Charged Nanoparticles Research Articles

Dynamic interactions of negatively charged gold nanoparticles (AuNPs) in aqueous environments with different ionic compositions

This study provides a comprehensive analysis of the interactions between negatively charged gold nanoparticles (Au)144(SRCOO1−)60 and both divalent (Mg2+, Ca2+) and monovalent (Na+, K+) ions in aqueous solution, employing molecular dynamics simulations. The investigation focuses on elucidating the energetics, hydrogen bond patterns and radial distribution of ions surrounding gold nanoparticles. Our results reveal distinct differences in the Coulombic and van der Waals energies between gold nanoparticles and ions, as well as between gold nanoparticles and water, which exert influence on hydrogen bond patterns and lifetimes, as even as ion and water mobility. These findings have important implications for potential applications in nanotechnology and materials science. This research contributes to a deeper understanding of ion-nanoparticle interactions and provides valuable insights for the design and development of new nanomaterials with properties and functionalities.

Effects of 2-ethylbutyric acid, 2-ethyl-1-butanol, and 3-methylpentane on the micellization thermodynamics and physicochemical properties of HS 15 and TW 80 micelles based on differences in functional groups

Herein, we investigated the effects of 2-ethylbutyric acid, 2-ethyl-1-butanol, and 3-methylpentane, each possessing varying functional groups, on polyoxyl 15 hydroxystearate (HS 15) and polysorbate 80 (TW 80) micelles. Initially, the critical micelle concentration (CMC) for both systems was determined. Subsequent measurements included the particle size, zeta potential, cloud point, micropolarity, number of aggregates, and fluorophore release profile. Finally, the number of hydrogen bonds was confirmed through molecular docking technology. Results showed distinct effects of different functional groups on TW 80 and HS 15 micelles, exhibiting a decreasing trend of CMC, Amin, Gmin, particle size, and polydispersity index (PDI) with increased functional group polarity, alongside increased zeta potential, decreased cloud point, enlarged hydrophobic region, and rapid fluorophore quenching. In particular, acids with carboxyl groups exhibited enhanced stability with HS 15 and TW 80 micelles owing to differences in polarity, solubilization sites, and intermolecular forces. Using tanshinone extract as a model drug, the study explored HS 15 and TW 80 micelles as drug carriers, and results indicated that 2-ethylbutyric acid micelles exhibited better bacterial inhibition against Staphylococcus aureus. Considering that the surface of bacteria was negatively charged, the positively charged nanoparticles exhibited strong electrostatic interactions with the bacteria, which exerted a superior antibacterial effect. In summary, 2-ethylbutyric acid micelles displayed the smallest CMC, Amin, Gmin, particle size, and PDI, along with a positive charge, highlighting the potential application of 2-ethylbutyric acid.

Mechanism of charge self-reversal nano-nutrient delivery system to overcome the mucosal barrier

When delivering hydrophobic nutrients such as curcumin (Cur) in the gastrointestinal tract (GIT), oral protein nanoparticles (NPs) will encounter several physiological barriers, including gastric acidity, digestive enzymes, mucus, and the epithelial layer. It is worth noting that overcoming both mucus and epithelial barriers requires NPs with completely opposite surface properties. To address this challenge, this study developed enzyme-responsive NPs using chitosan (CS) and tripolyphosphate (TPP) co-modification of zein (Cur/ZCT NPs). Three types of ZCT NPs were studied: positively charged NPs (Cur/ZCT0.2), neutrally charged NPs (Cur/ZCT0.8), and negatively charged NPs (Cur/ZCT3.0), which exhibit good stability in GIT while preserving the bioactivity of Cur. ZCT0.8 (0.86 ± 3.86 mV) and ZCT3.0 (–32.75 ± 1.07 mV) demonstrated superior mucus penetration capabilities. ZCT NPs were shown to effectively undergo charge reversal in the presence of intestinal alkaline phosphatase (IAP). The enhanced cellular uptake of ZCT NPs compared to zein NPs can be attributed to two factors: (1) enzyme-responsive dephosphorylation leading to a hydrophobic and positively charged surface, and (2) the ability of NPs to enter cells via transcellular and paracellular pathways. In vivo experiments revealed that ZCT0.8 and ZCT3.0 NPs exhibited extended retention times in the small intestine and higher uptake by epithelial cells compared to other samples. In conclusion, the enzyme-responsive charge reversal mechanism in ZCT3.0 NPs results in enhancing stability and enabling effective traversal of mucus and epithelial barriers. Consequently, they exhibit significant potential as a nutrient delivery system.

Synthesis of succinate derivatives using a magnetically separable Fe3O4@gly@Furfural@Co(NO3)2 nanocatalyst at room temperature

A simple, one-pot synthesis of nine 3-(4-oxo-4,5-dihydro-thiazole-2-yl sulfanyl) succinate derivatives has been achieved in moderate to good yields via a three-component reaction of dialkyl acetylenedicarboxylates, phosphites, and rhodanine at room temperature conditions and a magnetically-separable Fe3O4@gly@Furfural@Co(NO3)2 nanocatalyst. The size, surface charge, superparamagnetic properties, crystalline structure, and surface functional groups of nanoparticles were characterized and carried out utilizing several techniques such as X-ray diffraction analysis (XRD), Field emission scanning electron microscopy (FESEM), and Value stream mapping (VSM).

Tuning the surface charge and colloidal stability of hybrid gold-chitosan derivative nanoparticles for siRNA delivery

In recent years, the therapeutic potential of small interfering RNA (siRNA) has been confirmed by the emergence of commercially available siRNA-based drugs and by advances in the clinical trials phase. However, the many biological barriers faced by siRNA up to its delivery to the intended target make the advances in siRNA therapies highly dependent on the use of efficient gene vectors. In this study, the design of a new nanoparticle structured with a gold core and a diisopropylethylamine-chitosan shell was devised for application as a siRNA carrier. Thiol functionalized diisopropylethylamine-chitosan polymers were grafted onto gold nanoparticles (AuNPs) to obtain pH-responsive hybrid siRNA carriers (AuNP@polymers). The precise control of the diisopropylethylamine (DIPEA) graft and the tuning of the amount of polymer linked to the AuNPs enabled the assembly of hybrid carriers with good colloidal stability in physiological ionic strength (150 mmol L−1), sizes between 50 and 100 nm and positive zeta potentials (up to +17 mV), over a wide range of pH (5.5–7.4). The coated AuNPs were able to bind siRNA at N/P ratios in the range of 5–20, providing protection for the siRNA against RNAse degradation and making the hybrid vectors structurally and colloidally stable even in a protein-supplemented medium. The AuNP@polymers nanocarriers displayed non-cytotoxic effects in both 3T3/NIH fibroblast and HeLa-GFP cells up to an N/P ratio of 20 and the uptake of AuNP@polymers by RAW 264.7 macrophages was similar to Lipofectamine™ RNAiMAX. The zeta potential of the hybrid vectors was accurately adjusted by controlling the DIPEA graft and the pH of the formulation medium, which in turn drove the silencing efficiency of the siRNA nanocarrier as observed by the green fluorescent protein (GFP) knockdowns in HeLa cells. GFP knockdown levels close to that of Lipofectamine (up to 70 %) were achieved for the vectors formulated at pH 5.5. Overall, the results showed that the DIPEA-chitosan/AuNP association is a promising strategy to formulate hybrid nanocarriers for siRNA delivery with potential for in vivo studies.

Colloidal dispersions of cobalt ferrite nanoparticles in EMIM TFSI, propylene carbonate and their mixtures

Liquid thermocells are promising devices for the recovery of low-grade waste heat and its conversion into electricity. The present study proposes dispersing charged magnetic nanoparticles in liquids to improve thermoelectric conversion, due to their thermodiffusive and magnetic properties. Core@shell cobalt ferrite@maghemite nanoparticles (NPs) of various sizes with three different kinds of coatings are tested for dispersion in EMIM TFSI (ethyl-methylimidazolium bistriflimide), an ionic liquid (IL) of high electrical conductivity. Among the tested ligands, PAC6MIM±Br− (1-(6-hexylphosphonate) 3-methyl imidazolium bromide) emerges as the most efficient due to its phosphonic group. This ligand leads to dispersions of clusters of a few dozen NPs in water and a few NPs in EMIM TFSI. For improving both the viscosity and the electrical conductivity, dispersions in binary mixtures of propylene carbonate (PC), a polar medium, and EMIM-TFSI are further investigated with the sample based on NPs of ∼ 9 nm diameter. Through a pumping and heating procedure, stable dispersions are obtained with a subsequent reduction of the size of the NP clusters, down to 1 to 2 NPs in EMIM TFSI and a few NPs in PC and their binary mixtures. The mixture with an IL mole fraction ∼0.2–0.3 and maximal electrical conductivity is a promising candidate for further thermoelectric investigations.

Dissolution Mechanisms and Surface Charge of Clay Mineral Nanoparticles: Insights from Kinetic Monte Carlo Simulations

The widespread use of clay minerals and clays in environmental engineering, industry, medicine, and cosmetics largely stems from their adsorption properties and surface charge, as well as their ability to react with water. The dissolution and growth of minerals as a function of pH are closely related to acid–base reactions at their surface sites and their surface charge. The vivid tapestry of different types of surface sites across different types of clay minerals generates difficulties in experimental studies of structure–property relationships. The aim of this paper is to demonstrate how a mesoscale stochastic kinetic Monte Carlo (kMC) approach altogether with atomistic acid-base models and empirical data can be used for understanding the mechanisms of dissolution and surface charge behavior of clay minerals. The surface charge is modeled based on equilibrium equations for de/protonated site populations, which are defined by the pH and site-specific acidity constants (pKas). Lowered activation energy barriers for these sites in de/protonated states introduce pH-dependent effects into the dissolution kinetics. The V-shaped curve observed in laboratory experiments is reproduced with the new kMC model. A generic rate law for clay mineral dissolution as a function of pH is derived from this study. Thus, the kMC approach can be used as a hypothesis-testing tool for the verification of acid–base models for clay and other minerals and their influence on the kinetics of mineral dissolution and growth.

Interaction of charged magnetic nanoparticles with surfaces

The behavior of magnetic nanoparticles covering the surface with positive charges (MN), suspended in a continuous medium, was simulated by Brownian dynamics. Then, we studied the behavior of the MN in an aqueous-like suspension and their adsorption on a negatively charged surface, mimicking a mica surface. After several microseconds, particles are deposited onto the charged surface. Experimental results of ordered magnetic nanoparticles in surfaces are compared with the present simulation results of MN in two dimensions. We also demonstrate the effect of charged MN on the hexagonal structure when electrical repulsions dominate against magnetic dipole-dipole and van der Waals attractions. On one hand, the adsorption of MN on the surface depends on the electrostatic attraction force with the surface, while the surface organization of MN results from balancing electrostatic repulsion forces and magnetic attraction forces among particles. In magnetic nanoparticles simulated with a non-charged surface or weakly charged surface, dipole-dipole interactions dominate the particle-particle interactions, and the interactions between particles and a mica-like surface are conducted by van der Waals forces.

Colloidal droplet desiccation on a electrowetting-on-dielectric (EWOD) platform

The physics of the effects of electric field on the desiccation of colloidal droplets, comprising of dispersed negatively charged nanoparticles [2 μl, 1(w/w. %)], are studied in a standard electrowetting-on-a-dielectric configuration. The extent of contact line pinning during evaporation is found to be a function of the magnitude of the applied voltage and quantified in terms of the dimensionless electrowetting number (η). The pinned contact line led to higher particle compaction as evidenced by the characterization of dried colloidal film thicknesses. Crack formation and their dynamics have been analyzed in detail to elicit the interplay of forces near the contact line region and on the compaction front. These aspects of crack formation are elucidated in the light of magnitude and polarity of the applied electric field. It is found to influence the crack front initiation velocity, the geometry, the number of cracks, and an attempt is made to explain the same via first principle-based approaches. Therefore, this study indicates the possibility of using electrowetting as a technique to fine-tune the crack formation behavior in thin colloidal films.

Supramolecular assembly of polycation/mRNA nanoparticles and in vivo monocyte programming

Size-dependent phagocytosis is a well-characterized phenomenon in monocytes and macrophages. However, this size effect for preferential gene delivery to these important cell targets has not been fully exploited because commonly adopted stabilization methods for electrostatically complexed nucleic acid nanoparticles, such as PEGylation and charge repulsion, typically arrest the vehicle size below 200 nm. Here, we bridge the technical gap in scalable synthesis of larger submicron gene delivery vehicles by electrostatic self-assembly of charged nanoparticles, facilitated by a polymer structurally designed to modulate internanoparticle Coulombic and van der Waals forces. Specifically, our strategy permits controlled assembly of small poly(β-amino ester)/messenger ribonucleic acid (mRNA) nanoparticles into particles with a size that is kinetically tunable between 200 and 1,000 nm with high colloidal stability in physiological media. We found that assembled particles with an average size of 400 nm safely and most efficiently transfect monocytes following intravenous administration and mediate their differentiation into macrophages in the periphery. When a CpG adjuvant is co-loaded into the particles with an antigen mRNA, the monocytes differentiate into inflammatory dendritic cells and prime adaptive anticancer immunity in the tumor-draining lymph node. This platform technology offers a unique ligand-independent, particle-size-mediated strategy for preferential mRNA delivery and enables therapeutic paradigms via monocyte programming.

The fate and impact of Co3O4 nanoparticles in the soil environment: Observing the dose effect of nanoparticles on soybeans

The widespread presence and distribution of metal-based nanoparticles (NPs) in soil is threatening crop growth and food security. However, little is known about the fate of Co3O4 NPs in the soil-soybean system and their phytotoxicity. The study demonstrated the effects of Co3O4 NPs on soybean growth and yield in soil after 60 days and 140 days, and compared them with the phytotoxic effects of Co2+. The results showed that Co3O4 NPs (10–500 mg/kg) had no significant toxic effect on soybeans. Soil available Co content was significantly increased under 500 mg/kg Co3O4 NPs treatment. Compared with Co2+, Co3O4 NPs mainly accumulated in roots and had limited transport to the shoots, which was related to the particle size, surface charge and chemical stability of Co3O4 NPs. The significant accumulation of Co3O4 NPs in roots further led to a significant decrease in root antioxidant enzyme activity and changes in functional gene expression. Co3O4 NPs reduced soybean yield after 140 days, but interestingly, at specific doses, it increased grain nutrients (Fe content increased by 17.38% at 100 mg/kg, soluble protein and vitamin E increased by 14.34% and 16.81% at 10 mg/kg). Target hazard quotient (THQ) assessment results showed that consuming soybean seeds exposed to Co3O4 NPs (≥100 mg/kg) and Co2+ (≥10 mg/kg) would pose potential health risks. Generally, Co3O4 NPs could exist stably in the environment and had lower environmental risks than Co2+. These results help to better understand the environmental behavior and plant effect mechanisms of Co3O4 NPs in soil-plant systems.

Significance of 3D rectangular closed domain filled with charged particles and nanoparticles engaging finite element methodology

Abstract This article aims to use passive flow control to analyze the transportation of heat, mass, and charged particles toward a 3D plate. The current problem offers a novel exploration of the flexible domain of non-Newtonian materials, which are well known for their wide range of applications in the engineering and industrial domains. The current study explores the complex dynamics of heat and mass transfer in a fluid that flows over an elongating sheet. The motion of the nanofluid on the surface is caused by the stretching of the 3D plate. The suspension of mixtures of tetra-hybrid nanoparticles can enhance thermal performance and cooling mechanism. Moreover, the 3D model includes modeling of multiple important parameters, such as heat source, thermal radiation, and Hall and Ion slip effects, in Cartesian coordinates for a three-dimensional stretched plate. This comprehensive analysis of various effects offers a new perspective to the field. Partial differential equations represent the emergent phenomena in the problem formulation process. It was estimated that an enhancement of charged particles and motion regarding nanoparticles is enhanced versus an enhancement of charged particles. With the greater power law index, suction, and Weissenberg number, the acceleration of nanoparticles is enhanced.

Label-free SELEX of aptamers for ultra-sensitive electrochemical aptasensor detection of amanitin in wild mushrooms

BackgroundMushroom poisoning poses a significant global health concern, with high morbidity and mortality rates. The primary lethal toxins responsible for this condition are alpha-amanitin (ɑ-AMA) and beta-amanitin (β-AMA). As a promising bio-recognition molecules in biosensors, aptamers, have been broadly used in the field of food detection. However, the current SELEX-based methods for screening aptamers for structurally similar small molecules were limited by the labelling or salt ion induction. In this study, we aimed to develop a novel label-free SELEX strategy for the screening of aptamers with high affinity and constructed new aptasensors for the detection of ɑ-AMA and β-AMA. ResultsA novel label-free SELEX strategy based on the positively charged gold nanoparticles (AuNPs) was proposed to simultaneous screening of aptamers for ɑ-AMA and β-AMA. Only 18 rounds of SELEX were required to obtain new aptamers. The candidate aptamers were analyzed by colloidal gold assay, and the sequences of ɑ-30 and β-37 displayed great affinity with Kd values of 22.26 nM and 23.32 nM, respectively, without interference from botanical toxins. Notably, the truncated aptamers ɑ-30-2 (50 bp) and β-37-2 (57 bp) exhibited higher affinity than their original counterpart (79 bp). Subsequently, the selected aptamers were utilized to construct recognition probes for electrochemical aptasensors based on hairpin cyclic cleavage of substrates by Cu2+ dependent DNAzyme and Exo I-triggered recycling cascades. The detection platform showed excellent analytical performance with limits of detection as low as 4.57 pg/mL (ɑ-AMA) and 8.49 pg/mL (β-AMA). Moreover, the aptasensors exhibited superior performance in mushroom and urine samples. SignificanceThis work developed a simple and efficient label-free SELEX method for screening new aptamers for ɑ-AMA and β-AMA, which employed the positively charged AuNPs as the screening medium, without the need for chemical labelling of libraries or induction of salt ions. Furthermore, two novel electrochemical aptasensors were developed based on our newly obtained aptamers, which offer the new biosensing tool for ultrasensitive detection of the AMA poisoning, showing great potential in practical applications.

Unraveling the Complexities of Silica Nanoparticle Adsorption onto Polymer Latexes in Pickering Emulsion Polymerization.

Incorporating unmodified silica nanoparticles onto polymer latexes to fabricate aqueous polymer dispersions without relying on electrostatic attraction during the Pickering emulsion polymerization process still faces challenges. For negatively charged silica nanoparticles to successfully adsorb onto polymer latexes, particularly in an anionic initiator emulsion polymerization system, they have remained elusive without the use of auxiliary monomers and cationic initiators. This study investigates various experimental parameters, such as emulsion polymerization temperature, monomer solubility, salt concentration, and cation type, to elucidate the factors influencing the adsorption of unmodified silica nanoparticles in Pickering emulsion polymerization. While poly(methyl methacrylate) (PMMA)/SiO2 hybrid latexes can be obtained under pH conditions of 5-6 and at temperatures of 65 °C or below, the loading rate of silica nanoparticles decreases as the reaction temperature increases, resulting in bare PMMA latexes without silica nanoparticle adsorption at temperatures exceeding 70 °C. Introducing styrene (St) into the monomer mixture with methyl methacrylate in a ratio of up to 10 wt % leads to a gradual decrease in silica nanoparticle loading rate, from 27.3 to 8.2 wt %, attributed to the low solubility of St in water. Furthermore, the presence of sodium ions (Na+) is found to be crucial for silica nanoparticle adsorption onto PMMA latexes, as the sodium ions have a stabilizing effect on both the silica nanoparticles and the silica nanoparticle-armored latexes. These findings highlight the complex nature of Pickering emulsion polymerization in the presence of unmodified silica nanoparticles, demonstrating that the loading rate of silica nanoparticles onto polymer latexes is influenced by various factors. These insights pave the way for developing aqueous polymer dispersions with high silica nanoparticle loading rates onto polymer latexes, which is a desirable trait in the coating industry.

Synthesis of Amphiphilic Amino Poly-Amido-Saccharide and Poly(lactic) Acid Block Copolymers and Fabrication of Paclitaxel-Loaded Mucoadhesive Nanoparticles.

Drug delivery to the esophagus through systemic administration remains challenging, as minimal drug reaches the desired target. Local delivery offers the potential for improved efficacy while minimizing off-target toxicities but necessitates bioadhesive properties for mucosal delivery. Herein, we describe the synthesis of two new mucoadhesive amphiphilic copolymers prepared by sequential ring-opening copolymerization or postpolymerization click conjugation. Both strategies yield block copolymers containing a hydrophilic amine-functionalized poly-amido-saccharide and either a hydrophobic alkyl derivatized poly-amido-saccharide or poly(lactic acid), respectively. The latter resulting copolymers readily self-assemble into spherical, ≈200 nm diameter, positively charged mucoadhesive nanoparticles. The NPs entrap ultrahigh levels of paclitaxel via encapsulation of free paclitaxel and paclitaxel conjugated to a biodegradable, biocompatible poly(1,2-glycerol carbonate). Paclitaxel-loaded NPs rapidly enter cells, release paclitaxel, are cytotoxic to esophageal OE33 and OE19 tumor cells in vitro, and, importantly, demonstrate improved mucoadhesion compared to conventional poly(ethylene glycol)-poly(lactic acid) nanoparticles to ex vivo esophageal tissue.

Spin Charge of Co Nanoparticles Loaded on the Carbon Substrate Enabling Rate‐Capable Lithium Storage at High Mass‐Loadings

AbstractDeveloping high mass‐loading electrodes is crucial for enhancing the energy density of current batteries, yet challenges such as poor rate performance and cycling instability must be addressed. Spin charge storage on transition metal nanoparticle surfaces, characterized by rapid charging and the absence of phase transitions, offers an ideal storage behavior for high mass‐loading electrodes. In this study, electrospinning is utilized to fabricate free‐standing carbon nanofibers incorporating Co nanoparticles for high‐mass loading and high‐performance anodes. The resulting anode, with a maximum mass loading of 6.8 mg cm−2, exhibits remarkable cycle stability and high‐rate performance of 2 A g−1 at a capacity over 3 mAh cm−2, superior than reported results. Magnetometry and electron paramagnetic resonance spectroscopy are employed to monitor the charge storage mechanism of the Co@CNFs, involving both the reversible formation of a spin capacitance and the growth of radical anions in the solid electrolyte interface. Additionally, in situ X‐ray diffraction and optical microscopy provide direct evidence of the absence of mechanical stress‐induced phenomena within the spin charge process, attributed to high‐rate capable lithium storage under high mass loading. The strategic approach presented herein offers a reliable methodology for engineering high‐energy‐density lithium‐ion batteries.

Biomimetic Calcium Phosphate Nanoparticles: Biomineralization Models and Precursors for Composite Materials.

The formation of calcium phosphate under the control of water-soluble polymers is important for understanding bone growth in living organisms. These experiments also have spin-offs in the creation of composite materials, including for regenerative medicine applications. The formation of calcium phosphate (hydroxyapatite) from calcium chloride and diammonium phosphate was studied in the presence of polymers containing carboxyl, amine, and imidazole groups. Depending on the polymer composition, solid products and stable dispersions of positively or negatively charged nanoparticles were obtained. Oppositely charged nanoparticles can interact with each other to form a macroporous composite material, which holds promise as a filler for bone defects. The formation of a calcium phosphate layer around a living cell (dinoflagellate Gymnodinium corollarium A. M. Sundström, Kremp et Daugbjerg) using positive composite nanoparticles is a one-step approach to cell mineralization.

Construction of magnetic recoverable porous electron-rich organic frameworks for efficiently enrichment of phenylurea herbicides from water and milk samples prior to HPLC detection

Porous electron-rich organic frameworks have attracted an increased attention in the adsorption and removal of pollutants due to their abundant electron-rich nitrogen atoms, which can effectively interact with positively charged substance. In this study, a porous electron-rich organic framework (Car-POF) and positively charged amino-functionalized magnetic nanoparticles (Fe3O4-NH2) were used to construct a magnetic electron-rich Fe3O4-NH2@Car-POF for the enrichment of some phenylurea herbicides from water and milk samples prior to high performance liquid chromatographic detection. The adsorption capacity of Fe3O4-NH2@Car-POF for the phenylureas ranged from 14.93 to 28.83 mg g−1. The LODs were observed in the range of 0.05–0.20 ng mL−1 and 0.5–1.5 ng mL−1, and LOQs in the range of 0.17–0.66 ng mL−1 and 1.7–5.0 ng mL−1 for water and milk samples with RSD less than 9.0. The adsorption studies with cationic and anionic dyes revealed that Fe3O4-NH2@Car-POF is favorable for the adsorption of positively charged compounds.

Negatively Charged Carbon Dots Employed Symplastic and Apoplastic Pathways to Enable Better Plant Delivery than Positively Charged Carbon Dots.

Efficient delivery of nanoparticles (NPs) to plants is important for agricultural application. However, to date, we still lack knowledge about how NPs' charge matters for its translocation pathway, i.e., symplastic and apoplastic pathways, in plants. In this study, we synthesized and used negatively charged citrate sourced carbon dots (C-CDs, -37.97 ± 1.89 mV), Cy5 coated C-CDs (Cy5-C-CDs, -41.90 ± 2.55 mV), positively charged PEI coated carbon dots (P-CDs, +43.03 ± 1.71 mV), and Cy5 coated P-CDs (Cy5-P-CDs, +48.80 ± 1.21 mV) to investigate the role of surface charges and coatings on the employed translocation pathways (symplastic and apoplastic pathways) of charged NPs in plants. Our results showed that, different from the higher fluorescence intensity of P-CDs and Cy5-P-CDs in extracellular than intracellular space, the fluorescence intensity of C-CDs and Cy5-C-CDs was similar between intracellular and extracellular space in cucumber and cotton roots. It suggests that the negatively charged CDs were translocated via both symplastic and apoplastic pathways, but the positively charged CDs were mainly translocated via the apoplastic pathway. Furthermore, our results showed that root applied negatively charged C-CDs demonstrated higher leaf fluorescence than did positively charged P-CDs in both cucumber (8.09 ± 0.99 vs 3.75 ± 0.23) and cotton (7.27 ± 1.06 vs 3.23 ± 0.22), indicating that negatively charged CDs have a higher translocation efficiency from root to leaf than do positively charged CDs. It should be noted that CDs do not affect root cell activities, ROS level, and photosynthetic performance in cucumber and cotton, showing its good biocompatibility. Overall, this study not only figured out that root applied negatively charged CDs employed both symplastic and apoplastic pathways to do the transportation in roots compared with mainly the employment of apoplastic pathway for positively charge CDs, but also found that negatively charge CDs could be more efficiently translocated from root to leaf than positively charged CDs, indicating that imparting negative charge to NPs, at least CDs, matters for its efficient delivery in crops.

Influence of particle parameters on deposition onto healthy and damaged human hair.

This research investigates how particle parameters, such as zeta potential, size, functional group, material composition, and hydrophobicity affect their affinity and deposition of particles onto hair. Streaming potential was used as the technique for analysis. The streaming potential data obtained was then converted to surface coverage data. Scanning electron microscopy (SEM) was also done to visualize particle localization on the hair surface. This study found stronger particle affinity on healthy than on damaged (oxidatively bleached) hair, due to diminished interaction sites from the removal of the hair shaft's external lipid layer. SEM imaging supported these findings and offered insights into particle localization. Hydrophilic silica particles accumulated along the exposed hydrophilic cuticle edges of healthy hair, due to hydrogen bonding with the exposed endocuticle. This localization is hypothesized to be due to the limited hydrophilic binding sites on the hydrophobic healthy hair cuticle surface. In damaged hair, an abundance of hydrophilic sites across the cuticle surface results in more dispersed binding. Hydrogen bonding and electrostatic attraction were shown to be the predominant forces influencing deposition, with hydrophobic interactions playing a less influential role. The affinity studies also proved that electrostatic attractions work over a longer range and are more effective at lower particle conditions compared with hydrogen bonding which only start to play a bigger role at higher particle concentrations. Steric hindrance of bulky side groups acted as a significant repulsive force. Results also revealed that larger particles deposit poorly on both healthy and damaged hair compared with smaller ones. Compared with neutrally charged silica nanoparticles (SN-2), positively charged PMMA particles (PN+16) have a stronger affinity to healthy hair, with highly charged particles (PN+49) depositing most rapidly. This study provides a fundamental understanding of how particle-surface parameters influence their affinity to hair and how damaging hair affects deposition.