Molecular-Level Release of Coumarin-3-Carboxylic Acid and Warfarin-Derivatives from BSA-Based Hydrogels

Abstract

This investigation aimed at developing BSA hydrogels as a controlled release system to study the release behavior of spin-labeled coumarin-3-carboxylic acid (SL-CCS) and warfarin (SL-WFR). The release profiles of these spin-labeled (SL-) pharmaceuticals from BSA hydrogels prepared with different procedures are compared in detail. The mechanical properties of the gels during formation and release were studied via rheology, while a nanoscopic view on the release behavior was achieved by analyzing SL-drugs–BSA interaction using continuous wave electron paramagnetic resonance (CW EPR) spectroscopy. The influence of type of drug, drug concentration, duration of gel formation, and gelation methods on release behavior were characterized by CW EPR spectroscopy, EPR imaging (EPRI), and dynamic light scattering (DLS), which provide information on the interaction of BSA with SL-drugs, the percentage of drug inside the hydrogel and the nature and size of the released structures, respectively. We found that the release rate of SL-CCS and SL-WFR from BSA hydrogels is tunable through drug ratios, hydrogel incubation time and gelation procedures. All of the results indicate that BSA hydrogels can be potentially exploited in controlled drug delivery applications.

The Release of a Highly Cytotoxic Paullone Bearing a TEMPO Free Radical from the HSA Hydrogel: An EPR Spectroscopic Characterization

“…This helical-structure protein possesses multiple ligand-binding sites, allowing for the tight binding of fatty acids, bilirubin, free metal ions, and a broad spectrum of drugs [43][44][45][46]. Most recently, BSA-based hydrogels with different mechanical properties were evaluated in vitro as delivery systems for coumarin-3carboxylic acid and warfarin, demonstrating the significance of the drug-to-protein ratio, as well as different hydrogel incubation time and gelation procedures, for tunable controlled release [47].…”

“…EPR has many advantages over typical methods for drug binding and release studies (i.e., ultracentrifugation, UV-visible spectrophotometry, fluorimetry, Raman spectroscopy), namely a nanomolar detection limit, requirement of extremely small sample volumes (30 µL), sensitivity to protein conformational changes, and experiment time efficiency. Although EPR spectroscopy has not been frequently used for this purpose, since it requires covalent modification of the ligand/drug with a stable radical (EPR-active group), it has been useful for the mechanistic study of HSA-drug association for over 20 different spin-labeled pharmaceuticals [63], as well as for controlled release studies of TEMPO-labeled coumarin-3-carboxylic acid and warfarin from BSA-based hydrogels [47]. Furthermore, the EPR spin labeling technique has also been used to investigate the binding of a mononitrosyl ruthenium complex to HSA, based on its competition with spin-labeled fatty acids for the binding sites on the protein [64], and for monitoring the drug-induced conformational changes in a triazine spin-labeled BSA [65].…”

Macro- and Nanoscale Effect of Ethanol on Bovine Serum Albumin Gelation and Naproxen Release

“…Figure 2B shows the BSA hydrogels prepared by thermally and pH-induced methods. In our previous work, BSA hydrogels generated slightly above and slightly below the denaturation temperature (at 65 °C and 59 °C) at pH 7, and by lowering the pH to 3.5 at 37 °C, have been extensively investigated [14,15]. We obtain thermally induced hydrogels by heating the precursor solution of 1000 µL, 5 mM BSA above the denaturation temperature of this protein at 65 °C.…”

“…To counteract these deficiencies, controlled and sustained drug delivery systems, providing a constant and prolonged drug concentration, have been developed and have attracted significant attention [5]. Several systems, among them nanofibers [6,7], microparticles [8][9][10], smart polymers [11,12], hydrogels [13][14][15], nanocarriers [16], etc., have been explored for drug delivery applications.…”

“…The present investigation was directed towards the development of a controlled drug delivery system that may be applied in local delivery based on BSA hydrogels that were prepared by mixing different amounts of ethanol and BSA and incubation at 37 • C and studying the release behavior of SL-NPX from the prepared gel. In previous studies, the release behavior of 16-doxyl stearic acid (16-DSA) as a model drug, spin-labeled warfarin, and coumarin-3-carboxylic acid from BSA hydrogels, prepared by thermally and pH-induced methods, and nanoscopic properties of small molecule-hydrogel interactions was analyzed in depth [14,15]. The objective of the present contribution is to investigate the potential and the effect of ethanol concentration on hydrogel formation as well as the influence of parameters such as incubation time (time required for gel formation), BSA, ethanol, and SL-NPX concentrations on release rate.…”