Polyphosphate as a Bioactive and Biodegradable Implant Material: Induction of Bone Regeneration in Rats

Abstract

Inorganic polyphosphate (polyP) is a naturally occurring polymer that is bioresorbable and anabolically active on bone forming cells in vitro. In order to demonstrate if polyP also shows morphogenetic activity in vivo, animal studies are performed applying the rat calvarial defect model. Poly(D,L-lactide-co-glycolide) (PLGA) microspheres with a narrow size distribution (%820 mm) are prepared, containing either encapsulated polyP or b-tricalcium phosphate (b-TCP), used as a reference material. Discs are prepared from the microspheres and inserted into 10 mm large defects created in the calvaria of rats. Both the formation of COL-I and the expression of ALP is upregulated, as well as the extent of mineralization within and around the polyP implant. Our data demonstrate that amorphous and resorbable inorganic polyP is also morphogenetically active in vivo.

Amorphous polyphosphate, a smart bioinspired nano-/bio-material for bone and cartilage regeneration: towards a new paradigm in tissue engineering

“…166 A further gene anabolically implicated during bone formation, collagen type I 190 is also strongly upregulated in the presence of these particles, while b-TCP caused no effect. 191 Scaffold architecture: for small defects the sphere technology has been applied until now. In anticipation of future animal studies a preparation technology has been introduced for larger implants.…”

“…Those spheres have been implanted into cranial defects and were shown to undergo dissolution during a 4-week period in rats. 166,191 This initial phase is accompanied by an invasion of new cells, comprising bone-mineralizing activity (Fig. 14).…”

Transformation of Amorphous Polyphosphate Nanoparticles into Coacervate Complexes: An Approach for the Encapsulation of Mesenchymal Stem Cells

“…In addition, polyP has been proven to function as extracellular fuel deposit allowing, after enzymatic cleavage of the phosphoanhydride bonds by the alkaline phosphatase [ALP], the transfer of the released metabolic energy to ADP and AMP . The polymer can be characterized as being smart because it exhibits different and specific functions according to the counterion (cation) [Ca 2+ , Mg 2+ , or Sr 2+ ] used for salt/nanoparticle formation such as Ca–polyP and Sr–polyP for acceleration of bone regeneration or Mg–polyP for cartilage repair . Since to date polyP has the most promising future as a biomaterial/scaffold for bone implants, we have selected for the present study the Ca 2+ –polyP salt.…”

Amorphous, Smart, and Bioinspired Polyphosphate Nano/Microparticles: A Biomaterial for Regeneration and Repair of Osteo-Articular Impairments In-Situ

“…It has been shown that polyP particles can be incorporated in a straightforward way into pearls or implants, e.g., by embedding them into poly( d , l -lactide- co -glycolide) [ 44 , 75 ], which proved firstly, to accelerate the physiological bone regeneration, and secondly, to be superior than β-tricalcium phosphate. In addition, such a scaffold material allows MSC to proliferate.…”