Protein Corona-Mediated Inhibition of Nanozyme Activity: Impact of Protein Shape.

During biomedical applications, nanozymes, exhibiting enzyme-like characteristics, inevitably come into contact with biological fluids in living systems, leading to the formation of a protein corona on their surface. Although it is acknowledged that molecular adsorption can influence the catalytic activity of nanozymes, there is a dearth of understanding regarding the impact of the protein corona on nanozyme activity and its determinant factors. In order to address this gap, we employed the AuNR@Pt@PDDAC [PDDAC, poly(diallyldimethylammonium chloride)] nanorod (NR) as a model nanozyme with multiple activities, including peroxidase, oxidase, and catalase-mimetic activities, to investigate the inhibitory effects of the protein corona on the catalytic activity. After the identification of major components in the plasma protein corona on the NR, we observed that spherical proteins and fibrous proteins induced distinct inhibitory effects on the catalytic activity of nanozymes. To elucidate the underlying mechanism, we uncovered that the adsorbed proteins assembled on the surface of the nanozymes, forming protein networks (PNs). Notably, the PNs derived from fibrous proteins exhibited a screen mesh-like structure with smaller pore sizes compared to those formed by spherical proteins. This structural disparity resulted in a reduced efficiency for the permeation of substrate molecules, leading to a more robust inhibition in activity. These findings underscore the significance of the protein shape as a crucial factor influencing nanozyme activity. This revelation provides valuable insights for the rational design and application of nanozymes in the biomedical fields.

A colorimetric chemosensor for sensitive and selective detection of copper(II) ions based on catalytic oxidation of 1-naphthylamine.

Rapid on-site detection of copper(II) ions (Cu2+) with high sensitivity and selectivity is of great significance in the safety monitoring of drinking water and food. Colorimetric detection is a robust fast determination method with the main drawback of low sensitivity. Herein, we developed a colorimetric chemosensor based on a colored polymer product. Via a Cu-Fenton mechanism, 1-naphthylamine (α-NA) was oxidized by H2O2 and brownish-red poly(1-naphthylamine) (PNA) was produced. The obtained Cu2+ sensor showed a linear response from 0.05 µM to 7 µM, with a detection limit of 62 nM. Our findings expanded chromogenic reaction types for colorimetric detection.

Modulation of plasmonic chiral shell growth on gold nanorods via nonchiral surfactants.

Recently, in combination with seed-mediated growth, thiolated chiral molecule-guided growth has shown great promise in obtaining chiral plasmonic nanostructures. Previously, with the assistance of chiral cysteines (Cys), we realized helical growth of plasmonic shells on gold nanorod (AuNR) seeds dispersed in cetyltrimethylammonium bromide (CTAB) solution. Herein, we further studied the roles of non-chiral cationic surfactants in tuning the helical growth. Both the counter anion and the hydrocarbon chain length of the surfactants were found to affect the formation of helical shells greatly. In particular, we exhibited surfactant-modulated conversion of the chiral shell deposition mode between layer growth and island growth. By optimizing growth conditions, an obvious plasmonic circular dichroism (PCD) response could be achieved for the island helical shell. Our findings demonstrated promising potential of nanochemical synthesis in fabricating chiral plasmonic nanostructures with small structural sizes.

Enhanced chiroptic properties of nanocomposites of achiral plasmonic nanoparticles decorated with chiral dye-loaded micelles.

The development of circularly polarized luminescence (CPL)-active materials with both large luminescence dissymmetry factor (glum) and high emission efficiency continues to be a major challenge. Here, we present an approach to improve the overall CPL performance by integrating triplet-triplet annihilation-based photon upconversion (TTA-UC) with localized surface plasmon resonance. Dye-loaded chiral micelles possessing TTA-UC ability are designed and attached on the surface of achiral gold nanorods (AuNRs). The longitudinal and transversal resonance peaks of AuNRs overlap with the absorption and emission of dye-loaded chiral micelles, respectively. Typically, 43-fold amplification of glum value accompanied by 3-fold enhancement of upconversion are obtained simultaneously when Au@Ag nanorods are employed in the composites. More importantly, transient absorption spectra reveal a fast accumulation of spin-polarized triplet excitons in the composites. Therefore, the enhancement of chirality-induced spin polarization should be in charge of the amplification of glum value. Our design strategy suggests that combining plasmonic nanomaterials with chiral organic materials could aid in the development of chiroptical nanomaterials.

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.

Morphological analysis of Rhynchospio aff. asiatica (Annelida: Spionidae) and comments on the phylogeny and reproduction of the family Spionidae.

The genus Rhynchospio has fronto-lateral horns on prostomium, paired branchiae from chaetiger 2 to near the posterior end, capillary notochaetae only, and more than two pairs of pygidial cirri. Rhynchospio species are common in coastal soft bottom communities; nevertheless, many recorded Rhynchospio specimens around the world are currently undescribed. Here we described a Rhynchospio species based on specimens collected from Qingdao, China. Comparison with the reported DNA sequences of four gene markers (16S rRNA, 18S rRNA, 28S rRNA, and Histone H3) and brief morphological description of specimens collected from Jinhae Bay, South Korea, previously reported as Rhynchospio aff asiatica, indicated that they are conspecific. Morphologically, specimens of R. aff. asiatica from Qingdao are characterized by having neuropodial hooded hooks from chaetigers 14-17 (vs. 10-23 in R. asiatica) to near pygidial chaetigers, sperm from chaetiger 11 to 14 (vs. from chaetiger 11 to 21-22 in R. asiatica), oocytes from chaetigers 16-17 to 26-39 (vs. from 22-24 in R. asiatica), and 4-6 (vs. up to 6 in R. asiatica) pygidial cirri. Genetically, Rhynchospio aff. asiatica is most closely related to R. arenincola Hartman, 1936 from California, USA with the interspecific distances of 20.02% (16S rRNA), 4.50% (18S rRNA), 8.44% (28S rRNA), 2.74% (Histone H3), and 6.10% (concatenated sequences). Water flow across the dorsum created by ciliary beating of the branchiae and nototrochs, observed on live specimens, may help transport gametes from reproductive segments in anterior and middle parts to the posterior brooding segments. Phylogenetic trees based on concatenated sequences of four gene markers of 54 spioniform species in 25 genera revealed two clades, covering the two subfamilies Spioninae and Nerininae respectively. Two families (i.e., Poecilochaetidae and Trochochaetidae) in the order Spionida were clustered within Spionidae, supporting a morphology-based proposal that these families bearing a pair of prehensile, grooved palps should be grouped within a more broadly defined family Spionidae. Mapping morphological and reproductive characteristics to the phylogenetic trees indicated that the ancestor of spionids might lack branchiae, broadcast spawn thick-envelop oocytes and ect-aquasperm, and produce planktotrophic larvae.

Spatiotemporal Tracing of the Cellular Internalization Process of Rod-Shaped Nanostructures.

Endocytosis, as one of the main ways for nanostructures enter cells, is affected by several aspects, and shape is an especially critical aspect during the endocytosis of nanostructures. However, it has remained challenging to capture the dynamic internalization behaviors of rod-shaped nanostructures while also probing the mechanical aspects of the internalization. Here, using the atomic force microscopy-based force tracing technique, transmission electron microscopy, and molecular dynamic simulation, we mapped the detailed internalization behaviors of rod-shaped nanostructures with different aspect ratios at the single-particle level. We found that the gold nanorod is endocytosed in a noncontinuous and force-rebound rotation manner, herein named "intermittent rotation". The force tracing test indicated that the internalization force (∼81 pN, ∼108 pN, and ∼157 pN) and time (∼0.56 s, ∼0.66 s, and ∼1.14 s for a 12.10 nm × 11.96 nm gold nanosphere and 26.15 nm × 13.05 nm and 48.71 nm × 12.45 nm gold nanorods, respectively) are positively correlated with the aspect ratios. However, internalization speed is negatively correlated with internalization time, irrespective of the aspect ratio. Further, the energy analysis suggested that intermittent rotation from the horizontal to vertical direction can reduce energy dissipation during the internalization process. Thus, to overcome the energy barrier of internalization, the number and angle of rotation increases with aspect ratios. Our findings provide critical missing evidence of rod-shaped nanostructure's internalization, which is essential for fundamentally understanding the internalization mechanism in living cells.

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.

Bottom-Up Synthesis of Helical Plasmonic Nanorods and Their Application in Generating Circularly Polarized Luminescence.

Chiral growth and chirality transfer associated with plasmonic nanostructures have rejuvenated the field of chirality. As the precise regioselective growth of inorganic crystals into chiral shapes at the nanoscale is extremely challenging, "bottom-up" synthesis of intrinsically chiral nanoparticles with structural stability is obviously attractive and important. With the thiolated bimolecular cosurfactants, we demonstrated a chemical strategy for the synthesis of intrinsically helical plasmonic nanorods (HPNRs) with strong and tailorable plasmonic circular dichroism (PCD) responses, deriving from the zwitterionic interactions between the -NH3+ and -COO- groups of the cysteine molecules (Cys). The influence of structural parameters of HPNRs on PCD responses was analyzed systematically by theoretical simulations. Among the different structural parameters, the pitch depth was found to have the greatest impact on the PCD signals, in agreement with the experimental results. Moreover, the obtained HPNRs with the strong, tunable, and stable chiroptical properties were found to be able to induce circularly polarized luminescence of achiral luminophores. Due to the generality of this effect, this chiral plasmonic nanostructure may have great potential for use in the fields of chiral sensors, chiral catalysis, and displays.

Improving peroxidase activity of gold nanorod nanozymes by dragging substrates to the catalysis sites via cysteine modification.

Surface chemistry control is a key means to improve substrate selectivity and enhance catalytic activity of nanozymes, a kind of novel artificial enzymes. Herein, we demonstrated that apart from chemical properties of functional groups, their spatial distance to the catalytic sites is also very important to improve the catalytic performance of nanozymes. Using cetyltrimethylammonium bromide (CTAB) coated gold nanorods (AuNR) as the example, we showed that cysteine (Cys) surface modification can greatly enhance the peroxidase activity of AuNR for the oxidation of substrate 3,3',5,5'-tetramethylbenzidine (TMB). By using cysteine derivatives, the key role of the carboxylic group in cysteine is revealed in improving substrate binding and activity enhancement. The electrostatic interactions of carboxylic groups from adsorbed cysteine molecules with protonated amino groups of TMB bring TMB molecules to the surface Au active sites and thus markedly increase catalytic activity. In contrast, despite having two carboxylic groups, glutathione (GSH) surface modification only leads to quite limited improvement of catalytic activity. We speculated that due to large molecular size of GSH, the spatial distance between TMB-GSH and Au is larger than that between TMB-Cys and Au. Furthermore, Raman characterization indicated that at high Cys coverage, they form patches on rod surface via zwitterionic interactions, which may give additional benefits by decreasing the steric hindrance of TMB diffusion to surface Au atom sites. In all, our study highlights the importance of fine surface tuning in the design of nanozymes.

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.

Nonlinear Amplification of Chirality in Self-Assembled Plasmonic Nanostructures.

Molecular chirality transfer and amplification is at the heart of the fundamental understanding of chiral origin and fabrication of artificial chiral materials. We investigate here the nonlinear amplification effect in the chiral transfer from small molecules to assembled plasmonic nanoparticles. Our results show clearly a recognizable nonlinear behavior of the electronic and plasmonic circular dichroism activities, demonstrating the validity of the "majority-rules" principle operating in both the three-dimensional interface-confined molecularly chiral environment and the assembled plasmonic nanoparticles. Such twin "majority-rules" effects from the self-assembled organic-inorganic nanocomposite system have not been reported previously. By establishing a direct correlation between the dynamic template of the molecularly chiral environment and the nonlinear chiral amplification in the nanoparticle assemblies, this study may provide an insightful understanding of the hierarchical and cooperative chiral information transfer from molecular levels to nanoscales.

Roles of ROS and cell cycle arrest in the genotoxicity induced by gold nanorod core/silver shell nanostructure.

To understand the genotoxicity induced in the liver by silver nanoparticles (AgNPs) and silver ions, an engineered gold nanorod core/silver shell nanostructure (Au@Ag NR) and humanized hepatocyte HepaRG cells were used in this study. The involvement of oxidative stress and cell cycle arrest in the DNA and chromosome damage induced by 0.4-20 µg mL-1 Au@Ag NR were investigated by comet assay, γ-H2AX assay and micronucleus test. Further, the distribution of Au@Ag NR was analyzed. Our results demonstrated that both Ag+ and Au@Ag NR led to DNA cleavage and chromosome damage (clastogenicity) in HepaRG cells and that the Au@Ag NR retained in the nucleus may further release Ag+, aggravating the damages, which are mainly caused by cell cycle arrest and ROS formation. The results reveal the correlation between the intracellular accumulation, Ag+ ion release and the potential genotoxicity of AgNPs.

Gold Nanorod-Based Nanoplatform Catalyzes Constant NO Generation and Protects from Cardiovascular Injury.

Cardiovascular disease is a leading cause of death, and one of the effective therapeutic strategies for cardiovascular disease is to provide a controlled, constant supply of nitric oxide (NO) in a mild manner; however, this has proved challenging in the clinic. To address this problem, we built a nitric oxide synthase (NOS)-like nanoplatform (NanoNOS) that consists of a noble metal nanoparticle core and a mesoporous silica shell and demonstrated the ability of NanoNOS to catalyze production of NO in vitro. Mechanistic studies show that the catalysis consists of a three-step reaction: the oxidation of NADPH to produce O2-via oxidase-like activity and the subsequent dismutation of O2- to H2O2via SOD-like activity, followed by H2O2-mediated oxidation of l-arginine to produce NO via a nonenzymatic pathway. The generation of NO is precisely regulated by both the content of the NanoNOS species and the plasmon excitation. We found that NanoNOS greatly suppressed injury-driven monocyte-endothelial cell adhesion, suggesting the NanoNOS treatment could help prevent cardiovascular disease. With such a design as well as plasmon excitation that allows for controlled and constant catalytic activity, NanoNOS technology could have a variety of biomedical applications.

Initiation of protective autophagy in hepatocytes by gold nanorod core/silver shell nanostructures.

The high reactivity of silver nanoparticles leads to their broad applications in the anti-bacterial field; however, the safety of silver nanoparticles has attracted increasing public attention. After exposure to silver nanoparticles in vivo, the liver serves as their potential deposition site; however the potential biological effects of such nanoparticles on hepatocytes at low dosages are not well understood. Here, we study the interaction between gold nanorod core/silver shell nanostructures (Au@Ag NRs) and human hepatocytes, HepG2 cells, and determine that Au@Ag NRs at sub-lethal doses can induce autophagy. After uptake, Au@Ag NRs mainly localize in the lysosomes where they release silver ions and promote the production of reactive oxygen species (ROS). The ROS then suppress the AKT-mTOR signaling pathway and activate autophagy. In addition, oxidative stress results in lysosomal impairment, causing decreased ability for lysosomal digestion. Moreover, oxidative stress also affects the structure and function of mitochondria, leading to the initiation of protective autophagy to eliminate the damaged mitochondrion. Our study shows that at sub-lethal dosages, silver nanomaterials may alter the physiological functions of hepatic cells by activating protective autophagy and cause potential health risks, indicating that cautious consideration of the safety of nanomaterials for certain applications is necessary.

In Vivo Metabolic Response upon Exposure to Gold Nanorod Core/Silver Shell Nanostructures: Modulation of Inflammation and Upregulation of Dopamine.

With the increasing applications of silver nanoparticles (Ag NPs), the concerns of widespread human exposure as well as subsequent health risks have been continuously growing. The acute and chronic toxicities of Ag NPs in cellular tests and animal tests have been widely investigated. Accumulating evidence shows that Ag NPs can induce inflammation, yet the overall mechanism is incomplete. Herein, using gold nanorod core/silver shell nanostructures (Au@Ag NRs) as a model system, we studied the influence on mice liver and lungs from the viewpoint of metabolism. In agreement with previous studies, Au@Ag NRs' intravenous exposure caused inflammatory reaction, accompanying with metabolic alterations, including energy metabolism, membrane/choline metabolism, redox metabolism, and purine metabolism, the disturbances of which contribute to inflammation. At the same time, dopamine metabolism in liver was also changed. This is the first time to observe the production of dopamine in non-neural tissue after treatment with Ag NPs. As the upregulation of dopamine resists inflammation, it indicates the activation of antioxidant defense systems against oxidative stress induced by Au@Ag NRs. In the end, our findings deepened the understanding of molecular mechanisms of Ag NPs-induced inflammation and provide assistance in the rational design of their biomedical applications.

Corona of Thorns: The Surface Chemistry-Mediated Protein Corona Perturbs the Recognition and Immune Response of Macrophages.

The significance of protein coronas on the biological fates of nanoparticles has been widely recognized. Therefore, the alterations on biological effects caused by protein coronas need systemic study and interpretation to design novel safe and efficient nanomedicines. In the present study, we present a comprehensive quantitative analysis of the protein coronas on gold nanorods  modified with various surface ligands of different chemical compositions and charges. The design of surface ligands is of utmost importance for the functionalization of nanoparticles, and further, the ligand-induced biological identity determines the fate of nanoparticles in the human body. We found that the surface chemistry influences the composition of the protein corona more profoundly than surface charge. Since the first and most important challenge for administrated nanomedicines is navigating the interaction with macrophages, we further investigated how the surface chemistry-induced specific protein corona affects the phagocytosis and immune responses of macrophages exposed to the corona-nanoparticle complexes. Our results reveal that the protein corona alters the internalization pathways of gold nanorods by macrophages via the interactions of the predominant coronal proteins with specific receptors on the cell membrane. The cytokine secretion profile of macrophages is also highly dependent on the adsorption pattern of the protein corona. The more abundant proteins involved in immune responses, such as acute phase, complement, and tissue leakage proteins, present in the acquired nanoparticle corona, the more macrophage interleukin-1ß (IL-1ß) released is stimulated. The ligand-protein corona composition-immune response coefficient analysis may serve next-generation nanomedicines with high efficiency and good safety for better clinical translation.

Antigen-labeled mesoporous silica-coated Au-core Pt-shell nanostructure: a novel nanoprobe for highly efficient virus diagnosis.

BACKGROUND: As an emerging research area of artificial enzymes, nanozyme, the catalytic nanomaterials with enzyme-like characteristics, have attracted enormous attention in research. Here, a nanozyme probe has been realized by utilizing antigen-labeled mesoporous silica-encapsulated Au-core Pt-shell (Au@Pt@SiO2) nanostructures for the diagnosis of rubella virus (RV). Pt nanoparticles have been suggested to act as potent peroxidase mimetics with high activities. However, smaller Pt nanoparticles are very easily aggregated, which has negative effects on the catalytic activities. RESULTS: In this work, the use of gold nanorod as the support favours the well dispersion of the small Pt nanoparticles to improve the stability of them. Furthermore, the designed the silica shell could also isolate the recognition antigens from the surface reactive sites, retaining catalytic activity of the inner nanozyme. In addition, compared with antigen-labeled horseradish peroxidase (HRP), the antigen-labeled Au@Pt@SiO2 nanozyme was more stable and robust. A capture enzyme-linked immunosorbent assay (ELISA) for the determination of RV showed that the antigen-labeled Au@Pt@SiO2 nanozyme-based ELISA exhibited good sensitivity. CONCLUSIONS: The highly sensitive peroxidase-like activity of antigen-labeled Au@Pt@SiO2 nanozyme, along with their catalytic stability and robustness, can facilitate their utilization in biochemical assays and clinical diagnosis.

Plasmon-Enhanced Oxidase-Like Activity and Cellular Effect of Pd-Coated Gold Nanorods.

Local surface plasmon resonance (LSPR)-enhanced catalysis has attracted much attention recently. Palladium nanoparticles have been reported to have various nanozyme activities and exhibit promising potentials for biomedical applications. However, as Pd is a poor plasmonic metal, little attention has been paid to its LSPR-regulated nanozyme activity. Herein, by using Au nanorods (AuNRs) as a strong plasmonic core, we coated a thin layer Pd to form a rod-shaped core-shell structure. The obtained Au@PdNRs showed tunable LSPR bands in the near-infrared (NIR) spectral range inheriting from the Au core and yet an exposed Pd surface for catalysis. The oxidase-like activity was investigated in the dark and upon SPR excitation. The plasmon-enhanced activity was observed and was mainly ascribed to the local photothermal effect. Finally, to enhance biocompatibility, mesoporous silica-coated nanorods were used to detect the oxidase-like activity in cells. After being endocytosed by cells, upon plasmon excitation, the oxidase activity of Au@PdNRs could be manifested and lead to higher cytotoxicity and depolarization of mitochondrial membrane potential. Our studies highlight the feasibility of regulating the nanozyme activity of plasmonic nanostructures using their unique NIR plasmonic features with spatiotemporal control.