Structure Of Micelles Research Articles

Experimental and simulation study of reverse micelles formed by aerosol-OT and water in non-polar solvents.

The formation of reverse micelles by aerosol-OT [sodium bis(2-ethylhexyl) sulfosuccinate] in hydrocarbon solvents, and in the presence of water, is studied using a combination of atomistic molecular-dynamics simulations and small-angle neutron scattering (SANS). There have been many previous studies of aerosol-OT and its self-assembly in both water and non-aqueous solvents, but this work is focused on a combined experimental and simulation study of reverse-micelle formation. The effects of hydration (with water-to-surfactant molar ratios in the range 0-60) and solvent (cyclohexane and n-dodecane) are investigated. A force field is adapted that results in spontaneous formation of reverse micelles starting from completely randomized configurations. The computed dimensions of the reverse micelles compare very favourably with those determined in SANS experiments, providing validation of the simulation model. The kinetics of reverse-micelle formation are studied with a 50-ns, 1.7-million-atom system which contains, in the steady state, about 50 reverse micelles. The internal structures of reverse micelles are characterized with mass density profiles, and the effects of solvent, and the structural crossover from highly structured water to 'bulk' water in the core, are detailed. The corresponding changes in the molecular reorientation times of sequestered water are also determined. Overall, the combination of experiment and simulation gives a detailed picture of reverse-micelle self-assembly and structure.

Low Fouling Molecular Selective Channels through Self-assembly of Cross-linked Block Copolymer Micelles for Selective Separation of Dye and Salt.

We report the solvent-evaporation and ionic cross-linking mediated self-assembly of the shell cross-linked micelles of the amphiphilic triblock copolymer containing middle poly(methyl methacrylate) block (hydrophobic) and poly(2-dimethylamino)ethyl methacrylate end blocks (hydrophilic) on the membrane substrate to create molecular selective channels. The formation of selective channels on the substrate is attributed to the local increase of micelle concentration upon solvent evaporation, which leads to the core-core hydrophobic interaction. The post-ionic cross-linking of the shell part further reduces the intermicelle distance, thereby creating interstices for selective separation. The TUF-1:1 membrane prepared by the self-assembly of the cross-linked micelles (triblock copolymer:halide-terminated PEG-based = 1:1 w w-1) and by the post-ionic cross-linking shows molecular weight cutoff of 3000 g mol-1 and pure water permeance of 52 L m-2 h-1 bar-1. The membrane shows 99.5-99.9% rejection of Congo red and Direct red-80 in the presence or absence of salts and Na2SO4 to dye separation factor of about 900. The added functionality (PEG) in the micelle structure provides good fouling-resistant properties toward dye and bovine serum albumin. This work provides the membrane formation mechanism and the advantages of the membrane for fractionation and resource recovery applications.

Development of oral pH-sensitive redox nanotherapeutics for gastric ulcer therapy

Gastric ulcer is a common gastrointestinal disorder worldwide. Although its pathogenesis is unclear, the overproduction of reactive oxygen species (ROS), which results in an oxidative imbalance, has been reported as a central driving mechanism. Within the scope of this investigation, we developed two different self-assembling redox nanoparticles (RNPs) with ROS-scavenging features for the oral treatment of gastric ulcers. One of them, referred to as RNPN, disintegrates in response to acidic pH, whereas the other, denoted as RNPO, remains intact regardless of pH variations. Both types of RNPs showed different free radical scavenging activities in vitro. Protonation of the amino linkages in the side chains of RNPN caused the micelle structure to collapse and the nitroxide radicals encapsulated in the core were exposed to the outside, resulting in a significant increase in antioxidant capacity as the pH decreases. In contrast, RNPO maintained its spherical structure and consistent antioxidant reactivity irrespective of pH changes. The in vivo gastric retention of orally administered RNPN was significantly improved compared to that of RNPO which might be explained by the increased exposure of cationic protonating segments in RNPN on the negatively charged gastric mucosal surface. Owing to its improved gastric retention and enhanced ROS scavenging capacity under acidic pH conditions, RNPN exhibited superior protective effects against oxidative stress induced by aspirin in a gastric ulcer mouse model compared to RNPO. In addition, neither RNPN nor RNPO resulted in severe lethal effects or significant changes in the morphology of zebrafish embryos, indicating their biosafety. Our results suggest that the oral administration of RNPs has a high therapeutic potential for gastric ulcer treatment.

Enzymatic interlocking aptamer-micelles for enhanced cellular internalization and nucleus-targeted cancer phototherapy

Multifunctional micelles that permit both diagnosis and treatment present enormous advantage and potential for precision medicine. However, the inherent complexities and structural instability of these systems often cause unsatisfactory targeting and therapeutic performances. Herein, by ingenious design of a 2,5-bis(2-thienyl)pyrrole (SNS) modifier to covalently link with AS1411 aptamer and lipid segment, a simple strategy is proposed for one-step enzymatic preparation of interlocked aptamer-micelle (IApM) under bio-friendly conditions. The interlocked poly(SNS) skeleton in IApM can not only stabilize the micelle structure but also enhance near-infrared (NIR) absorption ability, thus further enhancing cellular internalization and photothermal therapy. In addition, the multivalent AS1411 aptamers tethered in the hydrophilic shell can simultaneously increase the specific binding affinity of DNA micelles and induce nucleus-targeted accumulation for DNA damage-triggered apoptosis. This DNA micelle achieves “best of both worlds” with enhanced biostability for cellular internalization and improved NIR photothermal conversion efficiency for nucleus-targeted therapy, which provides a promising formulation strategy for precision cancer treatment.

Ultrafine Network-Like Monolayer Structures of Amphiphilic Hyperbranched Copolymers Revealed by the Relative Aggregation Number Method.

The aggregation behavior of two amphiphilic hyperbranched copolymers of poly[oligo(ethylene glycol) methacrylate-co-lauryl methacrylate] (H-[P(OEGMA-co-LMA)]) at the air/water interface was investigated by using the Langmuir film balance technique and atomic force microscopy (AFM). At the air/water interface, H-[P(OEGMA-co-LMA)] copolymers spontaneously form the ultrafine network-like monolayer structures of micelles; each micelle consists of a tiny hydrophobic core of one or two carbon backbones and lauryl side groups and a short hydrophilic shell of oligo(ethylene glycol) (OEG) side groups, and the micellar cores are connected by the branching agent ethylene glycol dimethacrylate (EGDMA). These ultrafine micellar structures are successfully revealed by our relative aggregation number method presented in this work, which is based on our previous relative mass method and methylene number method. The surface pressure-molecular area isotherms of POEGMA29%-PLMA71% (weight percent) and POEGMA69%-PLMA31% are condensed and expanded, respectively, because the density/number of OEG side groups in the former shells is smaller than that in the latter case. Upon monolayer compression, the isotherms of the former are classified into regions I-IV, whereas those of the latter are classified into regions II and III based on their different variation trends of surface pressure. Subphase pH has little influence on the isotherms of the two copolymers because the stretching degrees of hydrophilic OEG side groups in the shells are probably limited by the connected cores, which is different from the large effects in our previous block copolymers containing POEGMA or poly[oligo(ethylene glycol) acrylate] blocks. Under neutral and alkaline conditions, in region III, the mean molecular area (mmA) values of the isotherms of the two copolymers at 20 °C are smaller than those at 10 °C due to the collapse of the OEG side groups above 15 °C. Furthermore, the isotherms of POEGMA69%-PLMA31% move to larger mmA values at 30 °C due to the increased thermal mobility and stretching degrees of more OEG side groups.

PH and redox dually responsive micelles loaded with anti-cancer drug and OA-Bi2S3 nanodots for chemo-photothermal synergistic treatment of cancers

In order to achieve the effective therapy of cancer through targeting and synergistic strategy, methyl-capped poly(ethylene glycol)-poly(caprolactone) block copolymers modified with imine and disulfide bonds (mPEG-imine-SS-PCL) was designed and synthesized, which encapsulated the therapeutic agent, doxorubicin (DOX) and oleic acid-coated bismuth sulfide nanodots (OA-Bi2S3), into the hydrophobic core to form composite micelles by self-assembly in aqueous solution. The imine and disulfide bonds in the composite micelles structure remain stable in the normal physiological environment, but can be broken in the weakly acidic and reducing tumor micro-environment, causing disruption of the micelle structure and release of the therapeutic agent for chemo-photothermal synergistic therapy.

Effects of dilution and age on perfume release from two mixed‐surfactant systems containing hydrotropes

AbstractThis study investigates the encapsulation and controlled release of perfume within micellar systems. We explored how perfume‐surfactant interactions and micelle structure influence fragrance delivery. Two mixed‐micelle systems, one with branched‐tail and the other with linear‐tail surfactants, were subjected to varying perfume concentrations, dilution, and time. Using small‐angle neutron scattering (SANS), gas chromatography‐mass spectrometry (GC‐MS), and statistical analysis, we determined that micelle size and shape are significantly affected by perfume content and dilution. While both systems exhibited similar trends, the branched‐tail system uniquely formed a lamellar phase at higher perfume levels. Our findings reveal a strong correlation between micelle geometry and headspace perfume concentration, highlighting the role of surfactant tail structure. This research provides fundamental insights into perfume‐micelle interactions, with potential applications in materials science and active ingredient delivery.

Influence of chirality and sequence in lysine-rich lipopeptide biosurfactants and micellar model colloid systems

Lipopeptides can self-assemble into diverse nanostructures which can be programmed to incorporate peptide sequences to achieve a remarkable range of bioactivities. Here, the influence of peptide sequence and chirality on micelle structure and interactions is investigated in a series of lipopeptides bearing two lysine or D-lysine residues and tyrosine or tryptophan residues, attached to a hexadecyl lipid chain. All molecules self-assemble into micelles above a critical micelle concentration (CMC). Small-angle x-ray scattering (SAXS) is used to probe micelle shape and structure from the form factor and to probe inter-micellar interactions via analysis of structure factor. The CMC is obtained consistently from surface tension and electrical conductivity measurements. We introduce a method to obtain the zeta potential from the SAXS structure factor which is in good agreement with directly measured values. Atomistic molecular dynamics simulations provide insights into molecular packing and conformation within the lipopeptide micelles which constitute model self-assembling colloidal systems and biomaterials.

Elucidating effect of dicarboxylate anions on nanostructural organization of dicationic imidazolium-based ionic liquids

This work reports the influence of the dicarboxylate anion (oxalate, malonate succinate, glutarate, adipate, pimelate) on the aggregation process of ionic liquids derived from 1,8-bis(3-methylimidazolium-1-yl)-octane [C8(MIM)2] and 1,10-bis(3-methylimidazolium-1-yl)-decano [C10(MIM)2] in water solution. The aggregation behavior was investigated using electrical conductivity, nuclear magnetic resonance, transmission electron microscopy, atomic force microscopy, and zeta potential. Results showed that the aggregates have a wormlike morphology. The CAC values for [C10(MIM)2]2+ increase in the following order: [Oxa] < [Suc] < [Mal] < [Glu] < [Adi] < [Pim], which indicates a direct relationship with the increase in the number of methylene groups of the dianion spacer. In the case of [C8(MIM)2]2+, there was no relationship between the CAC value and the anion’s alkyl spacer chain length, which was attributed to the flexibility and complexity of the dynamic behavior of the aggregates. Anions on the nanorganized structures of micelles are oriented in the way that carboxylate groups are at the aggregate surface (forming hydrogen bonds with cationic heads and water), and apolar alkyl chains are in the hydrophobic (downshift) region of the micelles making an arrangement where they also adopt the bend conformation of alkyl chains. The aggregation of dicationic ILs with dicarboxylate anions is a very innovative topic of investigation in the literature, and more research on different structures, system conditions, and techniques could be done to gain a better understanding of these systems.

Enhancing extinguishing efficiency for lithium-ion battery fire: Investigating the extinguishing mechanism and surface/interfacial activity of F-500 microcapsule extinguishing agent

Due to the high flammability and combustion enthalpy, electrolyte solvents such as dimethyl carbonate (DMC) are regarded as the main fuel in combustion reactions for lithium-ion batteries (LIBs). Herein, to understand the combustion reaction kinetics of LIB fires and explore the efficient extinguishing agent, the chemical oxidation kinetics of DMC at 740–1160 K are studied through a jet-stirred reactor system coupled to the synchrotron vacuum ultraviolet photoionization mass spectrometry and GC. The major consumption path of DMC is the H-abstraction reaction of OH∙ and H∙ radicals. CH3∙ radicals produce to CH4, C2H4 and other common alkane gases in LIB fires through H-abstraction reactions and compound reaction. On this basis, the extinguishing mechanism of F-500 extinguishing agent for LIB fires is studied. The hydrophilic (-[CH2-CH2-O]5) and oleophilic ([C16H33]-) groups give F-500 molecules the amphiphilic characteristics of adsorbing on the solution surface and associating inside the solution to form micelles. Based on the results of dynamic light scattering and cryo-electron microscopy, the size and number of micelles continue to increase and the structure of micelles gradually changes from spherical to rod-shaped, which enhance the solubilization effect. F-500 can strengthen the extinguishing effectiveness of water mist by capturing and encapsulating the DMC inside the water to form “DMC-F-500-Water” microcapsule. DMC is dispersed in the water, which leads to the heat loss and the reduction of concentration and flammability. Moreover, the adsorption of F-500 molecules along the solid-liquid-gas three-phase contact line can reduce the interfacial tension of water and promote wetting process, which leads to the larger spreading area and speed of evaporation. During the application of the extinguishing agent, F-500 agent can improve the cooling efficiency of water. This work provides a reference for the design and development of novel extinguishing agent for LIB fires.

Zinc ferro- and ferri-cyanides catalyst structures from point of colloid chemistry view

The aim of this research was to comprehensively analyze zinc ferro- and ferri-cyanides for rationally choose or modify hexacyanoferrates in a range of application focused on catalysing the ring-opening copolymerization of epoxides and CO2 to reduce the environmental toll. Scripts of the synthesis of 14 samples with variable morphology are given. Thermogravimetry, FT-IR, and XRD indicates the formation of two predominant types of bridging cyanide groups with different coordination environment, which accounts for a lack crystallinity aggregate with an amorphous part. Involving dynamic light scattering and laser Doppler electrophoresis as distinguishing features the formation of colloidal fractions is demonstrated and characterized. The switch from a negative surface rich in Lewis basic sites (Me–CN–) to a surface rich in open-metal sites is either jump and stepwise successfully completed. The proposed structures of micelles of the catalysts allow great attention to be paid to every small detail of their catalytic activity.

Morphology evolution of lipid nanoparticle discovered by small angle neutron scattering

The structure of mRNA lipid nanoparticles (LNPs) is still under debate, with different studies presenting varying morphological characteristics, significantly hindering their biomedical potential. A typical formulation process of mRNA LNPs involves three steps: initial rapid mixing of lipids in an ethanol phase and mRNA in an acidic aqueous phase, followed by the swift removal of ethanol, and finally adjusting the solution to a neutral environment. In this study, we utilize Small Angle Neutron Scattering (SANS) with contrast matching to reveal the kinetic pathway-dependent of mRNA LNPs morphology. We find that the formulation process of the Moderna COVID-19 vaccine is controlled by a competition between aggregation and microphase separation, dictating the diverse morphologies observed in mRNA LNPs. The first step leads to the formation of polydisperse spherical droplets with an average diameter of 42±6.0 nm in an acidic ethanol aqueous solution. Ethanol removal initiates both aggregation and internal microphase separation, resulting in a polydisperse core-shell structure with an average diameter of 48±3.7 nm. Heptadecan-9-yl 8-((2-hydroxyethyl) (6-oxo-6-(undecyloxy) hexyl) amino) octanoate (SM-102) binds to mRNA via electrostatic interaction to form a reverse-wormlike micelle structure inside. The 1,2-Distearoyl-sn‑glycero-3-phosphocholine (DSPC) and PEG-lipid are just in the shell and cholesterol acting as a filler throughout the core-shell structure. Upon transitioning to a neutral environment, SM-102 loses its charge and neither the periphery nor the reverse-wormlike micelle can maintain their stabilities, leading to further aggregation and microphase separation. The average diameter of core-shell structure turns to be 66±5.2 nm. In the actual formulation process of the Moderna COVID-19 vaccine, steps 2 and 3 occur simultaneously, and the competition between aggregation and microphase separation determines the final morphology. These findings offer crucial insights into optimizing the morphology of mRNA LNPs, thereby facilitating advancements in vaccine development and mRNA vaccine delivery technologies.

Aggregation behavior of micellar casein during in vitro simulated digestion triggered by serum Ca2+ in the gastric fluids

The gastric aggregation characteristics of micellar casein (MC) are closely related to the surrounding digestive environment. Together with pepsin and gastric acid, the effect of serum Ca2+ in a digestive fluid is inevitable for the formation of those aggregates. In this study, MC powders with different levels of colloidal calcium phosphate (CCP) were controlled by quick-freezing process. The unique aggregation behaviors accompanied by the addition of exogenous Ca2+ during in vitro simulated digestion were investigated. The results showed that quick-freezing could significantly reduce the CCP level up to 50 % compared to controls. The dissociated micelle structure provided plenty of exposed binding sites, which was prone to recombine with serum Ca2+ in gastric fluids and thus formed the oversized nanoclusters and massive aggregates in stomach. Only about 40 % of the aggregates were dissolved and hydrolyzed after 120 min of gastric digestion. The results of wide-angle coupled small-angle X-ray scattering demonstrated that serum Ca2+ triggered aggregation behaviors largely depend on the pepsin and gastric acids. The para-κ-casein produced by pepsin could be quickly cross-linked by Ca2+-induced connections; while the exposed phosphoserine residues caused by gastric acids allowed more monomers to become nanoclusters by the effect of Ca2+ bridges.

Effect of Acetaminophen on Poloxamer 407 Micelles and Hydrogels: The Relationship between Structural and Physical Properties.

Poloxamer hydrogel possesses thermosensitive sol-gel transition characteristics and is widely used as a drug-controlled-release carrier for topical or injectable formulations. In this study, the effect of loading of a drug, acetaminophen (ACE), on the physical and structural properties of poloxamer 407 (P407) micelles and hydrogels was investigated. Differential scanning calorimetry measurements revealed that ACE reduced the critical micelle temperature and enthalpy of micellization of P407 solutions. The P407 micellization was promoted by ACE incorporation. Rheometry showed that ACE increased the sol-gel transition temperature and reduced the gel strength of P407. In situ small-angle X-ray scattering (SAXS) using synchrotron radiation revealed that ACE altered the structure of P407 micelles and their packing in the P407 gels. As ACE concentration increased, the P407 micelle packing changed from a face-centered cubic phase to a body-centered cubic phase. Furthermore, ACE disordered the micelle packing structure and induced the formation of an amorphous phase. Structural analysis of the P407 micelle packing indicated that ACE reduced the aggregation number (Nagg) of P407 micelles in the gels. The SAXS study for diluted P407 solutions revealed that ACE reduced the P407 micelle size and its uniformity. The structural changes in P407 micelles by ACE loading (e.g., the reduction of Nagg, size, and size uniformity) would alter the micelle packing structure. It was found that these structural changes of micelle packing, especially the formation of an amorphous phase, could destabilize the P407 gel. As a result, the physical properties of P407 gels, such as gelation temperature and gel strength, were changed. This relationship between the structure and physical property of drug-loaded P407 gels was well-explained by correlating the micelle and gel structures. The mechanistic understanding of the change in the physical properties of P407 gels by drug loading is essential for the effective development of poloxamer gel formulations.

Effects of side-chain lengths on the structure and properties of anhydrides modified starch micelles: Experimental and DPD simulation studies

Anhydride-modified starch micelles have great potential in the delivery of hydrophobic guest molecules. This study aimed to experimentally explore the effects of side-chain lengths on the structure and properties of anhydride-modified starch micelles, and to visualize the self-assembly and loading process of these micelles through Dissipative particle dynamics (DPD) simulations. Starch micelles could only form when the carbon chain length exceeded four. The highly hydrophobic C18 starch micelle exhibited the minimum particle size (65 nm) and maximum loading capability (59.10 μg/mg). For each addition carbon atom in the anhydride side chains, the critical micelle concentration (CMC) of starch micelles decreased average of 1.79 %. Thermodynamic results showed that the micellization was an entropy-dominated driven process, and longer carbon chains enhanced the stability of starch micelles. DPD results showed that the starch chains formed the small clusters then spherical aggregates and finally core-shell structure spherical micelle. Curcumin was loaded into micelles by adjoint aggregation-micellization-adsorption mechanism. Overall, this study provides microscopic insight into the micellization and drug-loading mechanisms for anhydrides modified starch micelles.

Manipulating the hydrophilic / hydrophobic balance in novel cationic surfactants by ethoxylation: The impact on adsorption and self-assembly

HypothesisCationic surfactants have a wide range of applications, often associated with their affinity for a range of solid surfaces and their anti-microbial properties. Manipulating their adsorption and self-assembly properties is key to most applications, and this is commonly achieved through surfactant mixtures or manipulating their headgroup or alkyl chain structure. Achieving this through adjustments to their headgroup structure is less common in cationic surfactants than in anionic surfactants. Ethoxylation provides the ability to adjust the hydrophilic / hydrophobic balance, as extensively demonstrated in a range of anionic surfactants. ExperimentsThis same approach has been applied here to a range of ethoxylated cationic surfactants in the form of the quaternary ammonium salts, and their tertiary nonionic equivalents before quaternisation. Their adsorption and self-assembly properties are investigated using predominantly the neutron scattering techniques of neutron reflectivity, NR, and small angle neutron scattering, SANS. FindingsThe trends in the adsorption at the air–water interface and the self-assembly in aqueous solution demonstrate how the hydrophilic / hydrophobic balance can be adjusted by varying the degree of ethoxylation and the alkyl chain length, and illustrate the degree of interdependence of the different structural changes. The variation in the adsorption and the micelle structure shows how the surfactant conformation / packing changes as the degree of ethoxylation and alkyl chain length increases and how the introduction of charge induces further changes.

Qualitative analysis of hydrophilic headgroup water molecular space dependence and wetting effects of solution systems on polluting coal dust

The hydrophilic head groups of the surfactants affect the interfacial tension of surfactant solutions and the internal micelle structure of the bulk surfactants. Because of this, investigating the effect of the hydrophilic head groups on the adsorption performance of surfactants is helpful in terms of revealing the wetting mechanism of surfactants on coal at the molecular level. In this work we combine molecular dynamics simulations and quantum chemistry calculations with a collection of experiments to analyze the interaction patterns between sodium dodecyl sulfonate (SDSO), sodium dodecyl sulfate (SDS), sodium fatty alcohol polyoxyethylene ether carboxylate (SSN), and sodium lauryl phosphate (LSN) with coal. The radial distribution results show that SDSO formed the closest first peak of the hydrated layer at 1.31 Å, with a probability peak of 3.92, which exhibited strong hydrogen bonding interactions that are consistent with the relative concentration and average azimuthal shift trends obtained from molecular trajectory simulations. The priority interaction types between four surfactants and water molecules were determined using the energy difference of molecular orbitals in quantum mechanics. The weak interaction between hydrophilic head groups and water molecules was qualitatively and quantitatively analyzed using the Independent Gradient Model (IGMH), and the fundamental reasons affecting the wetting of long flame coal were obtained.

Preparation and characterization of fluconazole-loaded sodium caseinate matrix films for oral candidiasis

Sodium caseinates (SCs), which are milk proteins, can form micelle structures by self-assembly and can be applied as film-forming agents. The aim of this study was to investigate the physicochemical properties of SC films loaded with fluconazole (FCZ) for use as a drug delivery system with anticandidal activity. A tablet film-coating instrument was used for film production via the spraying method. FCZ molecules can interact with the SC micelles in films via hydrogen bond formation. The FCZ-loaded SC films with a 1:0.1 SC:FCZ ratio presented an amorphous form of FCZ and greater flexibility than films with higher loadings. The FCZ particles (in monohydrate form) can be embedded in the film matrix, resulting in changes in the thermal and mechanical properties. The film dissolution time and drug release rate increased with an increase in FCZ content. The released FCZ was efficient against Candida albicans and possessed mucoadhesive properties on porcine mucosa. In addition, the FCZ-loaded SC films still presented good stability under ambient conditions after 3-months of storage. This study indicates that FCZ-loaded SC films have strong potential for use in oral candidiasis treatment.

Position Matters: Pyridine Regioisomers Influence Secondary Structure and Micelle Morphology in Polymer-Homopolypeptide Micelles.

Polymer-homopolypeptide block copolymers are a class of bioinspired materials that combine the processability and stability of synthetic polymers with the biocompatibility and unique secondary structures of peptides, such as α-helices and β-sheets. These properties make them ideal candidates for a wide variety of applications, for example, in the pharmaceutical field, where they are frequently explored as building blocks for polymeric micelle drug delivery systems. While homopolypeptide side chains can be furnished with an array of different moieties to impart the copolymers with desirable properties, such as stimulus responsivity, pyridine derivatives represent an underutilized functional group for this purpose. Additionally, the interplay between polypeptide side chain structure, secondary conformation, and micelle morphology is not yet well understood, particularly in the case of structural regioisomers. Therefore, in this work, a series of polymer-homopolypeptide copolymers were prepared from a poly(ethylene glycol)-b-poly(glutamic acid) (PEG-b-PGA) backbone, where the pendant carboxylic acid groups were covalently conjugated to a series of pyridine regioisomers by carbodiimide coupling. These pyridine regioisomers differed only in the position of the nitrogen heteroatom, ortho, meta or para, relative to the linking group, generating a series of PEG-b-poly(pyridinylmethyl glutamate) (PEG-b-PMG) copolymers. Following self-assembly of the copolymers in aqueous solutions, dynamic light scattering (DLS) revealed differences in micelle hydrodynamic diameter (Dh) (ranging from ∼60 to 120 nm), while transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) revealed distinctive morphologies ranging from ellipsoidal, to cylindrical, and disc-like, suggesting that subtle changes in positional isomers in the polypeptide block may influence the micelle structure. Analysis of the PEG-b-PMG copolymer micelles by circular dichroism (CD) and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy revealed that differences in the morphology were associated with changes in polypeptide secondary structure, which in turn was influenced by the position of the pyridine heteroatom. Overall, these findings contribute to the broader understanding of the relationship between polypeptide structure and micelle morphology and serve as useful insight for the rational design of polymer-polypeptide nanoparticles.

Influence of Heating Temperature and pH on Acid Gelation of Micellar Calcium Phosphate-Adjusted Skim Milk.

Micellar calcium phosphate (MCP) plays an important role in maintaining the structure and stability of the casein micelle and its properties during processing. The objective of this study was to investigate how heating (10 min at 80 or 90 °C) at different pH levels (6.3, 6.6, 6.9, or 7.2) impacted the acid-induced gelation of MCP-adjusted milk, containing 67 (MCP67), 100 (MCP100), or 113 (MCP113) % of the original MCP content. The unheated sample MCP100 at pH 6.6 was considered the control. pH acidification to pH 4.5 at 30 °C was achieved with glucono delta-lactone while monitoring viscoelastic behaviour by small-amplitude oscillatory rheology. The partitioning of calcium and proteins between colloidal and soluble phases was also examined. In MCP-depleted skim milk samples, the concentrations of non-sedimentable caseins and whey proteins were higher compared to the control and MCP-enriched skim milk samples. The influence of MCP adjustment on gelation was dependent on pH. Acid gels from sample MCP67 exhibited the highest storage modulus (G'). At other pH levels, MCP100 resulted in the greatest G'. The pH of MCP-adjusted skim milk also impacted the gel properties after heating. Overall, this study highlights the substantial impact of MCP content on the acid gelation of milk, with a pronounced dependency of the MCP adjustment effect on pH variations.