Release from biodegradable polymers

Drug release from biodegradable polymer microparticles is determined by the polymer degradation kinetics, structural features of the microparticles, and distribution of the drugs within the particle matrix. The ultimate goal of microparticle systems in the controlled drug delivery is to achieve readily tunable release profiles, which has been pursued in various perspectives. 

Gupta, R.K. Griffin, P.J. Rivera, R. Siber, G.R. Development of an animal model to assess the immu-nogenicity of single-dose tetanus and diphtheria vaccines based on controlled release from biodegradable polymer microspheres. Dev. Biol. Stand. 1998, 92, 277-287. 

Peter, S. J., Lu, L., Kim, D. J., Stamatas, G. N., Miller, M. J., Yaszemski, M, J., and Mikos, A. G. (2000), Effects of transforming growth factor betal released from biodegradable polymer microparticles on marrow stromal osteoblasts cultured on poly(propylene fumarate) substrates, J. Biomed. Mater. Res. 50(3) 452-462. 

Mechanisms of Action of Drug Release from Biodegradable Polymers... 

A controlled rate of drug release from biodegradable polymers can be ensured by several factors, including the biodegradation kinetics of the polymers [56], the physicochemical properties of the polymers and drugs [57], the thermodynamic compatibility between the polymers and drugs [58], and the shape of the devices [59]. 

Lu, L., Yaszemski, M.J., and Mikos, A.G. TGF-betal release from biodegradable polymer microparticles its effects on marrow stromal osteoblast function. /. Bone Joint Surg. Am. 83-A (Suppl 1) ... 

Hydrophobic polymers are often used to deliver biomacromolecules regardless of the route of administration. The rapid transit time of approximately 8 hours limits the time of a device in the gastrointestinal (GI) system, consequently the mechanisms possible for oral drug release are limited. The predominant method of release from hydrophobic polymers has been degradation, or biodegradation, of a polymeric matrix by hydrolysis (Figure 11.1). In fact, all of the hydrophobic polymers described in this chapter for use as oral protein or peptide delivery are hydrolytically unstable. 

For matrices made from biodegradable polymers, longer release periods have been reported. When loaded with malaria antigen, one single injection was sufficient to induce an immune response without the help of adjuvant. Polycaprolactone proved to be superior to polylactide, which was explained by polycaprolactone s slower degradation behavior [20],... 

Camarata PJ, Suryanarayanan R, Turner DA, Parker RG, Ebner TJ. Sustained release of nerve growth factor from biodegradable polymer microspheres. Neurosurgery 1992 30 313-319. 

Controlled Drag Release from Biodegradable Shape-Memory Polymers... 

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