PEGylation of genistein-loaded bovine serum albumin nanoparticles and its effect on in vitro cell viability and genotoxicity properties.

Self-assembled bovine serum albumin nanoparticles loaded with the isoflavone genistein have shown apoptosis-mediated cytotoxicity against murine mammary adenocarcinoma F3II cells. Due to their protein nature and small particle size (13-15 nm), their parenteral administration could be affected by possible immunogenic reactions and rapid clearance from the bloodstream. To avoid these problems, PEGylation of the systems was achieved in this work by using a 30 kDa methoxy-polyethylene glycol carbonyl imidazole derivative through the reaction between the carbonyl imidazole group and the amino groups of Lys residues on the protein surface, which was confirmed by a 17% reduction in the available amino groups content measured by the o-phthaldialdehyde method. PEGylated isoforms were obtained, showing an increase of particle size from 13 to 15 nm to around 260 nm, and were purified by SEC-FPLC and characterized by SDS-PAGE, DLS and AFM techniques. The effect of PEGylation on BSAnp-Gen cytotoxicity and genotoxicity against F3II cells was evaluated in vitro by MTT assay, flow cytometry analysis and micronucleus assay. From the results, PEGylation produced an improvement of the biological properties of genistein-loaded nanoparticles in terms of cytotoxicity (lower IC50), not affecting the induction of apoptosis, decreasing the genotoxicity of the systems (less induction of micronucleus formation).

Genistein loaded in self-assembled bovine serum albumin nanovehicles and their effects on mouse mammary adenocarcinoma cells.

Antitumor activity of plant-derived flavonoids has been researched during recent decades. Among them, genistein (Gen) stands out for showing cytotoxic activity against breast cancer cells. However, its low water solubility, limited bioavailability, and fast metabolism hinder its administration in chemopreventive therapies. To overcome these obstacles, bovine serum albumin nanovehicles (BSAnp) were obtained by a heat-induced self-assembly process at 70 °C and two aqueous medium pH (9.0 and 11.0) and assayed for the Gen loading. Thus, in this work, Gen loading in BSAnp was studied by spectroscopic techniques and compared with the one obtained for its stereoisomer, chrysin (Chrys). Results revealed that Gen binds to BSAnp via fluorescence quenching mechanism forming inclusion complexes. Compared to Chrys, Gen binding to BSAnp involved more molecules, whereas the association constant was similar for both flavonoids. In general, flavonoid loading in protein systems was strongly affected by the combined effects of BSA conformational state (native vs. aggregated), nanovehicle size, and flavonoid chemical structure. To evaluate the antitumor properties freeze-dried powders were obtained, and they were assayed in vitro after reconstitution by XTT technique and Annexin V-FITC flow cytometry against mouse mammary adenocarcinoma F3II cells. Gen-loaded BSAnp produced a significant decrease in cell viability compared with unloaded BSAnp systems, being the highest cytotoxic effects found for the lowest sized Gen-loaded BSAnp. The leading cytotoxicity mechanism for Gen-loaded systems was apoptosis. Summarizing, it can be concluded that BSAnp constitute versatile nanovehicles for potential flavonoid incorporation in pharmaceutical and nutraceutical matrices.

Chrysin-loaded bovine serum albumin particles as bioactive nanosupplements.

Development of nanosupplements based on bioactive compound encapsulation and their incorporation into diet constitutes a field that is growing exponentially. Among flavonoids, chrysin (Chrys) shows high antitumor activity but its poor water solubility limits its applications. Bovine serum albumin nanoparticles (BSAnp) with sizes in the range of 13-28 nm were previously prepared by applying a heat-induced self-assembly method, and they were able to load Chrys. Hence, the aim of this study is to provide information about elaboration of Chrys nanosupplements considering the incidence of the freeze-drying process of Chrys-loaded and unloaded BSAnp systems on aqueous redispersibility and on the retention of their physicochemical properties as examined by DSC, turbidity and DLS measurements. In general, the physicochemical properties of Chrys-loaded BSAnp were retained after the freeze-drying process. The cytotoxic activity of the reconstituted powders was assayed on MCF-7 and MDA-MB-231 cell lines (as models of cancer cell lines) by using the MTT assay. Furthermore, the mechanism of cell death was researched by Annexin V-FITC flow cytometry. The apoptosis-mediated cytotoxicity was higher for Chrys-loaded BSAnp than for the BSAnp system. The greatest in vitro cytotoxic effect was observed for the smallest sized Chrys-loaded BSAnp, which was obtained at pH 11.0 and 70 °C. Finally, this system was subjected to static in vitro gastrointestinal digestion using the standardized protocol, and ∼14% Chrys was released from BSAnp after digestion. These results would provide a procedure to obtain bioactive nanosupplements in a soluble form, and they would suggest that smaller sized Chrys-loaded BSAnp could be a promising oral delivery system for potential cancer therapies.

Formation and characterization of self-assembled bovine serum albumin nanoparticles as chrysin delivery systems.

Chrysin (5,7-dihydroxyflavone) (Chrys) is a natural flavone extracted from many plants, and it has been proposed as a bioactive agent for cancer therapy. Nevertheless, its use is limited mainly due to its poor water solubility. Bovine serum albumin (BSA) is a water soluble, biocompatible and non-toxic protein with a promising application in lipophilic bioactive compound delivery. Moreover, BSA is heat sensitive, feature that could be used for producing self-assembled nanoparticle with tailor-made properties. In this contribution, we studied the formation of BSA nanoparticles (BSAnp) by thermal treatment at different conditions of temperature (70 °C/5 min and 85 °C/5 min), protein concentration (1.0-4.0%wt.) and aqueous medium pH values (9.0 and 11.0) in which it is known that BSA is found in different unfolded conformations. Binding of Chrys dissolved in dimethyl sulfoxide (DMSO) was studied by fluorescence titration experiments. Characterization of Chrys-loaded and unloaded BSAnp was performed in phosphate buffered saline (PBS) pH 7.4 by applying a set of complementary techniques: dynamic light scattering (DLS), size exclusion fast protein liquid chromatography (SEC-FPLC) and transmission electron microscopy (TEM). Different populations of BSAnp were obtained, which showed different diameters in the range of 1328 nm, ζ potentials around -10.0 mV, molecular weight in the range of 400-1000 kDa and spherical shape. Chrys encapsulation efficiency (EE. %) was also determined, and values between 44-84% were obtained, which mainly depended on the mode of Chrys binding and physicochemical BSAnp properties. Results highlight the ability of self-assembled BSAnp for Chrys vehiculization in an aqueous medium which could found potential application in antitumor therapies.