Peptide-Programmable Nanoparticle Superstructures with Tailored Electrocatalytic Activity

Imparting Stability to Chiral Helical Gold Nanoparticle Superstructures

Realizing the promise of chiral inorganic nanomaterials hinges on improving their structural stability under various chemical and environmental conditions. Here, we examine the stability of 1-D gold nanoparticle (Au NP) single helices prepared using the amphiphilic peptide conjugate Cx-(PEPAuM-ox)2 (PEPAuM-ox = AYSSGAPPMoxPPF; x = 16-22). We present a general template-independent strategy of tuning helix stability that relies on controlling the dimensions of constituent NPs. As NP dimensions increase, Au NP single helices become both more thermally stable and more stable in the presence of chemical denaturants and protein digestion agents (e.g., urea and proteinase K, respectively). We use this strategy for imparting helix stability to create colloidal suspensions of thermally robust Au NP single helices which maintain their plasmonic chiroptical activity up to ∼80 °C.

Structure-Guided Engineering of Thermodynamically Enhanced SaCas9 for Improved Gene Suppression

Proteins with multiple domains play pivotal roles in various biological processes, necessitating a thorough understanding of their structural stability and functional interplay. Here, a structure-guided protein engineering approach is proposed to develop thermostable Cas9 (CRISPR-associated protein 9) variant for CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) interference applications. By employing thermodynamic analysis, combining distance mapping and molecular dynamics simulations, deletable domains are identified to enhance stability while preserving the DNA recognition function of Cas9. The resulting engineered Cas9, termed small and dead form Cas9, exhibits improved thermostability and maintains target DNA recognition function. Cryo-electron microscopy analysis reveals structural integrity with reduced atomic density in the deleted domain. Fusion with functional elements enables intracellular delivery and nuclear localization, demonstrating efficient gene suppression in diverse cell types. Direct delivery in the mouse brain shows enhanced knockdown efficiency, highlighting the potential of structure-guided engineering to develop functional CRISPR systems tailored for specific applications. This study underscores the significance of integrating computational and experimental approaches for protein engineering, offering insights into designing tailored molecular tools for precise biological interventions.

Utilizing peptide-anchored DNA templates for novel programmable nanoparticle assemblies in biological macromolecules: A review

Biological macromolecules such as proteins and DNA are known to self-assemble into various structural moieties with distinct functions. While nucleic acids are the structural building blocks, peptides exemplify diversity as tailorable biochemical units. Thus, combining the scaffold properties of the biomacromolecule DNA and the functionality of peptides could evolve into a powerful method to obtain tailorable nano assemblies. In this review, we discuss the assembly of non-DNA-coated colloidal NPs on DNA/peptide templates using functional anchors. We begin with strategies for directly attaching metallic NPs to DNA templates to ascertain the functional role of DNA as a scaffold. Followed by methods to assemble peptides onto DNA templates to emphasize the functional versatility of biologically abundant DNA-binding peptides. Next, we focus on studies corroborating peptide self-assembling into macromolecular templates onto which NPs can attach to emphasize the properties of NP-binding peptides. Finally, we discuss the assembly of NPs on a DNA template with a focus on the bifunctional DNA-binding peptides with NP-binding affinity (peptide anchors). This review aims to highlight the immense potential of combining the functional power of DNA scaffolds and tailorable functionalities of peptides for NP assembly and the need to utilize them effectively to obtain tailorable hierarchical NP assemblies.

Active targeting schemes for nano-drug delivery systems in osteosarcoma therapeutics

Osteosarcoma, the most common malignant tumor of the bone, seriously influences people's lives and increases their economic burden. Conventional chemotherapy drugs achieve limited therapeutic effects owing to poor targeting and severe systemic toxicity. Nanocarrier-based drug delivery systems can significantly enhance the utilization efficiency of chemotherapeutic drugs through targeting ligand modifications and reduce the occurrence of systemic adverse effects. A variety of ligand-modified nano-drug delivery systems have been developed for different targeting schemes. Here we review the biological characteristics and the main challenges of current drug therapy of OS, and further elaborate on different targeting schemes and ligand selection for nano-drug delivery systems of osteosarcoma, which may provide new horizons for the development of advanced targeted drug delivery systems in the future.

Linear One-Dimensional Assembly of Metal Nanostructures onto an Asymmetric Peptide Nanofiber with High Persistence Length

Self-assembled peptide fibrils have been used extensively to template the organization of metal nanoparticles in a one-dimensional (1D) array. It has been observed that the formation of the 1D arrays with a width of a single or few nanoparticles (viz. 20 nm diameter) is only possible if the templating fibers have comparable diameters (viz. ≤20 nm). Accordingly, until today, all the peptide-based templates enabling such 1D arrays have very low persistence lengths, a property that depends strongly on the diameter of the template, owing to the inherent flexibility of only a few nanometer-wide fibers. Here, we demonstrate the formation of high persistence length 1D arrays templated by a short self-assembling peptide fibril with an asymmetrically distributed charged surface. The asymmetric nature of the peptide fibril allows charge-dependent deposition of the nanoparticles only to the part of the fiber with complementary charges, and the rest of the fibril surface remains free of nanoparticles. Consequently, fibers with a much higher diameter, which will have a higher persistence length, are able to template single or few nanoparticle-wide 1D arrays. Detailed microscopy, molecular dynamics simulations, and crystal structure analysis provide molecular-level insights into fiber asymmetry and its interactions with diverse nanostructures such as gold and magnetic nanoparticles. This study will afford an alternative paradigm for high persistence length 1D array fabrication comparable to DNA nanotechnology and lithography but with tremendous cost-effectiveness.

1D Colloidal chains: recent progress from formation to emergent properties and applications

Integrating nanoscale building blocks of low dimensionality (0D; i.e., spheres) into higher dimensional structures endows them and their corresponding materials with emergent properties non-existent or only weakly existent in the individual building blocks. Constructing 1D chains, 2D arrays and 3D superlattices using nanoparticles and colloids therefore continues to be one of the grand goals in colloid and nanomaterial science. Amongst these higher order structures, 1D colloidal chains are of particular interest, as they possess unique anisotropic properties. In recent years, the most relevant advances in 1D colloidal chain research have been made in novel synthetic methodologies and applications. In this review, we first address a comprehensive description of the research progress concerning various synthetic strategies developed to construct 1D colloidal chains. Following this, we highlight the amplified and emergent properties of the resulting materials, originating from the assembly of the individual building blocks and their collective behavior, and discuss relevant applications in advanced materials. In the discussion of synthetic strategies, properties, and applications, particular attention will be paid to overarching concepts, fresh trends, and potential areas of future research. We believe that this comprehensive review will be a driver to guide the interdisciplinary field of 1D colloidal chains, where nanomaterial synthesis, self-assembly, physical property studies, and material applications meet, to a higher level, and open up new research opportunities at the interface of classical disciplines.

Tumor Customized 2D Supramolecular Nanodiscs for Ultralong Tumor Retention and Precise Photothermal Therapy of Highly Heterogeneous Cancers

Target therapy for highly heterogeneous cancers represents a major clinical challenge due to the lack of recurrent therapeutic targets identified in these tumors. Herein, the authors report a tumor-customized targeting photothermal therapy (PTT) strategy for highly heterogeneous cancers, by which 2D supramolecular self-assembled nanodiscs are modified with tumor-specific binding peptides identified by phage display techniques. Taking osteosarcoma (OS) as a model heterogeneous cancer, an OS targeting peptide (OTP) is first selected after biopanning and is demonstrated to successfully bind to this heterogeneous cancer cells/tissues. Successful conjugation of OTP to heptamethine cyanine (Cy7)-based 2D nanodiscs Cy7-TCF (2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran,TCF) enables the 2D nanodiscs to specifically target the heterogeneous tumor. Notably, a single dose injection of this targeted nanodisc (T-ND) not only effectively induces enhanced photothermal tumor ablation under near-infrared light, but also exhibits sevenfold increase of tumor retention time (more than 24 days) compared to generic nanomedicine. Thus, the authors' findings suggest that the combination of phage display-based affinity peptides selection and 2D supramolecular nanodiscs leads to the development of a platform technology for highly heterogeneous cancers precise therapy, offering specific tumor targeting, ultralong tumor retention, and precise PTT.

Recent Progress on Revealing 3D Structure of Electrocatalysts Using Advanced 3D Electron Tomography: A Mini Review

Electrocatalysis plays a key role in clean energy innovation. In order to design more efficient, durable and selective electrocatalysts, a thorough understanding of the unique link between 3D structures and properties is essential yet challenging. Advanced 3D electron tomography offers an effective approach to reveal 3D structures by transmission electron microscopy. This mini-review summarizes recent progress on revealing 3D structures of electrocatalysts using 3D electron tomography. 3D electron tomography at nanoscale and atomic scale are discussed, respectively, where morphology, composition, porous structure, surface crystallography and atomic distribution can be revealed and correlated to the performance of electrocatalysts. (Quasi) in-situ 3D electron tomography is further discussed with particular focus on its impact on electrocatalysts' durability investigation and post-treatment. Finally, perspectives on future developments of 3D electron tomography for eletrocatalysis is discussed.

A platinum nanoparticle doped self-assembled peptide bolaamphiphile hydrogel as an efficient electrocatalyst for the hydrogen evolution reaction

Noble metal-based nanomaterials have shown great potential for catalytic application with higher selectivity and activity. Owing to their self-assembly properties with various molecular interactions, peptides play an essential role in the controlled synthesis of noble metal-based catalysts with high surface area. In this work, a phenylalanine (F) and tyrosine (Y) based peptide bolaamphiphile is prepared by solution-phase peptide synthesis. The peptide bolaamphiphile readily self-assembles into a hydrogel with a cross-linked nanofibrillar network. The platinum nanoparticles (Pt NPs) are in situ generated within the cross-linked nanofibrillar network of the hydrogel matrix of the peptide bolaamphiphile. Benefiting from the synergistic properties of the Pt nanoparticles doped on three-dimensional fibrous networks, Pt6@hydrogel shows efficient catalytic activity for the electrochemical hydrogen evolution reaction (HER) in 0.5 M H2SO4 solution. The Pt6@hydrogel requires an overpotential of 45 mV at -10 mA cm-2 with a Tafel slope of 52 mV dec-1. The Pt6@hydrogel also shows electrocatalytic activity in basic and neutral pH solutions. The excellent activity and stability of Pt6@hydrogel for the HER shows great potential for energy conversion applications.

Tuning Materials-Binding Peptide Sequences toward Gold- and Silver-Binding Selectivity with Bayesian Optimization

Peptide sequence engineering can potentially deliver materials-selective binding capabilities, which would be highly attractive in numerous biotic and abiotic nanomaterials applications. However, the number of known materials-selective peptide sequences is small, and identification of new sequences is laborious and haphazard. Previous attempts have sought to use machine learning and other informatics approaches that rely on existing data sets to accelerate the discovery of materials-selective peptides, but too few materials-selective sequences are known to enable reliable prediction. Moreover, this knowledge base is expensive to expand. Here, we combine a comprehensive and integrated experimental and modeling effort and introduce a Bayesian Effective Search for Optimal Sequences (BESOS) approach to address this challenge. Through this combined approach, we significantly expand the data set of Au-selective peptide sequences and identify an additional Ag-selective peptide sequence. Analysis of the binding motifs for the Ag-binders offers a roadmap for future prediction with machine learning, which should guide identification of further Ag-selective sequences. These discoveries will enable wider and more versatile integration of Ag nanoparticles in biological platforms.

Tunable Assembly of Protein Enables Fabrication of Platinum Nanostructures with Different Catalytic Activity

Proteins are promising biofunctional units for the construction of nanomaterials (NMs) due to their abundant binding sites, intriguing self-assembly properties, and mild NM synthetic conditions. Tobacco mosaic virus coat protein (TMVCP) is a protein capable of self-assembly into distinct morphologies depending on the solution pH and ionic strength. Herein, we report the use of TMVCP as a building block to organize nanosized platinum into discrete nanorings and isolated nanoparticles by varying the solution pH to modulate the protein assembly state. Compared with a commercial Pt/C catalyst, the TMVCP-templated platinum materials exhibited significant promotion of the catalytic activity and stability toward methanol electrooxidation in both neutral and alkaline conditions. The enhanced catalytic performance is likely facilitated by the protein support. Additionally, Pt nanorings outperformed isolated nanoparticles, although they are both synthesized on TMVCP templates. This could be due to the higher mechanical stability of the protein disk structure and possible cooperative effects between adjacent nanoparticles in the ring with narrow interparticle spacing.

Recent Advances in Bio-Templated Metallic Nanomaterial Synthesis and Electrocatalytic Applications

Developing metallic nanocatalysts with high reaction activity, selectivity and practical durability is a promising and active subfield in electrocatalysis. In the classical "bottom-up" approach to synthesize stable nanomaterials by chemical reduction, stabilizing additives such as polymers or organic surfactants must be present to cap the nanoparticle to prevent material bulk aggregation. In recent years, biological systems have emerged as green alternatives to support the uncoated inorganic components. One key advantage of biological templates is their inherent ability to produce nanostructures with controllable composition, facet, size and morphology under ecologically friendly synthetic conditions, which are difficult to achieve with traditional inorganic synthesis. In addition, through genetic engineering or bioconjugation, bio-templates can provide numerous possibilities for surface functionalization to incorporate specific binding sites for the target metals. Therefore, in bio-templated systems, the electrocatalytic performance of the formed nanocatalyst can be tuned by precisely controlling the material surface chemistry. With controlled improvements in size, morphology, facet exposure, surface area and electron conductivity, bio-inspired nanomaterials often exhibit enhanced catalytic activity towards electrode reactions. In this Review, recent research developments are presented in bio-approaches for metallic nanomaterial synthesis and their applications in electrocatalysis for sustainable energy storage and conversion systems.

Self-Assembly of Au Nanoclusters into Helical Ribbons by Manipulating the Flexibility of Capping Ligands

Self-assembly is a powerful technology to construct nanomaterials with helical structures. However, using metal nanoclusters (NCs) as the building blocks for the construction of helical architectures is still rarely reported. In this paper, Au NC assembled helical ribbons (Au NCHRs) are successfully constructed by using Au NCs as the building blocks. Effects of heating mode, solvent polarity and ligand length on the self-assembly process of Au NCs are discussed. The results indicate that the lengths of overlapped and nonoverlapped ligands between adjacent Au NCs play the dominated role on adjusting the morphologies of the resulting assemblies. Ligands with appropriate overlap can provide sufficient flexibility for the helical assembly of Au NCs without losing the stability. If the length of the overlapped parts is too long, the assemblies are usually rigid without the helical structure. Instead, the overlength of nonoverlapped ligands will boost the flexibility but damage the structural stability of the assemblies. Since everything in the world is assembled by atoms and molecules, recognizing the self-assembly mechanism of NCs may promote our understanding on the bountiful complexity of life and nature.

Construction of Chiral, Helical Nanoparticle Superstructures: Progress and Prospects

Chiral nanoparticle (NP) superstructures, in which discrete NPs are assembled into chiral architectures, represent an exciting and growing class of nanomaterials. Their enantiospecific properties make them promising candidates for a variety of potential applications. Helical NP superstructures are a rapidly expanding subclass of chiral nanomaterials in which NPs are arranged in three dimensions about a screw axis. Their intrinsic asymmetry gives rise to a variety of interesting properties, including plasmonic chiroptical activity in the visible spectrum, and they hold immense promise as chiroptical sensors and as components of optical metamaterials. Herein, a concise history of the foundational conceptual advances that helped define the field of chiral nanomaterials is provided, and some of the major achievements in the development of helical nanomaterials are highlighted. Next, the key methodologies employed to construct these materials are discussed, and specific merits that are offered by each assembly methodology are identified, as well as their potential disadvantages. Finally, some specific examples of the emerging applications of these materials are discussed and some areas of future development and research focus are proposed.

De novo protein design, a retrospective

Proteins are molecular machines whose function depends on their ability to achieve complex folds with precisely defined structural and dynamic properties. The rational design of proteins from first-principles, or de novo, was once considered to be impossible, but today proteins with a variety of folds and functions have been realized. We review the evolution of the field from its earliest days, placing particular emphasis on how this endeavor has illuminated our understanding of the principles underlying the folding and function of natural proteins, and is informing the design of macromolecules with unprecedented structures and properties. An initial set of milestones in de novo protein design focused on the construction of sequences that folded in water and membranes to adopt folded conformations. The first proteins were designed from first-principles using very simple physical models. As computers became more powerful, the use of the rotamer approximation allowed one to discover amino acid sequences that stabilize the desired fold. As the crystallographic database of protein structures expanded in subsequent years, it became possible to construct proteins by assembling short backbone fragments that frequently recur in Nature. The second set of milestones in de novo design involves the discovery of complex functions. Proteins have been designed to bind a variety of metals, porphyrins, and other cofactors. The design of proteins that catalyze hydrolysis and oxygen-dependent reactions has progressed significantly. However, de novo design of catalysts for energetically demanding reactions, or even proteins that bind with high affinity and specificity to highly functionalized complex polar molecules remains an importnant challenge that is now being achieved. Finally, the protein design contributed significantly to our understanding of membrane protein folding and transport of ions across membranes. The area of membrane protein design, or more generally of biomimetic polymers that function in mixed or non-aqueous environments, is now becoming increasingly possible.

AuPt/MOF-Graphene: A Synergistic Catalyst with Surprisingly High Peroxidase-Like Activity and Its Application for H2O2 Detection

Here, we report ZIF-8-reduced graphene oxide (ZIF-8-rGO)-supported bimetallic AuPt nanoparticles (AuPtNPs) as a novel peroxidase mimic for high-sensitivity detection of H₂O₂ in neutral solution. ZIF-8-graphene oxide (ZIF-8-GO) is first synthesized via a simple wet-chemistry process and subsequently immobilized with AuPtNPs via a reduction method. The resultant AuPt/ZIF-8-rGO shows enhanced peroxidase-like catalytic activity and it is applied for the electrochemical detection of H₂O₂ in a wide concentration range, from 100 nM to 18 mM, with a very low detection limit of 19 nM (S/N = 3). This good electroanalytical performance of AuPt/ZIF-8-rGO is owing to the ultrasmall size and high dispersion of the AuPtNPs, the strong metal-support interaction between the AuPtNPs and ZIF-8-rGO bisupport, and the sandwich-like structure comprising porous ZIF-8 and loosely packed rGO nanosheets. The AuPt/ZIF-8-rGO is employed for the practical detection of H₂O₂ in human serum samples with desirable properties. Therefore, the novel AuPt/ZIF-8-rGO is a promising nanozyme for various biotechnological and environmental applications.

Artificial intelligence in nanomedicine

The field of nanomedicine has made substantial strides in the areas of therapeutic and diagnostic development. For example, nanoparticle-modified drug compounds and imaging agents have resulted in markedly enhanced treatment outcomes and contrast efficiency. In recent years, investigational nanomedicine platforms have also been taken into the clinic, with regulatory approval for Abraxane® and other products being awarded. As the nanomedicine field has continued to evolve, multifunctional approaches have been explored to simultaneously integrate therapeutic and diagnostic agents onto a single particle, or deliver multiple nanomedicine-functionalized therapies in unison. Similar to the objectives of conventional combination therapy, these strategies may further improve treatment outcomes through targeted, multi-agent delivery that preserves drug synergy. Also, similar to conventional/unmodified combination therapy, nanomedicine-based drug delivery is often explored at fixed doses. A persistent challenge in all forms of drug administration is that drug synergy is time-dependent, dose-dependent and patient-specific at any given point of treatment. To overcome this challenge, the evolution towards nanomedicine-mediated co-delivery of multiple therapies has made the potential of interfacing artificial intelligence (AI) with nanomedicine to sustain optimization in combinatorial nanotherapy a reality. Specifically, optimizing drug and dose parameters in combinatorial nanomedicine administration is a specific area where AI can actionably realize the full potential of nanomedicine. To this end, this review will examine the role that AI can have in substantially improving nanomedicine-based treatment outcomes, particularly in the context of combination nanotherapy for both N-of-1 and population-optimized treatment.