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.
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.
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