Solubilization of poorly water-soluble drug carbamezapine in Pluronic® micelles: Effect of molecular characteristics, temperature and added salt on the solubilizing capacity

Specificity of hexarhenium cluster anions for synthesis of Mn2+-based nanoparticles with lamellar shape and pH-induced leaching for specific organ selectivity in MRI contrasting

The present work demonstrates the structure variation of hexarhenium anionic cluster units [{Re6S8}(CN)(6-n)(OH)n]4- (n = 0, 2, 4) as the strategy to develop Mn2+-containing nanoparticles (NPs) exhibiting pH-dependent leaching. The dicyanotetrahydroxo complex [{Re6S8}(CN)2(OH)4]4- is the optimal for the synthesis of the Mn2+-based NPs with a lamellar shape exhibiting the pH-dependent aggregation and magnetic relaxation behavior. The pH-dependent behavior of the NPs derives from the easy protonation of the apical hydroxo ligands of [{Re6S8}(CN)2(OH)4]4- cluster, which triggers partial leaching of Mn2+ ions and aggregation of the NPs driven by the surface neutralization. The in vivo MRI scanning of the mice intravenously injected with the NPs indicates the preferable accumulation of the lamellar NPs within mouse intestine over liver and kidneys. This differs from the spherical NPs constructed from [{Re6Se8}(CN)6]4- units, which provide the preferable brightening of mouse liver over kidneys and intestine.

Mechanistic Insight in Permeability through Different Membranes in the Presence of Pharmaceutical Excipients: A Case of Model Hydrophobic Carbamazepine

The present study reports the effects of two pharmaceutical excipients of differing natures-non-ionic surfactant pluronic F127 (F127) and anionic sulfobutylether-β-cyclodextrin (SBE-β-CD)-on the permeation of the model compound, carbamazepine (CBZ). The permeability coefficients of CBZ at three concentrations of the excipients were measured through two different artificial barriers: hydrophilic cellulose membrane (RC) and lipophilic polydimethylsiloxane-polycarbonate membrane (PDS). The equilibrium solubility of CBZ in F127 and SBE-β-CD solutions was determined. The micellization, complexation, and aggregation tendencies were investigated. Systemically increasing the solubility and the reduction of permeation upon the excipients' concentration growth was revealed. The quantitative evaluation of the permeability tendencies was carried out using a Pratio parameter, a quasi-equilibrium mathematical mass transport model, and a correction of permeability coefficients for the free drug concentration ("true" permeability values). The results revealed the mutual influence of the excipient properties and the membrane nature on the permeability variations.

Pluronic F68 Micelles as Carriers for an Anti-Inflammatory Drug: A Rheological and Scattering Investigation

Age-long ambition of medical scientists has always been advancement in healthcare and therapeutic medicine. Biomedical research indeed claims paramount importance in nanomedicine and drug delivery, and the development of biocompatible storage structures for delivering drugs stands at the heart of emerging scientific works. The delivery of drugs into the human body is nevertheless a nontrivial and challenging task, and it is often addressed by using amphiphilic compounds as nanosized delivery vehicles. Pluronics belong to a peculiar class of biocompatible and thermosensitive nonionic amphiphilic copolymers, and their self-assemblies are employed as drug delivery excipients because of their unique properties. We herein report on the encapsulation of diclofenac sodium within Pluronic F68 self-assemblies in water, underpinning the impact of the drug on the rheological and microstructural evolution of pluronic-based systems. The self-assembly and thermoresponsive micellization were studied through isothermal steady rheological experiments at different temperatures on samples containing 45 wt % Pluronic F68 and different amounts of diclofenac sodium. The adoption of scattering techniques, small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS), allowed for the description of the system features at the nanometer length scale, providing information about the characteristic size of each part of the micellar structures as a function of temperature and drug concentration. Diclofenac sodium is not a good fellow for Pluronic F68. The triblock copolymer aids the encapsulation of the drug, highly improving its water solubility, whereas diclofenac sodium somehow hinders Pluronic self-assembly. By using a simple empirical model and no fitting parameters, the steady viscosity can be predicted, although qualitatively, through the volume fraction of the micelles extracted through scattering techniques and compared to the rheological one. A tunable control of the viscous behavior of such biomedical systems may be achieved through the suitable choice of their composition.

Ophthalmic Bimatoprost-Loaded Niosomal In Situ Gel: Preparation, Optimization, and In Vivo Pharmacodynamics Study

This study aimed at formulating the antiglaucoma agent, Bimatoprost (BMT), into niosomal in situ gel (BMT-ISG) for ocular delivery. Niosomes containing cholesterol/span 60 entrapping BMT were fabricated using a thin-film hydration method. The fabricated niosomes were optimized and characterized for entrapment efficiency (%EE) and size. The optimized BMT-loaded niosomal formulation prepared at a cholesterol/span 60 ratio of 1:2 exhibited the highest entrapment (81.2 ± 1.2%) and a small particle size (167.3 ± 9.1 nm), and they were selected for incorporation into in situ gelling systems (BMT-ISGs) based on Pluronic F127/Pluronic F68. Finally, the in vivo efficiency of the BMT-ISG formulation, in terms of lowering the intraocular pressure (IOP) in normotensive male albino rabbits following ocular administration, was assessed and compared to that of BMT ophthalmic solution. All the formulated BMT-ISGs showed sol-gel transition temperatures ranging from 28.1 °C to 40.5 ± 1.6 °C. In addition, the BMT-ISG formulation sustained in vitro BMT release for up to 24 h. Interestingly, in vivo experiments depicted that topical ocular administration of optimized BMT-ISG formulation elicited a significant decline in IOP, with maximum mean decreases in IOP of 9.7 ± 0.6 mm Hg, compared to BMT aqueous solution (5.8 ± 0.6 mm Hg). Most importantly, no signs of irritation to the rabbit's eye were observed following topical ocular administration of the optimized BMT-ISG formulation. Collectively, our results suggested that niosomal in situ gels might be a feasible delivery vehicle for topical ocular administration of anti-glaucoma agents, particularly those with poor ocular bioavailability.

Direct and Reverse Pluronic Micelles: Design and Characterization of Promising Drug Delivery Nanosystems

Pluronics are a family of amphiphilic block copolymers broadly explored in the pharmaceutical field. Under certain conditions, Pluronics self-assemble in different structures including nanosized direct and reverse micelles. This review provides an overview about the main parameters affecting the micellization process of Pluronics, such as polymer length, fragments distribution within the chain, solvents, additives and loading of cargo. Furthermore, it offers a guide about the most common techniques used to characterize the structure and properties of the micelles. Finally, it presents up-to-date approaches to improve the stability and drug loading of Pluronic micelles. Special attention is paid to reverse Pluronics and reverse micelles, currently underexplored in the literature. Pluronic micelles present a bright future as drug delivery agents. A smart design and thorough characterization will improve the transfer to clinical applications.

Polyelectrolyte-Surfactant Complexes As a Formulation Tool for Drug Delivery

Aqueous polyelectrolyte-surfactant complexes (PESCs) are very rich with respect to their properties and the structures formed by them. By design they normally contain hydrophobic micellar surfactant aggregates complexed by long polyelectrolyte chains, thereby combining the formation of small hydrophobic domains given by the surfactant with large-scale structuring due to the presence of the polyelectrolyte chain. In addition, they contain highly polar regions of surfactant head groups in contact with polyelectrolyte, forming a shell around the micellar aggregates, which often also possesses a certain hydrophobic character. Accordingly, the ability for solubilization of water-insoluble compounds of different sorts is particularly versatile in PESCs. Their solubilization sites with very different polarities and hydrophobic characters make them very flexible in adapting to the requirements of a given drug molecule. This renders them attractive for potential applications in drug delivery. In addition, modification of the rheological properties via self-assembly and network formation can be very important in PESC applications. In the following, we discuss the structures of PESCs and their properties, with a focus on the solubilization properties. Subsequently, examples are described where PESCs have been employed in the context of drug solubilization and delivery. These comprise examples with individual aggregates, cross-linked hydrogels, and ones taking advantage of the high solubilization capacity of microemulsions.

Unusual Correlation between the Apparent Amorphous Solubility of a Drug and Solubilizer Concentration Revealed by NMR Analysis

Herein, we investigated the effect of the solubilizers, cetyltrimethylammonium bromide (CTAB) and amino methacrylate copolymer (Eudragit E PO, EUD-E), on the apparent amorphous solubility of ketoprofen (KTP) and free KTP concentrations in an aqueous phase when a KTP-rich phase was generated by liquid-liquid phase separation. Quantitative analysis by solution nuclear magnetic resonance (NMR) revealed that the apparent amorphous solubility of KTP increased with increasing EUD-E concentrations by the solubilization of KTP into the EUD-E micelles; this was reminiscent of the improvement in the apparent crystalline solubility of KTP observed when EUD-E was added. In contrast, the apparent amorphous solubility of KTP decreased with increasing CTAB concentrations, although the solubilizing ability of CTAB was stronger than that of EUD-E when the KTP-rich phase was absent. NMR analysis revealed that CTAB was distributed into the KTP-rich phase to a relatively large extent. This resulted in a significant reduction of the chemical potential of KTP in the KTP-rich phase in the CTAB solution. Thus, the maximum free KTP concentration in the aqueous phase was reduced more significantly in the CTAB solution than in the EUD-E solution. Moreover, the solubilization effect of KTP by the CTAB micelles in the aqueous phase was drastically diminished due to the distribution of CTAB into the KTP-rich phase. As a result, the apparent amorphous solubility of KTP reached a minimum at a CTAB concentration of 200 μg/mL. A further increase in the CTAB concentration resulted in an improvement in the apparent amorphous solubility of KTP due to the solubilization effect of CTAB remaining in the aqueous phase. The present study highlights the impact of solubilizer selection on the apparent amorphous solubility and attainable supersaturation of the drug, which should be considered during the development of supersaturating formulations to obtain preferable oral absorption.

Molecular and Nano-Structural Optimization of Nanoparticulate Mn2+-Hexarhenium Cluster Complexes for Optimal Balance of High T1- and T2-Weighted Contrast Ability with Low Hemoagglutination and Cytotoxicity

The present work introduces rational design of nanoparticulate Mn(II)-based contrast agents through both variation of the μ₃ (inner) ligands within a series of hexarhenium cluster complexes [{Re₆(μ₃-Q)₈}(CN)₆]⁴⁻ (Re₆Q₈, Q = S²⁻, Se²⁻ or Te²⁻) and interfacial decoration of the nanoparticles (NPs) K_4−2xMn_xRe₆Q₈ (x = 1.3 − 1.8) by a series of pluronics (F-68, P-123, F-127). The results highlight an impact of the ligand and pluronic for the optimal colloid behavior of the NPs allowing high colloid stability in ambient conditions and efficient phase separation under the centrifugation. It has been revealed that the K_4−2xMn_xRe₆Se₈ NPs and those decorated by F-127 are optimal from the viewpoint of magnetic relaxivities r₁ and r₂ (8.9 and 10.9 mM⁻¹s⁻¹, respectively, at 0.47 T) and low hemoagglutination activity. The insignificant leaching of Mn²⁺ ions from the NPs correlates with their insignificant effect on the cell viability of both M-HeLa and Chang Liver cell lines. The T₁- and T₂-weighted contrast ability of F-127–K_4−2xMn_xRe₆Q₈ NPs was demonstrated through the measurements of phantoms at whole body 1.5 T scanner.

Micellar assembly leading to structural growth/transition in normal and reverse Tetronics® in single and mixed solution environment

This study scrutinizes the self-association of ethylene oxide (EO)-propylene oxide (PO)-based star-shaped block copolymers as normal Tetronic® (T904) and reverse Tetronic® R (T90R4) with varying molecular characteristics and different hydrophilic-hydrophobic ratios in an aqueous solution environment. These thermo-responsive solutions appear clear, transparent or bluish up to 10%w/v, which anticipated the probable transition of unimers to spherical or ellipsoidal micelles which is complemented by scattering experiments. In a single-solution environment, 10%w/v T904 formed star-shaped micelles at ambient temperature and exhibited a micellar growth/transition with temperature ageing. While 10%w/v T90R4 exists as unimers or a Gaussian coil over a wide range of temperature. Very interestingly, close to the cloud point (CP) flower-shaped spherical and ellipsoidal micelles were formed. A similar proposed micellar scheme was also examined for mixed systems T904 : T90R4 in varying ratios (1 : 0, 3 : 1, 1 : 1, 1 : 3 and 0 : 1) giving an account to the solution behavior of the mixtures. An amalgamation of dynamic light scattering (DLS) and small-angle neutron scattering (SANS) techniques achieved the thorough extraction of the structural parameters of the micellar system. The hydrodynamic diameter (D_h) of the micelles with temperature variation was evaluated from dynamic light scattering (DLS) while the structure factor of the micelles was found by employing small-angle neutron scattering (SANS). Furthermore, the single and mixed micellar systems were quantitatively and qualitatively examined for anticancer drug solubilization using UV-vis spectroscopy for their superior use as potential nanocargos.

Aceclofenac-loaded pluronic F108/L81 mixed polymeric micelles: effect of HLB on solubilization

Pluronic block copolymers have phase behavioural characteristics which are extensively studied for drug delivery applications. In this study, we explored hydrophilic pluronic F108 (HLB = 27), hydrophobic pluronic L81 (HLB = 2) and their mixed micelles acting as solubilising mediums for model drug aceclofenac. The drug solubilisation and interactions have been analysed using UV-visible spectroscopy, Fluorescence spectroscopy, Rheology studies, Fourier-transform infrared spectroscopy, Scanning electron microscope, Dynamic light scattering, Cloud point and partition coefficient measurements. The investigation from UV-spectrophotometry demonstrated that mixed pluronic entrapped greater number of aceclofenac molecules than both the neat pluronics at same concentration. Excimer formation was evidenced from fluorescence spectra with pyrene as a probe. The rheological studies showed difference in viscosity over low shear range. Studies on FTIR demonstrated probable bonding between the aceclofenac and mixed pluronic molecules. The DLS studies on mixed pluronic showed swelling of micellar diameter from 317.6 nm to 413.5 nm. Thermodynamic parameters of the above system revealed higher partition coefficient value for mixed pluronic and spontaneity in drug solubilisation. This study can be exploited to use a hydrophobic copolymeric micelle in mixed pluronic formulation for better drug solubilisation.

Mixed Poloxamer Nanomicelles for the Anticonvulsant Lamotrigine Drug: Solubility, Micellar Characterization, and In-Vitro Release Studies

Recently the applications of Poloxamers in drug development is promising as it facilitated the drug molecule for delivering to the correct place, at the correct time and in the correct amount. Poloxamers can form nanomicelles to encapsulate hydrophobic drugs in order to increase solubility, stability and facilitate delivery at target. In this context, the solubilization of anticonvulsant lamotrigine (LMN) drug in a chain of Poloxamers containing different polyethylene oxide and polypropylene oxide noieties were examined. The results showed better solubilization of LMN in Poloxamers contain low CMTs while poor with Poloxamers having high CMTs. Systematic investigation of two mixed Poloxamer nanomicelles (P407:P403 and P407:P105) for LMN bioavailability at body temperature (37 °C) were investigated. The solubility of LMN was enhanced in mixed P407:P403 nanomicelles with the amount of P403 and reduced in mixed P407:P105 nanomicelles with the amount of P105. LMN encapsulated mixed Poloxamer nanomicelles were found spherical in shape with ~25 nm D_h sizes. The In-Vitro release profiles of mixed Poloxamer nanomicelles demonstrated the biphasic model with initial burst release and then slowly release of LMN. Better biocompatibility of LMN in the mixed P407:P403 nanomicelles was confirmed with stability data. The results of this work were proven the mixed P407:P403 nanomicelles as efficient nanocarriers for LMN.

Pluronic-based nanovehicles: Recent advances in anticancer therapeutic applications

Pluronics are a class of amphiphilic tri-block copolymers with wide pharmaceutical applicability. In the past decades, the ability to form biocompatible nanosized micelles was exploited to formulate stable drug nanovehicles with potential use in antitumor therapy. Due to the great potential for tuning physical and structural properties of Pluronic unimers, a panoply of drug or polynucleotide-loaded micelles was prepared and tested for their antitumoral activity. The attractive inherent antitumor properties of Pluronic polymers in combination with cell targeting and stimuli-responsive ligands greatly improved antitumoral therapeutic effects of tested drugs. In spite of that, the extraordinary complexity of biological challenges in the delivery of micellar drug payload makes their therapeutic potential still not exploited to the fullest. In this review paper we attempt to present the latest developments in the field of Pluronic based nanovehicles and their application in anticancer therapy with an overview of the chemistry involved in the preparation of these nanovehicles.

In Vitro Cytotoxicity and Cellular Uptake of Tamoxifen Citrate-Loaded Polymeric Micelles

The main intent of this treatise was to encapsulate tamoxifen citrate (TMXC) into polymeric micellar delivery system and evaluate the influence of TMXC-loaded micelles as a promising carrier on the in vitro cytotoxicity and cellular uptake of TMXC in treatment of breast cancer. Different formulae of polymeric micelles loaded with TMXC using mixtures of different Pluronic polymers were fabricated by thin-film hydration method and evaluated for morphology, drug entrapment efficiency, particle size, surface charge, in vitro liberation of TMXC, uptake by cancer cell lines, and cytotoxic effect against breast cancer cell lines such as MCF-7. The optimal TMXC-loaded micelles exhibited nano-sized particles and entrapped about 89.09 ± 4.2% of TMXC. In vitro liberation study revealed an extended TMXC escape of about 70.23 ± 5.9% over a period of 36 h. The optimized TMXC-loaded micelles formula showed enhanced cellular uptake of TMXC by 2.28 folds and showed a significant cytotoxic effect with MCF-7 breast cancer cells compared to TMXC solution. The obtained yield proposed that Pluronic micelles could be a promising potential delivery system for anticancer moieties.

pH interferes in photoinhibitory activity of curcumin nanoencapsulated with pluronic® P123 against Staphylococcus aureus

Microbial contamination control is a public health concern and challenge for the food industry. Antimicrobial technologies employing natural agents may be useful in the food industry for these purposes. This work aimed to investigate the effect of photodynamic inactivation using curcumin in Pluronic® P123 nanoparticles (Cur/P123) at different pH and blue LED light against Staphylococcus aureus. Bacterial photoinactivation was conducted using different photosensitizer concentrations and exposure times at pH 5.0, 7.2 and 9.0. A mixture design was applied to evaluate the effects of exposure time (dark and light incubation) on the photoinhibitory effect. S. aureus was completely inactivated at pH 5.0 by combining low concentrations of Cur/P123 (7.80-30.25 μmol/L) and light doses (6.50-37.74 J/cm²). According to the mathematical model, dark incubation had low significance in bacterial inactivation at pH 5.0 and 9.0. No effect in bacterial inactivation was observed at pH 7.2. Cur/P123 with blue LED was effective in inactivating S. aureus. The antimicrobial effect of photodynamic inactivation was also pH-dependent.

Self-Assemble Amphiphilic PEO-PPO-PEO Tri-Block Co-Polymeric Methotrexate Nanomicelles to Combat MCF7 Cancer Cells

BACKGROUND

Methotrexate (MTX) is a water-insoluble, anti-tumor agent that causes adverse effects like bone marrow suppression, chronic interstitial obstructive pulmonary disease, hepatotoxicity, leukopenia, interstitial pneumonitis and nephrotoxicity with slow drug release rate.

OBJECTIVE

The present study aimed to successfully incorporate MTX into novel-targeted Pluronic (PEOPPO- PEO tri-block co-polymer) F127 polymeric micelles intended for intravenous administration with improved drug loading and sustained release behavior necessary to achieve better efficacy of MTX.

METHODS

MTX-loaded Pluronic F127 micelles were characterized for critical micelle concentration, particle size and zeta potential,¹H NMR, drug loading, encapsulation efficiency characterization, cell uptake, in vitro release study along with partition coefficient and solubilization thermodynamics.

RESULTS

The micellar formulation resulted in nano size 27.32±1.43nm of PF127/SDS, as compared to Pluronic F127 micelles or PF127/Phosphatidyl choline which were 30.52±1.18nm and 154.35±5.5nm in size, respectively. The uptake of PF127/SDS micellar formulation incorporating Rhodamine 123 in MCF7 cancer cells was found to be higher (84.25%) than PF127/PC, PF127 and MTX i.e. 66.26%, 73.59% and 53% respectively. The in vitro MTX release from PF127, PF127/SDS and PF127/PC polymeric micelles formulations was observed to be 69%, 69.5% and 66% at 12 h whereas 80.89%, 77.67% and 78.54% after 24 h, respectively and revealed a sustained release. MTX-loaded PF127/SDS micelles showed high partition coefficient and negative free energy of solubilization compared to PF127 and PF127/PC which signify self-assembly behavior and thermodynamic stability towards higher dissociation.

CONCLUSION

It was finally concluded that MTX-loaded PF127/SDS micelles act as a potential anticancer delivery system in comparison to PF127/PC and PF127 to combat tumor cells by enhancing their cellular uptake targeting with sustained release pattern and reducing the thermodynamic instability. Thus, PF127/SDS micellar formulation can provide a useful alternative dosage form for intravenous administration of MTX.

Casein nanoparticles as oral delivery carriers of mequindox for the improved bioavailability

Mequindox (Meq) is a promising broad-spectrum antibacterial agent, but the clinical application of Meq has been hampered by its low oral bioavailability. Casein (Cas) can bind to a variety of poorly water-soluble drugs to improve their water solubility through a micellar solubilization mechanism. Here, a low-cost and convenient method was introduced to prepare mequindox-loaded casein nanoparticles (Meq-Cas). Meq-Cas was characterized by several methods including differential scanning calorimetry (DSC), X-ray diffraction (XRD), and fourier transform infrared (FTIR) to illuminate the mutual effect between the drug and carriers. Meq-Cas presented nearly spherical nanoparticles with smooth surfaces and its mean particle size was lower than untreated Cas. Meq-Cas showed a nearly complete release of Meq, which displayed a biphasic drug release pattern in both phosphate-buffered solution (PBS) and simulated gastric fluid (SGF). The relative oral bioavailability of Meq-Cas was found to be about 1.20 times higher than that of the animals treated with Meq suspension (control). These results suggest that Cas is a good candidate to load in Meq for pharmaceutical purposes.

Colloidal stability of graphene oxide nanosheets in association with triblock copolymers: A neutron scattering analysis

This study investigates stabilization of graphene oxide (GO) nanosheets in polyethylene oxide-polypropylene oxide (PEO-PPO) block copolymers (P103, P123 and F127). Changes in micellization of copolymers upon GO addition were monitored using dynamic light (DLS) and small angle neutron scattering (SANS). Structural developments at sheet surface were studied with two possibilities; (i) adsorption of PPO block over hydrophobic basal plane allowing the engagement of hydrophilic PEO with aqueous bulk, and (ii) adsorption of micelles mediated via carboxylated groups. Insignificant changes in micellar parameters for P123 and P127 were indicative of their inferior interaction with GO. On the other hand, P103 micelles exhibited high affinity for sheets, noticeable as emergence of mass fractals and more than two-fold enhancement in micelle number density. The latter allowed coverage of entire surface with P103 micelles. Existence of mass fractals was verified by extracting the form and structure factors from the fitted SANS data. Spectroscopic and thermogravimetric analyses illustrated non-covalent adsorption of copolymer aggregates. It was interesting to note that the dispersion remained stable against protein and electrolyte addition. A comprehensive understanding on colloidal stability can be valuable for drug delivery applications of GO sheets.

Temperature-Dependent Solubilization of the Hydrophobic Antiepileptic Drug Lamotrigine in Different Pluronic Micelles-A Spectroscopic, Heat Transfer Method, Small-Angle Neutron Scattering, Dynamic Light Scattering, and in Vitro Release Study

Pluronics (tri-block copolymers) have a significant role in the pharmaceutical industry and are being used to enhance the solubility and delivery of hydrophobic drugs in different marketed formulations. However, instability and unsatisfactory drug-loading capacity are the major weak spots of these pluronic micelles. The present research work is designed to solve the existing issues by the solubilization study of hydrophobic drugs in different pluronic micelles at variable temperatures. The solubilization of the hydrophobic antiepileptic drug lamotrigine (LAM) in five different pluronic micelles viz. P84, P85, F127, F108, and F68 was studied at different temperatures, 37, 47, and 57 °C, using UV-visible spectroscopy. The solubilization of LAM in pluronic micelles increased with the increase in temperature. Small-angle neutron scattering (SANS) measurements were used to observe the morphological and structural changes taking place in pluronics by increasing the temperature. The SANS results showed the morphological changes of spherical P84 micelles to prolate ellipsoidal micelles at 57 °C due to remarkable increase in the aggregation number. This morphological conversion was further confirmed by the heat transfer method (HTM) and dynamic light scattering (DLS) measurements. DLS measurements confirmed that LAM-loaded micelles showed a greater hydrodynamic diameter (D h) compared to unloaded micelles, assuring LAM solubilization in the pluronic micelles. The rate of controlled release of LAM from five different pluronic micelles was accessed by using different kinetic models to evaluate the in vitro release profile. This is the first report in which HTM measurements are established for the analysis of morphological changes in the thermoresponsive pluronic micelles in real time. The present work corroborates how we can control the drug-loading capacity, morphological structure of the drug carrier, as well as drug release by simply changing the temperature of pluronic micellar media.

Solubilization of Carbamazepine in TPGS Micelles: Effect of Temperature and Electrolyte Addition

D-α-Tocopheryl polyethylene glycol succinate (TPGS), a polyethylene glycol condensate, is a biologically important nonionic amphiphile. In this study, we report on aqueous solution behavior of TPGS with a focus on its clouding, surface activity, micellar characteristics, and solubilization capacity for a model hydrophobic drug, carbamazepine (CBZ). Micelles were characterized by dynamic light and small-angle neutron scattering studies as a function of temperature, salt addition, and CBZ solubilization. TPGS showed a cloud point of 78°C and possessed good surface activity (as observed from surface tension reduction and adsorption parameters). The critical micelle concentration (CMC), obtained from surface tension and fluorescence studies, was 0.02 mM. Scattering studies showed formation of stable micelles (average diameter-12 nm), exhibiting no significant changes in size upon salt addition (up to 1 M NaCl), CBZ incorporation (up to 5 mM), and temperature increase (40°C). Micelles in 5 wt% TPGS showed about twentyfold enhancement in CBZ solubility. Considering the remarkable CBZ solubilization and its positioning in the core, we suggest that the formulation can be exploited as a sustained delivery vehicle.

A fugacity model assessment of ibuprofen, diclofenac, carbamazepine, and their transformation product concentrations in an aquatic environment

An updated version of FATEMOD, a multimedia fugacity model for environmental fate of organic chemicals, was set up to assess environmental behaviour of three pharmaceuticals in northern Lake Päijänne, Finland. Concentrations of ibuprofen, diclofenac, and carbamazepine were estimated at various depths at two sites: near a wastewater treatment plant and 3.5 km downstream the plant. When compared with environmental sampling data from corresponding depths and sites, the predicted concentrations, ranging from nanograms to hundreds of nanograms per litre, were found to be in good agreement. Weather data were utilised with the model to rationalise the effects of various environmental parameters on the sampling results, and, e.g. the roles of various properties of lake dynamics and photodegradation were identified. The new model also enables simultaneous assessment of transformation products. Environmentally formed transformation product concentrations were estimated to be at highest an order of magnitude lower than those of the parent compounds, and unlikely to reach a detectable level. However, a possibility that conjugates of ibuprofen are present at higher levels than the parent compound was identified. Simulation results suggest that environmental degradation half-lives of the inspected contaminants under stratified lake conditions are in the range of some weeks to months.

Different types, applications and limits of enabling excipients of pharmaceutical dosage forms

Along with the development of novel drug delivery systems the material science is also advancing. Conventional and novel synthetic or natural excipients provide opportunities to design dosage forms of the required features including their bioavailability. Emerging trends in the design and development of drug products indicate an increasing need for the functionality-related characterization of excipients. The purpose of this review is to provide an overview of different types of excipients in relation to their application possibilities in various dosage forms with special focus on the enabling excipients. The study also summarizes the applied excipient systems of research formulations and dosage forms available on the market.

Synergistic Effect of Binary Mixed-Pluronic Systems on Temperature Dependent Self-assembly Process and Drug Solubility

Mixed Pluronic micelles from very hydrophobic and very hydrophilic copolymers were selected to scrutinize the synergistic effect on the self-assembly process as well as the solubilization capacity of ibuprofen. The tendency of mixing behavior between parent copolymers was systematically examined from two perspectives: different block chain lengths at same hydrophilicity (L92 + F108, +F98, +F88, and +F68), as well as various hydrophobicities at the same PPO moiety (L92 + F88, +F87, and +P84). Temperature-dependent micellization in these binary systems was clearly inspected by the combined use of high sensitivity differential scanning calorimeter (HSDSC) and dynamic light scattering (DLS). Changes in heat capacity and size of aggregates at different temperatures during the whole micellization process were simultaneously observed and examined. While distinction of block chain length between parent copolymers increases, the monodispersity of the binary Pluronic systems decreases. However, parent copolymers with distinct PPO moieties do not affirmatively lead to non-cooperative binding, such as the L92 + P84 system. The addition of ibuprofen promotes micellization as well as stabilizes aggregates in the solution. The partial replacement of the hydrophilic Pluronic by a more hydrophobic Pluronic L92 would increase the total hydrophobicity of mixed Pluronics used in the system to substantially enhance the solubility of ibuprofen. The solubility of ibuprofen in the 0.5 wt % L92 + 0.368 wt % P84 system is as high as 4.29 mg/mL, which is 1.4 times more than that of the 0.868 wt % P84 system and 147 times more than that in pure water at 37 °C.