Guanosine Assembly Enabled Gold Nanorods with Dual Thermo- and Photoswitchable Plasmonic Chiroptical Activity

Chiral cysteine-copper ion-based assemblies for improved phototherapy

Phototherapy, encompassing photothermal therapy and photodynamic therapy, is gaining attention as an appealing cancer treatment modality. To enhance its clinical implementation, a comprehensive exploration of the pivotal factors influencing phototherapy is warranted. In this study, the L/d-cysteine (Cys)-copper ion (Cu2+) chiral nanoparticles, through the assembly of L/d-Cys-Cu2+ coordination complexes, were constructed. We found that these nanoparticles interacted with chiral liposomes in a chirality-dependent manner, with d-Cys-Cu2+ nanoparticles exhibiting more than three times stronger binding affinity than l-Cys-Cu2+ nanoparticles. Furthermore, we demonstrated that the d-Cys-Cu2+ nanoparticles were more efficiently internalized by Hela cells in contrast with l-Cys-Cu2+. On this basis, indocyanine green (ICG), acting as both photothermal and photodynamic agent, was encapsulated into L/d-Cys-Cu2+ nanoparticles. Experimental results showed that the l-Cys-Cu2+-ICG and d-Cys-Cu2+-ICG nanoparticles displayed almost identical photothermal performance and singlet oxygen (1O2) generation capability in aqueous solution. However, upon laser irradiation, the d-Cys-Cu2+-ICG nanoparticles achieved enhanced anti-tumor effects compared to l-Cys-Cu2+-ICG due to their chirality-promoted higher cellular uptake efficiency. These findings highlight the crucial role of chirality in phototherapy and provide new perspectives for engineering cancer therapeutic agents.

Axial assembly of AuNR for tumor theranostics via Zn2+-GSH chelation induced degradation of AuNR@ZIF-8 heterostructures

Tumor microenvironment responsive photothermal ablation is a noninvasive and accurately targeted approach for cancer therapy. Herein, an intracellular directional assembly strategy for enhanced photothermal therapy (PTT) was realized by using ZIF-8 encapsulated Au nanorod (AuNR) heterostructure as the precursor of photothermal convertible material. The ZIF-8 shell selectively degraded in tumor cells upon the chelation between GSH and Zn2+, while the as-formed Zn(SG) connected the released AuNR in end-to-end fashion. The coating of ZIF-8 shell significantly improves the stability and targeting of AuNR, and the released Zn2+ shielded the GSH binding site on the lateral side of AuNR, increased the plasmonic coupling efficiency of AuNR assembly geometer. This design enabled atomic-economical, efficient and low-side effect targeted photothermal therapy through the effective integration of heterostructures.

Nanoparticle Self-Assembly: From Design Principles to Complex Matter to Functional Materials

The creation of matter with varying degrees of complexities and desired functions is one of the ultimate targets of self-assembly. The ability to regulate the complex interactions between the individual components is essential in achieving this target. In this direction, the initial success of controlling the pathways and final thermodynamic states of a self-assembly process is promising. Despite the progress made in the field, there has been a growing interest in pushing the limits of self-assembly processes. The main inception of this interest is that the intended self-assembled state, with varying complexities, may not be "at equilibrium (or at global minimum)", rendering free energy minimization unsuitable to form the desired product. Thus, we believe that a thorough understanding of the design principles as well as the ability to predict the outcome of a self-assembly process is essential to form a collection of the next generation of complex matter. The present review highlights the potent role of finely tuned interparticle interactions in nanomaterials to achieve the preferred self-assembled structures with the desired properties. We believe that bringing the design and prediction to nanoparticle self-assembly processes will have a similar effect as retrosynthesis had on the logic of chemical synthesis. Along with the guiding principles, the review gives a summary of the different types of products created from nanoparticle assemblies and the functional properties emerging from them. Finally, we highlight the reasonable expectations from the field and the challenges lying ahead in the creation of complex and evolvable matter.

Self-Assembled Charge-Transfer Chiral π-Materials: Stimuli-Responsive Circularly Polarized Luminescence and Chiroptical Photothermic Effects

Despite significant achievements in the field of chiroptical organic materials, the full utilization of both the excited state and ground state chiroptical properties in a single supramolecular system is still rarely disclosed. Here, we report that the rational combination of the charge-transfer (CT) interaction with the spacer effect and controlled protonation of π-histidine leads to chiroptical organic π-materials with both circularly polarized luminescence (CPL) and the supramolecular chirality-directed chiroptical photothermic effect. Three pyrene-conjugated histidine derivatives with varied acyl linkers (PyHis, PyC1His, and PyC3His) were designed to coassemble with electron-deficient 1,2,4,5-tetracyanobenzene (TCNB), leading to the formation of supramolecular CT complexes with intense orange to red CPL depending on the linker length. The linker length also affected the protonation-induced CPL responsiveness of the corresponding CT assemblies. Upon protonation of the histidine moiety, PyC3His/TCNB CT assemblies exhibited an inverted CPL signal, while PyHis/TCNB pairs gave quenched CPL due to the disassembly. The protonation-controlled PyC3His/TCNB CT assemblies at varied pH values showed different chiroptical photothermic effects (CPEs) for the same incident chiral light despite the molecular chirality of PyC3His remaining unchanged, supporting an interesting supramolecular chirality-directed photothermic effect.

Voltage-Modulated Untwist Deformations and Multispectral Optical Effects from Ion Intercalation into Chiral Ceramic Nanoparticles

Reconfiguration of chiral ceramic nanostructures after ion intercalation should favor specific nanoscale twists leading to strong chiroptical effects.  In this work, V₂ O₃ nanoparticles are shown to have "built-in" chiral distortions caused by binding of tartaric acid enantiomers to the nanoparticle surface. As evidenced by spectroscopy/microscopy techniques and calculations of nanoscale chirality measures, the intercalation of Zn²⁺ ions into the V₂ O₃ lattice results in particle expansion, untwist deformations, and chirality reduction. Coherent deformations in the particle ensemble manifest as changes in sign and positions of circular polarization bands at ultraviolet, visible, mid-infrared (IR), near-IR (NIR), and IR wavelengths. The g-factors observed for IR and NIR spectral diapasons are ≈100-400 times higher than those for previously reported dielectric, semiconductor, and plasmonic nanoparticles. Nanocomposite films layer-by-layer assembled (LBL) from V₂ O₃ nanoparticles reveal cyclic-voltage-driven modulation of optical activity. Device prototypes for IR and NIR range problematic for liquid crystals and other organic materials are demonstrated. High optical activity, synthetic simplicity, sustainable processability, and environmental robustness of the chiral LBL nanocomposites provide a versatile platform for photonic devices. Similar reconfigurations of particle shapes are expected for multiple chiral ceramic nanostructures, leading to unique optical, electrical, and magnetic properties.

Circularly Polarized Light Responsive Materials: Design Strategies and Applications

Circularly polarized light (CPL) with the end of optical vector traveling along circumferential trajectory shows left- and right-handedness, which transmits chiral information to materials via complicated CPL-matter interactions. Materials with circular dichroism respond to CPL illumination selectively with differential outputs that can be used to design novel photodetectors. Racemic or achiral compounds under CPL go through photodestruction, photoresolution, and asymmetric synthesis pathways to generate enantiomeric bias and optical activity. By this strategy, helical polymers and chiral inorganic plasmonic nanostructures are synthesized directly, and their intramolecular folding and subsequent self-assembly are photomodulable as well. In the aggregated state of self-assembly and liquid crystal phase, helical sense of the dynamic molecular packing is sensitive to enantiomeric bias brought by CPL, enabling the chiral amplification to supramolecular scale. In this review, the application-guided design strategies of CPL-responsive materials are aimed to be systematically summarized and discussed. Asymmetric synthesis, resolution, and property-modulation of small organic compounds, polymers, inorganic nanoparticles, supramolecular assemblies and liquid crystals are highlighted based on the important developments during the last decades. Besides, applications of light-matter interactions including CPL detection and biomedical applications are also referred.

Biomimetic retractable DNA nanocarrier with sensitive responsivity for efficient drug delivery and enhanced photothermal therapy

BACKGROUND

The coalition of DNA nanotechnology with diversiform inorganic nanoparticles offers powerful tools for the design and construction of stimuli-responsive drug delivery systems with spatiotemporal controllability, but it remains challenging to achieve high-density oligonucleotides modification close to inorganic nanocores for their sensitive responsivity to optical or thermal signals.

RESULTS

Inspired by Actinia with retractable tentacles, here we design an artificial nano-Actinia consisted of collapsible DNA architectures attached on gold nanoparticle (AuNP) for efficient drug delivery and enhanced photothermal therapy. The collapsible spheroidal architectures are formed by the hybridization of long DNA strand produced in situ through rolling circle amplification with bundling DNA strands, and contain numerous double-helical segments for the intercalative binding of quercetin as the anti-cancer drug. Under 800-nm light irradiation, the photothermal conversion of AuNPs induces intensive localized heating, which unwinds the double helixes and leads to the disassembly of DNA nanospheres on the surface of AuNPs. The consequently released quercetin can inhibit the expression of heat shock protein 27 and decrease the thermal resistance of tumor cells, thus enhancing photothermal therapy efficacy.

CONCLUSIONS

By combining the deformable DNA nanostructures with gold nanocores, this Actinia-mimetic nanocarrier presents a promising tool for the development of DNA-AuNPs complex and opens a new horizon for the stimuli-responsive drug delivery.

Light-triggered Modulation of Supramolecular Chirality

Dynamically controlling the supramolecular chirality is of great significance in development of functional chiral materials, which is thus essential for the specific function implementation. As an external energy input, light is remote and accurate for modulating chiral assemblies. In non-polarized light control, some photochemically reactive units (e. g., azobenzene, ɑ-cyanostilbene, spiropyran, anthracene) or photo-induced directionally rotating molecular motors were designed to drive chiral transfer or amplification. Besides, photoexcitation induced assembly based physical approach was also explored recently to regulate supramolecular chirality beyond photochemical reactions. In addition, circularly polarized light was applied to induce asymmetric arrangement of organic molecules and asymmetric photochemical synthesis of inorganic metallic nanostructures, in which both wavelength and handedness of circularly polarized light have effects on the induced supramolecular chirality. Although light-triggered chiral assemblies have been widely applied in photoelectric materials, biomedical fields, soft actuator, chiral catalysis and chiral sensing, there is a lack of systematic review on this topic. In this review, we summarized the recent studies and perspectives in the constructions and applications of light-responsive chiral assembled systems, aiming to provide better knowledge for the development of multifunctional chiral nanomaterials.

Circularly Polarized Light-Enabled Chiral Nanomaterials: From Fabrication to Application

For decades, chiral nanomaterials have been extensively studied because of their extraordinary properties. Chiral nanostructures have attracted a lot of interest because of their potential applications including biosensing, asymmetric catalysis, optical devices, and negative index materials. Circularly polarized light (CPL) is the most attractive source for chirality owing to its high availability, and now it has been used as a chiral source for the preparation of chiral matter. In this review, the recent progress in the field of CPL-enabled chiral nanomaterials is summarized. Firstly, the recent advancements in the fabrication of chiral materials using circularly polarized light are described, focusing on the unique strategies. Secondly, an overview of the potential applications of chiral nanomaterials driven by CPL is provided, with a particular emphasis on biosensing, catalysis, and phototherapy. Finally, a perspective on the challenges in the field of CPL-enabled chiral nanomaterials is given.

Modular mixing in plasmonic metal oxide nanocrystal gels with thermoreversible links

Gelation offers a powerful strategy to assemble plasmonic nanocrystal networks incorporating both the distinctive optical properties of constituent building blocks and customizable collective properties. Beyond what a single-component assembly can offer, the characteristics of nanocrystal networks can be tuned in a broader range when two or more components are intimately combined. Here, we demonstrate mixed nanocrystal gel networks using thermoresponsive metal-terpyridine links that enable rapid gel assembly and disassembly with thermal cycling. Plasmonic indium oxide nanocrystals with different sizes, doping concentrations, and shapes are reliably intermixed in linked gel assemblies, exhibiting collective infrared absorption that reflects the contributions of each component while also deviating systematically from a linear combination of the spectra for single-component gels. We extend a many-bodied, mutual polarization method to simulate the optical response of mixed nanocrystal gels, reproducing the experimental trends with no free parameters and revealing that spectral deviations originate from cross-coupling between nanocrystals with distinct plasmonic properties. Our thermoreversible linking strategy directs the assembly of mixed nanocrystal gels with continuously tunable far- and near-field optical properties that are distinct from those of the building blocks or mixed close-packed structures.

Charge-Transfer Complex Doped Photothermal Hydrogels for Discriminating Circularly Polarized Near-Infrared Light

Hydrogels behave as potential candidates to investigate circularly polarized light (CP)-matter interaction, which however suffer from small sensitivity towards circular polarization. Here we report a general protocol to build hydrogels from π-conjugated amino acids with coassembled charge-transfer (CT) complexes, covering a wide scope of donors and acceptors, which were incorporated into stable hydrogel matrices. CT complexes formed block coassemblies with gelators, induced the emergence of macroscopic chiral helices, where efficient chirality transfer occurs to realize tunable Cotton effects from visible light to NIR-I region depending on the structures of CT pairs. The hybrid hydrogels showed tunable photothermal performances with excellent heating-cooling cycling durability. Circularly polarized NIR light selectively triggered gel-solution phase transition at different timescales. Left- and right-CP illumination generates up to 2.5 folds difference in gel collapse time that allows for direct discrimination by naked eyes.

Chiral Au Nanorods: Synthesis, Chirality Origin, and Applications

Chiral Au nanorods (c-Au NRs) with diverse architectures constitute an interesting nanospecies in the field of chiral nanophotonics. The numerous possible plasmonic behaviors of Au NRs can be coupled with chirality to initiate, tune, and amplify their chiroptical response. Interdisciplinary technologies have boosted the development of fabrication and applications of c-Au NRs. Herein, we have focused on the role of chirality in c-Au NRs which helps to manipulate the light-matter interaction in nontraditional ways. A broad overview on the chirality origin, chirality transfer, chiroptical activities, artificially synthetic methodologies, and circularly polarized applications of c-Au NRs will be summarized and discussed. A deeper understanding of light-matter interaction in c-Au NRs will help to manipulate the chirality at the nanoscale, reveal the natural evolution process taking place, and set up a series of circularly polarized applications.

Gold-Nanoparticle-Based Chiral Plasmonic Nanostructures and Their Biomedical Applications

As chiral antennas, plasmonic nanoparticles (NPs) can enhance chiral responses of chiral materials by forming hybrid structures and improving their own chirality preference as well. Chirality-dependent properties of plasmonic NPs broaden application potentials of chiral nanostructures in the biomedical field. Herein, we review the wet-chemical synthesis and self-assembly fabrication of gold-NP-based chiral nanostructures. Discrete chiral NPs are mainly obtained via the seed-mediated growth of achiral gold NPs under the guide of chiral molecules during growth. Irradiation with chiral light during growth is demonstrated to be a promising method for chirality control. Chiral assemblies are fabricated via the bottom-up assembly of achiral gold NPs using chiral linkers or guided by chiral templates, which exhibit large chiroplasmonic activities. In describing recent advances, emphasis is placed on the design and synthesis of chiral nanostructures with the tuning and amplification of plasmonic circular dichroism responses. In addition, the review discusses the most recent or even emerging trends in biomedical fields from biosensing and imaging to disease diagnosis and therapy.

Electrostatically Directed Long-Range Self-Assembly of Nucleotides with Cationic Nanoparticles To Form Multifunctional Bioplasmonic Networks

Precise control over interparticle interactions is essential to retain the functions of individual components in a self-assembled superstructure. Here, we report the design of a multifunctional bioplasmonic network via an electrostatically directed self-assembly process involving adenosine 5'-triphosphate (ATP). The present study unveils the ability of ATP to undergo a long-range self-assembly in the presence of cations and gold nanoparticles (AuNP). Modelling and NMR studies gave a qualitative insight into the major interactions driving the bioplasmonic network formation. ATP-Ca²⁺ coordination helps in regulating the electrostatic interaction, which is crucial in transforming an uncontrolled precipitation into a kinetically controlled aggregation process. Remarkably, ATP and AuNP retained their inherent properties in the multifunctional bioplasmonic network. The generality of electrostatically directed self-assembly process was extended to different nucleotide-nanoparticle systems.

Plasmonic Nanosensors with Extraordinary Sensitivity to Molecularly Enantioselective Recognition at Nanoscale Interfaces

Molecular chirality recognition plays a pivotal role in chiral generation and transfer in living systems and makes important contribution to the development of diverse applications spanning from chiral separation to soft nanorobots. To detect chirality recognition, most of the molecular sensors described to date are based on the design and preparation of the host-guest complexation with chromophore or fluorophore at the reporter unit. Nevertheless, the involved tedious procedures and complicated chemical syntheses hamper their practical applications. Here, we report the plasmonically chiroptical detection of molecular chirality recognition without the need for a chromophore or fluorophore unit. This facile methodology is based on plasmonic nanotransducers that can convert molecular chirality recognitions occurring at nanoscale interfaces into asymmetrically amplified plasmonic circular dichroism readouts, enabling enantiospecific recognition and quantitative determination of the enantiomeric excess of small amino acids. Importantly, such a plasmon-based chirality sensing shows 10²-10³ amplification in the plasmonic circular dichroism signals from the detections of racemate and near-racemate of molecular analysts, demonstrating an extraordinary sensitivity to the host-guest enantioselective interactions. Furthermore, with advantages of easy-processing, cost-effective, and specific to interfacial molecular chirality, our chiroptical sensing scheme could hold considerable promise toward applications of enantioselective high-throughput screening in biology, stereochemistry, and pharmaceutics.

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.

Circularly Polarized Light-Driven Supramolecular Chirality

Introduction of asymmetry into a supramolecular system via external chiral stimuli can contribute to the understanding of the intriguing homochirality found in nature. Circularly polarized light (CPL) is regarded as a chiral physical force with right- or left-handedness. It can induce and modulate supramolecular chirality due to preferential interaction with one enantiomer. Herein, this review focuses on the photon-to-matter chirality transfer mechanisms at the supramolecular level. Thus, asymmetric photochemical reactions are reviewed, and the creation of a chiral bias upon CPL irradiation is discussed. Furthermore, the possible mechanisms for the amplification and propagation of the bias into the supramolecular level are outlined based on the nature of the photochromic building block. Representative examples, including azobenzene derivatives, polydiacetylene, bicyclic ketone, polyfluorenes, C_n -symmetric molecules, and inorganic nanomaterials, are presented.

Supramolecular Chirality from Hierarchical Self-Assembly of Atomically Precise Silver Nanoclusters Induced by Secondary Metal Coordination

Chiral assembly of metal nanoparticles (NPs) into complex superstructures has been widely studied, but their formation mechanisms still remain mysterious due to the lack of precise structural information from the metal-organic interface to metallic kernel. As "molecular models" of metal NPs, atomically precise metal nanoclusters (NCs) used in the assembly of a macroscale superstructure will provide details of microscopic structure for deep understanding of such highly sophisticated assemblies; however, chiral superstructures have not been realized starting from achiral metal NCs with atomic precision. Herein, we report the supramolecular assembly of a water-soluble silver NC ((NH₄)₉[Ag₉(mba)₉], H₂mba = 2-mercaptobenzoic acid, abbreviated as Ag₉-NCs hereafter) into chiral hydrogels induced by the coordination of secondary metal ions. Single crystal X-ray diffraction reveals the triskelion-like structure of Ag₉-NCs with a pseudochiral conformation caused by special arrangement of the peripheral mba^2- ligands. The enantioselective orientation of the peripheral carboxyl group facilitates the assembly of Ag₉-NCs into nanotubes with a chiral cubic (I*) lattice when coordinating to Ba²⁺. The nanotubes can further intertwine into one-dimensional chiral nanobraids with a preferred left-handed arrangement. These multiple levels of chirality can be tuned by drying, during which the I* phase is missing but the chiral entanglement of the nanotubes is enhanced. Through the gelation of atomically precise, achiral NCs coordination of secondary metal ions, chiral amplification of superstructures was realized. The origination of the chirality at different length scales was also discussed.

Importance of Substrate-Particle Repulsion for Protein-Templated Assembly of Metal Nanoparticles

We study the protein-directed assembly of colloidal gold nanoparticles on de novo designed protein nanofiber templates. Using sequential assembly on glass substrates, we attach positively charged gold nanoparticles to protein nanofibers engineered to have a high density of negatively charged surface residues. Using a combination of electron and optical microscopy, we measure the density of particle attachment and characterize binding specificity. By varying nanoparticle size and pH of the solution, we explore the importance of charge-dependent particle-fiber and particle-substrate interactions. We find an inverse correlation between particle size and attachment density to protein nanofibers, attributed to the balance between size-dependent electrostatic particle-fiber attraction and particle-substrate repulsion. We show pH-dependent particle attachment density and binding specificity in relation to the protonation fraction of each assembly layer. Finally, we employ hyperspectral scattering microscopy to draw conclusions about particle density and interparticle spacings of optically observable particle assemblies.

Serum albumin guided plasmonic nanoassemblies with opposite chiralities

Chiral assemblies by combining natural biomolecules with plasmonic nanostructures hold great promise for plasmonic enhanced sensing, imaging, and catalytic applications. Herein, we demonstrate that human serum albumin (HSA) and porcine serum albumin (PSA) can guide the chiral assembly of gold nanorods (GNRs) with left-handed chiroptical responses opposite to those by a series of other homologous animal serum albumins (SAs) due to the difference of their surface charge distributions. Under physiological pH conditions, the assembly of HSA or PSA with GNRs yielded left-handed twisted aggregates, while bovine serum albumin (BSA), sheep serum albumin, and equine serum albumin behaved on the contrary. The driving force for the chiral assembly is mainly attributed to electrostatic interaction. The opposite chiroptical signals acquired are correlated with the chiral surface charge distributions of the tertiary structures of SAs. Moreover, the chirality of the assembly induced by both HSA and BSA can be enhanced or reversed by adjusting the pH values. This work provides new insights into the modulation of protein-induced chiral assemblies and promotes their applications.

Constructing chiral gold nanorod oligomers using a spatially separated sergeants-and-soldiers effect

A sergeants-and-soldiers (S&S) effect is very useful to the fabrication of supramolecular chirality. This strategy has not yet been explored in the construction of chiral plasmonic superstructures. Herein, we demonstrate a spatially separated S&S effect in fabricating plasmonic superstructures and modulating their chiroptical responses. Specifically, chiral cysteine (Cys) molecules, acting as sergeants, are sandwiched between a gold nanorod (AuNR) core and a Au shell via AuNR-templated Au overgrowth. Cationic surfactants, CTAB (cetyltrimethylammonium bromide) or CPC (cetylpyridinium chloride), are modified on the AuNR@Cys@Au shell surface, thus spatially separating from the chiral sergeants. During the assembly process, the surfactants act as soldiers which could transfer and amplify the local chirality induced by the adsorbed chiral molecules from the plasmonic monomers to the oligomers. Huge PCD signals could be achieved in the plasmonic oligomers by finely tuning chiral sergeants and achiral soldiers, indicating the feasibility of the S&S effect in fabricating chiral plasmonic superstructures.

Active Plasmonics and Active Chiral Plasmonics through Orientation-Dependent Multipolar Interactions

While most active plasmonic efforts focus on responsive metamaterials to modulate optical response, we present a simple alternative based on applied orientation control that can likely be implemented for many passive plasmonic materials. Passive plasmonic motifs are simpler to prepare but cannot be altered postfabrication. We show that such systems can be easily manipulated through substrate orientation control to generate both active plasmonic and active chiral plasmonic responses. Using gold nanocrescents as our model platform, we demonstrate tuning of optical extinction from -21% to +36% at oblique incidence relative to normal incidence. Variation of substrate orientation in relation to incident polarization is also demonstrated to controllably switch chiroptical handedness (e.g., Δg = ± 0.55). These active plasmonic responses arise from the multipolar character of resonant modes. In particular, we correlate magnetoelectric and dipole-quadrupole polarizabilities with different light-matter orientation-dependence in both near- and far-field localized surface plasmon activity. Additionally, the attribution of far-field optical response to higher-order multipoles highlights the sensitivity offered by these orientation-dependent characterization techniques to probe the influence of localized electromagnetic field gradients on a plasmonic response. The sensitivity afforded by orientation-dependent optical characterization is further observed by the manifestation in both plasmon and chiral plasmon responses of unpredicted structural nanocrescent variance (e.g., left- and right-tip asymmetry) not physically resolved through topographical imaging.