Amorphous polyphosphate nanoparticles: application of the morphogenetically active inorganic polymer for personalized tissue regeneration

Inorganic polyphosphate (polyP) is one of the oldest chemical energy-providing molecules in biological systems. This polymer, containing a much longer sequence of high-energy phosphate units than the universal energy donor adenosine triphosphate, has attracted increasing attention for potential biomedical applications because of its diverse metabolic and regulatory functions and its ability to form biologically active nano/microparticles. The morphogenetic properties (stimulation of cell growth and differentiation via gene induction) of polyP nano/microparticles, prepared in an amorphous form, and their combination with hydrogel-forming polymers enabled the development of 3D-printable and hardenable hybrid materials for personalized tissue regeneration/repair. Depending on the counterion of the polyanionic polyP, both the physical (hardness, stiffness) and the biological properties (induction of cytokines, enzymes or structural proteins) of the 3D-printed scaffolds can be modulated. In this way, individualized scaffolds/implants, even loaded with cells, which can be adapted to specific tissue defects (e.g. of bone and cartilage), can be fabricated. This topical review summarizes the physical–chemical properties and biological effects of polyP, formulated as smart amorphous nano/microparticles, and its application to produce personalized 3D-scaffolds/implants that open new possibilities in regenerative medicine. (topical review)