The effect of polymeric additives on the solubilisation of a poorly-soluble drug in micellar solutions of Pluronic F127

Hypotonic, gel-forming delivery system for vaginal drug administration

Vaginal drug delivery is often preferred over systemic delivery to reduce side effects and increase efficacy in treating diseases and conditions of the female reproductive tract (FRT). Current vaginal products have drawbacks, including spontaneous ejection of drug-eluting rings and unpleasant discharge from vaginal creams. Here, we describe the development and characterization of a hypotonic, gel-forming, Pluronic-based delivery system for vaginal drug administration. The rheological properties were characterized with and without common hydrogel polymers to demonstrate the versatility. Both qualitative and quantitative approaches were used to determine the Pluronic F127 concentration below the critical gel concentration (CGC) that was sufficient to achieve gelation when formulated to be hypotonic to the mouse vagina. The hypotonic, gel-forming formulation was found to form a thin, uniform gel layer along the vaginal epithelium in mice, in contrast to the rapidly forming conventional gelling formulation containing polymer above the CGC. When the hypotonic, gel-forming vehicle was formulated in combination with a progesterone nanosuspension (ProGel), equivalent efficacy was observed in the prevention of chemically-induced preterm birth (PTB) compared to commercial Crinone® vaginal cream. Further, ProGel showed marked benefits in reducing unpleasant discharge, reducing product-related toxicity, and improving compatibility with vaginal bacteria in vitro. A hypotonic, gel-forming delivery system may be a viable option for therapeutic delivery to the FRT.

Antimicrobial potential of a biosurfactant gel for the prevention of mixed biofilms formed by fluconazole-resistant C. albicans and methicillin-resistant S. aureus in catheters

Dual-species biofilms formed by Candida albicans and Staphylococcus aureus have high virulence and drug resistance. In this context, biosurfactants produced by Pseudomonas aeruginosa have been widely studied, of which a new derivative (RLmix_Arg) stands out for possible application in formulations. The objective of this study was to evaluate the antibiofilm activity of RLmix_Arg, both alone and incorporated in a gel prepared with Pluronic F-127, against dual-species biofilms of fluconazole-resistant C. albicans (FRCA) and methicillin-resistant S. aureus (MRSA) in impregnated catheters. Broth microdilution tests, MTT reduction assays of mature biofilms, impregnation of RLmix_Arg and its gel in peripheral venous catheters, durability tests and scanning electron microscopy (SEM) were performed. RLmix_Arg showed antimicrobial activity against Candida spp. and S. aureus, by reducing the cell viability of mixed biofilms of FRCA and MRSA, and preventing their formation in a peripheral venous catheter. The incorporation of this biosurfactant in the Pluronic F-127 gel considerably enhanced its antibiofilm activity. Thus, RLmix_Arg has potential application in gels for impregnation in peripheral venous catheters, helping to prevent development of dual-species biofilms of FRCA and MRSA.

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.

Recent progress in biomedical applications of Pluronic (PF127): Pharmaceutical perspectives

Most of the administered anti-cancer drugs are hydrophobic in nature and are known to have poor water solubility, short residence time, rapid clearance from the body and systemic side effects. Polymeric-based targeted particulate carrier system has shown to directly deliver the encapsulated anti-cancer drug to the desired site of action and prevent the interaction of encapsulated drug with the normal cells. Pluronic F127 (PF127) has been widely investigated for its broad-range of therodiagnostic applications in biomedical and pharmaceutical sciences, but rapid dissolution in the physiological fluids, short residence time, rapid clearance, and weak mechanical strength are the main shortcomings that are associated with PF127 and have recently been overcome by making various modifications in the structure of PF127 notably through preparation of PF127-based mixed polymeric micelles, PF127-conjugated nanoparticles and PF127-based hydrophobically modified thermogels. In this article, we have briefly discussed the recent studies that have been conducted on various anti-cancer drugs using PF127 as nano-carrier modified with other copolymers and/or conjugated with magnetic nanoparticles. The key findings of these studies demonstrated that the modified form of PF127 can significantly increase the stability of incorporated hydrophobic drugs with enhanced in vitro cytotoxicity and cellular uptake of anti-cancer drugs. Moreover, the modified form of PF127 has also shown its therapeutic potentials as therodiagnostics in various types of tumors and cancers. Hence, it can be concluded that the modified form of PF127 exhibits significant therodiagnostic effects with increased tumor-specific delivery of anti-cancer drugs having minimal toxic effects as compared to PF127 alone and/or other copolymers.

Effect of chain length of PEO on the gelation and micellization of the pluronic F127 copolymer aqueous system

The effect of adding homopolymer poly(ethylene oxide) (PEO) on the sol/gel behavior of amphiphilic triblock copolymer Pluronic F127 ((EO)98(PO)67(EO)98) in aqueous media is explored. Emphasis is placed on the influence of the PEO molecular weight and concentration on micellization and gelation and the exploration of their correlation. PEO is always found to lower the critical micellization temperature modestly. However, short PEO chains promote the gelation of F127, and long chains delay or even curb gel formation. Micelle size measurements and cryo-TEM micrographs provide evidence for micellar aggregation via the bridging of long PEO chains or depletion flocculation, thereby impeding the ordering of micelles for gel formation.

Doxorubicin-loaded micelles of reverse poly(butylene oxide)-poly(ethylene oxide)-poly(butylene oxide) block copolymers as efficient "active" chemotherapeutic agents

Five reverse poly(butylene oxide)-poly(ethylene oxide)-poly(butylene oxide) block copolymers, BOnEOmBOn, with BO ranging from 8 to 21 units and EO from 90 to 411 were synthesized and evaluated as efficient chemotherapeutic drug delivery nanocarriers and inhibitors of the P-glycoprotein (P-gp) efflux pump in a multidrug resistant (MDR) cell line. The copolymers were obtained by reverse polymerization of poly(butylene oxide), which avoids transfer reaction and widening of the EO block distribution, commonly found in commercial poly(ethylene oxide)-poly(propylene oxide) block copolymers (poloxamers). BOnEOmBOn copolymers formed spherical micelles of 10-40 nm diameter at lower concentrations (one order of magnitude) than those of equivalent poloxamers. The influence of copolymer block lengths and BO/EO ratios on the solubilization capacity and protective environment for doxorubicin (DOXO) was investigated. Micelles showed drug loading capacity ranging from ca. 0.04% to 1.5%, more than 150 times the aqueous solubility of DOXO, and protected the cargo from hydrolysis for more than a month due to their greater colloidal stability in solution. Drug release profiles at various pHs, and the cytocompatibility and cytotoxicity of the DOXO-loaded micelles were assessed in vitro. DOXO loaded in the polymeric micelles accumulated more slowly inside the cells than free DOXO due to its sustained release. All copolymers were found to be cytocompatible, with viability extents larger than 95%. In addition, the cytotoxicity of DOXO-loaded micelles was higher than that observed for free drug solutions in a MDR ovarian NCI-ADR-RES cell line which overexpressed P-gp. The inhibition of the P-gp efflux pump by some BOnEOmBOn copolymers, similar to that measured for the common P-gp inhibitor verapamil, favored the retention of DOXO inside the cell increasing its cytotoxic activity. Therefore, poly(butylene oxide)-poly(ethylene oxide) block copolymers offer interesting features as cell response modifiers to complement their role as efficient nanocarriers for cancer chemotherapy.

Mechanism of inhibition of P-glycoprotein mediated efflux by Pluronic P123/F127 block copolymers: relationship between copolymer concentration and inhibitory activity

The aim of this study was to clarify the relationship between the concentration of Pluronic P123/F127 block copolymers and P-glycoprotein (P-gp) inhibitory potency. Modulation of multidrug resistance (MDR) by Pluronic P123/F127 was evaluated in P-gp over-expressing human breast cancer cell line MCF-7/ADR and its non-P-gp over-expressing counterpart MCF-7 cells. Four different probes (known as P-gp substrates) including rhodamine 123 (R-123), rhodamine 6G (R-6G), doxorubicin (DOX), and paclitaxel (PTX) were applied to investigate the impact of Pluronic P123/F127 copolymers with different concentrations on the intracellular accumulation of these probes. Additionally, the intracellular ATP and mitochondrial transmembrane potential in MCF-7/ADR cells were determined over a wide concentration range of Pluronic P123/F127. Furthermore, the endocytic mechanisms of Pluronic micelles were performed. It was suggested that P-gp substrate hydrophobicity and the concentration of P123/F127 copolymers had little impact on P-gp inhibitory activity of Pluronic P123/F127 itself. Intracellular ATP depletion was the main mechanism of Pluronic P123/F127 for P-gp inhibition. In vitro cytotoxicity study was also conducted in order to compare cytotoxic effect among different PTX formulations. It indicated that the IC50 of PTX-loaded Pluronic P123/F127 mixed micelles was 6.3-fold lower than free PTX and 2.3-fold lower than Taxol, respectively. Therefore, Pluronic P123/F127 polymeric micelles could be considered a promising drug delivery system to overcome MDR in cancer therapy.

Peculiar mechanism of solubilization of a sparingly water soluble drug into polymeric micelles. Kinetic and equilibrium studies

Complementary kinetic and equilibrium studies on the solubilization process of the sparingly water soluble tamoxifen (TAM) drug in polymeric aqueous solutions have been performed by using the spectrophotometric method. In particular, the amphiphilic copolymers obtained by derivatization of polymeric chain of poly(N-2-hydroxyethyl)-dl-aspartamide, PHEA, with poly(ethylene glycol)s, PEG (2000 or 5000 Da), and/or hexadecylamine chain, C16, namely PHEA-PEG2000-C16, PHEA-PEG5000-C16, PHEA-C16, have been employed. Preliminary to the kinetic and equilibrium data quantitative treatment, the molar absorption coefficient of TAM in polymeric micelle aqueous solution has been determined. By these studies the solubization sites of TAM into the polymeric micelles have been determined and the solubilization mechanism has been elucidated through a nonconventional approach by considering the TAM partitioned between three pseudophases, i.e., the aqueous pseudophase, the hydrophilic corona, and the hydrophobic core. The simultaneous solution of the rate laws associated with each step of the proposed mechanism allowed the calculation of the rate constants associated with the involved processes, the values of which are independent of both the copolymer concentration and nature, with the exception of the rate of the TAM transfer from the corona to the core. This has been attributed to the steric barrier, represented by the corona, which hampers the solubilization into the core. The binding constant values of the TAM to the hydrophilic corona of the polymeric micelles, calculated through the quantitative analysis of the equilibrium data, depend on the thickness of the hydrophilic headgroup, while those of the hydrophobic core are almost independent of the copolymer type. Further confirmation to the proposed solubilization mechanism has been provided by performing the kinetic and equilibrium measurements in the presence of PHEA-PEG2000 and PHEA-PEG5000 copolymers.