Designer Amyloid Cell-Penetrating Peptides for Potential Use as Gene Transfer Vehicles

PicoGreen assay for nucleic acid quantification - Applications, challenges, and solutions

Various analytical methods and reagents have been employed for nucleic acid analysis in cells, biological fluids, and formulations. Standard techniques like gel electrophoresis and qRT-PCR are widely used for qualitative and quantitative nucleic acid analysis. However, these methods can be time-consuming and labor-intensive, with limitations such as inapplicability to small RNA at low concentrations and high costs associated with qRT-PCR reagents and instruments. As an alternative, PicoGreen (PG) has emerged as a valuable method for the quantitative analysis of nucleic acids. PG, a fluorescent dye, enables the quantitation of double-stranded DNA (dsDNA) or double-stranded RNA, including miRNA mimic and siRNA, in solution. It is also applicable to DNA and RNA analysis within cells using techniques like FACS and fluorescence microscopy. Despite its advantages, PG's fluorescence intensity is affected by various experimental conditions, such as pH, salts, and chemical reagents. This review explores the recent applications of PG as a rapid, cost-effective, robust, and accurate assay tool for nucleic acid quantification. We also address the limitations of PG and discuss approaches to overcome these challenges, recognizing the expanding range of its applications.

Exploring pathological link between antimicrobial and amyloid peptides

Amyloid peptides (AMYs) and antimicrobial peptides (AMPs) are considered as the two distinct families of peptides, characterized by their unique sequences, structures, biological functions, and specific pathological targets. However, accumulating evidence has revealed intriguing pathological connections between these peptide families in the context of microbial infection and neurodegenerative diseases. Some AMYs and AMPs share certain structural and functional characteristics, including the ability to self-assemble, the presence of β-sheet-rich structures, and membrane-disrupting mechanisms. These shared features enable AMYs to possess antimicrobial activity and AMPs to acquire amyloidogenic properties. Despite limited studies on AMYs-AMPs systems, the cross-seeding phenomenon between AMYs and AMPs has emerged as a crucial factor in the bidirectional communication between the pathogenesis of neurodegenerative diseases and host defense against microbial infections. In this review, we examine recent developments in the potential interplay between AMYs and AMPs, as well as their pathological implications for both infectious and neurodegenerative diseases. By discussing the current progress and challenges in this emerging field, this account aims to inspire further research and investments to enhance our understanding of the intricate molecular crosstalk between AMYs and AMPs. This knowledge holds great promise for the development of innovative therapies to combat both microbial infections and neurodegenerative disorders.

Co-Assembly of Cancer Drugs with Cyclo-HH Peptides: Insights from Simulations and Experiments

Peptide-based nanomaterials can serve as promising drug delivery agents, facilitating the release of active pharmaceutical ingredients while reducing the risk of adverse reactions. We previously demonstrated that Cyclo-Histidine-Histidine (Cyclo-HH), co-assembled with cancer drug Epirubicin, zinc, and nitrate ions, can constitute an attractive drug delivery system, combining drug self-encapsulation, enhanced fluorescence, and the ability to transport the drug into cells. Here, we investigated both computationally and experimentally whether Cyclo-HH could co-assemble, in the presence of zinc and nitrate ions, with other cancer drugs with different physicochemical properties. Our studies indicated that Methotrexate, in addition to Epirubicin and its epimer Doxorubicin, and to a lesser extent Mitomycin-C and 5-Fluorouracil, have the capacity to co-assemble with Cyclo-HH, zinc, and nitrate ions, while a significantly lower propensity was observed for Cisplatin. Epirubicin, Doxorubicin, and Methorexate showed improved drug encapsulation and drug release properties, compared to Mitomycin-C and 5-Fluorouracil. We demonstrated the biocompatibility of the co-assembled systems, as well as their ability to intracellularly release the drugs, particularly for Epirubicin, Doxorubicin, and Methorexate. Zinc and nitrate were shown to be important in the co-assembly, coordinating with drugs and/or Cyclo-HH, thereby enabling drug-peptide as well as drug-drug interactions in successfully formed nanocarriers. The insights could be used in the future design of advanced cancer therapeutic systems with improved properties.

Peptide Self-Assembled Nanocarriers for Cancer Drug Delivery

The design of novel cancer drug nanocarriers is critical in the framework of cancer therapeutics. Nanomaterials are gaining increased interest as cancer drug delivery systems. Self-assembling peptides constitute an emerging novel class of highly attractive nanomaterials with highly promising applications in drug delivery, as they can be used to facilitate drug release and/or stability while reducing side effects. Here, we provide a perspective on peptide self-assembled nanocarriers for cancer drug delivery and highlight the aspects of metal coordination, structure stabilization, and cyclization, as well as minimalism. We review particular challenges in nanomedicine design criteria and, finally, provide future perspectives on addressing a portion of the challenges via self-assembling peptide systems. We consider that the intrinsic advantages of such systems, along with the increasing progress in computational and experimental approaches for their study and design, could possibly lead to novel classes of single or multicomponent systems incorporating such materials for cancer drug delivery.

Disassembly of Amyloid Fibril with Infrared Free Electron Laser

Amyloid fibril causes serious amyloidosis such as neurodegenerative diseases. The structure is composed of rigid β-sheet stacking conformation which makes it hard to disassemble the fibril state without denaturants. Infrared free electron laser (IR-FEL) is an intense picosecond pulsed laser that is oscillated through a linear accelerator, and the oscillation wavelengths are tunable from 3 μm to 100 μm. Many biological and organic compounds can be structurally altered by the mode-selective vibrational excitations due to the wavelength variability and the high-power oscillation energy (10-50 mJ/cm²). We have found that several different kinds of amyloid fibrils in amino acid sequences were commonly disassembled by the irradiation tuned to amide I (6.1-6.2 μm) where the abundance of β-sheet decreased while that of α-helix increased by the vibrational excitation of amide bonds. In this review, we would like to introduce the IR-FEL oscillation system briefly and describe combination studies of experiments and molecular dynamics simulations on disassembling amyloid fibrils of a short peptide (GNNQQNY) from yeast prion and 11-residue peptide (NFLNCYVSGFH) from β2-microglobulin as representative models. Finally, possible applications of IR-FEL for amyloid research can be proposed as a future outlook.

Amyloid peptides with antimicrobial and/or microbial agglutination activity

Microbe (including bacteria, fungi, and virus) infection in brains is associated with amyloid fibril deposit and neurodegeneration. Increasing findings suggest that amyloid proteins, like Abeta (Aβ), are important innate immune effectors in preventing infections. In some previous studies, amyloid peptides have been linked to antimicrobial peptides due to their common mechanisms in membrane-disruption ability, while the other mechanisms of bactericidal protein aggregation and protein function knockdown are less discussed. Besides, another important function of amyloid peptides in pathogen agglutination is rarely illustrated. In this review, we summarized and divided the different roles and mechanisms of amyloid peptides against microbes in antimicrobial activity and microbe agglutination activity. Besides, the range of amyloids' antimicrobial spectrum, the effectiveness of amyloid peptide states (monomers, oligomers, and fibrils), and cytotoxicity are discussed. The good properties of amyloid peptides against microbes might provide implications for the development of novel antimicrobial drug. KEY POINTS: • Antimicrobial and/or microbial agglutination is a characteristic of amyloid peptides. • Various mechanisms of amyloid peptides against microbes are discovered recently. • Amyloid peptides might be developed into novel antimicrobial drugs.

Exploring Biomolecular Self-Assembly with Far-Infrared Radiation

Physical engineering technology using far-infrared radiation has been gathering attention in chemical, biological, and material research fields. In particular, the high-power radiation at the terahertz region can give remarkable effects on biological materials distinct from a simple thermal treatment. Self-assembly of biological molecules such as amyloid proteins and cellulose fiber plays various roles in medical and biomaterials fields. A common characteristic of those biomolecular aggregates is a sheet-like fibrous structure that is rigid and insoluble in water, and it is often hard to manipulate the stacking conformation without heating, organic solvents, or chemical reagents. We discovered that those fibrous formats can be conformationally regulated by means of intense far-infrared radiations from a free-electron laser and gyrotron. In this review, we would like to show the latest and the past studies on the effects of far-infrared radiation on the fibrous biomaterials and to suggest the potential use of the far-infrared radiation for regulation of the biomolecular self-assembly.

Environmental factors modulating protein conformations and their role in protein aggregation diseases

The adverse physiological conditions have been long known to impact protein synthesis, folding and functionality. Major physiological factors such as the effect of pH, temperature, salt and pressure are extensively studied for their impact on protein structure and homeostasis. However, in the current scenario, the environmental risk factors (pollutants) have gained impetus in research because of their increasing concentrations in the environment and strong epidemiologic link with protein aggregation disorders. Here, we review the physiological and environmental risk factors for their impact on protein conformational changes, misfolding, aggregation, and associated pathological conditions, especially environmental risk factors associated pathologies.

Emerging landscape of cell-penetrating peptide-mediated nucleic acid delivery and their utility in imaging, gene-editing, and RNA-sequencing

The safety issues like immunogenicity and unacceptable cancer risk of viral vectors for DNA/mRNA vaccine delivery necessitate the development of non-viral vectors with no toxicity. Among the non-viral strategies, cell-penetrating peptides (CPPs) have been a topic of interest recently because of their ability to cross plasma membranes and facilitate nucleic acids delivery both in vivo and in vitro. In addition to the application in the field of gene vaccine and gene therapy, CPPs based nucleic acids delivery have been proved by its potential application like gene editing, RNA-sequencing, and imaging. Here, we focus on summarizing the recent applications and progress of CPPs-mediated nucleic acids delivery and discuss the current problems and solutions in this field.

The amyloid-inhibiting NCAM-PrP peptide targets Aβ peptide aggregation in membrane-mimetic environments

Substantial research efforts have gone into elucidating the role of protein misfolding and self-assembly in the onset and progression of Alzheimer's disease (AD). Aggregation of the Amyloid-β (Aβ) peptide into insoluble fibrils is closely associated with AD. Here, we use biophysical techniques to study a peptide-based approach to target Aβ amyloid aggregation. A peptide construct, NCAM-PrP, consists of a largely hydrophobic signal sequence linked to a positively charged hexapeptide. The NCAM-PrP peptide inhibits Aβ amyloid formation by forming aggregates which are unavailable for further amyloid aggregation. In a membrane-mimetic environment, Aβ and NCAM-PrP form specific heterooligomeric complexes, which are of lower aggregation states compared to Aβ homooligomers. The Aβ:NCAM-PrP interaction appears to take place on different aggregation states depending on the absence or presence of a membrane-mimicking environment. These insights can be useful for the development of potential future therapeutic strategies targeting Aβ at several aggregation states.

Amyloid-like Self-Assembly of a Hydrophobic Cell-Penetrating Peptide and Its Use as a Carrier for Nucleic Acids

Cell-penetrating peptides (CPPs) are a topical subject potentially exploitable for creating nanotherapeutics for the delivery of bioactive loads. These compounds are often classified into three major categories according to their physicochemical characteristics: cationic, amphiphilic, and hydrophobic. Among them, the group of hydrophobic CPPs has received increasing attention in recent years due to toxicity concerns posed by highly cationic CPPs. The hexapeptide PFVYLI (P, proline; F, phenylalanine; V, valine; Y, tyrosine; L, leucine; and I, isoleucine), a fragment derived from the C-terminal portion of α1-antitrypsin, is a prototypal example of hydrophobic CPP. This sequence shows reduced cytotoxicity and a capacity of nuclear localization, and its small size readily hints at its suitability as a building block to construct nanostructured materials. In this study, we examine the self-assembling properties of PFVYLI and investigate its ability to form noncovalent complexes with nucleic acids. By using a combination of biophysical tools including synchrotron small-angle X-ray scattering and atomic force microscopy-based infrared spectroscopy, we discovered that this CPP self-assembles into discrete nanofibrils with remarkable amyloidogenic features. Over the course of days, these fibrils coalesce into rodlike crystals that easily reach the micrometer range. Despite lacking cationic residues in the composition, PFVYLI forms noncovalent complexes with nucleic acids that retain β-sheet pairing found in amyloid aggregates. In vitro vectorization experiments performed with double-stranded DNA fragments indicate that complexes promote the internalization of nucleic acids, revealing that tropism toward cell membranes is preserved upon complexation. On the other hand, transfection assays with splice-correction oligonucleotides (SCOs) for luciferase expression show limited bioactivity across a narrow concentration window, suggesting that the propensity to form amyloidogenic aggregates may trigger endosomal entrapment. We anticipate that the findings presented here open perspectives for using this archetypical hydrophobic CPP in the fabrication of nanostructured scaffolds, which potentially integrate properties of amyloids and translocation capabilities of CPPs.

Biomolecules from Different Angles

Special Issue "2019 Feature Papers by Biomolecules' Editorial Board Members" represents a set of papers based on the results of the research in the laboratories of the Editorial Board Members (EBMs) of Biomolecules focused (a big surprise!) on different aspects of biomolecules [...].

Ultrashort Cell-Penetrating Peptides for Enhanced Sonophoresis-Mediated Transdermal Transport

The skin is a key site for drug administration because of its large surface area and noninvasive accessibility. However, the dermal architecture serves as an excellent barrier, protecting from external mechanical, chemical, microbial, and physical perturbations. Most drugs display poor permeability through this barrier, thus making dermal and subdermal delivery challenging. Cell-penetrating peptides (CPPs), a diverse group of relatively short cationic and amphipathic membrane-interacting peptides, are fast becoming an important class of drug carriers and could potentially be developed for the dermal delivery of active molecules. However, the mechanism of CPP transdermal delivery is not fully understood, and there is a genuine need for a minimal model to understand this important phenomenon. Here, we demonstrate the potent membrane interactions of a minimal four-amino-acid-long CPP as well as the significance of guanidinium patterning and cationic nature of this palindromic peptide on its bioactivity. Furthermore, we demonstrate the biocompatibility of this peptide as well as its rapid cellular uptake and endosomal distribution. Finally, by utilizing a porcine full-thickness skin model, we demonstrate the substantial independent dermal and sonophoresis-based transdermal penetration of this minimal model. These results provide a minimal model for CPPs which can be easily manipulated for further biophysical and biochemical evaluations as well as a potent functional CPP with excellent skin permeability, which can be utilized for a wide variety of cosmetic and medical applications.

Amyloid-Like Peptide Aggregates

Self-assembly of proteins and peptides into the amyloid fold is a widespread phenomenon in the natural world. The structural hallmark of self-assembly into amyloid fibrillar assemblies is the cross-beta motif, which conveys distinct morphological and mechanical properties. The amyloid fibril formation has contrasting results depending on the organism, in the sense that it can bestow an organism with the advantages of mechanical strength and improved functionality or, on the contrary, could give rise to pathological states. In this chapter we review the existing information on amyloid-like peptide aggregates, which could either be derived from protein sequences, but also could be rationally or de novo designed in order to self-assemble into amyloid fibrils under physiological conditions. Moreover, the development of self-assembled fibrillar biomaterials that are tailored for the desired properties towards applications in biomedical or environmental areas is extensively analyzed. We also review computational studies predicting the amyloid propensity of the natural amino acid sequences and the structure of amyloids, as well as designing novel functional amyloid materials.

"What Doesn't Kill You Makes You Stronger": Future Applications of Amyloid Aggregates in Biomedicine

Amyloid proteins are linked to the pathogenesis of several diseases including Alzheimer's disease, but at the same time a range of functional amyloids are physiologically important in humans. Although the disease pathogenies have been associated with protein aggregation, the mechanisms and factors that lead to protein aggregation are not completely understood. Paradoxically, unique characteristics of amyloids provide new opportunities for engineering innovative materials with biomedical applications. In this review, we discuss not only outstanding advances in biomedical applications of amyloid peptides, but also the mechanism of amyloid aggregation, factors affecting the process, and core sequences driving the aggregation. We aim with this review to provide a useful manual for those who engineer amyloids for innovative medicine solutions.