Spectroscopic analysis of human serum albumin nanoparticles with encapsulated phenothiazine derivative (6-acetylaminobutyl-9-chloroquino[3,2-b]benzo[1,4]thiazine) – continuation studies

Nanoparticles (NPs) provide a potential opportunity to reduce toxicity, optimize drug effects, and properly distribute drugs in the body and/or overcome multidrug resistance. Human serum albumin (HSA) is widely used as a drug carrier due to its biocompatibility and specific affinity to cancer cells. 6-Acetylaminobutyl-9-chloroquino[3,2-b]benzo[1, 4]thiazine (QBT) is a tetracyclic, acetylaminobutyl phenothiazine derivative in which one of the benzene rings has been replaced by a quinoline. This compound has shown very promising in vitro and in vivo biological properties. The aim of this study was the spectroscopic analysis of QBT and the development of albumin nanoparticles (HSA-NPs) with encapsulated QBT (QBT-HSA-NPs). This study is a continuation of attempts to encapsulate phenothiazine derivatives in nanoparticles. To examine the spectroscopic properties of QBT, UV-Vis spectroscopy was applied. To investigate the properties of QBT to be encapsulated in HSA nanoparticles, the desolvation method was used. By using scanning electron microscopy (SEM), the size and shape of the nanoparticles were ascertained. The QBT release study was determined using the sampling and separation method and the mathematical drug release kinetics mechanism was estimated. Changes in the secondary structure of HSA were verified using circular dichroism (CD) spectropolarimetry. QBT has an ability to absorb radiation in the UV-Vis range. The encapsulation efficiency was 97.44 ± 0.11%, confirming that QBT can be encapsulated in HSA nanoparticles. SEM examination showed smooth nanoparticles of their size of 101.445 ± 9.907 nm for QBT-HSA-NPs and 92.680 ± 12.797 nm for HSA-NPs. QBT released according to the zero-order mechanism, via QBT diffusion and HSA swelling. The presence of QBT in nanoparticles partially protected the secondary structure of HSA. The observed changes in the structure of native HSA, influenced by the presence of QBT at the molecular level, may not have a strong influence on the side effects generated in the in vivo system. Despite reports on albumin nanoparticles and QBT, no one has published studies on QBT encapsulation in nanoparticles to date.