Polymeric drug delivery systems, surface

Surface Chemical Analysis of Polymeric Drug Delivery Systems by Static Secondary Ion Mass Spectrometry (SSIMS) and SIMS Imaging... 

The interest in the surface chemical characterization of polymeric drug delivery systems is primarily two-fold firstly, the... 

Lee, P. I. and Good, W. R., Eds. Surface chemical analysis of polymeric drug delivery systems by static secondary ion mass spectrometry (SSIMS) and SIMS imaging. In American Chemical Society Symposium Series Controlled-Release Technology, Pharmaceutical Applications. American Chemical Society, Washington, DC, 1987. 

Various characterization methods both in vitro and in vivo can provide information to understand, predict, and improve the performance of drug delivery systems. Selection of methods depends on the material properties and their applications. Viscoelastic properties can be measured using both DMA and oscillatory shear rheometry. DSC is a most useful method of measuring thermal transitions. Various microscopic methods are available to obtain the microstrac-ture and shape of the materials. Amorphous and crystaUine materials have different packing patterns of molecules, and these properties can be determined from XRD or density measurements. Surface properties such as surface elemental composition and material porosity can be obtained from various spectroscopic methods as well as from BET measurements. The biocompatibility of the material can be determined from both in vitro and in vivo assays. In vitro dissolution testing can be utilized to correlate with the in vivo performance of polymeric drug delivery systems. All these characterization methods can provide valuable information... 

A large variety of drug delivery systems are described in the literature, such as liposomes (Torchilin, 2006), micro and nanoparticles (Kumar, 2000), polymeric micelles (Torchilin, 2006), nanocrystals (Muller et al., 2011), among others. Microparticles are usually classified as microcapsules or microspheres (Figure 8). Microspheres are matrix spherical microparticles where the drug may be located on the surface or dissolved into the matrix. Microcapsules are characterized as spherical particles more than Ipm containing a core substance (aqueous or lipid), normally lipid, and are used to deliver poor soluble molecules... 

Stancell et. al. ( 0) reported the possible use of ultrathin films deposited onto relatively permeable substrates as permselective membranes. Ultrathin and highly crosslinked coatings effectively distinguish between molecules of different sizes and increase the permselectivity of the substrate film. Chang et. al. ( ) demonstrated that the permeability coefficient of silicone rubber to oxygen decreased noticeably after depositing a plasma-polymerized ethylene film on the surface. Colter, et. al. (92.93) found similar effects of plasma polymerized films as diffusion barriers in controlled-released drug delivery systems. 

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