Biological functions of supramolecular assemblies of small molecules in cellular environment

Engineering of Nucleobase-Functionalized Coassembled Hydrogel to Study Cellular Behavior

Hydrogels derived from self-assembling peptides provide considerable benefits in tissue engineering including their biocompatibility and extensive molecular diversity. Short peptides are especially advantageous due to their ease of production, ability to self-assemble, and repeatability. However, their application is currently limited owing to possible toxicity resulting from the chemical modifications required for self-assembly and the coarse gelation conditions. Nucleobase-functionalized derivatives provide an opportunity to use naturally obtained species to minimize cytotoxicity. Therefore, nucleobase-functionalized hydrogels are currently attracting significant interest due to their varied architectures. Herein, we have synthesized a guanine-functionalized alanine derivative and investigated the formation of a coassembled hydrogel with guanosine. The development of the nucleic acid secondary structure within the coassembled hydrogel is studied using circular dichroism and wide-angle powder X-ray diffraction experiments. The thermoreversible nature of the coassembled hydrogel is explored. The biocompatibility of the coassembled hydrogel is evaluated by performing the MTT assay. The coassembled hydrogel is used for cell growth, and 2D cell cultures are carried out on fibroblast McCoy and epithelial A549 cell lines. Live-dead cell imaging is performed by staining with fluorescein diacetate and propidium iodide. The cell proliferation is studied over different time periods using the Alamar Blue assay. Cytoskeletal staining is performed on both cell lines to determine the impact of the coassembled hydrogel on the cells.

Fabricating N-Cadherin Mimetic Peptide-Based Diverse Self-Assembled Hydrogels in the Presence of Biologically Relevant Cations

N-cadherin, a crucial extracellular matrix protein, is crucial in mediating cellular interactions and promoting cell migration. Herein, we have attempted to create N-cadherin mimetic peptide (NcMP) hydrogel scaffolds by incorporating cations as the external stimulus to create a suitable interface for favorable cellular interactions. Inspired by the Hofmeister series, we selected four biologically significant cations, classified as kosmotropes and chaotropes, and varied their concentrations to investigate how increasing ionic strength affects the self-assembly of the NcMP. Interestingly, the incorporation of these ions greatly influenced the self-assembling propensity of the Fmoc-HAVDI hydrogel, which resulted in diverse structural and mechanical properties. Such diverse physical properties led to differential cellular responses. Thus, we were able to access diverse physical and biological properties in a single gelator molecule by simply changing the nature and concentration of the biologically relevant cations. We anticipate that these diverse hydrogel systems hold great potential in various biomedical applications.

Visual Monitoring of Biomolecular Self-Assembly Dynamics and Imaging of Protein Aggregates by Distinct Emission of a Unique Hydrophobic Carbon Dot

Here, we report a novel and unique application of a special hydrophobic carbon dot (HCD) to monitor biomolecular self-assembly, along with the detection of metastable intermediates and self-aggregates. We exploited the restricted rotation of the S-S bond of the HCD synthesized from dithiosalicylic acid and melamine to illuminate different emission behaviors during the self-assembly of amino acids and proteins. The HCD that exhibits blue emission in amino acid droplets or protein aggregates dynamically changes its emission from blue to red over the time course of the amino acid self-assembly process. This unique and distinct change in emission can be visualized by the naked eye under a UV lamp. The ability of HCD to distinguish the biomolecular self-aggregated structures and monitor the self-assembly dynamics can be utilized for the visual detection of uncontrolled aggregation of proteins and peptides related to neurodegenerative diseases like Alzheimer's disease and Parkinson's disease.

Synthetic Nanoassemblies for Regulating Organelles: From Molecular Design to Precision Therapeutics

Each organelle referring to a complex multiorder architecture executes respective biological processes via its distinct spatial organization and internal microenvironment. As the assembly of biomolecules is the structural basis of living cells, creating synthetic nanoassemblies with specific physicochemical and morphological properties in living cells to interfere or couple with the natural organelle architectures has attracted great attention in precision therapeutics of cancers. In this review, we give an overview of the latest advances in the synthetic nanoassemblies for precise organelle regulation, including the formation mechanisms, triggering strategies, and biomedical applications in precision therapeutics. We summarize the emerging material systems, including polymers, peptides, and deoxyribonucleic acids (DNAs), and their respective intermolecular interactions for intercellular synthetic nanoassemblies, and highlight their design principles in constructing precursors that assemble into synthetic nanoassemblies targeting specific organelles in the complex cellular environment. We further showcase the developed intracellular synthetic nanoassemblies targeting specific organelles including mitochondria, the endoplasmic reticulum, lysosome, Golgi apparatus, and nucleus and describe their underlying mechanisms for organelle regulation and precision therapeutics for cancer. Last, the essential challenges in this field and prospects for future precision therapeutics of synthetic nanoassemblies are discussed. This review should facilitate the rational design of organelle-targeting synthetic nanoassemblies and the comprehensive recognition of organelles by materials and contribute to the deep understanding and application of the synthetic nanoassemblies for precision therapeutics.

Designing Pathway-Controlled Multicomponent Ultrashort Peptide Hydrogels with Diverse Functionalities at the Nanoscale for Directing Cellular Behavior

Tuning self-assembling pathways by implementing different external stimuli has been extensively studied, owing to their effective control over structural and mechanical properties. Consequently, multicomponent peptide hydrogels with high structural tunability and stimuli responsiveness are crucial in dictating cellular behavior. Herein, we have implemented both coassembly approach and pathway-dependent self-assembly to design nonequilibrium nanostructures to understand the thermodynamic and kinetic aspects of peptide self-assembly toward controlling cellular response. Our system involved an ultrashort peptide gelator and a hydrophilic surfactant which coassembled through different pathways, i.e., heat-cool and sonication methods with variable energy input. Interestingly, it was possible to access diverse structural and mechanical properties at the nanoscale in a single coassembled system. Further, the hydrophilic surfactant provided additional surface functionalities, thus creating an efficient hydrophilic matrix for cellular interaction. Such diverse functionalities in a single coassembled system could lead to the development of advanced scaffolds, with applications in various biomedical fields.

Highly Efficient Photoswitchable Smart Polymeric Nanovehicle for Gene and Anticancer Drug Delivery in Triple-Negative Breast Cancer

Over the past few decades, there has been significant interest in smart drug delivery systems capable of carrying multiple drugs efficiently, particularly for treating genetic diseases such as cancer. Despite the development of various drug delivery systems, a safe and effective method for delivering both anticancer drugs and therapeutic genes for cancer therapy remains elusive. In this study, we describe the synthesis of a photoswitchable smart polymeric vehicle comprising a photoswitchable spiropyran moiety and an amino-acid-based cationic monomer-based block copolymer using reversible addition-fragmentation chain transfer (RAFT) polymerization. This system aims at diagnosing triple-negative breast cancer and subsequently delivering genes and anticancer agents. Triple-negative breast cancer patients have elevated concentrations of Cu2+ ions, making them excellent targets for diagnosis. The polymer can detect Cu2+ ions with a low limit of detection value of 9.06 nM. In vitro studies on doxorubicin drug release demonstrated sustained delivery at acidic pH level similar to the tumor environment. Furthermore, the polymer exhibited excellent blood compatibility even at the concentration as high as 500 μg/mL. Additionally, it displayed a high transfection efficiency of approximately 82 ± 5% in MDA-MB-231 triple-negative breast cancer cells at an N/P ratio of 50:1. It is observed that mitochondrial membrane depolarization and intracellular reactive oxygen species generation are responsible for apoptosis and the higher number of apoptotic cells, which occurred through the arrest of the G2/M phase of the cell cycle were observed. Therefore, the synthesized light-responsive cationic polymer may be an effective system for diagnosis, with an efficient anticancer drug and gene carrier for the treatment of triple-negative breast cancer in the future.

Self-Assembly, Bioactivity, and Nanomaterials Applications of Peptide Conjugates with Bulky Aromatic Terminal Groups

The self-assembly and structural and functional properties of peptide conjugates containing bulky terminal aromatic substituents are reviewed with a particular focus on bioactivity. Terminal moieties include Fmoc [fluorenylmethyloxycarbonyl], naphthalene, pyrene, naproxen, diimides of naphthalene or pyrene, and others. These provide a driving force for self-assembly due to π-stacking and hydrophobic interactions, in addition to the hydrogen bonding, electrostatic, and other forces between short peptides. The balance of these interactions leads to a propensity to self-assembly, even for conjugates to single amino acids. The hybrid molecules often form hydrogels built from a network of β-sheet fibrils. The properties of these as biomaterials to support cell culture, or in the development of molecules that can assemble in cells (in response to cellular enzymes, or otherwise) with a range of fascinating bioactivities such as anticancer or antimicrobial activity, are highlighted. In addition, applications of hydrogels as slow-release drug delivery systems and in catalysis and other applications are discussed. The aromatic nature of the substituents also provides a diversity of interesting optoelectronic properties that have been demonstrated in the literature, and an overview of this is also provided. Also discussed are coassembly and enzyme-instructed self-assembly which enable precise tuning and (stimulus-responsive) functionalization of peptide nanostructures.

Advanced nanomaterial for prostate cancer theranostics

Prostate cancer (PC) has the second highest incidence in men, according to global statistical data. The symptoms of PC in the early stage are not obvious, causing late diagnosis in most patients, which is the cause for missing the optimal treatment time. Thus, highly sensitive and precise early diagnosis methods are very important. Additionally, precise therapy regimens for good targeting and innocuous to the body are indispensable to treat cancer. This review first introduced two diagnosis methods, containing prostate-specific biomarkers detection and molecular imaging. Then, it recommended advanced therapy approaches, such as chemotherapy, gene therapy, and therapeutic nanomaterial. Afterward, we summarized the development of nanomaterial in PC, highlighting the importance of integration of diagnosis and therapy as the future direction against cancer.

Localized Enzyme-Assisted Self-Assembly of low molecular weight hydrogelators. Mechanism, applications and perspectives

Nature uses systems of high complexity coordinated by the precise spatial and temporal control of associated processes, working from the molecular to the macroscopic scale. This living organization is mainly ensured by enzymatic actions. Herein, we review the concept of Localized Enzyme-Assisted Self-Assembly (LEASA). It is defined and presented as a straightforward and insightful strategy to achieve high levels of control in artificial systems. Indeed, the use of immobilized enzymes to drive self-assembly events leads not only to the local formation of supramolecular structures but also to tune their kinetics and their morphologies. The possibility to design tailored complex systems taking advantage of self-assembled networks through their inherent and emergent properties offers new perspectives for the design of novel, more adaptable materials. As a result, some applications have already been developed and are gathered in this review. Finally, challenges and perspectives of LEASA are introduced and discussed.

Supramolecular Biomaterials in the Netherlands

Synthetically designed biomaterials strive to recapitulate and mimic the complex environment of natural systems. Using natural materials as a guide, the ability to create high performance biomaterials that control cell fate, and support the next generation of cell and tissue-based therapeutics, is starting to emerge. Supramolecular chemistry takes inspiration from the wealth of non-covalent interactions found in natural materials that are inherently complex, and using the skills of synthetic and polymer chemistry, recreates simple systems to imitate their features. Within the past decade, supramolecular biomaterials have shown utility in tissue engineering and the progress predicts a bright future. On this 30th anniversary of the Netherlands Biomaterials and Tissue Engineering society, we will briefly recount the state of supramolecular biomaterials in the Dutch academic and industrial research and development context. This review will provide the background, recent advances, industrial successes and challenges, as well as future directions of the field, as we see it. Throughout this work, we notice the intricate interplay between simplicity and complexity in creating more advanced solutions. We hope that the interplay and juxtaposition between these two forces can propel the field forward.

A New Approach to Supramolecular Structure Determination in Pharmaceutical Preparation of Self-Assembling Peptides: A Case Study of Lanreotide Autogel

The supramolecular structure in peptides’ prolonged-released gel formulations is the most critical parameter for the determination of the pharmaceutical profile of the drug. Here, we report our investigation on lanreotide Autogel as a case study. For the first time, we describe the use of the pulsed field gradient (PFG) diffusion-ordered spectroscopy (DOSY) magic-angle spinning NMR to characterize the supramolecular self-assembly and molecular mobility of different samples of lanreotide Autogel formulations prepared according to different formulation protocols. The diffusion coefficient was used to calculate the hydrodynamic radii of supramolecular assemblies and build relative molecular models. DOSY data were integrated with NMR imaging (MRI) measurements and atomic force microscopy (AFM) imaging.

Columnar Aggregates of Azobenzene Stars: Exploring Intermolecular Interactions, Structure, and Stability in Atomistic Simulations

We present a simulation study of supramolecular aggregates formed by three-arm azobenzene (Azo) stars with a benzene-1,3,5-tricarboxamide (BTA) core in water. Previous experimental works by other research groups demonstrate that such Azo stars assemble into needle-like structures with light-responsive properties. Disregarding the response to light, we intend to characterize the equilibrium state of this system on the molecular scale. In particular, we aim to develop a thorough understanding of the binding mechanism between the molecules and analyze the structural properties of columnar stacks of Azo stars. Our study employs fully atomistic molecular dynamics (MD) simulations to model pre-assembled aggregates with various sizes and arrangements in water. In our detailed approach, we decompose the binding energies of the aggregates into the contributions due to the different types of non-covalent interactions and the contributions of the functional groups in the Azo stars. Initially, we investigate the origin and strength of the non-covalent interactions within a stacked dimer. Based on these findings, three arrangements of longer columnar stacks are prepared and equilibrated. We confirm that the binding energies of the stacks are mainly composed of π-π interactions between the conjugated parts of the molecules and hydrogen bonds formed between the stacked BTA cores. Our study quantifies the strength of these interactions and shows that the π-π interactions, especially between the Azo moieties, dominate the binding energies. We clarify that hydrogen bonds, which are predominant in BTA stacks, have only secondary energetic contributions in stacks of Azo stars but remain necessary stabilizers. Both types of interactions, π-π stacking and H-bonds, are required to maintain the columnar arrangement of the aggregates.