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Stimuli-Responsive Polymers for Engineered Emulsions. Macromol Rapid Commun 2024; 45:e2300723. [PMID: 38395416 DOI: 10.1002/marc.202300723] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2023] [Revised: 02/14/2024] [Indexed: 02/25/2024]
Abstract
Emulsions are complex. Dispersing two immiscible phases, thus expanding an interface, requires effort to achieve and the resultant dispersion is thermodynamically unstable, driving the system toward coalescence. Furthermore, physical instabilities, including creaming, arise due to presence of dispersed droplets of different densities to a continuous phase. Emulsions allow the formulation of oils, can act as vehicles to solubilize both hydrophilic and lipophilic molecules, and can be tailored to desirable rheological profiles, including "gel-like" behavior and shear thinning. The usefulness of emulsions can be further expanded by imparting stimuli-responsive or "smart" behaviors by inclusion of a stimuli-responsive emulsifier, polymer or surfactant. This enables manipulation like gelation, breaking, or aggregation, by external triggers such as pH, temperature, or salt concentration changes. This platform generates functional materials for pharmaceuticals, cosmetics, oil recovery, and colloid engineering, combining both smart behaviors and intrinsic benefit of emulsions. However, with increased functionality comes greater complexity. This review focuses on the use of stimuli-responsive polymers for the generation of smart emulsions, motivated by the great adaptability of polymers for this application and their efficacy as steric stabilizers. Stimuli-responsive emulsions are described according to the trigger used to provide the reader with an overview of progress in this field.
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Dynamic covalent surfactants and their uses in the development of smart materials. Adv Colloid Interface Sci 2024; 327:103159. [PMID: 38640843 DOI: 10.1016/j.cis.2024.103159] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2023] [Revised: 03/08/2024] [Accepted: 04/14/2024] [Indexed: 04/21/2024]
Abstract
Dynamic covalent chemistry, which leverages the dynamic nature of reversible covalent bonds controlled by the conditions of reaction equilibrium, has demonstrated great potential in diverse applications related to both the stability of covalent bonds and the possibility of exchanging building blocks, imparting to the systems the possibility of "error checking" and "proof-reading". By incorporating dynamic covalent bonds into surfactant molecular architectures, combinatorial libraries of surfactants with bespoke functionalities can be readily fabricated through a facile strategy, with minimum effort in organic synthesis. Consequently, a multidisciplinary field of research involving the creation and application of dynamic covalent surfactants has recently emerged, which has aroused great attention in surfactant and colloid science, supramolecular chemistry, self-assembly, smart materials, drug delivery, and nanotechnology. This review reports results in this field published over recent years, discusses the possibilities presented by dynamic covalent surfactants and their applications in developing smart self-assembled materials, and outlines some future perspectives.
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Cover Picture. Chem Asian J 2022. [DOI: 10.1002/asia.202200331] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Supramolecular Hydrogels: Design Strategies and Contemporary Biomedical Applications. Chem Asian J 2022; 17:e202200081. [PMID: 35304978 DOI: 10.1002/asia.202200081] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Revised: 03/08/2022] [Indexed: 12/19/2022]
Abstract
Self-assembly of supramolecular hydrogels is driven by dynamic, non-covalent interactions between molecules. Considerable research effort has been exerted to fabricate and optimise supramolecular hydrogels that display shear-thinning, self-healing, and reversibility, in order to develop materials for biomedical applications. This review provides a detailed overview of the chemistry behind the dynamic physicochemical interactions that sustain hydrogel formation (hydrogen bonding, hydrophobic interactions, ionic interactions, metal-ligand coordination, and host-guest interactions). Novel design strategies and methodologies to create supramolecular hydrogels are highlighted, which offer promise for a wide range of applications, specifically drug delivery, wound healing, tissue engineering and 3D bioprinting. To conclude, future prospects are briefly discussed, and consideration given to the steps required to ultimately bring these biomaterials into clinical settings.
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Evaluating hyaluronic acid dermal fillers: a critique of current characterization methods. Dermatol Ther 2022; 35:e15453. [PMID: 35293660 PMCID: PMC9285697 DOI: 10.1111/dth.15453] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Revised: 01/26/2022] [Accepted: 03/03/2022] [Indexed: 11/28/2022]
Abstract
Soft‐tissue augmentation has gained much popularity in recent years. Hyaluronic acid (HA) based dermal fillers; a non‐permanent injectable device, can restore volume loss, fill fine lines and wrinkles and add curves and contours. HA based dermal fillers entered the non‐surgical treatment market in the late 1990s, however there is a lack of data and literature comparing the range of products and detailing the complexities of these products and how it relates to tissue performance. Measuring the physico‐chemical properties of these dermal fillers provide key parameters to predict their performance after injection into the body. This article reviews the currently reported methods and parameters used to characterize dermal fillers. The review of these methods and data from the literature provides a useful guide to clinicians and injectors in selecting the optimal product suitable for the needs of each patient.
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Selectively Cross-Linked Tetra-PEG Hydrogels Provide Control over Mechanical Strength with Minimal Impact on Diffusivity. ACS Biomater Sci Eng 2021; 7:4293-4304. [PMID: 34151570 PMCID: PMC7611660 DOI: 10.1021/acsbiomaterials.0c01723] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
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Synthetic hydrogels
formed from poly(ethylene glycol) (PEG) are
widely used to study how cells interact with their extracellular matrix.
These in vivo-like 3D environments provide a basis
for tissue engineering and cell therapies but also for research into
fundamental biological questions and disease modeling. The physical
properties of PEG hydrogels can be modulated to provide mechanical
cues to encapsulated cells; however, the impact of changing hydrogel
stiffness on the diffusivity of solutes to and from encapsulated cells
has received only limited attention. This is particularly true in
selectively cross-linked “tetra-PEG” hydrogels, whose
design limits network inhomogeneities. Here, we used a combination
of theoretical calculations, predictive modeling, and experimental
measurements of hydrogel swelling, rheological behavior, and diffusion
kinetics to characterize tetra-PEG hydrogels’ permissiveness
to the diffusion of molecules of biologically relevant size as we
changed polymer concentration, and thus hydrogel mechanical strength.
Our models predict that hydrogel mesh size has little effect on the
diffusivity of model molecules and instead predicts that diffusion
rates are more highly dependent on solute size. Indeed, our model
predicts that changes in hydrogel mesh size only begin to have a non-negligible
impact on the concentration of a solute that diffuses out of hydrogels
for the smallest mesh sizes and largest diffusing solutes. Experimental
measurements characterizing the diffusion of fluorescein isothiocyanate
(FITC)-labeled dextran molecules of known size aligned well with modeling
predictions and suggest that doubling the polymer concentration from
2.5% (w/v) to 5% produces stiffer gels with faster gelling kinetics
without affecting the diffusivity of solutes of biologically relevant
size but that 10% hydrogels can slow their diffusion. Our findings
provide confidence that the stiffness of tetra-PEG hydrogels can be
modulated over a physiological range without significantly impacting
the transport rates of solutes to and from encapsulated cells.
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Unsupervised Learning Unravels the Structure of Four-Arm and Linear Block Copolymer Micelles. Macromolecules 2021. [DOI: 10.1021/acs.macromol.0c02523] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Drug reformulation for a neglected disease. The NANOHAT project to develop a safer more effective sleeping sickness drug. PLoS Negl Trop Dis 2021; 15:e0009276. [PMID: 33857146 PMCID: PMC8078842 DOI: 10.1371/journal.pntd.0009276] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 04/27/2021] [Accepted: 02/26/2021] [Indexed: 01/16/2023] Open
Abstract
Background Human African trypanosomiasis (HAT or sleeping sickness) is caused by the
parasite Trypanosoma brucei sspp. The disease has two
stages, a haemolymphatic stage after the bite of an infected tsetse fly,
followed by a central nervous system stage where the parasite penetrates the
brain, causing death if untreated. Treatment is stage-specific, due to the
blood-brain barrier, with less toxic drugs such as pentamidine used to treat
stage 1. The objective of our research programme was to develop an
intravenous formulation of pentamidine which increases CNS exposure by some
10–100 fold, leading to efficacy against a model of stage 2 HAT. This target
candidate profile is in line with drugs for neglected diseases inititative
recommendations. Methodology To do this, we evaluated the physicochemical and structural characteristics
of formulations of pentamidine with Pluronic micelles (triblock-copolymers
of polyethylene-oxide and polypropylene oxide), selected candidates for
efficacy and toxicity evaluation in vitro, quantified
pentamidine CNS delivery of a sub-set of formulations in vitro and
in vivo, and progressed one pentamidine-Pluronic formulation
for further evaluation using an in vivo single dose brain
penetration study. Principal Findings Screening pentamidine against 40 CNS targets did not reveal any major
neurotoxicity concerns, however, pentamidine had a high affinity for the
imidazoline2 receptor. The reduction in insulin secretion in
MIN6 β-cells by pentamidine may be secondary to pentamidine-mediated
activation of β-cell imidazoline receptors and impairment of cell viability.
Pluronic F68 (0.01%w/v)-pentamidine formulation had a similar inhibitory
effect on insulin secretion as pentamidine alone and an additive
trypanocidal effect in vitro. However, all Pluronics tested
(P85, P105 and F68) did not significantly enhance brain exposure of
pentamidine. Significance These results are relevant to further developing block-copolymers as
nanocarriers, improving BBB drug penetration and understanding the side
effects of pentamidine. Sleeping sickness or human African Trypanosomiasis (HAT) is a disease caused by a
parasite, which is transferred to humans by the bite of an infected tsetse fly.
There are two disease stages: the first stage is the blood-based stage of the
disease and the second stage affects the brain. It is fatal if left untreated.
The blood-brain barrier (BBB) makes the brain stage difficult to treat because
it prevents 99% of all drugs from entering the brain from the blood. Those
anti-HAT drugs that do enter the brain are toxic and have serious side effects.
Pentamidine is a less toxic blood stage drug, which our research has shown has a
limited ability to cross the BBB due to its removal by proteins called
transporters. The objective of this study was to use Pluronic to improve
pentamidine delivery to target sites, whilst reducing its side effects. Pluronic
is a polymer, which can assemble into micelles and encapsulate the drug. Thus,
prolonging its circulation time and protecting it. Our study indicated that the
selected Pluronics did not increase the brain delivery of pentamidine. However.
Pluronic-pentamidine formulations were identified that harboured trypanocidal
activity and did not increase safety concerns compared to unformulated
pentamidine.
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ILC1 drive intestinal epithelial and matrix remodelling. NATURE MATERIALS 2021; 20:250-259. [PMID: 32895507 PMCID: PMC7611574 DOI: 10.1038/s41563-020-0783-8] [Citation(s) in RCA: 50] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2019] [Accepted: 07/23/2020] [Indexed: 05/02/2023]
Abstract
Organoids can shed light on the dynamic interplay between complex tissues and rare cell types within a controlled microenvironment. Here, we develop gut organoid cocultures with type-1 innate lymphoid cells (ILC1) to dissect the impact of their accumulation in inflamed intestines. We demonstrate that murine and human ILC1 secrete transforming growth factor β1, driving expansion of CD44v6+ epithelial crypts. ILC1 additionally express MMP9 and drive gene signatures indicative of extracellular matrix remodelling. We therefore encapsulated human epithelial-mesenchymal intestinal organoids in MMP-sensitive, synthetic hydrogels designed to form efficient networks at low polymer concentrations. Harnessing this defined system, we demonstrate that ILC1 drive matrix softening and stiffening, which we suggest occurs through balanced matrix degradation and deposition. Our platform enabled us to elucidate previously undescribed interactions between ILC1 and their microenvironment, which suggest that they may exacerbate fibrosis and tumour growth when enriched in inflamed patient tissues.
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Solubilisation of salicylate in F127 micelles: Effect of pH and temperature on morphology and interactions with cyclodextrin. J Mol Liq 2021. [DOI: 10.1016/j.molliq.2020.114892] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Morphology of bile salts micelles and mixed micelles with lipolysis products, from scattering techniques and atomistic simulations. J Colloid Interface Sci 2020; 587:522-537. [PMID: 33189321 DOI: 10.1016/j.jcis.2020.10.101] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Revised: 10/23/2020] [Accepted: 10/25/2020] [Indexed: 12/17/2022]
Abstract
HYPOTHESES Bile salts (BS) are biosurfactants released into the small intestine, which play key and contrasting roles in lipid digestion: they adsorb at interfaces and promote the adsorption of digestive enzymes onto fat droplets, while they also remove lipolysis products from that interface, solubilising them into mixed micelles. Small architectural variations on their chemical structure, specifically their bile acid moiety, are hypothesised to underlie these conflicting functionalities, which should be reflected in different aggregation and solubilisation behaviour. EXPERIMENTS The micellisation of two BS, sodium taurocholate (NaTC) and sodium taurodeoxycholate (NaTDC), which differ by one hydroxyl group on the bile acid moiety, was assessed by pyrene fluorescence spectroscopy, and the morphology of aggregates formed in the absence and presence of fatty acids (FA) and monoacylglycerols (MAG) - typical lipolysis products - was resolved by small-angle X-ray/neutron scattering (SAXS, SANS) and molecular dynamics simulations. The solubilisation by BS of triacylglycerol-incorporating liposomes - mimicking ingested lipids - was studied by neutron reflectometry and SANS. FINDINGS Our results demonstrate that BS micelles exhibit an ellipsoidal shape. NaTDC displays a lower critical micellar concentration and forms larger and more spherical aggregates than NaTC. Similar observations were made for BS micelles mixed with FA and MAG. Structural studies with liposomes show that the addition of BS induces their solubilisation into mixed micelles, with NaTDC displaying a higher solubilising capacity.
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Morphology, gelation and cytotoxicity evaluation of D-α-Tocopheryl polyethylene glycol succinate (TPGS) - Tetronic mixed micelles. J Colloid Interface Sci 2020; 582:353-363. [PMID: 32858401 DOI: 10.1016/j.jcis.2020.08.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Revised: 07/22/2020] [Accepted: 08/02/2020] [Indexed: 01/01/2023]
Abstract
HYPOTHESIS The combination of polymeric surfactants into mixed micelles is expected to improve properties relevant to their use in drug delivery, such as micellar size, gelation, and toxicity. We investigated synergistic effects in mixtures of D-α-Tocopheryl polyethylene glycol succinate (TPGS), an FDA-approved PEGylated derivative of vitamin E, and Tetronic surfactants, pH-responsive and thermogelling polyethylene oxide (PEO)-polypropylene oxide (PPO) 4-arm block copolymers. We hypothesized that mixed micelles would form under specific conditions and provide a handle to tune formulation characteristics. EXPERIMENTS We examined the morphology of the self-assembled structures in mixtures of TPGS with two Tetronic: T1107 and T908, using a combination of dynamic light scattering (DLS), small-angle neutron scattering (SANS), NMR spectroscopy (NOESY and diffusion NMR) and oscillatory rheology, over a range of compositions, temperatures and pH. Cell viability was assessed in NIH/3T3 fibroblasts. FINDINGS The combination of TPGS with either of the two Tetronic produces spherical core-shell micelles that comprise both surfactants in their structure (mixed micelles). T1107 unimers incorporate into TPGS aggregates below the critical micelle temperature of the poloxamine, while mixed micelles only form under limited conditions with T908. At high concentration/temperature, small proportions of TPGS extend the gel phase, more markedly with T1107, with similar elastic moduli (30-50 kPa) and a BCC crystalline structure. Cell viability of NIH/3T3 fibroblasts grown in the hydrogels increases significantly when the poloxamine gels are doped with TPGS, making the combination of poloxamines and TPGS a promising platform for drug delivery.
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Corrigendum to 'Molecular insights into the behaviour of bile salts at interfaces: a key to their role in lipid digestion'. [Journal of Colloid and Interface Science 556 (2019) 266-277]. J Colloid Interface Sci 2020; 568:282-283. [PMID: 32199634 DOI: 10.1016/j.jcis.2020.03.024] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Antibiotic-in-Cyclodextrin-in-Liposomes: Formulation Development and Interactions with Model Bacterial Membranes. Mol Pharm 2020; 17:2354-2369. [DOI: 10.1021/acs.molpharmaceut.0c00096] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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Threading Different Rings on X-Shaped Block Copolymers: Hybrid Pseudopolyrotaxanes of Cyclodextrins and Tetronics. Macromolecules 2020. [DOI: 10.1021/acs.macromol.0c00409] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Interactions of bile salts with a dietary fibre, methylcellulose, and impact on lipolysis. Carbohydr Polym 2020; 231:115741. [PMID: 31888817 DOI: 10.1016/j.carbpol.2019.115741] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Revised: 12/10/2019] [Accepted: 12/13/2019] [Indexed: 12/13/2022]
Abstract
Methylcellulose (MC) has a demonstrated capacity to reduce fat absorption, hypothetically through bile salt (BS) activity inhibition. We investigated MC cholesterol-lowering mechanism, and compared the influence of two BS, sodium taurocholate (NaTC) and sodium taurodeoxycholate (NaTDC), which differ slightly by their architecture and exhibit contrasting functions during lipolysis. BS/MC bulk interactions were investigated by rheology, and BS behaviour at the MC/water interface studied with surface pressure and ellipsometry measurements. In vitro lipolysis studies were performed to evaluate the effect of BS on MC-stabilised emulsion droplets microstructure, with confocal microscopy, and free fatty acids release, with the pH-stat method. Our results demonstrate that BS structure dictates their interactions with MC, which, in turn, impact lipolysis. Compared to NaTC, NaTDC alters MC viscoelasticity more significantly, which may correlate with its weaker ability to promote lipolysis, and desorbs from the interface at lower concentrations, which may explain its higher propensity to destabilise emulsions.
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Adhesive Hydrogels for Maxillofacial Tissue Regeneration Using Minimally Invasive Procedures. Adv Healthc Mater 2020; 9:e1901134. [PMID: 31943865 PMCID: PMC7041972 DOI: 10.1002/adhm.201901134] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Revised: 11/29/2019] [Indexed: 12/20/2022]
Abstract
Minimally invasive surgical procedures aiming to repair damaged maxillofacial tissues are hampered by its small, complex structures and difficult surgical access. Indeed, while arthroscopic procedures that deliver regenerative materials and/or cells are common in articulating joints such as the knee, there are currently no treatments that surgically place cells, regenerative factors or materials into maxillofacial tissues to foster bone, cartilage or muscle repair. Here, hyaluronic acid (HA)-based hydrogels are developed, which are suitable for use in minimally invasive procedures, that can adhere to the surrounding tissue, and deliver cells and potentially drugs. By modifying HA with both methacrylate (MA) and 3,4-dihydroxyphenylalanine (Dopa) groups using a completely aqueous synthesis route, it is shown that MA-HA-Dopa hydrogels can be applied under aqueous conditions, gel quickly using a standard surgical light, and adhere to tissue. Moreover, upon oxidation of the Dopa, human marrow stromal cells attach to hydrogels and survive when encapsulated within them. These observations show that when incorporated into HA-based hydrogels, Dopa moieties can foster cell and tissue interactions, ensuring surgical placement and potentially enabling delivery/recruitment of regenerative cells. The findings suggest that MA-HA-Dopa hydrogels may find use in minimally invasive procedures to foster maxillofacial tissue repair.
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Conjugated polymers as nanoparticle probes for fluorescence and photoacoustic imaging. J Mater Chem B 2020; 8:592-606. [DOI: 10.1039/c9tb02582k] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
In this review, the role of conjugated polymer nanoparticles (CPNs) in emerging bioimaging techniques is described.
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Supramolecular gels of cholesterol-modified gellan gum with disc-like and worm-like micelles. J Colloid Interface Sci 2019; 556:301-312. [DOI: 10.1016/j.jcis.2019.08.057] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2019] [Revised: 08/11/2019] [Accepted: 08/15/2019] [Indexed: 01/23/2023]
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Molecular insights into the behaviour of bile salts at interfaces: a key to their role in lipid digestion. J Colloid Interface Sci 2019; 556:266-277. [PMID: 31450021 DOI: 10.1016/j.jcis.2019.08.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Revised: 06/21/2019] [Accepted: 08/03/2019] [Indexed: 11/19/2022]
Abstract
HYPOTHESES Understanding the mechanisms underlying lipolysis is crucial to address the ongoing obesity crisis and associated cardiometabolic disorders. Bile salts (BS), biosurfactants present in the small intestine, play key roles in lipid digestion and absorption. It is hypothesised that their contrasting functionalities - adsorption at oil/water interfaces and shuttling of lipolysis products away from these interfaces - are linked to their structural diversity. We investigate the interfacial films formed by two BS, sodium taurocholate (NaTC) and sodium taurodeoxycholate (NaTDC), differing by the presence or absence of a hydroxyl group on their steroid skeleton. EXPERIMENTS Their adsorption behaviour at the air/water interface and interaction with a phospholipid monolayer - used to mimic a fat droplet interface - were assessed by surface pressure measurements and ellipsometry, while interfacial morphologies were characterised in the lateral and perpendicular directions by Brewster angle microscopy, X-ray and neutron reflectometry, and molecular dynamics simulations. FINDINGS Our results provide a comprehensive molecular-level understanding of the mechanisms governing BS interfacial behaviour. NaTC shows a higher affinity for the air/water and lipid/water interfaces, and may therefore favour enzyme adsorption, whereas NaTDC exhibits a higher propensity for desorption from these interfaces, and may thus more effectively displace hydrolysis products from the interface, through dynamic exchange.
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Low molecular weight PEG-PLGA polymers provide a superior matrix for conjugated polymer nanoparticles in terms of physicochemical properties, biocompatibility and optical/photoacoustic performance. J Mater Chem B 2019; 7:5115-5124. [PMID: 31363720 DOI: 10.1039/c9tb00937j] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The near-infrared absorbing conjugated polymer poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']-dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT) has been investigated as a contrast agent for optical and photoacoustic imaging. Lipophilic π-conjugated polymers can be efficiently encapsulated within self-assembling diblock copolymer poly(ethylene glycol) methyl ether-block-poly(lactide-co-glycolide) (PEG-PLGA) nanoparticles, although the effect of variations in PEG and PLGA chain lengths on nanoparticle properties, performance and biocompatibility have not yet been investigated. In this study, PEG-PLGA with different block lengths (PEG2kDa-PLGA4kDa, PEG2kDa-PLGA15kDa and PEG5kDa-PLGA55kDa) were used to encapsulate PCPDTBT. Nanoparticle sizes were smallest (<100 nm) when using PEG2kDa-PLGA4kDa, with <5% PCPDTBT content and a reduction in the total solids concentration of the organic phase. All PEG-PLGA nanoparticles were colloidally stable in water and serum-supplemented cell culture medium over 24 h at 37 °C, with slight evidence of protein surface adsorption. PEG2kDa-PLGA4kDa systems showed a threefold lower cytotoxicity (IC50 value) than the other two systems. Haemolytic activity was <2.5% for all systems and no platelet aggregation or inhibition of ADP-induced platelet aggregation was observed. Encapsulation of PCPDTBT within a PEG-PLGA matrix shifted fluorescence emission towards red wavelengths (760 nm in THF vs. 840 nm in nanoparticles) and reduced the quantum yield by 30-70-fold compared to THF. Nonetheless, PCPDTBT:PEG2kDa-PLGA4kDa systems had a marginally higher quantum yield and signal-to-background ratio in a phantom mouse compared with PEG2kDa-PLGA15kDa and PEG5kDa-PLGA55kDa systems. As a photoacoustic imaging probe, PCPDTBT:PEG2kDa-PLGA4kDa systems also showed a higher photoacoustic amplitude compared to higher molecular weight PEG-PLGA systems. Overall, the low molecular weight PEG2kDa-PLGA4kDa nanoparticle systems conferred the benefits of smaller sizes, reduced cytotoxicity and enhanced imaging performance compared to higher molecular weight matrix polymers.
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Targeted fluorescence lifetime probes reveal responsive organelle viscosity and membrane fluidity. PLoS One 2019; 14:e0211165. [PMID: 30763333 PMCID: PMC6375549 DOI: 10.1371/journal.pone.0211165] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Accepted: 01/08/2019] [Indexed: 11/19/2022] Open
Abstract
The only way to visually observe cellular viscosity, which can greatly influence biological reactions and has been linked to several human diseases, is through viscosity imaging. Imaging cellular viscosity has allowed the mapping of viscosity in cells, and the next frontier is targeted viscosity imaging of organelles and their microenvironments. Here we present a fluorescent molecular rotor/FLIM framework to image both organellar viscosity and membrane fluidity, using a combination of chemical targeting and organelle extraction. For demonstration, we image matrix viscosity and membrane fluidity of mitochondria, which have been linked to human diseases, including Alzheimer's Disease and Leigh's syndrome. We find that both are highly dynamic and responsive to small environmental and physiological changes, even under non-pathological conditions. This shows that neither viscosity nor fluidity can be assumed to be fixed and underlines the need for single-cell, and now even single-organelle, imaging.
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Pseudo-Polyrotaxanes of Cyclodextrins with Direct and Reverse X-Shaped Block Copolymers: A Kinetic and Structural Study. Macromolecules 2019. [DOI: 10.1021/acs.macromol.8b02509] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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Activity enhancement of selective antitumoral selenodiazoles formulated with poloxamine micelles. Colloids Surf B Biointerfaces 2018; 170:463-469. [DOI: 10.1016/j.colsurfb.2018.06.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Revised: 05/21/2018] [Accepted: 06/06/2018] [Indexed: 01/07/2023]
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Supramolecular Hybrid Structures and Gels from Host-Guest Interactions between α-Cyclodextrin and PEGylated Organosilica Nanoparticles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:10591-10602. [PMID: 30095271 DOI: 10.1021/acs.langmuir.8b01744] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Polypseudorotaxanes are polymer chains threaded by molecular rings that are free to unthread; these "pearl-necklace" can self-assemble further, leading to higher-order supramolecular structures with interesting functionalities. In this work, the complexation between α-cyclodextrin (α-CD), a cyclic oligosaccharide of glucopyranose units, and poly(ethylene glycol) (PEG) grafted to silica nanoparticles was studied. The threading of α-CD onto the polymeric chains leads to their aggregation into bundles, followed by either the precipitation of the inclusion complex or the formation of a gel phase, in which silica nanoparticles are incorporated. The kinetics of threading, followed by turbidimetry, revealed a dependence of the rate of complexation on the following parameters: the concentration of α-CD, temperature, PEG length (750, 4000, and 5000 g mol-1), whether the polymer is grafted or free in solution, and the density of grafting. Complexation is slower, and temperature has a higher impact on PEG grafted on silica nanoparticles compared to PEG free in solution. Thermodynamic parameters extracted from the transition-state theory showed that inclusion complex formation is favored with grafted PEG compared to free PEG and establishes a ratio of complexation of five to six ethylene oxide units per cyclodextrin. The complexation yields, determined by gravimetry, revealed that much higher yields are obtained with longer chains and higher grafting density. Thermogravimetric analysis and Fourier transform infrared spectroscopy on the inclusion complex corroborate the number of macrocycles threaded on the chains. A sol-gel transition was observed with the longer PEG chain (5k) at specific mixing ratios; oscillatory shear rheology measurements confirmed a highly solid-like behavior, with an elastic modulus G' of up to 25 kPa, higher than that in the absence of silica. These results thus provide the key parameters dictating inclusion complex formation between cyclodextrin and PEG covalently attached to colloidal silica and demonstrate a facile route toward soft nanoparticle gels based on host-guest interactions.
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Fate of Liposomes in the Presence of Phospholipase C and D: From Atomic to Supramolecular Lipid Arrangement. ACS CENTRAL SCIENCE 2018; 4:1023-1030. [PMID: 30159399 PMCID: PMC6107861 DOI: 10.1021/acscentsci.8b00286] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2018] [Indexed: 05/04/2023]
Abstract
Understanding the origins of lipid membrane bilayer rearrangement in response to external stimuli is an essential component of cell biology and the bottom-up design of liposomes for biomedical applications. The enzymes phospholipase C and D (PLC and PLD) both cleave the phosphorus-oxygen bonds of phosphate esters in phosphatidylcholine (PC) lipids. The atomic position of this hydrolysis reaction has huge implications for the stability of PC-containing self-assembled structures, such as the cell wall and lipid-based vesicle drug delivery vectors. While PLC converts PC to diacylglycerol (DAG), the interaction of PC with PLD produces phosphatidic acid (PA). Here we present a combination of small-angle scattering data and all-atom molecular dynamics simulations, providing insights into the effects of atomic-scale reorganization on the supramolecular assembly of PC membrane bilayers upon enzyme-mediated incorporation of DAG or PA. We observed that PC liposomes completely disintegrate in the presence of PLC, as conversion of PC to DAG progresses. At lower concentrations, DAG molecules within fluid PC bilayers form hydrogen bonds with backbone carbonyl oxygens in neighboring PC molecules and burrow into the hydrophobic region. This leads initially to membrane thinning followed by a swelling of the lamellar phase with increased DAG. At higher DAG concentrations, localized membrane tension causes a change in lipid phase from lamellar to the hexagonal and micellar cubic phases. Molecular dynamics simulations show that this destabilization is also caused in part by the decreased ability of DAG-containing PC membranes to coordinate sodium ions. Conversely, PLD-treated PC liposomes remain stable up to extremely high conversions to PA. Here, the negatively charged PA headgroup attracts significant amounts of sodium ions from the bulk solution to the membrane surface, leading to a swelling of the coordinated water layer. These findings are a vital step toward a fundamental understanding of the degradation behavior of PC lipid membranes in the presence of these clinically relevant enzymes, and toward the rational design of diagnostic and drug delivery technologies for phospholipase-dysregulation-based diseases.
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Influence of the Surfactant Structure on Photoluminescent π-Conjugated Polymer Nanoparticles: Interfacial Properties and Protein Binding. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:6125-6137. [PMID: 29726688 DOI: 10.1021/acs.langmuir.8b00561] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
π-Conjugated polymer nanoparticles (CPNs) are under investigation as photoluminescent agents for diagnostics and bioimaging. To determine whether the choice of surfactant can improve CPN properties and prevent protein adsorption, five nonionic polyethylene glycol alkyl ether surfactants were used to produce CPNs from three representative π-conjugated polymers. The surfactant structure did not influence size or yield, which was dependent on the nature of the conjugated polymer. Hydrophobic interaction chromatography, contact angle, quartz crystal microbalance, and neutron reflectivity studies were used to assess the affinity of the surfactant to the conjugated polymer surface and indicated that all surfactants were displaced by the addition of a model serum protein. In summary, CPN preparation methods which rely on surface coating of a conjugated polymer core with amphiphilic surfactants may produce systems with good yields and colloidal stability in vitro, but may be susceptible to significant surface alterations in physiological fluids.
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Soft nanocomposites of gelatin and poly(3-hydroxybutyrate) nanoparticles for dual drug release. Colloids Surf B Biointerfaces 2017; 157:191-198. [PMID: 28595135 DOI: 10.1016/j.colsurfb.2017.05.051] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Revised: 04/28/2017] [Accepted: 05/20/2017] [Indexed: 02/07/2023]
Abstract
We developed a nanocomposite gel composed of gelatin and poly(3-hydroxybutyrate) polymeric nanoparticles (PNP) to be used as an injectable gel for the contemporaneous, dual sustained release of bioactive molecules. The hydrogel matrix was formed by a very simple process, using either the physical gelation of gelatin or the natural enzyme transglutaminase to covalently cross-link the gelatin chains in the presence of embedded PNP. Oscillatory rheological measurements showed that the addition of the PNP induced an increase in the storage modulus compared to pure gelatin gels, for both physical and chemical gels. Micrographs from scanning electron microscopy revealed that the presence of PNP disrupted the native structure of the gelatin chains in the hydrogel matrix. Dual drug encapsulation was achieved with curcumin (CM) in the PNP and naproxen sodium(NS) in the gelatin matrix. In vitro release studies showed that the hydrogel matrix acts both as a physical and chemical barrier, delaying the diffusion of the drugs. An initial burst release was observed in the first hours of the measurement, and around 90% was released on the third day for naproxen sodium. In free PNP, 82% of curcumin was relased after four days, while when PNP were embedded in the gelatin matrix only 40% was released over the same time period. Overall, these simple, sustainable soft nanocomposites show potential as an injectable co-sustained drug release system.
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Structural and Spectroscopic Characterization of TPGS Micelles: Disruptive Role of Cyclodextrins and Kinetic Pathways. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:4737-4747. [PMID: 28412819 DOI: 10.1021/acs.langmuir.7b00701] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The aggregation and structure of d-α-tocopheryl polyethylene glycol succinate micelles, TPGS-1000, an amphiphilic derivative of vitamin E, were characterized using scattering and spectroscopic methods, and the impact of different cyclodextrins (CDs) on the self-assembly was investigated, with the view of combining these two versatile pharmaceutical excipients in drug formulations. Combined small-angle neutron scattering (SANS), dynamic light scattering, and time-resolved and steady-state fluorescence emission experiments revealed a core-shell architecture with a high aggregation number (Nagg ≈ 100) and a highly hydrated poly(ethylene oxide) corona (∼11 molecules of solvent per ethylene oxide unit). Micelles form gradually, with no sharp onset. Structural parameters and hydration of the aggregates were surprisingly stable with both temperature and concentration, which is a critical advantage for their use in pharmaceutical formulations. CDs were shown to affect the self-assembly of TPGS in different ways. Whereas native CDs induced the precipitation of a solid complex (pseudopolyrotaxane), methylated β-CDs led to different outcomes: constructive (micellar expansion), destructive (micellar rupture), or no effect, depending on the number of substituents and whether the substitution pattern was regular or random on the rims of the macrocycle. Time-resolved SANS studies on mixtures of TPGS with regularly dimethylated β-CD (DIMEB), which ruptures the micelles, revealed an almost instantaneous demicellization (<100 ms) and showed that the process involved the formation of large aggregates whose size evolved over time. Micellar rupture is caused by the formation of a TPGS-DIMEB inclusion complex, involving the incorporation of up to three macrocycles on the tocopherol, as shown by proton nuclear magnetic resonance (NMR) and ROESY NMR. Analysis of NMR data using Hill's equation revealed that the binding is rather cooperative, with the threading of the CD favoring the subsequent inclusion of additional CDs on the aliphatic moiety.
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Bright conjugated polymer nanoparticles containing a biodegradable shell produced at high yields and with tuneable optical properties by a scalable microfluidic device. NANOSCALE 2017; 9:2009-2019. [PMID: 28106200 DOI: 10.1039/c6nr09162h] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
This study compares the performance of a microfluidic technique and a conventional bulk method to manufacture conjugated polymer nanoparticles (CPNs) embedded within a biodegradable poly(ethylene glycol) methyl ether-block-poly(lactide-co-glycolide) (PEG5K-PLGA55K) matrix. The influence of PEG5K-PLGA55K and conjugated polymers cyano-substituted poly(p-phenylene vinylene) (CN-PPV) and poly(9,9-dioctylfluorene-2,1,3-benzothiadiazole) (F8BT) on the physicochemical properties of the CPNs was also evaluated. Both techniques enabled CPN production with high end product yields (∼70-95%). However, while the bulk technique (solvent displacement) under optimal conditions generated small nanoparticles (∼70-100 nm) with similar optical properties (quantum yields ∼35%), the microfluidic approach produced larger CPNs (140-260 nm) with significantly superior quantum yields (49-55%) and tailored emission spectra. CPNs containing CN-PPV showed smaller size distributions and tuneable emission spectra compared to F8BT systems prepared under the same conditions. The presence of PEG5K-PLGA55K did not affect the size or optical properties of the CPNs and provided a neutral net electric charge as is often required for biomedical applications. The microfluidics flow-based device was successfully used for the continuous preparation of CPNs over a 24 hour period. On the basis of the results presented here, it can be concluded that the microfluidic device used in this study can be used to optimize the production of bright CPNs with tailored properties with good reproducibility.
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Competitive and Synergistic Interactions between Polymer Micelles, Drugs, and Cyclodextrins: The Importance of Drug Solubilization Locus. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:13174-13186. [PMID: 27951706 DOI: 10.1021/acs.langmuir.6b03367] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Polymeric micelles, in particular PEO-PPO-based Pluronic, have emerged as promising drug carriers, while cyclodextrins (CD), cyclic oligosaccharides with an apolar cavity, have long been used for their capacity to form inclusion complexes with drugs. Dimethylated β-cyclodextrin (DIMEB) has the capacity to fully breakup F127 Pluronic micelles, while this effect is substantially hindered if drugs are loaded within the micellar aggregates. Four drugs were studied at physiological temperature: lidocaine (LD), pentobarbital sodium salt (PB), sodium naproxen (NP), and sodium salicylate (SAL); higher temperatures shift the equilibrium toward higher drug partitioning and lower drug/CD binding compared to 25 °C ( Valero, M.; Dreiss, C. A. Growth, Shrinking, and Breaking of Pluronic Micelles in the Presence of Drugs and/or β-Cyclodextrin, a Study by Small-Angle Neutron Scattering and Fluorescence Spectroscopy . Langmuir 2010 , 26 , 10561 - 10571 ). The impact of drugs on micellar structure was characterized by small-angle neutron scattering (SANS), while their solubilization locus was revealed by 2D NOESY NMR. UV and fluorescence spectroscopy, Dynamic and Static Light Scattering were employed to measure a range of micellar properties and drug:CD interactions: binding constant, drug partitioning within the micelles, critical micellar concentration of the loaded micelles, aggregation number (Nagg). Critically, time-resolved SANS (TR-SANS) reveal that micellar breakup in the presence of drugs is substantially slower (100s of seconds) than for the free micelles (<100 ms) ( Valero, M.; Grillo, I.; Dreiss, C. A. Rupture of Pluronic Micelles by Di-Methylated β-Cyclodextrin Is Not Due to Polypseudorotaxane Formation . J. Phys. Chem. B 2012 , 116 , 1273 - 1281 ). These results combined together give new insights into the mechanisms of protection of the drugs against CD-induced micellar breakup. The outcomes are practical guidelines to improve the design of drug delivery systems as well as a better understanding of competitive assembly mechanisms leading to shape and function modulation.
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Structure and Rheology of Poloxamine T1107 and Its Nanocomposite Hydrogels with Cyclodextrin-Modified Barium Titanate Nanoparticles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:6398-6408. [PMID: 27245639 DOI: 10.1021/acs.langmuir.6b01544] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We report the preparation of a nanocomposite hydrogel based on a poloxamine gel matrix (Tetronic T1107) and cyclodextrin (CD)-modified barium titanate (BT) nanoparticles. The micellization and sol-gel behavior of pH-responsive block copolymer T1107 were fully characterized by small-angle neutron scattering (SANS), dynamic light scattering (DLS), and Fourier transform infrared attenuated total reflectance (FTIR-ATR) spectroscopy as a function of concentration, pH and temperature. SANS results reveal that spherical micelles in the low concentration regime present a dehydrated core and highly hydrated shell, with a small aggregation number and size, highly dependent on the degree of protonation of the central amine spacer. At high concentration, T1107 undergoes a sol-gel transition, which is inhibited at acidic pH. Nanocomposites were prepared by incorporating CD-modified BT of two different sizes (50 and 200 nm) in concentrated polymer solutions. Rheological measurements show a broadening of the gel region, as well as an improvement of the mechanical properties, as assessed by the shear elastic modulus, G' (up to 200% increase). Initial cytocompatibility studies of the nanocomposites show that the materials are nontoxic with viabilities over 70% for NIH3T3 fibroblast cell lines. Overall, the combination of Tetronics and modified BaTiO3 provides easily customizable systems with promising applications as soft piezoelectric materials.
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Selective tuning of the self-assembly and gelation of a hydrophilic poloxamine by cyclodextrins. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:5645-5655. [PMID: 25938931 DOI: 10.1021/acs.langmuir.5b01081] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Complexes formed between cyclodextrins (CDs) and polymers - pseudopolyrotaxanes (PPRs) - are the starting point of a multitude of supramolecular structures, which are proposed for a wide range of biomedical and technological applications. In this work, we investigate the complexation of a range of cyclodextrins with Tetronic T1307, a four-arm block copolymer of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) with a pH-responsive central ethylene diamine spacer, and its impact on micellization and the sol-gel transition. At low concentrations, small-angle neutron scattering (SANS) combined with dynamic light scattering (DLS) measurements show the presence of spherical micelles with a highly hydrated shell and a dehydrated core. Increasing the temperature leads to more compact micelles and larger aggregation numbers, whereas acidic conditions induce a shrinking of the micelles, with fewer unimers per micelle and a more hydrated corona. At high concentrations, T1307 undergoes a sol-gel transition, which is suppressed at pH below the pKa,1 (4.6). SANS data analysis reveals that the gels result from a random packing of the micelles, which have an increasing aggregation number and increasingly dehydrated shell and hydrated core with the temperature. Native CDs (α, β, γ-CD) can complex T1307, resulting in the precipitation of a PPR. Instead, modified CDs compete with micellization to an extent that is critically dependent on the nature of the substitution. (1)H and ROESY NMR combined with SANS demonstrate that dimethylated β-CD can thread onto the polymer, preferentially binding to the PO units, thus hindering self-aggregation by solubilizing the hydrophobic block. The various CDs are able to modulate the onset of gelation and the extent of the gel phase, and the effect correlates with the ability of the CDs to disrupt the micelles, with the exception of a sulfated sodium salt of β-CD, which, while not affecting the CMT, is able to fully suppress the gel phase.
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Modulating the self-assembly of amphiphilic X-shaped block copolymers with cyclodextrins: structure and mechanisms. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:4096-4105. [PMID: 25785814 DOI: 10.1021/acs.langmuir.5b00334] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Inclusion complexes between cyclodextrins and polymers-so-called pseudopolyrotaxanes (PPR)-are at the origin of fascinating supramolecular structures, which are finding increasing uses in biomedical and technological fields. Here we explore the impact of both native and a range of modified cyclodextrins (CD) on the self-assembly of X-shaped poly(ethylene oxide)-poly(propylene oxide) block copolymers, so-called Tetronics or poloxamines, by focusing on Tetronic 904 (T904, Mw 6700). The effects are markedly dependent on the type and arrangement of the substituents on the macrocycle. While native CDs drive the formation of a solid PPR, most substituted CDs induce micellar breakup, with dimethylated β-CD (DIMEB) having the strongest impact and randomly substituted CDs a much weaker disruptive effect. Using native α-CD as a "molecular trap", we perform competitive binding experiments-where two types of CDs thread together onto the polymer chains-to establish that DIMEB indeed has the highest propensity to form an inclusion complex with the polymer, while hydroxypropylated CDs do not thread. 1D (1)H NMR and ROESY experiments confirm the formation of a soluble PPR with DIMEB in which the CD binds preferentially to the PO units, thus providing the drive for the observed demicellization. A combination of dynamic light scattering (DLS) and small-angle neutron scattering (SANS) is used to extract detailed structural parameters on the micelles. A binding model is proposed, which exploits the chemical shifts of selected protons from the CD in conjunction with the Hill equation, to prove that the formation of the PPR is a negatively cooperative process, in which threaded DIMEBs hamper the entrance of subsequent macrocycles.
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Exploring the Kinetics of Gelation and Final Architecture of Enzymatically Cross-Linked Chitosan/Gelatin Gels. Biomacromolecules 2015; 16:1401-9. [DOI: 10.1021/acs.biomac.5b00205] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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Using inclusion complexes with cyclodextrins to explore the aggregation behavior of a ruthenium metallosurfactant. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:2677-2688. [PMID: 25672530 DOI: 10.1021/la504929x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The aggregation behavior of a chiral metallosurfactant, bis(2,2'-bipyridine)(4,4'-ditridecyl-2,2'-bipyridine)ruthenium(II) dichloride (Ru2(4)C13), synthesized as a racemic mixture was characterized by small-angle neutron scattering, light scattering, NMR, and electronic spectroscopies. The analysis of the SANS data indicates that micelles are prolate ellipsoids over the range of concentrations studied, with a relatively low aggregation number, and the micellization takes place gradually with increasing concentration. The presence of cyclodextrins (β-CD and γ-CD) induces the breakup of the micelles and helps to establish that micellization occurs at a very slow exchange rate compared to the NMR time scale. The open structure of this metallosurfactant enables the formation of very stable complexes of 3:1 stoichiometry, in which one CD threads one of the hydrocarbon tails and two CDs the other, in close contact with the polar head. The complex formed with β-CD, more stable than the one formed with the wider γ-CD, is capable of resolving the Δ and Λ enantiomers at high CD/surfactant molar ratios. The chiral recognition is possible due to the very specific interactions taking place when the β-CD covers-via its secondary rim-part of the diimine moiety connected to the hydrophobic tails. A SANS model comprising a binary mixture of hard spheres (complex + micelles) was successfully used to study quantitatively the effect of the CDs on the aggregation of the surfactant.
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Remarkable viscoelasticity in mixtures of cyclodextrins and nonionic surfactants. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:11552-11562. [PMID: 25201697 DOI: 10.1021/la503000z] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We report the effect of native cyclodextrins (α, β, and γ) and selected derivatives in modulating the self-assembly of the nonionic surfactant polyoxyethylene cholesteryl ether (ChEO10) and its mixtures with triethylene glycol monododecyl ether (C12EO3), which form wormlike micelles. Cyclodextrins (CDs) generally induce micellar breakup through a host-guest interaction with surfactants; instead, we show that a constructive effect, leading to gel formation, is obtained with specific CDs and that the widely invoked host-guest interaction may not be the only key to the association. When added to wormlike micelles of ChEO10 and C12EO3, native β-CD, 2-hydroxyethyl-β-CD (HEBCD), and a sulfated sodium salt of β-CD (SULFBCD) induce a substantial increase of the viscoelasticity, while methylated CDs rupture the micelles, leading to a loss of the viscosity, and the other CDs studied (native α- and γ- and hydroxypropylated CDs) show a weak interaction. Most remarkably, the addition of HEBCD or SULFBCD to pure ChEO10 solutions (which are low-viscosity, Newtonian fluids of small, ellipsoidal micelles) induces the formation of transparent gels. The combination of small-angle neutron scattering, dynamic light scattering, and cryo-TEM reveals that both CDs drive the elongation of ChEO10 aggregates into an entangled network of wormlike micelles. (1)H NMR and fluorescence spectroscopy demonstrate the formation of inclusion complexes between ChEO10 and methylated CDs, consistent with the demicellization observed. Instead, HEBCD forms a weak complex with ChEO10, while no complex is detected with SULFBCD. This shows that inclusion complex formation is not the determinant event leading to micellar growth. HEBCD:ChEO10 complex, which coexists with the aggregated surfactant, could act as a cosurfactant with a different headgroup area. For SULFBCD, intermolecular interactions via the external surface of the CD may be more relevant.
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Molecular variations in aromatic cosolutes: critical role in the rheology of cationic wormlike micelles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:11535-42. [PMID: 25222020 DOI: 10.1021/la502649j] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Wormlike micelles formed by the addition to cetyltrimethylammonium bromide (CTAB) of a range of aromatic cosolutes with small molecular variations in their structure were systematically studied. Phenol and derivatives of benzoate and cinnamate were used, and the resulting mixtures were studied by oscillatory, steady-shear rheology, and the microstructure was probed by small-angle neutron scattering. The lengthening of the micelles and their entanglement result in remarkable viscoelastic properties, making rheology a useful tool to assess the effect of structural variations of the cosolutes on wormlike micelle formation. For a fixed concentration of CTAB and cosolute (200 mmol L(-1)), the relaxation time decreases in the following order: phenol > cinnamate> o-hydroxycinnamate > salicylate > o-methoxycinnamate > benzoate > o-methoxybenzoate. The variations in viscoelastic response are rationalized by using Mulliken population analysis to map out the electronic density of the cosolutes and quantify the barrier to rotation of specific groups on the aromatics. We find that the ability of the group attached to the aromatic ring to rotate is crucial in determining the packing of the cosolute at the micellar interface and thus critically impacts the micellar growth and, in turn, the rheological response. These results enable us for the first time to propose design rules for the self-assembly of the surfactants and cosolutes resulting in the formation of wormlike micelles with the cationic surfactant CTAB.
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CO2-switchable multi-compartment micelles with segregated corona. SOFT MATTER 2014; 10:6387-6391. [PMID: 25055723 DOI: 10.1039/c4sm01207k] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
CO2-switchable multi-compartment micelles (MCMs) with a segregated corona formed by a purpose-designed ABC triblock copolymer are reported. They can be switched "on" and "off" when sequentially treated with CO2 and N2, due to the protonation-deprotonation of the tertiary amine groups along the polymer skeleton.
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Enzymatically cross-linked gelatin/chitosan hydrogels: tuning gel properties and cellular response. Macromol Biosci 2014; 14:817-30. [PMID: 24550134 PMCID: PMC5412957 DOI: 10.1002/mabi.201300472] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Revised: 01/08/2014] [Indexed: 02/01/2023]
Abstract
This work investigates the effect of combining physical and chemical gelation processes in a biopolymer blend: chitosan and tilapia fish gelatin. Chemical (C) gels are obtained by cross-linking with the microbial enzyme transglutaminase at 37 °C. Hybrid physical-co-chemical (PC) gels are cross-linked at 21 °C, below gelatin gelation temperature. These protocols provide two microenvironments for the gelation process: in C gels, both gelatin and chitosan are present as single strands; in PC gels, cross-linking proceeds within a transient physical gel of gelatin, filled by chitosan strands. The chitosan/gelatin chemical networks generated in PC gels show a consistently higher shear modulus than pure C gels; they are also less turbid than their C gels counterparts, suggesting a more homogeneous network. Finally, chitosan enhances the gels' shear modulus in all gels. Proliferation assays show that MC3T3 cells proliferate in these mixed, hybrid gels and better so on PC gels than in C mixed gels.
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Effect of particle polydispersity on the structure and dynamics of complex formation between small particles and large polymer. RSC Adv 2014. [DOI: 10.1039/c4ra00929k] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
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Hybrid processes in enzymatically gelled gelatin: impact on , macroscopic properties and cellular response. SOFT MATTER 2013; 9:6986-6999. [PMID: 25310528 DOI: 10.1039/c3sm00125c] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Physical, chemical and hybrid tilapia fish gelatin hydrogels were investigated by small-angle neutron scattering (), molecular dynamic simulations and their biological effect in cell cultures studied; results from the different experimental techniques were then correlated and linked to the rheological properties of the gels (F. Bode et al., Biomacromolecules, 2011, 12, 3741-3752). Hydrogels were obtained by cross-linking with the microbial enzyme transglutaminase (mTGase) under two conditions: above and below gelatin physical temperature (ca. 23 °C). Hydrogels cross-linked at 37 °C, from the sol-state, are referred to as 'chemical' gels (C); hydrogels cross-linked at 21 °C, thus with concurrent physical , are referred to as 'physical-co-chemical' gels (PC). The data were appropriately described by a combination of a Lorentzian and a power law model. For physical gels, the correlation length (ξ) obtained from the fits decreased linearly with gelatin concentration, from 42 to 26 Å for 3.5 to 10% w/w gelatin, respectively. Independently of temperature, all physical gels at a given concentration showed a similar correlation length ξ (26 ± 2 Å), with no significant difference with the sol-state (23 ± 2 Å). In both C and PC gels, ξ increased with mTGase concentration over the range studied: 40 to 167 Å for 10 and 40 U mTGase per g gelatin in C gels (after 120 min cross-linking) and 40 to 82 Å for 10 and 40 U mTGase per g gelatin for PC gels. ξ reached a plateau at the highest mTGase concentration studied for both types of gels. In addition, kinetic studies on C gels revealed that ξ increased linearly with time in the first two hours and grew faster with increasing mTGase concentration. ξ values in the PC gels were smaller than in the corresponding C gels. Cell proliferation studies showed that the gels were compatible with cell growth and indicated no statistically relevant dependence on mTGase concentration for C gels. For PC gels, cell proliferation decreased with increases in mTGase concentration, by approximately 80% from 10 to 40 U mTGase per g gelatin. With the exception of the highest mTGase concentration studied, PC gels overall showed a slightly (but statistically significant) higher cell proliferation than the corresponding chemical gels.
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Tuning the viscoelasticity of nonionic wormlike micelles with β-cyclodextrin derivatives: a highly discriminative process. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:7697-7708. [PMID: 23682968 DOI: 10.1021/la4015338] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We report the influence of five β-cyclodextrin (β-CD) derivatives, namely: randomly methylated β-cyclodextrin (MBCD), heptakis (2,6-di-O-methyl)-β-cyclodextrin (DIMEB), heptakis (2,3,6-tri-O-methyl)-β-cyclodextrin (TRIMEB), 2-hydroxyethyl-β-cyclodextrin (HEBCD) and 2-hydroxypropyl-β-cyclodextrin (HPBCD), on the self-assembly of mixtures of nonionic surfactants: polyoxyethylene cholesteryl ether (ChEO10) and monocaprylin (MCL). Mixtures of ChEO10/MCL in water form highly viscoelastic wormlike micelle solutions (WLM) over a range of concentrations; herein, the composition was fixed at 10 wt % ChEO10/3 wt % MCL. The addition of methylated β-CDs (MBCD, DIMEB, TRIMEB) induced a substantial disruption of the solid-like viscoelastic behavior, as shown from a loss of the Maxwell behavior, a large reduction in G' and G″ in oscillatory frequency-sweep measurements, and a drop of the viscosity. The disruption increased with the degree of substitution, following: MBCD < DIMEB < TRIMEB. Cryo-TEM images confirmed a loss of the WLM networks, revealing short rods and disc-like aggregates, which were corroborated by small-angle neutron scattering (SANS) measurements. Critical aggregation concentrations (CAC), measured by fluorescence spectroscopy, increased in the presence of DIMEB for both ChEO10 and MCL, suggesting the existence of interactions between methylated β-CDs and both surfactants involved in WLM formation. Instead, hydroxyl-β-CDs had a very different effect on the WLM. HPBCD only slightly reduced the solid-like behavior, without suppressing it. Quite remarkably, the addition of HEBCD reinforced the solid-like characteristics and increased the viscosity 10-fold. Cryo-TEM images confirmed the subsistence of WLM in ChEO10/MCL/HEBCD solutions, while SANS data revealed a slight elongation and thickening of the worms, and an increase of associated water molecules. CAC data showed that HPBCD had little effect on either surfactant, while HEBCD strongly affected the CAC of MCL and only slightly affected the ChEO10. For both DIMEB and HEBCD, time-resolved SANS measurements showed that morphology changes underlying these macroscopic changes occur in less than 100 ms.
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Decrypting Prion Protein Conversion into a β-Rich Conformer by Molecular Dynamics. J Chem Theory Comput 2013; 9:2455-2465. [PMID: 23700393 PMCID: PMC3656828 DOI: 10.1021/ct301118j] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Indexed: 01/08/2023]
Abstract
Prion diseases are fatal neurodegenerative diseases characterized by the formation of β-rich oligomers and the accumulation of amyloid fibrillar deposits in the central nervous system. Understanding the conversion of the cellular prion protein into its β-rich polymeric conformers is fundamental to tackling the early stages of the development of prion diseases. In this paper, we have identified unfolding and refolding steps critical to the conversion into a β-rich conformer for different constructs of the ovine prion protein by molecular dynamics simulations. By combining our results with in vitro experiments, we show that the folded C-terminus of the ovine prion protein is able to recurrently undergo a drastic conformational change by displacement of the H1 helix, uncovering of the H2H3 domain, and formation of persistent β-sheets between H2 and H3 residues. The observed β-sheets refold toward the C-terminus exposing what we call a "bending region" comprising residues 204-214. This is strikingly coincident with the region harboring mutations determining the fate of the prion oligomerization process. The β-rich intermediate is used here for the construction of a putative model for the assembly into an oligomeric aggregate. The results presented here confirm the importance of the H2H3 domain for prion oligomer formation and therefore its potential use as molecular target in the design of novel prion inhibitors.
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Abstract
A major scientific challenge of the past decade pertaining to the field of soft matter has been to craft 'adaptable' materials, inspired by nature, which can dynamically alter their structure and functionality on demand, in response to triggers produced by environmental changes. Amongst these, 'smart' surfactant wormlike micelles, responsive to external stimuli, are a particularly recent area of development, yet highly promising, given the versatility of the materials but simplicity of the design-relying on small amphiphilic molecules and their spontaneous self-assembly. The switching 'on' and 'off' of the micellar assembly structures has been reported using electrical, optical, thermal or pH triggers and is now envisaged for multiple stimuli. The structural changes, in turn, can induce major variations in the macroscopic characteristics, affecting properties such as viscosity and elasticity and sometimes even leading to a spontaneous and effective 'sol-gel' transition. These original smart materials based on wormlike micelles have been successfully used in the oil industry, and offer a significant potential in a wide range of other technological applications, including biomedicine, cleaning processes, drag reduction, template synthesis, to name but a few. This review will report results in this field published over the last few years, describe the potential and practical applications of stimuli-responsive wormlike micelles and point out future challenges.
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Tuning the viscoelastic properties of bis(urea)-based supramolecular polymer solutions by adding cosolutes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:14531-14539. [PMID: 22967205 DOI: 10.1021/la3025606] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Polymers formed by the self-assembly of a bis(urea)-based polymer, 2,4-bis(2-ethylhexylureido)toluene (EHUT), in organic solvents such as octane are promising systems with remarkable rheological properties. This is the first self-assembled polymer recently reported as a hydrodynamic drag reducer for hydrocarbons. The rheology of diluted and semidiluted EHUT solutions can be tuned by specific interactions between the chains, modulated by the nature of the solvent and the presence of additives. In this article, rheological, thermal and SANS measurements were performed in order to investigate the competition between EHUT self-assembly and its interaction with specific molecules (benzene, benzyl alcohol, and ethanol) that can interact with EHUT unimers via hydrogen bonds and π-π interactions. No substantial rheological, thermal, or structural effect is observed when benzene is added to the systems. However, ethanol and benzyl alcohol interact with EHUT unimers through hydrogen bonds, drastically decreasing the viscoelasticity of the solutions. In addition, benzyl alcohol can interact with EHUT polymers by π-stacking interactions, playing an important role in tuning the rheological properties of the systems.
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