Catalytic Synthesis and Characterization of Biodegradable ...
Catalytic Synthesis and Characterization of Biodegradable ...
Catalytic Synthesis and Characterization of Biodegradable ...
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Chapter 1<br />
PBCLA could be achieved. Though the TAM content was improved, the release <strong>of</strong> TAM from<br />
the materials seen to be less effective even in the presence <strong>of</strong> hydrolysis lipase. Only less than<br />
10 % <strong>of</strong> the TAM was released after 6 days. In order to solve this issue, a more versatile<br />
method has been investigated recently. The TAM nitroxyl radicals were loaded in the<br />
biodegradable PEAs nan<strong>of</strong>iber membranes instead <strong>of</strong> chemical conjugation. 195 The payload<br />
<strong>of</strong> the TAM in the nan<strong>of</strong>iber could be tunable by pre-loading different amount <strong>of</strong> TAM <strong>and</strong><br />
the release kinetic study revealed that the encapsulated TAM would be completely released<br />
from the membranes within 5 days.<br />
Figure 1.6.6 The effect <strong>of</strong> TAM-PGA on the proliferation <strong>of</strong> human smooth muscle. 196<br />
1.6.2.2 Magnetic Resonance Imaging (MRI)<br />
MRI allows noninvasive imaging <strong>of</strong> deep internal structure <strong>of</strong> the body <strong>and</strong>, is<br />
widespread use in clinical diagnostic <strong>of</strong> physiologic <strong>and</strong> pathologic changes <strong>of</strong> disease. For<br />
MRI, the paramagnetic species are needed to serve as the contrast agents to enhance the<br />
image contrast. The most commercially used MR contrast agents are the gadolinium chelates,<br />
such as gadolinium diethylenetriaminepentaacetic aicd (Gd-DTPA). However, these agents<br />
are non-selective distribution in tissues <strong>and</strong> have short resistant time in tumors. Nitroxyl<br />
radicals are only well-known for their electronic paramagnetic resonance (EPR) properties<br />
until 1984, the T1 contrast property was found. Afterward, MRI applications <strong>of</strong> the nitroxyl<br />
radicals have been extensively investigated owing to their chemical flexibility, feasible<br />
preparation <strong>and</strong> low toxicity as comparison with conventional gadolinium chelates.<br />
Unfortunately, there are two fetal flaws would emerge when applied the nitroxyl radical MRI<br />
reagents in vivo. One is the relatively low MR relaxivities, while the other is the<br />
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