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•Spherical P123 micelles transform to rod-like at elevated temperature.•Bile salts transform spherical polymer micelles to small size mixed micelles.•The micelle size depends on ...nature, concentration of bile salt and solution pH.
The present study was aimed to examine the interaction of two bile salts viz. sodium cholate (NaC) and sodium deoxycholate (NaDC) with three ethylene polyoxide-polypropylene polyoxide (PEO-PPO-PEO) triblock copolymers with similar PPO but varying PEO micelles with a focus on the effect of pH on mixed micelles. Mixed micelles of moderately hydrophobic Pluronic® P123 were examined in the presence of two bile salts and compared with those from very hydrophobic L121 and very hydrophilic F127. Both the bile salts increase the cloud point (CP) of copolymer solution and decreased apparent micelle hydrodynamic diameter (Dh). SANS study revealed that P123 forms small spherical micelles showing a decrease in size on progressive addition of bile salts. The negatively charged mixed micelles contained fewer P123 molecules but progressively rich in bile salt. NaDC being more hydrophobic displays more pronounced effect than NaC. Interestingly, NaC shows micellar growth in acidic media which has been attributed to the formation of bile acids by protonation of carboxylate ion and subsequent solubilization. In contrast, NaDC showed phase separation at higher concentration. Nuclear Overhauser effect spectroscopy (NOESY) experiments provided information on interaction and location of bile salts in micelles. Results are discussed in terms of hydrophobicity of bile salts and Pluronics® and the site of bile salt in polymer micelles. Proposed molecular interactions are useful to understand more about bile salts which play important role in physiological processes.
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•Sonication assisted destartification to pristine grapheme has been synthesised.•In situ nanocomposite hydrogel is mechanically robust, highly stretchable, rubber-like elastic and ...reversibly ductile.•Prepared hydrogel showed conductivity and promoted as dual responsive (pH and electric impulse) controlled release device.•Hydrogel is non-toxic and shows superior result in live-dead assay.
Nanohybrid hydrogels based on pristine graphene with enhanced toughness and dual responsive drug delivery feature is opening a new era for smart materials. Here pristine graphene hydrogels are synthesized by in situ free radical polymerization where graphene platelets are the nanobuiliding blocks to withstand external stress and shows reversible ductility. Such uniqueness is a mere reflection of rubber-like elasticity on the hydrogels. These nanobuilding blocks serve also the extensive physisorption which enhances the physical crosslinking inside the gel matrix. Besides the pH-responsive drug release features, these hydrogels are also implemented as a pulsatile drug delivery device. The electric responsive drug release behaviours are noticed and hypothesized by the formation of conducting network in the polyelectrolytic hydrogel matrix. The hydrogels are also tested as good biocompatibility and feasible cell-attachment during live-dead cell adhesion study. The drug release characteristics can also be tuned by adjusting the conducting filler loading into the gel matrix. As of our knowledge, this type of hydrogels with rubber-like consistency, high mechanical property, tunable and dual responsive drug delivery feature and very good human cell compatible is the first to report.
Despite the rapid growth in cationic host defence peptide (CHDP)-mimicking synthetic antibacterial polymers, the importance of the well-defined secondary structure of synthetic polymers, similar to ...CHDP, has not been studied in the context of bacterial membrane perturbation, which is the key focus of this article. Amongst the seven tested amphiphilic cationic alternating copolymers, five (F-PUs) contain flexible (F) linear hydrocarbons (C4, C6, C8) and two (R-PUs) contain rigid (R) cyclic hydrocarbons (C6, C13) in the segmented biodegradable polyurethane (PU) backbone. F-PUs adopt an intra-chain H-bonding driven pleated structure, followed by hierarchical assembly, producing cationic polymersomes in water. In sharp contrast, R-PUs, deprived of such chain-folding possibility due to rigid linkers, exhibit immiscibility driven aggregation, producing spherical particles. F-PUs exhibit antibacterial activity with a rather low minimum inhibitory concentration (MIC), while R-PUs do not show even moderate activity. F-PUs with the C6 linker represent the most optimal balance between the hydrophobicity and the charge density and consequently exhibit the most lethal activity. F-PU-C6a with a pendant primary amine group shows exemplary activity selectively against Gram negative
E. coli
over Gram positive bacteria MIC
S. aureus
/MIC
E. coli
= 64. On the other hand, F-PU-C6b or F-PU-C6c with a pendant quaternary amine or guanidium group exhibits broad-spectrum activity with very low MIC values of ∼2.0 μg mL
−1
in some cases, which is rarely reported in the literature. While these polymers are lethal against bacteria, they exhibit negligible toxicity against mammalian cells as evident from the lack of hemolysis (HC
10
> 200 μg mL
−1
) of red blood cells and MTT assay results. Mechanistic investigation establishes the cell-killing
via
a non-specific membrane disruption pathway, similar to CHDPs present in the innate immunity. Beyond planktonic bacteria, F-PUs also exhibit extraordinary biofilm eradication efficiency as ∼100% eradication of a 3-day aged biofilm is noticed with ∼30 μg mL
−1
F-PU-C6 in just 3 h. Antibacterial activity and biofilm eradication ability of selected polymers in the present series are comparable to the benchmark of polymyxin-B or levofloxacin, the well-known commercially available antibiotics.
Chain-folding regulated hierarchical self-assembly of cationic host defense peptide mimicking amphiphilic polyurethanes exhibit excellent antibacterial activity and biofilm killing.
This article outlines a sustainable method towards the synthesis of advanced materials such as core/shell Quantum Dots (QDs) and their
in situ
stabilization using microemulsions (MEs). QDs are ...versatile materials which show unusual optical properties. We have constructed MEs consisting of an Ionic Liquid (IL) based surfactant
i.e.
choline dioctylsulfosuccinate, ChoAOT as an emulsifier, toluene as a nonpolar phase and water as a polar phase. The system forms a large single-phase region in the phase diagram without any co-surfactant. Spontaneous formation of micelles has been observed and studied through tensiometry and fluorescence and isothermal titration calorimetry (ITC). The exceptional swelling behaviour of the MEs was studied using Dynamic Light Scattering (DLS) and small angle neutron scattering (SANS). In ME droplets,
i.e.
Reverse Micelles (RMs), we successfully synthesized spherical core/shell QDs (size ∼3 to ∼6 nm) with precise control over the size and morphology. The QDs have been characterized using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Powder X-ray Diffraction (PXRD). QDs stabilized in MEs exhibited excellent optical properties and can be suitably used as light harvesting materials for diverse applications.
This article outlines a sustainable method towards the synthesis of advanced materials such as core/shell Quantum Dots (QDs) and their
in situ
stabilization using microemulsions (MEs).
The effect of lavender oil on aggregation characteristics of P123 in aqueous-ethanolic solutions is investigated systematically by DLS, SANS, and rheology. The solubilization capacity of the P123 ...based formulations toward Lavender oil increased by increasing P123 concentration. The study unveiled the importance of the short chain alcohol-ethanol, as solubilization enhancer. The apparent hydrodynamic radius (R h) increased significantly with an increase in lavender oil concentration up to maximum oil solubilization capacity of the copolymer at a particular ethanol concentration. DLS measurements on 5, 10, and 15 wt% P123 in the presence of 25% ethanol revealed the presence of large-sized micellar clusters in addition to the oil swollen micelles. The core size (R C), radius of hard sphere (R HS), and aggregation number (N) obtained from SANS profiles showed considerable enhancement with the addition of lavender oil confirming penetration of oil inside the copolymer. Rheological studies showed that viscosity also increased significantly with the addition of lavender oil near the maximum loading limit of the P123 concentration. Quite interestingly, the sol–gel transition temperature displayed a strong dependence on both P123 as well as oil concentration and decreased almost linearly by increasing oil concentration. This study demonstrates the use of a biocompatible and temperature sensitive self-assembled P123 based formulation for lavender oil solubilization that can be beneficial in the cosmetic industry wherein controlled release of fragrances and so forth is demanded.
In this report, the solubilization behaviour of a hydrophobic drug Clozapine (CLZ) in micellar suspensions of pluronics having different hydrophilic lipophilic balance (HLB) ratios viz. P84, F127 and ...F108 in the absence and presence of bile salt sodium deoxycholate (SDC) has been studied. UV–Vis spectroscopy has been exploited to determine the solubilization capacity of the investigated micellar systems in terms of drug loading efficiency, average number of drug molecules solubilized per micelle (ns), partition coefficient (P) and standard free energy of solubilization (∆G°). The morphological and structural changes taking place in pluronics in different concentration regimes of SDC and with the addition of drug CLZ has been explored using dynamic light scattering (DLS) and small angle neutron scattering (SANS) measurements. The SANS results revealed that aggregation behaviour of pluronic-SDC mixed micelles gets improved in the presence of drug. The micropolarity measurements have been performed to shed light on the locus of solubilization of the drug in pure and mixed micellar systems. The compatibility between CLZ and drug carriers (pluronics and SDC) was confirmed using powder X-ray diffraction (PXRD) and Fourier transform infrared spectroscopy (FTIR) techniques. Among the investigated systems, P84-SDC mixed system was found to be highly efficient for CLZ loading. The long term stability data indicated that CLZ loaded P84-SDC mixed micellar formulation remained stable for 3months at room temperature. Further, it was revealed that the CLZ loaded P84-SDC mixed micelles are converted into CLZ loaded pure P84 micelles at 30-fold dilutions which remain stable up to 48-fold dilutions. The results from the present studies suggest that P84-SDC mixed micelles can serve as suitable delivery vehicles for hydrophobic drug CLZ.
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•Solubility of CLZ drug is studiedin Pluronic and Pluronic-Sodium deoxycholate mixed micelles by UV-Visiblespectroscopy.•Stability of Clozapine found to be more in Pluronic-Sodium deoxycholate mixed micelles than pure Pluronic micelles.•Clozapine loaded Pluronic P84-Sodium deoxycholate mixed micelles are stable for 3 months.•Upon the dilution CLZ loaded Pluronic P84-SDC mixed micelles are converted in to CLZ loaded pure P84 micelles.
Polymer-mediated interactions such as DNA-protein binding, protein aggregation, and filler reinforcement in polymers play crucial roles in many important biological and industrial processes. In this ...work, we report a detailed investigation of interactions between nanoparticles in the presence of high volume fractions of an adsorbing polymer. Small-angle X-ray scattering (SAXS) revealed the existence of a stable gel-like structure in the polymer-nanoparticle dispersion, whereby anchored polymer molecules on nanoparticles acted as bridging centres, while basic interactions between nanoparticles remained repulsive. Time-resolved SAXS measurements showed that the local volume fraction of nanoparticles increased during the drying of the dispersion owing to the shrinkage of the gel-like structure. Further, nanoparticle clusters in the dehydrated composite films showed percolated networks of nanoparticles, except for 5% loading that showed a phase-separated morphology as the volume fraction of nanoparticles remained lower than the percolation threshold. A significant restructuring of nanoparticle clusters occurred upon the hydration of nanocomposite films caused by the expansion of polymer networks induced by hydration forces. Temporal evolution of the volume fraction of nanoparticles during dehydration unveiled three distinct stages similar to the logistic growth function and this was attributed to the evaporation of free, intermediate, and bound water in the different stages. A plausible mechanism was elucidated based on the spring action analogy between anchored polymer chains and nanoparticles during hydration and dehydration processes.
Polymer-mediated interactions such as DNA-protein binding, protein aggregation, and filler reinforcement in polymers play crucial roles in many important biological and industrial processes
•Complex coacervation between zein and agar showed concentration dependent mixing.•Zein nanoparticles were formed in situ which immediately provoked coacervation with agar.•In salt-free coacervates, ...the material rigidity decreased with mixing ratio that make material more viscoelastic.•Storage modulus decreased with ionic strength due to screened Coulomb interaction.•At higher ionic strength, van der Waals forces played a key role in the coacervates.
Herein, the complex coacervation between in situ formed spherical fluorescent zein nanoparticles and polyanion agar as function of mixing ratio (R=Agar/Zein) was investigated. This interaction yielded two distinguishable regions (at pH 5.4): Region I (R < 0.2), where fully charge neutralized soluble complexes with protein denaturation was noticed, and Region II (R > 0.2), where overcharged complexes were formed, with R = 0.2 defining the optimum binding. Small angle neutron scattering studies demonstrated that in the low-q region, nanoparticles formed the crosslink junctions and in the persistence regime of high-q region, the data captured the cross-sectional radius ( = 3.5 nm) for agar-zein complexes. The coacervates became more viscoelastic in salt-free samples because both the low frequency storage modulus and crosslink density were found to decrease with mixing ratio. Systematic decrease in storage modulus with ionic strength (0-0.01 M) implied screened Coulomb interaction was responsible for the observed coacervation. Further, we seek to find universality in complex coacervation of zein nanoparticle with biopolymers, and polysaccharides in particular.
Salicylic acid (SA) finds extensive applications in the treatment of rheumatic and skin diseases because of its analgesic, anti-inflammatory and exfoliating properties. As it is lipophilic in nature, ...there is a need for appropriate delivery systems to harness these properties for different applications. Herein, we examined the suitability of Pluronic P123/F127 micellar systems as delivery media by investigating the structural, flow and antimicrobial properties of P123/F127-SA solutions and hydrogels using DLS, SANS, rheological and zone inhibition measurement techniques. SA modulates the aggregation characteristics of these surfactant systems and brings about spherical-to-worm-like micelle-to-vesicular structural transitions in the hydrophobic Pluronic P123 system, a spherical-to-worm-like micellar transition in the mixed P123/F127 system and an onset of inter-micellar attraction in the hydrophilic Pluronic F127 system. SA-solubilized systems of both hydrophobic and hydrophilic Pluronics inhibit the growth of Gram-positive and Gram-negative bacteria with comparable MIC values. This suggests that the interaction of SA molecules with the bacterial cell membrane remains unobstructed upon encapsulation in Pluronic micelles. F127 hydrogel-based SA formulations with rheological properties suitable for topical applications and up to 15% SA loading were prepared. These will be useful SA ointments as F127 is an FDA-approved excipient for topical drug delivery applications. The results indicate that Pluronics remain effective as delivery agents for SA and exhibit interesting structural polymorphism upon its solubilization.
Salicylic acid (SA) finds extensive applications in the treatment of rheumatic and skin diseases because of its analgesic, anti-inflammatory and exfoliating properties.
In our current work we have developed a supported 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) bilayer with embedded hemoglobin, reconstituted via detergent-mediated method. Microscopic ...studies revealed that the hemoglobin molecules could be visualized without any labelling agents. The reconstituted proteins assemble themselves as supramolecular structures to adapt to lipid bilayer environment. The nonionic detergent, n-octyl-β-d-glucoside (NOG) used for insertion of hemoglobin played an important role in formation of these structures. When concentrations of lipid, protein and detergent were raised by four folds, we observed phase separation by protein molecules within bilayer via protein-protein assembly. This phase separation process exhibited extremely slow kinetics to form large stable domains with correlation times in the order of minutes. Confocal Z-scanning images showed that these supramolecular structures generated membrane deformities. UV–Vis, Fluorescence and Circular Dichroism (CD) measurement indicated minor structural change to expose the hydrophobic regions of the protein to adjust the hydrophobic stress of the lipid environment whilst Small Angle Neutron Scattering (SANS) results indicated that the hemoglobin molecules retained their overall tetrameric form in the system. In conclusion, we state that this investigation allowed us to closely inspect some rare but noteworthy phenomena like the formation of supramolecular structures, large domain formation and membrane deformation etc.
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