Folic acid conjugated with serum albumin for nano- and submicron delivery systems for applications in therapy and diagnostics

Folic acid (FA) residue is a well-known and widely spread targeting ligand, or biovector, used as a component in engineering artificial nanosized and submicron particles (NSPs) to target various cells and treat a variety of diseases that are associated with FA (or folate) receptors (FR) overexpression. A particular place in the list of these diseases is held by various cancer types, for which overexpression of FR on the cell surface is often accompanied by a more severe disease course, increased resistance to the conventional chemotherapy, and poorer prognosis. The incorporation of albumin into NSPs has been shown to enhance their biocompatibility, give high compatibility with drug molecules, prolong their circulation, reduce thrombogenic activity, and improve their colloidal stability. Nowadays albumin-based NSPs with FA residue as a targeting agent are used for chemotherapy, photothermal and photodynamic therapy, combined therapy, visualization, and theranostics (also known as theragnostics) for various types of cancer: breast, cervical, ovarian, prostate, nasopharyngeal, gastric, colorectal, liver cancer, and brain tumors. A limited number of studies have also focused on the use of NSPs in rheumatoid arthritis treatment. In this review, we discuss the ways of FA-albumin conjugation and conjugation of FA to albumin-modified NSPs systems. An application of nanosized and submicron delivery systems on the base of serum albumin and FA for therapy and diagnostics is discussed.