Chirality, a neglected physico-chemical property of nanomaterials? A mini-review on the occurrence and importance of chirality on their toxicity

Chiral silver nanoparticles with surface-anchored L(D)-Cys exhibit dissimilar biological characteristics in vitro but not in vivo

This work investigated the influence of surface chirality on cellular internalization, cytotoxicity, and tissue distribution of silver nanoparticles (AgNPs). D-cysteine and L-cysteine are chiral forms of the amino acid cysteine. These enantiomers exhibit distinct spatial arrangements, with D-cysteine having a different configuration from L-cysteine. This structural dissimilarity can lead to variations in how these forms interact with biological systems, potentially impacting their cytotoxic responses. Four distinct types of AgNPs were synthesized, each possessing a unique surface coating: pristine AgNPs (pAgNPs), L-cysteine coated AgNPs (AgNPs@L-Cys), D-cysteine coated AgNPs (AgNPs@D-Cys), and racemic AgNPs coated with both L-Cys and D-Cys (AgNPs@L/D-Cys). We found chiral-dependent cytotoxicity of AgNPs on J774A.1 cells. Specifically, AgNPs@L-Cys exhibited the highest toxicity, and AgNPs@D-Cys exhibited the lowest toxicity. Meanwhile, the cellular uptake of the AgNPs correlated nicely with their cytotoxicity, with AgNPs@L-Cys being internalized to the greatest extent while AgNPs@D-Cys displays the least internalization. Scavenger receptors and clathrin predominantly mediate the cellular internalization of these AgNPs. Strikingly, the dissimilar cellular internalization and cytotoxicity of AgNPs with different chirality were eliminated upon protein corona coverage. Notably, following intravenous injection in mice, these four types of AgNPs showed similar patterns among various organs due to the inevitable protein adsorption in the bloodstream. These findings underscored the pivotal role of surface chirality in governing the biological interactions and toxicity of AgNPs.

Toxic effect and mechanism of β-cypermethrin and its chiral isomers on HTR-8/SVneo cells

Beta-cypermethrin (β-CYP) consists of four chiral isomers, acting as an environmental estrogen and causing reproductive toxicity, neurotoxicity, and dysfunctions in multiple organ systems. This study investigated the toxic effects of β-CYP, its isomers, metabolite 3-phenoxybenzoic acid (3-PBA), and 17β-estradiol (E2) on HTR-8/SVneo cells. We focused on the toxic mechanisms of β-CYP and its specific isomers. Our results showed that β-CYP and its isomers inhibit HTR-8/SVneo cell proliferation similarly to E2, with 100 μM 1S-trans-αR displaying significant toxicity after 48 h. Notably, 1S-trans-αR, 1R-trans-αS, and β-CYP were more potent in inducing apoptosis and cell cycle arrest than 1R-cis-αS and 1S-cis-αR at 48 h. AO/EB staining and flow cytometry indicated dose-dependent apoptosis in HTR-8/SVneo cells, particularly at 100 μM 1R-trans-αS. Scratch assays revealed that β-CYP and its isomers variably reduced cell migration. Receptor inhibition assays demonstrated that post-ICI 182780 treatment, which inhibits estrogen receptor α (ERα) or estrogen receptor β (ERβ), β-CYP, its isomers, and E2 reduced HTR-8/SVneo cell viability, whereas milrinone, a phosphodiesterase 3 A (PDE3A) inhibitor, increased viability. Molecular docking studies indicated a higher affinity of β-CYP, its isomers, and E2 for PDE3A than for ERα or ERβ. Consequently, β-CYP, its isomers, and E2 consistently led to decreased cell viability. Transcriptomics and RT-qPCR analyses showed differential expression in treated cells: up-regulation of Il24 and Ptgs2, and down-regulation of Myo7a and Pdgfrb, suggesting the PI3K-AKT signaling pathway as a potential route for toxicity. This study aims to provide a comprehensive evaluation of the cytotoxicity of chiral pesticides and their mechanisms.

Expanding the Horizons of Machine Learning in Nanomaterials to Chiral Nanostructures

Machine learning holds significant research potential in the field of nanotechnology, enabling nanomaterial structure and property predictions, facilitating materials design and discovery, and reducing the need for time-consuming and labor-intensive experiments and simulations. In contrast to their achiral counterparts, the application of machine learning for chiral nanomaterials is still in its infancy, with a limited number of publications to date. This is despite the great potential of machine learning to advance the development of new sustainable chiral materials with high values of optical activity, circularly polarized luminescence, and enantioselectivity, as well as for the analysis of structural chirality by electron microscopy. In this review, an analysis of machine learning methods used for studying achiral nanomaterials is provided, subsequently offering guidance on adapting and extending this work to chiral nanomaterials. An overview of chiral nanomaterials within the framework of synthesis-structure-property-application relationships is presented and insights on how to leverage machine learning for the study of these highly complex relationships are provided. Some key recent publications are reviewed and discussed on the application of machine learning for chiral nanomaterials. Finally, the review captures the key achievements, ongoing challenges, and the prospective outlook for this very important research field.

Exploring the Influence of the Phosphorus-Heteroatom Substitution in Nicotine on Its Electronic and Vibrational Spectroscopic Properties

The influence of phosphorus substitution of nitrogen in heterocyclic compounds on the vibrational spectroscopy as well as frontier molecular orbitals are analyzed. Nicotine with two nitrogen atoms in its structure is taken as the sample system to be studied computationally. By replacing the nitrogen atom in one or both rings of this molecule with phosphorus, three nicotine derivatives are created. The vibrational circular dichroism and infrared spectra of these four molecules in their monomer state, as well as the assemblies up to trimers are determined. The aforementioned spectra are calculated using static quantum chemical calculations employing a cluster-weighted approach. The calculated gas phase spectra of nicotine are compared to their respective experimental spectra. It is observed that the nicotine derivatives with phosphorus in the methylpyrrolidine ring have considerably different gas phase and bulk phase vibrational circular dichroism spectra when compared to nicotine. The phosphorus substitution reduces the energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital as well as altering the polarizability and reactivity of the investigated molecules.

Chiral Carbon Dots and Chiral Carbon Dots with Circularly Polarized Luminescence: Synthesis, Mechanistic Investigation and Applications

Chiral carbon dots (CCDs) can be widely used in various fields such as chiral recognition, chiral catalysis and biomedicine because of their unique optical properties, low toxicity and good biocompatibility. In addition, CCDs with circularly polarized luminescence (CPL) can be synthesized, thus broadening the prospects of CCDs applications. Since the research on CCDs is still in its infancy, this paper reviews the chiral origin, formation mechanism, chiral evolution, synthesis and emerging applications of CCDs, with a special focus on CCDs with CPL activity. It is hoped that it will provide some reference to solve the current problems faced by CCDs. Finally, the opportunities and challenges of the current research on CCDs are described, and their future development trends have also been prospected.

Optimal weak measurement scheme for chiral molecular detection based on photonic spin Hall effect

In this paper, we propose a precision method to measure the chiroptical signal of Artemisinin solutions using the photonic spin Hall effect (PSHE) on the Ce:YIG-YIG-SiO2 structure as a probe. The effects of transmission distance, incident angles, applied magnetic fields of different directions, and beam waist of light on the weak measurement system are analytically investigated through simulations. It is found that decreasing the beam waist of the incident spot, increasing the incident angle, increasing the transmission distance, and adding a longitudinal magnetic field is conducive to enhancing the amplification transverse shift of PSHE, thus the measurement sensitivity is greatly improved. Based on the optimal weak measurement scheme, the detection limit for concentration measurement of artemisinin based on optical rotatory (OR) was reduced to 0.05 mg/ml. The measurement precision of the OR angle has been improved to 10-7rad.

Design and development of molten metal nanomaterials using sonochemistry for multiple applications

Molten metals have prospective applications as soft fluids with unique physical and chemical properties, yet materials based on them are still in their infancy and have great potential. Ultrasonic irradiation of molten metals in liquid media induces acoustic cavitation and dispersion of the liquid metal into micrometric and nanometric spheres. This review focuses on the synthesis of mmetallic materials via sonochemistry from molten metals with low melting point (< 420 ᴼC): Ga, Hg, In, Sn, Bi, Pb, and Zn, which can be melted in organic or inorganic media or water and of aqueous solutions of metallic ions to form two immiscible liquid phases. Organic molecule entrapment, polymer solubilization, chiral imprinting, and catalyst incorporation within metals or metallic particles were recently developed to provide novel hybrid nanomaterials for several applications including catalysis, fuel cells, and biomass-to-biofuel conversion. In all cases where molten metal was sonicated in an organic solvent, in addition to a solid precipitant, an interesting supernatant was obtained that contained metal-doped carbon dots (M@C-dots). Some of these M@C-dots were found to exhibit highly effective antimicrobial activity, promote neuronal tissue growth, or have utility in lithium-ion rechargeable batteries. The economic feasibility and commercial scalability of molten metal sonochemistry attract fundamental interest in the reaction mechanisms, as the versatility and controllability of the structure and material properties invite exploration of various applications.

Detection and analysis of chiral molecules as disease biomarkers

The chirality of small metabolic molecules is important in controlling physiological processes and indicating the health status of humans. Abnormal enantiomeric ratios of chiral molecules in biofluids and tissues occur in many diseases, including cancers and kidney and brain diseases. Thus, chiral small molecules are promising biomarkers for disease diagnosis, prognosis, adverse drug-effect monitoring, pharmacodynamic studies and personalized medicine. However, it remains difficult to achieve cost-effective and reliable analysis of small chiral molecules in clinical procedures, in part owing to their large variety and low concentration. In this Review, we describe current and emerging techniques that detect and quantify small-molecule enantiomers and their biological importance.

Stereoselective behaviors and enantiomeric effects of paclobutrazol on microorganisms during Chinese cabbage pickling process

Studies on the differences between chiral pesticide enantiomers have caused widespread concern in the last decade. In the current work, the selective behaviors and different biological activities of paclobutrazol enantiomers during Chinese cabbage pickling process were evaluated. Results of degradation kinetics indicated that when paclobutrazol reside in raw material (Chinese cabbage) and was introduced into the pickling process, the degradation rates of the two paclobutrazol enantiomers were significantly different, the half-lives of (2R, 3R)-paclobutrazol (R-paclobutrazol) and (2S, 3S)-paclobutrazol (S-paclobutrazol) were 18.24 and 6.19 d, respectively. Besides, the conversion between the two enantiomers could also be observed, and the conversion rate of R-paclobutrazol to S-paclobutrazol was slower than that of reverse process. In addition, from the analysis of 16S rRNA and ITS sequencing, we inferred that the degradation of paclobutrazol was probably due to the presence of Pseudomonas and Serratia. Moreover, there has a significant difference in biological activity between R-paclobutrazol and S-paclobutrazol and shown an obviously enantiomeric effects on microbial community composition of pickling system. Besides, the analysis of microbial community displayed R-paclobutrazol might inhibit the growth of Erwinia (a sort of plant pathogens). Results from this study served to enhance our understanding of chiral pesticide residues on food safety and the potential risks to human health.

Influence of surface chemistry and morphology of nanoparticles on protein corona formation

Nanomaterials offer promising solutions as drug delivery systems and imaging agents in response to the demand for better therapeutics and diagnostics. However, the limited understanding of the interaction between nanoparticles and biological entities is currently hampering the development of new systems and their applications in clinical settings. Proteins and lipids in biological fluids are known to complex with nanoparticles to form a "biomolecular corona". This has been shown to affect particles' morphology and behavior in biological systems and their interactions with cells. Hence, understanding how nanomaterials' physicochemical properties affect the formation and composition of this biocorona is a crucial step. This work evaluates existing literature on how morphology (size and shape), and surface chemistry (charge and hydrophobicity) of nanoparticles influence the formation of protein corona. The latest evidence suggest that although surface charge promotes the interaction with proteins and lipids, surface chemistry plays a leading role in determining the affinity of the nanoparticle for biomolecules and, ultimately, the composition of the corona. More recently the study of additional nanoparticles' properties like shape and surface chirality have demonstrated a significant effect on protein corona architecture, providing new tools to tailor biomolecular corona formation. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Toxicology and Regulatory Issues in Nanomedicine > Toxicology of Nanomaterials.

Enantioselective effect of cysteine functionalized mesoporous silica nanoparticles in U87 MG and GM08680 human cells and Staphylococcus aureus bacteria

Chirality is a fundamental phenomenon in biological systems, since most of the biomolecules and biological components and species are chiral and therefore recognize and respond differently depending on the enantiomer present. With increasing research into the use of nanomaterials for biomedical purposes, it is essential to understand the role that chirality of nanoparticles plays at the cellular level. Here, the chiral cysteine functionalization of mesoporous silica nanoparticles has been shown to broadly affect its interaction with U87 MG human glioblastoma cell, healthy human fibroblast (GM08680) and methicillin-resistant S. aureus bacteria. We believe that this research is important to further advancement of nano-biotechnology.

Molecular-level insights into the self-assembly driven enantioselective recognition process

The importance of the orientation of functional groups in a chiral environment on enantioselective recognition has been demonstrated. Orientation controlled interactions of functional groups in (R)/(S)-MA lead to a visually differentiable morphology with an arginine-based gelator. The crucial role of various molecular-level interactions discriminating the enantioselective self-assembly has been established using different analytical techniques, crystal structure analysis, and DFT calculations.

Brave new world revisited: Focus on nanomedicine

Nanomedicine is at a crossroads: with relatively few success stories in terms of clinical translation despite more and more research on increasingly sophisticated nanomaterials, it is important to consider whether we are on the right track. Indeed, it is crucial that we address the fact that while considerable efforts are being made to overcome barriers to translation from the bench to the clinic, scientists are still struggling to decipher fundamental aspects of nanomaterial interactions with biological systems. We believe that a key to the successful adoption of nanomedicines in oncology and beyond lies in a deeper understanding of underlying biological processes and in decoding interactions between engineered nanomaterials and biological systems. Here we provide an overview of progress in nanomedicine during the past 5 years.

Chirality Detection by Raman Spectroscopy: The Case of Enantioselective Interactions between Amino Acids and Polymer-Modified Chiral Silica

In chirality research area, it is of interest to reveal the chiral feature of inorganic nanomaterials and their enantioselective interactions with biomolecules. Although common Raman spectroscopy is not regarded as a direct chirality analysis tool, it is in fact effective and sensitive to study the enantioselectivity phenomena, which is demonstrated by the enantio-discrimination of amino acid enantiomers using the polydopamine-modified intrinsically chiral SiO₂ nanofibers in this work. The Raman scattering intensities of an enantiomer of cysteine are more than twice as high as those of the other enantiomer with opposite handedness. Similar results were also found in the cases of cystine, phenylalanine, and tryptophan enantiomers. In turn, these organic molecules could be used as chirality indicators for SiO₂, which was clarified by the unique Raman spectra-derived mirror-image relationships. Thus, an indirect chirality detection method for inorganic nanomaterials was developed.

Elucidating the potential neurotoxicity of chiral phenthoate: Molecular insight from experimental and computational studies

Chiral organophosphorus pollutants are existed ubiquitously in the ecological environment, but the enantioselective toxicities of these nerve agents to humans and their molecular bases have not been fully elucidated. Using experimental and computational approaches, this story was to explore the neurotoxic response process of the target acetylcholinesterase (AChE) to chiral phenthoate and further decipher the microscopic mechanism of such toxicological effect at the enantiomeric level. The results showed that the toxic reaction of AChE with chiral phenthoate exhibited significant enantioselectivity, and (R)-phenthoate (K＝1.486 × 10⁵ M^-1) has a bioaffinity for the nerve enzyme nearly three times that of (S)-phenthoate (K＝4.503 × 10⁴ M^-1). Dynamic research outcomes interpreted the wet experiments, and the inherent conformational flexibility of the target enzyme has a great influence on the enantioselective neurotoxicological action processes, especially reflected in the conformational changes of the three key loop regions (i.e. residues His-447, Gly-448, and Tyr-449; residues Gly-122, Phe-123, and Tyr-124; and residues Thr-75, Leu-76, and Tyr-77) around the reaction patch. This was supported by the quantitative results of conformational studies derived from circular dichroism spectroscopy (α-helix: 34.7%→30.2%/31.6%; β-sheet: 23.6%→19.5%/20.7%; turn: 19.2%→22.4%/21.9%; and random coil: 22.5%→27.9%/25.8%). Meanwhile, via analyzing the modes of toxic action and free energies, we can find that (R)-phenthoate has a strong inhibitory effect on the enzymatic activity of AChE, as compared with (S)-phenthoate, and electrostatic energy (-23.79/－17.77 kJ mol^-1) played a critical role in toxicological reactions. These points were the underlying causes of chiral phenthoate displaying different degrees of enantioselective neurotoxicity.

Stereospecific interactions between chiral inorganic nanomaterials and biological systems

Chirality is ubiquitous in nature and plays mysterious and essential roles in maintaining key biological and physiological processes.