Biodegradable microspheres for the sustained release of PDGF-receptor directed pPB-HSA targeted to the fibrotic kidney

Naomi Teekamp, Fransien van Dijk, Eleonora Beljaars, Wouter Hinrichs, Rob Steendam, Johan Zuidema, Klaas Poelstra, H.W. Frijlink, Peter Olinga



Platelet Derived Growth Factor (PDGF) plays a key role in the development of fibrotic processes in several tissues. Accordingly, the PDGF receptor is abundantly present in these fibrotic tissues. Specific targeting to this receptor is established for a series of compounds in different animal models, all sharing the same targeting moiety, i.e. the cyclic peptide pPB. One of those compounds is pPB-HSA, which might function as carrier vehicle that binds to the PDGFβ-receptor without eliciting an intracellular response itself. Aims When formulated as a solution for parenteral administration, targeting of fibrosis with pPB-HSA would involve long-term or even lifelong daily injections, which may jeopardize patient compliance. Therefore, the aim of this study was to develop a microsphere formulation for the sustained release of pPB-HSA and assess the delivery and targeting of the intact protein construct in vivo. Methods pPB-HSA was encapsulated in biodegradable polymeric microspheres using a water-in-oil-in-water (W/O/W) emulsification process and blends of two semi-crystalline multi-block copolymers composed of blocks of poly (-caprolactone) – polyethylene glycol – poly (-caprolactone) and poly (L-lactide). The delivery and targeting of the protein construct was evaluated in vivo using a mouse unilateral ureteral obstruction (UUO) kidney fibrosis model. Results and conclusions By varying the ratio of the two multi-block copolymers, the release of the model protein HSA from the microspheres could be tailored from 7 days to 2 months without burst release. The microsphere formulation with a 50:50 blend ratio of the polymers, showing first order sustained release for 14 days, was selected for further optimization. Optimization of microencapsulation process parameters resulted in an encapsulation efficiency of 83% and an in vitro release of >90% after 14 days for the final pPB-HSA formulation. The median particle size of these microspheres was 25 m, which enables injection with a 21G needle. All mice were sacrificed 7 days after ureteral obstruction and microsphere administration. The obstructed kidneys developed fibrosis and showed increased PDGFβ-receptor expression. The plasma concentration of pPB-HSA in the pPB-HSA treated mice (n=3) was 15 ± 4 ng/mL. Immunohistochemical staining and western blot analysis showed the presence of pPB-HSA in the fibrotic kidney of these mice, while the sham operated kidney was negative for pPB-HSA. In conclusion, the pPB-HSA construct was successfully formulated in polymeric microspheres produced by a W/O/W method, which showed a first order release profile in vitro. Furthermore, pPB-HSA was released from these microspheres in vivo. In addition, pPB-HSA was specifically localized in fibrotic tissue, where the target receptor, the PDGF receptor, is abundantly present. The delivery and site specific targeting of pPB-HSA for polymeric microspheres is thus confirmed in this study. Future studies include a pharmacokinetic in vivo study of the pPB-HSA microspheres in a mouse liver fibrosis model.
Originele taal-2English
StatusPublished - 2016
EvenementFIGON Dutch Medicine Days - Reehorst, Ede, Netherlands
Duur: 3-okt-20164-okt-2016


ConferenceFIGON Dutch Medicine Days

Citeer dit