The present work describes the functional and structural characterization of adenine phosphoribosyltransferase 2 from Thermus thermophilus HB8 (TtAPRT2). The combination of structural and substrate specificity data provided valuable information for immobilization studies. Dimeric TtAPRT2 was immobilized onto glutaraldehyde-activated MagReSyn®Amine magnetic iron oxide porous microparticles by two different strategies: a) an enzyme immobilization at pH 8.5 to encourage the immobilization process by N-termini (MTtAPRT2A, MTtAPRT2B, MTtAPRT2C) or b) an enzyme immobilization at pH 10.0 to encourage the immobilization process through surface exposed lysine residues (MTtAPRT2D, MTtAPRT2E, MTtAPRT2F). According to catalyst load experiments, MTtAPRT2B (activity: 480 IU g-1biocatalyst, activity recovery: 52%) and MTtAPRT2F (activity: 507 IU g-1biocatalyst, activity recovery: 44%) were chosen as optimal derivatives. The biochemical characterization studies demonstrated that immobilization process improved the thermostability of TtAPRT2. Moreover, the potential reusability of MTtAPRT2B and MTtAPRT2F was also tested. Finally, MTtAPRT2F was employed in the synthesis of nucleoside-5'-monophosphate analogues.

Among the different ways to reduce the secondary effects of antineoplastic drugs in cancer treatment, the use of nanoparticles has demonstrated good results due to the protection of the drug and the possibility of releasing compounds to a specific therapeutic target. The α-isoform of the folate receptor (FR) is overexpressed on a significant number of human cancers; therefore, folate-targeted crosslinked nanoparticles based on BSA and alginate mixtures and loaded with paclitaxel (PTX) have been prepared to maximize the proven antineoplastic activity of the drug against solid tumors. Nanometric-range-sized particles (169 ± 28 nm–296 ± 57 nm), with negative Z-potential values (between −0.12 ± 0.04 and −94.1± 0.4), were synthesized, and the loaded PTX (2.63 ± 0.19–3.56 ±0.13 µg PTX/mg Np) was sustainably released for 23 and 27 h. Three cell lines (MCF-7, MDA-MB-231 and HeLa) were selected to test the efficacy of the folate-targeted PTX-loaded BSA/ALG nanocarriers. The presence of FR on the cell membrane led to a significantly larger uptake of BSA/ALG–Fol nanoparticles compared with the equivalent nanoparticles without folic acid on their surface. The cell viability results demonstrated a cytocompatibility of unloaded nanoparticle–Fol and a gradual decrease in cell viability after treatment with PTX-loaded nanoparticle–Fol due to the sustainable PTX release.