Maha M. Abou El-Alamin

Stability-Indicating Chromatographic Methods for Determination of Agomelatine in Drug Substance and Drug Product

Three sensitive and validated chromatographic methods were developed for determination of Agomelatine (AGO) in the presence of its degradation products in drug substance and drug product. The first and second methods were normal thin layer chromatographic (NP-TLC) and reversed phase thin layer chromatographic (RP-TLC) methods. Mobile phase consisting of ethyl acetate-ammonia (33%)-methanol (8.5:0.5:1, v/v/v) was used for NP-TLC while for RP-TLC using 0.1% triethylamine (TEA): acetonitrile (60:40 v/v) at pH=2. The chromatograms were scanned at 230 and 280 nm and determined in the range of 0.1-4 and 0.3-4 μg/spot with mean percentage recovery of 99.89 ± 1.141 and 100.01 ± 1.062 for NP-TLC and RP-TLC respectively. The third method was Micellar Liquid Chromatographic (MLC) method using C18 column and a mobile phase consisting of 0.1 M Sodium Dodecyl Sulphate (SDS), 15% butan-1-ol, 0.2% TEA in water adjusted to pH=3. The UV detection was achieved at 230 nm and determined in the range of 0.5-5 μg/mL with mean percentage recovery of 100.13 ± 0.970. The proposed methods were successfully applied as stability indicating methods under different stressed conditions according to the International Conference of Harmonization (ICH) guidelines. The methods showed good selectivity, repeatability, linearity and sensitivity according to the evaluation of the validation parameters.

Optimized polydopamine coating and DNA conjugation onto gold nanorods for single nanoparticle bioaffinity measurements

Gold nanorods (NRs) have attracted a great deal of interest for a variety of biomedical and sensing applications. However, developing robust methods for biofunctionalizing NRs has continued to be challenging, especially for NR-DNA conjugates. This is due to the presence of cetyltrimethylammonium bromide (CTAB), which plays an essential role in controlling the anisotropic particle growth. In this article, we systematically explore the growth of a polydopamine (PDA) layer on a range of NR surfaces, comparing different polyelectrolyte and alkanethiol coatings as well as direct CTAB displacement. This revealed that the PDA layer thickness and growth rate is strongly dependent on the underlying nanorod functionalization chemistry and allowed us to establish a preferred route for the creation of stable, non-aggregated suspensions of PDA-coated NRs. The utility of this platform was then demonstrated by self-assembling packed monolayers of single-stranded DNA on the outer surface. Both the surface attachment and bioactivity of the resulting NR-DNA conjugates was then demonstrated by performing bulk solution and single nanoparticle imaging fluorescence measurements.

Stability-indicating methods for the determination of luliconazole by TLC and HPTLC—densitometry in bulk powder and cream dosage form

Rapid and sensitive thin-layer chromatography (TLC) and high-performance thin-layer chromatography (HPTLC)—densitometry methods were used to separate, identify and quantify luliconazole (LUL), a new azole antifungal, in bulk and pharmaceutical dosage form. The proposed method can be used as a stability-indicating assay for the determination of LUL in the presence of its degradation products under forced degradation conditions (alkaline, acidic, oxidative, thermal and photolytic degradation). Complete separation was achieved by TLC and HPTLC on silica gel F254 plates with the solvent system toluene—isopropanol—ammonia (90:10:0.5, v/v). The chromatographic bands were visualized under short-wave ultraviolet (UV) light, and the amount of LUL was determined by scanning densitometry at 297 nm using peak area. The linear ranges were 1–24 and 0.8–6 μg band−1 with mean percentage recoveries of 99.84% ± 0.623 and 99.98% ± 1.405 for TLC and HPTLC, respectively. The methods were validated according to the International Conference on Harmonization (ICH) guidelines. The statistical analysis of the results revealed high accuracy and good precision. The suggested procedures could be used as a stability-indicating assay for the determination of LUL in drug substance and drug products in the presence of its degradation products.