Pluronic System Research Articles

Efficacy of entomopathogenic nematodes combined with insecticides against Bradysia odoriphaga larvae

Summary Entomopathogenic nematodes (EPN) as an environmentally-friendly biocontrol agent in combination with low toxic insecticides can increase control efficacy against insect pests. In this study, Steinernema carpocapsae All (Sc-All) combined with four common insecticides was used to evaluate the control efficacy against chive root gnat (Bradysia odoriphaga), an important pest of vegetables, e.g., chive, onion or garlic. The compatibility of nematodes with insecticides and host-seeking behaviour were also evaluated by the laboratory bioassay. The results showed three insecticides (matrine, imidacloprid and chlorpyrifos) at the recommended concentrations (RC), 10% RC or 2% RC and insecticide phoxim at 10% RC or 2% RC had no effect on nematodes survival. Sc-All at 50 infective juveniles (IJ) per insect larva in the presence of the four insecticides at 10% RC demonstrated a potentiated, additive or a synergistic effect on the corrected mortality rates of insect up to 100% (imidacloprid) when compared with the corresponding insecticide and Sc-All alone. A synergistic effect resulting in lethal effect was found as early as at 24 h when 200 IJ of Sc-All per insect larva were combined with 10% RC imidacloprid, whilst only 9.4% and 0 corrected mortality were detected, respectively, when exposed to the same amount of imidacloprid and Sc-All alone. For the first time a Pluronic gel system assay revealed that the presence of insecticides significantly improved Sc-All host-seeking ability as early as 30 min post exposure. The results indicated that low doses of Sc-All-imidacloprid combination would be an effective strategy to control chive root gnat.

Implementing polymeric pseudorotaxanes for boosting corneal permeability and antiaspergillus activity of tolnaftate: formulation development, statistical optimization, ex vivo permeation and in vivo assessment

Fungal keratitis (FK) is a devastating ocular disease that can cause corneal opacity and blindness if not treated effectively. Tolnaftate (TOL) is a selective fungicidal drug against Aspergillus spp. which are among the most common causes of mycotic keratitis. TOL is lipophilic drug with low water solubility and permeation which act as obstacles for its clinical ocular efficacy. Hence, this study aimed to statistically optimize a novel polymeric pseudorotaxanes (PSRs) containing TOL for enhancing its ocular permeability and antifungal effect. For achieving this goal, a full 31.22 factorial design was fashioned for preparing and optimizing TOL-PSRs using film hydration technique. Three formulation variables were studied: drug amount (X1), weight ratio of Pluronics to HPβCD (X2) and Pluronic system (X3). Entrapment efficiency percent (EE%) (Y1), particle size (PS) (Y2) and zeta potential (ZP) (Y3) were set as dependent variables. The selected optimal TOL-PSRs (PSR1) showed EE% of 71.55 ± 2.90%, PS of 237.05 ± 12.80 nm and ZP of −32.65 ± 0.92 mV. In addition, PSR1 was compared to conventional polymeric mixed micelles (PMMs) and both carriers significantly increased the drug flux and resulted in higher amount permeated per unit area in 8 h compared to drug suspension. The histopathological studies assured the safety of PSR1 for ocular use. The in vivo susceptibility testing using Aspergillus niger confirmed that PSR1 displayed sustained antifungal activity up to 24 h. The obtained results revealed the admirable potential of PSR1 to be used as novel nanocarriers for promoting TOL ocular delivery.

Tailoring of chitosan/diacrylated pluronic system as a versatile nanoplatform for the amelioration of radiation-induced cognitive dysfunction

Rutin (RUT) is a biologically active flavonoid that is reported to modulate radiation-induced brain dysfunctions. However, RUT's poor water solubility and low brain bioavailability limit its clinical use. To increase its brain bioavailability, RUT was loaded onto nanoplatforms based on chitosan/diacrylated pluronic (CS/DA-PLUR) nanogels synthesized by gamma radiation. The optimized formulation was investigated as a carrier system for RUT. Based on pilot experiments' results, the cranial radiation (CR) dose that induced cognitive dysfunction was selected. In the main experiment, rats were pre-treated orally with either free RUT or RUT-CS/DA-PLUR. Rats' cognitive and motor functions were assessed; 24 h later, rats were sacrificed, and the whole brain was separated for histopathological examination and biochemical estimation of brain content of acetylcholine esterase (AChE), neurotransmitters, oxidative stress markers, and interleukin-1β. CR produced prominent impairment in spatial and non-spatial learning memory, motor coordination, and muscular strength. Moreover, histopathological and biochemical alterations in brain contents of neurotransmitters, oxidative stress, and interleukin-1β were induced by CR. Conversely, RUT-CS/DA-PLUR, but not free RUT, successfully guarded against all the detrimental effects induced by CR. Based on the current findings, loading of RUT enhanced its bioavailability and therapeutic effectiveness by restoring the cognitive functions impaired by CR.

Structural and therapeutic properties of curcumin solubilized pluronic F127 micellar solutions and hydrogels

Curcumin, the principle active constituent of turmeric, is known to have broad range of therapeutic properties. Its poor aqueous solubility and low bioavailability however, act as constraints for its biomedical applications. Recent studies have shown that incorporation of curcumin in nano-carriers like micelles, vesicles, polymeric nanoparticles etc. can help in overcoming these issues and improve its therapeutic abilities quite significantly. In this manuscript, we report preparation of curcumin solubilized pluronic F127 micellar solutions and hydrogels, along with their structural and therapeutic properties as obtained from SANS, rheological, anti-cancer and wound healing studies. Pluronic F127 being approved by FDA has been used quite extensively as excipient for drug delivery applications. Curcumin solubilization in the aqueous pluronic F127 system was carried out by briefly heating the copolymer solutions with curcumin at 90 °C. The concentrations of curcumin thus obtained were found to be comparable to those obtained by conventional methods of solubilization like thin film hydration or solvent evaporation method, and three orders of magnitude higher than that in pure water. SANS and rheological studies show that curcumin solubilization does not bring about any significant change in the structural and rheological properties of F127 micellar solutions and hydrogels. Curcumin solubilized F127 micellar solutions can be reconstituted after lyophilization, suggesting that curcumin remains nano-dispersed in lyophilized state. Micellar encapsulated curcumin exhibits very good stability in solution state in ambient condition but fails to show cytotoxicity against MCF7 cancer cells, presumably due to shielding of curcumin by large corona region of F127 micelles. Micellar curcumin containing F127 hydrogels on the other hand, exhibit wound healing abilities in mice model upon topical application. The results give an account of how some of the therapeutic properties of curcumin are manifested under micellar encapsulation and the role of pluronic F127 as excipient in those therapeutic applications.

NMR relaxation and self-diffusion in aqueous micellar gels of pluronic F-127

Abstract We studied the transverse NMR relaxation of protons of different chemical groups and diffusion of molecules in an aqueous pluronic F-127 system. The system was studied at concentrations of 15, 21 and 28 wt% and in the temperature range of 293–333 K. The dynamic peculiarities in different phases were analyzed based on the NMR relaxation and diffusion data. Our study demonstrated a correlation between phase states, T2 relaxation times of “solid-like” and “liquid” protons of selected chemical groups of polypropylene oxide (PPO) and polyethylene oxide (PEO) blocks, and diffusion coefficients. Transverse NMR relaxation established that the presence of a “solid-like” component of CH3 protons of PEO blocks is observed only at temperatures and concentrations corresponding to the rigid-gel phase, due to entanglements between micellar coronas. At all temperatures and concentrations, some CH3 protons of PPO blocks and some CH2 protons of PEO blocks show “liquid-like” transverse NMR relaxation. Under the conditions corresponding to formation of the rigid-gel phase of the pluronic, relaxation of the “liquid-like” protons additionally accelerates due to entanglements of micellar coronas. Transition of the system to the rigid-gel phase is accompanied by decrease of diffusion coefficients by a factor of 10–104 relative to the diffusivity of free-moving pluronic micelles in the sol phase. Diffusion measurements show that there are pre-transition phenomena, which are characteristic for temperatures and concentrations near sol-gel phase boundaries.

Correlation of the hierarchical structure with rheological behavior of polypseudorotaxane gel composed of pluronic and β-cyclodextrin.

We have identified the hierarchical (primary, secondary, tertiary and quaternary) structures of a polypseudorotaxane (PPR) gel composed of the Pluronic F108 and β-cyclodextrin system to be β-cyclodextrin crystalline, lamellar sheets, lamellar stacks and "grains", respectively. The correlation between the rheological properties and the proposed structures under shear flows was rationalized. Alignment of lamellar stacks and reorganization of grain boundaries under shear flows were investigated by rheo-SANS, small angle X-ray scattering and small-angle light scattering. The relaxation of highly aligned lamellar stacks is slow (>2 h) after flow cessation compared to that of the regrouped grains (a few minutes). The main contribution to thixotropic behavior is likely from the faster relaxation of the reorganized grains containing highly oriented lamellar stacks. The comprehensive understanding of structure-function relationship of the PPR gel will facilitate the rational design for its applications.

Effect of valency of cation on micellization behaviour of pluronic mixed micelle F127 and L64

In this work the effect of mono, di- and trivalent ions on the micellization and clouding behavior of mixed micellar system has been reported. A mixed pluronic micellar system constituting 0.5 wt%/0.5 wt% of pluronic F127 and L64 has been used for the investigation. The UV and Fluorescence studies were carried out using eosin yellow dye as the probe. Both studies indicate that the mixed micellar system displayed the spectral properties intermediate between the neat pluronic solutions. Also, it was observed that the spectral changes occurring were in the order trivalent > di valent > monovalent cations. The order was not strictly followed in the cloud point observation. With minimum discrepancies the clouding behavior of mixed pluronic followed the order Al3+>Mg2+>K+. Dynamic light scattering studies suggested that the addition of salt changed the particle size of the mixed micelles. This salt effect can be better explained considering the small particle size of cations, such as Na+, Mg2+, and Al3+. There was increase in diameter of mixed micelle from 42.81 nm to 54.99 nm for Na+, to 45.11 nm for Mg2+ and to 46.46 nm for Al3+. The infrared studies also indicated the spectral change of mixed micelle due to salt addition. Different ions affect the dehydration of the PPO core differently. To the best of our knowledge this is the first report of salt and cationic valence effect on mixed micellar system.

The proper strategy to compress and protect plasmid DNA in the Pluronic L64-electropulse system for enhanced intramuscular gene delivery.

Intramuscular expression of functional proteins is a promising strategy for therapeutic purposes. Previously, we developed an intramuscular gene delivery method by combining Pluronic L64 and optimized electropulse, which is among the most efficient methods to date. However, plasmid DNAs (pDNAs) in this method were not compressed, making them unstable and inefficient in vivo. We considered that a proper compression of pDNAs by an appropriate material should facilitate gene expression in this L64-electropulse system. Here, we reported our finding of such a material, Epigallocatechin gallate (EGCG), a natural compound in green teas, which could compress and protect pDNAs and significantly increase intramuscular gene expression in the L64-electropulse system. Meanwhile, we found that polyethylenimine (PEI) could also slightly improve exogenous gene expression in the optimal procedure. By analysing the characteristic differences between EGCG and PEI, we concluded that negatively charged materials with strong affinity to nucleic acids and/or other properties suitable for gene delivery, such as EGCG, are better alternatives than cationic materials (like PEI) for muscle-based gene delivery. The results revealed that a critical principle for material/pDNA complex benefitting intramuscular gene delivery/expression is to keep the complex negatively charged. This proof-of-concept study displays the breakthrough in compressing pDNAs and provides a principle and strategy to develop more efficient intramuscular gene delivery systems for therapeutic applications.

Cyclic RGD-conjugated Pluronic® blending system for active, targeted drug delivery.

BackgroundBlending micellar systems of different types of polymers has been proposed as an efficient approach for tailor-made drug formulations. The lamellar structure of hydrophobic polymers may provide a high drug loading capacity, and hydrophilic polymers may provide good colloidal stability.MethodsIn this study, the anticancer model drug docetaxel was loaded onto a nanosized blending micellar system with two pluronics (L121/F127). To achieve increased antitumor activity, the cyclic arginine-glycine-aspartic acid tripeptide (cRGD) as an active tumor targeting ligand was conjugated to the blending system.ResultsThe docetaxel-loaded Pluronic blending system exhibited a higher drug loading capacity than that of F127 and showed high colloidal stability with a spherical structure. cRGD conjugates demonstrated enhanced drug cellular uptake and anticancer activity against αvβ3 integrin-overexpressing U87MG cancer cells. In vivo animal imaging also revealed that the prepared cRGD-conjugated nanoparticles effectively accumulated at the targeted tumor site through an active and passive targeting strategy.ConclusionAccordingly, the prepared nanosized system shows potential as a tailor-made, active targeting, nanomedicinal platform for anticancer therapy. We believe that this novel nanoplatform will provide insights for advancement of tumor therapy.

Heat-induced solubilization of curcumin in kinetically stable pluronic P123 micelles and vesicles: An exploit of slow dynamics of the micellar restructuring processes in the aqueous pluronic system

Wide therapeutic potential combined with low cost and negligible toxicity makes curcumin one of the most sought after drugs in recent times. Its poor aqueous solubility and low bioavailability are often overcome by using micelles and vesicles as its carriers. The substances that are commonly used for this purpose are a class of nonionic surfactants called pluronics. Solubilization of curcumin in aqueous systems of these surfactants is carried out by thin film hydration method presumably because slow dynamics of micellar restructuring processes in them creates hindrance for direct solubilization. In this manuscript, we show that this problem can be overcome and curcumin can be solubilized directly in pluronic P123 micellar solutions by heating them to the phase separation temperature in the presence of curcumin. The obtained curcumin containing micellar solutions show cytotoxicity on human breast carcinoma (MCF7) cells with IC50 values similar to that shown by free curcumin solution. Addition of mucoadhesive polymer κ-Carrageenan into these solutions converts them to curcumin containing gels and patches with rheological properties suitable for topical application. These solutions also exhibit systematic spherical-to-worm like micellar-to-vesicular structural transitions in the presence of NaCl. The large curcumin containing aggregates thus formed show kinetic stability with respect to dilution, which is an important attribute for drug delivery application. Characterization of the micellar and vesicular systems and gels were carried out by SANS, DLS and rheological measurements. The obtained results represent first systematic study on solubilization of curcumin in pluronic aggregates of various shapes and size.

Mesoporous γ-Iron Oxide Nanoparticles for Magnetically Triggered Release of Doxorubicin and Hyperthermia Treatment.

Mesoporous iron-oxide nanoparticles (mNPs) were prepared by using a modified nanocasting approach with mesoporous carbon as a hard template. mNPs were first loaded with doxorubicin (Dox), an anticancer drug, and then coated with the thermosensitive polymer Pluronic F108 to prevent the leakage of Dox molecules from the pores that would otherwise occur under physiological conditions. The Dox-loaded, Pluronic F108-coated system (Dox@F108-mNPs) was stable at room temperature and physiological pH and released its Dox cargo slowly under acidic conditions or in a sudden burst with magnetic heating. No significant toxicity was observed in vitro when Dox@F108-mNPs were incubated with noncancerous cells, a result consistent with the minimal internalization of the particles that occurs with normal cells. On the other hand, the drug-loaded particles significantly reduced the viability of cervical cancer cells (HeLa, IC50 =0.70 μm), wild-type ovarian cancer cells (A2780, IC50 =0.50 μm) and Dox-resistant ovarian cancer cells (A2780/AD, IC50 =0.53 μm). In addition, the treatment of HeLa cells with both Dox@F108-mNPs and subsequent alternating magnetic-field-induced hyperthermia was significantly more effective at reducing cell viability than either Dox or Dox@F108-mNP treatment alone. Thus, Dox@F108-mNPs constitute a novel soft/hard hybrid nanocarrier system that is highly stable under physiological conditions, temperature-responsive, and has chemo- and thermotherapeutic modes of action.

Three dimensional study of wounded plant roots recruiting entomopathogenic nematodes with Pluronic gel as a medium

Pluronic F-127 is a non-toxic and thermoreversible transparent copolymer that allows nematodes to move freely inside the gel and be observed under a microscope. Pluronic gel has previously been shown to be a useful medium for three dimensional study of plant parasitic nematode host-finding behavior, but not for host-habitat finding of entomopathogenic nematodes (EPNs). In the current study, we used Pluronic gel for the first time to investigate the foraging behavior of EPNs, which are natural enemies of root-feeding insect pests, and to investigate the effect of storage duration of EPNs on attraction to wounded roots. We first tested one isolate of EPN, Heterorhabditis bacteriophora HBN (Hb-HBN), from northeastern China that is known to be an effective bio-control agent against Chinese chive gnat (Bradysia odoriphaga). The nematodes aggregate around wounded root parts, indicating that the nematodes are attracted to compounds released from freshly wounded root tissue, where insect hosts are more likely to be present. Among species/strains of EPNs that were tested, Hb-HBN showed the strongest attraction to Chinese chive roots. Surprisingly, attraction to a Chinese chive root following storage duration of up to 30days was much less than for Hb-HBN that were stored longer, with an optimal attraction observed for Hb-HBN that were stored 75–90days. This might be associated with phased infectivity. This study provides a better understanding of EPN foraging behavior and introduces the Pluronic gel system as a useful medium to study EPN attraction.

Selective distributions of functionalized single-walled carbon nanotubes in a polymeric reverse hexagonal phase.

We have investigated the distributions of individually isolated and hydrophilically functionalized single-walled carbon nanotubes (p-SWNTs) in the Pluronic L121-water system at the reverse hexagonal phase using small-angle X-ray scattering (SAXS) and contrast-matched small-angle neutron scattering (SANS) measurements. As the p-SWNT-L121-water system is transitioned from the lamellar phase to the reverse hexagonal phase with temperature, p-SWNTs which were selectively distributed in the polar layers of the lamellar structure become selectively distributed in the cylindrical polar cores of the reverse hexagonal structure, forming a hexagonal array of p-SWNTs. This was clearly confirmed by the contrast-matched SANS measurements. The selective distribution of p-SWNTs in the reverse hexagonal phase is driven by the selective affinity of p-SWNTs to the polar domains of the block copolymer system. The method demonstrated in this study provides a new route for fabricating ordered SWNT superstructures and may be applicable for inorganic 1D nanoparticles such as semiconducting, metallic and magnetic nanorods which are of great interest.

Abstract 160: Perivascular Administration of Rapamycin Through Nanoparticles Prolongs Inhibition of Arterial Restenosis

Open vascular reconstructions frequently fail due to the development of recurrent disease or intimal hyperplasia (IH). This paper reports a novel drug delivery method using a rapamycin-loaded poly(lactide-co-glycolide) (PLGA) nanoparticles (NPs)/pluronic gel system that can be applied periadventitially around the carotid artery immediately following the open surgery. In vitro studies revealed that rapamycin dispersed in pluronic gel was rapidly released over 3 days whereas release of rapamycin from rapamycin-loaded PLGA NPs embedded in pluronic gel was more gradual over 4 weeks. In cultured rat vascular smooth muscle cells (SMCs), rapamycin-loaded NPs produced durable (14 days versus 3 days for free rapamycin) inhibition of phosphorylation of S6 kinase (S6K1), a downstream target in the mTOR pathway. In a rat balloon injury model, periadventitial delivery of rapamycin-loaded NPs produced inhibition of phospho-S6K1 14 days after balloon injury. Immunostaining revealed that rapamycin-loaded NPs reduced SMC proliferation at both 14 and 28 days whereas rapamycin alone suppressed proliferation at day 14 only. Moreover, rapamycin-loaded NPs sustainably suppressed IH for at least 28 days following treatment, whereas rapamycin alone produced suppression on day 14 with rebound of IH by day 28. Since rapamycin, PLGA, and pluronic gel have all been approved by the FDA for other human therapies, this drug delivery method could potentially be translated into human use quickly to prevent failure of open vascular reconstructions.

Periadventitial Application of Rapamycin-Loaded Nanoparticles Produces Sustained Inhibition of Vascular Restenosis

Open vascular reconstructions frequently fail due to the development of recurrent disease or intimal hyperplasia (IH). This paper reports a novel drug delivery method using a rapamycin-loaded poly(lactide-co-glycolide) (PLGA) nanoparticles (NPs)/pluronic gel system that can be applied periadventitially around the carotid artery immediately following the open surgery. In vitro studies revealed that rapamycin dispersed in pluronic gel was rapidly released over 3 days whereas release of rapamycin from rapamycin-loaded PLGA NPs embedded in pluronic gel was more gradual over 4 weeks. In cultured rat vascular smooth muscle cells (SMCs), rapamycin-loaded NPs produced durable (14 days versus 3 days for free rapamycin) inhibition of phosphorylation of S6 kinase (S6K1), a downstream target in the mTOR pathway. In a rat balloon injury model, periadventitial delivery of rapamycin-loaded NPs produced inhibition of phospho-S6K1 14 days after balloon injury. Immunostaining revealed that rapamycin-loaded NPs reduced SMC proliferation at both 14 and 28 days whereas rapamycin alone suppressed proliferation at day 14 only. Moreover, rapamycin-loaded NPs sustainably suppressed IH for at least 28 days following treatment, whereas rapamycin alone produced suppression on day 14 with rebound of IH by day 28. Since rapamycin, PLGA, and pluronic gel have all been approved by the FDA for other human therapies, this drug delivery method could potentially be translated into human use quickly to prevent failure of open vascular reconstructions.

Additive induced core and corona specific dehydration and ensuing growth and interaction of Pluronic F127 micelles

Pluronic F127 is considered to be the most prominent member amongst Pluronics owing to its uses in the fields of drug delivery and fabrication of mesoporous materials. Though extensive studies were carried out on the phase behavior of this copolymer, the effect of additives on restructuring and growth processes of its micelles is not understood yet. In this manuscript we report DLS, SANS, fluorescence and rheological studies on the effects of NaCl and butan-1-ol on the properties of Pluronic F127 micelles in the aqueous medium. The studies show that corona specific micellar dehydration by NaCl induces inter micellar attraction and consequent formation of micellar clusters. Core specific micellar dehydration by butan-1-ol on the other hand, brings about sphere-to-rod micellar shape transition on approaching the cloud point of copolymer solutions. A room temperature sphere-to-rod shape transition of Pluronic F127 micelles can also be induced in the combined presence of butan-1-ol and NaCl. Observation of such micellar shape transition in aqueous Pluronic F127 system is first of its kind, which can have important bearing with their application in mesoporous structure formation and drug delivery.

Real-time UV imaging of piroxicam diffusion and distribution from oil solutions into gels mimicking the subcutaneous matrix

A novel real-time UV imaging approach for non-intrusive investigation of the diffusion and partitioning phenomena occurring during piroxicam release from medium chain triglyceride (MCT) solution into two hydrogel matrices is described. Two binary polymer/buffer gel matrices, 0.5% (w/v) agarose and 25% (w/v) Pluronic F127, were applied as simple models mimicking the subcutaneous tissue. The evolution of the absorbance maps as a function of time provided detailed information on the piroxicam release processes upon the exposure of the gel matrices to MCT. Using calibration curves, the concentration maps of piroxicam in the UV imaging area were determined. Regression of the longitudinal concentration–distance profiles, which were obtained using expressions derived from Fick’s second law, provided the diffusivity and the distribution coefficients of piroxicam penetrated into the gels. The obtained MCT–agarose (pH 7.4) distribution coefficient of 1.4 was identical to the MCT–aqueous (pH 7.4) distribution coefficient determined by the shake-flask method whereas that of the MCT–Pluronic F127 system was four times less. The experimental data show that UV imaging may have considerable potential for investigating the transport properties of drug formulations intended for the subcutaneous administration.

Gold-Nanoparticle-Stabilized Pluronic Micelles Exhibiting Glutathione Triggered Morphology Evolution Properties

Nanocomposites constructed from metallic nanoparticles and amphiphilic copolymers have attracted substantial interest for various potential applications. Here we report on the nanocomposites prepared through cross-linking pluronic micelles with gold nanoparticles. The covalent binding of gold nanoparticles onto the micelles and the thermoresponsibility of the system was followed via ultraviolet-visible spectroscopy, dynamic light scattering, transmission electron microscopy, and fluorescence spectroscopy. The gold-nanoparticle-stabilized pluronic micelles can take thiol-exchange reaction with glutathione and their morphology spontaneously evolved and reassembled into large "vesicular"-like nanocapsules. Obvious temperature responsibility was followed in the gold-nanoparticle-stabilized pluronic micelles system and also the glutathione triggered nanocapsules systems. It is believed that the high stability and glutathione responsibility of the Au-NPs shell-cross-linked micelles allowed for high potential in drug delivery and biosensors.

Time Dependent Sphere-to-Rod Growth of the Pluronic Micelles: Investigating the Role of Core and Corona Solvation in Determining the Micellar Growth Rate

The salt induced sphere-to-rod growth in the micelles of the PEO-PPO triblock copolymers, Pluronic P123 (EO(20)PO(70)PEO(20)) and Pluronic P103 (EO(16)PO(61)PEO(16)), has been studied by dynamic light scattering (DLS), viscometry, and small angle neutron scattering (SANS) techniques. The observed micellar growths are found to be time dependent and have a strong variation in their growth rate with changing anion type and copolymer composition. The rate of growth increases rather significantly with an increase in the water structure making abilities of the anions along the Hofmeister series in the order Cl(-) < F(-)< (PO(4))(3-). This has been attributed to an increasing ability of these ions to dehydrate the micellar corona, a factor that plays an important role in inducing sphere-to-rod shape transition of the micelles. The copolymer composition also has a significant influence on the micellar growth rate, as the P103 with a smaller molecular weight than P123 shows a significantly faster growth of its micelles under similar conditions. The observed time dependence in micellar growth in these systems has been attributed to a slow micellar restructuring process necessary to attain the equilibrium structure of the micelles. A remarkable improvement in the growth rate of the micelles, however, could be achieved in the presence of ethanol, a solvent that has affinity toward both the PPO and PEO blocks. Our spectroscopic studies suggest that the observed improvement in the micellar growth rate by ethanol is due to an accelerated restructuring process of the micelles in the presence of the solvated micellar core. These studies thus highlight the role of changing core and corona solvation characteristics of the pluronic micelles in determining their rearrangement and the growth rate, which is first of its kind in the aqueous pluronic system.

Pluronic and Chitosan basedIn situgel system for periodontal application

Pluronic and Chitosan based<i>In situ</i>gel system for periodontal application