Drug loading/release

Fig. 11 Drug loading, release, and antitumor activity of biodegradable polymersomes.

Both nanospheres and nanocapsules are prepared from either a polymerization reaction of dispersed monomers or from a solvent dispersion procedure using preformed polymers. In many instances, the latter procedure using preformed polymer is desirable, as potential reactions between drug and monomer are avoided and the potential toxicity of residual monomers, surfactant, and initiator is reduced [37], The final properties of nanoparticles, such as their size, morphology, drug loading, release characteristics, and biodisti-bution, are all influenced by the method of preparation [38],... 

Kim YH, Bae YH, Kim SW. pH/temperature-sensitive polymers for macromolecular drug loading release. J Control... 

In this way, structure-switchable nanoassemblies can control the drug loading/release, and the structure changes are also expected to affect the cell biology such as cell toxicity, improvement of immunity, and cell differentiation. Bellomo et al. prepared a polymer vesicle consisting of diblock copolymer peptides, and the encapsulated drug release was controlled via solution pH [87]. The copolymer peptides allow the construction of a... 

The earlier work of Miller (35), Outright (37), and Brady (5) on nonmedicated implants provided an excellent basis for further studies on specific controlled release formulations such as the determination of the biodegradation rates of lactide/glycolide drug-loaded microspheres (38). Those studies were done with l c-iabeled polymers produced from DL-lactic acid and glycolide. The final formulations tested in rats were microspheres loaded with H-labeled steroid and polymer as the matrix. The microspheres were administered intramuscularly and animals were serially sacrificed over a period of about a year. 

The rate of release of levonorgestrel from films of block copolymers of e-caprolactone and dl-lactic acid (drug load 30%) was shown to be a function of the copolymer composition. The rate was unchanged for compositions of 100% and 88% e-capirolactone, but decreased thereafter as the e-caprolactone content decreased (42). 

FIGURE 10 In vitro rates of release of progesterone from PCL films, illustrating their dependence on the film thickness and drug load. The deviation from (time)l/2 kinetics reflects the contribution of an aqueous boundary layer. The solid lines were calculated assuming an aqueous boundary layer thickness of 19 ym. (From Ref. 68.)... 

Surface erosion not only leads to zero-order drug release from devices that maintain a constant surface area, but has other important consequences. Among these are the following (1) the rate of drug release is directly proportional to drug loading, (2) the lifetime... 

FIGURE 9 Effect of drug loading on cumulative drug release from polymer discs prepared from 3,9-bis(ethylidene-2,4,8,10-tetraoxaspiro-[5,5]undecane) and a 50 5Q mole ratio of trans-cyclohexane dimethanol and 1,6-hexanediol at pH 7.4 and 37 C. Drug loading 8 wt% (o),... 

E Allemann, JC Leroux, R Gurny, E Doelker. In vitro extended-release properties of drug loaded poly (dl-lactic acid) nanoparticles produced by a salting-out procedure. Pharm Res 10(12) 1732—1737, 1993. 

Fattale, E. Rojas, J. Roblot-Treupal, L. Andremont, A., Couveur, P. Ampicillin-loaded liposomes and nanoparticles Comparison of drug loading, drug release and in vitro antimicrobial activity. J. Microcapsulation 8 (I), p. 29-36, 1991... 

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