the C domain of insulin-like growth factor-1 (IGF-1C) as a functional hydrogel-based scaffolds, and we hypothesized that this hydrogel could enhance the therapeutic efficiency of human placenta-derived mesenchymal stem cells (hP-MSCs) in a murine acute kidney injury (AKI) model.

Results

The self-assembling peptide was constrained into a classical β-sheet structure and showed hydrogel properties. Our results revealed that this hydrogel exhibited increased affinity for IGF-1 receptor. Furthermore, cotransplantation of the β-IGF-1C hydrogel and hP-MSCs contributed to endogenous regeneration post-injury and boosted angiogenesis in a murine AKI model, leading to recovery of renal function.

Conclusion

This hydrogel could provide a favorable niche for hP-MSCs and thereby rescue renal function in an AKI model by promoting cell survival and angiogenesis. In conclusion, by covalently linking the desired functional groups to D-form peptides to create functional hydrogels, self-assembling β-sheet peptide hydrogels may serve as a promising platform for tissue-engineering and stem cell therapy.

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First Aldol Cross-Linked Hyaluronic Acid Hydrogel: Fast and Hydrolytically Stable Hydrogel with Tissue Adhesive Properties

Currently, there are limited approaches to tailor 3D scaffolds cross-linked with a stable covalent C-C bond that does not require any catalysts or initiators. We present here the first hydrogels employing aldol condensation chemistry that exhibit exceptional physicochemical properties. We investigated the aldol-cross-linking chemistry using two types of aldehyde-modified hyaluronic acid (HA) derivatives, namely, an enolizable HA-aldehyde (HA-Eal) and a non-enolizable HA-aldehyde (HA-Nal). Hydrogels formed using HA-Eal demonstrate inferior cross-linking efficiency (due to intramolecular loop formation), when compared with hydrogels formed by mixing HA-Eal and HA-NaI leading to a cross-aldol product. The change in mechanical properties as a result of cross-linking at different pH values is determined using rheological measurements and is interpreted in terms of molecular weight between cross-links (M_c). The novel HA cross-aldol hydrogel demonstrate excellent hydrolytic stability and favorable mechanical properties but allow hyaluronidase-mediated enzymatic degradation. Interestingly, residual aldehyde functionality within the aldol product rendered the tissue-adhesive properties by bonding two bone tissues. The aldehyde functionality also facilitated facile post-synthetic modifications with nucleophilic reagents. Finally, we demonstrate that the novel hydrogel is biocompatible with encapsulated stem cells that show a linear rate of expansion in our 3-6 days of study.

Stimuli-Responsive Supramolecular Hydrogels and Their Applications in Regenerative Medicine

Supramolecular hydrogels are a class of self-assembled network structures formed via non-covalent interactions of the hydrogelators. These hydrogels capable of responding to external stimuli are considered to be smart materials due to their ability to undergo sol-gel and/or gel-sol transition upon subtle changes in their surroundings. Such stimuli-responsive hydrogels are intriguing biomaterials with applications in tissue engineering, delivery of cells and drugs, modulating tissue environment to promote innate tissue repair, and imaging for medical diagnostics among others. This review summarizes the recent developments in stimuli-responsive supramolecular hydrogels and their potential applications in regenerative medicine. Specifically, various structural aspects of supramolecular hydrogelators involved in self-assembly, the role of external stimuli in tuning/controlling their phase transitions, and how these functions could be harnessed to advance applications in regenerative medicine are focused on. Finally, the key challenges and future prospects for these versatile materials are briefly described.