The effects of Pluronic block copolymers on the aggregation state of nystatin

Entropy-Driven Liquid-Liquid Phase Separation Transition to Polymeric Micelles

In recent years, liquid-liquid phase separation (LLPS) has been recognized to act as a precursor to self-assembly in amphiphilic systems. In this study, we propose the use of entropy-driven LLPS to obtain a tunable precursor for polymeric micelle formation. In this new approach, an oligomer is utilized as a nonselective solvent for the block copolymer, allowing for the tuning of entropy and subsequent LLPS. A comprehensive model was developed using mean-field lattice theory to predict the conditions under which LLPS and micellization occur. The degree of polymerization of the solvent was found to have a significant impact on the phase behavior of the system, outweighing enthalpic contributions such as the interaction between the blocks of the copolymer and the solvent. Our model predicts that using a solvent with a degree of polymerization equal to or greater than 5 for a copolymer such as PEG4kDa-b-PLA2.2kDa will result in LLPS prior to complete micellization, regardless of the values of interaction parameters. It also suggests that phase-separated liquid and polymeric micelles can co-exist in such a mixture. We confirmed our model predictions using dynamic light scattering and phase microscopy when PEG200 was used as the solvent. Micellization for PEG4kDa-b-PLA2.2kDa/PEG200/water mixture occurred at 10-12% w/w water content, consistent with the model predictions. Furthermore, the LLPS-to-micelle transition was shown to be reversible by changing the temperature or water content, indicating that the phase-separated liquid may be in thermodynamic equilibrium with polymeric micelles.

Reviving the interest in the versatile drug nystatin: A multitude of strategies to increase its potential as an effective and safe antifungal agent

Nystatin is an antifungal molecule with a remarkable yet squandered versatility. In this review, its mechanism of action is explored, along with its extensive action spectrum and toxicity. A multitude of methodologies to tackle the drug's physical and chemical hurdles are outlined along with some proven-effective strategies to increase its activity and/or decrease its toxicity. A separate detailed section focused on micro and nanotechnology solutions addresses new drug delivery systems made of polymeric, metallic or lipid materials. Although the topical route depicts greater representativeness amongst these formulations, the intravenous, dental, oral, vaginal and inhalation routes are also mentioned. The unsuccessful previous attempts at developing parenteral formulations of nystatin or even the withdrawal of a nystatin-loaded multilamellar liposome should not divert research away from this drug. In fact, the interest in nystatin ought to be reawakened with the ongoing clinical trials on the promising nystatin-like genetically engineered derivate BSG005.

Influence of the Hydrophobicity of Pluronic Micelles Encapsulating Curcumin on the Membrane Permeability and Enhancement of Photoinduced Antibacterial Activity

Apart from its well-known activity as an antimicrobial agent, Curcumin (CURC) has recently started to arouse interest as a photosensitizer in the photodynamic therapy of bacterial infections. The aim of the present study was to evidence the influence of the encapsulation of Curcumin into polymeric micelles on the efficiency of photoinduced microbial inhibition. The influence of the hydrophobicity of the selected Pluronics (P84, P123, and F127) on the encapsulation, stability, and antimicrobial efficiency of CURC-loaded micelles was investigated. In addition, the size, morphology, and drug-loading capacity of the micellar drug delivery systems have been characterized. The influence of the presence of micellar aggregates and unassociated molecules of various Pluronics on the membrane permeability was investigated on both normal and resistant microbial strains of E. coli, S. aureus, and C. albicans. The antimicrobial efficiency on the common pathogens was assessed for CURC-loaded polymeric micelles in dark conditions and activated by blue laser light (470 nm). Significant results in the reduction of the microorganism’s growth were found in cultures of C. albicans, even at very low concentrations of surfactants and Curcumin. Unlike the membrane permeabilization effect of the monomeric solution of Pluronics, reported in the case of tumoral cells, a limited permeabilization effect was found on the studied microorganisms. Encapsulation of the Curcumin in Pluronic P84 and P123 at very low, nontoxic concentrations for photosensitizer and drug-carrier, produced CURC-loaded micelles that prove to be effective in the light-activated inhibition of resistant species of Gram-positive bacteria and fungi.

Production of paclitaxel-loaded PEG-b-PLA micelles using PEG for drug loading and freeze-drying

A new approach named PEG-assist is introduced for the production of drug-loaded polymeric micelles. The method is based on the use of PEG as the non-selective solvent for PEG-b-PLA in the fabrication procedure. Both hydration temperature and PEG molecular weight are shown to have a significant effect on the encapsulation efficiency of PTX in PEG_4kDa-b-PLA_2kDa micelles. The optimal procedure for fabrication includes the use of PEG_1kDa as the solvent at 60 °C, cooling the mixture to 40 °C, hydration at 40 °C, freezing at -80 °C and freeze-drying at -35 °C, 15 Pa. No significant difference (p > 0.05) in PTX encapsulation, average particle size and polydispersity index is observed between the samples before freeze-drying and after reconstitution of the freeze-dried cake. The prepared PTX formulations are stable at room temperature for at least 8 h. Scaling the batch size to 25× leads to no significant change (p > 0.05) in PTX encapsulation, average particle size and polydispersity index. PEG-assist method is applicable to other drugs such as 17-AAG, and copolymers of varied molecular weights. The use of no organic solvent, simplicity, cost-effectiveness, and efficiency makes PEG-assist a very promising approach for large scale production of drug-loaded polymeric micelles.

Alginate as a Promising Biopolymer in Drug Delivery and Wound Healing: A Review of the State-of-the-Art

Biopolymeric nanoparticulate systems hold favorable carrier properties for active delivery. The enhancement in the research interest in alginate formulations in biomedical and pharmaceutical research, owing to its biodegradable, biocompatible, and bioadhesive characteristics, reiterates its future use as an efficient drug delivery matrix. Alginates, obtained from natural sources, are the colloidal polysaccharide group, which are water-soluble, non-toxic, and non-irritant. These are linear copolymeric blocks of α-(1→4)-linked l-guluronic acid (G) and β-(1→4)-linked d-mannuronic acid (M) residues. Owing to the monosaccharide sequencing and the enzymatically governed reactions, alginates are well-known as an essential bio-polymer group for multifarious biomedical implementations. Additionally, alginate’s bio-adhesive property makes it significant in the pharmaceutical industry. Alginate has shown immense potential in wound healing and drug delivery applications to date because its gel-forming ability maintains the structural resemblance to the extracellular matrices in tissues and can be altered to perform numerous crucial functions. The initial section of this review will deliver a perception of the extraction source and alginate’s remarkable properties. Furthermore, we have aspired to discuss the current literature on alginate utilization as a biopolymeric carrier for drug delivery through numerous administration routes. Finally, the latest investigations on alginate composite utilization in wound healing are addressed.

Design of transfersomal nanocarriers of nystatin for combating vulvovaginal candidiasis; A different prospective

The objective of this study was to prepare and evaluate Nystatin (NYS) loaded transfersomes to achieve better treatment of vulvovaginal candidiasis. Nystatin transferosomes were formulated utilizing thin film hydration method. A 3² full factorial design was employed to evaluate the effect of different formulation variables. Two independent variables were chosen; the ratio between lecithin surfactant (X₁) was set at three levels (10-40), and the type of surfactants (X₂) was set at three levels (Span 60, Span 85 and Pluronic F-127). The dependent responses were; entrapment efficiency (Y₁: EE %), vesicles size (Y₂: VS) and release rate (Y₃: RR). Design Expert® software was utilized to statistically optimize formulation variables. The vesicles revealed high NYS encapsulation efficiency ranging from 97.35 ± 0.03 to 98.01 ± 0.20% whereas vesicle size ranged from 194.8 ± 20.42 to 400.8 ± 42.09 nm. High negative zeta potential values indicated good stability of the prepared formulations. NYS release from transfersomes was biphasic and the release pattern followed Higuchi's model. The optimized formulation (F7) exhibited spherical morphology under transmission electron microscopy (TEM). In-vitro and in-vivo antifungal efficiency studies revealed that the optimized formula F7 exhibited significant eradication of candida infestation in comparison to free NYS. The results revealed that the developed NYS transfersomes could be a promising drug delivery system to enhance antifungal efficacy of NYS.

New Antifungal Compound: Impact of Cosolvency, Micellization and Complexation on Solubility and Permeability Processes

Poor solubility of new antifungal of 1,2,4-triazole class (S-119)—a structural analogue of fluconazole in aqueous media was estimated. The solubility improvement using different excipients: biopolymers (PEGs, PVP), surfactants (Brij S20, pluronic F-127) and cyclodextrins (α-CD, β-CD, 2-HP-β-CD, 6-O-Maltosyl-β-CD) was assessed in buffer solutions pH 2.0 and pH 7.4. Additionally, 2-HP-β-CD and 6-O-Maltosyl-β-CD were proposed as promising solubilizers for S-119. According to the solubilization capacity and micelle/water partition coefficients in buffer pH 7.4 pluronic F-127 was shown to improve S-119 solubility better than Brij S20. Among biopolymers, the greatest increase in solubility was shown in PVP solutions (pH 7.4) at concentrations above 4 w/v%. Complex analysis of the driving forces of solubilization, micellization and complexation processes matched the solubility results and suggested pluronic F-127 and 6-O-Maltosyl-β-CD as the most effective solubilizing agents for S-119. The comparison of S-119 diffusion through the cellulose membrane and lipophilic PermeaPad barrier revealed a considerable effect of the lipid layer on the decrease in the permeability coefficient. According to the PermeaPad, S-119 was classified as a highly permeated substance. The addition of 1.5 w/v% CDs in donor solution moves it to low-medium permeability class.

A Systematic, Knowledge Space-Based Proposal on Quality by Design-Driven Polymeric Micelle Development

Nanoparticle research and development for pharmaceuticals is a challenging task in the era of personalized medicine. Specialized and increased patient expectations and requirements for proper therapy adherence, as well as sustainable environment safety and toxicology topics raise the necessity of well designed, advanced and smart drug delivery systems on the market. These stakeholder expectations and social responsibility of pharma sector open the space and call new methods on the floor for new strategic development tools, like Quality by Design (QbD) thinking. The extended model, namely the R&D QbD proved to be useful in case of complex and/or high risk/expectations containing or aiming developments. This is the case when we formulate polymeric micelles as promising nanotherapeutics; the risk assessment and knowledge-based quality targeted QbD approach provides a promising tool to support the development process. Based on risk assessment, many factors pose great risk in the manufacturing process and affect the quality, efficacy and safety profile. The quality-driven strategic development pathway, based on deep prior knowledge and an involving iterative risk estimation and management phases has proven to be an adequate tool, being able to handle their sensitive stability issues and make them efficient therapeutic aids in case of several diseases.

Engineering Polymeric Nanosystems against Oral Diseases

Nanotechnology and nanoparticles (NPs) are at the forefront of modern research, particularly in the case of healthcare therapeutic applications. Polymeric NPs, specifically, hold high promise for these purposes, including towards oral diseases. Careful optimisation of the production of polymeric NPs, however, is required to generate a product which can be easily translated from a laboratory environment to the actual clinical usage. Indeed, considerations such as biocompatibility, biodistribution, and biodegradability are paramount. Moreover, a pre-clinical assessment in adequate in vitro, ex vivo or in vivo model is also required. Last but not least, considerations for the scale-up are also important, together with an appropriate clinical testing pathway. This review aims to eviscerate the above topics, sourcing at examples from the recent literature to put in context the current most burdening oral diseases and the most promising polymeric NPs which would be suitable against them.

Mixed Pluronic-Cremophor Polymeric Micelles as Nanocarriers for Poorly Soluble Antibiotics-The Influence on the Antibacterial Activity

In this work, novel polymeric mixed micelles from Pluronic F127 and Cremophor EL were investigated as drug delivery systems for Norfloxacin as model antibiotic drug. The optimal molar ratio of surfactants was determined, in order to decrease critical micellar concentration (CMC) and prepare carriers with minimal surfactant concentrations. The particle size, zeta potential, and encapsulation efficiency were determined for both pure and mixed micelles with selected composition. In vitro release kinetics of Norfloxacin from micelles show that the composition of surfactant mixture generates tunable extended release. The mixed micelles exhibit good biocompatibility against normal fibroblasts MRC-5 cells, while some cytotoxicity was found in all micellar systems at high concentrations. The influence of the surfactant components in the carrier on the antibacterial properties of Norfloxacin was investigated. The drug loaded mixed micellar formulation exhibit good activity against clinical isolated strains, compared with the CLSI recommended standard strains (Staphylococcus aureus ATCC 25923, Enterococcus faecalis ATCC 29213, Pseudomonas aeruginosa ATCC 27853, Escherichia coli ATCC 25922). P. aeruginosa 5399 clinical strain shows low sensitivity to Norfloxacin in all tested micelle systems. The results suggest that Cremophor EL-Pluronic F127 mixed micelles can be considered as novel controlled release delivery systems for hydrophobic antimicrobial drugs.

Preparation and evaluation of an oral mucoadhesive gel containing nystatin-loaded alginate microparticles

Nystatin is an antifungal agent used for prophylaxis and treatment of candidiasis, especially oral mycosis. Efficacy of nystatin conventional dosage forms is limited by the short residence time and bitter taste of the drug. This research aims at designing an optimized formulation of oral mucoadhesive gel of nystatin-loaded alginate microparticles, which can be retained in the mouth. Sodium alginate solution containing nystatin was added to the solution of calcium chloride under stirring. Microparticles containing nystatin were incorporated into the Carbopol gel. Size, loading, and release profile and mucoadhesion were investigated. The most suitable microparticles with particle size of < 250 μm were prepared with alginate concentration of 1%(w/v), calcium chloride of 1%(w/v), drug:polymer concentration 1%, and ratio of alginate solution:calcium chloride of 1:10. This formulation showed 49.1% drug loading and 98.2% encapsulation efficiency. Carbopol 934 gel provided optimal mucoadhesive properties. Release profile proved a burst release, which can be attributed to the surface associated drug, followed by a slower sustained release phase for all microparticles. The developed system with ability to adhere to the oral mucosa has great appeal for treatment of localized infections and can mask bitter taste of the drug and be retained in the mouth for long periods.

Direct observation of nystatin binding to the plasma membrane of living cells

Nystatin is an antifungal polyene macrolide which is widely applied to treat yeast infections. Nystatin has also been used as a laboratory tool to inhibit endocytic processes in mammalian cells. The interaction of nystatin with model membranes has been studied thoroughly by various spectroscopic methods, making use of its weak fluorescence in the ultraviolet (UV). Studying its interaction with cells would require direct imaging, which, so far, required attachment of a fluorophore to nystatin. Using UV-sensitive microscopy, we show here how to visualize the interaction of nystatin with the plasma membrane (PM) directly. We find that nystatin forms micron-sized aggregates in buffer, and molecular dynamics simulations confirm that nystatin rapidly self-assembles into aggregates in aqueous solution. Using UV-sensitive microscopy, we find that large nystatin aggregates adhere to the surface of Chinese Hamster Ovarian (CHO) cells, causing slow spreading of nystatin fluorescence into the PM. Binding of nystatin to CHO cells does not interfere with cellular uptake or lateral membrane diffusion of the cholesterol analogue TopFluor-cholesterol (TF-Chol). Nystatin binds extensively to the PM of yeast cells as inferred from a strong UV signal in this membrane. Loading a yeast mutant unable to synthesize ergosterol with cholesterol gave much less nystatin membrane staining compared to loading such cells with ergosterol. These results explain the selective fungicidal effect of nystatin by differential interaction of nystatin with yeast membranes containing ergosterol compared to the mammalian cholesterol. Our combined experimental and computational approach provides a toolset for future design of new polyene macrolides.

Production, stabilisation and characterisation of silver nanoparticles coated with bioactive polymers pluronic F68, PVP and PVA

The increasing and alarming panorama of bacterial infections and associated morbidities that occur during medical and hospital procedures makes the development of technologies that aid in controlling such bacterial infections of utmost importance. Recent studies have shown that formulations with metal nanoparticles exhibit good antibacterial properties against a broad spectrum of microorganisms. Moreover, it was demonstrated that some biologically active polymeric materials, when applied in combination with chemical antimicrobial agents, enhance the therapeutic action of the latter. The research effort entertained herein aimed at the physico-chemical characterisation of silver nanoparticles obtained by chemical reduction, stabilised by bioactive polymers polyvinyl alcohol and polyvinylpyrrolidone, and further co-stabilised by pluronic F68. Scanning electron microscopy images of the nanoparticles produced, coated with different stabilisers, have shown that the chemical nature of the stabilisation effect promoted incorporation of pluronic in the nanoparticles and was closely related to an increase in the silver concentration in the nanoparticle samples obtained via energy-dispersive X-ray spectroscopy. The study described herein also shows that the nature of the stabiliser favours the interaction of pluronic F68 with samples containing silver nanoparticles.

In Vitro Release Test of Nano-drug Delivery Systems Based on Analytical and Technological Perspectives

Background:

Nanotech products are gaining more attention depending on their advantages for improving drug solubility, maintenance of drug targeting, and attenuation of drug toxicity. In vitro release test is the critical physical parameter to determine the pharmaceutical quality of the product, to monitor formulation design and batch-to-batch variation.

Methods:

Spectrophotometric and chromatographic methods are mostly used in quantification studies from in vitro release test of nano-drug delivery systems. These techniques have advantages and disadvantages with respect to each other considering dynamic range, selectivity, automation, compatibility with in vitro release media and cost per sample.

Results:

It is very important to determine the correct kinetic profile of active pharmaceutical substances. At this point, the analytical method used for in vitro release tests has become a very critical parameter to correctly assess the profiles. In this review, we provided an overview of analytical methods applied to the in vitro release assay of various nanopharmaceuticals.

Conclusion:

This review presents practical direction on analytical method selection for in vitro release test on nanopharmaceuticals. Moreover, precautions on analytical method selection, optimization and validation were discussed.

FLT3-specific curcumin micelles enhance activity of curcumin on FLT3-ITD overexpressing MV4-11 leukemic cells

Curcumin, a major active compound in the turmeric rhizome, has many biological properties, especially anti-leukemia activity. The overexpression of FMS-like tyrosine kinase 3 protein with internal tandem duplication (FLT3-ITD) mutation protein was related to the poor prognosis and disease progression of leukemia. In this study, the cytotoxicity and inhibitory effect of curcumin on cell cycle of FLT3-ITD overexpressing MV4-11 leukemic cells were evaluated. Moreover, curcumin polymeric micelles conjugated with FLT3-specific peptide (FLT3-Cur-micelles) were prepared using a film hydration method to increase curcumin solubility and the inhibitory effect on MV4-11 cells was evaluated. Cytotoxicity and cell cycle analysis were performed using an MTT assay and flow cytometry, respectively. Physical properties of FLT3-Cur-micelles, including particle size, size distribution, morphology, and entrapment efficiency (EE), were evaluated. Cellular uptake of the micelles on MV4-11 cells was determined by flow cytometry and fluorescence microscopy. FLT3-Cur-micelles were observed with size less than 50 nm and high EE of >75%. In addition, FLT3-Cur-micelles demonstrated excellent internalization and increased curcumin accumulation in leukemic cells when compared to free curcumin. Furthermore, FLT3-Cur-micelles exhibited a strong cytotoxic effect on MV4-11 cells with IC₅₀ value of 1.1 µM, whereas the blank micelles showed no effect. Furthermore, FLT3-Cur-micelles showed no significant effect on normal human PBMCs with IC₅₀ value >25 µM. In summary, FLT3-Cur-micelles are a promising nanocarrier system for enhancing anti-leukemic activity of curcumin and suitable for further preclinical studies.

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.

Stable curcumin-loaded polymeric micellar formulation for enhancing cellular uptake and cytotoxicity to FLT3 overexpressing EoL-1 leukemic cells

The present study aims to develop a stable polymeric micellar formulation of curcumin (CM) with improved solubility and stability, and that is suitable for clinical applications in leukemia patients. CM-loaded polymeric micelles (CM-micelles) were prepared using poloxamers. The chemical structure of the polymers influenced micellar properties. The best formulation of CM-micelles, namely CM-P407, was obtained from poloxamer 407 at drug to polymer ratio of 1:30 and rehydrated with phosphate buffer solution pH 7.4. CM-P407 exhibited the smallest size of 30.3±1.3nm and highest entrapment efficiency of 88.4±4.1%. When stored at -80°C for 60days, CM-P407 retained high protection of CM and had no significant size change. In comparison with CM solution in dimethyl sulfoxide (CM-DMSO), CM kinetic degradation in both formulations followed a pseudo-first-order reaction, but the half-life of CM in CM-P407 was approx. 200 times longer than in CM-DMSO. Regarding the activity against FLT3 overexpressing EoL-1 leukemic cells, CM-P407 showed higher cytotoxicity than CM-DMSO. Moreover, intracellular uptake to leukemic cells of CM-P407 was 2-3 times greater than that of CM-DMSO. These promising results for CM-P407 will be further investigated in rodents and in clinical studies for leukemia treatment.

Solubilization Behavior of Polyene Antibiotics in Nanomicellar System: Insights from Molecular Dynamics Simulation of the Amphotericin B and Nystatin Interactions with Polysorbate 80

Amphotericin B (AmB) and Nystatin (Nys) are the drugs of choice for treatment of systemic and superficial mycotic infections, respectively, with their full clinical potential unrealized due to the lack of high therapeutic index formulations for their solubilized delivery. In the present study, using a coarse-grained (CG) molecular dynamics (MD) simulation approach, we investigated the interaction of AmB and Nys with Polysorbate 80 (P80) to gain insight into the behavior of these polyene antibiotics (PAs) in nanomicellar solution and derive potential implications for their formulation development. While the encapsulation process was predominantly governed by hydrophobic forces, the dynamics, hydration, localization, orientation, and solvation of PAs in the micelle were largely controlled by hydrophilic interactions. Simulation results rationalized the experimentally observed capability of P80 in solubilizing PAs by indicating (i) the dominant kinetics of drugs encapsulation over self-association; (ii) significantly lower hydration of the drugs at encapsulated state compared with aggregated state; (iii) monomeric solubilization of the drugs; (iv) contribution of drug-micelle interactions to the solubilization; (v) suppressed diffusivity of the encapsulated drugs; (vi) high loading capacity of the micelle; and (vii) the structural robustness of the micelle against drug loading. Supported from the experimental data, our simulations determined the preferred location of PAs to be the core-shell interface at the relatively shallow depth of 75% of micelle radius. Deeper penetration of PAs was impeded by the synergistic effects of (i) limited diffusion of water; and (ii) perpendicular orientation of these drug molecules with respect to the micelle radius. PAs were solvated almost exclusively in the aqueous poly-oxyethylene (POE) medium due to the distance-related lack of interaction with the core, explaining the documented insensitivity of Nys solubilization to drug-core compatibility in detergent micelles. Based on the obtained results, the dearth of water at interior sites of micelle and the large lateral occupation space of PAs lead to shallow insertion, broad radial distribution, and lack of core interactions of the amphiphilic drugs. Hence, controlled promotion of micelle permeability and optimization of chain crowding in palisade layer may help to achieve more efficient solubilization of the PAs.

A New Approach for Quantitative Determination of γ-Cyclodextrin in Aqueous Solutions: Application in Aggregate Determinations and Solubility in Hydrocortisone/γ-Cyclodextrin Inclusion Complex

Fast and simple high-pressure liquid chromatographic (HPLC) method with charged aerosol detector (CAD) was developed for quantitation of γ-cyclodextrin (γCD) in aqueous solutions. The chromatographic system consisted of a C18 column (i.e., the stationary phase) and an aqueous mobile phase containing 7% (v/v) methanol. Calibration curve was obtained over the γCD concentration range of 0.005%-1% (w/v). The limit of detection and quantitation of γCD were 0.0001% and 0.0002% (w/v), respectively. Formation of γCD aggregates in aqueous solution and their critical aggregation concentration (cac) were determined by both conventional dynamic light scattering method and permeation method using HPLC-CAD for quantitative determination of γCD. The cac of γCD was determined to be 0.95% (w/v) and the amount of γCD self-aggregates increased with increasing γCD concentrations. Also, the developed HPLC-CAD method was used to determine the γCD phase-solubility profile in an aqueous hydrocortisone (HC)/γCD complexation medium. The maximum concentration of dissolved γCD and HC was determined to be 1.47% and 0.31% (w/v), respectively. The membrane permeation method was shown to be a reliable method for determination of metastable γCD aggregates. The HPLC-CAD method was successfully applied for quantitative determination of γCD in aqueous solutions during permeation and phase-solubility studies.

Novel Redox-Responsive Amphiphilic Copolymer Micelles for Drug Delivery: Synthesis and Characterization

A novel redox-responsive amphiphilic polymer was synthesized with bioreductive trimethyl-locked quinone propionic acid for a potential triggered drug delivery application. The aim of this study was to synthesize and characterize the redox-responsive amphiphilic block copolymer micelles containing pendant bioreductive quinone propionic acid (QPA) switches. The redox-responsive hydrophobic block (polyQPA), synthesized from QPA-serinol and adipoyl chloride, was end-capped with methoxy poly(ethylene glycol) of molecular weight 750 (mPEG750) to achieve a redox-responsive amphiphilic block copolymer, polyQPA-mPEG750. PolyQPA-mPEG750 was able to self-assemble as micelles to show a critical micelle concentration (CMC) of 0.039% w/v (0.39 mg/ml, 0.107 mM) determined by a dye solubilization method using 1,6-diphenyl-1,3,5-hexatriene (DPH) in phosphate-buffered saline (PBS). The mean diameter of polymeric micelles was found to be 27.50 nm (PI = 0.064) by dynamic light scattering. Furthermore, redox-triggered destabilization of the polymeric micelles was confirmed by (1)H-NMR spectroscopy and particle size measurements in a simulated redox state. PolyQPA-mPEG750 underwent triggered reduction to shed pendant redox-responsive QPA groups and its polymeric micelles were swollen to be dissembled in the presence of a reducing agent, thereby enabling the release of loaded model drug, paclitaxel. The redox-responsive polyQPA-mPEG750 polymer micelles would be useful as a drug delivery system allowing triggered drug release in an altered redox state such as tumor microenvironments with an altered redox potential and/or redox enzyme upregulation.

Development of an antifungal denture adhesive film for oral candidiasis utilizing hot melt extrusion technology

OBJECTIVES

The overall goal of this research was to produce a stable hot-melt extruded 'Antifungal Denture Adhesive film' (ADA) system for the treatment of oral candidiasis.

METHODS

The ADA systems with hydroxypropyl cellulose (HPC) and/or polyethylene oxide (PEO) containing clotrimazole (10%) or nystatin (10%) were extruded utilizing a lab scale twin-screw hot-melt extruder. Rolls of the antifungal-containing films were collected and subsequently die-cut into shapes adapted for a maxillary (upper) and mandibular (lower) denture.

RESULTS

Differential scanning calorimeter and powder X-ray diffraction results indicated that the crystallinity of both APIs was changed to amorphous phase after hot-melt extrusion. The ADA system, containing blends of HPC and PEO, enhanced the effectiveness of the antimicrobials a maximum of fivefold toward the inhibition of cell adherence of Candida albicans to mammalian cells/Vero cells. Remarkably, a combination of the two polymers without drug also demonstrated a 38% decrease in cell adhesion to the fungi due to the viscosity and the flexibility of the polymers. Drug-release profiles indicated that both drug concentrations were above the minimum inhibitory concentration (MIC) for C. albicans within 10 min and was maintained for over 10 h. In addition, based on the IC50 and MIC values, it was observed that the antifungal activities of both drugs were increased significantly in the ADA systems.

CONCLUSIONS

Based on these findings, the ADA system may be used for primary, prophylaxis or adjunct treatment of oral or pharyngeal candidiasis via controlled release of the antifungal agent from the polymer matrix.

Polymeric micelles for oral drug administration enabling locoregional and systemic treatments

INTRODUCTION

Amphiphilic block copolymers are recognized components of parenteral drug nanocarriers. However, their performance in oral administration has barely been evaluated to any great extent.

AREAS COVERED

This review provides an overview of the methods used to prepare drug-loaded polymeric micelles and to evaluate their stability in gastrointestinal (GI) fluids, and then analyzes in detail recent in vitro and in vivo results about their performance in oral drug delivery. Oral administration of polymeric micelles has been tested for a variety of therapeutic purposes, namely, to increase apparent drug solubility in the GI fluids and facilitate absorption, to penetrate in pathological regions of the GI tract for locoregional treatment, to carry the drug directly toward the blood stream minimizing presystemic loses, and to target the drug after oral absorption to specific tissue or cells in the body.

EXPERT OPINION

Each therapeutic purpose demands micelles with different performance regarding stability in the GI tract, ability to overcome physiological barriers and drug release patterns. Depending on the block copolymer composition and structure, a wealth of self-assembled micelles with different morphologies and stability can be prepared. Moreover, copolymer unimers can play a role in improving drug absorption through the GI mucosa, either by increasing membrane permeability to the drug and/or the carrier or by inhibiting drug efflux transporters or first-pass metabolism. Therefore, polymeric micelles can be pointed out as versatile vehicles to increase oral bioavailability of drugs that exhibit poor solubility or permeability and may even be an alternative to parenteral carriers when targeting is pursued.

Antifungal Activity of Apple Cider Vinegar on Candida Species Involved in Denture Stomatitis

PURPOSE

To evaluate the in vitro antifungal activity of apple cider vinegar on Candida spp. involved in denture stomatitis.

MATERIAL AND METHODS

The microdilution technique was used to determine the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of apple cider vinegar containing 4% maleic acid, and nystatin (control). Further tests of microbial kinetics and inhibition of adherence to acrylic resin were performed testing different concentrations (MIC, MICx2, MICx4) of the products at time intervals of 0, 30, 60, 120 and 180 minutes. A roughness meter was used to measure the changes in surface roughness; color change of the acrylic resin specimens exposed to the test products in different concentrations and time intervals were also evaluated.

RESULTS

Apple cider vinegar (4%) showed MIC of 2500 μg/ml and MFC of 2500, 5000, and 10,000 μg/ml depending on the strain tested. Nystatin showed MIC of 3.125 μg/ml and strain-dependent MFC values ranging from 3.125 to 12.5 μg/ml. The microbial kinetic assay showed a statistical difference between apple cider vinegar and nystatin (p < 0.0001). After 30 minutes of exposure, apple cider vinegar showed fungicidal effect at MICx4, whereas nystatin maintained its fungistatic effect. Apple cider vinegar showed greater inhibition of adherence (p < 0.001) compared to control. Apple cider vinegar did not significantly alter the surface roughness of the acrylic resin specimens compared to nystatin (p > 0.05), and both had no influence on their color.

CONCLUSION

Apple cider vinegar showed antifungal properties against Candida spp., thus representing a possible therapeutic alternative for patients with denture stomatitis.

Novel mineralized heparin-gelatin nanoparticles for potential application in tissue engineering of bone

Nanoparticles (NPs) were prepared from succinylated gelatin (s-GL) cross-linked with aldehyde heparin (a-HEP) and used subsequently as a nano-template for the mineralization of hydroxyapatite (HAP). Gelatin was functionalized with succinyl groups that made it soluble at room temperature. Heparin was oxidized to generate aldehyde groups and then used as a cross-linker that can react with s-GL to form NPs via Schiff's base linkage. The polymer concentrations, feed molar ratios and pH conditions were varied to fabricate NPs suspension. NPs were obtained with a spheroid shape of an average size of 196 nm at pH 2.5 and 202 nm at pH 7.4. These NPs had a positive zeta potential of 7.3 ± 3.0 mV and a narrow distribution with PDI 0.123 at pH 2.5, while they had a negative zeta potential of -2.6 ± 0.3 mV and formed aggregates (PDI 0.257) at pH 7.4. The NPs prepared at pH 2.5 with a mean particle size of 196 nm were further used for mineralization studies. The mineralization process was mediated by solution without calcination at 37 °C. The HAP formed on NPs was analyzed by Fourier transform infrared spectroscopy and X-ray diffraction. HAP coated s-GL/a-HEP NPs developed in this study may be used in future as osteoinductive fillers enhancing the mechanical properties of injectable hydrogel or use as potential multifunctional device for nanotherapeutic approaches.

Thermally responsive nanoparticle-encapsulated curcumin and its combination with mild hyperthermia for enhanced cancer cell destruction

In this study, thermally responsive polymeric nanoparticle-encapsulated curcumin (nCCM) was prepared and characterized. The nCCM is ≈ 22 and 300 nm in diameter at 37 and 22 °C, respectively. The smaller size of the nCCM at 37 °C was found to significantly facilitate its uptake in vitro by human prostate adenocarcinoma PC-3 cancer cells. However, the intracellular nCCM decreases rapidly (rather than plateaus) after reaching its peak at ≈ 1.5 h during a 3-day incubation of the PC-3 cells with nCCM. Moreover, a mild hyperthermia (with negligible cytotoxicity alone) at 43 °C applied between 1 and 1.5 h during the 3-day incubation not only increases the peak uptake but also alters intracellular distribution of nCCM (facilitating its delivery into cell nuclei), which helps to retain a significantly much higher level of intracellular curcumin. These effects of mild hyperthermia could be due in part to the thermal responsiveness of the nCCM: they are more positively charged at 43 °C and can be more easily attracted to the negatively charged nuclear membrane to enter nuclei as a result of electrostatic interaction. Ultimately, a combination of the thermally responsive nCCM and mild hyperthermia significantly enhances the anticancer capability of nCCM, resulting in a more than 7-fold decrease in its inhibitory concentration to reduce cell viability to 50% (IC50). Further mechanistic studies suggest injury pathways associated with heat shock proteins 27 and 70 should contribute to the enhanced cancer cell destruction by inducing cell apoptosis and necrosis. Overall, this study demonstrates the potential of combining mild hyperthermia and thermally responsive nanodrugs such as nCCM for augmented cancer therapy.

Strategies to address low drug solubility in discovery and development

Drugs with low water solubility are predisposed to low and variable oral bioavailability and, therefore, to variability in clinical response. Despite significant efforts to "design in" acceptable developability properties (including aqueous solubility) during lead optimization, approximately 40% of currently marketed compounds and most current drug development candidates remain poorly water-soluble. The fact that so many drug candidates of this type are advanced into development and clinical assessment is testament to an increasingly sophisticated understanding of the approaches that can be taken to promote apparent solubility in the gastrointestinal tract and to support drug exposure after oral administration. Here we provide a detailed commentary on the major challenges to the progression of a poorly water-soluble lead or development candidate and review the approaches and strategies that can be taken to facilitate compound progression. In particular, we address the fundamental principles that underpin the use of strategies, including pH adjustment and salt-form selection, polymorphs, cocrystals, cosolvents, surfactants, cyclodextrins, particle size reduction, amorphous solid dispersions, and lipid-based formulations. In each case, the theoretical basis for utility is described along with a detailed review of recent advances in the field. The article provides an integrated and contemporary discussion of current approaches to solubility and dissolution enhancement but has been deliberately structured as a series of stand-alone sections to allow also directed access to a specific technology (e.g., solid dispersions, lipid-based formulations, or salt forms) where required.

Micelles, mixed micelles, and applications of polyoxypropylene (PPO)-polyoxyethylene (PEO)-polyoxypropylene (PPO) triblock polymers

This review gives a brief outline of various micellar properties of triblock polymers such as critical micellization concentration, critical micellization temperature, and microviscosity. Detailed discussion of the effect of temperature on micellar properties of various triblock polymer mixtures is given. Applications of triblock polymers in solubilization as drug delivery agents, as nano drug, for the synthesis of gold nanoparticles, for cobalt determination, etc. are discussed.

Antimicrobial effectiveness of silver nanoparticles co-stabilized by the bioactive copolymer pluronic F68

BACKGROUND

Silver nanoparticles (AgNps) have attracted much interest in biomedical engineering, since they have excellent antimicrobial properties. Therefore, AgNps have often been considered for incorporation into medical products for skin pathologies to reduce the risk of contamination. This study aims at evaluating the antimicrobial effectiveness of AgNps stabilized by pluronic™ F68 associated with other polymers such as polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP).

METHODS

AgNps antimicrobial activity was evaluated using the minimum inhibitory concentration (MIC) method. The action spectrum was evaluated for different polymers associated with pluronic™ F68 against the gram negative bacteria P. aeuroginosa and E. coli and the gram positive bacteria S. Aureus.

RESULTS

AgNps stabilized with PVP or PVA and co-stabilized with pluronic™ F68 are effective against E. coli and P. aeruginosa microorganisms, with MIC values as low as 0.78% of the concentration of the original AgNps dispersion. The antimicrobial action against S. aureus is poor, with MIC values not lower than 25%.

CONCLUSIONS

AgNps stabilized by different polymeric systems have shown improved antimicrobial activity against gram-negative microorganisms in comparison to unstabilized AgNps. Co-stabilization with the bioactive copolymer pluronic™ F68 has further enhanced the antimicrobial effectiveness against both microorganisms. A poor effectiveness has been found against the gram-positive S. aureus microorganism. Future assays are being delineated targeting possible therapeutic applications.

Production of polymeric micelles by microfluidic technology for combined drug delivery: application to osteogenic differentiation of human periodontal ligament mesenchymal stem cells (hPDLSCs)

The current paper reports the production of polymeric micelles (PMs), based on pluronic block-copolymers, as drug carriers, precisely controlling the cellular delivery of drugs with various physico-chemical characteristics. PMs were produced with a microfluidic platform to exploit further control on the size characteristic of the PMs. PMs were designed for the co-delivery of dexamethasone (Dex) and ascorbyl-palmitate (AP) to in vitro cultured human periodontal ligament mesenchymal stem cells (hPDLSCs) for the combined induction of osteogenic differentiation. Mixtures of block-copolymers and drugs in organic, water miscible solvent, were conveniently converted in PMs within microfluidic channel leveraging the fast mixing at the microscale. Our results demonstrated that the drugs can be efficiently co-encapsulated in PMs and that different production parameters can be adjusted in order to modulate the PM characteristics. The comparative analysis of PM produced by microfluidic and conventional procedures confirmed that the use of microfluidics platforms allowed the production of PMs in a robust manner with improved controllability, reproducibility, smaller size and polydispersity. Finally, the analysis of the effect of PMs, containing Dex and AP, on the osteogenic differentiation of hPDLSCs is reported. The data demonstrated the effectiveness and safety of PM treatment on hPDLSC. In conclusion, this report indicates that microfluidic approach represents an innovative and useful method for PM controlled preparation, warrant further evaluation as general methodology for the production of colloidal systems for the simultaneous drug delivery.