New polymers for drug delivery systems in orthopaedics: in vivo biocompatibility evaluation

Giavaresi, G. and Tschon, M. and Borsari, V. and Daly, J.H. and Liggat, J.J. and Fini, M. and Bonazzi, V. and Nicolini, A. and Carpi, A. and Morra, M. and Cassinelli, C. and Giardino, R. (2004) New polymers for drug delivery systems in orthopaedics: in vivo biocompatibility evaluation. Biomedicine and Pharmacotherapy, 58 (8). pp. 411-417. ISSN 0753-3322 (

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The use of biodegradable polymers for drug delivery systems excluded the need for a second operation to remove the carrier. However, the development of an avascular fibrous capsule, reducing drug release, has raised concern about these polymers in terms of tissue-implant reaction. Five novel polymers were evaluated in vivo after implantation in the rat dorsal subcutis and compared to the reference polycaprolactone (PCL). Poly(cyclohexyl-sebacate) (PCS), poly(L-lactide-b-1,5-dioxepan-2-one-b-L-lactide) (PLLA-PDXO-PLLA), two 3-hydroxybutyrate-co-3-hydroxyvalerate copolymers (D400G and D600G), and a poly(organo)phosphazene (POS-PheOEt:Imidazole) specimens were histologically evaluated in terms of the inflammatory tissue thickness and vascular density at 4 and 12 weeks from surgery. The highest values of inflammatory tissue thickness were observed in D600G (P < 0.01), PCS (P < 0.001) and PLLA-PDXO-PLLA (P < 0.001) at 4 weeks, while POP - PheOEt:Imidazole showed the lowest value of inflammatory tissue thickness (P < 0.05) at 12 weeks. D400G, D600G, PLLA-PDXO-PPLA and POP - PheOEt:Imidazole showed higher (P < 0.001) values of vascular density near the implants in comparison to PCL at 4 weeks. Finally, D400G and D600G increased their vessel densities while POP - PheOEt:Imidazole and the synthetic polyester PLLA-PDXO-PLLA presented similar vessel density values during experimental times. These different behaviours to improve neoangiogenesis without severe inflammatory tissue-responses could be further investigated with drugs in order to obtain time-programmable drug delivery systems for musculoskeletal therapy.


Giavaresi, G., Tschon, M., Borsari, V., Daly, J.H., Liggat, J.J. ORCID logoORCID:, Fini, M., Bonazzi, V., Nicolini, A., Carpi, A., Morra, M., Cassinelli, C. and Giardino, R.;