Concurrent quantification of novel cyclometalated iridium-based photosensitizer and 5-fluorouracil using RP-HPLC: Applications in nanoformulation analysis, drug release, and skin permeation studies.

BACKGROUND Combination therapies for skin cancer are emerging as effective strategies to overcome limitations of monotherapies, such as limited efficacy, resistance development, and recurrence. Chemo-photodynamic therapy represents a promising approach for this. In this study, novel cyclometalated iridium-based photosensitizer was investigated in combination with 5-fluorouracil. As the photosensitizer is novel, no analytical method has been reported for its simultaneous estimation with 5-FU. Such a method is essential for quantifying both analytes in nanoformulations, enabling pharmacokinetic/pharmacodynamic and skin permeation studies critical for development of chemo-photodynamic therapy.

METHOD A simultaneous RP-HPLC method was developed using a C18-column with an isocratic mobile phase of acetonitrile and pH 4.0 buffer (80:20v/v) at a flow rate of 1.0 mL/min. Detection was performed at 265 nm. The method was validated in accordance with ICH guidelines, including forced-degradation studies, and applicability was evaluated using nanodispersion and skin permeation samples.

RESULTS Good resolution (>3) was achieved between CIBP and 5-FU, with retention times of 5.944 and 2.714 min, respectively. The method showed excellent linearity (r2 > 0.999) at concentration range of 500-12,000 ng/mL. High accuracy was observed, with recoveries of 100.74-101.35% for CIBP and 100.94-101.05% for 5-FU. High sensitivity was demonstrated, with LOD/LOQ values of 6.89/20.90 ng/mL for CIBP and 5.62/17.04 ng/mL for 5-FU. Precision studies showed %RSD < 2% for both analytes.

CONCLUSION The validated method is reliable, economical, and suitable for routine quantification of both analytes in stability studies, drug-encapsulation, in-vitro release, and ex-vivo skin permeation samples, supporting quality control and dermatokinetics profiling of dual-drug-loaded nanodispersion.