Soft Nanoparticles Research Articles

Magnetosome-inspired synthesis of soft ferrimagnetic nanoparticles for magnetic tumor targeting

Magnetic targeting is one of the most promising approaches for improving the targeting efficiency by which magnetic drug carriers are directed using external magnetic fields to reach their targets. As a natural magnetic nanoparticle (MNP) of biological origin, the magnetosome is a special "organelle" formed by biomineralization in magnetotactic bacteria (MTB) and is essential for MTB magnetic navigation to respond to geomagnetic fields. The magnetic targeting of magnetosomes, however, can be hindered by the aggregation and precipitation of magnetosomes in water and biological fluid environments due to the strong magnetic attraction between particles. In this study, we constructed a magnetosome-like nanoreactor by introducing MTB Mms6 protein into a reverse micelle system. MNPs synthesized by thermal decomposition exhibit the same crystal morphology and magnetism (high saturation magnetization and low coercivity) as natural magnetosomes but have a smaller particle size. The DSPE-mPEG-coated magnetosome-like MNPs exhibit good monodispersion, penetrating the lesion area of a tumor mouse model to achieve magnetic enrichment by an order of magnitude more than in the control groups, demonstrating great prospects for biomedical magnetic targeting applications.

Computational study on the uptake of soft nanoparticles and nanoparticle cluster by cells

Nanoparticles (NPs) and exosomes used to transport therapeutic drug molecules to cells have attracted considerable attention in biopharmaceuticals. However, soft NPs entering cells with different angles are hard to be simulated by traditional theoretical endocytic models, let alone clustering of NPs with varied shapes. Here, the endocytic model based on the co-rotational grid method is implemented. The endocytosis of a single soft NP and a nanoparticle cluster (NPC) are investigated. Both the actin force and the dynamic assembly of the clathrin coat have been considered. The results show that NP size is the main factor affecting the internalization efficiency, followed by the aspect ratio, and finally the entry angle. The increase in NP size, aspect ratio, and entry angle will lead to a decrease in internalization efficiency. However, the final configuration of the endocytic vesicle and the internalization efficiency are both independent of the entry angle for NPs with an equivalent radius greater than 15 nm. Besides, a large entry angle can assist a large soft NP in successfully entering cells. The increase in NP stiffness also reduces the internalization efficiency considering the actin force required during endocytosis. The transformation of the NP from the inclined configuration to the vertical configuration is mainly due to NP deformation. Compared with a single NP, NPC has a lower internalization efficiency. The results provide new mechanistic insights into the endocytosis of soft NPs and NPCs.

Longest relaxation time versus maximum loss peak in the field-dependent longitudinal dynamics of suspended magnetic nanoparticles

Magnetic nanoparticles in suspensions provide fascinating model systems to study field-induced effects. Their response to external fields also opens up promising new applications, e.g., in hyperthermia. Despite significant research efforts, several basic questions regarding the influence of external fields on the magnetization dynamics are still open. Here we revisit the classical model of a suspended magnetic nanoparticle with combined internal and Brownian dynamics in the presence of an external field and discuss the field-dependent longitudinal relaxation. While internal and Brownian dynamics are independent in the field-free case, the coupling of both processes when an external field is present leads to richer and more complicated behavior. Using a highly efficient and accurate solver to the underlying Fokker-Planck equation allows us to study a broad parameter range. We identify different dynamical regimes and study their respective properties. In particular, we discuss corrections to the popular rigid-dipole approximation which are captured in terms of a simplified diffusion-jump model in the Brownian-dominated regime with rare N\'eel relaxation events. In addition, we discover a regime with surprising mode-coupling effects for magnetically soft nanoparticles. We explain our findings with the help of a perturbation theory, showing that in this regime the magnetization relaxation at late times is slaved by the slow Brownian motion of the nanoparticle. We discuss consequences of these findings such as the discrepancy of the longest relaxation time and the inverse frequency of the loss peak of the magnetic susceptibility.

Solution combustion route for Ni and Al co-doped lithium ferrite nanoparticles: Synthesis, the effect of doping on the structural, morphological, optical, and magnetic properties

Nickel and Aluminum co-doped Lithium Ferrite Nano-particles, (Li1-xNi0.5xAlxFe1-xO2), (0 ≤ x ≤ 0.3) are synthesized through the solution combustion route with the fuel urea as a reducing agent. The prepared Nano-particles at different doping concentrations are investigated using several tools. The thermal analysis thermographs revealed a combustion reaction at around 300 °C. Doping lithium ferrite with different concentrations changes the structural, morphological, optical, and magnetic characteristics significantly. The increase of the lattice constant to 5.8 Å, and the decrement of the crystallite sizes can be related to the differences in the ionic radius of the incorporated elements, and the increment of Al content. Additional induced sub-band gap energy levels as a result of the numerous surface and interface defects in the nanoparticle structure result in a modest narrowing of the band gap (direct and indirect). The associate shift of the band gap with the decrement of the crystallite size can be attributed to the quantum confinement effect as a result in the tiny size regime. The reduction of the sample's disorder structure and the creation of pure phases were both credited with increasing the saturation magnetization of the undoped sample, but the saturation magnetization decreased when magnetic Fe3+ ions are replaced by nonmagnetic Al3+ ions. The optically active and soft ferrite nanoparticles were confirmed by the behaviour of the physical parameters before them. The synthesized nanoparticles are considered as promising materials for nonlinear optics and memory recording applications.

Transfer Phenomena of Nanoliposomes by Live Imaging of Primary Cultures of Cortical Neurons.

Soft nanoparticles, and in particular, nanoliposomes (NL), have attracted increasing interest for their use in food, nutraceuticals, and in particular, in pharmaceutics for drug delivery. Recent data using salmon lecithin NL suggest that these NL, rich in omega-3 (n-3) fatty acids, can improve the bioavailability and transport of molecules through the blood brain barrier (BBB) to target the brain for the prevention and treatment of neurodegenerative diseases. The objective of this study was to characterize the physicochemical properties and analyze the transfer phenomena of salmon lecithin NL over time in neurons to better understand the behavior of NL in an intracellular environment. To test this, primary cultures of cortical neurons from rat embryos were incubated with salmon lecithin NL from day 3 after cell culture, for up to 104 h. The physicochemical properties of NL such as size, speed, morphology and the diffusion coefficient in the live cultures, were studied over time. Image analysis of cell morphology showed dendritic growth and neuronal arborization after 48 h of exposure to NL, for up to 104 h. Results showed an NL stability in size, speed and diffusion coefficient over time, with a peak at 48 h, and then a return to baseline value at the end of incubation. The average speed and diffusion coefficient achieved provided important information on the mode of entry of NL into neurons, and on the slow diffusion rate of NL into the cells. Analysis of videos from 2 h to 104 h showed that significant levels of NL were already internalized by neurons after 3 h incubation. NL appearance and intracellular distribution indicated that they were packed in intracellular compartments similar to endocytic vesicles, suggesting internalization by an active endocytic-like process. The results obtained here demonstrate internalization of NL by cortical neurons by an active endocytic-like process, and suggest the potential use of NL for time-release of therapeutics aimed towards prevention or treatment of neurodegenerative diseases.

Investigating the Langevin behaviour of Faraday rotation in soft ferrimagnetic CoFe2O4 nanoparticles dispersed in PVA-water medium

Soft ferrimagnetic (FM) cobalt ferrite, CoFe2O4 (CoF) nanoparticles (NP) were synthesized using chemical co-precipitation technique. The constraint related to forming stable dispersion of the synthesized NP was successfully overcome by using an efficient dispersing medium namely, a 2 Wt% Polyvinyl Alcohol (PVA) - water solution, the PVA molecules of which played an important role in offering excellent stability by preventing the agglomeration of the NP considerably. Magneto-optic Faraday Rotation (MOFR) studies performed on the prepared stable dispersions at 532 nm laser wavelength for applied magnetic fields upto 2400 Oe indicated a Langevin behaviour consistent with the chain/cluster formation in them. The studies were carried out at two different concentrations, where the saturated value of MOFR, Bs , was higher for the more concentrated sample, while the saturation magnetic field, HS , followed the reverse trend. It was interesting to see that HS , was as large as 1800 Oe for the concentrated sample, and still higher for the less concentrated one, which may be due to an obstruction effect due to PVA molecules, which delay the formation and saturation of NP chains. The MOFR studies in soft FM NP dispersions open up an interesting domain, both for fundamental understanding of physical phenomena as well as for applications.

A simple, robust and scalable route to prepare sub-50 nm soft PDMS nanoparticles for intracellular delivery of anticancer drugs

Soft nanoparticles (NPs) have recently emerged as a promising material for intracellular drug delivery. In this regard, NPs derived from polydimethylsiloxane (PDMS), an FDA approved polymer can be a suitable alternative to conventional soft NPs due to their intrinsic organelle targeting ability. However, the available synthesis methods of PDMS NPs are complicated or require inorganic fillers, forming composite NPs and compromising their native softness. Herein, for the first time, we present a simple, robust and scalable strategy for preparation of virgin sub-50 nm PDMS NPs at room temperature. The NPs are soft in nature, hydrophobic and about 30 nm in size. They are stable in physiological medium for two months and biocompatible. The NPs have been successful in delivering anticancer drug doxorubicin to mitochondria and nucleus of cervical and breast cancer cells with more than four-fold decrease in IC50 value of doxorubicin as compared to its free form. Furthermore, evaluation of cytotoxicity in reactive oxygen species detection, DNA fragmentation, apoptosis-associated gene expression and tumor spheroid growth inhibition demonstrate the PDMS NPs to be an excellent candidate for delivery of anticancer drugs in mitochondria and nucleus of cancer cells.

Surface Roughness, Hardness and FTIR of the Modified Soft Liner with Different Metal Oxide Nanoparticles

Aims: To study the effect of metal oxide nanoparticles (MgO, ZrO2, ZnO) on acrylic based soft liner surface properties and FTIR. Materials and Methods: Acrylic-based soft-liner specimens were prepared by adding three different concentrations (0.5, 1, and 2) %wt of metal oxide nanoparticles (MgO, ZrO2, ZnO). A disk-shaped specimens with 30mm diameter and 3mm thickness were prepared for shore (A) hardness test to evaluate the surface hardness of modified soft liner. The surface roughness of soft-liner samples (10X10X2mm) was tested by a profilometer. FTIR analysis was conducted to evaluate chemical reaction that may occur between acrylic-based soft liner and nanoparticles. Results: there were no chemical reaction carried out between soft liner and metal oxide nanoparticles at different concentration- surface hardness (shore A) was increased as nanoparticles concentration increased in modified resin. Nanoparticles with 1 and 2% concentration incorporated in soft liner had lower surface roughness value. Conclusions: Metal oxide nanoparticles have improved the surface texture of acrylic-based soft liner, while the hardness of modified soft liner was increased with nanoparticles concentration increases.

The effect of nanoparticle softness on the interfacial dynamics of a model polymer nanocomposite.

The introduction of soft organic nanoparticles (NPs) into polymer melts has recently expanded the material design space for polymer nanocomposites, compared to traditional nanocomposites that utilize rigid NPs, such as silica, metallic NPs, and other inorganic NPs. Despite advances in the fabrication and characterization of this new class of materials, the effect of NP stiffness on the polymer structure and dynamics has not been systematically investigated. Here, we use molecular dynamics to investigate the segmental dynamics of the polymer interfacial region of isolated NPs of variable stiffness in a polymer matrix. When the NP-polymer interactions are stronger than the polymer-polymer interactions, we find that the slowing of segmental dynamics in the interfacial region is more pronounced for stiff NPs. In contrast, when the NP-polymer interaction strength is smaller than the matrix interaction, the NP stiffness has relatively little impact on the changes in the polymer interfacial dynamics. We also find that the segmental relaxation time τα of segments in the NP interfacial region changes from values lower than to higher than the bulk material when the NP-polymer interaction strength is increased beyond a "critical" strength, reminiscent of a binding-unbinding transition. Both the NP stiffness and the polymer-surface interaction strength can thus greatly influence the relative segmental relaxation and interfacial mobility in comparison to the bulk material.

Enhanced Thermoelectric Performance of GeTe-Based Composites Incorporated with Fe Nanoparticles.

Incorporated nanoscale phases in thermoelectric (TE) materials can optimize the electronic and thermal transport properties to obtain high-performance TE materials. The rapid spark plasma sintering (SPS) technique is adopted to synthesize Ge0.96Bi0.06Te composites incorporated with soft magnetic Fe nanoparticles (nano-Fe) and their thermoelectric performance is researched in this study. With the phase transition of the Ge0.96Bi0.06Te matrix from the low-temperature rhombohedral phase to the high-temperature cubic one, the interface contact between Ge0.96Bi0.06Te and nano-Fe is transformed from Schottky contact to Ohmic one, which improves its electronic transport performance at high temperatures. At the same time, the additional Fe nanoprecipitation phonon scattering can reduce the lattice thermal conductivity to ∼0.66 W m-1 K-1. These mechanisms result in a high ZT value of 1.65 and a relatively highquality factor B of 1.05 at 785 K for Ge0.96Bi0.06Te/2 mol % Fe. This work suggests that the thermoelectric performance of composite materials can be enhanced by introducing a variable interface band structure.

Pharmacokinetic behaviors of soft nanoparticulate formulations of chemotherapeutics.

Chemotherapeutic treatment with conventional drug formulations pose numerous challenges, such as poor solubility, high cytotoxicity and serious off-target side effects, low bioavailability, and ultimately subtherapeutic tumoral concentration leading to poor therapeutic outcomes. In the field of Nanomedicine, advances in nanotechnology have been applied with great success to design and develop novel nanoparticle-based formulations for the treatment of various types of cancer. The approval of the first nanomedicine, Doxil® (liposomal doxorubicin) in 1995, paved the path for further development for various types of novel delivery platforms. Several different types of nanoparticles, especially organic (soft) nanoparticles (liposomes, polymeric micelles, and albumin-bound nanoparticles), have been developed and approved for several anticancer drugs. Nanoparticulate drug delivery platformhave facilitated to overcome of these challenges and offered key advantages of improved bioavailability, higher intra-tumoral concentration of the drug, reduced toxicity, and improved efficacy. This review introduces various commonly used nanoparticulate systems in biomedical research and their pharmacokinetic (PK) attributes, then focuses on the various physicochemical and physiological factors affecting the in vivo disposition of chemotherapeutic agents encapsulated in nanoparticles in recent years. Further, it provides a review of the current landscape of soft nanoparticulate formulations for the two most widely investigated anticancer drugs, paclitaxel, and doxorubicin, that are either approved or under investigation. Formulation details, PK profiles, and therapeutic outcomes of these novel strategies have been discussed individually and in comparison, to traditional formulations. This article is categorized under: Nanotechnology Approaches to Biology > Cells at the Nanoscale Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Stimuli-Responsive Miktoarm Polymer-Based Formulations for Fisetin Delivery and Regulatory Effects in Hyperactive Human Microglia.

Branched star polymers offer exciting opportunities in enhancing the efficacy of nanocarriers in delivering biologically active lipophilic agents. It is demonstrated that the star polymeric architecture can be leveraged to yield soft nanoparticles of vesicular morphology with precisely located stimuli-sensitive chemical entities. Amphiphilic stars of AB2 (A = PEG, B = PCL) composition with/without oxidative stress or reduction responsive units at the core junction of A and B arms, are constructed using synthetic articulation. Fisetin, a natural flavonoid with remarkable anti-inflammatory and antioxidant properties, but of limited clinical value due to its poor aqueous solubility, is physically encapsulated into miktoarm star-derived aqueous polymersomes. Polymersomes and fisetin are evaluated separately, and in combination, in human microglia (HMC3), to show if i) polymersomes are toxic; ii) fisetin reduces the abundance of reactive oxygen species (ROS); and iii) fisetin modulates the activation of ERK1/2. These signaling molecules and pathways are implicated in inflammatory processes and cell survival. Fisetin, both incorporated and nonincorporated into polymersomes, reduces ROS and ERK1/2 phosphorylation in lipopolysaccharide-treated human microglia, normalizing excessive oxidative stress and ERK-mediated signaling.

Hybrid colloidal gels with tunable elasticity formed by charge-driven assembly between spherical soft nanoparticles and discotic nanosilicates

Colloidal gels based on electrostatic interparticle attractions hold unexploited potential for tailoring their microstructure and properties. Here, we demonstrate that hetero-aggregation between oppositely charged particles with different geometries is a viable strategy for controlling their properties. Specifically, we studied hybrid colloidal gels prepared by the charge-driven assembly of oppositely charged spherical gelatin nanoparticles and two-dimensional (2D) nanosilicates. We show that the asymmetry between the building blocks and the resulting anisotropic interparticle interactions produces a variety of nanostructures and hybrid colloidal gels that exhibit high elasticity at low colloidal volume fractions. Tuning the competition between different attractive interactions in the system by varying the spatial charge heterogeneity on the 2D nanosheets, composition, and ionic strength was found to alter the mechanism of gel formation and their rheological properties. Remarkably, increasing the mass ratio of 2D nanosheets to spherical nanoparticles at a constant total mass fraction affords hybrid gels that exhibit an inverse relationship between elasticity and volume fraction. However, these hybrid gels are easily fluidized and exhibit rapid structural recovery once the stress is removed. These features allow for the engineering of versatile 3D-printable hybrid colloidal gels, whose structure and viscoelastic response are governed by parameters that have not been explored before.

Protein Corona Formation on Hard and Polymeric Nanoparticles – Towards Understanding Biocompatibility, Biodistribution, and Efficacy

Unpredictable protein adsorption on both hard and soft nanoparticles remains a considerable challenge towards effectively applying nanotechnologies in biological environments. Hard nanoparticles form the basis of many chemical nanosensors. Conversely, soft nanoparticles such as lipid nanoparticles (LNPs) are vital for the successful delivery of mRNA-based vaccines, and offer promising applications in neonatal gene therapy, immunotherapy, and protein replacement therapy. Understanding the biological interactions that both hard and soft nanoparticles undergo upon introduction into biological systems is central to optimize the outcomes of nanoparticle-based delivery biotechnologies in clinical settings.Herein, we present a multimodal study of protein corona composition and dynamics, first on ‘hard’ nanoparticles: spherical polystyrene nanoparticles (a previously studied model nanoparticle) and high aspect ratio single-walled carbon nanotubes (SWCNTs, an understudied nanoparticle). These nanoparticles are exposed to two biofluids of interest: blood plasma (relevant for intravenous applications) and cerebrospinal fluid (relevant for brain imaging and sensing applications). To study these protein coronas, we develop a methodology based on quantitative proteomic mass spectrometry [1] and chemical thermodynamic analysis of real-time protein binding to identify protein corona ‘fingerprints’, enabling quantification of protein abundance and enrichment/depletion relative to the native biofluid, transient kinetics [2], and end-state topology. Interestingly, we find that the heavily studied polystyrene nanoparticles are relatively agnostic in the formation of their protein coronas, demonstrating little preference for particular protein classes or physicochemical properties. Conversely, we find that SWCNTs show strong preference for certain protein classes. Our additional work in machine learing-based analysis shows that corona compositions, and more broadly nanoparticle biofouling, can be drastically different for each nanoparticle type [3].Lastly, we study nano-bio interactions encountered by ‘soft’ nanoparticles: LNPs commonly used for the therapeutic delivery of mRNA. We investigate how modifying (i) the mRNA packaged inside the LNPs and (ii) the ionizable lipid within the LNPs modulate the subsequently formed protein corona in (iii) various biological environments of relevance for delivery applications. Importantly, this workflow is readily translatable across soft polymer-based nanotechnologies of interest, which are understudied due to the experimental complexity of separating nanoparticle-corona complexes from free proteins. This fundamental understanding of protein-LNP interactions could enable more seamless design and clinical application of next-generation LNP carriers to bolster the safe and effective delivery of mRNA and other therapeutics to patients. References Pinals, R.L., et al., Quantitative Protein Corona Composition and Dynamics on Carbon Nanotubes in Biological Environments. Angewandte Chemie (2020).Pinals, R. L., Yang, D., Lui, A., Cao, W. & Landry, M. P. Corona Exchange Dynamics on Carbon Nanotubes by Multiplexed Fluorescence Monitoring. JACS (2020).Ouassil, N.*, Pinals, R.L.*, O’Donnell, J.T.D., Wang, J., Landry, M.P.‡ Supervised Learning Model to Predict Protein Adsorption to Nanoparticles. Science Advances (2022).

Nanoparticle-blockage-enabled rapid and reversible nanopore gating with tunable memory

Gated protein channels act as rapid, reversible, and fully-closeable nanoscale valves to gate chemical transport across the cell membrane. Replicating or outperforming such a high-performance gating and valving function in artificial solid-state nanopores is considered an important yet unsolved challenge. Here we report a bioinspired rapid and reversible nanopore gating strategy based on controlled nanoparticle blockage. By using rigid or soft nanoparticles, we respectively achieve a trapping blockage gating mode with volatile memory where gating is realized by electrokinetically trapped nanoparticles near the pore and contact blockage gating modes with nonvolatile memory where gating is realized by a nanoparticle physically blocking the pore. This gating strategy can respond to an external voltage stimulus (∼200 mV) or pressure stimulus (∼1 atm) with response time down to milliseconds. In particular, when 1,2-diphytanoyl-sn-glycero-3-phosphocholine liposomes are used as the nanoparticles, the gating efficiency, defined as the extent of nanopore closing compared to the opening state, can reach 100%. We investigate the mechanisms for this nanoparticle-blockage-enabled nanopore gating and use it to demonstrate repeatable controlled chemical releasing via single nanopores. Because of the exceptional spatial and temporal control offered by this nanopore gating strategy, we expect it to find applications for drug delivery, biotic-abiotic interfacing, and neuromorphic computing.

Soft Poly(N-vinylcaprolactam) Based Aqueous Particles.

Soft nanoparticles are an important class of material with potential to be used as carriers of active compounds. Swollen, penetrable particles can act as a host for the active ingredients and provide stability, stimuli-responsiveness and recyclability for the guest. Thermoresponsive colloidal gel particles are especially attractive for such applications due to the extremely soft structure, size and responsiveness. Poly(N-vinylcaprolactam) (PNVCL) is a much studied, popular thermoresponsive polymer. The polymer has low toxicity and the phase transition temperature is close to body temperature. During the phase transition, the polymer becomes less soluble, the particle expels a large part of water and the particle collapses to a more compact form. The diffusion of material in and from the particles is largely affected by this transition. As the solubility of the polymer changes, so do the interactions with the loaded compound. This feature article focuses on the synthetic methods, properties and applications of soft PNVCL particles.

Single Entity Electrochemistry and Its Application to Nanomaterial Synthesis

AbstractSingle entity analysis is an important research topic in electrochemistry. Thus far, collisions of nanomaterials and subsequent interaction between electrodes and particles have been studied. Single entity electrochemistry exhibited inherent heterogeneity distinct from that of ensembles. By showing various current responses, single entity electrochemistry allows us to investigate the adsorbed chemical species on the electrode surface (dielectrics, hard nanoparticles, soft nanoparticles), enabling analysis of electrode‐particle interaction at the nanoscale. Electrochemical analysis of soft nanoparticles enabled the detection of biological materials and was applied to the synthesis of nanoparticles to be used as electrocatalysts. It shows great promise as a synthetic method for various structures of nanoparticles by reducing metal ions volume confined emulsion nanodroplets.

Sustained endosomal release of a neurokinin-1 receptor antagonist from nanostars provides long-lasting relief of chronic pain

Soft polymer nanoparticles designed to disassemble and release an antagonist of the neurokinin 1 receptor (NK1R) in endosomes provide efficacious yet transient relief from chronic pain. These micellar nanoparticles are unstable and rapidly release cargo, which may limit the duration of analgesia. We examined the efficacy of stable star polymer nanostars containing the NK1R antagonist aprepitant-amine for the treatment of chronic pain in mice. Nanostars continually released cargo for 24 h, trafficked through the endosomal system, and disrupted NK1R endosomal signaling. After intrathecal injection, nanostars accumulated in endosomes of spinal neurons. Nanostar-aprepitant reversed mechanical, thermal and cold allodynia and normalized nociceptive behavior more efficaciously than free aprepitant in preclinical models of neuropathic and inflammatory pain. Analgesia was maintained for >10 h. The sustained endosomal delivery of antagonists from slow-release nanostars provides effective and long-lasting reversal of chronic pain.

Transition in the Glassy Dynamics of Melts of Acid-Hydrolyzed Phytoglycogen Nanoparticles.

The deformability, responsiveness, and tunability of soft nanoparticles (NPs) offer unique opportunities to learn about their complex properties and the interactions between particles. In the present study, we provide new insights into the physical properties of phytoglycogen (PG) NPs, which are soft, compact particles with a dendritic architecture that are produced in the kernels of sweet corn. In particular, we study PG NPs modified using acid hydrolysis, which not only reduces their diameter but also alters their stiffness, internal structure, and the interactions between particles in aqueous dispersions. We used steady shear rheology to determine the dependence of the relative zero-shear viscosity ηr of aqueous dispersions of acid-hydrolyzed PG NPs on the effective volume fraction ϕeff, which indicated a reduction in stiffness of the particles relative to that of native PG NPs. We quantified this difference by analyzing the nature of the colloidal glasses formed at high ϕeff. We measured a smaller value of the fragility index m for acid-hydrolyzed PG NP glasses than that for native PG NP glasses, indicating that acid-hydrolyzed PG NPs form stronger glasses and are therefore softer than native PG NPs. Unlike the native PG NPs, we observed a distinctive change in the character of the glass transition of the acid-hydrolyzed PG NPs as ϕeff was increased above ϕeff∼1: a crossover in the dependence of ηr on ϕeff from Vogel-Fulcher-Tammann behavior to a more gradual, Arrhenius-like behavior. By expressing the steady shear and oscillatory rheology data in terms of generalized Péclet numbers, we obtained collapse of the data onto master curves. We interpret this result in terms of the acid-hydrolyzed PG NPs predominantly interpenetrating neighboring particles at large ϕeff, for which fluctuations of the outer chains enhance the mobility of the particles and make α-relaxation times τα experimentally accessible.

Polymersomes: Soft Nanoparticles from Miktoarm Stars for Applications in Drug Delivery.

Self-assembly of amphiphilic macromolecules has provided an advantageous platform to address significant issues in a variety of areas, including biology. Such soft nanoparticles with a hydrophobic core and hydrophilic corona, referred to as micelles, have been extensively investigated for delivering lipophilic therapeutics by physical encapsulation. Polymeric vesicles or polymersomes with similarities in morphology to liposomes continue to play an essential role in understanding the behavior of cell membranes and, in addition, have offered opportunities in designing smart nanoformulations. With the evolution in synthetic methodologies to macromolecular precursors, the construction of such assemblies can now be modulated to tailor their properties to match desired needs. This review brings into focus the current state-of-the-art in the design of polymersomes using amphiphilic miktoarm star polymers through a detailed analysis of the synthesis of miktoarm star polymers with tuned lengths of varied polymeric arms, their self-assembly, and applications in drug delivery.