Fluorescent behavior of B-phycoerythrin in microemulsions of aerosol OT/water/isooctane

Microemulsified Gel Formulations for Topical Delivery of Clotrimazole: Structural and In Vitro Evaluation

Microemulsified gels (μEGs) with fascinating functions have become indispensable as topical drug delivery systems due to their structural flexibility, high stability, and facile manufacturing process. Topical administration is an attractive alternative to traditional methods because of advantages such as noninvasive administration, bypassing first-pass metabolism, and improving patient compliance. In this article, we report on the new formulations of microemulsion-based gels suitable for topical pharmaceutical applications using biocompatible and ecological ingredients. For this, two biocompatible μE formulations comprising clove oil/Brij-35/water/ethanol (formulation A) and clove oil/Brij-35/water/1-propanol (formulation B) were developed to encapsulate and improve the load of an antimycotic drug, Clotrimazole (CTZ), and further gelatinized to control the release of CTZ through skin barriers. By delimiting the pseudo-ternary phase diagram, optimum μE formulations with clove oil (∼15%) and Brij-35 (∼30%) were developed, keeping constant surfactant/co-surfactant ratio (1:1), to upheld 2.0 wt % CTZ. The as-developed formulations were further converted into smart gels by adding 2.0 wt % carboxymethyl cellulose (CMC) as a cross-linker to adhere to the controlled release of CTZ through complex skin barriers. Electron micrographs show a fine, monodispersed collection of CTZ-μE nanodroplets (∼60 nm), which did not coalesce even after gelation, forming spherical CTZ-μEG (∼90 nm). However, the maturity of CTZ nanodroplets observed by dynamic light scattering suggests the affinity of CTZ for the nonpolar microenvironment, which was further supported by the peak-to-peak correlation of Fourier transform infrared (FTIR) analysis and fluorescence measurement. In addition, HPLC analysis showed that the in vitro permeation release of CTZ-μEG from rabbit skin in the ethanolic phosphate buffer (pH = 7.4) was significantly increased by >98% within 6.0 h. This indicates the sustained release of CTZ in μEBG and the improvement in transdermal therapeutic efficacy of CTZ over its traditional topical formulations.

Implementation of kLa-Based Strategy for Scaling Up Porphyridium purpureum (Red Marine Microalga) to Produce High-Value Phycoerythrin, Fatty Acids, and Proteins

Porphyridium purpureum is a well-known Rhodophyta that recently has attracted enormous attention because of its capacity to produce many high-value metabolites such as the pigment phycoerythrin and several high-value fatty acids. Phycoerythrin is a fluorescent red protein-pigment commercially relevant with antioxidant, antimicrobial activity, and fluorescent properties. The volumetric mass transfer coefficient (k_La) was kept constant within the different scaling-up stages in the present study. This scaling-up strategy was sought to maintain phycoerythrin production and other high-value metabolites by Porphyridium purpureum, using hanging-bag photobioreactors. The k_La was monitored to ensure the appropriate mixing and CO₂ diffusion in the entire culture during the scaling process (16, 80, and 400 L). Then, biomass concentration, proteins, fatty acids, carbohydrates, and phycoerythrin were determined in each step of the scaling-up process. The k_La at 16 L reached a level of 0.0052 s^-1, while at 80 L, a value of 0.0024 s^-1 was achieved. This work result indicated that at 400 L, 1.22 g L^-1 of biomass was obtained, and total carbohydrates (117.24 mg L^-1), proteins (240.63 mg L^-1), and lipids (17.75% DW) were accumulated. Regarding fatty acids production, 46.03% palmitic, 8.03% linoleic, 22.67% arachidonic, and 2.55% eicosapentaenoic acid were identified, principally. The phycoerythrin production was 20.88 mg L^-1 with a purity of 2.75, making it viable for food-related applications. The results of these experiments provide insight into the high-scale production of phycoerythrin via the cultivation of P. purpureum in an inexpensive and straightforward culture system.

Fourth-Generation Antibiotic Gatifloxacin Encapsulated by Microemulsions: Structural and Probing Dynamics

To overcome the increased disease rate, utilization of the versatile broad spectrum antibiotic drugs in controlled drug-delivery systems has been a challenging and complex consignment. However, with the development of microemulsion (μE)-based formulations, drugs can be effectively encapsulated and transferred to the target source. Herein, two biocompatible oil-in-water (o/w) μE formulations comprising clove oil/Tween 20/ethylene glycol/water (formulation A) and clove oil/Tween 20/1-butanol/water (formulation B) were developed for encapsulating the gatifloxacin (GTF), a fourth-generation antibiotic. The pseudoternary phase diagrams were mapped at a constant surfactant/co-surfactant (1:1) ratio to bound the existence of a monophasic isotropic region for as-formulated μEs. Multiple complementary characterization techniques, namely, conductivity (σ), viscosity (η), and optical microscopy analyses, were used to study the gradual changes that occurred in the microstructure of the as-formulated μEs, indicating the presence of a percolation transformation to a bicontinuous permeate flow. GTF showed good solubility, 3.2 wt % at pH 6.2 and 4.0 wt % at pH 6.8, in optimum μE of formulation A and formulation B, respectively. Each loaded μE formulation showed long-term stability over 8 months of storage. Moreover, no observable aggregation of GTF was found, as revealed by scanning transmission electron microscopy and peak-to-peak correlation of IR analysis, indicating the stability of GTF inside the formulation. The average particle size of each μE, measured by dynamic light scattering, increased upon loading GTF, intending the accretion of drug in the interfacial layers of microdomains. Likewise, fluorescence probing sense an interfacial hydrophobic environment to GTF molecules in any of the examined formulations, which may be of significant interest for understanding the kinetics of drug release.

Encapsulation of Antibiotic Levofloxacin in Biocompatible Microemulsion Formulation: Insights from Microstructure Analysis

Microemulsions (μEs) are unique systems that offer exciting perspectives in biophysical research for mimicing biomembranes at the molecular level. In the present study, biocompatible μE formulation of a new oil-in-water (o/w) system comprising clove oil/Tween 20/2-propanol/water was accomplished for encapsulating an antibiotic, levofloxacin (LVF). The pseudoternary phase diagram was delineated at a constant cosurfactant/surfactant (2:1) ratio to meet the economic feasibility. The gradual changes occurring in the microstructure of the as-formulated four-component μEs were explored via multiple complementary characterization techniques. The results of electrical conductivity (σ), viscosity (η), and optical microscopic measurements suggested the existence of a percolation transition to a bicontinuous structure in the microregions of the as-formulated μE. LVF displayed a high solubility (5.0 wt %) at the pH of 6.9 in an optimum μE formulation comprising 2-propanol (36.4%), Tween 20 (18.2%), clove oil (20.7%), and water (24.7%). The LVF-loaded μE composition showed long-term stability for over 6 months of storage. Fourier transform IR analysis showed that LVF was stable inside the μE formulation, indicating the absence of any possible aggregation of LVF. Dynamic light scattering revealed that the average particle size of drug-free μE (64.5 ± 3.4 nm) increases to 129.7 ± 5.8 nm upon loading of LVF, suggesting the accumulation of LVF in the interfacial layers of the micelles. Moreover, fluorescence measurements indicated that LVF might be localized in the interfacial film of μE system, which may result in a controlled release of drug.

Effect of lipolysis on drug release from self-microemulsifying drug delivery systems (SMEDDS) with different core/shell drug location

The objective of this study is to investigate the effect of lipolysis on the release of poorly water-soluble drug from SMEDDS in the perspective of drug core/shell location. For this purpose, four SMEDDS formulations with various core/shell properties were developed based on long-chain lipid or medium-chain lipid as well as different surfactant/oil ratios. Poorly water-soluble drugs, hymecromone and resveratrol, were significantly solubilized in all SMEDDS formulations and the diluted microemulsions. Fluorescence spectra analysis indicated that hymecromone was mainly located in the shell of microemulsions, while resveratrol was located in the core. The effect of lipolysis on the release rates of drugs with different core/shell locations were investigated by a modified in vitro drug release model. For the drug located in the shell, hymecromone, the release profiles were not affected during the lipolysis process and no significant differences were observed among four formulations. For the drug located in the core, resveratrol, the release rates were increased to various degrees depending on the extent of digestion. In conclusion, the drug core/shell location plays an important role for determining the effect of lipolysis on drug release from SMEDDS formulation.

The 42.1 and 53.7 kDa bands in SDS-PAGE of R-phycoerythrin from Polysiphonia urceolata

In SDS-PAGE gels of three purified R-phycoerythrins (R-PEs) isolated from three species of red algae, two bands whose molecular weights were about 40 kDa and 50 kDa can stably be found when the sample loading amount was enough. It is important for structure study of R-PE to clarify what these bands represent and how they are formed. According to results of the second SDS-PAGE, as well as molecular weights, fluorescences under UV and abundance, the 42.1 kDa and 53.7 kDa bands in SDS-PAGE gels of R-PE from Polysiphonia urceolata were believed to be complexes of αβ and βγ1, respectively. Formation of these bands may be related to light and phycourobilins (PUB) in subunits; and appearance of these two bands provided some proofs on position of chromophores and directions of energy transfer in R-PE. R-PE containing γ1 subunit was obviously more stable than R-PE containing γ2 subunit when they were exposed to protein denaturants, so γ subunits of R-PE may play important roles in structural stability of R-PE aggregates and the main forces that maintain the stability of R-PE may be interactions between γ subunit and β subunits.

Isolation and characterization of macromolecular protein R-Phycoerythrin from Portieria hornemannii

R-Phycoerythrin (R-PE) is one of the three phycobiliproteins which are extensively used as fluorescent probes, and it is prepared from red macro-algae. This macromolecular protein has gained importance in many biotechnological applications in food science, immunodiagnostic, therapy, cosmetics, protein and cell labeling, and analytical processes. In the present investigation, R-PE was isolated and purified from a red alga Portieria hornemannii. R-PE extracted and purified through ammonium sulfate precipitation (55%) followed by Q-Sepharose column chromatography had yielded a maximum purity of 5.2%. R-PE exhibited a typical "three-peak" with absorption maxima at 499, 545 and 565 nm. CD spectrum of R-PE yielded the following secondary structure data: alpha helix (14.30%), beta helix (28.10%), turn helix (19.20%) and random coil helix (38.40%). The molecular mass of R-PE was 240 kDa under Native-PAGE. Three different subunits such as α, β and γ of 16 kDa, 21 kDa and 39 kDa were segregated under SDS-PAGE. On two dimensional gel electrophoresis, one basic and four acidic subunits were detected. Five different tryptic peptides were assigned under MALDI-TOF. The sequences of N-terminus of R-PE of 10 different amino acids are Met Lys Gln Met Trp Asp Arg Met Val Val. The preparative procedures of the R-PE extraction and purification established based on the experiments exhibit advantages and can offer a reference for R-PE preparation from other marine red macro-alga P. hornemannii.

Dynamics of water-in-oil nanoemulsions revealed by fluorescence lifetime correlation spectroscopy

The size, diffusional properties, and dynamics of reverse water-in-oil nanoemulsions, or reverse micelles (RMs), have been widely investigated because of interest in this system as a model for biological compartmentalization. Here, we have employed fluorescence lifetime correlation spectroscopy (FLCS) to reveal the dynamics and sizes of aerosol-OT (AOT)/isooctane RMs using a fluorescent xanthene derivative called Tokyo Green II (TG-II). The dye undergoes a partition and a shift in its tautomeric equilibrium such that the TG-II anion remains in the inner micellar aqueous core, and the neutral quinoid form lies in the interfacial region. By applying FLCS, we specifically obtained the lifetime filtered autocorrelation curves of the anionic TG-II, which shows a characteristic lifetime of approximately 4 ns. Analysis of the FLCS curves provides the diffusion coefficient and hydrodynamic radius of the RMs as well as micelle dynamics in the same experiment. The FLCS curves show dynamics in the microsecond time range, which represents an interconversion rate that changes the distribution of the TG-II neutral and anionic forms in the hydrophobic interface and the water core.

Purification, crystallization and preliminary X-ray analysis of phycocyanin and phycoerythrin from Porphyra yezoensis Ueda

Porphyra yezoensis is one of the most important and widely cultured seaweeds in China. Phycobiliproteins exhibit excellent spectroscopic properties and play versatile roles in the biomedical, food, cosmetics and chemical synthetic dye industries. Here, the purification and crystallization of phycoerythrin and phycocyanin, two phycobiliproteins extracted from P. yezoensis, are described. Using a novel protocol including co-precipitation with ammonium sulfate and hydroxyapatite column chromatography, both phycobiliproteins were produced on a large scale with improved quality and yield compared with those previously reported. Native PAGE analysis indicated that phycoerythrin and phycocyanin exist as (αβ)(3) heterohexamers in solution. The crystals of phycoerythrin diffracted to 2.07 Å resolution and belonged to space group R3. The unit-cell parameters referred to hexagonal axes are a = b = 187.7, c = 59.7 Å, with nine (αβ)(2) heterotetramers per unit cell. The crystals of phycocyanin diffracted to 2.70 Å resolution in space group P2(1). Matthews coefficient analysis shows that 10-19 (αβ) heterodimers of phycocyanin in the asymmetric unit would be reasonable. A self-rotation function calculation clarified this ambiguity and indicated that 12 (αβ) heterodimers of phycocyanin are assembled in the asymmetric unit.