Peptide-Decorated Dendrimers and Their Bioapplications

Dexamethasone loaded DNA scavenger nanogel for systemic lupus erythematosus treatment

Lupus nephritis (LN) poses a severe risk for individuals with systemic lupus erythematosus (SLE), prompting extensive research into targeted delivery systems capable of modulating immune responses and clearing cell-free DNA (cfDNA). Here, we propose a novel renal homing nanogel that acts as a cfDNA scavenger and a dexamethasone (DXM) delivery carrier for LN treatment. Based on the generation 3 polylysine dendrimers, the created cationic nanogels (G3DSP) exhibit minimal toxicity and outstanding DXM loading efficiency. Our studies confirm that these nanogels can competitively bind with anionic cfDNA in vitro, leading to the suppression of toll-like receptor 9 (TLR9) activation. When administered systemically to MRL/lpr mice, the nanogels preferentially localize to and are retained in the inflamed kidneys, releasing their payload in response to reactive oxygen species (ROS), therefore effectively ameliorating SLE symptoms. Consequently, G3DSP nanogels emerge as a promising effective combined therapy for LN, minimizing cfDNA accumulation in vital organs and delivering immunomodulatory benefits through DXM.

Dendrimers, Dendrons, and the Dendritic State: Reflection on the Last Decade with Expected New Roles in Pharma, Medicine, and the Life Sciences

This perspective begins with an overview of the major impact that the dendron, dendrimer, and dendritic state (DDDS) discovery has made on traditional polymer science. The entire DDDS technology is underpinned by an unprecedented new polymerization strategy referred to as step-growth, amplification-controlled polymerization (SGACP). This new SGACP paradigm allows for routine polymerization of common monomers and organic materials into precise monodispersed, dendritic macromolecules (i.e., dendrons/dendrimers) with nanoscale sizes and structure-controlled features that match and rival discrete in vivo biopolymers such as proteins and nucleic acids (i.e., DNA, siRNA, mRNA, etc.). These dendritic architectures exhibit unprecedented new intrinsic properties widely recognized to define a new fourth major polymer architecture class, namely: Category (IV): dendrons, dendrimers, and random hyperbranched polymers after traditional categories: (I) linear, (II) cross-linked, and (III) simple-branched types. Historical confusion over the first examples of the structure confirmed and verified cascade, dendron, dendrimer, and arborol syntheses, while associated misuse of accepted dendritic terminology is also reviewed and clarified. The importance of classifying all dendrons and dendrimers based on branch cell symmetry and the significant role of critical nanoscale-design parameters (CNDPs) for optimizing dendritic products for pharma/nanomedicine applications with a focus on enhancing stealth, non-complement activation properties is presented. This is followed by an overview of the extraordinary growth observed for amphiphilic dendron/dendrimer syntheses and their self-assembly into dendritic supramolecular assemblies, as well as many unique applications demonstrated in pharma and nanomedicine, especially involving siRNA delivery and mRNA vaccine development. This perspective is concluded with optimistic expectations predicted for new dendron and dendrimer application roles in pharma, nanomedicine, and life sciences.

Access to Diverse Glutamic Acid Dendrons and a Janus Peptide Dendrimer Using an Atypical Solid Phase Synthesis

The negligible cytotoxicity of anion surface-linked dendrons makes glutamic acid-based dendrons a potential candidate for materials and biological applications. Despite the inherent drawbacks of the conventional solution phase synthesis of glutamic acid-based dendrons, there have been no advancements in these protocols. Herein, we demonstrate the first-ever convergent solid phase synthesis of dendrons, up to fourth generation, having glutamic acid branching points produced by preactivation of dicarboxylic acid groups with N-hydroxysuccinimide and simultaneous coupling with amine groups of two growing peptide chains, with excellent yields (30-70%). In addition to the general advantages, such as the easy workup, a final single purification step, and an overall short synthesis duration, the convergent solid phase synthesis allowed us to chemically synthesize glutamic acid branching-based dendrons that cannot be accessed by standard divergent solid phase synthesis. This method has also been validated for its application in synthesizing hard-to-achieve Janus peptide dendrimers in a single stretch on a solid support. Our work corroborates the efficacy of controlled -COOH activation to accomplish an atypical solid phase synthesis of diverse glutamic acid dendrons in a convergent fashion. This is the first example of a Janus peptide dendrimer being synthesized on a solid support, utilizing both convergent and divergent approaches simultaneously.

Non-canonical amino acid bioincorporation into antimicrobial peptides and its challenges

The rise of antimicrobial resistance and multi-drug resistant pathogens has necessitated explorations for novel antibiotic agents as the discovery of conventional antibiotics is becoming economically less viable and technically more challenging for biopharma. Antimicrobial peptides (AMPs) have emerged as a promising alternative because of their particular mode of action, broad spectrum and difficulty that microbes have in becoming resistant to them. The AMPs bacitracin, gramicidin, polymyxins and daptomycin are currently used clinically. However, their susceptibility to proteolytic degradation, toxicity profile, and complexities in large-scale manufacture have hindered their development. To improve their proteolytic stability, methods such as integrating non-canonical amino acids (ncAAs) into their peptide sequence have been adopted, which also improves their potency and spectrum of action. The benefits of ncAA incorporation have been made possible by solid-phase peptide synthesis. However, this method is not always suitable for commercial production of AMPs because of poor yield, scale-up difficulties, and its non-'green' nature. Bioincorporation of ncAA as a method of integration is an emerging field geared towards tackling the challenges of solid-phase synthesis as a green, cheaper, and scalable alternative for commercialisation of AMPs. This review focusses on the bioincorporation of ncAAs; some challenges associated with the methods are outlined, and notes are given on how to overcome these challenges. The review focusses particularly on addressing two key challenges: AMP cytotoxicity towards microbial cell factories and the uptake of ncAAs that are unfavourable to them. Overcoming these challenges will draw us closer to a greater yield and an environmentally friendly and sustainable approach to make AMPs more druggable.

Dendritic nanoparticles for immune modulation: a potential next-generation nanocarrier for cancer immunotherapy

Immune activation, whether occurring from direct immune checkpoint blockade or indirectly as a result of chemotherapy, is an approach that has drastically impacted the way we treat cancer. Utilizing patients' own immune systems for anti-tumor efficacy has been translated to robust immunotherapies; however, clinically significant successes have been achieved in only a subset of patient populations. Dendrimers and dendritic polymers have recently emerged as a potential nanocarrier platform that significantly improves the therapeutic efficacy of current and next-generation cancer immunotherapies. In this paper, we highlight the recent progress in developing dendritic polymer-based therapeutics with immune-modulating properties. Specifically, dendrimers, dendrimer hybrids, and dendronized copolymers have demonstrated promising results and are currently in pre-clinical development. Despite their early stage of development, these nanocarriers hold immense potential to make profound impact on cancer immunotherapy and combination therapy. This overview provides insights into the potential impact of dendrimers and dendron-based polymers, offering a preview of their potential utilities for various aspects of cancer treatment.

Peptide Dendrimer-Based Antibacterial Agents: Synthesis and Applications

Pathogenic bacteria cause the deaths of millions of people every year. With the development of antibiotics, hundreds and thousands of people's lives have been saved. Nevertheless, bacteria can develop resistance to antibiotics, rendering them insensitive to antibiotics over time. Peptides containing specific amino acids can be used as antibacterial agents; however, they can be easily degraded by proteases in vivo. To address these issues, branched peptide dendrimers are now being considered as good antibacterial agents due to their high efficacy, resistance to protease degradation, and low cytotoxicity. The ease with which peptide dendrimers can be synthesized and modified makes them accessible for use in various biological and nonbiological fields. That is, peptide dendrimers hold a promising future as antibacterial agents with prolonged efficacy without bacterial resistance development. Their in vivo stability and multivalence allow them to effectively target multi-drug-resistant strains and prevent biofilm formation. Thus, it is interesting to have an overview of the development and applications of peptide dendrimers in antibacterial research, including the possibility of employing machine learning approaches for the design of AMPs and dendrimers. This review summarizes the synthesis and applications of peptide dendrimers as antibacterial agents. The challenges and perspectives of using peptide dendrimers as the antibacterial agents are also discussed.

Advances in targeted tracking and detection of soluble amyloid-β aggregates as a biomarker of Alzheimer's disease

Misfolding and aggregation of amyloid-β (Aβ) peptides are key hallmarks of Alzheimer's disease (AD). With accumulating evidence suggesting that different Aβ species have varied neurotoxicity and implications in AD development, the discovery of affinity ligands and analytical approaches to selective distinguish, detect, and monitor Aβ becomes an active research area. Remarkable advances have been achieved, which not only promote our understanding of the biophysical chemistry of the protein aggregation during neurodegeneration, but also provide promising tools for early detection of the disease. In view of this, we summarize the recent progress in selective and sensitive approaches for tracking and detection of Aβ species. Specific attentions are given to soluble Aβ oligomers, due to their crucial roles in AD development and occurrence at early stages. The design principle, performance of targeting units, and their cooperative effects with signal reporters for Aβ analysis are discussed. The applications of the novel targeting probes and sensing systems for dynamic monitoring oligomerization, measuring Aβ in biosamples and in vivo imaging in brain are summarized. Finally, the perspective and challenges are discussed regarding the future development of Aβ-targeting analytical tools to explore the unknown field to contribute to the early diagnosis and treatment of AD.

Polyvalent aptamer scaffold coordinating light-responsive oxidase-like nanozyme for sensitive detection of zearalenone

An efficient aptasensor was developed for the colorimetric determination of zearalenone (ZEN) based on polyvalent aptamer scaffold and light-responsive oxidase-like nanozyme. The sensitivity and efficiency of the development method were significantly improved owing to rich aptamers and signal labels (3, 4-dihydroxybenzoic acid, PCA) packed in the scaffold. The scaffold integrated functions of target recognition, surface immobilization and signal transduction. The photoresponsive nanoenzyme of TiO2-PCA was formed by PCA coordinated with Ti (IV) on the surface of TiO2. TiO2-PCA catalyzed dissolved oxygen rather than H2O2 to generate colorimetric signal by stimulating the chromogenic substrate, which made the assay greener and safer. The detection limit of colorimetric mode was 0.0087 ng/mL and the satisfactory recoveries 92.00 %-111.00 % were achieved in spiked food samples. This strategy opens new horizons for sensitive detection of small molecule hazards and promises to be a powerful tool for safeguarding food safety.

Branched Multimeric Peptides as Affinity Reagents for the Detection of α-Klotho Protein

α-Klotho, an aging-related protein found in the kidney, parathyroid gland, and choroid plexus, acts as an essential co-receptor with the fibroblast growth factor 23 receptor complex to regulate serum phosphate and vitamin D levels. Decreased levels of α-Klotho are a hallmark of age-associated diseases. Detecting or labeling α-Klotho in biological milieu has long been a challenge, however, hampering the understanding of its role. Here, we developed branched peptides by single-shot parallel automated fast-flow synthesis that recognize α-Klotho with improved affinity relative to their monomeric versions. These peptides were further shown to selectively label Klotho for live imaging in kidney cells. Our results demonstrate that automated flow technology enables rapid synthesis of complex peptide architectures, showing promise for future detection of α-Klotho in physiological settings.

Self-Assembly of Antimicrobial Peptide-Based Micelles Breaks the Limitation of Trypsin

Targeting the limitation of antimicrobial peptides (AMPs) application in vivo, self-assembled AMPs library with specific nanostructures is expected to gradually overtake monomer AMPs libraries in the future. Peptide polymers are fascinating self-assembling nanoscale structures that have great advantage in biomedical applications because of their satisfactory biocompatibility and versatile properties. Herein, we describe a strategy for inducing the self-assembly of T9W into nanostructured antimicrobial micelles with evidently improved pharmacological properties, that is, PEGylation at the C-terminal of T9W (CT9W₁₀₀₀), an antibacterial biomaterial that self-assembles in aqueous media without exogenous excipients, has been developed. Compared with parental molecular, the CT9W₁₀₀₀ is more effective against Pseudomonas aeruginosa, and its antibacterial spectrum had also been broadened. Additionally, CT9W₁₀₀₀ micelles had higher stability under salt ion, serum, and acid-base environments. Importantly, the self-assembled structure is highly resistant to trypsin degradation, probably allowing T9W to be applied in clinical settings in the future. Mechanistically, by acting on membranes and through supplementary bactericidal mechanisms, CT9W₁₀₀₀ micelles contribute to the antibacterial process. Collectively, CT9W₁₀₀₀ micelles exhibited good biocompatibility in vitro and in vivo, resulting in highly effective treatment in a mouse acute lung injury model induced by P. aeruginosa PAO1 without drug resistance. These advances may profoundly accelerate the clinical transformation of T9W and promote the development of a combination of peptide-based antibiotics and PEGylated nanotechnology.

Peptide mimotopes to emulate carbohydrates

Glycoconjugates on animal cell surfaces are involved in numerous biological functions and diseases, especially the adhesion/metastasis of cancer cells, infection, and the onset of glycan-related diseases. In addition to glycoantigen detection, the regulation of glycan (carbohydrate)-protein interactions is needed to develop therapeutic strategies for glycan-related diseases. Preparation of a diverse range of glycan derivatives requires a massive effort, but the preparation and identification of alternative glycan-mimetic peptide mimotopes may provide a solution to this issue. Peptide mimotopes are recognized by glycan-binding proteins, such as lectins, enzymes, and antibodies, alternative to glycan ligands. Phage-display technology is the first choice in the selection of "glycan (carbohydrate)-mimetic peptide mimotopes" from a large repertoire of library sequences. This tutorial review describes the advantages of peptide mimotopes in comparison to glycan ligands, as well as their structural and functional mimicry. The detailed library design is followed by a description of the strategy used to improve affinity, and finally, an outline of the vaccine application of glycan-mimetic peptides is provided.

Tumor-oriented mathematical models in hydrogel regulation for precise topical administration regimens

Increasing knowledge of drug delivery properties, tumor profiles and their relationship promotes precise administration regimens, representing a promising pattern to personalized tumor treatment. Herein, we propose a regulatory hydrogel depot toward metastatic cancer by establishing mathematical models between tumor characteristics and administration regimens. Specifically, a thermo-sensitive PLGA-PEG-PLGA polymer is introduced as injectable hydrogel matrix, of which the administration volume and frequency are manipulated elaborately according to tumor size and gel-degradation kinetics. Structurally, doxorubicin (Dox) and arginine-terminated nanoparticles containing KIAA1199 specific shRNA (shKIAARPDNs) are incorporated into hydrogels, thereby formulating a topical and sustained drug depot to achieve synergy treatment. For dual-targeting therapy, Dox interdicts DNA replication/transcription, and shKIAA persistently silences KIAA1199 protein to modulate aggressive phenotypes. After individual peritumoral injection, Gel/shKIAARPDNs/Dox demonstrates desirable distribution patterns and gel degradation kinetics with enhanced tumor penetration. Moreover, a preferable inhibition of tumor proliferation and metastasis is confirmed after twice treatment in 12 days, indicating better therapeutic efficacy with less dosage and frequency. Consequently, the controllable administration regimen inspired mathematical models of thermosensitive hydrogel provides an intelligent platform for personalized treatment to metastatic cancer.

Self-assembly of Peptide dendrimers and their bio-applications in theranostics

Nanotechnology has brought revolutionized advances in disease diagnosis and therapy. Self-assembled peptide dendrimers own novel physicochemical properties through the synergistic effects of the polypeptide chain, dendrimer and nano-structure, exhibiting great potential in theranostic. This review provides comprehensive insights into various peptide dendrimers for self-assembly. Their nanosize, morphology and composition are presented to understand self-assembly behaviors precisely. We further introduce the emerging theranostic applications based on specific imaging and efficient delivery recently.

Peptide Multimerization as Leads for Therapeutic Development

Multimerization of peptide structures has been a logical evolution in their development as potential therapeutic molecules. The multivalent properties of these assemblies have attracted much attention from researchers in the past and the development of more complex branching dendrimeric structures, with a wide array of biocompatible building blocks is revealing previously unseen properties and activities. These branching multimer and dendrimer structures can induce greater effect on cellular targets than monomeric forms and act as potent antimicrobials, potential vaccine alternatives and promising candidates in biomedical imaging and drug delivery applications. This review aims to outline the chemical synthetic innovations for the development of these highly complex structures and highlight the extensive capabilities of these molecules to rival those of natural biomolecules.

A manganese (II)-based coordinative dendrimer with robust efficiency in intracellular peptide delivery

Peptides have gained increasing interests as drug candidates in modern pharmaceutical industry, however, the development of peptide drugs acting on intracellular targets is limited due to their membrane impermeability. Here, we reported the use of metal-terpyridine based coordinative dendrimer for cytosolic peptide delivery. Among the investigated transition metal ions, Mn²⁺-coordinated polymer showed the highest delivery efficiency due to balanced peptide binding and release. It showed robust efficiency in the delivery of peptides with different charge property and hydrophobicity into various primary cells. The efficiency of Mn²⁺-terpyridine based polymer is superior to cell penetrating peptides such as oligoarginines. The material also delivered an autophagy-inducing peptide derived from Beclin-1 into cells and efficiently induced autophagy in the cells. This study provides a promising alternative to cell penetrating peptides for cytosolic peptide delivery.

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A Mn²⁺/terpyridine based polymer is rationally designed for cytosolic peptide delivery.

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The polymer shows robust efficiency in the delivery of 22 peptides with different properties into various primary cells.

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The polymer delivers an autophagy-inducing peptide derived from Beclin-1 into cells and efficiently induces autophagy.

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This study provides a promising alternative to cell penetrating peptides for cytosolic peptide delivery.

Antiviral Peptides with in vivo Activity: Development and Modes of Action

The viral pandemic has resulted in a growing demand for antiviral drugs. The existing small-molecule antiviral drugs are limited, due to their incidence of drug resistance and adverse side effects. As potential drugs, antiviral peptides have the benefits of high activity, high stability, and few side effects. Furthermore, the diversity of acquisition methods allows antiviral peptides to be quickly designed and yielded. The drug properties (such as high bioavailability and in vivo stability) of antiviral peptides can be improved by the developed modifications. Currently, two peptide antiviral drugs have been approved for the treatment of acquired immunodeficiency syndrome (AIDS). Many antiviral peptides have entered clinical trials for the treatment of diseases caused by viruses. In addition, new antiviral peptides are continuously being identified and validated against virus infections. Given the benefits of antiviral peptides, they will become major antiviral drugs to combat new outbreaks caused by unknown viruses in the future. This review provides an overview of recent developments in antiviral peptides with in vivo activity.

Molecular level precision and high molecular weight peptide dendrimers for drug-specific delivery

Peptide dendrimers have a broad application in biomedical science due to their biocompatibility, diversity, and multifunctionality, but the precision synthesis of high-molecule weight peptide dendrimers remains challenging. We here report the facile and liquid-phase synthesis of molecular level precision and amino-acid built-in polylysine (PLL) dendrimers with molecular weights as high as ∼60 kDa. Three types of polyhedral oligosilsesquioxane (POSS)-cored PLL dendrimers with phenylalanine, tyrosine, or histidine as building blocks were synthesized. The precise structures of the dendrimers were confirmed by MALDI-TOF MS, GPC, and ¹H NMR spectroscopy. The interior functionalized peptide dendrimers improved the encapsulation capability of SN38 and sustained the release profiles. Enhanced molecular interactions between the peptide dendrimers and drugs were explored by both NMR experiments and computer simulations. The peptide dendrimer/SN38 formulations showed potent antitumor activity against multiple cancer cell lines. We believe that this strategy can be applied to the synthesis of tailor-made functional peptide dendrimers for drug-specific delivery and other diverse biomedical applications.

Self-Assembling Peptide Dendron Nanoparticles with High Stability and a Multimodal Antimicrobial Mechanism of Action

Self-assembling nanometer-scale structured peptide polymers and peptide dendrimers have shown promise in biomedical applications due to their versatile properties and easy availability. Herein, self-assembling peptide dendron nanoparticles (SPDNs) with potent antimicrobial activity against a range of bacteria were developed based on the nanoscale self-assembly of an arginine-proline repeat branched peptide dendron bearing a hexadecanoic acid chain. The SPDNs are biocompatible, and our most active peptide dendron nanoparticle, C₁₆-3RP, was found to have negligible toxicity after both in vitro and in vivo studies. Furthermore, the C₁₆-3RP nanoparticles showed excellent stability under physiological concentrations of salt ions and against serum and protease degradation, resulting in highly effective treatment in a mouse acute peritonitis model. Comprehensive analyses using a series of biofluorescence, microscopy, and transcriptome sequencing techniques revealed that C₁₆-3RP nanoparticles kill Gram-negative bacteria by increasing bacterial membrane permeability, inducing cytoplasmic membrane depolarization and drastic membrane disruption, inhibiting ribosome biogenesis, and influencing energy generation and other processes. Collectively, C₁₆-3RP nanoparticles show promising biocompatibility and in vivo therapeutic efficacy without apparent resistance development. These advancements may facilitate the development of peptide-based antibiotics in clinical settings.

Chemically modified and conjugated antimicrobial peptides against superbugs

Antimicrobial resistance (AMR) is one of the greatest threats to human health that, by 2050, will lead to more deaths from bacterial infections than cancer. New antimicrobial agents, both broad-spectrum and selective, that do not induce AMR are urgently required. Antimicrobial peptides (AMPs) are a novel class of alternatives that possess potent activity against a wide range of Gram-negative and positive bacteria with little or no capacity to induce AMR. This has stimulated substantial chemical development of novel peptide-based antibiotics possessing improved therapeutic index. This review summarises recent synthetic efforts and their impact on analogue design as well as their various applications in AMP development. It includes modifications that have been reported to enhance antimicrobial activity including lipidation, glycosylation and multimerization through to the broad application of novel bio-orthogonal chemistry, as well as perspectives on the direction of future research. The subject area is primarily the development of next-generation antimicrobial agents through selective, rational chemical modification of AMPs. The review further serves as a guide toward the most promising directions in this field to stimulate broad scientific attention, and will lead to new, effective and selective solutions for the several biomedical challenges to which antimicrobial peptidomimetics are being applied.

Engineering Peptide-Functionalized Biomimetic Nanointerfaces for Synergetic Capture of Circulating Tumor Cells in an EpCAM-Independent Manner

Broad-spectrum detection and long-term monitoring of circulating tumor cells (CTCs) remain challenging due to the extreme rarity, heterogeneity, and dynamic nature of CTCs. Herein, a dual-affinity nanostructured platform was developed for capturing different subpopulations of CTCs and monitoring CTCs during treatment. Stepwise assembly of fibrous scaffolds, a ligand-exchangeable spacer, and a lysosomal protein transmembrane 4 β (LAPTM4B)-targeting peptide creates biomimetic, stimuli-responsive, and multivalent-binding nanointerfaces, which enable harvest of CTCs directly from whole blood with high yield, purity, and viability. The stable overexpression of the target LAPTM4B protein in CTCs and the enhanced peptide-protein binding facilitate the capture of rare CTCs in patients at an early stage, detection of both epithelial-positive and nonepithelial CTCs, and tracking of therapeutic responses. The reversible release of CTCs allows downstream molecular analysis and identification of specific liver cancer genes. The consistency of the information with clinical diagnosis presents the prospect of this platform for early diagnosis, metastasis prediction, and prognosis assessment.

The multifaceted nature of antimicrobial peptides: current synthetic chemistry approaches and future directions

Bacterial infections caused by 'superbugs' are increasing globally, and conventional antibiotics are becoming less effective against these bacteria, such that we risk entering a post-antibiotic era. In recent years, antimicrobial peptides (AMPs) have gained significant attention for their clinical potential as a new class of antibiotics to combat antimicrobial resistance. In this review, we discuss several facets of AMPs including their diversity, physicochemical properties, mechanisms of action, and effects of environmental factors on these features. This review outlines various chemical synthetic strategies that have been applied to develop novel AMPs, including chemical modifications of existing peptides, semi-synthesis, and computer-aided design. We will also highlight novel AMP structures, including hybrids, antimicrobial dendrimers and polypeptides, peptidomimetics, and AMP-drug conjugates and consider recent developments in their chemical synthesis.

Increased Valency Improves Inhibitory Activity of Peptides Targeting Proprotein Convertase Subtilisin/Kexin Type 9 (PCSK9)

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a clinically validated target for treating hypercholesterolemia. Peptide-based PCSK9 inhibitors have attracted pharmaceutical interest, but the effect of multivalency on bioactivity is poorly understood. Here we designed bivalent and tetravalent dendrimers, decorated with the PCSK9 inhibitory peptides Pep2-8[RRG] or P9-38, to study relationships between peptide binding affinity, peptide valency, and PCSK9 inhibition. Increased valency resulted in improved PCSK9 inhibition for both peptides, with activity improvements of up to 100-fold achieved for the P9-38-decorated dendrimers compared to monomeric P9-38 in in vitro competition binding assays. Furthermore, the P9-38-decorated dendrimers showed improved potency at restoring functional low-density lipoprotein (LDL) receptor levels and internalizing LDL in the presence of PCSK9, demonstrating significant cell-based activity at picomolar concentrations. This study demonstrates the potential of increasing valency as a strategy for increasing the efficacy of peptide-based PCSK9 therapeutics.

Polyvalent Biotinylated Aptamer Scaffold for Rapid and Sensitive Detection of Tau Proteins

Biomimetic construction of artificial scaffolds has attracted increasing attention. However, the construction methods usually require redundant materials and procedures, which is inconvenient for further application. Herein, inspired by the polyvalent multifunctional structure in nature, we have designed a polyvalent biotinylated aptamer scaffold (PBAS) which can conduct analytical performance with high sensitivity and simplified procedures. To construct a PBAS, the aptamers are designed to hybridize with prepared linker probes to form polyvalent biotinylated scaffolds, which contain both multiple aptamers and signal labels. Therefore, multifunctional scaffolds can be constructed with high recognition and capture efficiency as well as significant signal amplification. Furthermore, the scaffold can be used for the assay of some disease marker proteins. By taking tau proteins as an example, the proposed aptasensor can exhibit excellent performance with a low detection limit of 153 pg mL^-1 and a short assay time of 50 min, which is much better than most of the previous methods. By assays of tau proteins in both serum and artificial cerebro spinal fluid, the PBAS-based aptasensor can work well. Therefore, the scaffold may be expected to be a powerful analytical tool which may have wide applications in the detection of a variety of analytes.

Silver (I) N-Heterocyclic Carbenes Carbosilane Dendritic Systems and Their Imidazolium-Terminated Analogues as Antibacterial Agents: Study of Their Mode of Action

Spherical dendrimers and dendrons containing silver(I) N-heterocyclic carbenes (Ag(I)-NHC) and additionally bow-tie metal-free dendritic systems were synthesized in a simple and straightforward synthetic procedure and subsequently characterized. The antibacterial activity was evaluated, and in parallel, a comparative study with the cationic analogue precursors was performed to explore the effect of silver ions in the dendritic structure. Other parameters, such as topology, generation, and hydrophobicity, of the imidazole substituents were also studied. All these dendritic systems presented antibacterial activity against three different bacterial strains, two Gram-positive (Staphylococcus aureus and Bacillus subtilis) and one Gram-negative (Escherichia coli). Several assays were conducted to elucidate their mechanism of action against Bacillus subtilis, by using bacterial biosensors or specific probes and fluorescent proteins sensitive to changes in the cell membrane potential. These studies are specially focused on the role of the polyvalence of our systems containing silver atoms, which may provoke interesting effects in the mode of action.

Dendrimer Conjugation Enhances Tumor Penetration and Efficacy of Doxorubicin in Extracellular Matrix-Expressing 3D Lung Cancer Models

Doxorubicin (DOX) is a chemotherapeutic agent broadly used in the treatment of a range of solid tumors. In spite of its high potency, as is the case for many other chemotherapeutic drugs, there are many challenges associated with the use of DOX in clinical oncology. This is particularly true for DOX in the treatment of lung cancer, where in vitro potency is shown to be very high, but low lung distribution and off-target toxicity (particularly cardiotoxicity) restrict its use. Nanocarrier-based drug delivery systems (nanoDDS) have been shown to help alter biodistribution and alleviate off-target toxicity associated with DOX. While significant understanding exists regarding the design parameters to achieve those clinical benefits, much less is known regarding the design of nanoDDS capable of enhancing tumor penetration of DOX (and other drugs), which is another major factor leading to DOX's reduced efficacy. The purpose of this study was to design a dendrimer-based nanoDDS capable of enhancing the penetration of DOX as measured in an in vitro 3D lung tumor model and to correlate those results with its efficacy. Spheroids formed with the A549 human lung adenocarcinoma cells/murine fibroblast cell line (NIH/3T3 cell line) are shown to produce the essential components of the extracellular matrix (ECM), which is known as a physical barrier that hinders the transport of DOX. DOX was conjugated to generation 4 succinamic acid-terminated poly(amido-amine) (PAMAM) dendrimers (G4SA) through an enzyme-liable tetrapeptide (G4SA-GFLG-DOX), resulting in a nanoDDS with ∼5.5 DOX, -17 mV surface (ζ) potential, and a 10 nm hydrodynamic diameter (HD). The penetration of DOX to the core of the spheroid in terms of DOX fluorescence was determined to be 3.1-fold greater compared to free DOX, which positively correlated with enhanced efficacy as measured by the Caspase 3/7 assay. This improved penetration happens as the interactions between the G4SA-GFLG-DOX and the highly negatively charged ECM are minimized by shielding the protonatable amine of DOX upon conjugation, and the HD of the conjugate is kept smaller than the estimated mesh size of the ECM. Interestingly, the conjugate provided more specificity for DOX to tumor cells compared to fibroblasts, while free DOX is equally distributed in both tumor and fibroblasts as assessed in the coculture spheroids. Growth inhibition studies show that the released DOX maintains its activity and leads to tumor reduction to the same extent as free DOX. The results obtained here are of relevance for the design of dendrimer-based nanoDDS and for the treatment of solid tumors as they provide critical information regarding desirable surface characteristics and sizes for efficient tumor penetration.

Rational Design and In Vitro Evaluation of Novel Peptides Binding to Neuroligin-1 for Synaptic Targeting

Neuroligin-1 (NL1) is a postsynaptic cell adhesion protein that plays a crucial role in synapsis and signaling between neurons. Due to its clustered distribution in synaptic clefts, NL1 appears as a novel potential site for synaptic targeting purposes. In this work, in silico protein topography analysis was employed to identify two prospective binding sites on the NL1 dimer surface in the 2:2 synaptic adhesion complex with β-neurexin (PDB code 3B3Q ). Receptor-based rational design, cell-penetrating capability prediction, molecular docking, molecular dynamics simulations, and binding free energy calculations were used to identify five heptapeptides candidates with favorable predicted profiles as non cell-penetrating NL1-binding agents. Preliminary in vitro colocalization assays with NL1-transfected HEK 293 cells confirmed that peptides remain in the extracellular space without inducing detectable changes in cell morphology. The highest NL1-colocatization capability was attained by the peptide ADEAIVA, which appears as a promising candidate for the future development of specific NL1-targeting systems as part of synapse-directed therapies against central nervous system diseases.

Nanoparticles with surface features of dendritic oligopeptides as potential oral drug delivery systems

Endowing the NPs with specific surface features of dendritic oligopeptides holds great potential for the oral delivery of peptide/protein drugs.

Natural protein bioinspired materials for regeneration of hard tissues

This review describes the protein bioinspired materials for the repair of hard tissues such as enamel, dentin and bone.

A KLVFFAE-Derived Peptide Probe for Detection of Alpha-Synuclein Fibrils

Aggregation of an amyloid protein, α-synuclein (αS), is a critical step in the neurodegenerative pathway of Parkinson's diseases (PD). Specific detection of amyloid conformers (i.e., monomers, oligomers, and fibrils) produced during αS aggregation is critical in better understanding a molecular basis of PD and developing a diagnostic tool. While various molecular probes are available for detection of αS fibrils, which may serve as a reservoir of toxic αS aggregate forms, these probes suffer from limited conformer-specificity and operational flexibility. In the present study, we explored the potential of non-self-aggregating peptides derived from the highly aggregation-prone KLVFFAE region of an amyloid protein, β-amyloid, as molecular probes for αS aggregates. We show that of the four peptides tested (KLVFWAK, ELVFWAE, and their C-terminal capping variants, all of which were attached with fluorescein isothiocyanate at their respective N-termini), KLVFWAK with C-terminal capping was selectively bound to αS fibrils over monomers and oligomers and readily used for monitoring αS fibrilization. Our analyses suggest that binding of the peptide to αS fibrils is mediated by both electrostatic and hydrophobic interactions. We anticipate that our peptide can readily be optimized for conformer-specificity and operational flexibility. Overall, this study presents the creation of a KLVFFAE-based molecular probe for αS fibrils and demonstrates fine-tuning of its conformer-specificity by terminal mutations and capping.

Targeting Peptide-Based Probes for Molecular Imaging and Diagnosis

A series of novel peptide-based molecular probes for different biomarkers is highlighted herein. These probes can provide targeted recognition with high affinity, high specificity, high penetration, and rapid excretion ability. These sensitive peptides can achieve rapid and specific detection when they are conjugated with imaging moieties or are formed into nanoprobes, which can be adapted for in vivo molecular imaging in targeted diagnosis and therapy.

Designer Peptide and Protein Dendrimers: A Cross-Sectional Analysis

Dendrimers have attracted immense interest in science and technology due to their unique chemical structure that offers a myriad of opportunities for researchers. Dendritic design allows us to present peptides in a branched three-dimensional fashion that eventually leads to a globular shape, thus mimicking globular proteins. Peptide dendrimers, unlike other classes of dendrimers, have immense applications in biomedical research due to their biological origin. The diversity of potential building blocks and innumerable possibilities for design, along with the fact that the area is relatively underexplored, make peptide dendrimers sought-after candidates for various applications. This review summarizes the stepwise evolution of peptidic dendrimers along with their multifaceted applications in various fields. Further, the introduction of biomacromolecules such as proteins to a dendritic scaffold, resulting in complex macromolecules with discrete molecular weights, is an altogether new addition to the area of organic chemistry. The synthesis of highly complex and fully folded biomacromolecules on a dendritic scaffold requires expertise in synthetic organic chemistry and biology. Presently, there are only a handful of examples of protein dendrimers; we believe that these limited examples will fuel further research in this area.

Peptide dendrimers as valuable biomaterials in medical sciences

Peptides are oligomers of amino acids, which have been used in a wide range of applications, particularly in medical and pharmaceutical sciences. Linear peptides have been extensively developed in various fields of medicine as therapeutics or targeting agents. The branched structure of peptide dendrimers with peptide (commonly, poly l‑Lysine) or non-peptide (commonly poly‑amidoamine) core, often exhibits valuable novel features, improves stability and enhances the functionality of peptide in comparison with small linear peptides. The potential applications of Branched and hyper-branched peptidic structures which are known as peptide dendrimers in biomedical sciences have been approved vastly. A peptide dendrimer contains three distinct parts including core, building blocks and branching units or surface functional groups. These structures provide a lot of opportunities in the pharmaceutical field, particularly for novel drug development. In this review, a brief summary of different biomedical applications of peptide dendrimers is presented, and peptide dendrimers as active pharmaceutical ingredients and drug delivery carriers are discussed. Applications of peptide dendrimers in vaccines and diagnostic tools are also presented, in brief. Generally, peptide dendrimers are promising biomaterials with high evolution rate for clinical and non-clinical applications in medicine.

Carbosilane Dendron-Peptide Nanoconjugates as Antimicrobial Agents

Over the last decades, multidrug-resistant bacteria have emerged and spread, increasing the number of bacteria, against which commonly used antibiotics are no longer effective. It has become a serious public health problem whose solution requires medical research in order to explore novel effective antimicrobial molecules. On the one hand, antimicrobial peptides (AMPs) are regarded as good alternatives because of their generally broad-spectrum activities, but sometimes they can be easily degraded by the organism or be toxic to animal cells. On the other hand, cationic carbosilane dendrons, whose focal point can be functionalized in many different ways, have also shown good antimicrobial activity. In this work, we synthetized first- and second-generation cationic carbosilane dendrons with a maleimide molecule on their focal point, enabling their functionalization with three different AMPs. After different microbiology studies, we found an additive effect between first-generation dendron and AMP3 whose study reveals three interesting effects: (i) bacteria aggregation due to AMP3, which could facilitate bacteria detection or even contribute to antibacterial activity by preventing host cell attack, (ii) bacteria disaggregation capability of second-generation cationic dendrons, and (iii) a higher AMP3 aggregation ability when dendrons were added previously to peptide treatment. These compounds and their different effects observed over bacteria constitute an interesting system for further mechanism studies.

N-Heterocyclic Carbenes in Materials Chemistry

N-Heterocyclic carbenes (NHCs) have become one of the most widely studied class of ligands in molecular chemistry and have found applications in fields as varied as catalysis, the stabilization of reactive molecular fragments, and biochemistry. More recently, NHCs have found applications in materials chemistry and have allowed for the functionalization of surfaces, polymers, nanoparticles, and discrete, well-defined clusters. In this review, we provide an in-depth look at recent advances in the use of NHCs for the development of functional materials.

Anticancer Activity of Dendriplexes against Advanced Prostate Cancer from Protumoral Peptides and Cationic Carbosilane Dendrimers

The interaction of neuropeptides, vasoactive intestinal peptide (VIP), or growth hormone-releasing hormone (GHRH), with a cationic carbosilane dendrimer forms dendriplexes with antitumoral behavior in advanced prostate cancer cells PC3. At the concentrations used for dendriplexes formation, the free peptides were protumoral and prometastatic in advanced prostate cancer, while dendrimer only showed low cytotoxicity, but did not avoid the metastatic behavior of PC3 cells. However, these nanoplexes favored also cell adhesion and avoided cell migration. Also, the dendriplexes were not toxic for no tumoral prostate cells (RPWE-1) or fibroblasts. The use of labeled GHRH peptide (rhodamine labeled) and a dendrimer (fluorescein labeled) allowed us to observe that both systems reach the intracellular milieu after dendriplex formation. The treatment of PC3 cells with the nanoplexes reduced expression of vascular endothelial growth factor (VEGF) and cyclic adenosine monophosphate (cAMP). Molecular modeling analysis highlights the important contribution of the carbosilane framework in the stabilization of the dendriplex, since dendrimer interacts with a peptide region where hydrophobic amino acids are presented.

A star-shaped molecularly imprinted polymer derived from polyhedral oligomeric silsesquioxanes with improved site accessibility and capacity for enantiomeric separation via capillary electrochromatography

A star-shaped molecularly imprinted coating was prepared starting from octavinyl-modified polyhedral oligomeric silsesquioxanes (Ov-POSS). It possesses a relatively open structure and has good site accessibility and a larger capacity even at lower cross-linking. The imprinted coating was prepared from S-amlodipine (S-AML) as the template and analyte, Ov-POSS as the cross-linker, and methacrylic acid as the functional monomer. The preparation and chromatographic parameters were optimized, including ratio of template to functional monomer, apparent cross-linking degree, pH value, ACN content and salt concentration in the mobile phase. The best resolution in enantiomer separation by means of capillary electrochromatography reaches a value of 33. A good recognition ability (α = 2.60) was obtained and the column efficiency for S-AML was 54,000 plates m^-1. The use of Ov-POSS as a cross-linker significantly improves the column capacity and thus the detection sensitivity. The results show that Ov-POSS is an effective cross-linker for the preparation of imprinted polymers with good accessibility and large capacity. Graphical abstract Schematic presentation of the preparation of star-shaped imprinted polymer using octavinyl-modified polyhedral oligomeric silsesquioxanes (Ov-POSS) and by using methacrylic acid (MAA) as functional monomer. The best enantiometric resolution (33) for amlodipine (AML) can be achieved in capillary chromatography (CEC).

Engineering Anticancer Amphipathic Peptide-Dendronized Compounds for Highly-Efficient Plasma/Organelle Membrane Perturbation and Multidrug Resistance Reversal

Discovering new strategies for combating drug-resistant tumors becomes a worldwide challenge. Thereinto, stubborn drug-resistant tumor membrane is a leading obstacle on chemotherapy. Herein, we report a novel tumor-activatable amphipathic peptide-dendronized compound, which could form nanoaggregates in aqueous solutions, for perturbing tumor plasma/organelle membrane and reversing multidrug resistance. Distinguished from classical linear amphipathic peptide drugs for membrane disturbance, dendritic lysine-based architecture is designed as a multivalent scaffold to amplify the supramolecular interactions of cationic compound with drug-resistant tumor membrane. Moreover, arginine-rich residues as terminal groups are hopeful to generate multiple hydrogen bonding and electrostatic interactions with tumor membrane. On the other hand, antitumor molecule (doxorubicin) is devised as a hydrophobic moiety to intensify the membrane-inserting ability owing to the prominent interactions with hydrophobic domains of drug-resistant tumor membrane. As expected, these amphipathic peptide-dendronized compounds within the nanoaggregates could severely disturb both the structures and functions of tumor plasma/organelle membrane system, thereby resulting in the rapid leakage of many critical biomolecules, highly efficient apoptotic activation and antiapoptotic inhibition. This strategy on tumor membrane perturbation demonstrates a bran-new antitumor activity with high contributions to cell cycle arrest (at the S phase), strong apoptosis-inducing ability and satisfying cytotoxicity to a variety of drug-resistant tumor cell lines.

Expedient on-resin modification of a peptide C-terminus through a benzotriazole linker

Peptides with various C-terminal functionalization, including peptides and dendrimers, were prepared via SPPS and an efficient on-resin modification.

A convenient and efficient chemical toolbox was developed for the on-resin C-terminal functionalization of various peptides. By transforming resin-bound 3,4-diaminobenzoic acid species with isoamyl nitrite, the resulting resin-bound benzotriazole entity can be efficiently displaced by nucleophiles during cleavage of the peptide–resin connection in a short reaction time. The resin cleavage step allowed for the use of various nucleophiles including water, EtOH, amines, thiol, and G5 poly(amidoamino) dendrimers with yields ranging from 66% to 82% within 5 h. This method was successfully applied to prepare the elastin sequence (VPGVG)₄ through on-resin ligation in 77% yield in one day and a head-to-tail cyclic peptide, sunflower trypsin inhibitor-1, in 42% yield.

Dendrimers, Carotenoids, and Monoclonal Antibodies

Dendrimers are unimolecular architectural nano- or microparticle entities that can accommodate various nutraceuticals and pharmaceuticals between their branches (dendrons) and provide targeted delivery of biomimetics into different tissues upon addition of functionalized groups to the dendrimer's surface. Covalent binding, hydrogen bonds, and electrostatic interactions between dendrimer-composing molecules are known to form and stabilize dendrimer structure. Carotenoids have recently been shown to form dendrimer-like structures and promote targeted delivery of "cargo" molecules into organs characterized by high-carotenoid uptake (adrenal glands, prostate, liver, and brain). The use of carotenoid dendrimers, in particular lycosome particles loaded with various xenobiotics (resveratrol, cocoa flavanols, and HMG-CoA reductase inhibitors), reportedly has a beneficial effect in diabetic foot syndrome, prehypertension, and cardiovascular disease. New applications for carotenoid dendrimers may arise from the use of complexes formed by carotenoid dendrimers and monoclonal antibodies (mAbs). The internalization of carotenoid dendrimer-mAb complexes through receptor-mediated mechanisms may prevent interactions of dendrimer-incorporated xenobiotics with membrane-associated P-glycoprotein, a major factor of drug resistance in tumor cells. The incorporation of mAb fragments with higher binding capacity to the membrane receptors and higher affinity to the target molecule may further increase the bioavailability of "cargo" molecules transported by the carotenoid dendrimer-mAb complexes and open new doors in nanodelivery technologies.

Function Oriented Molecular Design: Dendrimers as Novel Antimicrobials

In recent years innovative nanostructures are attracting increasing interest and, among them, dendrimers have shown several fields of application. Dendrimers can be designed and modified in plentiful ways giving rise to hundreds of different molecules with specific characteristics and functionalities. Biomedicine is probably the field where these molecules find extraordinary applicability, and this is probably due to their multi-valency and to the fact that several other chemicals can be coupled to them to obtain desired compounds. In this review we will describe the different production strategies and the tools and technologies for the study of their characteristics. Finally, we provide a panoramic overview of their applications to meet biomedical needs, especially their use as novel antimicrobials.

Peptide dendrimers: drug/gene delivery and other approaches

Dendrimers are versatile hyperbranched molecules, which have deserved attention especially for their potential in many applications, including biological. Peptide dendrimers comprise interesting classes of dendrimers, and their use has been emphasized as a drug/bioactive compound delivery system, mostly in the antineoplastic area. The bioactive molecules can be covalently linked or entrapped inside the peptide derivative. Self-assembled nanocarriers are a recent trend in the design of potential delivery systems, and pH-sensitive carriers, one of their methods, have been designed to control their systems. In addition, the use of targeting peptides or other specific groups that direct the drug/bioactive compounds to specific organs is an important trend in the search for better drug delivery systems. Recent examples have been given in the literature, showing that gene delivery as another important peptide dendrimer application. It is worth emphasizing that some peptide dendrimers show activity per se, without bioactive compounds. Immune compounds and vaccines are presented herein, as well as uses of other peptide dendrimers are briefly discussed in this review, which encompasses around 10 years of work.

New Modalities for Challenging Targets in Drug Discovery

Our ever-increasing understanding of biological systems is providing a range of exciting novel biological targets, whose modulation may enable novel therapeutic options for many diseases. These targets include protein-protein and protein-nucleic acid interactions, which are, however, often refractory to classical small-molecule approaches. Other types of molecules, or modalities, are therefore required to address these targets, which has led several academic research groups and pharmaceutical companies to increasingly use the concept of so-called "new modalities". This Review defines for the first time the scope of this term, which includes novel peptidic scaffolds, oligonucleotides, hybrids, molecular conjugates, as well as new uses of classical small molecules. We provide the most representative examples of these modalities to target large binding surface areas such as those found in protein-protein interactions and for biological processes at the center of cell regulation.