Natural absorbable polymers, limitation

By their nature, many UV absorbers are amenable to analysis by fluorimetric analysis. In many instances visible fluorescence techniques are less subject to interference by other polymer additives in a polymer extract than are UV methods of analysis. In fluorescence analysis (ex at 367 nm, em at 400-440 nm) of a PS/Uvitex OB chloroform dissolution AOs such as Ionol CP, Ionox 330, Polygard and Wingstay T/W do not interfere detection limit of 10 ppm [41]. 

LDMS is particularly well suited for the analysis of porphyrins.35-39 The heme molecule—a 22 rc-electron conjugated protoporphyrin system (Figure 8.1)—is an efficient photo-absorber in the visible and near UV (with an absorption maximum—the Soret band—near 400nm). This feature, concurrently with its low ionization potential, warrants that direct LDMS will possess extremely low limits for heme detection. The uses of IR or UV LDMS for structural characterization of natural porphyrins and their metabolites, synthetic monomeric porphyrins (e.g., used in photodynamic therapy), porphyrin polymers, and multimeric arrays, have been well documented.41148 In addition fast atom bombardment MS has been used to characterize purified hemozoin, isolated from the spleens and livers of Plasmodium yoelii infected mice.49... 

Subsequent investigations showed that identical hydration reactions occurred on both bare aluminum surfaces as well as bonded surfaces, but at very different rates of hydration [45]. An Arrhenius plot of incubation times prior to hydration of bare and buried FPL surfaces clearly showed that the hydration process exhibited the same energy of activation ( 82 kJ/mol) regardless of the bare or covered nature of the surface (Fig. 6). On the other hand, the rate of hydration varies dramatically, depending on the concentration of moisture available to react at the oxide/polymer interface or the oxide surface. The epoxy-covered surfaces have incubation times (and rate constants) three to four orders of magnitude longer than bare, immersed specimens, reflecting the limited amount of moisture absorbed by the epoxy and free to react with the oxide. 

Advantages of the oral mucosal route of delivery include its capacity to bypass all the limitations associated with the oral route, ease of administration, relatively low content of enzymes, and adequate vascular drainage. As described in the following sections, most of the limitations of the oral mucosa epithelium arise from its stratified nature and its intercellular content characteristics. Nonetheless, due to its direct connection to systemic circulation, delivery systems could potentially be formulated to show either bolus-like or controlled release profiles for specific therapeutic needs. Polymers used in the development of such delivery systems play a major role in the release profile, permeation enhancement, and the localization of the active in the vicinity of the absorbing mucosa. Among the various uses of polymers in delivery systems, their mucoadhesive nature is the most prominent application in the oral mucosal route and is the main focus of this entry. After describing the physiological considerations in the oral cavity mucosa, this entry will review the literature pertinent to the use of polymers in delivery systems for the oral mucosal route. 

---