Self-assembly of spherical and rod-shaped nanoparticles with full positional control

Nanotechnology based drug delivery systems: Does shape really matter?

As of today, the era of nanomedicine has brought numerous breakthroughs and overcome challenges in the treatment of various disorders. Various factors like size, charge and surface hydrophilicity have garnered significant attention by nanotechnologists. However, more exploration in the field of nanoparticle shape and geometry, one of the basic physical phenomenon is required. Tuning nanoparticle shape and geometry could potentially overcome pitfalls in therapeutics and biomedical fields. Thus, in this article, we unveil the importance of tuning nanoparticle shape selection across the delivery platforms. This article provides an in-depth understanding of nanoparticle shape modulation and advise the researchers on the ideal morphology selection tailored for each implication. We deliberated the importance of nanoparticle shape selection for specific implications with respect to organ targeting, cellular internalization, pharmacokinetics and bio-distribution, protein corona formation as well as RES evasion and tumor targeting. An additional section on the significance of shape transformation, a recently introduced novel avenue with applications in drug delivery was discussed. Furthermore, regulatory concerns towards nanoparticle shape which need to be addressed for harnessing their clinical translation will be explained.

Surface-enhanced Raman scattering biosensors for detection of oncomiRs in breast cancer

Surface-enhanced Raman scattering (SERS) has emerged as one of the most promising platforms for various biosensing applications. These sensing systems encompass the advantages of specificity, ultra-high sensitivity, stability, low cost, repeatability, and easy-to-use methods. Moreover, their ability to offer a molecular fingerprint and identify the target analyte at low levels make SERS a promising technique for detecting circulating cancer biomarkers with greater sensitivity and reliability. Among the various circulating biomolecules, oncomiRs are emerging as prominent biomarkers for the early screening of breast cancers (BCs). In this review, we provide a comprehensive understanding of different SERS-based biosensors and their application to identify BC-specific oncomiRs. We also discuss different SERS-based sensing strategies, nano-analytical frameworks, and challenges to be addressed for effective clinical translation.

Cysteine-induced one-pot synthesis of Au nanoparticle chains with tuneable NIR absorption and application in photothermal-chemo cancer therapy

facile L-cysteine (L-cys) mediated one-pot green method is explored to prepare chain-like Au nanoparticles (AuNPs) assembly structure. In such method, the L-cys can be used as a morphology inducer to...

Gold Nanorods: The Most Versatile Plasmonic Nanoparticles

Gold nanorods (NRs), pseudo-one-dimensional rod-shaped nanoparticles (NPs), have become one of the burgeoning materials in the recent years due to their anisotropic shape and adjustable plasmonic properties. With the continuous improvement in synthetic methods, a variety of materials have been attached around Au NRs to achieve unexpected or improved plasmonic properties and explore state-of-the-art technologies. In this review, we comprehensively summarize the latest progress on Au NRs, the most versatile anisotropic plasmonic NPs. We present a representative overview of the advances in the synthetic strategies and outline an extensive catalogue of Au-NR-based heterostructures with tailored architectures and special functionalities. The bottom-up assembly of Au NRs into preprogrammed metastructures is then discussed, as well as the design principles. We also provide a systematic elucidation of the different plasmonic properties associated with the Au-NR-based structures, followed by a discussion of the promising applications of Au NRs in various fields. We finally discuss the future research directions and challenges of Au NRs.

Effect of Ionic Strength, Nanoparticle Surface Charge Density, and Template Diameter on Self-Limiting Single-Particle Placement: A Numerical Study

For the bottom-up approach where functional materials are constructed out of nanoscale building blocks (e.g., nanoparticles), it is essential to have methods that are capable of placing the individual nanoscale building blocks onto exact substrate positions on a large scale and on a large area. One of the promising placement methods is the self-limiting single-particle placement (SPP), in which a single nanoparticle in a colloidal solution is electrostatically guided by electrostatic templates and exactly one single nanoparticle is placed on each target position in a self-limiting way. This paper presents a numerical study on SPP, where the effects of three key parameters, (1) ionic strength (IS), (2) nanoparticle surface charge density (σ_NP), and (3) circular template diameter (d), on SPP are investigated. For 40 different parameter sets of (IS, σ_NP, d), a 30 nm nanoparticle positioned at R⃗ above the substrate was modeled in two configurations (i) without and (ii) with the presence of a 30 nm nanoparticle at the center of a circular template. For each parameter set and each configuration, the electrostatic potentials were calculated by numerically solving the Poisson-Boltzmann equation, from which interaction forces and interaction free energies were subsequently calculated. These have identified realms of parameter sets that enable a successful SPP. A few exemplary parameter sets include (IS, σ_NP, d) = (0.5 mM, -1.5 μC/cm², 100 nm), (0.05 mM, -0.5 μC/cm², 100 nm), (0.5 mM, -1.5 μC/cm², 150 nm), and (0.05 mM, -0.8 μC/cm², 150 nm). This study provides clear guidance toward experimental realizations of large-scale and large-area SPPs, which could lead to bottom-up fabrications of novel electronic, photonic, plasmonic, and spintronic devices and sensors.

Crystal nucleation in colloidal rod suspensions: The effect of depletant size

In order to better control the assembly of nanorods, knowledge of the pathways by which they form ordered structures is desirable. In this paper, we characterize crystal nucleation in suspensions of spherocylindrical rods with aspect ratio L/D = 2.3 in the presence of both small and large polymer depletants. Using a combination of Langevin dynamics and Monte Carlo simulations, together with biased sampling techniques, we show that the preferred pathway always involves the formation of monolayer assemblies irrespective of the volume fraction of the initial isotropic phase and the diameter of the depletants. This includes the previously neglected case of nucleation from the colloidal liquid phase and shows that the presence of depletion attraction can alter nucleation pathways even when the initial phase is dense.

Filamentous Phages as Building Blocks for Bioactive Hydrogels

Filamentous bacteriophages (bacterial viruses) are semiflexible proteinous nanofilaments with high aspect ratios for which the surface chemistry can be controlled with atomic precision via genetic engineering. That, in addition to their ability to self-propagate and replicate a nearly monodisperse batch of biologically and chemically identical nanofilaments, makes these bionanofilaments superior to most synthetic nanoparticles and thus a powerful tool in the bioengineers' toolbox. Furthermore, filamentous phages form liquid crystalline structures at high concentrations; these ordered assemblies create hierarchically ordered macro-, micro-, and nanostructures that, once cross-linked, can form hierarchically ordered hydrogels, hydrated soft material with a variety of physical and chemical properties suitable for biomedical applications (e.g., wound dressings and tissue engineering scaffolds) as well as biosensing, diagnostic assays. We provide a critical review of these hydrogels of filamentous phage, and their physical, mechanical, chemical, and biological properties and current applications, as well as an overview of limitations and challenges and outlook for future applications. In addition, we present a list of design parameters for filamentous phage hydrogels to serve as a guide for the (bio)engineer and (bio)chemist interested in utilizing these powerful bionanofilaments for designing smart, bioactive materials and devices.

Signaling in Systems Chemistry: Programing Gold Nanoparticles Formation and Assembly Using a Dynamic Bistable Network

Living cells exploit bistable and oscillatory behaviors as memory mechanisms, facilitating the integration of transient stimuli into sustained molecular responses that control downstream functions. Synthetic bistable networks have also been studied as memory entities, but have rarely been utilized to control orthogonal functions in coupled dynamic systems. We herein present a new cascade pathway, for which we have exploited a well-characterized switchable peptide-based replicating network, operating far from equilibrium, that yields two alternative steady-state outputs, which in turn serve as the input signals for consecutive processes that regulate various features of Au nanoparticle shape and assembly. This study further sheds light on how bridging together the fields of systems chemistry and nanotechnology may open up new opportunities for the dynamically controlled design of functional materials.

Self-Assembly of Polymer End-Tethered Gold Nanorods into Two-Dimensional Arrays with Tunable Tilt Structures

We demonstrated a facile yet effective strategy for self-assembly of polymer end-tethered gold nanorods (GNRs) into tunable two-dimensional (2D) arrays with the assistance of supramolecules of hydrogen bonded poly(4-vinyl pyridine) (P4VP) and 3-n-pentadecylphenol (PDP). Well-ordered 2D arrays with micrometer size were obtained by rupturing the assembled supramolecular matrix with a selective solvent. The formation of long-range ordered 2D arrays during a drying process was observed via small-angle X-ray scattering. Interestingly, the packing structure of the ordered arrays strongly depends on the molecular weight (M_w) of the polymer ligands and the size of the GNRs. By increasing M_w of the polymer ligands, tilted arrays can be obtained. The average angle between GNRs and the surface normal direction of the layered 2D arrays changes from 0 to 37° with the increase in M_w of the polymer ligands. A mechanism for assembly behavior of dumbbell shapes with a soft shell structure has been proposed. The resulting GNR arrays with different orientations showed anisotropic surface-enhanced Raman scattering (SERS) performance. We showed that the vertically ordered GNR arrays exhibited ∼3 times higher SERS signals than the tilt ordered arrays. The results prove that the polymer end-tethered GNRs can be used as a building block for preparing the tilted 2D arrays with tunable physicochemical properties, which could have a wide range of potential applications in photonics, electronics, plasmonics, etc.